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diff --git a/old/7oxac10.txt b/old/7oxac10.txt new file mode 100644 index 0000000..baa560a --- /dev/null +++ b/old/7oxac10.txt @@ -0,0 +1,5902 @@ +Project Gutenberg's Oxy-Acetylene Welding and Cutting, by Harold P. Manly + +Copyright laws are changing all over the world. Be sure to check the +copyright laws for your country before downloading or redistributing +this or any other Project Gutenberg eBook. + +This header should be the first thing seen when viewing this Project +Gutenberg file. Please do not remove it. Do not change or edit the +header without written permission. + +Please read the "legal small print," and other information about the +eBook and Project Gutenberg at the bottom of this file. Included is +important information about your specific rights and restrictions in +how the file may be used. You can also find out about how to make a +donation to Project Gutenberg, and how to get involved. + + +**Welcome To The World of Free Plain Vanilla Electronic Texts** + +**eBooks Readable By Both Humans and By Computers, Since 1971** + +*****These eBooks Were Prepared By Thousands of Volunteers!***** + + +Title: Oxy-Acetylene Welding and Cutting + Electric, Forge and Thermit Welding together with related methods + and materials used in metal working and the oxygen process + for removal of carbon + +Author: Harold P. Manly + +Release Date: April, 2005 [EBook #7969] +[Yes, we are more than one year ahead of schedule] +[This file was first posted on June 7, 2003] + +Edition: 10 + +Language: English + +Character set encoding: ASCII + +*** START OF THE PROJECT GUTENBERG EBOOK OXY-ACETYLENE WELDING AND CUTTING *** + + + + +Produced by Juliet Sutherland, John Argus, Tonya Allen, +Charles Franks and the Online Distributed Proofreading Team. + + + + +Oxy-Acetylene Welding and Cutting + +Electric, Forge and Thermit Welding + +Together with Related Methods and Materials Used in Metal Working +And +The Oxygen Process for Removal of Carbon + +By +HAROLD P. MANLY + + + + +PREFACE + +In the preparation of this work, the object has been to cover not only the +several processes of welding, but also those other processes which are so +closely allied in method and results as to make them a part of the whole +subject of joining metal to metal with the aid of heat. + +The workman who wishes to handle his trade from start to finish finds that +it is necessary to become familiar with certain other operations which +precede or follow the actual joining of the metal parts, the purpose of +these operations being to add or retain certain desirable qualities in the +materials being handled. For this reason the following subjects have been +included: Annealing, tempering, hardening, heat treatment and the +restoration of steel. + +In order that the user may understand the underlying principles and the +materials employed in this work, much practical information is given on the +uses and characteristics of the various metals; on the production, handling +and use of the gases and other materials which are a part of the equipment; +and on the tools and accessories for the production and handling of these +materials. + +An examination will show that the greatest usefulness of this book lies in +the fact that all necessary information and data has been included in one +volume, making it possible for the workman to use one source for securing a +knowledge of both principle and practice, preparation and finishing of the +work, and both large and small repair work as well as manufacturing methods +used in metal working. + +An effort has been made to eliminate all matter which is not of direct +usefulness in practical work, while including all that those engaged in +this trade find necessary. To this end, the descriptions have been limited +to those methods and accessories which are found in actual use today. For +the same reason, the work includes the application of the rules laid down +by the insurance underwriters which govern this work as well as +instructions for the proper care and handling of the generators, torches +and materials found in the shop. + +Special attention has been given to definite directions for handling the +different metals and alloys which must be handled. The instructions have +been arranged to form rules which are placed in the order of their use +during the work described and the work has been subdivided in such a way +that it will be found possible to secure information on any one point +desired without the necessity of spending time in other fields. + +The facts which the expert welder and metalworker finds it most necessary +to have readily available have been secured, and prepared especially for +this work, and those of most general use have been combined with the +chapter on welding practice to which they apply. + +The size of this volume has been kept as small as possible, but an +examination of the alphabetical index will show that the range of subjects +and details covered is complete in all respects. This has been accomplished +through careful classification of the contents and the elimination of all +repetition and all theoretical, historical and similar matter that is not +absolutely necessary. + +Free use has been made of the information given by those manufacturers who +are recognized as the leaders in their respective fields, thus insuring +that the work is thoroughly practical and that it represents present day +methods and practice. + +THE AUTHOR. + + + + +CONTENTS + + CHAPTER I + +METALS AND ALLOYS--HEAT TREATMENT:--The Use and Characteristics of the +Industrial Alloys and Metal Elements--Annealing, Hardening, Tempering and +Case Hardening of Steel + + CHAPTER II + +WELDING MATERIALS:--Production, Handling and Use of the Gases, Oxygen and +Acetylene--Welding Rods--Fluxes--Supplies and Fixtures + + CHAPTER III + +ACETYLENE GENERATORS:--Generator Requirements and Types--Construction--Care +and Operation of Generators. + + CHAPTER IV + +WELDING INSTRUMENTS:--Tank and Regulating Valves and Gauges--High, Low and +Medium Pressure Torches--Cutting Torches--Acetylene-Air Torches + + CHAPTER V + +OXY-ACETYLENE WELDING PRACTICE:--Preparation of Work--Torch Practice-- +Control of the Flame--Welding Various Metals and Alloys--Tables of +Information Required in Welding Operations + + CHAPTER VI + +ELECTRIC WELDING:--Resistance Method--Butt, Spot and Lap Welding--Troubles +and Remedies--Electric Arc Welding + + CHAPTER VII + +HAND FORGING AND WELDING:--Blacksmithing, Forging and Bending--Forge +Welding Methods + + CHAPTER VIII + +SOLDERING, BRAZING AND THERMIT WELDING:--Soldering Materials and Practice-- +Brazing--Thermit Welding + + CHAPTER IX + +OXYGEN PROCESS FOR REMOVAL OF CARBON + +INDEX + + + + + +OXY-ACETYLENE WELDING AND CUTTING, ELECTRIC AND THERMIT WELDING + + + + +CHAPTER I + +METALS AND THEIR ALLOYS--HEAT TREATMENT + + +THE METALS + +_Iron._--Iron, in its pure state, is a soft, white, easily worked +metal. It is the most important of all the metallic elements, and is, next +to aluminum, the commonest metal found in the earth. + +Mechanically speaking, we have three kinds of iron: wrought iron, cast iron +and steel. Wrought iron is very nearly pure iron; cast iron contains carbon +and silicon, also chemical impurities; and steel contains a definite +proportion of carbon, but in smaller quantities than cast iron. + +Pure iron is never obtained commercially, the metal always being mixed with +various proportions of carbon, silicon, sulphur, phosphorus, and other +elements, making it more or less suitable for different purposes. Iron is +magnetic to the extent that it is attracted by magnets, but it does not +retain magnetism itself, as does steel. Iron forms, with other elements, +many important combinations, such as its alloys, oxides, and sulphates. + +[Illustration: Figure 1.--Section Through a Blast Furnace] + +_Cast Iron._--Metallic iron is separated from iron ore in the blast +furnace (Figure 1), and when allowed to run into moulds is called cast +iron. This form is used for engine cylinders and pistons, for brackets, +covers, housings and at any point where its brittleness is not +objectionable. Good cast iron breaks with a gray fracture, is free from +blowholes or roughness, and is easily machined, drilled, etc. Cast iron is +slightly lighter than steel, melts at about 2,400 degrees in practice, is +about one-eighth as good an electrical conductor as copper and has a +tensile strength of 13,000 to 30,000 pounds per square inch. Its +compressive strength, or resistance to crushing, is very great. It has +excellent wearing qualities and is not easily warped and deformed by heat. +Chilled iron is cast into a metal mould so that the outside is cooled +quickly, making the surface very hard and difficult to cut and giving great +resistance to wear. It is used for making cheap gear wheels and parts that +must withstand surface friction. + +_Malleable Cast Iron._--This is often called simply malleable iron. It +is a form of cast iron obtained by removing much of the carbon from cast +iron, making it softer and less brittle. It has a tensile strength of +25,000 to 45,000 pounds per square inch, is easily machined, will stand a +small amount of bending at a low red heat and is used chiefly in making +brackets, fittings and supports where low cost is of considerable +importance. It is often used in cheap constructions in place of steel +forgings. The greatest strength of a malleable casting, like a steel +forging, is in the surface, therefore but little machining should be done. + +_Wrought Iron._--This grade is made by treating the cast iron to +remove almost all of the carbon, silicon, phosphorus, sulphur, manganese +and other impurities. This process leaves a small amount of the slag from +the ore mixed with the wrought iron. + +Wrought iron is used for making bars to be machined into various parts. If +drawn through the rolls at the mill once, while being made, it is called +"muck bar;" if rolled twice, it is called "merchant bar" (the commonest +kind), and a still better grade is made by rolling a third time. Wrought +iron is being gradually replaced in use by mild rolled steels. + +Wrought iron is slightly heavier than cast iron, is a much better +electrical conductor than either cast iron or steel, has a tensile strength +of 40,000 to 60,000 pounds per square inch and costs slightly more than +steel. Unlike either steel or cast iron, wrought iron does not harden when +cooled suddenly from a red heat. + +_Grades of Irons._--The mechanical properties of cast iron differ +greatly according to the amount of other materials it contains. The most +important of these contained elements is carbon, which is present to a +degree varying from 2 to 5-1/2 per cent. When iron containing much carbon +is quickly cooled and then broken, the fracture is nearly white in color +and the metal is found to be hard and brittle. When the iron is slowly +cooled and then broken the fracture is gray and the iron is more malleable +and less brittle. If cast iron contains sulphur or phosphorus, it will show +a white fracture regardless of the rapidity of cooling, being brittle and +less desirable for general work. + +_Steel._--Steel is composed of extremely minute particles of iron and +carbon, forming a network of layers and bands. This carbon is a smaller +proportion of the metal than found in cast iron, the percentage being from +3/10 to 2-1/2 per cent. + +Carbon steel is specified according to the number of "points" of carbon, a +point being one one-hundredth of one per cent of the weight of the steel. +Steel may contain anywhere from 30 to 250 points, which is equivalent to +saying, anywhere from 3/10 to 2-1/2 per cent, as above. A 70-point steel +would contain 70/100 of one per cent or 7/10 of one per cent of carbon by +weight. The percentage of carbon determines the hardness of the steel, also +many other qualities, and its suitability for various kinds of work. The +more carbon contained in the steel, the harder the metal will be, and, of +course, its brittleness increases with the hardness. The smaller the grains +or particles of iron which are separated by the carbon, the stronger the +steel will be, and the control of the size of these particles is the object +of the science of heat treatment. + +In addition to the carbon, steel may contain the following: + +Silicon, which increases the hardness, brittleness, strength and difficulty + of working if from 2 to 3 per cent is present. + +Phosphorus, which hardens and weakens the metal but makes it easier to + cast. Three-tenths per cent of phosphorus serves as a hardening agent and + may be present in good steel if the percentage of carbon is low. More + than this weakens the metal. + +Sulphur, which tends to make the metal hard and filled with small holes. + +Manganese, which makes the steel so hard and tough that it can with + difficulty be cut with steel tools. Its hardness is not lessened by + annealing, and it has great tensile strength. + +Alloy steel has a varying but small percentage of other elements mixed with +it to give certain desired qualities. Silicon steel and manganese steel are +sometimes classed as alloy steels. This subject is taken up in the latter +part of this chapter under _Alloys_, where the various combinations +and their characteristics are given consideration. + +Steel has a tensile strength varying from 50,000 to 300,000 pounds per +square inch, depending on the carbon percentage and the other alloys +present, as well as upon the texture of the grain. Steel is heavier than +cast iron and weighs about the same as wrought iron. It is about one-ninth +as good a conductor of electricity as copper. + +Steel is made from cast iron by three principal processes: the crucible, +Bessemer and open hearth. + +_Crucible steel_ is made by placing pieces of iron in a clay or +graphite crucible, mixed with charcoal and a small amount of any desired +alloy. The crucible is then heated with coal, oil or gas fires until the +iron melts, and, by absorbing the desired elements and giving up or +changing its percentage of carbon, becomes steel. The molten steel is then +poured from the crucible into moulds or bars for use. Crucible steel may +also be made by placing crude steel in the crucibles in place of the iron. +This last method gives the finest grade of metal and the crucible process +in general gives the best grades of steel for mechanical use. + +[Illustration: Figure 2.--A Bessemer Converter] + +_Bessemer steel_ is made by heating iron until all the undesirable +elements are burned out by air blasts which furnish the necessary oxygen. +The iron is placed in a large retort called a converter, being poured, +while at a melting heat, directly from the blast furnace into the +converter. While the iron in the converter is molten, blasts of air are +forced through the liquid, making it still hotter and burning out the +impurities together with the carbon and manganese. These two elements are +then restored to the iron by adding spiegeleisen (an alloy of iron, carbon +and manganese). A converter holds from 5 to 25 tons of metal and requires +about 20 minutes to finish a charge. This makes the cheapest steel. + +[Illustration: Figure 3.--An Open Hearth Furnace] + +_Open hearth steel_ is made by placing the molten iron in a receptacle +while currents of air pass over it, this air having itself been highly +heated by just passing over white hot brick (Figure. 3). Open hearth steel +is considered more uniform and reliable than Bessemer, and is used for +springs, bar steel, tool steel, steel plates, etc. + +_Aluminum_ is one of the commonest industrial metals. It is used for +gear cases, engine crank cases, covers, fittings, and wherever lightness +and moderate strength are desirable. + +Aluminum is about one-third the weight of iron and about the same weight as +glass and porcelain; it is a good electrical conductor (about one-half as +good as copper); is fairly strong itself and gives great strength to other +metals when alloyed with them. One of the greatest advantages of aluminum +is that it will not rust or corrode under ordinary conditions. The granular +formation of aluminum makes its strength very unreliable and it is too soft +to resist wear. + +_Copper_ is one of the most important metals used in the trades, and +the best commercial conductor of electricity, being exceeded in this +respect only by silver, which is but slightly better. Copper is very +malleable and ductile when cold, and in this state may be easily worked +under the hammer. Working in this way makes the copper stronger and harder, +but less ductile. Copper is not affected by air, but acids cause the +formation of a green deposit called verdigris. + +Copper is one of the best conductors of heat, as well as electricity, being +used for kettles, boilers, stills and wherever this quality is desirable. +Copper is also used in alloys with other metals, forming an important part +of brass, bronze, german silver, bell metal and gun metal. It is about +one-eighth heavier than steel and has a tensile strength of about 25,000 to +50,000 pounds per square inch. + +_Lead._--The peculiar properties of lead, and especially its quality +of showing but little action or chemical change in the presence of other +elements, makes it valuable under certain conditions of use. Its principal +use is in pipes for water and gas, coverings for roofs and linings for vats +and tanks. It is also used to coat sheet iron for similar uses and as an +important part of ordinary solder. + +Lead is the softest and weakest of all the commercial metals, being very +pliable and inelastic. It should be remembered that lead and all its +compounds are poisonous when received into the system. Lead is more than +one-third heavier than steel, has a tensile strength of only about 2,000 +pounds per square inch, and is only about one-tenth as good a conductor of +electricity as copper. + +_Zinc._--This is a bluish-white metal of crystalline form. It is +brittle at ordinary temperatures and becomes malleable at about 250 to 300 +degrees Fahrenheit, but beyond this point becomes even more brittle than at +ordinary temperatures. Zinc is practically unaffected by air or moisture +through becoming covered with one of its own compounds which immediately +resists further action. Zinc melts at low temperatures, and when heated +beyond the melting point gives off very poisonous fumes. + +The principal use of zinc is as an alloy with other metals to form brass, +bronze, german silver and bearing metals. It is also used to cover the +surface of steel and iron plates, the plates being then called galvanized. + +Zinc weighs slightly less than steel, has a tensile strength of 5,000 +pounds per square inch, and is not quite half as good as copper in +conducting electricity. + +_Tin_ resembles silver in color and luster. Tin is ductile and +malleable and slightly crystalline in form, almost as heavy as steel, and +has a tensile strength of 4,500 pounds per square inch. + +The principal use of tin is for protective platings on household utensils +and in wrappings of tin-foil. Tin forms an important part of many alloys +such as babbitt, Britannia metal, bronze, gun metal and bearing metals. + +_Nickel_ is important in mechanics because of its combinations with +other metals as alloys. Pure nickel is grayish-white, malleable, ductile +and tenacious. It weighs almost as much as steel and, next to manganese, is +the hardest of metals. Nickel is one of the three magnetic metals, the +others being iron and cobalt. The commonest alloy containing nickel is +german silver, although one of its most important alloys is found in nickel +steel. Nickel is about ten per cent heavier than steel, and has a tensile +strength of 90,000 pounds per square inch. + +_Platinum._--This metal is valuable for two reasons: it is not +affected by the air or moisture or any ordinary acid or salt, and in +addition to this property it melts only at the highest temperatures. It is +a fairly good electrical conductor, being better than iron or steel. It is +nearly three times as heavy as steel and its tensile strength is 25,000 +pounds per square inch. + + +ALLOYS + +An alloy is formed by the union of a metal with some other material, either +metal or non-metallic, this union being composed of two or more elements +and usually brought about by heating the substances together until they +melt and unite. Metals are alloyed with materials which have been found to +give to the metal certain characteristics which are desired according to +the use the metal will be put to. + +The alloys of metals are, almost without exception, more important from an +industrial standpoint than the metals themselves. There are innumerable +possible combinations, the most useful of which are here classed under the +head of the principal metal entering into their composition. + +_Steel._--Steel may be alloyed with almost any of the metals or +elements, the combinations that have proven valuable numbering more than a +score. The principal ones are given in alphabetical order, as follows: + +Aluminum is added to steel in very small amounts for the purpose of +preventing blow holes in castings. + +Boron increases the density and toughness of the metal. + +Bronze, added by alloying copper, tin and iron, is used for gun metal. + +Carbon has already been considered under the head of steel in the section +devoted to the metals. Carbon, while increasing the strength and hardness, +decreases the ease of forging and bending and decreases the magnetism and +electrical conductivity. High carbon steel can be welded only with +difficulty. When the percentage of carbon is low, the steel is called "low +carbon" or "mild" steel. This is used for rods and shafts, and called +"machine" steel. When the carbon percentage is high, the steel is called +"high carbon" steel, and it is used in the shop as tool steel. One-tenth +per cent of carbon gives steel a tensile strength of 50,000 to 65,000 +pounds per square inch; two-tenths per cent gives from 60,000 to 80,000; +four-tenths per cent gives 70,000 to 100,000, and six-tenths per cent +gives 90,000 to 120,000. + +Chromium forms chrome steel, and with the further addition of nickel is +called chrome nickel steel. This increases the hardness to a high degree +and adds strength without much decrease in ductility. Chrome steels are +used for high-speed cutting tools, armor plate, files, springs, safes, +dies, etc. + +Manganese has been mentioned under _Steel_. Its alloy is much used for +high-speed cutting tools, the steel hardening when cooled in the air and +being called self-hardening. + +Molybdenum is used to increase the hardness to a high degree and makes the +steel suitable for high-speed cutting and gives it self-hardening +properties. + +Nickel, with which is often combined chromium, increases the strength, +springiness and toughness and helps to prevent corrosion. + +Silicon has already been described. It suits the metal for use in +high-speed tools. + +Silver added to steel has many of the properties of nickel. + +Tungsten increases the hardness without making the steel brittle. This +makes the steel well suited for gas engine valves as it resists corrosion +and pitting. Chromium and manganese are often used in combination with +tungsten when high-speed cutting tools are made. + +Vanadium as an alloy increases the elastic limit, making the steel +stronger, tougher and harder. It also makes the steel able to stand much +bending and vibration. + +_Copper._--The principal copper alloys include brass, bronze, german +silver and gun metal. + +Brass is composed of approximately one-third zinc and two-thirds copper. It +is used for bearings and bushings where the speeds are slow and the loads +rather heavy for the bearing size. It also finds use in washers, collars +and forms of brackets where the metal should be non-magnetic, also for many +highly finished parts. + +Brass is about one-third as good an electrical conductor as copper, is +slightly heavier than steel and has a tensile strength of 15,000 pounds +when cast and about 75,000 to 100,000 pounds when drawn into wire. + +Bronze is composed of copper and tin in various proportions, according to +the use to which it is to be put. There will always be from six-tenths to +nine-tenths of copper in the mixture. Bronze is used for bearings, +bushings, thrust washers, brackets and gear wheels. It is heavier than +steel, about 1/15 as good an electrical conductor as pure copper and has a +tensile strength of 30,000 to 60,000 pounds. + +Aluminum bronze, composed of copper, zinc and aluminum has high tensile +strength combined with ductility and is used for parts requiring this +combination. + +Bearing bronze is a variable material, its composition and proportion +depending on the maker and the use for which it is designed. It usually +contains from 75 to 85 per cent of copper combined with one or more +elements, such as tin, zinc, antimony and lead. + +White metal is one form of bearing bronze containing over 80 per cent of +zinc together with copper, tin, antimony and lead. Another form is made +with nearly 90 per cent of tin combined with copper and antimony. + +Gun metal bronze is made from 90 per cent copper with 10 per cent of tin +and is used for heavy bearings, brackets and highly finished parts. + +Phosphor bronze is used for very strong castings and bearings. It is +similar to gun metal bronze, except that about 1-1/2 per cent of phosphorus +has been added. + +Manganese bronze contains about 1 per cent of manganese and is used for +parts requiring great strength while being free from corrosion. + +German silver is made from 60 per cent of copper with 20 per cent each of +zinc and nickel. Its high electrical resistance makes it valuable for +regulating devices and rheostats. + +_Tin_ is the principal part of _babbitt_ and _solder_. A +commonly used babbitt is composed of 89 per cent tin, 8 per cent antimony +and 3 per cent of copper. A grade suitable for repairing is made from +80 per cent of lead and 20 per cent antimony. This last formula should not +be used for particular work or heavy loads, being more suitable for +spacers. Innumerable proportions of metals are marketed under the name of +babbitt. + +Solder is made from 50 per cent tin and 50 per cent lead, this grade being +called "half-and-half." Hard solder is made from two-thirds tin and +one-third lead. + +Aluminum forms many different alloys, giving increased strength to whatever +metal it unites with. + +Aluminum brass is composed of approximately 65 per cent copper, 30 per cent +zinc and 5 per cent aluminum. It forms a metal with high tensile strength +while being ductile and malleable. + +Aluminum zinc is suitable for castings which must be stiff and hard. + +Nickel aluminum has a tensile strength of 40,000 pounds per square inch. + +Magnalium is a silver-white alloy of aluminum with from 5 to 20 per cent of +magnesium, forming a metal even lighter than aluminum and strong enough to +be used in making high-speed gasoline engines. + + +HEAT TREATMENT OF STEEL + +The processes of heat treatment are designed to suit the steel for various +purposes by changing the size of the grain in the metal, therefore the +strength; and by altering the chemical composition of the alloys in the +metal to give it different physical properties. Heat treatment, as applied +in ordinary shop work, includes the three processes of annealing, hardening +and tempering, each designed to accomplish a certain definite result. + +All of these processes require that the metal treated be gradually brought +to a certain predetermined degree of heat which shall be uniform throughout +the piece being handled and, from this point, cooled according to certain +rules, the selection of which forms the difference in the three methods. + +_Annealing._--This is the process which relieves all internal strains +and distortion in the metal and softens it so that it may more easily be +cut, machined or bent to the required form. In some cases annealing is used +only to relieve the strains, this being the case after forging or welding +operations have been performed. In other cases it is only desired to soften +the metal sufficiently that it may be handled easily. In some cases both of +these things must be accomplished, as after a piece has been forged and +must be machined. No matter what the object, the procedure is the same. + +The steel to be annealed must first be heated to a dull red. This heating +should be done slowly so that all parts of the piece have time to reach the +same temperature at very nearly the same time. The piece may be heated in +the forge, but a much better way is to heat in an oven or furnace of some +type where the work is protected against air currents, either hot or cold, +and is also protected against the direct action of the fire. + +[Illustration: Figure 4.--A Gaspipe Annealing Oven] + +Probably the simplest of all ovens for small tools is made by placing a +piece of ordinary gas pipe in the fire (Figure 4), and heating until the +inside of the pipe is bright red. Parts placed in this pipe, after one end +has been closed, may be brought to the desired heat without danger of +cooling draughts or chemical change from the action of the fire. More +elaborate ovens may be bought which use gas, fuel oils or coal to produce +the heat and in which the work may be placed on trays so that the fire will +not strike directly on the steel being treated. + +If the work is not very important, it may be withdrawn from the fire or +oven, after heating to the desired point, and allowed to cool in the air +until all traces of red have disappeared when held in a dark place. The +work should be held where it is reasonably free from cold air currents. If, +upon touching a pine stick to the piece being annealed, the wood does not +smoke, the work may then be cooled in water. + +Better annealing is secured and harder metal may be annealed if the cooling +is extended over a number of hours by placing the work in a bed of +non-heat-conducting material, such as ashes, charred bone, asbestos fibre, +lime, sand or fire clay. It should be well covered with the heat retaining +material and allowed to remain until cool. Cooling may be accomplished by +allowing the fire in an oven or furnace to die down and go out, leaving the +work inside the oven with all openings closed. The greater the time taken +for gradual cooling from the red heat, the more perfect will be the results +of the annealing. + +While steel is annealed by slow cooling, copper or brass is annealed by +bringing to a low red heat and quickly plunging into cold water. + +_Hardening._--Steel is hardened by bringing to a proper temperature, +slowly and evenly as for annealing, and then cooling more or less quickly, +according to the grade of steel being handled. The degree of hardening is +determined by the kind of steel, the temperature from which the metal is +cooled and the temperature and nature of the bath into which it is plunged +for cooling. + +Steel to be hardened is often heated in the fire until at some heat around +600 to 700 degrees is reached, then placed in a heating bath of molten +lead, heated mercury, fused cyanate of potassium, etc., the heating bath +itself being kept at the proper temperature by fires acting on it. While +these baths have the advantage of heating the metal evenly and to exactly +the temperature desired throughout without any part becoming over or under +heated, their disadvantages consist of the fact that their materials and +the fumes are poisonous in most all cases, and if not poisonous, are +extremely disagreeable. + +The degree of heat that a piece of steel must be brought to in order that +it may be hardened depends on the percentage of carbon in the steel. The +greater the percentage of carbon, the lower the heat necessary to harden. + +[Illustration: Figure 5.--Cooling the Test Bar for Hardening] + +To find the proper heat from which any steel must be cooled, a simple test +may be carried out provided a sample of the steel, about six inches long +can be secured. One end of this test bar should be heated almost to its +melting point, and held at this heat until the other end just turns red. +Now cool the piece in water by plunging it so that both ends enter at the +same time (Figure 5), that is, hold it parallel with the surface of the +water when plunged in. This serves the purpose of cooling each point along +the bar from a different heat. When it has cooled in the water remove the +piece and break it at short intervals, about 1/2 inch, along its length. +The point along the test bar which was cooled from the best possible +temperature will show a very fine smooth grain and the piece cannot be cut +by a file at this point. It will be necessary to remember the exact color +of that point when taken from the fire, making another test if necessary, +and heat all pieces of this same steel to this heat. It will be necessary +to have the cooling bath always at the same temperature, or the results +cannot be alike. + +While steel to be hardened is usually cooled in water, many other liquids +may be used. If cooled in strong brine, the heat will be extracted much +quicker, and the degree of hardness will be greater. A still greater degree +of hardness is secured by cooling in a bath of mercury. Care should be used +with the mercury bath, as the fumes that arise are poisonous. + +Should toughness be desired, without extreme hardness, the steel may be +cooled in a bath of lard oil, neatsfoot oil or fish oil. To secure a result +between water and oil, it is customary to place a thick layer of oil on top +of water. In cooling, the piece will pass through the oil first, thus +avoiding the sudden shock of the cold water, yet producing a degree of +hardness almost as great as if the oil were not used. + +It will, of course, be necessary to make a separate test for each cooling +medium used. If the fracture of the test piece shows a coarse grain, the +steel was too hot at that point; if the fracture can be cut with a file, +the metal was not hot enough at that point. + +When hardening carbon tool steel its heat should be brought to a cherry +red, the exact degree of heat depending on the amount of carbon and the +test made, then plunged into water and held there until all hissing sound +and vibration ceases. Brine may be used for this purpose; it is even better +than plain water. As soon as the hissing stops, remove the work from the +water or brine and plunge in oil for complete cooling. + +[Illustration: Figure 6.--Cooling the Tool for Tempering] + +In hardening high-speed tool steel, or air hardening steels, the tool +should be handled as for carbon steel, except that after the body reaches +a cherry red, the cutting point must be quickly brought to a white heat, +almost melting, so that it seems ready for welding. Then cool in an oil +bath or in a current of cool air. + +Hardening of copper, brass and bronze is accomplished by hammering or +working them while cold. + +_Tempering_ is the process of making steel tough after it has been +hardened, so that it will hold a cutting edge and resist cracking. +Tempering makes the grain finer and the metal stronger. It does not affect +the hardness, but increases the elastic limit and reduces the brittleness +of the steel. In that tempering is usually performed immediately after +hardening, it might be considered as a continuation of the former process. + +The work or tool to be tempered is slowly heated to a cherry red and the +cutting end is then dipped into water to a depth of 1/2 to 3/4 inch above +the point (Figure 6). As soon as the point cools, still leaving the tool +red above the part in water, remove the work from the bath and quickly rub +the end with a fine emery cloth. + +As the heat from the uncooled part gradually heats the point again, the +color of the polished portion changes rapidly. When a certain color is +reached, the tool should be completely immersed in the water until cold. + +For lathe, planer, shaper and slotter tools, this color should be a light +straw. + +Reamers and taps should be cooled from an ordinary straw color. + +Drills, punches and wood working tools should have a brown color. + +Blue or light purple is right for cold chisels and screwdrivers. + +Dark blue should be reached for springs and wood saws. + +Darker colors than this, ranging through green and gray, denote that the +piece has reached its ordinary temper, that is, it is partially annealed. + +After properly hardening a spring by dipping in lard or fish oil, it should +be held over a fire while still wet with the oil. The oil takes fire and +burns off, properly tempering the spring. + +Remember that self-hardening steels must never be dipped in water, and +always remember for all work requiring degrees of heat, that the more +carbon, the less heat. + +_Case Hardening._--This is a process for adding more carbon to the +surface of a piece of steel, so that it will have good wear-resisting +qualities, while being tough and strong on the inside. It has the effect of +forming a very hard and durable skin on the surface of soft steel, leaving +the inside unaffected. + +The simplest way, although not the most efficient, is to heat the piece to +be case hardened to a red heat and then sprinkle or rub the part of the +surface to be hardened with potassium ferrocyanide. This material is a +deadly poison and should be handled with care. Allow the cyanide to fuse on +the surface of the metal and then plunge into water, brine or mercury. +Repeating the process makes the surface harder and the hard skin deeper +each time. + +Another method consists of placing the piece to be hardened in a bed of +powdered bone (bone which has been burned and then powdered) and cover with +more powdered bone, holding the whole in an iron tray. Now heat the tray +and bone with the work in an oven to a bright red heat for 30 minutes to an +hour and then plunge the work into water or brine. + + + + +CHAPTER II + +OXY-ACETYLENE WELDING AND CUTTING MATERIALS + + +_Welding._--Oxy-acetylene welding is an autogenous welding process, in +which two parts of the same or different metals are joined by causing the +edges to melt and unite while molten without the aid of hammering or +compression. When cool, the parts form one piece of metal. + +The oxy-acetylene flame is made by mixing oxygen and acetylene gases in a +special welding torch or blowpipe, producing, when burned, a heat of 6,300 +degrees, which is more than twice the melting temperature of the common +metals. This flame, while being of intense heat, is of very small size. + +_Cutting._--The process of cutting metals with the flame produced from +oxygen and acetylene depends on the fact that a jet of oxygen directed upon +hot metal causes the metal itself to burn away with great rapidity, +resulting in a narrow slot through the section cut. The action is so fast +that metal is not injured on either side of the cut. + +_Carbon Removal._--This process depends on the fact that carbon will +burn and almost completely vanish if the action is assisted with a supply +of pure oxygen gas. After the combustion is started with any convenient +flame, it continues as long as carbon remains in the path of the jet of +oxygen. + +_Materials._--For the performance of the above operations we require +the two gases, oxygen and acetylene, to produce the flames; rods of metal +which may be added to the joints while molten in order to give the weld +sufficient strength and proper form, and various chemical powders, called +fluxes, which assist in the flow of metal and in doing away with many of +the impurities and other objectionable features. + +_Instruments._--To control the combustion of the gases and add to the +convenience of the operator a number of accessories are required. + +The pressure of the gases in their usual containers is much too high for +their proper use in the torch and we therefore need suitable valves which +allow the gas to escape from the containers when wanted, and other +specially designed valves which reduce the pressure. Hose, composed of +rubber and fabric, together with suitable connections, is used to carry the +gas to the torch. + +The torches for welding and cutting form a class of highly developed +instruments of the greatest accuracy in manufacture, and must be thoroughly +understood by the welder. Tables, stands and special supports are provided +for holding the work while being welded, and in order to handle the various +metals and allow for their peculiarities while heated use is made of ovens +and torches for preheating. The operator requires the protection of +goggles, masks, gloves and appliances which prevent undue radiation of the +heat. + +_Torch Practice._--The actual work of welding and cutting requires +preliminary preparation in the form of heat treatment for the metals, +including preheating, annealing and tempering. The surfaces to be joined +must be properly prepared for the flame, and the operation of the torches +for best results requires careful and correct regulation of the gases and +the flame produced. + +Finally, the different metals that are to be welded require special +treatment for each one, depending on the physical and chemical +characteristics of the material. + +It will thus be seen that the apparently simple operations of welding and +cutting require special materials, instruments and preparation on the part +of the operator and it is a proved fact that failures, which have been +attributed to the method, are really due to lack of these necessary +qualifications. + + +OXYGEN + +Oxygen, the gas which supports the rapid combustion of the acetylene in the +torch flame, is one of the elements of the air. It is the cause and the +active agent of all combustion that takes place in the atmosphere. Oxygen +was first discovered as a separate gas in 1774, when it was produced by +heating red oxide of mercury and was given its present name by the famous +chemist, Lavoisier. + +Oxygen is prepared in the laboratory by various methods, these including +the heating of chloride of lime and peroxide of cobalt mixed in a retort, +the heating of chlorate of potash, and the separation of water into its +elements, hydrogen and oxygen, by the passage of an electric current. While +the last process is used on a large scale in commercial work, the others +are not practical for work other than that of an experimental or temporary +nature. + +This gas is a colorless, odorless, tasteless element. It is sixteen times +as heavy as the gas hydrogen when measured by volume under the same +temperature and pressure. Under all ordinary conditions oxygen remains in +a gaseous form, although it turns to a liquid when compressed to 4,400 +pounds to the square inch and at a temperature of 220 below zero. + +Oxygen unites with almost every other element, this union often taking +place with great heat and much light, producing flame. Steel and iron will +burn rapidly when placed in this gas if the combustion is started with a +flame of high heat playing on the metal. If the end of a wire is heated +bright red and quickly plunged into a jar containing this gas, the wire +will burn away with a dazzling light and be entirely consumed except for +the molten drops that separate themselves. This property of oxygen is used +in oxy-acetylene cutting of steel. + +The combination of oxygen with other substances does not necessarily cause +great heat, in fact the combination may be so slow and gradual that the +change of temperature can not be noticed. An example of this slow +combustion, or oxidation, is found in the conversion of iron into rust as +the metal combines with the active gas. The respiration of human beings +and animals is a form of slow combustion and is the source of animal heat. +It is a general rule that the process of oxidation takes place with +increasing rapidity as the temperature of the body being acted upon rises. +Iron and steel at a red heat oxidize rapidly with the formation of a scale +and possible damage to the metal. + +_Air._--Atmospheric air is a mixture of oxygen and nitrogen with +traces of carbonic acid gas and water vapor. Twenty-one per cent of the +air, by volume, is oxygen and the remaining seventy-nine per cent is the +inactive gas, nitrogen. But for the presence of the nitrogen, which deadens +the action of the other gas, combustion would take place at a destructive +rate and be beyond human control in almost all cases. These two gases exist +simply as a mixture to form the air and are not chemically combined. It is +therefore a comparatively simple matter to separate them with the processes +now available. + +_Water._--Water is a combination of oxygen and hydrogen, being +composed of exactly two volumes of hydrogen to one volume of oxygen. If +these two gases be separated from each other and then allowed to mix in +these proportions they unite with explosive violence and form water. Water +itself may be separated into the gases by any one of several means, one +making use of a temperature of 2,200 to bring about this separation. + +[Illustration: Figure 7.--Obtaining Oxygen by Electrolysis] + +The easiest way to separate water into its two parts is by the process +called electrolysis (Figure 7). Water, with which has been mixed a small +quantity of acid, is placed in a vat through the walls of which enter the +platinum tipped ends of two electrical conductors, one positive and the +other negative. + +Tubes are placed directly above these wire terminals in the vat, one tube +being over each electrode and separated from each other by some distance. +With the passage of an electric current from one wire terminal to the +other, bubbles of gas rise from each and pass into the tubes. The gas that +comes from the negative terminal is hydrogen and that from the positive +pole is oxygen, both gases being almost pure if the work is properly +conducted. This method produces electrolytic oxygen and electrolytic +hydrogen. + +_The Liquid Air Process._--While several of the foregoing methods of +securing oxygen are successful as far as this result is concerned, they are +not profitable from a financial standpoint. A process for separating oxygen +from the nitrogen in the air has been brought to a high state of perfection +and is now supplying a major part of this gas for oxy-acetylene welding. It +is known as the Linde process and the gas is distributed by the Linde Air +Products Company from its plants and warehouses located in the large cities +of the country. + +The air is first liquefied by compression, after which the gases are +separated and the oxygen collected. The air is purified and then compressed +by successive stages in powerful machines designed for this purpose until +it reaches a pressure of about 3,000 pounds to the square inch. The large +amount of heat produced is absorbed by special coolers during the process +of compression. The highly compressed air is then dried and the +temperature further reduced by other coolers. + +The next point in the separation is that at which the air is introduced +into an apparatus called an interchanger and is allowed to escape through a +valve, causing it to turn to a liquid. This liquid air is sprayed onto +plates and as it falls, the nitrogen return to its gaseous state and leaves + the oxygen to run to the bottom of the container. This liquid oxygen is +then allowed to return to a gas and is stored in large gasometers or tanks. + +The oxygen gas is taken from the storage tanks and compressed to +approximately 1,800 pounds to the square inch, under which pressure it is +passed into steel cylinders and made ready for delivery to the customer. +This oxygen is guaranteed to be ninety-seven per cent pure. + +Another process, known as the Hildebrandt process, is coming into use in +this country. It is a later process and is used in Germany to a much +greater extent than the Linde process. The Superior Oxygen Co. has secured +the American rights and has established several plants. + +_Oxygen Cylinders_.--Two sizes of cylinders are in use, one containing +100 cubic feet of gas when it is at atmospheric pressure and the other +containing 250 cubic feet under similar conditions. The cylinders are made +from one piece of steel and are without seams. These containers are tested +at double the pressure of the gas contained to insure safety while +handling. + +One hundred cubic feet of oxygen weighs nearly nine pounds (8.921), and +therefore the cylinders will weigh practically nine pounds more when full +than after emptying, if of the 100 cubic feet size. The large cylinders +weigh about eighteen and one-quarter pounds more when full than when empty, +making approximately 212 pounds empty and 230 pounds full. + +The following table gives the number of cubic feet of oxygen remaining in +the cylinders according to various gauge pressures from an initial pressure +of 1,800 pounds. The amounts given are not exactly correct as this would +necessitate lengthy calculations which would not make great enough +difference to affect the practical usefulness of the table: + +Cylinder of 100 Cu. Ft. Capacity at 68 Fahr. + + Gauge Volume Gauge Volume +Pressure Remaining Pressure Remaining + + 1800 100 700 39 + 1620 90 500 28 + 1440 80 300 17 + 1260 70 100 6 + 1080 60 18 1 + 900 50 9 1/2 + +Cylinder of 250 Cu. Ft. Capacity at 68 Fahr. + + Gauge Volume Gauge Volume +Pressure Remaining Pressure Remaining + + 1800 250 700 97 + 1620 225 500 70 + 1440 200 300 42 + 1260 175 100 15 + 1080 150 18 8 + 900 125 9 1-1/4 + +The temperature of the cylinder affects the pressure in a large degree, the +pressure increasing with a rise in temperature and falling with a fall in +temperature. The variation for a 100 cubic foot cylinder at various +temperatures is given in the following tabulation: + +At 150 Fahr........................ 2090 pounds. +At 100 Fahr........................ 1912 pounds. +At 80 Fahr........................ 1844 pounds. +At 68 Fahr........................ 1800 pounds. +At 50 Fahr........................ 1736 pounds. +At 32 Fahr........................ 1672 pounds. +At 0 Fahr........................ 1558 pounds. +At -10 Fahr........................ 1522 pounds. + +_Chlorate of Potash Method._--In spite of its higher cost and the +inferior gas produced, the chlorate of potash method of producing oxygen is +used to a limited extent when it is impossible to secure the gas in +cylinders. + +[Illustration: Figure 8.--Oxygen from Chlorate of Potash] + +An iron retort (Figure 8) is arranged to receive about fifteen pounds of +chlorate of potash mixed with three pounds of manganese dioxide, after +which the cylinder is closed with a tight cap, clamped on. This retort is +carried above a burner using fuel gas or other means of generating heat and +this burner is lighted after the chemical charge is mixed and compressed in +the tube. + +The generation of gas commences and the oxygen is led through water baths +which wash and cool it before storing in a tank connected with the plant. +From this tank the gas is compressed into portable cylinders at a pressure +of about 300 pounds to the square inch for use as required in welding +operations. + +Each pound of chlorate of potash liberates about three cubic feet of +oxygen, and taking everything into consideration, the cost of gas produced +in this way is several times that of the purer product secured by the +liquid air process. + +These chemical generators are oftentimes a source of great danger, +especially when used with or near the acetylene gas generator, as is +sometimes the case with cheap portable outfits. Their use should not be +tolerated when any other method is available, as the danger from accident +alone should prohibit the practice except when properly installed and +cared for away from other sources of combustible gases. + + +ACETYLENE + +In 1862 a chemist, Woehler, announced the discovery of the preparation of +acetylene gas from calcium carbide, which he had made by heating to a high +temperature a mixture of charcoal with an alloy of zinc and calcium. His +product would decompose water and yield the gas. For nearly thirty years +these substances were neglected, with the result that acetylene was +practically unknown, and up to 1892 an acetylene flame was seen by very few +persons and its possibilities were not dreamed of. With the development of +the modern electric furnace the possibility of calcium carbide as a +commercial product became known. + +In the above year, Thomas L. Willson, an electrical engineer of Spray, +North Carolina, was experimenting in an attempt to prepare metallic +calcium, for which purpose he employed an electric furnace operating on a +mixture of lime and coal tar with about ninety-five horse power. The result +was a molten mass which became hard and brittle when cool. This apparently +useless product was discarded and thrown in a nearby stream, when, to the +astonishment of onlookers, a large volume of gas was immediately +liberated, which, when ignited, burned with a bright and smoky flame and +gave off quantities of soot. The solid material proved to be calcium +carbide and the gas acetylene. + +Thus, through the incidental study of a by-product, and as the result of an +accident, the possibilities in carbide were made known, and in the spring +of 1895 the first factory in the world for the production of this substance +was established by the Willson Aluminum Company. + +When water and calcium carbide are brought together an action takes place +which results in the formation of acetylene gas and slaked lime. + + +CARBIDE + +Calcium carbide is a chemical combination of the elements carbon and +calcium, being dark brown, black or gray with sometimes a blue or red +tinge. It looks like stone and will only burn when heated with oxygen. + +Calcium carbide may be preserved for any length of time if protected from +the air, but the ordinary moisture in the atmosphere gradually affects it +until nothing remains but slaked lime. It always possesses a penetrating +odor, which is not due to the carbide itself but to the fact that it is +being constantly affected by moisture and producing small quantities of +acetylene gas. + +This material is not readily dissolved by liquids, but if allowed to come +in contact with water, a decomposition takes place with the evolution of +large quantities of gas. Carbide is not affected by shock, jarring or age. + +A pound of absolutely pure carbide will yield five and one-half cubic feet +of acetylene. Absolute purity cannot be attained commercially, and in +practice good carbide will produce from four and one-half to five cubic +feet for each pound used. + +Carbide is prepared by fusing lime and carbon in the electric furnace under +a heat in excess of 6,000 degrees Fahrenheit. These materials are among the +most difficult to melt that are known. Lime is so infusible that it is +frequently employed for the materials of crucibles in which the highest +melting metals are fused, and for the pencils in the calcium light because +it will stand extremely high temperatures. + +Carbon is the material employed in the manufacture of arc light electrodes +and other electrical appliances that must stand extreme heat. Yet these two +substances are forced into combination in the manufacture of calcium +carbide. It is the excessively high temperature attainable in the electric +furnace that causes this combination and not any effect of the electricity +other than the heat produced. + +A mixture of ground coke and lime is introduced into the furnace through +which an electric arc has been drawn. The materials unite and form an ingot +of very pure carbide surrounded by a crust of less purity. The poorer crust +is rejected in breaking up the mass into lumps which are graded according +to their size. The largest size is 2 by 3-1/2 inches and is called "lump," +a medium size is 1/2 by 2 inches and is called "egg," an intermediate size +for certain types of generators is 3/8 by 1-1/4 inches and called "nut," +and the finely crushed pieces for use in still other types of generators +are 1/12 by 1/4 inch in size and are called "quarter." Instructions as to +the size best suited to different generators are furnished by the makers +of those instruments. + +These sizes are packed in air-tight sheet steel drums containing 100 pounds +each. The Union Carbide Company of Chicago and New York, operating under +patents, manufactures and distributes the supply of calcium carbide for the +entire United States. Plants for this manufacture are established at +Niagara Falls, New York, and Sault Ste. Marie, Michigan. This company +maintains a system of warehouses in more than one hundred and ten cities, +where large stocks of all sizes are carried. + +The National Board of Fire Underwriters gives the following rules for the +storage of carbide: + +Calcium carbide in quantities not to exceed six hundred pounds may be +stored, when contained in approved metal packages not to exceed one hundred +pounds each, inside insured property, provided that the place of storage be +dry, waterproof and well ventilated and also provided that all but one of +the packages in any one building shall be sealed and that seals shall not +be broken so long as there is carbide in excess of one pound in any other +unsealed package in the building. + +Calcium carbide in quantities in excess of six hundred pounds must be +stored above ground in detached buildings, used exclusively for the storage +of calcium carbide, in approved metal packages, and such buildings shall be +constructed to be dry, waterproof and well ventilated. + +_Properties of Acetylene._--This gas is composed of twenty-four parts +of carbon and two parts of hydrogen by weight and is classed with natural +gas, petroleum, etc., as one of the hydrocarbons. This gas contains the +highest percentage of carbon known to exist in any combination of this form +and it may therefore be considered as gaseous carbon. Carbon is the fuel +that is used in all forms of combustion and is present in all fuels from +whatever source or in whatever form. Acetylene is therefore the most +powerful of all fuel gases and is able to give to the torch flame in +welding the highest temperature of any flame. + +Acetylene is a colorless and tasteless gas, possessed of a peculiar and +penetrating odor. The least trace in the air of a room is easily noticed, +and if this odor is detected about an apparatus in operation, it is certain +to indicate a leakage of gas through faulty piping, open valves, broken +hose or otherwise. This leakage must be prevented before proceeding with +the work to be done. + +All gases which burn in air will, when mixed with air previous to ignition, +produce more or less violent explosions, if fired. To this rule acetylene +is no exception. One measure of acetylene and twelve and one-half of air +are required for complete combustion; this is therefore the proportion for +the most perfect explosion. This is not the only possible mixture that will +explode, for all proportions from three to thirty per cent of acetylene in +air will explode with more or less force if ignited. + +The igniting point of acetylene is lower than that of coal gas, being about +900 degrees Fahrenheit as against eleven hundred degrees for coal gas. The +gas issuing from a torch will ignite if allowed to play on the tip of a +lighted cigar. + +It is still further true that acetylene, at some pressures, greater than +normal, has under most favorable conditions for the effect, been found to +explode; yet it may be stated with perfect confidence that under no +circumstances has anyone ever secured an explosion in it when subjected to +pressures not exceeding fifteen pounds to the square inch. + +Although not exploded by the application of high heat, acetylene is injured +by such treatment. It is partly converted, by high heat, into other +compounds, thus lessening the actual quantity of the gas, wasting it and +polluting the rest by the introduction of substances which do not belong +there. These compounds remain in part with the gas, causing it to burn with +a persistent smoky flame and with the deposit of objectionable tarry +substances. Where the gas is generated without undue rise of temperature +these difficulties are avoided. + +_Purification of Acetylene._--Impurities in this gas are caused by +impurities in the calcium carbide from which it is made or by improper +methods and lack of care in generation. Impurities from the material will +be considered first. + +Impurities in the carbide may be further divided into two classes: those +which exert no action on water and those which act with the water to throw +off other gaseous products which remain in the acetylene. Those impurities +which exert no action on the water consist of coke that has not been +changed in the furnace and sand and some other substances which are +harmless except that they increase the ash left after the acetylene has +been generated. + +An analysis of the gas coming from a typical generator is as follows: + + Per cent + Acetylene ................................ 99.36 + Oxygen ................................... .08 + Nitrogen ................................. .11 + Hydrogen ................................. .06 + Sulphuretted Hydrogen .................... .17 + Phosphoretted Hydrogen ................... .04 + Ammonia .................................. .10 + Silicon Hydride .......................... .03 + Carbon Monoxide .......................... .01 + Methane .................................. .04 + +The oxygen, nitrogen, hydrogen, methane and carbon monoxide are either +harmless or are present in such small quantities as to be neglected. The +phosphoretted hydrogen and silicon hydride are self-inflammable gases when +exposed to the air, but their quantity is so very small that this +possibility may be dismissed. The ammonia and sulphuretted hydrogen are +almost entirely dissolved by the water used in the gas generator. The +surest way to avoid impure gas is to use high-grade calcium carbide in the +generator and the carbide of American manufacture is now so pure that it +never causes trouble. + +The first and most important purification to which the gas is subjected is +its passage through the body of water in the generator as it bubbles to the +top. It is then filtered through felt to remove the solid particles of lime +dust and other impurities which float in the gas. + +Further purification to remove the remaining ammonia, sulphuretted hydrogen +and phosphorus containing compounds is accomplished by chemical means. If +this is considered necessary it can be easily accomplished by readily +available purifying apparatus which can be attached to any generator or +inserted between the generator and torch outlets. The following mixtures +have been used. + +"_Heratol,_" a solution of chromic acid or sulphuric acid absorbed in +porous earth. + +"_Acagine,_" a mixture of bleaching powder with fifteen per cent of +lead chromate. + +"_Puratylene,_" a mixture of bleaching powder and hydroxide of lime, +made very porous, and containing from eighteen to twenty per cent of active +chlorine. + +"_Frankoline,_" a mixture of cuprous and ferric chlorides dissolved in +strong hydrochloric acid absorbed in infusorial earth. + +A test for impure acetylene gas is made by placing a drop of ten per cent +solution of silver nitrate on a white blotter and holding the paper in a +stream of gas coming from the torch tip. Blackening of the paper in a short +length of time indicates impurities. + +_Acetylene in Tanks._--Acetylene is soluble in water to a very limited +extent, too limited to be of practical use. There is only one liquid that +possesses sufficient power of containing acetylene in solution to be of +commercial value, this being the liquid acetone. Acetone is produced in +various ways, oftentimes from the distillation of wood. It is a +transparent, colorless liquid that flows with ease. It boils at 133 +Fahrenheit, is inflammable and burns with a luminous flame. It has a +peculiar but rather agreeable odor. + +Acetone dissolves twenty-four times its own bulk of acetylene at ordinary +atmospheric pressure. If this pressure is increased to two atmospheres, +14.7 pounds above ordinary pressure, it will dissolve just twice as much of +the gas and for each atmosphere that the pressure is increased it will +dissolve as much more. + +If acetylene be compressed above fifteen pounds per square inch at ordinary +temperature without first being dissolved in acetone a danger is present of +self-ignition. This danger, while practically nothing at fifteen pounds, +increases with the pressure until at forty atmospheres it is very +explosive. Mixed with acetone, the gas loses this dangerous property and is +safe for handling and transportation. As acetylene is dissolved in the +liquid the acetone increases its volume slightly so that when the gas has +been drawn out of a closed tank a space is left full of free acetylene. + +This last difficulty is removed by first filling the cylinder or tank with +some porous material, such as asbestos, wood charcoal, infusorial earth, +etc. Asbestos is used in practice and by a system of packing and supporting +the absorbent material no space is left for the free gas, even when the +acetylene has been completely withdrawn. + +The acetylene is generated in the usual way and is washed, purified and +dried. Great care is used to make the gas as free as possible from all +impurities and from air. The gas is forced into containers filled with +acetone as described and is compressed to one hundred and fifty pounds to +the square inch. From these tanks it is transferred to the smaller portable +cylinders for consumers' use. + +The exact volume of gas remaining in a cylinder at atmospheric temperature +may be calculated if the weight of the cylinder empty is known. One pound +of the gas occupies 13.6 cubic feet, so that if the difference in weight +between the empty cylinder and the one considered be multiplied by 13.6. +the result will be the number of cubic feet of gas contained. + +The cylinders contain from 100 to 500 cubic feet of acetylene under +pressure. They cannot be filled with the ordinary type of generator as they +require special purifying and compressing apparatus, which should never be +installed in any building where other work is being carried on, or near +other buildings which are occupied, because of the danger of explosion. + +Dissolved acetylene is manufactured by the Prest-O-Lite Company, the +Commercial Acetylene Company and the Searchlight Gas Company and is +distributed from warehouses in various cities. + +These tanks should not be discharged at a rate per hour greater than +one-seventh of their total capacity, that is, from a tank of 100 cubic feet +capacity, the discharge should not be more than fourteen cubic feet per +hour. If discharge is carried on at an excessive rate the acetone is drawn +out with the gas and reduces the heat of the welding flame. + +For this reason welding should not be attempted with cylinders designed for +automobile and boat lighting. When the work demands a greater delivery than +one of the larger tanks will give, two or more tanks may be connected with +a special coupler such as may be secured from the makers and distributers +of the gas. These couplers may be arranged for two, three, four or five +tanks in one battery by removing the plugs on the body of the coupler and +attaching additional connecting pipes. The coupler body carries a pressure +gauge and the valve for controlling the pressure of the gas as it flows to +the welding torches. The following capacities should be provided for: + +Acetylene Consumption Combined Capacity of + of Torches per Hour Cylinders in Use +Up to 15 feet.......................100 cubic feet +16 to 30 feet.......................200 cubic feet +31 to 45 feet.......................300 cubic feet +46 to 60 feet.......................400 cubic feet +61 to 75 feet.......................500 cubic feet + + +WELDING RODS + +The best welding cannot be done without using the best grade of materials, +and the added cost of these materials over less desirable forms is so +slight when compared to the quality of work performed and the waste of +gases with inferior supplies, that it is very unprofitable to take any +chances in this respect. The makers of welding equipment carry an +assortment of supplies that have been standardized and that may be relied +upon to produce the desired result when properly used. The safest plan is +to secure this class of material from the makers. + +Welding rods, or welding sticks, are used to supply the additional metal +required in the body of the weld to replace that broken or cut away and +also to add to the joint whenever possible so that the work may have the +same or greater strength than that found in the original piece. A rod of +the same material as that being welded is used when both parts of the work +are the same. When dissimilar metals are to be joined rods of a composition +suited to the work are employed. + +These filling rods are required in all work except steel of less than 16 +gauge. Alloy iron rods are used for cast iron. These rods have a high +silicon content, the silicon reacting with the carbon in the iron to +produce a softer and more easily machined weld than would otherwise be the +case. These rods are often made so that they melt at a slightly lower point +than cast iron. This is done for the reason that when the part being welded +has been brought to the fusing heat by the torch, the filling material can +be instantly melted in without allowing the parts to cool. The metal can be +added faster and more easily controlled. + +Rods or wires of Norway iron are used for steel welding in almost all +cases. The purity of this grade of iron gives a homogeneous, soft weld of +even texture, great ductility and exceptionally good machining qualities. +For welding heavy steel castings, a rod of rolled carbon steel is employed. +For working on high carbon steel, a rod of the steel being welded must be +employed and for alloy steels, such as nickel, manganese, vanadium, etc., +special rods of suitable alloy composition are preferable. + +Aluminum welding rods are made from this metal alloyed to give the even +flowing that is essential. Aluminum is one of the most difficult of all the +metals to handle in this work and the selection of the proper rod is of +great importance. + +Brass is filled with brass wire when in small castings and sheets. For +general work with brass castings, manganese bronze or Tobin bronze may be +used. + +Bronze is welded with manganese bronze or Tobin bronze, while copper is +filled with copper wire. + +These welding rods should always be used to fill the weld when the +thickness of material makes their employment necessary, and additional +metal should always be added at the weld when possible as the joint cannot +have the same strength as the original piece if made or dressed off flush +with the surfaces around the weld. This is true because the metal welded +into the joint is a casting and will never have more strength than a +casting of the material used for filling. + +Great care should be exercised when adding metal from welding rods to make +sure that no metal is added at a point that is not itself melted and molten +when the addition is made. When molten metal is placed upon cooler surfaces +the result is not a weld but merely a sticking together of the two parts +without any strength in the joint. + + +FLUXES + +Difficulty would be experienced in welding with only the metal and rod to +work with because of the scale that forms on many materials under heat, the +oxides of other metals and the impurities found in almost all metals. These +things tend to prevent a perfect joining of the metals and some means are +necessary to prevent their action. + +Various chemicals, usually in powder form, are used to accomplish the +result of cleaning the weld and making the work of the operator less +difficult. They are called fluxes. + +A flux is used to float off physical impurities from the molten metal; to +furnish a protecting coating around the weld; to assist in the removal of +any objectionable oxide of the metals being handled; to lower the +temperature at which the materials flow; to make a cleaner weld and to +produce a better quality of metal in the finished work. + +The flux must be of such composition that it will accomplish the desired +result without introducing new difficulties. They may be prepared by the +operator in many cases or may be secured from the makers of welding +apparatus, the same remarks applying to their quality as were made +regarding the welding rods, that is, only the best should be considered. + +The flux used for cast iron should have a softening effect and should +prevent burning of the metal. In many cases it is possible and even +preferable to weld cast iron without the use of a flux, and in any event +the smaller the quantity used the better the result should be. Flux should +not be added just before the completion of the work because the heat will +not have time to drive the added elements out of the metal or to +incorporate them with the metal properly. + +Aluminum should never be welded without using a flux because of the oxide +formed. This oxide, called alumina, does not melt until a heat of 5,000 +Fahrenheit is reached, four times the heat needed to melt the aluminum +itself. It is necessary that this oxide be broken down or dissolved so that +the aluminum may have a chance to flow together. Copper is another metal +that requires a flux because of its rapid oxidation under heat. + +While the flux is often thrown or sprinkled along the break while welding, +much better results will be obtained by dipping the hot end of the welding +rod into the flux whenever the work needs it. Sufficient powder will stick +on the end of the rod for all purposes, and with some fluxes too much will +adhere. Care should always be used to avoid the application of excessive +flux, as this is usually worse than using too little. + + +SUPPLIES AND FIXTURES + +_Goggles._--The oxy-acetylene torch should not be used without the +protection to the eyes afforded by goggles. These not only relieve +unnecessary strain, but make it much easier to watch the exact progress of +the work with the molten metal. The difficulty of protecting the sight +while welding is even greater than when cutting metal with the torch. + +Acetylene gives a light which is nearest to sunlight of any artificial +illuminant. But for the fact that this gas light gives a little more green +and less blue in its composition, it would be the same in quality and +practically the same in intensity. This light from the gas is almost absent +during welding, being lost with the addition of the extra oxygen needed to +produce the welding heat. The light that is dangerous comes from the molten +metal which flows under the torch at a bright white heat. + +Goggles for protection against this light and the heat that goes with it +may be secured in various tints, the darker glass being for welding and +the lighter for cutting. Those having frames in which the metal parts do +not touch the flesh directly are most desirable because of the high +temperature reached by these parts. + +_Gloves._--While not as necessary as are the goggles, gloves are a +convenience in many cases. Those in which leather touches the hands +directly are really of little value as the heat that protection is desired +against makes the leather so hot that nothing is gained in comfort. Gloves +are made with asbestos cloth, which are not open to this objection in so +great a degree. + +[Illustration: Figure 9.--Frame for Welding Stand] + +_Tables and Stands._--Tables for holding work while being welded +(Figure 9) are usually made from lengths of angle steel welded together. +The top should be rectangular, about two feet wide and two and one-half +feet long. The legs should support the working surface at a height of +thirty-two to thirty-six inches from the floor. Metal lattice work may be +fastened or laid in the top framework and used to support a layer of +firebrick bound together with a mixture of one-third cement and two-thirds +fireclay. The piece being welded is braced and supported on this table with +pieces of firebrick so that it will remain stationary during the operation. + +Holders for supporting the tanks of gas may be +made or purchased in forms that rest directly on the floor or that are +mounted on wheels. These holders are quite useful where the floor or ground +is very uneven. + +_Hose._--All permanent lines from tanks and generators to the torches +are made with piping rigidly supported, but the short distance from the end +of the pipe line to the torch itself is completed with a flexible hose so +that the operator may be free in his movements while welding. An accident +through which the gases mix in the hose and are ignited will burst this +part of the equipment, with more or less painful results to the person +handling it. For that reason it is well to use hose with great enough +strength to withstand excessive pressure. + +A poor grade of hose will also break down inside and clog the flow of gas, +both through itself and through the parts of the torch. To avoid outside +damage and cuts this hose is sometimes encased with coiled sheet metal. +Hose may be secured with a bursting strength of more than 1,000 pounds to +the square inch. Many operators prefer to distinguish between the oxygen +and acetylene lines by their color and to allow this, red is used for the +oxygen and black for acetylene. + +_Other Materials._--Sheet asbestos and asbestos fibre in flakes are +used to cover parts of the work while preparing them for welding and during +the operation itself. The flakes and small pieces that become detached from +the large sheets are thrown into a bin where the completed small work is +placed to allow slow and even cooling while protected by the asbestos. + +Asbestos fibre and also ordinary fireclay are often used to make a backing +or mould into a form that may be placed behind aluminum and some other +metals that flow at a low heat and which are accordingly difficult to +handle under ordinary methods. This forms a solid mould into which the +metal is practically cast as melted by the torch so that the desired shape +is secured without danger of the walls of metal breaking through and +flowing away. + +Carbon blocks and rods are made in various shapes and sizes so that they +may be used to fill threaded holes and other places that it is desired to +protect during welding. These may be secured in rods of various diameters +up to one inch and in blocks of several different dimensions. + + + + +CHAPTER III + +ACETYLENE GENERATORS + + +Acetylene generators used for producing the gas from the action of water on +calcium carbide are divided into three principal classes according to the +pressure under which they operate. + +Low pressure generators are designed to operate at one pound or less per +square inch. Medium pressure systems deliver the gas at not to exceed +fifteen pounds to the square inch while high pressure types furnish gas +above fifteen pounds per square inch. High pressure systems are almost +unknown in this country, the medium pressure type being often referred to +as "high pressure." + +Another important distinction is formed by the method of bringing the +carbide and water together. The majority of those now in use operate by +dropping small quantities of carbide into a large volume of water, allowing +the generated gas to bubble up through the water before being collected +above the surface. This type is known as the "carbide to water" generator. + +A less used type brings a measured and small quantity of water to a +comparatively large body of the carbide, the gas being formed and collected +from the chamber in which the action takes place. This is called the "water +to carbide" type. Another way of expressing the difference in feed is that +of designating the two types as "carbide feed" for the former and "water +feed" for the latter. + +A further division of the carbide to water machines is made by mentioning +the exact method of feeding the carbide. One type, called "gravity feed" +operates by allowing the carbide to escape and fall by the action of its +own weight, or gravity; the other type, called "forced feed," includes a +separate mechanism driven by power. This mechanism feeds definite amounts +of the carbide to the water as required by the demands on the generator. +The action of either feed is controlled by the withdrawal of gas from the +generator, the aim being to supply sufficient carbide to maintain a nearly +constant supply. + +_Generator Requirements._--The qualities of a good generator are +outlined as follows: [Footnote: See Pond's "Calcium Carbide and +Acetylene."] + +It must allow no possibility of the existence of an explosive mixture in +any of its parts at any time. It is not enough to argue that a mixture, +even if it exists, cannot be exploded unless kindled. It is necessary to +demand that a dangerous mixture can at no time be formed, even if the +machine is tampered with by an ignorant person. The perfect machine must be +so constructed that it shall be impossible at any time, under any +circumstances, to blow it up. + +It must insure cool generation. Since this is a relative term, all machines +being heated somewhat during the generation of gas, this amounts to saying +that a machine must heat but little. A pound of carbide decomposed by water +develops the same amount of heat under all circumstances, but that heat +can be allowed to increase locally to a high point, or it can be equalized +by water so that no part of the material becomes heated enough to do +damage. + +It must be well constructed. A good generator does not need, perhaps, to be +"built like a watch," but it should be solid, substantial and of good +material. It should be built for service, to last and not simply to sell; +anything short of this is to be avoided as unsafe and unreliable. + +It must be simple. The more complicated the machine the sooner it will get +out of order. Understand your generator. Know what is inside of it and +beware of an apparatus, however attractive its exterior, whose interior is +filled with pipes and tubes, valves and diaphragms whose functions you do +not perfectly understand. + +It should be capable of being cleaned and recharged and of receiving all +other necessary attention without loss of gas, both for economy's sake, and +more particularly to avoid danger of fire. + +It should require little attention. All machines have to be emptied and +recharged periodically; but the more this process is simplified and the +more quickly this can be accomplished, the better. + +It should be provided with a suitable indicator to designate how low the +charge is in order that the refilling may be done in good season. + +It should completely use up the carbide, generating the maximum amount of +gas. + +_Overheating._--A large amount of heat is liberated when acetylene gas +is formed from the union of calcium carbide and water. Overheating during +this process, that is to say, an intense local heat rather than a large +amount of heat well distributed, brings about the phenomenon of +polymerization, converting the gas, or part of it, into oily matters, which +can do nothing but harm. This tarry mass coming through the small openings +in the torches causes them to become partly closed and alters the +proportions of the gases to the detriment of the welding flame. The only +remedy for this trouble is to avoid its cause and secure cool generation. + +Overheating can be detected by the appearance of the sludge remaining after +the gas has been made. Discoloration, yellow or brown, shows that there has +been trouble in this direction and the resultant effects at the torches may +be looked for. The abundance of water in the carbide to water machines +effects this cooling naturally and is a characteristic of well designed +machines of this class. It has been found best and has practically become a +fundamental rule of generation that a gallon of water must be provided for +each pound of carbide placed in the generator. With this ratio and a +generator large enough for the number of torches to be supplied, little +trouble need be looked for with overheating. + +_Water to Carbide Generators._--It is, of course, much easier to +obtain a measured and regular flow of water than to obtain such a flow of +any solid substance, especially when the solid substance is in the form of +lumps, as is carbide This fact led to the use of a great many water-feed +generators for all classes of work, and this type is still in common use +for the small portable machines, such, for instance, as those used on motor +cars for the lamps. The water-feed machine is not, however, favored for +welding plants, as is the carbide feed, in spite of the greater +difficulties attending the handling of the solid material. + +A water-feed generator is made up of the gas producing part and a holder +for the acetylene after it is made. The carbide is held in a tray formed of +a number of small compartments so that the charge in each compartment is +nearly equal to that in each of the others. The water is allowed to flow +into one of these compartments in a volume sufficient to produce the +desired amount of gas and the carbide is completely used from this one +division. The water then floods the first compartment and finally overflows +into the next one, where the same process is repeated. After using the +carbide in this division, it is flooded in turn and the water passing on to +those next in order, uses the entire charge of the whole tray. + +These generators are charged with the larger sizes of carbide and are +easily taken care of. The residue is removed in the tray and emptied, +making the generator ready for a fresh supply of carbide. + +_Carbide to Water Generators._--This type also is made up of two +principal parts, the generating chamber and a gas holder, the holder being +part of the generating chamber or a separate device. The generator (Figure +10) contains a hopper to receive the charge of carbide and is fitted with +the feeding mechanism to drop the proper amount of carbide into the water +as required by the demands of the torches. The charge of carbide is of one +of the smaller sizes, usually "nut" or "quarter." + +_Feed Mechanisms._--The device for dropping the carbide into the water +is the only part of the machine that is at all complicated. This +complication is brought about by the necessity of controlling the mass of +carbide so that it can never be discharged into the water at an excessive +rate, feeding it at a regular rate and in definite amounts, feeding it +positively whenever required and shutting off the feed just as positively +when the supply of gas in the holder is enough for the immediate needs. + +[Illustration: Figure 10.--Carbide to Water Generator. A. Feed motor weight; +B. Carbide feed motor; C. Carbide hopper; D. Water for gas generation; +E. Agitator for loosening residuum; F. Water seal in gas bell; G. Filter; +H. Hydraulic Valve; J. Motor control levers.] + +The charge of carbide is unavoidably acted upon by the water vapor in the +generator and will in time become more or less pasty and sticky. This is +more noticeable if the generator stands idle for a considerable length of +time This condition imposes another duty on the feeding mechanism; that is, +the necessity of self-cleaning so that the carbide, no matter in what +condition, cannot prevent the positive action of this part of the device, +especially so that it cannot prevent the supply from being stopped at the +proper time. + +The gas holder is usually made in the bell form so that the upper portion +rises and falls with the addition to or withdrawal from the supply of gas +in the holder. The rise and fall of this bell is often used to control the +feed mechanism because this movement indicates positively whether enough +gas has been made or that more is required. As the bell lowers it sets the +feed mechanism in motion, and when the gas passing into the holder has +raised the bell a sufficient distance, the movement causes the feed +mechanism to stop the fall of carbide into the water. In practice, the +movement of this part of the holder is held within very narrow limits. + +_Gas Holders._--No matter how close the adjustment of the feeding +device, there will always be a slight amount of gas made after the fall of +carbide is stopped, this being caused by the evolution of gas from the +carbide with which water is already in contact. This action is called +"after generation" and the gas holder in any type of generator must +provide sufficient capacity to accommodate this excess gas. As a general +rule the water to carbide generator requires a larger gas holder than the +carbide to water type because of the greater amount of carbide being acted +upon by the water at any one time, also because the surface of carbide +presented to the moist air within the generating chamber is greater with +this type. + +_Freezing._--Because of the rather large body of water contained in +any type of generator, there is always danger of its freezing and +rendering the device inoperative unless placed in a temperature above the +freezing point of the water. It is, of course, dangerous and against the +insurance rules to place a generator in the same room with a fire of any +kind, but the room may be heated by steam or hot water coils from a furnace +in another building or in another part of the same building. + +When the generator is housed in a separate structure the walls should be +made of materials or construction that prevents the passage of heat or +cold through them to any great extent. This may be accomplished by the use +of hollow tile or concrete blocks or by any other form of double wall +providing air spaces between the outer and inner facings. The space between +the parts of the wall may be filled with materials that further retard the +loss of heat if this is necessary under the conditions prevailing. + +_Residue From Generators._--The sludge remaining in the carbide to +water generator may be drawn off into the sewer if the piping is run at a +slant great enough to give a fall that carries the whole quantity, both +water and ash, away without allowing settling and consequent clogging. +Generators are provided with agitators which are operated to stir the ash +up with the water so that the whole mass is carried off when the drain cock +is opened. + +If sewer connections cannot be made in such a way that the ash is entirely +carried away, it is best to run the liquid mass into a settling basin +outside of the building. This should be in the form of a shallow pit which +will allow the water to pass off by soaking into the ground and by +evaporation, leaving the comparatively dry ash in the pit. This ash which +remains is essentially slaked lime and can often be disposed of to more or +less advantage to be used in mortar, whitewash, marking paths and any other +use for which slaked lime is suited. The disposition of the ash depends +entirely on local conditions. An average analysis of this ash is as +follows: + +Sand....................... 1.10 per cent. +Carbon..................... 2.72 " +Oxide of iron and alumina.. 2.77 " +Lime....................... 64.06 " +Water and carbonic acid.... 29.35 " + ------ + 100.00 + + +GENERATOR CONSTRUCTION + +The water for generating purposes is carried in the large tank-like +compartment directly below the carbide chamber. See Figure 11. This water +compartment is filled through a pipe of such a height that the water level +cannot be brought above the proper point or else the water compartment is +provided with a drain connection which accomplishes this same result by +allowing an excess to flow away. + +The quantity of water depends on the capacity of the generator inasmuch as +there must be one gallon for each pound of carbide required. The generator +should be of sufficient capacity to furnish gas under working conditions +from one charge of carbide to all torches installed for at least five hours +continuous use. + +After calculating the withdrawal of the whole number of torches according +to the work they are to do for this period of five hours the proper +generator capacity may be found on the basis of one cubic foot of gas per +hour for each pound of carbide. Thus if the torches were to use sixty cubic +feet of gas per hour, five hours would call for three hundred cubic feet +and a three hundred pound generator should be installed. Generators are +rated according to their carbide capacity in pounds. + +_Charging._--The carbide capacity of the generator should be great +enough to furnish a continuous supply of gas for the maximum operating +time, basing the quantity of gas generated on four and one-half cubic feet +from each pound of lump carbide and on four cubic feet from each pound of +quarter, intermediate sizes being in proportion. + +Generators are built in such a way that it is impossible for the acetylene +to escape from the gas holding compartment during the recharging process. +This is accomplished (1) by connecting the water inlet pipe opening with a +shut off valve in such a way that the inlet cannot be uncovered or opened +without first closing the shut off valve with the same movement of the +operator; (2) by incorporating an automatic or hydraulic one-way valve so +that this valve closes and acts as a check when the gas attempts to flow +from the holder back to the generating chamber, or by any other means that +will positively accomplish this result. + +In generators having no separate gas holding chamber but carrying the +supply in the same compartment in which it is generated, the gas contained +under pressure is allowed to escape through vent pipes into the outside +air before recharging with carbide. As in the former case, the parts are +so interlocked that it is impossible to introduce carbide or water without +first allowing the escape of the gas in the generator. + +It is required by the insurance rules that the entire change of carbide +while in the generator be held in such a way that it may be entirely +removed without difficulty in case the necessity should arise. + +Generators should be cleaned and recharged at regular stated intervals. +This work should be done during daylight hours only and likewise all +repairs should be made at such a time that artificial light is not needed. +Where it is absolutely necessary to use artificial light it should be +provided only by incandescent electric lamps enclosed in gas tight globes. + +In charging generating chambers the old ash and all residue must first be +cleaned out and the operator should be sure that no drain or other pipe has +become clogged. The generator should then be filled with the required +amount of water. In charging carbide feed machines be careful not to place +less than a gallon of water in the water compartment for each pound of +carbide to be used and the water must be brought to, but not above, the +proper level as indicated by the mark or the maker's instructions. The +generating chamber must be filled with the proper amount of water before +any attempt is made to place the carbide in its holder. This rule must +always be followed. It is also necessary that all automatic water seals +and valves, as well as any other water tanks, be filled with clean water +at this time. + +Never recharge with carbide without first cleaning the generating chamber +and completely refilling with clean water. Never test the generator or +piping for leaks with any flame, and never apply flame to any open pipe or +at any point other than the torch, and only to the torch after it has a +welding or cutting nozzle attached. Never use a lighted match, lamp, +candle, lantern, cigar or any open flame near a generator. Failure to +observe these precautions is liable to endanger life and property. + +_Operation and Care of Generators._--The following instructions apply +especially to the Davis Bournonville pressure generator, illustrated in +Figure 11. The motor feed mechanism is illustrated in Figure 12. + +Before filling the machine, the cover should be removed and the hopper +taken out and examined to see that the feeding disc revolves freely; that +no chains have been displaced or broken, and that the carbide displacer +itself hangs barely free of the feeding disc when it is revolved. After +replacing the cover, replace the bolts and tighten them equally, a little +at a time all around the circumference of the cover--not screwing tight in +one place only. Do not screw the cover down any more than is necessary to +make a tight fit. + +To charge the generator, proceed as follows: Open the vent valve by turning +the handle which extends over the filling tube until it stands at a right +angle with the generator. Open the valve in the water filling pipe, and +through this fill with water until it runs out of the overflow pipe of the +drainage chamber, then close the valve in the water filling pipe and vent +valve. Remove the carbide filling plugs and fill the hopper with +1-1/4"x3/8" carbide ("nut" size). Then replace the plugs and the +safety-locking lever chains. Now rewind the motor weight. Run the pressure +up to about five pounds by raising the controlling diaphragm valve lever +by hand (Figure 12, lever marked _E_). Then raise the blow-off lever, +allowing the gas to blow off until the gauge shows about two pounds; this +to clear the generator of air mixture. Then run the pressure up to about +eight pounds by raising the controlling valve lever _E_, or until +this controlling lever rests against the upper wing of the fan governor, +and prevents operation of the feed motor. After this is done, the motor +will operate automatically as the gas is consumed. + +[Illustration: Figure 11.--Pressure Generator (Davis Bournonville). +_A_, Feed motor weight; +_B_, Carbide feed motor; +_C_, Motor Control diaphragm; +_D_, Carbide hopper; +_E_, Carbide feed disc; +_F_, Overflow pipe; +_G_, Overflow pipe seal; +_H_, Overflow pipe valve; +_J_, Filling funnel; +_K_, Hydraulic valve; +_L_, Expansion chamber; +_M_, Escape pipe; +_N_, Feed pipe; +_O_, Agitator for residuum; +_P_, Residuum valve; +_Q_, Water level] + +[Illustration: Figure 12.--Feed Mechanism of Pressure Generator] + +Should the pressure rise much above the blow-off point, the safety +controlling diaphragm valve will operate and throw the safety clutch in +interference and thus stop the motor. This interference clutch will then +have to be returned to its former position before the motor will operate, +but cannot be replaced before the pressure has been reduced below the +blow-off point. + +The parts of the feed mechanism illustrated in Figure 12 are as follows: +_A_, motor drum for weight cable. _B_, carbide filling plugs. +_C_, chains for connecting safety locking lever of motor to pins on +the top of the carbide plugs. _D_, interference clutch of motor. +_E_, lever on feed controlling diaphragm valve. _F_, lever of +interference controlling diaphragm valve that operates interference clutch. +_G_, feed controlling diaphragm valve. _H_, diaphragm valve +controlling operation of interference clutch. _I_, interference pin +to engage emergency clutch. _J_, main shaft driving carbide feeding +disc. _Y_, safety locking lever. + +_Recharging Generator._--Turn the agitator handle rapidly for several +revolutions, and then open the residuum valve, having five or six pounds +gas pressure on the machine. If the carbide charge has been exhausted and +the motor has stopped, there is generally enough carbide remaining in the +feeding disc that can be shaken off, and fed by running the motor to +obtain some pressure in the generator. The desirability of discharging +the residuum with some gas pressure is because the pressure facilitates +the discharge and at the same time keeps the generator full of gas, +preventing air mixture to a great extent. As soon as the pressure is +relieved by the withdrawal of the residuum, the vent valve should be +opened, as if the pressure is maintained until all of the residuum is +discharged gas would escape through the discharge valve. + +Having opened the vent pipe valve and relieved the pressure, open the +valve in the water filling tube. Close the residuum valve, then run in +several gallons of water and revolve the agitator, after which draw out the +remaining residuum; then again close the residuum valve and pour in water +until it discharges from the overflow pipe of the drainage chamber. It is +desirable in filling the generator to pour the water in rapidly enough to +keep the filling pipe full of water, so that air will not pass in at the +same time. + +After the generator is cleaned and filled with water, fill with carbide and +proceed in the same manner as when first charging. + +_Carbide Feed Mechanism._--Any form of carbide to water machine should +be so designed that the carbide never falls directly from its holder into +the water, but so that it must take a more or less circuitous path. This +should be true, no matter what position the mechanism is in. One of the +commonest types of forced feed machine carries the carbide in a hopper with +slanting sides, this hopper having a large opening in the bottom through +which the carbide passes to a revolving circular plate. As the pieces of +carbide work out toward the edge of the plate under the influence of the +mass behind them, they are thrown off into the water by small stationary +fins or plows which are in such a position that they catch the pieces +nearest the edges and force them off as the plate revolves. This +arrangement, while allowing a free passage for the carbide, prevents an +excess from falling should the machine stop in any position. + +When, as is usually the case, the feed mechanism is actuated by the rise +or fall of pressure in the generator or of the level of some part of the +gas holder, it must be built in such a way that the feeding remains +inoperative as long as the filling opening on the carbide holder remains +open. + +The feed of carbide should always be shut off and controlled so that under +no condition can more gas be generated than could be cared for by the +relief valve provided. It is necessary also to have the feed mechanism at +least ten inches above the surface of the water so that the parts will +never become clogged with damp lime dust. + +_Motor Feed._--The feed mechanism itself is usually operated by power +secured from a slowly falling weight which, through a cable, revolves a +drum. To this drum is attached suitable gearing for moving the feed parts +with sufficient power and in the way desired. This part, called the motor, +is controlled by two levers, one releasing a brake and allowing the motor +to operate the feed, the other locking the gearing so that no more carbide +will be dropped into the water. These levers are moved either by the +quantity of gas in the holder or by the pressure of the gas, depending on +the type of machine. + +With a separate gas holder, such as used with low pressure systems, the +levers are operated by the rise and fall of the bell of the holder or +gasometer, alternately starting and stopping the motor as the bell falls +and rises again. Medium pressure generators are provided with a diaphragm +to control the feed motor. + +This diaphragm is carried so that the pressure within the generator acts +on one side while a spring, whose tension is under the control of the +operator, acts on the other side. The diaphragm is connected to the brake +and locking device on the motor in such a way that increasing the tension +on the spring presses the diaphragm and moves a rod that releases the brake +and starts the feed. The gas pressure, increasing with the continuation of +carbide feed, acts on the other side and finally overcomes the pressure of +the spring tension, moving the control rod the other way and stopping the +motor and carbide feed. This spring tension is adjusted and checked with +the help of a pressure gauge attached to the generating chamber. + +_Gravity Feed._--This type of feed differs from the foregoing in that +the carbide is simply released and is allowed to fall into the water +without being forced to do so. Any form of valve that is sufficiently +powerful in action to close with the carbide passing through is used and is +operated by the power secured from the rise and fall of the gas holder +bell. When this valve is first opened the carbide runs into the water until +sufficient pressure and volume of gas is generated to raise the bell. This +movement operates the arm attached to the carbide shut off valve and slowly +closes it. A fall of the bell occasioned by gas being withdrawn again opens +the valve and more gas is generated. + +_Mechanical Feed._--The previously described methods of feeding +carbide to the water have all been automatic in action and do not depend +on the operator for their proper action. + +Some types of large generating plants have a power-driven feed, the power +usually being from some kind of motor other than one operated by a weight, +such as a water motor, for instance. This motor is started and stopped by +the operator when, in his judgment, more gas is wanted or enough has been +generated. This type of machine, often called a "non-automatic generator," +is suitable for large installations and is attached to a gas holder of +sufficient size to hold a day's supply of acetylene. The generator can then +be operated until a quantity of gas has been made that will fill the large +holder, or gasometer, and then allowed to remain idle for some time. + +_Gas Holders._--The commonest type of gas container is that known as a +gasometer. This consists of a circular tank partly filled with water, into +which is lowered another circular tank, inverted, which is made enough +smaller in diameter than the first one so that three-quarters of an inch is +left between them. This upper and inverted portion, called the bell, +receives the gas from the generator and rises or falls in the bath of water +provided in the lower tank as a greater or less amount of gas is contained +in it. + +These holders are made large enough so that they will provide a means of +caring for any after generation and so that they maintain a steady and even +flow. The generator, however, must be of a capacity great enough so that +the gas holder will not be drawn on for part of the supply with all torches +in operation. That is, the holder must not be depended on for a reserve +supply. + +The bell of the holder is made so that when full of gas its lower edge is +still under a depth of at least nine inches of water in the lower tank. Any +further rise beyond this point should always release the gas, or at least +part of it, to the escape pipe so that the gas will under no circumstances +be forced into the room from, between the bell and tank. The bell is guided +in its rise and fall by vertical rods so that it will not wedge at any +point in its travel. + +A condensing chamber to receive the water which condenses from the +acetylene gas in the holder is usually placed under this part and is +provided with a drain so that this water of condensation may be easily +removed. + +_Filtering._--A small chamber containing some closely packed but +porous material such as felt is placed in the pipe leading to the torch +lines. As the acetylene gas passes through this filter the particles of +lime dust and other impurities are extracted from it so that danger of +clogging the torch openings is avoided as much as possible. + +The gas is also filtered to a large extent by its passage through the water +in the generating chamber, this filtering or "scrubbing" often being +facilitated by the form of piping through which the gas must pass from the +generating chamber into the holder. If the gas passes out of a number of +small openings when going into the holder the small bubbles give a better +washing than large ones would. + +_Piping._--Connections from generators to service pipes should +preferably be made with right and left couplings or long thread nipples +with lock nuts. If unions are used, they should be of a type that does not +require gaskets. The piping should be carried and supported so that any +moisture condensing in the lines will drain back toward the generator and +where low points occur they should be drained through tees leading into +drip cups which are permanently closed with screw caps or plugs. No pet +cocks should be used for this purpose. + +For the feed pipes to the torch lines the following pipe sizes are +recommended. + + 3/8 inch pipe. 26 feet long. 2 cubic feet per hour. + 1/2 inch pipe. 30 feet long. 4 cubic feet per hour. + 3/4 inch pipe. 50 feet long. 15 cubic feet per hour. + 1 inch pipe. 70 feet long. 27 cubic feet per hour. + 1-1/4 inch pipe. 100 feet long. 50 cubic feet per hour. + 1-1/2 inch pipe. 150 feet long. 65 cubic feet per hour. + 2 inch pipe. 200 feet long. 125 cubic feet per hour. + 2-1/2 inch pipe. 300 feet long. 190 cubic feet per hour. + 3 inch pipe. 450 feet long. 335 cubic feet per hour. + +When drainage is possible into a sewer, the generator should not be +connected directly into the sewer but should first discharge into an open +receptacle, which may in turn be connected to the sewer. + +No valves or pet cocks should open into the generator room or any other +room when it would be possible, by opening them for draining purposes, to +allow any escape of gas. Any condensation must be removed without the use +of valves or other working parts, being drained into closed receptacles. It +should be needless to say that all the piping for gas must be perfectly +tight at every point in its length. + +_Safety Devices._--Good generators are built in such a way that the +operator must follow the proper order of operation in charging and cleaning +as well as in all other necessary care. It has been mentioned that the gas +pressure is released or shut off before it is possible to fill the water +compartment, and this same idea is carried further in making the generator +inoperative and free from gas pressure before opening the residue drain of +the carbide filling opening on top of the hopper. Some machines are made so +that they automatically cease to generate should there be a sudden and +abnormal withdrawal of gas such as would be caused by a bad leak. This +method of adding safety by automatic means and interlocking parts may be +carried to any extent that seems desirable or necessary to the maker. + +All generators should be provided with escape or relief pipes of large size +which lead to the open air. These pipes are carried so that condensation +will drain back toward the generator and after being led out of the +building to a point at least twelve feet above ground, they end in a +protecting hood so that no rain or solid matter can find its way into them. +Any escape of gas which might ordinarily pass into the generator room is +led into these escape pipes, all parts of the system being connected with +the pipe so that the gas will find this way out. + +Safety blow off valves are provided so that any excess gas which cannot be +contained by the gas holder may be allowed to escape without causing an +undue rise in pressure. This valve also allows the escape of pressure above +that for which the generator was designed. Gas released in this way passes +into the escape pipe just described. + +Inasmuch as the pressure of the oxygen is much greater than that of the +acetylene when used in the torch, it will be seen that anything that caused +the torch outlet to become closed would allow the oxygen to force the +acetylene back into the generator and the oxygen would follow it, making a +very explosive mixture. This return of the gas is prevented by a hydraulic +safety valve or back pressure valve, as it is often called. + +Mechanical check valves have been found unsuitable for this use and those +which employ water as a seal are now required by the insurance rules. The +valve itself (Figure 13) consists of a large cylinder containing water to a +certain depth, which is indicated on the valve body. Two pipes come into +the upper end of this cylinder and lead down into the water, one being +longer than the other. The shorter pipe leads to the escape pipe mentioned +above, while the longer one comes from the generator. The upper end of the +cylinder has an opening to which is attached the pipe leading to the +torches. + +[Illustration: Figure 13.--Hydraulic Back-Pressure Valve. +_A_, Acetylene supply line; +_B_, Vent pipe; +_C_, Water filling plug; +_D_, Acetylene service cock; +_E_, Plug to gauge height of water; +_F_, Gas openings under water; +_G_, Return pipe for sealing water; +_H_, Tube to carry gas below water line; +_I_, Tube to carry gas to escape pipe; +_J_, Gas chamber; +_K_, Plug in upper gas chamber; +_L_, High water level; +_M_, Opening through which water returns; +_O_, Bottom clean out casting] + +The gas coming from the generator through the longer pipe passes out of the +lower end of the pipe which is under water and bubbles up through the water +to the space in the top of the cylinder. From there the gas goes to the +pipe leading to the torches. The shorter pipe is closed by the depth of +water so that the gas does not escape to the relief pipe. As long as the +gas flows in the normal direction as described there will be no escape to +the air. Should the gas in the torch line return into the hydraulic valve +its pressure will lower the level of water in the cylinder by forcing some +of the liquid up into the two pipes. As the level of the water lowers, the +shorter pipe will be uncovered first, and as this is the pipe leading to +the open air the gas will be allowed to escape, while the pipe leading back +to the generator is still closed by the water seal. As soon as this reverse +flow ceases, the water will again resume its level and the action will +continue. Because of the small amount of water blown out of the escape pipe +each time the valve is called upon to perform this duty, it is necessary to +see that the correct water level is always maintained. + +While there are modifications of this construction, the same principle is +used in all types. The pressure escape valve is often attached to this +hydraulic valve body. + +_Construction Details._--Flexible tubing (except at torches), swing +pipe joints, springs, mechanical check valves, chains, pulleys and lead or +fusible piping should never be used on acetylene apparatus except where the +failure of those parts will not affect the safety of the machine or permit, +either directly or indirectly, the escape of gas into a room. Floats should +not be used except where failure will only render the machine inoperative. + +It should be said that the National Board of Fire Underwriters have +established an inspection service for acetylene generators and any +apparatus which bears their label, stating that that particular model and +type has been passed, is safe to use. This service is for the best +interests of all concerned and looks toward the prevention of accidents. +Such inspection is a very important and desirable feature of any outfit and +should be insisted upon. + +_Location of Generators._--Generators should preferably be placed +outside of insured buildings and in properly constructed generator houses. +The operating mechanism should have ample room to work in and there should +be room enough for the attendant to reach the various parts and perform the +required duties without hindrance or the need of artificial light. They +should also be protected from tampering by unauthorized persons. + +Generator houses should not be within five feet of any opening into, nor +have any opening toward, any adjacent building, and should be kept under +lock and key. The size of the house should be no greater than called for by +the requirements mentioned above and it should be well ventilated. + +The foundation for the generator itself should be of brick, stone, concrete +or iron, if possible. If of wood, they should be extra heavy, located in a +dry place and open to circulation of air. A board platform is not +satisfactory, but the foundation should be of heavy planking or timber to +make a firm base and so that the air can circulate around the wood. + +The generator should stand level and no strain should be placed on any of +the pipes or connections or any parts of the generator proper. + + + + +CHAPTER IV + +WELDING INSTRUMENTS + + +VALVES + +_Tank Valves._--The acetylene tank valve is of the needle type, fitted +with suitable stuffing box nuts and ending in an exposed square shank to +which the special wrench may be fitted when the valve is to be opened or +closed. + +The valve used on Linde oxygen cylinders is also a needle type, but of +slightly more complex construction. The body of the valve, which screws +into the top of the cylinder, has an opening below through which the gas +comes from the cylinder, and another opening on the side through which it +issues to the torch line. A needle screws down from above to close this +lower opening. The needle which closes the valve is not connected directly +to the threaded member, but fits loosely into it. The threaded part is +turned by a small hand wheel attached to the upper end. When this hand +wheel is turned to the left, or up, as far as it will go, opening the +valve, a rubber disc is compressed inside of the valve body and this disc +serves to prevent leakage of the gas around the spindle. + +The oxygen valve also includes a safety nut having a small hole through it +closed by a fusible metal which melts at 250 Fahrenheit. Melting of this +plug allows the gas to exert its pressure against a thin copper diaphragm, +this diaphragm bursting under the gas pressure and allowing the oxygen to +escape into the air. + +The hand wheel and upper end of the valve mechanism are protected during +shipment by a large steel cap which covers them when screwed on to the end +of the cylinder. This cap should always be in place when tanks are received +from the makers or returned to them. + +[Illustration: Figure 14.--Regulating Valve] + +_Regulating Valves._--While the pressure in the gas containers may be +anything from zero to 1,800 pounds, and will vary as the gas is withdrawn, +the pressure of the gas admitted to the torch must be held steady and at a +definite point. This is accomplished by various forms of automatic +regulating valves, which, while they differ somewhat in details of +construction, all operate on the same principle. + +The regulator body (Figure 14) carries a union which attaches to the side +outlet on the oxygen tank valve. The gas passes through this union, +following an opening which leads to a large gauge which registers the +pressure on the oxygen remaining in the tank and also to a very small +opening in the end of a tube. The gas passes through this opening and into +the interior of the regulator body. Inside of the body is a metal or rubber +diaphragm placed so that the pressure of the incoming gas causes it to +bulge slightly. Attached to the diaphragm is a sleeve or an arm tipped +with a small piece of fibre, the fibre being placed so that it is directly +opposite the small hole through which the gas entered the diaphragm +chamber. The slight movement of the diaphragm draws the fibre tightly over +the small opening through which the gas is entering, with the result that +further flow is prevented. + +Against the opposite side of the diaphragm is the end of a plunger. This +plunger is pressed against the diaphragm by a coiled spring. The tension on +the coiled spring is controlled by the operator through a threaded spindle +ending in a wing or milled nut on the outside of the regulator body. +Screwing in on the nut causes the tension on the spring to increase, with a +consequent increase of pressure on the side of the diaphragm opposite to +that on which the gas acts. Inasmuch as the gas pressure acted to close the +small gas opening and the spring pressure acts in the opposite direction +from the gas, it will be seen that the spring pressure tends to keep the +valve open. + +When the nut is turned way out there is of course, no pressure on the +spring side of the diaphragm and the first gas coming through automatically +closes the opening through which it entered. If now the tension on the +spring be slightly increased, the valve will again open and admit gas until +the pressure of gas within the regulator is just sufficient to overcome the +spring pressure and again close the opening. There will then be a pressure +of gas within the regulator that corresponds to the pressure placed on the +spring by the operator. An opening leads from the regulator interior to the +torch lines so that all gas going to the torches is drawn from the +diaphragm chamber. + +Any withdrawal of gas will, of course, lower the pressure of that remaining +inside the regulator. The spring tension, remaining at the point determined +by the operator, will overcome this lessened pressure of the gas, and the +valve will again open and admit enough more gas to bring the pressure back +to the starting point. This action continues as long as the spring tension +remains at this point and as long as any gas is taken from the regulator. +Increasing the spring tension will require a greater gas pressure to close +the valve and the pressure of that in the regulator will be correspondingly +higher. + +When the regulator is not being used, the hand nut should be unscrewed +until no tension remains on the spring, thus closing the valve. After the +oxygen tank valve is open, the regulator hand nut is slowly screwed in +until the spring tension is sufficient to give the required pressure in the +torch lines. Another gauge is attached to the regulator so that it +communicates with the interior of the diaphragm chamber, this gauge showing +the gas pressure going to the torch. It is customary to incorporate a +safety valve in the regulator which will blow off at a dangerous pressure. + +In regulating valves and tank valves, as well as all other parts with which +the oxygen comes in contact, it is not permissible to use any form of oil +or grease because of danger of ignition and explosion. The mechanism of a +regulator is too delicate to be handled in the ordinary shop and should any +trouble or leakage develop in this part of the equipment it should be sent +to a company familiar with this class of work for the necessary repairs. +Gas must never be admitted to a regulator until the hand nut is all the way +out, because of danger to the regulator itself and to the operator as well. +A regulator can only be properly adjusted when the tank valve and torch +valves are fully opened. + +[Illustration: Figure 15.--High and Low Pressure Gauges with Regulator] + +Acetylene regulators are used in connection with tanks of compressed gas. +They are built on exactly the same lines as the oxygen regulating valve and +operate in a similar way. One gauge only, the low pressure indicator, is +used for acetylene regulators, although both high and low pressure may be +used if desired. (See Figure 15.) + + +TORCHES + +Flame is always produced by the combustion of a gas with oxygen and in no +other way. When we burn oil or candles or anything else, the material of +the fuel is first turned to a gas by the heat and is then burned by +combining with the oxygen of the air. If more than a normal supply of air +is forced into the flame, a greater heat and more active burning follows. +If the amount of air, and consequently oxygen, is reduced, the flame +becomes smaller and weaker and the combustion is less rapid. A flame may be +easily extinguished by shutting off all of its air supply. + +The oxygen of the combustion only forms one-fifth of the total volume of +air; therefore, if we were to supply pure oxygen in place of air, and in +equal volume, the action would be several times as intense. If the oxygen +is mixed with the fuel gas in the proportion that burns to the very best +advantage, the flame is still further strengthened and still more heat is +developed because of the perfect combustion. The greater the amount of fuel +gas that can be burned in a certain space and within a certain time, the +more heat will be developed from that fuel. + +The great amount of heat contained in acetylene gas, greater than that +found in any other gaseous fuel, is used by leading this gas to the +oxy-acetylene torch and there combining it with just the right amount of +oxygen to make a flame of the greatest power and heat than can possibly be +produced by any form of combustion of fuels of this kind. The heat +developed by the flame is about 6300 Fahrenheit and easily melts all the +metals, as well as other solids. + +Other gases have been and are now being used in the torch. None of them, +however, produce the heat that acetylene does, and therefore the +oxy-acetylene process has proved the most useful of all. Hydrogen was used +for many years before acetylene was introduced in this field. The +oxy-hydrogen flame develops a heat far below that of oxy-acetylene, namely +4500 Fahrenheit. Coal gas, benzine gas, blaugas and others have also been +used in successful applications, but for the present we will deal +exclusively with the acetylene fuel. + +It was only with great difficulty that the obstacles in the way of +successfully using acetylene were overcome by the development of +practicable controlling devices and torches, as well as generators. At +present the oxy-acetylene process is the most universally adaptable, and +probably finds the most widely extended field of usefulness of any welding +process. + +The theoretical proportion of the gases for perfect combustion is two and +one-half volumes of oxygen to one of acetylene. In practice this proportion +is one and one-eighth or one and one-quarter volumes of oxygen to one +volume of acetylene, so that the cost is considerably reduced below what it +would be if the theoretical quantity were really necessary, as oxygen costs +much more than acetylene in all cases. + +While the heat is so intense as to fuse anything brought into the path of +the flame, it is localized in the small "welding cone" at the torch tip so +that the torch is not at all difficult to handle without special protection +except for the eyes, as already noted. The art of successful welding may be +acquired by any operator of average intelligence within a reasonable time +and with some practice. One trouble met with in the adoption of this +process has been that the operation looks so simple and so easy of +performance that unskilled and unprepared persons have been tempted to try +welding, with results that often caused condemnation of the process, when +the real fault lay entirely with the operator. + +The form of torch usually employed is from twelve to twenty-four inches +long and is composed of a handle at one end with tubes leading from this +handle to the "welding head" or torch proper. At or near one end of the +handle are adjustable cocks or valves for allowing the gases to flow into +the torch or to prevent them from doing so. These cocks are often used for +regulating the pressure and amount of gas flowing to the welding head, but +are not always constructed for this purpose and should not be so used when +it is possible to secure pressure adjustment at the regulators (Figure 16). + +Figure 16 shows three different sizes of torches. The number 5 torch is +designed especially for jewelers' work and thin sheet steel welding. It is +eleven inches in length and weighs nineteen ounces. The tips for the number +10 torch are interchangeable with the number 5. The number 10 torch is +adapted for general use on light and medium heavy work. It has six tips and +its length is sixteen inches, with a weight of twenty-three ounces. + +The number 15 torch is designed for heavy work, being twenty-five inches in +length, permitting the operator to stand away from the heat of the metal +being worked. These heavy tips are in two parts, the oxygen check being +renewable. + +[Illustration: Figure 16.--Three Sizes of Torches, with Tips] + +Figures 17 and 18 show two sizes of another welding torch. Still another +type is shown in Figure 19 with four interchangeable tips, the function of +each being as follows: + + No. 1. For heavy castings. + No. 2. Light castings and heavy sheet metal. + No. 3. Light sheet metal. + No. 4. Very light sheet metal and wire. + +[Illustration: Figure 17.--Cox Welding Torch (No. 1)] + +[Illustration: Figure 18.--Cox Welding Torch (No. 2)] + +[Illustration: Figure 19.--Monarch Welding Torch] + +At the side of the shut off cock away from the torch handle the gas tubes +end in standard forms of hose nozzles, to which the rubber hose from the +gas supply tanks or generators can be attached. The tubes from the handle +to the head may be entirely separate from each other, or one may be +contained within the other. As a general rule the upper one of two +separate tubes carries the oxygen, while this gas is carried in the inside +tube when they are concentric with each other. + +In the welding head is the mixing chamber designed to produce an intimate +mixture of the two gases before they issue from the nozzle to the flame. +The nozzle, or welding tip, of a suitable size are design for the work to +be handled and the pressure of gases being used, is attached to the welding +head and consists essentially of the passage at the outer end of which the +flame appears. + +The torch body and tubes are usually made of brass, although copper is +sometimes used. The joint must be very strong, and are usually threaded and +soldered with silver solder. The nozzle proper is made from copper, because +it withstands the heat of the flame better than other less suitable metals. +The torch must be built in such a way that it is not at all liable to come +apart under the influence of high temperatures. + +All torches are constructed in such a way that it is impossible for the +gases to mix by any possible chance before they reach the head, and the +amount of gas contained in the head and tip after being mixed is made as +small as possible. In order to prevent the return of the flame through the +acetylene tube under the influence of the high pressure oxygen some form of +back flash preventer is usually incorporated in the torch at or near the +point at which the acetylene enters. This preventer takes the form of some +porous and heat absorbing material, such as aluminum shavings, contained in +a small cavity through which the gas passes on its way to the head. + +_High Pressure Torches._--Torches are divided into the same classes as +are the generators; that is, high pressure, medium pressure and low +pressure. As mentioned before, the medium pressure is usually called the +high pressure, because there are very few true high pressure systems in +use, and comparatively speaking the medium pressure type is one of high +pressure. + +[Illustration: Figure 20.--High Pressure Torch Head] + +With a true high pressure torch (Figure 20) the gases are used at very +nearly equal heads so that the mixing before ignition is a simple matter. +This type admits the oxygen at the inner end of a straight passage leading +to the tip of the nozzle. The acetylene comes into this same passage from +openings at one side and near the inner end. The difference in direction of +the two gases as they enter the passage assists in making a homogeneous +mixture. The construction of this nozzle is perfectly simple and is easily +understood. The true high pressure torch nozzle is only suited for use with +compressed and dissolved acetylene, no other gas being at a sufficient +pressure to make the action necessary in mixing the gases. + +_Medium Pressure Torches._--The medium pressure (usually called high +pressure) torch (Figure 21) uses acetylene from a medium pressure generator +or from tanks of compressed gas, but will not take the acetylene from low +pressure generators. + +[Illustration: Figure 21.--Medium Pressure Torch Head] + +The construction of the mixing chamber and nozzle is very similar to that +of the high pressure torch, the gases entering in the same way and from the +same positions of openings. The pressure of the acetylene is but little +lower than that of the oxygen, and the two gases, meeting at right angles, +form a very intimate mixture at this point of juncture. The mixture in its +proportions of gases depends entirely on the sizes of the oxygen and +acetylene openings into the mixing chamber and on the pressures at which +the gases are admitted. There is a very slight injector action as the fast +moving stream of oxygen tends to draw the acetylene from the side openings +into the chamber, but the operation of the torch does not depend on this +action to any extent. + +_Low Pressure Torches._--The low pressure torch (Figure 22) will use +gas from low pressure generators from medium pressure machines or from +tanks in which it has been compressed and dissolved. This type depends for +a perfect mixture of gas upon the principle of the injector just as it is +applied in steam boiler practice. + +[Illustration: Figure 22.--Low Pressure Torch with Separate Injector +Nozzle] + +The oxygen enters the head at considerable pressure and passes through its +tube to a small jet within the head. The opening of this jet is directly +opposite the end of the opening through the nozzle which forms the mixing +chamber and the path of the gases to the flame. A small distance remains +between the opening from which the oxygen issues and the inner opening into +the mixing passage. The stream of oxygen rushes across this space and +enters the mixing chamber, being driven by its own pressure. + +The acetylene enters the head in an annular space surrounding the oxygen +tube. The space between oxygen jet and mixing chamber opening is at one end +of this acetylene space and the stream of oxygen seizes the acetylene and +under the injector action draws it into the mixing chamber, it being +necessary only to have a sufficient supply of acetylene flowing into the +head to allow the oxygen to draw the required proportion for a proper +mixture. + +The volume of gas drawn into the mixing chamber depends on the size of the +injector openings and the pressure of the oxygen. In practice the oxygen +pressure is not altered to produce different sized flames, but a new nozzle +is substituted which is designed to give the required flame. Each nozzle +carries its own injector, so that the design is always suited to the +conditions. While torches are made having the injector as a permanent part +of the torch body, the replaceable nozzle is more commonly used because it +makes the one torch suitable for a large range of work and a large number +of different sized flames. With the replaceable head a definite pressure of +oxygen is required for the size being used, this pressure being the one for +which the injector and corresponding mixing chamber were designed in +producing the correct mixture. + +_Adjustable Injectors._-Another form of low pressure torch operates on +the injector principle, but the injector itself is a permanent part of the +torch, the nozzle only being changed for different sizes of work and flame. +The injector is placed in or near the handle and its opening is the largest +required by any work that can be handled by this particular torch. The +opening through the tip of the injector through which the oxygen issues on +its way to the mixing chamber may be wholly or partly closed by a needle +valve which may be screwed into the opening or withdrawn from it, according +to the operator's judgment. The needle valve ends in a milled nut outside +the torch handle, this being the adjustment provided for the different +nozzles. + +_Torch Construction._--A well designed torch is so designed that the +weight distribution is best for holding it in the proper position for +welding. When a torch is grasped by its handle with the gas hose attached, +it should balance so that it does not feel appreciably heavier on one end +than on the other. + +The head and nozzle may be placed so that the flame issues in a line at +right angles with the torch body, or they may be attached at an angle +convenient for the work to be done. The head set at an angle of from 120 to +170 degrees with the body is usually preferred for general work in welding, +while the cutting torch usually has its head at right angles to the body. + +Removable nozzles have various size openings through them and the different +sizes are designated by numbers from 1 up. The same number does not always +indicate the same size opening in torches of different makes, nor does it +indicate a nozzle of the same capacity. + +The design of the nozzle, the mixing chamber, the injector, when one is +used, and the size of the gas openings must be such that all these things +are suited to each other if a proper mixture of gas is to be secured. Parts +that are not made to work together are unsafe if used because of the danger +of a flash back of the flame into the mixing chamber and gas tubes. It is +well known that flame travels through any inflammable gas at a certain +definite rate of speed, depending on the degree of inflammability of the +gas. The easier and quicker the gas burns, the faster will the flame travel +through it. + +If the gas in the nozzle and mixing chamber stood still, the flame would +immediately travel back into these parts and produce an explosion of more +or less violence. The speed with which the gases issue from the nozzle +prevent this from happening because the flame travels back through the gas +at the same speed at which the gas issues from the torch tip. Should the +velocity of the gas be greater than the speed of flame propagation through +it, it will be impossible to keep the flame at the tip, the tendency being +for a space of unburned gas to appear between tip and flame. On the other +hand, should the speed of the flame exceed the velocity with which the gas +comes from the torch there will result a flash back and explosion. + +_Care of Torches._--An oxy-acetylene torch is a very delicate and +sensitive device, much more so that appears on the surface. It must be +given equally as good care and attention as any other high-priced piece of +machinery if it is to be maintained in good condition for use. + +It requires cleaning of the nozzles at regular intervals if used regularly. +This cleaning is accomplished with a piece of copper or brass wire run +through the opening, and never with any metal such as steel or iron that is +harder than the nozzle itself, because of the danger of changing the size +of the openings. The torch head and nozzle can often be cleaned by allowing +the oxygen to blow through at high pressure without the use of any tools. + +In using a torch a deposit of carbon will gradually form inside of the +head, and this deposit will be more rapid if the operator lights the stream +of acetylene before turning any oxygen into the torch. This deposit may be +removed by running kerosene through the nozzle while it is removed from the +torch, setting fire to the kerosene and allowing oxygen to flow through +while the oil is burning. + +Should a torch become clogged in the head or tubes, it may usually be +cleaned by removing the oxygen hose from the handle end, closing the +acetylene cock on the torch, placing the end of the oxygen hose over the +opening in the nozzle and turning on the oxygen under pressure to blow the +obstruction back through the passage that it has entered. By opening the +acetylene cock and closing the oxygen cock at the handle, the acetylene +passages may then be cleaned in the same way. Under no conditions should a +torch be taken apart any more than to remove the changeable nozzle, except +in the hands of those experienced in this work. + +_Nozzle Sizes._--The size of opening through the nozzle is determined +according to the thickness and kind of metal being handled. The following +sizes are recommended for steel: + + Davis-Bournonville. Oxweld Low + Thickness of Metal (Medium Pressure.) Pressure + 1/32 Tip No. 1 Head No. 2 + 1/16 2 + 5/64 3 + 3/32 3 4 + 3/8 4 5 + 3/16 5 6 + 1/4 6 7 + 5/16 7 + 3/8 8 8 + 1/2 9 10 + 5/8 10 12 + 3/4 11 15 + Very heavy 12 15 + +_Cutting Torches._--Steel may be cut with a jet of oxygen at a rate of +speed greater than in any other practicable way under usual conditions. The +action consists of burning away a thin section of the metal by allowing a +stream of oxygen to flow onto it while the gas is at high pressure and the +metal at a white heat. + +[Illustration: Figure 23.--Cutting Torch] + +The cutting torch (Figure 23) has the same characteristics as the welding +torch, but has an additional nozzle or means for temporarily using the +welding opening for the high pressure oxygen. The oxygen issues from the +opening while cutting at a pressure of from ten to 100 pounds to the square +inch. + +The work is first heated to a white heat by adjusting the torch for a +welding flame. As soon as the metal reaches this temperature, the high +pressure oxygen is turned on to the white-hot portion of the steel. When +the jet of gas strikes the metal it cuts straight through, leaving a very +narrow slot and removing but little metal. Thicknesses of steel up to ten +inches can be economically handled in this way. + +The oxygen nozzle is usually arranged so that it is surrounded by a number +of small jets for the heating flame. It will be seen that this arrangement +makes the heating flame always precede the oxygen jet, no matter in which +direction the torch is moved. + +The torch is held firmly, either by hand or with the help of special +mechanism for guiding it in the desired path, and is steadily advanced in +the direction it is desired to extend the cut, the rate of advance being +from three inches to two feet per minute through metal from nine inches +down to one-quarter of an inch in thickness. + +The following data on cutting is given by the Davis-Bournonville Company: + + Cubic + Feet Cost of +Thickness of Gas Inches Gases +of Cutting Heating per Foot Oxygen Cut per per Foot +Steel Oxygen Oxygen of Cut Acetylene Min. of Cut + 1/4 10 lbs. 4 lbs. .40 .086 24 $ .013 + 1/2 20 4 .91 .150 15 .029 + 3/4 30 4 1.16 .150 15 .036 +1 30 4 1.45 .172 12 .045 +1 1/2 30 5 2.40 .380 12 .076 +2 40 5 2.96 .380 12 .093 +4 50 5 9.70 .800 7 .299 +6 70 6 21.09 1.50 4 .648 +9 100 6 43.20 2.00 3 1.311 + +_Acetylene-Air Torch._--A form of torch which burns the acetylene after +mixing it with atmospheric air at normal pressure rather than with the +oxygen under higher pressures has been found useful in certain pre-heating, +brazing and similar operations. This torch (Figure 24) is attached by a +rubber gas hose to any compressed acetylene tank and is regulated as to +flame size and temperature by opening or closing the tank valve more or +less. + +After attaching the torch to the tank, the gas is turned on very slowly and +is lighted at the torch tip. The adjustment should cause the presence of a +greenish-white cone of flame surrounded by a larger body of burning gas, +the cone starting at the mouth of the torch. + +[Illustration: Figure 24.--Acetylene-Air Torch] + +By opening the tank valve more, a longer and hotter flame is produced, the +length being regulated by the tank valve also. This torch will give +sufficient heat to melt steel, although not under conditions suited to +welding. Because of the excess of acetylene always present there is no +danger of oxidizing the metal being heated. + +The only care required by this torch is to keep the small air passages at +the nozzle clean and free from carbon deposits. The flame should be +extinguished when not in use rather than turned low, because this low flame +rapidly deposits large quantities of soot in the burner. + + + + +CHAPTER V + +OXY-ACETYLENE WELDING PRACTICE + + +PREPARATION OF WORK + +_Preheating._--The practice of heating the metal around the weld +before applying the torch flame is a desirable one for two reasons. First, +it makes the whole process more economical; second, it avoids the danger of +breakage through expansion and contraction of the work as it is heated and +as it cools. + +When it is desired to join two surfaces by welding them, it is, of course, +necessary to raise the metal from the temperature of the surrounding air to +its melting point, involving an increase in temperature of from one +thousand to nearly three thousand degrees. To obtain this entire increase +of temperature with the torch flame is very wasteful of fuel and of the +operator's time. The total amount of heat necessary to put into metal is +increased by the conductivity of that metal because the heat applied at the +weld is carried to other parts of the piece being handled until the whole +mass is considerably raised in temperature. To secure this widely +distributed increase the various methods of preheating are adopted. + +As to the second reason for preliminary heating. It is understood that the +metal added to the joint is molten at the time it flows into place. All the +metals used in welding contract as they cool and occupy a much smaller +space than when molten. If additional metal is run between two adjoining +surfaces which are parts of a surrounding body of cool metal, this added +metal will cool while the surfaces themselves are held stationary in the +position they originally occupied. The inevitable result is that the metal +added will crack under the strain, or, if the weld is exceptionally strong, +the main body of the work will he broken by the force of contraction. To +overcome these difficulties is the second and most important reason for +preheating and also for slow cooling following the completion of the weld. + +There are many ways of securing this preheating. The work may be brought to +a red heat in the forge if it is cast iron or steel; it may he heated in +special ovens built for the purpose; it may be placed in a bed of charcoal +while suitably supported; it may be heated by gas or gasoline preheating +torches, and with very small work the outer flame of the welding torch +automatically provides means to this end. + +The temperature of the parts heated should be gradually raised in all +cases, giving the entire mass of metal a chance to expand equally and to +adjust itself to the strains imposed by the preheating. After the region +around the weld has been brought to a proper temperature the opening to be +filled is exposed so that the torch flame can reach it, while the remaining +surfaces are still protected from cold air currents and from cooling +through natural radiation. + +One of the commonest methods and one of the best for handling work of +rather large size is to place the piece to be welded on a bed of fire brick +and build a loose wall around it with other fire brick placed in rows, one +on top of the other, with air spaces left between adjacent bricks in each +row. The space between the brick retaining wall and the work is filled with +charcoal, which is lighted from below. The top opening of the temporary +oven is then covered with asbestos and the fire kept up until the work has +been uniformly raised in temperature to the desired point. + +When much work of the same general character and size is to be handled, a +permanent oven may be constructed of fire brick, leaving a large opening +through the top and also through one side. Charcoal may be used in this +form of oven as with the temporary arrangement, or the heat may be secured +from any form of burner or torch giving a large volume of flame. In any +method employing flame to do the heating, the work itself must be protected +from the direct blast of the fire. Baffles of brick or metal should be +placed between the mouth of the torch and the nearest surface of the work +so that the flame will be deflected to either side and around the piece +being heated. + +The heat should be applied to bring the point of welding to the highest +temperature desired and, except in the smallest work, the heat should +gradually shade off from this point to the other parts of the piece. In the +case of cast iron and steel the temperature at the point to be welded +should be great enough to produce a dull red heat. This will make the whole +operation much easier, because there will be no surrounding cool metal to +reduce the temperature of the molten material from the welding rod below +the point at which it will join the work. From this red heat the mass of +metal should grow cooler as the distance from the weld becomes greater, so +that no great strain is placed upon any one part. With work of a very +irregular shape it is always best to heat the entire piece so that the +strains will be so evenly distributed that they can cause no distortion or +breakage under any conditions. + +The melting point of the work which is being preheated should be kept in +mind and care exercised not to approach it too closely. Special care is +necessary with aluminum in this respect, because of its low melting +temperature and the sudden weakening and flowing without warning. Workmen +have carelessly overheated aluminum castings and, upon uncovering the piece +to make the weld, have been astonished to find that it had disappeared. +Six hundred degrees is about the safe limit for this metal. It is possible +to gauge the exact temperature of the work with a pyrometer, but when this +instrument cannot be procured, it might be well to secure a number of +"temperature cones" from a chemical or laboratory supply house. These cones +are made from material that will soften at a certain heat and in form they +are long and pointed. Placed in position on the part being heated, the +point may be watched, and when it bends over it is sure that the metal +itself has reached a temperature considerably in excess of the temperature +at which that particular cone was designed to soften. + +The object in preheating the metal around the weld is to cause it to expand +sufficiently to open the crack a distance equal to the contraction when +cooling from the melting point. In the case of a crack running from the +edge of a piece into the body or of a crack wholly within the body, it is +usually satisfactory to heat the metal at each end of the opening. This +will cause the whole length of the crack to open sufficiently to receive +the molten material from the rod. + +The judgment of the operator will be called upon to decide just where a +piece of metal should be heated to open the weld properly. It is often +possible to apply the preheating flame to a point some distance from the +point of work if the parts are so connected that the expansion of the +heated part will serve to draw the edges of the weld apart. Whatever part +of the work is heated to cause expansion and separation, this part must +remain hot during the entire time of welding and must then cool slowly at +the same time as the metal in the weld cools. + +[Illustration: Figure 25.--Preheating at _A_ While Welding at +_B_. _C_ also May Be Heated.] + +An example of heating points away from the crack might be found in welding +a lattice work with one of the bars cracked through (Figure 25). If the +strips parallel and near to the broken bar are heated gradually, the work +will be so expanded that the edges of the break are drawn apart and the +weld can be successfully made. In this case, the parallel bars next to the +broken one would be heated highest, the next row not quite so hot and so on +for some distance away. If only the one row were heated, the strains set up +in the next ones would be sufficient to cause a new break to appear. + +[Illustration: Figure 26.--Cutting Through the Rim of a Wheel (Cut Shown +at A)] + +If welding is to be done near the central portion of a large piece, the +strains will be brought to bear on the parts farthest away from the center. +Should a fly wheel spoke be broken and made ready to weld, the greatest +strain will come on the rim of the wheel. In cases like this it is often +desirable to cut through at the point of greatest strain with a saw or +cutting torch, allowing free movement while the weld is made at the +original break (Figure 26). After the inside weld is completed, the cut may +be welded without danger, for the reason that it will always be at some +point at which severe strains cannot be set up by the contraction of the +cooling metal. + +[Illustration: Figure 27.--Using a Wedge While Welding] + +In materials that will spring to some extent without breakage, that is, in +parts that are not brittle, it may be possible to force the work out of +shape with jacks or wedges (Figure 27) in the same way that it would be +distorted by heating and expanding some portion of it as described. A +careful examination will show whether this method can be followed in such a +way as to force the edges of the break to separate. If the plan seems +feasible, the wedges may be put in place and allowed to remain while the +weld is completed. As soon as the work is finished the wedges should be +removed so that the natural contraction can take place without damage. + +It should always be remembered that it is not so much the expansion of the +work when heated as it is the contraction caused by cooling that will do +the damage. A weld may be made that, to all appearances, is perfect and it +may be perfect when completed; but if provision has not been made to allow +for the contraction that is certain to follow, there will be a breakage at +some point. It is not possible to weld the simplest shapes, other than +straight bars, without considering this difficulty and making provision to +take care of it. + +The exact method to employ in preheating will always call for good judgment +on the part of the workman, and he should remember that the success or +failure of his work will depend fully as much on proper preparation as on +correct handling of the weld itself. It should be remembered that the outer +flame of the oxy-acetylene torch may be depended on for a certain amount of +preheating, as this flame gives a very large volume of heat, but a heat +that is not so intense nor so localized as the welding flame itself. The +heat of this part of the flame should be fully utilized during the +operation of melting the metal and it should be so directed, when possible, +that it will bring the parts next to be joined to as high a temperature as +possible. + +When the work has been brought to the desired temperature, all parts except +the break and the surface immediately surrounding it on both sides should +be covered with heavy sheet asbestos. This protecting cover should remain +in place throughout the operation and should only be moved a distance +sufficient to allow the torch flame to travel in the path of the weld. The +use of asbestos in this way serves a twofold purpose. It retains the heat +in the work and prevents the breakage that would follow if a draught of air +were to strike the heated metal, and it also prevents such a radiation of +heat through the surrounding air as would make it almost impossible for the +operator to perform his work, especially in the case of large and heavy +castings when the amount of heat utilized is large. + +_Cleaning and Champfering._--A perfect weld can never be made unless +the surfaces to be joined have been properly prepared to receive the new +metal. + +All spoiled, burned, corroded and rough particles must positively be +removed with chisel and hammer and with a free application of emery cloth +and wire brush. The metal exposed to the welding flame should be perfectly +clean and bright all over, or else the additional material will not unite, +but will only stick at best. + +[Illustration: Figure 28.--Tapering the Opening Formed by a Break] + +Following the cleaning it is always necessary to bevel, or champfer, the +edges except in the thinnest sheet metal. To make a weld that will hold, +the metal must be made into one piece, without holes or unfilled portions +at any point, and must be solid from inside to outside. This can only be +accomplished by starting the addition of metal at one point and gradually +building it up until the outside, or top, is reached. With comparatively +thin plates the molten metal may be started from the side farthest from the +operator and brought through, but with thicker sections the addition is +started in the middle and brought flush with one side and then with the +other. + +It will readily be seen that the molten material cannot be depended upon to +flow between the tightly closed surfaces of a crack in a way that can be at +all sure to make a true weld. It will be necessary for the operator to +reach to the farthest side with the flame and welding rod, and to start the +new surfaces there. To allow this, the edges that are to be joined are +beveled from one side to the other (Figure 28), so that when placed +together in approximately the position they are to occupy they will leave a +grooved channel between them with its sides at an angle with each other +sufficient in size to allow access to every point of each surface. + +[Illustration: Figure 29.--Beveling for Thin Work] + +[Illustration: Figure 30.--Beveling for Thick Work] + +With work less than one-fourth inch thick, this angle should be forty-five +degrees on each piece (Figure 29), so that when they are placed together +the extreme edges will meet at the bottom of a groove whose sides are +square, or at right angles, to each other. This beveling should be done so +that only a thin edge is left where the two parts come together, just +enough points in contact to make the alignment easy to hold. With work of a +thickness greater than a quarter of an inch, the angle of bevel on each +piece may be sixty degrees (Figure 30), so that when placed together the +angle included between the sloping sides will also be sixty degrees. If the +plate is less than one-eighth of an inch thick the beveling is not +necessary, as the edges may be melted all the way through without danger of +leaving blowholes at any point. + +[Illustration: Figure 31.--Beveling Both Sides of a Thick Piece] + +[Illustration: Figure 32.--Beveling the End of a Pipe] + +This beveling may be done in any convenient way. A chisel is usually most +satisfactory and also quickest. Small sections may be handled by filing, +while metal that is too hard to cut in either of these ways may be shaped +on the emery wheel. It is not necessary that the edges be perfectly +finished and absolutely smooth, but they should be of regular outline and +should always taper off to a thin edge so that when the flame is first +applied it can be seen issuing from the far side of the crack. If the work +is quite thick and is of a shape that will allow it to be turned over, the +bevel may be brought from both sides (Figure 31), so that there will be two +grooves, one on each surface of the work. After completing the weld on one +side, the piece is reversed and finished on the other side. Figure 32 shows +the proper beveling for welding pipe. Figure 33 shows how sheet metal may +be flanged for welding. + +Welding should not be attempted with the edges separated in place of +beveled, because it will be found impossible to build up a solid web of new +metal from one side clear through to the other by this method. The flame +cannot reach the surfaces to make them molten while receiving new material +from the rod, and if the flame does not reach them it will only serve to +cause a few drops of the metal to join and will surely cause a weak and +defective weld. + +[Illustration: Figure 33.--Flanging Sheet Metal for Welding] + +_Supporting Work._--During the operation of welding it is necessary +that the work be well supported in the position it should occupy. This may +be done with fire brick placed under the pieces in the correct position, +or, better still, with some form of clamp. The edges of the crack should +touch each other at the point where welding is to start and from there +should gradually separate at the rate of about one-fourth inch to the foot. +This is done so that the cooling of the molten metal as it is added will +draw the edges together by its contraction. + +Care must be used to see that the work is supported so that it will +maintain the same relative position between the parts as must be present +when the work is finished. In this connection it must be remembered that +the expansion of the metal when heated may be great enough to cause serious +distortion and to provide against this is one of the difficulties to be +overcome. + +Perfect alignment should be secured between the separate parts that are to +be joined and the two edges must be held up so that they will be in the +same plane while welding is carried out. If, by any chance, one drops +below the other while molten metal is being added, the whole job may have +to be undone and done over again. One precaution that is necessary is that +of making sure that the clamping or supporting does not in itself pull the +work out of shape while melted. + + +TORCH PRACTICE + +[Illustration: Figure 34.--Rotary Movement of Torch in Welding] + +The weld is made by bringing the tip of the welding flame to the edges of +the metals to be joined. The torch should be held in the right hand and +moved slowly along the crack with a rotating motion, traveling in small +circles (Figure 34), so that the Welding flame touches first on one side of +the crack and then on the other. On large work the motion may be simply +back and forth across the crack, advancing regularly as the metal unites. +It is usually best to weld toward the operator rather than from him, +although this rule is governed by circumstances. The head of the torch +should be inclined at an angle of about 60 degrees to the surface of the +work. The torch handle should extend in the same line with the break +(Figure 35) and not across it, except when welding very light plates. + +[Illustration: Figure 35.--Torch Held in Line with the Break] + +If the metal is 1/16 inch or less in thickness it is only necessary to +circle along the crack, the metal itself furnishing enough material to +complete the weld without additions. Heat both sides evenly until they flow +together. + +Material thicker than the above requires the addition of more metal of the +same or different kind from the welding rod, this rod being held by the +left hand. The proper size rod for cast iron is one having a diameter equal +to the thickness of metal being welded up to a one-half inch rod, which is +the largest used. For steel the rod should be one-half the thickness of the +metal being joined up to one-fourth inch rod. As a general rule, better +results will be obtained by the use of smaller rods, the very small sizes +being twisted together to furnish enough material while retaining the free +melting qualities. + +[Illustration: Figure 36.--The Welding Rod Should Be Held in the Molten +Metal] + +The tip of the rod must at all times be held in contact with the pieces +being welded and the flame must be so directed that the two sides of the +crack and the end of the rod are melted at the same time (Figure 36). +Before anything is added from the rod, the sides of the crack are melted +down sufficiently to fill the bottom of the groove and join the two sides. +Afterward, as metal comes from the rod in filling the crack, the flame is +circled along the joint being made, the rod always following the flame. + +[Illustration: Figure 37.--Welding Pieces of Unequal Thickness] + +Figure 37 illustrates the welding of pieces of unequal thickness. + +Figure 38 illustrates welding at an angle. + +The molten metal may be directed as to where it should go by the tip of the +welding flame, which has considerable force, but care must be taken not to +blow melted metal on to cooler surfaces which it cannot join. If, while +welding, a spot appears which does not unite with the weld, it may be +handled by heating all around it to a white heat and then immediately +welding the bad place. + +[Illustration: Figure 38.--Welding at an Angle] + +Never stop in the middle of a weld, as it is extremely difficult to +continue smoothly when resuming work. + +_The Flame._--The welding flame must have exactly the right +proportions of each gas. If there is too much oxygen, the metal will be +burned or oxidized; the presence of too much acetylene carbonizes the +metal; that is to say, it adds carbon and makes the work harder. Just the +right mixture will neither burn nor carbonize and is said to be a "neutral" +flame. The neutral flame, if of the correct size for the work, reduces the +metal to a melted condition, not too fluid, and for a width about the same +as the thickness of the metal being welded. + +When ready to light the torch, after attaching the right tip or head as +directed in accordance with the thickness of metal to be handled, it will +be necessary to regulate the pressure of gases to secure the neutral flame. + +The oxygen will have a pressure of from 2 to 20 pounds, according to the +nozzle used. The acetylene will have much less. Even with the compressed +gas, the pressure should never exceed 10 pounds for the largest work, and +it will usually be from 4 to 6. In low pressure systems, the acetylene will +be received at generator pressure. It should first be seen that the +hand-screws on the regulators are turned way out so that the springs are +free from any tension. It will do no harm if these screws are turned back +until they come out of the threads. This must be done with both oxygen and +acetylene regulators. + +Next, open the valve from the generator, or on the acetylene tank, and +carefully note whether there is any odor of escaping gas. Any leakage of +this gas must be stopped before going on with the work. + +The hand wheel controlling the oxygen cylinder valve should now be turned +very slowly to the left as far as it will go, which opens the valve, and +it should be borne in mind the pressure that is being released. Turn in the +hand screw on the oxygen regulator until the small pressure gauge shows a +reading according to the requirements of the nozzle being used. This oxygen +regulator adjustment should be made with the cock on the torch open, and +after the regulator is thus adjusted the torch cock may be closed. + +Open the acetylene cock on the torch and screw in on the acetylene +regulator hand-screw until gas commences to come through the torch. Light +this flow of acetylene and adjust the regulator screw to the pressure +desired, or, if there is no gauge, so that there is a good full flame. With +the pressure of acetylene controlled by the type of generator it will only +be necessary to open the torch cock. + +With the acetylene burning, slowly open the oxygen cock on the torch and +allow this gas to join the flame. The flame will turn intensely bright and +then blue white. There will be an outer flame from four to eight inches +long and from one to three inches thick. Inside of this flame will be two +more rather distinctly defined flames. The inner one at the torch tip is +very small, and the intermediate one is long and pointed. The oxygen should +be turned on until the two inner flames unite into one blue-white cone from +one-fourth to one-half inch long and one-eighth to one-fourth inch in +diameter. If this single, clearly defined cone does not appear when the +oxygen torch cock has been fully opened, turn off some of the acetylene +until it does appear. + +If too much oxygen is added to the flame, there will still be the central +blue-white cone, but it will be smaller and more or less ragged around the +edges (Figure 39). When there is just enough oxygen to make the single +cone, and when, by turning on more acetylene or by turning off oxygen, two +cones are caused to appear, the flame is neutral (Figure 40), and the small +blue-white cone is called the welding flame. + +[Illustration: Figure 39.--Oxidizing Flame--Too Much Oxygen] + +[Illustration: Figure 40.--Neutral Flame] + +[Illustration: Figure 41.--Reducing Flame--Showing an Excess of Acetylene] + +While welding, test the correctness of the flame adjustment occasionally by +turning on more acetylene or by turning off some oxygen until two flames or +cones appear. Then regulate as before to secure the single distinct cone. +Too much oxygen is not usually so harmful as too much acetylene, except +with aluminum. (See Figure 41.) An excessive amount of sparks coming from +the weld denotes that there is too much oxygen in the flame. Should the +opening in the tip become partly clogged, it will be difficult to secure a +neutral flame and the tip should be cleaned with a brass or copper +wire--never with iron or steel tools or wire of any kind. While the torch +is doing its work, the tip may become excessively hot due to the heat +radiated from the molten metal. The tip may be cooled by turning off the +acetylene and dipping in water with a slight flow of oxygen through the +nozzle to prevent water finding its way into the mixing chamber. + +The regulators for cutting are similar to those for welding, except that +higher pressures may be handled, and they are fitted with gauges reading up +to 200 or 250 pounds pressure. + +In welding metals which conduct the heat very rapidly it is necessary to +use a much larger nozzle and flame than for metals which have not this +property. This peculiarity is found to the greatest extent in copper, +aluminum and brass. + +Should a hole be blown through the work, it may be closed by withdrawing +the flame for a few seconds and then commencing to build additional metal +around the edges, working all the way around and finally closing the small +opening left at the center with a drop or two from the welding rod. + + +WELDING VARIOUS METALS + +Because of the varying melting points, rates of expansion and contraction, +and other peculiarities of different metals, it is necessary to give +detailed consideration to the most important ones. + +_Characteristics of Metals._--The welder should thoroughly understand +the peculiarities of the various metals with which he has to deal. The +metals and their alloys are described under this heading in the first +chapter of this book and a tabulated list of the most important points +relating to each metal will be found at the end of the present chapter. +All this information should be noted by the operator of a welding +installation before commencing actual work. + +Because of the nature of welding, the melting point of a metal is of great +importance. A metal melting at a low temperature should have more careful +treatment to avoid undesired flow than one which melts at a temperature +which is relatively high. When two dissimilar metals are to be joined, the +one which melts at the higher temperature must be acted upon by the flame +first and when it is in a molten condition the heat contained in it will in +many cases be sufficient to cause fusion of the lower melting metal and +allow them to unite without playing the flame on the lower metal to any +great extent. + +The heat conductivity bears a very important relation to welding, inasmuch +as a metal with a high rate of conductance requires more protection from +cooling air currents and heat radiation than one not having this quality to +such a marked extent. A metal which conducts heat rapidly will require a +larger volume of flame, a larger nozzle, than otherwise, this being +necessary to supply the additional heat taken away from the welding point +by this conductance. + +The relative rates of expansion of the various metals under heat should be +understood in order that parts made from such material may have proper +preparation to compensate for this expansion and contraction. Parts made +from metals having widely varying rates of expansion must have special +treatment to allow for this quality, otherwise breakage is sure to occur. + +_Cast Iron._--All spoiled metal should he cut away and if the work is +more than one-eighth inch in thickness the sides of the crack should be +beveled to a 45 degree angle, leaving a number of points touching at the +bottom of the bevel so that the work may be joined in its original +relation. + +The entire piece should be preheated in a bricked-up oven or with charcoal +placed on the forge, when size does not warrant building a temporary oven. +The entire piece should be slowly heated and the portion immediately +surrounding the weld should be brought to a dull red. Care should be used +that the heat does not warp the metal through application to one part more +than the others. After welding, the work should be slowly cooled by +covering with ashes, slaked lime, asbestos fibre or some other +non-conductor of heat. These precautions are absolutely essential in the +case of cast iron. + +A neutral flame, from a nozzle proportioned to the thickness of the work, +should be held with the point of the blue-white cone about one-eighth inch +from the surface of the iron. + +A cast iron rod of correct diameter, usually made with an excess of +silicon, is used by keeping its end in contact with the molten metal and +flowing it into the puddle formed at the point of fusion. Metal should be +added so that the weld stands about one-eighth inch above the surrounding +surface of the work. + +Various forms of flux may be used and they are applied by dipping the end +of the welding rod into the powder at intervals. These powders may contain +borax or salt, and to prevent a hard, brittle weld, graphite or +ferro-silicon may be added. Flux should be added only after the iron is +molten and as little as possible should be used. No flux should be used +just before completion of the work. + +The welding flame should be played on the work around the crack and +gradually brought to bear on the work. The bottom of the bevel should be +joined first and it will be noted that the cast iron tends to run toward +the flame, but does not stick together easily. A hard and porous weld +should be carefully guarded against, as described above, and upon +completion of the work the welded surface should be scraped with a file, +while still red hot, in order to remove the surface scale. + +_Malleable Iron._--This material should be beveled in the same way +that cast iron is handled, and preheating and slow cooling are equally +desirable. The flame used is the same as for cast iron and so is the flux. +The welding rod may be of cast iron, although better results are secured +with Norway iron wire or else a mild steel wire wrapped with a coil of +copper wire. + +It will be understood that malleable iron turns to ordinary cast iron when +melted and cooled. Welds in malleable iron are usually far from +satisfactory and a better joint is secured by brazing the edges together +with bronze. The edges to be joined are brought to a heat just a little +below the point at which they will flow and the opening is then +quickly-filled from a rod of Tobin bronze or manganese bronze, a brass or +bronze flux being used in this work. + +_Wrought Iron or Semi-Steel._--This metal should be beveled and heated +in the same way as described for cast iron. The flame should be neutral, of +the same size as for steel, and used with the tip of the blue-white cone +just touching the work. The welding rod should be of mild steel, or, if +wrought iron is to be welded to steel, a cast iron rod may be used. A cast +iron flux is well suited for this work. It should be noted that wrought +iron turns to ordinary cast iron if kept heated for any length of time. + +_Steel._--Steel should be beveled if more than one-eighth inch in +thickness. It requires only a local preheating around the point to be +welded. The welding flame should be absolutely neutral, without excess of +either gas. If the metal is one-sixteenth inch or less in thickness, the +tip of the blue-white cone must be held a short distance from the surface +of the work; in all other cases the tip of this cone is touched to the +metal being welded. + +The welding rod may be of mild, low carbon steel or of Norway iron. Nickel +steel rods may be used for parts requiring great strength, but vanadium +alloys are very difficult to handle. A very satisfactory rod is made by +twisting together two wires of the required material. The rod must be kept +constantly in contact with the work and should not be added until the edges +are thoroughly melted. The flux may or may not be used. If one is wanted, +it may be made from three parts iron filings, six parts borax and one part +sal ammoniac. + +It will be noticed that the steel runs from the flame, but tends to hold +together. Should foaming commence in the molten metal, it shows an excess +of oxygen and that the metal is being burned. + +High carbon steels are very difficult to handle. It is claimed that a drop +or two of copper added to the weld will assist the flow, but will also +harden the work. An excess of oxygen reduces the amount of carbon and +softens the steel, while an excess of acetylene increases the proportion of +carbon and hardens the metal. High speed steels may sometimes be welded if +first coated with semi-steel before welding. + +_Aluminum._--This is the most difficult of the commonly found metals +to weld. This is caused by its high rate of expansion and contraction and +its liability to melt and fall away from under the flame. The aluminum +seems to melt on the inside first, and, without previous warning, a portion +of the work will simply vanish from in front of the operator's eyes. The +metal tends to run from the flame and separate at the same time. To keep +the metal in shape and free from oxide, it is worked or puddled while in a +plastic condition by an iron rod which has been flattened at one end. +Several of these rods should be at hand and may be kept in a jar of salt +water while not being used. These rods must not become coated with aluminum +and they must not get red hot while in the weld. + +The surfaces to be joined, together with the adjacent parts, should be +cleaned thoroughly and then washed with a 25 per cent solution of nitric +acid in hot water, used on a swab. The parts should then be rinsed in clean +water and dried with sawdust. It is also well to make temporary fire clay +moulds back of the parts to be heated, so that the metal may be flowed into +place and allowed to cool without danger of breakage. + +Aluminum must invariably be preheated to about 600 degrees, and the whole +piece being handled should be well covered with sheet asbestos to prevent +excessive heat radiation. + +The flame is formed with an excess of acetylene such that the second cone +extends about an inch, or slightly more, beyond the small blue-white point. +The torch should be held so that the end of this second cone is in contact +with the work, the small cone ordinarily used being kept an inch or an inch +and a half from the surface of the work. + +Welding rods of special aluminum are used and must be handled with their +end submerged in the molten metal of the weld at all times. + +When aluminum is melted it forms alumina, an oxide of the metal. This +alumina surrounds small masses of the metal, and as it does not melt at +temperatures below 5000 degrees (while aluminum melts at about 1200), it +prevents a weld from being made. The formation of this oxide is retarded +and the oxide itself is dissolved by a suitable flux, which usually +contains phosphorus to break down the alumina. + +_Copper._--The whole piece should be preheated and kept well covered +while welding. The flame must be much larger than for the same thickness of +steel and neutral in character. A slight excess of acetylene would be +preferable to an excess of oxygen, and in all cases the molten metal should +be kept enveloped with the flame. The welding rod is of copper which +contains phosphorus; and a flux, also containing phosphorus, should be +spread for about an inch each side of the joint. These assist in preventing +oxidation, which is sure to occur with heated copper. + +Copper breaks very easily at a heat slightly under the welding temperature +and after cooling it is simply cast copper in all cases. + +_Brass and Bronze._--It is necessary to preheat these metals, although +not to a very high temperature. They must be kept well covered at all times +to prevent undue radiation. The flame should be produced with a nozzle one +size larger than for the same thickness of steel and the small blue-white +cone should be held from one-fourth to one-half inch above the surface of +the work. The flame should be neutral in character. + +A rod or wire of soft brass containing a large percentage of zinc is +suitable for adding to brass, while copper requires the use of copper or +manganese bronze rods. Special flux or borax may be used to assist the +flow. + +The emission of white smoke indicates that the zinc contained in these +alloys is being burned away and the heat should immediately be turned away +or reduced. The fumes from brass and bronze welding are very poisonous and +should not be breathed. + + +RESTORATION OF STEEL + +The result of the high heat to which the steel has been subjected is that +it is weakened and of a different character than before welding. The +operator may avoid this as much as possible by first playing the outer +flame of the torch all over the surfaces of the work just completed until +these faces are all of uniform color, after which the metal should be well +covered with asbestos and allowed to cool without being disturbed. If a +temporary heating oven has been employed, the work and oven should be +allowed to cool together while protected with the sheet asbestos. If the +outside air strikes the freshly welded work, even for a moment, the result +will be breakage. + +A weld in steel will always leave the metal with a coarse grain and with +all the characteristics of rather low grade cast steel. As previously +mentioned in another chapter, the larger the grain size in steel the weaker +the metal will be, and it is the purpose of the good workman to avoid, as +far as possible, this weakening. + +The structure of the metal in one piece of steel will differ according to +the heat that it has under gone. The parts of the work that have been at +the melting point will, therefore, have the largest grain size and the +least strength. Those parts that have not suffered any great rise in +temperature will be practically unaffected, and all the parts between these +two extremes will be weaker or stronger according to their distance from +the weld itself. To restore the steel so that it will have the best grain +size, the operator may resort to either of two methods: (1) The grain may +be improved by forging. That means that the metal added to the weld and the +surfaces that have been at the welding heat are hammered much as a +blacksmith would hammer his finished work to give it greater strength. The +hammering should continue from the time the metal first starts to cool +until it has reached the temperature at which the grain size is best for +strength. This temperature will vary somewhat with the composition of the +metal being handled, but in a general way, it may be stated that the +hammering should continue without intermission from the time the flame is +removed from the weld until the steel just begins to show attraction for a +magnet presented to it. This temperature of magnetic attraction will always +be low enough and the hammering should be immediately discontinued at this +point. (2) A method that is more satisfactory, although harder to apply, is +that of reheating the steel to a certain temperature throughout its whole +mass where the heat has had any effect, and then allowing slow and even +cooling from this temperature. The grain size is affected by the +temperature at which the reheating is stopped, and not by the cooling, yet +the cooling should be slow enough to avoid strains caused by uneven +contraction. + +After the weld has been completed the steel must be allowed to cool until +below 1200 Fahrenheit. The next step is to heat the work slowly until all +those parts to be restored have reached a temperature at which the magnet +just ceases to be attracted. While the very best temperature will vary +according to the nature and hardness of the steel being handled, it will be +safe to carry the heating to the point indicated by the magnet in the +absence of suitable means of measuring accurately these high temperatures. +In using a magnet for testing, it will be most satisfactory if it is an +electromagnet and not of the permanent type. The electric current may be +secured from any small battery and will be the means of making sure of the +test. The permanent magnet will quickly lose its power of attraction under +the combined action of the heat and the jarring to which it will be +subjected. + +In reheating the work it is necessary to make sure that no part reaches a +temperature above that desired for best grain size and also to see that all +parts are brought to this temperature. Here enters the greatest difficulty +in restoring the metal. The heating may be done so slowly that no part of +the work on the outside reaches too high a temperature and then keeps the +outside at this heat until the entire mass is at the same temperature. A +less desirable way is to heat the outside higher than this temperature and +allow the conductivity of the metal to distribute the excess to the inside. + +The most satisfactory method, where it can be employed, is to make use of a +bath of some molten metal or some chemical mixture that can be kept at the +exact heat necessary by means of gas fires that admit of close regulation. +The temperature of these baths may be maintained at a constant point by +watching a pyrometer, and the finished work may be allowed to remain in the +bath until all parts have reached the desired temperature. + + +WELDING INFORMATION + +The following tables include much of the information that the operator must +use continually to handle the various metals successfully. The temperature +scales are given for convenience only. The composition of various alloys +will give an idea of the difficulties to be contended with by consulting +the information on welding various metals. The remaining tables are of +self-evident value in this work. + +TEMPERATURE SCALES +Centigrade Fahrenheit Centigrade Fahrenheit + 200 392 1000 1832 + 225 437 1050 1922 + 250 482 1100 2012 + 275 527 1150 2102 + 300 572 1200 2192 + 325 617 1250 2282 + 350 662 1300 2372 + 375 707 1350 2462 + 400 752 1400 2552 + 425 797 1450 2642 + 450 842 1500 2732 + 475 887 1550 2822 + 500 932 1600 2912 + 525 977 1650 3002 + 550 1022 1700 3092 + 575 1067 1750 3182 + 600 1112 1800 3272 + 625 1157 1850 3362 + 650 1202 1900 3452 + 675 1247 2000 3632 + 700 1292 2050 3722 + 725 1337 2100 3812 + 750 1382 2150 3902 + 775 1427 2200 3992 + 800 1472 2250 4082 + 825 1517 2300 4172 + 850 1562 2350 4262 + 875 1607 2400 4352 + 900 1652 2450 4442 + 925 1697 2500 4532 + 950 1742 2550 4622 + 975 1787 2600 4712 + +METAL ALLOYS +(Society of Automobile Engineers) + +Babbitt-- + Tin........................... 84.00% + Antimony...................... 9.00% + Copper........................ 7.00% + +Brass, White-- + Copper........................ 3.00% to 6.00% + Tin (minimum) ................ 65.00% + Zinc.......................... 28.00% to 30.00% + +Brass, Red Cast-- + Copper........................ 85.00% + Tin........................... 5.00% + Lead.......................... 5.00% + Zinc.......................... 5.00% + +Brass, Yellow-- + Copper........................ 62.00% to 65.00% + Lead.......................... 2.00% to 4.00% + Zinc.......................... 36.00% to 31.00% + +Bronze, Hard-- + Copper........................ 87.00% to 88.00% + Tin........................... 9.50% to 10.50% + Zinc.......................... 1.50% to 2.50% + +Bronze, Phosphor-- + Copper........................ 80.00% + Tin........................... 10.00% + Lead.......................... 10.00% + Phosphorus.................... .50% to .25% + +Bronze, Manganese-- + Copper (approximate) ......... 60.00% + Zinc (approximate) ........... 40.00% + Manganese (variable) ......... small + +Bronze, Gear-- + Copper........................ 88.00% to 89.00% + Tin........................... 11.00% to 12.00% + +Aluminum Alloys-- + Aluminum Copper Zinc Manganese + No. 1.. 90.00% 8.5-7.0% + No. 2.. 80.00% 2.0-3.0% 15% Not over 0.40% + No. 3.. 65.00% 35.0% + +Cast Iron-- + Gray Iron Malleable + Total carbon........3.0 to 3.5% + Combined carbon.....0.4 to 0.7% + Manganese...........0.4 to 0.7% 0.3 to 0.7% + Phosphorus..........0.6 to 1.0% Not over 0.2% + Sulphur...........Not over 0.1% Not over 0.6% + Silicon............1.75 to 2.25% Not over 1.0% + +Carbon Steel (10 Point)-- + Carbon........................ .05% to .15% + Manganese..................... .30% to .60% + Phosphorus (maximum).......... .045% + Sulphur (maximum)............. .05% +(20 Point)-- + Carbon........................ .15% to .25% + Manganese..................... .30% to .60% + Phosphorus (maximum).......... .045% + Sulphur (maximum)............. .05% +(35 Point)-- + Manganese..................... .50% to .80% + Carbon........................ .30% to .40% + Phosphorus (maximum).......... .05% + Sulphur (maximum)............. .05% +(95 Point)-- + Carbon........................ .90% to 1.05% + Manganese..................... .25% to .50% + Phosphorus (maximum).......... .04% + Sulphur (maximum)............. .05% + +HEATING POWER OF FUEL GASES + +(In B.T.U. per Cubic Foot.) + Acetylene....... 1498.99 Ethylene....... 1562.9 + Hydrogen........ 291.96 Methane........ 953.6 + Alcohol......... 1501.76 + +MELTING POINTS OF METALS + Platinum....................3200 + Iron, wrought...............2900 + malleable.................2500 + cast......................2400 + pure......................2760 + Steel, mild.................2700 + Medium....................2600 + Hard......................2500 + Copper......................1950 + Brass.......................1800 + Silver......................1750 + Bronze......................1700 + Aluminum....................1175 + Antimony....................1150 + Zinc........................ 800 + Lead........................ 620 + Babbitt..................500-700 + Solder...................500-575 + Tin......................... 450 + +_NOTE.--These melting points are for average compositions and conditions. +The exact proportion of elements entering into the metals affects their +melting points one way or the other in practice._ + +TENSILE STRENGTH OF METALS + +Alloy steels can be made with tensile strengths as high as 300,000 pounds +per square inch. Some carbon steels are given below according to "points": + + Pounds per Square Inch +Steel, 10 point................ 50,000 to 65,000 + 20 point..................... 60,000 to 80,000 + 40 point..................... 70,000 to 100,000 + 60 point..................... 90,000 to 120,000 +Iron, Cast..................... 13,000 to 30,000 + Wrought...................... 40,000 to 60,000 + Malleable.................... 25,000 to 45,000 +Copper......................... 24,000 to 50,000 +Bronze......................... 30,000 to 60,000 +Brass, Cast.................... 12,000 to 18,000 + Rolled....................... 30,000 to 40,000 + Wire......................... 60,000 to 75,000 +Aluminum....................... 12,000 to 23,000 +Zinc........................... 5,000 to 15,000 +Tin............................ 3,000 to 5,000 +Lead........................... 1,500 to 2,500 + +CONDUCTIVITY OF METALS + +(Based on the Value of Silver as 100) + + Heat Electricity +Silver....................100 100 +Copper.................... 74 99 +Aluminum.................. 38 63 +Brass..................... 23 22 +Zinc...................... 19 29 +Tin....................... 14 15 +Wrought Iron.............. 12 16 +Steel..................... 11.5 12 +Cast Iron................. 11 12 +Bronze.................... 9 7 +Lead...................... 8 9 + +WEIGHT OF METALS + +(Per Cubic Inch) + Pounds Pounds +Lead............ .410 Wrought Iron..... .278 +Copper.......... .320 Tin.............. .263 +Bronze.......... .313 Cast Iron........ .260 +Brass........... .300 Zinc............. .258 +Steel........... .283 Aluminum......... .093 + +EXPANSION OF METALS + +(Measured in Thousandths of an Inch per Foot of +Length When Raised 1000 Degrees in Temperature) + Inch Inch +Lead............ .188 Brass............ .115 +Zinc............ .168 Copper........... .106 +Aluminum........ .148 Steel............ .083 +Silver.......... .129 Wrought Iron..... .078 +Bronze.......... .118 Cast Iron........ .068 + + + + +CHAPTER VI + +ELECTRIC WELDING + + +RESISTANCE METHOD + +Two distinct forms of electric welding apparatus are in use, one producing +heat by the resistance of the metal being treated to the passage of +electric current, the other using the heat of the electric arc. + +The resistance process is of the greatest use in manufacturing lines where +there is a large quantity of one kind of work to do, many thousand pieces +of one kind, for instance. The arc method may be applied in practically any +case where any other form of weld may be made. The resistance process will +be described first. + +It is a well known fact that a poor conductor of electricity will offer so +much resistance to the flow of electricity that it will heat. Copper is a +good conductor, and a bar of iron, a comparatively poor conductor, when +placed between heavy copper conductors of a welder, becomes heated in +attempting to carry the large volume of current. The degree of heat depends +on the amount of current and the resistance of the conductor. + +In an electric circuit the ends of two pieces of metal brought together +form the point of greatest resistance in the electric circuit, and the +abutting ends instantly begin to heat. The hotter this metal becomes, the +greater the resistance to the flow of current; consequently, as the edges +of the abutting ends heat, the current is forced into the adjacent cooler +parts, until there is a uniform heat throughout the entire mass. The heat +is first developed in the interior of the metal so that it is welded there +as perfectly as at the surface. + +[Illustration: Figure 42.--Spot Welding Machine] + +The electric welder (Figure 42) is built to hold the parts to be joined +between two heavy copper dies or contacts. A current of three to five +volts, but of very great volume (amperage), is allowed to pass across +these dies, and in going through the metal to be welded, heats the edges +to a welding temperature. It may be explained that the voltage of an +electric current measures the pressure or force with which it is being sent +through the circuit and has nothing to do with the quantity or volume +passing. Amperes measure the rate at which the current is passing through +the circuit and consequently give a measure of the quantity which passes in +any given time. Volts correspond to water pressure measured by pounds to +the square inch; amperes represent the flow in gallons per minute. The low +voltage used avoids all danger to the operator, this pressure not being +sufficient to be felt even with the hands resting on the copper contacts. + +Current is supplied to the welding machine at a higher voltage and lower +amperage than is actually used between the dies, the low voltage and high +amperage being produced by a transformer incorporated in the machine +itself. By means of windings of suitable size wire, the outside current may +be received at voltages ranging from 110 to 550 and converted to the low +pressure needed. + +The source of current for the resistance welder must be alternating, that +is, the current must first be negative in value and then positive, passing +from one extreme to the other at rates varying from 25 to 133 times a +second. This form is known as alternating current, as opposed to direct +current, in which there is no changing of positive and negative. + +The current must also be what is known as single phase, that is, a current +which rises from zero in value to the highest point as a positive current +and then recedes to zero before rising to the highest point of negative +value. Two-phase of three-phase currents would give two or three positive +impulses during this time. + +As long as the current is single phase alternating, the voltage and cycles +(number of alternations per second) may be anything convenient. Various +voltages and cycles are taken care of by specifying all these points when +designing the transformer which is to handle the current. + +Direct current is not used because there is no way of reducing the voltage +conveniently without placing resistance wires in the circuit and this uses +power without producing useful work. Direct current may be changed to +alternating by having a direct current motor running an alternating current +dynamo, or the change may be made by a rotary converter, although this last +method is not so satisfactory as the first. + +The voltage used in welding being so low to start with, it is absolutely +necessary that it be maintained at the correct point. If the source of +current supply is not of ample capacity for the welder being used, it will +be very hard to avoid a fall of voltage when the current is forced to pass +through the high resistance of the weld. The current voltage for various +work is calculated accurately, and the efficiency of the outfit depends to +a great extent on the voltage being constant. + +A simple test for fall of voltage is made by connecting an incandescent +electric lamp across the supply lines at some point near the welder. The +lamp should burn with the same brilliancy when the weld is being made as at +any other time. If the lamp burns dim at any time, it indicates a drop in +voltage, and this condition should be corrected. + +The dynamo furnishing the alternating current may be in the same building +with the welder and operated from a direct current motor, as mentioned +above, or operated from any convenient shafting or source of power. When +the dynamo is a part of the welding plant it should be placed as close to +the welding machine as possible, because the length of the wire used +affects the voltage appreciably. + +In order to hold the voltage constant, the Toledo Electric Welder Company +has devised connections which include a rheostat to insert a variable +resistance in the field windings of the dynamo so that the voltage may be +increased by cutting this resistance out at the proper time. An auxiliary +switch is connected to the welder switch so that both switches act +together. When the welder switch is closed in making a weld, that portion +of the rheostat resistance between two arms determining the voltage is +short circuited. This lowers the resistance and the field magnets of the +dynamo are made stronger so that additional voltage is provided to care for +the resistance in the metal being heated. + +A typical machine is shown in the accompanying cut (Figure 43). On top of +the welder are two jaws for holding the ends of the pieces to be welded. +The lower part of the jaws is rigid while the top is brought down on top of +the work, acting as a clamp. These jaws carry the copper dies through which +the current enters the work being handled. After the work is clamped +between the jaws, the upper set is forced closer to the lower set by a long +compression lever. The current being turned on with the surfaces of the +work in contact, they immediately heat to the welding point when added +pressure on the lever forces them together and completes the weld. + +[Illustration: Figure 43--Operating Parts of a Toledo Spot Welder] + +[Illustration: Figure 43a.--Method of Testing Electric Welder] +[Illustration: Figure 44.--Detail of Water-Cooled Spot Welding Head] + +The transformer is carried in the base of the machine and on the left-hand +side is a regulator for controlling the voltage for various kinds of work. +The clamps are applied by treadles convenient to the foot of the operator. +A treadle is provided which instantly releases both jaws upon the +completion of the weld. One or both of the copper dies may be cooled by a +stream of water circulating through it from the city water mains +(Figure 44). The regulator and switch give the operator control of the +heat, anything from a dull red to the melting point being easily obtained +by movement of the lever (figure 45). + +[Illustration: Figure 45.--Welding Head of a Water-Cooled Welder] + +_Welding._--It is not necessary to give the metal to be welded any +special preparation, although when very rusty or covered with scale, the +rust and scale should be removed sufficiently to allow good contact of +clean metal on the copper dies. The cleaner and better the stock, the less +current it takes, and there is less wear on the dies. The dies should be +kept firm and tight in their holders to make a good contact. All bolts and +nuts fastening the electrical contacts should be clean and tight at all +times. + +The scale may be removed from forgings by immersing them in a pickling +solution in a wood, stone or lead-lined tank. + +The solution is made with five gallons of commercial sulphuric acid in +150 gallons of water. To get the quickest and best results from this +method, the solution should be kept as near the boiling point as possible +by having a coil of extra heavy lead pipe running inside the tank and +carrying live steam. A very few minutes in this bath will remove the scale +and the parts should then be washed in running water. After this washing +they should be dipped into a bath of 50 pounds of unslaked lime in 150 +gallons of water to neutralize any trace of acid. + +Cast iron cannot be commercially welded, as it is high in carbon and +silicon, and passes suddenly from a crystalline to a fluid state when +brought to the welding temperature. With steel or wrought iron the +temperature must be kept below the melting point to avoid injury to the +metal. The metal must be heated quickly and pressed together with +sufficient force to push all burnt metal out of the joint. + +High carbon steel can be welded, but must be annealed after welding to +overcome the strains set up by the heat being applied at one place. Good +results are hard to obtain when the carbon runs as high as 75 points, and +steel of this class can only be handled by an experienced operator. If the +steel is below 25 points in carbon content, good welds will always be the +result. To weld high carbon to low carbon steel, the stock should be +clamped in the dies with the low carbon stock sticking considerably further +out from the die than the high carbon stock. Nickel steel welds readily, +the nickel increasing the strength of the weld. + +Iron and copper may be welded together by reducing the size of the copper +end where it comes in contact with the iron. When welding copper and brass +the pressure must be less than when welding iron. The metal is allowed to +actually fuse or melt at the juncture and the pressure must be sufficient +to force the burned metal out. The current is cut off the instant the metal +ends begin to soften, this being done by means of an automatic switch which +opens when the softening of the metal allows the ends to come together. The +pressure is applied to the weld by having the sliding jaw moved by a weight +on the end of an arm. + +Copper and brass require a larger volume of current at a lower voltage than +for steel and iron. The die faces are set apart three times the diameter of +the stock for brass and four times the diameter for copper. + +Light gauges of sheet steel can be welded to heavy gauges or to solid bars +of steel by "spot" welding, which will be described later. Galvanized iron +can be welded, but the zinc coating will be burned off. Sheet steel can be +welded to cast iron, but will pull apart, tearing out particles of the +iron. + +Sheet copper and sheet brass may be welded, although this work requires +more experience than with iron and steel. Some grades of sheet aluminum can +be spot-welded if the slight roughness left on the surface under the die +is not objectionable. + +_Butt Welding._--This is the process which joins the ends of two +pieces of metal as described in the foregoing part of this chapter. The +ends are in plain sight of the operator at all times and it can easily be +seen when the metal reaches the welding heat and begins to soften (Figure +46). It is at this point that the pressure must be applied with the lever +and the ends forced together in the weld. + +[Illustration: Figure 46.--Butt Welder] + +The parts are placed in the clamping jaws (Figure 47) with 1/8 to 1/2 inch +of metal extending beyond the jaw. The ends of the metal touch each other +and the current is turned on by means of a switch. To raise the ends to the +proper heat requires from 3 seconds for 1/4-inch rods to 35 seconds for a +1-1/2-inch bar. + +This method is applicable to metals having practically the same area of +metal to be brought into contact on each end. When such parts are forced +together a slight projection will be left in the form of a fin or an +enlarged portion called an upset. The degree of heat required for any work +is found by moving the handle of the regulator one way or the other while +testing several parts. When this setting is right the work can continue as +long as the same sizes are being handled. + +[Illustration: Figure 47.--Clamping Dies of a Butt Welder] + +Copper, brass, tool steel and all other metals that are harmed by high +temperatures must be heated quickly and pressed together with sufficient +force to force all burned metal from the weld. + +In case it is desired to make a weld in the form of a capital letter T, it +is necessary to heat the part corresponding to the top bar of the T to a +bright red, then bring the lower bar to the pre-heated one and again turn +on the current, when a weld can be quickly made. + +_Spot Welding._--This is a method of joining metal sheets together at +any desired point by a welded spot about the size of a rivet. It is done on +a spot welder by fusing the metal at the point desired and at the same +instant applying sufficient pressure to force the particles of molten metal +together. The dies are usually placed one above the other so that the work +may rest on the lower one while the upper one is brought down on top of the +upper sheet to be welded. + +One of the dies is usually pointed slightly, the opposing one being left +flat. The pointed die leaves a slight indentation on one side of the metal, +while the other side is left smooth. The dies may be reversed so that the +outside surface of any work may be left smooth. The current is allowed to +flow through the dies by a switch which is closed after pressure is applied +to the work. + +There is a limit to the thickness of sheet metal that can be welded by this +process because of the fact that the copper rods can only carry a certain +quantity of current without becoming unduly heated themselves. Another +reason is that it is difficult to make heavy sections of metal touch at the +welding point without excessive pressure. + +_Lap welding_ is the process used when two pieces of metal are caused +to overlap and when brought to a welding heat are forced together by +passing through rollers, or under a press, thus leaving the welded joint +practically the same thickness as the balance of the work. + +Where it is desirable to make a continuous seam, a special machine is +required, or an attachment for one of the other types. In this form of work +the stock must be thoroughly cleaned and is then passed between copper +rollers which act in the same capacity as the copper dies. + +_Other Applications._--Hardening and tempering can be done by clamping +the work in the welding dies and setting the control and time to bring the +metal to the proper color, when it is cooled in the usual manner. + +Brazing is done by clamping the work in the jaws and heating until the +flux, then the spelter has melted and run into the joint. Riveting and +heading of rivets can be done by bringing the dies down on opposite ends of +the rivet after it has been inserted in the hole, the dies being shaped to +form the heads properly. + +Hardened steel may be softened and annealed so that it can be machined by +connecting the dies of the welder to each side of the point to be softened. +The current is then applied until the work has reached a point at which it +will soften when cooled. + +_Troubles and Remedies._--The following methods have been furnished by +the Toledo Electric Welder Company and are recommended for this class of +work whenever necessary. + +To locate grounds in the primary or high voltage side of the circuit, +connect incandescent lamps in series by means of a long piece of lamp cord, +as shown, in Figure 43a. For 110 volts use one lamp, for 220 volts use two +lamps and for 440 volts use four lamps. Attach one end of the lamp cord to +one side of the switch, and close the switch. Take the other end of the +cord in the hand and press it against some part of the welder frame where +the metal is clean and bright. Paint, grease and dirt act as insulators and +prevent electrical contact. If the lamp lights, the circuit is in +electrical contact with the frame; in other words, grounded. If the lamps +do not light, connect the wire to a terminal block, die or slide. If the +lamps then light, the circuit, coils or leads are in electrical contact +with the large coil in the transformer or its connections. + +If, however, the lamps do not light in either case, the lamp cord should be +disconnected from the switch and connected to the other side, and the +operations of connecting to welder frame, dies, terminal blocks, etc., as +explained above, should be repeated. If the lamps light at any of these +connections, a "ground" is indicated. "Grounds" can usually be found by +carefully tracing the primary circuit until a place is found where the +insulation is defective. Reinsulate and make the above tests again to make +sure everything is clear. If the ground can not be located by observation, +the various parts of the primary circuit should be disconnected, and the +transformer, switch, regulator, etc., tested separately. + +To locate a ground in the regulator or other part, disconnect the lines +running to the welder from the switch. The test lamps used in the previous +tests are connected, one end of lamp cord to the switch, the other end to a +binding post of the regulator. Connect the other side of the switch to some +part of the regulator housing. (This must be a clean connection to a bolt +head or the paint should be scraped off.) Close the switch. If the lamps +light, the regulator winding or some part of the switch is "grounded" to +the iron base or core of the regulator. If the lamps do not light, this +part of the apparatus is clear. + +This test can be easily applied to any part of the welder outfit by +connecting to the current carrying part of the apparatus, and to the iron +base or frame that should not carry current. If the lamps light, it +indicates that the insulation is broken down or is defective. + +An A.C. voltmeter can, of course, be substituted for the lamps, or a D.C. +voltmeter with D.C. current can be used in making the tests. + +A short circuit in the primary is caused by the insulation of the coils +becoming defective and allowing the bare copper wires to touch each other. +This may result in a "burn out" of one or more of the transformer coils, if +the trouble is in the transformer, or in the continued blowing of fuses in +the line. Feel of each coil separately. If a short circuit exists in a coil +it will heat excessively. Examine all the wires; the insulation may have +worn through and two of them may cross, or be in contact with the frame or +other part of the welder. A short circuit in the regulator winding is +indicated by failure of the apparatus to regulate properly, and sometimes, +though not always, by the heating of the regulator coils. + +The remedy for a short circuit is to reinsulate the defective parts. It is +a good plan to prevent trouble by examining the wiring occasionally and see +that the insulation is perfect. + +_To Locate Grounds and Short Circuits in the Secondary, or Low Voltage +Side._--Trouble of this kind is indicated by the machine acting sluggish +or, perhaps, refusing to operate. To make a test, it will be necessary to +first ascertain the exciting current of your particular transformer. This +is the current the transformer draws on "open circuit," or when supplied +with current from the line with no stock in the welder dies. The following +table will give this information close enough for all practical purposes: + +K.W. ----------------- Amperes at ---------------- +Rating 110 Volts 220 Volts 440 Volts 550 Volts +3 1.5 .75 .38 .3 +5 2.5 1.25 .63 .5 +8 3.6 1.8 .9 .72 +10 4.25 2.13 1.07 .85 +15 6. 3. 1.5 1.2 +20 7. 3.5 1.75 1.4 +30 9. 4.5 2.25 1.8 +35 9.6 4.8 2.4 1.92 +50 10. 5. 2.5 2 + +Remove the fuses from the wall switch and substitute fuses just large +enough to carry the "exciting" current. If no suitable fuses are at hand, +fine strands of copper from an ordinary lamp cord may be used. These +strands are usually No. 30 gauge wire and will fuse at about 10 amperes. +One or more strands should be used, depending on the amount of exciting +current, and are connected across the fuse clips in place of fuse wire. +Place a piece of wood or fibre between the welding dies in the welder as +though you were going to weld them. See that the regulator is on the +highest point and close the welder switch. If the secondary circuit is +badly grounded, current will flow through the ground, and the small fuses +or small strands of wire will burn out. This is an indication that both +sides of the secondary circuit are grounded or that a short circuit exists +in a primary coil. In either case the welder should not be operated until +the trouble is found and removed. If, however, the small fuses do not +"blow," remove same and replace the large fuses, then disconnect wires +running from the wall switch to the welder and substitute two pieces of +No. 8 or No. 6 insulated copper wire, after scraping off the insulation for +an inch or two at each end. Connect one wire from the switch to the frame +of welder; this will leave one loose end. Hold this a foot or so away from +the place where the insulation is cut off; then turn on the current and +strike the free end of this wire lightly against one of the copper dies, +drawing it away quickly. If no sparking is produced, the secondary circuit +is free from ground, and you will then look for a broken connection in the +circuit. Some caution must be used in making the above test, as in case one +terminal is heavily grounded the testing wire may be fused if allowed to +stay in contact with the die. + +_The Remedy._--Clean the slides, dies and terminal blocks thoroughly +and dry out the fibre insulation if it is damp. See that no scale or metal +has worked under the sliding parts, and that the secondary leads do not +touch the frame. If the ground is very heavy it may be necessary to remove +the slides in order to facilitate the examination and removal of the +ground. Insulation, where torn or worn through, must be carefully replaced +or taped. If the transformer coils are grounded to the iron core of the +transformer or to the secondary, it may be necessary to remove the coils +and reinsulate them at the points of contact. A short circuited coil will +heat excessively and eventually burn out. This may mean a new coil if you +are unable to repair the old one. In all cases the transformer windings +should be protected from mechanical injury or dampness. Unless excessively +overloaded, transformers will last for years without giving a moment's +trouble, if they are not exposed to moisture or are not injured +mechanically. + +The most common trouble arises from poor electrical contacts, and they are +the cause of endless trouble and annoyance. See that all connections are +clean and bright. Take out the dies every day or two and see that there is +no scale, grease or dirt between them and the holders. Clean them +thoroughly before replacing. Tighten the bolts running from the transformer +leads to the work jaws. + + +ELECTRIC ARC WELDING + +This method bears no relation to the one just considered, except that the +source of heat is the same in both cases. Arc welding makes use of the +flame produced by the voltaic arc in practically the same way that +oxy-acetylene welding uses the flame from the gases. + +If the ends of two pieces of carbon through which a current of electricity +is flowing while they are in contact are separated from each other quite +slowly, a brilliant arc of flame is formed between them which consists +mainly of carbon vapor. The carbons are consumed by combination with the +oxygen in the air and through being turned to a gas under the intense heat. + +The most intense action takes place at the center of the carbon which +carries the positive current and this is the point of greatest heat. The +temperature at this point in the arc is greater than can be produced by any +other means under human control. + +An arc may be formed between pieces of metal, called electrodes, in the +same way as between carbon. The metallic arc is called a flaming arc and as +the metal of the electrode burns with the heat, it gives the flame a color +characteristic of the material being used. The metallic arc may be drawn +out to a much greater length than one formed between carbon electrodes. + +Arc Welding is carried out by drawing a piece of carbon which is of +negative polarity away from the pieces of metal to be welded while the +metal is made positive in polarity. The negative wire is fastened to the +carbon electrode and the work is laid on a table made of cast or wrought +iron to which the positive wire is made fast. The direction of the flame is +then from the metal being welded to the carbon and the work is thus +prevented from being saturated with carbon, which would prove very +detrimental to its strength. A secondary advantage is found in the fact +that the greatest heat is at the metal being welded because of its being +the positive electrode. + +The carbon electrode is usually made from one quarter to one and a half +inches in diameter and from six to twelve inches in length. The length of +the arc may be anywhere from one inch to four inches, depending on the size +of the work being handled. + +While the parts are carefully insulated to avoid danger of shock, it is +necessary for the operator to wear rubber gloves as a further protection, +and to wear some form of hood over the head to shield him against the +extreme heat liberated. This hood may be made from metal, although some +material that does not conduct electricity is to be preferred. The work is +watched through pieces of glass formed with one sheet, which is either blue +or green, placed over another which is red. Screens of glass are sometimes +used without the head protector. Some protection for the eyes is absolutely +necessary because of the intense white light. + +It is seldom necessary to preheat the work as with the gas processes, +because the heat is localized at the point of welding and the action is so +rapid that the expansion is not so great. The necessity of preheating, +however, depends entirely on the material, form and size of the work being +handled. The same advice applies to arc welding as to the gas flame method +but in a lesser degree. Filling rods are used in the same way as with any +other flame process. + +It is the purpose of this explanation to state the fundamental principles +of the application of the electric arc to welding metals, and by applying +the principles the following questions will be answered: + +What metals can be welded by the electric arc? + +What difficulties are to be encountered in applying the electric arc to +welding? + +What is the strength of the weld in comparison with the original piece? + +What is the function of the arc welding machine itself? + +What is the comparative application of the electric arc and the +oxy-acetylene method and others of a similar nature? + +The answers to these questions will make it possible to understand the +application of this process to any work. In a great many places the use of +the arc is cutting the cost of welding to a very small fraction of what it +would be by any other method, so that the importance of this method may be +well understood. + +Any two metals which are brought to the melting temperature and applied to +each other will adhere so that they are no more apt to break at the weld +than at any other point outside of the weld. It is the property of all +metals to stick together under these conditions. The electric arc is used +in this connection merely as a heating agent. This is its only function in +the process. + +It has advantages in its ease of application and the cheapness with which +heat can be liberated at any given point by its use. There is nothing in +connection with arc welding that the above principles will not answer; that +is, that metals at the melting point will weld and that the electric arc +will furnish the heat to bring them to this point. As to the first +question, what metals can be welded, all metals can be welded. + +The difficulties which are encountered are as follows: + +In the case of brass or zinc, the metals will be covered with a coat of +zinc oxide before they reach a welding heat. This zinc oxide makes it +impossible for two clean surfaces to come together and some method has to +be used for eliminating this possibility and allowing the two surfaces to +join without the possibility of the oxide intervening. The same is true of +aluminum, in which the oxide, alumina, will be formed, and with several +other alloys comprising elements of different melting points. + +In order to eliminate these oxides, it is necessary in practical work, to +puddle the weld; this is, to have a sufficient quantity of molten metal at +the weld so that the oxide is floated away. When this is done, the two +surfaces which are to be joined are covered with a coat of melted metal on +which floats the oxide and other impurities. The two pieces are thus +allowed to join while their surfaces are protected. This precaution is not +necessary in working with steel except in extreme cases. + +Another difficulty which is met with in the welding of a great many metals +is their expansion under heat, which results in so great a contraction when +the weld cools that the metal is left with a considerable strain on it. In +extreme cases this will result in cracking at the weld or near it. To +eliminate this danger it is necessary to apply heat either all over the +piece to be welded or at certain points. In the case of cast iron and +sometimes with copper it is necessary to anneal after welding, since +otherwise the welded pieces will be very brittle on account of the +chilling. This is also true of malleable iron. + +Very thin metals which are welded together and are not backed up by +something to carry away the excess heat, are very apt to burn through, +leaving a hole where the weld should be. This difficulty can be eliminated +by backing up the weld with a metal face or by decreasing the intensity of +the arc so that this melting through will not occur. However, the practical +limit for arc welding without backing up the work with a metal face or +decreasing the intensity of the arc is approximately 22 gauge, although +thinner metal can be welded by a very skillful and careful operator. + +One difficulty with arc welding is the lack of skillful operators. This +method is often looked upon as being something out of the ordinary and +governed by laws entirely different from other welding. As a matter of +fact, it does not take as much skill to make a good arc weld as it does to +make a good weld in a forge fire as the blacksmith does it. There are few +jobs which cannot be handled successfully by an operator of average +intelligence with one week's instructions, although his work will become +better and better in quality as he continues to use the arc. + +Now comes the question of the strength of the weld after it has been made. +This strength is equally as great as that of the metal that is used to make +the weld. It should be remembered, however, that the metal which goes into +the weld is put in there as a casting and has not been rolled. This would +make the strength of the weld as great as the same metal that is used for +filling if in the cast form. + +Two pieces of steel could be welded together having a tensile strength at +the weld of 50,000 pounds. Higher strengths than this can be obtained by +the use of special alloys for the filling material or by rolling. Welds +with a tensile strength as great as mentioned will give a result which is +perfectly satisfactory in almost all cases. + +There are a great many jobs where it is possible to fill up the weld, that +is, make the section at the point of the weld a little larger than the +section through the rest of the piece. By doing this, the disadvantages +of the weld being in the form of a casting in comparison with the rest of +the piece being in the form of rolled steel can be overcome, and make the +weld itself even stronger than the original piece. + +The next question is the adaptability of the electric arc in comparison +with forge fire, oxy-acetylene or other method. The answer is somewhat +difficult if made general. There are no doubt some cases where the use of a +drop hammer and forge fire or the use of the oxy-acetylene torch will make, +all things being considered, a better job than the use of the electric arc, +although a case where this is absolutely proved is rare. + +The electric arc will melt metal in a weld for less than the same metal can +be melted by the use of the oxy-acetylene torch, and, on account of the +fact that the heat can be applied exactly where it is required and in the +amount required, the arc can in almost all cases supply welding heat for +less cost than a forge fire or heating furnace. + +The one great advantage of the oxy-acetylene method in comparison with +other methods of welding is the fact that in some cases of very thin sheet, +the weld can be made somewhat sooner than is possible otherwise. With metal +of 18 gauge or thicker, this advantage is eliminated. In cutting steel, the +oxy-acetylene torch is superior to almost any other possible method. + +_Arc Welding Machines._--A consideration of the function and purpose +of the various types of arc welding machines shows that the only reason for +the use of any machine is either for conversion of the current from +alternating to direct, or, if the current is already direct, then the +saving in the application of this current in the arc. + +It is practically out of the question to apply an alternating current arc +to welding for the reason that in any arc practically all the heat is +liberated at the positive electrode, which means that, in alternating +current, half the heat is liberated at each electrode as the current +changes its direction of flow or alternates. Another disadvantage of the +alternating arc is that it is difficult of control and application. + +In all arc welding by the use of the carbon arc, the positive electrode is +made the piece to be welded, while in welding with metallic electrodes this +may be either the piece to be welded of the rod that is used as a filler. +The voltage across the arc is a variable quantity, depending on the length +of the flame, its temperature and the gases liberated in the arc. With a +carbon electrode the voltage will vary from zero to forty-five volts. With +the metallic electrode the voltage will vary from zero to thirty volts. It +is, therefore, necessary for the welding machine to be able to furnish to +the arc the requisite amount of current, this amount being varied, and +furnish it at all times at the voltage required. + +The simplest welding apparatus is a resistance in series with the arc. This +is entirely satisfactory in every way except in cost of current. By the use +of resistance in series with the arc and using 220 volts as the supply, +from eighty to ninety per cent of the current is lost in heat at the +resistance. Another disadvantage is the fact that most materials change +their resistance as their temperature changes, thus making the amount of +current for the arc a variable quantity, depending on the temperature of +the resistance. + +There have been various methods originated for saving the power mentioned +and a good many machines have been put on the market for this purpose. All +of them save some power over what a plain resistance would use. Practically +all arc welding machines at the present time are motor generator sets, the +motor of which is arranged for the supply voltage and current, this motor +being direct connected to a compound wound generator delivering +approximately seventy-five volts direct current. Then by the use of a +resistance, this seventy-five volt supply is applied to the arc. Since the +voltage across the arc will vary from zero to fifty volts, this machine +will save from zero up to seventy per cent of the power that the machine +delivers. The rest of the power, of course, has to be dissipated in the +resistance used in series with the arc. + +A motor generator set which can be purchased from any electrical company, +with a long piece of fence wire wound around a piece of asbestos, gives +results equally as good and at a very small part of the first cost. + +It is possible to construct a machine which will eliminate all losses in +the resistance; in other words, eliminate all resistance in series with the +arc. A machine of this kind will save its cost within a very short time, +providing the welder is used to any extent. + +Putting it in figures, the results are as follows for average conditions. +Current at 2c per kilowatt hour, metallic electrode arc of 150 amperes, +carbon arc 500 amperes; voltage across the metallic electrode arc 20, +voltage across the carbon arc 35. Supply current 220 volts, direct. In the +case of the metallic electrode, if resistance is used, the cost of running +this arc is sixty-six cents per hour. With the carbon electrode, $2.20 per +hour. If a motor generator set with a seventy volt constant potential +machine is used for a welder, the cost will be as follows: + +Metallic electrode 25.2c. Carbon electrode 84c per hour. With a machine +which will deliver the required voltage at the arc and eliminate all the +resistance in series with the arc, the cost will be as follows: Metallic +electrode 7.2c per hour; carbon electrode 42c per hour. This is with the +understanding that the arc is held constant and continuously at its full +value. This, however, is practically impossible and the actual load factor +is approximately fifty per cent, which would mean that operating a welder +as it is usually operated, this result will be reduced to one-half of that +stated in all cases. + + + + +CHAPTER VII + +HAND FORGING AND WELDING + + +Smithing, or blacksmithing, is the process of working heated iron, steel or +other metals by forging, bending or welding them. + +_The Forge._--The metal is heated in a forge consisting of a shallow +pan for holding the fire, in the center of which is an opening from below +through which air is forced to make a hot fire. + +[Illustration: Figure 48.--Tuyere Construction on a Forge] + +Air is forced through this hole, called a "tuyere" (Figure 48) by means of +a hand bellows, a rotary fan operated with crank or lever, or with a fan +driven from an electric motor. The harder the air is driven into the fire +above the tuyere the more oxygen is furnished and the hotter the fire +becomes. + +Directly below the tuyere is an opening through which the ashes that drop +from the fire may be cleaned out. + +_The Fire._--The fire is made by placing a small piece of waste soaked +in oil, kerosene or gasoline, over the tuyere, lighting the waste, then +starting the fan or blower slowly. Gradually cover the waste, while it is +burning brightly, with a layer of soft coal. The coal will catch fire and +burn after the waste has been consumed. A piece of waste half the size of a +person's hand is ample for this purpose. + +The fuel should be "smithing coal." A lump of smithing coal breaks easily, +shows clean and even on all sides and should not break into layers. The +coal is broken into fine pieces and wet before being used on the fire. + +The fire should be kept deep enough so that there is always three or four +inches of fire below the piece of metal to be heated and there should be +enough fire above the work so that no part of the metal being heated comes +in contact with the air. The fire should be kept as small as possible while +following these rules as to depth. + +To make the fire larger, loosen the coal around the edges. To make the fire +smaller, pack wet coal around the edges in a compact mass and loosen the +fire in the center. Add fresh coal only around the edges of the fire. It +will turn to coke and can then be raked onto the fire. Blow only enough air +into the fire to keep it burning brightly, not so much that the fire is +blown up through the top of the coal pack. To prevent the fire from going +out between jobs, stick a piece of soft wood into it and cover with fresh +wet coal. + +_Tools._--The _hammer_ is a ball pene, or blacksmith's hammer, +weighing about a pound and a half. + +The _sledge_ is a heavy hammer, weighing from 5 to 20 pounds and +having a handle 30 to 36 inches long. + +The _anvil_ is a heavy piece of wrought iron (Figure 49), faced with +steel and having four legs. It has a pointed horn on one end, an +overhanging tail on the other end and a flat top. In the tail there is a +square hole called the "hardie" hole and a round one called the "spud" +hole. + +[Illustration: Figure 49.--Anvil, Showing Horn, Tail, Hardie Hole and Spud +Hole] + +_Tongs_, with handles about one foot long and jaws suitable for +holding the work, are used. To secure a firm grip on the work, the jaws may +be heated red hot and hammered into shape over the piece to be held, thus +giving a properly formed jaw. Jaws should touch the work along their entire +length. + +The _set hammer_ is a hammer, one end of whose head is square and +flat, and from this face the head tapers evenly to the other face. The +large face is about 1-1/4 inches square. + +The _flatter_ is a hammer having one face of its head flat and about +2-1/2 inches square. + +_Swages_ are hammers having specially formed faces for finishing +rounds, squares, hexagons, ovals, tapers, etc. + +_Fullers_ are hammers having a rounded face, long in one direction. +They are used for spreading metal in one direction only. + +The _hardy_ is a form of chisel with a short, square shank which may +be set into the hardie hole for cutting off hot bars. + +_Operations._--Blacksmithing consists of bending, drawing or upsetting +with the various hammers, or in punching holes. + +Bending is done over the square corners of the anvil if square cornered +bends are desired, or over the horn of the anvil if rounding bends, eyes, +hooks, etc., are wanted. + +To bend a ring or eye in the end of a bar, first figure the length of stock +needed by multiplying the diameter of the hole by 31/7, then heat the piece +to a good full red at a point this distance back from the end. Next bend +the iron over at a 90 degree angle (square) at this point. Next, heat the +iron from the bend just made clear to the point and make the eye by laying +the part that was bent square over the horn of the anvil and bending the +extreme tip into part of a circle. Keep pushing the piece farther and +farther over the horn of the anvil, bending it as you go. Do not hammer +directly over the horn of the anvil, but on the side where you are doing +the bending. + +To make the outside of a bend square, sharp and full, rather than slightly +rounding, the bent piece must be laid edgewise on the face of the anvil. +That is, after making the bend over the corner of the anvil, lay the piece +on top of the anvil so that its edge and not the flat side rests on the +anvil top. With the work in this position, strike directly against the +corner with the hammer so that the blows come in line, first with one leg +of the work, then the other, and always directly on the corner of the +piece. This operation cannot be performed by laying the work so that one +leg hangs over the anvil's corner. + +To make a shoulder on a rod or bar, heat the work and lay flat across the +top of the anvil with the point at which the shoulder is desired at the +edge of the anvil. Then place the set hammer on top of the piece, with the +outside edge of the set hammer directly over the edge of the anvil. While +hammering in this position keep the work turning continually. + +To draw stock means to make it longer and thinner by hammering. A piece to +be drawn out is usually laid across the horn of the anvil while being +struck with the hammer. The metal is then spread in only one direction in +place of being spread in every direction, as it would be if laid on the +anvil face. To draw the work, heat it to as high a temperature as it will +stand without throwing sparks and burning. The fuller may be used for +drawing metal in place of laying the work over the horn of the anvil. + +When drawing round stock, it should be first drawn out square, and when +almost down to size it may be rounded. When pointing stock, the same rule +of first drawing out square applies. + +Upsetting means to make a piece shorter in length and greater in thickness +or width, or both shorter and thicker. To upset short pieces, heat to a +bright red at the place to be upset, then stand on end on the anvil face +and hammer directly down on top until of the right form. Longer pieces may +be swung against the anvil or placed upright on a heavy piece of metal +lying on the floor or that is sunk into the floor. While standing on this +heavy piece the metal may be upset by striking down on the end with a heavy +hammer or the sledge. If a bend appears while upsetting, it should be +straightened by hammering back into shape on the anvil face. + +Light blows affect the metal for only a short distance from the point of +striking, but heavy blows tend to swell the metal more equally through its +entire length. In driving rivets that should fill the holes, heavy blows +should be struck, but to shape the end of a rivet or to make a head on a +rod, light blows should be used. + +The part of the piece that is heated most will upset the most. + +To punch a hole through metal, use a tool steel punch with its end slightly +tapering to a size a little smaller than the hole to be punched. The end of +the punch must be square across and never pointed or rounded. + +First drive the punch part way through from one side and then turn the work +over. When you turn it over, notice where the bulge appears and in that way +locate the hole and drive the punch through from the second side. This +makes a cleaner and more even hole than to drive completely through from +one side. When the punch is driven in from the second side, the place to be +punched through should be laid over the spud hole in the tail of the anvil +and the piece driven out of the work. + +Work when hot is larger than it will be after cooling. This must be +remembered when fitting parts or trouble will result. A two-foot bar of +steel will be 1/4 inch longer when red hot than when cold. + +The temperatures of iron correspond to the following colors: + + Dullest red seen in the dark... 878 + Dullest red seen in daylight... 887 + Dull red....................... 1100 + Full red....................... 1370 + Light red...................... 1550 + Orange......................... 1650 + Light orange................... 1725 + Yellow......................... 1825 + Light yellow................... 1950 + +_Bending Pipes and Tubes._--It is difficult to make bends or curves in +pipes and tubing without leaving a noticeable bulge at some point of the +work. Seamless steel tubing may be handled without very great danger of +this trouble if care is used, but iron pipe, having a seam running +lengthwise, must be given special attention to avoid opening the seam. + +Bends may be made without kinking if the tube or pipe is brought to a full +red heat all the way around its circumference and at the place where the +bend is desired. Hold the cool portion solidly in a vise and, by taking +hold of the free end, bend very slowly and with a steady pull. The pipe +must be kept at full red heat with the flames from one or more torches and +must not be hammered to produce the bend. If a sufficient purchase cannot +be secured on the free end by the hand, insert a piece of rod or a smaller +pipe into the opening. + +While making the bend, should small bulges appear, they may be hammered +back into shape before proceeding with the work. + +Tubing or pipes may be bent while being held between two flat metal +surfaces while at a bright red heat. The metal plates at each side of the +work prevent bulging. + +Another method by which tubing may be bent consists of filling completely +with tightly packed sand and fitting a solid cap or plug at each end. + +Thin brass tubing may be filled with melted resin and may be bent after the +resin cools. To remove the resin it is necessary to heat the tube, allowing +it to run out. + +Large jobs of bending should be handled in special pipe bending machines in +which the work is forced through formed rolls which prevent its bulging. + + +WELDING + +Welding with the heat of a blacksmith forge fire, or a coal or illuminating +gas fire, can only be performed with iron and steel because of the low heat +which is not localized as with the oxy-acetylene and electric processes. +Iron to be welded in this manner is heated until it reaches the temperature +indicated by an orange color, not white, as is often stated, this orange +color being slightly above 3600 degrees Fahrenheit. Steel is usually welded +at a bright red heat because of the danger of oxidizing or burning the +metal if the temperature is carried above this point. + +_The Fire._--If made in a forge, the fire should be built from good +smithing coal or, better still, from coke. Gas fires are, of course, +produced by suitable burners and require no special preparation except +adjustment of the heat to the proper degree for the size and thickness of +the metal being welded so that it will not be burned. + +A coal fire used for ordinary forging operations should not be used for +welding because of the impurities it contains. A fresh fire should be built +with a rather deep bed of coal, four to eight inches being about right for +work ordinarily met with. The fire should be kept burning until the coal +around the edges has been thoroughly coked and a sufficient quantity of +fuel should be on and around the fire so that no fresh coal will have to +be added while working. + +After the coking process has progressed sufficiently, the edges should be +packed down and the fire made as small as possible while still surrounding +the ends to be joined. The fire should not be altered by poking it while +the metal is being heated. The best form of fire to use is one having +rather high banks of coked coal on each side of the mass, leaving an +opening or channel from end to end. This will allow the added fuel to be +brought down on top of the fire with a small amount of disturbance. + +_Preparing to Weld._--If the operator is not familiar with the metal +to be handled, it is best to secure a test piece if at all possible and try +heating it and joining the ends. Various grades of iron and steel call for +different methods of handling and for different degrees of heat, the proper +method and temperature being determined best by actual test under the +hammer. + +The form of the pieces also has a great deal to do with their handling, +especially in the case of a more or less inexperienced workman. If the +pieces are at all irregular in shape, the motions should be gone through +with before the metal is heated and the best positions on the anvil as well +as in the fire determined with regard to the convenience of the workman and +speed of handling the work after being brought to a welding temperature. +Unnatural positions at the anvil should be avoided as good work is most +difficult of performance under these conditions. + +_Scarfing._--While there are many forms of welds, depending on the +relative shape of the pieces to be joined, the portions that are to meet +and form one piece are always shaped in the same general way, this shape +being called a "scarf." The end of a piece of work, when scarfed, is +tapered off on one side so that the extremity comes to a rather sharp edge. +The other side of the piece is left flat and a continuation in the same +straight plane with its side of the whole piece of work. The end is then in +the form of a bevel or mitre joint (Figure 50). + +[Illustration: Figure 50.--Scarfing Ends of Work Ready for Welding] + +Scarfing may be produced in any one of several ways. The usual method is to +bring the ends to a forging heat, at which time they are upset to give a +larger body of metal at the ends to be joined. This body of metal is then +hammered down to the taper on one side, the length of the tapered portion +being about one and a half times the thickness of the whole piece being +handled. Each piece should be given this shape before proceeding farther. + +The scarf may be produced by filing, sawing or chiseling the ends, although +this is not good practice because it is then impossible to give the desired +upset and additional metal for the weld. This added thickness is called for +by the fact that the metal burns away to a certain extent or turns to +scale, which is removed before welding. + +When the two ends have been given this shape they should not fit as closely +together as might be expected, but should touch only at the center of the +area to be joined (Figure 51). That is to say, the surface of the beveled +portion should bulge in the middle or should be convex in shape so that the +edges are separated by a little distance when the pieces are laid together +with the bevels toward each other. This is done so that the scale which is +formed on the metal by the heat of the fire can have a chance to escape +from the interior of the weld as the two parts are forced together. + +[Illustration: Figure 51.--Proper Shape of Scarfed Ends] + +If the scarf were to be formed with one or more of the edges touching each +other at the same time or before the centers did so, the scale would be +imprisoned within the body of the weld and would cause the finished work to +be weak, while possibly giving a satisfactory appearance from the outside. + +_Fluxes._--In order to assist in removing the scale and other +impurities and to make the welding surfaces as clean as possible while +being joined, various fluxing materials are used as in other methods of +welding. + +For welding iron, a flux of white sand is usually used, this material being +placed on the metal after it has been brought to a red heat in the fire. +Steel is welded with dry borax powder, this flux being applied at the same +time as the iron flux just mentioned. Borax may also be used for iron +welding and a mixture of borax with steel borings may also be used for +either class of work. Mixtures of sal ammoniac with borax have been +successfully used, the proportions being about four parts of borax to one +of sal ammoniac. Various prepared fluxing powders are on the market for +this work, practically all of them producing satisfactory results. + +After the metal has been in the fire long enough to reach a red heat, it is +removed temporarily and, if small enough in size, the ends are dipped into +a box of flux. If the pieces are large, they may simply be pulled to the +edge of the fire and the flux then sprinkled on the portions to be joined. +A greater quantity of flux is required in forge welding than in electric or +oxy-acetylene processes because of the losses in the fire. After the powder +has been applied to the surfaces, the work is returned to the fire and +heated to the welding temperature. + +_Heating the Work._--After being scarfed, the two pieces to be welded +are placed in the fire and brought to the correct temperature. This +temperature can only be recognized by experiment and experience. The metal +must be just below that point at which small sparks begin to be thrown out +of the fire and naturally this is a hard point to distinguish. At the +welding heat the metal is almost ready to flow and is about the consistency +of putty. Against the background of the fire and coal the color appears to +be a cream or very light yellow and the work feels soft as it is handled. + +It is absolutely necessary that both parts be heated uniformly and so that +they reach the welding temperature at the same time. For this reason they +should be as close together in the fire as possible and side by side. When +removed to be hammered together, time is saved if they are picked up in +such a way that when laid together naturally the beveled surfaces come +together. This makes it necessary that the workman remember whether the +scarfed side is up or down, and to assist in this it is a good thing to +mark the scarfed side with chalk or in some other noticeable manner, so +that no mistake will be made in the hurry of placing the work on the anvil. + +The common practice in heating allows the temperature to rise until the +small white sparks are seen to come from the fire. Any heating above this +point will surely result in burning that will ruin the iron or steel being +handled. The best welding heat can be discerned by the appearance of the +metal and its color after experience has been gained with this particular +material. Test welds can be made and then broken, if possible, so that the +strength gained through different degrees of heat can be known before +attempting more important work. + +_Welding._--When the work has reached the welding temperature after +having been replaced in the fire with the flux applied, the two parts are +quickly tapped to remove the loose scale from their surfaces. They are then +immediately laid across the top of the anvil, being placed in a diagonal +position if both pieces are straight. The lower piece is rested on the +anvil first with the scarf turned up and ready to receive the top piece in +the position desired. The second piece must be laid in exactly the position +it is to finally occupy because the two parts will stick together as soon +as they touch and they cannot well be moved after having once been allowed +to come in contact with each other. This part of the work must be done +without any unnecessary loss of time because the comparatively low heat at +which the parts weld allows them to cool below the working temperature in +a few seconds. + +The greatest difficulty will be experienced in withdrawing the metal from +the fire before it becomes burned and in getting it joined before it cools +below this critical point. The beveled edges of the scarf are, of course, +the first parts to cool and the weld must be made before they reach a point +at which they will not join, or else the work will be defective in +appearance and in fact. + +If the parts being handled are of such a shape that there is danger of +bending a portion back of the weld, this part may be cooled by quickly +dipping it into water before laying the work on the anvil to be joined. + +The workman uses a heavy hand hammer in making the joint, and his helper, +if one is employed, uses a sledge. With the two parts of the work in place +on the anvil, the workman strikes several light blows, the first ones being +at a point directly over the center of the weld, so that the joint will +start from this point and be worked toward the edges. After the pieces have +united the helper strikes alternate blows with his sledge, always striking +in exactly the same place as the last stroke of the workman. The hammer +blows are carried nearer and nearer to the edges of the weld and are made +steadily heavier as the work progresses. + +The aim during the first part of the operation should be to make a perfect +joint, with every part of the surfaces united, and too much attention +should not be paid to appearance, at least not enough to take any chance +with the strength of the work. + +It will be found, after completion of the weld, that there has been a loss +in length equal to one-half the thickness of the metal being welded. This +loss is occasioned by the burned metal and the scale which has been formed. + +_Finishing the Weld._--If it is possible to do so, the material should +be hammered into the shape that it should remain with the same heat that +was used for welding. It will usually be found, however, that the metal has +cooled below the point at which it can be worked to advantage. It should +then be replaced in the fire and brought back to a forging heat. + +[Illustration: Figure 52.--Upsetting and Scarfing the End of a Rod] + +While shaping the work at this forging heat every part that has been at a +red heat should be hammered with uniformly light and even blows as it +cools. This restores the grain and strength of the iron or steel to a great +extent and makes the unavoidable weakness as small as possible. + +_Forms of Welds._--The simplest of all welds is that called a "lap +weld." This is made between the ends of two pieces of equal size and +similar form by scarfing them as described and then laying one on top of +the other while they are hammered together. + +A butt weld (Figure 52) is made between the ends of two pieces of shaft or +other bar shapes by upsetting the ends so that they have a considerable +flare and shaping the face of the end so that it is slightly higher in the +center than around the edges, this being done to make the centers come +together first. The pieces are heated and pushed into contact, after which +the hammering is done as with any other weld. + +[Illustration: Figure 53.--Scarfing for a T Weld] + +A form similar to the butt weld in some ways is used for joining the end of +a bar to a flat surface and is called a jump weld. The bar is shaped in the +same way as for a butt weld. The flat plate may be left as it is, but if +possible a depression should be made at the point where the shaft is to be +placed. With the two parts heated as usual, the bar is dropped into +position and hammered from above. As soon as the center of the weld has +been made perfect, the joint may be finished with a fuller driven all the +way around the edge of the joint. + +When it is required to join a bar to another bar or to the edge of any +piece at right angles the work is called a "T" weld from its shape when +complete (Figure 53). The end of the bar is scarfed as described and the +point of the other bar or piece where the weld is to be made is hammered so +that it tapers to a thin edge like one-half of a circular depression. The +pieces are then laid together and hammered as for a lap weld. + +The ends of heavy bar shapes are often joined with a "V," or cleft, weld. +One bar end is shaped so that it is tapering on both sides and comes to a +broad edge like the end of a chisel. The other bar is heated to a forging +temperature and then slit open in a lengthwise direction so that the +V-shaped opening which is formed will just receive the pointed edge of the +first piece. With the work at welding heat, the two parts are driven +together by hammering on the rear ends and the hammering then continues as +with a lap weld, except that the work is turned over to complete both sides +of the joint. + +[Illustration: Figure 54.-Splitting Ends to Be Welded in Thin Work] + +The forms so far described all require that the pieces be laid together in +the proper position after removal from the fire, and this always causes a +slight loss of time and a consequent lowering of the temperature. With very +light stock, this fall of temperature would be so rapid that the weld would +be unsuccessful, and in this case the "lock" weld is resorted to. The ends +of the two pieces to be joined are split for some distance back, and +one-half of each end is bent up and the other half down (Figure 54). The +two are then pushed together and placed in the fire in this position. When +the welding heat is reached, it is only necessary to take the work out of +the fire and hammer the parts together, inasmuch as they are already in the +correct position. + +Other forms of welds in which the parts are too small to retain their heat, +can be made by first riveting them together or cutting them so that they +can be temporarily fastened in any convenient way when first placed in the +fire. + + + + +CHAPTER VIII + +SOLDERING, BRAZING AND THERMIT WELDING + + +SOLDERING + +Common solder is an alloy of one-half lead with one-half tin, and is called +"half and half." Hard solder is made with two-thirds tin and one-third +lead. These alloys, when heated, are used to join surfaces of the same or +dissimilar metals such as copper, brass, lead, galvanized iron, zinc, +tinned plate, etc. These metals are easily joined, but the action of solder +with iron, steel and aluminum is not so satisfactory and requires greater +care and skill. + +The solder is caused to make a perfect union with the surfaces treated with +the help of heat from a soldering iron. The soldering iron is made from a +piece of copper, pointed at one end and with the other end attached to an +iron rod and wooden handle. A flux is used to remove impurities from the +joint and allow the solder to secure a firm union with the metal surface. +The iron, and in many cases the work, is heated with a gasoline blow torch, +a small gas furnace, an electric heater or an acetylene and air torch. + +The gasoline torch which is most commonly used should be filled two-thirds +full of gasoline through the hole in the bottom, which is closed by a screw +plug. After working the small hand pump for 10 to 20 strokes, hold the palm +of your hand over the end of the large iron tube on top of the torch and +open the gasoline needle valve about a half turn. Hold the torch so that +the liquid runs down into the cup below the tube and fills it. Shut the +gasoline needle valve, wipe the hands dry, and set fire to the fuel in the +cup. Just as the gasoline fire goes out, open the gasoline needle valve +about a half turn and hold a lighted match at the end of the iron tube to +ignite the mixture of vaporized gasoline and air. Open or close the needle +valve to secure a flame about 4 inches long. + +On top of the iron tube from which the flame issues there is a rest for +supporting the soldering iron with the copper part in the flame. Place the +iron in the flame and allow it to remain until the copper becomes very hot, +not quite red, but almost so. + +A new soldering iron or one that has been misused will have to be "tinned" +before using. To do this, take the iron from the fire while very hot and +rub the tip on some flux or dip it into soldering acid. Then rub the tip of +the iron on a stick of solder or rub the solder on the iron. If the solder +melts off the stick without coating the end of the iron, allow a few drops +to fall on a piece of tin plate, then nil the end of the iron on the tin +plate with considerable force. Alternately rub the iron on the solder and +dip into flux until the tip has a coating of bright solder for about half +an inch from the end. If the iron is in very bad shape, it may be necessary +to scrape or file the end before dipping in the flux for the first time. +After the end of the iron is tinned in this way, replace it on the rest of +the torch so that the tinned point is not directly in the flame, turning +the flame down to accomplish this. + +_Flux._--The commonest flux, which is called "soldering acid," is made +by placing pieces of zinc in muriatic (hydrochloric) acid contained in a +heavy glass or porcelain dish. There will be bubbles and considerable heat +evolved and zinc should be added until this action ceases and the zinc +remains in the liquid, which is now chloride of zinc. + +This soldering acid may be used on any metal to be soldered by applying +with a brush or swab. For electrical work, this acid should be made neutral +by the addition of one part ammonia and one part water to each three parts +of the acid. This neutralized flux will not corrode metal as will the +ordinary acid. + +Powdered resin makes a good flux for lead, tin plate, galvanized iron and +aluminum. Tallow, olive oil, beeswax and vaseline are also used for this +purpose. Muriatic acid may be used for zinc or galvanized iron without the +addition of the zinc, as described in making zinc chloride. The addition of +two heaping teaspoonfuls of sal ammoniac to each pint of the chloride of +zinc is sometimes found to improve its action. + +_Soldering Metal Parts._--All surfaces to be joined should be fitted +to each other as accurately as possible and then thoroughly cleaned with a +file, emery cloth, scratch bush or by dipping in lye. Work may be cleaned +by dipping it into nitric acid which has been diluted with an equal volume +of water. The work should be heated as hot as possible without danger of +melting, as this causes the solder to flow better and secure a much better +hold on the surfaces. Hard solder gives better results than half and half, +but is more difficult to work. It is very important that the soldering iron +be kept at a high heat during all work, otherwise the solder will only +stick to the surfaces and will not join with them. + +Sweating is a form of soldering in which the surfaces of the work are first +covered with a thin layer of solder by rubbing them with the hot iron after +it has been dipped in or touched to the soldering stick. These surfaces are +then placed in contact and heated to a point at which the solder melts and +unites. Sweating is much to be preferred to ordinary soldering where the +form of the work permits it. This is the only method which should ever be +used when a fitting is to be placed over the end of a length of tube. + +_Soldering Holes._--Clean the surfaces for some distance around the +hole until they are bright, and apply flux while holding the hot iron near +the hole. Touch the tip of the iron to some solder until the solder is +picked up on the iron, and then place this solder, which was just picked +up, around the edge of the hole. It will leave the soldering iron and stick +to the metal. Keep adding solder in this way until the hole has been closed +up by working from the edges and building toward the center. After the hole +is closed, apply more flux to the job and smooth over with the hot iron +until there are no rough spots. Should the solder refuse to flow smoothly, +the iron is not hot enough. + +_Soldering Seams._--Clean back from the seam or split for at least +half an inch all around and then build up the solder in the same way as was +done with the hole. After closing the opening, apply more flux to the work +and run the hot iron lengthwise to smooth the job. + +_Soldering Wires._--Clean all insulation from the ends to be soldered +and scrape the ends bright. Lay the ends parallel to each other and, +starting at the middle of the cleaned portion, wrap the ends around each +other, one being wrapped to the right, the other to the left. Hold the hot +iron under the twisted joint and apply flux to the wire. Then dip the iron +in the solder and apply to the twisted portion until the spaces between the +wires are filled with solder. Finish by smoothing the joint and cleaning +away all excess metal by rubbing the hot iron lengthwise. The joint should +now be covered with a layer of rubber tape and this covered with a layer of +ordinary friction tape. + +_Steel and Iron._--Steel surfaces should be cleaned, then covered with +clear muriatic acid. While the acid is on the metal, rub with a stick of +zinc and then tin the surfaces with the hot iron as directed. Cast iron +should be cleaned and dipped in strong lye to remove grease. Wash the lye +away with clean water and cover with muriatic acid as with steel. Then rub +with a piece of zinc and tin the surfaces by using resin as a flux. + +It is very difficult to solder aluminum with ordinary solder. A special +aluminum solder should be secured, which is easily applied and makes a +strong joint. Zinc or phosphor tin may be used in place of ordinary solder +to tin the surfaces or to fill small holes or cracks. The aluminum must be +thoroughly heated before attempting to solder and the flux may be either +resin or soldering acid. The aluminum must be thoroughly cleaned with +dilute nitric acid and kept hot while the solder is applied by forcible +rubbing with the hot iron. + + +BRAZING + +This is a process for joining metal parts, very similar to soldering, +except that brass is used to make the joint in place of the lead and zinc +alloys which form solder. Brazing must not be attempted on metals whose +melting point is less than that of sheet brass. + +Two pieces of brass to be brazed together are heated to a temperature at +which the brass used in the process will melt and flow between the +surfaces. The brass amalgamates with the surfaces and makes a very strong +and perfect joint, which is far superior to any form of soldering where the +work allows this process to be used, and in many cases is the equal of +welding for the particular field in which it applies. + +_Brazing Heat and Tools._--The metal commonly used for brazing will +melt at heats between 1350 and 1650 Fahrenheit. To bring the parts to +this temperature, various methods are in use, using solid, liquid or +gaseous fuels. While brazing may be accomplished with the fire of the +blacksmith forge, this method is seldom satisfactory because of the +difficulty of making a sufficiently clean fire with smithing coal, and it +should not be used when anything else is available. Large jobs of brazing +may be handled with a charcoal fire built in the forge, as this fuel +produces a very satisfactory and clean fire. The only objection is in the +difficulty of confining the heat to the desired parts of the work. + +The most satisfactory fire is that from a fuel gas torch built for this +work. These torches are simply forms of Bunsen burners, mixing the proper +quantity of air with the gas to bring about a perfect combustion. Hose +lines lead to the mixing tube of the gas torch, one line carrying the gas +and the other air under a moderate pressure. The air line is often +dispensed with, allowing the gas to draw air into the burner on the +injector principle, much the same as with illuminating gas burners for use +with incandescent mantles. Valves are provided with which the operator may +regulate the amount of both gas and air, and ordinarily the quality and +intensity of the flame. + +When gas is not available, recourse may be had to the gasoline torch made +for brazing. This torch is built in the same way as the small portable +gasoline torches for soldering operations, with the exception that two +regulating needle valves are incorporated in place of only one. + +The torches are carried on a framework, which also supports the work being +handled. Fuel is forced to the torch from a large tank of gasoline into +which air pressure is pumped by hand. The torches are regulated to give +the desired flame by means of the needle valves in much the same way as +with any other form of pressure torch using liquid fuel. + +Another very satisfactory form of torch for brazing is the acetylene-air +combination described in the chapter on welding instruments. This torch +gives the correct degree of heat and may be regulated to give a clean and +easily controlled flame. + +Regardless of the source of heat, the fire or flame must be adjusted so +that no soot is deposited on the metal surfaces of the work. This can only +be accomplished by supplying the exact amounts of gas and air that will +produce a complete burning of the fuel. With the brazing torches in common +use two heads are furnished, being supplied from the same source of fuel, +but with separate regulating devices. The torches are adjustably mounted in +such a way that the flames may be directed toward each other, heating two +sides of the work at the same time and allowing the pieces to be completely +surrounded with the flame. + +Except for the source of heat, but one tool is required for ordinary +brazing operations, this being a spatula formed by flattening one end of a +quarter-inch steel rod. The spatula is used for placing the brazing metal +on the work and for handling the flux that is required in this work as in +all other similar operations. + +_Spelter._--The metal that is melted into the joint is called spelter. +While this name originally applied to but one particular grade or +composition of metal, common use has extended the meaning until it is +generally applied to all grades. + +Spelter is variously composed of alloys containing copper, zinc, tin and +antimony, the mixture employed depending on the work to be done. The +different grades are of varying hardness, the harder kinds melting at +higher temperatures than the soft ones and producing a stronger joint when +used. The reason for not using hard spelter in all cases is the increased +difficulty of working it and the fact that its melting point is so near to +some of the metals brazed that there is great danger of melting the work as +well as the spelter. + +The hardest grade of spelter is made from three-fourths copper with +one-fourth zinc and is used for working on malleable and cast iron and for +steel. + +This hard spelter melts at about 1650 and is correspondingly difficult to +handle. + +A spelter suitable for working with copper is made from equal parts of +copper and zinc, melting at about 1400 Fahrenheit, 500 below the melting +point of the copper itself. A still softer brazing metal is composed of +half copper, three-eighths zinc and one-eighth tin. This grade is used for +fastening brass to iron and copper and for working with large pieces of +brass to brass. For brazing thin sheet brass and light brass castings, a +metal is used which contains two-thirds tin and one-third antimony. The +low melting point of this last composition makes it very easy to work with +and the danger of melting the work is very slight. However, as might be +expected, a comparatively weak joint is secured, which will not stand any +great strain. + +All of the above brazing metals are used in powder form so that they may be +applied with the spatula where the joint is exposed on the outside of the +work. In case it is necessary to braze on the inside of a tube or any deep +recess, the spelter may be placed on a flat rod long enough to reach to +the farthest point. By distributing the spelter at the proper points along +the rod it may be placed at the right points by turning the rod over after +inserting into the recess. + +_Flux._--In order to remove the oxides produced under brazing heat and +to allow the brazing metal to flow freely into place, a flux of some kind +must be used. The commonest flux is simply a pure calcined borax powder, +that is, a borax powder that has been heated until practically all the +water has been driven off. + +Calcined borax may also be mixed with about 15 per cent of sal ammoniac to +make a satisfactory fluxing powder. It is absolutely necessary to use flux +of some kind and a part of whatever is used should be made into a paste +with water so that it can be applied to the joint to be brazed before +heating. The remainder of the powder should be kept dry for use during the +operation and after the heat has been applied. + +_Preparing the Work._--The surfaces to be brazed are first thoroughly +cleaned with files, emery cloth or sand paper. If the work is greasy, it +should be dipped into a bath of lye or hot soda water so that all trace of +oil is removed. The parts are then placed in the relation to each other +that they are to occupy when the work has been completed. The edges to be +joined should make a secure and tight fit, and should match each other at +all points so that the smallest possible space is left between them. This +fit should not be so tight that it is necessary to force the work into +place, neither should it be loose enough to allow any considerable space +between the surfaces. The molten spelter will penetrate between surfaces +that water will flow between when the work and spelter have both been +brought to the proper heat. It is, of course, necessary that the two parts +have a sufficient number of points of contact so that they will remain in +the proper relative position. + +The work is placed on the surface of the brazing table in such a position +that the flame from the torches will strike the parts to be heated, and +with the joint in such a position that the melted spelter will flow down +through it and fill every possible part of the space between the surfaces +under the action of gravity. That means that the edge of the joint must be +uppermost and the crack to be filled must not lie horizontal, but at the +greatest slant possible. Better than any degree of slant would be to have +the line of the joint vertical. + +The work is braced up or clamped in the proper position before commencing +to braze, and it is best to place fire brick in such positions that it will +be impossible for cooling draughts of air to reach the heated metal should +the flame be removed temporarily during the process. In case there is a +large body of iron, steel or copper to be handled, it is often advisable to +place charcoal around the work, igniting this with the flame of the torch +before starting to braze so that the metal will be maintained at the +correct heat without depending entirely on the torch. + +When handling brass pieces having thin sections there is danger of melting +the brass and causing it to flow away from under the flame, with the result +that the work is ruined. If, in the judgment of the workman, this may +happen with the particular job in hand, it is well to build up a mould of +fire clay back of the thin parts or preferably back of the whole piece, so +that the metal will have the necessary support. This mould may be made by +mixing the fire clay into a stiff paste with water and then packing it +against the piece to be supported tightly enough so that the form will be +retained even if the metal softens. + +_Brazing._--With the work in place, it should be well covered with the +paste of flux and water, then heated until this flux boils up and runs over +the surfaces. Spelter is then placed in such a position that it will run +into the joint and the heat is continued or increased until the spelter +melts and flows in between the two surfaces. The flame should surround the +work during the heating so that outside air is excluded as far as is +possible to prevent excessive oxidization. + +When handling brass or copper, the flame should not be directed so that its +center strikes the metal squarely, but so that it glances from one side or +the other. Directing the flame straight against the work is often the cause +of melting the pieces before the operation is completed. When brazing two +different metals, the flame should play only on the one that melts at the +higher temperature, the lower melting part receiving its heat from the +other. This avoids the danger of melting one before the other reaches the +brazing point. + +The heat should be continued only long enough to cause the spelter to flow +into place and no longer. Prolonged heating of any metal can do nothing but +oxidize and weaken it, and this practice should be avoided as much as +possible. If the spelter melts into small globules in place of flowing, it +may be caused to spread and run into the joint by lightly tapping the work. +More dry flux may be added with the spatula if the tapping does not produce +the desired result. + +Excessive use of flux, especially toward the end of the work, will result +in a very hard surface on all the work, a surface which will be extremely +difficult to finish properly. This trouble will be present to a certain +extent anyway, but it may be lessened by a vigorous scraping with a wire +brush just as soon as the work is removed from the fire. If allowed to cool +before cleaning, the final appearance will not be as good as with the +surplus metal and scale removed immediately upon completing the job. + +After the work has been cleaned with the brush it may be allowed to cool +and finished to the desired shape, size and surface by filing and +polishing. When filed, a very thin line of brass should appear where the +crack was at the beginning of the work. If it is desired to avoid a square +shoulder and fill in an angle joint to make it rounding, the filling is +best accomplished by winding a coil of very thin brass wire around the part +of the work that projects and then causing this to flow itself or else +allow the spelter to fill the spaces between the layers of wire. Copper +wire may also be used for this purpose, the spaces being filled with +melted spelter. + + +THERMIT WELDING + +The process of welding which makes use of the great heat produced by oxygen +combining with aluminum is known as the Thermit process and was perfected +by Dr. Hans Goldschmidt. The process, which is controlled by the +Goldschmidt Thermit Company, makes use of a mixture of finely powdered +aluminum with an oxide of iron called by the trade name, Thermit. + +The reaction is started with a special ignition powder, such as barium +superoxide and aluminum, and the oxygen from the iron oxide combining with +the aluminum, producing a mass of superheated steel at about 5000 degrees +Fahrenheit. After the reaction, which takes from. 30 seconds to a minute, +the molten metal is drawn from the crucible on to the surfaces to be +joined. Its extreme heat fuses the metal and a perfect joint is the result. +This process is suited for welding iron or steel parts of comparatively +large size. + +_Preparation._--The parts to be joined are thoroughly cleaned on the +surfaces and for several inches back from the joint, after which they are +supported in place. The surfaces between which the metal will flow are +separated from 1/4 to 1 inch, depending on the size of the parts, but +cutting or drilling part of the metal away. After this separation is made +for allowing the entrance of new metal, the effects of contraction of the +molten steel are cared for by preheating adjacent parts or by forcing the +ends apart with wedges and jacks. The amount of this last separation must +be determined by the shape and proportions of the parts in the same way as +would be done for any other class of welding which heats the parts to a +melting point. + +Yellow wax, which has been warmed until plastic, is then placed around the +joint to form a collar, the wax completely filling the space between the +ends and being provided with vent holes by imbedding a piece of stout cord, +which is pulled out after the wax cools. + +A retaining mould (Figure 55) made from sheet steel or fire brick is then +placed around the parts. This mould is then filled with a mixture of one +part fire clay, one part ground fire brick and one part fire sand. These +materials are well mixed and moistened with enough water so that they will +pack. This mixture is then placed in the mould, filling the space between +the walls and the wax, and is packed hard with a rammer so that the +material forms a wall several inches thick between any point of the mould +and the wax. The mixture must be placed in the mould in small quantities +and packed tight as the filling progresses. + +[Illustration: Figure 55.--Thermit Mould Construction] + +Three or more openings are provided through this moulding material by the +insertion of wood or pipe forms. One of these openings will lead from the +lowest point of the wax pattern and is used for the introduction of the +preheating flame. Another opening leads from the top of the mould into this +preheating gate, opening into the preheating gate at a point about one inch +from the wax pattern. Openings, called risers, are then provided from each +of the high points of the wax pattern to the top of the mould, these risers +ending at the top in a shallow basin. The molten metal comes up into these +risers and cares for contraction of the casting, as well as avoiding +defects in the collar of the weld. After the moulding material is well +packed, these gate patterns are tapped lightly and withdrawn, except in the +case of the metal pipes which are placed at points at which it would be +impossible to withdraw a pattern. + +_Preheating._--The ends to be welded are brought to a bright red heat +by introducing the flame from a torch through the preheating gate. The +torch must use either gasoline or kerosene, and not crude oil, as the crude +oil deposits too much carbon on the parts. Preheating of other adjacent +parts to care for contraction is done at this time by an additional torch +burner. + +The heating flame is started gently at first and gradually increased. The +wax will melt and may be allowed to run out of the preheating gate by +removing the flame at intervals for a few seconds. The heat is continued +until the mould is thoroughly dried and the parts to be joined are brought +to the red heat required. This leaves a mould just the shape of the wax +pattern. + +The heating gate should then be plugged with a sand core, iron plug or +piece of fitted fire brick, and backed up with several shovels full of the +moulding mixture, well packed. + +[Illustration: Figure 56.--Thermit Crucible Plug. +_A_, Hard burn magnesia stone; +_B_, Magnesia thimble; +_C_, Refractory sand; +_D_, Metal disc; +_E_, Asbestos washer; +_F_, Tapping pin] + +_Thermit Metal._--The reaction takes place in a special crucible lined +with magnesia tar, which is baked at a red heat until the tar is driven off +and the magnesia left. This lining should last from twelve to fifteen +reactions. This magnesia lining ends at the bottom of the crucible in a +ring of magnesia stone and this ring carries a magnesia thimble through +which the molten steel passes on its way to the mould. It will usually be +necessary to renew this thimble after each reaction. This lower opening is +closed before filling the crucible with thermit by means of a small disc or +iron carrying a stem, which is called a tapping pin (Figure 56). This pin, +_F_, is placed in the thimble with the stem extending down through the +opening and exposing about two inches. The top of this pin is covered with +an asbestos, washer, _E_, then with another iron disc. _D_, and +finally with a layer of refractory sand. The crucible is tapped by knocking +the stem of the pin upwards with a spade or piece of flat iron about four +feet long. + +The charge of thermit is added by placing a few handfuls over the +refractory sand and then pouring in the balance required. The amount of +thermit required is calculated from the wax used. The wax is weighed before +and after filling _the entire space that the thermit will occupy_. +This does not mean only the wax collar, but the space of the mould with all +gates filled with wax. The number of pounds of wax required for this +filling multiplied by 25 will give the number of pounds of thermit to be +used. To this quantity of thermit should be added I per cent of pure +manganese, 1 per cent nickel thermit and 15 per cent of steel punchings. + +It is necessary, when more than 10 pounds of thermit will be used, to mix +steel punchings not exceeding 3/8 inch diameter by 1/8 inch thick with the +powder in order to sufficiently retard the intensity of the reaction. + +Half a teaspoonful of ignition powder is placed on top of the thermit +charge and ignited with a storm match or piece of red hot iron. The cover +should be immediately closed on the top of the crucible and the operator +should get away to a safe distance because of the metal that may be thrown +out of the crucible. + +After allowing about 30 seconds to a minute for the reaction to take place +and the slag to rise to the top of the crucible, the tapping pin is struck +from below and the molten metal allowed to run into the mould. The mould +should be allowed to remain in place as long as possible, preferably over +night, so as to anneal the steel in the weld, but in no case should it be +disturbed for several hours after pouring. After removing the mould, drill +through the metal left in the riser and gates and knock these sections off. +No part of the collar should be removed unless absolutely necessary. + + + + +CHAPTER IX + +OXYGEN PROCESS FOR REMOVAL OF CARBON + + +Until recently the methods used for removing carbon deposits from gas +engine cylinders were very impractical and unsatisfactory. The job meant +dismantling the motor, tearing out all parts, and scraping the pistons and +cylinder walls by hand. + +The work was never done thoroughly. It required hours of time to do it, and +then there was always the danger of injuring the inside of the cylinders. + +These methods have been to a large extent superseded by the use of oxygen +under pressure. The various devices that are being manufactured are known +as carbon removers, decarbonizers, etc., and large numbers of them are in +use in the automobile and gasoline traction motor industry. + +_Outfit._--The oxygen carbon cleaner consists of a high pressure +oxygen cylinder with automatic reducing valve, usually constructed on the +diaphragm principle, thus assuring positive regulation of pressure. This +valve is fitted with a pressure gauge, rubber hose, decarbonizing torch +with shut off and flexible tube for insertion into the chamber from which +the carbon is to be removed. + +There should also be an asbestos swab for swabbing out the inside of the +cylinder or other chamber with kerosene previous to starting the operation. +The action consists in simply burning the carbon to a fine dust in the +presence of the stream of oxygen, this dust being then blown out. + +_Operation._--The following are instructions for operating the +cleaner:-- + +(1) Close valve in gasoline supply line and start the motor, letting it run +until the gasoline is exhausted. + +(2) If the cylinders be T or L head, remove either the inlet or the exhaust +valve cap, or a spark plug if the cap is tight. If the cylinders have +overhead valves, remove a spark plug. If any spark plug is then remaining +in the cylinder it should be removed and an old one or an iron pipe plug +substituted. + +(3) Raise the piston of the cylinder first to be cleaned to the top of the +compression stroke and continue this from cylinder to cylinder as the work +progresses. + +(4) In motors where carbon has been burned hard, the cylinder interior +should then be swabbed with kerosene before proceeding. Work the swab, +saturated with kerosene, around the inside of the cylinder until all the +carbon has been moistened with the oil. This same swab may be used to +ignite the gas in the cylinder in place of using a match or taper. + +(5) Make all connections to the oxygen cylinder. + +(6) Insert the torch nozzle in the cylinder, open the torch valve gradually +and regulate to about two lbs. pressure. Manipulate the nozzle inside the +cylinder and light a match or other flame at the opening so that the carbon +starts to burn. Cover the various points within the cylinder and when there +is no further burning the carbon has been removed. The regulating and +oxygen tank valves are operated in exactly the same way as for welding as +previously explained. + + +It should be carefully noted that when the piston is up, ready to start the +operation, both valves must be closed. There will be a considerable display +of sparks while this operation is taking place, but they will not set fire +to the grease and oil. Care should be used to see that no gasoline is +about. + + + + +INDEX + + +Acetylene + filtering + generators + in tanks + piping + properties of + purification of +Acetylene-air torches +Air + oxygen from +Alloys + table of +Alloy steel +Aluminum + alloys + welding +Annealing +Anvil +Arc welding, electric + machines +Asbestos, use of, in welding + +Babbitt +Bending pipes and tubes +Bessemer steel +Beveling +Brass + welding +Brazing + electric + heat and tools + spelter +Bronze + welding +Butt welding + +Calcium carbide +Carbide + storage of, Fire Underwriters' Rules + to water generator +Carbon removal + by oxygen process +Case hardening steel +Cast iron + welding +Champfering +Charging generator +Chlorate of potash oxygen +Conductivity of metals +Copper + alloys + welding +Crucible steel +Cutting, oxy-acetylene + torches + +Dissolved acetylene + +Electric arc welding +Electric welding + troubles and remedies +Expansion of metals + +Flame, welding +Fluxes + for brazing + for soldering +Forge + fire + practice + tools + tuvere construction of + welding + welding preparation + welds, forms of +Forging + +Gas holders +Gases, heating power of +Generator, acetylene + carbide to water + construction +Generator + location of + operation and care of + overheating + requirements + water to carbide +German silver +Gloves +Goggles + +Hand forging +Hardening steel +Heat treatment of steel +Hildebrandt process +Hose + +Injectors, adjuster +Iron + cast + grades of + malleable cast + wrought + +Jump weld + +Lap welding +Lead +Linde process +Liquid air oxygen + +Magnalium +Malleable iron + welding +Melting points of metals +Metal alloys, table of +Metals + characteristics of + conductivity of + expansion of + heat treatment of + melting points of + tensile strength of + weight of + +Nickel +Nozzle sizes, torch + +Open hearth steel +Oxy-acetylene cutting + welding practice +Oxygen + cylinders + weight of + +Pipes, bending +Platinum +Preheating + +Removal of carbon by oxygen process +Resistance method of electric welding +Restoration of steel +Rods, welding + +Safety devices +Scarfing +Solder +Soldering + flux + holes + seams + steel and iron + wires +Spelter +Spot welding +Steel + alloys + Bessemer + crucible + heat treatment of + open hearth + restoration of + tensile strength of + welding +Strength of metals + +Tank valves +Tapering +Tables of welding information +Tempering steel +Thermit metal + preheating + preparation + welding +Tin +Torch + acetylene-air + care + construction + cutting + high pressure + low pressure + medium pressure + nozzles + practice + +Valves, regulating + tank + +Water + to carbide generator +Welding aluminum + brass + bronze + butt + cast iron + copper + electric + electric arc + flame + forge + information and tables + instruments + lap + malleable iron + materials + practice, oxy-acetylene + rods + spot + steel + table + thermit + torches + various metals + wrought iron +Wrought iron + welding + +Zinc + + + + + +End of the Project Gutenberg EBook of Oxy-Acetylene Welding and Cutting +by Harold P. 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Do not change or edit the +header without written permission. + +Please read the "legal small print," and other information about the +eBook and Project Gutenberg at the bottom of this file. Included is +important information about your specific rights and restrictions in +how the file may be used. You can also find out about how to make a +donation to Project Gutenberg, and how to get involved. + + +**Welcome To The World of Free Plain Vanilla Electronic Texts** + +**eBooks Readable By Both Humans and By Computers, Since 1971** + +*****These eBooks Were Prepared By Thousands of Volunteers!***** + + +Title: Oxy-Acetylene Welding and Cutting + Electric, Forge and Thermit Welding together with related methods + and materials used in metal working and the oxygen process + for removal of carbon + +Author: Harold P. Manly + +Release Date: April, 2005 [EBook #7969] +[Yes, we are more than one year ahead of schedule] +[This file was first posted on June 7, 2003] + +Edition: 10 + +Language: English + +Character set encoding: ISO-Latin-1 + +*** START OF THE PROJECT GUTENBERG EBOOK OXY-ACETYLENE WELDING AND CUTTING *** + + + + +Produced by Juliet Sutherland, John Argus, Tonya Allen, +Charles Franks and the Online Distributed Proofreading Team. + + + + +Oxy-Acetylene Welding and Cutting + +Electric, Forge and Thermit Welding + +Together with Related Methods and Materials Used in Metal Working +And +The Oxygen Process for Removal of Carbon + +By +HAROLD P. MANLY + + + + +PREFACE + +In the preparation of this work, the object has been to cover not only the +several processes of welding, but also those other processes which are so +closely allied in method and results as to make them a part of the whole +subject of joining metal to metal with the aid of heat. + +The workman who wishes to handle his trade from start to finish finds that +it is necessary to become familiar with certain other operations which +precede or follow the actual joining of the metal parts, the purpose of +these operations being to add or retain certain desirable qualities in the +materials being handled. For this reason the following subjects have been +included: Annealing, tempering, hardening, heat treatment and the +restoration of steel. + +In order that the user may understand the underlying principles and the +materials employed in this work, much practical information is given on the +uses and characteristics of the various metals; on the production, handling +and use of the gases and other materials which are a part of the equipment; +and on the tools and accessories for the production and handling of these +materials. + +An examination will show that the greatest usefulness of this book lies in +the fact that all necessary information and data has been included in one +volume, making it possible for the workman to use one source for securing a +knowledge of both principle and practice, preparation and finishing of the +work, and both large and small repair work as well as manufacturing methods +used in metal working. + +An effort has been made to eliminate all matter which is not of direct +usefulness in practical work, while including all that those engaged in +this trade find necessary. To this end, the descriptions have been limited +to those methods and accessories which are found in actual use today. For +the same reason, the work includes the application of the rules laid down +by the insurance underwriters which govern this work as well as +instructions for the proper care and handling of the generators, torches +and materials found in the shop. + +Special attention has been given to definite directions for handling the +different metals and alloys which must be handled. The instructions have +been arranged to form rules which are placed in the order of their use +during the work described and the work has been subdivided in such a way +that it will be found possible to secure information on any one point +desired without the necessity of spending time in other fields. + +The facts which the expert welder and metalworker finds it most necessary +to have readily available have been secured, and prepared especially for +this work, and those of most general use have been combined with the +chapter on welding practice to which they apply. + +The size of this volume has been kept as small as possible, but an +examination of the alphabetical index will show that the range of subjects +and details covered is complete in all respects. This has been accomplished +through careful classification of the contents and the elimination of all +repetition and all theoretical, historical and similar matter that is not +absolutely necessary. + +Free use has been made of the information given by those manufacturers who +are recognized as the leaders in their respective fields, thus insuring +that the work is thoroughly practical and that it represents present day +methods and practice. + +THE AUTHOR. + + + + +CONTENTS + + CHAPTER I + +METALS AND ALLOYS--HEAT TREATMENT:--The Use and Characteristics of the +Industrial Alloys and Metal Elements--Annealing, Hardening, Tempering and +Case Hardening of Steel + + CHAPTER II + +WELDING MATERIALS:--Production, Handling and Use of the Gases, Oxygen and +Acetylene--Welding Rods--Fluxes--Supplies and Fixtures + + CHAPTER III + +ACETYLENE GENERATORS:--Generator Requirements and Types--Construction--Care +and Operation of Generators. + + CHAPTER IV + +WELDING INSTRUMENTS:--Tank and Regulating Valves and Gauges--High, Low and +Medium Pressure Torches--Cutting Torches--Acetylene-Air Torches + + CHAPTER V + +OXY-ACETYLENE WELDING PRACTICE:--Preparation of Work--Torch Practice-- +Control of the Flame--Welding Various Metals and Alloys--Tables of +Information Required in Welding Operations + + CHAPTER VI + +ELECTRIC WELDING:--Resistance Method--Butt, Spot and Lap Welding--Troubles +and Remedies--Electric Arc Welding + + CHAPTER VII + +HAND FORGING AND WELDING:--Blacksmithing, Forging and Bending--Forge +Welding Methods + + CHAPTER VIII + +SOLDERING, BRAZING AND THERMIT WELDING:--Soldering Materials and Practice-- +Brazing--Thermit Welding + + CHAPTER IX + +OXYGEN PROCESS FOR REMOVAL OF CARBON + +INDEX + + + + + +OXY-ACETYLENE WELDING AND CUTTING, ELECTRIC AND THERMIT WELDING + + + + +CHAPTER I + +METALS AND THEIR ALLOYS--HEAT TREATMENT + + +THE METALS + +_Iron._--Iron, in its pure state, is a soft, white, easily worked +metal. It is the most important of all the metallic elements, and is, next +to aluminum, the commonest metal found in the earth. + +Mechanically speaking, we have three kinds of iron: wrought iron, cast iron +and steel. Wrought iron is very nearly pure iron; cast iron contains carbon +and silicon, also chemical impurities; and steel contains a definite +proportion of carbon, but in smaller quantities than cast iron. + +Pure iron is never obtained commercially, the metal always being mixed with +various proportions of carbon, silicon, sulphur, phosphorus, and other +elements, making it more or less suitable for different purposes. Iron is +magnetic to the extent that it is attracted by magnets, but it does not +retain magnetism itself, as does steel. Iron forms, with other elements, +many important combinations, such as its alloys, oxides, and sulphates. + +[Illustration: Figure 1.--Section Through a Blast Furnace] + +_Cast Iron._--Metallic iron is separated from iron ore in the blast +furnace (Figure 1), and when allowed to run into moulds is called cast +iron. This form is used for engine cylinders and pistons, for brackets, +covers, housings and at any point where its brittleness is not +objectionable. Good cast iron breaks with a gray fracture, is free from +blowholes or roughness, and is easily machined, drilled, etc. Cast iron is +slightly lighter than steel, melts at about 2,400 degrees in practice, is +about one-eighth as good an electrical conductor as copper and has a +tensile strength of 13,000 to 30,000 pounds per square inch. Its +compressive strength, or resistance to crushing, is very great. It has +excellent wearing qualities and is not easily warped and deformed by heat. +Chilled iron is cast into a metal mould so that the outside is cooled +quickly, making the surface very hard and difficult to cut and giving great +resistance to wear. It is used for making cheap gear wheels and parts that +must withstand surface friction. + +_Malleable Cast Iron._--This is often called simply malleable iron. It +is a form of cast iron obtained by removing much of the carbon from cast +iron, making it softer and less brittle. It has a tensile strength of +25,000 to 45,000 pounds per square inch, is easily machined, will stand a +small amount of bending at a low red heat and is used chiefly in making +brackets, fittings and supports where low cost is of considerable +importance. It is often used in cheap constructions in place of steel +forgings. The greatest strength of a malleable casting, like a steel +forging, is in the surface, therefore but little machining should be done. + +_Wrought Iron._--This grade is made by treating the cast iron to +remove almost all of the carbon, silicon, phosphorus, sulphur, manganese +and other impurities. This process leaves a small amount of the slag from +the ore mixed with the wrought iron. + +Wrought iron is used for making bars to be machined into various parts. If +drawn through the rolls at the mill once, while being made, it is called +"muck bar;" if rolled twice, it is called "merchant bar" (the commonest +kind), and a still better grade is made by rolling a third time. Wrought +iron is being gradually replaced in use by mild rolled steels. + +Wrought iron is slightly heavier than cast iron, is a much better +electrical conductor than either cast iron or steel, has a tensile strength +of 40,000 to 60,000 pounds per square inch and costs slightly more than +steel. Unlike either steel or cast iron, wrought iron does not harden when +cooled suddenly from a red heat. + +_Grades of Irons._--The mechanical properties of cast iron differ +greatly according to the amount of other materials it contains. The most +important of these contained elements is carbon, which is present to a +degree varying from 2 to 5-1/2 per cent. When iron containing much carbon +is quickly cooled and then broken, the fracture is nearly white in color +and the metal is found to be hard and brittle. When the iron is slowly +cooled and then broken the fracture is gray and the iron is more malleable +and less brittle. If cast iron contains sulphur or phosphorus, it will show +a white fracture regardless of the rapidity of cooling, being brittle and +less desirable for general work. + +_Steel._--Steel is composed of extremely minute particles of iron and +carbon, forming a network of layers and bands. This carbon is a smaller +proportion of the metal than found in cast iron, the percentage being from +3/10 to 2-1/2 per cent. + +Carbon steel is specified according to the number of "points" of carbon, a +point being one one-hundredth of one per cent of the weight of the steel. +Steel may contain anywhere from 30 to 250 points, which is equivalent to +saying, anywhere from 3/10 to 2-1/2 per cent, as above. A 70-point steel +would contain 70/100 of one per cent or 7/10 of one per cent of carbon by +weight. The percentage of carbon determines the hardness of the steel, also +many other qualities, and its suitability for various kinds of work. The +more carbon contained in the steel, the harder the metal will be, and, of +course, its brittleness increases with the hardness. The smaller the grains +or particles of iron which are separated by the carbon, the stronger the +steel will be, and the control of the size of these particles is the object +of the science of heat treatment. + +In addition to the carbon, steel may contain the following: + +Silicon, which increases the hardness, brittleness, strength and difficulty + of working if from 2 to 3 per cent is present. + +Phosphorus, which hardens and weakens the metal but makes it easier to + cast. Three-tenths per cent of phosphorus serves as a hardening agent and + may be present in good steel if the percentage of carbon is low. More + than this weakens the metal. + +Sulphur, which tends to make the metal hard and filled with small holes. + +Manganese, which makes the steel so hard and tough that it can with + difficulty be cut with steel tools. Its hardness is not lessened by + annealing, and it has great tensile strength. + +Alloy steel has a varying but small percentage of other elements mixed with +it to give certain desired qualities. Silicon steel and manganese steel are +sometimes classed as alloy steels. This subject is taken up in the latter +part of this chapter under _Alloys_, where the various combinations +and their characteristics are given consideration. + +Steel has a tensile strength varying from 50,000 to 300,000 pounds per +square inch, depending on the carbon percentage and the other alloys +present, as well as upon the texture of the grain. Steel is heavier than +cast iron and weighs about the same as wrought iron. It is about one-ninth +as good a conductor of electricity as copper. + +Steel is made from cast iron by three principal processes: the crucible, +Bessemer and open hearth. + +_Crucible steel_ is made by placing pieces of iron in a clay or +graphite crucible, mixed with charcoal and a small amount of any desired +alloy. The crucible is then heated with coal, oil or gas fires until the +iron melts, and, by absorbing the desired elements and giving up or +changing its percentage of carbon, becomes steel. The molten steel is then +poured from the crucible into moulds or bars for use. Crucible steel may +also be made by placing crude steel in the crucibles in place of the iron. +This last method gives the finest grade of metal and the crucible process +in general gives the best grades of steel for mechanical use. + +[Illustration: Figure 2.--A Bessemer Converter] + +_Bessemer steel_ is made by heating iron until all the undesirable +elements are burned out by air blasts which furnish the necessary oxygen. +The iron is placed in a large retort called a converter, being poured, +while at a melting heat, directly from the blast furnace into the +converter. While the iron in the converter is molten, blasts of air are +forced through the liquid, making it still hotter and burning out the +impurities together with the carbon and manganese. These two elements are +then restored to the iron by adding spiegeleisen (an alloy of iron, carbon +and manganese). A converter holds from 5 to 25 tons of metal and requires +about 20 minutes to finish a charge. This makes the cheapest steel. + +[Illustration: Figure 3.--An Open Hearth Furnace] + +_Open hearth steel_ is made by placing the molten iron in a receptacle +while currents of air pass over it, this air having itself been highly +heated by just passing over white hot brick (Figure. 3). Open hearth steel +is considered more uniform and reliable than Bessemer, and is used for +springs, bar steel, tool steel, steel plates, etc. + +_Aluminum_ is one of the commonest industrial metals. It is used for +gear cases, engine crank cases, covers, fittings, and wherever lightness +and moderate strength are desirable. + +Aluminum is about one-third the weight of iron and about the same weight as +glass and porcelain; it is a good electrical conductor (about one-half as +good as copper); is fairly strong itself and gives great strength to other +metals when alloyed with them. One of the greatest advantages of aluminum +is that it will not rust or corrode under ordinary conditions. The granular +formation of aluminum makes its strength very unreliable and it is too soft +to resist wear. + +_Copper_ is one of the most important metals used in the trades, and +the best commercial conductor of electricity, being exceeded in this +respect only by silver, which is but slightly better. Copper is very +malleable and ductile when cold, and in this state may be easily worked +under the hammer. Working in this way makes the copper stronger and harder, +but less ductile. Copper is not affected by air, but acids cause the +formation of a green deposit called verdigris. + +Copper is one of the best conductors of heat, as well as electricity, being +used for kettles, boilers, stills and wherever this quality is desirable. +Copper is also used in alloys with other metals, forming an important part +of brass, bronze, german silver, bell metal and gun metal. It is about +one-eighth heavier than steel and has a tensile strength of about 25,000 to +50,000 pounds per square inch. + +_Lead._--The peculiar properties of lead, and especially its quality +of showing but little action or chemical change in the presence of other +elements, makes it valuable under certain conditions of use. Its principal +use is in pipes for water and gas, coverings for roofs and linings for vats +and tanks. It is also used to coat sheet iron for similar uses and as an +important part of ordinary solder. + +Lead is the softest and weakest of all the commercial metals, being very +pliable and inelastic. It should be remembered that lead and all its +compounds are poisonous when received into the system. Lead is more than +one-third heavier than steel, has a tensile strength of only about 2,000 +pounds per square inch, and is only about one-tenth as good a conductor of +electricity as copper. + +_Zinc._--This is a bluish-white metal of crystalline form. It is +brittle at ordinary temperatures and becomes malleable at about 250 to 300 +degrees Fahrenheit, but beyond this point becomes even more brittle than at +ordinary temperatures. Zinc is practically unaffected by air or moisture +through becoming covered with one of its own compounds which immediately +resists further action. Zinc melts at low temperatures, and when heated +beyond the melting point gives off very poisonous fumes. + +The principal use of zinc is as an alloy with other metals to form brass, +bronze, german silver and bearing metals. It is also used to cover the +surface of steel and iron plates, the plates being then called galvanized. + +Zinc weighs slightly less than steel, has a tensile strength of 5,000 +pounds per square inch, and is not quite half as good as copper in +conducting electricity. + +_Tin_ resembles silver in color and luster. Tin is ductile and +malleable and slightly crystalline in form, almost as heavy as steel, and +has a tensile strength of 4,500 pounds per square inch. + +The principal use of tin is for protective platings on household utensils +and in wrappings of tin-foil. Tin forms an important part of many alloys +such as babbitt, Britannia metal, bronze, gun metal and bearing metals. + +_Nickel_ is important in mechanics because of its combinations with +other metals as alloys. Pure nickel is grayish-white, malleable, ductile +and tenacious. It weighs almost as much as steel and, next to manganese, is +the hardest of metals. Nickel is one of the three magnetic metals, the +others being iron and cobalt. The commonest alloy containing nickel is +german silver, although one of its most important alloys is found in nickel +steel. Nickel is about ten per cent heavier than steel, and has a tensile +strength of 90,000 pounds per square inch. + +_Platinum._--This metal is valuable for two reasons: it is not +affected by the air or moisture or any ordinary acid or salt, and in +addition to this property it melts only at the highest temperatures. It is +a fairly good electrical conductor, being better than iron or steel. It is +nearly three times as heavy as steel and its tensile strength is 25,000 +pounds per square inch. + + +ALLOYS + +An alloy is formed by the union of a metal with some other material, either +metal or non-metallic, this union being composed of two or more elements +and usually brought about by heating the substances together until they +melt and unite. Metals are alloyed with materials which have been found to +give to the metal certain characteristics which are desired according to +the use the metal will be put to. + +The alloys of metals are, almost without exception, more important from an +industrial standpoint than the metals themselves. There are innumerable +possible combinations, the most useful of which are here classed under the +head of the principal metal entering into their composition. + +_Steel._--Steel may be alloyed with almost any of the metals or +elements, the combinations that have proven valuable numbering more than a +score. The principal ones are given in alphabetical order, as follows: + +Aluminum is added to steel in very small amounts for the purpose of +preventing blow holes in castings. + +Boron increases the density and toughness of the metal. + +Bronze, added by alloying copper, tin and iron, is used for gun metal. + +Carbon has already been considered under the head of steel in the section +devoted to the metals. Carbon, while increasing the strength and hardness, +decreases the ease of forging and bending and decreases the magnetism and +electrical conductivity. High carbon steel can be welded only with +difficulty. When the percentage of carbon is low, the steel is called "low +carbon" or "mild" steel. This is used for rods and shafts, and called +"machine" steel. When the carbon percentage is high, the steel is called +"high carbon" steel, and it is used in the shop as tool steel. One-tenth +per cent of carbon gives steel a tensile strength of 50,000 to 65,000 +pounds per square inch; two-tenths per cent gives from 60,000 to 80,000; +four-tenths per cent gives 70,000 to 100,000, and six-tenths per cent +gives 90,000 to 120,000. + +Chromium forms chrome steel, and with the further addition of nickel is +called chrome nickel steel. This increases the hardness to a high degree +and adds strength without much decrease in ductility. Chrome steels are +used for high-speed cutting tools, armor plate, files, springs, safes, +dies, etc. + +Manganese has been mentioned under _Steel_. Its alloy is much used for +high-speed cutting tools, the steel hardening when cooled in the air and +being called self-hardening. + +Molybdenum is used to increase the hardness to a high degree and makes the +steel suitable for high-speed cutting and gives it self-hardening +properties. + +Nickel, with which is often combined chromium, increases the strength, +springiness and toughness and helps to prevent corrosion. + +Silicon has already been described. It suits the metal for use in +high-speed tools. + +Silver added to steel has many of the properties of nickel. + +Tungsten increases the hardness without making the steel brittle. This +makes the steel well suited for gas engine valves as it resists corrosion +and pitting. Chromium and manganese are often used in combination with +tungsten when high-speed cutting tools are made. + +Vanadium as an alloy increases the elastic limit, making the steel +stronger, tougher and harder. It also makes the steel able to stand much +bending and vibration. + +_Copper._--The principal copper alloys include brass, bronze, german +silver and gun metal. + +Brass is composed of approximately one-third zinc and two-thirds copper. It +is used for bearings and bushings where the speeds are slow and the loads +rather heavy for the bearing size. It also finds use in washers, collars +and forms of brackets where the metal should be non-magnetic, also for many +highly finished parts. + +Brass is about one-third as good an electrical conductor as copper, is +slightly heavier than steel and has a tensile strength of 15,000 pounds +when cast and about 75,000 to 100,000 pounds when drawn into wire. + +Bronze is composed of copper and tin in various proportions, according to +the use to which it is to be put. There will always be from six-tenths to +nine-tenths of copper in the mixture. Bronze is used for bearings, +bushings, thrust washers, brackets and gear wheels. It is heavier than +steel, about 1/15 as good an electrical conductor as pure copper and has a +tensile strength of 30,000 to 60,000 pounds. + +Aluminum bronze, composed of copper, zinc and aluminum has high tensile +strength combined with ductility and is used for parts requiring this +combination. + +Bearing bronze is a variable material, its composition and proportion +depending on the maker and the use for which it is designed. It usually +contains from 75 to 85 per cent of copper combined with one or more +elements, such as tin, zinc, antimony and lead. + +White metal is one form of bearing bronze containing over 80 per cent of +zinc together with copper, tin, antimony and lead. Another form is made +with nearly 90 per cent of tin combined with copper and antimony. + +Gun metal bronze is made from 90 per cent copper with 10 per cent of tin +and is used for heavy bearings, brackets and highly finished parts. + +Phosphor bronze is used for very strong castings and bearings. It is +similar to gun metal bronze, except that about 1-1/2 per cent of phosphorus +has been added. + +Manganese bronze contains about 1 per cent of manganese and is used for +parts requiring great strength while being free from corrosion. + +German silver is made from 60 per cent of copper with 20 per cent each of +zinc and nickel. Its high electrical resistance makes it valuable for +regulating devices and rheostats. + +_Tin_ is the principal part of _babbitt_ and _solder_. A +commonly used babbitt is composed of 89 per cent tin, 8 per cent antimony +and 3 per cent of copper. A grade suitable for repairing is made from +80 per cent of lead and 20 per cent antimony. This last formula should not +be used for particular work or heavy loads, being more suitable for +spacers. Innumerable proportions of metals are marketed under the name of +babbitt. + +Solder is made from 50 per cent tin and 50 per cent lead, this grade being +called "half-and-half." Hard solder is made from two-thirds tin and +one-third lead. + +Aluminum forms many different alloys, giving increased strength to whatever +metal it unites with. + +Aluminum brass is composed of approximately 65 per cent copper, 30 per cent +zinc and 5 per cent aluminum. It forms a metal with high tensile strength +while being ductile and malleable. + +Aluminum zinc is suitable for castings which must be stiff and hard. + +Nickel aluminum has a tensile strength of 40,000 pounds per square inch. + +Magnalium is a silver-white alloy of aluminum with from 5 to 20 per cent of +magnesium, forming a metal even lighter than aluminum and strong enough to +be used in making high-speed gasoline engines. + + +HEAT TREATMENT OF STEEL + +The processes of heat treatment are designed to suit the steel for various +purposes by changing the size of the grain in the metal, therefore the +strength; and by altering the chemical composition of the alloys in the +metal to give it different physical properties. Heat treatment, as applied +in ordinary shop work, includes the three processes of annealing, hardening +and tempering, each designed to accomplish a certain definite result. + +All of these processes require that the metal treated be gradually brought +to a certain predetermined degree of heat which shall be uniform throughout +the piece being handled and, from this point, cooled according to certain +rules, the selection of which forms the difference in the three methods. + +_Annealing._--This is the process which relieves all internal strains +and distortion in the metal and softens it so that it may more easily be +cut, machined or bent to the required form. In some cases annealing is used +only to relieve the strains, this being the case after forging or welding +operations have been performed. In other cases it is only desired to soften +the metal sufficiently that it may be handled easily. In some cases both of +these things must be accomplished, as after a piece has been forged and +must be machined. No matter what the object, the procedure is the same. + +The steel to be annealed must first be heated to a dull red. This heating +should be done slowly so that all parts of the piece have time to reach the +same temperature at very nearly the same time. The piece may be heated in +the forge, but a much better way is to heat in an oven or furnace of some +type where the work is protected against air currents, either hot or cold, +and is also protected against the direct action of the fire. + +[Illustration: Figure 4.--A Gaspipe Annealing Oven] + +Probably the simplest of all ovens for small tools is made by placing a +piece of ordinary gas pipe in the fire (Figure 4), and heating until the +inside of the pipe is bright red. Parts placed in this pipe, after one end +has been closed, may be brought to the desired heat without danger of +cooling draughts or chemical change from the action of the fire. More +elaborate ovens may be bought which use gas, fuel oils or coal to produce +the heat and in which the work may be placed on trays so that the fire will +not strike directly on the steel being treated. + +If the work is not very important, it may be withdrawn from the fire or +oven, after heating to the desired point, and allowed to cool in the air +until all traces of red have disappeared when held in a dark place. The +work should be held where it is reasonably free from cold air currents. If, +upon touching a pine stick to the piece being annealed, the wood does not +smoke, the work may then be cooled in water. + +Better annealing is secured and harder metal may be annealed if the cooling +is extended over a number of hours by placing the work in a bed of +non-heat-conducting material, such as ashes, charred bone, asbestos fibre, +lime, sand or fire clay. It should be well covered with the heat retaining +material and allowed to remain until cool. Cooling may be accomplished by +allowing the fire in an oven or furnace to die down and go out, leaving the +work inside the oven with all openings closed. The greater the time taken +for gradual cooling from the red heat, the more perfect will be the results +of the annealing. + +While steel is annealed by slow cooling, copper or brass is annealed by +bringing to a low red heat and quickly plunging into cold water. + +_Hardening._--Steel is hardened by bringing to a proper temperature, +slowly and evenly as for annealing, and then cooling more or less quickly, +according to the grade of steel being handled. The degree of hardening is +determined by the kind of steel, the temperature from which the metal is +cooled and the temperature and nature of the bath into which it is plunged +for cooling. + +Steel to be hardened is often heated in the fire until at some heat around +600 to 700 degrees is reached, then placed in a heating bath of molten +lead, heated mercury, fused cyanate of potassium, etc., the heating bath +itself being kept at the proper temperature by fires acting on it. While +these baths have the advantage of heating the metal evenly and to exactly +the temperature desired throughout without any part becoming over or under +heated, their disadvantages consist of the fact that their materials and +the fumes are poisonous in most all cases, and if not poisonous, are +extremely disagreeable. + +The degree of heat that a piece of steel must be brought to in order that +it may be hardened depends on the percentage of carbon in the steel. The +greater the percentage of carbon, the lower the heat necessary to harden. + +[Illustration: Figure 5.--Cooling the Test Bar for Hardening] + +To find the proper heat from which any steel must be cooled, a simple test +may be carried out provided a sample of the steel, about six inches long +can be secured. One end of this test bar should be heated almost to its +melting point, and held at this heat until the other end just turns red. +Now cool the piece in water by plunging it so that both ends enter at the +same time (Figure 5), that is, hold it parallel with the surface of the +water when plunged in. This serves the purpose of cooling each point along +the bar from a different heat. When it has cooled in the water remove the +piece and break it at short intervals, about 1/2 inch, along its length. +The point along the test bar which was cooled from the best possible +temperature will show a very fine smooth grain and the piece cannot be cut +by a file at this point. It will be necessary to remember the exact color +of that point when taken from the fire, making another test if necessary, +and heat all pieces of this same steel to this heat. It will be necessary +to have the cooling bath always at the same temperature, or the results +cannot be alike. + +While steel to be hardened is usually cooled in water, many other liquids +may be used. If cooled in strong brine, the heat will be extracted much +quicker, and the degree of hardness will be greater. A still greater degree +of hardness is secured by cooling in a bath of mercury. Care should be used +with the mercury bath, as the fumes that arise are poisonous. + +Should toughness be desired, without extreme hardness, the steel may be +cooled in a bath of lard oil, neatsfoot oil or fish oil. To secure a result +between water and oil, it is customary to place a thick layer of oil on top +of water. In cooling, the piece will pass through the oil first, thus +avoiding the sudden shock of the cold water, yet producing a degree of +hardness almost as great as if the oil were not used. + +It will, of course, be necessary to make a separate test for each cooling +medium used. If the fracture of the test piece shows a coarse grain, the +steel was too hot at that point; if the fracture can be cut with a file, +the metal was not hot enough at that point. + +When hardening carbon tool steel its heat should be brought to a cherry +red, the exact degree of heat depending on the amount of carbon and the +test made, then plunged into water and held there until all hissing sound +and vibration ceases. Brine may be used for this purpose; it is even better +than plain water. As soon as the hissing stops, remove the work from the +water or brine and plunge in oil for complete cooling. + +[Illustration: Figure 6.--Cooling the Tool for Tempering] + +In hardening high-speed tool steel, or air hardening steels, the tool +should be handled as for carbon steel, except that after the body reaches +a cherry red, the cutting point must be quickly brought to a white heat, +almost melting, so that it seems ready for welding. Then cool in an oil +bath or in a current of cool air. + +Hardening of copper, brass and bronze is accomplished by hammering or +working them while cold. + +_Tempering_ is the process of making steel tough after it has been +hardened, so that it will hold a cutting edge and resist cracking. +Tempering makes the grain finer and the metal stronger. It does not affect +the hardness, but increases the elastic limit and reduces the brittleness +of the steel. In that tempering is usually performed immediately after +hardening, it might be considered as a continuation of the former process. + +The work or tool to be tempered is slowly heated to a cherry red and the +cutting end is then dipped into water to a depth of 1/2 to 3/4 inch above +the point (Figure 6). As soon as the point cools, still leaving the tool +red above the part in water, remove the work from the bath and quickly rub +the end with a fine emery cloth. + +As the heat from the uncooled part gradually heats the point again, the +color of the polished portion changes rapidly. When a certain color is +reached, the tool should be completely immersed in the water until cold. + +For lathe, planer, shaper and slotter tools, this color should be a light +straw. + +Reamers and taps should be cooled from an ordinary straw color. + +Drills, punches and wood working tools should have a brown color. + +Blue or light purple is right for cold chisels and screwdrivers. + +Dark blue should be reached for springs and wood saws. + +Darker colors than this, ranging through green and gray, denote that the +piece has reached its ordinary temper, that is, it is partially annealed. + +After properly hardening a spring by dipping in lard or fish oil, it should +be held over a fire while still wet with the oil. The oil takes fire and +burns off, properly tempering the spring. + +Remember that self-hardening steels must never be dipped in water, and +always remember for all work requiring degrees of heat, that the more +carbon, the less heat. + +_Case Hardening._--This is a process for adding more carbon to the +surface of a piece of steel, so that it will have good wear-resisting +qualities, while being tough and strong on the inside. It has the effect of +forming a very hard and durable skin on the surface of soft steel, leaving +the inside unaffected. + +The simplest way, although not the most efficient, is to heat the piece to +be case hardened to a red heat and then sprinkle or rub the part of the +surface to be hardened with potassium ferrocyanide. This material is a +deadly poison and should be handled with care. Allow the cyanide to fuse on +the surface of the metal and then plunge into water, brine or mercury. +Repeating the process makes the surface harder and the hard skin deeper +each time. + +Another method consists of placing the piece to be hardened in a bed of +powdered bone (bone which has been burned and then powdered) and cover with +more powdered bone, holding the whole in an iron tray. Now heat the tray +and bone with the work in an oven to a bright red heat for 30 minutes to an +hour and then plunge the work into water or brine. + + + + +CHAPTER II + +OXY-ACETYLENE WELDING AND CUTTING MATERIALS + + +_Welding._--Oxy-acetylene welding is an autogenous welding process, in +which two parts of the same or different metals are joined by causing the +edges to melt and unite while molten without the aid of hammering or +compression. When cool, the parts form one piece of metal. + +The oxy-acetylene flame is made by mixing oxygen and acetylene gases in a +special welding torch or blowpipe, producing, when burned, a heat of 6,300 +degrees, which is more than twice the melting temperature of the common +metals. This flame, while being of intense heat, is of very small size. + +_Cutting._--The process of cutting metals with the flame produced from +oxygen and acetylene depends on the fact that a jet of oxygen directed upon +hot metal causes the metal itself to burn away with great rapidity, +resulting in a narrow slot through the section cut. The action is so fast +that metal is not injured on either side of the cut. + +_Carbon Removal._--This process depends on the fact that carbon will +burn and almost completely vanish if the action is assisted with a supply +of pure oxygen gas. After the combustion is started with any convenient +flame, it continues as long as carbon remains in the path of the jet of +oxygen. + +_Materials._--For the performance of the above operations we require +the two gases, oxygen and acetylene, to produce the flames; rods of metal +which may be added to the joints while molten in order to give the weld +sufficient strength and proper form, and various chemical powders, called +fluxes, which assist in the flow of metal and in doing away with many of +the impurities and other objectionable features. + +_Instruments._--To control the combustion of the gases and add to the +convenience of the operator a number of accessories are required. + +The pressure of the gases in their usual containers is much too high for +their proper use in the torch and we therefore need suitable valves which +allow the gas to escape from the containers when wanted, and other +specially designed valves which reduce the pressure. Hose, composed of +rubber and fabric, together with suitable connections, is used to carry the +gas to the torch. + +The torches for welding and cutting form a class of highly developed +instruments of the greatest accuracy in manufacture, and must be thoroughly +understood by the welder. Tables, stands and special supports are provided +for holding the work while being welded, and in order to handle the various +metals and allow for their peculiarities while heated use is made of ovens +and torches for preheating. The operator requires the protection of +goggles, masks, gloves and appliances which prevent undue radiation of the +heat. + +_Torch Practice._--The actual work of welding and cutting requires +preliminary preparation in the form of heat treatment for the metals, +including preheating, annealing and tempering. The surfaces to be joined +must be properly prepared for the flame, and the operation of the torches +for best results requires careful and correct regulation of the gases and +the flame produced. + +Finally, the different metals that are to be welded require special +treatment for each one, depending on the physical and chemical +characteristics of the material. + +It will thus be seen that the apparently simple operations of welding and +cutting require special materials, instruments and preparation on the part +of the operator and it is a proved fact that failures, which have been +attributed to the method, are really due to lack of these necessary +qualifications. + + +OXYGEN + +Oxygen, the gas which supports the rapid combustion of the acetylene in the +torch flame, is one of the elements of the air. It is the cause and the +active agent of all combustion that takes place in the atmosphere. Oxygen +was first discovered as a separate gas in 1774, when it was produced by +heating red oxide of mercury and was given its present name by the famous +chemist, Lavoisier. + +Oxygen is prepared in the laboratory by various methods, these including +the heating of chloride of lime and peroxide of cobalt mixed in a retort, +the heating of chlorate of potash, and the separation of water into its +elements, hydrogen and oxygen, by the passage of an electric current. While +the last process is used on a large scale in commercial work, the others +are not practical for work other than that of an experimental or temporary +nature. + +This gas is a colorless, odorless, tasteless element. It is sixteen times +as heavy as the gas hydrogen when measured by volume under the same +temperature and pressure. Under all ordinary conditions oxygen remains in +a gaseous form, although it turns to a liquid when compressed to 4,400 +pounds to the square inch and at a temperature of 220° below zero. + +Oxygen unites with almost every other element, this union often taking +place with great heat and much light, producing flame. Steel and iron will +burn rapidly when placed in this gas if the combustion is started with a +flame of high heat playing on the metal. If the end of a wire is heated +bright red and quickly plunged into a jar containing this gas, the wire +will burn away with a dazzling light and be entirely consumed except for +the molten drops that separate themselves. This property of oxygen is used +in oxy-acetylene cutting of steel. + +The combination of oxygen with other substances does not necessarily cause +great heat, in fact the combination may be so slow and gradual that the +change of temperature can not be noticed. An example of this slow +combustion, or oxidation, is found in the conversion of iron into rust as +the metal combines with the active gas. The respiration of human beings +and animals is a form of slow combustion and is the source of animal heat. +It is a general rule that the process of oxidation takes place with +increasing rapidity as the temperature of the body being acted upon rises. +Iron and steel at a red heat oxidize rapidly with the formation of a scale +and possible damage to the metal. + +_Air._--Atmospheric air is a mixture of oxygen and nitrogen with +traces of carbonic acid gas and water vapor. Twenty-one per cent of the +air, by volume, is oxygen and the remaining seventy-nine per cent is the +inactive gas, nitrogen. But for the presence of the nitrogen, which deadens +the action of the other gas, combustion would take place at a destructive +rate and be beyond human control in almost all cases. These two gases exist +simply as a mixture to form the air and are not chemically combined. It is +therefore a comparatively simple matter to separate them with the processes +now available. + +_Water._--Water is a combination of oxygen and hydrogen, being +composed of exactly two volumes of hydrogen to one volume of oxygen. If +these two gases be separated from each other and then allowed to mix in +these proportions they unite with explosive violence and form water. Water +itself may be separated into the gases by any one of several means, one +making use of a temperature of 2,200° to bring about this separation. + +[Illustration: Figure 7.--Obtaining Oxygen by Electrolysis] + +The easiest way to separate water into its two parts is by the process +called electrolysis (Figure 7). Water, with which has been mixed a small +quantity of acid, is placed in a vat through the walls of which enter the +platinum tipped ends of two electrical conductors, one positive and the +other negative. + +Tubes are placed directly above these wire terminals in the vat, one tube +being over each electrode and separated from each other by some distance. +With the passage of an electric current from one wire terminal to the +other, bubbles of gas rise from each and pass into the tubes. The gas that +comes from the negative terminal is hydrogen and that from the positive +pole is oxygen, both gases being almost pure if the work is properly +conducted. This method produces electrolytic oxygen and electrolytic +hydrogen. + +_The Liquid Air Process._--While several of the foregoing methods of +securing oxygen are successful as far as this result is concerned, they are +not profitable from a financial standpoint. A process for separating oxygen +from the nitrogen in the air has been brought to a high state of perfection +and is now supplying a major part of this gas for oxy-acetylene welding. It +is known as the Linde process and the gas is distributed by the Linde Air +Products Company from its plants and warehouses located in the large cities +of the country. + +The air is first liquefied by compression, after which the gases are +separated and the oxygen collected. The air is purified and then compressed +by successive stages in powerful machines designed for this purpose until +it reaches a pressure of about 3,000 pounds to the square inch. The large +amount of heat produced is absorbed by special coolers during the process +of compression. The highly compressed air is then dried and the +temperature further reduced by other coolers. + +The next point in the separation is that at which the air is introduced +into an apparatus called an interchanger and is allowed to escape through a +valve, causing it to turn to a liquid. This liquid air is sprayed onto +plates and as it falls, the nitrogen return to its gaseous state and leaves + the oxygen to run to the bottom of the container. This liquid oxygen is +then allowed to return to a gas and is stored in large gasometers or tanks. + +The oxygen gas is taken from the storage tanks and compressed to +approximately 1,800 pounds to the square inch, under which pressure it is +passed into steel cylinders and made ready for delivery to the customer. +This oxygen is guaranteed to be ninety-seven per cent pure. + +Another process, known as the Hildebrandt process, is coming into use in +this country. It is a later process and is used in Germany to a much +greater extent than the Linde process. The Superior Oxygen Co. has secured +the American rights and has established several plants. + +_Oxygen Cylinders_.--Two sizes of cylinders are in use, one containing +100 cubic feet of gas when it is at atmospheric pressure and the other +containing 250 cubic feet under similar conditions. The cylinders are made +from one piece of steel and are without seams. These containers are tested +at double the pressure of the gas contained to insure safety while +handling. + +One hundred cubic feet of oxygen weighs nearly nine pounds (8.921), and +therefore the cylinders will weigh practically nine pounds more when full +than after emptying, if of the 100 cubic feet size. The large cylinders +weigh about eighteen and one-quarter pounds more when full than when empty, +making approximately 212 pounds empty and 230 pounds full. + +The following table gives the number of cubic feet of oxygen remaining in +the cylinders according to various gauge pressures from an initial pressure +of 1,800 pounds. The amounts given are not exactly correct as this would +necessitate lengthy calculations which would not make great enough +difference to affect the practical usefulness of the table: + +Cylinder of 100 Cu. Ft. Capacity at 68° Fahr. + + Gauge Volume Gauge Volume +Pressure Remaining Pressure Remaining + + 1800 100 700 39 + 1620 90 500 28 + 1440 80 300 17 + 1260 70 100 6 + 1080 60 18 1 + 900 50 9 1/2 + +Cylinder of 250 Cu. Ft. Capacity at 68° Fahr. + + Gauge Volume Gauge Volume +Pressure Remaining Pressure Remaining + + 1800 250 700 97 + 1620 225 500 70 + 1440 200 300 42 + 1260 175 100 15 + 1080 150 18 8 + 900 125 9 1-1/4 + +The temperature of the cylinder affects the pressure in a large degree, the +pressure increasing with a rise in temperature and falling with a fall in +temperature. The variation for a 100 cubic foot cylinder at various +temperatures is given in the following tabulation: + +At 150° Fahr........................ 2090 pounds. +At 100° Fahr........................ 1912 pounds. +At 80° Fahr........................ 1844 pounds. +At 68° Fahr........................ 1800 pounds. +At 50° Fahr........................ 1736 pounds. +At 32° Fahr........................ 1672 pounds. +At 0 Fahr........................ 1558 pounds. +At -10° Fahr........................ 1522 pounds. + +_Chlorate of Potash Method._--In spite of its higher cost and the +inferior gas produced, the chlorate of potash method of producing oxygen is +used to a limited extent when it is impossible to secure the gas in +cylinders. + +[Illustration: Figure 8.--Oxygen from Chlorate of Potash] + +An iron retort (Figure 8) is arranged to receive about fifteen pounds of +chlorate of potash mixed with three pounds of manganese dioxide, after +which the cylinder is closed with a tight cap, clamped on. This retort is +carried above a burner using fuel gas or other means of generating heat and +this burner is lighted after the chemical charge is mixed and compressed in +the tube. + +The generation of gas commences and the oxygen is led through water baths +which wash and cool it before storing in a tank connected with the plant. +From this tank the gas is compressed into portable cylinders at a pressure +of about 300 pounds to the square inch for use as required in welding +operations. + +Each pound of chlorate of potash liberates about three cubic feet of +oxygen, and taking everything into consideration, the cost of gas produced +in this way is several times that of the purer product secured by the +liquid air process. + +These chemical generators are oftentimes a source of great danger, +especially when used with or near the acetylene gas generator, as is +sometimes the case with cheap portable outfits. Their use should not be +tolerated when any other method is available, as the danger from accident +alone should prohibit the practice except when properly installed and +cared for away from other sources of combustible gases. + + +ACETYLENE + +In 1862 a chemist, Woehler, announced the discovery of the preparation of +acetylene gas from calcium carbide, which he had made by heating to a high +temperature a mixture of charcoal with an alloy of zinc and calcium. His +product would decompose water and yield the gas. For nearly thirty years +these substances were neglected, with the result that acetylene was +practically unknown, and up to 1892 an acetylene flame was seen by very few +persons and its possibilities were not dreamed of. With the development of +the modern electric furnace the possibility of calcium carbide as a +commercial product became known. + +In the above year, Thomas L. Willson, an electrical engineer of Spray, +North Carolina, was experimenting in an attempt to prepare metallic +calcium, for which purpose he employed an electric furnace operating on a +mixture of lime and coal tar with about ninety-five horse power. The result +was a molten mass which became hard and brittle when cool. This apparently +useless product was discarded and thrown in a nearby stream, when, to the +astonishment of onlookers, a large volume of gas was immediately +liberated, which, when ignited, burned with a bright and smoky flame and +gave off quantities of soot. The solid material proved to be calcium +carbide and the gas acetylene. + +Thus, through the incidental study of a by-product, and as the result of an +accident, the possibilities in carbide were made known, and in the spring +of 1895 the first factory in the world for the production of this substance +was established by the Willson Aluminum Company. + +When water and calcium carbide are brought together an action takes place +which results in the formation of acetylene gas and slaked lime. + + +CARBIDE + +Calcium carbide is a chemical combination of the elements carbon and +calcium, being dark brown, black or gray with sometimes a blue or red +tinge. It looks like stone and will only burn when heated with oxygen. + +Calcium carbide may be preserved for any length of time if protected from +the air, but the ordinary moisture in the atmosphere gradually affects it +until nothing remains but slaked lime. It always possesses a penetrating +odor, which is not due to the carbide itself but to the fact that it is +being constantly affected by moisture and producing small quantities of +acetylene gas. + +This material is not readily dissolved by liquids, but if allowed to come +in contact with water, a decomposition takes place with the evolution of +large quantities of gas. Carbide is not affected by shock, jarring or age. + +A pound of absolutely pure carbide will yield five and one-half cubic feet +of acetylene. Absolute purity cannot be attained commercially, and in +practice good carbide will produce from four and one-half to five cubic +feet for each pound used. + +Carbide is prepared by fusing lime and carbon in the electric furnace under +a heat in excess of 6,000 degrees Fahrenheit. These materials are among the +most difficult to melt that are known. Lime is so infusible that it is +frequently employed for the materials of crucibles in which the highest +melting metals are fused, and for the pencils in the calcium light because +it will stand extremely high temperatures. + +Carbon is the material employed in the manufacture of arc light electrodes +and other electrical appliances that must stand extreme heat. Yet these two +substances are forced into combination in the manufacture of calcium +carbide. It is the excessively high temperature attainable in the electric +furnace that causes this combination and not any effect of the electricity +other than the heat produced. + +A mixture of ground coke and lime is introduced into the furnace through +which an electric arc has been drawn. The materials unite and form an ingot +of very pure carbide surrounded by a crust of less purity. The poorer crust +is rejected in breaking up the mass into lumps which are graded according +to their size. The largest size is 2 by 3-1/2 inches and is called "lump," +a medium size is 1/2 by 2 inches and is called "egg," an intermediate size +for certain types of generators is 3/8 by 1-1/4 inches and called "nut," +and the finely crushed pieces for use in still other types of generators +are 1/12 by 1/4 inch in size and are called "quarter." Instructions as to +the size best suited to different generators are furnished by the makers +of those instruments. + +These sizes are packed in air-tight sheet steel drums containing 100 pounds +each. The Union Carbide Company of Chicago and New York, operating under +patents, manufactures and distributes the supply of calcium carbide for the +entire United States. Plants for this manufacture are established at +Niagara Falls, New York, and Sault Ste. Marie, Michigan. This company +maintains a system of warehouses in more than one hundred and ten cities, +where large stocks of all sizes are carried. + +The National Board of Fire Underwriters gives the following rules for the +storage of carbide: + +Calcium carbide in quantities not to exceed six hundred pounds may be +stored, when contained in approved metal packages not to exceed one hundred +pounds each, inside insured property, provided that the place of storage be +dry, waterproof and well ventilated and also provided that all but one of +the packages in any one building shall be sealed and that seals shall not +be broken so long as there is carbide in excess of one pound in any other +unsealed package in the building. + +Calcium carbide in quantities in excess of six hundred pounds must be +stored above ground in detached buildings, used exclusively for the storage +of calcium carbide, in approved metal packages, and such buildings shall be +constructed to be dry, waterproof and well ventilated. + +_Properties of Acetylene._--This gas is composed of twenty-four parts +of carbon and two parts of hydrogen by weight and is classed with natural +gas, petroleum, etc., as one of the hydrocarbons. This gas contains the +highest percentage of carbon known to exist in any combination of this form +and it may therefore be considered as gaseous carbon. Carbon is the fuel +that is used in all forms of combustion and is present in all fuels from +whatever source or in whatever form. Acetylene is therefore the most +powerful of all fuel gases and is able to give to the torch flame in +welding the highest temperature of any flame. + +Acetylene is a colorless and tasteless gas, possessed of a peculiar and +penetrating odor. The least trace in the air of a room is easily noticed, +and if this odor is detected about an apparatus in operation, it is certain +to indicate a leakage of gas through faulty piping, open valves, broken +hose or otherwise. This leakage must be prevented before proceeding with +the work to be done. + +All gases which burn in air will, when mixed with air previous to ignition, +produce more or less violent explosions, if fired. To this rule acetylene +is no exception. One measure of acetylene and twelve and one-half of air +are required for complete combustion; this is therefore the proportion for +the most perfect explosion. This is not the only possible mixture that will +explode, for all proportions from three to thirty per cent of acetylene in +air will explode with more or less force if ignited. + +The igniting point of acetylene is lower than that of coal gas, being about +900 degrees Fahrenheit as against eleven hundred degrees for coal gas. The +gas issuing from a torch will ignite if allowed to play on the tip of a +lighted cigar. + +It is still further true that acetylene, at some pressures, greater than +normal, has under most favorable conditions for the effect, been found to +explode; yet it may be stated with perfect confidence that under no +circumstances has anyone ever secured an explosion in it when subjected to +pressures not exceeding fifteen pounds to the square inch. + +Although not exploded by the application of high heat, acetylene is injured +by such treatment. It is partly converted, by high heat, into other +compounds, thus lessening the actual quantity of the gas, wasting it and +polluting the rest by the introduction of substances which do not belong +there. These compounds remain in part with the gas, causing it to burn with +a persistent smoky flame and with the deposit of objectionable tarry +substances. Where the gas is generated without undue rise of temperature +these difficulties are avoided. + +_Purification of Acetylene._--Impurities in this gas are caused by +impurities in the calcium carbide from which it is made or by improper +methods and lack of care in generation. Impurities from the material will +be considered first. + +Impurities in the carbide may be further divided into two classes: those +which exert no action on water and those which act with the water to throw +off other gaseous products which remain in the acetylene. Those impurities +which exert no action on the water consist of coke that has not been +changed in the furnace and sand and some other substances which are +harmless except that they increase the ash left after the acetylene has +been generated. + +An analysis of the gas coming from a typical generator is as follows: + + Per cent + Acetylene ................................ 99.36 + Oxygen ................................... .08 + Nitrogen ................................. .11 + Hydrogen ................................. .06 + Sulphuretted Hydrogen .................... .17 + Phosphoretted Hydrogen ................... .04 + Ammonia .................................. .10 + Silicon Hydride .......................... .03 + Carbon Monoxide .......................... .01 + Methane .................................. .04 + +The oxygen, nitrogen, hydrogen, methane and carbon monoxide are either +harmless or are present in such small quantities as to be neglected. The +phosphoretted hydrogen and silicon hydride are self-inflammable gases when +exposed to the air, but their quantity is so very small that this +possibility may be dismissed. The ammonia and sulphuretted hydrogen are +almost entirely dissolved by the water used in the gas generator. The +surest way to avoid impure gas is to use high-grade calcium carbide in the +generator and the carbide of American manufacture is now so pure that it +never causes trouble. + +The first and most important purification to which the gas is subjected is +its passage through the body of water in the generator as it bubbles to the +top. It is then filtered through felt to remove the solid particles of lime +dust and other impurities which float in the gas. + +Further purification to remove the remaining ammonia, sulphuretted hydrogen +and phosphorus containing compounds is accomplished by chemical means. If +this is considered necessary it can be easily accomplished by readily +available purifying apparatus which can be attached to any generator or +inserted between the generator and torch outlets. The following mixtures +have been used. + +"_Heratol,_" a solution of chromic acid or sulphuric acid absorbed in +porous earth. + +"_Acagine,_" a mixture of bleaching powder with fifteen per cent of +lead chromate. + +"_Puratylene,_" a mixture of bleaching powder and hydroxide of lime, +made very porous, and containing from eighteen to twenty per cent of active +chlorine. + +"_Frankoline,_" a mixture of cuprous and ferric chlorides dissolved in +strong hydrochloric acid absorbed in infusorial earth. + +A test for impure acetylene gas is made by placing a drop of ten per cent +solution of silver nitrate on a white blotter and holding the paper in a +stream of gas coming from the torch tip. Blackening of the paper in a short +length of time indicates impurities. + +_Acetylene in Tanks._--Acetylene is soluble in water to a very limited +extent, too limited to be of practical use. There is only one liquid that +possesses sufficient power of containing acetylene in solution to be of +commercial value, this being the liquid acetone. Acetone is produced in +various ways, oftentimes from the distillation of wood. It is a +transparent, colorless liquid that flows with ease. It boils at 133° +Fahrenheit, is inflammable and burns with a luminous flame. It has a +peculiar but rather agreeable odor. + +Acetone dissolves twenty-four times its own bulk of acetylene at ordinary +atmospheric pressure. If this pressure is increased to two atmospheres, +14.7 pounds above ordinary pressure, it will dissolve just twice as much of +the gas and for each atmosphere that the pressure is increased it will +dissolve as much more. + +If acetylene be compressed above fifteen pounds per square inch at ordinary +temperature without first being dissolved in acetone a danger is present of +self-ignition. This danger, while practically nothing at fifteen pounds, +increases with the pressure until at forty atmospheres it is very +explosive. Mixed with acetone, the gas loses this dangerous property and is +safe for handling and transportation. As acetylene is dissolved in the +liquid the acetone increases its volume slightly so that when the gas has +been drawn out of a closed tank a space is left full of free acetylene. + +This last difficulty is removed by first filling the cylinder or tank with +some porous material, such as asbestos, wood charcoal, infusorial earth, +etc. Asbestos is used in practice and by a system of packing and supporting +the absorbent material no space is left for the free gas, even when the +acetylene has been completely withdrawn. + +The acetylene is generated in the usual way and is washed, purified and +dried. Great care is used to make the gas as free as possible from all +impurities and from air. The gas is forced into containers filled with +acetone as described and is compressed to one hundred and fifty pounds to +the square inch. From these tanks it is transferred to the smaller portable +cylinders for consumers' use. + +The exact volume of gas remaining in a cylinder at atmospheric temperature +may be calculated if the weight of the cylinder empty is known. One pound +of the gas occupies 13.6 cubic feet, so that if the difference in weight +between the empty cylinder and the one considered be multiplied by 13.6. +the result will be the number of cubic feet of gas contained. + +The cylinders contain from 100 to 500 cubic feet of acetylene under +pressure. They cannot be filled with the ordinary type of generator as they +require special purifying and compressing apparatus, which should never be +installed in any building where other work is being carried on, or near +other buildings which are occupied, because of the danger of explosion. + +Dissolved acetylene is manufactured by the Prest-O-Lite Company, the +Commercial Acetylene Company and the Searchlight Gas Company and is +distributed from warehouses in various cities. + +These tanks should not be discharged at a rate per hour greater than +one-seventh of their total capacity, that is, from a tank of 100 cubic feet +capacity, the discharge should not be more than fourteen cubic feet per +hour. If discharge is carried on at an excessive rate the acetone is drawn +out with the gas and reduces the heat of the welding flame. + +For this reason welding should not be attempted with cylinders designed for +automobile and boat lighting. When the work demands a greater delivery than +one of the larger tanks will give, two or more tanks may be connected with +a special coupler such as may be secured from the makers and distributers +of the gas. These couplers may be arranged for two, three, four or five +tanks in one battery by removing the plugs on the body of the coupler and +attaching additional connecting pipes. The coupler body carries a pressure +gauge and the valve for controlling the pressure of the gas as it flows to +the welding torches. The following capacities should be provided for: + +Acetylene Consumption Combined Capacity of + of Torches per Hour Cylinders in Use +Up to 15 feet.......................100 cubic feet +16 to 30 feet.......................200 cubic feet +31 to 45 feet.......................300 cubic feet +46 to 60 feet.......................400 cubic feet +61 to 75 feet.......................500 cubic feet + + +WELDING RODS + +The best welding cannot be done without using the best grade of materials, +and the added cost of these materials over less desirable forms is so +slight when compared to the quality of work performed and the waste of +gases with inferior supplies, that it is very unprofitable to take any +chances in this respect. The makers of welding equipment carry an +assortment of supplies that have been standardized and that may be relied +upon to produce the desired result when properly used. The safest plan is +to secure this class of material from the makers. + +Welding rods, or welding sticks, are used to supply the additional metal +required in the body of the weld to replace that broken or cut away and +also to add to the joint whenever possible so that the work may have the +same or greater strength than that found in the original piece. A rod of +the same material as that being welded is used when both parts of the work +are the same. When dissimilar metals are to be joined rods of a composition +suited to the work are employed. + +These filling rods are required in all work except steel of less than 16 +gauge. Alloy iron rods are used for cast iron. These rods have a high +silicon content, the silicon reacting with the carbon in the iron to +produce a softer and more easily machined weld than would otherwise be the +case. These rods are often made so that they melt at a slightly lower point +than cast iron. This is done for the reason that when the part being welded +has been brought to the fusing heat by the torch, the filling material can +be instantly melted in without allowing the parts to cool. The metal can be +added faster and more easily controlled. + +Rods or wires of Norway iron are used for steel welding in almost all +cases. The purity of this grade of iron gives a homogeneous, soft weld of +even texture, great ductility and exceptionally good machining qualities. +For welding heavy steel castings, a rod of rolled carbon steel is employed. +For working on high carbon steel, a rod of the steel being welded must be +employed and for alloy steels, such as nickel, manganese, vanadium, etc., +special rods of suitable alloy composition are preferable. + +Aluminum welding rods are made from this metal alloyed to give the even +flowing that is essential. Aluminum is one of the most difficult of all the +metals to handle in this work and the selection of the proper rod is of +great importance. + +Brass is filled with brass wire when in small castings and sheets. For +general work with brass castings, manganese bronze or Tobin bronze may be +used. + +Bronze is welded with manganese bronze or Tobin bronze, while copper is +filled with copper wire. + +These welding rods should always be used to fill the weld when the +thickness of material makes their employment necessary, and additional +metal should always be added at the weld when possible as the joint cannot +have the same strength as the original piece if made or dressed off flush +with the surfaces around the weld. This is true because the metal welded +into the joint is a casting and will never have more strength than a +casting of the material used for filling. + +Great care should be exercised when adding metal from welding rods to make +sure that no metal is added at a point that is not itself melted and molten +when the addition is made. When molten metal is placed upon cooler surfaces +the result is not a weld but merely a sticking together of the two parts +without any strength in the joint. + + +FLUXES + +Difficulty would be experienced in welding with only the metal and rod to +work with because of the scale that forms on many materials under heat, the +oxides of other metals and the impurities found in almost all metals. These +things tend to prevent a perfect joining of the metals and some means are +necessary to prevent their action. + +Various chemicals, usually in powder form, are used to accomplish the +result of cleaning the weld and making the work of the operator less +difficult. They are called fluxes. + +A flux is used to float off physical impurities from the molten metal; to +furnish a protecting coating around the weld; to assist in the removal of +any objectionable oxide of the metals being handled; to lower the +temperature at which the materials flow; to make a cleaner weld and to +produce a better quality of metal in the finished work. + +The flux must be of such composition that it will accomplish the desired +result without introducing new difficulties. They may be prepared by the +operator in many cases or may be secured from the makers of welding +apparatus, the same remarks applying to their quality as were made +regarding the welding rods, that is, only the best should be considered. + +The flux used for cast iron should have a softening effect and should +prevent burning of the metal. In many cases it is possible and even +preferable to weld cast iron without the use of a flux, and in any event +the smaller the quantity used the better the result should be. Flux should +not be added just before the completion of the work because the heat will +not have time to drive the added elements out of the metal or to +incorporate them with the metal properly. + +Aluminum should never be welded without using a flux because of the oxide +formed. This oxide, called alumina, does not melt until a heat of 5,000° +Fahrenheit is reached, four times the heat needed to melt the aluminum +itself. It is necessary that this oxide be broken down or dissolved so that +the aluminum may have a chance to flow together. Copper is another metal +that requires a flux because of its rapid oxidation under heat. + +While the flux is often thrown or sprinkled along the break while welding, +much better results will be obtained by dipping the hot end of the welding +rod into the flux whenever the work needs it. Sufficient powder will stick +on the end of the rod for all purposes, and with some fluxes too much will +adhere. Care should always be used to avoid the application of excessive +flux, as this is usually worse than using too little. + + +SUPPLIES AND FIXTURES + +_Goggles._--The oxy-acetylene torch should not be used without the +protection to the eyes afforded by goggles. These not only relieve +unnecessary strain, but make it much easier to watch the exact progress of +the work with the molten metal. The difficulty of protecting the sight +while welding is even greater than when cutting metal with the torch. + +Acetylene gives a light which is nearest to sunlight of any artificial +illuminant. But for the fact that this gas light gives a little more green +and less blue in its composition, it would be the same in quality and +practically the same in intensity. This light from the gas is almost absent +during welding, being lost with the addition of the extra oxygen needed to +produce the welding heat. The light that is dangerous comes from the molten +metal which flows under the torch at a bright white heat. + +Goggles for protection against this light and the heat that goes with it +may be secured in various tints, the darker glass being for welding and +the lighter for cutting. Those having frames in which the metal parts do +not touch the flesh directly are most desirable because of the high +temperature reached by these parts. + +_Gloves._--While not as necessary as are the goggles, gloves are a +convenience in many cases. Those in which leather touches the hands +directly are really of little value as the heat that protection is desired +against makes the leather so hot that nothing is gained in comfort. Gloves +are made with asbestos cloth, which are not open to this objection in so +great a degree. + +[Illustration: Figure 9.--Frame for Welding Stand] + +_Tables and Stands._--Tables for holding work while being welded +(Figure 9) are usually made from lengths of angle steel welded together. +The top should be rectangular, about two feet wide and two and one-half +feet long. The legs should support the working surface at a height of +thirty-two to thirty-six inches from the floor. Metal lattice work may be +fastened or laid in the top framework and used to support a layer of +firebrick bound together with a mixture of one-third cement and two-thirds +fireclay. The piece being welded is braced and supported on this table with +pieces of firebrick so that it will remain stationary during the operation. + +Holders for supporting the tanks of gas may be +made or purchased in forms that rest directly on the floor or that are +mounted on wheels. These holders are quite useful where the floor or ground +is very uneven. + +_Hose._--All permanent lines from tanks and generators to the torches +are made with piping rigidly supported, but the short distance from the end +of the pipe line to the torch itself is completed with a flexible hose so +that the operator may be free in his movements while welding. An accident +through which the gases mix in the hose and are ignited will burst this +part of the equipment, with more or less painful results to the person +handling it. For that reason it is well to use hose with great enough +strength to withstand excessive pressure. + +A poor grade of hose will also break down inside and clog the flow of gas, +both through itself and through the parts of the torch. To avoid outside +damage and cuts this hose is sometimes encased with coiled sheet metal. +Hose may be secured with a bursting strength of more than 1,000 pounds to +the square inch. Many operators prefer to distinguish between the oxygen +and acetylene lines by their color and to allow this, red is used for the +oxygen and black for acetylene. + +_Other Materials._--Sheet asbestos and asbestos fibre in flakes are +used to cover parts of the work while preparing them for welding and during +the operation itself. The flakes and small pieces that become detached from +the large sheets are thrown into a bin where the completed small work is +placed to allow slow and even cooling while protected by the asbestos. + +Asbestos fibre and also ordinary fireclay are often used to make a backing +or mould into a form that may be placed behind aluminum and some other +metals that flow at a low heat and which are accordingly difficult to +handle under ordinary methods. This forms a solid mould into which the +metal is practically cast as melted by the torch so that the desired shape +is secured without danger of the walls of metal breaking through and +flowing away. + +Carbon blocks and rods are made in various shapes and sizes so that they +may be used to fill threaded holes and other places that it is desired to +protect during welding. These may be secured in rods of various diameters +up to one inch and in blocks of several different dimensions. + + + + +CHAPTER III + +ACETYLENE GENERATORS + + +Acetylene generators used for producing the gas from the action of water on +calcium carbide are divided into three principal classes according to the +pressure under which they operate. + +Low pressure generators are designed to operate at one pound or less per +square inch. Medium pressure systems deliver the gas at not to exceed +fifteen pounds to the square inch while high pressure types furnish gas +above fifteen pounds per square inch. High pressure systems are almost +unknown in this country, the medium pressure type being often referred to +as "high pressure." + +Another important distinction is formed by the method of bringing the +carbide and water together. The majority of those now in use operate by +dropping small quantities of carbide into a large volume of water, allowing +the generated gas to bubble up through the water before being collected +above the surface. This type is known as the "carbide to water" generator. + +A less used type brings a measured and small quantity of water to a +comparatively large body of the carbide, the gas being formed and collected +from the chamber in which the action takes place. This is called the "water +to carbide" type. Another way of expressing the difference in feed is that +of designating the two types as "carbide feed" for the former and "water +feed" for the latter. + +A further division of the carbide to water machines is made by mentioning +the exact method of feeding the carbide. One type, called "gravity feed" +operates by allowing the carbide to escape and fall by the action of its +own weight, or gravity; the other type, called "forced feed," includes a +separate mechanism driven by power. This mechanism feeds definite amounts +of the carbide to the water as required by the demands on the generator. +The action of either feed is controlled by the withdrawal of gas from the +generator, the aim being to supply sufficient carbide to maintain a nearly +constant supply. + +_Generator Requirements._--The qualities of a good generator are +outlined as follows: [Footnote: See Pond's "Calcium Carbide and +Acetylene."] + +It must allow no possibility of the existence of an explosive mixture in +any of its parts at any time. It is not enough to argue that a mixture, +even if it exists, cannot be exploded unless kindled. It is necessary to +demand that a dangerous mixture can at no time be formed, even if the +machine is tampered with by an ignorant person. The perfect machine must be +so constructed that it shall be impossible at any time, under any +circumstances, to blow it up. + +It must insure cool generation. Since this is a relative term, all machines +being heated somewhat during the generation of gas, this amounts to saying +that a machine must heat but little. A pound of carbide decomposed by water +develops the same amount of heat under all circumstances, but that heat +can be allowed to increase locally to a high point, or it can be equalized +by water so that no part of the material becomes heated enough to do +damage. + +It must be well constructed. A good generator does not need, perhaps, to be +"built like a watch," but it should be solid, substantial and of good +material. It should be built for service, to last and not simply to sell; +anything short of this is to be avoided as unsafe and unreliable. + +It must be simple. The more complicated the machine the sooner it will get +out of order. Understand your generator. Know what is inside of it and +beware of an apparatus, however attractive its exterior, whose interior is +filled with pipes and tubes, valves and diaphragms whose functions you do +not perfectly understand. + +It should be capable of being cleaned and recharged and of receiving all +other necessary attention without loss of gas, both for economy's sake, and +more particularly to avoid danger of fire. + +It should require little attention. All machines have to be emptied and +recharged periodically; but the more this process is simplified and the +more quickly this can be accomplished, the better. + +It should be provided with a suitable indicator to designate how low the +charge is in order that the refilling may be done in good season. + +It should completely use up the carbide, generating the maximum amount of +gas. + +_Overheating._--A large amount of heat is liberated when acetylene gas +is formed from the union of calcium carbide and water. Overheating during +this process, that is to say, an intense local heat rather than a large +amount of heat well distributed, brings about the phenomenon of +polymerization, converting the gas, or part of it, into oily matters, which +can do nothing but harm. This tarry mass coming through the small openings +in the torches causes them to become partly closed and alters the +proportions of the gases to the detriment of the welding flame. The only +remedy for this trouble is to avoid its cause and secure cool generation. + +Overheating can be detected by the appearance of the sludge remaining after +the gas has been made. Discoloration, yellow or brown, shows that there has +been trouble in this direction and the resultant effects at the torches may +be looked for. The abundance of water in the carbide to water machines +effects this cooling naturally and is a characteristic of well designed +machines of this class. It has been found best and has practically become a +fundamental rule of generation that a gallon of water must be provided for +each pound of carbide placed in the generator. With this ratio and a +generator large enough for the number of torches to be supplied, little +trouble need be looked for with overheating. + +_Water to Carbide Generators._--It is, of course, much easier to +obtain a measured and regular flow of water than to obtain such a flow of +any solid substance, especially when the solid substance is in the form of +lumps, as is carbide This fact led to the use of a great many water-feed +generators for all classes of work, and this type is still in common use +for the small portable machines, such, for instance, as those used on motor +cars for the lamps. The water-feed machine is not, however, favored for +welding plants, as is the carbide feed, in spite of the greater +difficulties attending the handling of the solid material. + +A water-feed generator is made up of the gas producing part and a holder +for the acetylene after it is made. The carbide is held in a tray formed of +a number of small compartments so that the charge in each compartment is +nearly equal to that in each of the others. The water is allowed to flow +into one of these compartments in a volume sufficient to produce the +desired amount of gas and the carbide is completely used from this one +division. The water then floods the first compartment and finally overflows +into the next one, where the same process is repeated. After using the +carbide in this division, it is flooded in turn and the water passing on to +those next in order, uses the entire charge of the whole tray. + +These generators are charged with the larger sizes of carbide and are +easily taken care of. The residue is removed in the tray and emptied, +making the generator ready for a fresh supply of carbide. + +_Carbide to Water Generators._--This type also is made up of two +principal parts, the generating chamber and a gas holder, the holder being +part of the generating chamber or a separate device. The generator (Figure +10) contains a hopper to receive the charge of carbide and is fitted with +the feeding mechanism to drop the proper amount of carbide into the water +as required by the demands of the torches. The charge of carbide is of one +of the smaller sizes, usually "nut" or "quarter." + +_Feed Mechanisms._--The device for dropping the carbide into the water +is the only part of the machine that is at all complicated. This +complication is brought about by the necessity of controlling the mass of +carbide so that it can never be discharged into the water at an excessive +rate, feeding it at a regular rate and in definite amounts, feeding it +positively whenever required and shutting off the feed just as positively +when the supply of gas in the holder is enough for the immediate needs. + +[Illustration: Figure 10.--Carbide to Water Generator. A. Feed motor weight; +B. Carbide feed motor; C. Carbide hopper; D. Water for gas generation; +E. Agitator for loosening residuum; F. Water seal in gas bell; G. Filter; +H. Hydraulic Valve; J. Motor control levers.] + +The charge of carbide is unavoidably acted upon by the water vapor in the +generator and will in time become more or less pasty and sticky. This is +more noticeable if the generator stands idle for a considerable length of +time This condition imposes another duty on the feeding mechanism; that is, +the necessity of self-cleaning so that the carbide, no matter in what +condition, cannot prevent the positive action of this part of the device, +especially so that it cannot prevent the supply from being stopped at the +proper time. + +The gas holder is usually made in the bell form so that the upper portion +rises and falls with the addition to or withdrawal from the supply of gas +in the holder. The rise and fall of this bell is often used to control the +feed mechanism because this movement indicates positively whether enough +gas has been made or that more is required. As the bell lowers it sets the +feed mechanism in motion, and when the gas passing into the holder has +raised the bell a sufficient distance, the movement causes the feed +mechanism to stop the fall of carbide into the water. In practice, the +movement of this part of the holder is held within very narrow limits. + +_Gas Holders._--No matter how close the adjustment of the feeding +device, there will always be a slight amount of gas made after the fall of +carbide is stopped, this being caused by the evolution of gas from the +carbide with which water is already in contact. This action is called +"after generation" and the gas holder in any type of generator must +provide sufficient capacity to accommodate this excess gas. As a general +rule the water to carbide generator requires a larger gas holder than the +carbide to water type because of the greater amount of carbide being acted +upon by the water at any one time, also because the surface of carbide +presented to the moist air within the generating chamber is greater with +this type. + +_Freezing._--Because of the rather large body of water contained in +any type of generator, there is always danger of its freezing and +rendering the device inoperative unless placed in a temperature above the +freezing point of the water. It is, of course, dangerous and against the +insurance rules to place a generator in the same room with a fire of any +kind, but the room may be heated by steam or hot water coils from a furnace +in another building or in another part of the same building. + +When the generator is housed in a separate structure the walls should be +made of materials or construction that prevents the passage of heat or +cold through them to any great extent. This may be accomplished by the use +of hollow tile or concrete blocks or by any other form of double wall +providing air spaces between the outer and inner facings. The space between +the parts of the wall may be filled with materials that further retard the +loss of heat if this is necessary under the conditions prevailing. + +_Residue From Generators._--The sludge remaining in the carbide to +water generator may be drawn off into the sewer if the piping is run at a +slant great enough to give a fall that carries the whole quantity, both +water and ash, away without allowing settling and consequent clogging. +Generators are provided with agitators which are operated to stir the ash +up with the water so that the whole mass is carried off when the drain cock +is opened. + +If sewer connections cannot be made in such a way that the ash is entirely +carried away, it is best to run the liquid mass into a settling basin +outside of the building. This should be in the form of a shallow pit which +will allow the water to pass off by soaking into the ground and by +evaporation, leaving the comparatively dry ash in the pit. This ash which +remains is essentially slaked lime and can often be disposed of to more or +less advantage to be used in mortar, whitewash, marking paths and any other +use for which slaked lime is suited. The disposition of the ash depends +entirely on local conditions. An average analysis of this ash is as +follows: + +Sand....................... 1.10 per cent. +Carbon..................... 2.72 " +Oxide of iron and alumina.. 2.77 " +Lime....................... 64.06 " +Water and carbonic acid.... 29.35 " + ------ + 100.00 + + +GENERATOR CONSTRUCTION + +The water for generating purposes is carried in the large tank-like +compartment directly below the carbide chamber. See Figure 11. This water +compartment is filled through a pipe of such a height that the water level +cannot be brought above the proper point or else the water compartment is +provided with a drain connection which accomplishes this same result by +allowing an excess to flow away. + +The quantity of water depends on the capacity of the generator inasmuch as +there must be one gallon for each pound of carbide required. The generator +should be of sufficient capacity to furnish gas under working conditions +from one charge of carbide to all torches installed for at least five hours +continuous use. + +After calculating the withdrawal of the whole number of torches according +to the work they are to do for this period of five hours the proper +generator capacity may be found on the basis of one cubic foot of gas per +hour for each pound of carbide. Thus if the torches were to use sixty cubic +feet of gas per hour, five hours would call for three hundred cubic feet +and a three hundred pound generator should be installed. Generators are +rated according to their carbide capacity in pounds. + +_Charging._--The carbide capacity of the generator should be great +enough to furnish a continuous supply of gas for the maximum operating +time, basing the quantity of gas generated on four and one-half cubic feet +from each pound of lump carbide and on four cubic feet from each pound of +quarter, intermediate sizes being in proportion. + +Generators are built in such a way that it is impossible for the acetylene +to escape from the gas holding compartment during the recharging process. +This is accomplished (1) by connecting the water inlet pipe opening with a +shut off valve in such a way that the inlet cannot be uncovered or opened +without first closing the shut off valve with the same movement of the +operator; (2) by incorporating an automatic or hydraulic one-way valve so +that this valve closes and acts as a check when the gas attempts to flow +from the holder back to the generating chamber, or by any other means that +will positively accomplish this result. + +In generators having no separate gas holding chamber but carrying the +supply in the same compartment in which it is generated, the gas contained +under pressure is allowed to escape through vent pipes into the outside +air before recharging with carbide. As in the former case, the parts are +so interlocked that it is impossible to introduce carbide or water without +first allowing the escape of the gas in the generator. + +It is required by the insurance rules that the entire change of carbide +while in the generator be held in such a way that it may be entirely +removed without difficulty in case the necessity should arise. + +Generators should be cleaned and recharged at regular stated intervals. +This work should be done during daylight hours only and likewise all +repairs should be made at such a time that artificial light is not needed. +Where it is absolutely necessary to use artificial light it should be +provided only by incandescent electric lamps enclosed in gas tight globes. + +In charging generating chambers the old ash and all residue must first be +cleaned out and the operator should be sure that no drain or other pipe has +become clogged. The generator should then be filled with the required +amount of water. In charging carbide feed machines be careful not to place +less than a gallon of water in the water compartment for each pound of +carbide to be used and the water must be brought to, but not above, the +proper level as indicated by the mark or the maker's instructions. The +generating chamber must be filled with the proper amount of water before +any attempt is made to place the carbide in its holder. This rule must +always be followed. It is also necessary that all automatic water seals +and valves, as well as any other water tanks, be filled with clean water +at this time. + +Never recharge with carbide without first cleaning the generating chamber +and completely refilling with clean water. Never test the generator or +piping for leaks with any flame, and never apply flame to any open pipe or +at any point other than the torch, and only to the torch after it has a +welding or cutting nozzle attached. Never use a lighted match, lamp, +candle, lantern, cigar or any open flame near a generator. Failure to +observe these precautions is liable to endanger life and property. + +_Operation and Care of Generators._--The following instructions apply +especially to the Davis Bournonville pressure generator, illustrated in +Figure 11. The motor feed mechanism is illustrated in Figure 12. + +Before filling the machine, the cover should be removed and the hopper +taken out and examined to see that the feeding disc revolves freely; that +no chains have been displaced or broken, and that the carbide displacer +itself hangs barely free of the feeding disc when it is revolved. After +replacing the cover, replace the bolts and tighten them equally, a little +at a time all around the circumference of the cover--not screwing tight in +one place only. Do not screw the cover down any more than is necessary to +make a tight fit. + +To charge the generator, proceed as follows: Open the vent valve by turning +the handle which extends over the filling tube until it stands at a right +angle with the generator. Open the valve in the water filling pipe, and +through this fill with water until it runs out of the overflow pipe of the +drainage chamber, then close the valve in the water filling pipe and vent +valve. Remove the carbide filling plugs and fill the hopper with +1-1/4"x3/8" carbide ("nut" size). Then replace the plugs and the +safety-locking lever chains. Now rewind the motor weight. Run the pressure +up to about five pounds by raising the controlling diaphragm valve lever +by hand (Figure 12, lever marked _E_). Then raise the blow-off lever, +allowing the gas to blow off until the gauge shows about two pounds; this +to clear the generator of air mixture. Then run the pressure up to about +eight pounds by raising the controlling valve lever _E_, or until +this controlling lever rests against the upper wing of the fan governor, +and prevents operation of the feed motor. After this is done, the motor +will operate automatically as the gas is consumed. + +[Illustration: Figure 11.--Pressure Generator (Davis Bournonville). +_A_, Feed motor weight; +_B_, Carbide feed motor; +_C_, Motor Control diaphragm; +_D_, Carbide hopper; +_E_, Carbide feed disc; +_F_, Overflow pipe; +_G_, Overflow pipe seal; +_H_, Overflow pipe valve; +_J_, Filling funnel; +_K_, Hydraulic valve; +_L_, Expansion chamber; +_M_, Escape pipe; +_N_, Feed pipe; +_O_, Agitator for residuum; +_P_, Residuum valve; +_Q_, Water level] + +[Illustration: Figure 12.--Feed Mechanism of Pressure Generator] + +Should the pressure rise much above the blow-off point, the safety +controlling diaphragm valve will operate and throw the safety clutch in +interference and thus stop the motor. This interference clutch will then +have to be returned to its former position before the motor will operate, +but cannot be replaced before the pressure has been reduced below the +blow-off point. + +The parts of the feed mechanism illustrated in Figure 12 are as follows: +_A_, motor drum for weight cable. _B_, carbide filling plugs. +_C_, chains for connecting safety locking lever of motor to pins on +the top of the carbide plugs. _D_, interference clutch of motor. +_E_, lever on feed controlling diaphragm valve. _F_, lever of +interference controlling diaphragm valve that operates interference clutch. +_G_, feed controlling diaphragm valve. _H_, diaphragm valve +controlling operation of interference clutch. _I_, interference pin +to engage emergency clutch. _J_, main shaft driving carbide feeding +disc. _Y_, safety locking lever. + +_Recharging Generator._--Turn the agitator handle rapidly for several +revolutions, and then open the residuum valve, having five or six pounds +gas pressure on the machine. If the carbide charge has been exhausted and +the motor has stopped, there is generally enough carbide remaining in the +feeding disc that can be shaken off, and fed by running the motor to +obtain some pressure in the generator. The desirability of discharging +the residuum with some gas pressure is because the pressure facilitates +the discharge and at the same time keeps the generator full of gas, +preventing air mixture to a great extent. As soon as the pressure is +relieved by the withdrawal of the residuum, the vent valve should be +opened, as if the pressure is maintained until all of the residuum is +discharged gas would escape through the discharge valve. + +Having opened the vent pipe valve and relieved the pressure, open the +valve in the water filling tube. Close the residuum valve, then run in +several gallons of water and revolve the agitator, after which draw out the +remaining residuum; then again close the residuum valve and pour in water +until it discharges from the overflow pipe of the drainage chamber. It is +desirable in filling the generator to pour the water in rapidly enough to +keep the filling pipe full of water, so that air will not pass in at the +same time. + +After the generator is cleaned and filled with water, fill with carbide and +proceed in the same manner as when first charging. + +_Carbide Feed Mechanism._--Any form of carbide to water machine should +be so designed that the carbide never falls directly from its holder into +the water, but so that it must take a more or less circuitous path. This +should be true, no matter what position the mechanism is in. One of the +commonest types of forced feed machine carries the carbide in a hopper with +slanting sides, this hopper having a large opening in the bottom through +which the carbide passes to a revolving circular plate. As the pieces of +carbide work out toward the edge of the plate under the influence of the +mass behind them, they are thrown off into the water by small stationary +fins or plows which are in such a position that they catch the pieces +nearest the edges and force them off as the plate revolves. This +arrangement, while allowing a free passage for the carbide, prevents an +excess from falling should the machine stop in any position. + +When, as is usually the case, the feed mechanism is actuated by the rise +or fall of pressure in the generator or of the level of some part of the +gas holder, it must be built in such a way that the feeding remains +inoperative as long as the filling opening on the carbide holder remains +open. + +The feed of carbide should always be shut off and controlled so that under +no condition can more gas be generated than could be cared for by the +relief valve provided. It is necessary also to have the feed mechanism at +least ten inches above the surface of the water so that the parts will +never become clogged with damp lime dust. + +_Motor Feed._--The feed mechanism itself is usually operated by power +secured from a slowly falling weight which, through a cable, revolves a +drum. To this drum is attached suitable gearing for moving the feed parts +with sufficient power and in the way desired. This part, called the motor, +is controlled by two levers, one releasing a brake and allowing the motor +to operate the feed, the other locking the gearing so that no more carbide +will be dropped into the water. These levers are moved either by the +quantity of gas in the holder or by the pressure of the gas, depending on +the type of machine. + +With a separate gas holder, such as used with low pressure systems, the +levers are operated by the rise and fall of the bell of the holder or +gasometer, alternately starting and stopping the motor as the bell falls +and rises again. Medium pressure generators are provided with a diaphragm +to control the feed motor. + +This diaphragm is carried so that the pressure within the generator acts +on one side while a spring, whose tension is under the control of the +operator, acts on the other side. The diaphragm is connected to the brake +and locking device on the motor in such a way that increasing the tension +on the spring presses the diaphragm and moves a rod that releases the brake +and starts the feed. The gas pressure, increasing with the continuation of +carbide feed, acts on the other side and finally overcomes the pressure of +the spring tension, moving the control rod the other way and stopping the +motor and carbide feed. This spring tension is adjusted and checked with +the help of a pressure gauge attached to the generating chamber. + +_Gravity Feed._--This type of feed differs from the foregoing in that +the carbide is simply released and is allowed to fall into the water +without being forced to do so. Any form of valve that is sufficiently +powerful in action to close with the carbide passing through is used and is +operated by the power secured from the rise and fall of the gas holder +bell. When this valve is first opened the carbide runs into the water until +sufficient pressure and volume of gas is generated to raise the bell. This +movement operates the arm attached to the carbide shut off valve and slowly +closes it. A fall of the bell occasioned by gas being withdrawn again opens +the valve and more gas is generated. + +_Mechanical Feed._--The previously described methods of feeding +carbide to the water have all been automatic in action and do not depend +on the operator for their proper action. + +Some types of large generating plants have a power-driven feed, the power +usually being from some kind of motor other than one operated by a weight, +such as a water motor, for instance. This motor is started and stopped by +the operator when, in his judgment, more gas is wanted or enough has been +generated. This type of machine, often called a "non-automatic generator," +is suitable for large installations and is attached to a gas holder of +sufficient size to hold a day's supply of acetylene. The generator can then +be operated until a quantity of gas has been made that will fill the large +holder, or gasometer, and then allowed to remain idle for some time. + +_Gas Holders._--The commonest type of gas container is that known as a +gasometer. This consists of a circular tank partly filled with water, into +which is lowered another circular tank, inverted, which is made enough +smaller in diameter than the first one so that three-quarters of an inch is +left between them. This upper and inverted portion, called the bell, +receives the gas from the generator and rises or falls in the bath of water +provided in the lower tank as a greater or less amount of gas is contained +in it. + +These holders are made large enough so that they will provide a means of +caring for any after generation and so that they maintain a steady and even +flow. The generator, however, must be of a capacity great enough so that +the gas holder will not be drawn on for part of the supply with all torches +in operation. That is, the holder must not be depended on for a reserve +supply. + +The bell of the holder is made so that when full of gas its lower edge is +still under a depth of at least nine inches of water in the lower tank. Any +further rise beyond this point should always release the gas, or at least +part of it, to the escape pipe so that the gas will under no circumstances +be forced into the room from, between the bell and tank. The bell is guided +in its rise and fall by vertical rods so that it will not wedge at any +point in its travel. + +A condensing chamber to receive the water which condenses from the +acetylene gas in the holder is usually placed under this part and is +provided with a drain so that this water of condensation may be easily +removed. + +_Filtering._--A small chamber containing some closely packed but +porous material such as felt is placed in the pipe leading to the torch +lines. As the acetylene gas passes through this filter the particles of +lime dust and other impurities are extracted from it so that danger of +clogging the torch openings is avoided as much as possible. + +The gas is also filtered to a large extent by its passage through the water +in the generating chamber, this filtering or "scrubbing" often being +facilitated by the form of piping through which the gas must pass from the +generating chamber into the holder. If the gas passes out of a number of +small openings when going into the holder the small bubbles give a better +washing than large ones would. + +_Piping._--Connections from generators to service pipes should +preferably be made with right and left couplings or long thread nipples +with lock nuts. If unions are used, they should be of a type that does not +require gaskets. The piping should be carried and supported so that any +moisture condensing in the lines will drain back toward the generator and +where low points occur they should be drained through tees leading into +drip cups which are permanently closed with screw caps or plugs. No pet +cocks should be used for this purpose. + +For the feed pipes to the torch lines the following pipe sizes are +recommended. + + 3/8 inch pipe. 26 feet long. 2 cubic feet per hour. + 1/2 inch pipe. 30 feet long. 4 cubic feet per hour. + 3/4 inch pipe. 50 feet long. 15 cubic feet per hour. + 1 inch pipe. 70 feet long. 27 cubic feet per hour. + 1-1/4 inch pipe. 100 feet long. 50 cubic feet per hour. + 1-1/2 inch pipe. 150 feet long. 65 cubic feet per hour. + 2 inch pipe. 200 feet long. 125 cubic feet per hour. + 2-1/2 inch pipe. 300 feet long. 190 cubic feet per hour. + 3 inch pipe. 450 feet long. 335 cubic feet per hour. + +When drainage is possible into a sewer, the generator should not be +connected directly into the sewer but should first discharge into an open +receptacle, which may in turn be connected to the sewer. + +No valves or pet cocks should open into the generator room or any other +room when it would be possible, by opening them for draining purposes, to +allow any escape of gas. Any condensation must be removed without the use +of valves or other working parts, being drained into closed receptacles. It +should be needless to say that all the piping for gas must be perfectly +tight at every point in its length. + +_Safety Devices._--Good generators are built in such a way that the +operator must follow the proper order of operation in charging and cleaning +as well as in all other necessary care. It has been mentioned that the gas +pressure is released or shut off before it is possible to fill the water +compartment, and this same idea is carried further in making the generator +inoperative and free from gas pressure before opening the residue drain of +the carbide filling opening on top of the hopper. Some machines are made so +that they automatically cease to generate should there be a sudden and +abnormal withdrawal of gas such as would be caused by a bad leak. This +method of adding safety by automatic means and interlocking parts may be +carried to any extent that seems desirable or necessary to the maker. + +All generators should be provided with escape or relief pipes of large size +which lead to the open air. These pipes are carried so that condensation +will drain back toward the generator and after being led out of the +building to a point at least twelve feet above ground, they end in a +protecting hood so that no rain or solid matter can find its way into them. +Any escape of gas which might ordinarily pass into the generator room is +led into these escape pipes, all parts of the system being connected with +the pipe so that the gas will find this way out. + +Safety blow off valves are provided so that any excess gas which cannot be +contained by the gas holder may be allowed to escape without causing an +undue rise in pressure. This valve also allows the escape of pressure above +that for which the generator was designed. Gas released in this way passes +into the escape pipe just described. + +Inasmuch as the pressure of the oxygen is much greater than that of the +acetylene when used in the torch, it will be seen that anything that caused +the torch outlet to become closed would allow the oxygen to force the +acetylene back into the generator and the oxygen would follow it, making a +very explosive mixture. This return of the gas is prevented by a hydraulic +safety valve or back pressure valve, as it is often called. + +Mechanical check valves have been found unsuitable for this use and those +which employ water as a seal are now required by the insurance rules. The +valve itself (Figure 13) consists of a large cylinder containing water to a +certain depth, which is indicated on the valve body. Two pipes come into +the upper end of this cylinder and lead down into the water, one being +longer than the other. The shorter pipe leads to the escape pipe mentioned +above, while the longer one comes from the generator. The upper end of the +cylinder has an opening to which is attached the pipe leading to the +torches. + +[Illustration: Figure 13.--Hydraulic Back-Pressure Valve. +_A_, Acetylene supply line; +_B_, Vent pipe; +_C_, Water filling plug; +_D_, Acetylene service cock; +_E_, Plug to gauge height of water; +_F_, Gas openings under water; +_G_, Return pipe for sealing water; +_H_, Tube to carry gas below water line; +_I_, Tube to carry gas to escape pipe; +_J_, Gas chamber; +_K_, Plug in upper gas chamber; +_L_, High water level; +_M_, Opening through which water returns; +_O_, Bottom clean out casting] + +The gas coming from the generator through the longer pipe passes out of the +lower end of the pipe which is under water and bubbles up through the water +to the space in the top of the cylinder. From there the gas goes to the +pipe leading to the torches. The shorter pipe is closed by the depth of +water so that the gas does not escape to the relief pipe. As long as the +gas flows in the normal direction as described there will be no escape to +the air. Should the gas in the torch line return into the hydraulic valve +its pressure will lower the level of water in the cylinder by forcing some +of the liquid up into the two pipes. As the level of the water lowers, the +shorter pipe will be uncovered first, and as this is the pipe leading to +the open air the gas will be allowed to escape, while the pipe leading back +to the generator is still closed by the water seal. As soon as this reverse +flow ceases, the water will again resume its level and the action will +continue. Because of the small amount of water blown out of the escape pipe +each time the valve is called upon to perform this duty, it is necessary to +see that the correct water level is always maintained. + +While there are modifications of this construction, the same principle is +used in all types. The pressure escape valve is often attached to this +hydraulic valve body. + +_Construction Details._--Flexible tubing (except at torches), swing +pipe joints, springs, mechanical check valves, chains, pulleys and lead or +fusible piping should never be used on acetylene apparatus except where the +failure of those parts will not affect the safety of the machine or permit, +either directly or indirectly, the escape of gas into a room. Floats should +not be used except where failure will only render the machine inoperative. + +It should be said that the National Board of Fire Underwriters have +established an inspection service for acetylene generators and any +apparatus which bears their label, stating that that particular model and +type has been passed, is safe to use. This service is for the best +interests of all concerned and looks toward the prevention of accidents. +Such inspection is a very important and desirable feature of any outfit and +should be insisted upon. + +_Location of Generators._--Generators should preferably be placed +outside of insured buildings and in properly constructed generator houses. +The operating mechanism should have ample room to work in and there should +be room enough for the attendant to reach the various parts and perform the +required duties without hindrance or the need of artificial light. They +should also be protected from tampering by unauthorized persons. + +Generator houses should not be within five feet of any opening into, nor +have any opening toward, any adjacent building, and should be kept under +lock and key. The size of the house should be no greater than called for by +the requirements mentioned above and it should be well ventilated. + +The foundation for the generator itself should be of brick, stone, concrete +or iron, if possible. If of wood, they should be extra heavy, located in a +dry place and open to circulation of air. A board platform is not +satisfactory, but the foundation should be of heavy planking or timber to +make a firm base and so that the air can circulate around the wood. + +The generator should stand level and no strain should be placed on any of +the pipes or connections or any parts of the generator proper. + + + + +CHAPTER IV + +WELDING INSTRUMENTS + + +VALVES + +_Tank Valves._--The acetylene tank valve is of the needle type, fitted +with suitable stuffing box nuts and ending in an exposed square shank to +which the special wrench may be fitted when the valve is to be opened or +closed. + +The valve used on Linde oxygen cylinders is also a needle type, but of +slightly more complex construction. The body of the valve, which screws +into the top of the cylinder, has an opening below through which the gas +comes from the cylinder, and another opening on the side through which it +issues to the torch line. A needle screws down from above to close this +lower opening. The needle which closes the valve is not connected directly +to the threaded member, but fits loosely into it. The threaded part is +turned by a small hand wheel attached to the upper end. When this hand +wheel is turned to the left, or up, as far as it will go, opening the +valve, a rubber disc is compressed inside of the valve body and this disc +serves to prevent leakage of the gas around the spindle. + +The oxygen valve also includes a safety nut having a small hole through it +closed by a fusible metal which melts at 250° Fahrenheit. Melting of this +plug allows the gas to exert its pressure against a thin copper diaphragm, +this diaphragm bursting under the gas pressure and allowing the oxygen to +escape into the air. + +The hand wheel and upper end of the valve mechanism are protected during +shipment by a large steel cap which covers them when screwed on to the end +of the cylinder. This cap should always be in place when tanks are received +from the makers or returned to them. + +[Illustration: Figure 14.--Regulating Valve] + +_Regulating Valves._--While the pressure in the gas containers may be +anything from zero to 1,800 pounds, and will vary as the gas is withdrawn, +the pressure of the gas admitted to the torch must be held steady and at a +definite point. This is accomplished by various forms of automatic +regulating valves, which, while they differ somewhat in details of +construction, all operate on the same principle. + +The regulator body (Figure 14) carries a union which attaches to the side +outlet on the oxygen tank valve. The gas passes through this union, +following an opening which leads to a large gauge which registers the +pressure on the oxygen remaining in the tank and also to a very small +opening in the end of a tube. The gas passes through this opening and into +the interior of the regulator body. Inside of the body is a metal or rubber +diaphragm placed so that the pressure of the incoming gas causes it to +bulge slightly. Attached to the diaphragm is a sleeve or an arm tipped +with a small piece of fibre, the fibre being placed so that it is directly +opposite the small hole through which the gas entered the diaphragm +chamber. The slight movement of the diaphragm draws the fibre tightly over +the small opening through which the gas is entering, with the result that +further flow is prevented. + +Against the opposite side of the diaphragm is the end of a plunger. This +plunger is pressed against the diaphragm by a coiled spring. The tension on +the coiled spring is controlled by the operator through a threaded spindle +ending in a wing or milled nut on the outside of the regulator body. +Screwing in on the nut causes the tension on the spring to increase, with a +consequent increase of pressure on the side of the diaphragm opposite to +that on which the gas acts. Inasmuch as the gas pressure acted to close the +small gas opening and the spring pressure acts in the opposite direction +from the gas, it will be seen that the spring pressure tends to keep the +valve open. + +When the nut is turned way out there is of course, no pressure on the +spring side of the diaphragm and the first gas coming through automatically +closes the opening through which it entered. If now the tension on the +spring be slightly increased, the valve will again open and admit gas until +the pressure of gas within the regulator is just sufficient to overcome the +spring pressure and again close the opening. There will then be a pressure +of gas within the regulator that corresponds to the pressure placed on the +spring by the operator. An opening leads from the regulator interior to the +torch lines so that all gas going to the torches is drawn from the +diaphragm chamber. + +Any withdrawal of gas will, of course, lower the pressure of that remaining +inside the regulator. The spring tension, remaining at the point determined +by the operator, will overcome this lessened pressure of the gas, and the +valve will again open and admit enough more gas to bring the pressure back +to the starting point. This action continues as long as the spring tension +remains at this point and as long as any gas is taken from the regulator. +Increasing the spring tension will require a greater gas pressure to close +the valve and the pressure of that in the regulator will be correspondingly +higher. + +When the regulator is not being used, the hand nut should be unscrewed +until no tension remains on the spring, thus closing the valve. After the +oxygen tank valve is open, the regulator hand nut is slowly screwed in +until the spring tension is sufficient to give the required pressure in the +torch lines. Another gauge is attached to the regulator so that it +communicates with the interior of the diaphragm chamber, this gauge showing +the gas pressure going to the torch. It is customary to incorporate a +safety valve in the regulator which will blow off at a dangerous pressure. + +In regulating valves and tank valves, as well as all other parts with which +the oxygen comes in contact, it is not permissible to use any form of oil +or grease because of danger of ignition and explosion. The mechanism of a +regulator is too delicate to be handled in the ordinary shop and should any +trouble or leakage develop in this part of the equipment it should be sent +to a company familiar with this class of work for the necessary repairs. +Gas must never be admitted to a regulator until the hand nut is all the way +out, because of danger to the regulator itself and to the operator as well. +A regulator can only be properly adjusted when the tank valve and torch +valves are fully opened. + +[Illustration: Figure 15.--High and Low Pressure Gauges with Regulator] + +Acetylene regulators are used in connection with tanks of compressed gas. +They are built on exactly the same lines as the oxygen regulating valve and +operate in a similar way. One gauge only, the low pressure indicator, is +used for acetylene regulators, although both high and low pressure may be +used if desired. (See Figure 15.) + + +TORCHES + +Flame is always produced by the combustion of a gas with oxygen and in no +other way. When we burn oil or candles or anything else, the material of +the fuel is first turned to a gas by the heat and is then burned by +combining with the oxygen of the air. If more than a normal supply of air +is forced into the flame, a greater heat and more active burning follows. +If the amount of air, and consequently oxygen, is reduced, the flame +becomes smaller and weaker and the combustion is less rapid. A flame may be +easily extinguished by shutting off all of its air supply. + +The oxygen of the combustion only forms one-fifth of the total volume of +air; therefore, if we were to supply pure oxygen in place of air, and in +equal volume, the action would be several times as intense. If the oxygen +is mixed with the fuel gas in the proportion that burns to the very best +advantage, the flame is still further strengthened and still more heat is +developed because of the perfect combustion. The greater the amount of fuel +gas that can be burned in a certain space and within a certain time, the +more heat will be developed from that fuel. + +The great amount of heat contained in acetylene gas, greater than that +found in any other gaseous fuel, is used by leading this gas to the +oxy-acetylene torch and there combining it with just the right amount of +oxygen to make a flame of the greatest power and heat than can possibly be +produced by any form of combustion of fuels of this kind. The heat +developed by the flame is about 6300° Fahrenheit and easily melts all the +metals, as well as other solids. + +Other gases have been and are now being used in the torch. None of them, +however, produce the heat that acetylene does, and therefore the +oxy-acetylene process has proved the most useful of all. Hydrogen was used +for many years before acetylene was introduced in this field. The +oxy-hydrogen flame develops a heat far below that of oxy-acetylene, namely +4500° Fahrenheit. Coal gas, benzine gas, blaugas and others have also been +used in successful applications, but for the present we will deal +exclusively with the acetylene fuel. + +It was only with great difficulty that the obstacles in the way of +successfully using acetylene were overcome by the development of +practicable controlling devices and torches, as well as generators. At +present the oxy-acetylene process is the most universally adaptable, and +probably finds the most widely extended field of usefulness of any welding +process. + +The theoretical proportion of the gases for perfect combustion is two and +one-half volumes of oxygen to one of acetylene. In practice this proportion +is one and one-eighth or one and one-quarter volumes of oxygen to one +volume of acetylene, so that the cost is considerably reduced below what it +would be if the theoretical quantity were really necessary, as oxygen costs +much more than acetylene in all cases. + +While the heat is so intense as to fuse anything brought into the path of +the flame, it is localized in the small "welding cone" at the torch tip so +that the torch is not at all difficult to handle without special protection +except for the eyes, as already noted. The art of successful welding may be +acquired by any operator of average intelligence within a reasonable time +and with some practice. One trouble met with in the adoption of this +process has been that the operation looks so simple and so easy of +performance that unskilled and unprepared persons have been tempted to try +welding, with results that often caused condemnation of the process, when +the real fault lay entirely with the operator. + +The form of torch usually employed is from twelve to twenty-four inches +long and is composed of a handle at one end with tubes leading from this +handle to the "welding head" or torch proper. At or near one end of the +handle are adjustable cocks or valves for allowing the gases to flow into +the torch or to prevent them from doing so. These cocks are often used for +regulating the pressure and amount of gas flowing to the welding head, but +are not always constructed for this purpose and should not be so used when +it is possible to secure pressure adjustment at the regulators (Figure 16). + +Figure 16 shows three different sizes of torches. The number 5 torch is +designed especially for jewelers' work and thin sheet steel welding. It is +eleven inches in length and weighs nineteen ounces. The tips for the number +10 torch are interchangeable with the number 5. The number 10 torch is +adapted for general use on light and medium heavy work. It has six tips and +its length is sixteen inches, with a weight of twenty-three ounces. + +The number 15 torch is designed for heavy work, being twenty-five inches in +length, permitting the operator to stand away from the heat of the metal +being worked. These heavy tips are in two parts, the oxygen check being +renewable. + +[Illustration: Figure 16.--Three Sizes of Torches, with Tips] + +Figures 17 and 18 show two sizes of another welding torch. Still another +type is shown in Figure 19 with four interchangeable tips, the function of +each being as follows: + + No. 1. For heavy castings. + No. 2. Light castings and heavy sheet metal. + No. 3. Light sheet metal. + No. 4. Very light sheet metal and wire. + +[Illustration: Figure 17.--Cox Welding Torch (No. 1)] + +[Illustration: Figure 18.--Cox Welding Torch (No. 2)] + +[Illustration: Figure 19.--Monarch Welding Torch] + +At the side of the shut off cock away from the torch handle the gas tubes +end in standard forms of hose nozzles, to which the rubber hose from the +gas supply tanks or generators can be attached. The tubes from the handle +to the head may be entirely separate from each other, or one may be +contained within the other. As a general rule the upper one of two +separate tubes carries the oxygen, while this gas is carried in the inside +tube when they are concentric with each other. + +In the welding head is the mixing chamber designed to produce an intimate +mixture of the two gases before they issue from the nozzle to the flame. +The nozzle, or welding tip, of a suitable size are design for the work to +be handled and the pressure of gases being used, is attached to the welding +head and consists essentially of the passage at the outer end of which the +flame appears. + +The torch body and tubes are usually made of brass, although copper is +sometimes used. The joint must be very strong, and are usually threaded and +soldered with silver solder. The nozzle proper is made from copper, because +it withstands the heat of the flame better than other less suitable metals. +The torch must be built in such a way that it is not at all liable to come +apart under the influence of high temperatures. + +All torches are constructed in such a way that it is impossible for the +gases to mix by any possible chance before they reach the head, and the +amount of gas contained in the head and tip after being mixed is made as +small as possible. In order to prevent the return of the flame through the +acetylene tube under the influence of the high pressure oxygen some form of +back flash preventer is usually incorporated in the torch at or near the +point at which the acetylene enters. This preventer takes the form of some +porous and heat absorbing material, such as aluminum shavings, contained in +a small cavity through which the gas passes on its way to the head. + +_High Pressure Torches._--Torches are divided into the same classes as +are the generators; that is, high pressure, medium pressure and low +pressure. As mentioned before, the medium pressure is usually called the +high pressure, because there are very few true high pressure systems in +use, and comparatively speaking the medium pressure type is one of high +pressure. + +[Illustration: Figure 20.--High Pressure Torch Head] + +With a true high pressure torch (Figure 20) the gases are used at very +nearly equal heads so that the mixing before ignition is a simple matter. +This type admits the oxygen at the inner end of a straight passage leading +to the tip of the nozzle. The acetylene comes into this same passage from +openings at one side and near the inner end. The difference in direction of +the two gases as they enter the passage assists in making a homogeneous +mixture. The construction of this nozzle is perfectly simple and is easily +understood. The true high pressure torch nozzle is only suited for use with +compressed and dissolved acetylene, no other gas being at a sufficient +pressure to make the action necessary in mixing the gases. + +_Medium Pressure Torches._--The medium pressure (usually called high +pressure) torch (Figure 21) uses acetylene from a medium pressure generator +or from tanks of compressed gas, but will not take the acetylene from low +pressure generators. + +[Illustration: Figure 21.--Medium Pressure Torch Head] + +The construction of the mixing chamber and nozzle is very similar to that +of the high pressure torch, the gases entering in the same way and from the +same positions of openings. The pressure of the acetylene is but little +lower than that of the oxygen, and the two gases, meeting at right angles, +form a very intimate mixture at this point of juncture. The mixture in its +proportions of gases depends entirely on the sizes of the oxygen and +acetylene openings into the mixing chamber and on the pressures at which +the gases are admitted. There is a very slight injector action as the fast +moving stream of oxygen tends to draw the acetylene from the side openings +into the chamber, but the operation of the torch does not depend on this +action to any extent. + +_Low Pressure Torches._--The low pressure torch (Figure 22) will use +gas from low pressure generators from medium pressure machines or from +tanks in which it has been compressed and dissolved. This type depends for +a perfect mixture of gas upon the principle of the injector just as it is +applied in steam boiler practice. + +[Illustration: Figure 22.--Low Pressure Torch with Separate Injector +Nozzle] + +The oxygen enters the head at considerable pressure and passes through its +tube to a small jet within the head. The opening of this jet is directly +opposite the end of the opening through the nozzle which forms the mixing +chamber and the path of the gases to the flame. A small distance remains +between the opening from which the oxygen issues and the inner opening into +the mixing passage. The stream of oxygen rushes across this space and +enters the mixing chamber, being driven by its own pressure. + +The acetylene enters the head in an annular space surrounding the oxygen +tube. The space between oxygen jet and mixing chamber opening is at one end +of this acetylene space and the stream of oxygen seizes the acetylene and +under the injector action draws it into the mixing chamber, it being +necessary only to have a sufficient supply of acetylene flowing into the +head to allow the oxygen to draw the required proportion for a proper +mixture. + +The volume of gas drawn into the mixing chamber depends on the size of the +injector openings and the pressure of the oxygen. In practice the oxygen +pressure is not altered to produce different sized flames, but a new nozzle +is substituted which is designed to give the required flame. Each nozzle +carries its own injector, so that the design is always suited to the +conditions. While torches are made having the injector as a permanent part +of the torch body, the replaceable nozzle is more commonly used because it +makes the one torch suitable for a large range of work and a large number +of different sized flames. With the replaceable head a definite pressure of +oxygen is required for the size being used, this pressure being the one for +which the injector and corresponding mixing chamber were designed in +producing the correct mixture. + +_Adjustable Injectors._-Another form of low pressure torch operates on +the injector principle, but the injector itself is a permanent part of the +torch, the nozzle only being changed for different sizes of work and flame. +The injector is placed in or near the handle and its opening is the largest +required by any work that can be handled by this particular torch. The +opening through the tip of the injector through which the oxygen issues on +its way to the mixing chamber may be wholly or partly closed by a needle +valve which may be screwed into the opening or withdrawn from it, according +to the operator's judgment. The needle valve ends in a milled nut outside +the torch handle, this being the adjustment provided for the different +nozzles. + +_Torch Construction._--A well designed torch is so designed that the +weight distribution is best for holding it in the proper position for +welding. When a torch is grasped by its handle with the gas hose attached, +it should balance so that it does not feel appreciably heavier on one end +than on the other. + +The head and nozzle may be placed so that the flame issues in a line at +right angles with the torch body, or they may be attached at an angle +convenient for the work to be done. The head set at an angle of from 120 to +170 degrees with the body is usually preferred for general work in welding, +while the cutting torch usually has its head at right angles to the body. + +Removable nozzles have various size openings through them and the different +sizes are designated by numbers from 1 up. The same number does not always +indicate the same size opening in torches of different makes, nor does it +indicate a nozzle of the same capacity. + +The design of the nozzle, the mixing chamber, the injector, when one is +used, and the size of the gas openings must be such that all these things +are suited to each other if a proper mixture of gas is to be secured. Parts +that are not made to work together are unsafe if used because of the danger +of a flash back of the flame into the mixing chamber and gas tubes. It is +well known that flame travels through any inflammable gas at a certain +definite rate of speed, depending on the degree of inflammability of the +gas. The easier and quicker the gas burns, the faster will the flame travel +through it. + +If the gas in the nozzle and mixing chamber stood still, the flame would +immediately travel back into these parts and produce an explosion of more +or less violence. The speed with which the gases issue from the nozzle +prevent this from happening because the flame travels back through the gas +at the same speed at which the gas issues from the torch tip. Should the +velocity of the gas be greater than the speed of flame propagation through +it, it will be impossible to keep the flame at the tip, the tendency being +for a space of unburned gas to appear between tip and flame. On the other +hand, should the speed of the flame exceed the velocity with which the gas +comes from the torch there will result a flash back and explosion. + +_Care of Torches._--An oxy-acetylene torch is a very delicate and +sensitive device, much more so that appears on the surface. It must be +given equally as good care and attention as any other high-priced piece of +machinery if it is to be maintained in good condition for use. + +It requires cleaning of the nozzles at regular intervals if used regularly. +This cleaning is accomplished with a piece of copper or brass wire run +through the opening, and never with any metal such as steel or iron that is +harder than the nozzle itself, because of the danger of changing the size +of the openings. The torch head and nozzle can often be cleaned by allowing +the oxygen to blow through at high pressure without the use of any tools. + +In using a torch a deposit of carbon will gradually form inside of the +head, and this deposit will be more rapid if the operator lights the stream +of acetylene before turning any oxygen into the torch. This deposit may be +removed by running kerosene through the nozzle while it is removed from the +torch, setting fire to the kerosene and allowing oxygen to flow through +while the oil is burning. + +Should a torch become clogged in the head or tubes, it may usually be +cleaned by removing the oxygen hose from the handle end, closing the +acetylene cock on the torch, placing the end of the oxygen hose over the +opening in the nozzle and turning on the oxygen under pressure to blow the +obstruction back through the passage that it has entered. By opening the +acetylene cock and closing the oxygen cock at the handle, the acetylene +passages may then be cleaned in the same way. Under no conditions should a +torch be taken apart any more than to remove the changeable nozzle, except +in the hands of those experienced in this work. + +_Nozzle Sizes._--The size of opening through the nozzle is determined +according to the thickness and kind of metal being handled. The following +sizes are recommended for steel: + + Davis-Bournonville. Oxweld Low + Thickness of Metal (Medium Pressure.) Pressure + 1/32 Tip No. 1 Head No. 2 + 1/16 2 + 5/64 3 + 3/32 3 4 + 3/8 4 5 + 3/16 5 6 + 1/4 6 7 + 5/16 7 + 3/8 8 8 + 1/2 9 10 + 5/8 10 12 + 3/4 11 15 + Very heavy 12 15 + +_Cutting Torches._--Steel may be cut with a jet of oxygen at a rate of +speed greater than in any other practicable way under usual conditions. The +action consists of burning away a thin section of the metal by allowing a +stream of oxygen to flow onto it while the gas is at high pressure and the +metal at a white heat. + +[Illustration: Figure 23.--Cutting Torch] + +The cutting torch (Figure 23) has the same characteristics as the welding +torch, but has an additional nozzle or means for temporarily using the +welding opening for the high pressure oxygen. The oxygen issues from the +opening while cutting at a pressure of from ten to 100 pounds to the square +inch. + +The work is first heated to a white heat by adjusting the torch for a +welding flame. As soon as the metal reaches this temperature, the high +pressure oxygen is turned on to the white-hot portion of the steel. When +the jet of gas strikes the metal it cuts straight through, leaving a very +narrow slot and removing but little metal. Thicknesses of steel up to ten +inches can be economically handled in this way. + +The oxygen nozzle is usually arranged so that it is surrounded by a number +of small jets for the heating flame. It will be seen that this arrangement +makes the heating flame always precede the oxygen jet, no matter in which +direction the torch is moved. + +The torch is held firmly, either by hand or with the help of special +mechanism for guiding it in the desired path, and is steadily advanced in +the direction it is desired to extend the cut, the rate of advance being +from three inches to two feet per minute through metal from nine inches +down to one-quarter of an inch in thickness. + +The following data on cutting is given by the Davis-Bournonville Company: + + Cubic + Feet Cost of +Thickness of Gas Inches Gases +of Cutting Heating per Foot Oxygen Cut per per Foot +Steel Oxygen Oxygen of Cut Acetylene Min. of Cut + 1/4 10 lbs. 4 lbs. .40 .086 24 $ .013 + 1/2 20 4 .91 .150 15 .029 + 3/4 30 4 1.16 .150 15 .036 +1 30 4 1.45 .172 12 .045 +1 1/2 30 5 2.40 .380 12 .076 +2 40 5 2.96 .380 12 .093 +4 50 5 9.70 .800 7 .299 +6 70 6 21.09 1.50 4 .648 +9 100 6 43.20 2.00 3 1.311 + +_Acetylene-Air Torch._--A form of torch which burns the acetylene after +mixing it with atmospheric air at normal pressure rather than with the +oxygen under higher pressures has been found useful in certain pre-heating, +brazing and similar operations. This torch (Figure 24) is attached by a +rubber gas hose to any compressed acetylene tank and is regulated as to +flame size and temperature by opening or closing the tank valve more or +less. + +After attaching the torch to the tank, the gas is turned on very slowly and +is lighted at the torch tip. The adjustment should cause the presence of a +greenish-white cone of flame surrounded by a larger body of burning gas, +the cone starting at the mouth of the torch. + +[Illustration: Figure 24.--Acetylene-Air Torch] + +By opening the tank valve more, a longer and hotter flame is produced, the +length being regulated by the tank valve also. This torch will give +sufficient heat to melt steel, although not under conditions suited to +welding. Because of the excess of acetylene always present there is no +danger of oxidizing the metal being heated. + +The only care required by this torch is to keep the small air passages at +the nozzle clean and free from carbon deposits. The flame should be +extinguished when not in use rather than turned low, because this low flame +rapidly deposits large quantities of soot in the burner. + + + + +CHAPTER V + +OXY-ACETYLENE WELDING PRACTICE + + +PREPARATION OF WORK + +_Preheating._--The practice of heating the metal around the weld +before applying the torch flame is a desirable one for two reasons. First, +it makes the whole process more economical; second, it avoids the danger of +breakage through expansion and contraction of the work as it is heated and +as it cools. + +When it is desired to join two surfaces by welding them, it is, of course, +necessary to raise the metal from the temperature of the surrounding air to +its melting point, involving an increase in temperature of from one +thousand to nearly three thousand degrees. To obtain this entire increase +of temperature with the torch flame is very wasteful of fuel and of the +operator's time. The total amount of heat necessary to put into metal is +increased by the conductivity of that metal because the heat applied at the +weld is carried to other parts of the piece being handled until the whole +mass is considerably raised in temperature. To secure this widely +distributed increase the various methods of preheating are adopted. + +As to the second reason for preliminary heating. It is understood that the +metal added to the joint is molten at the time it flows into place. All the +metals used in welding contract as they cool and occupy a much smaller +space than when molten. If additional metal is run between two adjoining +surfaces which are parts of a surrounding body of cool metal, this added +metal will cool while the surfaces themselves are held stationary in the +position they originally occupied. The inevitable result is that the metal +added will crack under the strain, or, if the weld is exceptionally strong, +the main body of the work will he broken by the force of contraction. To +overcome these difficulties is the second and most important reason for +preheating and also for slow cooling following the completion of the weld. + +There are many ways of securing this preheating. The work may be brought to +a red heat in the forge if it is cast iron or steel; it may he heated in +special ovens built for the purpose; it may be placed in a bed of charcoal +while suitably supported; it may be heated by gas or gasoline preheating +torches, and with very small work the outer flame of the welding torch +automatically provides means to this end. + +The temperature of the parts heated should be gradually raised in all +cases, giving the entire mass of metal a chance to expand equally and to +adjust itself to the strains imposed by the preheating. After the region +around the weld has been brought to a proper temperature the opening to be +filled is exposed so that the torch flame can reach it, while the remaining +surfaces are still protected from cold air currents and from cooling +through natural radiation. + +One of the commonest methods and one of the best for handling work of +rather large size is to place the piece to be welded on a bed of fire brick +and build a loose wall around it with other fire brick placed in rows, one +on top of the other, with air spaces left between adjacent bricks in each +row. The space between the brick retaining wall and the work is filled with +charcoal, which is lighted from below. The top opening of the temporary +oven is then covered with asbestos and the fire kept up until the work has +been uniformly raised in temperature to the desired point. + +When much work of the same general character and size is to be handled, a +permanent oven may be constructed of fire brick, leaving a large opening +through the top and also through one side. Charcoal may be used in this +form of oven as with the temporary arrangement, or the heat may be secured +from any form of burner or torch giving a large volume of flame. In any +method employing flame to do the heating, the work itself must be protected +from the direct blast of the fire. Baffles of brick or metal should be +placed between the mouth of the torch and the nearest surface of the work +so that the flame will be deflected to either side and around the piece +being heated. + +The heat should be applied to bring the point of welding to the highest +temperature desired and, except in the smallest work, the heat should +gradually shade off from this point to the other parts of the piece. In the +case of cast iron and steel the temperature at the point to be welded +should be great enough to produce a dull red heat. This will make the whole +operation much easier, because there will be no surrounding cool metal to +reduce the temperature of the molten material from the welding rod below +the point at which it will join the work. From this red heat the mass of +metal should grow cooler as the distance from the weld becomes greater, so +that no great strain is placed upon any one part. With work of a very +irregular shape it is always best to heat the entire piece so that the +strains will be so evenly distributed that they can cause no distortion or +breakage under any conditions. + +The melting point of the work which is being preheated should be kept in +mind and care exercised not to approach it too closely. Special care is +necessary with aluminum in this respect, because of its low melting +temperature and the sudden weakening and flowing without warning. Workmen +have carelessly overheated aluminum castings and, upon uncovering the piece +to make the weld, have been astonished to find that it had disappeared. +Six hundred degrees is about the safe limit for this metal. It is possible +to gauge the exact temperature of the work with a pyrometer, but when this +instrument cannot be procured, it might be well to secure a number of +"temperature cones" from a chemical or laboratory supply house. These cones +are made from material that will soften at a certain heat and in form they +are long and pointed. Placed in position on the part being heated, the +point may be watched, and when it bends over it is sure that the metal +itself has reached a temperature considerably in excess of the temperature +at which that particular cone was designed to soften. + +The object in preheating the metal around the weld is to cause it to expand +sufficiently to open the crack a distance equal to the contraction when +cooling from the melting point. In the case of a crack running from the +edge of a piece into the body or of a crack wholly within the body, it is +usually satisfactory to heat the metal at each end of the opening. This +will cause the whole length of the crack to open sufficiently to receive +the molten material from the rod. + +The judgment of the operator will be called upon to decide just where a +piece of metal should be heated to open the weld properly. It is often +possible to apply the preheating flame to a point some distance from the +point of work if the parts are so connected that the expansion of the +heated part will serve to draw the edges of the weld apart. Whatever part +of the work is heated to cause expansion and separation, this part must +remain hot during the entire time of welding and must then cool slowly at +the same time as the metal in the weld cools. + +[Illustration: Figure 25.--Preheating at _A_ While Welding at +_B_. _C_ also May Be Heated.] + +An example of heating points away from the crack might be found in welding +a lattice work with one of the bars cracked through (Figure 25). If the +strips parallel and near to the broken bar are heated gradually, the work +will be so expanded that the edges of the break are drawn apart and the +weld can be successfully made. In this case, the parallel bars next to the +broken one would be heated highest, the next row not quite so hot and so on +for some distance away. If only the one row were heated, the strains set up +in the next ones would be sufficient to cause a new break to appear. + +[Illustration: Figure 26.--Cutting Through the Rim of a Wheel (Cut Shown +at A)] + +If welding is to be done near the central portion of a large piece, the +strains will be brought to bear on the parts farthest away from the center. +Should a fly wheel spoke be broken and made ready to weld, the greatest +strain will come on the rim of the wheel. In cases like this it is often +desirable to cut through at the point of greatest strain with a saw or +cutting torch, allowing free movement while the weld is made at the +original break (Figure 26). After the inside weld is completed, the cut may +be welded without danger, for the reason that it will always be at some +point at which severe strains cannot be set up by the contraction of the +cooling metal. + +[Illustration: Figure 27.--Using a Wedge While Welding] + +In materials that will spring to some extent without breakage, that is, in +parts that are not brittle, it may be possible to force the work out of +shape with jacks or wedges (Figure 27) in the same way that it would be +distorted by heating and expanding some portion of it as described. A +careful examination will show whether this method can be followed in such a +way as to force the edges of the break to separate. If the plan seems +feasible, the wedges may be put in place and allowed to remain while the +weld is completed. As soon as the work is finished the wedges should be +removed so that the natural contraction can take place without damage. + +It should always be remembered that it is not so much the expansion of the +work when heated as it is the contraction caused by cooling that will do +the damage. A weld may be made that, to all appearances, is perfect and it +may be perfect when completed; but if provision has not been made to allow +for the contraction that is certain to follow, there will be a breakage at +some point. It is not possible to weld the simplest shapes, other than +straight bars, without considering this difficulty and making provision to +take care of it. + +The exact method to employ in preheating will always call for good judgment +on the part of the workman, and he should remember that the success or +failure of his work will depend fully as much on proper preparation as on +correct handling of the weld itself. It should be remembered that the outer +flame of the oxy-acetylene torch may be depended on for a certain amount of +preheating, as this flame gives a very large volume of heat, but a heat +that is not so intense nor so localized as the welding flame itself. The +heat of this part of the flame should be fully utilized during the +operation of melting the metal and it should be so directed, when possible, +that it will bring the parts next to be joined to as high a temperature as +possible. + +When the work has been brought to the desired temperature, all parts except +the break and the surface immediately surrounding it on both sides should +be covered with heavy sheet asbestos. This protecting cover should remain +in place throughout the operation and should only be moved a distance +sufficient to allow the torch flame to travel in the path of the weld. The +use of asbestos in this way serves a twofold purpose. It retains the heat +in the work and prevents the breakage that would follow if a draught of air +were to strike the heated metal, and it also prevents such a radiation of +heat through the surrounding air as would make it almost impossible for the +operator to perform his work, especially in the case of large and heavy +castings when the amount of heat utilized is large. + +_Cleaning and Champfering._--A perfect weld can never be made unless +the surfaces to be joined have been properly prepared to receive the new +metal. + +All spoiled, burned, corroded and rough particles must positively be +removed with chisel and hammer and with a free application of emery cloth +and wire brush. The metal exposed to the welding flame should be perfectly +clean and bright all over, or else the additional material will not unite, +but will only stick at best. + +[Illustration: Figure 28.--Tapering the Opening Formed by a Break] + +Following the cleaning it is always necessary to bevel, or champfer, the +edges except in the thinnest sheet metal. To make a weld that will hold, +the metal must be made into one piece, without holes or unfilled portions +at any point, and must be solid from inside to outside. This can only be +accomplished by starting the addition of metal at one point and gradually +building it up until the outside, or top, is reached. With comparatively +thin plates the molten metal may be started from the side farthest from the +operator and brought through, but with thicker sections the addition is +started in the middle and brought flush with one side and then with the +other. + +It will readily be seen that the molten material cannot be depended upon to +flow between the tightly closed surfaces of a crack in a way that can be at +all sure to make a true weld. It will be necessary for the operator to +reach to the farthest side with the flame and welding rod, and to start the +new surfaces there. To allow this, the edges that are to be joined are +beveled from one side to the other (Figure 28), so that when placed +together in approximately the position they are to occupy they will leave a +grooved channel between them with its sides at an angle with each other +sufficient in size to allow access to every point of each surface. + +[Illustration: Figure 29.--Beveling for Thin Work] + +[Illustration: Figure 30.--Beveling for Thick Work] + +With work less than one-fourth inch thick, this angle should be forty-five +degrees on each piece (Figure 29), so that when they are placed together +the extreme edges will meet at the bottom of a groove whose sides are +square, or at right angles, to each other. This beveling should be done so +that only a thin edge is left where the two parts come together, just +enough points in contact to make the alignment easy to hold. With work of a +thickness greater than a quarter of an inch, the angle of bevel on each +piece may be sixty degrees (Figure 30), so that when placed together the +angle included between the sloping sides will also be sixty degrees. If the +plate is less than one-eighth of an inch thick the beveling is not +necessary, as the edges may be melted all the way through without danger of +leaving blowholes at any point. + +[Illustration: Figure 31.--Beveling Both Sides of a Thick Piece] + +[Illustration: Figure 32.--Beveling the End of a Pipe] + +This beveling may be done in any convenient way. A chisel is usually most +satisfactory and also quickest. Small sections may be handled by filing, +while metal that is too hard to cut in either of these ways may be shaped +on the emery wheel. It is not necessary that the edges be perfectly +finished and absolutely smooth, but they should be of regular outline and +should always taper off to a thin edge so that when the flame is first +applied it can be seen issuing from the far side of the crack. If the work +is quite thick and is of a shape that will allow it to be turned over, the +bevel may be brought from both sides (Figure 31), so that there will be two +grooves, one on each surface of the work. After completing the weld on one +side, the piece is reversed and finished on the other side. Figure 32 shows +the proper beveling for welding pipe. Figure 33 shows how sheet metal may +be flanged for welding. + +Welding should not be attempted with the edges separated in place of +beveled, because it will be found impossible to build up a solid web of new +metal from one side clear through to the other by this method. The flame +cannot reach the surfaces to make them molten while receiving new material +from the rod, and if the flame does not reach them it will only serve to +cause a few drops of the metal to join and will surely cause a weak and +defective weld. + +[Illustration: Figure 33.--Flanging Sheet Metal for Welding] + +_Supporting Work._--During the operation of welding it is necessary +that the work be well supported in the position it should occupy. This may +be done with fire brick placed under the pieces in the correct position, +or, better still, with some form of clamp. The edges of the crack should +touch each other at the point where welding is to start and from there +should gradually separate at the rate of about one-fourth inch to the foot. +This is done so that the cooling of the molten metal as it is added will +draw the edges together by its contraction. + +Care must be used to see that the work is supported so that it will +maintain the same relative position between the parts as must be present +when the work is finished. In this connection it must be remembered that +the expansion of the metal when heated may be great enough to cause serious +distortion and to provide against this is one of the difficulties to be +overcome. + +Perfect alignment should be secured between the separate parts that are to +be joined and the two edges must be held up so that they will be in the +same plane while welding is carried out. If, by any chance, one drops +below the other while molten metal is being added, the whole job may have +to be undone and done over again. One precaution that is necessary is that +of making sure that the clamping or supporting does not in itself pull the +work out of shape while melted. + + +TORCH PRACTICE + +[Illustration: Figure 34.--Rotary Movement of Torch in Welding] + +The weld is made by bringing the tip of the welding flame to the edges of +the metals to be joined. The torch should be held in the right hand and +moved slowly along the crack with a rotating motion, traveling in small +circles (Figure 34), so that the Welding flame touches first on one side of +the crack and then on the other. On large work the motion may be simply +back and forth across the crack, advancing regularly as the metal unites. +It is usually best to weld toward the operator rather than from him, +although this rule is governed by circumstances. The head of the torch +should be inclined at an angle of about 60 degrees to the surface of the +work. The torch handle should extend in the same line with the break +(Figure 35) and not across it, except when welding very light plates. + +[Illustration: Figure 35.--Torch Held in Line with the Break] + +If the metal is 1/16 inch or less in thickness it is only necessary to +circle along the crack, the metal itself furnishing enough material to +complete the weld without additions. Heat both sides evenly until they flow +together. + +Material thicker than the above requires the addition of more metal of the +same or different kind from the welding rod, this rod being held by the +left hand. The proper size rod for cast iron is one having a diameter equal +to the thickness of metal being welded up to a one-half inch rod, which is +the largest used. For steel the rod should be one-half the thickness of the +metal being joined up to one-fourth inch rod. As a general rule, better +results will be obtained by the use of smaller rods, the very small sizes +being twisted together to furnish enough material while retaining the free +melting qualities. + +[Illustration: Figure 36.--The Welding Rod Should Be Held in the Molten +Metal] + +The tip of the rod must at all times be held in contact with the pieces +being welded and the flame must be so directed that the two sides of the +crack and the end of the rod are melted at the same time (Figure 36). +Before anything is added from the rod, the sides of the crack are melted +down sufficiently to fill the bottom of the groove and join the two sides. +Afterward, as metal comes from the rod in filling the crack, the flame is +circled along the joint being made, the rod always following the flame. + +[Illustration: Figure 37.--Welding Pieces of Unequal Thickness] + +Figure 37 illustrates the welding of pieces of unequal thickness. + +Figure 38 illustrates welding at an angle. + +The molten metal may be directed as to where it should go by the tip of the +welding flame, which has considerable force, but care must be taken not to +blow melted metal on to cooler surfaces which it cannot join. If, while +welding, a spot appears which does not unite with the weld, it may be +handled by heating all around it to a white heat and then immediately +welding the bad place. + +[Illustration: Figure 38.--Welding at an Angle] + +Never stop in the middle of a weld, as it is extremely difficult to +continue smoothly when resuming work. + +_The Flame._--The welding flame must have exactly the right +proportions of each gas. If there is too much oxygen, the metal will be +burned or oxidized; the presence of too much acetylene carbonizes the +metal; that is to say, it adds carbon and makes the work harder. Just the +right mixture will neither burn nor carbonize and is said to be a "neutral" +flame. The neutral flame, if of the correct size for the work, reduces the +metal to a melted condition, not too fluid, and for a width about the same +as the thickness of the metal being welded. + +When ready to light the torch, after attaching the right tip or head as +directed in accordance with the thickness of metal to be handled, it will +be necessary to regulate the pressure of gases to secure the neutral flame. + +The oxygen will have a pressure of from 2 to 20 pounds, according to the +nozzle used. The acetylene will have much less. Even with the compressed +gas, the pressure should never exceed 10 pounds for the largest work, and +it will usually be from 4 to 6. In low pressure systems, the acetylene will +be received at generator pressure. It should first be seen that the +hand-screws on the regulators are turned way out so that the springs are +free from any tension. It will do no harm if these screws are turned back +until they come out of the threads. This must be done with both oxygen and +acetylene regulators. + +Next, open the valve from the generator, or on the acetylene tank, and +carefully note whether there is any odor of escaping gas. Any leakage of +this gas must be stopped before going on with the work. + +The hand wheel controlling the oxygen cylinder valve should now be turned +very slowly to the left as far as it will go, which opens the valve, and +it should be borne in mind the pressure that is being released. Turn in the +hand screw on the oxygen regulator until the small pressure gauge shows a +reading according to the requirements of the nozzle being used. This oxygen +regulator adjustment should be made with the cock on the torch open, and +after the regulator is thus adjusted the torch cock may be closed. + +Open the acetylene cock on the torch and screw in on the acetylene +regulator hand-screw until gas commences to come through the torch. Light +this flow of acetylene and adjust the regulator screw to the pressure +desired, or, if there is no gauge, so that there is a good full flame. With +the pressure of acetylene controlled by the type of generator it will only +be necessary to open the torch cock. + +With the acetylene burning, slowly open the oxygen cock on the torch and +allow this gas to join the flame. The flame will turn intensely bright and +then blue white. There will be an outer flame from four to eight inches +long and from one to three inches thick. Inside of this flame will be two +more rather distinctly defined flames. The inner one at the torch tip is +very small, and the intermediate one is long and pointed. The oxygen should +be turned on until the two inner flames unite into one blue-white cone from +one-fourth to one-half inch long and one-eighth to one-fourth inch in +diameter. If this single, clearly defined cone does not appear when the +oxygen torch cock has been fully opened, turn off some of the acetylene +until it does appear. + +If too much oxygen is added to the flame, there will still be the central +blue-white cone, but it will be smaller and more or less ragged around the +edges (Figure 39). When there is just enough oxygen to make the single +cone, and when, by turning on more acetylene or by turning off oxygen, two +cones are caused to appear, the flame is neutral (Figure 40), and the small +blue-white cone is called the welding flame. + +[Illustration: Figure 39.--Oxidizing Flame--Too Much Oxygen] + +[Illustration: Figure 40.--Neutral Flame] + +[Illustration: Figure 41.--Reducing Flame--Showing an Excess of Acetylene] + +While welding, test the correctness of the flame adjustment occasionally by +turning on more acetylene or by turning off some oxygen until two flames or +cones appear. Then regulate as before to secure the single distinct cone. +Too much oxygen is not usually so harmful as too much acetylene, except +with aluminum. (See Figure 41.) An excessive amount of sparks coming from +the weld denotes that there is too much oxygen in the flame. Should the +opening in the tip become partly clogged, it will be difficult to secure a +neutral flame and the tip should be cleaned with a brass or copper +wire--never with iron or steel tools or wire of any kind. While the torch +is doing its work, the tip may become excessively hot due to the heat +radiated from the molten metal. The tip may be cooled by turning off the +acetylene and dipping in water with a slight flow of oxygen through the +nozzle to prevent water finding its way into the mixing chamber. + +The regulators for cutting are similar to those for welding, except that +higher pressures may be handled, and they are fitted with gauges reading up +to 200 or 250 pounds pressure. + +In welding metals which conduct the heat very rapidly it is necessary to +use a much larger nozzle and flame than for metals which have not this +property. This peculiarity is found to the greatest extent in copper, +aluminum and brass. + +Should a hole be blown through the work, it may be closed by withdrawing +the flame for a few seconds and then commencing to build additional metal +around the edges, working all the way around and finally closing the small +opening left at the center with a drop or two from the welding rod. + + +WELDING VARIOUS METALS + +Because of the varying melting points, rates of expansion and contraction, +and other peculiarities of different metals, it is necessary to give +detailed consideration to the most important ones. + +_Characteristics of Metals._--The welder should thoroughly understand +the peculiarities of the various metals with which he has to deal. The +metals and their alloys are described under this heading in the first +chapter of this book and a tabulated list of the most important points +relating to each metal will be found at the end of the present chapter. +All this information should be noted by the operator of a welding +installation before commencing actual work. + +Because of the nature of welding, the melting point of a metal is of great +importance. A metal melting at a low temperature should have more careful +treatment to avoid undesired flow than one which melts at a temperature +which is relatively high. When two dissimilar metals are to be joined, the +one which melts at the higher temperature must be acted upon by the flame +first and when it is in a molten condition the heat contained in it will in +many cases be sufficient to cause fusion of the lower melting metal and +allow them to unite without playing the flame on the lower metal to any +great extent. + +The heat conductivity bears a very important relation to welding, inasmuch +as a metal with a high rate of conductance requires more protection from +cooling air currents and heat radiation than one not having this quality to +such a marked extent. A metal which conducts heat rapidly will require a +larger volume of flame, a larger nozzle, than otherwise, this being +necessary to supply the additional heat taken away from the welding point +by this conductance. + +The relative rates of expansion of the various metals under heat should be +understood in order that parts made from such material may have proper +preparation to compensate for this expansion and contraction. Parts made +from metals having widely varying rates of expansion must have special +treatment to allow for this quality, otherwise breakage is sure to occur. + +_Cast Iron._--All spoiled metal should he cut away and if the work is +more than one-eighth inch in thickness the sides of the crack should be +beveled to a 45 degree angle, leaving a number of points touching at the +bottom of the bevel so that the work may be joined in its original +relation. + +The entire piece should be preheated in a bricked-up oven or with charcoal +placed on the forge, when size does not warrant building a temporary oven. +The entire piece should be slowly heated and the portion immediately +surrounding the weld should be brought to a dull red. Care should be used +that the heat does not warp the metal through application to one part more +than the others. After welding, the work should be slowly cooled by +covering with ashes, slaked lime, asbestos fibre or some other +non-conductor of heat. These precautions are absolutely essential in the +case of cast iron. + +A neutral flame, from a nozzle proportioned to the thickness of the work, +should be held with the point of the blue-white cone about one-eighth inch +from the surface of the iron. + +A cast iron rod of correct diameter, usually made with an excess of +silicon, is used by keeping its end in contact with the molten metal and +flowing it into the puddle formed at the point of fusion. Metal should be +added so that the weld stands about one-eighth inch above the surrounding +surface of the work. + +Various forms of flux may be used and they are applied by dipping the end +of the welding rod into the powder at intervals. These powders may contain +borax or salt, and to prevent a hard, brittle weld, graphite or +ferro-silicon may be added. Flux should be added only after the iron is +molten and as little as possible should be used. No flux should be used +just before completion of the work. + +The welding flame should be played on the work around the crack and +gradually brought to bear on the work. The bottom of the bevel should be +joined first and it will be noted that the cast iron tends to run toward +the flame, but does not stick together easily. A hard and porous weld +should be carefully guarded against, as described above, and upon +completion of the work the welded surface should be scraped with a file, +while still red hot, in order to remove the surface scale. + +_Malleable Iron._--This material should be beveled in the same way +that cast iron is handled, and preheating and slow cooling are equally +desirable. The flame used is the same as for cast iron and so is the flux. +The welding rod may be of cast iron, although better results are secured +with Norway iron wire or else a mild steel wire wrapped with a coil of +copper wire. + +It will be understood that malleable iron turns to ordinary cast iron when +melted and cooled. Welds in malleable iron are usually far from +satisfactory and a better joint is secured by brazing the edges together +with bronze. The edges to be joined are brought to a heat just a little +below the point at which they will flow and the opening is then +quickly-filled from a rod of Tobin bronze or manganese bronze, a brass or +bronze flux being used in this work. + +_Wrought Iron or Semi-Steel._--This metal should be beveled and heated +in the same way as described for cast iron. The flame should be neutral, of +the same size as for steel, and used with the tip of the blue-white cone +just touching the work. The welding rod should be of mild steel, or, if +wrought iron is to be welded to steel, a cast iron rod may be used. A cast +iron flux is well suited for this work. It should be noted that wrought +iron turns to ordinary cast iron if kept heated for any length of time. + +_Steel._--Steel should be beveled if more than one-eighth inch in +thickness. It requires only a local preheating around the point to be +welded. The welding flame should be absolutely neutral, without excess of +either gas. If the metal is one-sixteenth inch or less in thickness, the +tip of the blue-white cone must be held a short distance from the surface +of the work; in all other cases the tip of this cone is touched to the +metal being welded. + +The welding rod may be of mild, low carbon steel or of Norway iron. Nickel +steel rods may be used for parts requiring great strength, but vanadium +alloys are very difficult to handle. A very satisfactory rod is made by +twisting together two wires of the required material. The rod must be kept +constantly in contact with the work and should not be added until the edges +are thoroughly melted. The flux may or may not be used. If one is wanted, +it may be made from three parts iron filings, six parts borax and one part +sal ammoniac. + +It will be noticed that the steel runs from the flame, but tends to hold +together. Should foaming commence in the molten metal, it shows an excess +of oxygen and that the metal is being burned. + +High carbon steels are very difficult to handle. It is claimed that a drop +or two of copper added to the weld will assist the flow, but will also +harden the work. An excess of oxygen reduces the amount of carbon and +softens the steel, while an excess of acetylene increases the proportion of +carbon and hardens the metal. High speed steels may sometimes be welded if +first coated with semi-steel before welding. + +_Aluminum._--This is the most difficult of the commonly found metals +to weld. This is caused by its high rate of expansion and contraction and +its liability to melt and fall away from under the flame. The aluminum +seems to melt on the inside first, and, without previous warning, a portion +of the work will simply vanish from in front of the operator's eyes. The +metal tends to run from the flame and separate at the same time. To keep +the metal in shape and free from oxide, it is worked or puddled while in a +plastic condition by an iron rod which has been flattened at one end. +Several of these rods should be at hand and may be kept in a jar of salt +water while not being used. These rods must not become coated with aluminum +and they must not get red hot while in the weld. + +The surfaces to be joined, together with the adjacent parts, should be +cleaned thoroughly and then washed with a 25 per cent solution of nitric +acid in hot water, used on a swab. The parts should then be rinsed in clean +water and dried with sawdust. It is also well to make temporary fire clay +moulds back of the parts to be heated, so that the metal may be flowed into +place and allowed to cool without danger of breakage. + +Aluminum must invariably be preheated to about 600 degrees, and the whole +piece being handled should be well covered with sheet asbestos to prevent +excessive heat radiation. + +The flame is formed with an excess of acetylene such that the second cone +extends about an inch, or slightly more, beyond the small blue-white point. +The torch should be held so that the end of this second cone is in contact +with the work, the small cone ordinarily used being kept an inch or an inch +and a half from the surface of the work. + +Welding rods of special aluminum are used and must be handled with their +end submerged in the molten metal of the weld at all times. + +When aluminum is melted it forms alumina, an oxide of the metal. This +alumina surrounds small masses of the metal, and as it does not melt at +temperatures below 5000 degrees (while aluminum melts at about 1200), it +prevents a weld from being made. The formation of this oxide is retarded +and the oxide itself is dissolved by a suitable flux, which usually +contains phosphorus to break down the alumina. + +_Copper._--The whole piece should be preheated and kept well covered +while welding. The flame must be much larger than for the same thickness of +steel and neutral in character. A slight excess of acetylene would be +preferable to an excess of oxygen, and in all cases the molten metal should +be kept enveloped with the flame. The welding rod is of copper which +contains phosphorus; and a flux, also containing phosphorus, should be +spread for about an inch each side of the joint. These assist in preventing +oxidation, which is sure to occur with heated copper. + +Copper breaks very easily at a heat slightly under the welding temperature +and after cooling it is simply cast copper in all cases. + +_Brass and Bronze._--It is necessary to preheat these metals, although +not to a very high temperature. They must be kept well covered at all times +to prevent undue radiation. The flame should be produced with a nozzle one +size larger than for the same thickness of steel and the small blue-white +cone should be held from one-fourth to one-half inch above the surface of +the work. The flame should be neutral in character. + +A rod or wire of soft brass containing a large percentage of zinc is +suitable for adding to brass, while copper requires the use of copper or +manganese bronze rods. Special flux or borax may be used to assist the +flow. + +The emission of white smoke indicates that the zinc contained in these +alloys is being burned away and the heat should immediately be turned away +or reduced. The fumes from brass and bronze welding are very poisonous and +should not be breathed. + + +RESTORATION OF STEEL + +The result of the high heat to which the steel has been subjected is that +it is weakened and of a different character than before welding. The +operator may avoid this as much as possible by first playing the outer +flame of the torch all over the surfaces of the work just completed until +these faces are all of uniform color, after which the metal should be well +covered with asbestos and allowed to cool without being disturbed. If a +temporary heating oven has been employed, the work and oven should be +allowed to cool together while protected with the sheet asbestos. If the +outside air strikes the freshly welded work, even for a moment, the result +will be breakage. + +A weld in steel will always leave the metal with a coarse grain and with +all the characteristics of rather low grade cast steel. As previously +mentioned in another chapter, the larger the grain size in steel the weaker +the metal will be, and it is the purpose of the good workman to avoid, as +far as possible, this weakening. + +The structure of the metal in one piece of steel will differ according to +the heat that it has under gone. The parts of the work that have been at +the melting point will, therefore, have the largest grain size and the +least strength. Those parts that have not suffered any great rise in +temperature will be practically unaffected, and all the parts between these +two extremes will be weaker or stronger according to their distance from +the weld itself. To restore the steel so that it will have the best grain +size, the operator may resort to either of two methods: (1) The grain may +be improved by forging. That means that the metal added to the weld and the +surfaces that have been at the welding heat are hammered much as a +blacksmith would hammer his finished work to give it greater strength. The +hammering should continue from the time the metal first starts to cool +until it has reached the temperature at which the grain size is best for +strength. This temperature will vary somewhat with the composition of the +metal being handled, but in a general way, it may be stated that the +hammering should continue without intermission from the time the flame is +removed from the weld until the steel just begins to show attraction for a +magnet presented to it. This temperature of magnetic attraction will always +be low enough and the hammering should be immediately discontinued at this +point. (2) A method that is more satisfactory, although harder to apply, is +that of reheating the steel to a certain temperature throughout its whole +mass where the heat has had any effect, and then allowing slow and even +cooling from this temperature. The grain size is affected by the +temperature at which the reheating is stopped, and not by the cooling, yet +the cooling should be slow enough to avoid strains caused by uneven +contraction. + +After the weld has been completed the steel must be allowed to cool until +below 1200° Fahrenheit. The next step is to heat the work slowly until all +those parts to be restored have reached a temperature at which the magnet +just ceases to be attracted. While the very best temperature will vary +according to the nature and hardness of the steel being handled, it will be +safe to carry the heating to the point indicated by the magnet in the +absence of suitable means of measuring accurately these high temperatures. +In using a magnet for testing, it will be most satisfactory if it is an +electromagnet and not of the permanent type. The electric current may be +secured from any small battery and will be the means of making sure of the +test. The permanent magnet will quickly lose its power of attraction under +the combined action of the heat and the jarring to which it will be +subjected. + +In reheating the work it is necessary to make sure that no part reaches a +temperature above that desired for best grain size and also to see that all +parts are brought to this temperature. Here enters the greatest difficulty +in restoring the metal. The heating may be done so slowly that no part of +the work on the outside reaches too high a temperature and then keeps the +outside at this heat until the entire mass is at the same temperature. A +less desirable way is to heat the outside higher than this temperature and +allow the conductivity of the metal to distribute the excess to the inside. + +The most satisfactory method, where it can be employed, is to make use of a +bath of some molten metal or some chemical mixture that can be kept at the +exact heat necessary by means of gas fires that admit of close regulation. +The temperature of these baths may be maintained at a constant point by +watching a pyrometer, and the finished work may be allowed to remain in the +bath until all parts have reached the desired temperature. + + +WELDING INFORMATION + +The following tables include much of the information that the operator must +use continually to handle the various metals successfully. The temperature +scales are given for convenience only. The composition of various alloys +will give an idea of the difficulties to be contended with by consulting +the information on welding various metals. The remaining tables are of +self-evident value in this work. + +TEMPERATURE SCALES +Centigrade Fahrenheit Centigrade Fahrenheit + 200° 392° 1000° 1832° + 225° 437° 1050° 1922° + 250° 482° 1100° 2012° + 275° 527° 1150° 2102° + 300° 572° 1200° 2192° + 325° 617° 1250° 2282° + 350° 662° 1300° 2372° + 375° 707° 1350° 2462° + 400° 752° 1400° 2552° + 425° 797° 1450° 2642° + 450° 842° 1500° 2732° + 475° 887° 1550° 2822° + 500° 932° 1600° 2912° + 525° 977° 1650° 3002° + 550° 1022° 1700° 3092° + 575° 1067° 1750° 3182° + 600° 1112° 1800° 3272° + 625° 1157° 1850° 3362° + 650° 1202° 1900° 3452° + 675° 1247° 2000° 3632° + 700° 1292° 2050° 3722° + 725° 1337° 2100° 3812° + 750° 1382° 2150° 3902° + 775° 1427° 2200° 3992° + 800° 1472° 2250° 4082° + 825° 1517° 2300° 4172° + 850° 1562° 2350° 4262° + 875° 1607° 2400° 4352° + 900° 1652° 2450° 4442° + 925° 1697° 2500° 4532° + 950° 1742° 2550° 4622° + 975° 1787° 2600° 4712° + +METAL ALLOYS +(Society of Automobile Engineers) + +Babbitt-- + Tin........................... 84.00% + Antimony...................... 9.00% + Copper........................ 7.00% + +Brass, White-- + Copper........................ 3.00% to 6.00% + Tin (minimum) ................ 65.00% + Zinc.......................... 28.00% to 30.00% + +Brass, Red Cast-- + Copper........................ 85.00% + Tin........................... 5.00% + Lead.......................... 5.00% + Zinc.......................... 5.00% + +Brass, Yellow-- + Copper........................ 62.00% to 65.00% + Lead.......................... 2.00% to 4.00% + Zinc.......................... 36.00% to 31.00% + +Bronze, Hard-- + Copper........................ 87.00% to 88.00% + Tin........................... 9.50% to 10.50% + Zinc.......................... 1.50% to 2.50% + +Bronze, Phosphor-- + Copper........................ 80.00% + Tin........................... 10.00% + Lead.......................... 10.00% + Phosphorus.................... .50% to .25% + +Bronze, Manganese-- + Copper (approximate) ......... 60.00% + Zinc (approximate) ........... 40.00% + Manganese (variable) ......... small + +Bronze, Gear-- + Copper........................ 88.00% to 89.00% + Tin........................... 11.00% to 12.00% + +Aluminum Alloys-- + Aluminum Copper Zinc Manganese + No. 1.. 90.00% 8.5-7.0% + No. 2.. 80.00% 2.0-3.0% 15% Not over 0.40% + No. 3.. 65.00% 35.0% + +Cast Iron-- + Gray Iron Malleable + Total carbon........3.0 to 3.5% + Combined carbon.....0.4 to 0.7% + Manganese...........0.4 to 0.7% 0.3 to 0.7% + Phosphorus..........0.6 to 1.0% Not over 0.2% + Sulphur...........Not over 0.1% Not over 0.6% + Silicon............1.75 to 2.25% Not over 1.0% + +Carbon Steel (10 Point)-- + Carbon........................ .05% to .15% + Manganese..................... .30% to .60% + Phosphorus (maximum).......... .045% + Sulphur (maximum)............. .05% +(20 Point)-- + Carbon........................ .15% to .25% + Manganese..................... .30% to .60% + Phosphorus (maximum).......... .045% + Sulphur (maximum)............. .05% +(35 Point)-- + Manganese..................... .50% to .80% + Carbon........................ .30% to .40% + Phosphorus (maximum).......... .05% + Sulphur (maximum)............. .05% +(95 Point)-- + Carbon........................ .90% to 1.05% + Manganese..................... .25% to .50% + Phosphorus (maximum).......... .04% + Sulphur (maximum)............. .05% + +HEATING POWER OF FUEL GASES + +(In B.T.U. per Cubic Foot.) + Acetylene....... 1498.99 Ethylene....... 1562.9 + Hydrogen........ 291.96 Methane........ 953.6 + Alcohol......... 1501.76 + +MELTING POINTS OF METALS + Platinum....................3200° + Iron, wrought...............2900° + malleable.................2500° + cast......................2400° + pure......................2760° + Steel, mild.................2700° + Medium....................2600° + Hard......................2500° + Copper......................1950° + Brass.......................1800° + Silver......................1750° + Bronze......................1700° + Aluminum....................1175° + Antimony....................1150° + Zinc........................ 800° + Lead........................ 620° + Babbitt..................500-700° + Solder...................500-575° + Tin......................... 450° + +_NOTE.--These melting points are for average compositions and conditions. +The exact proportion of elements entering into the metals affects their +melting points one way or the other in practice._ + +TENSILE STRENGTH OF METALS + +Alloy steels can be made with tensile strengths as high as 300,000 pounds +per square inch. Some carbon steels are given below according to "points": + + Pounds per Square Inch +Steel, 10 point................ 50,000 to 65,000 + 20 point..................... 60,000 to 80,000 + 40 point..................... 70,000 to 100,000 + 60 point..................... 90,000 to 120,000 +Iron, Cast..................... 13,000 to 30,000 + Wrought...................... 40,000 to 60,000 + Malleable.................... 25,000 to 45,000 +Copper......................... 24,000 to 50,000 +Bronze......................... 30,000 to 60,000 +Brass, Cast.................... 12,000 to 18,000 + Rolled....................... 30,000 to 40,000 + Wire......................... 60,000 to 75,000 +Aluminum....................... 12,000 to 23,000 +Zinc........................... 5,000 to 15,000 +Tin............................ 3,000 to 5,000 +Lead........................... 1,500 to 2,500 + +CONDUCTIVITY OF METALS + +(Based on the Value of Silver as 100) + + Heat Electricity +Silver....................100 100 +Copper.................... 74 99 +Aluminum.................. 38 63 +Brass..................... 23 22 +Zinc...................... 19 29 +Tin....................... 14 15 +Wrought Iron.............. 12 16 +Steel..................... 11.5 12 +Cast Iron................. 11 12 +Bronze.................... 9 7 +Lead...................... 8 9 + +WEIGHT OF METALS + +(Per Cubic Inch) + Pounds Pounds +Lead............ .410 Wrought Iron..... .278 +Copper.......... .320 Tin.............. .263 +Bronze.......... .313 Cast Iron........ .260 +Brass........... .300 Zinc............. .258 +Steel........... .283 Aluminum......... .093 + +EXPANSION OF METALS + +(Measured in Thousandths of an Inch per Foot of +Length When Raised 1000 Degrees in Temperature) + Inch Inch +Lead............ .188 Brass............ .115 +Zinc............ .168 Copper........... .106 +Aluminum........ .148 Steel............ .083 +Silver.......... .129 Wrought Iron..... .078 +Bronze.......... .118 Cast Iron........ .068 + + + + +CHAPTER VI + +ELECTRIC WELDING + + +RESISTANCE METHOD + +Two distinct forms of electric welding apparatus are in use, one producing +heat by the resistance of the metal being treated to the passage of +electric current, the other using the heat of the electric arc. + +The resistance process is of the greatest use in manufacturing lines where +there is a large quantity of one kind of work to do, many thousand pieces +of one kind, for instance. The arc method may be applied in practically any +case where any other form of weld may be made. The resistance process will +be described first. + +It is a well known fact that a poor conductor of electricity will offer so +much resistance to the flow of electricity that it will heat. Copper is a +good conductor, and a bar of iron, a comparatively poor conductor, when +placed between heavy copper conductors of a welder, becomes heated in +attempting to carry the large volume of current. The degree of heat depends +on the amount of current and the resistance of the conductor. + +In an electric circuit the ends of two pieces of metal brought together +form the point of greatest resistance in the electric circuit, and the +abutting ends instantly begin to heat. The hotter this metal becomes, the +greater the resistance to the flow of current; consequently, as the edges +of the abutting ends heat, the current is forced into the adjacent cooler +parts, until there is a uniform heat throughout the entire mass. The heat +is first developed in the interior of the metal so that it is welded there +as perfectly as at the surface. + +[Illustration: Figure 42.--Spot Welding Machine] + +The electric welder (Figure 42) is built to hold the parts to be joined +between two heavy copper dies or contacts. A current of three to five +volts, but of very great volume (amperage), is allowed to pass across +these dies, and in going through the metal to be welded, heats the edges +to a welding temperature. It may be explained that the voltage of an +electric current measures the pressure or force with which it is being sent +through the circuit and has nothing to do with the quantity or volume +passing. Amperes measure the rate at which the current is passing through +the circuit and consequently give a measure of the quantity which passes in +any given time. Volts correspond to water pressure measured by pounds to +the square inch; amperes represent the flow in gallons per minute. The low +voltage used avoids all danger to the operator, this pressure not being +sufficient to be felt even with the hands resting on the copper contacts. + +Current is supplied to the welding machine at a higher voltage and lower +amperage than is actually used between the dies, the low voltage and high +amperage being produced by a transformer incorporated in the machine +itself. By means of windings of suitable size wire, the outside current may +be received at voltages ranging from 110 to 550 and converted to the low +pressure needed. + +The source of current for the resistance welder must be alternating, that +is, the current must first be negative in value and then positive, passing +from one extreme to the other at rates varying from 25 to 133 times a +second. This form is known as alternating current, as opposed to direct +current, in which there is no changing of positive and negative. + +The current must also be what is known as single phase, that is, a current +which rises from zero in value to the highest point as a positive current +and then recedes to zero before rising to the highest point of negative +value. Two-phase of three-phase currents would give two or three positive +impulses during this time. + +As long as the current is single phase alternating, the voltage and cycles +(number of alternations per second) may be anything convenient. Various +voltages and cycles are taken care of by specifying all these points when +designing the transformer which is to handle the current. + +Direct current is not used because there is no way of reducing the voltage +conveniently without placing resistance wires in the circuit and this uses +power without producing useful work. Direct current may be changed to +alternating by having a direct current motor running an alternating current +dynamo, or the change may be made by a rotary converter, although this last +method is not so satisfactory as the first. + +The voltage used in welding being so low to start with, it is absolutely +necessary that it be maintained at the correct point. If the source of +current supply is not of ample capacity for the welder being used, it will +be very hard to avoid a fall of voltage when the current is forced to pass +through the high resistance of the weld. The current voltage for various +work is calculated accurately, and the efficiency of the outfit depends to +a great extent on the voltage being constant. + +A simple test for fall of voltage is made by connecting an incandescent +electric lamp across the supply lines at some point near the welder. The +lamp should burn with the same brilliancy when the weld is being made as at +any other time. If the lamp burns dim at any time, it indicates a drop in +voltage, and this condition should be corrected. + +The dynamo furnishing the alternating current may be in the same building +with the welder and operated from a direct current motor, as mentioned +above, or operated from any convenient shafting or source of power. When +the dynamo is a part of the welding plant it should be placed as close to +the welding machine as possible, because the length of the wire used +affects the voltage appreciably. + +In order to hold the voltage constant, the Toledo Electric Welder Company +has devised connections which include a rheostat to insert a variable +resistance in the field windings of the dynamo so that the voltage may be +increased by cutting this resistance out at the proper time. An auxiliary +switch is connected to the welder switch so that both switches act +together. When the welder switch is closed in making a weld, that portion +of the rheostat resistance between two arms determining the voltage is +short circuited. This lowers the resistance and the field magnets of the +dynamo are made stronger so that additional voltage is provided to care for +the resistance in the metal being heated. + +A typical machine is shown in the accompanying cut (Figure 43). On top of +the welder are two jaws for holding the ends of the pieces to be welded. +The lower part of the jaws is rigid while the top is brought down on top of +the work, acting as a clamp. These jaws carry the copper dies through which +the current enters the work being handled. After the work is clamped +between the jaws, the upper set is forced closer to the lower set by a long +compression lever. The current being turned on with the surfaces of the +work in contact, they immediately heat to the welding point when added +pressure on the lever forces them together and completes the weld. + +[Illustration: Figure 43--Operating Parts of a Toledo Spot Welder] + +[Illustration: Figure 43a.--Method of Testing Electric Welder] +[Illustration: Figure 44.--Detail of Water-Cooled Spot Welding Head] + +The transformer is carried in the base of the machine and on the left-hand +side is a regulator for controlling the voltage for various kinds of work. +The clamps are applied by treadles convenient to the foot of the operator. +A treadle is provided which instantly releases both jaws upon the +completion of the weld. One or both of the copper dies may be cooled by a +stream of water circulating through it from the city water mains +(Figure 44). The regulator and switch give the operator control of the +heat, anything from a dull red to the melting point being easily obtained +by movement of the lever (figure 45). + +[Illustration: Figure 45.--Welding Head of a Water-Cooled Welder] + +_Welding._--It is not necessary to give the metal to be welded any +special preparation, although when very rusty or covered with scale, the +rust and scale should be removed sufficiently to allow good contact of +clean metal on the copper dies. The cleaner and better the stock, the less +current it takes, and there is less wear on the dies. The dies should be +kept firm and tight in their holders to make a good contact. All bolts and +nuts fastening the electrical contacts should be clean and tight at all +times. + +The scale may be removed from forgings by immersing them in a pickling +solution in a wood, stone or lead-lined tank. + +The solution is made with five gallons of commercial sulphuric acid in +150 gallons of water. To get the quickest and best results from this +method, the solution should be kept as near the boiling point as possible +by having a coil of extra heavy lead pipe running inside the tank and +carrying live steam. A very few minutes in this bath will remove the scale +and the parts should then be washed in running water. After this washing +they should be dipped into a bath of 50 pounds of unslaked lime in 150 +gallons of water to neutralize any trace of acid. + +Cast iron cannot be commercially welded, as it is high in carbon and +silicon, and passes suddenly from a crystalline to a fluid state when +brought to the welding temperature. With steel or wrought iron the +temperature must be kept below the melting point to avoid injury to the +metal. The metal must be heated quickly and pressed together with +sufficient force to push all burnt metal out of the joint. + +High carbon steel can be welded, but must be annealed after welding to +overcome the strains set up by the heat being applied at one place. Good +results are hard to obtain when the carbon runs as high as 75 points, and +steel of this class can only be handled by an experienced operator. If the +steel is below 25 points in carbon content, good welds will always be the +result. To weld high carbon to low carbon steel, the stock should be +clamped in the dies with the low carbon stock sticking considerably further +out from the die than the high carbon stock. Nickel steel welds readily, +the nickel increasing the strength of the weld. + +Iron and copper may be welded together by reducing the size of the copper +end where it comes in contact with the iron. When welding copper and brass +the pressure must be less than when welding iron. The metal is allowed to +actually fuse or melt at the juncture and the pressure must be sufficient +to force the burned metal out. The current is cut off the instant the metal +ends begin to soften, this being done by means of an automatic switch which +opens when the softening of the metal allows the ends to come together. The +pressure is applied to the weld by having the sliding jaw moved by a weight +on the end of an arm. + +Copper and brass require a larger volume of current at a lower voltage than +for steel and iron. The die faces are set apart three times the diameter of +the stock for brass and four times the diameter for copper. + +Light gauges of sheet steel can be welded to heavy gauges or to solid bars +of steel by "spot" welding, which will be described later. Galvanized iron +can be welded, but the zinc coating will be burned off. Sheet steel can be +welded to cast iron, but will pull apart, tearing out particles of the +iron. + +Sheet copper and sheet brass may be welded, although this work requires +more experience than with iron and steel. Some grades of sheet aluminum can +be spot-welded if the slight roughness left on the surface under the die +is not objectionable. + +_Butt Welding._--This is the process which joins the ends of two +pieces of metal as described in the foregoing part of this chapter. The +ends are in plain sight of the operator at all times and it can easily be +seen when the metal reaches the welding heat and begins to soften (Figure +46). It is at this point that the pressure must be applied with the lever +and the ends forced together in the weld. + +[Illustration: Figure 46.--Butt Welder] + +The parts are placed in the clamping jaws (Figure 47) with 1/8 to 1/2 inch +of metal extending beyond the jaw. The ends of the metal touch each other +and the current is turned on by means of a switch. To raise the ends to the +proper heat requires from 3 seconds for 1/4-inch rods to 35 seconds for a +1-1/2-inch bar. + +This method is applicable to metals having practically the same area of +metal to be brought into contact on each end. When such parts are forced +together a slight projection will be left in the form of a fin or an +enlarged portion called an upset. The degree of heat required for any work +is found by moving the handle of the regulator one way or the other while +testing several parts. When this setting is right the work can continue as +long as the same sizes are being handled. + +[Illustration: Figure 47.--Clamping Dies of a Butt Welder] + +Copper, brass, tool steel and all other metals that are harmed by high +temperatures must be heated quickly and pressed together with sufficient +force to force all burned metal from the weld. + +In case it is desired to make a weld in the form of a capital letter T, it +is necessary to heat the part corresponding to the top bar of the T to a +bright red, then bring the lower bar to the pre-heated one and again turn +on the current, when a weld can be quickly made. + +_Spot Welding._--This is a method of joining metal sheets together at +any desired point by a welded spot about the size of a rivet. It is done on +a spot welder by fusing the metal at the point desired and at the same +instant applying sufficient pressure to force the particles of molten metal +together. The dies are usually placed one above the other so that the work +may rest on the lower one while the upper one is brought down on top of the +upper sheet to be welded. + +One of the dies is usually pointed slightly, the opposing one being left +flat. The pointed die leaves a slight indentation on one side of the metal, +while the other side is left smooth. The dies may be reversed so that the +outside surface of any work may be left smooth. The current is allowed to +flow through the dies by a switch which is closed after pressure is applied +to the work. + +There is a limit to the thickness of sheet metal that can be welded by this +process because of the fact that the copper rods can only carry a certain +quantity of current without becoming unduly heated themselves. Another +reason is that it is difficult to make heavy sections of metal touch at the +welding point without excessive pressure. + +_Lap welding_ is the process used when two pieces of metal are caused +to overlap and when brought to a welding heat are forced together by +passing through rollers, or under a press, thus leaving the welded joint +practically the same thickness as the balance of the work. + +Where it is desirable to make a continuous seam, a special machine is +required, or an attachment for one of the other types. In this form of work +the stock must be thoroughly cleaned and is then passed between copper +rollers which act in the same capacity as the copper dies. + +_Other Applications._--Hardening and tempering can be done by clamping +the work in the welding dies and setting the control and time to bring the +metal to the proper color, when it is cooled in the usual manner. + +Brazing is done by clamping the work in the jaws and heating until the +flux, then the spelter has melted and run into the joint. Riveting and +heading of rivets can be done by bringing the dies down on opposite ends of +the rivet after it has been inserted in the hole, the dies being shaped to +form the heads properly. + +Hardened steel may be softened and annealed so that it can be machined by +connecting the dies of the welder to each side of the point to be softened. +The current is then applied until the work has reached a point at which it +will soften when cooled. + +_Troubles and Remedies._--The following methods have been furnished by +the Toledo Electric Welder Company and are recommended for this class of +work whenever necessary. + +To locate grounds in the primary or high voltage side of the circuit, +connect incandescent lamps in series by means of a long piece of lamp cord, +as shown, in Figure 43a. For 110 volts use one lamp, for 220 volts use two +lamps and for 440 volts use four lamps. Attach one end of the lamp cord to +one side of the switch, and close the switch. Take the other end of the +cord in the hand and press it against some part of the welder frame where +the metal is clean and bright. Paint, grease and dirt act as insulators and +prevent electrical contact. If the lamp lights, the circuit is in +electrical contact with the frame; in other words, grounded. If the lamps +do not light, connect the wire to a terminal block, die or slide. If the +lamps then light, the circuit, coils or leads are in electrical contact +with the large coil in the transformer or its connections. + +If, however, the lamps do not light in either case, the lamp cord should be +disconnected from the switch and connected to the other side, and the +operations of connecting to welder frame, dies, terminal blocks, etc., as +explained above, should be repeated. If the lamps light at any of these +connections, a "ground" is indicated. "Grounds" can usually be found by +carefully tracing the primary circuit until a place is found where the +insulation is defective. Reinsulate and make the above tests again to make +sure everything is clear. If the ground can not be located by observation, +the various parts of the primary circuit should be disconnected, and the +transformer, switch, regulator, etc., tested separately. + +To locate a ground in the regulator or other part, disconnect the lines +running to the welder from the switch. The test lamps used in the previous +tests are connected, one end of lamp cord to the switch, the other end to a +binding post of the regulator. Connect the other side of the switch to some +part of the regulator housing. (This must be a clean connection to a bolt +head or the paint should be scraped off.) Close the switch. If the lamps +light, the regulator winding or some part of the switch is "grounded" to +the iron base or core of the regulator. If the lamps do not light, this +part of the apparatus is clear. + +This test can be easily applied to any part of the welder outfit by +connecting to the current carrying part of the apparatus, and to the iron +base or frame that should not carry current. If the lamps light, it +indicates that the insulation is broken down or is defective. + +An A.C. voltmeter can, of course, be substituted for the lamps, or a D.C. +voltmeter with D.C. current can be used in making the tests. + +A short circuit in the primary is caused by the insulation of the coils +becoming defective and allowing the bare copper wires to touch each other. +This may result in a "burn out" of one or more of the transformer coils, if +the trouble is in the transformer, or in the continued blowing of fuses in +the line. Feel of each coil separately. If a short circuit exists in a coil +it will heat excessively. Examine all the wires; the insulation may have +worn through and two of them may cross, or be in contact with the frame or +other part of the welder. A short circuit in the regulator winding is +indicated by failure of the apparatus to regulate properly, and sometimes, +though not always, by the heating of the regulator coils. + +The remedy for a short circuit is to reinsulate the defective parts. It is +a good plan to prevent trouble by examining the wiring occasionally and see +that the insulation is perfect. + +_To Locate Grounds and Short Circuits in the Secondary, or Low Voltage +Side._--Trouble of this kind is indicated by the machine acting sluggish +or, perhaps, refusing to operate. To make a test, it will be necessary to +first ascertain the exciting current of your particular transformer. This +is the current the transformer draws on "open circuit," or when supplied +with current from the line with no stock in the welder dies. The following +table will give this information close enough for all practical purposes: + +K.W. ----------------- Amperes at ---------------- +Rating 110 Volts 220 Volts 440 Volts 550 Volts +3 1.5 .75 .38 .3 +5 2.5 1.25 .63 .5 +8 3.6 1.8 .9 .72 +10 4.25 2.13 1.07 .85 +15 6. 3. 1.5 1.2 +20 7. 3.5 1.75 1.4 +30 9. 4.5 2.25 1.8 +35 9.6 4.8 2.4 1.92 +50 10. 5. 2.5 2 + +Remove the fuses from the wall switch and substitute fuses just large +enough to carry the "exciting" current. If no suitable fuses are at hand, +fine strands of copper from an ordinary lamp cord may be used. These +strands are usually No. 30 gauge wire and will fuse at about 10 amperes. +One or more strands should be used, depending on the amount of exciting +current, and are connected across the fuse clips in place of fuse wire. +Place a piece of wood or fibre between the welding dies in the welder as +though you were going to weld them. See that the regulator is on the +highest point and close the welder switch. If the secondary circuit is +badly grounded, current will flow through the ground, and the small fuses +or small strands of wire will burn out. This is an indication that both +sides of the secondary circuit are grounded or that a short circuit exists +in a primary coil. In either case the welder should not be operated until +the trouble is found and removed. If, however, the small fuses do not +"blow," remove same and replace the large fuses, then disconnect wires +running from the wall switch to the welder and substitute two pieces of +No. 8 or No. 6 insulated copper wire, after scraping off the insulation for +an inch or two at each end. Connect one wire from the switch to the frame +of welder; this will leave one loose end. Hold this a foot or so away from +the place where the insulation is cut off; then turn on the current and +strike the free end of this wire lightly against one of the copper dies, +drawing it away quickly. If no sparking is produced, the secondary circuit +is free from ground, and you will then look for a broken connection in the +circuit. Some caution must be used in making the above test, as in case one +terminal is heavily grounded the testing wire may be fused if allowed to +stay in contact with the die. + +_The Remedy._--Clean the slides, dies and terminal blocks thoroughly +and dry out the fibre insulation if it is damp. See that no scale or metal +has worked under the sliding parts, and that the secondary leads do not +touch the frame. If the ground is very heavy it may be necessary to remove +the slides in order to facilitate the examination and removal of the +ground. Insulation, where torn or worn through, must be carefully replaced +or taped. If the transformer coils are grounded to the iron core of the +transformer or to the secondary, it may be necessary to remove the coils +and reinsulate them at the points of contact. A short circuited coil will +heat excessively and eventually burn out. This may mean a new coil if you +are unable to repair the old one. In all cases the transformer windings +should be protected from mechanical injury or dampness. Unless excessively +overloaded, transformers will last for years without giving a moment's +trouble, if they are not exposed to moisture or are not injured +mechanically. + +The most common trouble arises from poor electrical contacts, and they are +the cause of endless trouble and annoyance. See that all connections are +clean and bright. Take out the dies every day or two and see that there is +no scale, grease or dirt between them and the holders. Clean them +thoroughly before replacing. Tighten the bolts running from the transformer +leads to the work jaws. + + +ELECTRIC ARC WELDING + +This method bears no relation to the one just considered, except that the +source of heat is the same in both cases. Arc welding makes use of the +flame produced by the voltaic arc in practically the same way that +oxy-acetylene welding uses the flame from the gases. + +If the ends of two pieces of carbon through which a current of electricity +is flowing while they are in contact are separated from each other quite +slowly, a brilliant arc of flame is formed between them which consists +mainly of carbon vapor. The carbons are consumed by combination with the +oxygen in the air and through being turned to a gas under the intense heat. + +The most intense action takes place at the center of the carbon which +carries the positive current and this is the point of greatest heat. The +temperature at this point in the arc is greater than can be produced by any +other means under human control. + +An arc may be formed between pieces of metal, called electrodes, in the +same way as between carbon. The metallic arc is called a flaming arc and as +the metal of the electrode burns with the heat, it gives the flame a color +characteristic of the material being used. The metallic arc may be drawn +out to a much greater length than one formed between carbon electrodes. + +Arc Welding is carried out by drawing a piece of carbon which is of +negative polarity away from the pieces of metal to be welded while the +metal is made positive in polarity. The negative wire is fastened to the +carbon electrode and the work is laid on a table made of cast or wrought +iron to which the positive wire is made fast. The direction of the flame is +then from the metal being welded to the carbon and the work is thus +prevented from being saturated with carbon, which would prove very +detrimental to its strength. A secondary advantage is found in the fact +that the greatest heat is at the metal being welded because of its being +the positive electrode. + +The carbon electrode is usually made from one quarter to one and a half +inches in diameter and from six to twelve inches in length. The length of +the arc may be anywhere from one inch to four inches, depending on the size +of the work being handled. + +While the parts are carefully insulated to avoid danger of shock, it is +necessary for the operator to wear rubber gloves as a further protection, +and to wear some form of hood over the head to shield him against the +extreme heat liberated. This hood may be made from metal, although some +material that does not conduct electricity is to be preferred. The work is +watched through pieces of glass formed with one sheet, which is either blue +or green, placed over another which is red. Screens of glass are sometimes +used without the head protector. Some protection for the eyes is absolutely +necessary because of the intense white light. + +It is seldom necessary to preheat the work as with the gas processes, +because the heat is localized at the point of welding and the action is so +rapid that the expansion is not so great. The necessity of preheating, +however, depends entirely on the material, form and size of the work being +handled. The same advice applies to arc welding as to the gas flame method +but in a lesser degree. Filling rods are used in the same way as with any +other flame process. + +It is the purpose of this explanation to state the fundamental principles +of the application of the electric arc to welding metals, and by applying +the principles the following questions will be answered: + +What metals can be welded by the electric arc? + +What difficulties are to be encountered in applying the electric arc to +welding? + +What is the strength of the weld in comparison with the original piece? + +What is the function of the arc welding machine itself? + +What is the comparative application of the electric arc and the +oxy-acetylene method and others of a similar nature? + +The answers to these questions will make it possible to understand the +application of this process to any work. In a great many places the use of +the arc is cutting the cost of welding to a very small fraction of what it +would be by any other method, so that the importance of this method may be +well understood. + +Any two metals which are brought to the melting temperature and applied to +each other will adhere so that they are no more apt to break at the weld +than at any other point outside of the weld. It is the property of all +metals to stick together under these conditions. The electric arc is used +in this connection merely as a heating agent. This is its only function in +the process. + +It has advantages in its ease of application and the cheapness with which +heat can be liberated at any given point by its use. There is nothing in +connection with arc welding that the above principles will not answer; that +is, that metals at the melting point will weld and that the electric arc +will furnish the heat to bring them to this point. As to the first +question, what metals can be welded, all metals can be welded. + +The difficulties which are encountered are as follows: + +In the case of brass or zinc, the metals will be covered with a coat of +zinc oxide before they reach a welding heat. This zinc oxide makes it +impossible for two clean surfaces to come together and some method has to +be used for eliminating this possibility and allowing the two surfaces to +join without the possibility of the oxide intervening. The same is true of +aluminum, in which the oxide, alumina, will be formed, and with several +other alloys comprising elements of different melting points. + +In order to eliminate these oxides, it is necessary in practical work, to +puddle the weld; this is, to have a sufficient quantity of molten metal at +the weld so that the oxide is floated away. When this is done, the two +surfaces which are to be joined are covered with a coat of melted metal on +which floats the oxide and other impurities. The two pieces are thus +allowed to join while their surfaces are protected. This precaution is not +necessary in working with steel except in extreme cases. + +Another difficulty which is met with in the welding of a great many metals +is their expansion under heat, which results in so great a contraction when +the weld cools that the metal is left with a considerable strain on it. In +extreme cases this will result in cracking at the weld or near it. To +eliminate this danger it is necessary to apply heat either all over the +piece to be welded or at certain points. In the case of cast iron and +sometimes with copper it is necessary to anneal after welding, since +otherwise the welded pieces will be very brittle on account of the +chilling. This is also true of malleable iron. + +Very thin metals which are welded together and are not backed up by +something to carry away the excess heat, are very apt to burn through, +leaving a hole where the weld should be. This difficulty can be eliminated +by backing up the weld with a metal face or by decreasing the intensity of +the arc so that this melting through will not occur. However, the practical +limit for arc welding without backing up the work with a metal face or +decreasing the intensity of the arc is approximately 22 gauge, although +thinner metal can be welded by a very skillful and careful operator. + +One difficulty with arc welding is the lack of skillful operators. This +method is often looked upon as being something out of the ordinary and +governed by laws entirely different from other welding. As a matter of +fact, it does not take as much skill to make a good arc weld as it does to +make a good weld in a forge fire as the blacksmith does it. There are few +jobs which cannot be handled successfully by an operator of average +intelligence with one week's instructions, although his work will become +better and better in quality as he continues to use the arc. + +Now comes the question of the strength of the weld after it has been made. +This strength is equally as great as that of the metal that is used to make +the weld. It should be remembered, however, that the metal which goes into +the weld is put in there as a casting and has not been rolled. This would +make the strength of the weld as great as the same metal that is used for +filling if in the cast form. + +Two pieces of steel could be welded together having a tensile strength at +the weld of 50,000 pounds. Higher strengths than this can be obtained by +the use of special alloys for the filling material or by rolling. Welds +with a tensile strength as great as mentioned will give a result which is +perfectly satisfactory in almost all cases. + +There are a great many jobs where it is possible to fill up the weld, that +is, make the section at the point of the weld a little larger than the +section through the rest of the piece. By doing this, the disadvantages +of the weld being in the form of a casting in comparison with the rest of +the piece being in the form of rolled steel can be overcome, and make the +weld itself even stronger than the original piece. + +The next question is the adaptability of the electric arc in comparison +with forge fire, oxy-acetylene or other method. The answer is somewhat +difficult if made general. There are no doubt some cases where the use of a +drop hammer and forge fire or the use of the oxy-acetylene torch will make, +all things being considered, a better job than the use of the electric arc, +although a case where this is absolutely proved is rare. + +The electric arc will melt metal in a weld for less than the same metal can +be melted by the use of the oxy-acetylene torch, and, on account of the +fact that the heat can be applied exactly where it is required and in the +amount required, the arc can in almost all cases supply welding heat for +less cost than a forge fire or heating furnace. + +The one great advantage of the oxy-acetylene method in comparison with +other methods of welding is the fact that in some cases of very thin sheet, +the weld can be made somewhat sooner than is possible otherwise. With metal +of 18 gauge or thicker, this advantage is eliminated. In cutting steel, the +oxy-acetylene torch is superior to almost any other possible method. + +_Arc Welding Machines._--A consideration of the function and purpose +of the various types of arc welding machines shows that the only reason for +the use of any machine is either for conversion of the current from +alternating to direct, or, if the current is already direct, then the +saving in the application of this current in the arc. + +It is practically out of the question to apply an alternating current arc +to welding for the reason that in any arc practically all the heat is +liberated at the positive electrode, which means that, in alternating +current, half the heat is liberated at each electrode as the current +changes its direction of flow or alternates. Another disadvantage of the +alternating arc is that it is difficult of control and application. + +In all arc welding by the use of the carbon arc, the positive electrode is +made the piece to be welded, while in welding with metallic electrodes this +may be either the piece to be welded of the rod that is used as a filler. +The voltage across the arc is a variable quantity, depending on the length +of the flame, its temperature and the gases liberated in the arc. With a +carbon electrode the voltage will vary from zero to forty-five volts. With +the metallic electrode the voltage will vary from zero to thirty volts. It +is, therefore, necessary for the welding machine to be able to furnish to +the arc the requisite amount of current, this amount being varied, and +furnish it at all times at the voltage required. + +The simplest welding apparatus is a resistance in series with the arc. This +is entirely satisfactory in every way except in cost of current. By the use +of resistance in series with the arc and using 220 volts as the supply, +from eighty to ninety per cent of the current is lost in heat at the +resistance. Another disadvantage is the fact that most materials change +their resistance as their temperature changes, thus making the amount of +current for the arc a variable quantity, depending on the temperature of +the resistance. + +There have been various methods originated for saving the power mentioned +and a good many machines have been put on the market for this purpose. All +of them save some power over what a plain resistance would use. Practically +all arc welding machines at the present time are motor generator sets, the +motor of which is arranged for the supply voltage and current, this motor +being direct connected to a compound wound generator delivering +approximately seventy-five volts direct current. Then by the use of a +resistance, this seventy-five volt supply is applied to the arc. Since the +voltage across the arc will vary from zero to fifty volts, this machine +will save from zero up to seventy per cent of the power that the machine +delivers. The rest of the power, of course, has to be dissipated in the +resistance used in series with the arc. + +A motor generator set which can be purchased from any electrical company, +with a long piece of fence wire wound around a piece of asbestos, gives +results equally as good and at a very small part of the first cost. + +It is possible to construct a machine which will eliminate all losses in +the resistance; in other words, eliminate all resistance in series with the +arc. A machine of this kind will save its cost within a very short time, +providing the welder is used to any extent. + +Putting it in figures, the results are as follows for average conditions. +Current at 2c per kilowatt hour, metallic electrode arc of 150 amperes, +carbon arc 500 amperes; voltage across the metallic electrode arc 20, +voltage across the carbon arc 35. Supply current 220 volts, direct. In the +case of the metallic electrode, if resistance is used, the cost of running +this arc is sixty-six cents per hour. With the carbon electrode, $2.20 per +hour. If a motor generator set with a seventy volt constant potential +machine is used for a welder, the cost will be as follows: + +Metallic electrode 25.2c. Carbon electrode 84c per hour. With a machine +which will deliver the required voltage at the arc and eliminate all the +resistance in series with the arc, the cost will be as follows: Metallic +electrode 7.2c per hour; carbon electrode 42c per hour. This is with the +understanding that the arc is held constant and continuously at its full +value. This, however, is practically impossible and the actual load factor +is approximately fifty per cent, which would mean that operating a welder +as it is usually operated, this result will be reduced to one-half of that +stated in all cases. + + + + +CHAPTER VII + +HAND FORGING AND WELDING + + +Smithing, or blacksmithing, is the process of working heated iron, steel or +other metals by forging, bending or welding them. + +_The Forge._--The metal is heated in a forge consisting of a shallow +pan for holding the fire, in the center of which is an opening from below +through which air is forced to make a hot fire. + +[Illustration: Figure 48.--Tuyere Construction on a Forge] + +Air is forced through this hole, called a "tuyere" (Figure 48) by means of +a hand bellows, a rotary fan operated with crank or lever, or with a fan +driven from an electric motor. The harder the air is driven into the fire +above the tuyere the more oxygen is furnished and the hotter the fire +becomes. + +Directly below the tuyere is an opening through which the ashes that drop +from the fire may be cleaned out. + +_The Fire._--The fire is made by placing a small piece of waste soaked +in oil, kerosene or gasoline, over the tuyere, lighting the waste, then +starting the fan or blower slowly. Gradually cover the waste, while it is +burning brightly, with a layer of soft coal. The coal will catch fire and +burn after the waste has been consumed. A piece of waste half the size of a +person's hand is ample for this purpose. + +The fuel should be "smithing coal." A lump of smithing coal breaks easily, +shows clean and even on all sides and should not break into layers. The +coal is broken into fine pieces and wet before being used on the fire. + +The fire should be kept deep enough so that there is always three or four +inches of fire below the piece of metal to be heated and there should be +enough fire above the work so that no part of the metal being heated comes +in contact with the air. The fire should be kept as small as possible while +following these rules as to depth. + +To make the fire larger, loosen the coal around the edges. To make the fire +smaller, pack wet coal around the edges in a compact mass and loosen the +fire in the center. Add fresh coal only around the edges of the fire. It +will turn to coke and can then be raked onto the fire. Blow only enough air +into the fire to keep it burning brightly, not so much that the fire is +blown up through the top of the coal pack. To prevent the fire from going +out between jobs, stick a piece of soft wood into it and cover with fresh +wet coal. + +_Tools._--The _hammer_ is a ball pene, or blacksmith's hammer, +weighing about a pound and a half. + +The _sledge_ is a heavy hammer, weighing from 5 to 20 pounds and +having a handle 30 to 36 inches long. + +The _anvil_ is a heavy piece of wrought iron (Figure 49), faced with +steel and having four legs. It has a pointed horn on one end, an +overhanging tail on the other end and a flat top. In the tail there is a +square hole called the "hardie" hole and a round one called the "spud" +hole. + +[Illustration: Figure 49.--Anvil, Showing Horn, Tail, Hardie Hole and Spud +Hole] + +_Tongs_, with handles about one foot long and jaws suitable for +holding the work, are used. To secure a firm grip on the work, the jaws may +be heated red hot and hammered into shape over the piece to be held, thus +giving a properly formed jaw. Jaws should touch the work along their entire +length. + +The _set hammer_ is a hammer, one end of whose head is square and +flat, and from this face the head tapers evenly to the other face. The +large face is about 1-1/4 inches square. + +The _flatter_ is a hammer having one face of its head flat and about +2-1/2 inches square. + +_Swages_ are hammers having specially formed faces for finishing +rounds, squares, hexagons, ovals, tapers, etc. + +_Fullers_ are hammers having a rounded face, long in one direction. +They are used for spreading metal in one direction only. + +The _hardy_ is a form of chisel with a short, square shank which may +be set into the hardie hole for cutting off hot bars. + +_Operations._--Blacksmithing consists of bending, drawing or upsetting +with the various hammers, or in punching holes. + +Bending is done over the square corners of the anvil if square cornered +bends are desired, or over the horn of the anvil if rounding bends, eyes, +hooks, etc., are wanted. + +To bend a ring or eye in the end of a bar, first figure the length of stock +needed by multiplying the diameter of the hole by 31/7, then heat the piece +to a good full red at a point this distance back from the end. Next bend +the iron over at a 90 degree angle (square) at this point. Next, heat the +iron from the bend just made clear to the point and make the eye by laying +the part that was bent square over the horn of the anvil and bending the +extreme tip into part of a circle. Keep pushing the piece farther and +farther over the horn of the anvil, bending it as you go. Do not hammer +directly over the horn of the anvil, but on the side where you are doing +the bending. + +To make the outside of a bend square, sharp and full, rather than slightly +rounding, the bent piece must be laid edgewise on the face of the anvil. +That is, after making the bend over the corner of the anvil, lay the piece +on top of the anvil so that its edge and not the flat side rests on the +anvil top. With the work in this position, strike directly against the +corner with the hammer so that the blows come in line, first with one leg +of the work, then the other, and always directly on the corner of the +piece. This operation cannot be performed by laying the work so that one +leg hangs over the anvil's corner. + +To make a shoulder on a rod or bar, heat the work and lay flat across the +top of the anvil with the point at which the shoulder is desired at the +edge of the anvil. Then place the set hammer on top of the piece, with the +outside edge of the set hammer directly over the edge of the anvil. While +hammering in this position keep the work turning continually. + +To draw stock means to make it longer and thinner by hammering. A piece to +be drawn out is usually laid across the horn of the anvil while being +struck with the hammer. The metal is then spread in only one direction in +place of being spread in every direction, as it would be if laid on the +anvil face. To draw the work, heat it to as high a temperature as it will +stand without throwing sparks and burning. The fuller may be used for +drawing metal in place of laying the work over the horn of the anvil. + +When drawing round stock, it should be first drawn out square, and when +almost down to size it may be rounded. When pointing stock, the same rule +of first drawing out square applies. + +Upsetting means to make a piece shorter in length and greater in thickness +or width, or both shorter and thicker. To upset short pieces, heat to a +bright red at the place to be upset, then stand on end on the anvil face +and hammer directly down on top until of the right form. Longer pieces may +be swung against the anvil or placed upright on a heavy piece of metal +lying on the floor or that is sunk into the floor. While standing on this +heavy piece the metal may be upset by striking down on the end with a heavy +hammer or the sledge. If a bend appears while upsetting, it should be +straightened by hammering back into shape on the anvil face. + +Light blows affect the metal for only a short distance from the point of +striking, but heavy blows tend to swell the metal more equally through its +entire length. In driving rivets that should fill the holes, heavy blows +should be struck, but to shape the end of a rivet or to make a head on a +rod, light blows should be used. + +The part of the piece that is heated most will upset the most. + +To punch a hole through metal, use a tool steel punch with its end slightly +tapering to a size a little smaller than the hole to be punched. The end of +the punch must be square across and never pointed or rounded. + +First drive the punch part way through from one side and then turn the work +over. When you turn it over, notice where the bulge appears and in that way +locate the hole and drive the punch through from the second side. This +makes a cleaner and more even hole than to drive completely through from +one side. When the punch is driven in from the second side, the place to be +punched through should be laid over the spud hole in the tail of the anvil +and the piece driven out of the work. + +Work when hot is larger than it will be after cooling. This must be +remembered when fitting parts or trouble will result. A two-foot bar of +steel will be 1/4 inch longer when red hot than when cold. + +The temperatures of iron correspond to the following colors: + + Dullest red seen in the dark... 878° + Dullest red seen in daylight... 887° + Dull red....................... 1100° + Full red....................... 1370° + Light red...................... 1550° + Orange......................... 1650° + Light orange................... 1725° + Yellow......................... 1825° + Light yellow................... 1950° + +_Bending Pipes and Tubes._--It is difficult to make bends or curves in +pipes and tubing without leaving a noticeable bulge at some point of the +work. Seamless steel tubing may be handled without very great danger of +this trouble if care is used, but iron pipe, having a seam running +lengthwise, must be given special attention to avoid opening the seam. + +Bends may be made without kinking if the tube or pipe is brought to a full +red heat all the way around its circumference and at the place where the +bend is desired. Hold the cool portion solidly in a vise and, by taking +hold of the free end, bend very slowly and with a steady pull. The pipe +must be kept at full red heat with the flames from one or more torches and +must not be hammered to produce the bend. If a sufficient purchase cannot +be secured on the free end by the hand, insert a piece of rod or a smaller +pipe into the opening. + +While making the bend, should small bulges appear, they may be hammered +back into shape before proceeding with the work. + +Tubing or pipes may be bent while being held between two flat metal +surfaces while at a bright red heat. The metal plates at each side of the +work prevent bulging. + +Another method by which tubing may be bent consists of filling completely +with tightly packed sand and fitting a solid cap or plug at each end. + +Thin brass tubing may be filled with melted resin and may be bent after the +resin cools. To remove the resin it is necessary to heat the tube, allowing +it to run out. + +Large jobs of bending should be handled in special pipe bending machines in +which the work is forced through formed rolls which prevent its bulging. + + +WELDING + +Welding with the heat of a blacksmith forge fire, or a coal or illuminating +gas fire, can only be performed with iron and steel because of the low heat +which is not localized as with the oxy-acetylene and electric processes. +Iron to be welded in this manner is heated until it reaches the temperature +indicated by an orange color, not white, as is often stated, this orange +color being slightly above 3600 degrees Fahrenheit. Steel is usually welded +at a bright red heat because of the danger of oxidizing or burning the +metal if the temperature is carried above this point. + +_The Fire._--If made in a forge, the fire should be built from good +smithing coal or, better still, from coke. Gas fires are, of course, +produced by suitable burners and require no special preparation except +adjustment of the heat to the proper degree for the size and thickness of +the metal being welded so that it will not be burned. + +A coal fire used for ordinary forging operations should not be used for +welding because of the impurities it contains. A fresh fire should be built +with a rather deep bed of coal, four to eight inches being about right for +work ordinarily met with. The fire should be kept burning until the coal +around the edges has been thoroughly coked and a sufficient quantity of +fuel should be on and around the fire so that no fresh coal will have to +be added while working. + +After the coking process has progressed sufficiently, the edges should be +packed down and the fire made as small as possible while still surrounding +the ends to be joined. The fire should not be altered by poking it while +the metal is being heated. The best form of fire to use is one having +rather high banks of coked coal on each side of the mass, leaving an +opening or channel from end to end. This will allow the added fuel to be +brought down on top of the fire with a small amount of disturbance. + +_Preparing to Weld._--If the operator is not familiar with the metal +to be handled, it is best to secure a test piece if at all possible and try +heating it and joining the ends. Various grades of iron and steel call for +different methods of handling and for different degrees of heat, the proper +method and temperature being determined best by actual test under the +hammer. + +The form of the pieces also has a great deal to do with their handling, +especially in the case of a more or less inexperienced workman. If the +pieces are at all irregular in shape, the motions should be gone through +with before the metal is heated and the best positions on the anvil as well +as in the fire determined with regard to the convenience of the workman and +speed of handling the work after being brought to a welding temperature. +Unnatural positions at the anvil should be avoided as good work is most +difficult of performance under these conditions. + +_Scarfing._--While there are many forms of welds, depending on the +relative shape of the pieces to be joined, the portions that are to meet +and form one piece are always shaped in the same general way, this shape +being called a "scarf." The end of a piece of work, when scarfed, is +tapered off on one side so that the extremity comes to a rather sharp edge. +The other side of the piece is left flat and a continuation in the same +straight plane with its side of the whole piece of work. The end is then in +the form of a bevel or mitre joint (Figure 50). + +[Illustration: Figure 50.--Scarfing Ends of Work Ready for Welding] + +Scarfing may be produced in any one of several ways. The usual method is to +bring the ends to a forging heat, at which time they are upset to give a +larger body of metal at the ends to be joined. This body of metal is then +hammered down to the taper on one side, the length of the tapered portion +being about one and a half times the thickness of the whole piece being +handled. Each piece should be given this shape before proceeding farther. + +The scarf may be produced by filing, sawing or chiseling the ends, although +this is not good practice because it is then impossible to give the desired +upset and additional metal for the weld. This added thickness is called for +by the fact that the metal burns away to a certain extent or turns to +scale, which is removed before welding. + +When the two ends have been given this shape they should not fit as closely +together as might be expected, but should touch only at the center of the +area to be joined (Figure 51). That is to say, the surface of the beveled +portion should bulge in the middle or should be convex in shape so that the +edges are separated by a little distance when the pieces are laid together +with the bevels toward each other. This is done so that the scale which is +formed on the metal by the heat of the fire can have a chance to escape +from the interior of the weld as the two parts are forced together. + +[Illustration: Figure 51.--Proper Shape of Scarfed Ends] + +If the scarf were to be formed with one or more of the edges touching each +other at the same time or before the centers did so, the scale would be +imprisoned within the body of the weld and would cause the finished work to +be weak, while possibly giving a satisfactory appearance from the outside. + +_Fluxes._--In order to assist in removing the scale and other +impurities and to make the welding surfaces as clean as possible while +being joined, various fluxing materials are used as in other methods of +welding. + +For welding iron, a flux of white sand is usually used, this material being +placed on the metal after it has been brought to a red heat in the fire. +Steel is welded with dry borax powder, this flux being applied at the same +time as the iron flux just mentioned. Borax may also be used for iron +welding and a mixture of borax with steel borings may also be used for +either class of work. Mixtures of sal ammoniac with borax have been +successfully used, the proportions being about four parts of borax to one +of sal ammoniac. Various prepared fluxing powders are on the market for +this work, practically all of them producing satisfactory results. + +After the metal has been in the fire long enough to reach a red heat, it is +removed temporarily and, if small enough in size, the ends are dipped into +a box of flux. If the pieces are large, they may simply be pulled to the +edge of the fire and the flux then sprinkled on the portions to be joined. +A greater quantity of flux is required in forge welding than in electric or +oxy-acetylene processes because of the losses in the fire. After the powder +has been applied to the surfaces, the work is returned to the fire and +heated to the welding temperature. + +_Heating the Work._--After being scarfed, the two pieces to be welded +are placed in the fire and brought to the correct temperature. This +temperature can only be recognized by experiment and experience. The metal +must be just below that point at which small sparks begin to be thrown out +of the fire and naturally this is a hard point to distinguish. At the +welding heat the metal is almost ready to flow and is about the consistency +of putty. Against the background of the fire and coal the color appears to +be a cream or very light yellow and the work feels soft as it is handled. + +It is absolutely necessary that both parts be heated uniformly and so that +they reach the welding temperature at the same time. For this reason they +should be as close together in the fire as possible and side by side. When +removed to be hammered together, time is saved if they are picked up in +such a way that when laid together naturally the beveled surfaces come +together. This makes it necessary that the workman remember whether the +scarfed side is up or down, and to assist in this it is a good thing to +mark the scarfed side with chalk or in some other noticeable manner, so +that no mistake will be made in the hurry of placing the work on the anvil. + +The common practice in heating allows the temperature to rise until the +small white sparks are seen to come from the fire. Any heating above this +point will surely result in burning that will ruin the iron or steel being +handled. The best welding heat can be discerned by the appearance of the +metal and its color after experience has been gained with this particular +material. Test welds can be made and then broken, if possible, so that the +strength gained through different degrees of heat can be known before +attempting more important work. + +_Welding._--When the work has reached the welding temperature after +having been replaced in the fire with the flux applied, the two parts are +quickly tapped to remove the loose scale from their surfaces. They are then +immediately laid across the top of the anvil, being placed in a diagonal +position if both pieces are straight. The lower piece is rested on the +anvil first with the scarf turned up and ready to receive the top piece in +the position desired. The second piece must be laid in exactly the position +it is to finally occupy because the two parts will stick together as soon +as they touch and they cannot well be moved after having once been allowed +to come in contact with each other. This part of the work must be done +without any unnecessary loss of time because the comparatively low heat at +which the parts weld allows them to cool below the working temperature in +a few seconds. + +The greatest difficulty will be experienced in withdrawing the metal from +the fire before it becomes burned and in getting it joined before it cools +below this critical point. The beveled edges of the scarf are, of course, +the first parts to cool and the weld must be made before they reach a point +at which they will not join, or else the work will be defective in +appearance and in fact. + +If the parts being handled are of such a shape that there is danger of +bending a portion back of the weld, this part may be cooled by quickly +dipping it into water before laying the work on the anvil to be joined. + +The workman uses a heavy hand hammer in making the joint, and his helper, +if one is employed, uses a sledge. With the two parts of the work in place +on the anvil, the workman strikes several light blows, the first ones being +at a point directly over the center of the weld, so that the joint will +start from this point and be worked toward the edges. After the pieces have +united the helper strikes alternate blows with his sledge, always striking +in exactly the same place as the last stroke of the workman. The hammer +blows are carried nearer and nearer to the edges of the weld and are made +steadily heavier as the work progresses. + +The aim during the first part of the operation should be to make a perfect +joint, with every part of the surfaces united, and too much attention +should not be paid to appearance, at least not enough to take any chance +with the strength of the work. + +It will be found, after completion of the weld, that there has been a loss +in length equal to one-half the thickness of the metal being welded. This +loss is occasioned by the burned metal and the scale which has been formed. + +_Finishing the Weld._--If it is possible to do so, the material should +be hammered into the shape that it should remain with the same heat that +was used for welding. It will usually be found, however, that the metal has +cooled below the point at which it can be worked to advantage. It should +then be replaced in the fire and brought back to a forging heat. + +[Illustration: Figure 52.--Upsetting and Scarfing the End of a Rod] + +While shaping the work at this forging heat every part that has been at a +red heat should be hammered with uniformly light and even blows as it +cools. This restores the grain and strength of the iron or steel to a great +extent and makes the unavoidable weakness as small as possible. + +_Forms of Welds._--The simplest of all welds is that called a "lap +weld." This is made between the ends of two pieces of equal size and +similar form by scarfing them as described and then laying one on top of +the other while they are hammered together. + +A butt weld (Figure 52) is made between the ends of two pieces of shaft or +other bar shapes by upsetting the ends so that they have a considerable +flare and shaping the face of the end so that it is slightly higher in the +center than around the edges, this being done to make the centers come +together first. The pieces are heated and pushed into contact, after which +the hammering is done as with any other weld. + +[Illustration: Figure 53.--Scarfing for a T Weld] + +A form similar to the butt weld in some ways is used for joining the end of +a bar to a flat surface and is called a jump weld. The bar is shaped in the +same way as for a butt weld. The flat plate may be left as it is, but if +possible a depression should be made at the point where the shaft is to be +placed. With the two parts heated as usual, the bar is dropped into +position and hammered from above. As soon as the center of the weld has +been made perfect, the joint may be finished with a fuller driven all the +way around the edge of the joint. + +When it is required to join a bar to another bar or to the edge of any +piece at right angles the work is called a "T" weld from its shape when +complete (Figure 53). The end of the bar is scarfed as described and the +point of the other bar or piece where the weld is to be made is hammered so +that it tapers to a thin edge like one-half of a circular depression. The +pieces are then laid together and hammered as for a lap weld. + +The ends of heavy bar shapes are often joined with a "V," or cleft, weld. +One bar end is shaped so that it is tapering on both sides and comes to a +broad edge like the end of a chisel. The other bar is heated to a forging +temperature and then slit open in a lengthwise direction so that the +V-shaped opening which is formed will just receive the pointed edge of the +first piece. With the work at welding heat, the two parts are driven +together by hammering on the rear ends and the hammering then continues as +with a lap weld, except that the work is turned over to complete both sides +of the joint. + +[Illustration: Figure 54.-Splitting Ends to Be Welded in Thin Work] + +The forms so far described all require that the pieces be laid together in +the proper position after removal from the fire, and this always causes a +slight loss of time and a consequent lowering of the temperature. With very +light stock, this fall of temperature would be so rapid that the weld would +be unsuccessful, and in this case the "lock" weld is resorted to. The ends +of the two pieces to be joined are split for some distance back, and +one-half of each end is bent up and the other half down (Figure 54). The +two are then pushed together and placed in the fire in this position. When +the welding heat is reached, it is only necessary to take the work out of +the fire and hammer the parts together, inasmuch as they are already in the +correct position. + +Other forms of welds in which the parts are too small to retain their heat, +can be made by first riveting them together or cutting them so that they +can be temporarily fastened in any convenient way when first placed in the +fire. + + + + +CHAPTER VIII + +SOLDERING, BRAZING AND THERMIT WELDING + + +SOLDERING + +Common solder is an alloy of one-half lead with one-half tin, and is called +"half and half." Hard solder is made with two-thirds tin and one-third +lead. These alloys, when heated, are used to join surfaces of the same or +dissimilar metals such as copper, brass, lead, galvanized iron, zinc, +tinned plate, etc. These metals are easily joined, but the action of solder +with iron, steel and aluminum is not so satisfactory and requires greater +care and skill. + +The solder is caused to make a perfect union with the surfaces treated with +the help of heat from a soldering iron. The soldering iron is made from a +piece of copper, pointed at one end and with the other end attached to an +iron rod and wooden handle. A flux is used to remove impurities from the +joint and allow the solder to secure a firm union with the metal surface. +The iron, and in many cases the work, is heated with a gasoline blow torch, +a small gas furnace, an electric heater or an acetylene and air torch. + +The gasoline torch which is most commonly used should be filled two-thirds +full of gasoline through the hole in the bottom, which is closed by a screw +plug. After working the small hand pump for 10 to 20 strokes, hold the palm +of your hand over the end of the large iron tube on top of the torch and +open the gasoline needle valve about a half turn. Hold the torch so that +the liquid runs down into the cup below the tube and fills it. Shut the +gasoline needle valve, wipe the hands dry, and set fire to the fuel in the +cup. Just as the gasoline fire goes out, open the gasoline needle valve +about a half turn and hold a lighted match at the end of the iron tube to +ignite the mixture of vaporized gasoline and air. Open or close the needle +valve to secure a flame about 4 inches long. + +On top of the iron tube from which the flame issues there is a rest for +supporting the soldering iron with the copper part in the flame. Place the +iron in the flame and allow it to remain until the copper becomes very hot, +not quite red, but almost so. + +A new soldering iron or one that has been misused will have to be "tinned" +before using. To do this, take the iron from the fire while very hot and +rub the tip on some flux or dip it into soldering acid. Then rub the tip of +the iron on a stick of solder or rub the solder on the iron. If the solder +melts off the stick without coating the end of the iron, allow a few drops +to fall on a piece of tin plate, then nil the end of the iron on the tin +plate with considerable force. Alternately rub the iron on the solder and +dip into flux until the tip has a coating of bright solder for about half +an inch from the end. If the iron is in very bad shape, it may be necessary +to scrape or file the end before dipping in the flux for the first time. +After the end of the iron is tinned in this way, replace it on the rest of +the torch so that the tinned point is not directly in the flame, turning +the flame down to accomplish this. + +_Flux._--The commonest flux, which is called "soldering acid," is made +by placing pieces of zinc in muriatic (hydrochloric) acid contained in a +heavy glass or porcelain dish. There will be bubbles and considerable heat +evolved and zinc should be added until this action ceases and the zinc +remains in the liquid, which is now chloride of zinc. + +This soldering acid may be used on any metal to be soldered by applying +with a brush or swab. For electrical work, this acid should be made neutral +by the addition of one part ammonia and one part water to each three parts +of the acid. This neutralized flux will not corrode metal as will the +ordinary acid. + +Powdered resin makes a good flux for lead, tin plate, galvanized iron and +aluminum. Tallow, olive oil, beeswax and vaseline are also used for this +purpose. Muriatic acid may be used for zinc or galvanized iron without the +addition of the zinc, as described in making zinc chloride. The addition of +two heaping teaspoonfuls of sal ammoniac to each pint of the chloride of +zinc is sometimes found to improve its action. + +_Soldering Metal Parts._--All surfaces to be joined should be fitted +to each other as accurately as possible and then thoroughly cleaned with a +file, emery cloth, scratch bush or by dipping in lye. Work may be cleaned +by dipping it into nitric acid which has been diluted with an equal volume +of water. The work should be heated as hot as possible without danger of +melting, as this causes the solder to flow better and secure a much better +hold on the surfaces. Hard solder gives better results than half and half, +but is more difficult to work. It is very important that the soldering iron +be kept at a high heat during all work, otherwise the solder will only +stick to the surfaces and will not join with them. + +Sweating is a form of soldering in which the surfaces of the work are first +covered with a thin layer of solder by rubbing them with the hot iron after +it has been dipped in or touched to the soldering stick. These surfaces are +then placed in contact and heated to a point at which the solder melts and +unites. Sweating is much to be preferred to ordinary soldering where the +form of the work permits it. This is the only method which should ever be +used when a fitting is to be placed over the end of a length of tube. + +_Soldering Holes._--Clean the surfaces for some distance around the +hole until they are bright, and apply flux while holding the hot iron near +the hole. Touch the tip of the iron to some solder until the solder is +picked up on the iron, and then place this solder, which was just picked +up, around the edge of the hole. It will leave the soldering iron and stick +to the metal. Keep adding solder in this way until the hole has been closed +up by working from the edges and building toward the center. After the hole +is closed, apply more flux to the job and smooth over with the hot iron +until there are no rough spots. Should the solder refuse to flow smoothly, +the iron is not hot enough. + +_Soldering Seams._--Clean back from the seam or split for at least +half an inch all around and then build up the solder in the same way as was +done with the hole. After closing the opening, apply more flux to the work +and run the hot iron lengthwise to smooth the job. + +_Soldering Wires._--Clean all insulation from the ends to be soldered +and scrape the ends bright. Lay the ends parallel to each other and, +starting at the middle of the cleaned portion, wrap the ends around each +other, one being wrapped to the right, the other to the left. Hold the hot +iron under the twisted joint and apply flux to the wire. Then dip the iron +in the solder and apply to the twisted portion until the spaces between the +wires are filled with solder. Finish by smoothing the joint and cleaning +away all excess metal by rubbing the hot iron lengthwise. The joint should +now be covered with a layer of rubber tape and this covered with a layer of +ordinary friction tape. + +_Steel and Iron._--Steel surfaces should be cleaned, then covered with +clear muriatic acid. While the acid is on the metal, rub with a stick of +zinc and then tin the surfaces with the hot iron as directed. Cast iron +should be cleaned and dipped in strong lye to remove grease. Wash the lye +away with clean water and cover with muriatic acid as with steel. Then rub +with a piece of zinc and tin the surfaces by using resin as a flux. + +It is very difficult to solder aluminum with ordinary solder. A special +aluminum solder should be secured, which is easily applied and makes a +strong joint. Zinc or phosphor tin may be used in place of ordinary solder +to tin the surfaces or to fill small holes or cracks. The aluminum must be +thoroughly heated before attempting to solder and the flux may be either +resin or soldering acid. The aluminum must be thoroughly cleaned with +dilute nitric acid and kept hot while the solder is applied by forcible +rubbing with the hot iron. + + +BRAZING + +This is a process for joining metal parts, very similar to soldering, +except that brass is used to make the joint in place of the lead and zinc +alloys which form solder. Brazing must not be attempted on metals whose +melting point is less than that of sheet brass. + +Two pieces of brass to be brazed together are heated to a temperature at +which the brass used in the process will melt and flow between the +surfaces. The brass amalgamates with the surfaces and makes a very strong +and perfect joint, which is far superior to any form of soldering where the +work allows this process to be used, and in many cases is the equal of +welding for the particular field in which it applies. + +_Brazing Heat and Tools._--The metal commonly used for brazing will +melt at heats between 1350° and 1650° Fahrenheit. To bring the parts to +this temperature, various methods are in use, using solid, liquid or +gaseous fuels. While brazing may be accomplished with the fire of the +blacksmith forge, this method is seldom satisfactory because of the +difficulty of making a sufficiently clean fire with smithing coal, and it +should not be used when anything else is available. Large jobs of brazing +may be handled with a charcoal fire built in the forge, as this fuel +produces a very satisfactory and clean fire. The only objection is in the +difficulty of confining the heat to the desired parts of the work. + +The most satisfactory fire is that from a fuel gas torch built for this +work. These torches are simply forms of Bunsen burners, mixing the proper +quantity of air with the gas to bring about a perfect combustion. Hose +lines lead to the mixing tube of the gas torch, one line carrying the gas +and the other air under a moderate pressure. The air line is often +dispensed with, allowing the gas to draw air into the burner on the +injector principle, much the same as with illuminating gas burners for use +with incandescent mantles. Valves are provided with which the operator may +regulate the amount of both gas and air, and ordinarily the quality and +intensity of the flame. + +When gas is not available, recourse may be had to the gasoline torch made +for brazing. This torch is built in the same way as the small portable +gasoline torches for soldering operations, with the exception that two +regulating needle valves are incorporated in place of only one. + +The torches are carried on a framework, which also supports the work being +handled. Fuel is forced to the torch from a large tank of gasoline into +which air pressure is pumped by hand. The torches are regulated to give +the desired flame by means of the needle valves in much the same way as +with any other form of pressure torch using liquid fuel. + +Another very satisfactory form of torch for brazing is the acetylene-air +combination described in the chapter on welding instruments. This torch +gives the correct degree of heat and may be regulated to give a clean and +easily controlled flame. + +Regardless of the source of heat, the fire or flame must be adjusted so +that no soot is deposited on the metal surfaces of the work. This can only +be accomplished by supplying the exact amounts of gas and air that will +produce a complete burning of the fuel. With the brazing torches in common +use two heads are furnished, being supplied from the same source of fuel, +but with separate regulating devices. The torches are adjustably mounted in +such a way that the flames may be directed toward each other, heating two +sides of the work at the same time and allowing the pieces to be completely +surrounded with the flame. + +Except for the source of heat, but one tool is required for ordinary +brazing operations, this being a spatula formed by flattening one end of a +quarter-inch steel rod. The spatula is used for placing the brazing metal +on the work and for handling the flux that is required in this work as in +all other similar operations. + +_Spelter._--The metal that is melted into the joint is called spelter. +While this name originally applied to but one particular grade or +composition of metal, common use has extended the meaning until it is +generally applied to all grades. + +Spelter is variously composed of alloys containing copper, zinc, tin and +antimony, the mixture employed depending on the work to be done. The +different grades are of varying hardness, the harder kinds melting at +higher temperatures than the soft ones and producing a stronger joint when +used. The reason for not using hard spelter in all cases is the increased +difficulty of working it and the fact that its melting point is so near to +some of the metals brazed that there is great danger of melting the work as +well as the spelter. + +The hardest grade of spelter is made from three-fourths copper with +one-fourth zinc and is used for working on malleable and cast iron and for +steel. + +This hard spelter melts at about 1650° and is correspondingly difficult to +handle. + +A spelter suitable for working with copper is made from equal parts of +copper and zinc, melting at about 1400° Fahrenheit, 500° below the melting +point of the copper itself. A still softer brazing metal is composed of +half copper, three-eighths zinc and one-eighth tin. This grade is used for +fastening brass to iron and copper and for working with large pieces of +brass to brass. For brazing thin sheet brass and light brass castings, a +metal is used which contains two-thirds tin and one-third antimony. The +low melting point of this last composition makes it very easy to work with +and the danger of melting the work is very slight. However, as might be +expected, a comparatively weak joint is secured, which will not stand any +great strain. + +All of the above brazing metals are used in powder form so that they may be +applied with the spatula where the joint is exposed on the outside of the +work. In case it is necessary to braze on the inside of a tube or any deep +recess, the spelter may be placed on a flat rod long enough to reach to +the farthest point. By distributing the spelter at the proper points along +the rod it may be placed at the right points by turning the rod over after +inserting into the recess. + +_Flux._--In order to remove the oxides produced under brazing heat and +to allow the brazing metal to flow freely into place, a flux of some kind +must be used. The commonest flux is simply a pure calcined borax powder, +that is, a borax powder that has been heated until practically all the +water has been driven off. + +Calcined borax may also be mixed with about 15 per cent of sal ammoniac to +make a satisfactory fluxing powder. It is absolutely necessary to use flux +of some kind and a part of whatever is used should be made into a paste +with water so that it can be applied to the joint to be brazed before +heating. The remainder of the powder should be kept dry for use during the +operation and after the heat has been applied. + +_Preparing the Work._--The surfaces to be brazed are first thoroughly +cleaned with files, emery cloth or sand paper. If the work is greasy, it +should be dipped into a bath of lye or hot soda water so that all trace of +oil is removed. The parts are then placed in the relation to each other +that they are to occupy when the work has been completed. The edges to be +joined should make a secure and tight fit, and should match each other at +all points so that the smallest possible space is left between them. This +fit should not be so tight that it is necessary to force the work into +place, neither should it be loose enough to allow any considerable space +between the surfaces. The molten spelter will penetrate between surfaces +that water will flow between when the work and spelter have both been +brought to the proper heat. It is, of course, necessary that the two parts +have a sufficient number of points of contact so that they will remain in +the proper relative position. + +The work is placed on the surface of the brazing table in such a position +that the flame from the torches will strike the parts to be heated, and +with the joint in such a position that the melted spelter will flow down +through it and fill every possible part of the space between the surfaces +under the action of gravity. That means that the edge of the joint must be +uppermost and the crack to be filled must not lie horizontal, but at the +greatest slant possible. Better than any degree of slant would be to have +the line of the joint vertical. + +The work is braced up or clamped in the proper position before commencing +to braze, and it is best to place fire brick in such positions that it will +be impossible for cooling draughts of air to reach the heated metal should +the flame be removed temporarily during the process. In case there is a +large body of iron, steel or copper to be handled, it is often advisable to +place charcoal around the work, igniting this with the flame of the torch +before starting to braze so that the metal will be maintained at the +correct heat without depending entirely on the torch. + +When handling brass pieces having thin sections there is danger of melting +the brass and causing it to flow away from under the flame, with the result +that the work is ruined. If, in the judgment of the workman, this may +happen with the particular job in hand, it is well to build up a mould of +fire clay back of the thin parts or preferably back of the whole piece, so +that the metal will have the necessary support. This mould may be made by +mixing the fire clay into a stiff paste with water and then packing it +against the piece to be supported tightly enough so that the form will be +retained even if the metal softens. + +_Brazing._--With the work in place, it should be well covered with the +paste of flux and water, then heated until this flux boils up and runs over +the surfaces. Spelter is then placed in such a position that it will run +into the joint and the heat is continued or increased until the spelter +melts and flows in between the two surfaces. The flame should surround the +work during the heating so that outside air is excluded as far as is +possible to prevent excessive oxidization. + +When handling brass or copper, the flame should not be directed so that its +center strikes the metal squarely, but so that it glances from one side or +the other. Directing the flame straight against the work is often the cause +of melting the pieces before the operation is completed. When brazing two +different metals, the flame should play only on the one that melts at the +higher temperature, the lower melting part receiving its heat from the +other. This avoids the danger of melting one before the other reaches the +brazing point. + +The heat should be continued only long enough to cause the spelter to flow +into place and no longer. Prolonged heating of any metal can do nothing but +oxidize and weaken it, and this practice should be avoided as much as +possible. If the spelter melts into small globules in place of flowing, it +may be caused to spread and run into the joint by lightly tapping the work. +More dry flux may be added with the spatula if the tapping does not produce +the desired result. + +Excessive use of flux, especially toward the end of the work, will result +in a very hard surface on all the work, a surface which will be extremely +difficult to finish properly. This trouble will be present to a certain +extent anyway, but it may be lessened by a vigorous scraping with a wire +brush just as soon as the work is removed from the fire. If allowed to cool +before cleaning, the final appearance will not be as good as with the +surplus metal and scale removed immediately upon completing the job. + +After the work has been cleaned with the brush it may be allowed to cool +and finished to the desired shape, size and surface by filing and +polishing. When filed, a very thin line of brass should appear where the +crack was at the beginning of the work. If it is desired to avoid a square +shoulder and fill in an angle joint to make it rounding, the filling is +best accomplished by winding a coil of very thin brass wire around the part +of the work that projects and then causing this to flow itself or else +allow the spelter to fill the spaces between the layers of wire. Copper +wire may also be used for this purpose, the spaces being filled with +melted spelter. + + +THERMIT WELDING + +The process of welding which makes use of the great heat produced by oxygen +combining with aluminum is known as the Thermit process and was perfected +by Dr. Hans Goldschmidt. The process, which is controlled by the +Goldschmidt Thermit Company, makes use of a mixture of finely powdered +aluminum with an oxide of iron called by the trade name, Thermit. + +The reaction is started with a special ignition powder, such as barium +superoxide and aluminum, and the oxygen from the iron oxide combining with +the aluminum, producing a mass of superheated steel at about 5000 degrees +Fahrenheit. After the reaction, which takes from. 30 seconds to a minute, +the molten metal is drawn from the crucible on to the surfaces to be +joined. Its extreme heat fuses the metal and a perfect joint is the result. +This process is suited for welding iron or steel parts of comparatively +large size. + +_Preparation._--The parts to be joined are thoroughly cleaned on the +surfaces and for several inches back from the joint, after which they are +supported in place. The surfaces between which the metal will flow are +separated from 1/4 to 1 inch, depending on the size of the parts, but +cutting or drilling part of the metal away. After this separation is made +for allowing the entrance of new metal, the effects of contraction of the +molten steel are cared for by preheating adjacent parts or by forcing the +ends apart with wedges and jacks. The amount of this last separation must +be determined by the shape and proportions of the parts in the same way as +would be done for any other class of welding which heats the parts to a +melting point. + +Yellow wax, which has been warmed until plastic, is then placed around the +joint to form a collar, the wax completely filling the space between the +ends and being provided with vent holes by imbedding a piece of stout cord, +which is pulled out after the wax cools. + +A retaining mould (Figure 55) made from sheet steel or fire brick is then +placed around the parts. This mould is then filled with a mixture of one +part fire clay, one part ground fire brick and one part fire sand. These +materials are well mixed and moistened with enough water so that they will +pack. This mixture is then placed in the mould, filling the space between +the walls and the wax, and is packed hard with a rammer so that the +material forms a wall several inches thick between any point of the mould +and the wax. The mixture must be placed in the mould in small quantities +and packed tight as the filling progresses. + +[Illustration: Figure 55.--Thermit Mould Construction] + +Three or more openings are provided through this moulding material by the +insertion of wood or pipe forms. One of these openings will lead from the +lowest point of the wax pattern and is used for the introduction of the +preheating flame. Another opening leads from the top of the mould into this +preheating gate, opening into the preheating gate at a point about one inch +from the wax pattern. Openings, called risers, are then provided from each +of the high points of the wax pattern to the top of the mould, these risers +ending at the top in a shallow basin. The molten metal comes up into these +risers and cares for contraction of the casting, as well as avoiding +defects in the collar of the weld. After the moulding material is well +packed, these gate patterns are tapped lightly and withdrawn, except in the +case of the metal pipes which are placed at points at which it would be +impossible to withdraw a pattern. + +_Preheating._--The ends to be welded are brought to a bright red heat +by introducing the flame from a torch through the preheating gate. The +torch must use either gasoline or kerosene, and not crude oil, as the crude +oil deposits too much carbon on the parts. Preheating of other adjacent +parts to care for contraction is done at this time by an additional torch +burner. + +The heating flame is started gently at first and gradually increased. The +wax will melt and may be allowed to run out of the preheating gate by +removing the flame at intervals for a few seconds. The heat is continued +until the mould is thoroughly dried and the parts to be joined are brought +to the red heat required. This leaves a mould just the shape of the wax +pattern. + +The heating gate should then be plugged with a sand core, iron plug or +piece of fitted fire brick, and backed up with several shovels full of the +moulding mixture, well packed. + +[Illustration: Figure 56.--Thermit Crucible Plug. +_A_, Hard burn magnesia stone; +_B_, Magnesia thimble; +_C_, Refractory sand; +_D_, Metal disc; +_E_, Asbestos washer; +_F_, Tapping pin] + +_Thermit Metal._--The reaction takes place in a special crucible lined +with magnesia tar, which is baked at a red heat until the tar is driven off +and the magnesia left. This lining should last from twelve to fifteen +reactions. This magnesia lining ends at the bottom of the crucible in a +ring of magnesia stone and this ring carries a magnesia thimble through +which the molten steel passes on its way to the mould. It will usually be +necessary to renew this thimble after each reaction. This lower opening is +closed before filling the crucible with thermit by means of a small disc or +iron carrying a stem, which is called a tapping pin (Figure 56). This pin, +_F_, is placed in the thimble with the stem extending down through the +opening and exposing about two inches. The top of this pin is covered with +an asbestos, washer, _E_, then with another iron disc. _D_, and +finally with a layer of refractory sand. The crucible is tapped by knocking +the stem of the pin upwards with a spade or piece of flat iron about four +feet long. + +The charge of thermit is added by placing a few handfuls over the +refractory sand and then pouring in the balance required. The amount of +thermit required is calculated from the wax used. The wax is weighed before +and after filling _the entire space that the thermit will occupy_. +This does not mean only the wax collar, but the space of the mould with all +gates filled with wax. The number of pounds of wax required for this +filling multiplied by 25 will give the number of pounds of thermit to be +used. To this quantity of thermit should be added I per cent of pure +manganese, 1 per cent nickel thermit and 15 per cent of steel punchings. + +It is necessary, when more than 10 pounds of thermit will be used, to mix +steel punchings not exceeding 3/8 inch diameter by 1/8 inch thick with the +powder in order to sufficiently retard the intensity of the reaction. + +Half a teaspoonful of ignition powder is placed on top of the thermit +charge and ignited with a storm match or piece of red hot iron. The cover +should be immediately closed on the top of the crucible and the operator +should get away to a safe distance because of the metal that may be thrown +out of the crucible. + +After allowing about 30 seconds to a minute for the reaction to take place +and the slag to rise to the top of the crucible, the tapping pin is struck +from below and the molten metal allowed to run into the mould. The mould +should be allowed to remain in place as long as possible, preferably over +night, so as to anneal the steel in the weld, but in no case should it be +disturbed for several hours after pouring. After removing the mould, drill +through the metal left in the riser and gates and knock these sections off. +No part of the collar should be removed unless absolutely necessary. + + + + +CHAPTER IX + +OXYGEN PROCESS FOR REMOVAL OF CARBON + + +Until recently the methods used for removing carbon deposits from gas +engine cylinders were very impractical and unsatisfactory. The job meant +dismantling the motor, tearing out all parts, and scraping the pistons and +cylinder walls by hand. + +The work was never done thoroughly. It required hours of time to do it, and +then there was always the danger of injuring the inside of the cylinders. + +These methods have been to a large extent superseded by the use of oxygen +under pressure. The various devices that are being manufactured are known +as carbon removers, decarbonizers, etc., and large numbers of them are in +use in the automobile and gasoline traction motor industry. + +_Outfit._--The oxygen carbon cleaner consists of a high pressure +oxygen cylinder with automatic reducing valve, usually constructed on the +diaphragm principle, thus assuring positive regulation of pressure. This +valve is fitted with a pressure gauge, rubber hose, decarbonizing torch +with shut off and flexible tube for insertion into the chamber from which +the carbon is to be removed. + +There should also be an asbestos swab for swabbing out the inside of the +cylinder or other chamber with kerosene previous to starting the operation. +The action consists in simply burning the carbon to a fine dust in the +presence of the stream of oxygen, this dust being then blown out. + +_Operation._--The following are instructions for operating the +cleaner:-- + +(1) Close valve in gasoline supply line and start the motor, letting it run +until the gasoline is exhausted. + +(2) If the cylinders be T or L head, remove either the inlet or the exhaust +valve cap, or a spark plug if the cap is tight. If the cylinders have +overhead valves, remove a spark plug. If any spark plug is then remaining +in the cylinder it should be removed and an old one or an iron pipe plug +substituted. + +(3) Raise the piston of the cylinder first to be cleaned to the top of the +compression stroke and continue this from cylinder to cylinder as the work +progresses. + +(4) In motors where carbon has been burned hard, the cylinder interior +should then be swabbed with kerosene before proceeding. Work the swab, +saturated with kerosene, around the inside of the cylinder until all the +carbon has been moistened with the oil. This same swab may be used to +ignite the gas in the cylinder in place of using a match or taper. + +(5) Make all connections to the oxygen cylinder. + +(6) Insert the torch nozzle in the cylinder, open the torch valve gradually +and regulate to about two lbs. pressure. Manipulate the nozzle inside the +cylinder and light a match or other flame at the opening so that the carbon +starts to burn. Cover the various points within the cylinder and when there +is no further burning the carbon has been removed. The regulating and +oxygen tank valves are operated in exactly the same way as for welding as +previously explained. + + +It should be carefully noted that when the piston is up, ready to start the +operation, both valves must be closed. There will be a considerable display +of sparks while this operation is taking place, but they will not set fire +to the grease and oil. Care should be used to see that no gasoline is +about. + + + + +INDEX + + +Acetylene + filtering + generators + in tanks + piping + properties of + purification of +Acetylene-air torches +Air + oxygen from +Alloys + table of +Alloy steel +Aluminum + alloys + welding +Annealing +Anvil +Arc welding, electric + machines +Asbestos, use of, in welding + +Babbitt +Bending pipes and tubes +Bessemer steel +Beveling +Brass + welding +Brazing + electric + heat and tools + spelter +Bronze + welding +Butt welding + +Calcium carbide +Carbide + storage of, Fire Underwriters' Rules + to water generator +Carbon removal + by oxygen process +Case hardening steel +Cast iron + welding +Champfering +Charging generator +Chlorate of potash oxygen +Conductivity of metals +Copper + alloys + welding +Crucible steel +Cutting, oxy-acetylene + torches + +Dissolved acetylene + +Electric arc welding +Electric welding + troubles and remedies +Expansion of metals + +Flame, welding +Fluxes + for brazing + for soldering +Forge + fire + practice + tools + tuvere construction of + welding + welding preparation + welds, forms of +Forging + +Gas holders +Gases, heating power of +Generator, acetylene + carbide to water + construction +Generator + location of + operation and care of + overheating + requirements + water to carbide +German silver +Gloves +Goggles + +Hand forging +Hardening steel +Heat treatment of steel +Hildebrandt process +Hose + +Injectors, adjuster +Iron + cast + grades of + malleable cast + wrought + +Jump weld + +Lap welding +Lead +Linde process +Liquid air oxygen + +Magnalium +Malleable iron + welding +Melting points of metals +Metal alloys, table of +Metals + characteristics of + conductivity of + expansion of + heat treatment of + melting points of + tensile strength of + weight of + +Nickel +Nozzle sizes, torch + +Open hearth steel +Oxy-acetylene cutting + welding practice +Oxygen + cylinders + weight of + +Pipes, bending +Platinum +Preheating + +Removal of carbon by oxygen process +Resistance method of electric welding +Restoration of steel +Rods, welding + +Safety devices +Scarfing +Solder +Soldering + flux + holes + seams + steel and iron + wires +Spelter +Spot welding +Steel + alloys + Bessemer + crucible + heat treatment of + open hearth + restoration of + tensile strength of + welding +Strength of metals + +Tank valves +Tapering +Tables of welding information +Tempering steel +Thermit metal + preheating + preparation + welding +Tin +Torch + acetylene-air + care + construction + cutting + high pressure + low pressure + medium pressure + nozzles + practice + +Valves, regulating + tank + +Water + to carbide generator +Welding aluminum + brass + bronze + butt + cast iron + copper + electric + electric arc + flame + forge + information and tables + instruments + lap + malleable iron + materials + practice, oxy-acetylene + rods + spot + steel + table + thermit + torches + various metals + wrought iron +Wrought iron + welding + +Zinc + + + + + +End of the Project Gutenberg EBook of Oxy-Acetylene Welding and Cutting +by Harold P. 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