How to Weld and Cut Steel

7/30/2019 How to Weld and Cut Steel

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How To Weld and Cut Steel

PREFACE

In the preparation of this work,the object has been to cover notonly theseveral processes of welding, butalso those other processes whichare soclosely allied in method andresults as to make them a part ofthe wholesubject of joining metal to metalwith the aid of heat.

The workman who wishes to handle

his trade from start to finishfinds thatit is necessary to become familiarwith certain other operations whichprecede or follow the actualjoining of the metal parts, thepurpose ofthese operations being to add orretain certain desirable qualitiesin thematerials being handled. For thisreason the following subjects havebeenincluded: Annealing, tempering,hardening, heat treatment and therestoration of steel.

In order that the user mayunderstand the underlyingprinciples and thematerials employed in this work,much practical information is givenon theuses and characteristics of thevarious metals; on the production,handlingand use of the gases and other

materials which are a part of theequipment;and on the tools and accessoriesfor the production and handling ofthesematerials.

An examination will show that thegreatest usefulness of this booklies in


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the fact that all necessaryinformation and data has beenincluded in onevolume, making it possible for theworkman to use one source forsecuring aknowledge of both principle and

practice, preparation and finishingof thework, and both large and smallrepair work as well asmanufacturing methodsused in metal working.

An effort has been made toeliminate all matter which is notof directusefulness in practical work, whileincluding all that those engaged inthis trade find necessary. To this

end, the descriptions have beenlimitedto those methods and accessorieswhich are found in actual usetoday. Forthe same reason, the work includesthe application of the rules laiddownby the insurance underwriters whichgovern this work as well asinstructions for the proper careand handling of the generators,torchesand materials found in the shop.

Special attention has been given todefinite directions for handling thedifferent metals and alloys whichmust be handled. The instructionshavebeen arranged to form rules whichare placed in the order of their useduring the work described and thework has been subdivided in such awaythat it will be found possible tosecure information on any one point

desired without the necessity ofspending time in other fields.

The facts which the expert welderand metalworker finds it mostnecessaryto have readily available have beensecured, and prepared especially for


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this work, and those of mostgeneral use have been combined withthechapter on welding practice towhich they apply.

The size of this volume has been

kept as small as possible, but anexamination of the alphabeticalindex will show that the range ofsubjectsand details covered is complete inall respects. This has beenaccomplishedthrough careful classification ofthe contents and the elimination ofallrepetition and all theoretical,historical and similar matter thatis not

absolutely necessary.

Free use has been made of theinformation given by thosemanufacturers whoare recognized as the leaders intheir respective fields, thusinsuringthat the work is thoroughlypractical and that it representspresent daymethods and practice.

THE AUTHOR.

CONTENTS

CHAPTER I

METALS AND ALLOYS--HEATTREATMENT:--The Use andCharacteristics of theIndustrial Alloys and MetalElements--Annealing, Hardening,

Tempering andCase Hardening of Steel

CHAPTER II

WELDING MATERIALS:--Production,Handling and Use of the Gases,Oxygen andAcetylene--Welding Rods--Fluxes--Supplies and Fixtures


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CHAPTER III

ACETYLENE GENERATORS:--GeneratorRequirements and Types--Construction--Careand Operation of Generators.

CHAPTER IV

WELDING INSTRUMENTS:--Tank andRegulating Valves and Gauges--High,Low andMedium Pressure Torches--CuttingTorches--Acetylene-Air Torches

CHAPTER V

OXY-ACETYLENE WELDING PRACTICE:--Preparation of Work--Torch

Practice--Control of the Flame--WeldingVarious Metals and Alloys--Tables ofInformation Required in WeldingOperations

CHAPTER VI

ELECTRIC WELDING:--ResistanceMethod--Butt, Spot and LapWelding--Troublesand Remedies--Electric Arc Welding

CHAPTER VII

HAND FORGING AND WELDING:--Blacksmithing, Forging andBending--ForgeWelding Methods

CHAPTER VIII

SOLDERING, BRAZING AND THERMITWELDING:--Soldering Materials andPractice--Brazing--Thermit Welding

CHAPTER IX

OXYGEN PROCESS FOR REMOVAL OF CARBON

INDEX


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OXY-ACETYLENE WELDING AND CUTTING,ELECTRIC AND THERMIT WELDING

CHAPTER I

METALS AND THEIR ALLOYS--HEATTREATMENT

THE METALS

Iron.--Iron, in its pure state, isa soft, white, easily workedmetal. It is the most important ofall the metallic elements, and is,nextto aluminum, the commonest metal

found in the earth.

Mechanically speaking, we havethree kinds of iron: wrought iron,cast ironand steel. Wrought iron is verynearly pure iron; cast ironcontains carbonand silicon, also chemicalimpurities; and steel contains adefiniteproportion of carbon, but insmaller quantities than cast iron.

Pure iron is never obtainedcommercially, the metal alwaysbeing mixed withvarious proportions of carbon,silicon, sulphur, phosphorus, andotherelements, making it more or lesssuitable for different purposes.Iron is


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magnetic to the extent that it isattracted by magnets, but it doesnotretain magnetism itself, as doessteel. Iron forms, with otherelements,many important combinations, such

as its alloys, oxides, andsulphates.

Image Figure 1.--Section Through aBlast Furnace

Cast Iron.--Metallic iron isseparated from iron ore in the blastfurnace (Figure 1), and whenallowed to run into moulds iscalled castiron. This form is used for enginecylinders and pistons, for brackets,

covers, housings and at any pointwhere its brittleness is notobjectionable. Good cast ironbreaks with a gray fracture, isfree fromblowholes or roughness, and iseasily machined, drilled, etc. Castiron isslightly lighter than steel, meltsat about 2,400 degrees in practice,isabout one-eighth as good anelectrical conductor as copper andhas a

tensile strength of 13,000 to30,000 pounds per square inch. Itscompressive strength, or resistanceto crushing, is very great. It hasexcellent wearing qualities and isnot easily warped and deformed byheat.Chilled iron is cast into a metalmould so that the outside is cooled


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quickly, making the surface veryhard and difficult to cut andgiving greatresistance to wear. It is used formaking cheap gear wheels and partsthatmust withstand surface friction.

Malleable Cast Iron.--This is oftencalled simply malleable iron. Itis a form of cast iron obtained byremoving much of the carbon fromcastiron, making it softer and lessbrittle. It has a tensile strengthof25,000 to 45,000 pounds per squareinch, is easily machined, willstand asmall amount of bending at a low

red heat and is used chiefly inmakingbrackets, fittings and supportswhere low cost is of considerableimportance. It is often used incheap constructions in place ofsteelforgings. The greatest strength ofa malleable casting, like a steelforging, is in the surface,therefore but little machiningshould be done.

Wrought Iron.--This grade is madeby treating the cast iron toremove almost all of the carbon,silicon, phosphorus, sulphur,manganeseand other impurities. This processleaves a small amount of the slagfromthe ore mixed with the wrought iron.

Wrought iron is used for makingbars to be machined into variousparts. Ifdrawn through the rolls at the mill

once, while being made, it is called"muck bar;" if rolled twice, it iscalled "merchant bar" (the commonestkind), and a still better grade ismade by rolling a third time.Wroughtiron is being gradually replaced inuse by mild rolled steels.


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Wrought iron is slightly heavierthan cast iron, is a much betterelectrical conductor than eithercast iron or steel, has a tensilestrengthof 40,000 to 60,000 pounds persquare inch and costs slightly more

thansteel. Unlike either steel or castiron, wrought iron does not hardenwhencooled suddenly from a red heat.

Grades of Irons.--The mechanicalproperties of cast iron differgreatly according to the amount ofother materials it contains. Themostimportant of these containedelements is carbon, which is

present to adegree varying from 2 to 5-1/2 percent. When iron containing muchcarbonis quickly cooled and then broken,the fracture is nearly white incolorand the metal is found to be hardand brittle. When the iron is slowlycooled and then broken the fractureis gray and the iron is moremalleableand less brittle. If cast ironcontains sulphur or phosphorus, itwill showa white fracture regardless of therapidity of cooling, being brittleandless desirable for general work.

Steel.--Steel is composed ofextremely minute particles of ironandcarbon, forming a network of layersand bands. This carbon is a smallerproportion of the metal than foundin cast iron, the percentage being

from3/10 to 2-1/2 per cent.

Carbon steel is specified accordingto the number of "points" ofcarbon, apoint being one one-hundredth ofone per cent of the weight of thesteel.


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Steel may contain anywhere from 30to 250 points, which is equivalenttosaying, anywhere from 3/10 to 2-1/2per cent, as above. A 70-point steelwould contain 70/100 of one percent or 7/10 of one per cent of

carbon byweight. The percentage of carbondetermines the hardness of thesteel, alsomany other qualities, and itssuitability for various kinds ofwork. Themore carbon contained in the steel,the harder the metal will be, and,ofcourse, its brittleness increaseswith the hardness. The smaller thegrains

or particles of iron which areseparated by the carbon, thestronger thesteel will be, and the control ofthe size of these particles is theobjectof the science of heat treatment.

In addition to the carbon, steelmay contain the following:

Silicon, which increases thehardness, brittleness, strength anddifficulty

of working if from 2 to 3 percent is present.

Phosphorus, which hardens andweakens the metal but makes iteasier to

cast. Three-tenths per cent ofphosphorus serves as a hardeningagent and

may be present in good steel ifthe percentage of carbon is low.More

than this weakens the metal.

Sulphur, which tends to make themetal hard and filled with smallholes.

Manganese, which makes the steel sohard and tough that it can with

difficulty be cut with steeltools. Its hardness is not lessenedby


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annealing, and it has greattensile strength.

Alloy steel has a varying but smallpercentage of other elements mixedwithit to give certain desired

qualities. Silicon steel andmanganese steel aresometimes classed as alloy steels.This subject is taken up in thelatterpart of this chapter under Alloys,where the various combinationsand their characteristics are givenconsideration.

Steel has a tensile strengthvarying from 50,000 to 300,000pounds per

square inch, depending on thecarbon percentage and the otheralloyspresent, as well as upon thetexture of the grain. Steel isheavier thancast iron and weighs about the sameas wrought iron. It is about one-ninthas good a conductor of electricityas copper.

Steel is made from cast iron bythree principal processes: thecrucible,Bessemer and open hearth.

Crucible steel is made by placingpieces of iron in a clay orgraphite crucible, mixed withcharcoal and a small amount of anydesiredalloy. The crucible is then heatedwith coal, oil or gas fires untiltheiron melts, and, by absorbing thedesired elements and giving up or

changing its percentage of carbon,becomes steel. The molten steel isthenpoured from the crucible intomoulds or bars for use. Cruciblesteel mayalso be made by placing crude steelin the crucibles in place of theiron.


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This last method gives the finestgrade of metal and the crucibleprocessin general gives the best grades ofsteel for mechanical use.

Image Figure 2.--A BessemerConverter

Bessemer steel is made by heatingiron until all the undesirableelements are burned out by airblasts which furnish the necessaryoxygen.The iron is placed in a largeretort called a converter, beingpoured,while at a melting heat, directlyfrom the blast furnace into theconverter. While the iron in theconverter is molten, blasts of airareforced through the liquid, making

it still hotter and burning out theimpurities together with the carbonand manganese. These two elementsarethen restored to the iron by addingspiegeleisen (an alloy of iron,carbonand manganese). A converter holdsfrom 5 to 25 tons of metal andrequiresabout 20 minutes to finish acharge. This makes the cheapeststeel.


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Image Figure 3.--An Open HearthFurnace

Open hearth steel is made byplacing the molten iron in areceptaclewhile currents of air pass over it,

this air having itself been highlyheated by just passing over whitehot brick (Figure. 3). Open hearthsteelis considered more uniform andreliable than Bessemer, and is usedforsprings, bar steel, tool steel,steel plates, etc.

Aluminum is one of the commonestindustrial metals. It is used forgear cases, engine crank cases,

covers, fittings, and whereverlightnessand moderate strength are desirable.

Aluminum is about one-third theweight of iron and about the sameweight asglass and porcelain; it is a goodelectrical conductor (about one-half asgood as copper); is fairly strongitself and gives great strength toothermetals when alloyed with them. Oneof the greatest advantages ofaluminumis that it will not rust or corrodeunder ordinary conditions. Thegranularformation of aluminum makes itsstrength very unreliable and it istoo softto resist wear.

Copper is one of the most importantmetals used in the trades, andthe best commercial conductor of

electricity, being exceeded in thisrespect only by silver, which isbut slightly better. Copper is verymalleable and ductile when cold,and in this state may be easilyworkedunder the hammer. Working in thisway makes the copper stronger andharder,


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but less ductile. Copper is notaffected by air, but acids cause theformation of a green deposit calledverdigris.

Copper is one of the bestconductors of heat, as well as

electricity, beingused for kettles, boilers, stillsand wherever this quality isdesirable.Copper is also used in alloys withother metals, forming an importantpartof brass, bronze, german silver,bell metal and gun metal. It isaboutone-eighth heavier than steel andhas a tensile strength of about25,000 to

50,000 pounds per square inch.

Lead.--The peculiar properties oflead, and especially its qualityof showing but little action orchemical change in the presence ofotherelements, makes it valuable undercertain conditions of use. Itsprincipaluse is in pipes for water and gas,coverings for roofs and linings forvatsand tanks. It is also used to coatsheet iron for similar uses and asanimportant part of ordinary solder.

Lead is the softest and weakest ofall the commercial metals, beingverypliable and inelastic. It should beremembered that lead and all itscompounds are poisonous whenreceived into the system. Lead ismore thanone-third heavier than steel, has a

tensile strength of only about 2,000pounds per square inch, and is onlyabout one-tenth as good a conductorofelectricity as copper.

Zinc.--This is a bluish-white metalof crystalline form. It is


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brittle at ordinary temperaturesand becomes malleable at about 250to 300degrees Fahrenheit, but beyond thispoint becomes even more brittlethan atordinary temperatures. Zinc is

practically unaffected by air ormoisturethrough becoming covered with oneof its own compounds whichimmediatelyresists further action. Zinc meltsat low temperatures, and when heatedbeyond the melting point gives offvery poisonous fumes.

The principal use of zinc is as analloy with other metals to formbrass,

bronze, german silver and bearingmetals. It is also used to cover thesurface of steel and iron plates,the plates being then calledgalvanized.

Zinc weighs slightly less thansteel, has a tensile strength of5,000pounds per square inch, and is notquite half as good as copper inconducting electricity.

Tin resembles silver in color andluster. Tin is ductile andmalleable and slightly crystallinein form, almost as heavy as steel,andhas a tensile strength of 4,500pounds per square inch.

The principal use of tin is forprotective platings on householdutensilsand in wrappings of tin-foil. Tinforms an important part of manyalloys

such as babbitt, Britannia metal,bronze, gun metal and bearingmetals.

Nickel is important in mechanicsbecause of its combinations withother metals as alloys. Pure nickelis grayish-white, malleable, ductile


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and tenacious. It weighs almost asmuch as steel and, next tomanganese, isthe hardest of metals. Nickel isone of the three magnetic metals,theothers being iron and cobalt. The

commonest alloy containing nickel isgerman silver, although one of itsmost important alloys is found innickelsteel. Nickel is about ten per centheavier than steel, and has atensilestrength of 90,000 pounds persquare inch.

Platinum.--This metal is valuablefor two reasons: it is notaffected by the air or moisture or

any ordinary acid or salt, and inaddition to this property it meltsonly at the highest temperatures.It isa fairly good electrical conductor,being better than iron or steel. Itisnearly three times as heavy assteel and its tensile strength is25,000pounds per square inch.

ALLOYS

An alloy is formed by the union ofa metal with some other material,eithermetal or non-metallic, this unionbeing composed of two or moreelementsand usually brought about byheating the substances togetheruntil theymelt and unite. Metals are alloyedwith materials which have beenfound to

give to the metal certaincharacteristics which are desiredaccording tothe use the metal will be put to.

The alloys of metals are, almostwithout exception, more importantfrom an


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industrial standpoint than themetals themselves. There areinnumerablepossible combinations, the mostuseful of which are here classedunder thehead of the principal metal

entering into their composition.

Steel.--Steel may be alloyed withalmost any of the metals orelements, the combinations thathave proven valuable numbering morethan ascore. The principal ones are givenin alphabetical order, as follows:

Aluminum is added to steel in verysmall amounts for the purpose ofpreventing blow holes in castings.

Boron increases the density andtoughness of the metal.

Bronze, added by alloying copper,tin and iron, is used for gun metal.

Carbon has already been consideredunder the head of steel in thesectiondevoted to the metals. Carbon,while increasing the strength andhardness,decreases the ease of forging andbending and decreases the magnetismandelectrical conductivity. Highcarbon steel can be welded only withdifficulty. When the percentage ofcarbon is low, the steel is called"lowcarbon" or "mild" steel. This isused for rods and shafts, and called"machine" steel. When the carbonpercentage is high, the steel iscalled"high carbon" steel, and it is used

in the shop as tool steel. One-tenthper cent of carbon gives steel atensile strength of 50,000 to 65,000pounds per square inch; two-tenthsper cent gives from 60,000 to80,000;four-tenths per cent gives 70,000to 100,000, and six-tenths per centgives 90,000 to 120,000.


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Chromium forms chrome steel, andwith the further addition of nickeliscalled chrome nickel steel. Thisincreases the hardness to a highdegreeand adds strength without much

decrease in ductility. Chromesteels areused for high-speed cutting tools,armor plate, files, springs, safes,dies, etc.

Manganese has been mentioned underSteel. Its alloy is much used forhigh-speed cutting tools, the steelhardening when cooled in the air andbeing called self-hardening.

Molybdenum is used to increase the

hardness to a high degree and makesthesteel suitable for high-speedcutting and gives it self-hardeningproperties.

Nickel, with which is oftencombined chromium, increases thestrength,springiness and toughness and helpsto prevent corrosion.

Silicon has already been described.It suits the metal for use inhigh-speed tools.

Silver added to steel has many ofthe properties of nickel.

Tungsten increases the hardnesswithout making the steel brittle.Thismakes the steel well suited for gasengine valves as it resistscorrosionand pitting. Chromium and manganeseare often used in combination with

tungsten when high-speed cuttingtools are made.

Vanadium as an alloy increases theelastic limit, making the steelstronger, tougher and harder. Italso makes the steel able to standmuchbending and vibration.


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Copper.--The principal copperalloys include brass, bronze, germansilver and gun metal.

Brass is composed of approximatelyone-third zinc and two-thirdscopper. It

is used for bearings and bushingswhere the speeds are slow and theloadsrather heavy for the bearing size.It also finds use in washers,collarsand forms of brackets where themetal should be non-magnetic, alsofor manyhighly finished parts.

Brass is about one-third as good anelectrical conductor as copper, is

slightly heavier than steel and hasa tensile strength of 15,000 poundswhen cast and about 75,000 to100,000 pounds when drawn into wire.

Bronze is composed of copper andtin in various proportions,according tothe use to which it is to be put.There will always be from six-tenths tonine-tenths of copper in themixture. Bronze is used forbearings,bushings, thrust washers, bracketsand gear wheels. It is heavier thansteel, about 1/15 as good anelectrical conductor as pure copperand has atensile strength of 30,000 to60,000 pounds.

Aluminum bronze, composed ofcopper, zinc and aluminum has hightensilestrength combined with ductilityand is used for parts requiring this

combination.

Bearing bronze is a variablematerial, its composition andproportiondepending on the maker and the usefor which it is designed. It usuallycontains from 75 to 85 per cent ofcopper combined with one or more


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elements, such as tin, zinc,antimony and lead.

White metal is one form of bearingbronze containing over 80 per centofzinc together with copper, tin,

antimony and lead. Another form ismadewith nearly 90 per cent of tincombined with copper and antimony.

Gun metal bronze is made from 90per cent copper with 10 per cent oftinand is used for heavy bearings,brackets and highly finished parts.

Phosphor bronze is used for verystrong castings and bearings. It is

similar to gun metal bronze, exceptthat about 1-1/2 per cent ofphosphorushas been added.

Manganese bronze contains about 1per cent of manganese and is usedforparts requiring great strengthwhile being free from corrosion.

German silver is made from 60 percent of copper with 20 per centeach ofzinc and nickel. Its highelectrical resistance makes itvaluable forregulating devices and rheostats.

Tin is the principal part ofbabbitt and solder. Acommonly used babbitt is composedof 89 per cent tin, 8 per centantimonyand 3 per cent of copper. A gradesuitable for repairing is made from80 per cent of lead and 20 per cent

antimony. This last formula shouldnotbe used for particular work orheavy loads, being more suitable forspacers. Innumerable proportions ofmetals are marketed under the nameofbabbitt.


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Solder is made from 50 per cent tinand 50 per cent lead, this gradebeingcalled "half-and-half." Hard solderis made from two-thirds tin andone-third lead.

Aluminum forms many differentalloys, giving increased strengthto whatevermetal it unites with.

Aluminum brass is composed ofapproximately 65 per cent copper,30 per centzinc and 5 per cent aluminum. Itforms a metal with high tensilestrengthwhile being ductile and malleable.

Aluminum zinc is suitable forcastings which must be stiff andhard.

Nickel aluminum has a tensilestrength of 40,000 pounds persquare inch.

Magnalium is a silver-white alloyof aluminum with from 5 to 20 percent ofmagnesium, forming a metal evenlighter than aluminum and strongenough tobe used in making high-speedgasoline engines.

HEAT TREATMENT OF STEEL

The processes of heat treatment aredesigned to suit the steel forvariouspurposes by changing the size ofthe grain in the metal, thereforethestrength; and by altering the

chemical composition of the alloysin themetal to give it different physicalproperties. Heat treatment, asappliedin ordinary shop work, includes thethree processes of annealing,hardening


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and tempering, each designed toaccomplish a certain definiteresult.

All of these processes require thatthe metal treated be graduallybrought

to a certain predetermined degreeof heat which shall be uniformthroughoutthe piece being handled and, fromthis point, cooled according tocertainrules, the selection of which formsthe difference in the three methods.

Annealing.--This is the processwhich relieves all internal strainsand distortion in the metal andsoftens it so that it may more

easily becut, machined or bent to therequired form. In some casesannealing is usedonly to relieve the strains, thisbeing the case after forging orweldingoperations have been performed. Inother cases it is only desired tosoftenthe metal sufficiently that it maybe handled easily. In some casesboth ofthese things must be accomplished,as after a piece has been forged andmust be machined. No matter whatthe object, the procedure is thesame.

The steel to be annealed must firstbe heated to a dull red. Thisheatingshould be done slowly so that allparts of the piece have time toreach thesame temperature at very nearly thesame time. The piece may be heated

inthe forge, but a much better way isto heat in an oven or furnace ofsometype where the work is protectedagainst air currents, either hot orcold,and is also protected against thedirect action of the fire.


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Image Figure 4.--A GaspipeAnnealing Oven

Probably the simplest of all ovensfor small tools is made by placing apiece of ordinary gas pipe in thefire (Figure 4), and heating untiltheinside of the pipe is bright red.Parts placed in this pipe, afterone endhas been closed, may be brought to

the desired heat without danger ofcooling draughts or chemical changefrom the action of the fire. Moreelaborate ovens may be bought whichuse gas, fuel oils or coal toproducethe heat and in which the work maybe placed on trays so that the firewillnot strike directly on the steelbeing treated.

If the work is not very important,

it may be withdrawn from the fire oroven, after heating to the desiredpoint, and allowed to cool in theairuntil all traces of red havedisappeared when held in a darkplace. Thework should be held where it isreasonably free from cold aircurrents. If,upon touching a pine stick to the

piece being annealed, the wood doesnotsmoke, the work may then be cooled

in water.

Better annealing is secured andharder metal may be annealed if thecoolingis extended over a number of hoursby placing the work in a bed of


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non-heat-conducting material, suchas ashes, charred bone, asbestosfiber,lime, sand or fire clay. It shouldbe well covered with the heatretainingmaterial and allowed to remain

until cool. Cooling may beaccomplished byallowing the fire in an oven orfurnace to die down and go out,leaving thework inside the oven with allopenings closed. The greater thetime takenfor gradual cooling from the redheat, the more perfect will be theresultsof the annealing.

While steel is annealed by slowcooling, copper or brass isannealed bybringing to a low red heat andquickly plunging into cold water.

Hardening.--Steel is hardened bybringing to a proper temperature,slowly and evenly as for annealing,and then cooling more or lessquickly,according to the grade of steelbeing handled. The degree ofhardening isdetermined by the kind of steel,the temperature from which themetal iscooled and the temperature andnature of the bath into which it isplungedfor cooling.

Steel to be hardened is oftenheated in the fire until at someheat around600 to 700 degrees is reached, thenplaced in a heating bath of molten

lead, heated mercury, fused cyanateof potassium, etc., the heating bathitself being kept at the propertemperature by fires acting on it.Whilethese baths have the advantage ofheating the metal evenly and toexactly


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the temperature desired throughoutwithout any part becoming over orunderheated, their disadvantages consistof the fact that their materials andthe fumes are poisonous in most allcases, and if not poisonous, are

extremely disagreeable.

The degree of heat that a piece ofsteel must be brought to in orderthatit may be hardened depends on thepercentage of carbon in the steel.Thegreater the percentage of carbon,the lower the heat necessary toharden.

Image Figure 5.--Cooling the TestBar for Hardening

To find the proper heat from whichany steel must be cooled, a simpletestmay be carried out provided asample of the steel, about sixinches long

can be secured. One end of thistest bar should be heated almost toitsmelting point, and held at thisheat until the other end just turnsred.Now cool the piece in water byplunging it so that both ends enterat thesame time (Figure 5), that is, holdit parallel with the surface of thewater when plunged in. This servesthe purpose of cooling each point

alongthe bar from a different heat. Whenit has cooled in the water removethepiece and break it at shortintervals, about 1/2 inch, alongits length.The point along the test bar whichwas cooled from the best possible


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temperature will show a very finesmooth grain and the piece cannotbe cutby a file at this point. It will benecessary to remember the exactcolorof that point when taken from the

fire, making another test ifnecessary,and heat all pieces of this samesteel to this heat. It will benecessaryto have the cooling bath always atthe same temperature, or the resultscannot be alike.

While steel to be hardened isusually cooled in water, many otherliquidsmay be used. If cooled in strong

brine, the heat will be extractedmuchquicker, and the degree of hardnesswill be greater. A still greaterdegreeof hardness is secured by coolingin a bath of mercury. Care shouldbe usedwith the mercury bath, as the fumesthat arise are poisonous.

Should toughness be desired,without extreme hardness, the steelmay becooled in a bath of lard oil,neatsfoot oil or fish oil. Tosecure a resultbetween water and oil, it iscustomary to place a thick layer ofoil on topof water. In cooling, the piecewill pass through the oil first,thusavoiding the sudden shock of thecold water, yet producing a degreeofhardness almost as great as if the

oil were not used.

It will, of course, be necessary tomake a separate test for eachcoolingmedium used. If the fracture of thetest piece shows a coarse grain, thesteel was too hot at that point; ifthe fracture can be cut with a file,


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the metal was not hot enough atthat point.

When hardening carbon tool steelits heat should be brought to acherryred, the exact degree of heat

depending on the amount of carbonand thetest made, then plunged into waterand held there until all hissingsoundand vibration ceases. Brine may beused for this purpose; it is evenbetterthan plain water. As soon as thehissing stops, remove the work fromthewater or brine and plunge in oilfor complete cooling.

Image Figure 6.--Cooling the Toolfor Tempering

In hardening high-speed tool steel,

or air hardening steels, the toolshould be handled as for carbonsteel, except that after the bodyreachesa cherry red, the cutting pointmust be quickly brought to a whiteheat,almost melting, so that it seemsready for welding. Then cool in anoilbath or in a current of cool air.

Hardening of copper, brass andbronze is accomplished by hammering

orworking them while cold.

Tempering is the process of makingsteel tough after it has beenhardened, so that it will hold acutting edge and resist cracking.


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Tempering makes the grain finer andthe metal stronger. It does notaffectthe hardness, but increases theelastic limit and reduces thebrittlenessof the steel. In that tempering is

usually performed immediately afterhardening, it might be consideredas a continuation of the formerprocess.

The work or tool to be tempered isslowly heated to a cherry red andthecutting end is then dipped intowater to a depth of 1/2 to 3/4 inchabovethe point (Figure 6). As soon asthe point cools, still leaving the

toolred above the part in water, removethe work from the bath and quicklyrubthe end with a fine emery cloth.

As the heat from the uncooled partgradually heats the point again, thecolor of the polished portionchanges rapidly. When a certaincolor isreached, the tool should becompletely immersed in the wateruntil cold.

For lathe, planer, shaper andslotter tools, this color should bea lightstraw.

Reamers and taps should be cooledfrom an ordinary straw color.

Drills, punches and wood workingtools should have a brown color.

Blue or light purple is right for

cold chisels and screwdrivers.

Dark blue should be reached forsprings and wood saws.

Darker colors than this, rangingthrough green and gray, denote thatthe


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piece has reached its ordinarytemper, that is, it is partiallyannealed.

After properly hardening a springby dipping in lard or fish oil, itshould

be held over a fire while still wetwith the oil. The oil takes fire andburns off, properly tempering thespring.

Remember that self-hardening steelsmust never be dipped in water, andalways remember for all workrequiring degrees of heat, that themorecarbon, the less heat.

Case Hardening.--This is a process

for adding more carbon to thesurface of a piece of steel, sothat it will have good wear-resistingqualities, while being tough andstrong on the inside. It has theeffect offorming a very hard and durableskin on the surface of soft steel,leavingthe inside unaffected.

The simplest way, although not themost efficient, is to heat thepiece tobe case hardened to a red heat andthen sprinkle or rub the part of thesurface to be hardened withpotassium ferrocyanide. Thismaterial is adeadly poison and should be handledwith care. Allow the cyanide tofuse onthe surface of the metal and thenplunge into water, brine or mercury.Repeating the process makes thesurface harder and the hard skin

deepereach time.

Another method consists of placingthe piece to be hardened in a bed ofpowdered bone (bone which has beenburned and then powdered) and coverwith


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more powdered bone, holding thewhole in an iron tray. Now heat thetrayand bone with the work in an ovento a bright red heat for 30 minutesto anhour and then plunge the work into

water or brine.

CHAPTER II

OXY-ACETYLENE WELDING AND CUTTINGMATERIALS

Welding.--Oxy-acetylene welding isan autogenous welding process, in

which two parts of the same ordifferent metals are joined bycausing theedges to melt and unite whilemolten without the aid of hammeringorcompression. When cool, the partsform one piece of metal.

The oxy-acetylene flame is made bymixing oxygen and acetylene gasesin aspecial welding torch or blowpipe,producing, when burned, a heat of6,300degrees, which is more than twicethe melting temperature of the

commonmetals. This flame, while being ofintense heat, is of very small size.

Cutting.--The process of cuttingmetals with the flame produced fromoxygen and acetylene depends on thefact that a jet of oxygen directedupon


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hot metal causes the metal itselfto burn away with great rapidity,resulting in a narrow slot throughthe section cut. The action is sofastthat metal is not injured on eitherside of the cut.

Carbon Removal.--This processdepends on the fact that carbon willburn and almost completely vanishif the action is assisted with asupplyof pure oxygen gas. After thecombustion is started with anyconvenientflame, it continues as long ascarbon remains in the path of thejet ofoxygen.

Materials.--For the performance ofthe above operations we requirethe two gases, oxygen andacetylene, to produce the flames;rods of metalwhich may be added to the jointswhile molten in order to give theweldsufficient strength and properform, and various chemical powders,calledfluxes, which assist in the flow ofmetal and in doing away with many ofthe impurities and otherobjectionable features.

Instruments.--To control thecombustion of the gases and add totheconvenience of the operator anumber of accessories are required.

The pressure of the gases in theirusual containers is much too highfortheir proper use in the torch and

we therefore need suitable valveswhichallow the gas to escape from thecontainers when wanted, and otherspecially designed valves whichreduce the pressure. Hose, composedofrubber and fabric, together withsuitable connections, is used tocarry the


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gas to the torch.

The torches for welding and cuttingform a class of highly developedinstruments of the greatestaccuracy in manufacture, and mustbe thoroughly

understood by the welder. Tables,stands and special supports areprovidedfor holding the work while beingwelded, and in order to handle thevariousmetals and allow for theirpeculiarities while heated use ismade of ovensand torches for preheating. Theoperator requires the protection ofgoggles, masks, gloves andappliances which prevent undue

radiation of theheat.

Torch Practice.--The actual work ofwelding and cutting requirespreliminary preparation in the formof heat treatment for the metals,including preheating, annealing andtempering. The surfaces to be joinedmust be properly prepared for theflame, and the operation of thetorchesfor best results requires carefuland correct regulation of the gasesandthe flame produced.

Finally, the different metals thatare to be welded require specialtreatment for each one, dependingon the physical and chemicalcharacteristics of the material.

It will thus be seen that theapparently simple operations ofwelding andcutting require special materials,

instruments and preparation on thepartof the operator and it is a provedfact that failures, which have beenattributed to the method, arereally due to lack of thesenecessaryqualifications.


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OXYGEN

Oxygen, the gas which supports therapid combustion of the acetylenein thetorch flame, is one of the elementsof the air. It is the cause and the

active agent of all combustion thattakes place in the atmosphere.Oxygenwas first discovered as a separategas in 1774, when it was produced byheating red oxide of mercury andwas given its present name by thefamouschemist, Lavoisier.

Oxygen is prepared in thelaboratory by various methods,these including

the heating of chloride of lime andperoxide of cobalt mixed in aretort,the heating of chlorate of potash,and the separation of water into itselements, hydrogen and oxygen, bythe passage of an electric current.Whilethe last process is used on a largescale in commercial work, the othersare not practical for work otherthan that of an experimental ortemporarynature.

This gas is a colorless, odorless,tasteless element. It is sixteentimesas heavy as the gas hydrogen whenmeasured by volume under the sametemperature and pressure. Under allordinary conditions oxygen remainsina gaseous form, although it turnsto a liquid when compressed to 4,400pounds to the square inch and at atemperature of 220 below zero.

Oxygen unites with almost everyother element, this union oftentakingplace with great heat and muchlight, producing flame. Steel andiron willburn rapidly when placed in thisgas if the combustion is startedwith a


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flame of high heat playing on themetal. If the end of a wire isheatedbright red and quickly plunged intoa jar containing this gas, the wirewill burn away with a dazzlinglight and be entirely consumed

except forthe molten drops that separatethemselves. This property of oxygenis usedin oxy-acetylene cutting of steel.

The combination of oxygen withother substances does notnecessarily causegreat heat, in fact the combinationmay be so slow and gradual that thechange of temperature can not benoticed. An example of this slow

combustion, or oxidation, is foundin the conversion of iron into rustasthe metal combines with the activegas. The respiration of human beingsand animals is a form of slowcombustion and is the source ofanimal heat.It is a general rule that theprocess of oxidation takes placewithincreasing rapidity as thetemperature of the body being actedupon rises.Iron and steel at a red heatoxidize rapidly with the formationof a scaleand possible damage to the metal.

Air.--Atmospheric air is a mixtureof oxygen and nitrogen withtraces of carbonic acid gas andwater vapor. Twenty-one per cent oftheair, by volume, is oxygen and theremaining seventy-nine per cent isthe

inactive gas, nitrogen. But for thepresence of the nitrogen, whichdeadensthe action of the other gas,combustion would take place at adestructiverate and be beyond human control inalmost all cases. These two gasesexist


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simply as a mixture to form the airand are not chemically combined. Itistherefore a comparatively simplematter to separate them with theprocessesnow available.

Water.--Water is a combination ofoxygen and hydrogen, beingcomposed of exactly two volumes ofhydrogen to one volume of oxygen. Ifthese two gases be separated fromeach other and then allowed to mixinthese proportions they unite withexplosive violence and form water.Wateritself may be separated into thegases by any one of several means,

onemaking use of a temperature of2,200 to bring about thisseparation.

Image Figure 7.--Obtaining Oxygenby Electrolysis

The easiest way to separate waterinto its two parts is by the processcalled electrolysis (Figure 7).Water, with which has been mixed a

smallquantity of acid, is placed in avat through the walls of which

enter theplatinum tipped ends of twoelectrical conductors, one positiveand theother negative.

Tubes are placed directly abovethese wire terminals in the vat,one tube


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being over each electrode andseparated from each other by somedistance.With the passage of an electriccurrent from one wire terminal totheother, bubbles of gas rise from

each and pass into the tubes. Thegas thatcomes from the negative terminal ishydrogen and that from the positivepole is oxygen, both gases beingalmost pure if the work is properlyconducted. This method produceselectrolytic oxygen and electrolytichydrogen.

The Liquid Air Process.--Whileseveral of the foregoing methods ofsecuring oxygen are successful as

far as this result is concerned,they arenot profitable from a financialstandpoint. A process forseparating oxygenfrom the nitrogen in the air hasbeen brought to a high state ofperfectionand is now supplying a major partof this gas for oxy-acetylenewelding. Itis known as the Linde process andthe gas is distributed by the LindeAirProducts Company from its plantsand warehouses located in the largecitiesof the country.

The air is first liquefied bycompression, after which the gasesareseparated and the oxygen collected.The air is purified and thencompressedby successive stages in powerfulmachines designed for this purpose

untilit reaches a pressure of about3,000 pounds to the square inch.The largeamount of heat produced is absorbedby special coolers during theprocessof compression. The highlycompressed air is then dried and the


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temperature further reduced byother coolers.

The next point in the separation isthat at which the air is introducedinto an apparatus called aninterchanger and is allowed to

escape through avalve, causing it to turn to aliquid. This liquid air is sprayedontoplates and as it falls, thenitrogen return to its gaseousstate and leavesthe oxygen to run to the bottom of

the container. This liquid oxygen isthen allowed to return to a gas andis stored in large gasometers ortanks.

The oxygen gas is taken from thestorage tanks and compressed toapproximately 1,800 pounds to thesquare inch, under which pressureit ispassed into steel cylinders andmade ready for delivery to thecustomer.This oxygen is guaranteed to beninety-seven per cent pure.

Another process, known as theHildebrandt process, is coming intouse inthis country. It is a later processand is used in Germany to a muchgreater extent than the Lindeprocess. The Superior Oxygen Co.has securedthe American rights and hasestablished several plants.

Oxygen Cylinders.--Two sizes ofcylinders are in use, one containing100 cubic feet of gas when it is atatmospheric pressure and the othercontaining 250 cubic feet under

similar conditions. The cylindersare madefrom one piece of steel and arewithout seams. These containers aretestedat double the pressure of the gascontained to insure safety whilehandling.


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One hundred cubic feet of oxygenweighs nearly nine pounds (8.921),andtherefore the cylinders will weighpractically nine pounds more whenfullthan after emptying, if of the 100

cubic feet size. The large cylindersweigh about eighteen and one-quarter pounds more when full thanwhen empty,making approximately 212 poundsempty and 230 pounds full.

The following table gives thenumber of cubic feet of oxygenremaining inthe cylinders according to variousgauge pressures from an initialpressure

of 1,800 pounds. The amounts givenare not exactly correct as thiswouldnecessitate lengthy calculationswhich would not make great enoughdifference to affect the practicalusefulness of the table:

Cylinder of 100 Cu. Ft. Capacity at68 Fahr.

Gauge Volume GaugeVolumePressure Remaining PressureRemaining

1800 100 700 391620 90 500 281440 80 300 171260 70 100 61080 60 18 1900 50 9

1/2

Cylinder of 250 Cu. Ft. Capacity at68 Fahr.

Gauge Volume GaugeVolumePressure Remaining PressureRemaining

1800 250 700 971620 225 500 701440 200 300 421260 175 100 151080 150 18 8


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900 125 91-1/4

The temperature of the cylinderaffects the pressure in a largedegree, thepressure increasing with a rise in

temperature and falling with a fallintemperature. The variation for a100 cubic foot cylinder at varioustemperatures is given in thefollowing tabulation:

At 150Fahr........................ 2090pounds.At 100Fahr........................ 1912pounds.

At 80Fahr........................ 1844pounds.At 68Fahr........................ 1800pounds.At 50Fahr........................ 1736pounds.At 32Fahr........................ 1672pounds.At 0Fahr........................ 1558pounds.At -10Fahr........................ 1522pounds.

Chlorate of Potash Method.--Inspite of its higher cost and theinferior gas produced, the chlorateof potash method of producingoxygen isused to a limited extent when it isimpossible to secure the gas incylinders.

Image Figure 8.--Oxygen fromChlorate of Potash


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An iron retort (Figure 8) isarranged to receive about fifteenpounds ofchlorate of potash mixed with threepounds of manganese dioxide, afterwhich the cylinder is closed with atight cap, clamped on. This retort

iscarried above a burner using fuelgas or other means of generatingheat andthis burner is lighted after thechemical charge is mixed andcompressed inthe tube.

The generation of gas commences andthe oxygen is led through waterbathswhich wash and cool it before

storing in a tank connected withthe plant.From this tank the gas iscompressed into portable cylindersat a pressureof about 300 pounds to the squareinch for use as required in weldingoperations.

Each pound of chlorate of potashliberates about three cubic feet ofoxygen, and taking everything intoconsideration, the cost of gasproducedin this way is several times thatof the purer product secured by theliquid air process.

These chemical generators areoftentimes a source of great danger,especially when used with or nearthe acetylene gas generator, as issometimes the case with cheapportable outfits. Their use shouldnot betolerated when any other method isavailable, as the danger from

accidentalone should prohibit the practiceexcept when properly installed andcared for away from other sourcesof combustible gases.

ACETYLENE


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In 1862 a chemist, Woehler,announced the discovery of thepreparation ofacetylene gas from calcium carbide,which he had made by heating to ahightemperature a mixture of charcoal

with an alloy of zinc and calcium.Hisproduct would decompose water andyield the gas. For nearly thirtyyearsthese substances were neglected,with the result that acetylene waspractically unknown, and up to 1892an acetylene flame was seen by veryfewpersons and its possibilities werenot dreamed of. With thedevelopment of

the modern electric furnace thepossibility of calcium carbide as acommercial product became known.

In the above year, Thomas L.Willson, an electrical engineer ofSpray,North Carolina, was experimentingin an attempt to prepare metalliccalcium, for which purpose heemployed an electric furnaceoperating on amixture of lime and coal tar withabout ninety-five horse power. Theresultwas a molten mass which became hardand brittle when cool. Thisapparentlyuseless product was discarded andthrown in a nearby stream, when, totheastonishment of onlookers, a largevolume of gas was immediatelyliberated, which, when ignited,burned with a bright and smokyflame andgave off quantities of soot. The

solid material proved to be calciumcarbide and the gas acetylene.

Thus, through the incidental studyof a by-product, and as the resultof anaccident, the possibilities incarbide were made known, and in thespring


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of 1895 the first factory in theworld for the production of thissubstancewas established by the WillsonAluminum Company.

When water and calcium carbide are

brought together an action takesplacewhich results in the formation ofacetylene gas and slaked lime.

CARBIDE

Calcium carbide is a chemicalcombination of the elements carbonandcalcium, being dark brown, black orgray with sometimes a blue or red

tinge. It looks like stone and willonly burn when heated with oxygen.

Calcium carbide may be preservedfor any length of time if protectedfromthe air, but the ordinary moisturein the atmosphere gradually affectsituntil nothing remains but slakedlime. It always possesses apenetratingodor, which is not due to thecarbide itself but to the fact thatit isbeing constantly affected bymoisture and producing smallquantities ofacetylene gas.

This material is not readilydissolved by liquids, but ifallowed to comein contact with water, adecomposition takes place with theevolution oflarge quantities of gas. Carbide is

not affected by shock, jarring orage.

A pound of absolutely pure carbidewill yield five and one-half cubicfeet

of acetylene. Absolute puritycannot be attained commercially,and in


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practice good carbide will producefrom four and one-half to five cubicfeet for each pound used.

Carbide is prepared by fusing limeand carbon in the electric furnaceunder

a heat in excess of 6,000 degreesFahrenheit. These materials areamong themost difficult to melt that areknown. Lime is so infusible that itisfrequently employed for thematerials of crucibles in which thehighestmelting metals are fused, and forthe pencils in the calcium lightbecauseit will stand extremely high

temperatures.

Carbon is the material employed inthe manufacture of arc lightelectrodesand other electrical appliancesthat must stand extreme heat. Yetthese twosubstances are forced intocombination in the manufacture ofcalciumcarbide. It is the excessively hightemperature attainable in theelectricfurnace that causes thiscombination and not any effect ofthe electricityother than the heat produced.

A mixture of ground coke and limeis introduced into the furnacethroughwhich an electric arc has beendrawn. The materials unite and forman ingotof very pure carbide surrounded bya crust of less purity. The poorer

crustis rejected in breaking up the massinto lumps which are gradedaccordingto their size. The largest size is2 by 3-1/2 inches and is called"lump,"a medium size is 1/2 by 2 inchesand is called "egg," anintermediate size


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for certain types of generators is3/8 by 1-1/4 inches and called"nut,"and the finely crushed pieces foruse in still other types ofgeneratorsare 1/12 by 1/4 inch in size and

are called "quarter." Instructionsas tothe size best suited to differentgenerators are furnished by themakersof those instruments.

These sizes are packed in air-tightsheet steel drums containing 100poundseach. The Union Carbide Company ofChicago and New York, operatingunder

patents, manufactures anddistributes the supply of calciumcarbide for theentire United States. Plants forthis manufacture are established atNiagara Falls, New York, and SaultSte. Marie, Michigan. This companymaintains a system of warehouses inmore than one hundred and tencities,where large stocks of all sizes arecarried.

The National Board of FireUnderwriters gives the followingrules for thestorage of carbide:

Calcium carbide in quantities notto exceed six hundred pounds may bestored, when contained in approvedmetal packages not to exceed onehundredpounds each, inside insuredproperty, provided that the placeof storage bedry, waterproof and well ventilated

and also provided that all but oneofthe packages in any one buildingshall be sealed and that sealsshall notbe broken so long as there iscarbide in excess of one pound inany otherunsealed package in the building.


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Calcium carbide in quantities inexcess of six hundred pounds must bestored above ground in detachedbuildings, used exclusively for thestorageof calcium carbide, in approvedmetal packages, and such buildings

shall beconstructed to be dry, waterproofand well ventilated.

Properties of Acetylene.--This gasis composed of twenty-four partsof carbon and two parts of hydrogenby weight and is classed withnaturalgas, petroleum, etc., as one of thehydrocarbons. This gas contains thehighest percentage of carbon knownto exist in any combination of this

formand it may therefore be consideredas gaseous carbon. Carbon is thefuelthat is used in all forms ofcombustion and is present in allfuels fromwhatever source or in whateverform. Acetylene is therefore themostpowerful of all fuel gases and isable to give to the torch flame inwelding the highest temperature ofany flame.

Acetylene is a colorless andtasteless gas, possessed of apeculiar andpenetrating odor. The least tracein the air of a room is easilynoticed,and if this odor is detected aboutan apparatus in operation, it iscertainto indicate a leakage of gasthrough faulty piping, open valves,broken

hose or otherwise. This leakagemust be prevented before proceedingwiththe work to be done.

All gases which burn in air will,when mixed with air previous toignition,


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produce more or less violentexplosions, if fired. To this ruleacetyleneis no exception. One measure ofacetylene and twelve and one-halfof airare required for complete

combustion; this is therefore theproportion forthe most perfect explosion. This isnot the only possible mixture thatwillexplode, for all proportions fromthree to thirty per cent ofacetylene inair will explode with more or lessforce if ignited.

The igniting point of acetylene islower than that of coal gas, being

about900 degrees Fahrenheit as againsteleven hundred degrees for coalgas. Thegas issuing from a torch willignite if allowed to play on thetip of alighted cigar.

It is still further true thatacetylene, at some pressures,greater thannormal, has under most favorableconditions for the effect, beenfound toexplode; yet it may be stated withperfect confidence that under nocircumstances has anyone eversecured an explosion in it whensubjected topressures not exceeding fifteenpounds to the square inch.

Although not exploded by theapplication of high heat, acetyleneis injuredby such treatment. It is partly

converted, by high heat, into othercompounds, thus lessening theactual quantity of the gas, wastingit andpolluting the rest by theintroduction of substances which donot belongthere. These compounds remain inpart with the gas, causing it toburn with


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a persistent smoky flame and withthe deposit of objectionable tarrysubstances. Where the gas isgenerated without undue rise oftemperaturethese difficulties are avoided.

Purification of Acetylene.--Impurities in this gas are caused byimpurities in the calcium carbidefrom which it is made or by impropermethods and lack of care ingeneration. Impurities from thematerial willbe considered first.

Impurities in the carbide may befurther divided into two classes:thosewhich exert no action on water and

those which act with the water tothrowoff other gaseous products whichremain in the acetylene. Thoseimpuritieswhich exert no action on the waterconsist of coke that has not beenchanged in the furnace and sand andsome other substances which areharmless except that they increasethe ash left after the acetylene hasbeen generated.

An analysis of the gas coming froma typical generator is as follows:

Per cent

Acetylene ................................ 99.36

Oxygen ................................... .08

Nitrogen ................................. .11

Hydrogen ................................. .06

Sulphuretted

Hydrogen .................... .17Phosphoretted

Hydrogen ................... .04Ammonia .........................

......... .10Silicon

Hydride ...........................03


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CarbonMonoxide ...........................01

Methane .................................. .04

The oxygen, nitrogen, hydrogen,

methane and carbon monoxide areeitherharmless or are present in suchsmall quantities as to beneglected. Thephosphoretted hydrogen and siliconhydride are self-inflammable gaseswhenexposed to the air, but theirquantity is so very small that thispossibility may be dismissed. Theammonia and sulphuretted hydrogenare

almost entirely dissolved by thewater used in the gas generator. Thesurest way to avoid impure gas isto use high-grade calcium carbidein thegenerator and the carbide ofAmerican manufacture is now so purethat itnever causes trouble.

The first and most importantpurification to which the gas issubjected isits passage through the body ofwater in the generator as itbubbles to thetop. It is then filtered throughfelt to remove the solid particlesof limedust and other impurities whichfloat in the gas.

Further purification to remove theremaining ammonia, sulphurettedhydrogenand phosphorus containing compoundsis accomplished by chemical means.

Ifthis is considered necessary it canbe easily accomplished by readilyavailable purifying apparatus whichcan be attached to any generator orinserted between the generator andtorch outlets. The followingmixtureshave been used.


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"Heratol," a solution of chromicacid or sulphuric acid absorbed inporous earth.

"Acagine," a mixture of bleachingpowder with fifteen per cent oflead chromate.

"Puratylene," a mixture ofbleaching powder and hydroxide oflime,made very porous, and containingfrom eighteen to twenty per cent ofactivechlorine.

"Frankoline," a mixture of cuprousand ferric chlorides dissolved instrong hydrochloric acid absorbedin infusorial earth.

A test for impure acetylene gas ismade by placing a drop of ten percentsolution of silver nitrate on awhite blotter and holding the paperin astream of gas coming from the torchtip. Blackening of the paper in ashortlength of time indicates impurities.

Acetylene in Tanks.--Acetylene issoluble in water to a very limitedextent, too limited to be ofpractical use. There is only oneliquid thatpossesses sufficient power ofcontaining acetylene in solution tobe ofcommercial value, this being theliquid acetone. Acetone is producedinvarious ways, oftentimes from thedistillation of wood. It is atransparent, colorless liquid thatflows with ease. It boils at 133

Fahrenheit, is inflammable andburns with a luminous flame. It hasapeculiar but rather agreeable odor.

Acetone dissolves twenty-four timesits own bulk of acetylene atordinary


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atmospheric pressure. If thispressure is increased to twoatmospheres,14.7 pounds above ordinarypressure, it will dissolve justtwice as much ofthe gas and for each atmosphere

that the pressure is increased itwilldissolve as much more.

If acetylene be compressed abovefifteen pounds per square inch atordinarytemperature without first beingdissolved in acetone a danger ispresent ofself-ignition. This danger, whilepractically nothing at fifteenpounds,

increases with the pressure untilat forty atmospheres it is veryexplosive. Mixed with acetone, thegas loses this dangerous propertyand issafe for handling andtransportation. As acetylene isdissolved in theliquid the acetone increases itsvolume slightly so that when thegas hasbeen drawn out of a closed tank aspace is left full of freeacetylene.

This last difficulty is removed byfirst filling the cylinder or tankwithsome porous material, such asasbestos, wood charcoal, infusorialearth,etc. Asbestos is used in practiceand by a system of packing andsupportingthe absorbent material no space isleft for the free gas, even when theacetylene has been completely

withdrawn.

The acetylene is generated in theusual way and is washed, purifiedanddried. Great care is used to makethe gas as free as possible from allimpurities and from air. The gas isforced into containers filled with


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acetone as described and iscompressed to one hundred and fiftypounds tothe square inch. From these tanksit is transferred to the smallerportablecylinders for consumers' use.

The exact volume of gas remainingin a cylinder at atmospherictemperaturemay be calculated if the weight ofthe cylinder empty is known. Onepoundof the gas occupies 13.6 cubicfeet, so that if the difference inweightbetween the empty cylinder and theone considered be multiplied by13.6.

the result will be the number ofcubic feet of gas contained.

The cylinders contain from 100 to500 cubic feet of acetylene underpressure. They cannot be filledwith the ordinary type of generatoras theyrequire special purifying andcompressing apparatus, which shouldnever beinstalled in any building whereother work is being carried on, ornearother buildings which are occupied,because of the danger of explosion.

Dissolved acetylene is manufacturedby the Prest-O-Lite Company, theCommercial Acetylene Company andthe Searchlight Gas Company and isdistributed from warehouses invarious cities.

These tanks should not bedischarged at a rate per hourgreater than

one-seventh of their totalcapacity, that is, from a tank of100 cubic feetcapacity, the discharge should notbe more than fourteen cubic feet perhour. If discharge is carried on atan excessive rate the acetone isdrawnout with the gas and reduces theheat of the welding flame.


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For this reason welding should notbe attempted with cylindersdesigned forautomobile and boat lighting. Whenthe work demands a greater deliverythan

one of the larger tanks will give,two or more tanks may be connectedwitha special coupler such as may besecured from the makers anddistributersof the gas. These couplers may bearranged for two, three, four orfivetanks in one battery by removingthe plugs on the body of thecoupler andattaching additional connecting

pipes. The coupler body carries apressuregauge and the valve for controllingthe pressure of the gas as it flowstothe welding torches. The followingcapacities should be provided for:

Acetylene ConsumptionCombined Capacity of

of Torches per HourCylinders in UseUp to 15feet.......................100cubic feet16 to 30feet.......................200cubic feet31 to 45feet.......................300cubic feet46 to 60feet.......................400cubic feet61 to 75feet.......................500cubic feet

WELDING RODS

The best welding cannot be donewithout using the best grade ofmaterials,and the added cost of thesematerials over less desirable formsis so


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slight when compared to the qualityof work performed and the waste ofgases with inferior supplies, thatit is very unprofitable to take anychances in this respect. The makersof welding equipment carry anassortment of supplies that have

been standardized and that may bereliedupon to produce the desired resultwhen properly used. The safest planisto secure this class of materialfrom the makers.

Welding rods, or welding sticks,are used to supply the additionalmetalrequired in the body of the weld toreplace that broken or cut away and

also to add to the joint wheneverpossible so that the work may havethesame or greater strength than thatfound in the original piece. A rodofthe same material as that beingwelded is used when both parts ofthe workare the same. When dissimilarmetals are to be joined rods of acompositionsuited to the work are employed.

These filling rods are required inall work except steel of less than16gauge. Alloy iron rods are used forcast iron. These rods have a highsilicon content, the siliconreacting with the carbon in theiron toproduce a softer and more easilymachined weld than would otherwisebe thecase. These rods are often made sothat they melt at a slightly lower

pointthan cast iron. This is done forthe reason that when the part beingweldedhas been brought to the fusing heatby the torch, the filling materialcanbe instantly melted in withoutallowing the parts to cool. Themetal can be


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added faster and more easilycontrolled.

Rods or wires of Norway iron areused for steel welding in almost allcases. The purity of this grade ofiron gives a homogeneous, soft weld

ofeven texture, great ductility andexceptionally good machiningqualities.For welding heavy steel castings, arod of rolled carbon steel isemployed.For working on high carbon steel, arod of the steel being welded mustbeemployed and for alloy steels, suchas nickel, manganese, vanadium,etc.,

special rods of suitable alloycomposition are preferable.

Aluminum welding rods are made fromthis metal alloyed to give the evenflowing that is essential. Aluminumis one of the most difficult of allthemetals to handle in this work andthe selection of the proper rod isofgreat importance.

Brass is filled with brass wirewhen in small castings and sheets.Forgeneral work with brass castings,manganese bronze or Tobin bronzemay beused.

Bronze is welded with manganesebronze or Tobin bronze, whilecopper isfilled with copper wire.

These welding rods should always be

used to fill the weld when thethickness of material makes theiremployment necessary, and additionalmetal should always be added at theweld when possible as the jointcannothave the same strength as theoriginal piece if made or dressedoff flush


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with the surfaces around the weld.This is true because the metalweldedinto the joint is a casting andwill never have more strength than acasting of the material used forfilling.

Great care should be exercised whenadding metal from welding rods tomakesure that no metal is added at apoint that is not itself melted andmoltenwhen the addition is made. Whenmolten metal is placed upon coolersurfacesthe result is not a weld but merelya sticking together of the two partswithout any strength in the joint.

FLUXES

Difficulty would be experienced inwelding with only the metal and rodtowork with because of the scale thatforms on many materials under heat,theoxides of other metals and theimpurities found in almost allmetals. Thesethings tend to prevent a perfectjoining of the metals and somemeans arenecessary to prevent their action.

Various chemicals, usually inpowder form, are used to accomplishtheresult of cleaning the weld andmaking the work of the operator lessdifficult. They are called fluxes.

A flux is used to float offphysical impurities from the molten

metal; tofurnish a protecting coating aroundthe weld; to assist in the removalofany objectionable oxide of themetals being handled; to lower thetemperature at which the materialsflow; to make a cleaner weld and toproduce a better quality of metalin the finished work.


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The flux must be of suchcomposition that it will accomplishthe desiredresult without introducing newdifficulties. They may be preparedby the

operator in many cases or may besecured from the makers of weldingapparatus, the same remarksapplying to their quality as weremaderegarding the welding rods, thatis, only the best should beconsidered.

The flux used for cast iron shouldhave a softening effect and shouldprevent burning of the metal. Inmany cases it is possible and even

preferable to weld cast ironwithout the use of a flux, and inany eventthe smaller the quantity used thebetter the result should be. Fluxshouldnot be added just before thecompletion of the work because theheat willnot have time to drive the addedelements out of the metal or toincorporate them with the metalproperly.

Aluminum should never be weldedwithout using a flux because of theoxideformed. This oxide, called alumina,does not melt until a heat of 5,000Fahrenheit is reached, four timesthe heat needed to melt the aluminumitself. It is necessary that thisoxide be broken down or dissolvedso thatthe aluminum may have a chance toflow together. Copper is anothermetal

that requires a flux because of itsrapid oxidation under heat.

While the flux is often thrown orsprinkled along the break whilewelding,much better results will beobtained by dipping the hot end ofthe welding


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rod into the flux whenever the workneeds it. Sufficient powder willstickon the end of the rod for allpurposes, and with some fluxes toomuch willadhere. Care should always be used

to avoid the application ofexcessiveflux, as this is usually worse thanusing too little.

SUPPLIES AND FIXTURES

Goggles.--The oxy-acetylene torchshould not be used without theprotection to the eyes afforded bygoggles. These not only relieveunnecessary strain, but make it

much easier to watch the exactprogress ofthe work with the molten metal. Thedifficulty of protecting the sightwhile welding is even greater thanwhen cutting metal with the torch.

Acetylene gives a light which isnearest to sunlight of anyartificialilluminant. But for the fact thatthis gas light gives a little moregreenand less blue in its composition,it would be the same in quality andpractically the same in intensity.This light from the gas is almostabsentduring welding, being lost with theaddition of the extra oxygen neededtoproduce the welding heat. The lightthat is dangerous comes from themoltenmetal which flows under the torchat a bright white heat.

Goggles for protection against thislight and the heat that goes with itmay be secured in various tints,the darker glass being for weldingandthe lighter for cutting. Thosehaving frames in which the metalparts donot touch the flesh directly aremost desirable because of the high


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temperature reached by these parts.

Gloves.--While not as necessary asare the goggles, gloves are aconvenience in many cases. Those inwhich leather touches the handsdirectly are really of little value

as the heat that protection isdesiredagainst makes the leather so hotthat nothing is gained in comfort.Glovesare made with asbestos cloth, whichare not open to this objection in sogreat a degree.

Image Figure 9.--Frame for WeldingStand

Tables and Stands.--Tables forholding work while being welded(Figure 9) are usually made fromlengths of angle steel weldedtogether.The top should be rectangular,about two feet wide and two andone-halffeet long. The legs should supportthe working surface at a height ofthirty-two to thirty-six inchesfrom the floor. Metal lattice workmay befastened or laid in the topframework and used to support alayer offirebrick bound together with amixture of one-third cement andtwo-thirds

fireclay. The piece being welded isbraced and supported on this tablewithpieces of firebrick so that it willremain stationary during theoperation.

Holders for supporting the tanks of

gas may be


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made or purchased in forms thatrest directly on the floor or thataremounted on wheels. These holdersare quite useful where the floor orgroundis very uneven.

Hose.--All permanent lines fromtanks and generators to the torchesare made with piping rigidlysupported, but the short distancefrom the endof the pipe line to the torchitself is completed with a flexiblehose sothat the operator may be free inhis movements while welding. Anaccidentthrough which the gases mix in the

hose and are ignited will burst thispart of the equipment, with more orless painful results to the personhandling it. For that reason it iswell to use hose with great enoughstrength to withstand excessivepressure.

A poor grade of hose will alsobreak down inside and clog the flowof gas,both through itself and through theparts of the torch. To avoid outsidedamage and cuts this hose issometimes encased with coiled sheetmetal.Hose may be secured with a burstingstrength of more than 1,000 poundstothe square inch. Many operatorsprefer to distinguish between theoxygenand acetylene lines by their colorand to allow this, red is used fortheoxygen and black for acetylene.

Other Materials.--Sheet asbestosand asbestos fiber in flakes areused to cover parts of the workwhile preparing them for weldingand duringthe operation itself. The flakesand small pieces that becomedetached from


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the large sheets are thrown into abin where the completed small workisplaced to allow slow and evencooling while protected by theasbestos.

Asbestos fiber and also ordinaryfireclay are often used to make abackingor mould into a form that may beplaced behind aluminum and someothermetals that flow at a low heat andwhich are accordingly difficult tohandle under ordinary methods. Thisforms a solid mould into which themetal is practically cast as meltedby the torch so that the desiredshape

is secured without danger of thewalls of metal breaking through andflowing away.

Carbon blocks and rods are made invarious shapes and sizes so thattheymay be used to fill threaded holesand other places that it is desiredtoprotect during welding. These maybe secured in rods of variousdiametersup to one inch and in blocks ofseveral different dimensions.

CHAPTER III

ACETYLENE GENERATORS

Acetylene generators used forproducing the gas from the actionof water on

calcium carbide are divided intothree principal classes accordingto thepressure under which they operate.

Low pressure generators aredesigned to operate at one pound orless per


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square inch. Medium pressuresystems deliver the gas at not toexceedfifteen pounds to the square inchwhile high pressure types furnishgasabove fifteen pounds per square

inch. High pressure systems arealmostunknown in this country, the mediumpressure type being often referredtoas "high pressure."

Another important distinction isformed by the method of bringing thecarbide and water together. Themajority of those now in useoperate bydropping small quantities of

carbide into a large volume ofwater, allowingthe generated gas to bubble upthrough the water before beingcollectedabove the surface. This type isknown as the "carbide to water"generator.

A less used type brings a measuredand small quantity of water to acomparatively large body of thecarbide, the gas being formed andcollectedfrom the chamber in which theaction takes place. This is calledthe "waterto carbide" type. Another way ofexpressing the difference in feedis thatof designating the two types as"carbide feed" for the former and"waterfeed" for the latter.

A further division of the carbideto water machines is made by

mentioningthe exact method of feeding thecarbide. One type, called "gravityfeed"operates by allowing the carbide toescape and fall by the action of itsown weight, or gravity; the othertype, called "forced feed,"includes a


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separate mechanism driven by power.This mechanism feeds definiteamountsof the carbide to the water asrequired by the demands on thegenerator.The action of either feed is

controlled by the withdrawal of gasfrom thegenerator, the aim being to supplysufficient carbide to maintain anearlyconstant supply.

Generator Requirements.--Thequalities of a good generator areoutlined as follows: [Footnote: SeePond's "Calcium Carbide andAcetylene."

It must allow no possibility of theexistence of an explosive mixture inany of its parts at any time. It isnot enough to argue that a mixture,even if it exists, cannot beexploded unless kindled. It isnecessary todemand that a dangerous mixture canat no time be formed, even if themachine is tampered with by anignorant person. The perfectmachine must beso constructed that it shall beimpossible at any time, under anycircumstances, to blow it up.

It must insure cool generation.Since this is a relative term, allmachinesbeing heated somewhat during thegeneration of gas, this amounts tosayingthat a machine must heat butlittle. A pound of carbidedecomposed by waterdevelops the same amount of heatunder all circumstances, but that

heatcan be allowed to increase locallyto a high point, or it can beequalizedby water so that no part of thematerial becomes heated enough to dodamage.


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It must be well constructed. A goodgenerator does not need, perhaps,to be"built like a watch," but it shouldbe solid, substantial and of goodmaterial. It should be built forservice, to last and not simply to

sell;anything short of this is to beavoided as unsafe and unreliable.

It must be simple. The morecomplicated the machine the soonerit will getout of order. Understand yourgenerator. Know what is inside ofit andbeware of an apparatus, howeverattractive its exterior, whoseinterior is

filled with pipes and tubes, valvesand diaphragms whose functions youdonot perfectly understand.

It should be capable of beingcleaned and recharged and ofreceiving allother necessary attention withoutloss of gas, both for economy'ssake, andmore particularly to avoid dangerof fire.

It should require little attention.All machines have to be emptied andrecharged periodically; but themore this process is simplified andthemore quickly this can beaccomplished, the better.

It should be provided with asuitable indicator to designate howlow thecharge is in order that therefilling may be done in good

season.

It should completely use up thecarbide, generating the maximumamount ofgas.

Overheating.--A large amount ofheat is liberated when acetylene gas


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is formed from the union of calciumcarbide and water. Overheatingduringthis process, that is to say, anintense local heat rather than alargeamount of heat well distributed,

brings about the phenomenon ofpolymerization, converting the gas,or part of it, into oily matters,whichcan do nothing but harm. This tarrymass coming through the smallopeningsin the torches causes them tobecome partly closed and alters theproportions of the gases to thedetriment of the welding flame. Theonlyremedy for this trouble is to avoid

its cause and secure coolgeneration.

Overheating can be detected by theappearance of the sludge remainingafterthe gas has been made.Discoloration, yellow or brown,shows that there hasbeen trouble in this direction andthe resultant effects at thetorches maybe looked for. The abundance ofwater in the carbide to watermachineseffects this cooling naturally andis a characteristic of well designedmachines of this class. It has beenfound best and has practicallybecome afundamental rule of generation thata gallon of water must be providedforeach pound of carbide placed in thegenerator. With this ratio and agenerator large enough for thenumber of torches to be supplied,

littletrouble need be looked for withoverheating.

Water to Carbide Generators.--Itis, of course, much easier toobtain a measured and regular flowof water than to obtain such a flowof


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any solid substance, especiallywhen the solid substance is in theform oflumps, as is carbide This fact ledto the use of a great many water-feedgenerators for all classes of work,

and this type is still in common usefor the small portable machines,such, for instance, as those usedon motorcars for the lamps. The water-feedmachine is not, however, favored forwelding plants, as is the carbidefeed, in spite of the greaterdifficulties attending the handlingof the solid material.

A water-feed generator is made upof the gas producing part and a

holderfor the acetylene after it is made.The carbide is held in a trayformed ofa number of small compartments sothat the charge in each compartmentisnearly equal to that in each of theothers. The water is allowed to flowinto one of these compartments in avolume sufficient to produce thedesired amount of gas and thecarbide is completely used fromthis onedivision. The water then floods thefirst compartment and finallyoverflowsinto the next one, where the sameprocess is repeated. After using thecarbide in this division, it isflooded in turn and the waterpassing on tothose next in order, uses theentire charge of the whole tray.

These generators are charged withthe larger sizes of carbide and are

easily taken care of. The residueis removed in the tray and emptied,making the generator ready for afresh supply of carbide.

Carbide to Water Generators.--Thistype also is made up of twoprincipal parts, the generatingchamber and a gas holder, theholder being


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part of the generating chamber or aseparate device. The generator(Figure10) contains a hopper to receivethe charge of carbide and is fittedwiththe feeding mechanism to drop the

proper amount of carbide into thewateras required by the demands of thetorches. The charge of carbide isof oneof the smaller sizes, usually "nut"or "quarter."

Feed Mechanisms.--The device fordropping the carbide into the wateris the only part of the machinethat is at all complicated. Thiscomplication is brought about by

the necessity of controlling themass ofcarbide so that it can never bedischarged into the water at anexcessiverate, feeding it at a regular rateand in definite amounts, feeding itpositively whenever required andshutting off the feed just aspositivelywhen the supply of gas in theholder is enough for the immediateneeds.

Image Figure 10.--Carbide to WaterGenerator. A. Feed motor weight;B. Carbide feed motor; C. Carbidehopper; D. Water for gas generation;E. Agitator for loosening residuum;

F. Water seal in gas bell; G.Filter;H. Hydraulic Valve; J. Motorcontrol levers.

The charge of carbide isunavoidably acted upon by the watervapor in the


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generator and will in time becomemore or less pasty and sticky. Thisismore noticeable if the generatorstands idle for a considerablelength oftime This condition imposes another

duty on the feeding mechanism; thatis,the necessity of self-cleaning sothat the carbide, no matter in whatcondition, cannot prevent thepositive action of this part of thedevice,especially so that it cannotprevent the supply from beingstopped at theproper time.

The gas holder is usually made in

the bell form so that the upperportionrises and falls with the additionto or withdrawal from the supply ofgasin the holder. The rise and fall ofthis bell is often used to controlthefeed mechanism because thismovement indicates positivelywhether enoughgas has been made or that more isrequired. As the bell lowers itsets thefeed mechanism in motion, and whenthe gas passing into the holder hasraised the bell a sufficientdistance, the movement causes thefeedmechanism to stop the fall ofcarbide into the water. Inpractice, themovement of this part of the holderis held within very narrow limits.

Gas Holders.--No matter how closethe adjustment of the feeding

device, there will always be aslight amount of gas made after thefall ofcarbide is stopped, this beingcaused by the evolution of gas fromthecarbide with which water is alreadyin contact. This action is called"after generation" and the gashol

Documents

How to Weld and Cut Steel