[The Blacksmith and the Welder]
[From the U.S. Government Publishing Office, www.gpo.gov]

U)V35-jo-4
TM 10-440
Document
Reserve	WAR DEPARTMENT
TECHNICAL MANUAL
J-
THE BLACKSMITH AND
THE WELDER
June 16, 1941
NON-CIRCULATING
NTSU LIBRARY
TM 10-440
TECHNICAL MANUAL No. 10-440
WAR DEPARTMENT, Washington, June 16, 1941.
THE BLACKSMITH AND THE WELDER
Prepared under direction of The Quartermaster General
Section I.	General.	Paragraph
General ______________________________________ 1
Gl	ossary____________________________________ 2
II.	Blacksmithing.
General_______________________________________ 3
Forge ________________________________________ 4
Anvil_________________________________________ 5
Tools_________________________________________ 6
Procedure of forging__________________________ 7
Heat treating_________________________________ 8
Fires ________________________________________ 9
Basic shaping operations_____________________ 10
Calculation of stock for bent shapes_________ 11
Unit forging operations______________________ 12
III.	Gas welding and cutting.
General______________________________________ 13
Safety precautions___________________________ 14
Equipment____________________________________ 15
Acetylene____________________________________ 16
Oxygen_______________________________________ 17
Regulators __________________________________ 18
Welding torches______________________________ 19
Setting up equipment_________________________ 20
Oxyacetylene flame___________________________ 21
Adjusting the flame__________________________ 22
Joint design_________________________________ 23
Welding methods________■_____________________ 24
Expansion and contraction____________________ 25
Welding iron and steel_______________________ 26
Bronze welding or brazing____________________ 27
Welding aluminum_____________________________ 28
Welding copper_______________________________ 29
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Section III. Gas welding and cutting.—Continued.	Paragraph
Welding brass and bronze_____________________ 30
Oxyacetylene cutting_________________________ 31
Backfire and flashback_______________________ 32
Special precautions__________________________ 33
IV. Electric welding.
General _____________________________________ 34
Arc welding__________________________________ 35
Carbon arc method____________________________ 36
Metal arc method_____________________________ 37
Atomic hydrogen arc welding__________________ 38
Resistance welding___________________________ 39
Electric arc cutting_________________________ 40
Arc welding equipment________________________ 41
Welding arc__________________________________ 42
Arc polarity_________________________________ 43
Magnetic flare_______________________________ 44
Arc length___________________________________ 45
Arc voltage__________________________________ 46
Welding current______________________________ 47
Design of joints_____________________________ 48
Expansion and contraction____________________ 49
Preparation of work for	welding______________ 50
Striking the arc_____________________________ 51
Laying short beads___________________________ 52
Arc welding cast iron, alloy steels, and nonferrous metals______________________________ 53
Page
Appendix. Bibliography______________________________________ 97
Section I
GENERAL
Paragraph
General __________________________________________________ 1
Glossary _________________________________________________ 2
1. General.—Every automotive maintenance shop in the Army, stationary or mobile, should be prepared to do simple metalworking on sheet metal or heavier stock. This work unsually involves black
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smithing, welding, or cutting, or all three. The equipment and the procedure for such work are described in this manual.
2. Glossary.—For purposes of clarity and ready reference the following terms used in this text are defined:
Acetylene.—A colorless, inflammable, hydrocarbon gas (C2H2) with a distinctive odor. Usually formed by the action of water on calcium carbide.
Adhesion.—The molecular attraction exerted between the surfaces of bodies in contact.
Base metal.—The metal being welded—opposed to filler metal added by welding rod or electrode.
Bourdon tube.—A curved metal elastic tube, oval in cross section, open at one end to gas, steam, or other fluid pressure and closed at the other. Changes in pressure cause it to move and this movement is used to indicate the pressure.
Capillary attraction.—The action by which the surface of a liquid where it is in contact with a solid (as in a capillary tube) is elevated or depressed.
Carbon dioxide.—A heavy, colorless gas (CO2) which extinguishes flame—popularly called carbonic acid gas. It is produced by the action of acids on carbonates, by the fermentation of liquors, by the combustion and decomposition of organic substances, etc. Water will absorb more than its own volume of carbon dioxide under pressure, in which state it becomes soda, or carbonated, water. Compressed to a liquid it is used in some fire extinguishers and when frozen it becomes dry ice.
Carbon monoxide.—A colorless, odorless gas (CO) composed of carbon and oxygen. It is a product of the incomplete combustion of carbon, and burns with a pale blue flame to form carbon dioxide. It is very poisonous when inhaled because it drives oxygen from the blood. Its presence in the exhaust gases of internal-combustion engines has caused many fatalities.
Cohesion.—The molecular attraction exerted between the particles of a body which unites them.
Current density.—Amperes per square inch of surface.
Deposited metal.—Filler metal added from the electrode in arc welding.
Diaphragm.—A thin, flexible partition.
Dies.—A pair of cutting or shaping tools which, when moved toward each other, shape an object or surface between them by pressure or by a blow.
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Ductile.—Capable of being drawn out, as a wire.
Elastic.—Capable of being stretched or deformed by outside force, but returning to original form after outside force is removed.
Element.—One of the ninety some basic substances of which all materials are composed.
Extrude.—To shape by forcing through dies by pressure—opposed to draw.
Flux.—Any substance or mixture used to lower the melting point or to clean surfaces to be joined by soldering or welding and free them of oxide, and thus promote their union.
Fusion.—Melting or melting together.
Hydrogen.—An element commonly isolated as an inflammable, colorless, tasteless, odorless gas, which burns with an almost invisible flame to form water. It is the lightest known substance.
Infrared.—Light rays that are outside the red end of the visible spectrum.
Malleable.—Capable of being extended by beating with a hammer or by pressure of rollers.
Mandrel.—An axle, spindle, or arbor, usually tapered or cylindrical, forced into a piece of work having a hole in it, to support it while the work is machined or worked upon.
Nitride.—A compound of nitrogen with another element, as boron, silicon, and many metals, injurious to metal.
Nonferrous.—Not containing iron.
Oxide.—A compound of oxygen with another element or substance.
Oxidize.—To combine with oxygen; to add oxygen to.
Oxyacetylene.—Of, pertaining to, or consisting of a mixture of oxygen and acetylene.
Oxygen.—An element occurring free as a tasteless, colorless, odorless gas which forms about 23 percent by weight and 21 percent by volume of the atmosphere. It is the most abundant of all the elements in the earth’s surface.
Plastic.—Capable of being molded in a solid form by outside force, retaining that form after outside force is removed.
Reducing (in the sense of a reducing flame or agent).—Deoxidizing; capable of removing oxygen.
Scarf.—Bevel or chamfer.
Slag.—Superfluous matter, separated from metal in smelting, consisting mostly of silicates, which floats on molten iron.
Stress.—The external forces exerted on a body or the internal forces resisting them.
Tuyere.—A nozzle through which the air blast is delivered to a forge, blast furnace, etc.
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Ultraviolet.—Light rays outside the visible spectrum at its violet end.
Volatile.—Readily vaporizable or easily evaporated.
Section II
BLACKSMITHING
Paragraph
General_____________________________________________________________________ 3
Forge_______________________________________________________________________ 4
Anvil_______________________________________________________________________ 5
Tools____________________________________________________________________    6
Procedure of forgings_______________________________________________________ 7
Heat treating--------------------------------------------------------------- 8
Fires_______________________________________________________________________ 9
Basie shaping operations--------------------------------------------------- 10
Calculation of stock for bent shapes--------------------------------------- 11
Unit forging operations---------------------------------------------------  12
3. General.—All the tools listed here will not be available in the smaller shops. Some of them are designed to take the place of the blacksmith’s helper and are not required when he is available. Given a forge, an anvil, a hammer, a sledge, a few chisels, and a pair of tongs, the blacksmith can make many of the special tools he needs.
4. Forge.—A forge is the most important piece of blacksmith shop equipment. Forges are either portable or stationary.
a. Portable.— (1) A portable forge, the type used in mobile shops, is shown in figure 1. Its essential parts are a hearth, a tuyere and
BLOWER / jW,.
<	/ j||	' TUYERE
*‘3	/ JK 4 / HEARTH
• • ■ . . ■
TUYERE	i
VALVE
HANDLE I SPC	WATER
rtAJWix |	TANK.
ASH	\|
< GATE	1
/	I
Figure 1.—Portable forge.
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a blower. The hearth is a pan made from rolled-steel plate in which the fire is laid. The tuyere (fig. 2) directs an air blast into the fire. It is made of cast iron and consists of a fire pot, base, blast valve, and ash gate. The air blast enters the base, as shown in the illustration, and is admitted to the fire through the valve. A popular blast valve is a hollow cylinder having a large opening at the bottom through
i	VALVE POSITION
. An important use of the oxyacetylene process, especially in the small shop or in the field, is for heating. When forges and other blacksmithing equipment are not available, simple bending and forming operations can be performed easily by using the welding torch to heat the metal to forging temperature, or for annealing, hardening, and tempering operations, if necessary.
14.	Safety precautions.—Acetylene is an inflammable gas that is explosive when mixed with air. Oxygen is a chemically active gas. Both are compressed into cylinders under high pressures for industrial uses, and both are extremely dangerous unless the safety precautions mentioned throughout this section and in the manufacturers’ literature are strictly observed. One of the most important of these is never to oil regulators, torches, or any part of welding or cutting apparatus and never let oil or grease come in contact with or be near oxygen. Oil or grease coming in contact with pure oxygen under pressure will ignite violently or explode.
15.	Equipment.—In its simplest form an oxyacetylene welding and cutting outfit consists of a cylinder of oxygen, a cylinder of acetylene, two regulators, two lengths of hose with fittings, and a welding torch supplemented by a cutting attachment or a separate cutting torch. With this equipment all commercial metals can be welded; steel, wrought iron or cast iron can be cut; and local metal heating operations can be done effectively. Mounted on a hand truck as shown in figure 33, such an outfit is portable and can be taken wherever the work is located. In addition, goggles are required to protect the welder’s eyes, gloves to protect his hands, and a friction lighter to light the torch without danger of burning them. Wrenches are needed for cylinders, regulators, and torches. Welding rod or flux, or both, are also usually required. Interchangeable tips or heads of different sizes must be provided for the torches if the same handles are to be used for a variety of operations.
16.	Acetylene.—a. Acetylene is a fuel gas having a distinctive odor, composed of carbon and hydrogen, its chemical formula being C2H2. It is manufactured by the action of water on calcium carbide, a crushed, rock-like substance produced in an electric furnace from coke and limestone. The gas is contained in steel cylinders under a pressure of about 225 pounds per square inch when the cylinder is full. An acetylene cylinder is not hollow; it is filled with a porous material saturated with acetone, a liquid chemical which absorbs many times its
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own volume of acetylene. The acetylene is dissolved in the acetone under pressure in the same way that carbon dioxide gas (CO2) is dissolved under pressure in a bottle of soda water. This treatment makes the acetylene safe, even under the high 225-pound pressure, and allows enough acetylene to be stored in a cylinder for several days’ use under average conditions. The usual capacity of an acetylene cylinder is about 300 cubic feet. The cylinder itself is a strong steel container provided with a valve for attaching the regulator and drawing off the acetylene. Acetylene, once it has left the cylinder, is called “free.”
VALVE	Q
handle ~*^r
VALVE
WRENCH
/Bl t ACETYLENETOwl if
1 111V ■	°EOXYGFN
I	|«|^LiNDER
Tfijf WELDiNG 11	I f // il
/ » torch gu	'«
/M*.,	#
Figure 33.—Portable oxyacetylene welding outfit.
In this state it is liable to explode spontaneously when used at gage pressure over 15 pounds per square inch. A safety fuse plug which melts and releases the gas from the container is provided in case of fire. A cylinder of acetylene of 300 cubic feet capacity weighs 232.5 pounds full and 214 pounds empty. Smaller cylinders containing approximately 100 cubic feet are available. Empty cylinders must be returned to the manufacturer for recharging.
1). For safety’s sake, remember that acetylene will burn* and will form explosive mixtures with air. Handle acetylene cylinders carefully and store them in a well-ventilated, dry place away from com
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bustible materials, stoves, radiators, or furnaces. Keep the valve end up. Never tamper with fuse plugs.
17. Oxygen.—a. Oxygen is a colorless, odorless, and tasteless gas. It is necessary for the combustion of most substances and combines chemically with them when they burn. Oxygen itself is not inflammable but is said to support combustion. For ordinary fires, such as forge and furnace fires, the oxygen in the air supports combustion of the fuel. Except for a very small percentage of rare gases, such as argon, neon, and helium, the atmosphere is composed of about one-fifth oxygen and four-fifths nitrogen. Nitrogen does not aid in combustion but merely cools off the fire. It can be seen, therefore, that the pure oxygen is a much more active agent than air in supporting combustion.
b.	The bulk of the oxygen used in industry today is obtained from the atmosphere by the liquid air process; a small amount is made from water by the electrolytic process. Air is liquefied by a process of compression, cooling, and expansion, and oxygen is separated from the resulting extremely cold liquid by fractional distillation, in which advantage is taken of the fact that liquid nitrogen boils at a lower temperature than liquid oxygen. The distilling apparatus delivers practically pure oxygen to a storage holder, from which it is compressed into steel cylinders for distribution.
c.	Oxygen is produced by the electrolytic process, as follows: Water is a chemical compound of hydrogen and oxygen (H2O), each of which is a gas in its uncombined state. Under suitable conditions, an electric current passed through water decomposes it into its two elements. Bubbles of oxygen rise from the positive electrical terminal or electrode and hydrogen bubbles from the negative electrode. Each gas is led to a storage holder and then compressed in cylinders.
d.	Oxygen cylinders are very strong, seamless, drawn-steel containers into which the oxygen is compressed to the extremely high pressure of 2,000 pounds per square inch. This pressure is measureci at 70° F. and becomes somewhat greater when the cylinder is at a higher temperature and somewhat less when it is at a lower temperature. The pressure decreases as the oxygen is drawn off and the cylinder emptied. Unlike acetylene cylinders, oxygen cylinders are hollow. They are provided with specially designed valves to resist the high pressure. Every oxygen cylinder valve has some kind of a safety device to blow off the oxygen in case the cylinder is directly exposed to fire. The usual oxygen cylinder contains 220 cubic feet of oxygen and is 56 inches in height (including valve) and 9 inches in diameter. It weighs about 148 pounds full and 130 pounds empty. Smaller cylinders con
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taining 110 cubic feet are available. The cylinder must be returned to the manufacturer when empty.
e.	Oxygen is not an inflammable gas but causes other burning materials to burn more violently when they are exposed to it. It will cause oily or greasy substances to burst into flame with explosive violence without any other ignition. Always remember this when using it. Never confuse oxygen with compressed air and never use it to supply head pressure on a tank. It would be fatal to put pressure on the tank of a kerosene preheating torch, for instance. Never use oxygen for pneumatic tools, to start internal combustion engines, to blow out pipe, or to “dust” clothes. Oxygen cylinders are strong enough to withstand ordinary handling, but they should not be dropped off platforms,
CYLINDER	WORKING
if	GA6e	SAGE //
working ’ ^PRESSURE GAGE	CYLINDER WIWMeV
PRESSURE GAGE
CYLINDER	/J?	CYLINDER ».
CONNECTION	CONN EOT
OXYGEN REGULATOR
ACETYLENE REGULATOR
Figure 34.—Oxygen and acetylene regulators.
knocked about, or placed where heavy articles may drop on them. Do not store them in hot places or where oil may drop on them from overhead bearings or machines.
18.	Regulators.—a. General.—The function of a regulator (fig. 34) is to reduce the high pressure of the gas in the cylinder to a low constant working pressure at the torch. For example, a cylinder contains oxygen at a pressure of 2,000 pounds per square inch, and a pressure of only 10 pounds per square inch is wanted at the torch to do some welding. The regulator must reduce the cylinder pressure from 2,000 to 10 pounds per square inch and must maintain this working pressure as the cylinder pressure decreases. Therefore, a regulator must have a sensitive regulating mechanism in addition to a reducing valve.
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(1) A regulator for either an acetylene or an oxygen container has a union nipple for attaching it to the cylinder and an outlet connection for the hose leading to the torch. There are two gages on the body of the regulator: one shows the pressure in the cylinder, and the other the working pressure being supplied to the torch. The working pressure is adjusted by a hand screw. When this screw is turned to the left (counterclockwise) until it turns freely, the valve inside the regulator is closed and no gas can pass to the torch. Turning the handle to the right (clockwise) opens the valve, and gas passes to the torch at the pressure shown on the working pressure gage. The more the hand screw is turned to the right, the higher the pressure shown on the working pressure gage. Typical regulators are shown in figure 34.
(2) Before opening the valve on a cylinder to which a regulator is attached, the pressure-adjusting screw must be fully released by turning it to the left (counterclockwise) until it turns freely. Otherwise, when the cylinder valve is opened, the valve and seat will be forced together by the full pressure of the gas, which, in the case of an oxygen cylinder, may be as high as 2,200 pounds per square inch. The impact would ruin the valve seat, and the regulator would be unsafe to use until repaired.
5. Construction.—The details of regulator construction vary with different manufacturers but the fundamentals of operation are the same in all. The basic differences in the various makes are that some have movable valves with stationary seats, while others have stationary valves with movable seats, and some have rubber diaphragms while others have metal ones. A common type of regulator is shown in cross section in figure 35. Some type of safety release mechanism, such as a breakable disk or ball relief valve, is provided for the working pressure chamber of every regulator. If the regulator valve fails to close completely, a high pressure will be generated. This condition is sometimes known as “creep.” Cylinder pressure gages are provided with safety devices to relieve the pressure if the bourdon tube in the gage breaks. Working pressure gages are usually provided with vent holes for the same purpose.
c. Pressure reduction operation.—The cylinder pressure is reduced to working pressure as follows: When the pressure-adjusting screw (figure 35) is turned to the left (counterclockwise) until fully released, the high pressure valve is held closed by the small valve spring. When the cylinder valve is opened, gas from the cylinder enters the regulator through the inlet connection and passes through the inlet screen to the high pressure chamber where it assists the valve spring in keeping the valve seated. The screen keeps out particles of dirt
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or other matter that might damage the valve seat. As long as the valve is closed, the gas is confined to the high pressure chamber. The cylinder pressure gage is connected to this chamber through a drilled hole and registers the cylinder pressure. When the pressure-adjusting screw is turned to the right (clockwise), it compresses the pressure-adjusting spring and forces it against the diaphragm and the valve, which is connected to the diaphragm. When the pres-
■ haMMf pressure gage
-HIGH PRESSURE
/ VALVE
i j	DIAPHRAGM^ ?	‘/ HIGH PRESSURE
I j	< I CHAMBER
I	MA	' I Nd J SCREEN
v 'i*UI.	& / V
c V r r. ABMwt irnBT1- -yv "1 bwstuwi
’jPy jjl	■' ’ ■
I	■ / ; .	' <	'““M xvalve v --t
| ’•	< 1	' - a	I SEAT I
. 1 \ v----------AH j--mX	i
I 1 \	/	1	SMALL VALVE |
* J PRESSURE PRESSURE	*7 \ SPRING INLET
W ADJUSTING ADJUSTING	Lj V	CONNECTION
SCREW SPRING	/ I .-
WORKING <1 ® PRESSURE K Wx
CHAMBER I I| OUTLET
IjK HOSE
| CONNECTION
Figure 35.—Single stage regulator.
sure of the pressure-adjusting spring overcomes the opposing combined pressure of the valve spring and the high pressure gas on the head of the valve, the valve opens. Gas then flows from the high pressure chamber through the opening around the valve stem into the working pressure chamber, thence through the outlet and hose connection to the torch. If the torch valve is open, the gas flow will continue at the pressure indicated on the working pressure
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gage, which is connected with the working pressure chamber. Increasing the pressure by the pressure-adjusting spring increases the pressure in the working pressure chamber. Thus any working pressure, within the capacity of the regulator, can be obtained by turning the pressure-adjusting screw until the working pressure gage indicates the pressure wanted. The correct torch valve should always be open when the working pressure is being adjusted.
d.	Pressure regulation.—The gas pressure in the working pressure chamber to which the torch valve is connected is regulated as follows: If the torch valve is closed, pressure immediately builds up in the working pressure chamber and presses against the diaphragm. The diaphragm, being flexible, moves in or out with changes in pressure in the working pressure chamber. As the pressure on the diaphragm increases, it compresses the pressure-adjusting spring and closes the valve, shutting off the flow of gas. As soon as the pressure on the diaphragm is reduced slightly by opening the torch valve, the pressureadjusting spring decompresses and reopens the valve. For the sake of simplicity, only the action of the mechanism in starting and stopping the flow of gas has been explained. Actually the mechanism functions constantly while the torch valve is open. As gas is drawn from the cylinder the pressure in the cylinder falls. The sensitive diaphragm reacts constantly to the gradual drop in pressure and allows the pressure-adjusting spring to open the valve farther to compensate for this and maintain the working pressure fairly constant until the cylinder pressure is down to the working pressure.
e.	Two-stage regulators.—In more recently developed regulators, the pressure reduction is accomplished in two separate steps. This type of regulator has two independent diaphragm and valve assemblies, as shown in figure 36, which makes operation more efficient. The full cylinder pressure enters the regulator and is reduced to a lower pressure in the first stage, which is automatic and nonadjust-able. The second stage is the same as the first stage except that it has a larger diaphragm, lighter springs, and is adjustable by the operator. The second stage functions only within a limited range and insures more constant delivery pressure adjustment than is possible with single stage regulators.
f.	Oxygen regulator.—An oxygen regulator is designed so that the regulating mechanism will take care of the full cylinder pressure of about 2,000 pounds per square inch. It is customary to provide a cylinder pressure gage with a capacity of 3,000 pounds per square inch on an oxygen regulator. This gage usually has a second scale that indicates the contents of the cylinder in cubic feet at 70° F. For
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crq CTQ
welding, the regulator is designed to deliver a maximum workin pressure of 50 pounds per square inch and usually has a workin pressure gage with a. capacity of 100 pounds per square inch. For cutting, maximum oxygen pressures may vary from 125 to 200 pounds per square inch, so the working pressure gage usually has a capacity of 400 pounds per square inch.
g.	Acetylene regulator.—(1) Acetylene regulators operate the same as oxygen regulators, but since the cylinder pressure is not as high as
WORKING PRESSURE GAGE | j '	CYLINDER PRESSURE GAGE
i	SAFETY RELEASE AND HOSE
I	I	CONNECTION DO NOT SHOW
Li	i	IN THIS VIEW
( VALVE x \ . ifi	SPRING .	PRESSURE
\	\	■ '''hr------a	ADJUSTING
jgsrg-	SCREW
rff f f	V	; ./
J] J	j \	" I r****^‘“":’
J । i n.l
; fit .CYLINDER
SPRING SET TO ABOUT	j |||	/ CONNECTION
250 POUNDS PER SQUARE I 1*4
INCH IN FIRST STAGE • f I < H
j | J !
Figure 36.—Cross section of two-stage regulator.
oxygen cylinder pressure, lighter springs are used. An acetylene regulator has a cylinder pressure gage with a capacity of 350, 400, or 500 pounds per square inch and a working pressure gage with a capacity of from 30 to 50 pounds per square inch. Some acetylene working pressure gages are graduated only to 15 pounds per square inch, because it is unsafe to use acetylene at higher pressures. The same acetylene regulator is used either for welding or cutting. Unlike oxygen regulators, acetylene regulators do not fit all cylinders.
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Straight 45° and 90° adapters can be obtained for connecting regulators having cylinder connections of certain types and dimensions to cylinder valves of different types and dimensions.
(2) Note that all regulator gages have capacities greater than the pressures they are expected to handle. This excess capacity is provided as a safety factor to prevent the instruments being strained.
(3) The warning “Use no oil” applies to oxygen regulators as it does to all equipment 'where oxygen is handled under pressure. Use no oil on acetylene regulators because of their nearness to, and possible confusion with, oxygen regulators.
19. Welding* torches.—The oxyacetylene welding torch mixes acetylene with oxygen in definite proportions, burns the mixture at its tip, and directs the flame on the parts to be welded or heated.
a.	Construction.—The details of construction vary with different manufacturers, but all welding torches are essentially the same. They are made from brass tubing and brass castings or pressure forgings, fastened together by silver solder and threaded connections. Every welding torch has two needle valves, one for adjusting the acetylene pressure and one for adjusting the oxygen pressure. Welding heads or tips are made from drawn copper. Interchangeable tips or heads are usually provided so one torch can handle a wide range of work, from the lightest to the heaviest.
b.	Types.—There are two general types of welding torches—low pressure and medium pressure. Acetylene at a pressure of less than 1 pound per square inch is designated as low pressure; from 1 to 15 pounds per square inch, medium pressure. Low pressure torches employ the injector principle. Torches of this type are designed so the high pressure oxygen jet produces a suction effect which draws the acetylene in. Some medium pressure torches are designed to operate with equal pressures of oxygen and acetylene and are called equal pressure or balanced pressure torches.
(1) Low pressure.—A low pressure welding torch is shown in figure 37. Oxygen enters through the oxygen hose connections at the end of the torch and passes through the needle valve and through the tube and passage to the injector jet, which is in the detachable head of the torch. Acetylene enters the torch at the acetylene hose connection and passes through the needle valve and the tube and passages around the oxygen jet. It is drawn into the injector jet by the suction of the jet and mixes with the oxygen in the expansion chamber. The mixture then passes through the head to the tip where it is burned.
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(2) Medium, pressure.—A medium pressure welding torch is shown in figure 38. The oxygen and acetylene enter and pass through this torch in about the same way as they do in the low pressure torch. The principal difference is that a mixing chamber is provided instead of an injector. Here the acetylene, flowing longitudinally, meets the cross current of oxygen flowing in radially through the holes in the sides. (In other models the oxygen flows longitudinally and the acetylene radially.) The cross currents form a whirlpool, thoroughly mixing the two gases as they enter the welding head’ The mixture then passes to the tip where it is burned.
c. Interchangeable heads and tips.—IMw of the valuable features of the modern welding torch is the system of interchangeable heads
OXYGEN VALVE oxygen HOSE \	> CONNECT®#
#	acetylene hose
-JF	ACETYLENE - ’	CONNECTiON
VALVE
HEA&	SEATiNG	OXYSEN
NUT	SURFACES	PASSAGE	.HANDLE
INVESTOR A —
...../
expansion	*	" w1Sshk.?v *
CHAMBER	---------——
ACETYLENE
PASSAGE
Figure 37.—Low pressure welding torch.
and tips which allows one torch to be used for various jobs. Tables provided by the manufacturers give the sizes of tips to use for different kinds and thicknesses of metal. A welding torch with five standard interchangeable welding heads is shown in figure 39. These heads are available with detachable tips as shown in figure 40, or with an integral stem. A detachable tip is preferable when it receives rough handling.
el. IT elding accessories.—Welding accessories, such as hose and fittings, welding rod, flux, goggles, gloves, wrenches, friction lighters, 1 nicks, and tables, should be of good quality and made especially for the purpose. Makeshifts are dangerous. A welding table (fig. 41) while not essential is very convenient.
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OXYGEN NEEDLE
VALVE ASSEMBLY
TORCH HANDLE	*
_ „„, X„. n - .	—tX"LX)
#	HEAC MIT	ACETYLENE NEEQLEl|pW
JF	VALVE ASSEMBLY
/	sap
/	dl»
MIXING HEAD	OXYGEN TUBE	ySKv
■ jSSiiHiiiiiiiiiiiiiiiiiiiiliiiiimm^	iiiiiT ir'-----------^	' ~‘ - X~~~ -■ -~ ■’	' •■■	■■ - — I
g!/	ACETYLENE TUBE
,-O	HOSE CONNECTIONS - '-
fef—.TIP
Figure 38.—Medium pressure welding torch.
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20.	Setting up equipment.—a. Procedure.—So far the functions of individual items of equipment required for oxyacetylene welding have been discussed. The next requirement is to learn how to assemble them properly and safely into a unit ready for operation. This may be done with the usual equipment in 10 steps as follows:
(1)	Place the oxygen and acetylene cylinders erect on a truck or in a permanent location and fasten them securely so they cannot be
....... .
Z0CTACHA8LE HEAO TORCH
EXTRA
ft	DETACHABLE
if ,‘I	WRENCH
ft lit HEADS
Figure 39.—Welding torch with interchangeable heads.
Figure 40.—Detachable welding tip.
upset. Stand at the side of the cylinders and open the oxygen cylinder valve for an instant to blow out any dust or dirt that may have lodged in the valve during transit. Then do the same with the acetylene cylinder. This procedure is known as “cracking the valve.” Do not stand in front of valves.
(2)	Connect the oxygen regulator to the oxygen cylinder and the acetylene regulator to the acetylene cylinder and screw the nuts up
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tight, using the wrench macle specially for the purpose. To prevent a dangerous interchange of regulators, the threads on each cylinder valve are different. Usually oxygen valve threads are right hand and acetylene valve threads are left hand. Note this difference.
(3)	There are two hose, one green and the other red, which are often taped together at intervals of every 2 feet. Connect the green hose to the oxygen regulator and the red hose to the acetylene regulator and tighten the nuts with the wrench. Hose and regulator fittings are not interchangeable. Those for oxygen hose have right hand threads and those for acetylene hose have left hand threads.
Figure 41.—Welding table.
(4)	Fully release both regulator adjusting screws by turning them to the left (counterclockwise) until they turn freely, then open the cylinder valves slowly. After the hand on the cylinder pressure gage has stopped moving, open the oxygen cylinder valve all the way as this valve has a double seal. Do not open the acetylene valve more than iy2 turns and leave the special wrench on the valve while the cylinder is in use. Never open cylinder valves unless regulator adjusting screws are released.
(5)	Point the oxygen hose away from the body, and turn the regulator adjusting screw in for a moment until sufficient gas pressure
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is exerted to blow out any substance that may have lodged in the hose. Do the same with, the acetylene hose.
(6)	Connect the green oxygen hose to the oxygen needle valve on the torch. Then connect the red acetylene hose to the acetylene needle valve on the torch. The oxygen and acetylene valves are marked and the hose connections are not interchangeable. The oxygen hose connection has a right hand thread and the acetylene connection has a left hand thread.
(7)	Attach the correct welding head or tip to the torch, setting the tip at the proper angle, and tighten the nut.
(8)	Open the oxygen needle valve on the torch and turn the oxygen regulator pressure-adjusting screw in until the required pressure is shown on the working pressure gage. Then close the oxygen needle valve. Open the acetylene needle valve and adjust the acetylene pressure.
(9)	Light the acetylene at the tip with a friction lighter or spark lighter as it is sometimes called.
(10)	Open the oxygen needle valve and adjust the flame until it becomes neutral.
1).	Precautions.— (1) The foregoing operations should be performed away from, open fires or sparks, because the operations of cracking the valve, blowing out the hose, and adjusting the working pressure release inflammable gas.
(2)	Hose will burn but slowly unless it is filled with oxygen; then it will burn with explosive violence if exposed to fire.
(3)	Do not use a flame for locating leaks. Use soapy water.
c. Stopping work.—If work is stopped for a short length of time, release the pressure adjusting screws of the regulators by turning them to the left (counterclockwise) until they turn freely. When welding or cutting is stopped for a longer period, such as during lunch hour or overnight, close the cylinder valves and release all gas pressure from the regulators by opening the torch valves for a moment. Then close the torch valves and release the regulator pressure-adjusting screws.
21. Oxy acetylene flame.—a. General.—The sole purpose of the equipment and procedure so far described is to produce an oxyacetylene flame.
(1)	A flame is a stream of burning gas. This is true whether the combustible material producing the flame is a solid, liquid, or gas. If the fuel is solid or liquid it is changed to a gas by heat before it burns as a flame. The oxyacetylene flame is particularly suitable for welding because of its very high temperature (estimated at 6,000° F.) and because if properly adjusted it will not harm most metals.
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(2)	When the torch is first lighted, and before the oxygen needle valve has been opened, the flame is long and bushy with a yellowish appearance. Oxygen for combustion is being provided by the air. The flame is smoky, containing a large quantity of unburned carbon soot, indicating that combustion of the acetylene is not completed.
(3)	As the oxygen valve is opened a bright inner cone of flame, white to blue in color, appears. Here the premixed gases burn at extremely high temperatures. Surrounding this inner cone is an outer flame envelope or sheath, flame of cooler burning gases, which contains varying amounts of incandescent carbon soot, depending upon the proportion of oxygen to acetylene.
(4)	Mixtures of pure oxygen and acetylene cannot burn completely to form a single-cone flame. The temperature produced is so high that the products of complete combustion (carbon dioxide and water vapor) would be decomposed into their elements. Thus acetylene burns in the inner cone of the flame with the oxygen supplied through the torch to form carbon monoxide and hydrogen, both combustible gases. These gases burn completely, as they cool off, with the oxygen from the surrounding air to form the cooler sheath flame. Theoretically, 1 part of acetylene requires 2% parts of oxygen for complete combustion. This mixture will not result in complete burning of acetylene since the elements of acetylene cannot completely combine with oxygen because of the high temperature. Actually, a mixture of 1 part of acetylene and 1 part of oxygen is used, the oxygen of the surrounding air supplying the additional 1% parts of oxygen necessary for complete combustion. Since the inner cone of the flame contains only the gases, carbon monoxide and hydrogen, which are reducing (able to combine with oxygen and remove it) in character, oxidation of the metal does not occur.
b.	Neutral flame.—This equal mixture of gases gives a neutral or balanced flame. The neutral flame has a characteristic appearance and is easily obtained with a little practice. It has two sharply defined zones. The inside portion consists of a brilliant white cone from i/16 to % inch long. Surrounding this is a larger cone or envelope flame, only faintly luminous and of a delicate bluish color. It is shown in figure 42. The neutral flame is of particular importance to the operator because it is used for most welding, cutting, and heating operations, and is the basis of reference for other flame adjustments.
c.	Reducing -flame.—The excess-acetylene, reducing, or carbonizing flame, as it is variously known, is formed when there is more acetylene than oxygen in the mixture. When this occurs, the flame consists of three easily recognizable cones instead of the two existing in the
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OUTER CONE -----=---INNER
OR ENVELOPE FLAME	CONE
NEUTRAL FLAME
INTERMEDIATE
_-------------------
OUTER CONE -------------- INNER
OR ENVELOPE FLAME	CONE
REDUCING FLAME
OUTER CONE OR „
ENVELOPE FLAME x. _ --------------------^^'flNNER
OXIDIZING FLAME C0NE
Figure 42.—Oxyacetylene flames.
neutral flame. There is still the sharply defined inner cone and the bluish outer envelope, but between these there is a third cone of whitish color surrounding the inner cone (see fig. 42). The length of the intermediate cone may be taken as a measure of the amount of excess acetylene in the flame. The reducing flame is used for certain special techniques in welding steel (Lindeweld, Aircoweld), and sometimes for welding high-carbon steels, stove castings, and furnace grates. A slightly reducing flame is sometimes used for welding aluminum, nickel, and monel metal, and for applying hard facing materials.
d.	Oxidizing flame.—When there is more oxygen than acetylene in the mixture the flame has the general appearance of the neutral flame, but the inner cone is shorter, more pointed, and becomes somewhat purplish. There is also a distinct hissing sound. These are the characteristics of the oxidizing flame, also shown in figure 42. This flame is ruinous to most metals and should generally be avoided. A slightly oxidizing flame is sometimes used in bronze welding, or brazing, and a stronger oxidizing flame is sometimes used for fusion welding of brass and bronze.
22.	Adjusting the flame.—After the torch is lighted, with only the acetylene turned on, adjust the acetylene needle valve until acety
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lene is coming out fast enough to cause a gap of about y16 to % inch between the tip and the flame. Then open the oxygen needle valve slowly. The flame will change gradually from yellow to blue and show the three distinct parts of the excess acetylene flame. The intermediate cone will become smaller and smaller, and the instant it disappears completely, the neutral flame is formed. As the oxygen needle valve is opened still more (or the acetylene needle valve is partially closed), the oxidizing flame appears. The length the inner cone is decreased, compared to the inner cone of the neutral flame, indicates the amount of excess oxygen in the flame. Because of the difficulty of distinguishing exactly between oxidizing and neutral flames, an adjustment to neutral is always made from the excess acetylene flame.
23.	Joint design.—Proper joint design for welding sheet, plate, or pipe is of particular importance because even the most skillful welding may fail to produce a strong joint if it is not properly designed.
a.	Sheet metal.—Metal up to % inch in thickness is considered sheet metal.
(1)	The butt weld (fig. 43) is the simplest joint in sheet metal. It is used between two pieces lying in the same plane and for joints in rounded sections, such as the lengthwise seam in a cylindrical tank.
Figure 43.—Butt weld for sheet metal.
(2)	The corner weld (fig. 44) is widely used in sheet metal work. It is very similar to the butt weld. The parts to be joined are usually held in correct alinement by jigs or fixtures during welding.
Figure 44.—Corner weld.
317254°—41----4
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(3)	The flange weld (fig. 45) is used mostly in sheet metal lighter than 20-gage (0.0375 inch). The edges are prepared for welding by turning up a flange extending above the upper surface of the sheet a distance equal to the thickness of the sheet. Flange welds are usually made by melting down the flange without adding welding
Figure 45.—Flange weld for thin sheet metal.
rod. When this weld is used the operator must be careful to secure penetration to the bottom of the point.
(4)	The single lap weld (fig. 46) made along the edge of overlapping sheets is not recommended because it has little resistance to bending.
Figure 46.—Lap weld ; second weld necessary to form double lap weld is shown by dotted line.
(5)	The double lap weld (indicated by the dotted line in the figure) has more strength, but it requires nearly twice as much welding as the simpler and more satisfactory butt weld. Lap welds should be avoided whenever possible.
Figure 47.—Square butt weld.
b.	Plate.— (1) The square butt weld (fig. 47) is used for plate %6 inch or less in thickness. The edges of the pieces to be joined are squared accurately and spaced about % inch apart. The welder should fuse the metal completely through to the bottom of the plate. All butt welds are known as “open” when there is a space left between the pieces to be joined and “closed” when the pieces are pressed tightly together.
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Figure 48.—Single-V butt weld.
(2)	The single-V butt weld (fig. 48) is used for plate over %6 inch and up to % inch in thickness. Both edges forming the joint are beveled, usually to 45°, to form a 90° V. This beveling can be done either by grinding, by a milling machine, or by use of a cutting torch. If done with a cutting torch, the oxide should be carefully removed from the bevel by chipping or grinding, before welding. Beveling in plate or pipe is never carried clear across the section. About % 6 inch of the original edge is left for lining up the edges as shown in figures 48 and 49. Weld penetration and reinforcement should be as shown in figure 48. By reinforcement is meant the part of the weld that extends beyond the cross section of the plate.
Figure 49.—Double-V butt weld.
(3)	Plate thicker than % inch should be beveled from both sides to form a double V, whenever possible, as shown in figure 49.
(4)	Outside corner welds should be made the same as for sheet metal as shown in figure 44. For cylindrical tanks it is preferable to dish the heads and use butt welds. Sometimes inside corner welds are necessary. In such cases the edges of the plate should be beveled to aid the welder in obtaining full penetration to the bottom of the weld.
(5)	Fillet welds (fig. 50) should be avoided whenever possible in plate work. They are used to join flanges or sleeves to the surfaces
Figure 50.—Fillet weld.
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of pipes or tanks. For pressure vessels, codes governing the construction of such equipment should be followed.
c. Pipe.— (1) Pipe joints are essentially the same as plate joints. For Hue joints in pipe, that is, joints in straight runs of pipe, the square butt weld (fig. 47) is recommended for pipe having a wall less than %6 inch thick; the single-V butt weld (fig. 48) for pipe %6 inch thick and over. The ends should be beveled 45° to form a 90° V.
(2) In the case of a branch connection, where one pipe fits into an opening in another pipe, the opening should be beveled to form a proper V at all points. The beveling will not be uniform but will vary continuously.

OUTSIDE CORNER WELDS ON PIPE TURNS
\	\ n'\ a>./\ > >«>• ■'
INSIDE CORNER WELDS ON PIPE TURNS
Figure 51.—Outside and inside corner welds in pipe turns.
(3) In welded pipe turns, the weld varies from an outside corner weld on the outside of the turn to an inside corner weld at the inside of the turn. Here again, beveling is not uniform but varies continuously. Figure 51 shows weld sections at the outside and inside of pipe turns of various degrees.
cl. Castings.—In repair welding of castings, the edges of the break are usually beveled to form a 90° V. Where the metal is very thick and welding can be done from both sides, a double-V weld is preferable. Castings must often be beveled with a cold chisel.
24. Welding methods.—a. General.— (1) Right-handed welders usually hold the torch in the right hand and the welding rod in the left, while left-handed welders usually hold the torch in the left hand and the welding rod in the right. Some prefer to weld from right
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to left, while others prefer to weld from left to right. However, the various methods are based upon the same general procedures.
(a) A pool or puddle of molten metal should be made to advance even along the seam as the weld is made.
(&) The end of the welding rod should melt by placing it in the puddle; it should not be held over the puddle and allowed to drip into it.
([BREAK; [	EXPAND
----	। ( ^tXl/32IN. /q j 1heatc\
lliiiiiii ।
I”----- HEAT'""^	I
BREAKS
Figure 54.—Methods of expanding castings prior to welding.
described in paragraph 24. A neutral flame is generally used. An oxidizing flame cannot be used. A reducing flame is sometimes used for tool steel. Tool steel is not very satisfactorily welded, however; more often it is bronze-welded or brazed.
(2) Goggles are worn during all welding operations to protect the welder’s eyes from flying hot particles and from the intense light. When galvanized material is being welded, inhaling the resulting zinc-oxide fumes may cause nausea. Therefore, always weld this material in a well-ventilated location when possible. The nausea may be overcome by drinking milk.
b. Welding cast iron.—In preparing a gray-iron casting for welding, it should first be cleaned of all grease, oil, sand, scale, rust, paint, or other foreign matter. Then bevels are chipped, ground, or cut to form 90° V’s. The casting is then preheated either locally or in its entirety. Cast iron welding rod is used and ripple welding is most commonly employed. Puddling with the cast iron rod works out the oxides and foreign matter and brings them to the surface of the puddle. Blow holes can be prevented by holding the envelope flame over the weld puddle, thus keeping the oxygen of the air from coming in contact with the molten metal. Whenever possible, welds should be completed without stopping, even if welders have to relieve each other. Cast iron melts at a temperature below that of iron oxides which makes the use of a good flux essential. Cast iron will run freely without warning if heated sufficiently. For this reason skill
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is required to control the molten metal at the edge of a casting, in building up a lug, and in making a vertical weld. Iron castings should be carefully reheated and annealed after welding by leaving them in the temporary furnace for several hours or overnight, or by burying them in warm, dry sand, spent lime, or crumbled asbestos paper until they become cool.
27.	Bronze welding or brazing.—a. This is not a true fusion welding process although it has extensive and very useful applications. It consists of joining metals with a higher melting point than bronze, such as cast iron, steel, nickel, and copper, by a bronze bonding material of considerably lower melting point. Molten brass or bronze will flow onto the properly heated and fluxed surface of higher melting point metals and give a bond of excellent strength. The bronze is supplied in the form of welding rod. Bronze welding is the only satisfactory process for joining malleable iron and high-carbon or tool steels, whose valuable properties are either destroyed or impaired by fusion. Bronze welding also provides a convenient method of joining dissimilar metals, such as malleable iron or copper, to iron or steel. Bronze welding cannot be used where the part is to be heated subsequently to a temperature higher than the melting point of bronze. Also, bronze loses strength rapidly at temperatures above 500° F. Bronze welding is widely used for building up wearing surfaces, particularly on cast iron, steel, and manganese bronze. Holes and bushings that have become worn can be repaired quickly by filling the hole and redrilling.
b.	For bronze welding it is important that the base metal be clean and free from foreign matter so the bronze can “wet” the base metal. If the edges to be joined are % inch or less in thickness, surface chipping or grinding to bright metal will suffice. Thicker metal should be beveled to a 90° V. The edges of the metal for about % inch back of the bevel should be cleaned off. Even after such cleaning, many metals retain a superficial coating of oxide that will prevent the bronze from coming into intimate contact with the base metal. Therefore, it is necessary to remove this coating by means of a suitable flux.
c.	Only enough preheating to take the chill off the parts to be welded, that is to a black heat, is required for bronze welding.
d.	A slightly oxidizing flame is recommended for bronze welding. A spot on the cleaned surface of the base metal about 2 inches in diameter is heated with a circular motion of the torch to a red heat. When the metal just begins to glow, heat the end of the welding rod in the flame and dip it into brazing flux. Then touch the end of the fluxed rod on the heated spot on the metal. If the metal is the proper
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temperature, the bronze will flow in a thin layer and spread out over the heated area. If the metal is too hot the bronze will boil and form into drops which roll off as fast as the rod is melted. The tinning and building up of the bronze are done in one continuous operation, the tinning action taking place just ahead of the puddle of weld metal. The inner cone of the flame should be kept y8 to 14 inch from the metal. Usually the flame is pointed ahead of the completed weld at an angle of about 45°, with the puddle under and slightly behind the flame. In heavy sections the weld is made in layers. When the bronze weld is completed, it should be allowed to cool slowly to room temperature, which can be done conveniently by covering it with asbestos paper. No stress should be placed upon a bronze-welded joint until it is completely cool.
e.	Bronze welding rod contains zinc which gives off fumes during welding. The same precautions regarding ventilation etc., recommended for welding galvanized iron in paragraph 26 should be observed.
28.	Welding aluminum.—a. As the behavior of aluminum under the welding flame is quite different from that of steel, a different welding technique is required. Pure aluminum has a relatively low melting point (1,215° F.) and it conducts heat more than four times as fast as steel. Because of this high heat conductivity it is advisable to use a welding tip one size larger than that used for steel of the same thickness. Because of its light color and low melting point, aluminum does not give any indication by change of color that the metal is approaching the welding heat. When the melting point is reached, the metal collapses suddenly. By observing the behavior of aluminum as it melts under the torch flame, the welder will learn how to control the rate of fusion.
5. The surface of a molten puddle of aluminum oxidizes rapidly, forming an oxide that has a higher melting point than aluminum. For this reason it is customary to use a suitable flux which combines chemically with this oxide to form a fusible slag that rises to the surface of the puddle where it is easily removed. Cast aluminum can be welded successfully without flux by the use of a pick and paddle. The pick, which is simply a piece of steel wire pointed at the end and bent in the form of a hook, is used to pick out the oxide from the weld. The paddle, which is a piece of steel wire flattened at the end and bent at an angle, is used for smoothing the weld. The pick and paddle method is much slower than welding with flux and is not recommended if flux is available.
c.	The flange joint can be used for 16-gage and lighter sheet. The upturned edges of the flanges should be painted with flux before
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welding. Aluminum sheet up to 17-gage can also be welded with the square butt joint. Before welding, paint flux on the edges of the sheet. For aluminum from 17- to 7-gage, it is recommended that the edges of the joint be notched through their entire thickness, as shown in figure 55. The notches are best made %6 inch deep and %6 inch apart with a sharp cold chisel. These notches help the welder obtain full penetration because flux works down to the bottom of the sheet. There is less chance of melting holes through the sheet and less distortion of the work. For heavier stock, notched single-V and double-V joints are used (fig. 56).
d.	The selection of welding rod for welding aluminum depends upon the composition of the base metal. Manufacturers’ recommendations should be followed. For welding commercially pure aluminum, wire or strips cut from the base metal may be used.
Figure 55.—Notched square butt joint for aluminum.
e.	The torch flame should be neutral or have a very slight excess of acetylene. The flame should be soft and of low velocity. Hold the tip at an angle of about 30° to the work to avoid blowing holes through the heated metal. The end of the inner cone of the flame should be about % inch away from the work, and the flame directed so it heats both edges of the joint evenly and also the end of the welding rod. The edges should begin to melt before the welding rod is added. It is necessary to direct a considerable portion of the flame on the rod itself as the molten puddle will not melt the rod as in steel welding. Metal from the welding rod should be fused thoroughly with the base metal as it is added. Inasmuch as fusion takes place rapidly, the weld progresses quickly along the seam.
/. Even in the case of sheet aluminum it is good practice to warm up the entire sheet with the blowpipe flame before welding. It is customary to preheat aluminum plate % inch or more in thickness
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before welding and is particularly necessary when it is to be welded from both sides. This can be done with a second oxyacetylene torch or by city gas or kerosene torch. Aluminum castings require preheating prior to welding. If a stick drawn across the metal as a test chars and leaves a black mark, the metal is hot enough, or if
80 TO 90°
l/IGTOI/SINCH 7
1/16 TO l/SINchV/
Figure 56.—Notched single- and double-V joints for aluminum.
sawdust thrown on the work chars and becomes black the casting is ready for welding. This is about the same temperature that will melt half-and-half spool solder when it is touched to the work. After welding, castings should be covered and cooled slowly.
g. After aluminum is welded, the flux should be carefully removed to prevent subsequent corrosion. This is sometimes done with a
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steam jet. Washing in a hot 2-percent nitric acid solution or a warm 10-percent sulphuric acid solution, followed by rinsing, is sometimes done.
29. Welding copper.—a. Copper is a red metal which is difficult to distinguish from some of the bronzes. If the metal is melted under the blowpipe, using a neutral flame, it can usually be distinguished readily. If it gives off white smoke, or contains enough volatile metal to leave a ring of whitish or yellowish crust around the edges of a cold frozen puddle, the metal is bronze.
Z>. Commercially pure (electrolytic) copper contains a small amount of oxide and is not suited to welding because a weak zone invariably develops in the base metal adjacent to the weld. Deoxidized copper is entirely satisfactory for fusion welding. It is made by adding a small amount of silicon (manganese, phosphorus, or boron have also been used) which removes the last trace of oxygen from the copper.
c.	The weldability of copper can be tested by heating a piece of it to a bright red, just below the melting point, and then hammering it vigorously on an anvil. If it breaks, it contains oxide and is unsuitable for fusion welding. It can be joined satisfactorily by bronze welding, although deoxidized copper is preferable even for that.
d.	For fusion welds in copper, completely deoxidized welding rod, as well as base metal, must be used. A welding head one or two sizes larger than that required for steel of the same thickness is used, since copper conducts heat away much faster than steel. A neutral flame is necessary; no flux is required. The same joint designs as described for steel are used and the same welding technique employed, except that the molten puddle is somewhat more “runny.” Whenever possible, cover the work with asbestos paper to reduce heat losses. Large sections should always be preheated to a dull red before welding, and the same practice is desirable even for small parts.
e.	Copper pipe can be fusion welded, but it is usually either bronze-welded or fabricated with sweat solder fittings.
30. Welding brass and bronze.—a. Brass is essentially an alloy of copper and zinc, and bronze is essentially an alloy of copper and tin. However, other alloying elements such as lead, tin, manganese, and iron often appear in brass; and zinc, lead, and nickel are often found in bronze.
b. In fusion welding either brasses or bronzes, the more volatile metals, zinc, tin, and lead, start to boil out before the base metal is red hot. This tendency can be overcome by making the flame just sufficiently oxidizing to stop the boiling without forming too heavy
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a coating of oxide on the puddle. Flux is used freely, usually being mixed to a paste with water and painted on the welding rod and along the scarf of the base metal. Welding rods of different composition are provided by the manufacturers, or strips cut from the base metal may be used. Forehand welding is recommended. Castings should be preheated.
c. Bronze welding is widely used to produce satisfactory joints for general industrial purposes. Yellow brass has a melting point so near that of the welding rod that the welding operation is a cross between bronze welding and fusion welding. This applies to the welding of brass pipe. The important factor is to melt the wall of the V just sufficiently to insure positive sweating of the base metal in advance of the puddle.
31. Oxyacetylene cutting.—a. General.— (1) The procedure of torch cutting is based on the fact that steel will burn in an atmosphere of pure oxygen after it is brought up to the kindling temperature, just as a piece of paper will burn in air after being brought up to the kindling temperature by means of a match. The main difference is that in the case of the paper, the products of combustion, carbon dioxide and water vapor, are gaseous and pass off into the air, while in the case of the steel, the product of combustion is iron oxide, which is a solid at ordinary temperatures. Its melting point is, however, somewhat below the melting point of steel. The heat generated by the burning iron is sufficient to melt the iron oxide so that it runs off as molten slag, exposing more iron to the oxygen jet. The jet can thus be moved along to produce a clean cut.
(2)	Another way of looking at it is that burning iron is extremely rapid-rusting, the rust being molten.
(3)	Theoretically the heat generated by the burning iron would be sufficient to heat adjacent iron red hot, so that once started, the cut could be continued indefinitely with oxygen only. Practically, the smoothness of this operation is disturbed by excessive radiation at the surface, and by pieces of dirt, paint, or scale on the metal. Accordingly, the preheating flames of the cutting torch remain burning throughout the cutting operation.
(4)	Although it resembles the welding torch in some respects, the cutting torch (fig. 57) is a different tool, its function being to sever rather than to unite. It has an additional tube for high pressure oxygen, and the cutting tip or nozzle is made with a number of holes. Through the center hole passes a jet of pure oxygen under pressure, which can be directed against the steel to be cut. Mixed
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*
fZb-—-----------------f-tg
l-LW.W'"
, REAR TUBE
W M	l-- -l	x*,^™*"*	torch handle
U 75’HEAD	W/X ACETYLENE
HIS c u	^WWNEEOUE VALVE
Uff	STRALCHT.HEAD	tg~ ASSEMBLY
gff	torch cross section through handle
SO*HEAD	W PREHEATING	CUTTING	OXYGEN	OXYGEN VALVE HANDLE
L	OXYGEN TUBE OXYGEN TUBE '	VALVE SPRING fjgft AND SEAT .	HOSE
. w^^M>>^eo«ww>WK^. Cutting steel, wrought iron, and cast steel.— (1) Attach the proper welding tip for the thickness of metal to be cut to the cutting torch and adjust the oxygen and acetylene pressures according to the manufacturer’s instructions. The preheating flames are first adjusted to neutral. To start cutting, hold the torch perpendicular to the work with the inner cones of the preheating flame about Vig inch above the end of the line to be cut. The torch is held stationary in this position until this spot has been raised to bright reel heat; then open the cutting oxygen valve slowly and move the torch slowly but steadily over the line to be cut. If the cut has started properly, a shower of sparks will fall from the opposite side of the work, indicating that the cut is penetrating clear through. The
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movement should be just fast enough so the cut continues to penetrate the work completely. If cutting has been properly done the result will be a clean, narrow cut comparable to one made by hot sawing. When cutting billets or round bars, time and gas are saved if a small point of steel is raised with a chisel where the cut is to start. This small raised portion will heat quickly, and cutting may commence immediately as the metal becomes a fuel once the cutting starts.
(2) Steels with a carbon content higher than 0.35 percent and most alloy steels should be preheated to 500° or 600° F. before cutting. This will avoid the surface checking that occurs when such steels are cut at ordinary temperatures. These steels may also require annealing or heat treatment after cutting. Manufacturers of cutting torches furnish definite procedure instructions for this work.
CUTTING NOZZLE
\______^Tj75°-9o\
%	L \
\	CAST IRON
MOLTEN
 ARC
>' STREAM /# STREAM
\	\ /J / ARC
/*^**W^	’	'	\	/& 'akx/x	FLAME
dSgr1-—— > lf/tS& /
* WORK
L . , „.METAL -
Figure 70.—Diagram of carbon welding arc.
obvious. Except for the different method of applying the additional metal, which flows through the arc stream, the component parts of the arc are similar to those of the carbon arc (fig. 71).
(2) It is generally believed that most of the metal transferred from the electrode to the work is in the form of small molten globules carried across in the arc stream. This is particularly true with nonferrous metals, which cannot usually be welded overhead because the globules are larger than they are in steel welding and must be helped across the arc by gravity. With steel electrodes, however, it
IWk-BARE
I® £LECTROOE
t 'will	ARC
ARC \ W ARG FLAME
ARG STREAM I W STREAM
WORK	GORE\ \ t •	/	/	DEPOSITED
METAL	ARG \ \ K /	*	METAL
I	FLAME'\jk	vW
PENETRATION	''O \ A, ,	. r
. .... .... ....
WvuUUT < : J •	<	■ • U	Uv
Figure 71.-—Diagram of bare-metal welding arc.
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is believed that at least a part of the electrode material is vaporized by the intense heat of the arc so that it expands; the resulting pressure forces it across to the lower pressure area of the work where the lower temperature causes it to condense. The theories of cohesion and capillary attraction are also involved. It is practical to weld overhead or vertically with steel electrodes.
d. Shielded arc.— (1) The shielded arc, whose component parts are illustrated in figure 72, is also a metallic arc. The electrode itself is usually the same type as the bare electrode but is heavily coated by wrapping, extruding, or dipping. Wrapped or extruded coatings have found favor in most applications because of their greater uni-
HEAVY IBj|!| COATING KO
MILD STEEL i t //■ I ROD
DIRECTION OF WELO	ARG
Mijil fcs/ GASEOUS
WORK r	r	8EAD
METAL\ Jp ............—.........
ARC CRATER PENETRATION
Figure 72.—Diagram of shielded-metal welding arc.
formity. In either case the coating is of materials that, when subjected to the heat of the arc, form a gaseous shield around the arc as indicated in the illustration. The coating melts slower than the metal of the electrode and therefore extends slightly beyond the end of it, which has a directing and stabilizing effect on the arc.
(2) The gases in the shield do not affect the molten weld metals themselves while forming a dense wall that protects the molten metal from the oxygen and nitrogen in the atmosphere. Part of the electrode coating material floats to the top of the welding bead to form a slag coating which serves the same purpose after the metal is deposited as the gaseous shield does while the metal is passing across the arc. Molten metal is extremely susceptible to the action of oxy
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gen and nitrogen. Oxidation means corrosion, and nitrides (compounds of nitrogen) have a weakening effect upon the structure of metal. The metal deposited with a shielded arc is therefore of better quality than that deposited with an unshielded arc, and due to the greater heat developed in a shielded arc the metal is deposited more rapidly, as has been pointed out heretofore. Also, the shielded arc is more stable and easier to maintain.
(3) After the weld has cooled, the slag coating is easily removed by chipping and wire brushing. It is very important that it be removed from every bead, before depositing another on top of it, to avoid trapping slag in the weld.
43.	Arc polarity.—a. The effect of polarity is something that must be taken into consideration when using the welding arc. It is believed that approximately two-thirds of the heat is developed on the positive side of the arc. Since the work metal usually represents the greater mass, the polarity of the welding arc is said to be “straight” when the positive cable is grounded to the work and the negative cable is connected to the electrode. When this polarity is used, the arc is a great deal more stable and effective with carbon and bare metallic electrodes.
b.	When the connections are macle so that the work metal is negative and the electrode positive, the polarity is said to be “reverse.” Most coated electrodes in use today give better results when used with reverse polarity. One reason is that with maximum heat on the electrode side of the arc the special coating on the electrode is burned off at a speed more consistent with the melting rate of the electrode metal. Some coated electrodes, however, are intended for use with straight polarity and when any certain make of coated electrode is used the supplier’s recommendation as to the correct polarity should be followed.
c.	Reverse-polarity electrodes have given best results in metallic arc welding of cast iron, in which case it is desirable to keep the heat out of the casting as much as possible. The most successful electrodes for cast iron are especially coated, although not so heavily as the shielded-arc type of electrodes for welding mild steel. Nonferrous electrodes, such as copper, bronze, aluminum, nickel, and monel metal, either coated or uncoated, are used with reverse polarity when welding with the metallic arc.
d.	The carbon arc should always be used with straight polarity no matter what type of filler rod is used or on what kind of metal it is deposited. A certain amount of the carbon electrode is carried across the arc to the pool of molten work metal, and it is usually desirable to hold this transfer to a minimum. Observation of a direct-current
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carbon-arc lamp shows that the positive carbon burns up far more rapidly than the negative carbon and that the latter actually increases in size, indicating a considerable transfer of carbon from positive to negative. With the welding carbon on the negative side, therefore, it will be consumed less rapidly and less carbon will be carried into the weld. Further, experience shows that the carbon arc is very unstable when reverse polarity is used. Straight and reverse polarity apply only to d. c. machines, as explained in paragraph 35&.
44.	Magnetic flare.—a. The arc is a conductor of electricity and as part of the circuit through which current flows from the generator through the welding cable, arc, work metal, and ground cable back to the generator, it is subject to magnetic influences. Magnetic flare, usually called “arc blow,” is more pronounced with direct current than with alternating current, which is an important reason for the increasing use of alternating current. Where welding must be done in corners on heavy plates, magnetic flare presents a serious problem, and alternating current, if available, is generally used for such work.
b. In average work there are ways of reducing the annoyance of magnetic flare with the direct-current arc. Often this can be accomplished by changing the location of the ground connection on the work metal. In other cases, wrapping a few turns of the ground cable around the work may give the desired results. Sometimes a small electric magnet, connected to the shop power lines and located near the point at which welding is being done, will give a neutralizing effect.
45.	Arc length.—a. Experience has shown that, with bare electrodes, better welds may be expected from a short arc, although too short an arc may result in undesirable porosity in the weld. On the other hand, a long arc means more exposure of the molten weld metal to the harmful effects of oxygen and nitrogen in the air. A short arc concentrates the heat on the work, while a long arc allows more heat to escape into the air and is more inclined to “blow.” A long arc is more likely to go out frequently and tends to deposit the weld metal on the work without proper penetration and fusion. In general, the length of the arc with a bare electrode should not exceed the diameter of the electrode.
b. With coated electrodes a longer arc is used. The resulting shielded arc protects the weld metal from the oxygen and nitrogen in the air, and its greater heat insures better penetration and fusion. With some types of coated electrodes the metal melts up somewThat inside the coating as the latter burns off, so that the true length of the arc may not be visible.
317254°—41---7
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46.	Arc voltage.—a. The voltage across the arc is determined by the length of the arc; the shorter the arc, the lower the voltage and vice versa. This is due to the peculiar characteristics of the arc that cause its resistance to decrease as current passing through it increases. The open-circuit voltage of a welding machine is measured across the welding terminals at no-load. The arc is more stable and less susceptible to the effects of air currents, magnetic conditions, or vapors rising from' the work when the open-circuit voltage is at least double the arc voltage.
b. If the open-circuit voltage is too low it is difficult to start the arc, particularly when low current values are being used as when welding light sheet metal. For practical purposes the open-circuit voltage should be not less than 50 or 60 volts and should be adjustable to the higher values required for certain welding conditions. The arc voltage is not accurately registered by the voltmeter on a welding machine because it shows voltage across the welding terminals and does not take into consideration the voltage drop in the welding cables, etc. The voltage across an arc of proper length with bare electrodes will be from 14 to 25 volts, depending upon the diameter of the electrode used. With coated electrodes, the voltage will be somewhat higher due to the longer arc used, as heretofore discussed, this being the reason for the development of welding machines rated at 40 instead of 25 volts as formerly.
47.	Welding current.—a. The amount of welding current to be used depends upon so many variables that it is impossible to tabulate exact values. The operator must learn by practice, and experience the proper values for various welding jobs. In many large plants
Table TV.—Approximate range of current values for metallic electrodes
Thickness of metal to be welded	Diameter of electrode (inch)	Bare electrodes		Coated electrodes	
		Voltage across arc	Welding current (amperes)	Voltage across arc	Welding current (amperes)
22-18 gauge		Y16	15-17	25-30	16-18	30-35
18-16 gauge		%2	15-17	35-80	16-18	40-90
Yi6-% inch		%	17-20	90-135	20-22	90-140
inch		%2	18-20	115-175	20-25	115-220
Ya, inch and up		%6	18-25	150-260	28-30	150-275
% inch and up		%	18-25	200-300	30-32	200-325
% inch and up		■%6	18-25	'250-325	30-32	250-400
Yi inch and up		%	20-28	300-400	32-36	300-500
Note.—Bare electrodes larger than % inch are very rarely used.
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THE BLACKSMITH AND THE WELDER
where arc welding is used extensively, welding engineers are in charge of procedure. They make exhaustive studies of the work to be done and issue special instructions as to the current values to be used by the operators for each welding operation, as well as the type and size of electrodes, etc.
b. While greater speed may be attained by using higher currents with a given size of electrode, care should be taken not to use currents excessive enough to injure the weld metal. The approximate values in table IV are merely suggestions. Adjustments must be made according to the kind of material welded, type of electrode used, size and shape of the work, type of joint, position in which the welding is to be done, speed required on the job, skill of the operator, and equipment available.
48- Design of joints.—Design of joints for arc welding is about the same as for gas welding described in paragraph 23>. However, U-joints and J-joints are advocated by some, authorities for arc welding as a means of economizing electrodes.
a.	The single-U butt joint (fig. 73) is suitable for all usual load conditions and is used for work of the highest quality. It replaces the single- or double-V joint for joining plates t° % Meh* thick, although it is also used on heavier plate. For plates of this thickness, single- or double-V joints would require a considerable amount of weld metal. Machining the plate to a single U reduces the amount of weld metal needed but increases machining costs. The joint is welded from one side except for a single bead which is put in last on the side opposite the U.
b.	The clouble-U butt joint (fig. 74) is suitable for all load conditions and is used for welding heavy plates (% inch and thicker) where the welding can be done from both sides. This joint requires
Figure 73.—Open single-U butt joint.
Figure 74.—Open double-U butt joint.
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QUARTERMASTER CORPS
less weld metal than the single U but costs more to machine. Choice between double U and double V should be made by comparing the machining and welding costs of the two, then selecting the joint which is cheaper.
c.	The single-J T-joint (fig. 75) is suitable for severe loads, and while it may be used for usual size plates it is more often applied to 1-inch and heavier plates. The welding is done from one side only. However, it is advisable to put in a final finish bead on the side opposite the J. Although somewhat more costly to machine than the single V, the single-J T-joint is lower in electrode cost.
Figure 75.—Single-J T-joint.
Figure 76.—Double-J T-joint.
cl. The double-J T-joint (fig. 7G) is suitable for exceedingly severe loads of all types in heavy plate (iy2 inches and heavier) where welding can be done from both sides. Although the machining costs for the double-J T-joints are higher than for other types of T-joints, less electrode is required, and consequently the cost per joint is reduced.
e. Examples of arc welds and their locations are shown in figure 77.
49.	Expansion and contraction.—The theories of expansion and contraction discussed in paragraph 25 are the same for arc welding as for gas welding except that the former usually proceeds faster, and the base metal does not heat up as much; that is, the heat is localized
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nearer the weld. Therefore, somewhat different allowances are made in some cases.
50.	Preparation of work for welding.—a. In addition to beveling, if used, the work should be clean. Scale, rust, grease, oil, paint, and any other foreign matter should be removed by a chisel, wire brush, or rag. Otherwise, it will be difficult to strike and maintain a welding arc and good results cannot be expected.
b. When cleanliness of the finished weld is important for the sake of appearance, it is common practice to spray or paint the joint and adjacent surfaces before welding with an especially prepared coating material to prevent weld spatter adhering. This does not make the weld metal brittle or porous or cause injurious fumes and corrosion.
HORIZONTAL VERTICAL..	______
FLAT^	'
EDGE WELD.	.	' FtAT
IF™
fillet	f r
/ FLAT flat	\	:	At.
... ' "',
.......	-----;'OVERHt«>
SUTT WELD — LAP WELD ' OVERHEAD PLUG WELD	DOUBLE DUTT WELD
Figure 77.—Examples of arc welds and their locations.
It withstands preheating temperatures and does not have to be removed afterwards.
51. Striking the arc.—a. Precaution.—No matter where you are working—in the school, in the shop, or outdoors—never strike an arc, even for an instant, unless your eyes and the eyes of everyone in the vicinity are protected from the rays. While no permanent injury has been known to result from exposure to the rays of an arc, such exposure may cause extreme pain if eyes or skin are exposed frequently, even for very short periods of time. Remedies have been prescribed in paragraph 41c in case this precaution is neglected.
b. Procedure.—(1) Place the electrode in the holder. Strike an arc between the lower end of the electrode and the work, using one of the two methods shown in figure 78. The method shown at the left is by the straight up and down motion and must be executed very rapidly
89
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51	QUARTERMASTER CORPS
to prevent the electrode sticking to the plate. Some operators find it easier to employ the scratching method shown at the right. In this, the electrode tip is brought quickly along the dotted line from point A to point B where instantaneous contact is made with the plate and the electrode withdrawn more slowly to point C, where it is held.
(2) In either case the electrode should be withdrawn promptly as soon as it strikes the plate until the lower end is about % inch above the surface of the plate and the arc gives off a continuous crackling or “frying” sound. Beginners should practice striking an arc until they can consistently strike and hold it for 3 or 4 seconds without sticking the electrode to the plate or breaking the arc. Hold the electrode perpendicular to the plate while practicing.
c. Freeing the electrode.—When the electrode sticks to the plate it should be broken loose very quickly with a rapid twisting or bend-
STMT	rti (1
■-♦—START	\ ■
\ %START
FINISH II	|
—*4	■ FINISH	i A
CONTACT	■*-----
I ^WITH	■
PLATE	_ ''4* „
' jK •	C X 8
.......................„...............
......j .......................:	...A---. ■•-/'J
Figure 78.—Two methods of striking the arc.
ing motion, otherwise it will heat up very rapidly. In this case the electrode holder must be disengaged and the electrode broken loose with a hammer or chisel after it cools. Practice for accuracy in striking the arc at a predetermined point may be obtained by covering one side of a plate with crosses made with a piece of soapstone as shown in figure 79. Hold the shield away from your face so you can see to bring the tip of the electrode to a point directly above the center of one of the crosses, to a point in the air about % inch from the surface of the plate. Then place the shield in front of your face and try to strike the arc in the center of the cross at which you have aimed. Practice this exercise, using both sides of the plate, until you can strike the arc accurately at the center of any cross selected. Move the shield away in order to aim at the selected cross, but always replace the shield in front of your face and eyes before allowing the electrode to touch the plate. You should be able to strike the arc
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in the center of at least 10 consecutive crosses and hold it there for 3 or 4 seconds without sticking or breaking the arc, before you go on to the next exercise.
52. Laying short beads.—a. Preparation.— (1) The student should start with ^-inch mild-steel plate laid flat on the bench, a %2-inch bare mild-steel electrode, a current of about 150 amperes, and
Figure 79,—Practice-for-accuracy chart.
straight polarity. Before proceeding, it is important to know the difference between good and bad beads so the student can practice the right way and learn to avoid the wrong ways. Depositing a length of weld metal is generally called “laying a bead” and a finished weld may consist of one or more beads. A bead may be laid alongside or on top of others in order to produce a completely welded joint in heavy metal or a built-up pad of the desired thickness.
NO UNOERCUTTING,,	.S yntFORM X NO OVERLAP
.....................—GROSS SECTION	•——•--------—>
I 8000 PENETRATION ,MM	M ™	« MM ■*&."*> M. MM, MM MM	«■ MM MM M* M* M ,
Figure 80.—Cross section of good bead.
(2)	A good bead must penetrate the work metal to a reasonable depth to insure complete fusion, which can be accomplished only when deposited metal and work metal are melted together. The penetration of the weld metal as indicated by the depth of the crater in the weld is generally a good test of fusion. The bead should also be uniform in cross section without overlapping or undercutting the work metal, as shown in figure 80. Only metal that is properly fused with
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QUARTERMASTER CORPS
the work metal is worth depositing from the electrode. Overlapping-metal is wasted and undercutting weakens the weld.
(3)	Good beads result from using good quality electrodes of the right type for the job, on work metal that has been properly cleaned and prepared, with the proper current value, the correct length of arc, and by moving the electrode at the correct speed along the line of
Figure 81.	—Examples of good and bad beads.
weld. Feed it down at a rate which will provide the correct amount of additional metal in the joint with sufficient penetration to insure ample and uniform fusion. Study the photographs of actual beads in figure 81.
(a)	Bead No. 1 shows the results when insufficient current is used. Note the excessive height of deposited metal with excess metal overlapping along the edges of the bead, and the shallow crater which indicates insufficient penetration.
92
siftOI Kim Spa
•-•IB Kao s
Hk«
I	2	3
I- Mr B
i w	Hr Iwi
•S ! a# .	m
4	5	6
TM 10-440
THE BLACKSMITH AND THE WELDER	52
(6)	Bead No. 2 is the result of holding too long an arc. Note the poor penetration and irregularity of form of the bead. Holding too short an arc may cause some porosity but too long an arc is worse, particularly when working with bare electrodes.
(c)	Bead No. 3 is the effect produced when using too high current. Note the excessive spattering which wastes electrodes and requires extra cleaning. Also note the evidence of weakening undercutting along the edges of the bead. Quality should not be sacrificed for speed.
(-■'A
gA..A...-A AlA.C 1A---AL.- ’ AJ
m___-_- ___ _______-
90’.- ’ --.90’
/	\	............... ~Lg.L_
so8. ...so-
f	«	v-;-'wWtw' e4 t H i
■
““““
Figure 82.	—Method of practicing short beads.
electrode too long in one spot. Also note how the deposited metal overlaps along the edges of the bead.
(/) Bead No. 6 is an example of a good welding head. It is smooth and regular in form. The edges are sharply defined without overlapping or undercutting along the edges. Spattering is reduced to the minimum. The deep crater indicates that the weld metal has penetrated thoroughly into the plate to insure good fusion with the work metal.
(4)	Study these examples until you thoroughly understand the difference between good and bad beads and the reasons for unsatisfactory performance. Then practice until you can consistently match the bead illustrated in No. 6'.
Z>. Procedure.— (1) Holding the electrode perpendicular to the work, as indicated in figure 82, lay a dozen beads inches long, about % inch apart, working from left to right, as indicated at the left in (1), figure 82. Then lay another dozen similar beads, working from right
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to left as indicated at the right in (1), figure 82. The electrode must be fed down into the crater to maintain a short arc at all times, and progress along the line of weld must be at the correct rate of speed to result in a bead of proper characteristics.
(2)	Wire-brush the beads and compare them with the beads in figure 81 to determine what you may be doing incorrectly. Inspect the craters at the ends of all beads. In this exercise the crater should be about % 6 inch in diameter and % 6 inch deep in the work metal. Saw through some of the beads and compare the cross sections with the diagram in figure 80. Chip off some of the beads with hammer and chisel to determine whether or not penetration is uniform for their full length. When you have discovered your weaknesses, practice this exercise over and over until you can consistently lay these short beads perfectly in either direction. In practical work you will not always be able to choose the direction in which you work, so it is important to be able to lay a bead in any direction.
(3)	On another plate repeat the same procedure as in (1) above but lay the beads in the two directions indicated at left and right ends of (2), figure 82. First, move the electrode away from you and then toward you. Inspect as before and practice until you are proficient in laying short beads of correct characteristics in these two directions.
(4)	On another plate lay beads iy2 inches long, from left to right and from right to left alternately, as indicated at the left end of (3), figure 82. In this exercise it is important to break the arc at the end of each bead and wire-brush that bead thoroughly before laying the next one in the opposite direction, immediately alongside the previous one. Continue this exercise until you have both sides of the plate covered with a smooth, regular pad of weld metal having thorough penetration into the plate. Saw through the padded plate frequently to check for penetration and uniform thickness of weld metal which is free from porosity.
(5)	On another plate repeat the same procedure as in (4) above, but lay the alternate beads away from you and toward you, as indicated at the right end (3), figure 82. Inspect the pads as before and continue until you are proficient.
c.	Varieties of beads.—The fundamentals of laying a good bead have been described. If the student has become proficient in these procedures, the various types and combinations of beads used in practical welding will come easily with further practice. It is beyond the scope of this manual to provide a complete course of exercises in
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laying the various beads used in making arc welded joints. Complete exercise courses are furnished in the literature of the manufacturers of arc welding equipment, and cover: laying long beads, weaving the bead, building up pads of metal, welding butt joints (various types), welding outside corner joints, welding inside corner joints, and welding lap joints, all with the welds in the horizontal or flat position. Exercises are also given for the same welds in the vertical and overhead position, both with bare and coated electrodes, some of which require reverse polarity for best results. Still other practice exercises are prescribed for welding light-gage steel, which requires a small electrode, low current and special care to avoid “burning through” the thin metal.
d.	Vertical and overhead welds.—These are more difficult than flat welds and require more practice on the part of the welder before they can be accomplished successfully. The molten metal must be controlled in such a way that it will not become fluid enough to run out of the joint. This is done by moving the electrode away from the molten pool until it solidifies without interrupting the arc. This requires a fraction of a second, following which the arc is returned to the nonfluid metal and another deposit made. Electrodes no larger than %6 inch are used f°r vertical and overhead welding. With bare electrodes more current is generally used than for flat welding; with coated rods less current is ordinarily used. Reverse polarity is often an advantage. In vertical welding of thin stock (up to %6 inch), better results are usually obtained by starting at the top and welding down, with a single straight bead. Heavier stock is welded from the bottom up; the metal already deposited furnishes support for the molten metal as the weld progresses. The first pass is a straight bead and subsequent beads are woven. Overhead welds are built up by a series of straight beads; they are not woven.
53. Arc welding* cast iron, alloy steels, and nonferrous metals.—a. While the great bulk of arc welding is done on low- or medium-carbon steel, the process is used to some extent for repairing iron castings, welding alloy steels (such as stainless steels), and for welding nonferrous metals, such as aluminum, copper, brass, and bronze. These wTelding processes require special electrodes containing proper shielding and fluxing elements, as well as excess alloying elements to replace those burned out. Different operating techniques must be employed because of the lower melting points and greater fluidity of most of these metals, and because their rates of expansion and contraction when heated differ from those of steel. Most non
95
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QUARTERMASTER CORPS
ferrous metals cannot be welded in the overhead position because the arc transfers larger globules of these metals than of steel, and so must be assisted by gravity in depositing the metal.
b. The melting points of the more commonly welded metals are given in table V. These temperatures are approximate except for the pure metals. The melting point of every alloy varies according to its composition.
Table V
Metal
Melting point 0 F.
Metal
Melting point ° F.
Aluminum__________________
Brass_____________________
Bronze____________________
Copper____________________
Cast iron_________________
Lead______________________
1, 215
1, 742
1, 652
1, 981
2, 192
621
Nickel_____________________
Steel (mild)_______________
Steel (hard)_______________
Tin________________________
Wrought iron_______________
Zinc_______________________
2, 646
2, 768
2, 552
450
2, 730
786
c. Copper, cast iron, nickel, and wrought iron expand at about the same rate as steel when heated. Brass and bronze expand about one and one-half times as much; aluminum and tin about twice as much; lead about two and one-half times as much; and zinc about three times as much.
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Appendix
BIBLIOGRAPHY
In the preparation of this manual the following sources have been consulted for illustrations and text material. They contain more detailed information than is contained herein, and it is suggested that it would be advantageous for the student to consult them as collateral reading.
American Machinists'1 Handbook (Seventh Edition, 1940) : McGraw-Hill Book Company, Inc., New York, N. Y.
Kent's Mechanical Engineers Handbook (Eleventh Edition, 1938, Volume III) : John Wiley & Sons, Inc., New York, N. Y.
Modern Shop Practice (Volume IV, 1939) : American Technical Society, Chicago, Ill.
The Oxwelder's Handbook (Fifteenth Edition, 1939) : Linde Air Products Company, New York, N. Y.
Instructions in Oxy acetylene 'Welding and Cutting Processes (Lectures) (1940): Air Reduction, New York, N. Y.
Procedure Handbook of Arc 'Welding Design and Practice (Sixth Edition, 1940) : Lincoln Electric Company, Cleveland, Ohio.
Arc Welding and How to Use It (Third Edition, 1938) : Hobart Brothers Company, Troy, Ohio.
Arc Welding Manual (1940) : General Electric Company, Schenectady, N. Y.
[A. G. 062.11 (4-12M1).]-
By order of the Secretary of War :
G. C. MARSHALL,
Chief of Staff.
Official :
E. S. ADAMS,
Major General,
The Adjutant General.
Distribution :
B and H (3) ; R 1-8, 10, 17 (5) ; IR 10 (10); Bn 1-6, 8-11, 17 (5) ; C17 (3) ; IC 2-11 (3).
(For explanation of symbols, see FM 21-6.)
o
For sale by the Superintendent of Documents, Washington, D. C. ----- - Price 25 cents
97
UNT LIBRARIES DENTON TX 7S203 lllllillllllll 1001895682
NlbU LIBRARY