Welding Techniques.

Welding Operations, I
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can be satisfactorily welded by metal-arc, carbon-arc, and other

arc-welding processes. The principal advantage of using the arc-

welding processes is that a highly concentrated heating zone is

obtained with the arc and, for this reason, excessive expansion

and distortion of the metal is prevented. With the exception of

the welding rod used, the welding techniques used for other

nonferrous metals, namely titanium, nickel, bronze, brass,

magnesium, and monel, are the same as those used for aluminum.

Welding Techniques.

(1) Because of the difficulty of controlling the arc, butt and

fillet welds are difficult to produce in plates less than 1/8

inch thick. In welding plate heavier than 1/8 inch, a plate with

a 30 bevel will have strength equal to a weld made by the

oxyacetylene process, but this weld may be porous and unsuited

for liquid- or gas-tight joints. Metal arc welding is, however,

particularly suitable for heavy material and is used on plates up

to 2 1/2 inches thick.

(2) The current and polarity settings will vary with each

manufacturer's type of electrodes, and the polarity to be used

should be determined by trial on the joints to be made.

(3) Before being welded, a broken aluminum casting should be

carefully cleaned by wire brushing with mineral spirits, paint

thinner, or dry cleaning solvent used to remove all oil, grease,

and other foreign matter.

If the casting has a heavy cross

section, the crack should be tooled out to form a "V."

(4) Either metal arc or carbon arc welding can be used for

aluminum castings, but the carbon arc is preferred because it

produces welds free of oxides and porosity. Flux-coated rods are

essential for good arc welds. All slag and flux must be removed

from the finished weld to prevent corrosion of the joint and the

entire piece should be covered with sand or asbestos to afford

slow cooling.