TM 9-237 Welding Theory and Application by United States. Department of the Army

Author:United States. Department of the Army
Language: eng
Format: epub
Tags: Technical Manual, Solder and soldering -- Handbooks, manuals, etc, Brazing -- Handbooks, manuals, etc, Welding -- Handbooks, manuals, etc, United States. -- Army -- Handbooks, manuals, etc, Vietnam War, 1961-1975, Field Manual, United States. Army, US Army, Cold War
Published: 1967-11-06T05:00:00+00:00

WE 30413

Figure 7-30. Studding method for cast iron repair.

f. Carbon-Arc Welding of Cast Iron. Iron castings may be welded with a carbon-arc, a cast iron rod, and a cast iron welding flux. The joint should be preheated by moving the carbon electrode along the surface, thereby preventing too rapid cooling after welding. The molten puddle of metal can be worked with the carbon electrode so as to move any slag or oxides that are formed to the surface. Welds made with the carbon arc coool more slowly and are not as hard as those made with the metal arc and a cast iron electrode. The welds are machinable.

Section IV. ELECTRIC-ARC WELDING OF NONFERROUS METALS

7-20. Aluminum Welding

a. General. Aluminum and aluminum alloys can be satisfactorily welded by metal-arc, carbon-arc, and other arc welding processes. The principal advantage of using arc-welding processes is that a highly concentrated heating zone is obtained with the arc and, for this reason, excessive expansion and distoriton of the metal are prevented.

b. Metal-Arc Welding.

(1) PLATE WELDING. Because of the difficulty of controlling the arc, butt and fillet welds are difficult to produce in plates less than i/s-mch in thickness. In welding plate heavier than Vs-inch, a plate with a 30 deg bevel will have strength equal to a weld made by the oxy-acetylene 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 2'4-inches in thickness.

<2) CURRENT AND POLARITY SETTINGS. 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.

(8) PLATE EDGE PREPARATION. In general, the design of welded joints for aluminum is quite consistent with that for steel joints. However, because of the higher fluidity of aluminum under the welding arc, some important general principles should be kept in mind. In the lighter gages of aluminum sheet less groove spacing is advantageous when weld dilution is not a factor. The controlling criterior is joint preparation. A special joint design V groove that is applicable to aluminum is shown at A, figure 7-31. This type of joint is excellent where welding can be done from one side only and where a smooth, penetrating bead is desired. The effectiveness of this particular design is dependent upon surface tension and should be applied on all material thicknesses over V6-inch. The bottom of the special V groove must be wide enough to contain the root pass completely. This necessitates adding a relatively large amount of filler alloy to fill the groove, but it results in excellent control of penetration and sound root pass welds. This edge preparation can be employed for welding in all positions with elimination of suckback difficulties in the overhead and horizontal welding positions. It is applicable to all weldable base alloys and all filler alloys.

c. Welding Aluminum Castings.

(1) Aluminum castings that have been heat treated should not be welded unless facilities for reheating after welding are available.

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