WELDING OPERATIONS I - OD1651 - LESSON 1/TASK 1
The following subparagraphs describe the welding
techniques used only for aluminum. Aluminum and aluminum alloys
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.
(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