kept in mind. Wrought iron contains a slag that is
GUIDE FOR OXYACETYLENE WELDING
incorporated in it during the manufacturing process.
OF NONFERROUS METALS
This slag gives the surface of the molten puddle of
Although brazing is used extensively to make
weld metal a greasy appearance. Do not confuse this
joints in nonferrous metals, there are many situations
greasy appearance with the appearance of actual
in which oxyacetylene welding is suitable for this
fusion. Continue heating the metal until the side walls
purpose. In general, joint designs are the same for
of the joint break down into the puddle. Best results
nonferrous metals as for ferrous metals. Oxyacetylene
with wrought iron are obtained when the filler metal
welding of nonferrous metals may require mechanical
(usually mild steel) and the base metal are mixed in the
cleaning of the surfaces before welding and the use of
molten puddle with as little agitation as possible.
a flux during welding. Filler metal must be suitable for
Oxyacetylene welding of cast iron requires
the base metal being welded.
different procedures than those used for welding
steels. Special edge preparation is usually required.
Copper
The entire weldment should be preheated to between
750 and 900F before the welding is begun. The
Where high joint strength is required, the only kind
welding should be done with a neutral flame, by a
of copper that can be successfully welded by
backhand technique. Use a cast iron filler metal. Flux
oxyacetylene welding is DEOXIDIZED copper
is required but should be used sparingly, as needed, to
(copper that contains no oxygen). Either a neutral or a
overcome temporary difficulties. The filler metal is
slightly oxidizing flame adjustment may be used. With
added by directing the inner cone of the flame against
a neutral flame, a flux is necessary; with an oxidizing
the rod into the puddle. The filler metal should be
flame, no flux is needed because the oxide formed on
deposited in layers that are no more than one-eighth
the surface protects the molten metal. Because of the
inch thick. The weldment must be stress relieved after
welding; heat it to a temperature of between 1100 and
preheat the joint area to between 500 and 800F and
1150F and then cool it slowly.
to use a large size torch tip for welding. The larger size
Oxyacetylene welding is successful with some
tip supplies more heat to the joint and thus makes it
possible to maintain the required temperature at the
chromium-nickel steels (stainless steels). As a rule,
oxyacetylene welding is used only for light gauge
joint. After welding has been completed, the part
sheet metal. Heavier pieces of these steels are usually
should be cooled slowly.
joined by one of the electric arc welding processes,
which will be discussed in chapter 10. On material
Copper-Zinc Alloys
0.040 inch or less in thickness, a flange equal to the
thickness of the metal is turned up and the weld is made
Copper-zinc alloys (brasses) may be welded in the
without filler metal. Before being welded, the joint
same way as deoxidized copper. However, a
surfaces of the metal should be cleaned with sandpaper
silicon-copper rod is used for welding brasses. Preheat
or other abrasive and then coated with stainless steel
temperature is from 200 to 300F. Copper-silicon
flux. The torch tip used for welding stainless steel
alloy (silicon bronze) requires a different oxyacetylene
should be one or two sizes smaller than the tip used to
welding technique. This material should be welded
weld mild steel of the same thickness. The torch should
with a slightly oxidizing flame. A flux with a high
be adjusted to produce a carburizing flame that has an
boric acid content should be used. Add filler metal of
e x c e s s acetylene feather extending about
one-sixteenth inch beyond the tip of the inner cone, as
progresses, dip the tip of the rod under the viscous film
seen through the goggles. The torch should be held so
that covers the puddle. Keep the puddle small so that
that the flame makes an angle of 80 with the surface
the weld will solidify rapidly.
of the sheet. The tip of the cone should almost, but not
quite, touch the molten metal. Make the weld in one
Copper-Nickel Alloys
pass, using a forehand technique. Do not puddle or
retrace the weld. Uniform speed is essential in welding
Oxyacetylene welding of copper-nickel alloys
stainless steels. If it is necessary to stop the welding
requires surface preparation and preheating. The flux
before it is completed, or to reweld a section, wait until
used for this welding is in the form of a thin paste; it
the entire weld has cooled before beginning to weld
is applied by brush to all parts of the joint and to the
again.
welding rod. The torch should be adjusted to give a
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