13
COPPER Copper,
like aluminum, is also a material having an extremely high heat conductivity.
Therefore, the spray arc
process should be used for all position welding. To help overcome the sluggish
weld puddle of copper wires
(E Cu), helium-argon (75% He - 25% Ar) should be used on the thicker materials.
Although pure argon shielding
will provide better arc stability, its use should be restricted to thinner materials
(1/4 in./6.4mm and below).
However, argon may be used on the following materials, as the alloy content improves
puddle fluidity:
1. copper-nickel alloys (E Cu Ni wire
electrodes) 2.
silicon-bronze (E Cu Si wire electrodes) Another
practice used to increase the weld puddle fluidity is initially preheating the
plate before welding and maintaining
a high interpass temperature while multi-pass welding. The
forehand welding technique should be used to produce a well-shaped weld bead.
Because the arc is on the
leading edge of the puddle, some preheating of the plate will take place, thus
permitting better wetting. Continued
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