OM-272384 Page 24
B. Welding Techniques
l Make sure the welding power source is set up to weld DCEP (DC Electrode Positive).
l For MIG welding aluminum you need to use a 10 to 15 degree push travel angle (tip and nozzle pointing in the direction of travel). See Fig-
ure Figure 6-1.
10
°
-15
°
10
°
-15
°
Direction Of Welding
Forehand (Push)
Technique
Backhand (Drag)
Technique
Figure 6-1. Side View Of Gun Tip Angle
l Pulling or using a drag angle will produce porous, dirty welds due to a lack of gas coverage.
l The reflective heat and weld puddle that is present when MIG welding aluminum is very hot. Holding the tip closer than 3/4 in. could lead to
the wire burning back to the contact tip and other feeding problems.
l The most common shielding gas for MIG welding aluminum is 100% argon. Flow rates of 20 to 30 CFH [cubic feet per hour (0.57 to 0.85 m
3
/
hr)] are acceptable. C25 or argon CO
2
shielding gases are not acceptable.
l Maintain a 3/4 in. (19 mm) tip-to-work distance, and have the contact tip recessed approximately 1/8 in. inside the nozzle if possible. See
Figure Figure 6-2.
Gas Nozzle
Contact Tube Recessed 1/8
in. (3.2 mm) Inside The Nozzle
Contact Tip To Work
Distance 3/4 in. (19 mm)
Figure 6-2. Contact Tube Position And Tip-To-Work Distance
l Avoid large weave beads on aluminum. If larger fillet welds are needed, multiple pass stringer beads will provide better appearance and
have less chance of cold lapping, melt through, and other weld defects.
l It will be necessary to increase torch travel speed as the base material becomes heated during the welding process.
l The skill level of the operator, joint types, fit up, and positions, as well as the welding power supply will all have a great influence on the weld-
ability of the aluminum and your success.
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