For both new and experienced welders, aluminum welding can be challenging. Over-welding of the aluminum alloys can easily happen because of its “higher thermal conductivity and low melting point. Also, feeding aluminum welding wire during gas-metal-arc-welding (GMAW) presents a challenge because the wire is softer than steel, has a lower column strength, and tends to tangle at the drive roll.”
Welding Design and Fabrication magazine printed a helpful article on aluminum welding. They cover issues such as equipment selection, material preparation, welding technique, and more. Here are the tips presented in the article:
Gas Metal Arc Welding
Base-metal preparation: Base material must be clean before you begin to work on it. This mean removing “any aluminum oxide and hydrocarbon contamination from oils or cutting solvents.” This can be accomplished by using:
A stainless-steel bristle wire brush – brush in one direction only, not too harshly, and only use a brush that has never been used on stainless or carbon steel
Solvents and etching solutions – remember to clean them off of the work before you begin welding
Preheating: Doing this to your aluminum before you weld can prevent weld cracking. The temperature should not be more than 230F
The push technique: To produce cleaning action, less weld contamination, and better shielding-gas protection, push (not pull) the gun away from the weld puddle.
Travel speed: Travel speed for aluminum welding must be fast. You risk over-heating (burnthrough) if the travel speed is too slow.
Shielding Gas: The most common gas used is Argon.
Welding Wire: Choose an aluminum filler wire is similar to the base material in melting temperature and 3/64 (or 1/16) inch diameter.