An arc welder creates an electrical current through an electrode, which melts the metal to form a weld between two work pieces. In some arc welding processes, the metal in the electrode also melts to make the weld. Arc welding machines may produce an alternating current (AC) or direct (DC) current, depending on the specific application. Aluminum is generally harder to weld than steel, and you'll need to select a welding machine specifically for welding aluminum.
Examine the difficulties of welding with aluminum. This metal conducts heat better than steel and has a lower melting point than steel. This combination of factors means that it's much easier to completely melt the aluminum pieces. Aluminum is also more chemically active than steel.
Select a more powerful welding machine so that you can make the weld more quickly. A 115-volt arc welder can weld aluminum up to 1/8-inch thick and a 230-volt machine can handle aluminum that's up to 1/4-inch thick.
Use welding machines that provide a constant current and voltage for spray-arc welding. This type of arc welding uses an arc that sprays a small stream of molten metal from the electrode to the base metal.
Ensure that the contact tips on the electrode feeder are larger than the electrodes. Aluminum expands more than steel in response to heat, and the contact tips will need to be approximately 0.015 inch larger than the electrode.
Push the welding gun away from the weld puddle, rather than pulling it towards the weld puddle. This will make the arc less likely to overheat the base metal.You must make aluminum welds much more quickly than steel welds.