Top 10 tips for better aluminium welding.

Material thicknesses of aluminium that can be welded using the MIG method are 14 gauge and heavier; the output capacity of your welder determines the thickness you can weld. It may be necessary to use specialized welding equipment to MIG weld aluminium thinner than 14 gauge (.074 inch).

Thoroughly clean the aluminium prior to welding, including the removal of any lubricants from the material. Oxide removal should be done after degreasing either a hand wire brush or a cup wire brush. To avoid contaminating the base material, use the wire brush on aluminium only and always clean the brush before use.

Aluminium is a non-ferrous metal; therefore, it will require a 100 percent argon shielding gas. Flow rates of 20 to 30 cubic feet per hour are recommended.

When MIG welding aluminium, the spray transfer method is most common. This process is a very smooth transfer of very small molten metal droplets from the end of the electrode to the molten pool. There is no short-circuiting in spray transfer, and the deposition rate and efficiency are relatively high. Be aware, as the spray transfer method involves a high amount of heat, which creates a large weld pool with good penetration; this can be difficult to control. It should not be used on materials thinner than 14 gauge.

Before MIG welding aluminium, choosing an appropriate gun and wire feeding system is an important step. A spool gun or a push-pull system are the most common method for feeding an aluminium wire.

Spool guns improve the feeding of soft wires by locating a small spool of wire on the back of a pistol-grip style gun. A spool gun allows the wire to feed only a few inches at a time, eliminating the possibility of “birdnesting”.

The other method is the push-pull system, which uses a motor in the gun to pull the wire through the liner, while a motor on the feeder acts as an assist motor. This option can be more ergonomic and user-friendly and is ideal when welding far from the power source.

Aluminium forms a thin aluminium oxide coating (or “skin”) on its exterior which has a higher melting point than the aluminium itself. Cleaning the aluminium oxide from the aluminium, even a brand-new piece, is a must before you can begin welding.

Set your TIG welder to AC (alternating current); this will give the electrode positive polarity and the metal surface negative polarity. A current flowing from negative to positive will “clean” the metal of oxides, exposing a fresh surface for welding.

Heat up the aluminium in the oven or using a gas torch to the heat sink with the work clamped on. It will make the aluminium much easier to weld if it is already much hotter than the room temperature. Trying to weld thick pieces of aluminium without preheating will result in a weak and shallow bond.

Breaking of the arc abruptly when you reach the end of a weld can leave the weld cracked and faulty. To avoid this problem, gently reduce the current with a foot control as you near the end of a weld.

When welding aluminium, the colour remains silver, unlike steel which will glow red as it heats up. Consequently, when welding with aluminium you must pay closer attention to ensure your materials aren’t overheating.