Aluminum welding, the right equipment can make it easier

Aluminum Welding Wire

While aluminum welding presents a challenge for even a well-trained welder, the right equipment can make it easier. Welders can achieve high-quality gas metal arc welds (GMAW) on aluminum alloys by following a few simple rules, including choosing the proper welding wire and properly preparing base materials.

To successfully MIG weld aluminum, use a spray transfer mode instead of the short circuit transfer mode used for welding steel. The spray transfer mode delivers molten droplets to the weld puddle, resulting in a smooth and stable arc that offers excellent appearance and strength. In contrast, the short circuit transfer mode delivers a steady flow of molten aluminum to the puddle, which can result in poor appearance and brittle, weak welds.

When MIG welding aluminum, choose a wire with a low-sulfur content and a high magnesium content. The higher magnesium content helps aluminum welds to be stronger and more resistant to corrosion and hot cracking. Hobart's MaxalMig(r) 4043 and 5356 aluminum welding wires are two of the most popular choices.

Like all welding processes, MIG welding requires a clean and consistent wire feed. A contaminated wire feed can lead to arc blows, poor appearance, and burn-through on the aluminum workpiece. The best way to ensure a clean and constant feed is to keep the electrodes in good condition and to use a stainless-steel brush on the workpiece to remove any aluminum oxide before welding.

Since aluminum is a highly conductive metal, it heats up quickly and requires higher amperages than many other metals. However, if the welder runs too high a voltage for an extended period, it can burn through the aluminum workpiece and cause internal stresses in the welded area that can eventually crack the entire weld. Using a standard rosebud to preheat the workpiece to 200°F can help prevent this.

Another option for MIG welding aluminum is pulse transfer GMAW, which can be performed on all aluminum alloys. Pulsed GMAW allows the welder to weld aluminum at lower amperages and voltages while still producing positive droplet transfer. It also allows the welder to use thinner-gauge aluminum wire for better control of heat input and to avoid burn-through on thin-gage material.

Another type of gun that can be used when MIG welding aluminum is the spool gun. This is a pistol-grip-style gun that holds a wire spool in its compartment and has an independent feed system with drive rolls designed for feeding the sensitive aluminum wire. It eliminates the possibility of birdnesting by limiting the amount of time the soft aluminum wire spends on its journey from the spool to the weld. However, it's limited to a 1 lb spool and is heavy to hold for long periods. Fortunately, there are push-pull guns available that offer the same functionality without the spool limitation and weight. They can be found at most welding supply stores.