Think you need a TIG welder to weld aluminum? Think again! A MIG welder equipped with a spool gun can handle a lot of basic aluminum welding projects. In this article, we’ll introduce you to a simpler, more accessible approach to welding aluminum. Whether you’re a seasoned welder or a novice looking to expand your skills, we’ll show you how to run your first bead with a machine you may already own.
MIG welding aluminum differs from welding steel due to aluminum’s properties like its higher thermal conductivity and lower melting point. Carbon steel typically used for welding becomes liquid at around 2500-2750 °F. Aluminum’s melting point, however, is much lower at 1100-1220 °F, depending on the specific alloy. MIG welding aluminum, therefore, demands specific machine requirements to ensure successful welds.
Machine Requirements
Spool gun – Feeding aluminum wire through a traditional MIG torch from a spool inside the machine can be challenging. Because aluminum wire is softer, it has the potential to become tangled or jammed. A hand-held spool gun is typically used for MIG welding aluminum. These feed the wire smoothly over a very short distance – just a few inches – to prevent bunching up.
(Tip: When shopping for a MIG welder, it may be cheaper to buy one with a spool gun included in the package.)
High-frequency start – Some MIG welders designed for aluminum welding may include high-frequency start capabilities. This feature helps establish the arc when initiating the weld, which can be beneficial for aluminum welding.
Pulse settings – Pulse welding is often used when MIG welding aluminum to control heat input and minimize distortion. Look for a machine that offers pulse welding capabilities and adjustable pulse parameters.
Shielding gas – MIG welding aluminum requires the use of shielding gas to protect the weld from atmospheric contamination. The most common shielding gas for aluminum welding is pure argon, though some use a mixture of argon and helium. Ensure that your welding machine can accommodate the appropriate shielding gas and has the necessary gas flow control.
Adjustable voltage and wire feed speed – Like welding other materials, MIG welding aluminum requires control over voltage and wire feed speed. Aluminum typically requires higher voltage and wire feed speed settings compared to steel. Look for a machine with adjustable settings to fine-tune the welding parameters based on the thickness of the aluminum being welded.
Stable power supply – A stable power supply is essential for consistent and high-quality welding results, especially when welding aluminum. Ensure that your welding machine is connected to a reliable power source with sufficient capacity to meet the demands of aluminum welding. A generator may not be adequate to power a MIG weld for aluminum, for instance.
Process
Aluminum is a much more finicky material to weld than steel. While you can often get acceptable results welding steel that’s been poorly prepped, aluminum must be perfectly clean to get good welds. Prepare the material thoroughly to remove any oxidation or contaminants. Use a stainless steel wire brush or a dedicated aluminum brush to scrub the surface. Acetone or a low-VOC prep solvent work well for degreasing and a final wipe.
Make sure your welding machine is made for aluminum welding. Plug the spool gun into the welder and switch the machine to spool gun feed, if required. Connect the welder to a gas bottle with pure argon for shielding gas.
Follow your welder’s instructions to set it for the thickness of the aluminum you’re welding. You may need to experiment a bit to find the right settings for your specific setup. Generally, you’ll want a higher voltage and wire feed speed compared to welding steel.
As always, put on appropriate protective gear before starting your welds. This includes gloves and a welding helmet with a suitable shade lens for aluminum welding. Long sleeves or a welding jacket will protect your skin from both UV radiation and spatter.
Position your workpieces properly, ensuring they’re securely clamped together. Attach the ground clamp to the work directly, if possible. Hold the gun at a slight angle to the workpiece and maintain a consistent travel speed. You may need to push the puddle more than you would with steel welding. Practice on scrap pieces before attempting critical welds and be patient as you refine your technique.
A “whipping” motion – moving the gun in a slight crescent shape – helps prevent burn-through and ensures good fusion. Pay close attention to the puddle, as aluminum can quickly go from liquid to solid. Preheating the work to around 115 degrees F can help the initial welds go easier before heat builds up from welding.
After welding, allow the work to cool naturally. You may need to clean off any residual spatter or flux with a wire brush. Check the weld for any defects or inconsistencies before grinding down any rough areas, if required.
Welding aluminum can be challenging, especially for beginners. But with patience and practice, a MIG welder with a spool gun offers a compelling alternative to TIG welding. And if you already have a MIG machine, you might discover it opens doors to a world of new projects.
Aluminum, I was taught to sweat any moisture from the weld area before starting a bead – I suppose preheat will do this, but it’s easy to see the moisture coming off the Aluminum as I take a propane or a small butane torch in tight a area ! That is a good visual indicator that I use – *also any Stainless brush / cutting tools such as my 4-1/2″ cutter/grinder wheels etc. You use to prep the Aluminum for Weld, I mark them for use on Aluminum Only or keep those tools in a separate container to prevent contamination from other metals ! If someone borrowed that wire brush to clean a piece of Steel, ( probably while you’re not around ) – it’s not usable for Aluminum again, it will embed contamination in the Softer Aluminum – Keep it Clean & have Aluminum only tools set aside & labeled 🏷 – Practice and it will be useful, more Aluminum out there all the time