Welding Aluminium with MIG – A Short Guide

First off, lets start by stating that MIG Welding aluminium with a general purpose MIG welder is not recommended, and a DIY type machine is even less suitable. One of the best types of machines to weld aluminium with would be an AC/DC TIG Welder. Having said that, most MIG Welders can be used for welding aluminium, provided they have been set up correctly.

The Challenges of MIG Welding Aluminium

MIG Welding steel is not difficult, this is because when it comes to setting up the machine there is a reasonable margin for error with regards to the roller tension, torch liner quality, power settings and wire feed speed.

For example, if your wire feed speed is a little high, or low, you’ll get away with it.  Unfortunately, if you’re trying to weld Aluminium you wont get away with it.  A wire feed speed that’s too low will cause the wire to burn back on to the tip, too high and it will hit the job, potentially causing a “Birds Nest” of wire inside the machine. All of which can be very frustrating.

For MIG Welding Aluminium, you will need:

• Pure argon gas, NOT Co2 or an Argon/Co2 mix
• Plastic or Teflon liner in your torch (more on this later)
• An oversize tip for the end of the torch (more on this later)
• A reel of aluminium wire suitable for the grade of aluminium you intend welding
• Plenty of patience – Getting the power and wire feed speed right takes time.

Torch Liner, Wire & Tip for MIG Welding Aluminium

A Regular steel liner (looks like bicycle brake cable), will scrape the surface of the Aluminium Welding Wire, causing the wire to bind/jam in the liner.  A Plastic or Teflon Liner must be used to avoid this.  If your MIG Torch already has a plastic liner, but you’ve been using it to weld steel, we would recommend fitting a new liner for MIG Welding Aluminium. Because Aluminium has binding properties, it may jam in a regular tip, especially when the tip gets hot.  Some types of tip can be purchased in an “Aluminium” version, these are slightly over-sized to compensate.

Several grades of aluminium MIG Welding Wire are available and the grade selected needs to be compatible with the aluminium to be welded. If you’re welding a straightforward commercial grade of aluminium, our suggestion would be to use a 5356 grade Aluminium MIG Wire  You can use a 4043 grade, but this is a softer wire and therefore more prone to feed problems.

Setting Up for MIG Welding Aluminium

Alright, so you have Argon Gas, you have fitted a Plastic/Teflon Liner and over sized tip and you have fitted your spool of 5356 Welding wire. In the next step you will need to pay close attention to the tension on your feed rollers.  Ideally, you’ll be using ‘U’ shaped rollers, but if all that’s available for your machine is ‘V’ shape, these will have to suffice.  Set the ‘Roller Tension’ as low as possible. Do this by starting at a point where the rollers slip and stop feeding the wire.  Then slowly increase it until the wire feeds properly.

Power Setting – This will be determined by the job.  If you’re an experienced welder of steel, start by setting the power about 50% higher than you would for the same thickness of steel.
Wire Feed Speed – This will be determined by the job.  If you’re an experienced welder of steel, start by setting the ‘Wire Feed Speed’ about 100% higher than you would for the same thickness of steel.
Ambient temperature – If you’re doing a job in cold weather, try warming the job up a little.  What you’re looking for is the job to not be cold to the touch, so if it is, put a fan heater on it for a few minutes.  A job that’s warm to the touch will weld easier.  This obviously wont be necessary in Summer.

Getting Started – Patience Patience Patience

Make sure metal you intend welding is clean, running a sanding disc over the area to be welded can also help if the aluminium is old as this will reduce the effects of surface oxide.

Getting the balance of power and Wire Feed Speed when trying to MIG Weld Aluminium is a frustrating exercise of trial and error. Start by angling the torch at 45⁰ as this will minimise the risk of birds nesting wire inside the machine if the wire feed speed is too high. Once you’ve got the power and Wire Feed Speed set correctly the process is similar to welding steel, just hold the torch at approximately 70⁰, and slowly move along. Patience and practice will turn you into an accomplished MIG welder in no time!

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