Firstly, Mig Welding Aluminium with a general purpose Mig Welder is not ideal, a DIY type machine is even less suitable.
The best type of machine to weld Aluminium with is an AC/DC Tig Welder
Having said that, with the right set up, most Mig Welders can be used for welding aluminium (more or less), provided they’re set up correctly.
Mig Welding steel is not difficult, this is because when it comes to setting the machine up:
> Roller Tension
> Torch Liner Quality
> Power Setting
> Wire Feed Speed
there is a reasonable margin of error.
For example, if your wire feed speed is a little High, or Low, you’ll get away with it. If you’re trying to weld Aluminium you WON’T get away with it. 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 very frustrating.
> 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
> LOTS of patience getting the Power and Wire Feed Speed right
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, I 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 oversized to compensate. If your machine’s tip type is not available in an Aluminium version, I would suggest using 1.0mm tip for 0.8mm wire.
Several grades of Aluminium Mig Welding Wire are available and the grade selected needs to be compatible with the Aluminium to be welded.
If your welding a straightforward commercial grade of Aluminium, my 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.
OK, you’ve got Argon Gas, you’ve fitted a Plastic/Teflon Liner and oversized tip and you’ve fitted your spool of 5356 Welding Wire.
Next you’ll need to place 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 don’t feed the wire. Then slowly increase until the wire does feed OK. More info on Roller tension can be found in our Knowledge Zone
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.
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.
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 shouldn’t be necessary in Summer.
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 not dissimilar to welding steel. Hold the torch at around 70⁰, and move slowly along.
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