Miging Aluminium

[Bsmith]

I would like to get set up for welding aluminium with my mig welder just incase the need arises . My mig is a SIP Autoplus 180amp, uses .6 or .8 wire I have argon, what else do I need plz? A teflon liner? I can buy some grade 4043 wire, would this be a general purpose wire? I dont know alumin grades.

 

[Shox Dr]

Don't bother, you need the very miniuim of 250 amp DC for Ali with a MIG 350amp would be better.

0.6mm Ali wire is sooooooo thin it sticks inside the liner, whatever you use. Even when using a 350+ machine that can use +1mm wire, they tend to use hand spools.

 

[malcolm]

It's possible with smaller MIGs. There's some reading on:
http://www.mig-welding.co.uk/aluminium-setup.htm and
http://www.mig-welding.co.uk/aluminium-welding.htm

I thought I had added some notes from Shenion on that page. He used a 5356 wire which is stiffer and less prone to birdsnesting. 0.8mm would be the smallest wire you'd want to try.

There are a number of threads on the forum that might be useful too.

 

[ArcAid]

We have a 180a mig set up for ali welding. Teflon liner, Ali drive roll (not completely necessary) . Welds like a champion... has done for years.

 

[Bsmith]

So, the higher the grade number the harder the wire? Would 5356 be usable as a general purpose wire or would it only do for 5356 alumin if this exists? Thanks very much.

 

[hotrodder]

^ 5356 will work with most of the common alloys, a poor match for alloys containing much in the way silicon (that'll be most castings). 4043 is usually considered the closest thing there is to a general purpose wire (with regards to hot cracking sensitivity).

While 4043 is softer, actual weld metal is typically lower in strength than with 5356 and more brittle. 4043 turns a manky grey colour if anodised, 5356 can suffer from corrosion cracking issues when subjected to elevetated temps

Properties and common applications of aluminium alloys
Filler selection and a bunch of other stuff

Edit. I'm with Shox Dr for the most part on this. Thinish (say under 3mm) Al and MIG is not fun, especially if after neat and/or air tight welds. Makes far more sense for thick sections but then you need a big machine

 

[shenion]

Yes, I found 1/8" easy on a small mig. Lots of fiddling with settings, wire speed and technique to get it right. I have done 0.090 (2.2mm) with the Clarke 130 and was doable with a steel backer.

hotrodder makes a good point. 4043 and 5356 work ok on aluminum stock. I tried a casting with 5356 and had cracking issues as it cooled too fast (preheat would have helped.) 4043 was too hard to feed on my 4m torch (only time I miss that 2m torch on the Clarke.)

The corrosion cracking with 5356 is hard to pin down. Many sites just say not to be used at elevated temps. I have seen users that swear by 5356 on repairing aluminum heads and have never seen a problem. I did find one table that implied the temp problem was using 5356 on 6xxx grades.

It is doable and can be good for production. I would want an 180+A MIG though and a spool gun if I was doing more than just an occasional fix. It starts cold, so air-tight welds are difficult.

I have not messed with MIG on alum in a long time. I have sice picked up a used AC/DC TIG and never looked back.

 

[English Steve]

I worked for a transport refrigeration company some time ago, who used aluminium MIG quite a lot. To get around the cold start / hot finish issue, we used run-on and run-off tabs which were then removed after welding.

The welds never looked especially tidy, but they were sound enough. The frameworks carried 3 and 4 cylinder diesels coupled to V4 compressors, so were subject to a fair bit of vibration but never failed in normal use.

Typical material thicknesses were 3 to 6mm from memory, some machines used spool guns while others were standard wire feed due to access difficulties.

 

[hotrodder]

The corrosion cracking with 5356 is hard to pin down. Many sites just say not to be used at elevated temps. I have seen users that swear by 5356 on repairing aluminum heads and have never seen a problem. I did find one table that implied the temp problem was using 5356 on 6xxx grades.

Stress corrosion cracking, barely scratches the surface of a heavy going subject but that article suggests that even the boffins don't have a complete handle on it yet so we don't stand much of a chance. I guess it's just easier/safer for the manufacturers to not recommend it's use for weldments that'll see sustained service over 65C regardless of other factors.

Cylinder heads... i suppose the nice thing about/reasoning behind using 5356 is more to do with the following machine work. 4043 is a bitch to machine and while there are better matching wires (4145, 2319) for the alloys that cylinder heads are cast from finding 'em ain't easy.