DC aluminum welding

[BrokenBiker]

yes or no?

not often I get asked but every now and then I am asked if I can weld up a little aluminium bracket for a motor bike or trike. nothing structural or load bearing, usually things like heel plates and so on being welded onto a set of aluminium footpeg brackets.

problem is I only have dc tig from my inverter arc welder. I have the tig torch, plenty of tungstens and argon, but didn't think dc tig was good for aluminium, but have been tol a few times now that it will work.

is it a good idea or not

 

[Llama]

The issue is DC doesn't clean off the oxide like AC does, so you get inclusions in the weld. You can do the same as DC MIG ally, which is where you scrub all the oxide off with a clean stainless brush, then weld it before it oxidises again (ie, straight away).

 

[BrokenBiker]

so a good thorough clean with a clean stainless brush and acetone then weld straight away and it should be ok?

like I say its nothing structural but none the less I would still like it to be a good weld

 

[hotrodder]

DCEP is the polarity which provides cathodic cleaning and is the usual polarity with MIG. Approx 2/3 of the arcs heat occurs at the positive electrode which isn't an issue with MIG as we need the wire to melt. Doesn't work so with TIG as we don't want the tungsten to melt, more indepth explanation here... http://www.mig-welding.co.uk/forum/showpost.php?p=454582&postcount=5

Search the TIG forum for 'DCEP' and you'll find a bunch of threads on the topic for example... http://www.mig-welding.co.uk/forum/showthread.php?t=32549&highlight=dcep

Cliff notes version... DCEP with a GIANT tungsten works after a fashion but is limited to the thinnest of very thin aluminium. Forget DCEN... with a helium rich mix on thick stuff it has it's place. Try it with thin stuff and argon and you'll just make a mess no matter how well you clean the ally. No balloon helium won't work, it's air with enough helium in it to make balloons float (so that kids don't die when doing chipmonk impressions).