welding aluminum

[thepj]

i bought a lincoln invertec v145-s stick/tig from ebay never used got it for $550 its dc only. i've really just done mig and stick, i've had some people say you can weld aluminum in dc- also had ppl say you can only do it ac i bought it befor i heard about the 2 difference. just wondering if i'm better off just selling it and look for one that does ac or hang on to it and learn to use it?

[BANDITROD]

mate i have news for ya and its all bad ..........what you need is an ac tig although that would be the perfect tool to get you ready to use the ac so i would have a play with the dc before you piss it off

[Booster]

I'm thinking of upgrading to something with a foot control and gas control, currently have an old Miller type,
what are the current ebay 4 in one ac,dc,arc,plazma cutter, like do they weld ok or am i better off spending more ???

Thepj maybe we can get a deal buying a couple at once ??

[Anakist]

You can DC TIG Al. The AC TIGs vary the waveform to clean the weld are when electrode negative, then put heat into the metal when electrode positive (I think that is the right way around). When the electrode is negative, the electrons are flowing from the job up to the tungsten, this pulling action breaks up the oxide layer and removes it, and heats up the tungsten. When the electrode is positive, the electrons are flowing from the tungsten down to the job, as they hit the work metal they heat it up and melt it.

I have read two theories.

The first is electrode positive, fucking huge amperage to melt the aluminium oxide layer (Al Oxide melts at ~2000deg, Al about 600), and thick material so the oxide inclusions don't matter so much. I have heard you need very pure helium as a shielding gas and preferably in a sealed gas charged room, laboratory grade cleanliness (whatever moron made that up I don't know. It needs to be fucking clean though. Try nitric acid bath inside the helium room to exclude all oxygen).

The second is electrode negative, low amperage (as low as you can go and still melt the material), fucking big tungsten to dissipate the heat it is receiving, thin material so you don't need as much heat to do it.

If you have all the gear anyway and feel like playing have a go on something like a coke can with both polarities and see. It might work well enough to be worth it for you. Or do what this guy did and purge a bead blasting cabinet and welded in there.
http://www.locostbuilders.co.uk/viewthread.php?tid=50458

James

[thepj]

hmmm i think i'd rather a ac/dc setup then save stuffing around, well brand new unused lincoln invertec v145-s welder for sale with stick welding gear $550 although this is probly the wrong place to advertise.

[Zed14]

i just bought a unimig 200p ac/dc mma tig. unit was $1600. foot controller $180 then a bit of other stuff. all up $2300 but it will weld anything as soon as i learn to use it.

[thepj]

ye thats way out of my budget, i'll just wait till later on in life to get propper setup.