I'd like help for the following problem: for the first time I tried to weld machined aluminium. I milled two blocks, cleaned them with acetone and a stainless brush, then tried the tig machine. Ka-boom, all I get is black soot everywhere.
I think the problem is that the cutting fluid was not perfectly cleaned away. Is that a likely explanation?
Bonus question: if it's the cutting oil, what is the right procedure to clean it (since acetone obviously did not work)?
What alloy was it?
6061, and 6063 are fine. If it was 7075, you are screwed. 7075 is not meant to be welded, ever.It depends on the cutting fluid. That is one of the reasons why I use ZEP Big Orange as my aluminum cutting fluid. You can weld right through a puddle of the stuff with no weld contamination.
Try re-cleaning the blocks, and then preheat them to about 600 - 800 degF before attempting to weld them.
It is the famous sort: "undetermined trash yard junk", so I have little hope there. But surely clean 7075 would not produce soot, would it? I thought that unweldable aluminium alloys would rather crack, be porous whatever...
Another good reason to go and look for that cutting fluid, but I do not have the slightest idea where to find it on my side of the planet. Thanks anyway.
So I take that heating the block is the proper method to clean them? I should have thought about it myself...
Preheating reduces the necessary amperage to weld to large chunks of aluminum. It will also help burn off any oils or other volatile contaminates on the surface.
Preheat, and then wire brush the area thoroughly.
Make sure your Argon bottle is good and gas is flowing.
Another possibiity is a leak in a tig hose, especially if it's a water cooled torch.
Tom
I use 50/50 Acetone/Xylol for cleaning solvent and find it works much better than Acetone alone.
Ted
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