[AT] Spam> welding aluminum

[Mike Reggie]

    I might be able to offer a suggestion, could it be that what you have is 
magnesium, and not an aluminum casting at all, from what you have described 
it seems that is what it is. Magnesium will often react the way you describe 
when it is welded with aluminum filler rod. As someone else suggested 
aluminum castings can be hit or miss but this doesn't sound like that.  You 
could try sanding or grinding the piece and take note if the grindings are 
coming off stringy rather than grainy, that would indicate magnesium, or try 
to take note of how the arc burns, sometimes magnesium will  have a colorful 
arc.

    If you are fairly certain it is just a fussy aluminum casting or just 
want to eliminate the possibility, you could try changing your filler, if 
you are using 4043, change to 5356, or vice versa, also you could try 
changing the cup size  on the torch, especially if the part is round, try a 
smaller cup, and lastly, make sure your shielding gas flow is within the 
proper parameters, sometimes overgassing can cause cracking, more so with 
helium than argon.
  Aside from these things it sounds like everything else is as good as it 
could be. I hope this will be of some help and let us know how things turn 
out.
  Good luck with the repair.

  Mike



----Original Message Follows----
From: "John Hall" <jthall at worldnet.att.net>
Reply-To: Antique tractor email discussion group 
<at at lists.antique-tractor.com>
To: "Antique tractor email discussion group" <at at lists.antique-tractor.com>
Subject: [AT] Spam> welding aluminum
Date: Mon, 10 Sep 2007 18:14:02 -0400

Not tractor related but it's 60 years old. Need some advice welding cast
alum. Appears to be good quality casting--no sign of porosity. The guy
trying to weld the part for me slightly preheated the part and then started
Tig welding. About 5 seconds after he would stop, the weld would crack.
After he welded and let the part cool for 2 hours I could pull it apart by
hand. Besides the hairline cracks the weld looked great--no signs of
contamination or air pockets. Oh yeah the parts had been degreased and then
bead blasted.

Any suggestions?

John Hall

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