Crappy bead w/ Miller Spoolmatic 30A

I tried tacking some ears onto a Muncie transmission with my Spoolmatic
30A that is running off my Millermatic 250/ meters mig. I meticulously
cleaned both the tranmission and also the 6061-T6 ears. I have had the
gun for a year and just decided to hook it up. Gun is positive as per
the directions and ground is negative. 20cfh on the argon and a roll of
4043 in .035". Tip is correct and ground was good and I gave a
substantial preflow of argon before striking the arc. Gun at about 10
degees from veritcal and pushing.
Lots of smoke and a bead that looked like Mount St. Helens. Zero
penetration and a black soot on each side of the weld bead. The gun was
set as per the specs for 1/4" aluminum. The transmission is 365
aluminum and is quite weldable. The gas is good because it is the same
bottle I run off of my TIG machine.
I then tried it on an old scrap transmission after cleaning it also. I
got the same results.
Anybody have any idea what is going on here?
Any help or tips greatly appreciated.
Thanks, Steve
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My experience with trying to weld automotive aluminum is that there is too much oil/dirt/stuff in the metal. You can clean and clean, but you need the power of a TIG to really create a molten crucible where it can boil out. And then there's the contamination that's coming in from the back of the piece being welded. I never had much luck with my Miller Spoolmatic except for welding 1/4" or thicker flat aluminum in a flat position. Then the welding characteristics would change as the base metal got heated up.
I hear of guys all the time who can weld aluminum with MIG. I never had much luck with it.
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Steve B
Sounds like the Argon isn't reaching the nogas nozzle or is heavily contaminated. Have you; 1. checked for leaks? 2. measured the gas flow at the gun?
The soot either side of the bead is actually carbon deposit from decomp of grease either on the wire or the job, and actually indicates at least some gas is getting through.
What arc voltage and current are you running at? A rule of thumb is Arc Volts=14+(Amps/20)
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Oops! for Nogas Nozzle, read Gas Nozzle! (Freudian slip!)
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It sounds like you may have gotten some cheap recycled aluminum, for some reason welding requires virgin al.
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