hi guys im having an issue, when welding aluminum i grind my tungsten to a point and ball my tungsten on a piece on scrap metal without switching my polarity on my welder. it ***** up fine, after i finish my first pass and try to restart my weld ,i cant strike an arc i have to keep scratching the balled tungsten on the aluminum until it finally strikes an arc. anyone know what causes this and whats the fix. by the way im using 2% ceriated tungsten

 

You should be using pure or lanthanated for aluminum on a transformer machine. If you have an inverter, you shouldn't be balling your tungston, period.

Having to "scratch" the tungsten to the work piece every time is a symptom of several problems:

1) contaminated tungsten
2) insufficient post-flow
3) bad ground or cable connection
4) spark gap out of adjustment (if on a transformer)

 

as Pat said...i use 2% lanthanated (light blue)

 

When I was in welding school I used 2% ceriated for certain procedures with no issues. I say "certain" procedures because really there was only one procedure I ever used it on... Vertical up. I sharpened the tungsten and then put a flat on the end of it (a bit bigger flat than you would use when tigging carbon). I never had any major issues. I did this because when I was doing vertical up, I had issues with penetration using the pure tungsten since the arc fanned out too much. I didn't try this on my own whim, my welding instructor suggested it because he said that's what they did back in the day to help with penetration on vertical welds. I also noticed it definitely helped keep burn-through to a minimum since the heat was a bit more concentrated. Also, all of this applies to transformer machines, we didn't have any inverter high-freq machines for aluminum.

Other than what I just said, I would stick to pure (green) tungsten. The ceriated only really worked for the procedure I mentioned, pure worked much better for everything else. I actually tried 2% thoriated once, and it worked, although it seemed to become contaminated more quickly.