[castweldsolutions]

I'm trying to figure out how much DCEP I can turn on the AC balance knob before the tungsten craps out. My goal is: I'm just trying to get the most cleaning action possible when I repair cast aluminum.

Can anyone shed some light? I've merely approached this with the perspective "positive current gets more cleaning action, therefor I need the most I can possibly get". Is this false thinking? Is there a better way?

I've always welded on basic tig machines that didn't have the ability to adjust AC balance (Miller Diversion 180), and yesterday was the first time I got to use a machine with this option (Lincoln Precision 225). So for curiosity sake, I cranked the knob to the maximum positive side thinking, "Heck yeah! My cast aluminum problems are over! And of course the tungsten couldn't stand the amount of positive current and took a dump in my weld pool (good thing it was a practice scrap piece).

After several beads, I found that the most positive current I could afford was right about 50% to 55%

Here are the parameters:

Lincoln Precision 225
2% Lanthanated 3/32nd tungsten
100-125 amps
1/4 inch thick cast aluminum.
75 he / 25 ar

Ok, Before I get my head bit off by ya'll lol, I realize that 75% Helium is WAY too much and probably didn't help at all with the heat input, but yesterday it was all I had available. I plan to do some more practice tonight with some straight Argon.

I've hit the books this morning trying to find some answers, but the material I have just doesn't emphasize enough on tig welding and I cant find anything that helps with this question.

Any suggestions?

[Cricket]

Just from my little experience in cast aluminum repairs:
1/4" thick is easy to weld with just Argon.
Cleaning action(percentage) is adjusted to a particular piece and case. Alloys, contamination, ambient conditions, welder, etc. makes a difference.
2% Thoriated I thought to be the toughest(heat resistant) but I weld with 2% Lanthanated at up to 200A.
Sometimes I have to make a first "dry pass" (no filler) just to clean and prep the base metal.

[rick9345]

cleaning action,tungsten size, tungsten type, material condition.
As stated case by case adjustments,each affects the other.
And the hand on the torch.
Twist the dials for results desired.
Not a set and forget.

[Otto Nobedder]

The ball will tell you.

On some scrap, set your balance to 50%, and turn up amps a little at a time, weld 20-30 seconds (filler not required), and focus on the ball. When you hit the limit, the end of the tungsten will actually begin to quiver, as it's surface begins to melt. Write this down. Then set your balance to 40%, and repeat; 60% and repeat, etc. Then you have a table that tells you how much cleaning action you can have at a given amperage.

Always take this as the absolute limit, and dial back a bit in use, as different alloys will retain/reflect heat slightly differently.

You'll find the larger the tungsten you use, the more amps you get at a given balance setting, and vice-versa.

Steve S

[rick9345]

"Always take this as the absolute limit, and dial back a bit in use, as different alloys will retain/reflect heat slightly differently.

You'll find the larger the tungsten you use, the more amps you get at a given balance setting, and vice-versa."

per Steve/Otto LIKE

[MosquitoMoto]

The ball will tell you.

On some scrap, set your balance to 50%, and turn up amps a little at a time, weld 20-30 seconds (filler not required), and focus on the ball. When you hit the limit, the end of the tungsten will actually begin to quiver, as it's surface begins to melt. Write this down. Then set your balance to 40%, and repeat; 60% and repeat, etc. Then you have a table that tells you how much cleaning action you can have at a given amperage.

Always take this as the absolute limit, and dial back a bit in use, as different alloys will retain/reflect heat slightly differently.

You'll find the larger the tungsten you use, the more amps you get at a given balance setting, and vice-versa.

Steve S

That looks like really sound thinking, Steve. I'm going to give this a shot right now.


Kym

[Rick_H]

Steve its more fun to push through the quiver and ball dance and let it fly off...lol I went through this the other day with a coworker practicing on alum, the 3/32" tungsten was shaken like mad, he was at 190amps.

[castweldsolutions]

Thanks a lot for the info Steve! Sound advice for sure!