Tig weld problem

[BeezFun]

Not sure if this is contamination or what, but I've been welding this frame together with no problem on all the other joints. All of a sudden this one joint causes sparkling and popping, it contaminates the tungsten even though the tungsten doesn't touch. In the photo you can see it leaves a brown residue and a very pock marked looking attempt at a weld. What's causing this? This is the same material I used on the whole frame, it's 3/4" square steel tubing with .065 wall, same welder, same filler, same human doing the welding. Could this be oil or something that's inside this one piece of material?

 

[Shield Arc]

It could very well be some oil.
Is it possible a breeze may have blown your gas coverage away?

 

[k0ua]

That looks about like what I get when I forget to turn the gas on. Can you hear the gas flow? Solenoid stuck? out of gas?

 

[BeezFun]

It could very well be some oil.
Is it possible a breeze may have blown your gas coverage away?

I'm in the garage, no breezes. Plus it's just this joint. I'm thinking oil, but wow, I've never had anything like this.

 

[BeezFun]

That looks about like what I get when I forget to turn the gas on. Can you hear the gas flow? Solenoid stuck? out of gas?

Gas is working, I welded a few other pieces and it worked fine, but you're right it's kind of similar. There's something about just this joint, so either the metal itself has some kind of contamination in it (not likely), or there was some oil inside that I didn't get out.

 

[Shield Arc]

I've never had it happen when Tig welding steel. But Tig welding aluminum, when the argon bottle gets low, it will play havoc on aluminum welds.

 

[Furu]

I've never had it happen when Tig welding steel. But Tig welding aluminum, when the argon bottle gets low, it will play havoc on aluminum welds.

SA
Did the flow meter/regulator still show a steady 15-20cfh or did it vary as it got low in the bottle when this happened?

 

[Shield Arc]

SA
Did the flow meter/regulator still show a steady 15-20cfh or did it vary as it got low in the bottle when this happened?

Yes the flow meter showed 20-cfh. The bottle still had some argon in it, so I didn't worry about it. Then the welds went bad. Guys on the Miller forum informed me not to let the bottle get that low when Tig welding aluminum.

 

[mrmikey]

Is the tubing closed on the other end? Pressure will build up and force the atmospheric air out the joint contaminating the puddle. I ran into that problem a lot when doing s/s tubing rails, same with aluminum as well. I ended up drilling holes that would be covered by the pipe before I tacked it together to prevent pressure build up....Mike

 

[BeezFun]

Problem solved, here's what I did. I drilled an 1/8" hole in the bottom of the square tube near the end that had the contamination problem. Then I stood the frame up on end so that piece is oriented vertically and injected acetone in that hole with a horse syringe. I collected the acetone that ran out the bottom through the parts of the bad joint that I hadn't welded yet. There was a lot of dark sediment that looked like grinding dust that came out, presumable there was also oil. There was still a little hissing and spitting when I rewelded that joint because there was trapped impurities in the old weld, but it came out pretty good all things considered. When I originally cut all these pieces I cleaned them in a parts washer with hot solvent, my guess is I somehow forgot to clean this piece. Won't make that mistake again.