[timsch]

I've been having problems with contamination of my tungsten, which is 2% thoriated. I'm running 100% argon @ 15 cfh. Cup size 8-10. Welding CS with ER70s as well as 304 w/ 308 fillers, both with similar problems. I'm using a Primeweld 225 with the CK17 torch, both of which are fairly new.


Here's the gas diffuser


Here's the 3/32 tungsten stickout. The cup has seen better days, but is serviceable AFIAK


Here's the tungsten showing contamination.

I can understand contamination at the tip, but am surprised that there's contamination where it sits inside the diffuser. It builds up so that it is hard, but not too hard, to pull out for sharpening. I've made the mistake of removing some of that buildup on the grinder wheel used for sharpening. I see now that once that part becomes near the taper it'll cause problems, so won't do that anymore.

These pics are taken after welding for 5 minutes or so. Arc starts out alright, but then becomes unstable as contamination gets worse. Occasionally I'll get too close to the puddle or the filler, but don't recall that happening before these pictures. No matter what I do, I start getting a ball, or more really a flat mushroom on the tip. I'm starting out with a typical taper and a flat at the tip.

I weld in my garage, and get similar results whether the door is open or closed. I don't weld if I'm in a breeze.

[timsch]

I'd edit, but can't find how.

I'm using lanthanated, not thoriated tungsten. Still too green to keep them straight.

[cj737]

Tungsten shows a lack of gas coming through the diffuser. Is that a cheap eBay gas lens? Also, 15cfh is on the lower side of recommended for larger cups. What amperage are you welding with?

Double check you’re on DC and not inadvertently on AC. (The balling you describe is associated with AC, but may well be the lack of gas.)

[martinr]

A couple of thoughts:

How long are your pre-gas and post-gas flows?

Is your bottle nearly empty? When the bottle’s getting low, even though you think there’s plenty of pressure, sometimes you get contamination. I don’t fully understand it, but I believe I have encountered it. Have you had the problem since you got the bottle of gas; sometimes you can get a bad bottle.

Possible air leakage into the torch.

You need to cut off the contaminated portion and grind a fresh taper to be sure you have fixed the problem.

Are you welding in a turbulent environment? It might not be obviously breezy, but you can generate turbulence welding on an edge. And there can be air currents you’re unaware of.

Make sure you have a good clean earth/ground. And a good clean workpiece. The instability and mushrooming at the tip could be a function of poor grounding. They are also indicative of a possible problem with gas shielding. Try a different or another electrode.

I have had this problem and even changed torches, which ruled out that part of the circuit.

It can be very frustrating and takes lots of troubleshooting, and, in the end, when it’s fixed, you probably won’t be entirely sure where the problem lay.

[BillE.Dee]

get a pea shooter and make certain that you're getting proper gas flow at the torch.