Bad Argon, bad materials, bad operator?

Folks,

I've been working on a frame with a "lugged" ST cluster. Noticed that when I welded (yes, I mean TIG) the TT to the lug it the weld would pop + spit a little bit. Seemed strange to me. Nothing crazy ugly with the weld but I don't usually experience that kind've thing.

I prepped like I normally do:

2% Lanthanated Tungsten sharpened on a "blue only" wheel.
Wipe rod with acetone. Usually Weldmold
Outside + inside of tube is sanded.
Wiped with clean acetone.
Re-sand.
Re-wipe.
Same thing with the ST lug.

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Today I was welding the SS to the cluster and I started getting a LOT of popping and spitting. Ugly bead. Porosity. Blew through at one point.
Same prep. Tried ER70S (made sure to clean that too). Looks similar to welding hot-rolled steel w/out cleaning off the mill scale or when you forget to open the argon bottle.

Checked the hose. Checked the lens. They're fine. CFH ~25.

Things that I think it could be:

1. Me / prep.
2. Argon. It's a new tank.
3. Lug.
4. Dunno, fill me in.

1. If it's my prep, what else do I need to be doing? I've never experienced this before even when I've bought crap metal from our local supplier.

2. If it's the argon. I guess I just take it back and what? Ask the shop to test it? Is there a way to test every time I get a new bottle?

3. The lug is a Ritchey Break-Away. I'm removing the casting marks and scale with emory (To quote Jody, "Shiny bright steel."). Wiping down 2x with acetone (and using a clean cloth).

4. Other thoughts?

The question I have isn't related to the welding happenings- why weld a lug? All the lugs I've known of are made to be sweated with a capillary action filler (brazing).

Have you tried to weld on a different piece of steel without changing anything right after the problems? Andy

I just had a similar experience with a bad bottle. All you can do is bring it back and ask them to purge and refill...
Also check for a leak in your shielding line. A small leak can sometimes pull a bit of air in while it flows.
Oh, and if you've moved your workspace around, the welder's cooling fans might be messing with your shielding if they can blow air near your work (had that happen welding something beside the weld cart last year).

Your Argon is fine, it's the cast lug

Quote:

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Originally Posted by Andrew R Stewart

The question I have isn't related to the welding happenings- why weld a lug? All the lugs I've known of are made to be sweated with a capillary action filler (brazing).

Have you tried to weld on a different piece of steel without changing anything right after the problems? Andy

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Andy, maybe lug isn't the best word. It's the top of a Ritchey Break-Away system.

I did try running a pass or 2 on some other steel and while it wasn't popping, the welds were coming out a bit grey.

Quote:

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Originally Posted by Amaro Bikes

Your Argon is fine, it's the cast lug

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Aimar, the production Ritchey Break-Away bikes (steel) are TIG. Do I need to alter my prep in some way?

If you think it's the welding setup (including argon) weld on something else and see how it goes. Change one thing at a time until you figure it out. Don't assume any part of your setup is OK until you figure it out. You're using 25cfh with what size orifice? How clean is your tungsten? Has it ever been dipped and did you grind it until you stopped seeing orange sparks?

Anything cast is notoriously crappy to weld. Are your results the same on other joints without a cast fitting involved?

They're not porous but there was popping and spitting on some Nova + Dedacciai tubing. But I haven't had a chance to get back to the shop and run things through detailed testing.

Eric, do you have an idea of how the factory making the Ritchey break-away frames are getting decent results TIGing? Seems like the Weldmold and ER70S-2 wasn't liking things.

Hi Tom.

I've done couple of brake away frames and the cast lug certainly does not behave as nicely as any of the usual tubes or machined steel parts (bb, ht, etc). Cast feels "sandy" compared to a more "solid" structure of the machined parts, therefore the welding is not as stable (tig speaking) as usual. You need to really go into that part making it as shiny/smooth as possible, not just sanding, some filing too, clean it about 101 times with acetone and isopropilic alochol and get your tungsten resharpen and cleaned each and every time the slightest contamination (pop/spits) happens. Even then, cast will be as annoying and unpredictable as a drunk ant, so just be ready, think of it as if welding a dried spounge, even if the outside is perfectly smooth and flat, inside there might be hidden "holes" (of course, all this talking at microstucture scale)

https://c1.staticflickr.com/1/275/32...2dc8084c_z.jpg

Anyway, you got some good advise, first you should try is to isolate any possible failures by repeating same action on a step-by-step test by changing only one variable at a time, so to find out which is the one causing a difference. And as Sean very well said (as always), make 10000% sure to get your tugnsten clean and sharp every single time it gets damned or none of the test would be of any use. You should be able to solve 2 out of your 4 questions by simply doing the step-by-step test.

Cheers

Just in case, if you're actually welding the SS I guess you're doing so to the brazed ST lug, which includes yet another possible demon which is silver/brass. Even the smallest bit of that around your welding area will make things ugly, although sure you already know that, but just in case, specially if you didn't have issues when tig welding the top lug to TT junction

Bad argon tanks are rare, but they happen. I was tearing my hair out over a simple weld on a bridge a couple months ago. Tungsten? Good. Grind out popping mess to shiny steel, clean with acetone, it just gunked up again. Checked gas line, lens, everything. Worse yet, it was sporadic. One length of good weld, then bang, crap. Sometimes other pieces would weld fine, sometimes not so fine. I finally bought a small bottle and fill from another gas supplier and switched tanks. Bingo. Perfect beads. My regular supplier heard me out, told me that once in a while they get a tank that is contaminated, for some reason they think it's via a return from the same customer.

No time for testing the argon this weekend but I did spend a bit of time trying to brush up my skills on fillet brazing. I got a long way to go. :/
Looks like I'm gonna be spending a bunch of bench time brushing up those skills. I guess it's a good way to spend December + January.