Welding Tips and Tricks

Hi, I'm new to the forum, and have only been TIG welding for about 5 years as a hobby. I am working with a new machine (Lincoln TIG 200), after upgrading from an Eastwood 200 DC. I'm welding a 1/8" stainless plate (say 3" x 5") to the end of a 1.25" diameter 16 gauge stainless tubing. I know I'm not an experienced welder, but I'm having trouble with this. I've read/watched a lot of info on welding thin to thick and know to focus the heat on the thicker piece and just to have it brush up against the thinner piece, but this is really giving me fits. I finally got it done, but I'm not satisfied with how it looks. And I burnt through the tubing a few times and had to cut it down and retry.

There are three specific problems I could use help on:

(1) I even had trouble getting it tacked. Almost every time I would tack it, it would burn through the tube if I gave it enough time to form a puddle. I could see the puddle forming on the tube and on the plate, but they wouldn't combine properly, even with a tightly fitted, clamped joint.

(2) Even when I did get it tacked, I had trouble with the weld. If I put more heat into it, either with more current or a slower speed, I would overheat the part and sometimes burn through. But If I tried less current and a slower speed, say 60A, the puddle wouldn't form properly on the thicker piece.

(3) I'm a lefty and had trouble with hand position. I tried laying the plate flat on the table with the tube sticking up, and also putting the edge of the plate in a vice so the tube was horizontal. This was better but not great.

My set up is as follows:
- Lincoln TIG 200, and I tried everything from 60A to 90A
- Stubby #8 cup on a 17 torch, with a Furick gas lens. 16 CFH and about 1/2" stick out
- 308 filler rod, tried both 1/16" and 3/32"
- Tried no pulse and up to 3x/sec

I know this is a lot of problems, but any help/tips would be greatly appreciated. Thanks!

I generally try to avoid 1/2" stick out, but seeing this is an inside corner with a #8 cup, it's probably not too much.

What type of tungsten (2% Thoriated?) and how sharp are you making it?
Is the tungsten clean enough for brain surgery or is there contamination on it?
Goes without saying the parts need to be very clean.
1/8 to 1/16 should not be very difficult.

My guess is you are long arc'ing it. If you are not in super tight, you'll get wetting away from the root without the root wetting in. You might want to post a pic of the tungsten and it may get you more help. While it's generally said that a more blunt angle is better, on this I'd go to a somewhat longer taper on the electrode. You need to really get that down in the root to get good fusion.

Point as much toward the thicker plate as you can, and just let the tubing get the stray heat that's there. In a pinch, you could try putting a small amount of weld metal on the edge of the tubing, just enough to light up on when you put it back in place to weld, and it may help equalize the heat absorption so it doesn't blow out. From there though, you need to concentrate heat on the plate again.

Purging from inside the tube might help to keep contamination coming in from the inside of the tubing. Also, did you clean the inside of the tubing, because if you did not, that dirt inside there will get pulled into the weld and keep the two parts from joining.

I might also try some smaller filler...maybe 045. You could also use an aluminum slug inside the tube as a heat sink/chill bar.

BugHunter wrote: What type of tungsten (2% Thoriated?) and how sharp are you making it?
Is the tungsten clean enough for brain surgery or is there contamination on it?
Goes without saying the parts need to be very clean.

Also, did you clean the inside of the tubing, because if you did not, that dirt inside there will get pulled into the weld and keep the two parts from joining.

Those are good tips, thanks.

The tungsten is 2% Lanthanated, ground at about 20 degrees. When I contaminate a piece I always cut off the end with a diamond wheel on a Dremel, and grind it on a dedicated Aluminum Oxide wheel. But I don't clean it any more than that and there is often a heat mark from the grinding.

I cleaned the outside of the parts carefully, first with a Scotch-brite wheel and then with Acetone. But I didn't clean the inside. I should've thought of that.

There are several ways to do this. Use scrap material to do the testing. Because stainless is not that thermally conductive you can do it on lower amps (around 60 amps), use smaller size filler, really tight arc that is focused on the thicker plate. Don't try to focus the arc even a bit on the thinner part, it will jump. Just get close enough that your puddle will touch the thinner part, and the arc is focused on the thicker part. This method will result in slow travel speed and possibly cooking the parts of you don't have the feel for it.
The second method is using higher amperage (around 120amps), start the puddle away (1/8) from the thinner part and get it close enough so when you add the filler, the thinner part will fuse. For this method use larger filter (around 1/16).
I can't exactly explain those methods, it's mostly done by feel. You should also purge the parts.

The 60 amps won’t puddle the 1/8” plate. You need to be closer to 100 for that, but that is more than you want for the 1/16” tubing. So... hit the plate with all the amps and arc, lay a dab of filler in the root. Then taper your heat and wet the dab to the tube. Get 3-4 tacks in this manner.

Then use 0.45-1/16 filler, 90-95 amps. Lay the cup in a 45* angle pointed at the joint, only enough stick out to come just short of the weld. Hit it and go, but keep the wire pushed into the puddle. Stop often and reposition as you need.

If you want to run pulse... I’d use 40%, 15%, 1.2pps and set the machine to 105. Have a go-

Lippy wrote:I've read/watched a lot of info on welding thin to thick and know to focus the heat on the thicker piece and just to have it brush up against the thinner piece,

run enough amps that you puddle on the thicker part reasonable quickly. do not reduce your amps otherwise you will crawl and overheat it.
once you get the puddle you wash the puddle up to the thin material.
the trick is getting the speed of the washing right. its fairly quick. do not pause on the thin material, you barely even go onto it. adding filler, you can add filler first and wash it up, or wash up first then add filler to cool the puddle.

the other thing, is to do short segments and let it COOL DOWN.

That joint needs heaps of tacks, speed tacks every 1/2" or so, otherwise the flat sheet is gonna warp and make gaps to fill. That will make you sad. Practice the speed tack and settings on similar scrap till you get it right.
Then do the joint with pulse, again practice on scrap till you dial it in. 1/8" is getting thick for pulse, my go to is 50% on, 50% background, 2.5 pps and on the peddle to control heat. If you are using filler, use 1/16", laywire, move and pause with the pulse. No weaving.
Purge is a must in the tube.

cj737 wrote:The 60 amps won’t puddle the 1/8” plate.

It will, you won't get an average size puddle, but it will puddle enough so you can fuse the thicker and the thinner part. You don't want penetration here, just a small puddle. I've been using this method when I started welding for the same configuration on mild steel using 70 amps. Of course, mild steel is way more forgiving on overheating and slow travel speed, but I'm pretty sure that this will work on stainless as well, just stop very often and wait for the part to cool down.
I've also used nitrogen to purge austenitic stainless, and it feels like it has more cooling effect on the part compared to argon.