[MosquitoMoto]

Please excuse my crappy photos...and my crappy welding!

Here I am welding 5mm carbon steel plate to 3mm wall square carbon steel tubing. Amps are 60, using 8lpm argon, 2.4mm electrode (2% Lanth) and 2.4mm ER70-S2 filler. Number 7 gas lens.

I get a puddle going fast and everything behaves itself nicely, but in retrospect I can see where, on the tube, the arc is 'nibbling back' the metal on the tube, right at the edge of the puddle (left side of pic.)

Am I hanging around too long in one spot? Should I use more filler? Would love some tips on what is going on here.

Cheers,


Kym

[Otto Nobedder]

I think, if you were to cut that tube a few cm from the plate and look inside, you'd see a bunch of "push-through", meaning the heat on the thinner tube allowed the puddle to move toward the center. The trick here is simply to move fast on the tube side vs. the plate... Don't linger.

I suspect you're using a uniform motion, perhaps even a count (left... one, right... one) where the differing thicknesses require you to hold a beat and a half on the heavy side but only half a beat on the thin side (example only; not actual timing advice). The heat on the thick side will carry through to the thin material to a degree, so it's a matter of timing your motions.

Steve S

[MosquitoMoto]

Thanks Steve.

While there's no push through, I think you're right about me spending something close to an equal amount of time with the arc on the tube (thinner) side as on the plate (thicker).

When I first started Tigging I used to weld too cold and too slow, taking ages to get a puddle started, wasting gas, sinking lots of heat into the work. Now I'm welding at higher amps, faster and I think a little better...but still definitely need to pay more attention to details and technique.

Thanks again for your help.


Kym

[exnailpounder]

Welding thick to thin is always a challenge. I do quite a bit of it and I have found what works is to concentrate your heat on the thicker metal and then wash onto the thinner metal. Choosing amps gets to be a challenge as you will probably need enough amps to easily blow through your thinner metal. Thats where pedal control comes into play. Do you have the same undercutting on filet welds? How is your fitup? Trying weld big gaps causes undercutting. The only reason I ask is because it looks like you kind of lay-wired that weld. NIce tight fit and you can stack dimes alot easier. Nice thing about TIG is if you get an ugly weld, you can go over it again and pretty it up.

[LtBadd]

All good advice, you can add the filler on the thinner metal side, and keep the puddle full

[MosquitoMoto]

Welding thick to thin is always a challenge. I do quite a bit of it and I have found what works is to concentrate your heat on the thicker metal and then wash onto the thinner metal. Choosing amps gets to be a challenge as you will probably need enough amps to easily blow through your thinner metal. Thats where pedal control comes into play. Do you have the same undercutting on filet welds? How is your fitup? Trying weld big gaps causes undercutting. The only reason I ask is because it looks like you kind of lay-wired that weld. NIce tight fit and you can stack dimes alot easier. Nice thing about TIG is if you get an ugly weld, you can go over it again and pretty it up.

Hey Ex, thanks for your thoughts.

For once in my life, the fit up was actually good and tight! No fillet welds on this project but for what it's worth, I am also seeing this same undercutting where I am welding same thickness tube together.


Kym

[Poland308]

I try to make a mental note to position my body so the torch angle points to the thick side. Not always possible but the timing thing is key. You may want to weld it in several passes not just one.

[MosquitoMoto]

I try to make a mental note to position my body so the torch angle points to the thick side. Not always possible but the timing thing is key. You may want to weld it in several passes not just one.

I agree body position is very important - am often surprised at how great a difference being 'just a little out of kilter' can make. I try to make a point of rehearsing my runs like Jody often demonstrates.

I don't know how I'd go about welding several passes but I'm happy to hear your suggestions. Like most parts I weld this one is tiny - the main steel tube is just 1 inch wide.


Kym

[Braehill]

Kym,
When I have to weld thin tubing to thicker plate I usually start my puddle about 2 mm into the plate and place my filler in the joint where they meet. A slight weave will let the leading edge of the puddle draw the filler in as you progress. I always add the filler to the thin side as was mentioned and on a fillet weld I add it to the top leg. It also helps to start your puddle on the plate 1 or 2 mm before the tubing to get some heat in the thicker part.

The filler metal is drawn to the heat and the localized heat will favor the thinner metal but it can't retain the heat like the thicker side can. When you move the torch back to the thicker piece it wants to draw the heat out of the thinner part, taking the puddle with it. If there isn't enough filler there to fill the puddle as it cools it will be under filled or even undercut as you have there. I tend to push the filler in and use a laywire technique in a case like yours, more often than not I end up overfilled.

That's way harder to explain than it is to actually weld.

Len

[MosquitoMoto]

Kym,
When I have to weld thin tubing to thicker plate I usually start my puddle about 2 mm into the plate and place my filler in the joint where they meet. A slight weave will let the leading edge of the puddle draw the filler in as you progress. I always add the filler to the thin side as was mentioned and on a fillet weld I add it to the top leg. It also helps to start your puddle on the plate 1 or 2 mm before the tubing to get some heat in the thicker part.

The filler metal is drawn to the heat and the localized heat will favor the thinner metal but it can't retain the heat like the thicker side can. When you move the torch back to the thicker piece it wants to draw the heat out of the thinner part, taking the puddle with it. If there isn't enough filler there to fill the puddle as it cools it will be under filled or even undercut as you have there. I tend to push the filler in and use a laywire technique in a case like yours, more often than not I end up overfilled.

That's way harder to explain than it is to actually weld.

Len

Lenny -


Thank you. As always, a carefully considered and clearly conveyed piece of advice. Perfect.

I'm going to let that soak in for awhile and then go light up, enlightened as I now am.

I owe you a beer.


Kym

[motox]

kym,
all great advice, try experimenting with rod size as well.
craig

[GarryH]

"Here I am welding 5mm carbon steel plate to 3mm wall square carbon steel tubing. Amps are 60, using 8lpm argon, 2.4mm electrode (2% Lanth) and 2.4mm ER70-S2 filler. Number 7 gas lens."

Hi Kym, I am surprised at the low Amps where the minimum material thickness is 3mm. If I were to just try a 3mm butt weld I would be in the 90-120 Amp range and probably moving pretty quickly. No expert, but 60A just seems low to me. Any others got comments on that? Am I way out in my thinking?

[ignatz200]

I'm in agreement with Garry on the low amps. Over here on my side of the pond the rule is 25 amps for every millimeter of thickness for ordinary steel. That would make a minimum setting of 75 amps for the three mm of your thinnest plate.

Of course, if you can handle it, upping the amps slightly will allow one (if practiced) to move the puddle along slightly faster with a slightly smaller heat affected zone (HAZ). From your photo it looks like the HAZ has spread out pretty far away from the weld area.

And then, of course, you are joining 3 mm steel to 5 mm steel, so, yeah, I'm pretty much with Garry on his idea of starting out somewhere between 80 and 120 amps.

[MosquitoMoto]

I'm in agreement with Garry on the low amps. Over here on my side of the pond the rule is 25 amps for every millimeter of thickness for ordinary steel. That would make a minimum setting of 75 amps for the three mm of your thinnest plate.

Of course, if you can handle it, upping the amps slightly will allow one (if practiced) to move the puddle along slightly faster with a slightly smaller heat affected zone (HAZ). From your photo it looks like the HAZ has spread out pretty far away from the weld area.

And then, of course, you are joining 3 mm steel to 5 mm steel, so, yeah, I'm pretty much with Garry on his idea of starting out somewhere between 80 and 120 amps.

This is interesting.

After starting my Tig experience definitely moving too slow and at amps too low, lately I've been ramping up, with the thought being that skilled Tig welders (not me yet!) often use high amps to get a puddle going fast, move faster, put less heat into the work.

I started out at 90 amps on this piece and it was way too much - from puddle to melt through in no time, even lighting up on the thick plate. I backed off in 5 amp increments and wound up at 60 amps. Still get a puddle very quickly and can move out nicely, but these are short welds (1 inch long) and I can't go much hotter or I am in trouble. My skills are still very limited.

But that said, I often see amps on videos/web from the U.S that seem very high to me. Most recent one that sticks out to me is Jody welding an outside corner joint on 1mm aluminium at 83 amps. I'd never (again, I have no skills...) be able to weld that piece on any more than 50 amps.

How great a variation is there between machines? Is one machine's '50 amps' often a long way from another's '50 amps?'


Kym