Welding 1/4" Steel( and thicker) multi-pass

[chpwags]

Hi I am building a got trikes tube bender and have to weld 1/4" 2x2 tubing and some tabs that are 1/2" and 5/8". I have a Miller Dynasty 200Dx and would like to tig weld it together using multiple passes. I was wondering what is the best way to go about this, the more I read about multipass welding the more confused I get because no 2 people seem to do it in the same way. I am running my welder on 110 currently but just built an extension chord that I can run inside to plug into my dryer plug if needed.

I did a test piece where i welded two pieces of tubing together in a L shape. I beveled the 2 sides of the 1/4" tubing so that it was about .150-165" thick. The other to sides i did not bevel because the round corners of the tubing acted like a bevel and and allowed me to get penetration. The first passes were done at 150amps with the pedal maxed out almost all the way. I had read you should use 60/80% on the cap passes so i turned the amperage down to 105 but am not sure if that was the right call especially since I went to eat supper between the the root passes and the cap passes so the piece cooled. I was also using 3/32" tungsten with 3/32" er70s-2 filler. I did 2 passes on 3 of the sides and 3 passes on the fillet joint.

I was wondering if the was a better way to do this or if anyone else has done it in a different manner?

For the 1/2" and 5/8" tabs I have access to both sides to weld so I can bevel both sides. How much material should I leave between when I bevel (believe that called a land)?

Another note I took the tig welding course at the local college 5 years ago but We never covered multipass tig welding. I have also forgotten most of the terminology so my post my be lacking some of the technical terms people are used to using.

[Olivero]

Well, I would go ahead and stick it if it was me, much easier to get penetration BUT if you must insist.

I would do what you are doing, bevel the pieces, turn it higher than 105 though, I would put it at like 130-140.

Doing multiple pass might not be a good idea, the more you weld on it, the more brittle and weak the area around the weld becomes. If it was me, I would bevel both sides or just one with a deep bevel and then just do 1 big pass, don't do it all at once but don't go welding over it again and again and again as it will weaken everything around it. Just keep it hot and zigzag back through the seam while you pour that rod into the weld and you just keep it going, not sure how long your seams are but make sure to tack the pieces really well before you start welding otherwise, it might move and that sucks because it won't move back as easy.

I once warped 3/8" flat bar by doing multiple passes, too fast and too many, won't do much good. Better to just hit it once, and hit it hard. If you make it through the weld without anything messed up, you are golden.

But once again, Stick is much easier, if you got a stinger, get some 3/32" or 1/8" rods and just run them sticks and you should be all good.

I used to consider TIG as the holy mother and would only TIG no matter what. Then one day I ran out of Argon and had no choice but to pull out the stinger, got some good burns on that, don't recommend sticking overhead as your first attempt but I learned my lesson and now I only TIG Stainless and Aluminum, Steel is always stick unless its some really small welding needed or its gotta be fused or something where stick is not feasible.
But it sounds like stick might be feasible here. If bead width is not a concern, I would get some 1/8" rods and just run those puppies as high as they can go, turn your dig to 100 and you will see penetration.

Let me know how it goes!

[tarry99]

That Miller 200 DX should be fine on 1/4" single pass especially tubing that does not heat sink like plate would............using 3/32" Tungsten and filler as long as you can tap into the 220v.....that circuit should have at least a 40-50 amp breaker and likewise the extension cord should also be rated as high as possible..........I've got a 280 DX here and I weld 1/4" plate all the time with an initial set of 150 amps , but on my 280 after welding it flashes average amperage for the last weld and when welding 1/4" I rarely see anything over 125 -130 amp average.

I have no problem with stick other than the mess it makes ..............I also have a Miller 211 here , but the 280 DX see's most of the activity.