321 stainless

[hunter59]

I am needing a starting suggestion for settings for welding up some 2" o.d. tubing 321 with .035 wall. All miter joints and some butt welds. I have a dynasty 350. I will be plugging and back purging. What size tungsten and what size wire. Thank you in advance.

[OscarJr]

that thin of a wall thickness, 0.030-0.035" wire, 347 alloy. I'd try to use pulse to stiffen the arc and reduce heat input. Ultimately it's up to you to try it out on scrap tubing first, but I'd try around 60-100PPS, 60A, 35-40% background, 40-50% on-time. Try it out on scrap, and fine-tune from there. Tungsten, anything good on DC such as 2%Th, 2%La, etc, etc will work just fine. 1/16" diameter, 3x taper length, pointed end.

[CODE4]

You will not need any wire. As long as you have solid fitups, walk the cup on it and fuse it. I weld process piping for a living and all 16/14/12 ga tubing is TIG welded without any filler. Adding filler will introduce more of a chance for the material to draw, especially if you have any gaps in your fit ups.

Such a thin wall will not need any more than 40-45 amps. 1/16" tungsten will be best, 3/32 will work. I use 3/32" 2% thoriated on everything from 30-150 amps. The arc just starts better at certain ranges. Majority of process piping is done with miller maxstar 150s using lift arc method.

[Ltbadd]

Adding filler will introduce more of a chance for the material to draw, especially if you have any gaps in your fit ups.

Such a thin wall will not need any more than 40-45 amps. 1/16" tungsten will be best, 3/32 will work. I use 3/32" 2% thoriated on everything from 30-150 amps. The arc just starts better at certain ranges. Majority of process piping is done with miller maxstar 150s using lift arc method.

What do you mean by "draw" here? Maybe suck back?

Walking the cup on a thin wall tube, I've never seen that done. I don't doubt you or your skills, just haven't seen that.

BTW I'd really like to see a pic of that weld on thin wall tubing, fused by walking the cup. I'd think walking the cup would be too wide, spend too much time on a thin wall tube, fusion joint. Post that pic!

If you had a 90° mitre joint, you'd walk the cup on that?