Stainless Filler Selection

[Laiky]

As i SLOWLY march forward with my Tig Cooler build, i am test welding (practicing) on some sample coupons of the matrial i am using. I do not know the stainless alloy i am using. The guy i bought it from thought it was 4xx, he sais he can weld it with 308. That works according to my research. The stainless is very shiny, magnetic and quite soft. It does weld with 308. My question is this: I am welding .035 sheet on the outside corner. It welds well without filler leaving a beautiful golden bead. The problem is i need to add a drop of filler to get the bead going without melting away. The section that gets the filler appears gray and not shiny and golden. Is there a general purpose 4xx filler? It seems that every 4xx alloy gets a different recommended filler but 308 is acceptable.

I could also use any tips for wlding thin metal you guys have. I am running 35-40 amps 4-6 pps with 70%/30% peak/backround.

[BigDTig]

Back up your stainless outside corner joints with a thicker piece of alum angle iron. Wicks the heat right away. Copper works too, but it's only sold in solids around here; heavy.

Fitup is key, but on an outside corner joint I might typically use a gas lens, 1/16 or .040 tungsten, about 10-11cfh argon, and 30-40 amps. Just wiggle right along the joint and seal the two pieces together. A little extra heat right at first will bring the beads together. 90% of my stainless welds are filler-free.

On a long weld keep in mind stainless' tendency to warp quite profoundly. A tack every inch or so is good practice.

I use .040 308L filler a for just dabbing every once in a while to keep a bead running.

[Laiky]

Thanks, that sounds right based on what little i've experienced. I am using an .040" 2% lanthanated tungsten. If i fit it up better, you think i'll have better luck starting the bead? I have some thin copper sheet, i'll try that for backing. i am also backgasing the stainless. Do you think i can avoid that if i use copper?

do you think it is adviseable to use MIG to tack the sheets?

[MAC702]

do you think it is adviseable to use MIG to tack the sheets?

Since MIG requires the filler, I would think it would be difficult to have a tack that would disappear when you did the rest of the welding.