[Goldhawg]

I'm trying to dial in my welds; ultimately this is for a gas tank. I'm using an aluminum piece flush with the stainless on the back, and using some copper chill blocks. I'm fairly happy with the weld. The question is how much "sugaring" is acceptable on the back side of the weld. I had a lot more on a previous sample, but just dialed down the amps to 65 with 1 PPS. Using a synchrowave 210 with 20 CFH.

[Oscar]

I see very little sugaring on the backside. If you're worried about it, you can make yourself an aluminum chill block from the back, just get two 1/4" thick flat bar to make a 90° angle and weld them together on the inside corner, to kind of simulate a rectangular aluminum block that the pieces are resting on. It will limit the exposure of oxygen by effectively displacing it, and will help draw out even more heat. Even steel would help out by physically displacing the oxygen out of that area. Heatsink, not so much as aluminum, but even it would help at least a little bit. Of course you wouldn't be able to do this to all pieces as you are fabricating the entire assembly, but it could help during part of the process.

[Arclight Ironworks]

@ Goldhawg - your welds look clean with minimal carbide precip in the root side of your OCJ. Rest the root faces of your joint sections on Copper or Aluminum chill blocks. The large differential in the heat of thermal coductivity between SS and Cu/Al helps tame the process.

Have a recomendation for you to try out for autogenously running your lines; however, your SW210 is relegated to 50% Peak Amperage and 50% Background Amperage during pulsing.

On our Dynasty 200DX and our industry partners 280DX and 350DX rigs, we use these settings for 18ga stainless: Pulsed. 0.8-0.9pps, 5-7% peak, 5%background, 100-105A; 0.8sec PreFlow and 15-20sec PostFlow. Note, approach is ideal for PJP versus CJP. Complete Joint Preparation on 18ga would be a horse of a slightly different color.

Executed properly with machine settings optimized and your technique dialed in, you'll achieve near total Golden lines with minimal to zero heat tint in the HAZ.

[Goldhawg]

I did have a piece of aluminum angle backing the inner side of the weld. Re welding it w/o filler, I had done that earlier on some practice material and I did have less sugaring because I was able to concentrate more on a steady travel speed. However this obviously leaves the corner a bit thinner (and I'm already working with 18 gauge). So the question is it better to have a bit of surgaring with added rod, or almost none with just melting the two panels together? This is for a gas tank for an older car I'm building, so I can't afford any cracking leading to leaks in the future.

[Oscar]

Three "real" solution IMO is to bite the bullet and back purge everything. Then you won't have any worries. You can get full penetration and no sugaring. It can be as simple as obtaining a dual flowmeter to run a separate hose for backpurging.

[kiwi2wheels]

To add to what Oscar suggested, I'd also suggest using a flanged return type joint as opposed to an edge to edge type.

Then the tank will be bullet proof and you could also use Cleco fasteners for assembly.

[Goldhawg]

One other option. will the Solar Flux work? I was reading that it leaves some sort of residue and not sure how that would interact with gasoline down the road. Thoughts?

[Goldhawg]

Super stoked. Tried out my new FUPA 12 cup, increased CFH to 25 and lowered to 55A at .7 PPS. Almost perfect golden color (except the first part where I went back to fill my initial tack) and the back side doesn't show any sugaring. Using 1/4" copper chill blocks with aluminum angle on the back side. I think I'm ready to make a tank!

[pgk]

Looks good