Stainless Welding

[ccracin]

I'm not sure where to put this. Mods feel free to move it as needed. I am almost done fitting our fuel cell. It is made from 16ga 304SS. I will be TIG welding it together. My question for those of you that may have done this is do you back purge the welds with Argon? I know this is the "Best and Correct" thing to do, but it will take more investment in regulator, hose, time. I have done some test pieces and the back side of the welds are not "pretty", but look sound. When I metal finish the welds they look good with no porosity. My other thought would be to try some Hastaloy W TIG rod. This is a good "catch all" rod that may not be as picky as 308 rod. I just wanted to get some input. Thanks! :cheers:

[Garage Dog 65]

There is a flux paste for stainless that you can brush onto the back so you don't need to back-gas it. I'll have to look it up - I have the docs at home in a welding folder....

Jim

[ccracin]

There is a flux paste for stainless that you can brush onto the back so you don't need to back-gas it. I'll have to look it up - I have the docs at home in a welding folder....

Jim

Thanks buddy. I may have to take back my comment about the size of your...........welding table! :lol:

[Garage Dog 65]

Solarflux

[ccracin]

Little car, little welding table, HUGE socks, I'm just saying. :lol:

Ah....yea, well back to Solarflux. I looked the stuff up. Looks like a potential solution. My concern is the residue left behind inside the tank. I'm not sure if exposure to fuel continually would dissolve it and cause me problems. Whatcha think?

[parsonsj]

On a fuel tank, you really ought to back purge. Too many things can go wrong when fuel drips or leaks, and all precautions should be taken. Free advice, and worth every penny!

[ccracin]

Thanks John. We are getting a cost on a dual tap flow meter and hose. Hopefully it won't be too bad. We'll see.

[parsonsj]

I back purge with two cylinders and two flow meters. Something like this:

http://image.superchevy.com/f/32344126+w750+st0/sucp-1104-21-o+how-to-make-custom-headers+.jpgj

Having a second cylinder around really helps prevent the dreaded "run out of gas on Saturday afternoon" problem that can ruin a weekend. :)

[ccracin]

Been there absolutely. We try to stay on top of it. 2 cylinders is on the list for sure though. What would you say to back purging with the cylinder I have on my MIG welder with 75/25?

[parsonsj]

Using CO2 (the 25 in 75/25) is controversial. The little nubbies you see on a non-back-purged SS weld are carbon based, and having CO2 present doesn't prevent them from forming, and increases the carbon content of the resultant weld, resulting in it being more brittle.

On the other hand, there are folks who claim it works well...

Your decision, but I don't do it. Argon all the way for me.

[LS1NOVA]

You can tee off the regulator line and just use a hose with a ball valve to regulate the purge flow. You will have to listen to the flow and adjust the regulator and ball valve. Its not exact, but does save from an dual regulator if it is not something you do regularly. I used this method for Tig welding some stainless exhaust and turbo pipes.

Solar flux works great, but I wouldnt use it inside a gas tank.

[Croaker]

Definitely back-purge to prevent sugaring. And avoid the 75/25, go with the pure Argon.

As for rods, if you're looking to pick up something that can work on multiple projects, 309L will weld stainless-to-stainless as well as stainless-to-ms.

If you're just buying for this project, 308L is better for 304 to 304.