Welding wire for stainless steel?

So I tried to weld a stainless coupler to my keggle for a ball valve setup which worked but after testing it overnight the weld is already showing signs of rusting. Cut the coupler back of and am trying to find some flux core stainless wire .035 or smaller so I can can have a weld that doesn't rust. Not an expert welder by any means just wanted to see if anyone else had similar issues?

Disclaimer - I am a total newb to welding and know very little.

Now... I was just doing a little research on this, and I saw that you need to use tri-mix gas for stainless mig welds, or they will rust. If I am wrong, folks, feel free to tell me so.

Anyway... were you using trimix?

That was I was kinda looking for. Whether I can use a flux core wire without gas or whether I'll need a different gas setup than the 75/25 argon o have now

98% Argon-2% CO2. The 90% Helium -7.5% Argon -2.5%CO2 Tri-Mix does not work as well as 98-2. ER308L stainless wire for 300 series stainless.

100% argon and 308 or 304 or 316 for filler. 0.023. or 0.030. or 0.035 diameter ekectrode for these thicknesses.

Using a CO2 mix gas in concentrations over 10% will have a negative effect on the metallurgy of the weld and adjacent area. Usually elevated hardness and high probability of cracking. You can pick up a 98/2 or 90/10 Ar/CO2 mix at the sametime you pick up a 10 lb spool of electrode.

I would not recommend flux core for this job. FC has its place and a brewing is not it.

Thanks everyone. Post pics when I get done.

You will still deal with rusting issues unless you remove all of the previous weld.

When welding, the base metals and filler mix together while molten so you may have an issue because the base metal(keggle) is so thin. Quite often you have to grind below the surface to remove all traces of a weld, and you don't have a lot of keggle wall thickness to spare.

I would wet the area after removing to old weld and wait to see if any rust develops. If it does then grind or sand a little more before welding on a new coupling. Just don't grind too much.

All is not lost if you can't stop it from rusting. In a case such as this it is a cosmetic issue, not a mechanical one.

Stainless welding requires proper process and prep to retain the rust free properties of the metal.... 75/25 on a mig aint it, you need to tig it with back gassing and 304 rod. 90/10 or 98/2 is good, but the 75/25 will embrittle the weld and allow martisite formation every time... Look it up in the J. F. Lincoln Arc Welding Procedure Manual and follow the procedure if you want a sanitary weld. Sorry

Wheelchair Bob (Retired Welder)

Cut the coupler completely, clean it up and silver solder a new one in place. MIG won't work for a sanitary weld. If it needs to be welded TIG it properly, or have someone who's done a lot of stainless sanitary welding do it.

I've go a nice keg with two ratty coupler welds I'm trying to fix. ARGH....

If I can make the assumption that this is preboil or on the boil kettle, then the weld process is less consequential then if it were on the cold side of the brew house.

Yes, there is a proper, proven way to do things. But as with all things except space travel and nuclear or biological experiments, there is wiggle room to achieve acceptable outcomes. While this may not be the bedt application for GMAW, it can still yield a decent result. The best chance of success is to purge the root side of the weld joint. This regardless of process.

Rbeckett said:

you need to tig it with back gassing and 304 rod. 90/10 or 98/2 is good, but the 75/25 will embrittle the weld and allow martisite formation every time... Look it up in the J. F. Lincoln Arc Welding Procedure Manual and follow the procedure if you want a sanitary weld. Sorry

Wheelchair Bob (Retired Welder)

Click to expand...

100% Argon is used when tig welding stainless, and 308L rod is used to weld 304.

They actually do make a gas-less flux core wire for welding stainless with a mig. I do know it's incredibly expensive though. Like $20 a pound.

For now I got a weldless fitting for it since its just the HLT. Once I get the proper gas I'll give it another go. Really just want to see if I can make it work with a MIG welder if at all possible since its what I have.