I need to weld stainless to carbon steel. I believe the stainless is 304 and the carbon steel is A36. The stainless was a solid piece of 4" round that was drilled out 2-1/2" and threaded, leaving approx 3/4" side wall. The piece of A36 is 1/2" thick plate with a 2-1/2" hole to line up with the stainless. The weld will be a multiple pass fillet, I don't know the size of the weld yet. The application is structural and will hold the flag mechanism at the top of a 36" diameter flag pole.
My question is can this be done and if so how? I would like to MIG weld if possible and if not Stick weld. So I need to know filler metal, gas mix, preheat, any special prep, and etc.
Any help would be greatly appreciated.
Thanks,
BF
Consider Inco 82 (MIG) use Argon 75%- Helium 25%. For stick you might try Inco 182 or 309L with ether process.
For stick you need 309 SS rod, I'd go with this, less $$$$ and trouble than setting up the mig.
For mig you need 309 SS wire and either 99/1 or 98/2 Ar/O2, or 95/5 Ar/CO2.
If part of the assembly is carbon steel, then apparently the customer does not really require the corrosion resistance of SS, so why is it even being used?
I agree with SWP. Use the 309 filler 98/2 ar/co2
Inco 182 is a good choice but a bit overkill in this application, IMO. If you were concerned with a pressure boundary or high stress or higher temp and carbon migration, etc the nickel is the way to go.
Also I think keeping the gas simple is adequate here as well. 98/2 is good. Even 75/25 if thats readily available. It will spread you penetration pattern a little more, give a little more energy to the puddle, but will be more highly oxidized. You'll generally see more surface deposits with 75/25.
By welderwv 
Date 07-19-2007 19:48
Edited 07-19-2007 19:50
309L flux cored w/ 75% Ar & 25% CO2 would be good choice also. If short circuit mig 309 filler w/ tri-mix is best, I think. 90% helium, 7.5% ar, 2.5% co2. Both are great for out of position welding.
By RonG 
Date 07-19-2007 19:52
Edited 07-21-2007 14:38
Oops! Preheat! You ask about that also. 200'F should be adequate. The other replys you received about 309 are most likely your best option. I sometimes forget what industry I am working in and do not always consider the cost of the filler material because procedures we have in place leave no room for it.
BF,
Joining an austenitic stainless steel such as 304 to a carbon steel is very common and is relatively simple. If the weld must be done vertical or out of position I would recommend you use a E309T1 which is a gas shielded flux core wire. McKay makes a wire called ChromaWeld 309LT1. Use a 75% argon/25% CO2 gas. This flux core will allow you to weld out of position with better root fusion than using a solid wire short circuit transfer with a trimx helium based gas. As this wire is all position you could also use it instead of a spray transfer solid wire, its up to you.
If the the weld can be done in the flat or horizontal position and you want to use a solid wire, I would recommend you use a spray transfer with at least an .045 diameter ER309 wire. You can use a 98% argon-2 % CO2 gas or even a 95% argon-5% CO2 gas. Keep in mind that this won't work if you are welding out of position as the weld puddle will be much too fluid.
304 stainless is nonallotropic and A36 has low carbon equivalency which means you won't need to preheat as long as your parts are room temperature, which shouldn't be much of a problem now that its July.
Thanks for all the responses. It sounds like this project won't be as difficult as originally thought.
Thanks again,
BF
Same old........Weld it, but just remember tha stainless retains hydrogen different than a36...........
