People use stainless fillers like 309 and 312 to weld steels of unknown metallurgy all the time. Some people weld everything with 312. There's no harm in what you are doing so long as the different thermal expansion rates of the dissimilar metals won't come into play. In other words, I wouldn't do it for something that is going to be heated and cooled a lot, like a wood stove or an automotive exhaust system.

 

/\ /\ Correct information above. Lost a race years ago because I welded a stainless pipe to a carbon pipe close to the engine. Heat finally got to it with one lap to go. Oh well still got 2nd.

 

So long as you are aware of the limitations it is fine. Technically you should probably be using like 309 filler, but 70S-6 seems to work just fine.

 

What is the application?
What grade stainless?
Will you be grinding or blending the weld?
Will the final piece be coated?


I have joined stainless and mild steel, but that was in a decorative fashion or an art piece.

Sent from my SM-G996U using Tapatalk

 

I have done it with E309/309L. In fact, my family's Bouldin & Lawson Maxi Flat Filler has the only known 304 stainless soil hopper lining (after it started rusting out). They no longer sell that model, but the new ones all have shiny unpainted soil hoppers (304 I'll bet).

 

greenhouse? nursery?


Sent from my iPad using Tapatalk

 

Year-round full service florist and greenhouses selling retail. Outdoor garden center in the summer. Residential neighborhood grew up around the site over the past 70 years or so.

About 20K square feet of glass greenhouses, all reglazed in the 70's with aluminum bars. Some plastic structures as well.

 

I do it all the time, replacing rusted sections of pipe with staino using 309 wire. That's it's job, joining dissimilar steels.

 

Yes you can weld stainless to carbon steel. For the best performance 309/309L is very good. If you don't know the exact composition then 312 is the better choice. Both have additional ferrites to check cracking and carbide precipitation. Given the choice I always pull out the 312. I did produce weld procedures for using ER70s-2 for welding 304 to A36 steel for economics so that works too. But the 70s-2 is less corrosion resistant.