oxy welding 409 s.s. to mild m.s.

[butterfly effect]

Is it ok to oxyweld 409 s.s. to m.s? If so what filler rods are used? I make mufflers using m.s. but I am thinking of using 409 s.s. perforated tube internally which would be but welded to m.s. tube inside the muffler. I tried it and it seems to work using m.s. filler rod but is there a problem?

 

[hotrodder]

309L is the correct wire. Welding stainless (or stainless to mild steel) with mild steel wire can result in brittle welds although you should get away with it for an exhaust. Again not likely to be an issue for an exhaust (especially when it's part mild steel) but really need to use flux for welding stainless with oxy fuel

 

[TechnicAl]

Exhaust gases contain Sulphur. Sulphur likes Nickel so if you use a filler that contains Nickel the gases will leach out the Nickel ie the weld will corrode.
This is why they use 409.....straight 12 / 13% Cr and no Nickel.

Hotrodder is right 309L is the usual choice and it will work but it will corrode quicker than it would normally. 307 is better because it has less Nickel. Many of the mass producers use 307.

In your case where I am assuming you are not mass producing these the mild steel you have tried will probably last long enough. If you find they are cracking or falling apart you may need to use 309L as its more readily available than 307.

 

[butterfly effect]

Thanks guys. I will go to boc and buy filler rod 307 and flux and give it a go.