Welding stainless

[rattle_snake]

I have been researching how to better weld stainless and mixed types of materials. Looking for some feedback from those who have done custom SS systems.

I am looking to swap out stinger mufflers for some magnapacks. The Bolra tubing is 'austenite' (guessing 304 or something similar) and the magnaflow mufflers are 409. I have a Lincoln MIG, and was thinking of getting 309L or 316L wire, run 100% C02 and purge the inside of the tubing with C02. Option B is to tack weld the muffs on the car with the MIG and have a friend finish weld with a TIG. I am not concerned with the look of the weld, they cannot be seen and I am not going to polish the mufflers or tubing under the car.

 

[SlowSVT]

Tack it and get it TIG'ed

Why the CO2? Worried about scaling.

I think Magnaflo's are 300 series SS (400 series rusts).

 

[rattle_snake]

All I've got at this point is C02, which is not ideal but should work.

Magnaflow's FAQ calls out the materail they use as 409:
http://www.magnaflow.com/07techtips/faq/question32.asp

 

[SlowSVT]

That's odd

400 series SS has poor corrosion resistance. I made a set of brake rotors from 410 and they rust just splashing water on them. My Magnaflows don't have a spot of rust on them. A magnet should stick pretty good to 400 series but not so well to 300 series which is one way to find out.

 

[04cobra88]

If its not butt welded together with a gap for penetration I wouldn't worrie about purging..argon with tig is your best bet , even if you want to purge use argon for sure if its just a lap weld just tig it up and be on your way

 

[rattle_snake]

Finally got access to a TIG machine and got the new mufflers welded in. After a quick lesson, I did the welding myself. Results aren't pretty but at least its done with the right materials/gas. Upon further inspection of the Bolra stinger catback, I believe that only the mufflers are 300 series SS, and the tubing is something different (400 series ?). The corrosion on the muffler is a white layer of oxide, where as the tubing has a rust colored oxide similar to the factory exhaust.

 

[SlowSVT]

Finally got access to a TIG machine and got the new mufflers welded in. After a quick lesson, I did the welding myself. Results aren't pretty but at least its done with the right materials/gas. Upon further inspection of the Bolra stinger catback, I believe that only the mufflers are 300 series SS, and the tubing is something different (400 series ?). The corrosion on the muffler is a white layer of oxide, where as the tubing has a rust colored oxide similar to the factory exhaust.

The problem with combining 300 and 400 series SS is the corrosion from the 400 series pipe will start the 300 series SS to corrode