Exhaust Material

I had a similar conversation with an aircraft exhaust manufacturer who was working on a custom Rotax 912iS exhaust system for an SLSA manufacturer.  He told me the Rotax exhaust parts were made of the materials listed below.  He seemed to know what he was talking about.  He also told me that the tubes should be purged with a shield gas (argon) while welding. The cracks typically show up in heat affected zone (HAZ] of the weld.  

Tubing, 304 SS

Muffler components, 304 SS.

Male ball sockets, 304 ss.

Cylinder connector OEM Rotax part, 316 SS.

Exhaust flange OEM Rotax, 304 SS

We've welded numerous broken exhaust pipes and they are all still good. Just find a good welder.

Thanks for the info!!!

Jeff Blakeslee wrote:

I had a similar conversation with an aircraft exhaust manufacturer who was working on a custom Rotax 912iS exhaust system for an SLSA manufacturer.  He told me the Rotax exhaust parts were made of the materials listed below.  He seemed to know what he was talking about.  He also told me that the tubes should be purged with a shield gas (argon) while welding. The cracks typically show up in heat affected zone (HAZ] of the weld.  

Tubing, 304 SS

Muffler components, 304 SS.

Male ball sockets, 304 ss.

Cylinder connector OEM Rotax part, 316 SS.

Exhaust flange OEM Rotax, 304 SS

So if I'm understanding the above, does that mean the pipe assembly is composed of  welding a 316 SS cylinder flange to a 304  SS tube?

Scott,

I wondered about that also.  I speculate that the cylinder flange is thicker than the tubing. And I know that 316 melts a bit lower than 304 (about 50 deg f lower). So maybe using the two different materials helps heat control. In other words, maybe it’s good the thicker material melts a bit easier than the thinner material. I’m way out on a limb here because I’m not a welding expert, but I believe when joining the two, 316 is the preferred filler. I’m all for a certified welder to chime in and tell me how wrong I am.