Question for ye:

I'm fabbing up a Turbo manifold for rotary motor. Exhaust temps will routinely be in the 800s (C), and maybe higher). I have an engine-flange already, but it's made of mild steel. The butt-welds (heehee) are only available in 304 SS for the tight bend radii I want (2"). I'm concerned about corrosion,fatigue, and expansion rates after welding the two metals together.

I've heard two schools of thought:

1) use Nickel 55 rods as they increase pliability so that when the MS and SS expand at different rates under high temps, the seams won't crack.

2) Use E 309 rods as they prevent corrosion, are easy to weld dissimilar metals together, and can withstand high temperatures (up to 1000 C).

Does anybody have any recommendations on what kind of rods to use to reduce both?

Much thanks,
Steve

P.S. Somebody else mentioned using ENiCrFe-2, but I'm unfamiliar with it.

 

Don't know much about the welding question, but: Why not make a new engine flange out of stainless and then not have to worry about it?

 

Use the 309 filler rod. That's what every certified welder has told me to do.

I'm currently building a bunch of headers for RX-8's, Cosmo 13B's and Mazdaspeed Protege's using 1/2" mild steel flanges and 304 SS primary tubes.
A 10lbs box of 309 filler rod isn't cheap either! lol....

 

Using a mild steel flange will be less likely to crack under extreme heat and flexing, the Mild steel flanges have a bit more give to them and they are cheaper than 1/2" SS by a longshot.

 

My experience doesn't include exhaust manifolds but I have done my fair share of welding. Any 300 series stainless rod is good for welding dissimilar steels. It is practically nickel rod. Which would be good also.

 

<---14 year vet welder. 3G plate and 6G high pressure pipe. Am also Cwi certed, Aws D1.1 structual, and Nuke certed.

Stick = 309.
Wire feed = stainless wire.

pre heat the welded area to 150 degrees but DO NOT exceed 300. The reason behind this is to assist the weldablity of the 2 metals, and to remove all moisture before weldment.

 

quick question, where are you getting these 2" radius 304 bends?

 

Mcmaster-carr. I've even got the part# handy: 45735K324. They're pricey though, $35 a pop for the 90 bend.

Many, many, many thanks everybody! This was very helpful.

Steve

 

Whats the thickness of those 90's?

 

They're schedule 10, .109" thick walls. Should be ok?

Steve

 

Oh nice, yeah schedule 10 is good stuff.

This is the latest header project for a Mazdaspeed Protege using mild steel flanges and schedule 10 304SS bends.

 

Any 300 series or higher, good heat/pre-heat before welding (higher then 150*f and lower then 230*f) and your good as gold. Let it cool slow, in otherwords, don't shock it with a wet rag, let it cool by itself or cover it in sand till its ambient.


~Mike..........