Exhaust materials for Induction Furnace - SS vs Copper

[tryangle]

We're in a situation with our induction furnaces. We heat treat up to 2400C. Our susceptors are graphite but we require an exhaust tube that's exposed to plant atmosphere for about 8" above the top furnace coil. Since graphite will oxidize at that temp we use a Copper tube that is cooled by a water cooled copper (type L) spiral jacket.

We recently had a failure of the copper tubing that cools the exhaust tube and water being sprayed on hot carbon black caused an explosion that put a hole in the ceiling.

So now I'm exploring our options for exhaust materials. I was thinking of using a copper tube with 304 SS tubing to cool it. My concerns are that the ferrite content in Stainless Steel would conduct more heat due to the induction field and that its heat transfer potential is much less than that of copper.

Any ideas would be much appreciated.

 

[CoryPad]

Are ceramics not possible?

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[tryangle]

Ceramics may be an option, I will look into it. Can you think of an appropriate one off hand?

 

[EdStainless]

for ceramics look at a lower density one that can handle thermal shock, perhaps a Mullite would do.

You could make the entire unit stanless, weld the cooling tube in place. I don't like the options for fastening the Cu to stainless. Brazing is the only good option.
For an all stainless option you could either use a low ferite grade (309 or 310) or you could anneal the assemble after the fabrication.
If you go stainless make the tube thinner. Have you thought about not cooling it? At least not close to the bottom? I hate water above a furnace.

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