Super Duplex CE8MN - Saveable or not?

[Hercules28]

Dear all,

I got a Super duplex stainless steel CE8MN and although composition seems in spec the ratio of ferrite to austenite is nowhere near 50-50.

Take a look at the micrograph. Etchant is Murakami which colors the Ferrite. I would say that I see 20-30% Ferrite which as you understand will cause reduced mechanical properties that are out of spec.

The castings have been heat treated with a resulting hardness of 260HV.

Q: Is it possible to alter the % ferrite to austenite ratio by tailoring the heat treatment? Or am I stuck with the schaeffler diagram which is based on the composition.?

Thanks,

Herc

 

[mcguire]

If the composition, especially the nitrogen, is correct, you may be able to do a high temperature solution anneal to grow the ferrite, say 1100C.

Michael McGuire

http://stainlesssteelforengineers.blogspot.com/

 

[arunmrao]

Hope they are raw castings to be reheat treated. If they have provided a test bar,you may want to test in a small furnace for the results.

_____________________________________
"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year

 

[Guest102023]

Resolutionize and cool by the book; i.e. manufacturer's process.

 

[EdStainless]

Yes, changing the anneal temp will shift the AF ratio.
A higher anneal temp with very aggressive cooling will result in higher ferrite levels. If you cool fast enough you will have higher than equilibrium amounts.

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