cryotreatment of 316L steel

[cryoteam]

Could you please give us any info on what kind of effect we would expect on a 316L liquid nitrogen straight immersion, If any? Furthermore is it possible that reheating of a 4340 steel to ambient temperature, after straight immerion to liquid nitrogen, could produce perlite/ferrite strucures? Thanks in advance.

 

[EdStainless]

316L and low temp, zero effect. It is used as piping to handle liquid hydrogen and helium all of the time.

The effects on 4130 will depend on what the structure was to start with. If it was poorly quenched or slack quenched and then cooled, you might get all sorts of strange structures.

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[TVP]

As EdStainless said, the microstructure of 4340 may be anything depending on what it was prior to low temperature exposure. Was it quenched and tempered? Normalized? Welded? Hot forged and slow cooled?

 

[Materials76]

All sorts of strange structures? I was under the impression that cryotreatment leads to a structure without retained austenite..
I dont really get it, the exact theory behind the process is seldom analyzed in the literature thus allowing a confusion behind the proper application of the process. Where is the problem with it? Which are the problems the researchers face? Is the need of speciallized equipment? No funds? What is the current trent on the cryogenic treatment, which is the next step?

 

[pwtomlin]

316L is primarily austentic, with some ferrite. I wouldn't expect this to change at low temperatures. If your 4340 underwent a vanilla quench and temper, I wouldn't expect any change in the structure (tempered matensite) unless you had some retained austenite. If you did, then you should see that austenite change to martensite.

I don't think there's much research on structural materials at cryogenic temperatures simply because there usually isn't much change microstructurally. The notable exception are alloys with sub-room temperature martensite finish tempeartures.