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How to obtain RH950 Condition

January 11, 2010

It is necessary to perform cryogenic treatment (-730C) to reach RH950 Condition? As known, this step only completes the martensite transformation.
And why this step relatively is so long?
CH Condition means (Cold Worked). What about R and T meanings?

Daniel Kurgansky
Materials Engineer - Israel

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Hello Daniel!

You're talking about the semi-austenitic precipitation hardening stainless steels, such as 17-7 and 15-7. These are not fully martensitic after solution treating, and need additional "pushing" to fully transform. Hence you either cold work the material, to get to condition C, or you give it an austenite conditioning step which will cause full transformation to martensite. The R and the T treatments are two that are recognized as successful, and are documented in heat treat specifications such as AMS2759/3 or Mil-H-6875.

You'd likely benefit from reading DMIC report 111, from April 1959, on "The Physical Metallurgy of Precipitation Hardening Stainless Steels". Send me an e-mail and I'll send you a copy. I'm not that hard to find...

Lee Gearhart
metallurgist - E. Aurora, New York
January 14, 2010