heat treatment nomenclature 1

[MVogl]

Can anyone explain the designations of heat treatments, specifically for precipitation hardened steels? I recently found a specification for 17-7PH TH1050, which I hadn't seen before. I believe 1050 is the heat treatment temperature. What do the T and H refer to?

 

[EdStainless]

T is transformation, or austenite conditioning, H is then aging.
17-7PH requires a 2 step process since it is stable as autenite when annealed.
The conditioning step actually forms a small amount of carbide, removing the caron leads to the austenite not being stable and both the formation of martensite and the superstauration of the Al. The aging then tempers the matensite and forms the Ni-Al precipitates.
There are really 3 final conditions for 17-7, TH1050, RH950, and CH900.
T is first 1400F, cooled to room temp, then aged at 1050F. Moderate strength and good ductility. The material must be annealed to start with.
R is more complicated, you start with 1750F. The higher temp lowers the Ms and Mf so much that you need to follow it with 8hrs at -100F, and then age at 950F. This is a high strength condition.
If the shape allows (wire or strip) and you can cold reduce it 50-60% then you can direct age at 900F for very high strength.

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P.E. Metallurgy, Plymouth Tube