17-4PH Material
17-4PH Material
(OP)
Quick question - well, hopefully.
We have a part which specifies using 17-4PH, heat treated to 34 R/C Min. Since we buy this material in Cond "A", already above the min hardness requirements, are there any advantages to post (or pre)-machining heat treat? Seems like we machine the Condition A, as is, and verify the hardness requirements. Am I missing something? I've had experiences in machining the H900 - H1150M grades,but they all had higher hardness requirements.
We have a part which specifies using 17-4PH, heat treated to 34 R/C Min. Since we buy this material in Cond "A", already above the min hardness requirements, are there any advantages to post (or pre)-machining heat treat? Seems like we machine the Condition A, as is, and verify the hardness requirements. Am I missing something? I've had experiences in machining the H900 - H1150M grades,but they all had higher hardness requirements.





RE: 17-4PH Material
RE: 17-4PH Material
Would it be acceptable to basically change the material spec to say "17-4PH, Condition A" .vs. "17-4PH Heat treated to R/C 34 Min"
RE: 17-4PH Material
I've have reservations about using 17/4 in Cond. A in dynamic situations.
RE: 17-4PH Material
The properties are highly variable and the ductility may be low.
If you don't need it very strong use the H1150 or H1150M to maximize toughness.
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http://www.trent-tube.com/contact/Tech_Assist.cfm
RE: 17-4PH Material
in Condition A or T."
RE: 17-4PH Material
It is also dimensionally unstable if heated. Suppliers don't guarantee mechanical properties in Condition A, so evidentally experience has shown that it shouldn't be used in this condition, as pointed out in above responses.
Hardness will vary due to variations in composition, solution cooling rate, and aging heat treatment. Carpenter Stainless Steels gives 'typical' values:
Condition A HRC 36
H 900 HRC 44
H1025 HRC 38
H1075 HRC 36
H1150 HRC 33
H1150M HRC 29
Note that Condition A has the same typical hardness as H1075. I expect HRC's to vary within +10% (maybe what israelkk meant?)
* "For applications where stress corrosion cracking is a possibility, 17-4 material should be aged at the highest temperature compatible with the strength requirements and a temperature not less than 1000oF (wrought), 935oF (cast) and not less than four hours hold time."
-- MIL-H-6875H
RE: 17-4PH Material
RE: 17-4PH Material
Seems like we would be better off with an age-hardening of the Cond 'A" material - before machining. We don't want to worry about dimensional changes AFTER a heat treatment. The application is for a disposable surgical device, so I don't know if stress corrosion cracking would really be an issue, but it certainly sounds like the material could not be received consistently enough in the Cond A, to meet RC34.
I also found the Carpenter technical website very helpful.
RE: 17-4PH Material
RE: 17-4PH Material
http://www.mmsonline.com/articles/100304.html
SCC shouldn't be a problem for disposable items (unless someone sterilizes & recycles).
israelkk, thanks for info on the hardness variability.