17-4PH HEAT TREATMENT

[Creech]

I'm not familiar with MIL specs. I was waondering if the following metal gets heat treated:
[UNS S17400(17-4PH) per ASTM A564 aged to condition H1150]. The bar that we received said 17-4 condition A. and also do we machine this part before heat treat if it gets heat treated. How does it react in heat treat? Any information would be helpful. Thanks ahead of time. The brackets denote the part print note.

 

[israelkk]

It is better to machine it after heat treatment to H1150. This way you get the machined surfaces clean without scale or discoloring as the result of the heat treatment thereby, better ready for passivation. It is even easier to machine at H1150 compared to condition A. Last, all PH alloys change dimension due to heat treatment (shrink or expand depends on the heat treatment) therefore, if the part has strict tolerances and hardness is less than 38RC it is prefered to heat treat first and then machine.

 

[rd400guy]

Yes this material gets heat treated. Condition H1150 is a very common heat treatment (or aging) for this grade. Equalize the material at 1150°F then hold for 4 hours. This will give you about 32-34 HRC.

The grade is difficult to machine, on par with 300 series stainless. There is a predictable, uniform contraction of about 0.0008" / inch when aged at 1150, so if your tolerances are very tight, you should probably age the material first, then machine it. Actually, if you age it first, it will be slightly easier to machine. No stress relief is required after machining.

 

[Creech]

Thank you both very much