Question abour heat treatment of PH stainless steels 2

[gtgrad2k]

Does anyone know why section 3.4.3.1 of AMS 2759/3 explicitly states that for PH stainless steels, only one resolution heat treatment is permitted? I don't recall any other specifications mentioning that, and from a metallurgical/microstructural standpoint, I can't think of any detrimental effects of resolutioning more than one time.

 

[TVP]

Potential for grain growth?

 

[EdStainless]

I have always take this restriction to apply to the final heat treatment only. We have jobs that get re-annealed many time during processing.
Since none of the anneals are above 1900F the risk of grain growth is limited.

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Plymouth Tube

 

[Metaljon]

Yes this applies only in the final ageing treatment not the solution treatment which can be done as many times as you like. The PH stands for precipitation hardening so not possible do a repeat ageing treatment without degrading the alloy.

 

[gtgrad2k]

The specification *says* re-solutioning, so if you are saying that they *meant* re-aging, that is a pretty major mistake in the specification. I agree with you that you should be able to re-solution a PH stainless multiple times, I just wanted to verify with others before I submitted a commment regarding this section to the SAE heat treat committee.

 

[EdStainless]

The anneal is really a conditioning step, you are only solutioning the precipitates, not carbides and other phases. That should have been taken care of earlier in processing.
The exact thermomechanical path is different for various alloys, but many times we reanneal and even age between forming or drawing operations.
When we get to the end we anneal and age, if we don't hit properties then we one more chance.
That is how I read it.

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Plymouth Tube

 

[JAWright]

I think grain growth is the concern. During solution treatment, the grains can potentially grow, depending upon the particular alloy and it's grain-pinning dispersion. If hot-working is going on, solution treatment is not as much of a concern because the recrystallization during forging is refining the grain size.