Material Movement 17-4PH Stainless steel Help 2

[brandnew1]

i'm not an expert regarding metallurgy, however i need some help or guideance in order to find a root cause to the following problem, any and all help much appreciated.

We utilize 17-4PH stainless steel, which went through one solution heat treatment until material movement was found after the part was machined. So customer sent them to be re-solution treated and were acceptable afterward.

Process changed to go through solution heat treatment twice before machining the part. But i have come across to see that there appears to be material movement (not as many but still an issue).

i came across a comment regarding 17-4PH indicating, "parts are very stable there is slight movement if parts are not stressed relieved".

So my question deals with stress relief. Is this the problem? How do i go about finding out for certain. The certification indicates stress relief by the vendor.

thank you and if you want specific numbers as indicated on certs that may help, let me know =)

 

[unclesyd]

Can you comeback with your heat treatment specs and general description of the part and movement seen.

We make and use thousands of precision parts made from the PH alloys including lots of 17/4 PH. We never have to Solution Anneal after the initial precipitation heat treatment. As we do all our machining after heat treatment we don't normally have any concern about the small shrinkage experienced during the precipitation heat treatment.

 

[EdStainless]

Don't confuse annealing with anything to do with residual stress. Annealed parts usually have residual stress that is 50-100% of the yield strength.
The anneal, and especially the cooling from anneal, would have to be done in a very controlled way in order to minimize residual stress.
The size of 17-4 changes when aged. This is very repeatable and can be compensated for if needed. If you are seeing variable results then your initial heat treatment was not done properly.

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Plymouth Tube

 

[brandnew1]

Hi everybody,

thank you for the response so far. i don't have access to the first solution heat treatment process but i have he 2nd phase which goes as follows:

Solution - Temp. 1900F - Time 2hrs 7min
Age - Temp. 1025F - 4 hrs 8 min
Cold stabilize - (-100F) - 2 hrs
Stress Relieve - 800 F - 2hrs 15 min

The first phase goes through the solution treatment at 1900F as well and is air cooled i believe. But then goes through another one.

These are pieces that are about 4" x 6" in size. i don't know how many of these parts are completed at once for each phase.

What i'm seeing, when you check flatness on one side on a surface plate (before machining) it is fairly flat, but after being cut the sides will not be as flat. Now it isn't as strong as before but i'm seeing this at times. So we went through this process twice due to recommendation from customer and vender (from what i'm told) but if we see still see this what could the problem be?

thanks again

 

[brandnew1]

Thanks EdStainless,

When you said that, "If you are seeing variable results then your initial heat treatment was not done properly".

Can you explain or direct me where i can learn why this is the thought behind variable results? We do a solution heat treatment twice (after recommendation from vendor and customer) and we're still seeing variations.

But again i'm not an expert but it looks as though its the stress reflief that causes us to see movements.

Is there some resource that i can investigate to have a better grounding on this?

thank you