Coarse grained IN625 by Grade 1 annealing? 1

[AnsAvi]

Is it possible to obtain a grain size of 2-4 (ASTM E112) in IN625 material using a Grade 1 annealing process? I am concerned that at Grade 1 temperatures, it would be hard to avoid recrystallization that would result in grain size reduction.

 

[EdStainless]

How large of a part is this?
What product form (casting, forging ...)?
Gr1 processing (full solution anneal) will increase GS a bit, but unless it was already 5 and coarser I don't see you getting 2-4 out of it.
We make tubing that starts as finer than 8, and after full solution anneal we are still finer than 6 with ease.
But our anneal times are measured in minutes.
We have customers that want higher creep resistance and larger grains, it is a pain to get them up to 5-6.

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P.E. Metallurgy, Plymouth Tube

 

[AnsAvi]

EdStainless,

Thanks for the reply. The parts are machined out of rd bar 0.75" dia and 0.5" dia. The length of the parts is no more than 3" max. The heat treat is being done by the material supplier, so I do not have information of the grain size prior to the Gr 1 annealing they are doing. All I know is that the bar stock we received has grain sizes between 8 and 13. From your response, it seems that even if we were to do a post machining heat treat, it would be very difficult to meet the ASTM size 2-4 requirement of our customer.

Just curious, do you think grade 2 annealing could do it? Since it is done at a higher temperature?

 

[EdStainless]

Yes, I mixed the two up in my reply, Gr2 is the full solution anneal.
This would take long time at 2200F.

http://www.specialmetals.com/assets/smc/documents/alloys/inconel/inconel-alloy-625.pdf

See page 11.

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P.E. Metallurgy, Plymouth Tube

 

[AnsAvi]

EdStainless,

Thanks again for the reference.
The grain size numbers 2-4 translate to a average grain diameter range of approximately 90 - 180 microns. And the customer has specified Grade 1 annealing requirement as well. That means annealing temperature has to be >1600 F.
As per the reference you have shared, it seems like it might be theoretically possible to meet their Grain size requirement for annealing temperatures between 1600 F and 1700 F. Am I reading this right?
Also, I would suspect that it would be difficult to find commercially available bar stock that would be annealed between 1600 and 1700 F. In that case, do you think we could get to this grain size if we annealed the final product between 1600 - 1700 F?

 

[EdStainless]

If they want that large of grain they will have to settle for very low mechanical properties.
A few hours at 2200F will blow the grains up, but the tensile will be very low.
The only way to get the higher tensile and large grains is if you are doing the manufacturing.
Then you could blow the grain size up in then ext to final anneal, do your final light reduction, and use a low temp anneal to keep properties up and GS large.


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P.E. Metallurgy, Plymouth Tube