Austenitic Solution Anneal

[monty011]

I've got a specification that requires a solution anneal (1900F) with soak time of 2 hours per inch of thickness. We are typically dealing with 1/2" to 1" plate. That amount of time seems a bit excessive to me and now I know why we have a fair amount of oxidation/scale when we get these parts back. For comparison, ASME UHA-44 (Sec 8, Div 1) provides soak times on solution annealing after strain hardening with a soak time of 20 min/inch or 10 min, whichever is greater.

So, what duration are you guys typically specifying for a full solution anneal of austenitic stainless?

 

[EdStainless]

What has been done to it?
If just cold work then something in the 10-15 min range (after reaching temp) is plenty.
If the material has been previously slow cooled and is sensitized then you will need something more like 30 min minimum + something (15min) per inch.
It all depends.
And 304 takes the least time. Any alloys with Mo in them take longer. 317 would take twice as long (if welded or sensitized) and 6%Mo like AL-6XN takes even longer to dissolve secondary phases.

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P.E. Metallurgy, Plymouth Tube

 

[metengr]

So, what duration are you guys typically specifying for a full solution anneal of austenitic stainless?

One size does not fit all for the above. We have specified a minimum of 1 hour per inch thickness for solution anneal after fabrication, depending on the Grade of austenitic stainless steel.
For cold work only after a proper solution anneal we specify ASME Section VIII, Div 1 requirements for thermal treatment.

 

[monty011]

The specific application is on 316L material. It is rolled into a conical shape and seam welded. The ends are welded up to flanges of the same material. Since the time to sensitization in the critical temp range is several hours for the L grade, i'd think that 2 hrs per inch is a little extreme. Just curious to see what others are specifying.

 

[EdStainless]

You don't mention a section thickness.
Then sensitization time only holds true if the material properly annealed previously.
If you are trying to also homogenize the welds in order to restore corrosion resistance then times of at least 1hr/inch make sense.

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P.E. Metallurgy, Plymouth Tube

 

[monty011]

In the OP, I said that typical section thicknesses were 1/2" to 1" typically.