It varies and is based on alloy content and prior cold work (or fabrication). You could use 1900 deg F for lower grades, like 304, 316 and for the higher temperature grades, the minimum could be 2000 deg F.
However, I want to caution you that you should review the material specification heat treatment requirements for the particular grade of stainless, period.
I have never seen good chromium carbide solution in 300 stainless at less than 1950F. If there is much you might want to go higher (up to 2150F) if you can stand the grain growth.
The time will have a lot to do with your part size and shape, your furnace, and how heavy the prior carbide formation is.
Thanks. Now let me pose a follow-up question.
Suppose you start with carbide solution treated bar (treated above 1950F), then hot or cold forge fasteners per A-193 Gr. B8. Per the A-193 Spec., after forging the fasteners shall be carbide solution treated (ref. A-193-'08 para. 7.3.3).
We started off with carbide solution treated material so the question is, ARE there carbides that need to be treated and if so, at what temperature? If there ARE NO carbides that need to be treated due to the original starting condition, at what temperature can I perform the carbide solution treatment?
FYI, we will be performing an A-262 intergranular corrosion test after all heat treats.
QAFitz;
The carbide solution treatment should be repeated for maximum corrosion resistance after hot or cold forming for this Class of material. I would re-solution heat treat at 1950 deg F min.
If the material never got above 800F there will be no carbides. Then all you are looking for is strain relief and 1900F will work fine for that. (I have done it at 1850F but that is cheating)
If the parts have been hot formed then you need to go back to 1950F min for full solution.
If it is Class 1, then you must perform the heat treatment after forming:
ASTM A 193 said:
Classes 1 and 1B, and Class 1C Grades B8R and B8S—After rolling of the bar, forging, or heading, whether done hot or cold, the material shall be heated from ambient temperature and held a sufficient time at a temperature at which the chromium carbide will go into solution and then shall be cooled at a rate sufficient to prevent the precipitation of the carbide.
