Missed the Temepring procedure during heat treatment of D2

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hello,I was trying to heat treat a D2 tool steel block of 1" thickness which had to be used as a clamp for a compression test of plastic parts. Unfortunately, the TEMPERING process could not be performed and the metal was left to cool back to room temperature after annealing at 1850 F.I am concerned  that this unfinished process must have left the metal very brittle and if used in the compression press, it might shatter.I just wanted to point out that the metal was left to cool on firebricks without any cooling agents and wasn't rapidly oil quenched as mentioned in most guides. this less rapid method of cooling might have allowed the atoms to get back to its original state (Wishful Thinking i say)But eitherways, do you think it is now possible to finish the tempering now? Or maybe do a RE-heat treatment?
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Reply:I'd read up on the HT process. If you are saying the steel was never quenched after reaching proper critical heat, this is not the tempering process. Tempering would be done after quench.
Reply:the metal was definitely quenched for the required time (45mins) after reaching critical temp of 1850 F. Then instead of letting it drop to 150 and tempering, it was allowed to fall to room temperature an that was it.(Here's the procedure I was to follow,1. preheat to 1250 F, let it soak for 45 mins2. Heat to 1850 F and let it soat for 45 mins3. air cool to 150 F4. temper to 900 F5. let it cool to room temp and Temper again.I could perform only till 2. and the metal was let to cool to room temp)
Reply:Well, D2 should be tempered immediately after the air quench (which is still air in a controlled atmosphere at best, SS wrapped as a secondary ). If you missed your tempering effort, I suppose you could start all over again. I really don't know what the ramifications are of attempting a delayed temper, maybe someone else would.  As I don't know how critical your app is here, might not hurt to try.
Reply:Tempering is critical for any piece of metal that has been hardened.  It is quite literally a bit like a bomb in the dead hard state.  There have been cases when an untempered piece of hardened tool steel shattered when the diamond penetrator of a hardness tester made contact.  Tempering should be performed immediately, and if that is not possible, the part should not be allowed to cool below ~200 deg F until tempering is performed.  If this happens the part is basically junk.  This last part applies to wear resistance properties more so than what you are using it for I'm sure.The reason tempering is so crucial is because it stress relieves the part.  As you can imagine, tremendous stresses are introduced into a part when heat treating and quenching.  Also machining stresses are relieved when tempering.  I believe it also helps to transform retained austenite into martensite which is the fine, close-grained structure that is desireable.You can always temper later but the quality of the part will suffer.
Reply:I looked Up D2 steel Heat treat on google and there is a tremendous amount of information on there.  From what I read its inadvisable to reheat treat D2 after letting it fully cool in its hard state because it sometimes has developed cracks at that point.   Mac