How cool did it get before tempering? What temper temperature? Any chance you can have a good met. lab. examine the cracks?
"You see, wire telegraph is like a very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Do you understand this? Radio operates the same way: You send signals here, they receive them there. The only difference is there is no cat." A. Einstein
Did you oil quench? From what temperature? What was the temperature of the quench oil initially? How long, specifically, was it left in the quench, and what was the measured temperature of the part when it came out of the quench?
Can you provide a photograph illustrating the cracks?
It is suggested that you normalize the forging before ,hardening and tempering. This will minimize the cracking. Also suggest using a warm oil rather than cold oil. Finally temper based on the hardness after quenching .
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Thank you Metalguy, Maui, and arunmarao for answering. I think I got my answer from Maui's answer in an old thread with similar issue.
Maui - Your answer was that "if oil quenched, the part has to be removed from oil before its temp goes below 500F and let it cool in air to avoid cracking". Our part was oil quenched from 1900F and left in oil until it went below 150F.
