My Guess as a guide: Heated to 500F a few 1,000 times, with no fatigue. Above 500F thru 1300 F and the heat-treat set has a slippery slope.
Cherry orange after that and the grain reorientates, the heat anneals. At such orange level, I don't know about the proper cool-down or quench to restore strength. Probably an natural oil dip.
Cast or Steel?
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