thank the gods that it doesn't cast cast in skulls, the question of hardening (tempering) is a good one though,
reminds me of the K series Leyland engine, the local engine reconditioner reckons that the K series paid the mortgage on his house, all by itself. the vast majority of head repairs on that engine were "temporary" because tempering did not take place.
CLEM
genuine comment, not an intended pun