Annealing is the process of softening steel, usually
done in preparation for working and grinding the steel.
Heating up the steel past the critical temperature
(the austenizing temperature) and then letting it
cool slowly does annealing.
Hardenizing consists of two steps, austenizing and
quenching. First, to austenize, the steel is heated
to its critical temperature. To harden, the steel
has to cool down more quickly than in the annealing
step describe previously. So the steel is quenched
-- allowed to cool -- in some medium such as oil,
water, air, or molten salt, depending on the steel.
Once the blade has been hardened, tempering is done
to reduce the hardness and relieve internal stresses
in the steel.
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