Cold and cryogenic treating

Although quenching steel causes the austenite to transform into martensite, all of the austenite usually does not transform. Some austenite crystals will remain unchanged even after quenching below the martensite finish (Mf) temperature.

Further transformation of the austenite into martensite can be induced by slowly cooling the metal to extremely low temperatures. Cold treating generally consists of cooling the steel to around -115 ˚F (-81 ˚C), but does not eliminate all of the austenite.

Cryogenic treating usually consists of cooling to much lower temperatures, often in the range of -315 ˚F (-192 ˚C), to transform most of the austenite into martensite.