A heat treat process which converts unstable retained Austenite into stable untempered Martensite. Deep Freeze is usually performed at -73°C to -100°C in dry ice mixed with alcohol or mechanical refrigeration. Deep freezing is actually an extension of quenching. In some instances, the Mf (Martensite finish) temperature may be well below room temperature which favors the retention of large amounts of unstable, soft retained Austenite - deep freeze transforms Austenite to stable, hard Martensite. Retained Austenite in a finished part can cause dimensional instability and/or excessive residual stress or cracking.
See also: Work Hardening.
Subjects: Mechanical Engineering