liquid nitrogen and 5160 in Metallurgy and other enigmas Posted January 24, 2012 My understanding matches Doug -- that cryo converts retained austenite on high alloy steels (stainless, D2, 1V, 3V,...). The low alloy tool steels like 5160 won't have a bunch of retained austenite if heat treated correctly. More importantly, the heat treat sheets from Carpenter, Crucible et al indicate that cryo has to be done on high alloy tool steels almost immediately after quench to be effective. What will happen when you quench steel in liquid nitrogen is that the LN2 will immediately turn to vapor and you will get a very persistent vapor phase - it is a very slow quench. Only vigerous agitation will break up the vapor phase. Another thing to concern yourself with is that all the LN2 will also turn to gas and create a suffocation hazard. This was well documented about 30 years ago when several people died when a manufacturer tried it.