CRYOGENIC TREATMENT OF MARTENSITE STEEL WITH MIXED HARDENING Russian patent published in 2015 - IPC C21D6/00 C22C38/52 

FIELD: metallurgy.

SUBSTANCE: invention relates to the method of martensite steel production. To improve mechanical properties and to reduce their scattering in steel containing other metals ensuring its hardening upon allocation of intermetallic joints and carbides, as well as Al from 0.4% to 3%; this steel is subjected to heat treatment including steel heating above its austenisation temperature, steel cooling to about ambient temperature, steel location in the cryogenic environment at temperature T₁, at that temperature T₁ is lower than temperature Mf of the martensite transformation, and steel holding in the cryogenic environment for time period at least equal to non-zero time t₁ of holding until the hottest part of steel achieves temperature below temperature Mf of the martensite transformation, at that temperature T₁ (in °C) and holding time t₁ (in hours) are determined by equation T₁= ƒ (t₁), at that first derivative of function ƒ' (t), is positive, and second derivative of function ƒ” (t) is negative.

EFFECT: improved mechanical properties and reduced values scattering in steel.

8 cl, 1 tbl, 4 dwg