Cryogenic treatment martensitic steels with mixed hardening

摘要

The present invention relates to a process for the treatment of a martensitic steel, comprising the contents of other metals, such that it is able to be hardened by precipitation of intermetallic compounds and of carbides, with an al content of 0,4% to 3%, comprising the following steps: (a) is heated, the whole of the steel at the top of its temperature of austenite, (b) the steel is cooled to about ambient temperature, (c) is placed said steel in a cryogenic. The temperature t is substantially below the martensitic transformation temperature ms, and the holding time t of the steel in the cryogenic environment at a temperature t from the moment when the hottest part of the steel has reached a temperature below the martensitic transformation temperature ms, is at least equal to a time t not - zero, the temperature t (in °C.) and the time t (in hours) being linked by the relationship: t = f (t), the first derivative of the function f with respect to t, f ′ (t), is positive, and the second derivative of f with respect to t, f (t), being negative.