METHOD FOR PRODUCING MARTENSITIC STAINLESS STEEL

摘要

The delayed fracture occurring after the hot working of a martensitic stainless steel is prevented by, after the hot working and prior to an heat treatment in which a quenching from a temperature equal to or higher than an Ac<SUB>1</SUB> temperature of the steel is carried out, subjecting the martensitic stainless steel to a pre-softening heat treatment under such conditions that a softening parameter (P) defined by the following formula is 15,400 or more and a softening temperature (T) is lower than an Ac<SUB>1</SUB> temperature of the steel: P (softening parameter) = T(20 + log t) wherein T: softening temperature [K] t: softening time [Hr]. This method is particularly effective for a martensitic stainless steel having such a steel composition that the amount of effective solid solution C and N (C* + 10N*) calculated by the following formulae is more than 0.45: C* = C - [12{(Cr/52) x (6/23/10]; and N* = N - [14{(V/51) + (Nb/93/10 - [{(Ti/48) + (B/11) + (Al/27)}/10].