METHOD FOR PRODUCING PRECIPITATION HARDENING TYPE MARTENSITIC STAINLESS STEEL HAVING EXCELLENT COLD FORGEABILITY AND WARM FORGEABILITY

摘要

PROBLEM TO BE SOLVED: To provide a method for producing precipitation hardening type martensitic stainless steel by which the workability of SUS630 for which cold forging has been difficult can remarkably be improved.;SOLUTION: In the method for producing precipitation hardening type martensitic stainless steel, steel having a composition containing, by weight, ≤0.07% C, ≤1.00% Si, ≤1.50% Mn, ≤0.015% S, 2.5 to 4.0% Cu, 3.50 to 6.00% Ni, 14.00 to 17.00% Cr, 0.15 to 0.55% Nb and ≤0.030% N, and also satisfying C+N=≤0.090% and Nb/(C+N)≥5.00, and the balance Fe with impurity elements is hot-rolled, and is thereafter cooled to a room temperature. Subsequently, the steel is subjected to solution heat treatment so as to be heated at 980 to 1,080°C, to be held for 15 min to 6 hr, and to be cooled. After that, the steel is subjected to process annealing treatment so as to be heated at 850 to 950°C, to be held to the temperature for 1 to 16 hr, to further be cooled at 700 to 800°C, to be held to the temperature for 1 to 16 hr, and to be cooled until the completion of martensitic transformation. The steel is finally subjected to softening treatment so as to be heated at 600 to 680°C.;COPYRIGHT: (C)2003,JPO