METHOD FOR WARM-FORGING PRECIPITATION-HARDENING MARTENSITIC STAINLESS STEEL, AND FORGED PARTS MANUFACTURED BY THE METHOD

摘要

PROBLEM TO BE SOLVED: To provide a warm forging method which improves a workability of a precipitation-hardening stainless steel.;SOLUTION: The steel contains by weight ratio, 0.060% or less C, 0.60% or less Si, 1.00% or less Mn, 0.015% or less S, 2.5-4.0% Cu, 3.50-6.00% Ni, 14.00-16.00% Cr, 0.15-0.55% Nb, 0.030% or less N, so as to satisfy Nb/(C+N)≥5.00, and the balance Fe and impurities, or further includes one or more elements among (1) to (3) as needed, where (1) expresses 0.30-2.00% Mo, (2) one or more elements of 0.0005-0.0100% B, 0.0005-0.0100% Ca, 0.0005-0.0100% Mg and 0.0005-0.0100% REM, and (3) 0.05-0.50% Ti. The hot forging method comprises hot-rolling the above steel, then heating it to 850-950°C and keeping it at the temperature for 1-16 hours, further cooling it to 700-800°C and keeping it at the temperature for 1-16 hours, then cooling it until the end of martensitic transformation, heating it to 600-680°C, and then warm-forging it into a predetermined shape.;COPYRIGHT: (C)2004,JPO