High-strength, high-toughness martensitic stainless steel sheet, method of inhibiting cold-rolled steel sheet edge cracking, and method of producing the steel sheet

摘要

A high-strength, high-toughness martensitic stainless steel sheet has a chemical composition comprising, in, mass percent, more than 0.03 to 0.15% of C, 0.2-2.0% of Si, not more than 1.0% of Mn, not more than 0.06% of P, not more than 0.006% of S, 2.0-5.0% of Ni, 14.0-17.0% of Cr, more than 0.03 to 0.10% of N, 0.0010-0.0070% of B, and the balance of Fe and unavoidable impurities and has an A value of not less than −1.8, where A value=30(C+N)−1.5Si+0.5Mn+Ni−1.3Cr+11.8. The suitability of the steel sheet as a gasket material is enhanced by producing it to include not less than 85 vol % of martensite phase and to have a spring bending elastic limit Kb_0.1 after application of tensile strain of 0.1% of not less than 700 N/mm². Edge cracking during cold rolling is inhibited by conducting cold rolling after subjecting the hot-rolled sheet to 600-800° C.×10 hr or less intermediate annealing to impart a steel hardness of not greater than Hv 380.