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

A high-strength, high-toughness martensitic stainless steel sheet for metal gaskets 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 including not less than 85 vol % martensite phase, a test specimen of which imparted with a nominal tensile strain of 0.1% exhibits a spring bending elastic limit Kb0.1 measured in conformity with JIS H 3130 of not less than 700 N/mm2.

A method of inhibiting cold-rolled steel sheet edge cracking of a high-strength, high-toughness martensitic stainless steel sheet, which method is applied with respect to a hot-rolled steel sheet of matensitic stainless steel having 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 having an A value defined by Equation (1) of not less than −1.8:
• A value=30(C+N)−1.5Si+0.5Mn+Ni−1.3Cr+11.8 (1),
• and comprises a step of subjecting the sheet to a single cycle or multiple repeated cycles of a process (intermediate annealing and cold rolling process) consisting of intermediate-annealing the sheet at a soaking temperature of 600-800° C. for a soaking period of not more than 10 hr to adjust steel hardness to Vickers hardness (Hv) of not greater than 380, followed by cold rolling.