High strength martensitic steel having superior rusting resistance.

摘要

High strength martensitic stainless steel having high rusting resistance which comprises, by weight, 0.13 to 0.20% of C, 0.5 or less of Si, 2.0% or less of Mn, 1.0 to 2.5% of Ni, 12.0 to 16.0% of Cr, 1.3 to 3.5% of Mo, 0.06 to 0.13% of N, if necessary, 0.001 to 0.010% of B, or 0.05 to 1.0% of Ti, 0.05 to 1.0% of Nb, which satisfies 16 to 21% of ARI value for a rusting resistance index (Formula (1)), less than 0% of DI value for a delta -ferrite content index (Formula (2)), less than 0% of MI value for martensite content index (Formula (3)), less than 260% of W1 or W2 value for a cold workability index (Formulas (4) or (5)), with the balance comprising substantially Fe and inevitable impurities, said steel being characterized in that the martensite structure or the tempered martensite structure is contained, in which a Cr carbide of 0.2 mu m or less in grain size is deposited, especially enabling to produce a self drilling-tapping screw superior in screwing ability and rusting resistance, a nail superior in driving ability and rusting resistance, a cutter having high rusting resistance, a high strength spring superior in rusting resistance, etc.. ARI = Cr + 2.4Mo Formula ... (1> DI = Cr + 1.21Mo + 0.48Si + 2.48Al - (24.5C + 18.4N + Ni + 0.11Mn) - 10.0 Formula ... (2> MI = Ni + 30C + 0.12Mn + 18N + 0.83(Cr + 1.5Si + 1.4Mo) - 25.0 Formula ... (3> W1 = 24Mo + 13.3Cr + 6Mn + 6Si + Ni Formula ... (4> W2 = 24Mo + 13.3Cr + 6Mn + 6Si + Ni + 10Ti + 10Nb Formula ... (5)