Crankshaft And Method For Producing Crankshaft

Abstract: Provided is a crankshaft excellent in terms of crack resistance and fatigue strength. The crankshaft has a chemical composition comprising, in terms of mass%, 0.35-0.65% C, 0.01-0.60% Si, 1.00-2.00% Mn, 0.01-0.50% Cr, 0.001-0.050% Al, 0.010-0.100% S, 0.010-0.030% N, 0-0.020% Ti, and Fe and impurities as the remainder, the chemical composition satisfying expression (1). The crankshaft has a hardened layer in at least some of the surface. The hardened layer has a structure including 9.0 vol% or more ferrite, the remainder being martensite and/or bainite. The hardened layer has a Vickers hardness of 520 or greater. (1): ([C]-0.05)/[N]-300×[Ti]=30.0 In expression (1), the C content and the N content, in mass%, are substituted respectively for [C] and [N].

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