Steel Material And Crankshaft Formed Of Said Steel Material

Abstract: The present invention provides a steel material which has excellent machinability, bending fatigue strength, wear resistance and bending straightening properties. This steel material contains, in mass%, 0.25% to 0.35% of C, 0.05% to 0.35% of Si, 0.85% to 1.20% of Mn, 0.080% or less of P, 0.030% to 0.100% of S, 0.10% or less of Cr, 0.050% or less of Ti, 0.050% or less of Al, 0.005% to 0.024% of N and 0.0100% or less of O, with the balance being made up of Fe and impurities; and with respect to this steel material, Fn1 set forth in the description is 1.00 to 2.05, and Fn2 set forth in the description is 0.42 to 0.60. The surface number density of MnS simple inclusions and MnS composite inclusions, each having a circle-equivalent diameter of 5.0 µm or more, is 20 per mm2 or more; the ratio of the total number of MnS simple inclusions and MnS composite inclusions relative to the total number of inclusions is 70% or more; and the ratio of the number of MnS composite inclusions relative to the total number of oxides is 30% or more.

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