Steel material, and crankshaft made of the steel material

Abstract

The steel material consists of, in mass %, C: 0.25% to 0.35%, Si: 0.05 to 0.35%, Mn: 0.85 to 1.20%, P: 0.080% or less, S: 0.030 to 0.100%, Cr: 0.10% or less, Ti: 0.050% or less, Al: 0.050% or less, N: 0.005 to 0.024%, and O: 0.0100% or less, with the balance being Fe and impurities, and Fn1 defined in the specification is 1.00 to 2.05, and Fn2 defined in the specification is 0.42 to 0.60. A surface number density of MnS single inclusions and MnS composite inclusions having an equivalent circular diameter of 5.0 μm or more is 20/mmor more. A ratio of the total number of MnS single inclusions and MnS composite inclusions with respect to the total number of inclusions is 70% or more. A ratio of the number of MnS composite oxides with respect to the total number of oxides is 30% or more.