Steel shaft component

A steel shaft component, comprising:

• one or a plurality of shaft parts, each of the shaft part having a circular shape in a cross section perpendicular to an axial direction, and having a hardened layer having a Vickers hardness of 620 HV or more in an outer layer;
• wherein:
• a chemical composition of the steel shaft component consists of, by mass %,
• C:
• 0.40 to 0.60%,
• Si:
• 0.05 to 1.00%,
• Mn:
• 1.00 to 2.00%,
• P:
• 0.030% or less,
• S:
• 0.005 to 0.100%,
• Cr:
• 0.10 to 0.50%,
• V:
• 0.10 to 0.30%,
• Al:
• 0.005 to 0.050%,
• N:
• 0.0050 to 0.0200%,
• Ti:
• 0 to 0.050%, and
• the balance:
• Fe and impurities;
• a Vickers hardness Hs of a surface of the shaft part is 620 HV or more;
• in the cross section perpendicular to the axial direction of the shaft part, a Vickers hardness Hb at an R/2 position that corresponds to a center position of a radius R of the shaft part satisfies Formula (1);
• a microstructure at the R/2 position is composed of ferrite and pearlite;
• a depth Hr (mm) of the hardened layer having a Vickers hardness of 620 HV or more satisfies Formula (2);
• and
• in the hardened layer of the cross section perpendicular to the axial direction of the shaft part, a number of density of V-containing precipitates which contain V and which have an equivalent circular diameter of more than 100 nm is 10 particles/276 μm2 or less:
• Hs/2.3≤Hb≤350 (1)
• 0.05≤Hr/R≤0.40 (2)
• where, R in Formula (2) represents a radius (mm) of the shaft part.