Railway axle

A railway axle, comprising:

• a fitting portion that has a circular columnar shape having a diameter DW mm and is press-fittable to a railway wheel;
• and
• a non-fitting portion continuous with the fitting portion,
• wherein the non-fitting portion includes:
• a circular columnar parallel portion having a diameter DA mm that is smaller than the diameter DW mm, and
• a fillet R portion that is disposed between the fitting portion and the parallel portion and has a surface that is curved and recessed in a cross section including a center axis of the railway axle,
• the fitting portion and the non-fitting portion include:
• a hardened layer formed in a surface layer of the fitting portion and a surface layer of the non-fitting portion, and
• a base metal portion located inward of the hardened layer,
• a chemical composition of the base metal portion contains, in mass %,
• C:
• 0.30 to 0.42%,
• Si:
• 0.10 to 0.50%,
• Mn:
• 0.40 to 1.20%,
• P:
• more than 0% and 0.020% or less,
• S:
• more than 0% and 0.0400% or less,
• N:
• more than 0% and 0.0200% or less,
• O:
• more than 0% and 0.0040% or less,
• Ca:
• 0 to 0.0010%,
• Cr:
• 0 to 0.30%,
• Mo:
• 0 to 0.10%,
• Cu:
• 0 to 0.30%,
• Ni:
• 0 to 0.30%,
• Al:
• 0 to 0.100%,
• V:
• 0 to 0.060%,
• Ti:
• 0 to 0.020%,
• Nb:
• 0 to 0.030%, and
• B:
• 0 to 0.0050%,
• with the balance being Fe and impurities,
• DW/DA, which is a ratio of the diameter DW to the diameter DA, is 1.10 to 1.30, and
• a radius of curvature Rf is greater than or equal to a critical radius of curvature Rcr mm defined by Formula (1) and smaller than or equal to 60.0 mm,
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• where Rf is a radius of curvature of a portion of a surface of the fillet R portion in a cross section including a center axis of the railway axle, the portion being adjacent to a surface of the parallel portion, and a reference total case depth CAT mm is a smaller depth out of total case depths at a 0.23 Rf position and a 0.57 Rf position in an axial direction of the railway axle from an R end of the fillet R portion toward the parallel portion side, the R end being an end that is in contact with the parallel portion.