Steel material for steel piston

A steel material for a steel piston, that has a chemical composition which consists of, in mass %,

• C:
• 0.15 to 0.30%,
• Si:
• 0.02 to 1.00%,
• Mn:
• 0.20 to 0.80%,
• P:
• more than 0 to 0.020%,
• S:
• 0.009 to 0.028%,
• Cr:
• 0.80 to 1.50%,
• Mo:
• 0.08 to 0.40%,
• V:
• 0.10 to 0.40%,
• Al:
• 0.005 to 0.060%,
• N:
• more than 0 to 0.0150%,
• O:
• more than 0 to 0.0030%,
• Cu:
• 0 to 0.50%,
• Ni:
• 0 to 1.00%,
• Nb:
• 0 to 0.100%, and
• the balance:
• Fe and impurities,
• and satisfies Formula (1) and Formula (2),
• wherein:
• at a cross section parallel to an axial direction of the steel material for a steel piston,
• a number of Mn sulfides containing 10.0 mass % or more of Mn and containing 10.0 mass % or more of S is 100.0 per mm2 or less,
• among the Mn sulfides, a number of coarse Mn sulfides having an equivalent circular diameter of 3.0 μm or more is within a range of 1.0 to 10.0 per mm2, and
• a number of oxides containing 10.0 mass % or more of oxygen is 15.0 per mm2 or less;
• 0.42≤Mo+3V≤1.50 Formula (1)
• V/Mo≥0.50 Formula (2)
• where, a content (mass %) of a corresponding element is substituted for each symbol of an element in Formula (1) and Formula (2).