Steel material suitable for use in sour environment

A steel material comprising:

• a chemical composition consisting of, in mass %:
• C:
• 0.15 to 0.45%,
• Si:
• 0.05 to 1.00%,
• Mn:
• 0.01 to 1.00%,
• P:
• 0.030% or less,
• S:
• 0.0050% or less,
• Al:
• 0.005 to 0.100%,
• Cr:
• 0.55 to 1.10%,
• Mo:
• 0.70 to 1.00%,
• Ti:
• 0.002 to 0.020%,
• V:
• 0.05 to 0.30%,
• Nb:
• 0.002 to 0.100%,
• B:
• 0.0005 to 0.0040%,
• N:
• 0.0100% or less,
• O:
• less than 0.0020%,
• Ca:
• 0 to 0.0100%,
• Mg:
• 0 to 0.0100%,
• Zr:
• 0 to 0.0100%,
• rare earth metal:
• 0 to 0.0100%,
• Cu:
• 0 to 0.50%,
• Ni:
• 0 to 0.50%,
• Co:
• 0 to 0.50%, and
• W:
• 0 to 0.50%,
• with the balance being Fe and impurities,
• and satisfying Formula (1),
• wherein
• in the steel material, a grain diameter of a prior-austenite grain is 15.0 μm or less,
• an average area of precipitate which is precipitated in a prior-austenite grain boundary is 12.5×10−3 μm2 or less, and
• a yield strength is 758 to 862 MPa:
• Mo/Cr≥1.90 (1)
• where, content in mass % of a corresponding element is substituted for each symbol of an element in Formula (1).