Steel material suitable for use in sour environment

A steel material consisting of, in mass %,

• C:
• more than 0.20 to 0.60%,
• Si:
• 0.05 to 2.00%,
• Mn:
• 0.02 to 0.60%,
• P:
• 0.025% or less,
• S:
• 0.0100% or less,
• Al:
• 0.005 to 0.100%,
• Cr:
• 0.20 to 1.50%,
• Mo:
• 0.35 to 1.50%,
• V:
• 0.01 to 0.60%,
• Ti:
• 0.002 to 0.050%,
• B:
• 0.0001 to 0.0050%,
• N:
• 0.0100% or less,
• O:
• 0.0100% or less,
• Nb:
• 0 to 0.030%,
• Ca:
• 0 to 0.0100%,
• Mg:
• 0 to 0.0100%,
• Zr:
• 0 to 0.0100%,
• rare earth metal:
• 0 to 0.0100%,
• Co:
• 0 to 0.50%,
• W:
• 0 to 0.50%,
• Ni:
• 0 to 0.20%, and
• Cu:
• 0 to 0.50%,
• with the balance being Fe and impurities;
• wherein:
• a yield strength σYS is 758 MPa or more;
• in the steel material, a content of Mo near prior-austenite grain boundaries γMo is 5.0% by mass or more;
• in a case where the yield strength σYS is less than 862 MPa, Fn1 defined by Formula (1) satisfies −300 or more;
• and
• in a case where the yield strength σYS is 862 MPa or more, Fn1 defined by Formula (1) satisfies −520 or more;
• Fn
• ⁢
• 1
• =
• 8
• ⁢
• 3
• ×
• (
• γ
• Mo
• -
• 10
• -
• 7
• ×
• √
• ρ
• )
• -
• σ
• YS
• (
• 1
• )
• where, the content of Mo near prior-austenite grain boundaries in percent by mass is substituted for γMo in Formula (1), a dislocation density in m−2 is substituted for ρ in Formula (1), and the yield strength in MPa is substituted for σYS in Formula (1).