Steel sheet and method of production of same

A steel sheet having a chemical composition comprising, by mass %,

• C:
• 0.040 to 0.200%,
• Si:
• 0.30 to 2.00%,
• Mn:
• 1.00 to 4.00%,
• sol. Al:
• 0.001 to 0.500%,
• P:
• 0.100% or less,
• S:
• 0.0300% or less,
• N:
• 0.0070% or less,
• O:
• 0.0100% or less,
• Nb:
• 0.001 to 1.000%,
• Ti:
• 0 to 0.200%,
• V:
• 0 to 0.300%,
• Cu:
• 0 to 0.40%,
• Cr:
• 0 to 0.90%,
• Mo:
• 0 to 0.12%,
• Ni:
• 0 to 0.30%,
• B:
• 0 to 0.0030%,
• Ca:
• 0 to 0.0010%,
• Mg:
• 0 to 0.0010%,
• Bi:
• 0 to 0.010%,
• Zr:
• 0 to 0.050%,
• Co:
• 0 to 0.010%,
• Zn:
• 0 to 0.010%,
• W:
• 0 to 0.100%,
• Sn:
• 0 to 0.040%,
• As:
• 0 to 0.100%,
• REM:
• 0 to 0.0100%, and
• balance:
• Fe and impurities, and
• a microstructure comprising, by area %,
• martensite:
• 90.0% or more, and
• retained austenite:
• 3.0% or less, wherein
• a mean particle size of prior austenite grains is 30.0 μm or less, and
• a standard deviation in particle size of prior austenite grains is 4.0 μm or more.