Steel sheet and production method for same

A steel sheet,

• wherein a chemical composition contains, by mass %,
• C:
• 0.050% to 0.180%,
• Si:
• 0.01% to 1.20%,
• Mn:
• 0.80% to 3.00%,
• Al:
• 0.005% to 0.600%,
• Ti:
• 0.005% to 0.120%,
• P:
• 0.050% or less,
• S:
• 0.0080% or less,
• N:
• 0.0125% or less,
• O:
• 0.0040% or less,
• Nb:
• 0% to 0.075%,
• V:
• 0% to 1.000%,
• Cr:
• 0% to 1.50%,
• Ni:
• 0% to 1.50%,
• Cu:
• 0% to 1.50%,
• Mo:
• 0% to 1.00%,
• W:
• 0% to 1.000%,
• B:
• 0% to 0.0060%,
• Sn:
• 0% to 1.000%,
• Sb:
• 0% to 0.200%, and
• one or more of Ca, Ce, Mg, Zr, La, and REM in total:
• 0% to 0.0100%,
• with a remainder of Fe and impurities,
• a microstructure within a range from a position of ⅛ of a sheet thickness from a surface in a sheet thickness direction to a position of ⅜ of the sheet thickness from the surface in the sheet thickness direction contains, in terms of a volume fraction,
• ferrite:
• 10% to 75%,
• martensite:
• 20% to 90%,
• retained austenite:
• 0% to 5%,
• bainite and bainitic ferrite in total:
• 0% to 50%, and
• pearlite:
• 0% to 5%,
• a proportion of unrecrystallized ferrite in the ferrite is 0% to 25%,
• cementite that is contained in the martensite satisfies Expression (1),
• a density of transition carbide included in the martensite is 1.0×1013 pieces/m3 or more,
• a density of coarse inclusion having an equivalent circle diameter of 10 μm or more is 0.50 pieces/mm2 or less,
• in a surface parallel to the surface at a position of ¼ of the sheet thickness from the surface in the sheet thickness direction,
• a ratio of a maximum value Hvmax of Vickers hardness to a minimum value Hvmin of the Vickers hardness is 1.40 or less, and
• in a distribution map of the Vickers hardness, wherein the Vickers hardness is measured in the surface parallel to the surface at the position ¼ of the sheet thickness from the surface in the sheet thickness direction, an average value of minimum distances between peaks of the Vickers hardness is 1.00 mm or less,
• [Math. 1]
• 1.00≤Σi=15di0.80·ai1.30≤10.00 Expression (1)
• in the Expression (1), di represents a particle diameter of a cementite particle having an ith largest equivalent circle diameter in unit μm in the cementite, and ai indicates an aspect ratio of the cementite particle having the ith largest equivalent circle diameter.