Steel sheet

A steel sheet with a tensile strength of 780 MPa or more,

• a region down to 30 μm from a surface of the steel sheet in a sheet thickness direction being defined as a “surface layer part”,
• at the surface layer part of at least one side,
• particle size 20 nm or more Al oxide grains being present in 3000 to 6000/mm2 in number density,
• an average of natural logarithms of the particle sizes of the Al oxide grains measured in μm units being −5.0 to −3.5,
• a standard error of the natural logarithms of the particle sizes being 0.8 or less,
• a number of Al oxide grains with deviations of the natural logarithms of the particle sizes from the average of larger than 2 times the standard error being 5% or less of the total number of Al oxide grains,
• a chemical composition at a position of ¼ of the thickness from the surface of the steel sheet comprising, by mass %,
• C:
• 0.050 to 0.800%,
• Si:
• 0.01 to 1.20%,
• Mn:
• 0.01 to 8.00%,
• P:
• 0.100% or less,
• S:
• 0.050% or less,
• Al:
• 0 to 3.000%,
• N:
• 0.010% or less,
• O:
• 0 to 0.020%,
• Cr:
• 0 to 3.00%,
• Mo:
• 0 to 1.00%,
• B:
• 0 to 0.0100%,
• Ti:
• 0 to 0.200%,
• Nb:
• 0 to 0.200%,
• V:
• 0 to 0.20%,
• Cu:
• 0 to 1.000%,
• Ni:
• 0 to 1.000%, and
• bal.:
• Fe and impurities,
• a number density of Al oxide grains at a position of ½ of the thickness of the steel sheet being 1000/mm2 or less.