Steel sheet, method for manufacturing same and plated steel sheet

A steel sheet having a chemical composition containing, by mass %:

• C:
• 0.02% to 0.15%,
• Si:
• 0.005% to 2.000%,
• Mn:
• 1.00% to 3.00%,
• Ti:
• 0.010% to 0.200%,
• sol. Al:
• 0.001% to 1.000%,
• N:
• 0.0010% to 0.0100%,
• P:
• 0.100% or less,
• S:
• 0.0100% or less,
• Nb:
• 0% to 0.100%,
• V:
• 0% to 0.500%,
• Mo:
• 0% to 0.500%,
• Cu:
• 0% to 1.00%,
• Ni:
• 0% to 1.00%,
• Cr:
• 0% to 2.00%,
• B:
• 0% to 0.0020%,
• Ca:
• 0% to 0.0100%,
• Mg:
• 0% to 0.0100%,
• REM:
• 0% to 0.0100%, and
• Bi:
• 0% to 0.0200%
• with a remainder consisting of Fe and an impurity,
• wherein, at a ¼ depth position of a sheet thickness from a surface, a total area fraction of tempered martensite and tempered bainite is 10% or more and 100% or less, an area fraction of ferrite is 0% or more and 90% or less, an area fraction of residual austenite is 0% or more and less than 4%, a total area fraction of the residual austenite, fresh martensite, cementite, and pearlite is 0% or more and 10% or less,
• an average grain size is 15.0 μm or less,
• a total grain boundary number density of solute C and solute B is 1.0 solute/nm2 or more and 12.0 solutes/nm2 or less,
• a total of pole densities of {211}<011> and {332}<113> in a thickness middle portion is 12.0 or less, and
• a tensile strength is 780 MPa or more.