Steel sheet and plated steel sheet

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

• wherein
• a chemical composition of the steel sheet comprises, by mass %,
• C:
• 0.05 to 0.40%,
• Si:
• 0.7 to 3.0%,
• Mn:
• 0.1 to 5.0%,
• sol. Al:
• 0.5 to 2.0%,
• P:
• 0.0300% or less,
• S:
• 0.0300% or less,
• N:
• 0.0100% or less,
• B:
• 0 to 0.0100%,
• Ti:
• 0 to 0.1500%,
• Nb:
• 0 to 0.1500%,
• V:
• 0 to 0.150%,
• Cr:
• 0 to 2.00%,
• Ni:
• 0 to 2.00%,
• Cu:
• 0 to 2.0000%,
• Mo:
• 0 to 1.00%,
• W:
• 0 to 1.000%,
• Ca:
• 0 to 0.1000%,
• Mg:
• 0 to 0.100%,
• Zr:
• 0 to 0.100%,
• Hf:
• 0 to 0100%,
• REM:
• 0 to 0.1000% and
• a balance of Fe and impurities, a total of the contents of the Si and sol. Al being 1.3% or more;
• a depth in a thickness direction of the steel sheet from a surface of the steel sheet wherein a C concentration measured by GDS of 0.05% or less is 8 μm or more;
• a thickness in a thickness direction of the steel sheet from a surface of the steel sheet of the layer with an area ratio of the ferrite phase of 90% or more is 8 μm or more;
• and
• at a position of 4 μm in a thickness direction of the steel sheet from a surface of the steel sheet, the solute amounts of the metal Si and metal Al in the ferrite phase are a total of 0.3% or more.