Steel sheet and method for manufacturing same

A steel sheet comprising, as a chemical composition, by mass %:

• C:
• 0.15% to 0.40%;
• Si:
• 0.01% to 2.00%;
• Mn:
• 0.10% to 4.00%;
• Al:
• 0.005% to 1.500;
• P:
• 0.001% to 0.100%;
• S:
• 0.0005% to 0.0100%;
• N:
• 0.0005% to 0.0100%;
• Ti:
• 0% to 0.200%;
• Mo:
• 0% to 0.300%;
• Nb:
• 0% to 0.200%;
• Cr:
• 0% to 4.000%;
• B:
• 0% to 0.0050%;
• V:
• 0% to 0.300%;
• Ni:
• 0% to 4.00%;
• Cu:
• 0% to 4.00%;
• W:
• 0% to 2.00%;
• Ca:
• 0% to 0.0100%;
• Ce:
• 0% to 0.0100%;
• Mg:
• 0% to 0.0100%;
• Zr:
• 0% to 0.0100%;
• La:
• 0% to 0.0100%;
• REM other than Ce and La:
• 0%to 0.0100%;
• Sn:
• 0% to 1.000%;
• Sb:
• 0% to 0.200%;
• and
• a remainder:
• Fe and impurities,
• wherein a microstructure at a ¼ thickness which is a range between a ⅛ thickness position in a sheet thickness direction from a surface of the steel sheet and a ⅜ thickness position in the sheet thickness direction from the surface includes, by area ratio,
• ferrite:
• 0% to 10%,
• retained austenite:
• 0% to 10%,
• upper bainite:
• 0% to 10%,
• martensite:
• 70% to 100%, and
• pearlite:
• 0% to 5%,
• an area ratio of plate martensite contained in the martensite is 10% to 35% with respect to an area of an entire structure of the steel sheet,
• an average grain size of prior austenite grains is 2.0 μm to 10.0 and a maximum diameter of the prior austenite grains is 20.0 μm or less,
• an amount of solid solution C in the martensite is 0.20 mass % or less,
• an average carbide size in the martensite is 0.25 μm or less,
• a crystal orientation difference between the plate martensite and another martensite adjacent to the plate martensite in the same prior austenite grain is 10.0° or less, and
• a P concentration at grain boundaries of the prior austenite grains is 4.0 at % or less.