Steel sheet, member, and method for producing the same

A steel sheet having a chemical composition comprising, in mass %:

• C:
• not less than 0.15% and not more than 0.45%;
• Si:
• not more than 2.0%;
• Mn:
• not more than 4.0%;
• P:
• not more than 0.10%;
• S:
• not more than 0.01%;
• sol. Al:
• not more than 0.50%;
• N:
• not more than 0.010%;
• and
• B:
• not less than 0.0008% and not more than 0.0100%,
• with the balance being Fe and incidental impurities,
• wherein the steel sheet has a steel microstructure where the area ratio of martensite to the entire microstructure is not less than 85% and less than 95%, the area ratio of ferrite to the entire microstructure is not less than 5% and not more than 15%, and the average crystal grain size of ferrite is 10 μm or less, and
• wherein the number density A of precipitates having an equivalent circular diameter of 500 nm or more satisfies the following formula (1):
• A(number/mm2)≤8.5×105×[B] formula (1)
• where [B] represents the content (mass %) of B,
• and optionally the steel sheet has a coating layer on a surface of the steel sheet.