High-strength cold-rolled steel sheet, high-strength hot-dip galvanized steel sheet, and high-strength hot-dip galvannealed steel sheet having excellent ductility, stretch-flangeability, and weldability

A high-strength cold-rolled steel sheet with a tensile strength of 980 MPa or higher and a 0.2% yield strength of 700 MPa or higher,

• the high-strength cold-rolled steel sheet comprising:
• in percent by mass,
• C:
• 0.07% to 0.15%,
• Si:
• 1.1% to 1.6%,
• Mn:
• 2.0% to 2.8%,
• P:
• more than 0% to 0.015%,
• S:
• more than 0% to 0.005%,
• Al:
• 0.015% to 0.06%,
• Ti:
• 0.010% to 0.03%, and
• B:
• 0.0010% to 0.004%,
• with the balance being iron and inevitable impurities,
• wherein
• an area ratio of following metal structures at a position of ¼ sheet thickness in the steel sheet satisfies following requirements:
• tempered martensite:
• 30 area % or more,
• bainite:
• 15 area % to 70 area %,
• total of tempered martensite and bainite:
• 90 area % or more,
• ferrite:
• 0 area % to 5 area %, and
• retained austenite:
• 0 area % to 2 area %,
• an area ratio of following metal structures in a surface layer region at 20 μm in a sheet thickness direction from an outermost surface layer portion of the steel sheet satisfies following requirements:
• ferrite:
• 80 area % or more, and
• a total area ratio of martensite and bainite:
• 0 area % to 20 area %.