| 摘要 |
Provided are a high-strength galvanized steel sheet including a high-strength galvannealed steel sheet having a tensile strength (TS) of 1180 MPa or more and excellent spot weldability, anti-crash property, and bending formability which can preferably be used as a material for automobile parts and a method for manufacturing the steel sheet. The steel sheet has a C content of 0.15% or less, in which an area ratio of ferrite is 10% or less, an area ratio of bainitic ferrite is 2% or more and 30% or less, an area ratio of martensite is 60% or more and 98% or less, an area ratio of retained austenite is less than 2%, an average grain diameter of martensite adjacent to bainite is 15 µm or less, a proportion of massive martensite adjacent only to bainite to the whole metallographic structure is 10% or less, and a value (”Hv) calculated by subtracting the Vickers hardness at a position located at 20 µm from the surface of the steel sheet from the Vickers hardness at a position located at 100 µm from the surface of the steel sheet is 30 or more. |
