HIGH-STRENGTH STEEL SHEET AND PRODUCTION METHOD THEREFOR

摘要

Provided are: a high-strength steel sheet having excellent punchability and a tensile strength of at least 780 MPa; and a production method therefor. The high-strength steel sheet has a tensile strength of at least 780 MPa and comprises a prescribed component composition and a steel structure. The steel structure comprises a ferrite phase, a martensite phase, and a bainite phase; the area ratio of the martensite phase is 20%-50%; the ratio of crystal grains having an average crystal grain diameter of less than 1.0 µm in the martensite phase is 5%-30%, by area ratio; the ratio of crystal grains having an average crystal grain diameter of 1.0-4.0 µm is 70%-95%, by area ratio; and the ratio of crystal grains having an average crystal grain diameter of more than 4.0 µm is less than 5%, by area ratio.