HIGH-STRENGTH STEEL SHEET AND PRODUCTION METHOD THEREFOR

摘要

This steel sheet has a prescribed component composition, and a microstructure which has a ferrite area ratio of at least 20%, a martensite area ratio of at least 5%, and a tempered martensite area ratio of at least 5%. In the microstructure, the average crystal grain size of the ferrite is not more than 20.0 µm, and the inverse intensity ratios of γ-fibres to α-fibres in the ferrite and the martensite including the tempered martensite respectively are at least 1.00.