高強度冷延鋼板、高強度めっき鋼板、高強度溶融亜鉛めっき鋼板および高強度合金化溶融亜鉛めっき鋼板、並びにそれらの製造方法

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-fibers to α-fibers in the ferrite and the martensite including the tempered martensite respectively are at least 1.00.