HIGH-STRENGTH ZINC-PLATED STEEL SHEET AND HIGH-STRENGTH STEEL SHEET HAVING SUPERIOR MOLDABILITY, AND METHOD FOR PRODUCING EACH

摘要

High strength steel sheet which secures tensile maximum strength 900 MPa or more high strength while having excellent shapeability, which high strength steel sheet which is excellent in shapeability characterized by having a predetermined composition of ingredients, by the steel sheet structure including a ferrite phase and martensite phase, by the ratio of Cu particles incoherent with the bcc iron being 15% or more with respect to the Cu particles as a whole, by a density of Cu particles in the ferrite phase being 1.0×10 18 /m 3 or more, and by an average particle size of Cu particles in the ferrite phase being 2.0 nm or more.