THIN STEEL PLATE, GALVANIZED STEEL PLATE, HOT ROLLED STEEL PLATE PRODUCTION METHOD, COLD ROLLED FULL HARD STEEL PLATE PRODUCTION METHOD, HEAT TREATED PLATE PRODUCTION METHOD, THIN STEEL PLATE PRODUCTION METHOD, AND GALVANIZED STEEL PLATE PRODUCTION METHOD.

摘要

Provided are a thin steel plate, etc., said thin steel plate having a TS of at least 590 MPa, excellent strength-ductility balance, a low yield ratio, excellent YP in-plane anisotropy, and excellent plating properties. The thin steel plate has: a specific component composition; and a steel structure including a prescribed amount of ferrite and martensite, by area ratio, the average ferrite crystal grain size being no more than 20 µm, the average martensite size being no more than 15 µm, the ratio between the average ferrite crystal grain size and the average martensite size (average ferrite crystal grain size/the average martensite size) being 0.5-10.0, the hardness ratio between ferrite and the martensite (ferrite hardness/martensite hardness) being 1.0-5.0, and the ferrite aggregate composition being 0.8-7.0, by inverse intensity ratio of γ-fibers to a-fibers. The thin steel plate has a tensile strength of at least 590 MPa.