HIGH-STRENGTH HOT-DIPPED GALVANIZED STEEL SHEET AND HIGH-STRENGTH ALLOYED HOT-DIPPED GALVANIZED STEEL SHEET, EACH HAVING TENSILE STRENGTH OF 980 MPA OR MORE, EXCELLENT PLATING ADHESION, EXCELLENT FORMABILITY AND EXCELLENT BORE EXPANDING PROPERTIES, AND METHOD FOR PRODUCING SAME

摘要

Provided is a high-strength hot-dip galvanized steel sheet having excellent plating adhesion, formability, and hole expandability with an ultimate tensile strength of 980 MPa or more, the hot-dip galvanized steel sheet comprising a hot-dip galvanized layer formed on a surface of a base steel sheet. The base steel sheet contains, by mass%, C: 0.05% to 0.4%; Si: 0.01% to 3.0%; Mn: 0.1% to 3.0%; Al: 0.01 to 2.0%; in which Si + Al > 0.5%, P: limited to 0.04% or less; S: limited to 0.05% or less; N: limited to 0.01% or less; and a balance including Fe and inevitable impurities, a microstructure of the base steel sheet contains 40% or more by total volume fraction of martensite and bainite, 8% or more by volume fraction of residual austenite, and a balance of the microstructure being ferrite or ferrite and 10% or less by volume fraction of pearlite. The martensite contains 10% or more by total volume fraction of two or more kinds of three kinds of martensites (1), (2), and (3), and the hot-dip galvanized layer contains less than 7 mass% of Fe.