HIGH-STRENGTH HOT DIP GALVANIZED STEEL SHEET AND HIGH-STRENGTH ALLOYED HOT-DIP GALVANIZED STEEL SHEET HAVING EXCELLENT FORMABILITY AND SMALL MATERIAL ANISOTROPY WITH ULTIMATE TENSILE STRENGTH OF 980 MPa OR MORE AND MANUFACTURING METHOD THEREFOR

摘要

[Abstract] Provided is a high-strength hot-dip galvanized steel sheet having small material anisotropy and excellent formability with an ultimate tensile strength of 980 MPa or more. The hot-dip galvanized steel sheet includes a hot-dip galvanized layer formed on a surface of a base steel plate. The base steel plate contains, by mass%, C: 0.1 to less than 0.40%, Si: 0.5 to 3.0%, Mn: 1.5 to 3.0%, O: limited to 0.006% or less, P: limited to 0.04% or less, S: limited to 0.01% or less, Al: limited to 2.0% 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 ferrite of 40% or more, residual austenite of 8 to less than 60%, by volume fraction, and a balance being bainite or martensite. In a sheet thickness range of 5/8 to 3/8 from the surface of the base steel sheet, a pole density of specific crystal orientation is within a predetermined range. The hot-dip galvanized layer contains Fe: less than 7 mass% and a balance including Zn, Al, and inevitable impurities.