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

Provided is a high-strength hot-dip galvanized steel sheet having smallmaterialanisotropy and excellent formability with an ultimate tensile strength of 980MPa or more.The hot-dip galvanized steel sheet includes a hot-dip galvanized layer formedon asurface of a base steel plate. The base steel plate contains, by mass%, C: 0.1to less than0.40%, Si: 0.5 to 3.0%, Mn: 1.5 to 3.0%, O: limited to 0.006% or less, P:limited to0.04% 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. Amicrostructure of thebase steel sheet contains ferrite of 40% or more, residual austenite of 8 toless than 60%,by volume fraction, and a balance being bainite or martensite. In a sheetthickness rangeof 5/8 to 3/8 from the surface of the base steel sheet, a pole density ofspecific crystalorientation is within a predetermined range. The hot-dip galvanized layercontains Fe:less than 7 mass% and a balance including Zn, Al, and inevitable impurities.