HIGH-STRENGTH AND HIGH-DUCTILITY HOT-DIP GALVANIZED STEEL SHEET SUPERIOR IN HOLE EXPANDABILITY, AND MANUFACTURING METHOD THEREFOR

摘要

PPROBLEM TO BE SOLVED: To provide a high-strength galvanized steel sheet having a tensile strength of 850 MPa or higher, and improved hole expandability together with improved ductility. PSOLUTION: The high-strength hot-dip galvanized steel sheet includes, by mass, 0.03 to 0.20% C, 1.0% Si, 0.01 to 3% Mn, 0.0010 to 0.1% P, 0.0010 to 0.05% S, 0.3 to 2.0% Al and 0.01 to 5.0% Mo, and further includes one or more selected from 0.001 to 0.5% Ti, 0.001 to 0.5% Nb, 0.0001 to 0.0050% B and 0.01 to 5% Cr, and the balance Fe with inevitable impurities, and has a microstructure containing ferrite of 30% by area ratio. PCOPYRIGHT: (C)2010,JPO&INPIT