HIGH-STRENGTH HOT-DIP GALVANIZED STEEL SHEET AND MANUFACTURING METHOD THEREFOR

摘要

Provided are a high-strength hot-dip galvanized steel sheet that requires no addition of large amounts of Mo, Cr or other expensive elements or any special CGL heat history, and has low YP, high BH, excellent aging resistance and excellent corrosion resistance, and a manufacturing method therefor. The steel includes, by mass%, C: more than 0.015% and less than 0.100%, Si: 0.3% or less, Mn: less than 1.90%, P: 0.15-0.05%, S: 0.03% or less, sol. Al: 0.01-0.5%, N: 0.005% or less, Cr: less than 0.30%, B: 0.0003-0.005%, and Ti: less than 0.014%, where 2.2 ? [Mneq] ? 3.1 and 0.42 ? 8[%P] + 150B* ? 0.73 are satisfied. The steel structure has ferrite and a second phase. The surface area ratio of the second phase is 3-15%, the ratio of martensite and residual ? surface area ratio to the second phase surface area ratio is more than 70%, and the ratio of the surface area ratio present at the grain boundary triple points, of the second phase surface area ratio, is 50% or more.