HIGH-YIELD-RATIO HIGH-STRENGTH THIN STEEL SHEET AND HIGH-YIELD-RATIO HIGH-STRENGTH HOT-DIP GALVANIZED THIN STEEL SHEET EXCELLING IN WELDABILITY AND DUCTILITY AS WELL AS HIGH-YIELD-RATIO HIGH-STRENGTH ALLOYED HOT-DIP GALVANIZED THIN STEEL SHEET AND PROCESS FOR PRODUCING THE SAME

摘要

mass% , C: 0.030% to 0.10% less than , Si: 0.30 to 0.80%, Mn: 1.7 to 3.2%, P: 0.001 to 0.02%, S: 0.0001 to 0.006%, Al: 0.060% or less, N: 0.0001 to 0.0070% , and containing , Ti: 0.01 to 0.055%, Nb: 0.012 to 0.055%, Mo: 0.07 to 0.55%, B: 0.0005 to simultaneously further contains a 0.0040%, 1.1 14 Ti (%) + 20 Nb (%) + 3 Mo (%) + 300 B (%) 3.7 is satisfied , the balance of a steel consisting of iron and unavoidable impurities , and the yield ratio is more than 0.64 less than 0.92, TS El is also more than 3320 YR TS El ^{1 / 2} 2320, the highest tensile strength (TS) gohang weldability and ductility , characterized in that there is more than 780 high yield ratio high-strength thin steel sheet .