High yield ratio and high-strength thin steel sheet superior in weldability and ductility, high-yield ratio high-strength hot-dip galvanized thin steel sheet, high-yield ratio high-strength hot-dip galvannealed thin steel sheet, and methods of production of same

Abstract From the Canadian patent

High yield ratio high-strength thin hot rolled steel sheet superior in weldability and ductility comprising steel containing, by mass%, C: over 0.030 to less than 0.10% 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%, containing further Ti: 0.01 to 0.055% Nb: 0.012 to 0.055%, Mo: 0.07 to 0.55% B: 0.0005 to 0.0040%, and simultaneously satisfying 1.1<=14xTi(%)+20xNb(%)+3xMo($)+300xB(%)<=3.7 the balance comprised of iron and unavoidable impurities and having a yield ratio of 0.64 to less than 0.92 a TSxEl , of 3320 or more, an YRxTSxEl 1/2 of 2320 or more and a , maximum tensile strength (TS) of 780 MPa or more.