METHOD FOR MANUFACTURING LOW-ALLOY HIGH-STRENGTH COLD ROLLED THIN STEEL SHEET WITH EXCELLENT WELDABILITY AND THE STEEL SHEET MANUFACTURED THEREBY

摘要

PURPOSE: A method for manufacturing low-alloy and high-strength thin steel sheets with excellent weldability and cold-rolled thin steel sheets manufactured through the same are provided to improve productivity and reduce energy consumption by using casting heat directly by transferring thin slab through a roughing mill directly without passing through a reheating furnace. CONSTITUTION: A method for manufacturing low-alloy and high-strength thin steel sheets with excellent weldability is as follows. C, Si, Mn, Cr, P, and S of a thin slab(a) steel are satisfy C+Mn/6+Cr/50.55 and C+Mn/20+Si/30+2P+4S0.27. In a coiling step, finally rolled strip is cooled over 20C/s cooling speed and the strip is coiled in 555-440C-14Si-26Mn-11CrCT600-58C-35Mn-34Cr coiling temperature.