| 摘要 |
<p>PURPOSE: A steel sheet and a manufacturing method thereof are provided to secure superior weldability by minimizing alloying elements and improve low temperature durability by optimizing cooling speed in the process of reheating-quenching. CONSTITUTION: A steel slab is re-heated to a temperature of 1100-1250°C. The heated steel slab is reduction-rolled more than 10wt% per pass to total more than 70wt%. The hot-rolling of the steel slab is finished above Ar3 temperature. The hot-rolled steel sheet is re-heated to a temperature of 850-950°C and cooled. The steel slab comprises C: 0.05~0.18wt%, Si: 0.15~0.3wt%, Mn: 0.5~1.5wt%, Cr: 0.1~1.5wt%, Mo: 0.1~0.5wt%, Ni: 0.1~0.5wt%, B: 0.0005~0.0050wt%, Ti: 0.01~0.03wt%, Nb: 0.01~0.05wt%, Al: 0.005~0.1wt%, P: 0.015wt% or less, S: 0.010wt% or less, and the remaining amount of Fe and inevitable impurities.</p> |
