| 摘要 |
<p>PURPOSE: A steel sheet for a line pipe with excellent low-temperature fracture toughness and uniform elongation and a manufacturing method thereof are provided to control cooling starting timing and a cooling speed per a cooling section after austenite recrystallization rolling and un-recrystallization rolling. CONSTITUTION: A steel sheet for a line pipe with excellent low-temperature fracture toughness and uniform elongation contains 0.04-0.10 wt% of C, 0.05-0.50 wt% of Si, 1.4-2.0 wt% of Mn, 0.01-0.05 wt% of Al, 0.005-0.02 wt% of Ti, 0.002-0.01 wt% of N, 0.02-0.07 wt% of Nb, 0.05-0.3 wt% of Mo, 0.3wt% or less of Ni, 0.02wt% or less of P, 0.005wt% or less of S, 0.0005-0.004 wt% of Ca, and the rest of Fe and unavoidable impurities. A microstructure of the steel sheet includes 30%-60% by an area percentage of a ferrite structure and 40-70% by an area percentage of a bainite mixed structure.</p> |
