CTOD THICK STEEL PLATE HAVING EXCELLENT LOW-TEMPERATURE IMPACT TOUGHNESS AND CTOD PROPERTIES AND METHOD FOR MANUFACTURING THE SAME

摘要

An aspect of the present invention relates to a thick steel sheet excellent in low-temperature impact toughness and CTOD properties containing : 0.02 to 0.06 wt% of C, 0.005 to 0.08 wt% of Si, 1.0 to 2.0 wt% of Mn, 0.01 wt% or less of P, 0.003 wt% or less of S, 0.001 to 0.01 wt% of Al, 0.5 to 2.0 wt% of Ni, 0.001 to 0.02 wt% of Ti, 0.005 to 0.03 wt% of Nb, 0.05 to 0.4 wt% of Cu, 0.002 to 0.006 wt% of N, and the balance Fe and unavoidable impurities, satisfying the following Expressions 1 and 2, having a microstructure with at least 95 area wt% of ferrite, and including an MA-cementite sum of 2 area wt% or less. Expression 1: 3.0=Mn+2Ni=4.3 Expression 2: 0.05=C+Si+10Al=0.25 (In the Expressions 1 and 2, each element symbol represents the content of each element in wt%).