HIGH STRENGTH THICK STEEL PLATE FOR LINEPIPE HAVING EXCELLENT FRACTURE PROPAGATION ARRESTABILITY CHARACTERISTICS IN CENTER THEREOF AND METHOD FOR MANUFACTURING THE SAME

摘要

The present invention relates to a high-strength thick steel material for a line pipe having excellent crack propagation arresting performance on a center, and a manufacturing method thereof. An embodiment of the present invention provides a high-strength thick steel material for a line pipe having excellent crack propagation arresting performance on the center comprising: 0.04-0.09 wt% of C; 0.05-0.50 wt% of Si; 0.5-2.0 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; 0.01-0.05 wt% of V; 0.05-0.35 wt% of Cr; 0.1-0.4 wt% of Ni; 0.05-0.3 wt% of Mo; 0.015 wt% or less of P; 0.003 wt% or less of S; 0.0005-0.004 wt% of Ca; and the remainder consisting of Fe and inevitable impurities including fine structures containing 50-65% of acicular ferrite, 30-45% bainite, less than 10% of polygonal ferrite, and less than 5% of island martensite with respect to a total area and a manufacturing method thereof. According to the present invention, a thick steel sheet for a line pipe of a thickness of 25 mm obtaining excellent low-temperature crack propagation arresting performance and yield strength of 555 MPa or higher by securing a drop weight tear tester (DWTT) shear fracture ratio of 85% or higher on the center at a guarantee temperature of -30°C or less is provided.