LINE-PIPE STEEL SHEET AND METHOD FOR MANUFACTURING THE SAME

The present invention relates to a line-pipe steel sheet with excellent fracture propagation resistance and high uniform elongation ratio and a method for manufacturing the same. The line-pipe steel sheet includes 0.08-0.10 wt% of carbon (C), 0.05-0.50 wt% of silicon (Si), 1.4-2.0 wt% of manganese (Mn), 0.01-0.05 wt% of aluminum (Al), 0.005-0.02 wt% of titanium (Ti), 0.002-0.01 wt% of nitrogen (N), 0.02-0.07 wt% of niobium (Nb), 0.05-0.08 wt% of vanadium (V), 0.1-0.4 wt% of nickel (Ni), less than 0.015 wt% of phosphorus (P), less than 0.005 wt% of sulfur (S), 0.0005-0.004 wt% of calcium (Ca), the remainder consisting of iron (Fe) and inevitable impurities. The microstructure of the steel sheet includes 65-80% of air-cooled ferrite and 20-35% of pearlite in an area fraction. According to the present invention, provided is the steel sheet of a line pipe capable of ensuring a DWTT of shear fracture area percent of more than 90% under a guaranteed temperature of -20°C and having a uniform elongation ratio of more than 10% at the same time, and having a yield strength of 70 ksi.