Abstract: The present invention relates to a steel material used for a line pipe for transporting crude oil or natural gas and the like and, more specifically, to a steel material for a welded steel pipe, having excellent longitudinal uniform elongation for the pipe, a manufacturing method therefor, and a steel pipe using the same.

Abstract: A high-strength steel having excellent low-yield-ratio characteristics, according to one embodiment of the present invention, comprises, by wt %, 0.06-0.12% of C, 0.2-0.5% of Si, 1.5-2.0% of Mn, 0.003-0.05% of Al, 0.01% or less of N, 0.02% or less of P, 0.003% or less of S, 0.05-0.5% of Cr, 0.05-0.5% of Mo, 0.01-0.05% of Nb, 0.0005-0.005% of Ca and the balance of Fe and other inevitable impurities, and comprises polygonal ferrite as a microstructure, wherein the area fraction of the polygonal ferrite is 10-30% and the average hardness of the polygonal ferrite can be 180 Hv or less.

Abstract: A high-strength steel having excellent low-yield-ratio characteristics, according to one embodiment of the present invention, comprises, by wt %, 0.06-0.12% of C, 0.2-0.5% of Si, 1.5-2.0% of Mn, 0.003-0.05% of Al, 0.01% or less of N, 0.02% or less of P, 0.003% or less of S, 0.05-0.5% of Cr, 0.05-0.5% of Mo, 0.01-0.05% of Nb, 0.0005-0.005% of Ca and the balance of Fe and other inevitable impurities, and comprises polygonal ferrite as a microstructure, wherein the area fraction of the polygonal ferrite is 10-30% and the average hardness of the polygonal ferrite can be 180 Hv or less.

Abstract: The present invention relates to a steel material to which post weld heat treatment (PWHT) is applied after pipe making and, more specifically, to a steel material that maintains excellent low-temperature toughness even after undergoing a PWHT process, a steel material which is obtained therefrom, and which has undergone PWHT, and a method for manufacturing the same.

Abstract: The present invention relates to a steel material used for a line pipe for transporting crude oil or natural gas and the like and, more specifically, to a steel material for a welded steel pipe, having excellent longitudinal uniform elongation for the pipe, a manufacturing method therefor, and a steel pipe using the same.

Abstract: Provided is a steel sheet for an oil sand slurry pipe having excellent abrasion resistance, corrosion resistance, and low-temperature toughness including 0.2 wt % to 0.35 wt % of carbon (C), 0.1 wt % to 0.5 wt % of silicon (Si), 0.5 wt % to 1.8 wt % of manganese (Mn), 0.1 wt % to 0.6 wt % of nickel (Ni), 0.005 wt % to 0.05 wt % of niobium (Nb), 0.005 wt % to 0.02 wt % of titanium (Ti), 0.03 wt % or less of phosphorous (P), 0.03 wt % or less of sulfur (S), 0.05 wt % or less (excluding 0 wt %) of aluminum (Al), 0.01 wt % or less (excluding 0 wt %) of nitrogen (N), and iron (Fe) as well as other unavoidable impurities as a remainder.

Abstract: Provided is a steel sheet for an oil sand slurry pipe having excellent abrasion resistance, corrosion resistance, and low-temperature toughness including 0.2 wt % to 0.35 wt % of carbon (C), 0.1 wt % to 0.5 wt % of silicon (Si), 0.5 wt % to 1.8 wt % of manganese (Mn), 0.1 wt % to 0.6 wt % of nickel (Ni), 0.005 wt % to 0.05 wt % of niobium (Nb), 0.005 wt % to 0.02 wt % of titanium (Ti), 0.03 wt % or less of phosphorous (P), 0.03 wt % or less of sulfur (S), 0.05 wt % or less (excluding 0 wt %) of aluminum (Al), 0.01 wt % or less (excluding 0 wt %) of nitrogen (N), and iron (Fe) as well as other unavoidable impurities as a remainder.