Longitudinal submerged arc welded pipe with excellent low-temperature toughness for oil-gas transmission and preparation method thereof

The invention discloses a longitudinal submerged arc welded pipe with excellent low-temperature toughness for oil-gas transmission and a preparation method thereof. The longitudinal submerged arc welded pipe comprises a steel pipe body and weld seams, wherein the steel pipe body has the toughness not smaller than 100J and the shear area larger than 85% at the temperature of -40 DEG C; and the weld seams have the toughness not smaller than 47J at the temperature of -40 DEG C. The steel pipe body comprises the following ingredients in percentage by mass: 0.05-0.12% of C, 0.3-0.5% of Si, 1.0-2.0% of Mn, 0.2-0.5% of Cr, 0.1-1.0% of Ni, 0.1-0.5% of Cu, 0.2-0.5% of Mo, 0.005-0.05% of Ti, 0.001-0.008% of N, 0.001-0.005% of Ca, 0.001-0.005% of REM, 0.001-0.01% of Al, not higher than 0.015% of P, not higher than 0.002% of S, and the balance of Fe and unavoidable impurity elements. The preparation method has the beneficial effect that through the method disclosed by the invention, the impact toughness of pipeline steel pipe base materials and weld seam positions can be improved effectively without carrying out heat treatment. The longitudinal submerged arc welded steel pipe for oil-gas transmission, produced by the preparation method, can meet the needs of constructing oil-gas transmission pipelines in cold regions at the temperature above -40 DEG C.