Patent ID: 8124247

Claim:
A high-strength welded steel pipe including a weld metal having high cold-cracking resistance, wherein the welded, steel pipe is manufactured by double one layer submerged arc welding performed on an internal surface and an external surface of a base metal, both the base metal of the welded steel pipe and the weld metal have a tensile strength of 800 MPa or more, the weld metal contains C: 0.04% to 0.09% by mass, Si: 0.30% to 0.50% by mass, Mn: 1.4% to 2.0% by mask Cu: than 0.5% by mass, more than 0.9% by mass but not more than 4.2% by mass, Mo: 0.4% to 1.6% by mass, Cr: less than 0.3% by mass, V: less than 0.2% by mass, and the remainder of Fe and incidental impurities, and CS Values calculated from the weld metal components using the following equation (1) are equal to zero or more at both the internal surface and the external surface: CS= 5.1+1.4[Mo]−[Ni]−[Mn]−36.3[ C ] (1), with the following definitions [Mo]: Mo content of weld metal (% by mass) [Ni]: Ni content of weld metal (% by mass) [Mn]: Mn content of weld metal (% by mass) and [C]: C content of weld metal (% by mass), wherein the base metal contains C: 0.03% to 0.12% by mass, Si: 0.01% to 0.5% by mass, Mn: 1.5% to 3.0% by mass, Al: 0.01% to 0.08% by mass, Nb: 0.01% to 0.08% by mass, Ti: 0.0005% to 0.024% by mass, N: 0.001% to 0.01% by mass, O: 0.004% by mass or less, S: 0.002% by mass or less, Ca: 0.0005% to 0.01% by mass, at least one selected from the group consisting of Cu: 0.01% to 1.3% by mass, Ni: 0.1% to 3.0% by mass, Mo: 0.01% to 1.0% by mass, Cr: 0.01% to 1.0% by mass, and V: 0.01% to 0.1% by mass, and the remainder of Fe and incidental impurities.