HIGH-STRENGTH WELDED STEEL PIPE INCLUDING WELD METAL HAVING HIGH COLD-CRACKING RESISTANCE AND METHOD FOR MANUFACTURING THE SAME

摘要

A high-strength steel pipe having a tensile strength of 800 MPa or more that includes a weld metal having high cold--cracking resistance and high low-temperature toughness is provided. The high-strength steel pipe is a high-strength welded steel pipe in which the welded steel pipe is manufactured by double one layer submerged arc welding performed on the internal surface and the external surface of a base metal, both the base metal of the welded steel pipe and a weld metal have a tensile strength of 800 MPa or more, the weld metal contains C: 0.04% to 0.09% by mass, Si: 0.32% to 0.50% by mass, Mn: 1.4% to 2.0% by mass, Cu: less than 0.5% by mass, Ni: more than 0.9% by mass but not more than 4.2% by mass, Mo: 0.4% to 1.5% by mass, Cr: less than 0.5% by mass, V: less than 0.2% by mass, and the remainder of Fe and incidental impurities, and the CS values calculated from the weld metal components using the equation CS = 5.1 + 1.4[Mo] -[Ni] - 0.6[Mn] - 36.3[C] are equal to zero or more at both the internal surface side and the external surface side.