| 摘要 |
A high-strength steel pipe excellent in deformability and low-temperature toughness being a steel pipe obtained by a base steel plate formed into a pipe shape being welded, in which the base steel plate contains, in mass%, C: 0.010 to 0.080%, Si: 0.01 to 0.50%, Mn: 1.2 to 2.8%, S: 0.0001 to 0.0050%, Ti: 0.003 to 0.030%, B: 0.0003 to 0.005%, N: 0.0010 to 0.008%, O: 0.0001 to 0.0080%, one or more of Cr, Cu, and Ni, P: limited to 0.050% or less, Al: limited to 0.020% or less, Mo: limited to 0.03% or less, a Ceq obtained by (Expression 1) below of 0.30 to 0.53 and a Pcm obtained by (Expression 2) below of 0.10 to 0.20, and a balance being composed of iron and inevitable impurities, and a metal structure of the base steel plate contains 27 to 90% in area ratio of polygonal ferrite and a hard phase composed of one or both of bainite and martensite as its balance. |
