| 摘要 |
A high-strength steel pipe excellent in formability and burst resistance wherein, when a high-strength steel pipe exceeding 850 N/mm<2 >in tensile strength is produced by a UOE method, a ratio (R/r) of an average radius of curvature in a range of 120 mm in a circumferential direction including a weld of the steel pipe before pipe expansion in a pipe expansion process (R) to the radius of the steel pipe after pipe expansion (r) is 0.65 to 2.0, and preferably the ratio (R/r) is 0.90 to 2.0. Preferably, Vickers hardness of the base metal Hv, the minimum Vickers hardness at the HAZ Hz, pipe wall thickness t, and a peaking amount at the weld of the steel pipe before pipe expansion in a pipe expansion process delta satisfy the following expression,
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