| 摘要 |
PROBLEM TO BE SOLVED: To provide a high-strength steel pipe excellent in low-temperature toughness and buckling resistance and suitable for a pipeline (e.g. a line pipe) or a structural pipe (e.g. a steel pipe column or a steel pipe pile). SOLUTION: This high-strength steel pipe has a microstructure wherein the average grain size of ferrite is 10μm or lower and the r value in the pipe axis direction is 0.8 or higher. The pipe is produced by repeating a rolling schedule with a rolling reduction per pass of 8% or more, a pass time of 3 sec or less, a sum of rolling reduction of 32% or more, and a retention time after rolling of 10-300 sec, at least twice until a cumulative rolling reduction reaches 65% or higher, then conducting rolling at Ar<SB>3</SB>[°C] or higher but lower than the recrystallization temperature with a cumulative rolling reduction of 65% or less, and cooling to 500°C or lower at a cooling rate of 20°C/s or lower. COPYRIGHT: (C)2004,JPO
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