| 摘要 |
PURPOSE:To improve a shock resistance and a fatigue resistance by performing a rational heating control to a pipe end of a drill pipe material, and suppressing a generation of a stress concentration in a thickness increased part of the inside surface of the pipe end. CONSTITUTION:A pipe end part 10A of a drill pipe material 10 is heated up to a set temperature. Subsequently, a temperature of the pipe end part 10A heated to this set temperature is held for a prescribed time in a state of the set temperature. Next, after the prescribed time has elapsed, the pipe end part 10 is upsetted. Also, it is prevented that a stress concentration is generated in a thickness increased part A of the inside surface of the pipe end. A drill pipe obtained in this way is excellent in its shock resistance and fatigue resistance.
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