| 摘要 |
PURPOSE:To perform rolling which cancels variations in wall thickness caused by a hexagonal lining by forming an intermediate region between the groove bottom part and the flange part into a circular arc shape having a larger curvature than that of other parts. CONSTITUTION:In the front stand, a grooved roll 11 is put in a lower position from the pass line of a pipe stock P with the axis of the roll 11 horizontal and other two grooved rolls 12, 13 are installed in positions around the pass line by respective 120 deg. apart from the roll 11 sequentially. The rolls 11-13 substantially equal to each other. A groove profile of the rolls 11-13 is such that a curvature radius R2 of the intermediate region G is set to be smaller than a curvature radius R3 of flange parts F, F and a curvature radius R1 of the groove bottom part. By that, thinning of a wall of the part of a pipe stock faced to and rolled by the intermediate regions G of respective rolls 11-13 is restrained and variations in a wall thickness in the total peripheral direction are reduced. |
