| 摘要 |
PURPOSE:To manufacture the seamless steel pipe free from lapping flaws, by placing each corner of a square bloom at the bottom of caliber of each of rolls arranged in a vertical couple and a horizontal couple, and by applying the press piercing work to the bloom. CONSTITUTION:A vertical couple of rolls 1, 1', and a horizontal couple of rolls 2, 2', are provided in the press piercing mill; each corner of a square bloom 3 is respectively placed at the bottom of caliber of each of rolls 1, 1', and 2, 2'. The aquare bloom 3 is pushed forward while holding above stated positional relation, and the press piercing work is performed. The force to smash each of four corners of the square bloom 3 by the bottom of caliber, is always directed to the center of the square bloom 3, so that the formed hollow blank pipe is quite free from generation of lapping flaws. Moreover, if the grooves 1a, 1a', and 2a, 2a', are respectively provided in the bottom of caliber of each roll, the turnover of the square bloom 3 can be prevented. |
