| 摘要 |
PURPOSE:To effectively prevent the thickness deviation in the wall thickness of the pipe, by bearing the rolling load of the mandrel bar as the tension, in case of performing the second piercing work for the hollow blank pipe. CONSTITUTION:The hollow blank pipe 1 is prepared by the piercing work of the first piercer; the mandrel bar 4 is provided with the plug 3 at its forefront head, and is inserted into the hollow blank pipe 1; hereupon, the mandrel bar 4 is freely rotatably held by the thrust block 5 on the front table side A. The blank pipe 1 is rotated and is advanced to the rear table side B; hereby, the blank pipe 1 is rolled and expanded at its inner diameter by the plug 3. During this piercing work, the mandrel bar 4 receives the tension and continues to hold the plug 3; as a result, the 4 receives the tension and continues to hold the plug 3; as a result, the mandrel bar 4 does not cause the distortion. Accordingly, the precession of the plug 3 never causes, so that the bar-steadier rollers are not required for the piercing work. |
