| 摘要 |
PURPOSE:To reduce the space of installation, the number of workers, the material's temperature drop, the nick, etc., by successively simultaneously carrying out the first piercing pass to obtain the tubular material from the rod material and the second piercing pass to reduce the wall thickness of above tubular material. CONSTITUTION:The first piercer 30 for obtaining the thick-walled tubular material 10a from the rod material 10 by the first plug 32, and the second piercer 34 for obtaining the thin-walled tubular material 10b using the second plug 36 for reducing the wall thickness of the tubular material 10a obtained by the first piercer 30, are arranged in series adjacently; hereupon, the second plug 36 of the second piercer 34, and the first piercer 30's first plug 32 freely sliding inside the second plug 36 are constituted so as to be successively simultaneously inserted into the material 10. The helical rolls 30a, 30b, of the first piercer 30 and the helical rolls 34a, 34b, of the second piercer 34, are driven by respective independent drivers or by a common driver, and the plugs 32, 36, are also made possible to be held by respective independent holders or by a common holder. |
