| 摘要 |
PURPOSE:To prevent occurrence of waving and buckling of edge and reduce defective butting and welding sharply by peviously giving an extensional deformation larger than the edge to the central part of a band steel. CONSTITUTION:Variable crown rolls 1, 1 give the amount of roll crown by a hydraulic device so that an extensional deformation larger than both side edges E, E is given to the central part of a band steel B. Then, the band steel B is bent from C-shaped section to nealy O-shaped section in which two side edges E, E are opposed through side rolls 2, break down rolls 3 and fin pass rolls 4 that constitute forming roll group for bending the band steel B. Finally, both edges E, E are passed through squeeze rolls 5 while being heated and molten, and the both side edges E, E are butted and welded to form a tube P. |
