| 摘要 |
PURPOSE:To enlarge the both serving range of a side roll and bottom roll by arranging the fin pass which is provided exchangeably with a fin roll of different caliber more than one step or by making the roll length of the fin pass varying. CONSTITUTION:A fin roll 3 is arranged changeably against a side roll 1 and bottom roll 2 and a fin pass 4 is formed. The radius of curvature of the caliber of rolls 1, 2, 3 is made smaller at each step. In the formation of the larger diameter pipe the fin roll 3 is changed by the fin roll 3' having smaller radius of curvature of the caliber and the formation is performed with retreating the side roll 1 and bottom roll 2. Otherwise the roll length of the side roll 1, bottom roll 2 and fin roll 3 at each step is changed respectively and a shifting is made so as to avoid an overlapping of the cut edges of each roll 1, 2, 3. The application range of the side rool 1 and bottom roll 2 is thus enlarged. |
