| 摘要 |
PROBLEM TO BE SOLVED: To manufacture a small diameter welded tube with high production efficiency by forming the small diameter welded tube cylindrical with high accuracy in a non-lubricated manner using a large diameter roll stand in which rolls having diameters obviously larger than an external diameter of a tube to be formed are arranged.SOLUTION: A roll stand includes a pair of large diameter side rolls and a shoe or a die. The pair of large diameter side rolls comprises large diameter side rolls each of which is designed in such a manner that an external diameter ratio &phgr;/&phgr;of an external diameter &phgr;of a forming roll to an external diameter &phgr;of a formed tube is 10 or more. The shoe is disposed in a lower side between the large diameter side rolls and by being offset in a line inlet side, and is composed of a plate-like body including a flat surface that is a nearly isosceles triangle whose isosceles side is curved along the outer periphery of the large diameter side roll. The die is disposed in a lower side between the pair of large diameter side rolls and in a direction perpendicular to the axis of the large diameter side roll, and is composed of a long body having a cross-section whose upper portion has an isosceles triangle salient. With the use of the roll stand, a metal band is passed through the roll stand that is a single stand and is formed cylindrical, then an abutted portions of the metal band edge is welded and joined. |
