| 摘要 |
PURPOSE:To minimize the deformation resistance of a stock after piercing by juxtaposing plural pieces of guide roller shoes in an axial direction and providing variable angles to these guide roller shoes with respect to the center line perpendicular to the axial direction of main rolls to synchronize the shoes with the spiral advance of the stock. CONSTITUTION:A prescribed billet 11 is spirally advanced and while the billet is guided by the guide roller shoes 2 having an angle theta of inclination between inlet sides 1b of the main rolls 1, 1, the billet is rolled down. The billet is pierced by a plug 13 of mandrel and a gorge part 1a of the main roll 1. The solid billet 11 is sectionally deformed to a hollow shell 12 while the billet is guided by the shoes 2. The wear of the shoes 2 is thereby decreased and the life is extended. The quality of the stock after piercing is thus improved.
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