| 摘要 |
A solid billet is piercing-rolled using a 4 roll-type inclined rolling mill including larger-diameter cone-type main rolls (1, 1') arranged horizontally or vertically to face each other across a pass line (X-X) and smaller-diameter auxiliary rolls (7, 7') arranged vertically or horizontally to face each other similarly across the pass line between the facing main rolls, while maintaining a feed angle (²) and cross angle (³) of the main rolls and a feed angle (²') and cross angle (³') of the auxiliary rolls to be within the ranges: 5° ‰¤ "², ²'" ‰¤ 25°; 3° ‰¤ "³, ³'" ‰¤ 35°; and 10° ‰¤ "² + ³, ²' + ³'" ‰¤ 55°. Preferably, a diameter (do) of the solid billet and a diameter (d) and wall thickness (t) of the hollow piece after the piercing satisfy the relationship: 1.5 ‰¤ -È r /È ¸ ‰¤ 4.5 (where È r = ln(2t/d 0 ), and È ¸ = ln{2(d - t)/d 0 }). With this configuration, it is possible to produce a thin-wall hollow piece at a high reduction rate from a billet made of a less formable material. |
