Piercing-rolling method and piercing-rolling apparatus for seamless tubes

Abstract

[Objective] To provide a method and apparatus for seamless tubes in which the occurrence of material peeling can be prevented even when the skew angle δ and tube expansion ratio are increased. [Means for solution] A piercing-rolling method for seamless tubes using a piercer, which is provided with a pair of cone-shaped main rolls and a pair of disk rolls, each pair being arranged in an opposing manner with a pass line therebetween as a center axis, and a plug whose center axis coincides with the pass line, wherein a billet to be pierced and rolled is advanced while being spirally rotated by a drive rotation of the main rolls; the method of which is characterized in each of the disk rolls being arranged in an inclined state at a fixed skew angle δ to the pass line.

Dependencies are inferred from the claim text.