Patent ID: 9254511
Filing Date: 2016-02-09
CPC Classification: B21B

Claim Text:
1. A method for producing a seamless tube/pipe by using a piercing mill including a pusher on the entrance side, a plug on the exit side along a pass line, and a plurality of angled rolls as being provided around the plug, the method comprising the steps of: supplying a billet on the pass line, the billet including an unsound region consisting of center segregation and porosity in a cross section of the billet; pushing the billet to convey the billet toward the angled rolls; and piercing-rolling the billet by the piercing mill so that a plug nose rolling ratio (TDF) expressed by Formula (1) satisfies Formula (2): where, in Formulae (1) and (2), Bd: billet diameter [mm], D d: maximum diameter [mm] of the unsound region in the cross section of the billet.