Nippon Steel Corporation

Shusuke Shimooka

Kazuhiro Shimoda

Yuji Inoue

Kouji Yamane

Koichi Kuroda

Kazuyuki Murakami

Yuichi Yamanari

Kota Shindo

A method disclosed herewith is a method for producing a first seamless metal tube with a first wall thickness and a second seamless metal tube with a second wall thickness by using a three-roll-type inclined rolling mill, and the method includes a first inclination rolling step (#5), a setting changing step (#10), and a second inclination rolling step (#15). At the first inclination rolling step, a first workpiece is rolled by the inclined rolling mill. At the setting changing step, a setup condition of the inclined rolling mill is changed in a manner (a) or (b) as described below. At the second inclined rolling step, a second workpiece is rolled by the inclined rolling mill under the changed condition. (a) When the second wall thickness is smaller than the first wall thickness, the cross angle of each of the inclined rolls is made greater than the cross angle set for the first inclination rolling step. (b) When the second wall thickness is larger than the first wall thickness, the cross angle of each of the inclined rolls is made smaller than the cross angle set for the first inclination rolling step.

Method for producing seamless metal tube

A method for producing a seamless metal pipe includes the steps of: preparing a billet having a diameter (B); heating the billet; forming, in a center part of a rear end of the heated billet, a hole including four grooves extending in an axial direction of the billet, the grooves each having a groove width (D) satisfying Formula (1), a groove height (H) satisfying Formula (2), and a groove depth (L) satisfying Formula (3); and subjecting the billet provided with the hole to piercing-rolling from a front end thereof by means of a piercing machine. By this means, the generation of burrs and internal defects at the rear end of a hollow shell after piercing-rolling can be suppressed.0.12&#x2264;&#x2264;0.25&#x2003;&#x2003;(1)0.10&#x2264;&#x2264;0.20&#x2003;&#x2003;(2)0.05&#x2264;1/&#x2264;0.10&#x2003;&#x2003;(3)

Method for producing seamless metal pipe

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Tokyo, Japan

Shusuke Shimooka