To provide a piercing rolling method for a billet by which scratches on the inner surface at a distal end part of a material to be rolled hardly occurs in piercing rolling a billet (seamless steel tube base stock) by means of a piercer such as a Mannesmann piercer.
In the piercing rolling method for a billet performing piercing rolling on the billet 10 after heating it, a conical hole piercing work 40 is applied to the center of the distal end face of the distal end part of the billet before performing piercing rolling. The conical hole is formed into a shape in which the depth of the hole is >50 mm and the inlet diameter of the hole is larger than the depth of the hole. The conical hole piercing work 40 is performed by pressing the distal end face of the billet by a projection part of a die by using the die having the projection part after the heating and before the piercing rolling. The seamless steel tube is manufactured by using the above piercing rolling method for the billet.
COPYRIGHT: (C)2010,JPO&INPIT
FUJISAWA KOTARO
JP2000190006A | 2000-07-11 | |||
JPH01181905A | 1989-07-19 | |||
JPS5372763A | 1978-06-28 | |||
JPS459055B1 | ||||
JP2000190006A | 2000-07-11 |
WO2007100042A1 | 2007-09-07 |