METHOD AND APPARATUS FOR PIERCING SEAMLESS METAL PIPE

WIPO Patent Application WO1996021526

A1

A method and apparatus for piercing a seamless metal pipe, by which a hollow pipe having a high quality and having no surface scratches is produced without causing any trouble during the piercing at a pipe expansion ratio of more than 1.15. Piercing is characteristically carried out at a pipe expansion ratio of more than 1.15 using a piercer equipped with a cone type main roll and a disc roll under the following condition, 3