SEAMLESS METAL TUBE PRODUCING METHOD

摘要

The invention relates to a seamless metal tube piercing-rolling method using an inclined roll type piercing-rolling machine, capable of greatly suppressing Mannesmann fracture or circumferential shear strain without causing a failure in billet feed. This enables a product of good inner surface quality with less inner surface flaw to be produced with high productivity. Further, strengthening the front end rolling section of a plug makes it possible to sharpen the plug, to enlarge the feed limit, and to further efficiently produce a product superior in inner surface quality. Therefore, the inventive method is applicable in a wide field in piercing-rolling of seamless metal tubes.