To provide a method for suppressing deviation in the wall-thickness of a seamless steel tube which can produce a seamless steel tube having a more even, that is, less deviated wall-thickness in a tubular circumferential direction than a conventional one, and to provide a guide for manufacturing a seamless steel tube.
A technique, wherein a heated round steel billet is passed through a tubular guide and led to a piercing mill, and rolled and pierced by pressing a shell-shaped plug against the front end of the billet, is improved. The outline of the improvement is as follows: the round steel billet is supplied to the piercing mill in a state that the outlet side position of the guide is set to be 250-300 mm apart from the position of the minimum roll-gap of the piercing mill while making the gap between the round steel billet and the guide to be 10-15 mm. Furthermore, a guide for manufacturing a seamless steel tube is also developed.
ITAYA SUSUMU
NANBU SEIICHIRO
Masaki Yamada