BORING DEVICE, PLUG USED IN BORING DEVICE, AND METHOD FOR MANUFACTURING STEAMLESS STEEL PIPE

摘要

There is provided a piercing apparatus in which the occurrence of an inner surface flaw in a hollow shell is suppressed. A piercing apparatus (10) according to an embodiment of the present invention is the piercing apparatus (10) which pierces a billet (18). The piercing apparatus (10) has a plug (14). The plug (14) has a through hole (30). The through hole (30) extends along the central axis, and allows the central portion of the billet (18) being pierced to pass therethrough.