METHOD OF PRODUCING SEAMLESS METAL TUBE AND PUNCH FOR USE THEREIN

摘要

A hole (30) is formed in the center of the rear end face (20) of a round billet (10). The hole (30) has a predetermined depth from the rear end face (20) and a plurality of grooves (31) are provided in the side surface thereof. Each groove (31) extends in the depth direction of the hole (30). Pierce-rolling of the round billet (10) having a hole (30) is performed using a punch having a plug. During pierce-rolling, the base of the hole (30) is broken through with the plug and a protrusion becoming the starting point of bur is formed, and the protrusion is absorbed by the groove (31) as the plug advances. Consequently, occurrence of burs at the rear end of a hollow bare tube after pierce-rolling thereof can be suppressed.