PUSHER DEVICE FOR PIERCING-ROLLING PROCESS AND SEAMLESS PIPE MANUFACTURING METHOD USING SAME

摘要

A pusher device (4) has a cylinder device (30) and a pusher core (34). The cylinder device (30) has a cylinder shaft (32). The pusher core (34) is fitted to the front end of the cylinder shaft (32). The front end of the pusher core (34) is made to come in contact with the rear end of a billet (20). The lateral cross-sectional area (Sp) of the pusher core (34) and the lateral cross-sectional area (Sb) of the billet (20) satisfy the expression (1). The length (Lp) of the pusher core (34) and the cross-sectional area (Sp) of the pusher core (34) satisfy the expression (2). The distance (Lc) of movement of the front end of the cylinder shaft (32) during piercing-rolling operation and the outer diameter (Dc) of the cylinder shaft (32) satisfy the expression (3). The pusher device (4) can minimize uneven wall-thickness distribution of the front end part of a blank pipe manufactured by piercing-rolling using the pusher device. 0.3 = Sp/Sb (1) Lp/Sp = 1.2 (2) Lc/Dc = 45 (3)