Pusher device for piercing and rolling and method of manufacturing seamless pipe or tube using the same

A method of manufacturing a seamless pipe produced by piercing and rolling a billet using a piercing mill including a plurality of inclined rolls and a pusher device provided on the inlet side of said piercing mill,

• said pusher device comprising:
• a cylinder device including a cylinder shaft;
• and
• a rod shaped pusher mandrel attached at a tip end of said cylinder shaft and having its tip end abutted against the rear end of said billet,
• the cross sectional area Sp of said pusher mandrel and the cross sectional area Sb of said billet satisfying Expression (1),
• the length Lp of said pusher mandrel and the cross sectional area Sp of said pusher mandrel satisfying Expression (2),
• the moving distance Lc of the tip end of said cylinder shaft during piercing and rolling and the outer diameter Dc of said cylinder shaft satisfying Expression (3),
• said method of manufacturing a seamless pipe comprising the steps of:
• providing said billet between said pusher device and said piercing mill;
• pushing the rear end of said billet by said pusher device, thereby having the tip end of said billet bitten between said inclined rolls;
• and
• pushing said billet forward by said pusher device until the tip end of said billet moves for a prescribed distance after the tip end of said billet is bitten.
• 0.3≦Sp/Sb (1)
• Lp/Sp≦1.2 (2)
• Lc/Dc≦45 (3)