Forward extrusion forging apparatus and forward extrusion forging method

Abstract

A forward extrusion forging apparatus includes: a die having a hollow portion whose diameter is reduced at an intermediate position; and a punch that is positioned behind a workpiece placed in the hollow portion, slides in the hollow portion, and extrudes the workpiece ahead of the hollow portion so that the workpiece is forged. An extruding surface of the punch, which extrudes the workpiece, is recessed in a direction opposite an extruding direction in a manner such that a center portion of the extruding surface is most recessed.

What is claimed is: 
     
         1 . A forward extrusion forging apparatus comprising:
 a die having a hollow portion whose diameter is reduced at an intermediate position; and   a punch that is positioned behind a workpiece placed in the hollow portion, slides in the hollow portion, and extrudes the workpiece ahead of the hollow portion so that the workpiece is forged, wherein   an extruding surface of the punch, which extrudes the workpiece, is recessed in a direction opposite an extruding direction in a manner such that a center portion of the extruding surface is most recessed.   
     
     
         2 . A forward extrusion forging method comprising:
 preparing a forward extrusion forging apparatus in which a die has a hollow portion, a diameter of the hollow portion is reduced at an intermediate position of the hollow portion, a workpiece placed in the hollow portion is extruded ahead of the hollow portion so as to be forged by a punch that is positioned behind the workpiece and slides in the hollow portion, and an extruding surface of the punch, which extrudes the workpiece, is recessed in a direction opposite an extruding direction in a manner such that a center portion of the extruding surface is most recessed; and   producing a first forged product by placing a first workpiece in the hollow portion and extruding the first workpiece forward with use of the punch so that the first workpiece is forged.   
     
     
         3 . The forward extrusion forging method according to  claim 2 , wherein
 before the first workpiece is placed in the hollow portion, a forward surface of the first workpiece in the extruding direction is recessed in the direction opposite the extruding direction in a manner such that a center portion of the forward surface of the first workpiece is most recessed.   
     
     
         4 . The forward extrusion forging method according to  claim 3 , wherein
 before the first workpiece is placed in the hollow portion, a rearward surface of the first workpiece, which is pressed by the punch, protrudes in the direction opposite the extruding direction in a manner such that a center portion of the rearward surface of the first workpiece is most protruding.   
     
     
         5 . The forward extrusion forging method according to  claim 2 , further comprising:
 producing, after the first forged product is produced, a second forged product by placing a second workpiece in the hollow portion behind the first forged product and extruding the second workpiece forward with use of the punch so that the second workpiece is forged, and extruding the first forged product from an exit of the hollow portion with use of the second forged product.   
     
     
         6 . The forward extrusion forging method according to  claim 5 , wherein
 before the second workpiece is placed in the hollow portion, a forward surface of the second workpiece in the extruding direction is recessed in the direction opposite the extruding direction in a manner such that a center portion of the forward surface of the second workpiece is most recessed.   
     
     
         7 . The forward extrusion forging method according to  claim 6 , wherein
 before the second workpiece is placed in the hollow portion, a rearward surface of the second workpiece, which is pressed by the punch, protrudes in the direction opposite the extruding direction in a manner such that a center portion of the rearward surface of the second workpiece is most protruding.   
     
     
         8 . The forward extrusion forging method according to  claim 2 , wherein
 the workpiece is a sintered compact produced by press-forming powder that is a rare earth magnet material,   the powder includes a RE-Fe—B-based main phase and a grain boundary phase of a RE-X alloy present around the main phase,   RE represents at least one of Nd and Pr,   X represents a metal element, and   a rare earth magnet is manufactured by performing hot working in which anisotropy is imparted to the sintered compact by forward extrusion forging.