Metalworking apparatus and metalworking method

Abstract

A pressing portion (11) formed in a tapered conical shape pushes away a metallic material of a to-be-opened portion (5) radially outward from the radial center. A portion pushed away (2b) is work-hardened (base-material-hardened) and a density of the plate material (2) increases as compared to that of the other portion of the plate material (2). A radial dimension (c2) of a work-hardened portion at a peripheral edge of the to-be-opened portion (5) is larger than a radial dimension (c1) of the pressing portion (11) (c1<c2).

1 . A metalworking apparatus comprising:
 a forging tool configured to work-harden a to-be-opened portion of a workpiece through forging; and   a punching tool configured to form an opening portion in the to-be-opened portion by punching,   wherein the punching tool has an insertion portion that has a diameter equal to a diameter of the opening portion, and a shoulder portion which is joined to the insertion portion and has a diameter which is larger than a diameter of the insertion portion and increases as the shoulder portion extends toward a proximal end of the punching tool, and   wherein when forming the opening portion by punching, the punching tool is inserted to such a position that the shoulder portion contacts a work-hardened portion remaining at an inner peripheral edge of the opening portion from an inner side surface.   
     
     
         2 . The metalworking apparatus according to  claim 1 , wherein the forging tool has a pressing portion that is provided in a protruding shape and configured to push away the to-be-opened portion radially outward from a radial center. 
     
     
         3 . The metalworking apparatus according to  claim 2 , wherein the pressing portion has a tapered conical shape. 
     
     
         4 . The metalworking apparatus according to  claim 2 , wherein, the forging tool has a flat portion which is provided around the pressing portion and configured to come into contact with a peripheral edge of the to-be-opened portion when the to-be-opened portion is forged. 
     
     
         5 . The metalworking apparatus according to  claim 1 , wherein the shoulder portion of the punching tool has a curved surface which increases in a rate of increase in diameter as the shoulder portion extends toward the proximal end. 
     
     
         6 . The metalworking apparatus according to  claim 1 , further comprising a striking tool configured to strike and flatten a region surrounding the opening portion while the opening portion is punched,
 wherein the striking tool has a striking surface that strikes and flattens a small protrusion which appears at a peripheral edge of the opening portion when the shoulder portion of the punching tool is inserted to the insertion portion.   
     
     
         7 . A metalworking method comprising:
 a forging step of work-hardening a to-be-opened portion of a workpiece through forging; and   a punching step of forming an opening portion in the forged to-be-opened portion of the workpiece by punching.   
     
     
         8 . The metalworking method according to  claim 7 , further comprising a striking step of striking and flatten a small protrusion appearing around the punched opening portion with a striking tool.