Piercing method, production method for structure having hole, and structure having hole

Abstract

A piercing method using a hot-press includes: a piercing process of piercing a workpiece with a piercing edge; a concave portion forming process of forming a concave portions around a hole formed in the workpiece by the piercing process to enlarge a diameter of the hole; and a cooling process of cooling the workpiece.

1 . A piercing method using a hot-press, comprising:
 a piercing process of piercing a structure with a cutting edge;   a concave/convex forming process of forming a concave/convex portion around a hole formed in the structure by the piercing process to enlarge a diameter of the hole; and   a cooling process of cooling the structure.   
     
     
         2 . The piercing method according to  claim 1 , wherein an enlarged diameter amount of the hole by the concave/convex portion which is formed by the concave/convex forming process is larger than a contraction diameter amount of the hole by the cooling process. 
     
     
         3 . The piercing method according to  claim 1 , wherein the enlarged diameter amount of the hole by the concave/convex portion which is formed by the concave/convex forming process is large as a direction of a radially contracted diameter amount of the hole by the cooling process is large. 
     
     
         4 . A method of fabricating a structure having a hole using a hot-press, comprising:
 a heating process of heating the structure;   a piercing process of piercing the structure with a cutting edge;   a concave/convex forming process of forming a concave/convex portion around a hole formed in the structure by the piercing process to enlarge a diameter of the hole; and   a cooling process of cooling the structure while the cutting edge is inserted in the hole,   wherein an enlarged diameter amount of the hole by the concave/convex portion which is formed by the concave/convex forming process is larger than a contraction diameter amount of the hole by the cooling process.   
     
     
         5 . A structure having a hole which is fabricated by a hot-press, comprising:
 a hole formed by a piercing process using a cutting edge; and   a concave/convex portion formed around the hole to enlarge a diameter of the hole, wherein the hole and the concave/convex portion are formed after a heating process of heating the structure in the hot-press and before a cooling process of cooling the structure.   
     
     
         6 . The piercing method according to  claim 1 , wherein the enlarged diameter amount of the hole by the concave/convex portion which is formed by the concave/convex forming process is large as a direction of a radially contracted diameter amount of the hole by the cooling process is large.