PUNCH FOR COLD BACKWARD EXTRUSION FORGING

摘要

A punch (1) comprises a molding land part (2) formed parallel to a punch axis (7), a molding R part (3) having an arc-shaped cross-section and formed continuously with the molding land part (2) on the front end side from the molding land part (2), and a recess part (5) formed on the base end side from the molding land part (2) and having a smaller diameter than the molding land part (2). The Rockwell hardness (HRF) of a material (20) is within the range of 65-105. The curvature radius (R) of the molding R part (3) of the punch (1) is larger than the thickness (L) of a cylindrical peripheral wall part (21) of a forged product (25). The length (B) of the molding land part (2) of the punch (1) is within the range of 0.05-0.15 mm. The recess width (C) with respect to the molding land part (2) of the recess part (5) of the punch (1) is within the range of 0.15-1.0 mm.