Effect of the geometry and the surface treatment of punching tools on the tool life and wear conditions in the piercing of thick steel plate

摘要

The process behavior in the punching of holes in a larger thickness circular steel plate using punches of different outer diameters, convex double-shear angles, convex lengths, and surface treatments was investigated. Experimental results showedthat the appearance of the punched hole for a small clearance between the punch and the die displays a great number of slips to extend almost to the end of the hole through shear. When punches of convex double-shear angles of 20° with surface treatmentare used, the straightness and surface finish of the punched hole show a better state. The worn conditions of the punch during shearing can be broadly classified into side wear, face wear, chipping, crack, and gross fracture. The failure mode of a punchwith a convex double-shear angle of l2.5° during the piercing holes was mainly side wear. In addition, the worn mode for a punch of a convex double-shear angle of 20° shows dominantly side wear and gross fracture. The tool life for a punch having aconvex double-shear angle of 20° is greater than that for a punch of 12.5° convex double-shear angle. The effect of the convex length of the punch on the tool life for a convex double-shear angle of 20° is significant. In addition, the tool life for apunch with a TiC coating or lapping treatment is greater than that of a punch without surface treatment by 25-60%.