Effect of Punch Shapes on Micro Backward Extrusion of Brass

Abstract

This study considered four types of punch, which were flat, conical, spherical and standardized punched, to investigate the effect of the punch shapes on the micro backward extrusion of brass. Brass (JIS C2600) materials were annealed at 500 °C, 600 °C, and 700 °C and resulted in different microstructures with grain sizes of 50 μm, 70 μm and 111 μm, respectively. The annealed brass materials were carefully machined as cylindrical billets with the same dimension of 1.1 mm in diameter and length. The billets were later used in the experiments of the micro backward extrusion to form cups with 1.1 mm diameter and 0.2 mm thickness. The experimental results show that the type of punch affecting load in an increasing order are spherical, standardized, conical and flat punches. The results also show that load increases with the punch speed, and reduces as grain size increases.