抄録
The behaviors of impact extrusion of Al and Cu were investigated at a constant extrusion ratio, i.e. 47.4 for Al and 19.6 for Cu, and at varying punch velocities of 6.2 to 10.8 m/sec. When extruded at high punch velocity, the inertia resistance and drawing forces becomes measurable. As a result the initial punch pressure is found to increase and the final punch pressure to decrease, and the difference of the initial and final punch pressures increases with increasing punch velocity. The critical velocities vcR at which the inertia parting takes place are found to be 324∼351 m/sec for Al at room temperature and 204∼211 m/sec for Cu at 400°C, respectively. It was confirmed that the inertia parting was detectable on the punch pressure vs. stroke curve as a sharp rise of pressure of the order of calculated inertia force. These observations predict that, in the impact extrusion at high velocity, metals show hydrodynamic behaviors. Finally the extrusion by multi-oriffice die is confirmed to be profitable for the extrusion of dense metals, making both the inertia force and the punch pressure small and avoiding the inertia parting to occur.
