Metal flow in forward cold extrusion

Abstract

In this work, experiments with a small-scale extrusion apparatus are described. Billets of commercially pure lead, which has the diameter of 50 mm were extruded at romm temperature into 25 mm diameter solid bars at an extrusion rate of 2.5 mm/sec. Metal flow directions were determined during a small stepwise deformation process from distorted, originally square, grid-line network scribed on a meridian plane. Certainly, general agreement is found in the variation of the plastic region with die aperture and with mode of lubrication amployed. It was further found that the metal located in the corner, formed by cylinder wall and die face, was in a state of plastic deformation, This observation shows that the surface quality of the finished extrusion is dependent on the surface quality of the billet from which the extrusion was pressed.