Metal flow behaviour of wide flat bar in the spreading extrusion process

Abstract

To examine metal flow behaviour experimentally in the spreading extrusion process, a round billet is spread by means of a spread ring and extruded through a die opening wider than the internal diameter of the container. In spreading extrusion, the extrusion load is reduced by about 30% in comparison with basic extrusion. However, the metal flow balance in spreading extrusion worsens, because of the high frictional force generated at the interface of the billet and spread ring during the filling process. When the profile is wide or when spread ring height is low, the geometry of the plastic deformation zone on the die face changes from an ellipse into a figure of eight at the wide zone at both ends of the die opening. As a result, the metal flow balance markedly worsens, due to an increase in the size of the plastic deformation zone and frictional resistance acting on the spread ring wall.