Evaluation of Polymers as Lubricants in the Extrusion of Aluminum

Abstract

The lubricating behavior of polytetrafluoroethylene, polyvinyl chloride, polychlorotrifluoroethylene, low density polyethylene, and high density polyethylene powders in the extrusion of 1100-0 aluminum has been investigated in terms of the extrusion force requirement and the quality of extrudate surface finish. Extrusion experiments which provided a measure of the extrusion force and friction force with varying ram travel were performed under both ambient and high temperature conditions. From these data the variation of coefficient of friction with ram travel and normal pressure has been calculated using the analysis based on von Mises’ yield criterion and spherical velocity fields. The effect of polymer powder particle size on the extrusion force was investigated. The extrudate surfaces were examined by scanning electron miscroscopy in order to study the film formation capability of polymers and to get an insight into the mechanism of polymer lubrication.