Hydrodynamic lubrication in hydrostatic extrusion using a double reduction die

Abstract Theories of hydrodynamic lubrication for the hydrostatic extrusion of rigid-perfectly plastic and work-hardening materials are derived. The conditions under which hydrodynamic lubrication may exist are determined. Factors involved include, amongst others, billet velocity, fluid properties, back pressure and augmenting stress. To take advantage of the effect of back tension in lubrication as indicated by the theory a double reduction die has been designed and preliminary experiments conducted. There is evidence to show the existence of fluid film lubrication in these cases.