An Accurate Analysis for Computation of Thermal Minimum Film Thickness in Inlet Zone in Hydrostatic Extrusion Process

Existence of thin lubricating film in inlet zone at the die and billet interface in hydrostatic extrusion process prevents metal-to-metal contacts in contact zone, which leads to reduction in interfacial solid friction. This enhances both the tooling life and surface quality of the products in addition to efficient extrusion operation. Hence, accurate prediction of the minimum film thickness of the lubricating oil in the inlet zone at the die and billet interface and its maintenance during the extrusion process in terms of operating parameters are vital issues from the operation and design point of views. Therefore, the objective of this work is to accurately analyze the inlet zone of extrusion operation for minimum film thickness considering the viscous heat dissipation in the lubricating film for proposing a handy empirical relation for minimum film thickness in terms of operating parameters for use in design and operation of extrusion process. Coupled solution of Reynolds equation, energy equation, and rheological relations are obtained for the minimum film thickness computations as functions of extrusion speed, material parameter, extrusion pressure, and die semi-angle.