Abstract: Glass lubricated hot extrusion process is a very important way to manufacture large-diameter, thick-walled seamless steel tubes. However, theoretical study on its lubrication behavior is still inadequate. The lubrication process is divided into two stages, the formation of the melted glass and the evolution of the film during the calibration phase. The temperature distribution, viscosity distribution and the velocity distribution throughout the lubrication pad is obtained. The glass flow rate based on two velocity boundary conditions and the stability parameter are obtained. The feasibility to extrude large steel tubes at 70 mm/s is verified theoretically. The way to predict the glass film thickness throughout the extruded product combining a FEM model to calculate the surface temperature of the billet and a theoretical model is proposed. The predicted glass film thicknesses are in good agreement with experimentally observed results.

Key words: Glass film thickness, Glass lubricated hot extrusion, Stability parameter, Distributor engaging in remanufacturing, multi-period, Remanufactureability design level, Closed-loop supply chain