Abstract: Lubrication plays an important role in hot extrusion of Ni-based superalloy tubes. A theoretical model is applied in this paper to investigate lubrication behavior of 61MG718, A5 and Up68/2886 glass pad during hot extrusion process of IN690 superalloy tubes. The results indicate that the thickness of melted glass film declines with rise of extrusion speed and angle of glass pad. The influence of temperature depends on both the value of temperature and corresponding viscosity gradient of glass. Glass film shows better flow stability with rise of extrusion speed and decline of temperature. 61MG178 glass pad performs the best lubrication behavior among three kinds of pads and A5 pad is only suitable for low speed extrusion. Given lubrication and the cost of production, glass pad can be made to be triangular or trapezoidal shape at cross section according to the angle of it. After rational geometry design, 61MG178 pad can show excellent lubrication effect at the whole temperature and extrusion speed in industry production.

Key words: Glass pad, Hot extrusion, Theoretical model, Eccentric drive mechanism, Electro-hydraulic pressure control servo valve, Nonlinear mathematical model, Prototype, Rotary direct drive