Characteristics of deformation in hot extrusion process of stainless steeltube

Effect of glass lubrication on metal flow in hot extrusion of stainless tub e in an example of Ugine-Sejournet process has been investigated experiment ally and theoretically, which has been closely related to the surface defec t of products. First, a relationship between viscosity of glass lubricants and friction coefficient is measured with a hot friction test. Friction coe fficient is proportional to logarithmic viscosity of glass lubricant. Glass lubrication for hot tube extrusion is found in hydrodynamic condition. The n finite element analyses of metal flow during hot tube extrusion is carrie d out to simulate metal flows, strains and stresses. Computed extrusion for ces and metal flows are in good agreement with experimental measurements. Q uantitative flow characteristics such as redundant work and abrupt change o f metal flow in bearing portion are evaluated with finite element analyses. It may be possible to optimize an extrusion condition of hot tube extrusio n to reduce surface defects such as transversal crack of products.