Prediction and control of part distortion during the hot extrusion of titanium alloys

When titanium and steel billets are hot extruded using flat dies and glass lubricant, the extrudate distorts. This distortion is even larger for non-symmetrical shapes and complex billet material behavior. The amount of distortion is often a complex interplay between the die design, glass lubrication and extrusion conditions. Many experimental try-outs are often needed to determine the die design and operating conditions for reduced distortion. In order to investigate distortion, a finite element model for the glass lubricated hot extrusion process was developed that included all relevant aspects of the hot extrusion process such as induction heating, billet transfer, glass lubrication and metal flow. A design strategy was developed that permitted modeling the three-dimensional metal flow field of a complex extrusion by a two-dimensional FEM model. This model was then used to study the effect of die design and process parameters in extrusion of a titanium aerospace structural. Die design strategy was used to modify design for reduced distortion. Model predictions were verified by experiments on an industrial 2000 t hydraulic press.