Effect of convex die angle of porthole die on elastic deformation and extrusion process in tube extrusion

Port hole die extrusion has a great advantage in the forming of hollow section tubes that are difficult to produce by conventional extrusion with a mandrel on the stem. Because of the complicated structure of the die assembly, the extrusion of hollow section tubes has been investigated experimentally. During the hot extrusion of aluminum alloy 6061, the change of process parameters will affect the mechanical properties of extruded products. In this study, Taguchi method is applied to optimize the process parameters in hot extrusion of Al 6061 tubes under extrusion ratio of 24.03. The experiments are arranged by orthogonal array method in which Die with three channels and four channels are used as outer arrays, the factors selected as inner arrays are the billet heating temperature, the convex die angle, bearing length and the container temperature. The extrusions are subsequently tested for tensile test, flattening test, expanding test using a conical punch, surface finish and micro-structure. Test results are analyzed by the quality measurement of Taguchi method to find the relationship between the design process parameters and mechanical properties of the products and to acquire the optimal combination of parameter. Then based on the results obtained from the additive model, conformity experiments are performed.