Process optimisation of hot extrusion of aluminium 6061 alloy using bridge-die

Abstract

Porthole-die extrusion has the great advantage of forming hollow section tubes that are difficult to produce by conventional extrusion with a mandrel on the stem. Due to the complicated structure of the die assembly, the extrusion of hollow section tubes has been investigated experimentally. During the hot extrusion process of aluminium alloy 6061, the process parameters significantly affect the mechanical properties of extruded products. For better extruded components, these process parameters need to be optimised. An experimental investigation and analysis has been carried out to optimise the billet temperature, mandrel length, convex die angle and tooling temperature on porthole-die hot-extruded aluminium alloy 6061 tubes under extrusion ratio of24.03. During the experiments the above parameters were varied and Taguchi’s optimisation approach was applied to obtain an optimal setting of parameters. From the experimental results and further analysis, it is concluded that under 95% confidence interval the billet temperature 420 °C, mandrel length 8 mm, convex die angle 105° with three-channel die method gave the minimum extrusion load, while the highest tensile strength was obtained with billet temperature 410 °C, mandrel length 11 mm, tooling temperature 400 °C. However, the most significant process parameters responsible for minimum extrusion load and maximum tensile strength with their percent contribution were convex die angle 97.83% and mandrel length 81.16%, respectively.