Determination of welding pressure in the non-steady-state porthole die extrusion of improved Al7003 hollow section tubes

Porthole 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. Analytic approaches that are useful in profitable die design and in the improvement of productivity are inevitably demanded. In porthole die extrusion the welding strength promises the possibility of producing sound hollow section tubes. Welding strength is affected by many parameters, such as extrusion ratio, extrusion speed, die shape, porthole number, bearing length, billet temperature and mandrel shape. In this paper, parameters such as billet temperature, bearing length and product thickness, are examined. The welding pressures are examined through 3D simulation of the non-steady state and compared with experimental results. The objective of this study is to analyze the metal flow and to predict the welding pressure of product by FE simulations and experiments. These results will be applied to porthole die design in the future.