Effects of Process Parameters on Charge Weld Length during Multi-Hole Porthole Die Extrusion

The evolution of charge weld during multi-hole porthole die extrusion was studied by means of finite element simulation and Taguchi’s design. Moreover, based on S/N analysis, the optimal process parameters that can reduce the charge weld length was obtained, where the billet diameter is 100 mm, extrusion speed is 2.0 mm/s, tool temperature is 430 °C and billet temperature is 465 °C. The accuracy and effectiveness of such optimal process parameters were also verified. The purpose of the present study is to provide some information about the controlling of charge weld for extrusion engineers.

On the Fundamental Mechanism of Seam Welding in Extrusion of Aluminum Alloys

In extrusion of hollow Al-profiles two kinds of pressure welds are present inside the extrusion. One is called the charge weld (CW) and forms across the boundary interface between two billets extruded in sequence. The other is the seam weld (SW) which extends longitudinally along the extruded profile and the extrusion metal behind each die bridge. It is considered to form because of the splitting of the extrusion metal over the die bridge into metal streams which flow past the bridge and rejoin as they encounter behind the bridge. Over the time attempts have been made to explain the mechanics of extrusion welding for both the CW and the SW. Still there is lack of understanding of how these welds form, the main reasons for this is that the deformation conditions around a die bridge are complex and difficult to investigate. Because of the recent advancement of two technological fields, experimental grid pattern analysis and simulation of metal flow by FEA; new tools for analysis of the mechanics of formation of the SW and the CW are now available. The simplest possible case of 2D-extrusion seam welding is considered here and an attempt is made to describe the fundamental deformation mechanisms present when this weld forms behind a butt-ended die bridge.