Finite element modelling simulation of transverse welding phenomenon in aluminium extrusion process

Transverse welds occur in the billet-to-billet extrusion process, which is often used in modern aluminium extrusion plants for the purpose of continuous production. The transverse weld introduces a discontinuity at the weld interface in the extruded product and in many structural applications. This is not acceptable because it can severely reduce the strength and is detrimental to the quality of the extruded product. For this reason the length of transverse weld material needs to be cut out of the extrusion. But this then decreases the overall yield of the product and so the transverse weld length should, therefore, be kept as minimum as possible. The experimental studies carried out in the past mainly concentrated on the quality and strength of the extruded products containing a weld interface. The behaviour of metal flow and the factors affecting the transverse weld length have not been systematically studied. Currently, the transverse welding pattern and length of the extrudate containing a transverse weld are determined purely by experience and simple empirical models. In this study, the formation and metal flow behaviour of transverse welds in the aluminium extrusion process were investigated using the finite element modelling (FEM) simulation technique. It was shown that inhomogeneous metal flow occur-red and a transverse welding pattern was revealed. The design parameters influencing the transverse weld length were also investigated and discussed. This study concentrated on improving the understanding of the behaviour and the formation mechanisms of transverse welds with the aim of providing general guidance for the aluminium extrusion industry in minimising the transverse weld length of the extrudate. (C) 2003 Elsevier Science Ltd. All rights reserved.