Prediction of longitudinal seam weld quality in multi-chamber aluminium extrusion

Abstract

In the extrusion of complex multi-chamber profiles, the longitudinal seam (L-seam) weld quality is significantly affected by the thermo-mechanical history and the ‘local’ formation conditions under which the weld is produced during the extrusion process. The L-seam welds can lead to non-uniform mechanical properties and variations with regard to the mechanical integrity of extruded products. Therefore, effective prediction and analysis of seam weld quality is crucial to quality insurance of extrusion products for advanced applications. This study deals with the prediction of L-seam weld quality and associated mechanism analysis in the extrusion of multi-chamber aluminium profiles to advance the understanding of how the ‘local’ thermo-mechanical history and conditions influence the weld quality. To this end, carefully controlled industrial-scale extrusion experiments were conducted to analyze the L-seam formation behaviour. Additionally, a finite element (FE) model was developed to investigate the thermo-mechanical history during the formation of L-seam welds. The model was also employed to predict the L-seam weld quality, incorporating several welding quality criteria, namely Q, K, and J criteria. Examination of the thermo-mechanical history within the welding chamber reveals a compromise in the welding quality at the centre of the L-seam compared to near the surfaces. Moreover, the findings highlight that the J-criterion can provide the most consistent predictions for the L-seam quality, providing a more accurate reflection of the thermo-mechanical history during the solid-bonding process than the Q and K criteria. The findings can contribute to the development of process guidelines and quality assurance strategies for producing multi-chamber aluminium extrusion profiles.