Possibilities of improving weld seam quality in laser welding of aluminum die cast

Abstract

The process of aluminum die-casting produces near-net-shape, complex and thin-walled prefabricated parts of aluminum that is more widely applied in all areas of the industry because it has economic advantages compared to other processes in productivity. The technique mostly used in the molding process of aluminum die-casting products is fusion welding, which shows multiple problems: The safe production of pore free welding seams requires an expensive optimization all over the die-casting process as well as the choice of a qualified welding process.Compared to arc welding, the beam welding processes are characterized by high welding speeds, low heat input and consequently by small heat-affected zones and minimal distortion. Thus, the beam procedures are suitable in particular for components in which narrow and deep weld seams are required. Exemplary, aluminum die cast housings are such parts. However, the welds have to meet the desired requirements on the tightness there. This is a great challenge because aluminum die cast tends to pore formation and melt ejection due to its production-related gas content.Respect to the achievable weld seam quality, in particular, electron beam welding exhibits best results. This is due to the process management under vacuum in the range of p=10−3 hPa, which makes it possible to eliminate atmospheric influences and generally contributes to better degassing.An alternative beam welding procedure is laser beam welding. Compared to the EB welding, however, laser beam weldings of aluminium die cast have an increased porosity. In this paper, different possibilities are presented by which an improvement of weld seam quality in laser beam welding of aluminum die casting can be achieved. Experiments with different laser optical configurations, as well as varying process parameters influence the formation of pores in a considerable extent. In addition, the ambient pressure is a decisive parameter to improve the weld quality. The welding process is more and more stable and the formation of pores is clearly suppressed by decreasing pressure.The process of aluminum die-casting produces near-net-shape, complex and thin-walled prefabricated parts of aluminum that is more widely applied in all areas of the industry because it has economic advantages compared to other processes in productivity. The technique mostly used in the molding process of aluminum die-casting products is fusion welding, which shows multiple problems: The safe production of pore free welding seams requires an expensive optimization all over the die-casting process as well as the choice of a qualified welding process.Compared to arc welding, the beam welding processes are characterized by high welding speeds, low heat input and consequently by small heat-affected zones and minimal distortion. Thus, the beam procedures are suitable in particular for components in which narrow and deep weld seams are required. Exemplary, aluminum die cast housings are such parts. However, the welds have to meet the desired requirements on the tightness there. This is a great challenge because ...