Characteristic line emissions of the metal vapour during laser beam welding

This article provides an insight into the origin of the radiation emissions during laser beam welding of aluminium and steel alloys. It is the fundamental basis for the development of a system monitoring the welding process of challenging alloys with respect to their chemical composition in the melt pool. To reduce welding faults, e.g. cracks, brittle phases or other metallurgical based defects, a high degree of process knowledge is necessary. This manuscript presents novel spectroscopic investigations used to analyse laser beam welding setups to gain a better understanding of the emission formation. Therefore, also the spatial origin of the emitted radiation of the deep penetration welding process was examined. These empirical results are accompanied by theoretical considerations about the excitation degree of different alloying elements. Together they are a progressive step to develop a system to control the chemical composition of the melt pool during the active welding process. Knowing the composition of the melt allows to control e.g. a filler unit to change the melt composition. The empirical results were conducted by processing common alloys of today’s manufacturing applications.