Geometry and stability of the capillary during deep-penetration laser welding of AlMgSi at high feed rates

Abstract

The influence of the feed rate on the geometry of the capillary and the process stability during laser beam welding of the AlMgSi aluminum alloy AA6082 was investigated by means of online-X-ray videography. Processes at feed rates between 4 m/min and 50 m/min with laser powers of up to 16 kW were considered. The X-ray images were used to generate three dimensional reconstructions of the geometry of the capillary which allowed to calculate the absorptance and the local distribution of the laser irradiance inside of the capillary by means of a ray-tracing approach. The stability of the capillary increased with increasing feed rates, which resulted in the avoidance of both depth fluctuations and processing pores. The stabilization of the capillary is attributed to the change of the capillary’s geometry which leads to a corresponding change of the absorptance of the laser power.