Experimental observations of the laser keyhole welding process of AA5182

Monitoring systems for the laser keyhole welding process of aluminium Tailor Welded Blanks, are in many cases vital to ensure a certain weld quality. Especially process visualization with camera based systems gives a lot of insight. Although for steel it has already been demonstrated that images can be obtained in real-time from the laser welding process using these cameras based on silicon chips, for aluminium this turns out to be not so easy. The light emitted by the weld plume hides the weld pool from the coaxially mounted camera.
In this paper recent experiments are discussed in which a monitoring system is used, that is composed of low cost standard components, to visualize the CW Nd:YAG laser keyhole welding process of AA5182. This monitoring system utilizes a diode laser to illuminate the welding process, combined with an optical interference filter and a CMOS camera. In this way the monitoring system is not over-radiated by the optical emissions of the sample material. It proved to be possible to eliminate the influence of the light emitted by the weld plume on the image and to detect the melt pool. Future efforts will focus on visualizing the keyhole in these images.