Characteristic line emissions of the metal vapour during laser beam welding

Abstract

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.

Progress and perspectives of in-situ optical monitoring in laser beam welding: Sensing, characterization and modeling

“…In [37]- [40], by using the spectrometer equipping with a CCD detector array, the acquired spectrum signals emitting from the plasma plume were acquired analyzed to relate the temperature of the plasma electron and the weld penetration depth, and the research findings could provide a solid foundation for the development of a closed-loop control system. In an effort by Zhang et al [32], the spectroscopic sensor was applied to gain a better understanding of the emission formation of plasma plume and in-situ detect the welding defects (i.e., blow out, undercut and humping) during the high-power disk laser welding process.…”

Quality assessment in laser welding: a critical review

“…The plasma electron temperature was monitored, and through a quantitative relationship between the penetration depth and the plasma temperature, extracted experimentally, the system reduced the rejected components due to incomplete or excessive weld penetrations. The phenomena related to the optical emission of the laser-induced plume have also been widely investigated, and various innovative spectroscopic systems such as the one presented have been developed in [71].…”

Quality Assessment Method Based on a Spectrometer in Laser Beam Welding Process

“…Sebestova et al [22] designed a sensor to monitor the pulsed Nd:YAG laser welding process, based on the measurement of the plasma electron temperature, and this sensor was used to detect the weld penetration depth. Zaeh and Huber [23] investigated the radiation emission of the laser-induced plume during LBW of aluminum and steel alloys, and they developed a system to control the chemical composition of the melt pool, during the active welding process. Chen et al [24] proposed a spectroscopic method based on a support vector machine (SVM) and artificial neural network (ANN) for the detection and classification of fiber laser welding defects.…”