Laser welding is a dynamic process in which the characteristics of the material change during welding, which affects its course. These changes can be monitored with a high-speed camera. We observed the process of laser overlap welding of AISI 304 steel, where we separated different characteristic regimes from the images - from conduction welding, spatter formation, plasma to keyhole welding and various defects. Different regimes have an impact on the final quality of the weld, so knowing them helps us in modelling laser welding to achieve optimal welding parameters. An experimental laser welding system was presented with a 3 kW continuous laser source, a fast moving table and an appropriately positioned high-speed camera and lighting for obtaining quality images of different welding regimes. We observed what happened during welding at different welding speeds and laser powers.
From the analyses, we found that with increasing power, the size of the melting pool and spatters increases, while increasing the welding speed changes the angle of the steam jet and, consequently, the direction of spatters. We also found that the welding parameters consequently affect the shape of the weld. From the recordings, we identified the limit speed of welding to ensure the stability of the keyhole, the limits between different regimes and the limit between conduction and keyhole welding. For higher powers, the Rosenthal, single-wave, elongated keyhole, pre-humping and humping regimes can be determined and their characteristics compared with the literature.
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