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A Mechanism Study of the Stability of a Hybrid Plasma for Nd:YAG Laser Welding with Selected Gas Metal Arc Welding Processes
Z-Y. Li, L. Xing, Q. Zhang, W. Wang and X-F. Xu

The Nd:YAG laser-gas metal arc (GMA) hybrid welding process is gaining prominence due to its high welding speed, improved bead formation and stable welding process. Researchers have paid great attentions to the coupling effect and a lot of research works had been done on it. However, laser-arc hybrid welding processes with different GMA welding bring totally different coupling effects, which are significant for understanding of the processes and selecting the welding parameters. In this paper high speed photos of three different hybrid processes were compared to analyse the stability of the hybrid processes. The three processes are Nd:YAG laser-pulsed metal active gas (MAG) hybrid welding process, Nd:YAG laser-short circuit transfer MAG (STMAG) hybrid welding process and Nd:YAG laser-short circuit CO2 shielding (STCO2) hybrid welding process. Furthermore, in order to explore the interaction mechanism between Nd:YAG laser and the arc plasmas, the spectra of radiation emitted by the hybrid plasmas were also collected for analysis. The results show that the interaction between laser and arc plasmas are quite different for the processes. For Nd:YAG laser-STCO2 hybrid welding, the weld pool fluctuates greatly due to the interaction. The reflection and absorption of laser beam by the wavy weld pool makes the welding process instable. However, for STMAG, the process is stable and less interaction is caused due to fluctuation of the weld pool. For pulsed spray transfer MAG welding, the hybrid process is mainly formed between the laser beam and arc plasma. The coupling effect helps to stabilize the welding process.

Keywords: Nd:YAG laser, gas metal arc, hybrid welding, coupling effect, spectrum

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