Spectral analysis of the arc plasma in laser-tig double-side welding of aluminium alloy

Laser-TIG hybrid welding is considered as high-efficiency and high-quality welding method. However, the arc plasma absorbing, refracting and defocusing the laser beam is inevitable during the laser-TIG hybrid welding process. To avoid the serious loss of laser energy in the hybrid process, a technology of laser-TIG double-side welding (LTDSW) was developed by our research group. In this paper, Based on the experiments of laser-TIG double-side welding for aluminium alloys, the laser radiation influencing on the arc physical property was investigated by the optical emission spectroscopic diagnosis of arc plasma. The result shows that more metal vapor spetral lines is detected in the arc of LTDSW compared to the conventional arc. The intensity of metal vapor spetral lines in the arc of LTDSW is much stronger than the conventional arc, in the mean time the argon spetral lines is much weaker in the arc of LTDSW than the conventional arc. It is indicated that the laser keyhole effect on the opposite side makes more metal vapor or plasma come into the arc during LTDSW process, which changes the composition and intensity of arc. It is analyzed that the composition change of arc makes the arc discharge different from conventional arc.