The Spectral Analysis Of Laser-Induced Plasma In Laser Welding Process With Dual Phase 1000 Steel

This paper mainly studied Nd: YAG laser welding technique of DP1000 high strength dual-phase steel sheets, and used the methods of spectroscopy to detect the laser-induced plasma and the spectral diagnosis to study the collected data. In addition, the electron temperature was calculated by the Relative spectral intensity method and the electron density was calculated by the Stark broadening method. The main purpose of this paper was to do a research on the parameters of laser-induced plasma such as electron temperature and electron density during the laser welding process with three conditions, namely reducing the shielding gas flow rate step by step, plate rusting and dislocation.With the analysis of the data collected from the laser welding process, we found that with the variation of the welding speed, the intensity of the laser-induced plasma merely changed very small. So we can suppose that the welding speed has little impact on the laser-induced plasma in our experiments.During the welding process of the Nd: YAG, the variation of the shielding gas had an important effect on the laser-induced plasma parameters such as electron temperature and electron density. When the protecting conditions were changed, the average electron temperature and the average electron density of the laser-induced plasma would change, so did their fluctuation range. In the relatively good protecting conditions(the shielding gas flow rate ranged from 10L/min to 20L/min), with the variation of the shielding gas flow rate, the electron temperature, the electron density and their fluctuation were all low. However, when the flow rate of the shielding gas decreased to 5L/min, the average of the electron temperature and the electron density increased, so did the fluctuation. When the flow rate of the shielding gas decreased to 0L/min, the average of the electron temperature and the electron density all increased largely, so did the fluctuation.Plate rusting and dislocation also have a significant influence of the laser-induced plasma parameters. During the welding process, when we started welding the rusting surface, the electron temperature and the electron density of laser-induced plasma were significantly increased and decreased and volatility and the fluctuations were high. During the welding process, when the dislocation started, the electron temperature and the electron density of laser-induced plasma were beginning to fluctuate. With the size of the dislocation from small to large, the electron temperature of laser-induced plasma and electron density were also having obviously raising and lowering.The results showed that the parameters of the laser-induced plasma can better reflect the characteristics of the changes during the laser welding process, which can be used to monitor the quality of the welding process in real-time.