保护气体在激光焊接过程中起重要的作用, 保护条件的改变对焊接质量会有显著地影响。 研究Nd∶YAG激光焊过程中保护条件的变化对激光等离子体的电子温度和电子密度等特征参数的影响, 通过设计分步减小保护气流量的激光焊试验进行规律性研究, 通过模拟实际可能发生的保护不良的激光焊试验进行验证性研究。 在试验研究过程中, 利用光谱仪采集激光焊接过程中产生的光致等离子体的光谱信息, 通过相对光强法计算不同保护条件下等离子体的电子温度, 通过斯塔克展宽机制计算不同保护条件下等离子体的电子密度。 研究结果表明, 保护条件的改变对Nd∶YAG激光焊接过程中产生的光致等离子体的电子温度和电子密度有重要影响, 随着保护条件的变化, 光致等离子体的电子温度和电子密度的平均值会发生变化, 其波动幅度也会发生变化。 在保护良好的条件下, 等离子体的电子温度和电子密度均较小, 且波动幅度也较小; 在保护不良的条件下, 等离子体的电子温度和电子密度都比较大, 且波动幅度也比较大, 这种变化的特征有助于对激光焊接过程进行质量监控。

The shielding gas plays an important role in the laser welding process and the variation of the protecting conditions has an obvious effect on the welding quality. This paper studied the influence of the change of protecting conditions on the parameters of laser-induced plasma such as electron temperature and electron density during the laser welding process by designing some experiments of reducing the shielding gas flow rate step by step and simulating the adverse conditions possibly occurring in the actual Nd∶YAG laser welding process. The laser-induced plasma was detected by a fiber spectrometer to get the spectral data. So the electron temperature of laser-induced plasma was calculated by using the method of relative spectral intensity and the electron density by the Stark Broadening. The results indicated that the variation of protecting conditions had an important effect on the electron temperature and the electron density in the laser welding. 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. When the weld was in a good protecting condition, the electron temperature, the electron density and their fluctuation were all low. Otherwise, the values would be high. These characteristics would have contribution to monitoring the process of laser welding.