钛合金激光焊接过程中等离子体光信号的检测与分析

Measurement and analysis of plasma optic signal during laser welding of titanium alloy

通过试验的方法探讨了钛合金激光焊接过程中的等离子体光信号与焊接质量的关系 ,结果分析表明 ,钛合金的激光焊接过程比低碳钢产生更强烈的等离子体云 ,等离子体光信号可以较好地反映焊接过程的稳定性和焊接质量的变化。焊接质量良好时 ,等离子体光信号幅值在某一固定值上下波动 ,当改变焊接参数使焊接熔深或熔宽改变时 ,信号的平均幅值亦有明显改变 ;当较大间隙或错边存在时 ,等离子体光信号的平均值明显降低 ,但两种信号的特征不尽相同 ,前者造成等离子体光信号剧烈动荡而均值很低 ,而后者一定范围内 ,随着错边量增加 ,信号幅值逐渐减小。上述试验结果表明 ,可以用等离子体光信号的幅值高低和波动大小作为焊接质量实时监测和控制的特征信号。

The relationship of titanium alloy laser welding quality and the plasma optic signal is discussed by experimental method. It is discovered that the plasma plume during titanium alloy laser welding is stronger than mild steel laser welding, and the plasma optic signal can reflect the stability of laser welding process and the change of weld quality. The amplitude of optic signal has a little fluctuation around a steady level when the good weld achieved, and changes obviously when the width or penetration of weld altered under the different welding conditions. If a gap or mismatch existed before welding, the average amplitude of signal decreases greatly, but the characteristics of two kinds of signals are different. The gap resulted in the strong fluctuation of the signal and its average amplitude was very low. As mismatch increased in a little range, the amplitude became lower and lower. The experiments indicate that the amplitude of plasma optic signal and fluctuation can be used as characteristic signal for real-time monitoring and control for titanium laser welding.