等离子云信号检测与影响因素分析

在等离子弧焊接中采用无电源探针法可以检测等离子云，判断焊接小孔是否形成。根据等离子体鞘层理论，伸入等离子云中的探针表面将产生一负电位，称其为鞘层电压。采用探针检测等离子弧焊接中的等离子云，其检测信号与鞘层电压密切相关。由于鞘层电压大小与探针检测处等离子体温度和成分有关，因此，在检测过程中，探针位置、焊接速度和焊接电流等影响等离子云温度的因素是影响检测电压大小的主要原因。试验证明，同样的焊接条件，探针位置不同，检测信号差别很大，甚至可能检测不到等离子云的信号。不同的焊接工艺参数，对应有不同的最佳探针位置，在最佳探针检测位置可以获得最大的检测电压值。

Signal detection of plasma cloud and analysis of influencing factors

A device without power is designed to detect plasmacloud to judge the keyhole information in plasma arc welding. Accordingto theory of plasma sheath, there is a negative electromotive force, calledsheath voltage ,on the surface of the probe located in plasma cloud. Detec-ting plasma cloud with a probe, experiments proved that the detecting sig-nal is very closed to sheath voltage, which is related to temperature andplasma component of detecting spot. Therefore, location of tungsten probe,welding velocity and welding current which influence the temperature ofplasma cloud are major factors that affect the detection signal. It provedthat with different location of probe detection signal is very different. Andsometimes no signal can be detected because of bad location of probe.There is different optimal location of probe to different welding parameter.In tile optimal location, the max detection signal can be detected.