等离子鞘层在等离子弧焊中的应用

Application of Plasma Sheath in Plasma Arc Welding

指出了尾焰电压和等离子云探针检测方法的本质,都是检测电弧的等离子焰.根据等离子体鞘层理论分析,用尾焰电压和等离子云探针检测等离子焰时,在金属检测板或金属探针表面附近将产生鞘层电压,相对于被焊工件为负电压值.鞘层电压与等离子体的温度及等离子体组分有关.动态平衡时,在金属检测板或金属探针表面的负电压值为一常量,可以根据公式计算该电压值.文中提出了一种无源探针检测等离子云的方法,该方法更加证明了等离子焰检测中等离子鞘层理论的重要性.

The high quality of the weld and the p ro cess stability in plasma arc welding can be obtained by the detection of the sta te of the keyhole (fully penetrated or not) through the efflux plasma voltage an d plasma cloud voltage. It is found that the essence of the efflux plasma voltag e detection and the plasma cloud probe detection is uniform. Both the detections are for the plasma flame. On the basis of the theory of plasma sheath, there is a negative potential (sheath voltage) near the surface of the detection plate o r the metallic probe. The value of the sheath voltage depends on the temperature and the component of the plasma. It is also found that the sheath voltage is a constant when the process is in dynamic equilibrium and a corresponding formula is brought forward. At the same time, a new device without electrical source to detect the plasma cloud is set up, which verifies the validity and the importanc e of the theory of plasma sheath.