Experimental research of thermal processing phenomena by micro-arc

实验研究了在氩气气氛下，在薄钨阴极与不锈钢板阳极间隙中产生微弧的现象。搭建了由微弧炬、压电器件和脉冲电机驱动的精确定位机构以及放电电源组成的实验装置。采用高速快门CCD相机，通过显微镜观察微放电的时间分辨率。结果表明：(1)当间隙长度超过10μm时，击穿电压随间隙长度的增加而增加。在几微米的小间隙长度范围内，与间隙长度无关，它需要几乎恒定的250-300 V电压。放电初期微弧高强度发光区域集中在电极尖端，随后随着放电时间的延长而扩大。(2)阳极表面微弧熔点的大小和/或形式主要取决于间隙长度。通过调节间隙长度、电流电平和脉冲宽度，可获得直径为5 ~ 10μm的平面熔点。

The phenomena associated with micro-arc, which is struck in argon gas atmosphere in the gap between thin tungsten cathode and stainless steel plate anode, were experimentally investigated. The experimental setup, which is consisted of a micro-arc torch, precise positioning mechanisms actuated by piezoelectric devices and pulse motors, and a power supply for discharge, was constructed. Time-resolution of micro-discharge appearance was observed through microscope with high-speed shutter CCD camera. The results obtained are summarized as follows :(1) Electrical breakdown voltage increases with increase of gap length beyond about 10μm. In the range of small gap length of a few micrometer, it requires almost constant voltage of 250-300 V independently of gap length. High intense luminous region of micro-arc is concentrated at the electrode tip in the early stage of the discharge and then expands with time.(2) The size and/or the form of melting spot at anode surface by micro-arc depend mainly on gap length. Melting spot with flat surface having diameter of 5-10μm can be obtained by adjusting gap length, current level and pulse width.