Experimental research of thermal processing phenomena by micro-arc

对氩气保护下薄钨阴极与不锈钢板阳极之间的差距中的微弧现象进行了实验研究。搭建了由微弧炬、压电陶瓷驱动的精密定位机构、脉冲电机和放电电源组成的实验装置。利用高速快门CCD相机在显微镜下观察了微放电形貌的时间分辨率。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的范围内，它需要与间隙长度无关的250-300 V的几乎恒定的电压。微弧的高强度发光区域在放电初期集中在电极尖端，然后随着时间的推移而扩大。(2)微弧在阳极表面形成的熔斑大小和形状主要取决于间隙长度。通过调节间隙长度、电流大小和脉冲宽度，可以得到直径为5-10μm的表面平整的熔斑。

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.