低圧下でのＧＨＴＡ放電の特性と母材の溶融特性

Abstract

In this work, a feasibility study has been conducted to determine if gas-hollow-tungsten-arc (GHTA) can be used for welding purposes in space.As described in the previous paper, the GHTA-method has been tested in a simulated space environment using aircraft. The test result shows that the method is very promising as a welding process in space.In this paper, some fundamental characteristics of GHTA in vacuum chamber, such as ignition voltage and arc voltagecurrent characteristic, have been made clear and the results of melting test on stainless steel plate by GHTA-method have been compared with the case by a conventional GTA (gas tungsten arc)-method under atmospheric pressure.The results are summarized as follows, (1) The ignition voltage of GHTA depends on the ambient pressure : P, and the voltage is minimized under condition of P=26.6 [Pa](2) The arc voltage-current characteristic of GHTA is nearly equal to that of GTA under atmospheric pressure.(3) The penetration shape by GHTA-method is quite different from that by GTA-method under atmospheric pressure. The GHTA method is characterized by shallow and wide penetration.(4) The current distribution on anode surface of GHTA is extremely diffused, and the anode area increases with the arc-length.(5) The diffused anode, which means diffused heat source, gives a satisfactory explanation for the shallow penetration in the GHTA-method.