GHTA Welding Experiments in the Space Station Orbital Pressure.

As a welding method in space, the authors have proposed the GHTA (Gas Hollow Tungsten Arc) welding method in the previous papers, where some GHTA welding experiments have been conducted under the condition of low pressure (10-2 Pa) and/or the micro-gravity. In the present paper, a feasibility study has been conducted whether the method can be used under such a high vacuum condition (10-5 Pa) as on the space station orbit. As a result, it is made clear that the GHTA method is quite feasible under the high vacuum condition and its melting process strongly depends on the operating gas species such as Ne, Ar and Kr. Increasing the flow rate of operating gas decreases the mass of metal vapor from molten pool and the use of a heavy operating gas such as Kr also decreases the mass of metal vapor.