Abstract
Aluminum alloys that have high specific strengths have been widely used in constructing various space structures including the International Space Station (ISS) and launch vehicles. Considering space applications, a series of welding experiments were performed in vacuum on an aluminum alloy using the GHTA (Gas Hollow Tungsten Arc) welding processes under d. c., a. c., and d. c. - pulsed conditions. Results observed in the GHTA welding experiments performed in vacuum can be summarized as follows:
(1) When GHTA welding was performed using a commercial a. c. welding machine, the arc discharge did not occur during the electrode positive polarity of alternating current. As a result, it was not possible to remove oxide films from the specimen surface resulting in the cleaning action.
(2) During the d. c. - pulsed GHTA process, it was possible to mechanically shatter and remove the oxide films covering the molten pool by the impact of the arc force.
(3) A study has been made to determine effects of pulse current during the d. c. pulse welding on characteristics of melting and bead appearances during the d. c. - pulsed GHTA welding.
The above-mentioned results show that welding phenomena observed in the experiments performed under vacuum conditions were very different from those observed in the experiments performed in the air.
