No abstract

Gas hollow tungsten arc (GHTA) welding experiments on aluminum pipe were performed in a simulated space environment and in a vacuum at 1 G. Square butt welding joints with a non-root gap on aluminum pipes were formed by orbital welding with filler metal using a pulsed DC power supply in a vacuum chamber under 10 À2 G and 1 G gravity conditions. The butt welding process during aluminum-pulsed DC GHTA welding with a filler metal was investigated by analyzing images obtained using a high-speed video camera. In addition, the macrostructure and mechanical properties of the butt welding joints were investigated. The results revealed that arc discharge and melting-solidification during pulsed DC GHTA welding were insensitive to the gravity conditions because welding is strongly affected by the impulsive arc pressure generated by the peak current. In addition, GHTA welding experiments performed in a simulated space environment demonstrated that pulsed DC GHTA welding with a filler metal can produce defect-free aluminum butt welding joints with sufficiently high strength.

The Gas Hollow Tungsten Arc (GHTA) welding experiments on aluminum pipe were carried out in a simulated space environment and a ground 1 G vacuum environment. The square butt welding joints with non root gap on aluminum pipe were made by orbital welding with filler metal using DC-pulsed power supply in the vacuum chamber under the 10 −2 G and 1 G gravity conditions. The butt welding phenomenon during the aluminum DC-pulsed GHTA welding with filler metal recorded in the high-speed video image were analyzed and also the macrostructure and mechanical properties of the butt weld joints were investigated. As the result, it was clarified that the arc discharge and melting-solidifying process during DC-pulsed GHTA welding were insensitive to the gravity condition, because the welding phenomenon greatly receives the effect of the impulsive arc pressure in pulsed current. And also, the GHTA welding experiments under simulated space environment proved that the DC-pulsed GHTA welding process with filler metal could produce the defect-free aluminum butt welding joints with the enough strength safely.