Gas hollow tungsten arc welding experiments in aircraft‐borne simulated space environment

Aluminum alloys have been used widely in constructing various space structures including the International Space Station (ISS) and launch vehicles. For space applications, welding experiments on aluminum alloy were performed using the GHTA (Gas Hollow Tungsten Arc) welding process using a filler wire feeder in a vacuum. We investigated the melting phenomenon of the base metal and filler wire, bead formation, and the effects of wire feed speed on melting characteristics. The melting mechanism in the base metal during the bead on a plate with wire feed was similar to that for the melt run without wire feed. We clarified the effects of wire feed speed on bead sizes and configurations. Furthermore, the butt welded joint welded using the optimum wire feed speed, and the joint tensile strengths were evaluated. The tensile strength of the square butt joint welded by the pulsed DC GHTA welding with wire feed in a vacuum is nearly equal to that of the same joint welded by conventional GTA (Gas Tungsten Arc) welding in air.

Section: Development and Technological Problems In Spacementioning

confidence: 99%

Butt Welding Joint of Aluminum Alloy by Space GHTA Welding Process in Vacuum

Suita¹,

Shinike²,

Ekuni³

et al. 2006

“…We are now performing research and development of the GHTA welding process [6][7][8][9][10] for space applications. The high-frequency device employed to start the arc in previous conventional experiments may be an obstacle for electric devices placed on the ISS due to the creation of electromagnetic noise.…”

Section: Introductionmentioning

confidence: 99%

Welding Experiments of Aluminum Alloy by Space GHTA Welding at ISS Orbital Pressure

Suita¹,

Takai²,

Sugiyama³

et al. 2005

As a feasible welding method in space, the authors previously proposed the space GHTA (Gas Hollow Tungsten Arc) welding process. However, space GHTA welding with a high-frequency device for arc start may cause electromagnetic noise problems for the computer equipment placed on the ISS (International Space Station). Therefore, in this report, welding experiments of space GHTA welding using aluminum alloy with a high-voltage DC device for arc start were carried out at the ISS orbital pressure, 10 À5 Pa. It is clear from the experiments using a high-voltage DC device in a high-vacuum condition, that there is a shifting phenomenon in which the spark discharge shifts to either a glow discharge or an arc discharge when starting the arc. Welding projects in space need an arc discharge, so we investigated the effects of welding parameters on the arc formation ratio. As a result, space GHTA welding with a high-voltage DC device can be used for arc start when welding at the ISS orbital pressure.

“…The U.S. also conducted research on electron beam welding 6) and Nd-YAG laser welding, 7) but the low efficiency and heavy weight of the laser system made space application difficult. Consequently, the authors proposed the Gas Hollow Tungsten Arc (GHTA) welding process 8,9) in 1992, and continue research and development of the process [10][11][12][13][14] for space applications.…”

Section: Introductionmentioning

confidence: 99%

Development of Space DL Welding Process for Construction and Repair of Space Structures in Space

Suita¹,

Tabakodani²,

Sugiyama³

et al. 2005

An ultra-high vacuum diode laser welding system capable of performing a diode laser (DL) welding experiment at the International Space Station orbital pressure of 10 À5 Pa was developed for investigating the effect of environmental pressure on DL welding phenomena. A DL welding experiment with a power density of about 100 kW/cm 2 was conducted on 304 stainless steel at pressure levels between 10 5 Pa and 10 À5 Pa. Although a laser-induced plasma plume was observed during welding at environmental pressures, 105 Pa and 10 3 Pa, no laser-induced plasma plume was found in the pressure range from 10 Pa to 10 À5 Pa. The mode of the melting process (weld pool shape) under these experimental conditions was a keyhole-type melting mode or a transition-type melting mode at environmental pressures of 10 5 Pa and 10 3 Pa. However, the melting mode at pressures lower than 10 Pa changed to a heat-conduction-type melting mode. Although the penetration depth decreased when the environmental pressure was dropped to 10 3 Pa, it did not change at pressures lower than 10 Pa. We also determined that the prevention technology of metal vapor deposition on optical devices needs to be developed for DL welding technologies used in space.