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Behavior of bubbles in weld under microgravity

1998; Elsevier BV; Volume: 46; Issue: 12 Linguagem: Inglês

10.1016/s1359-6454(98)00084-6

1873-2453

K. Nogi, Yasuhiro Aoki, Hidetoshi Fujii, Kazuya Nakata,

Mercury impact and mitigation studies

In order to investigate the effect of gravity on the behavior of bubbles in a weld, gas tungsten arc (GTA) welding was performed with an argon–1% hydrogen mixed shielding gas both in a microgravity environment and in a terrestrial environment. The microgravity environment was produced for 10 s with less than 10−5 G by a drop-shaft type microgravity system. The material used was an aluminum alloy. By classifying pores into blowholes and wormholes with the shape factor of pores and comparing the results in both environments, the following points have been found. In a terrestrial environment, bubbles smaller than 135 μm were not significantly affected by gravity. Larger bubbles move to the upper part of the molten metal due to buoyancy before the weld is solidified, but they scarcely combine together during the movement. In a microgravity environment, both blowholes and wormholes are distributed uniformly in the weld.