抄録
In order to investigate the effects of the gravity, surface tension electromagnetic force and plasma stream on convection in a molten pool, electron beam (EB) welding and gas tungsten arc (GTA) welding were performed under both terrestrial and microgravity conditions. For iron alloys, pure iron, an iron-tungsten alloy (SKD4), and for aluminum alloys, pure aluminum and an aluminum-copper alloy (A2219), were used for the specimens. The cross sections of the specimens were analyzed by EPMA after the welding. During the EB welding, the surface tension and the buoyancy determine the convection. Under microgravity, only the surface tension causes the convection because the buoyancy is considered to be negligible. As a result, it is found that the convection due to the surface tension is dominant for iron alloys but it is very weak for aluminum alloys. Accordingly, when aluminum alloys are welded by arc welding under microgravity, only the electromagnetic force and plasma stream are the dominant effects on the convection. Therefore, the convection can be controlled by changing the arc length to break the balance between the electromagnetic force and the plasma stream.
