REGULARITIES OF POROSITY FORMATION IN ELECTRON BEAM WELDING OF ALUMINUM ALLOYS UNDER LOW GRAVITY

Abstract

The use of welding processes in open space is necessary for the manufacture, assembly, and repair of large-sized structures of space stations both in the near-Earth orbit and during the exploration of the Moon, where it is planned the creation of longterm lunar bases, as well as other objects that ensure the activities and work of expeditions. These can be subassembly operations in creating pressure-tight buildings for residential and industrial use, as well as for storing energy resources, pipelines of space complexes, or repair for ensuring the long-term operation of existing systems. Electron beam welding (EBW) is an optimal and more technological process for these works in comparison with other welding methods. Deep vacuum and low temperatures, which are the natural environment under space conditions, encourage the use of electron beam technologies, including welding. The efficiency of this process is 85—90 %, which is the maximum one in comparison with other welding methods. EBW under Earth gravity allows gaining the mechanical and chemical properties, as well as vacuum tightness of welded joints at the level of the parent metal. Performing EBW in conditions of ultrahigh vacuum, low gravity, and low temperatures is complicated, therefore, the quality of welded joints may decrease. The obtained results of the experiments conducted under conditions of low gravity and low temperatures in space, as well as in the flying laboratory, showed an increased number of pores in the welds. First of all, this phenomenon was detected in the welding of samples made of aluminum alloys. They are widely used in creating space structures, which does not exclude the possibility of their application in the manufacture of welded structures on the Moon’s surface. The aim of this work is the studying the regularities of porosity formation in the metal of the welded joints made of aluminum alloys in EBW under low gravity by qualitative analysis of the main factors that determine the increased susceptibility to the formation of discontinuities of this type.