This work describes the activities carried out for developing an Electron Beam Welding procedure for building 2 cold-plates designed by Thales Alenia Space and made in AA 6061 T651. This special welding technology was used to minimize the distortions of the welded components. The cold-plates are the main components for the cooling system of the payload Mice Drawer System (MDS). Funded by ASI (Italian Space Agency) with Thales Alenia Space Italia as industrial Prime contractor, MDS will permit its utilization for other research programs with mice. The MDS is necessary to keep the required temperatures, both for the control electronic units and for the habitat of mice (cooling of recirculation air and drinking water of the cavies) during the transportation by space Shuttle and using onto International Space Station - ISS. The cold plates were realized by assembling two aluminum plates with variable thickness and finned surfaces, made by electro-discharge machining (EDM) which contain an AISI 316 serpentine for the water cooling system. The geometry of the welding is similar to a "partial penetration butt joint" around the 1700 mm long perimeter of the plates. The removable stock for the assembled components after welding (488 x 356 mm plate) were only 0.5 mm. So, the main target were the minimization the welding distortion while maximizing the penetration depth for reduce the mechanical stress on joint line. The main addressed issue was been the definition of welding parameters for avoiding porosity and "flashing" (interruption of electron beam during welding) typical of the aluminum alloy treatment. The qualification tests for the WPS were carried out to evaluate the welding efficiency and admissible stress concerning in NDT and destructive analysis. The tensile tests were performed on partial penetration butt joint with 5 0/+/ mm depth and give a linear strength over 1 kN/mm corresponding to about 154 M Pa for the analyzed welding sections. The welding strength is much than stress calculate in FEM analysis even in case of overloads caused by emergency situations (85.2 MPa). With the final parameters, summarized in the WPS-EBW (2006)001, were welded two cold-plates that very soon will reach the ISS.

cited By 0