마찰교반용접 기술의 항공우주분야 응용 동향

The more the launch vehicle weigh, the smaller payload the vehicle can carry. In order to make the space launcher as light as possible, strong and lightweight Al_Li alloys have been used in the cryogenic tankage of booster systems like Space Shuttle SLWT(Super Light Weight External Tank) and Falcon 9 of Space-X. However, weld porosity in this alloy has been a main problem in fusion welding due to the hygroscopic nature of Li-containing aluminum oxides. The benefits of friction stir welding(FSW) of Al-Li alloys were clearly evident since there is no liquid phase due to fusion or hot cracking problems in solid state welding process. For this reason, the friction stir welding method is currently used to manufacture lightweight launch vehicle structures with Al-Li alloys. In this paper, the FSW technology is introduced with the case studies of application for launch vehicles.