| 2219aluminum alloy has been applied to manufacture the new type tank of spacevehicle. The tank is important for the space vehicle for the reason that it suffers fromboth the inner and axial pressure. In addition, the tank is usually used in the lowtemperature. Therefore, high welding quality should be necessary. However, the defectssuch as porosity cannot be avoided when the conventional arc welding technique is used,which is adverse for the welding quality.In this paper, friction stir welding of vehicle tank was studied, and it focused onthe effects of the welding parameters on mechanical properties, microstructure anddefects formation of the FSW joint. In addition, the effects of the offset distance of thewelding tool, the sheet thickness deviation, the gap between the butt welded sheets andthe welding order were also investigated.With the increase of rotational speed, the joint mechanical performance, reaches acertain value after the joint mechanical performance peak and begin to reduce, changesits performance under different welding speed is not the same; The material in thewelding nugget zone (SZ) was weakest in the joint. The strengths of the transverse andlongitudinal welds were almost the equal. The size of the equiaxed grains decreasedfrom the top to the bottom of the joint, and the microstructures in thethermo-mechanically affected zone (TMAZ) were similar between the advancing sideand the retreating side. The size of the SZ was bigger of the double welded jointcompared with that of the single welded joint, while the welding times have noinfluence on the mechanical properties of the joint. The welding defects can beeliminated by filling the similar material or friction stir welding more times. Thewelding gap should not larger than10%of the sheet thickness, and the welding tooloffset value should smaller than10%of the pin diameter. The tank with the diameter of500mm was welded successfully by using the optimal welding process. |
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