Friction stir spot welding has been developed based on FSW, which is a new type of welding technology. The friction stir spot welding tool consist of a compression sleeve, a stir sleeve and a stir pin. By precisely controlling the relative movement of the components of the FSSW welding tool, the keyhole formed during the welding process will be filled while the stir pin is withdrawn. The welding process includes the insertion of the compression sleeve, the extraction of the stir pin, the extraction of the compression sleeve and the backfilling of the stir pin, and finally a solder joint with a flat surface is obtained. Compared to RSW, the strength, shear resistance and fatigue resistance of welding spots obtained by FSSW are more excellent.
（1）Common aluminum alloy (4XXX, 5XXX, 6XXX）
1.No additional materials are needed;
2.The strength, shear resistance and fatigue resistance of weld spot are more excellent;
Aluminum alloy structure products for airplanes, cars and trains
（3）Aluminum-Steel alloy welding