Ultrasonic composite stirring friction welding device and welding method

The ultrasonic composite friction stir welding device comprises a stirring head, a switching device and a transducer, the stirring head comprises a stirring needle and a static shaft shoulder, a lower bearing is arranged between the stirring needle and the static shaft shoulder, an inner hole of the static shaft shoulder is connected with a supporting cylinder through threads, and the supporting cylinder is used for fixing the lower bearing; the stirring needle is connected with a main shaft rotating cutter handle of welding equipment through the clamping part; the transducer comprises a pressing sleeve, a piezoelectric ceramic piece, an electrode and an insulating sleeve, and the piezoelectric ceramic piece, the electrode and the static shaft shoulder are designed to be of an integrated structure. The invention further discloses a welding method of the welding device. According to the ultrasonic-assisted friction stir welding device, ultrasonic-assisted friction stir welding is achieved, an ultrasonic transd