Method for eliminating residual stress in welding by ultrasonic peening and use thereof

The invention relates to a method for eliminating residual stress in welding by ultrasonic peening and use thereof. The method is implemented mainly by using an ultrasonic peening device which comprises an ultrasonic wave generator, an acoustic system and a machine frame, wherein the ultrasonic wave generator and the acoustic system are arranged on the machine frame; the acoustic system has an energy transducer; the ultrasonic wave generator converts 50Hz power frequency alternating current power in a grid into ultrasonic frequency 20kHz alternating current power for exciting the energy transducer of the acoustic system; and the energy transducer of the acoustic system converts electric energy into mechanical vibration at the same frequency and transmits the ultrasonic frequency mechanical vibration to a weld joint in a workpiece at the temperature of 400 to 800 DEG C, so that a deep enough plastic deformation is formed on the surface of the weld joint part. The method which adopts a simple process has high-efficiency, energy-saving and environmentally-friendly characteristics and other characteristics in the elimination of the residual stress generated in a repair and welding process of a cast steel piece such as a swing bolster and a side frame. In addition, the method improves the stress distribution and fatigue strength of the weld joint.