Research On Pulsed Ultrasonic MIG Hybrid Welding Of 7A52 Aluminum Alloy

The realization of smooth and controllable transition of molten drops has been the research problem and objectives in MIG welding. In view of the low transition frequency of molten drops and poor stability in MIG welding, the paper propose pulsed ultrasonic MIG hybrid welding method. Adjusting the pulse ultrasonic to control the intensity and direction of the ultrasonic radiation force, it changes the drop stress to realize faster and controlled droplet transition behavior. In addition, the pulsed ultrasonic MIG hybrid welding is used in 7A52 aluminum alloy welding, trying to solve the defects about the worse performance of aluminum alloy welded joint.According to the principle of experiment, pulsed ultrasonic- MIG welding equipment was accomplished. Through the acquisition of transducer input voltage signal, the equipment was proved be able to generate and control pulsed ultrasonic. The water dripping simulation experiments verified the existence of ultrasonic radiation force. The regulation of pulse ultrasonic vibration was analyzed and summarized, it is concluded that the pulsed ultrasonic vibration is stronger along with the increase of pulse frequency, the decrease of pulse duty ratio. This has important guiding significance to the follow-up study.By using high-speed cameras and synchronous data of welding electrical signal, arc behavior is firstly analyzed. The phenomenon of arc contraction is more obvious in the pulsed ultrasonic- MIG welding. The shape of arc changes from the bell shape to conical. The paper found arc shrinkage rate is the biggest in 6HZ pulse. By the change of the arc shape, the droplet transition type changes from the free transfer and spray transfer transition to a short circuit, short circuit-free mixed transition.The drop shape, velocity and transition behavior were analyzed. Under the action of ultrasonic pulse, molten droplets had smaller size and changed from the elliptic ball to ball. The paper achieve the goal of a smaller molten drops and faster transition. The decrease of the drop size affect drop transition type, making the droplet transition type change from drop wise transition to the droplet transition. Under the short arc, it also can make the molten drops change from the short-circuit transition to spray transfer. Under the pulsed ultrasonic, the uniformity of the weld dimension is higher and it had more dense scales lines. Under the same welding parameters, the pulsed ultrasonic-MIG welding can obtain more deep penetration and weld width ratio, the pulsed ultrasonic-MIG welding was used to 7A52 aluminum alloy welding. Compared to the common MIG welding, the pulsed ultrasonic-MIG welding can increase weld heat input, decrease the welding current, and get higher tensile properties and micro hardness, which solve the worse performance of aluminum alloy common MIG welding joint.