Research Of Cathode Cleaning And Weld Bead Formation During AC TIG Welding

AC power supply is widely used to weld aluminum and its alloy for the cathode cleaning phenomenon during which the surface oxides can be cleaned during the direct current electrode positive (DCEP) polarity. However, there are still many controversy over cathode cleaning, especially in the influencing factors, cleaning process and mechanics. Based on experiments, the influence of several welding parameters on the cathode cleaning effect are studied and the relationship curve are obtained, then the cathode cleaning mechanics and the cleaning process was studied.In this work, a simple criteria is raised to evaluate the cleaning effect. Both the width of the cleaning zone and molten pool are taken into account during the study of the influence of the welding parameters on the cathode cleaning effect. The influencing welding parameters of the cleaning are determined and the relations between the welding parameters and the cleaning effect are obtained. a vision system is designed to observe the molten pool and the cathode cleaning zone, and clear images are obtained, this will pave the way for the intelligent control of the cathode cleaning effect.Clear images of the cathode cleaning spots have been captured by a fast speed vision system, and the behavior of cathode spots is observed. The surface micro-topography of the molten pool and the cleaning area are examined by scanning electron microscope, and after cathode cleaning the oxide is found in two forms: the remaining oxide layer and the white oxide particles. It is suggested that the craters of the cathode spots are in the area adhering to the base metal. The formation process of the cleaning area surface and the cleaning process are explained.In addition, It's conventionally thought that the width and penetration of the weld bead will increase as a function of the increase of electrode positive polarity time in a period(or EP ratio),while in this research results contrary to conventional expectations are obtained, only several recent literatures agreed with this report. And in the article the effect of the EP ratio on the Voltage, the Current, the arc status and the heat generation and distribution is studied and the experiment result is well explained from theoretically perspective.