Synchronized Monitoring of Droplet Transition and Keyhole Bottom in High Power Laser-MAG Hybrid Welding Process

This present paper addresses the process monitoring of laser-MAG hybrid welding by using a double high-speed camera sensing system. Different welding parameter experiments are conducted under the normal penetration condition. The real-time surface physical phenomena of top and bottom in welding process are captured by the sensing system. The image processing method is proposed to quantify the process status, such as droplet transition, spatter, keyhole bottom, and metal vapor. The statistical method combined with detail analysis method is used to analyze the effects of droplet transition on keyhole status under different welding parameters. Also, the time distribution of opened keyhole bottom is analyzed. The synchronization analysis is conducted to demonstrate the status of the droplet transition and laser-induced keyhole, and the status of the opened keyhole bottom is separated as two types: opened keyhole bottom occurs during droplet transition or during droplet growing. The experimental analysis results demonstrate that the droplet transition mainly affects the status of keyhole under normal penetration condition, and the opened time of keyhole bottom is quite different which means the effects are unstable. Furthermore, the experimental results confirmed that the process monitoring method in this paper is an effective way for laser-MAG hybrid welding evaluation.