Stability information in plasma image of high-power CO2 laser welding |
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| Authors: | Guohua Li Yan Cai Yixiong Wu |
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| Institution: | 1. Shanghai Key Laboratory of Materials Laser Processing and Modification, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China;2. State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China |
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| Abstract: | In deep penetration laser welding, a capillary called keyhole is formed when the energy intensity reaches 106 W/cm2. During this process, the vaporized metal and the surrounding atmosphere can be ionized to form plasma both in and above the keyhole. The stability of the keyhole has an important influence on the properties of welded components and the fluctuations of plasma. In this paper, a method was developed to acquire the stability information from plasma images taken by high-speed photography. The influences of surface impurity and the flowrate of side-assist gas on the stability were investigated. Bead-on-plate welding was performed on 12 mm E-grade shipbuilding steel plates using a 15 kW CO2 laser, with helium as the blowing gas. Three characteristic parameters were used to evaluate the stability. It was found that these three characteristic parameters can effectively indicate the stability variation caused by the surface impurity and gas flowrate. The present research provides important insights into developing image-based sensors to monitor the welding process. |
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