Process stability analysis and weld formation evaluation during disk laser–mag hybrid welding

Abstract

For monitoring process stability and evaluating weld formation in laser–metal active gas arc welding (MAG) hybrid welding, this work proposes a new method that combines instantaneous status analysis and continuous stability analysis with a double high-speed photography system. Instantaneous physical phenomena were extracted from the top and bottom surfaces, which included information on arc light, metallic vapour, spatter, and the flow of the bottom molten pool. These features were used to evaluate the instantaneous status by analysing the keyhole status and droplet transition status in 316 stainless steel laser–MAG hybrid welding. The grey-level co-occurrence matrix (GLCM) and Gabor wavelet were used to measure the instantaneous status of the bottom molten pool in the spatial and frequency domains, respectively. Multiple physical phenomena of the top surface were obtained by morphological methods. The process stability mechanism was analysed based on visual features, and the time–frequency distributions of the process features were investigated for the stability analysis and formation evaluation. Unstable frequencies in the laser–MAG hybrid welding process and their influence factors were presented. Additionally, the relationship between the stability of the welding process and the weld formation was analysed by a continuous analysis method. The experimental results showed that the instantaneous analysis method effectively evaluated the instantaneous status of laser–MAG hybrid welding process, and the global stability of the continuous analysis method directly reflected the weld formation. The proposed method could be used to monitor the stability and weld formation of the laser–MAG hybrid welding process.