Analysis of molten pool configuration and welding stability during high-power fiber laser welding

During high-power fiber laser welding, the emission of a molten pool includes plenty of information about welding quality. The configuration and characteristics of a molten pool are related to the stability of welding process. An approach based upon infrared image processing was proposed to analyze the configuration of a molten pool and evaluate the stability of welding process for high-power fiber laser welding. In laser butt-joint welding of type 304 austenitic stainless steel plate with a high power 10 kW continuous wave fiber laser, an infrared sensitive high-speed video camera was used to capture the dynamic images of the molten pools. The configurations of a molten pool and a keyhole were analyzed through image processing techniques such as automatic segmentation by dynamic threshold and mathematical morphology to extract the molten pool edge and measure the molten pool width. The molten pool width, keyhole area and keyhole width were defined as the configuration parameters of a molten pool, and the welded seam width was defined as the parameter reflecting the stability of welding process. Therefore, the correlations among these parameters were investigated, and the actual laser welding experimental results showed that the stability of a high power fiber laser welding process could be monitored and estimated by the defined configuration parameters of the molten pools.