Analysis of characteristics of plasma image during highpower disk laser welding

A new approach for detecting and analyzing the deep welding quality in high-power disk laser welding based upon the plasma plume images is presented. During the laser butt-joint welding of 304 austenitic stainless steel plate with a high power 10 kW disk laser, an ultraviolet and visual sensitive high-speed video camera was used to capture the dynamic images of the plasma plume. The area and height of a plasma image were calculated as the characteristic parameters of plasma image using the image processing techniques. The weld bead width was defined as the parameter reflecting the stability of welding process. Moreover, the variation in the weld bead width and the plasma images in the welding process were monitored to research the correlation between the characteristics of the plasma image and the welding stability. To obtain the statistics of the characteristic parameters of plasma images that reflect the welding stability, the average and the percentage with different threshold values about the fluctuation of consecutive frames images for the plasma area and height at different parts of weld bead were studied. The actual laser welding experimental results showed that the stability of a high power disk laser welding process could be monitored and estimated by the defined characteristic parameters of the plasma images.