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| During deep penetration laser welding, a keyhole is formed in the molten pool. The characteristics of keyhole are related to the welding quality and stability. Analyzing the characteristic parameters of a keyhole during high power fiber laser welding is one of effective measures to realize seam tracking and improve the welding stability. Accurate seam tracking is precondition for successful laser welding quality and stability. It is meaningful to investigate the relationship between a keyhole status and the seam deviations. This paper studies a fiber laser butt-joint welding of Type 304 austenitic stainless steel plate with a high power 10 kW continuous wave fiber laser, and an infrared sensitive high-speed video camera was used to capture the dynamic images of the molten pools. A combination filtering system with a filter length of 960-990nm in front of the vision sensor was used to obtain the near infrared image and eliminate other light disturbances. The width, the area, the leftmost point, the rightmost point, the upmost point and the bottommost point of a keyhole were defined as the keyhole characteristic parameters. By using the image preprocessing method, such as median filtering, Wiener filtering, threshold segmentation and Canny edge detection methods, the characteristic parameters of a keyhole were obtained. By analyzing the change of the keyhole characteristic parameters during welding process, it was found that these parameters could reflect the condition of seam tracking and the quality of laser welding as well as the stability of laser welding effectively. |
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| Keywords:Mechanical manufacturing and automation; High power fiber laser welding; Keyhole; Characteristic parameters; Seam tracking |
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