Study On The Process Of Fiber Laser Welding Based On The Technology Of High-speed Camera

High-power fiber laser has been increasingly widely used in the automotive, energy, aviation manufacturing industry because of its high efficiency, high power, high beam quality, stability, easy to use, maintenance and other advantages .In the process of laser welding, plasma has an important effect on the energy coupling between the beam and workpiece, it contains important information about the quality control of welding, and the flow of the weld pool and the keyhole state have a direct affect on the welding quality and the stability of the welding process. But the interference from the high-temperature, high brightness, dynamic plasma have a big impact on the direct observation of laser deep penetration welding.A high speed camera system was set up in this paper, including a high speed camera, a ADQ card, a back light source, optical lenses. The selection and combination of those list above were meet the basic requirements of high-speed camera in fiber laser welding. Based on the characteristics of the specific target, back light system , optical lenses optical magnification and the parameters of the high-speed camera were selected and combined appropriately to obtain the dynamic and state characteristics of the plasma, the welding pool and the keyhole in fiber laser welding, in the situation of off-axis photographing. The actual size of the keyhole and the welding pool at different laser power were obtained which can provide important reference for numerical simulation of laser welding. After the study of the results of high-speed video, diffusive plasma grow up, detach from the welding pool and keyhole, then disappear gradually shows obviously periodic characteristic, which called periodic oscillation.The image processing module of the mathematical software MATLAB was used to process partial of the images of the plasma and the welding pool acquired by high-speed camera system. The edge of them were obtained; because of the characteristic of the images of the welding pool itself, the adaptability of the welding pool image processing program is not so good, while the adaptability of the plasma image processing program is well. GUI (Graphical User Interface) of plasma image processing was made to simplify operation. The results of the image processing of the plasma and keyhole showed that: the area of the plasma overall showed gradually ascending trend along with the increase of the laser power and decrease of the welding speed, which caused by the increase of the laser power density, however, the limitations of using the area of plasma reflect the size of it was found. The size of the keyhole in fiber laser penetration welding not only fluctuate with high frequency, but also with periodic low frequency.Formation of weld and the results of high-speed camera are studied together, the cycle of the fluctuate shape of the welding pool showing in the images and the weld face mapped well; that high-speed video images can reflect the stability of the welding process and whether the weld is good or not. It is high feasibility to carry out the online monitoring of laser welding technology research based on research in image processing and combined with the corresponding relationship between high-speed camera images and the welding process .