盘型激光焊金属蒸汽特征色调-色饱和度-亮度分析法研究

Study of characteristics of plume based on hue-saturation-intensity during high-power disk laser welding

对于大功率盘型激光焊,金属焊件表面在激光束辐射下强烈汽化并形成等离子体状的金属蒸汽羽状物.该金属蒸汽羽状物可逆向激光束传输,对激光有明显的屏蔽作用,降低激光辐射至焊件的能量密度,影响焊接效率和质量.因此研究金属蒸汽特征变化规律及其与焊接质量之间的关联,可实现由金属蒸汽特征实时监测激光焊接状态.以10 kW大功率盘型连续激光焊接304不锈钢钢板为试验对象,应用高速摄像机摄取金属蒸汽动态图像,将其转换至色调-色饱和度-亮度空间,提取金属蒸汽面积、激光束受影响路径长度等相关特征量,以焊缝熔宽的变化作为衡量焊接状态稳定性的参数.通过金属蒸汽特征值的均值统计和方差分析,试验证明根据金属蒸汽面积和激光束受影响路径长度等金属蒸汽特征可有效地反映熔宽质量,从而对焊接状况做出动态评估.

During high-power disk laser welding,the surface of the weldment is gasified strongly by the laser irradiation.Meanwhile,the metal vapor plume is generated and changed into the plasma state.This plume can transmit through the laser beam reversely and has a significant shielding effect on the laser beam.Therefore,the laser power which should be transferred inside the weldment is decreased, the welding efficiency and welding quality are seriously affected.By studying and exploring the relation between the characteristics and variation rules of plume and the welding quality,the state of laser welding can be monitored in real-time by the plume characteristics. In the high-power disk laser bead on plate welding of a type 304 austenitic stainless steel plate at a continuous laser power of 10 kW,an extraviolet and visible sensitive high speed color camera is used to capture the metal vapor plume dynamic images.These digital images are transfered to the hue-saturation-intensity color spaces from the red-green-blue color spaces.Also,the area of metal vapor plume and the path length which the laser beam runs through the metal vapor plume are segmented and defined as the plume eigenvalues. The fluctuation of weld bead width is used to evaluate the stability of welding quality.By analyzing the statistics of the variance and mean values of plume eigenvalues,the experimental results confirm that the stability of the welding could be evaluated by the plume characteristics dynamically.