激光熔覆同轴送粉喷嘴优化设计及试验研究

发布时间：2018-04-28 17:17

本文选题：激光熔覆 + 同轴送粉喷嘴　；参考：《大连海事大学》2017年硕士论文

【摘要】：同轴送粉喷嘴作为激光熔覆系统中的关键设备,因其能实现在载气流的作用下熔覆粉末与激光束同轴输出,具有加工效率高,熔覆层各向同性好,易于自动化控制等显著优点,目前已经成为激光熔覆材料供给设备的研究热点。本文针对目前同轴送粉喷嘴普遍存在的粉流汇聚形态不易控制,汇聚效果不理想,激光熔覆质量差等问题,进行了送粉喷嘴流场分析、结构优化和试验研究。基于欧拉双流体模型对三维条件下同轴送粉喷嘴的粉末流场进行了仿真模拟,并研究了载气流量和送粉量对粉末流场的影响。结果表明,粉末流由喷嘴喷出后,在喷嘴下端逐渐汇聚,焦点位置粉末浓度达到最大,粉流直径达到最小;为了获得合适的粉末流,确定了载气流量不小于9 L/min,送粉量不超过7.5 g/min的送粉工艺参数范围。采用响应面回归分析法以及中心复合试验方案对喷嘴主要结构参数进行了试验研究,并对其进行了显著性分析和回归拟合,得出了对粉流形态具有显著影响的一次项、二次项和交互项,最终建立了喷嘴结构参数与粉流形态特征间的数学回归模型。为了改善粉流汇聚效果,对喷嘴结构进行了优化设计,得到了喷嘴结构的最佳参数组合,即 θ=62.94°、w=1.00mm、r=5.83mm、λ=3.00°。针对优化前后的送粉喷嘴进行送粉试验,通过提取图像灰度,分析了优化前后粉末流的浓度分布情况并对仿真结果进行了验证。结果表明,优化后的送粉喷嘴粉流束腰直径降低了 39.4%,焦点深度降低了 46.4%,优化效果明显。仿真与实验结果误差均在10%以内,总体比较接近,说明仿真结果具有一定的准确性。采用优化后的同轴送粉喷嘴进行单道激光熔覆试验,顺利获得了单道熔覆层,研究了主要工艺参数对熔覆层几何形貌及稀释率的影响,并选取了一组合适的工艺参数进行熔覆试验,获得了具有良好几何形貌和合适稀释率的单道熔覆层,表明优化后的同轴送粉喷嘴具有良好工作性能,可以满足激光熔覆要求。
[Abstract]:Coaxial powder feeding nozzle is the key equipment in laser cladding system, because it can realize coaxial output of cladding powder and laser beam under the action of carrier airflow, which has many advantages such as high processing efficiency, good isotropy of cladding layer, easy automatic control and so on. At present, it has become the research hotspot of laser cladding material supply equipment. In this paper, the flow field analysis, structure optimization and experimental study of powder feeding nozzles are carried out in order to solve the problems such as difficult control of powder flow convergence, poor convergence effect and poor quality of laser cladding, which are commonly existed in coaxial powder feeding nozzles at present. Based on the Eulerian two-fluid model, the powder flow field of coaxial powder feeding nozzle is simulated and the effects of carrier gas flow rate and powder feed rate on the powder flow field are studied. The results show that the powder flow converges gradually at the lower end of the nozzle after ejection from the nozzle, the concentration of the powder reaches the maximum at the focal point and the diameter of the powder flow reaches the minimum. The technical parameters of powder feeding with carrier gas flow rate of more than 9 L / min and powder feed quantity of less than 7.5 g/min were determined. The main structural parameters of the nozzle were studied by the response surface regression analysis method and the central composite test scheme, and the significant analysis and regression fitting were carried out. Finally, the mathematical regression model between nozzle structure parameters and powder flow characteristics is established. In order to improve the effect of powder flow convergence, the optimum design of nozzle structure was carried out, and the optimum parameter combination of nozzle structure was obtained, namely, 胃 62.94 掳/ 1. 00 mm / r = 5.83 mm, 位 = 3.00 掳. The powder feeding test was carried out on the powder feeding nozzle before and after optimization. The concentration distribution of powder flow before and after optimization was analyzed and the simulation results were verified by extracting image grayscale. The results show that the diameter of powder flow waist of the powder feeding nozzle is reduced by 39.4 and the depth of focus is reduced by 46.4. the optimization effect is obvious. The error between simulation and experiment is less than 10%, which shows that the simulation results are accurate. The single pass laser cladding test was carried out with the optimized coaxial powder feeding nozzle, and the single pass cladding layer was successfully obtained. The influence of main process parameters on the geometrical morphology and dilution rate of the cladding layer was studied. A group of suitable technological parameters were selected for cladding test, and a single pass cladding layer with good geometry and proper dilution rate was obtained. It shows that the optimized coaxial powder feeding nozzle has good working performance and can meet the requirements of laser cladding.
【学位授予单位】：大连海事大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG173

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