本文選題：激光熔覆 + 同軸送粉噴嘴　； 參考：《大連海事大學(xué)》2017年碩士論文

【摘要】：同軸送粉噴嘴作為激光熔覆系統(tǒng)中的關(guān)鍵設(shè)備,因其能實(shí)現(xiàn)在載氣流的作用下熔覆粉末與激光束同軸輸出,具有加工效率高,熔覆層各向同性好,易于自動(dòng)化控制等顯著優(yōu)點(diǎn),目前已經(jīng)成為激光熔覆材料供給設(shè)備的研究熱點(diǎn)。本文針對(duì)目前同軸送粉噴嘴普遍存在的粉流匯聚形態(tài)不易控制,匯聚效果不理想,激光熔覆質(zhì)量差等問(wèn)題,進(jìn)行了送粉噴嘴流場(chǎng)分析、結(jié)構(gòu)優(yōu)化和試驗(yàn)研究�；跉W拉雙流體模型對(duì)三維條件下同軸送粉噴嘴的粉末流場(chǎng)進(jìn)行了仿真模擬,并研究了載氣流量和送粉量對(duì)粉末流場(chǎng)的影響。結(jié)果表明,粉末流由噴嘴噴出后,在噴嘴下端逐漸匯聚,焦點(diǎn)位置粉末濃度達(dá)到最大,粉流直徑達(dá)到最小;為了獲得合適的粉末流,確定了載氣流量不小于9 L/min,送粉量不超過(guò)7.5 g/min的送粉工藝參數(shù)范圍。采用響應(yīng)面回歸分析法以及中心復(fù)合試驗(yàn)方案對(duì)噴嘴主要結(jié)構(gòu)參數(shù)進(jìn)行了試驗(yàn)研究,并對(duì)其進(jìn)行了顯著性分析和回歸擬合,得出了對(duì)粉流形態(tài)具有顯著影響的一次項(xiàng)、二次項(xiàng)和交互項(xiàng),最終建立了噴嘴結(jié)構(gòu)參數(shù)與粉流形態(tài)特征間的數(shù)學(xué)回歸模型。為了改善粉流匯聚效果,對(duì)噴嘴結(jié)構(gòu)進(jìn)行了優(yōu)化設(shè)計(jì),得到了噴嘴結(jié)構(gòu)的最佳參數(shù)組合,即 θ=62.94°、w=1.00mm、r=5.83mm、λ=3.00°。針對(duì)優(yōu)化前后的送粉噴嘴進(jìn)行送粉試驗(yàn),通過(guò)提取圖像灰度,分析了優(yōu)化前后粉末流的濃度分布情況并對(duì)仿真結(jié)果進(jìn)行了驗(yàn)證。結(jié)果表明,優(yōu)化后的送粉噴嘴粉流束腰直徑降低了 39.4%,焦點(diǎn)深度降低了 46.4%,優(yōu)化效果明顯。仿真與實(shí)驗(yàn)結(jié)果誤差均在10%以內(nèi),總體比較接近,說(shuō)明仿真結(jié)果具有一定的準(zhǔn)確性。采用優(yōu)化后的同軸送粉噴嘴進(jìn)行單道激光熔覆試驗(yàn),順利獲得了單道熔覆層,研究了主要工藝參數(shù)對(duì)熔覆層幾何形貌及稀釋率的影響,并選取了一組合適的工藝參數(shù)進(jìn)行熔覆試驗(yàn),獲得了具有良好幾何形貌和合適稀釋率的單道熔覆層,表明優(yōu)化后的同軸送粉噴嘴具有良好工作性能,可以滿足激光熔覆要求。
[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 擄/ 1. 00 mm / r = 5.83 mm, 位 = 3.00 擄. 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.
【學(xué)位授予單位】：大連海事大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TG173

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