【摘要】：金屬零件增材制造是制造業(yè)領(lǐng)域取得的突破性進(jìn)展,為工業(yè)裝備中難加工金屬構(gòu)件的制造提供一條快速、柔性、高性能、短周期的技術(shù)新途徑。結(jié)合粉末漿料噴射增材制造的國內(nèi)外研究現(xiàn)狀,及氣動(dòng)噴射沉積的理論和粉末冶金技術(shù)成形經(jīng)驗(yàn),本文開展了鐵粉漿料氣動(dòng)噴射增材制造相關(guān)研究。該方法具有設(shè)備成本低、材料適用廣泛、無需保護(hù)氣氛、無需高能量束等優(yōu)點(diǎn),拓寬了金屬增材制造可用材料的范圍,在金屬增材制造領(lǐng)域具有廣泛的應(yīng)用前景。本研究選用甲基丙烯酰胺凝膠體系,通過優(yōu)化單體與交聯(lián)劑的組分比、分散劑質(zhì)量分?jǐn)?shù)、球磨時(shí)間等因素,制備均一、穩(wěn)定、適用于氣動(dòng)噴射增材制造的鐵粉漿料體系。通過漿料流變特性實(shí)驗(yàn)可知,鐵粉漿料為剪切變稀非牛頓流體,在恒剪切速率下漿料粘度隨球磨時(shí)間、分散劑WinSperse 4060質(zhì)量分?jǐn)?shù)以及固相體積分?jǐn)?shù)的增加而增大,在低剪切速率下變化更顯著�；贐ird-Carreau模型、Power-Law模型和H-B模型,結(jié)合逐步線化法和最小二乘法進(jìn)行參數(shù)擬合,對(duì)三種模型擬合結(jié)果對(duì)比分析,建立鐵粉漿料本構(gòu)方程。通過對(duì)噴嘴內(nèi)部鐵粉漿料的流動(dòng)狀態(tài)進(jìn)行合理性假設(shè)簡(jiǎn)化,建立鐵粉漿料運(yùn)動(dòng)控制方程�；谟邢拊治隼碚�,利用POLYFLOW軟件對(duì)噴嘴內(nèi)漿料流動(dòng)狀態(tài)進(jìn)行數(shù)值仿真分析,得到不同噴射壓力、噴嘴結(jié)構(gòu)參數(shù)下流體流場(chǎng)分布和噴嘴出口流速。采用網(wǎng)格重構(gòu)技術(shù)劃分自由段流體,分析不同噴嘴結(jié)構(gòu)下漿料的擠出脹大效應(yīng)。搭建了穩(wěn)定可控的鐵粉漿料氣動(dòng)噴射增材制造系統(tǒng)。建立了三種沉積線寬模型,研究噴射壓力、平臺(tái)速度、噴嘴結(jié)構(gòu)參數(shù)對(duì)成形線寬的影響規(guī)律以及線寬模型的選擇依據(jù)。研究層厚、延時(shí)時(shí)間、累積層數(shù)對(duì)增材制造樣件成形質(zhì)量的影響。對(duì)噴射成形坯體坍塌、斷裂、孔隙等缺陷問題的形成原因進(jìn)行分析并提出改進(jìn)方案。通過材料測(cè)試和實(shí)驗(yàn)結(jié)果分析,制定合理的干燥、脫脂、燒結(jié)制度,完成坯體強(qiáng)化成形過程,觀察不同階段下坯體微觀形貌變化情況,并對(duì)增材制造樣件燒失比、收縮率以及致密度進(jìn)行測(cè)量分析,最終實(shí)現(xiàn)金屬鐵粉漿料氣動(dòng)噴射增材制造過程。
[Abstract]:Metal parts manufacturing is a breakthrough in the field of manufacturing, which provides a rapid, flexible, high performance and short cycle technology for the manufacturing of metal components in industrial equipment. Based on the research status at home and abroad, the theory of pneumatic jet deposition and the forming experience of powder metallurgy technology, the research on the manufacture of iron powder slurry by pneumatic injection is carried out in this paper. This method has the advantages of low cost of equipment, wide application of materials, no need of protective atmosphere and no high energy beam, etc., which widens the scope of available materials for metal augmentation manufacturing, and has a wide application prospect in the field of metal augmentation manufacturing. In this study, the methacrylamide gel system was used to optimize the composition ratio of monomer to crosslinking agent, the mass fraction of dispersant, the milling time and other factors to prepare homogeneous and stable iron powder slurry system. The rheological properties of the slurry show that the slurry is a shear-thinning non-Newtonian fluid, and the viscosity of the slurry increases with the increase of ball milling time, the mass fraction of dispersant WinSperse 4060 and the volume fraction of solid phase at constant shear rate. The change is more obvious at low shear rate. Based on Bird-Carreau model, Power-Law model and H-B model, combined with stepwise linearization method and least square method, the fitting results of the three models were compared and analyzed, and the constitutive equation of iron powder slurry was established. By simplifying the flow state of iron powder slurry in nozzle, the governing equation of iron powder slurry movement is established. Based on the theory of finite element analysis, the flow state of slurry in nozzle was simulated by POLYFLOW software, and the flow field distribution and nozzle outlet velocity were obtained under different jet pressure and nozzle structure parameters. The mesh reconstruction technique is used to divide the free section fluid, and the extrusion swell effect of the slurry with different nozzle structure is analyzed. A stable and controllable manufacturing system for pneumatic injection of iron powder slurry was set up. Three kinds of deposition linewidth models were established to study the influence of jet pressure, platform velocity and nozzle structure parameters on the forming linewidth and the selection basis of the linewidth model. The effects of layer thickness, delay time and cumulative number of layers on the forming quality of the sample were studied. The causes of defects such as collapse, fracture and porosity of spray forming billet are analyzed and the improvement scheme is put forward. Through material test and experimental result analysis, the reasonable drying, degreasing and sintering system were worked out, the process of strengthening and forming of the billet was completed, the changes of the microstructure of the billet in different stages were observed, and the burning loss ratio of the sample made by adding material was also observed. The shrinkage rate and density were measured and analyzed to realize the process of aero-injection of metal iron powder slurry.
【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TH16

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