【摘要】：鋁合金作為汽車(chē)、電力和國(guó)防等領(lǐng)域普遍使用的有色金屬結(jié)構(gòu)材料,它具備一系列比其他有色金屬更優(yōu)良的特性。但由于鋁合金熔體中夾雜物和氣體等冶金缺陷的存在,會(huì)對(duì)產(chǎn)品的機(jī)械性能和使用性能產(chǎn)生極大的危害。因此為生產(chǎn)出高質(zhì)量的鋁合金鑄件并提高其綜合性能,對(duì)熔體進(jìn)行除雜凈化處理是必要的保證措施。過(guò)濾技術(shù)是公認(rèn)的在鑄造過(guò)程中能去除金屬熔體內(nèi)夾雜物的最簡(jiǎn)便、最便宜且有效的方法。泡沫陶瓷過(guò)濾器因其能顯著降低鑄件夾渣而被大量的應(yīng)用于金屬熔體的除雜凈化系統(tǒng)內(nèi)。為了提高過(guò)濾效果而采用大孔密度的泡沫陶瓷過(guò)濾器時(shí),熔體在泡沫陶瓷內(nèi)的流動(dòng)會(huì)受到較大的阻力作用,使熔體不能通過(guò)過(guò)濾器。因此基于泡沫陶瓷在重力場(chǎng)下過(guò)濾的方法,引入離心力場(chǎng)的作用,增加熔體在進(jìn)入泡沫陶瓷時(shí)所受的壓力,使鋁合金熔體能通過(guò)較小孔徑的泡沫陶瓷過(guò)濾器,從而有效地增強(qiáng)泡沫陶瓷的除雜凈化效果。本文通過(guò)對(duì)泡沫陶瓷進(jìn)行離心過(guò)濾鋁合金熔體的實(shí)驗(yàn)和數(shù)值模擬研究工作,深入了解了泡沫陶瓷過(guò)濾器內(nèi)鋁合金熔體的流動(dòng)與換熱過(guò)程,同時(shí)研究了泡沫陶瓷過(guò)濾器過(guò)濾夾雜物顆粒的機(jī)理及效率。數(shù)值模擬的關(guān)鍵步驟是建立表征泡沫陶瓷孔隙結(jié)構(gòu)的單元體。通過(guò)掃描電鏡獲取泡沫陶瓷的孔隙結(jié)構(gòu)特征參數(shù),然后基于Weaire-Phelan泡沫模型構(gòu)建了兩個(gè)表征不同孔隙率范圍的理想化的泡沫陶瓷孔隙結(jié)構(gòu)單元體,最后利用ANSYS-FLUENT軟件模擬泡沫陶瓷表征單元體內(nèi)鋁合金熔體的流動(dòng)行為和夾雜物顆粒的運(yùn)動(dòng)軌跡。在孔隙尺度下研究了離心過(guò)濾工藝參數(shù)和泡沫陶瓷結(jié)構(gòu)特性參數(shù),如鋁合金熔體溫度、過(guò)濾裝置的離心轉(zhuǎn)速、泡沫陶瓷的孔隙率和孔密度等關(guān)鍵參數(shù)對(duì)過(guò)濾模型內(nèi)流場(chǎng)和溫度場(chǎng)的分布情況以及夾雜物顆粒的運(yùn)動(dòng)軌跡的影響規(guī)律。研究表明:(1)鋁合金熔體在泡沫陶瓷內(nèi)流動(dòng)所受阻力的大小會(huì)隨著泡沫陶瓷孔密度和過(guò)濾裝置的離心轉(zhuǎn)速的增大而增大,但鋁合金熔體溫度和泡沫陶瓷孔隙率的增大則會(huì)導(dǎo)致流動(dòng)阻力的減小;(2)泡沫陶瓷的過(guò)濾效率會(huì)隨著過(guò)濾裝置的離心轉(zhuǎn)速、泡沫陶瓷孔密度和鋁合金熔體溫度的增大而增大,但泡沫陶瓷孔隙率的增大會(huì)導(dǎo)致過(guò)濾效率的減小;(3)各關(guān)鍵參數(shù)對(duì)泡沫陶瓷的過(guò)濾效率和熔體在泡沫陶瓷內(nèi)流動(dòng)所受阻力的影響的強(qiáng)弱順序?yàn)?泡沫陶瓷孔密度過(guò)濾裝置的離心轉(zhuǎn)速鋁合金熔體溫度泡沫陶瓷孔隙率。最后對(duì)夾雜物過(guò)濾的數(shù)值模擬結(jié)果與泡沫陶瓷離心過(guò)濾鋁合金熔體的實(shí)驗(yàn)結(jié)果進(jìn)行對(duì)比,發(fā)現(xiàn)它們具有較好的趨勢(shì)一致性,因此泡沫陶瓷離心過(guò)濾鋁合金熔體的數(shù)值模擬結(jié)果對(duì)鋁合金熔體的過(guò)濾工藝有一定的指導(dǎo)作用。為了提高泡沫陶瓷離心過(guò)濾鋁合金熔體的效率,可以選用高孔密度和低孔隙率的泡沫陶瓷,同時(shí)適當(dāng)提高鋁合金熔體的溫度和過(guò)濾裝置的離心轉(zhuǎn)速。
[Abstract]:Aluminum alloy is a widely used nonferrous metal structural material in automobile, electric power and national defense. It has a series of better properties than other nonferrous metals. However, the existence of metallurgical defects such as inclusions and gases in aluminum alloy melts will cause great harm to the mechanical properties and service properties of the products. Therefore, in order to produce high quality aluminum alloy castings and improve their comprehensive properties, it is necessary to remove impurities and purify the melt. Filtration technology is recognized as the simplest, cheapest and most effective method to remove inclusions in molten metal during casting. The foam ceramic filter is widely used in the metal melt removal and purification system because it can significantly reduce the slag inclusion of castings. When the foam ceramic filter with large pore density is used to improve the filtration effect, the flow of melt in the foam ceramic will be subjected to greater resistance, which makes the melt unable to pass through the filter. Therefore, based on the filtration method of foam ceramics under gravity field, the effect of centrifugal force field is introduced to increase the pressure of melt entering foam ceramics, so that aluminum alloy melt can pass through foam ceramic filter with small pore size. Thus, the effect of removing impurities and purifying foam ceramics is effectively enhanced. In this paper, the flow and heat transfer process of aluminum alloy melt in foam ceramic filter was studied by experiments and numerical simulation of centrifugal filtration of aluminum alloy melt. At the same time, the mechanism and efficiency of filtering inclusion particles by foam ceramic filter were studied. The key step of numerical simulation is to establish the unit which can characterize the pore structure of foam ceramics. The pore structure characteristic parameters of foam ceramics were obtained by scanning electron microscope, and then two ideal pore structure units of foam ceramics were constructed based on Weaire-Phelan foam model. Finally, the flow behavior of aluminum alloy melt and the movement track of inclusion particles were simulated by ANSYS-FLUENT software. The technological parameters of centrifugal filtration and the structural parameters of foam ceramics, such as melt temperature of aluminum alloy, centrifugal speed of filtration device, were studied at pore scale. The influence of the key parameters such as porosity and pore density on the distribution of flow field and temperature field and the movement track of inclusions in the filtration model. The results show that: (1) the resistance of aluminum alloy melt flow in ceramic foam increases with the increase of pore density and centrifugal speed of the filter. However, the increase of melt temperature and porosity of aluminum alloy will lead to the decrease of flow resistance. (2) the filtration efficiency of foam ceramics will increase with the increase of centrifugal speed, pore density of ceramic foam and melt temperature of aluminum alloy. However, the increase of porosity of foam ceramics will lead to the decrease of filtration efficiency. (3) the order of the influence of key parameters on the filtration efficiency of foam ceramics and the resistance of melt flow in foam ceramics is as follows: the pore density of foam ceramics is too high. The centrifugal rotation speed of the filtration device for aluminum alloy melt temperature foam ceramic porosity. Finally, the numerical simulation results of inclusion filtration are compared with the experimental results of foam ceramic centrifugal filtration of aluminum alloy melt, and it is found that they have a good trend of consistency. Therefore, the numerical simulation results of foam ceramic centrifugal filtration of aluminum alloy melt have a certain guiding effect on the filtration process of aluminum alloy melt. In order to improve the efficiency of centrifugal filtration of aluminum alloy melt with foam ceramics, foam ceramics with high pore density and low porosity can be selected, and the temperature of aluminum alloy melt and the centrifugal speed of filtration device can be increased appropriately at the same time.
【學(xué)位授予單位】：南昌航空大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類(lèi)號(hào)】：TG292

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本文編號(hào)：2248100