【摘要】：隨著我國經(jīng)濟社會發(fā)展與工業(yè)技術(shù)進步,人民生活水平日益提高,白銀的消費量逐年上升,尤其是工業(yè)用銀量越來越大,對白銀的生產(chǎn)能力和產(chǎn)品質(zhì)量提出更高要求。但是,銀的溶氧釋放特性產(chǎn)生“銀雨”現(xiàn)象,造成銀錠生產(chǎn)時的噴濺損失,采用小開口立模澆鑄可以削弱“銀雨”現(xiàn)象。然而,立模狹窄的型腔增加了澆鑄時引流的難度,使初級銀錠的生產(chǎn)仍然依靠手工完成,與工業(yè)現(xiàn)代化大趨勢格格不入。因此,為抑制“銀雨”現(xiàn)象,研究銀的溶氧釋放特性具有重要的理論價值和現(xiàn)實意義,探索澆鑄新工藝對改進銀錠生產(chǎn)過程也十分重要。結(jié)合Ag-O相圖和擴散理論,對銀熔液中溶氧與釋放的微觀行為進行分析。熔點以后銀中氧的飽和溶解度出現(xiàn)階躍性增加,但這個過程在時間上不是突變的,氧的溶入過程緩慢,其釋放過程則相對較快,從而引發(fā)“銀雨”現(xiàn)象。計算溶氧臨界形核半徑,其值為5gm左右。通過空冷試驗和水冷試驗研究溶氧釋放行為,探索銀錠水冷澆鑄新工藝,結(jié)果表明：空冷試驗銀錠表面氣孔凹坑尺寸為1～4mm,說明溶氧在熔液中經(jīng)歷原子氧和分子氧——臨界小氣泡——大氣泡的過程。水冷試驗加快凝固速度,“銀雨”現(xiàn)象被明顯減弱；水冷試驗得到的銀錠表面與空冷試驗得到的相比更加光滑,表面質(zhì)量明顯改善；普通水口在澆鑄進行一段時間后會出現(xiàn)堵塞現(xiàn)象,它在澆鑄中直接應(yīng)用的可行性還需要進一步研究；模具水冷兩側(cè)溫度降低效果明顯,可以有效減少模具在澆鑄時對環(huán)境釋放的熱量,降低環(huán)境溫度,改善澆鑄環(huán)境。利用FLUENT模擬水冷條件下熔液的冷卻情況,對熔液與模具的各接觸面和與空氣接觸面以及中心點的溫度變化情況進行監(jiān)測,得到了水流速在0.4m/s,0.6m/s,0.8m/s和1.0m/s下各監(jiān)測面和點的溫度變化情況。仿真結(jié)果表明,熔液在1.5s左右凝固完成,在10s時銀錠溫度降到300℃左右,該結(jié)果為銀澆鑄機的設(shè)計奠定一定基礎(chǔ)。在試驗研究和仿真分析的基礎(chǔ)上,對水冷澆鑄機的設(shè)計進行初步探索,提出一種設(shè)計方案。借助SolidWorks對澆鑄機的主體部分進行三維建模。對分模和取錠工況進行靜力學分析,模擬計算結(jié)果顯示,模具支架應(yīng)力屬于安全范圍,改進后的分模機構(gòu)最大應(yīng)力屬于安全范圍。仿真結(jié)果對后續(xù)的設(shè)計和研究具有一定的參考價值。
[Abstract]:With the development of economy and society and the progress of industrial technology, the living standard of the people is increasing day by day, the consumption of silver is increasing year by year, especially the amount of silver used in industry is increasing, so the production capacity and product quality of silver are higher and higher. However, the release characteristics of dissolved oxygen of silver produced "silver rain" phenomenon, which resulted in spatter loss in the production of silver ingot, and the phenomenon of "silver rain" could be weakened by using small opening die casting. However, the narrow cavity of the vertical mold increases the difficulty of drainage during casting, which makes the production of primary silver ingots still by hand, which is incompatible with the general trend of industrial modernization. Therefore, in order to restrain the phenomenon of "silver rain", it is of great theoretical value and practical significance to study the characteristics of dissolved oxygen release of silver. It is also very important to explore a new casting process for improving the production process of silver ingots. Based on the Ag-O phase diagram and diffusion theory, the microcosmic behavior of dissolved oxygen and release in silver melt was analyzed. The saturation solubility of oxygen in silver increases step by step after melting point, but this process is not abrupt in time, the process of oxygen dissolution is slow, and its release process is relatively fast, which leads to the phenomenon of "silver rain". The critical nucleation radius of dissolved oxygen is calculated, and its value is about 5gm. The dissolved oxygen release behavior of silver ingot was studied by air cooling test and water cooling test, and the new technology of water cooling casting of silver ingot was explored. The results show that the size of pore pit on the surface of silver ingot in air cooling test is 1? 4 mm. It shows that dissolved oxygen experiences atomic oxygen and molecular oxygen-critical small bubbles-atmospheric bubbles in the molten solution. The phenomenon of "silver rain" is obviously weakened by water cooling test, and the surface of silver ingot obtained by water cooling test is smoother than that obtained by air cooling test, and the surface quality of silver ingot is obviously improved. The common nozzle will be blocked after casting for a period of time, and the feasibility of its direct application in casting needs to be further studied. It can effectively reduce the heat released by the mould to the environment, reduce the ambient temperature and improve the casting environment. Using FLUENT to simulate the cooling condition of molten liquid under water cooling condition, the temperature variation of each contact surface, air contact surface and center point of molten liquid with air and air is monitored. The water flow rate is 0.4 m / s, 0.6 m / s, and the water flow rate is 0. 4 m / s and 0. 6 m / s, respectively. The temperature variation of each monitoring surface and point under 0.8m/s and 1.0m/s. The simulation results show that the molten liquid solidifies at about 1.5s and the temperature of silver ingot drops to about 300 鈩，

本文編號：2446520