臺灣博碩士論文加值系統

鋁胚連續鑄造的過程中，影響鑄造工件品質的因素很多，如：鑄造速度、冷卻水水量、環境溫度、鑄造溫度等。這些因素使得鑄件產生翹曲變形，嚴重的甚至於破裂或斷裂。針對此問題，本研究建立一預測系統來模擬鋁胚之連續鑄造過程的熱散失與翹曲變形的現象，並依此預測系統進行鋁胚連續鑄造之製程改善。
本研究採用有限元素軟體Workbench CFX來模擬鋁金屬液、鑄模與冷卻水之間的熱傳行為，使用CFX中熱-流耦合分析來處理鋁胚受冷卻水凝固時熱釋放的問題。本文將上述分析之熱傳導係數導入ANSYS軟體中，作為熱-固耦合模擬分析時之初始資料，運用ANSYS 的 Birth and Death技術，進行鋁合金7075的鑄造模擬，並針對不同之鑄造速度，來做鋁胚缺陷分析的比較。
由模擬計算結果發現鑄造速度愈快，鋁胚中心溫度沿鑄造方向之下降會越減緩、翹曲程度越小、表面凹陷量越少，鋁胚凸肚量則是越大。對照實際鑄造完成的鋁胚變形情況，結果顯示與模擬之形變現象一致。

During the continuous casting process of aluminum slab, there are many factors influencing the casting quality, such as the pour temperature, cooling water flow rate and casting speed. Due to these factors, the defects such as butt curl, serious cracking or even breaking will occur during processes. In this study, the forecasting system was established to simulate the heat transfer and butt curl phenomenon of the aluminum continuous casting.
The finite element method (FEM) commercial software named as ANSYS Workbench CFX was used to predict the release of latent heat during the liquid aluminum solidification and calculate the average coefficient of thermal conductivity. The results of CFX were used as initial boundary conditions of thermal analysis and the method of birth and death are adopted to analyze slabs defects of aluminum 7075 alloys with different casting speeds.
The results of FEM simulations indicate that the increase of casting speed will slow the decrease of temperature at center of slabs along the casting direction, and also reduce the butt curl and slab bow phenomenon. But on the contrary, the faster casting speed will produce bigger slab swell. The slab defects match with the actual phenomenon. Finally, the results show that simulated deformations consistent with the actual phenomena. Meanwhile, the predicted system would offer industries a good tool to reduce the manufacturing costs.

目錄
封面內頁
簽名頁
中文摘要.......................iii
Abstract.......................iv
誌謝...........................v
目錄...........................vi
圖目錄.........................viii
表目錄.........................xi

第一章 緒論...................1
1.1研究背景....................1
1.2鋁胚DC鑄造介紹..............2
1.3 研究目的...................8
1.4研究方法....................12
第二章 文獻回顧................15
2.1熱裂(Heat Tears)............25
2.2翹曲與凸肚..................30
2.3有限元素介紹................32
第三章 研究方法................35
3.1有限元素模型................36
3.2製程參數與邊界條件設定......40
3.3 熱對流邊界.................42
3.4 求解法.....................45
第四章 結果與討論..............50
4.1冷卻水量與熱對流係數........50
4.2材料性質....................54
4.3鑄造速度與鋁胚溫度場........58
4.4鑄造速度與鋁胚型變..........63
4.4.1鋁胚翹曲..................63
4.4.2鋁胚側凹..................65
4.4.3鋁胚凸肚..................67
4.5鑄造速度與鋁胚應力..........69
第五章 結論....................75
5.1結論........................75
5.2未來發展方向................76
參考文獻.......................78

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