臺灣博碩士論文加值系統

陶瓷泡沫濾網時常應用於鋁合金重力鑄造的方案設計，其使用目的，除了減低金屬流體速度小於鋁合金之入水口的臨界速度0.5 m/s外，最重要經過濾網後，金屬流體因動能回覆成靜壓力能，使得流體能達到整流效果；同時，可以避免在進入模穴時產生紊流而造成捲氣和氧化膜捲入形成所謂雙膜缺陷(bifilm defect)。
為了要瞭解鋁合金液體經由不同方式進入陶瓷泡沫濾網後，其流體外型改變的情形，以及對於鋁液品質的影響。本研究運用底澆方式，設計了三種不同方案設計之流道系統，控制三種澆鑄高度，並選用10ppi、20ppi陶瓷濾網及一組未設置濾網進行比較實驗。
觀察鋁合金液體通過濾網後的流體外型及流速的變化，是使用透明壓克力模具來做水流實驗模擬試驗，目的要類比模擬鋁合金液體通過濾網的情況，以便觀察三種流道設計與不同濾網條件下流體外觀的改變；並且以此流體外型的動畫資料，進行計算流體力學電腦模擬的驗證。
鑄造實驗後，探討金屬液體通過濾網後其鋁液品質變化，是針對濾網出口處附近的鑄件，進行切除取樣，並將這些出口處的試片，經過重熔(re-melting)及減壓測試RPT(reduced pressure test)，使用阿基米德法量測這些減壓測試後的試片的密度及孔隙率並進行切面觀察，並透過本研究所新提出的”面積分率”雙膜指數圖(“Area normalized” Bifilm index map)進行量化探討。

Ceramic foam filter is normally applied in the design of runner system in aluminum gravity casting. The purpose of using this filter is to reduce the velocity of liquid aluminum under the so-called critical gating velocity (e.g., 0.5 m/s for aluminum alloys). After liquid aluminum flows through the foam filter, its static pressure energy is recovered from kinetic energy. The foam filter then can be used for stabilizing the aluminum flow during the filling of mold cavity. The so-called bi-film defect, deriving from the surface turbulence and the entrapment of oxide films during filling process, can thus be avoided.
The purpose of this study was to understand the change of profile and melt quality of liquid aluminum after flowing through the foam filter in various runner system designs. Three types of bottom gating runner systems were designed.
For observing the flow going through the ceramic foam filter, water analogy method, dyed water filling test in a transparent PMMA material mold, was applied. This flowing profile had been used for the validating the result of computational modeling.
In the casting experiment, the aluminum casting sample in the outlet region of the foam filter was sectioned. These specimens then did re-re-melt reduced pressure test (re-melt RPT). The bulk density of the specimens was measured by Archimedes method. By comparing the density differences between the original degassed liquid aluminum and the casting specimens, the contamination of hydrogen of the liquid aluminum after flowing through the filter was measured. "Area normalized" Bifilm index map was proposed to quantify the content of bifilm defects within the casting samples.

摘要 ...................................................................................................................... I
Abstract ............................................................................................................... II
圖目錄 ............................................................................................................... VI
表目錄 ............................................................................................................... IX
第一章 序論 .................................................................................................. 1
1.1 前言 .................................................................................................. 1
第二章 文獻回顧 .......................................................................................... 3
2.1 雙膜缺陷(Bifilm defect) .................................................................. 3
2.2 雙膜指數(Bifilm index) ................................................................... 8
2.3 臨界澆鑄速度與方案設計 ............................................................ 11
2.4 陶瓷泡沫濾網 ................................................................................ 13
2.5 電腦模擬 ........................................................................................ 15
第三章 實驗方法 ........................................................................................ 17
3.1 流道方案系統 ................................................................................ 17
3.2 水流實驗模擬類比試驗 ................................................................ 18
3.3 砂模鑄造實驗 ................................................................................ 19
3.3.1 砂模製作 ............................................................................. 19
3.3.2 旋轉除氫 ............................................................................. 20
3.3.3 減壓含氣量測試(Reduced pressure test) ........................... 20
3.3.4 阿基米德密度量測(Archimedes method) .......................... 21
3.3.5 面積分率雙膜指數圖 (“Area normalized” Bifilm index map) ............................................................................................... 22
3.4 電腦模擬 ........................................................................................ 25
第四章 實驗結果 ........................................................................................ 28
V
4.1 水流實驗模擬類比試驗 ................................................................ 28
4.2 水流實驗模擬試驗與電腦模擬驗證 ............................................ 32
4.3 鑄造實驗 ........................................................................................ 40
4.3.1 重熔減壓測試孔洞體積百分比分析 ................................. 40
4.3.2 重熔減壓含氫量測試切面分析 ......................................... 42
第五章 結果討論 ........................................................................................ 45
5.1 電腦模擬 ........................................................................................ 45
5.2 面積分率雙膜指數圖(“Area normalized” Bifilm index map) ...... 50
第六章 結論 ................................................................................................ 56
參考文獻 ........................................................................................................... 58

[1]F.-Y. Hsu, "Further Development of Running System for Aluminium Castings," PhD thesis, The University of Birmingham, U.K, (2003).
[2]J. Campbell, “The 10 casting rules: guidelines for the reliable production of reliable castings; a draft process specification, 1st Int. Conference on Gating, Filling and Feeding of Aluminum Castings,” AFS society, pp. 35-48, (1999).
[3]J. Runyoro, J. Campbell, “The running and gating of light alloys,” The Foundryman, pp. 117-124, (1992).
[4]J. Campbell, Castings, Butterworth-Heinemann, 1991.
[5]N. R. Green , J. Campbell, “Statistical distributions of fracture strengths of cast Al-7Si-Mg,” Materials Science and Engineering, pp. 261-266, (1993).
[6]H. Hashemi and R. Raiszadeh, “Naturally-Pressurized Running Systems: the role of ceramic filters,” Journal of applied Sciences, pp. 2115-2122, (2009).
[7]J.-C. Gebelin and M. R. Jolly, “Modelling filters in light alloy casting processes (or “What really happens when aluminium flows through a filter”),” Transactions-american foundrymens society, 1 (2002): 109-120.
[8]C. REILLY, N.R. GREEN, and M.R. JOLLY, “Surface Oxide Film Entrainment Mechanisms in Shape Casting Running Systems,” Metallurgical and Materials Transactions B 40.6 (2009): 850-858.
[9]D. Dispinar, J. Campbell, Porosity, Hydrogen and Bifilm content in Al alloy castings, Department of Metallurgy and Materials, University of Birmingham.
[10]J. Campbell, “Entrainment defects", Materials Science and Technology, pp. 127-145, (2006).
[11]K. Tynelius, F. Major and D. Apelian, “A parametric study of microporosity in the A356 casting alloy system,” Transactions of the American Foundrymen's Society, pp. 401-413, (1993).
[12]N. Green and J. Campbell, “Influence of oxide film filling defects on the strength of Al-7Si-Mg alloy castings,” Transactions of the American Foundrymen's Society, pp. 341-347, (1995).
[13]Talbot, D.E.J, “Effects of hydrogen in aluminium, magnesium, copper, and their alloys,” International Metallurgical Reviews, pp. 166-184, 1975.
[14]Tiwari, S.N., A.K. Gupta, and S.L. Malhotra, “Effect of hydrogen gas content on shrinkage defects in aluminium alloy castings,” British Foundryman, pp. 129-32, (1986).
[15]D. Dispinar and J. Campbell, Critical assessment of reduced pressure test.Part 1: Porosity phenomena, The Department of Metallurgy and Materials, The University of Birmingham, Birmingham.
[16]D. Dispinar and J. Campbell, Critical assessment of reduced pressure test.Part 2: Quantification, The Department of Metallurgy and Materials, The University of Birmingham, Birmingham.
[17]Hsu, F.Y., M.R. Jolly, and J. Campbell, “A multiple-gate runner system
for gravity casting.,” Journal of Materials Processing Technology, pp. 5736-5750, (2009).
[18]Hsu, F.Y., M.R. Jolly, and J. Campbell, “The Design of L-Shaped Runners for Gravity Casting.,” The Minerals, Metals & Materials Society, (2007).
[19]Hsu, F.Y. and H.J. Lin, “Foam Filters Used in Gravity Casting.,” Metallurgical and Materials Transactions B, pp. 1-8.
[20]J.campell, Castings Practice the Ten rules of castings, Butterworth-Heinemann, (2004).
[21]B. Sirrell, J. Campbell, “Mechanism of Filtration in Reduction of Casting Defects due to Surface Turbulence during Mold Filling,” Trans. AFS, pp. 645-654, (1997).
[22]Din, T., Kendrick, R., Campbell, J., “Direct Filtration of A356 Alloy,” Trans AFS, vol. 111, pp. 91-100, (2003).
[23]A. C. Midea, “Pressure drop characteristics of iron filters,” AFS Transactions, pp. 01-042, (2001).
[24]R. Nariman, “Gating Design Via Computer Fluid Flow Modeling,” Modern Casting, pp. 35-38, (1998).
[25]Ono, T.; Ohtsuka, Y., “Computer Simulation of Flow and Solidification in Gravity Die Castings,” Proceedings of the Sixteenth International Die Cast Congress and Expo, pp. 321-327, (1991).
[26]Zadeh, A. Habibollah and J. Campbell., “Metal Flow Through a Filter System.,” AFS Transactions , pp. 1-17, (2002).
[27]Jean-Christophe Gebelin, Mark R. Jolly, “Modelling of the investment
casting process,” Journal of Materials Processing Technology 135, pp. 291-300, (2003).
[28]David Schwam,John F. Wallace,Tom Engle,and Qingming Chang, Gating of permanent molds for aluminum castings, Department of Materials Science,Case Western Reserve University, (2004).
[29]“Flow Science, manual, http://www.flow3d.com”.
[30]D.S. Richins and W.O. Wetmore, “Hydraulics applied to molten aluminum,” ASME Trans., 725-732, (1952).
[31]F. M. White, Fluid Mechine 2nd, McGraw-Hill Book Company.