本文透過套裝軟體Ansys Fluent建立一個三維暫態Volume of Fluid(VOF)之模型，模擬固定電子束能量直接加熱純鈷金屬之熔煉，金屬材料邊界以水冷銅坩鍋進行散熱，模擬具自由表面純鈷金屬之熔煉過程，考慮受熱後金屬膨脹之問題，討論各項熔池相關參數，如：不同電子束能量、不同電子束半徑與熱散失分析之影響。以模擬結果所示，透過表面浮動現象、熔煉過程之溫度變化、熔池表面平均溫度以及熔池擴散速度等等現象，發現電子束熔煉加熱純鈷金屬會在約30秒後近乎穩態。
固定電子束能量，使用不同的電子束半徑進行熔煉，以較大的電子束半徑能夠使得熔池表面溫度較低，也能有效的降低蒸發熱散失，避免熔池溫度梯度過大之問題，故以電子束半徑較大者進行熔煉過程。固定電子束半徑，使用不同之電子束能量進行熔煉，越大的電子束能量會使水冷銅坩鍋之冷卻效果降低，而增加熱平衡之能量占比，達到過濾金屬雜質之效果，故在適當電子束半徑下，應以較大之電子束能量作為電子束熔煉之使用參數。
電子束能量的增加，會使蒸發熱在平坦表面假設下，較自由表面之模擬結果較大，有多估之情況發生，而溫度場方面，在兩種模擬之結果也是自由表面考慮體積變化之模擬較為低。本研究改善了不考慮體積變化之問題，更能準確預測實際熔煉過程中熔池之行為。

In view of the evolution of semiconductor or the mobile phone technology with time, they use high-strength, high-purity and high stability of the materials by vacuum metallurgy. Therefore, in vacuum metallurgy process, a kind of process parameters have important effect to obtain the high-purity materials. In this study, a numerical simulation model is used to investigate the heat transfer characteristics of molten pool with free surface by electron beam melting (EBM). It is used to consider the increase of volume change with the temperature raise and the surface fluctuation. It also considers many effects, including buoyancy, Marangoni forces, evaporation and radiation losses. As the beam power increases, the evaporation and radiation losses of the cobalt by EBM increase. On the other hand, as the beam radius increases, it can effectively reduce the maximum temperature of the molten pool and increase the surface area of molten pool. The larger beam power can reduce the energy proportion of water cooling effect and increase the energy proportion of heat balance and the surface area of molten pool. For reasons outlined above, it is recommended to adopt the larger beam power and radius during EMB process. To compare the assumption of free surface and plat surface, the temperature trend of the result with free surface is lower than it with plat surface. Due to the assumption of free surface, we can more precisely predict the behaviors of molten pool in the actual EBM process.

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