本研究為模擬選擇性雷射熔融法以單層單軌掃描不鏽鋼316L基板與粉末，觀察特定截面之沉積流動情形與相關力作用之分析。使用商用軟體ANSYS FLUENT建立二維數值模型，並加入熱焓多孔法和VOF模型，模擬固液共存的熔融區以及液氣間體積分率的變化，考慮表面的金屬蒸發現象，加上馬蘭格尼效應、反衝壓力等作用力，預測金屬在熔化後自由表面的流動行為與沉積形狀。
研究首先探討暫態過程中流場與溫度場的發展，發現加工前期由於熔池還在成形，流動現象較不明顯；到了中期，表面溫度過蒸發點後，馬蘭格尼力與反衝壓力會主導其流動行為，使熔池產生像是被雷射衝開的現象，並藉由表面張力將液體拉回；而後期雷射逐漸遠離後，沉積慢慢冷卻成形。接著比較有無考慮質量蒸發對沉積結果的差異，顯示出熔覆情形會受到表面質量蒸發的影響，使得沉積高度減少但寬度增加，並且在高度方面的變化更為明顯。再來是針對不同的雷射與粉末加工參數進行模擬，藉由本研究的模型可以更加了解加工參數與熔覆結果的相關性，從中找出造成接合度與熔覆情形較差的原因，並且可以在實際加工前預測沉積形狀的外表輪廓，有利於加工前的決策與評估。最後，分別觀察反衝壓力與馬蘭格尼力對暫態流動的影響，反衝壓力可以抑制住因高溫造成的馬蘭格尼效應往中間流動之情形，並讓熔池可以快速往外流動發展，使得熱擴散更加均勻；馬蘭格尼力則是加強熔池表面以及內部的流動情形，並配合反衝壓力讓熔池的流動現象更加劇烈，溫度場也得以藉此效果達到更好的擴散。上述這些分析可以更加了解熔池的熱與質量傳遞情形，以及如何改變流動現象與沉積結果。

In this research, a two-dimensional model is established to simulate the flow behaviors on molten pool during Selective Laser Melting (SLM) of stainless steel 316L. The VOF model is used to capture the free surface. A Gaussian beam is used to melt the powder layer and substrate. Furthermore, mass removal through evaporation, Marangoni force, recoil pressure, and surface tension are considered simultaneously to predict the flow behaviors of the molten pool and the shape of cladding.
The study first discusses the change in the flow field and temperature field of the molten pool in the transient process of the heating, and then discovers that the molten pool is still developing in the early stage of melting. In the middle stage, Marangoni force and recoil pressure dominate the flow, and push the metal away from center to the edges of the molten pool. In the late stage, the metal cools down and the cladding forms after the laser leaves. Then, the case which considers mass loss through evaporation has been compared with another case that ignores the mass loss. The results show that considering mass loss through evaporation increase the height and decrease the width of cladding. The following topic compares the results from different processing parameters, and finds out the relationship between cladding and the parameters, so the shape of cladding could be predicted before processing. Finally, the change in flow behavior caused by recoil pressure and Marangoni force can be observed, respectively. The results show that recoil pressure can prevent the liquid from flowing to center which is caused by Marangoni force, and the heat diffusion is more homogeneous. Marangoni force can strengthen the flow in the molten pool, and also make the heat diffusion much better in temperature field.

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