近年來金屬積層製造的應用及技術逐漸成熟，而應用於生醫、半導體、航太產業之高潔淨粉末需求也隨之上升，但目前應用於高潔淨合金粉末製程之自由下落式噴嘴其相關研究資料甚少，且以傳統自由下落式霧化器所製造之金屬粉末平均粒徑坐落於100 μm左右，於SLM製程的使用率極低，限制其應用範圍。
本研究之目的在於設計漸縮–漸擴型自由下落式霧化器，以改進傳統自由下落式霧化器的缺點，提高微細粉末得料率，以便運用於SLM製程，其中分為兩部分來探討其霧化特性。第一部分進行霧化器性能特性分析實驗，以水作為被霧化介質，探討於不同霧化氣體壓力、液柱直徑、霧化頂角及氣液質量比對於霧化特性的影響，並以高速攝影觀察霧化流場狀態。第二部分進行氣霧化金屬粉末製程參數實驗分析，並以錫銀銅合金Sn-3Ag-0.5Cu作為先期研究之霧化材料，探討霧化氣體壓力、液柱直徑、霧化頂角及熔湯超熔溫度，對金屬粉末粒徑影響，並進行金屬粉末形貌、金相及微硬度分析。
研究結果顯示，霧化氣體壓力及霧化頂角，為霧化器性能特性分析實驗中控制噴霧粒徑之重要參數，例如：當霧化頂角固定為α3 (α/α0 = 1.5)之情況下，霧化氣體壓力由5 bar提升至20 bar時，液滴平均粒徑則由31.64 μm下降至4.40 μm。錫銀銅合金粉末製程結果顯示，於霧化頂角為α3 (α/α0 = 1.5)、液柱直徑d4 (d/d0 = 1.9)之情況下施以20 bar之霧化氣體壓力，其粉末平均粒徑為18.4 μm，且坐落於金屬積層製造需求之粒徑範圍10 ~ 63 μm之得料率高達82.17%。綜觀以上結果，此新型自由下落式霧化器優於傳統之製程結果，且滿足金屬積層製造之粉末需求。

In recent years, the application and techniques of metal additive manufacturing has grown rapidly, which leads to the requirement of high purity alloy powder of medical, semiconductor and aerospace industry were significant increased. However, the researches of free-fall atomizer used in high purity alloy production were rare and the mean particle size produce by traditional free-fall atomizer is about 100 μm, which restrict the development of high purity alloy powder used in SLM process. The aim of this research is to design a novel free-fall atomizer which has converging-diverging flow channel, so as to improve the yield rate of fine powder used in SLM process. The characteristic research of the atomizer were first performed by atomizing water, and then a high speed camera is used to observe the spray patterns, which can understand atomization mechanism of free-fall atomizer. Second, Sn-3Ag-0.5Cu alloy was chosen as atomized media for powder production parameters analysis, which can investigate the powder size and surface morphology affected by change of nozzle geometry and operating parameters. The size distribution of water droplet and metal powder were measured by INSITEC RT-Sizer and Coulter LS230 particle sizer, respectively. The characteristics analysis result of water spray show that the droplets diameter decrease as both atomization pressure and apex angle were increased. For example, the droplet size reduced from 31.64 μm to 4.40 μm as atomization pressure increases from 5 bar to 20 bar with apex angle α3 (α/α0 = 1.5). In the metal powder experiments, at the condition of apex angle α3 (α/α0 = 1.5), melt stream diameter d4 (d/d0 = 1.9), and apply 20 bar of atomization pressure, the result show that mean particle size (D50) is equal to 18.4 μm, which yield rate located at the range of 10 ~ 63 μm was about 82.17%. It can be concluded that this novel free-fall atomizer has better performance than traditional one, and the powder produced by this process also can meet the requirements of SLM process.

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