本研究探討高效率半內混式噴嘴之設計及其運用於金屬粉末之噴霧製程，並探討該噴嘴生產高熔點金屬粉末之特性。利用氣霧法所生產之金屬粉末，為圓球狀之微細粉末，目前廣泛應用於電子產業與精密機械工業中，如粉末冶金鑄造與金屬粉末射出成型等。其中，以鋁、銅以及不鏽鋼這三種金屬粉末的使用量最大；以銅粉為例，全世界銅之年消費量超過一億噸，而鋼鐵類的需求量約為銅的100 倍；藉由全球金屬粉末需求量可間接了解其產業價值及重要性。本研究所建構之設備為氣氛控制之乾式噴粉設備，噴粉塔高2.5m，在噴粉過程中，噴粉塔中的氧含量控制在100 ppm以下。本研究分三個階段進行：第一階段以低熔點660oC的純鋁進行可行性測試；第二階段提高其熔煉溫度，以熔點1083oC的純銅進行噴粉測試，並探討霧化條件對噴銅製程之影響；第三階段採用粉末冶金常用成分的青銅合金(C5121)來進行噴粉製程測試，並探討霧化氣體壓力對金屬粉末特性之影響。
純銅粉末的噴霧製程實驗結果顯示，當霧化氣體壓力固定於3.0 Bar下，銅粉平均粒徑隨金屬熔湯進料率降低而遞減。當金屬熔湯進料率由2.9 kg/min降至0.87 kg/min時，銅粉之平均粒徑由99.0μm降至65.1μm；另外，當金屬熔湯進料率固定，隨著霧化氣體壓力的增加，金屬熔湯獲得較大的霧化能量，可產生微細之粉末。例如，當霧化氣體壓力由3 Bar提升至5 Bar時，其銅粉之平均粒徑由99.0μm降至67.3μm。研究結果亦顯示，當氣液質量比由0.15增加至0.51時，其產生的銅粉平均粒徑，由85.56μm大幅降至23.2μm。銅粉之表面形貌方面，由電子掃描顯微鏡所獲得之照片顯示，本研究所生產之金屬粉末皆為圓球型，具有良好之真圓度及流動性。本研究亦進一步探討此種半內混式噴嘴應用於粉末冶金材料之噴霧製程特性。採用之青銅材料為C5121，在氣液質量比0.58±0.25下，探討霧化氣體壓力對金屬粉末粒徑分佈之影響。結果顯示，當霧化壓力由3.0 bar增加至 5.0 bar時，其粉末平均粒徑Dv(50)由69.53μm降至40.98μm，而Dv(32)亦由37.75μm降至23.34μm。結果顯示，增加霧化氣體壓力可有效的降低粉末平均粒徑。由於傳統外混式金屬粉末氣霧法製程之霧化壓力皆在50 Bar以上，比本研究之製程高出一個數量級，故本研究所發展之半內混式噴嘴可以在較低的氣液質量比下，獲得微細之金屬粉末，噴嘴效能遠高於國際上現行之外混式金屬噴嘴。

This research program is to design a high efficient semi-internal mixing nozzle that used for the gas atomization processes to produce the metal powder. This new system is then used to characterize the atomization performance of the high melt-point metals. The fine metal powder produced by gas atomization has been widely used in the electronic industry and precision industry, including powder metallurgy and extrusion forming products, etc. Huge amount of metal powders of aluminum, copper and stainless steel was consumed in the world, including more than hundred million tons per year of the copper powder consumption. The iron powder consumption is even hundred times of copper powders. The experimental facility is an oxygen controlled atomization system with 2.5 meter height. The oxygen concentration in atomization tower is controlled at 100ppm level during the atomization processes. There are three phases in this research program. In the first phase, atomization of aluminum with melt point of 660°C is performed for the feasibility study. In the second phase, atomization of copper with melt point of 1083°C is performed. In the third phase, parametric study of the atomization performance of copper alloy (C5121) is performed. Results show that, for the atomization of pure copper, the Sauter mean diameter of the powder depends on the flow rate of the melt. It turns out that SMD decreases from 99.0 m to 65.1 m as the melt flow rate is decreased from 2.9 kg/min to 0.87 kg/min under the atomization gas pressure of 3.0 bar. On the other hand, SMD decreases from 99.0 m to 67.3 m as the gas pressure is increased from 3.0 bar to 5.0 bar, indicating that the extra-fine powder can be produced by raising the atomization gas pressure to provide more atomization energy to the melt. Furthermore, SMD is decreased from 85.56 m to 23.2 m as the gas-to-melt mass ratio is increased from 0.15 to 0.51. The SEM photos show the metal powders are spherical. Finally, investigation of the atomization of copper alloy (C5121) shows that SMD and Dv(50) of the metal powder decreases from 37.75m to 23.34m and from 69.53m to 40.98m, respectively, as atomization gas pressure is increased from 3.0 bar to 5.0 bar. Since the atomization process of the conventional external-mixing nozzle normally performed with pressure more than 50 bar, it is concluded that the nozzle with semi-internal mixing mechanism performs better than the conventional external-mixing nozzle in the production of ultra-fine metal powder.

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