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유우경,정성수,이재성,You, Woo-Kyung,Jung, Sung-Soo,Lee, Jai-Sung 한국분말야금학회 2008 한국분말재료학회지 (KPMI) Vol.15 No.4
Sintering behavior of iron nanopowder agglomerate compact prepared by slurry compaction method was investigated. The Fe nanopowder agglomerates were prepared by hydrogen reduction of spray dried agglomerates of ball-milled $Fe_2O_3$ nanopowder at various reduction temperatures of $450^{\circ}C$, $500^{\circ}C$ and $550^{\circ}C$, respectively. It was found that the Fe nanopowder agglomerates produced at higher reduction temperature have a higher green density compact which consists of more densified nanopowder agglomerates with coarsed nanopowders. The sintering behavior of the Fe nanopowder agglomerates strongly depended on the powder packing density in the compact and microstructure of the agglomerated nanopowder. It was discussed in terms of two sintering factors affecting the entire densification process of the compact.
마이크로 PIM용 Fe 마이크로-나노 혼합분말 피드스톡의 다이성형 및 소결거동
유우경 ( Woo Kyung You ),최준필 ( Joon Phil Choi ),이재성 ( Jai Sung Lee ) 대한금속재료학회(구 대한금속학회) 2011 대한금속·재료학회지 Vol.49 No.1
The present investigation was performed on the die compaction and sintering behavior of Fe micronano mixed powder with a mixed binder for powder injection molding. Warm die compaction of the feedstock for simulation of the static injection molding process was conducted using a cylindrical mold of 10 mm diameter at 100℃ under 4MPa. The die compaction of the micro-nanopowder feedstock underwent a uniform molding behavior showing a homogeneous distribution of nanopowders among the micropowders without porosity and distortion. After debinding, the powder compact maintained a uniform structure without crack and distortion, leading to a high green density of 64.2% corresponding to the initial powder loading of 65%. The sintering experiment showed that the micro-nanopowder compact underwent a near full and isotropic densification process during sintering. It was observed that the nanopowders effectively suppressed the growth of micropowder grains during densification process. Conclusively, the use of nanopowder for PIM feedstock might provide a new concept for processing a full density PIM parts with fine microstructure.
마이크로PIM용Fe마이크로-나노복합분말피드스톡제조시혼합거동과미세구조변화
이원식 ( Won Sik Lee ),이재성 ( Jai Sung Lee ),고세현 ( Se Hyun Ko ),유우경 ( Woo Kyung You ) 대한금속재료학회 ( 구 대한금속학회 ) 2010 대한금속·재료학회지 Vol.48 No.7
The present investigation has been performed on the mixing behavior and microstructural development during fabrication of Fe micro-nano powder feedstock for a micro-powder injection molding process. The mixing experiment using a screw type blender system was conducted to measure the variations of torque and temperature during mixing of Fe powder-binder feedstock with progressive powder loading for various nano-powder compositions up to 25%. It was found that the torque and the temperature required in the mixing of feedstock increased proportionally with increasing cumulative powder loading. Such an increment was larger in the feedstock containing higher content of nano-powder at the same powder loading condition. However, the maximum value was obtained at the nano-powder composition of not 25% but 10%. It was owing to the 'roller bearing effect' of agglomerate type nano-powder acting as lubricant during mixing, consequently leading to the rearrangement of micro-nano powder in the feedstock. It is concluded that the improvement of packing density by rearrangement of nano-powders into interstices of micro-powders is responsible for the maximum powder loading of about 71 vol.% in the nano-powder composition of 25%.
차범하(Bermha Cha),장진만(Jin Man Jang),서정식(Jungsik Seo),고세현(Se-Hyun Ko),손성호(Seong Ho Son),이원식(Wonsik Lee),유우경(Woo Kyung You),이재성(Jai-Sung Lee) 한국생산제조학회 2011 한국생산제조시스템학회 학술발표대회 논문집 Vol.2011 No.4
재활용된 티타늄 수소화물 분말을 사용하여 피드스톡을 제조하고, 이를 이용하여 사출성형공정 조건을 최적화 하였다. 원료분말은 Ti chip의 재활용 공정을 통해 제조된 평균 350nm 크기의 분말을 사용하였으며, 피드스톡 제조 시 최적 분말 고상율은 68%였다. 제조된 피드스톡은 2000Pa.s 이하의 점도를 나타냈으며, 최적의 사출조건으로 미세한 부분까지 건전하게 성형된 사출체를 제조하였다. 또한 피드스톡의 열분석 결과를 이용하여 탈지 및 탈수소화 공정의 최적화를 이루었으며, 고진공하에서 소결 시 완전치밀화를 얻을 수 있었다.