• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.207-208
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• 2006

In this experimental work, the development of a multicomponent binder system based on high density polyethylene (HDPE) and paraffin wax for Powder Injection Molding of Alumina $(Al_2O_3)$ parts was carried out. The optimum composition of the injection mixture was established through mixing torque measurements and a rheological study. The maximum powder loading was 58 vol%. The miscibility of organic components and the optimum injection temperature was evaluated by thermal characterization of binder and feedstock. The thermal debinding cycle was developed on the basis of thermogravimetrical analysis of the binder. After sintering the densities achieved were closed to 98% of the theoretical one.

• 한국분말재료학회지
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• 제8권2호
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• pp.91-97
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• 2001

The conventional debinding process in metal injection molding is very long time-consuming and unfriendly environmental method. Especially, in such a case of injection molded parts from hard and fine metal powder, such as WC-Co, an extremely long period of time is necessary in the conventional slow binder removal process. On the other hand, supercritical debinding is thought to be the effective method which is appropriate to eliminate the aforementioned inconvenience in the prior art. The supercritical fluid has high diffusivity and density, it can penetrate quickly into the inside of the green metal bodies, and extract the binder. In this paper, super-critical debinding is compared with wicking debinding process. Wax-based binder system is used in this study. The binder removal rate in supercritical $CO_2$ have been measured at $65^{\circ}C$, 75$^{\circ}C$ in the pressure range from 20 MPa to 28 MPa. Pores and cracks in silver bodies after sintering were observed using SEM When the super-critical $CO_2$ debinding was carried out at 75$^{\circ}C$, almost all the wax (about 70 wt% of binder) was removed in 2 hours under 28 MPa and 2.5 hours under 25 MPa.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.763-764
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• 2006

Ceramic Injection Moulding (CIM) technology has been successfully used for the fabrication of Mn-Zn Ferrite part. The binder was composed by polypropylene and paraffin wax. The optimal powder loading (58% vol.) was determined by means of rheological measurements. Threedifferent parts, toroids, bending and tensile probes were injected. Thermal and solvent-thermal debinding was designed based on DSC and TGA studies of the binder. The time of the debinding cycle was reduced using n-heptane to dissolve previously the paraffin wax. Final properties have been determined and compared with uniaxial pressure parts values. The densities obtained were slightly higher than those of uniaxial pressure parts and the magnetic properties presented similar values.

• 한국산학기술학회논문지
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• 제21권10호
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• pp.574-580
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• 2020

무기바인더는 저온에서 경화가 가능하며, 유해가스를 배출하지 않는 친환경성과 중자 조형 시 성형된 제품의 결함이 작다는 장점으로 인해 주조 산업에 적용하고자 관련 연구가 급속도로 진행되고 있다. 그러나 실리케이트(SiO₂-Na₂O)를 주성분으로 하는 무기바인더는 실리케이트 특유의 흡습성으로 인해 공기 중 수분을 흡습하여 결합력이 약해져 주형의 강도가 급격히 감소하는 문제가 있다. 특히 주강 주조에 사용되는 사형 주형의 경우 알루미늄 주조보다 높은 주입 온도로 인해 고강도의 주물 특성을 요구한다. 이에 본 연구에서는 무기바인더의 강도와 흡습성을 개선하기 위해 에스테르기를 함유하는 왁스를 이용하여 이를 효율적으로 합성하는 방법을 연구하였다. 또한 합성된 무기바인더의 특성을 XRF와 TGA를 통해 확인하고, 일반강도와 내수강도 평가를 진행하여 주형의 강도 개선 여부를 확인하였다. 그 결과 에스테르기를 함유하는 왁스를 포함한 무기바인더의 경우 일반 강도가 증가하였으며, 특히 내수강도가 118 N/㎠에서 216 N/㎠까지 증가하여 약 55 %의 내수강도 개선 효과를 확인하였다. 또한 실제 주강 제품을 제작한 뒤 주조를 통해 우수한 주조 특성을 확인하였다.

• 소성∙가공
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• 제16권1호
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• pp.61-66
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• 2007

Powder injection molding(PIM) is widely used for many parts in the field of automotives, electronics and medical industries, due to the capability of net shaping for complex 3-D geometry. Powder injection mold design for the dental scaler tip, a component of medical appliance, was presented. In comparison with conventional machining process, powder injection molding has many advantages, specially in price and dimensional stability, for molding dental scaler tip which has complex geometry. Both product design and mold design for dental scaler tip were presented. A PIM feedstock was made of stainless series(17-4PH, 316L, 440C) powder and a wax based binder. The 'rapid mold' concept was applied to manufacture the various forms and materials of dental scaler tip including vibration characteristics.

• 유변학
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• 제11권1호
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• pp.57-65
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• 1999

분말사출재의 항복응력을 효과적이고 간단한 방법으로 측정하기 위해서 수차 장치를 사용한 항복응력 측정장치를 개발하였다. 수차 방식은 벽면 미끄러짐을 고려할 필요가 없는 장점이 있으나 전단률에 따른 점도 변화 측정에는 사용할 수 없는 단점도 있다. 수차 장치의 타당성 검토를 선형유체를 사용하여 검증하였으며, 수차 장치의 양단에서 나타나는 오차도 실험적으로 확인하였다. 분말 현탁액의 일반적인 특징이라고 여겨지는 항복 시 발생하는 순간 최대 토오크는 측정 장치의 제어기 특성에 따른 영향이 큰 것을 확인하고 안정 토오크 영역을 항복응력 계산의 기준으로 결정하였다. 측정되는 토오크에서 수차의 회전 저항에 따른 효과를 제거하기 위해 다양한 속도에서 측정된 토오크를 선형함수로 근사하여 회전 속도가 없을 때의 토오크를 얻었다. 측정 방법의 일반적인 검증을 위해 텅스텐 카바이드 분말과 왁스계 바인더를 이용한 분말사출재의 항복응력을 온도와 분말 충전률 변화에 따라서 측정하였다.

• 한국분말재료학회지
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• 제10권1호
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• pp.6-14
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• 2003

The purpose of the present study is to investigate the method decreasing debinding time as well as lowering operation condition than pure supercritical $CO_2$ debinding by using cosolvent or binary mixture of propane + $CO_2$. First method is to add cosolvent, such as n-hexane, DCM, methanol, 1-butanol, in supercritical $CO_2$. In case of adding cosolvent, we were found the addition of non-polar cosolvent (n-hexane) improves dramatically the binder removal rate (more than 2 times) compared with pure supercritical $CO_2$ debinding, second method is to use mixture of supercritical propane + $CO_2$, as solvent. In case of using mixture of supercritical propane + $CO_2$, the rate of debinding speeded up with increasing of pressure and concentration of propane at 348.15 K. It was found that addition of cosolvent (e.g., n-hexane, DCM) and binary mixture propane + $CO_2$ for supercritical solvent remarkably improved binder removal rate for the paraffin wax-based binder system, in comparison with using pure supercritical $CO_2$.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.493-494
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• 2006

Chip breaker of cutting tool is an important feature to enhance cutting performance. Powder injection molding process was used to produce a triangular-shape cermet grooving insert which has three chip breakers. Attrition milled cermet powders were mixed with wax-based binder system in continuous twin screw extruder. Three-plate injection mold with slide cores was used to produce injection-molded parts. After molding, solvent and thermal debinding was carried out. Sintering was conducted in a batch furnace with a graphite heater. The sintered parts satisfy the requirements of dimensional tolerances and material properties.

• 한국분말재료학회지
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• 제19권2호
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• pp.140-145
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• 2012

This paper describes the manufacturing process of tilting pad gas bearing with a diameter of 5 mm and a length of 0.5-1 mm for power MEMS (Micro Electomechanical Systems) applications. The bearing compacts with nanopowder feedstock were prepared by Ni-metal mold with 2-mold system using LIGA process. The effect of the manufacturing conditions on sintering properties of nanopowder gas bearing was investigated. In this work, Fe-45 wt%Ni nanopowder with an average diameter of 30-50 nm size was used as starting material. After mixing the nanopowder and the wax-based binders, the amount of powder was controlled to obtain the certain mixing ratio. The nanopowder bearing compacts were sintered with 1-2 hr holding time under hydrogen atmospheres and under temperatures of $600^{\circ}C$ to $1,000^{\circ}C$. Finally, the critical batch of mixed powder system was found to be 70% particle fraction in total volume. The maximum density of the sintered bearing specimen was about 94% of theoretical density.

• 한국분말재료학회지
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• 제24권3호
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• pp.223-228
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• 2017

Nanopowders provide better details for micro features and surface finish in powder injection molding processes. However, the small size of such powders induces processing challenges, such as low solid loading, high feedstock viscosity, difficulty in debinding, and distinctive sintering behavior. Therefore, the optimization of process conditions for nanopowder injection molding is essential, and it should be carefully performed. In this study, the powder injection molding process for Fe nanopowder has been optimized. The feedstock has been formulated using commercially available Fe nanopowder and a wax-based binder system. The optimal solid loading has been determined from the critical solid loading, measured by a torque rheometer. The homogeneously mixed feedstock is injected as a cylindrical green body, and solvent and thermal debinding conditions are determined by observing the weight change of the sample. The influence of the sintering temperature and holding time on the density has also been investigated. Thereafter, the Vickers hardness and grain size of the sintered samples have been measured to optimize the sintering conditions.