분말야금된 소결체의 가장 큰 특징 중의 하나는 피할 수 없는 소결체의 기공이다. 이러한 기공이 기계적 특성에 미치는 영향에 관해서는 많은 연구가 오래 전부터 진행되었었다. 그러나 기존의 연구는 거의 대부분 일반 분말야금에 의한 것이고 분말사출성형된 소결체의 기공율과 기계적 특성 광계는 거의 연구가 이루어 지지 않았다. 본 연구에서는 기공율의 조절이 용이한 분말사출성형 공정을 이용하여 소결 초기부터 완전 치밀화에 가까운 조직까지 다양한 소경율의 시편을 만

The purpose of the present study is to investigate the method decreasing debinding time as well as lowering operation condition than pure supercritical debinding by using cosolvent or binary mixture of propane + . First method is to add cosolvent, such as n-hexane, DCM, methanol, 1-butanol, in supercritical . 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 debinding, second method is to use mixture of supercritical propane + , as solvent. In case of using mixture of supercritical propane + , 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 + for supercritical solvent remarkably improved binder removal rate for the paraffin wax-based binder system, in comparison with using pure supercritical .

Defining the relationship between the quality of injection molded parts and the process condition is very complicate because of lots of factor are involved and each factor has a non-linearity. With the development of CAE(Computer Aided Engineering) technology, the estimation of volumetric shrinkage of injection mold parts is possible by computer simulation even though restricted application. In this research, the Taguchi method and Neural Network applied for finding optimal processing condition. The percent of volumetric shrinkage compared on each case and show neural network can be successfully applied.

The production of micro components is one of the leading technologies in the fields of information and communiation, medical and biotechnology, and micro sensor and micro actuator system. Microfabrication (micromachining) techniques such as X-ray lithography, electroforming, micromolding and excimer laser ablation are used for the production of micro components out of silicon, polymer and a limited number of pure metals or binary alloys. However, since the first development of microfabrication technologies there have been demands for the cost-effective replication in large scale series as well as the extended range of available material. One such promising process is micro powder injection molding (PIM), which inherits the advantages of the conventional PIM technology, such as low production cost, shape complexity, applicability to many materials, applicability to many materials, and good tolerance. This paper reports on a fundamental investigation of the application of W-Cu powder to micro metal injection molding (MIM), especially in view of achieving a good filling and a safe removal of a micro mold conducted in the experiment. It is absolutely legitimate and meaningful, at the present state of the technique, to continue developing the micro MIM towards production processes for micro components.

CAE technology is an integrated tool including all aspects such as powder, binder system, mixing, injection molding, debinding and sintering. Therefore, CAE technology is considered as one of core technologies for PIM industry in the future. Recently many researchers are developing not only CAE software itself but also application procedures of CAE software. In this study, the applications for CAE technology in PIM industry are presented including feedstock mixing effect, several cases of troubleshooting and optimization procedure.

In the viscosity measurement of PIM feedstock, slip correction methods require a number of experiments and produce a high level of error. In this study, a rotational rheometer with a parallel-discs configuration having different surface roughness was tried to minimize the effect of the slip phenomenon. Disc surface was prepared in 3 different roughness conditions - a smooth and 2 roughened surfaces. Results with the roughened surfaces were compared with the results obtained with a slip correction method. Relationship between powder characteristics such as size and shape and a surface roughness of the disc was examined for feedstock of 4 different powders with a same binder. As results, the effect of the slip phenomenon could be sufficiently minimized on the roughened surface in most cases. However, the effect of the slip phenomenon could not be sufficiently minimized for feedstock of a round-particular-shape powder and in the case of very narrow gap size.

In this paper we presented numerical method for the simulation of powder injection molding filling process, which is one of the key processes in powder injection molding. Rheological properties of powder binder mixture such as slip phenomena and yield stress were introduced into the numerical analysis model of powder injection molding filling simulation. Numerical model can be classified into two types. One is 2.5D model which can be introduced to a arbitrary thin geometry and the other is full 3D model which can be applied to a general 3D shape. For 2.5D model we showed the validity of our CAE system with several verification examples. Finally we suggested flow analysis model for 3D powder injection molding filling simulation.

The effects of residual impurities on solid state sintering of the powder injection molded (PIMed) W-15wt%Cu nanocomposite powder were investigated. The W-Cu nanocomposite powder was produced by the mech-ano-chemical process consisting of high energy ball-milling and hydrogen reduction of W blue powder-cuO mixture. Solid state sintering of the powder compacts was conducted at for 2~10 h in hydrogen atmosphere. The den-sification of PIM specimen was slightly larger than that of PM(conventional PM specimen), being due to fast coalescence of aggregate in the PIM. The only difference between PIM and PM specimens was the amount of residual impurities. The carbon as a strong reduction agent effectively reduced residual W oxide in the PIM specimen. The formed by reduction of oxide disintegrated W-Cu aggregates during removal process, on the contrary to this, micropore volume rapidly decreased due to coalescence of the disintegrated W-Cu aggregates during evolution of CO.It can be concluded that the higher densification was due to the earlier occurred Cu phase spreading that was induced by effective removal of residual oxides by carbon.

The purpose of the present study is to investigate the influence of thermal debinding and sintering conditions on the sintering behavior and mechanical properties of PIMed 316L stainless steel. The water atomized powders were mixed with multi-component wax-base binder system, injection molded into flat tensile specimens. Binder was removed by solvent immersion method followed by thermal debinding, which was carried out in air and hydrogen atmospheres. Sintering was done in hydrogen for 1 hour at temperatures ranging from 1000℃ to 1350℃ The weight loss, residual carbon and oxygen contents were monitored at each stage of debinding and sintering processes. Tensile properties of the sintered specimen varied depending on the densification and the characteristics of the grain boundaries, which includes the pore morphology and residual oxides at the boundaries. The sinter density, tensile strength (UTS), and elongation to fracture of the optimized specimen were 95%, 540 MPa, and 53%, respectively.

It is well known that the powder injection molding(PIM) process can overcome the shape limitations of traditional powder compaction, the costs of machining, the productivity limits of isostatic pressing and slip casting, and the defect and tolerance limitations of conventional casting. Increasing demands from industry for not only the dimensional accuracy nut mechanical strength in PIMed parts have had much effort focused on the investigation of mechanical properties of mechanical strength in PIMed parts have had much effort focused on the investigation of mechanical properties of sintered parts formed with high-strength metallic powders. The 17_4 PH were injection-molded into flat tensile specimens. Sintering of the compacts was carried out at the various temperatures ranging from 900 to . Sintering behavior of the compacts and tensile properties of sintered specimens were investigated.