• 한국주조공학회지
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• 제32권1호
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• pp.16-23
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• 2012

In this study, we develop the lower pressure die casting with rheo-forming process of A356 aluminum alloy and vacuum system which can control the crystal size and obtain the high strengthened-light material. Using this process, we fabricate the thin plate for bipolar plate through the low pressure die casting with electromagnetic stirring and vacuum-evacuation which can control the crystal grain by electromagnetic stirring. Thin plate ($110mm{\times}130mm{\times}1mm$) is fabricated by this process. The average Vickers hardness of thin plate is about 77 HV.

• 한국정밀공학회지
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• 제24권6호
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• pp.131-137
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• 2007

In metal casting process, it is very difficult to predict the form accuracy of cast part and reduce repeatability error. In this study, the variations of form accuracy were measured in the process of metal cast prototyping, where RP part is manufactured from CAD model in the first, and then, wax part is cast in the vacuum environment using the RP part as master model, and finally metal prototype is cast using ceramic mold and the wax part as pattern. To investigate the variations of form accuracy, the averages and standard deviations of error distribution of the parts measured by 3D scanner were compared. It was observed that the biggest shrinkage is generated during the extraction of wax part in the second step and the biggest deterioration of form accuracy is generated during the metal part casting in the last step.

• 한국정밀공학회지
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• 제16권11호
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• pp.74-80
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• 1999

In this study, a stereolithography apparatus (SLA) prototype is used as a master model to be transformed into the silicone pattern by vacuum tool forming. The tool for the first prototype is fabricated by using this silicone pattern. Following this procedure, a temporary tool with metal powder and epoxy for wax injection is prepared for the die set of quick change type which consists of upper and lower base die나 and an insert die. The die set of quick change type appears to be very effective in casting operation by changing tools rapidly. The original wax pattern is formed through the die set, and is made of lost-was. Finally the lost-wax pattern is applied to investment casting. The final casting product is checked regarding its dimensional accuracy.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2011년도 춘계학술대회 논문집
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• pp.905-906
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• 2011

• 한국재료학회지
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• 제11권12호
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• pp.1057-1062
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• 2001

We investigated the change of mechanical properties for TiNi shape memory alloy by heat treatment. 6061Al matrix composites with TiNi shape memory alloy as reinforcement were fabricated by vacuum casting. TiNi alloy has the maximum tensile strength at 673K treated and there is no change of tensile strength and hardness at 448K treated. The composites, prepared by vacuum casting, showed good interface bonding by vacuum casting. It was about 3$\mu\textrm{m}$ of thickness of the diffusion layer. Tensile strength of the composite was in higher than that of 6061Al alloy as increased value of about 70MPa at room temperature and about 110MPa at 363K. We thought that the increase of the tensile strength at 363K was due to reverse transformation of the TiNi shape memory alloy.

• 대한치과기공학회지
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• 제32권4호
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• pp.307-315
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• 2010

Purpose: The purpose of this study was to investigate the change of microstructures and mechanical properties of pure titanium casting specimens as a function of mold temperatures. Methods: The pure titanium castings were fabricated using the centrifugal vacuum casting method with different mold temperatures of $200{\sim}500^{\circ}C$. The resulting castings were characterized by optical microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and vicker,s hardness tester. Results: In case of the mold temperatures over $400^{\circ}C$, the porosity, surface crack and large grain size were observed in resulting castings. Conclusion: In this work, The most suitable mold temperature in casting of pure titanium was $300^{\circ}C$.

• 한국세라믹학회지
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• 제50권6호
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• pp.396-401
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• 2013

The size of various alumina ceramics used in the semiconductor and display industries must be increased to increase the size of wafers and panels. In this research, large alumina ceramics were fabricated by pressure-vacuum hybrid slip casting (PVHSC) employing a commercial powder, followed by sintering in a furnace. In the framework of the PVHSC method, the consolidation occurs not only by compression of the slip in the casting room but also by suction of the dispersion medium from the casting room. When sintered at $1650^{\circ}C$ for 4 h, the fabricated large-size alumina ($1,550{\times}300{\times}30mm^3$) exhibited a dense microstructure corresponding to more than 99.2% of the theoretical density and a high purity of 99.79%. The flexural and compressive strengths of the alumina plate were greater than 340 MPa and 2,600 MPa, respectively.

• 한국결정성장학회지
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• 제12권3호
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• pp.120-125
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• 2002

Si-wafers for solar cells were cast in a size of $50{\times}46{\times}0.5{\textrm}{mm}^3$ by vacuum casting method. The graphite mold coated by BN powder, which was to prevent the reaction of carbon with the molten silicon, was used. Without coating, the wetting and reaction of Si melt to graphite mold was very severe. In the case of BN coating, SiC was formed in the shape of tiny islands at the surface of Si wafer by the reaction between Si-melt and carbon of the graphite mold on the high temperature. The grain size was about 1 mm. The efficiency of Si solar cell was lower than that of Si solar cell fabricated on commercial single and poly crystalline Si wafer. The reason of low efficiency was discussed.

• 한국주조공학회지
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• 제20권3호
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• pp.188-196
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• 2000

A vacuum casting was proposed as a new fabrication method of Si wafer for solar cell substrate. It was tried to fabricate a Si plate with good properties and to reduce the production cost by direct vacuum casting. By $5{\sim}10$ cmHg of pressure difference Si plate with $50{\times}46{\times}1.5\;mm^3$ was fabricated. For the preventing of the reaction between graphite mold and Si melt, BN powder coating or BN insert were used. The Si wafer was poly crystalline with 100 ${\mu}m{\sim}1$ mm order of grain size. And there were some twins and dislocations in the grains.

• 한국주조공학회지
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• 제37권6호
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• pp.181-185
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• 2017

In the present study, the effect of cooling rate on the formation of the porosity in the thick aluminum sand casting was investigated. Nowadays, due to considerations of weight and cost reduction, large scale thick aluminum casting has replaces steel frames for vacuum chambers for semiconductor production. Several thick aluminum castings were manufactured using chill with temperature measurements. The castings were inspected using 3D computed tomography in order to quantify the porosity defect density in the castings. Effects of the thickness of the chill on the porosity defect density were discussed.