• 한국주조공학회지
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• 제26권2호
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• pp.98-103
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• 2006

Metal-mold reactions between investment mold and TiAl alloys were investigated for the economic net-shape forming of TiAl alloys. The effect of mold preheating temperatures on the metal-mold reaction were investigated using a vacuum induction-melting furnace. In the case of TiAl alloys, there were no ${\alpha}$-case formation reactions. There were neither interstitial nor substitutional ${\alpha}$-case formations as TiAl alloys have both negligible solubility of oxygen and low activity in molten states. The fluidity of TiAl alloys increases with mold preheating temperature since they have a peritectic reaction that appears in the form of envelope, surrounding each particles of the primary constituent. The results of the investment casting of TiAl alloys confirm that the casting route in our study can be an effective approach for the economic net-shape forming of TiAl alloys.

• 한국주조공학회지
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• 제8권3호
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• pp.271-281
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• 1988

Al-bronze has a good mechanical property, corrosion resistance and castability, so being highlighted for the new copper alloy. So, effects of alloy composition and cooling rate in the mechaincal properties and solidification behavior have been investigated. The results obtained are as follows; 1) Change in volume on solidification is larger in metal mold casting than in sand mold casting. And it decreases by the addition of Al. 2) The mechanical property in metal mold casting is superior to the one in sand mold casting, and the inclination is obvious up to 9% Al, after heat-treatment ($885^{\circ}C$, $1.5hrs\;{\rightarrow}\;W\;{\cdot}\;Q\;{\rightarrow}\;540^{\circ}C$, 3hrs) 3) By adding Al, the mechanical property is slightly increased up to 9% Al, Above 9% Al, it is increased rapidly, and is accelerated by adding Fe. 4) Cooling rate and hardness, and grain size and cooling rate are related as follows in the range of $1100^{\circ}C$ to $1200^{\circ}C$ pouring temperature. Grain size(${\mu}m$)=$929.6422{\times}cooling\;rate(^{\circ}C\;/\;sec)^{-0.51537}$ Hardness(BHN)=$765.45713{\times}grain\;size({\mu}m)^{-0.31058}$.

• 한국주조공학회지
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• 제27권6호
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• pp.237-242
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• 2007

To improve the quality of the product and the cost efficiency, the joining of A356 alloy to an Al-18wt%Si alloys has been performed by centrifugal casting. The influence of the mold preheating temperature, the pouring temperature and the rotational velocity of the mold on the microstructures of the shell in the centrifugal casting was investigated using the experimental and simulation methods. In the present study, the cellular automaton (CA) technique and the finite volume method (FVM) were adopted to simulate the evolution of the macro structures and to calculate the temperature profiles, respectively. The evolution of the microstructures was also simulated using a modified cellular automaton (MCA) model. The optimal rotational speed of the mold for obtaining the sound shape of the shell was estimated experimentally to be over 1200 rpm. For the uniform microstructure, the outer shell needs to be cast with higher preheated mold temperature and lower pouring temperature, and the melt was poured at lower temperature in the inner shell. In order to obtain the sound shape of the joining, the different materials were poured simultaneously.

• 한국정밀공학회지
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• 제17권7호
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• pp.124-131
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• 2000

Rapid Prototyping(RP) models are no longer used only for design verification. Currently, parts built utilizing layer manufacturing technology can be employed as functional prototypes and as patterns or tools for different manufacturing processes such as vacuum casting, investment casting, injection molding, precise casting and sand casting. This trend of Rapid Prototyping application meets the requirement of concurrent engineering and its range covers a more spreaded area. The aim of this paper is saving the manufacturing lead time and cost of plastic parts having hollow space shapes used by prototype-car. Using rapid prototype patterns, made by the Selective Laser Sintering(SLS) technique, a new approach of manufacturing resin-based blow mold is discussed. It has a great potential fur making prototype-car parts with the batch size of under 200 parts, in case of rapid modification due to a subsequent design changes in developing stage. So, the process proposed in this research shows reduction of process time and manufacturing cost when compared with the conventional process such as a Zinc Alloy fur Stamping(ZAS) mold.

• 한국정밀공학회지
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• 제16권6호
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• pp.52-57
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• 1999

Funtional metal prototypes are often required in numerous industrial applications. These components are typically needed in the early stage of a project to determine form, fit and function. Recent R/P(Rapid Prototyping) part are made of soft materials such as plastics, wax, paper, these master models cannot be employed durable test in real harsh working environment. Parts by direct metal rapid tooling method, such as laser sintering, by now are hard to get net shape, pores of the green parts of powder casting method must be infiltrated to get proper strength as tool, and new type of 3D direct tooling system combining fabrication welding arc and cutting process is reported by song etc. But a system which can build directly 3D parts of high performance functional material as metal part would need long period of system development, massive investment and other serious obstacles, such as patent. In this paper, through the rapid tooling process as silicon rubber molding using R/P master model, and fabricate wax pattern in that silicon rubber mold using vacuum casting method, then we tranlsated the wax patterns to numerous metal prototypes by new investment casting process combined conventional investment casting with rapid pototyping & rapid tooling process. with this wax-injection-mold-free investment casting, we developed new investment casting process of fabricating numerous functional metal prototypes from one master model, combined 3-D CAD, R/P and conventional investment casting and tried to expect net shape measuring total dimension shrinkage from R/P part to metal part.

• 한국산학기술학회논문지
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• 제14권6호
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• pp.2596-2603
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• 2013

타이어 몰드의 내구성과 정밀도는 타이어의 품질을 결정하는 매우 중요한 요인이다. 그러나 타이어 몰드를 제작하는데 있어서 밀폐된 주조장치 안에서 발생하는 주물의 열변형을 측정하는 데는 많은 어려움이 있다. 본 연구에서는 금형주조장치의 예열온도에 따른 타이어 몰드용 AC7A 주조재의 온도분포, 변위, 응력과 같은 열변형을 수치해석을 통해 분석하였고, 동일 조건하에서 AC7A 주조재의 온도분포를 실험을 통해 측정하여 수치해석 결과와 비교하였다. 수치해석을 위해 상용프로그램인 "COMSOL Multiphysics"를 사용하였고, 금형주조장치의 예열온도를 $150^{\circ}C$, $200^{\circ}C$, $250^{\circ}C$, $300^{\circ}C$로 바꾸어 수치해석을 실행하였다. 수치해석 결과 금형주조장치의 예열온도가 $300^{\circ}C$였을 경우에 주조재의 평균변위와 평균응력은 각각 0.25mm와 0.351GPa로 가장 작게 나타났고, 평균온도는 $374.27^{\circ}C$로 온도가 가장 높게 나타나는 것을 확인할 수 있었다. 수치해석에 의한 온도분포 결과와 실험에 의한 온도분포 결과를 비교하였을 때, 냉각 초기에 상변화과정에서 발생하는 잠열로 인해 약간의 온도차이가 발생하였으나, 그 구간을 제외하고는 거의 비슷한 냉각패턴을 나타내는 것을 확인할 수 있었다.

• 한국세라믹학회지
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• 제53권5호
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• pp.541-547
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• 2016

In developing high temperature molds with advantages of the sand and precision (investment) castings, mechanical properties of the mold were improved through homogeneous coating of starting powders with an inorganic binder and improvement of fabrication process. Beads with mullite composition were employed for properties of the mold under high temperature, which was compared with artificial sands. Precursors of silica and sodium oxide were used as starting materials for an inorganic binder to achieve homogeneous coating on the starting powders. Strength was enhanced by the glass phase converted from the inorganic binder through heat treatment process. Also, two kinds of process, wet and dry processes, were incorporated to prepare mold specimens. Consequently, fabrication process of the mold with superior strength and high temperature applicability, compared with the previous molds for sand casting, could be suggested through control of the starting material and enhancement of the vitrification efficiency.

• 한국주조공학회지
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• 제4권4호
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• pp.5-13
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• 1984

This paper is presented for showing the effect of cooling rate on dendrite arm spacing, correlated with the chilling power of molding materials (conventional plaster, foamed plaster, silica sand) and section thickness, and also showing relationship between dendrite arm spacing and mechanical properties for an aluminum - 8.6 percent silicon - 3.6 percent copper alloy. Local solidification time $(t_f)$ and secondary dendrite arm spacing (d) could be varied widely in accordance with the molding materials and casting thickness, and the following relationship is obtained: $d=9.4t_f\;^{0.31}$ A good correlation between dendrite arm spacing and mechanical properties such as ultimate tensile strength, yield strength, hardness was found, that is, mechanical properties decreased in a linear manner with increase in log of secondary dendrite arm spacing. Ultimate tensile strength in conventional plaster mold casting decreased by 15 percent comparing with the sand casting, where as in foamed plaster mold casting, it decreased by 30 percent comparing with the sand casting. From those results, it has been verified that DAS might be the most representative parameter for predicting mechanical properties varing with the different cooling condition.

• Design & Manufacturing
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• 제15권2호
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• pp.30-35
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• 2021

The casting method uses a mold to solidify a liquid metal to make a solid metal. Since it uses a liquid metal with the least deformation resistance, it has the characteristic that it can easily manufacture even a complex shape. However, the process of solidifying a liquid metal into a solid metal inevitably involves a volume change and contains internal defects such as shrinkage holes. Therefore, in the design of the casting plan, an excess volume called a pressurization compensates for the volume shrinkage. in the product, and it induces the shrinkage hole defects to occur in parts other than the product1). In this study, casting analysis was performed using casting analysis software (anycasting) in order to optimize the design of the tilting gravity casting method for automobile brackets. In particular, the filling and solidification analysis according to the shape and volume of the pressurized metal was conducted, and applied to the actual product to study the effect of the pressurized metal on the shrinkage defect. Through this study, it is possible to understand the effect of the pressure metal on shrinkage defects in the actual product and propose a design of the pressure metal that improves reliability and productivity.

• 한국주조공학회지
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• 제28권5호
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• pp.237-241
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• 2008

This study has been carried out to investigate the wear and heat resistant properties of durable moldwash agent for Al gravity casting according to mold washing process conditions. The wear properties of coated specimen were performed by sliding wear testing machine and heat resistance were evaluated by measuring the loss of coated moldwash agent during emerging of coated specimen in Al melts. During testing, experimental variables were mold surface temperature, moldwash agent/distilled wear, and additive concentrations. The lower additive concentration and mold temperature caused the smooth surface roughness of coated specimen, It was found that the specimen coated with moldwash/water ratio 1:3, additive concentration 9wt% and mold temperature higher than $200^{\circ}C$ showed superior wear and heat treatment. Also, these results were supported by fluidity test.