• 한국주조공학회지
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• 제18권6호
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• pp.578-585
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• 1998

A multi-purpose code MAGMA was employed for mold design and process control in producing Al wheel by lowpressure die casting. Three-dimensional solid modeling was followed by mesh generation of casting and molds(top, bottom and side). The simulation of stability of casting cycle time, mold filling simulation with pressure variation from P1 to P2, solidification simulation by solidification time and feeding criteria, and temperature distribution of molds during processes were studied in this research. The thermal stability of molds was attained after 5 cycles when molds were preheated at $400^{\circ}C$. The pressure increase from P1 to P2 for mold filling was evaluated as slightly higher, and 6 seconds were taken for the mold filling. The cycle time was believed to be designed properly judged from the solidification time of casting and open/close time of molds.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.76.4-76
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• 2001

ESR(ElectroSlag Remelting) Process is secondary fine process and melts steels by electric resistance heat and fines the melting steels by an approproate solidification process. The final products are determined through the velocity of melting and the course of solidification in the process that is achieved by way of proper course of solidification. Thus, it is very important to monitor and control the process parameters which affects the melting and solidification process to get the high quality products. This paper describes a method to derive the mathematical model and analysis the dynamic characteristics for designing a controller of the ESR processes. The process consists of a melting and solidifying process and electrical system include the contact resistance mechanism ...

• 소성∙가공
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• 제3권1호
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• pp.3-17
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• 1994

The semi-solid metal forming for vigorously agitated semi-solid alloys has been widely studied over the last decade. Metal forming processes are now being developed using alloys in the semi-solid state, among them are rolling, forging, extrusion, and die casting. Some of these are now employed commercially to produce a components and are also used to fabricate metal matrix composites. The semi-solid materials can be processed either directly during solidification and for this purpose mechanical stirring was demonstrated to produce a highly solidification. This paper is concerned with the influence of processing parameters on limitations of semi-solid forming.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.1364-1367
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• 1996

Recently, direct rolling process, called as strip casting process, has been interested in to save production cost by reducing forming processes. In direct rolling process, since a steel strip of thickness 1-5(mm) can be produced directly from molten metal, it can eliminate secondary hot rolling process. On the other hand, since many process variables are existed in this process and relation of these variables is very complex, it is difficult to realize the process design and the quality control. In this paper, as first step to overcome above difficulties, the quantitative relationship of the process variables affected to quality of the strip has been carried out through the numerical analysis. Also, we determined the process variable to monitor the quality in the direct rolling process. As a result, we show that the solidification final point, called as Nip point, was related directly to quality of the strip.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2006년도 춘계학술대회 논문집
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• pp.425-428
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• 2006

A semi-solid forming technology has some advantages compared with conventional forming processes such as die casting, squeeze casting and hot/cold forging. In this study, the numerical analysis of semi-solid filling has been studied with solid fraction fs = 30% of A356 aluminum alloys. The finite difference program of two-phase flow model of Navier Stokes' equation coupled with heat transfer and solidification has been developed to predict a filling pattern, liquid segregation and temperature distribution of semi-solid metals. It gives die filling patterns and final solidification area. It can predict mechanical properties of semi-solid forming processes.

• 한국주조공학회지
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• 제10권1호
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• pp.3-8
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• 1990

• 한국결정성장학회지
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• 제18권3호
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• pp.122-124
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• 2008

The partial phase diagram of $NaNO_3$-NaCl system was investigated and the eutectic temperature was determined as $294.5^{\circ}C$. A typical rod eutectics of $NaNO_3$-4.56 wt%NaCl was directionally solidified. The results of interrod spacing, ${\lambda}_E$ as a function of growth velocity, V, were. obtained as ${\lambda}_E\;V^{0.39}\;=\;5.26$ (temperature gradient, $G_l\;=\;21.4^{\circ}C/mm$) and ${\lambda}_E\;V^{0.32}\;=\;5.45$ ($G_l\;=\;3.9^{\circ}C/mm$) and the exponent numbers of growth velocity were smaller than the theoretical value, 1/2. The sample rotation applied during directional solidification made the interrod spacing decrease slightly.

• 소성∙가공
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• 제5권3호
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• pp.239-255
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• 1996

A new forming technology has been developed to fabricate near-net shape products using light metal. A semi-solid forming technology has some advantages compared with the conventional forming processes such as die casting squeeze casting and hot/cold forging. In this study the numerical analysis of semi-solid filling for a straight die shape and orifice die shape in gate pattern is studied on semi-solid materials(SSM) of solid fraction fs =30% in A356 aluminum alloy. The finite difference program of Navier-Stokes equation coupled with heat transfer and solidification has been developed to predict a filling pattern and the temperature distribution of SSM. The programdeveloped in this study gives die filling patterns of SSM and final solidifica-tion region.

• 한국재료학회지
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• 제9권2호
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• pp.139-143
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• 1999

Solidification simulation of gray cast iron sheave product was conducted with the consideration of graphite precipitation during solidification, and of casting processes such as post-inoculation method, treatment and rate, the result of which was aimed to be adopted in the field. In risering design(I), shrinkage cavities were predicted to occur in the part below the risers and center part of the product. While the former defect was considered to be due to the solidification behaviour of riser neck, the latter was due to the feeding channel. In design(II), the length of the riser neck was reduced and one top open riser was attached in the center of the product to prevent the formation of shrinkage cavities, whereby defect-free product was produced.

• Journal of Mechanical Science and Technology
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• 제19권7호
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• pp.1488-1502
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• 2005

A three dimensional model was developed to analyze the mold filling and solidification in the casting processes. The model uses the VOF method for the calculation of the free surface and the modified Equivalent Specific Heat method for the treatment of the latent heat evolution. The solution procedure is based on the SIMPLER algorithm. The complete model has been validated using the exact solutions for phase change heat transfer and the experimental results of broken water column. The three-dimensional model has been applied to the benchmark test and the results were compared to those from experiment, a two-dimensional analysis, and another three dimensional numerical model.