• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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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.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.1
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• pp.45-49
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• 2008

The development of manufacturing process of silicon (Si) ingots is one of the important issues to the growth of the photovoltaic industry. Polycrystalline Si wafers shares more than 60% of the photovoltaic market due to its cost advantage compared to mono crystalline silicon wafers. Several solidification processes have been developed by industry including casting, heat exchange method (HEM) and electromagnetic casting. In this paper, the advanced directional solidification (ADS) method is used to growth of large sized polycrystalline Si ingot. This method has the advantages of the small heat loss, short cycle time and efficient directional solidification. The numerical simulation of the process is applied using a fluid dynamics model to simulate the temperature distribution. The results of simulations are confirmed efficient directional solidification to the growth of large sized polycrystalline Si ingot above 240 kg.

• Korean Journal of Materials Research
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• v.30 no.12
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• pp.678-686
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• 2020

Microstructural characteristics of directionally solidified René 80 superalloy are investigated with optical microscope and scanning electron microscope; solidification velocity is found to change from 25 to 200 μm/s under the condition of constant thermal gradient (G) and constant alloy composition (Co). Based on differential scanning calorimetry (DSC) measurement, γ phase (1,322 ℃), MC carbide (1,278 ℃), γ/γ' eutectic phase (1,202 ℃), and γ' precipitate (1,136 ℃) are formed sequentially during cooling process. The size of the MC carbide and γ/γ' eutectic phases gradually decrease with increasing solidification velocity, whereas the area fractions of MC carbide and γ/γ' eutectic phase are nearly constant as a function of solidification velocity. It is estimated that the area fractions of MC carbide and γ/γ' eutectic phase are determined not by the solidification velocity but by the alloy composition. Microstructural characteristics of René 80 superalloy after solid solution heat-treatment and primary aging heat-treatment are such that the size and the area fraction of γ' precipitate are nearly constant with solidification velocity and the area fraction of γ/γ' eutectic phase decreases from 1.7 % to 0.955 %, which is also constant regardless of the solidification velocity. However, the size of carbide solely decreases with increasing solidification velocity, which influences the tensile properties at room temperature.

• Journal of Korea Foundry Society
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• v.30 no.1
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• pp.34-45
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• 2010

The effects of alloy elements and cooling rate on the solidification path and the formation behavior of $\beta$ phase in Fe-containing Al-Si alloys were studied based on the thermodynamic analysis and the pertinent experiments. The thermodynamic calculation was systematically performed by using Thermo-Calc program. For the thermodynamic analysis in high alloy region of Al-Si-Fe ternary system, a thermodynamic database for Thermo-Calc was correctly updated and revised by the collected up-to-date references. For the thermodynamic-based prediction of various solidification paths in Fe-containing Al-Si system, liquidus projection of Al-Si-Fe ternary system, including isotherms, invariant, monovariant, bivariant reactions and equilibrium temperatures, was calculated and analyzed as functions of composition and temperature. The calculated results were compared to the experimental results using various casting specimens. In order to analyze various solidification sequences as functions of Si and Fe content, 4 representative alloy compositions, low Fe content in both low and high Si contents and high Fe content again in both low and high Si contents, were designed in this study. For better understanding of the influence of cooling rate on the formation behavior of $\beta$ phase, 4 alloys were solidified under furnace and rapidly cooled conditions. Cooling curves of solidified alloys were recorded by thermal analysis. Various important solidification events were evaluated using the first derivative-cooling curves. Microstructures of the casting samples were studied by the combined analysis of optical microscopy (OM) and scanning electron microscopy (SEM).

• Journal of Korean Society of Industrial and Systems Engineering
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• v.36 no.4
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• pp.71-76
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• 2013

For a die casting mold, generally, the casting layout design should be considered based on the relation among injection system, casting condition, gate system, and cooling system. Also, the extent or the location of product defects was differentiated according to the various relations of the above conditions. In this research, in order to optimize the casting layout design of an automotive Oil Pan_DX2E, Computer Aided Engineering (CAE) simulation was performed with two layout designs by using the simulation software (AnyCasting). The simulation results were analyzed and compared carefully in order to apply them into the production die-casting mold. During the filling process with two models, internal porosities caused by air entrapments were predicted and also compared with the modification of the gate system and overflow. With the solidification analysis, internal porosities occurring during the solidification process were predicted and also compared with the modified gate system.

• Transactions of Materials Processing
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• v.5 no.3
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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.

• Journal of Korea Foundry Society
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• v.29 no.1
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• pp.38-44
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• 2009

Magnetic separation of Fe contaminated Al-Si cutting chip scraps was performed for the recyclability assessment. It was also aimed to investigate the casting and solidification characteristics of the cutting chip scraps. The magnetically separated cutting chip scraps were adequately treated for the casting procedure and test specimens were made into a stepped mold inducing different cooling rates. The test specimens were evaluated by the combined analysis of ICP, Spectroscopy, OM-image analyzer, SEM/EDS, etc. Solidification characteristics of cutting chip scraps were examined as functions of Fe content and cooling rate. It is concluded that the magnetic separation process can be utilized to recycle the Fe contaminated Al-Si cutting chip scraps in the high cooling rate foundry process.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.5 no.2
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• pp.111-121
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• 1993

Double-diffusive convection during solidification process of the binary mixture was studied numerically. Enthalpy method and finite element method were implemented in the analysis. Calculation carried out for $R{\alpha}_T=10^3-10^4$ and $R{\alpha}_T=0-10^5$. The results show that the variation of thermal Rayleigh number changes the fields of velocity, temperature and concentration, but the variation of solutal Rayleigh number gives little effects on those. In conclusion, concentration gradient can be negligible compared with temperature gradient in macroscopic point of view, although concentration gradient plays a role in forming dendrite.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2001.04a
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• pp.49-52
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• 2001

An experimental study was conducted to test the feasibility of degradative solidification/stabilization (DS/S) process in treating tetrachloroethylene (PCE) in solid phase systems. The Fe(II)-based ds/s process successfully treated PCE in a soil at the reaction rates that would not allow significant release of the contaminant in the environment. A leach model was also developed that could describe the relative importance of leaching and degradation in ds/s. The first and second Damkohler numbers and dimensionless time were important parameters that determined leaching precesses in wastes treated by ds/s.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.10a
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• pp.250-253
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• 2004

A finite element model is developed for the process of squeeze casting of metal matrix composites. The fluid flow and the heat transfer are fundamental phenomena in squeeze casting. The equations for the clear fluid flow and the flow in porous media are used to simulate the transient metal flow. To describe heat transfer in the solidification of molten aluminum, the energy equation is written in terms of temperature and enthalpy. A direct iteration technique is used to solve the resulting nonlinear algebraic equations. The cooling curves and temperature distribution during infiltration and solidification were calculated for a simplified model with pure aluminum. The developed program can be used for squeeze casting process of complex geometry, boundary conditions and processing parameter optimization.