• Journal of Korea Foundry Society
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• v.15 no.2
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• pp.164-174
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• 1995

New metallic powder making processes, named "Centrifugal Emulsification Process(CEP)" and "Mixer and Settler(MS)" have been developed to synthesize rapid solidified metallic powders. Through CEP and MS processings, the high temperature metals as well as the low temperature alloys are manufactured. Also, the effects of rapid solidification on the undercooling, solidification rate and crystallization behaviors can be evaluated effectively through the processes. The standard deviations of the synthesized typical Pb-Sn eutectic powders are 1.63 and 1.51 for CEP and MS respectively, and the average size of the MS powders was $18{\mu}m$. The possibility of the customized not only size and shape control but microstructure control was also shown. Both of the new methods can be applied to continuous powder making processes.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.3
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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.

• Journal of Korea Foundry Society
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• v.18 no.5
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• pp.462-466
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• 1998

Interest in rapid solidification of magnesium alloys stems from the fact that conventional ingot metallurgy alloys exhibit poor strength, ductility, and corrosion resistance. Such properties can be improved by microstructural refinement via rapid solidification processing. Mg-5wt%Zn alloys have been produced as continuous strips by melt overflow technique and the strips were consolidated by hot extrusion. The yield stress, tensile strengh and ductility obtained in asextruded Mg-5wt%Zn alloy were ${\sigma}_{0.2}=152\;MPa$, ${\sigma}_{T.S{\cdot}}=263\;MPa$ and ${\varepsilon}=21.8%$. In order to evaluate the influence of additional elements on mechanical properties, Th and Zr were added in rapidly solidified Mg-5wt%Zn alloy. An 130% increase in yield stress of as-extruded Mg-5wt%Zn-3wt%Th-1wt%Zr alloy was attributed to grain refinement by rapid solidification and elemental addition.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.83-84
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• 2002

For estimation of chain-matching phenomena between normal paraffin as a solvent and straight-chain fatty acid as an additive, the density measurement of n-dodecane, n-tetradecane and n-hexadecane were carried out at oil temperature 313K and pressure up to 1.3 GPa. Their solidification pressure were easily determined by the appearance of molecular crystal, abrupt volumetric contraction and generation of heat of solidification and showed minima under the matching condition. The bulk modulus K of molecular crystal was evaluated using phase diagram. The bulk modulus showed maxima under the each matching condition. The chain matching effect on the bulk modulus beyond the scope of the interfacial phenomena are confirmed.

• Journal of Korea Foundry Society
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• v.5 no.4
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• pp.289-297
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• 1985

Thin sections in castings solidify faster than thick sections. Solidification rates increase because of an increase in heat transfer from molten meltals to molds through these solidified thin sections. The cooling fin effect in pure zinc casting was studied about the solidification time, superheat, and fin size by adopting the pourout test. The following results could be obtained from the study: (1) The fin effect could be represented by the effective cooling surface area ($A_f/S$) increased. (2) The fin effect could be obtained as functions of solidification time, superheat, and fin size.

• 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.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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• pp.51-54
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• 2003

The continuous casting is primarily a heat-extraction process in which the heat transfer at various cooling zones profoundly influences quality of products. So development of numerical model is necessarily needed for more specific and clear investigations upon heat transfer mechanism at mold and secondary cooling zones. In this study, heat transfer coefficients which shows the characteristic of heat transfer mechanism in mold are calculated for more exact analysis with temperatures measured in bloom mold using optimal algorithm, and finally the validity of cooling conditions at secondary cooling zone which is actually used at field for 30 Ton bloom type continuous casting of 0.187%C is investigated. From the results of solidification analysis, the characteristic of bloom mold shows good agreements with that of previously studies by other authors and optimized cooling conditions for 0.187%C are presented.

• 한국전산유체공학회:학술대회논문집
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• 2009.04a
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• pp.355-362
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• 2009

Most material of engineering interest undergoes solidification process from liquid to solid state. Identifying the underlying mechanism during solidification process is essential to determine the microstructure of material which governs the physical properties of final product. In this paper, we expand our previous two-dimensional numerical technique to three-dimensional simulation for computing dendritic solidification process with fluid convection. We used Level Contour Reconstruction Method to track the moving liquid-solid interface and Sharp Interface Technique to correctly implement phase changing boundary condition. Three-dimensional results showed clear difference compared to two-dimensional simulation on tip growth rate and velocity.

• Journal of environmental and Sanitary engineering
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• v.14 no.3
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• pp.22-30
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• 1999

This study was carried out to examine the compressive strength characteristics of solids solidified with the lead sludge with mixture of cement and fly ashes as additive. And the additives are commercial fly ash and ESP(Electrostatic precipitator) fly ash. The compressive strength of solidified lead sludge solid was increased by adding fly ash up to 46~62%, which was the results of pozzolanic reaction. When replaced the cement with 10%of commercial fly ash, the solid showed the highest value $210{\;}kg/cm^2$, and the solidification conditions were 0.55 of the water/cement ratio and curing for 14 days. Also, the results of leaching test by EPT(Environmental Protection Agency-Toxicity Test) were showed that the solidified lead has leached out under 10%, which was less than 0.173 mg/L of EPA standard. As leaching solutions, the demineralized water, 0.1N acetic acid solution, and synthetic brine were used. and the observations by SEM of the solidified lead-laden solid after EPT leaching test were indicated the severe erosion on solid surface.