• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.5
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• pp.648-657
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• 2002

This paper presents a numerical analysis on the solidification characteristics in twin-roll strip casting. Unstructured fixed-grid system was employed to deal with phase change. Melting of pure gallium was analyzed to confirm the validity of present program in both structured and unstructured grid systems. An algorithm for simultaneous calculation of the temperature in the roll and the molten metal pool was developed. The flow field in the pool and heat transfer features between pool and roll were shown. The effect of process parameters was also studied. Since the geometry of the molten metal Pool significantly deforms along the casting direction, unstructured grid system is more efficient. The unstructured grid system gives almost the same accuracy, even though the number of grids is only 60% of the structure done.

• Journal of Korea Foundry Society
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• v.28 no.2
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• pp.74-78
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• 2008

An integrated riser heating equipment has been developed to control shrinkage defects originated from casting of a marine propeller. The integrated riser heating equipment is composed of up/down moving parts, heating power source parts and an integrated controller. Heat capacity putting into the riser was calculated quantitatively on the base of a heat transfer analysis, which consisted of the establishment of heating model and the theoretical analysis for heat transfer. The riser heating equipment was evaluated through arc heating and electro-slag heating method. With the results, the arc type heating method was selected by considering high thermal efficiency, inexpensive cost, and convenient workship. This equipment improves the quality of a propeller casting and the poor working environment.

• Journal of Technologic Dentistry
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• v.35 no.2
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• pp.89-95
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• 2013

Purpose: The purpose of this study was to evaluate bond strength of Metal Disk alloy and casting alloy. Methods: Metal specimens were divided into 4 groups for each alloy. Three point flexural test were used to measure the bond strength of CAD/CAM metal alloy and casting alloy. Statistical analysis was done using the Statistical Package for Social Sciences version 19.0 for Windows. As for the analysis methods, the study used Kruskal-Wallis test. Results: The average bonding strengths of Group 1 to porcelain was $36.7{\pm}9.90$ MPa, Group 2 to porcelain was $37.68{\pm}4.51$ MPa, Group 3 to porcelain was $36.43{\pm}6.57$ MPa, Group 4 to porcelain was $42.88{\pm}6.81$ MPa, Each group was not significantly different. Conclusion: Bond strength of Casting alloy is equal to or higher than bond strength of CAD/CAM Metal Disk alloy. Alloy clinical bond strength is 25 MPa, So CAD/CAM Metal Disk alloy can be used as dental material.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.405-408
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• 2003

Generally, the life of casting mold is limited by fatigue fracture or dimensional inaccuracy originated from wear in high temperature. Although recent research of metallic materials in high temperature fatigue have been much accomplished, many studies on brittle material as a die steel in high temperature fatigue does not have been reported. Especially, the study on the fatigue behavior over the transformation temperature is not studied sufficiently because of its difficult analysis and experiment. Therefore, reliable results of brittle material in high temperature fatigue behavior are needed. In this paper, stress-strain curves and stress-life curves in die STD61 steel are carefully examined between room temperature and 90$0^{\circ}C$, as the basic experimental data are used to predict from fatigue life of casting mold.

• Journal of Korea Foundry Society
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• v.13 no.5
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• pp.424-431
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• 1993

A Numerical technique has been developed for the coupled heat transfer and fluid flow calculation during the casting process. In this method the SMAC technique was coupled with the concept of Volume of Fluid(VOF) to calculate melt free surface and velocity profiles within the melt, and the Energy Marker method coupled with the finite difference method was proposed for the convective and conductive heat transfer analysis in the casting. When comparing numerical calculations with experimental observations, a close correlation was evident. It has been shown that this technique is useful for proper gating and casting design, especially for thin-walled castings.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.269-274
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• 2003

Vibration table is required to obtain high packing density in expendable pattern casting process. Packing density, which is an important manufacture factor, depends on the vibration pattern induced by vibration table. Modal test is utilized to identify the dynamic characteristics of vibration table. And finite element method is used to modify flask by fixing the stiffener. The positions of stiffener to modify are found and the natural frequency could be easily shifted to the objective value by using sensitivity analysis.

• Journal of Korea Foundry Society
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• v.32 no.2
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• pp.65-74
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• 2012

In this paper, we present the results of our studies on optimal die design towards development of a vacuum die casting process to fabricate fuel cell bipolar plate with micro-channel array. Cavity and overflow shape is designed by computational filling analysis of MAGMA soft. Optimal die design consists of seven overflows at the end of cavity and three overflows at each side wall of cavity. The molten metal that passed the gate and reached the side wall flowed into the side overflow, no turbulent flow occurred, and the filling behavior and velocity distribution were uniform. In addition, partially solidified molten metal passing through the channel was perfectly eliminated by overflow without back-flow. When vacuum pressure, injection speed of low and high region was 300 mbar, 0.3 m/s and 2.5 m/s respectively with Silafont 36 die casting alloy, sound sample without casting defects was obtained. The experimental results are nearly consistent with simulation results.

• Journal of Korea Foundry Society
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• v.40 no.3
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• pp.61-65
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• 2020

Rheo-diecasting with stirring has been used in many material industries. As the 4th Industrial Revolution approaches the world, eco-friendly high-strength and light-weight materials become more important. Casting methods have been studied and used for aluminum-alloy automobile parts. This study carried out the effect analysis of the micro-structure and mechanical properties, such as yield/ultimate tensile strength, elongation, and hardness, of A356 using the 6-pole EMS (electro-magnetic stirring) casting process with a high electromagnetic force. As a result, the hardness and elongation of the A356 after T6 heat-treatment show a significant improvement, respectively, by 20% and 50%.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.5
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• pp.111-117
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• 2020

Centrifugal casting is suitable for producing hollow-products using centrifugal force. Bush type metal bearings are the key parts that facilitate the rotational movement of various machinery. Metal bearings produced by conventional centrifugal casting machines show rotational imbalance. Therefore, after injecting a large amount of material, the product's precision is secured in the secondary processing. Rotational imbalance is caused by the force acting on the rotary disc plate. In order to minimize rotational imbalance, NASTRAN was used for the optimal design and structural analysis. It was concluded that the rotating plate of the conventional centrifugal casting machine should be prevented from tilting. For this purpose, the location & thickness of the stiffeners were obtained through the optimum design. In the conventional centrifugal casting machine, both ends of the product are lower in temperature than the center part, so internal stress occurs. This solves this problem by inserting a heating coil into the rotating plate.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1998.03a
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• pp.138-143
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• 1998

The continuous casting process has been adopted increasingly in recent years to save both energy and labor. It has experienced a rapid development in the production of semi-finished steel products, replacing the conventional route of ingot casting plus rolling. To achieve this good merit, however, more studies about a heat transfer mechanism between roll and slab are needed. So this paper shows the results of the deformation behavior of steel cast slabs, which are about the solidification and heat transfer. This study is used to prevent internal cracks of a slab in a bending and unbending zone. The value of moving strand shell bulging between two supporting rollers under ferrostatic pressure and slab-self weight has been computed in terms of creep and elastic-plasticity. The high strand distributions in solidified shell undergoes a series of bulging are calculated with boundary condition a very closed to continuous steel cast slabs productions.