• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.06a
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• pp.279-280
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• 2007

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.252-255
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• 2009

The roll gap set-up in the finishing mill is one of the most important technologies in the hot plate rolling process. As the target thickness can be obtained by the correct set-up of the roll gap, improving the roll gap set-up technology is very critical for plate thickness accuracy. The main cause of thickness variation in hot plate mills is the non-uniform temperature distribution along the length of the slab. The objective of this study is to adjust the roll gap set-up for the thickness accuracy of plate in hot rolling process considering top-end temperature drop. Therefore this study has concentrated on determining the correct amounts of roll gap to compensate thickness variation due to top-end temperature drop. The off-line simulation of compensated roil gap significantly decreases top-end thickness variation.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.186-189
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• 2008

The flex plate, an automotive part which mounts to the automotive engine to transfer torque to transmission, should have considerable hardness and shape accuracy. As a way to produce the flex plate, the hot press forming technology which takes advantages of high formability at elevated temperature, enhanced strength and shape stability was introduced. Therefore, as one of major process parameters the heat treatment condition should be determined to obtain appropriate hardness in the range of manufacturer's specifications. In this study, two heat treatments, austempering and quenching and tempering (QT), were compared as feasible conditions fur the hot press forming of high-carbon tool steel and the hardness and toughness after heat treatments were evaluated. The study showed that both heat treatments resulted in improved hardness but only quenching and tempering showed practicable range of toughness.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.2
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• pp.149-157
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• 2008

During CVD process of semiconductor wafer fabrication, maintaining the uniformity of temperature distribution at wafer top surface is one of the key factors affecting the quality of final products. Effect of contact conductance between wafer and hot plate on predicted temperature of wafer was investigated. The validity of opaque wafer assumption was also examined by comparing the predicted results with Discrete Ordinate solutions accounting for semitransparent radiative characteristics of silicon. As the contact conductance increases predicted wafer temperature increases and the differences between maximum and minimum temperatures within wafer and between wafer and hot plate top surface temperatures decrease. The opaque assumption always overpredicted the wafer temperature compared to semitransparent calculation. The influences of surrounding reactor inner wall temperature and hot plate configuration are then discussed.

• Transactions of Materials Processing
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• v.15 no.4 s.85
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• pp.311-318
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• 2006

One of the most important quality problems in flat plate leveled from hot rolled coils in cut-to-Iength lines is bowing and cambering when they are cut in small width parts. It is verified analytically and experimentally that residual stress remained in plate is th ε source of the problem. In order to produce low residual stress flat plate from hot rolled coils, the proper conditions of leveling are studied and two things are implemented. One is proper plastic deformation area ratio to reduce residual stress within customer requirement by applying suitable plastic deformation and maintain leveling load within structural strength limit of leveler. The other is maintaining uniform plastic deformation along the width of the plate during leveling. Customer requirement for residual stress is met by applying above 70% of plastic deformation area ratio and uniform deformation along width of coil by adjusting back up rolls according to deformation analysis of work roll and back up roll assembly and leveling tests.

• Proceedings of the KWS Conference
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• v.43
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• pp.231-233
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• 2004

• Journal of computational fluids engineering
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• v.21 no.2
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• pp.90-98
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• 2016

A numerical study is conducted on thermal performance of a large-area hot plate specially designed as a heating and cooling tool for thermal nanoimprint lithography process. The hot plate has a dimension of $240mm{\times}240mm{\times}20mm$, in which a series of cartridge heaters and cooling holes are installed. The material is stainless steel selected for enduring the high molding pressure. A numerical model based on the ANSYS Fluent is employed to predict the thermal behavior of the hot plate both in heating and cooling phases. The PID thermal control of the device is modeled by adding user defined functions. The results of numerical computation demonstrate that the use of cartridge heaters provides sufficient heat-up performance and the active liquid cooling in the cooling holes provides the required cool-down performance. However, a crucial technical issue is raised that the proposed design poses a large temperature non-uniformity in the steady heating phase and in the transient cooling phase. As a remedy, a new hot plate in which heat pipes are installed in the cooling holes is considered. The numerical results show that the installation of heat pipes could enhance the temperature uniformity both in the heating and cooling phases.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.11
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• pp.1190-1198
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• 2012

A hot forming of large thick Al plate using a grid-type hybrid die is a process to make a shell plate for the production of a spherical LNG tank. This process is characterized by using a grid-typed die with an additional air cooling system for reducing the cooling time of the heated plate after hot forming. The process consists of the plate's feeding, heating, forming and cooling in detail and each of them is continuously performed along the rail. This paper was designed to propose the analytical and experimental methods for determining the convection and interfacial heat transfer coefficients required in hot forming analysis of Al plate. These values in the analysis are to reproduce numerically the cooling performance of grid-typed die and cooling device. Interfacial heat transfer was obtained from the heat transfer experiments for different pressures and inverse analysis method. To verify the efficiency of the coefficient values obtained from above methods, FE analysis and experiment of the hot spherical-forming process were conducted for a small-scaled model. The convection coefficient was also calculated from flow analysis of air released by cooling device within grid-typed die using ANSYS-CFX.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.10a
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• pp.669-670
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• 2006

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.11
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• pp.1525-1533
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• 2003

In the precision hot plate for wafer processing, uniform temperature of the upper plate is one of key factors affecting the quality of wafers. The state-of-the-art precision hot plates require temperature Variations less than $\pm$0.4$^{\circ}C$ during heating to 15$0^{\circ}C$, Which is difficult to be obtained only by the improvement of manufacturing techniques alone. In this study, computer aided heat transfer analysis was carried out to obtain the temperature distribution of the currently used reference hot plate for 200mm wafer. The analysis on the reference model assuming constant heat generation rate and uniform heating area showed total variation of 0.926$^{\circ}C$ at 15$0^{\circ}C$. One of the new design approaches based on the change of heating location together with different heat generation rate resulted in total variation of 0.297$^{\circ}C$ which is a 68% improvement compared to that of the reference model.