• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.6
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• pp.913-922
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• 1987

In this paper the solidification phenomena at the molten pool has been modeled and simulated in terms with the one dimensional unsteady-state heat transfer of the solid and molten phase and the pressure distribution in the solid phase for the twin-roller continuous casting of Sn-15% Pb. The further purpose of this study was to effectively analyze the thermal and mechanical deformation of roll applying the results of the heat transfer and the pressure distribution to the boundary conditions. The strip thickness of rapidly solidified metallic strip decreases with increasing angular velocity of the roller and with increasing initial roll gap. For this reason the roll spacing and angular velocity of the rolls are considered to be main variables. The recommended optimal casting regimes for continuous strip dimensions is near 0.8mm-1.0mm in thickness at the given angular velocity .omega.=2.0 rad/sec. Results of the experiment using Sn-15% Pb are compared with model predictions. The calculated roll deformation has been in good agreement with the observed value of roll deformatiion. All the deformation. All the deformation of the roller is within the elastic range, the plastic yielding are not occured. However, these elastic stresses are sufficient to take place of the shortened roller life by the thermal fatigue and a notch fatigue. The higher cooling rates were obtained by a twin-roller quenching technique. Also the quenched microstructure of the rapidly solidified shell was verified.

• Journal of Korea Foundry Society
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• v.9 no.1
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• pp.20-28
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• 1989

• Transactions of Materials Processing
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• v.11 no.1
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• pp.24-35
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• 2002

Recent trend and future prospect of flat rolling of steel has been summarized based on the earlier reports. Key technology in the plate rolling is to have ultra fine microstructure having high resistance against crack propagation during application. Heavy accelerated cooling facility and high power rolling mill will be helpful to develope the high toughness steel. Precise modeling of properly prediction based on deformation and transformation imposed on microstructure of steel during processing is highly anticipated. For the hot strip rolling process, new trend is lies on the production of ultra-thin gauged hot strip to substitute cold rolled strip. For the substitution of cold rolled strip into hot rolled strip widely, high formable property of hot strip is highly required. For the formabilit, the ferritic rolling of extra low carbon steel under high lubricated condition is essential. Recently introduced semi-continuous thin slab and rolling mill line is very plausible to develope those kinds of products easily In the view groin facility combination. New idea to modify the existing continuous hot strip mill line to produce the ultra thin-gauged hot strip in an economic way is suggested in this report.

• Journal of Korea Foundry Society
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• v.15 no.4
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• pp.397-407
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• 1995

The objectives of this study are first, to expand our understanding of relationship between magnetic properties and microstructural features such as grain size and texture, and second to reduce core loss of Fe-6.5%Si strip through optimizing heat treatment conditions. A rapid solidification technique, planar flow casting(PFC), was adopted to produce Fe-6.5%Si strips. The strips were heat treated under various conditions. The results show that heat treatment conditions can change not only grain size but also (200) texture formation on the strip surface. Variation in magnetic properties of Fe-6.5%Si strip is analyzed in terms of the change in grain size as well as (200) texture on the strip surface. The heat treatment conditions of $1100^{\circ}C$ over 2 hr or $1150^{\circ}C$ $1{\sim}2hr$ in $N_2+5%H_2$ appear to minimize core loss of Fe-6.5%Si strips.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1992.04a
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• pp.274-278
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• 1992

냉간압연기술의 발달로 냉간압연기도 매우 다양하게 발달되었으며 냉간압연의 원자재인 열간압연재의 종류도 다양하다. 최근 열간압연가공시 회수율이 높은 연속주조재(Continuous casting strip)인 CC 재가 종전의 가공과정이 복잡하며 불량율이 높은 Ingot주조재(Ingot casting strip)인 IC 재 보다 생산비율이 점차 증대되어 냉간압연재료의 주종을 차지하고있다. CC재는 냉간압연가공시 IC재에 비해 Work roll 조도저하가 현저하게 크기 때문에 슬립(Slip)과 채팅(Charttering) 현상 등이 발생하여 압연가공성이 불안정 하게 되어 Work roll과 판표면에 손상이 생기게 되고, 압연가공시 Roll 사고 등의 문제가 발생하므로 Roll 마멸의 정도를 파악하여 Roll을 효과적으로 관리하므로써 Work roll과 판표면의 슬립현상 및 채터 링현상 등을 방지할 수 있다.

• Transactions of Materials Processing
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• v.4 no.3
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• pp.233-244
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• 1995

Rolling force in the direct rolling(or twin-roll strip continuous casting) process fo semi-solid material has been computed using rigid-viscoplastic finite element method. Temperature distributions for calculations of rolling force and roll deformation are obtained from thermofluid analysis. Three dimensional roll deformation analysis has also been performed by using commercial package ANSYS. From the results, behavior of metal flow, rolling force and roll deformation have been investigated according to the process conditions of semi-solid direct rolling.

• Proceedings of the KIEE Conference
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• 2001.07d
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• pp.1929-1931
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• 2001

An adaptive fuzzy logic controller to regulate molten steel level in the strip casting process is presented, where parameters of fuzzy controllers are adapted stably by using Lyapunov-stability theory and a switching controller is used together to deal with the approximation error of fuzzy logic system. The level error is proven to converge to zero asymptotically. In the simulation, the clogging/unclogging of a stopper nozzle is considered and overcome by the proposed controller. Robustness to uncertainty is shown to be superior to conventional PI controller.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.1
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• pp.189-205
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• 1996

The twin-roll type strip continuous casting process(or direct rolling process) of steel materials is characterized by two rotating water cooled rolls receiving a steady supply of molten metal which solidifies onto the rolls. A solidification analysis of molten metal considering phase transformation and thermofluid is performed using finite diffefence method with curvilinear coordinate to reduce computing time and molten region analysis with arbitrary shape. An enthalpy-specific heat method is used to determine the temperatures inthe roll and the steel. The temperature distribution of cooling roll is calculated using two dimensional finite element method, because of complex roll shape due to cooling hole in rolls and improvemnt accuracy of calculation result. The energy equaiton of cooling roll is solved simultanuously with the conservation equaiton of molten metal in order to consider heat transfer through the cooling roll. The calculated roll temperature is compared to experimental results and the heat transfer coefficient between cooling roll surface and rolling material(steel) is also determined from comparison of measured roll temperature and calculated temperature.

• Journal of Korea Foundry Society
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• v.15 no.4
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• pp.317-330
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• 1995

• Journal of Korea Foundry Society
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• v.10 no.5
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• pp.372-381
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• 1990