• Journal of Mechanical Science and Technology
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• v.17 no.12
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• pp.2010-2018
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• 2003

Although continuous casting process has highly developed, there still remain many problems to be considered. Specifically, two vortex flows resulting from impingement against narrow walls make a flow field unstable in a mold, and it is directly related to internal and external defects of steel products. To cope with this instability, EMBR (Electromagnetic Brake Ruler) technique has been lately studied for the stability of molten steel flow, and it is revealed that molten steel flow in a mold can be controlled with applied magnetic field. However, it is still difficult to clarify flow pattern in an EMBR caster due to complex correlations among variables such as geometric factors, casting conditions, and the place and the intensity of charged magnetic field. In the present study, flow field in a mold is focused with different conditions of electromagnetic effect. To accurately analyze the case, three dimensional low Reynolds turbulent model and appropriate boundary conditions are chosen. To evaluate the electromagnetic effect in molten steel flow, dimensionless numbers are employed. The results show that the location and the intensity of the applied magnetic field significantly influence the flow pattern. Both impingement and internal flow pattern are changed remarkably with the change of the location of applied magnetic field. It turns out that an insufficient magnetic force yields adverse effect like channeling, and rather lowers the quality of steel product.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.1
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• pp.12-24
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• 1999

A computer program has been developed for analyzing the two-dimensional, unsteady conservation equations for transport phenomena in the molten region of twin-roll continuous casting in order to predict the turbulent velocity, temperature fields, and solidification process of the molten steel. The energy equation of the cooling roll is solved simultaneously with the conservation equations of molten steel in order to consider heat transfer through the cooling roll. The results show the velocity, temperature and solidification pattern in the molten region with roll temperature as a function of time. The results for velocity and temperature fields with solidification are compared with those without solidification, giving different thermofluid characteristics in the molten region. We also investigated the effects of revolutional speed of roll, superheat and nozzle geometry on the turbulent flow, temperature and solidification in the molten steel and temperature fields in the cooling roll.

• Journal of the Korean Institute of Intelligent Systems
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• v.18 no.4
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• pp.488-493
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• 2008

A mathematical model of molten steel level for continuous casting process is presented, where the molten steel level, input and output flow in the mold, the relation between stopper position and input flow etc. are considered. The mathematical model is implemented and simulated by using MATLAB. Comparing the result of molten steel level from the simulator with that of real plant, the performance of the model is shown to be reasonable. By using this simulator, it is shown that PI controller with variable P gain, adjusted by fuzzy logic system, has better control result than conventional PI controller.

• Journal of the Korean Ceramic Society
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• v.35 no.1
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• pp.33-40
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• 1998

A MgO-CaO-based coating material for ferrous melt refining is applied to the tundish operation for mol-ten steel having low carbon. The changes in the total oxygen content insoluble aluminum content and the content of inclusions in molten steel during tundish operation were measured at the pouring part strand of tundish and mold. On the basis of the experimental results the interfacial reaction occurring between the coating materials and the molten steel in tundish was discussed and compared with the theoretical con-sideration. It is concluded that interfacial reaction is not active at the strand part of tundish but is active at the pouring part because of the turbulent flow in the molten steel.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.2139-2144
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• 2003

In steel-making processes of iron and steel industry, the purity and quality of steel can be dependent on the amount of CO contained in the molten metal. Recently, the supersonic oxygen jet is being applied to the molten metal in the electric furnace and thus reduces the CO amount through the chemical reactions between the oxygen jet and molten metal, leading to a better quality of steel. In this application, the supersonic oxygen jet is limited in the distance over which the supersonic velocity is maintained. In order to get longer supersonic jet propagation into the molten metal, a supersonic coherent jet is suggested as one of the alternatives which are applicable to the electric furnace system. It has a flame around the conventional supersonic jet and thus the entrainment effect of the surrounding gas into the supersonic jet is reduced, leading to a longer propagation of the supersonic jet. The objective of the present study is to investigate the supersonic coherent jet flow. A computational study is carried out to solve the compressible, axisymmetric Navier-Stokes equations. The computational results of the supersonic coherent jet are compared with the conventional supersonic jet.

• 한국전산유체공학회:학술대회논문집
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• 2003.10a
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• pp.12-12
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• 2003

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.490-495
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• 2003

In steel-making process of iron and steel industry, the purity and quality of steel can be dependent on the amount of CO contained in the molten metal. Recently, the supersonic oxygen jet is being applied to the molten metal in the electric furnace and thus reduces the CO amount through the chemical reactions between the oxygen jet and molten metal, leading to a better quality of steel. In this application, the supersonic oxygen jet is limited in the distance over which the supersonic velocity is maintained. In order to get longer supersonic jet propagation into the molten metal, a supersonic coherent jet is suggested as one of the alternatives which are applicable to the electric furnace system. It has a flame around the conventional supersonic jet and thus the entrainment effect of the surrounding gas into the supersonic jet is reduced, leading to a longer propagation of the supersonic jet. In this regard, gasdynamics mechanism about why the combustion phenomenon surrounding the supersonic jet causes the jet core length to be longer is not yet clarified. The present study investigates the major characteristics of the supersonic coherent jet, compared with the conventional supersonic jet. A computational study is carried out to solve the compressible, axisymmetric Navier-Stokes equations. The computational results of the supersonic coherent jet are compared with the conventional supersonic jets.

• Journal of the Korean Society of Combustion
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• v.13 no.2
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• pp.33-41
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• 2008

The high permeability of the gas in the molten iron of the dripping zone of the blast furnace is a major factor in achieving the stable operation of a furnace with high productivity. Basic studies of the liquid flow behavior in a packed bed are necessary to grasp the effect of various operational changes on conditions in the dropping zone. Molten iron and slag together playa critical role in the lower zone, transporting mass and energy, while impairing and redistributing the gas flow. In turn, molten iron and slag undergo physical and chemical changes, and are redistributed radially as they descend to the hearth. In this research, mathematical formulations are derived for the gas and the liquid. The solid phase is fixed with constant porosity. The information for the molten iron and slag includes the hold-up, velocity, pressure, and information related to the areas of interaction between the gas and the liquid, and the solid and the liquid. Predictable results include the velocity, pressure and temperature distribution. Additional parameters include the packed particle size and the air blast rate.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.612-615
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• 1996

In the continuous casting process, molten metal contacts the mold wall and the molten metal surface is subject to the mold oscillation. The mold oscillation results in the oscillation marks on the surface of solidified steel, which has undesirable effects on the quality of slabs. In order to reduce the oscillation marks by achieving soft contact of molten metal with the mold surface, alternating magnetic field is applied to the surface of molten metal. However, if the magnetic field strength becomes too strong, the melt flow induced by the magnetic field. causes the instability of the molten metal surface, which has also the bad influence on the slab quality. Therefore, it is very important to choose the optimal position of the inductor coil and the optimal level of electric power to minimize the surface defects. In the present work, as a first step toward the optimization problem of the process, numerical studies are performed to investigate the effects of coil position and the electric power level on the meniscus shape and the flow field. As numerical tools, the boundary integral equation method(BIEM) is used for the magnetic field analysis and the finite difference method (FDM) with orthogonal grid generation is used for the flow analysis.

• Korean Journal of Metals and Materials
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• v.50 no.2
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• pp.122-128
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• 2012

Water model experiments were carried out to understand the mixing behavior of reducing agents in molten slag through vortex stirrer, which makes use of a gravitational energy to mix reducing agent in the molten slag without imparting artificial energy. At a water flow rate of 6 L/min vortex was not generated, and a stable vortex was formed when the water flow rate was 7 L/min or higher with the present experimental apparatus. Water level increased linearly with increasing the water flow rate. In the upper vortex region, the vertical and horizontal velocities slightly decreased with increasing the water flow rate, whereas those in the lower vortex region increased remarkably. Accordingly, strong mixing behavior was obtained in the lower vortex region. Owing to the strong centrifugal force, particles move downwards with approaching the funnel wall. When 40 grams of polypropylene particles added to the lower vortex, they were instantaneously mixed well.