Simulation of fluid flow inside a continuous slab-casting machine
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INTRODUCTION
THE velocity distribution of molten steel contained within the solidifying shell of a continuous casting machine is very influential on the distribution of inclusion particles, which is important to the internal cleanliness and quality of the steel. In addition, the flow pattern has a great influence on heat transfer to the shell during the critical initial stages of solidification. To further understand this behavior, a 2-D finite element model has been developed to calculate the flow of molten steel within the liquid pool inside the shell in the mold region of a continuous slab-casting machine, fed by a bifurcated, submerged entry nozzle. The first objective of this project was to develop a mathematical model of the flow pattern in the liquid pool which determines how both molten steel and inclusion particles carried in by the nozzle are distributed. To verify acceptable accuracy of the model, its predictions were compared with experiments conducted using a transparent plastic water model of the system. The second objective was to investigate the effects of important casting operation and design variables on the fluid flow pattern. Of particular interest was the angle of the jet streaming in from the submerged nozzle, its approximate impingement point on the solidifying shell along the narrow face wall, and velocities down the wall. These parameters are important because of their influence on heat transfer and the growth of the solidifying shell. This work represents the first step in the development of a comprehensive system of mathematical models of fluid flow, heat transfer, shrinkage, and stress generation within the continuous slab-casting mold, which will ultimately be applied to predict and understand the effects of such diverse variables as nozzle design and mold
B.G. THOMAS, Assistant Professor, and F.M. NAJJAR, Graduate Student, are with the Department of Mechanical and Industrial Engineering, University of Illinois, Urbana, IL 61801. L.J. MIKA, formerly Graduate Student, Department of Mechanical and Industrial Engineering, University of Illinois-Urbana, is Research Engineer with Amoco Technology Company, Naperville, IL 60566. Manuscript submitted November 3, 1988. METALLURGICAL TRANSACTIONS B
taper on defect generation in the solidifying shell. The results of the flow calculations described here are input to a separate heat flow model to calculate the temperature field within the molten steel and the resulting heat flux to the solidifying shell on the narrow face mold wall. The superheat in the fluid steel can be convected to the shell and conducted through the shell to the copper mold walls, or it can be swept out of the mold region to be dissipated much lower in the caster. In addition, uneven dissipation of superheat to the shell will produce a maximum heat input near the point of jet impingement. This can produce local "hot spot(s)" on the shell, where growth is slow, and may cause shell thinning, erosion, and even lead to breakouts, particularly at higher casting speeds.t1] Equ
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