Optimization Of Seven-strand Continuous Casting Tundish Configuration Based On Gas Bubbling Curtain

The fluid flow in a seven-strand billet tundish in continuous casting was studied and optimized with physical and numerical simulations, and the optimum tundish configuration was obtained. A seven-strand continuous casting tundish model was set up in laboratory with1:3scale. Modeling experiments were carried out under the condition that Froude number was kept to be equal. The mathematical model describing the flow phenomena and heat transfer in the tundish was established from the continuity, momentum and energy equation. The ANSYS commercial software was used to numerically calculate the flow and temperature fields and RTD curves in the original and optimal cases.It was found that the former tundish configuration had small minimum residence and peak concentration times, small plug flow volume and big dead zone. The flow characteristics among the4strands were different. Compared with the former case, the minimum residence time from strand1to4was extended to41.5s,42.5s,39.0s,39.0s, maxiumum difference being only3.5s, the peak time was increased by272.7%,497.5%,993.2%and677.1%, average residence time was increased by32.2%,58.5%,109.5.5%and72.5%, the plug flow proportion was increased by132.4%,278%,626%and232.3%, and the dead volume proportion was decreased by53.4%,63.6%,69.7%and60.8%. Flow characteristics of fluid in the tundish among the4strands were almost the same with the flow control devices such as baffle and gas bubbling curtain which had been optimized.In the numerical simulation, by means of analyzing the flow and temperature fields of symmetry plain, free plain, bottom plain and longitudinal section throng nozzle. It is found that the flow and temperature gradient in the original case was very big, the flow characteristics among the4strands is obviously different, and the temperature difference between entrance and exit was up to17℃, The maximum and minimum temperature difference among the exits of the4strands was up to4℃, The simulation results indicated that the fluid flowing in the optimal case has been enhanced obviously. Streamline of molten steel is longer than the former case. The speed of liquid steel was more even. The temperature difference between the entrance and the exit was only up to11℃. The temperature of the outlet was almost the same. The temperature distribution in the optimal tundish is more reasonable.Results of the research showed that using the technology of gas bubbling curtain can be beneficial to improving the flow characteristics. There are two large circulation flows at both sides of the gas bubbling contain, which increases the flow route of liquid steel and sesidence time. The inclusions in liquid steel have enough time to float up. Gas bubbling curtain can be used to replace the dams and it can eliminate the short circuit flow in tundish, so that the fluid in the tundish can flow to the liquid surface. The two circulation flows at both sides of gas bubbling curtains can make the fluid at the two end walls more active, which can lead the dead volume decrease.