| Tundish is not only the buffer vessel for keeping stable pressure, distributing liquid steel, and ensuring the steel continuous casting but also is key equipment for preventing steel slag into mould, removing non-metallic inclusion of liquid steel and making the temperature of liquid steel uniform. Reasonable state molten steel flow in tundish can promote quality of casting improved. In recent years, metallurgists took a series of measures to strengthen and expand the tundish metallurgy function.And one of the important measures is to install the appropriate flow control devices to obtain reasonable flow pattern.In present work, according to the2-strand bloom casting tundish at a certain steelmaking plant, the mathematical and physical simulation methods were used to obtain the optimum flow control device. The mathematical model Applies simulation software simulating tundish flow field and temperature field under different scheme of flow control devices to choose the better solution. The physical model builds the experiment model as similarity principle in the condition of1/4of the prototype and made of Plexiglas and Froude similarity. Ultimately determines the optimal flow control scheme.The experimental results show that:(1) Prototype tundish structure is unreasonable. Fluid in the prototype tundish has very large dead volumes as well as obvious short circuit flow, actual average stay time of the molten steel is relatively short, and the flow field and temperature field distribution is uneven. These factors will lead to inclusion floatation remove difficulties, finally affect cleanliness of slab.(2) The setting of the dam block can make the bottom flow direction change, block the decline of the flow shares trend, and eliminate the short circuit flow. The rationale setting of the diversion wall can form the flow shares flowing to liquid surface and the dam cycle flow in the wall. This flow control means have many advantages. Firstly, it can extend the stay time of liquid steel in the tundish, promote the exchange energy of the liquid steel, avoid the stagnation of the end molten steel, thus reduce dead zone. Secondly, it can in favor of big pack note flow area resisting slag, ingredients and temperature of steel liquid in tundish uniformity and collision polymerization of inclusions in the liquid steel growing up and floating upward.(3) Apply the optimization of flow control devices which is controller+guide wall+dam could improve the flow of molten steel state in tundish, prolong efficiently the actual average of molten steel stay time, increase the volume rate of the piston flow, reduce the volume rate of the dead volumes, uniform temperature and composition of the molten steel.(4) Increase tundish capacity can further extend stay time of the molten steel. But if the reasonable flow control device set, even if not Increase tundish capacity can ensure the molten steel have enough stay time. In the end of casting, the vortex is easy to produce in tundish. So when the steel liquid surface arrives at the critical height, need to lower the drawing speed, pour off nozzle in advance and stop casting.(5) Slab quality improvement after optimizing. Inclusion particle samples which are less than5μm about90%, more than50μm are almost completely disappeared. So the defects of the rolling billet obviously reduced after optimizing.In this study, mathematical simulation and physical simulation has good consistency. In the future, if study the flow and heat transfer can apply the method which combining the physical simulation and mathematical simulation. |
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