Optimization Of The Flow Field Of Molten Steel In The Tundish Built-in Filter

With the development of industry,the demand of the quality of steel product is higher,so that the request of purity of molten steel is getting higher and higher.Tundish is the most important device to remove inclusions in continuous casting process.In order to improve slab quality,a series of studies have been carried out to make the tundish metallurgy functioning better.The main measure is to set suitable flow control devices in tundish to extend the mean residence time,reduce dead volume,and promote inclusion removing,as a result to improve steel quality.In order to study the effect of channel on flow field in tundish,a research on fluid flow and heat transport in a two-strand slab continuous casting tundish with different structure was carried out by using a water model and math model,and an optimum tundish configuration was obtained.At last,the optimum tundish was applied to the scene to analyze the effect of application..A water model with the ratio of model: prototype=0.29:1 was established in laboratory after considering the size of tundish and the water conditions of laboratory,and then slag entrapment was carried out on condition that the modified Froude number was equal.The results of physical simulation experiment showed that the average residence time of original tundish was short only with turbulence inhibitor、wall and dam,and the dead area was really large,so the effective volume was greatly decreased.The kind of flow field was not good for floatation of the inclusion.When the pulling rate was 0.8m/min,the dead area was up to 29.53%.The effect of optimization of scheme 2、3、4 was obvious after using the weir and channel filter,the fluid field in the impact zone was good for inclusions’ collision and floatation,and the streamline of molten steel in casting area was much longer,and the residence time was long enough,it was more beneficial to the floatation and removal of the inclusions.The results showed that both the distance between long nozzle and the weir and the insertion depth of long nozzle had great influence on the flow field of the tundish,and scheme 2(the distance between long nozzle and the weir was 1100)with 200 mm insertion depth of long nozzle was the best one.When the pulling rate were 0.8m/min、1.0m/min and 1.2m/min,the dead area was decreased to 13.52%、11.69% and 7.37%.Then the mathematical model describing the flow phenomena in the tundish was established,and the CFD software FLUENT was used to numerically calculate the flow and temperature fields in different tundish with different pulling rate and insertion depth of long nozzle.By means ofanalyzing the flow field and temperature field of symmetry plain、section of filter channel and the whole tundish,the results of numerical simulation and physical simulation results were in good agreement.The velocity distribution of molten steel in the original tundish was nonuniform,dead zone was formed behind the weir and the dam,and the top of the tundish,the temperature gradient was large.Both the flow field and temperature field of the were obviously improved,the velocity distribution of molten steel in the tundish was nuniform,low temperature zone was reduced,and the temperature distribution was more reasonable.The industrial experiments showed that the inclusion size of the casting area in the tundish is significantly smaller than that of the impact zone in the optimized tundish,and tundish metallurgical results meet the requirements.