| How to get high clean steel has always been the topic and goal of metallurgical workers,In recent years,in order to meet the needs of the market,new technologies are constantly being used in the steelmaking process.Tundish,as the last process before continuous casting,occupies a very important position in steelmaking process.The flow pattern of tundish not only affects the homogeneity of composition and temperature of molten steel,but also directly affects whether inclusions can float to remove slag layer.In this paper,the flow pattern and mixing characteristics of prototype tundish under external static magnetic field are studied by numerical simulation.At the same time,the flow field structure in tundish with different nozzles and bottom blowing was studied by using water physical model experiment in the ratio of 1:4 between the model and the prototype.Then,the flow field in the bottom blowing tundish under the applied static magnetic field was studied by numerical simulation under the verification of the hydrophysical model experiment.The main contents of the thesis are summarized as follows:1.The flow field in prototype tundish under external static magnetic field is studied by numerical simulation.The numerical results obtained from k-? ?k-? ?RNG?SST turbulence models are compared with those of the large eddy simulation.It is found that the velocity curve of RNG turbulence model is closer to the averaged large eddy simulation,and it is more suitable for the numerical calculation of tundish turbulence than the other three turbulence models.Under certain magnetic induction intensity,the molten steel after overturning the dam will mainly form two streams,one will flow along the free surface,the other will flow along the bottom of the tundish,and there will be a large area of slow flow between the two streams.Compared with no external static magnetic field,the piston area volume increased by 10.6% and the dead zone volume decreased by 9.3%.2.The flow pattern and mixing characteristics in tundish with different 1:4 ratios of nozzle and bottom blowing were comprehensively studied by means of water physical model experiment.The results show that the RNG turbulence model is reliable for the numerical simulation of the flow field in tundish.Horizontal circulation generated by 90 degree bend nozzle disturbs the surrounding liquid fairly uniformly,while the flow of 45 degree bend nozzle leans to one side,forming a horizontal circulation with a certain inclination.At the same time,the 45 degree bend nozzle increases the contact chance between the new molten steel inclusions and the mould flux,and prolongs the time of inclusion floating and promotes the removal of inclusions.By analyzing the flow mixing characteristics in tundish with or without blowing,it is found that the average residence time in tundish can be prolonged by 10 s,the dead zone volume can be reduced by 3.5%,and the piston zone volume can be increased by 2.8%.3.The numerical simulation method was used to study the flow field structure in the bottom blowing tundish under the applied static magnetic field.The results show that SST turbulence model is better than RNG turbulence model in predicting tundish flow field.The k-? turbulence model in the first half(distance direction 0.02-0.08 m)is closer to the measured value,and the SST turbulence model in the second half(distance direction 0.08-0.19 m)is closer to the measured value.The application of static magnetic field in the bottom blowing zone of tundish can effectively control the size of slag hole in tundish.In a sense,it is possible to further improve the quality of molten steel by choosing the best bottom blowing mode and applying static magnetic field in the bottom blowing zone to control the slag hole in tundish. |
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