Numerical Study On Flow And Solidification Of Molten Steel In Mold Of Super Large Hollow Tube Blank

With the improvement of industrial production level,the pipe diameter required by transportation,machinery and construction industries is increasing.However,there is little research on the production process of extra large hollow tube blank in China,so it is necessary to study the flow field and temperature field distribution in the mold under different process parameters.In this paper,the flow field,temperature field and thermal mechanical coupling simulation of the continuous casting mold of the super large hollow tube blank with the cross-section size of ?750mm × 150 mm are carried out based on the physical experiment verification.Finally,the influence of different nozzle structure and process parameters on the molten steel flow and solidification in the mold is obtained,which provides reference for the actual production It provides a theoretical reference.Based on the study of the continuous casting process of extra large hollow tube billet,the mold parameters are determined,the three-dimensional mathematical model of molten steel flow and heat transfer in the mold is established,and the transient simulation is completed.According to the similarity criterion,the physical experiment model is built,and the flow simulation results are compared with the water simulation results to verify the rationality of the model selection.According to the principle of single variable,the effects of different nozzle structure,nozzle layout and process parameters on the flow and heat transfer of molten steel in mold were studied.The k-? turbulence model and multiphase flow field model were used in the study,considering the turbulence characteristics of liquid steel flow and mold flux layer.In the heat transfer simulation calculation,different heat flux is used on the inner and outer surface of slab.The results show that the structure and arrangement of nozzle have great influence on the distribution of flow field and temperature field in the mold.When four nozzles are symmetrically arranged and three-way nozzles with horizontal angle of 166 ° and downward angle of 5 ° are selected,the impact depth of liquid steel is small and the temperature distribution of outlet section is uniform.When the casting speed is controlled at 0.6 m/min——1.0m/min and the submerged depth of nozzle is 150 mm,the velocity and fluctuation height of liquid surface are in a reasonable range.A three-dimensional coupled model of liquid steel flow,heat transfer and solidification in the mold was established by using the reasonable process parameters in the flow field simulation results.In the simulation of solidification coupling,the solid-liquid two-phase region is regarded as porous medium,and the influence of thermal buoyancy is added.The solidification and shrinkage of slab were simulated,and the crack index of slab was calculated.The effects of different casting speed and superheat on solidification,shrinkage and cracking of slab were analyzed.It has a certain guiding significance for the actual production.