Simulation Of Transient Flow In FTSC Thin Slab Continuous Casting Mold At High Casting Speed

With the increase of the casting speed of thin slab continuous casting,the amount of steel passing through the submerged entry nozzle(SEN)increases,and the disturbance of the molten steel level is easy to cause the problem of slag entrainment in continuous casting molds.Also the uneven distribution of the liquid slag layer easly cause the crack defects in the slab by the bad lubricating effect of the mold slag.Which are directly related to the flow field in the mold.Therefore,the characteristics of the flow field and its influencing factors in the continuous casting mold under the condition of high casting speed have become urgently needed research.In this paper,a large eddy simulation(LES)coupled with the volume-of-fluid(VOF)multiphase model were presented for numerical simulation to analyze the influence of parameters such as the SEN structure,the immersion depth of SEN,casting speed,the width of mold section and the electromagnetic braking(EMBr)on the flow field and temperature field in the flexible thin slab caster(FTSC)mold.The research in this paper is divided into two main parts: First,without EMBr,the numerical simulation method validated by using actual solid shell thickness measurement and mold level fluctuation data is used to study the flow field and temperature field distribution in the FTSC mold under different casting speed,section width,nozzle depth,and nozzle structure.Second,under the condition of a new type EMBr magnetic field validated by using the actual measured values,The validated LES+VOF three-phase flow model coupled with the Fluent electromagnetic fluid dynamics model is used for the simulation analysis to study the flow field and temperature field in the FTSC mold under the same cross-section width,immersion depth,and casting speed for the two type SENs,also the distribution of liquid slag layer and the thickness of the slab shell,and the liquid steel velocity magnitude on the meniscus and the level fluctuation height of the slag-steel interface.The simulation results of the flow field and temperature field in the FTSC mold show that during high-speed FTSC thin slab continuous casting,the immersion nozzles of both SENs form a typical “two-wheel” flow field structure in the mold.In the case of the high casting speed of 5.5m/min without EMBr,the new single-export SEN has obtained an ideal flow field in the mold(the maximum velocity on meniscus is 0.27m/s,the level fluctuation is less than ±3.24mm),the temperature on meniscus is higher and more uniform.Under a new EMBr of the five pairs of coils,the flow field in the mold of both nozzles is significantly improved with the increase of the current intensity.And the single-export SEN has obtained an more ideal flow field in the mold(the maximum speed on meniscus is 0.15m/s,the maximum The level fluctuation height difference is 2.61mm)than that of the three-export SEN in the production of medium and small cross-section slabs at a high casting speed of 6.0m/min under the current intensity of 500 A.When the current reaches 900 A,the braking effect of EMBr is too strong,which causes the temperature on meniscus to decrease significantly.The LES+VOF three-phase model established in this paper can well adapt to the simulation of the flow field in the FTSC thin slab continuous casting mold.