In Effect Of Electromagnetic Swirling Flow Nozzle On Meniscus Level Fluctuations In Mold During Slab Continuous Casting Process

Electromagnetic swirling flow in nozzle is a new technology for controlling the flow field in mold,which is important for improving the speed of casting and the quality of slab.At present,most studies of electromagnetic swirling flow in nozzle focus on the flow field and temperature field in mold.However,few study pays attention to the meniscus level fluctuation in mold which induced by flow field variation during the process of electromagnetic swirling flow.The appropriate meniscus level fluctuation is important to improve the final quality of slab during continuous casting process.Therefore,it is necessary to study the meniscus level fluctuation of molten steel in mold during the process of electromagnetic swirling flow.Through setting up three-dimensional mathematical model of molten steel in mold during the process of electromagnetic swirling flow in nozzle,the study focuses on the slab casting machine in a factory to study the distribution of electromagnetic field and flow field with different electric current,magnetic flux density,and casting speed by using numerical simulation method.Furthermore,the influence of electromagnetic field and flow field are investigated.Finally,the meniscus level fluctuations are studied by the height of meniscus,velocity below the free surface and the downward velocity near the narrow face(1)By comparing the flow field of molten steel in mold during traditional continuous casting and electromagnetic continuous casting,we can find that the wave height distributions of meniscus level fluctuation are not symmetrical near narrow areas in both sides of mold while tend to be more symmetrical when current intensity is 350A and frequency is 50Hz.(2)Longitudinal downward velocity variations of molten steel flowed out from submerged nozzle with different depths under meniscus level is investigated with and without electromagnetic swirling flow in nozzle.The longitudinal downward velocity of molten steel is decreased with the dependence of distance to meniscus increased during the process of traditional continuous casting.Moreover,the impact velocity is still keep larger when 1.5 m away from the meniscus.However,the longitudinal downward velocity is decreased rapidly with the dependence of distance to meniscus increased during the process of electromagnetic swirling flow in nozzle.The longitudinal downward velocity is closed to zero when 1.5 m away from the meniscus level.(3)The influence of flow field on the meniscus level fluctuation with different current intensity and frequency is studied.When both of current intensity and frequency are low,the peak value of meniscus level is higher near narrow areas of the mold.With current intensity and frequency increasing,most heights of meniscus level are below 10 mm and the velocity of molten steel under free surface is less than 0.4m/s.(4)The influence of different casting speed on the meniscus level fluctuation is investigated.The results show that the heights of meniscus level peak value increase linearly with the increase of casting speed.(5)The heights of meniscus level peak value increase with the decrease of nozzle immersing depth.Nevertheless,overlarge immersing depth will enhance the impact velocity of molten steel near narrow areas.By discussing wave heights of meniscus level with different immersing depths,velocity of molten steel under free surface,and impact velocity of molten steel near narrow areas,we find that immersing depth being 170 mm can be a suitable value.