Experimental Research Of The Flow Field In The Slab Mold Under The Multiple Magnetic Field Action

Studies have shown that the quality of the casting is closely related to the flow of the molten steel in the mold.With the increase of the casting speed,the nozzle outlet flow velocity and the flow rate increases,the liquid steel in the mold floes more quickly,the stability of the flow become worse,excessive large velocity causes slag entrapment free surface level fluctuation increases,the impact of the flow on the solidification shell becomes larger at the same time,the shell thickness uniformity becomes lower,vibration marks intensify,the impinge depth of the flow on the narrow face of the mold also increases,affecting the floating up of the inclusion and gas bubble deteriorate the slab internal quality consequently.The study of the mold internal flow of the liquid steel is of great importance to industrial production.Magnetic brake technology is well used in the continuous casting process since it can control effectively the impact of the nozzle outlet flow and steablize the free surface fluctuation.It work only in the cast of high casting speed.However the casting speed in china steel company is usually low.On the other hand,the surface becomes inactive in the case of excessive magnetic brake.Mold electromagnetic string technology is also widely used in the continuous casting process since it can active the meniscus flow,wash out the solidification front to reduce the entrapment of the inclusion and gas bubble.In this research we use multiple magnetic field to ensure not only the control of the nozzle outlet flow but also the activity of the meniscus.In this paper a quarter model of the real prototype of a continuous caster was set up for model experiment of continuous casting using low pnelting point allow(PbSnBi alloy)under multiple electromagnetic fields.The effects of the electromagnetic parameters of else upper and the lower magnetic field on the flow field in the mold are investigated.The velocity distribution in the mold is obtained by Ultrasonic Doppler Velocimeter(UDV)for better understanding the flow pattern in the mold under different combination of magnetic fields.This study obtained the following conclusions:1.The electromagnetic brake has a significant effect on the flow fields in the continuous casting mold,that is it can significantly restrain the fluid velocity in the mold.2.Under the magnetic brake,electromagnetic force acting on the nozzle outlet flow,the mold is not upwardly changes the outlet flow velocity and direction,make the upward flow intense changes the impinge point and the meniscus flow velocity,finally optimize the flow field in the mold.3.When the coil current intensity of the electromagnetic braking and the electromagnetic stirring change,the distribution of the magnetic field changes greatly,compared with the result with single magnetic field.4.Under the combination of the multiple magnetic field the flow field is better,the meniscus activities.