| Mold is the core part of continuous casting production,and the fluid state of molten steel inside it plays a vital role in the quality of slab.Due to the complex funnel-shaped structure of the compact strip production(CSP)continuous casting mold,the flow of molten steel is complicated.And this leads to dynamic instability and bias flow,which affects the continuous casting process operation and the quality of the slab.As a mature technology for controlling the flow of molten steel in mold,the ruler electromagnetic braking device(Ruler-EMBr)is widely used in CSP thin slab continuous casting.However,the horizontal magnetic poles are arranged below the submerged entry nozzle(SEN),which can effectively control the flow of molten steel in the lower recirculation zone.But the control effect on the upper recirculation zone and the free surface of the mold is relatively low.Based on this,a new type of vertical-combined electromagnetic braking technology(VC-EMBr)has been proposed.And the numerical simulation method is used to establish the numerical calculation model of the magnetic field and flow field coupling in the CSP crystallizer.The main researches are as follows:(1)The Ruler-EMBr can effectively control the downward flow of molten steel in the mold and weaken the impact of the downward stream on the inside of the casting slab.It also stabilizes the flow of molten steel in the lower recirculation zone.However,because of the position of its horizontal magnetic poles,Ruler-EMBr can only change the flux of the upwardly flowing molten steel,but cannot effectively control the reflux area and the free surface on the mold.The new VC-EMBr sets up two pairs of vertical magnetic poles connected to the horizontal magnetic poles of the Ruler-EMBr in narrow surface area of CSP mold.A steady-state magnetic field with an overall U-shape distribution is formed on the wide surface of the CSP crystallizer.The magnetic induction intensity of the vertical steady-state magnetic field reaches 0.25 T,which meets the basic requirements of electromagnetic braking.(2)When the magnetic induction intensity is increased from 0.25 T to 0.5 T,the Ruler-EMBr and the VC-EMBr have a certain increase in the control of the molten steel flow in CSP mold.Compared with the Ruler-EMBr condition,the VC-EMBr has more significant control effect on the free surface flow rate of molten steel in the mold,which reduces the maximum flowrate of the free surface of molten steel by 53.5%.(3)When the upper part of the unilateral nozzle is clogging,the angle of the molten steel flowing out of the clogging side of nozzle is deflected down.The flow velocity decreases and the flow velocity distribution in lower return zone is asymmetrical.The velocity distribution of the free surface has obvious difference,forming a bias flow phenomenon.Using Ruler-EMBr can effectively control the flow of molten steel in lower return zone of the CSP mold.Using a VC-EMBr can effectively control the flow of molten steel in the lower return zone in the CSP mold and adjust the unbalanced flow on both sides of the nozzle at the same time.VC-EMBr can further effectively control the flow of molten steel in the reflux zone on the mold,so that the flow rate of the entire free surface of the mold is reduced and the distribution is more uniform.(4)When the lower part of unilateral nozzle is 30%clogging,the angle of the molten steel flowing out of the clogging nozzle is deflected upwards.The impact area on the side wall of the mold moves upward,the flow rate of molten steel in the upper recirculation zone on the left side increases.The impact depth of the molten steel in the lower recirculation zone decreases.The flow velocity of the free surface on the clogging side increases,and there is a serious bias flow in the mold.After the Ruler-EMBr is applied,the flow rate of the molten steel in the upper left recirculation zone is reduced,and the bias flow phenomenon is controlled.The VC-EMBr is applied to further effectively control the flow of molten steel in the reflux zone on the mold,so that the flow rate of the entire free surface of the mold is reduced,and the distribution is more uniform. |
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