| The current Electromagnetic Brake(EMBr)technology is a kind of the flow control technology of molten steel,which was developed overseas in 1980s.EMBr can achieve to reduce slag,stabilize liquid surface fluctuations,promote nonmetallic inclusions floating and separating and prevent leakage of steel.However,the magnetic poles of the current EMBr are fixed in the horizontal direction of mold width face,when the submerged depth or outlet angle of Submerged Entry Nozzle(SEN)have some changes,the relative position of the main molten steel jet and the magnetic pole position will have changes.So that it is difficult to obtain the best matching effect,which affects the control effect of EMBr on the molten steel flow in the mold.Based on the matching problem and structural issue between the current horizontal EMBr technology and conditions of continuous casting process,two new patterns of EMBr technology are proposed for slab continuous casting process in this paper,they are called Vertical Electromagnetic Brake(V-EMBr)and Vertical Combination Electromagnetic Brake(VC-EMBr).By setting the vertical magnetic poles near the mold narrow face and along the height direction of mold,the impact strength of molten steel jet on the narrow face of the mold,flow velocity of molten steel on the free surface and impinging depth of lower recirculation are all suppressed to effectively controll the molten steel flow in mold,and the slab quality is improved.In this paper,the three-dimensional electromagnetic field model in slab continuous casting mold is firstly established by ANSYS softwave,the distribution of three-dimensional magnetic field in mold with EMBr is simulated.Then,the three-dimensional mathematical model of molten steel flow in slab continuous casting mold is established by FLUENT softwave.By means of calling MHD(Magnetohydrodynamics)module and User-Defined Function(UDF),and loading the magnetic flux density solved by ANSYS for coupling the calculation of magnetic field and fluid field,the behavior of molten steel flow in mold with EMBr is simulated.By means of calling Discrete Phase Model(DPM),the trajectories of nonmetallic inclusion particles in slab continuous casting mold are simulated.The numerical simulation of magnetic field and fluid flow field in two new EMBr continuous casting mold is carried out in this paper,the control effects of the electromagnetic parameters and process parameters(casting speed,submerged depth of SEN and outlet angle of SEN)on the molten steel flow are analyzed and compared with the current horizontal EMBr technology,which provide the theoretical basis for establishing and optimizing the process system of the new EMBr technology.The main conclusions of the numerical simulation of three-dimensional magnetic field of the two new EMBr technologies are as follows.(1)The magnetic field of V-EMBr is mainly concentrated in the coverage area of vertical magnetic poles from free surface of the mold to the impingement point of the main molten steel jet,and it gradually decays outside the coverage area of magnetic poles.With the electric current increasing,the magnetic flux density is gradually increased,which can meet the requirement of EMBr in continuous casting.(2)The magnetic field generated by the horizontal magnetic poles of the VC-EMBr cover the entire width of the mold,and the magnetic field generated by the vertical magnetic poles can cover the height range from free surface of the mold to the upper end of the main magnetic poles.With the electric current increasing,the magnetic flux density is gradually increased,which can meet the requirement of EMBr in continuous casting.The main conclusions of the numerical simulation of three-dimensional flow field and the movement of inclusion particles in slab continuous casting under the two new EMBr technologies are as follows.(1)When the casting speed,submerged depth and outlet angle of SEN have some changes,the V-EMBr is still able to produce a stable and effective braking effect,the maximum flow velocity of molten steel on the free surface is reduced by about 0.16m/s.With the increase of magnetic flux density,the impact strength of main molten steel jet and the divergent flow on the narrow face of the mold are restrained significantly.The flow velocity and turbulent kinetic energy near the narrow face of the mold are all decreased,the distance from vortex center of lower recirculation zone to the free surface of the mold is reduced.The impact depth of the lower recirculation zone becomes shallower,and the removal efficiency of inclusion particles is gradually increased.These indicate that V-EMBr can effectively control the flow of upper recirculation zone and the impact area of main molten steel jet,which can help to stablilize liquid surface fluctuations of mold,reduce slag and promote the floating and separating of nonmetallic inclusions.(2)Compared with EMBr-Ruler,the V-EMBr can produce more stable and effective control to the upper recirculation zone,the free surface and the the impingement area of the main molten steel jet in the mold.(3)VC-EMBr integrates the characteristics of V-EMBr and EMBr-Ruler,it can not only control the impact of the main molten steel jet on the whole narrow area of the mold,but also strengthen the control of impinging depth in lower recirculation zone,thus realizing the comprehensive and effective control of the molten steel flow in mold.When the casting speed,submerged depth and outlet angle of SEN have some changes,VC-EMBr can still produce a stable and effective braking effect,the maximum molten steel flow velocity on the free surface is reduced by about 0.12m/s.With the increase of magnetic flux density,the circulation strength and impact depth of lower recirculation zone are obviously weakened.The impact strength of main molten steel jet and the divergent flow on the narrow face of the mold are obviously reduced,and the flow velocity and turbulent kinetic energy near the narrow face of the mold are also decreased.The removal efficiency of inclusion particles is gradually increased.These indicate that VC-EMBr can fully stabilize the flow of molten steel in the mold,reduce liquid surface fluctuations,decrease slag and promote the floating and separating of nonmetallic inclusions,and bring more significant metallurgical effect to control the molten steel flow.(4)Compared with FC-Mold,VC-EMBr can also effectively control the impact of main molten steel jet on the mold narrow face while stability controlling the molten steel flow of upper and lower recirculation zone in mold,and its control effect is smaller affected by the change of submerged depth and outlet angle of SEN,VC-EMBr has the better,comprehensive and stable metallurgical effect to control the molten steel flow in mold.(5)The metallurgical effect of V-EMBr and VC-EMBr is less affected by the change of the submerged depth and outlet angle of SEN.They can overcome the drawback of the horizontal EMBr-Ruler and FC-Mold to the instability control of molten steel flow owing to the mismatch of the magnetic pole position and the continuous casting process parameters. |
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