| Electromagnetic brake(EMBr)and electromagnetic stirring(EMS),as the main control technology of molten steel flow in the mold,are of great significance for the continuous caster to improve slab quality and productivity.Therefore,it is of great significance to study the flow behavior of molten steel in th e mold under EMBr and EMS.However,there are few reports about the combination of EMBr and EMS.In this paper,the slab caster is taken as the research object,and the magnetic field model of EMBr and EMS is established,which is coupled with the flow field.Numerical simulation method is used to study the flow behavior of molten steel under the composite magnetic field of continuous casting mold.The main research contents and results are as follows:(1)The three-dimensional electromagnetic field mathematical model of EMS in slab continuous casting mold was established.The simulation results showed that the magnetic field produced by EMS is a linear moving magnetic field,and the magnetic induction intensity increases linearly with the increase of current intensity,but decreases with the increase of current frequency.The component of magnetic induction intensity in the corresponding area of EMBr is very small,which can be ignored.The Lorentz force is distributed clockwise around the meniscus,and its size increases with the increase of current intensity and stirring frequency When the frequency is between 1-8hz,the maximum Lorentz force increases about 500N/m3 for every 1Hz of frequency increase.When the current is between 100-200A,the maximum Lorentz force increases 1200N/m3 for every 50A of current increase.(2)The mathematical model of three-dimensional electromagnetic field for EMBr of slab continuous casting mold was established.The simulation results showed that the magnetic field produced by EMBr is static magnetic field,the magnetic induction intensity near the magnetic pole is the largest,and the magnetic induction intensity increases linearly with the increase of current intensity.The magnitude of the component of the magnetic induction intensity in the corresponding area of EMS is 10-2T,which can not be ignored;when the EMBr is between 240-400A,the magnetic induction intensity increases 0.05T for every 80A.(3)The mathematical model of three-dimensional electromagnetic field of slab continuous casting mold was established.The simulation results showed that the magnetic induction intensity in the EMBr area under the composite magnetic field will shift partially compared with that of the EMS area alone,and the shift will come from the magnetic field of EMBr.(4)Based on the results of electromagnetic field calculation of slab mold composite magnetic field,a three-dimensional mathematical model of molten steel flow behavior under the action of the magnetic field is established.The simulation calculation is carried out under the parameters of EMS current 100-200A,frequency 1-8Hz,EMBr current 240-400a,casting speed 1.0-1.6m/min,etc.The results show that:①Only the EMBr current is changed,the larger the current is,the more obvious the main stream rises,the lower backward flow is weakened,and the upper backward flow is enhanced;and with the increase of the EMBr current,the EMS effect at the meniscus will be restrained,so the turbulent kinetic energy intensity at the meniscus will also be weakened;with the increase of the EMBr current,the turbulent kinetic energy intensity at the narrow surface will first weaken and then increase.②Only change the EMS current or frequency,the greater the current or frequency is,the weaker the upper backward flow on the molten steel is,the more obvious the stirring effect is at the meniscus,which makes the turbulent kinetic energy at the meniscus larger,and the increase of the stirring current will also make the impact of the mainstream stock on the narrow surface weaker,but will make the invasion depth of the mainstream stock deeper.③ Changing the casting speed,the greater the casting speed is,the greater the overall velocity distribution in the mold is,and at the same time,it will weaken the EMS effect at the meniscus.However,due to the obvious increase of casting speed,the turbulent kinetic energy at the meniscus is increasing,and the impact strength of the mainstream stock on the narrow surface is also increasing,but the penetration depth of the mainstream stock is slightly weakened.④ Compared with the calculation results of pure flow field,it is found that the upper backward flow in pure flow field is obvious,but the upper backward flow in composite magnetic field is restrained by EMS;EMS makes the horizontal rotation flow between the whole meniscus and the section 100mm below it more active;on the narrow surface,the composite magnetic field can reduce the strength of the main stream impinging on the narrow surface,but because of the influence of EMS,the EMBr weakens the lifting effect of the main stream,which is almost the same as the invasion depth under the pure flow field. |
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