Numerical Study Of Droplet Dropping Characteristics In Electroslag Remelting Process With Rotating Electrode

Electroslag remelting is an advanced ingot production technology,its products can be used in aviation,military,nuclear power,medical equipment,special mold,and other fields.With the vigorous development of nuclear power,the market demand for large castings and forgings is increasing,and the quality requirements are also higher and higher.A series of complex physical and chemical changes,such as electromagnetic,heat and mass transfer,flow and solidification,will occur in the electroslag remelting system.The ingot refined by electroslag remelting technology has the advantages of uniform structure,compact structure,good mechanical properties,and long service life.However,factors such as high energy consumption and low production efficiency hinder the wider use of ESR(Electroslag Remelting)technology.In recent years,the theory that rotating the electrode of electroslag remelting system can further enhance the chemical refining effect of electroslag remelting process,reduce the energy consumption and improve the solidification quality of metal ingots has been recognized.In the process of electroslag remelting,electromagnetic field,flow field,temperature field,and solidification process play a decisive role in process operation and ingot quality.In this paper,the rotating electrode electroslag remelting system is studied by numerical calculation method for the physical quantities such as electromagnetic field,flow field,temperature field,and molten pool shape,which are difficult to measure in electroslag remelting production.The significance of rotating electrode electroslag remelting process is to enhance the heat transfer capacity between consumable electrode and molten slag by realizing the relative movement between them.The centrifugal force brought by electrode rotation changes the movement mode of metal droplet,thus changing the flow situation in slag pool,which is beneficial to reduce energy consumption and improve the solidification quality of ingot.In this paper,the effect of electrode rotation on electroslag remelting process is studied,and the influence of some important process parameters on the electroslag remelting system with rotating electrode is analyzed.The main research contents of this project are as follows:a three-dimensional unsteady mathematical model of electroslag remelting system with rotating electrode is established.Based on Maxwell equations,the Joule heat and Lorentz force in the system are solved by introducing magnetic potential vector,which are coupled into the energy and dynamic equations through user-defined functions.The solidification and growth process of ingot is realized by moving grid technology,and the slag/metal is tracked by VOF model.The anisotropic porous media model is used to simulate the momentum attenuation in the mushy region.The distribution of temperature field,electromagnetic field and flow field in ESR system with electrode rotation speed of 0 rpm,20 rpm,and 50 rpm,and the shape of molten pool were predicted by using the mathematical model.The effects of electrode filling ratio,current and slag viscosity on the electroslag remelting system with rotating electrode were studied by using the mathematical model.The simulation results show that the maximum Joule heat and current density increase with the increase of electrode rotation speed.When the electrode speed is 20 rpm,the temperature distribution changes periodically with the droplet dropping,but it is similar to the traditional electrode.When the rotating speed of the electrode reaches 50 rpm,the metal droplets are separated by centrifugal force at the edge of the electrode in more and smaller forms.The spiral dropping mode of the droplets makes the heat transfer between the metal droplets and the slag pool more complex,and the flow in the slag pool intensifies,which produces a similar stirring effect.The average temperature gradient in the slag pool decreases and the temperature distribution becomes more uniform.In the case of rotating electrode,the average diameter of metal droplet is smaller and the number is more,which is equivalent to increasing the reaction area between metal droplet and slag,which is conducive to improve the refining efficiency.Due to the influence of electrode rotation,the metal droplet has an additional horizontal velocity.In the process of passing through the slag layer,the metal droplet moves in a spiral path,which makes the flow in the slag pool more intense.However,due to the decrease of the droplet size,when it reaches the slag metal interface,its speed has been reduced to a very small level,and the fluctuation degree of the slag metal interface is also reduced.When the electrode speed is 20 rpm,the bath depth decreases from 48 mm to 43 mm compared with the static electrode condition,and it decreases to 27 mm when the electrode speed is 50 rpm.When the rotating speed increases from 0 rpm to 50 rpm,the length of the flat area at the bottom of the bath increases from 92 mm to 114 mm.With the increase of electrode speed,the molten pool tends to be shallow and flat.On the premise of the same electrode rotation speed,the greater the electrode filling ratio,the greater the maximum linear velocity of metal droplet,the better the stirring effect in slag pool;the greater the current value,the greater the electrode melting speed,the larger the diameter and quantity of metal droplets,the worse the stirring effect inside the slag pool and the deeper the metal molten pool;the larger the viscosity of slag system used,the smaller the size of metal droplet.Therefore,in the use of rotating electrode technology,the selection of appropriate process parameters is very important,which will directly affect the efficiency of the process.