Simulation Study Of Electrochemical Transport In Electroslag Remelting Process Under A DC Voltage

In recent years,with the development of science and technology,all walks of life have higher and higher requirements for energy efficiency and environmental protection.In order to comply with this trend,electroslag remelting has been widely used as a secondary remelting and refining technology to produce large quality ingots.Electroslag remelting process is accompanied by complex physical and chemical reactions,involving electrode melting,deoxidization and desulfurization,heat and mass transfer,solidification of molten steel,etc.Among them,the electrochemical reactions in the slag pool has important influence on smelting speed and the quality of the products.In order to grasp the occurrence conditions,reaction speed,reaction influencing factors,and ion transmission law of the electrochemical reaction in the slag pool,this paper established a mathematical model of electroslag considering both ion transport and Faraday reaction in an electric double layer under the action of an applied electric field.The Finite Volume Method was adopted to solve the momentum equation,energy equation and electromagnetic transmission equation to get the current density distribution,the magnetic induction intensity distribution,the electromagnetic force distribution,the joule heat distribution and the velocity distribution in the slag pool.The velocity field of the slag pool was coupled to the Possion-Nernst-Planck equation to obtain the ion concentration field,and the Butler-Volmer equation was used to describe the electrochemical reaction between the electrode and the slag pool interface.The conductivity of the slag pool was calculated based on the obtained ion concentrations,which further affected the current density and joule heat distribution in the slag pool.For a one-dimensional electrochemical physical model containing two parallel electrodes and a fully ionized electrolyte under a DC voltage,the established mathematical model was used to study the distribution of electric potential and ion concentration under the different applied voltage with the FeO content of CaF2-Al2O3,CaF2-Al2O3-CaO and CaF2-Al2O3-CaO-SiO2 slag were 0.1 wt%,0.5wt%,1.0wt%and 1.5wt%.That is to analyze the influence of the applied voltage and the changes in the composition of the electroslag on the electrochemical reaction in the slag pool,and calculate the current density at the boundary and the potential drop of the compact layer,and analyze the electrode melting situation based on the calculation results.Aimed at a two-dimensional axisymmetric electrochemical physical model of slag pool of a single electrode electroslag remelting furnace and an inner rod and outer tube type two-electrodeeletrodes electroslag remelting furnace,established mathematical model was used to simulate the steady distribution of current density,magnetic induction intensity,electromagnetic force,joule heat,velocity,ion concentration and conductivity in the CaF2-Al2O3 slag with the FeO content of 0.1wt%.The smelting characteristics were also analyzed.The numerical calculation results show that:the increase of the applied voltage and the content of FeO in the electroslag can accelerate the electrochemical reaction rate during the electroslag remelting process;The addition of CaO and SiO2 to the electroslag will reduce the electrochemical reaction rate;The melting rate of the cathode electrode is higher than that of the anode electrode.There is O2-enrichment near the electrode of the single electrode electroslag remelting furnace,which is easy to react with Fe2+ and Fe3+ to produce FeO and Fe2O3.The joule heat in the slag pool is mainly concentrated near the electrode,but there is also a considerable part of joule heat distribution at the bottom of the slag pool and the side wall of the mold.The ion concentration near the electrode of the the inner rod and outer tube type two-electrodeeletrodes electroslag remelting furnace varies greatly,and the FeO is easily generated in the slag pool area below the inner rod consumable electrode.Compared with the single electrode electroslag remelting furnace,joule heat in the slag pool is more concentrated in the area near the electrode,and the melting rate of the electrode is faster when the applied voltage is the same.In summary,the electrochemical mathematical model in the slag pool of the DC electroslag remelting process established in this research.It can accurately describe the Faraday reaction,multiphysics and ion transmission process in the slag pool.This research enriched the theory of electroslag remelting furnaces,providing reference for the design and operation of electroslag remelting furnace.