Thickness Variation Of Slag Skin In Two Series Electroslag Remelting Process

The thickness of slag skin is the "regulator" of heat and current distribution in electroslag remelting process,which has a great influence on the solidification condition of solid-liquid interface.Thin skins tend to have a smooth finish,but thicker slag skins can be a source of surface defects causing severe grinding losses from the finished product.The thickness of the slag skin is determined by the input and output heat of the slag pool.The input heat depends on the melting speed of electrode,and the output heat depends on the cooling effect of mold and bottom water tank.The thickness of slag skin can be adjusted automatically with the change of input and output heat,and it has great influence on the heat transfer from steel ingot to mold and the structure of molten pool.At present,there have been some research production about ESR skin,but most of the research is about single-electrode ESR or ignore the electrode,for two series electrodes ESR research is very few.Due to the high temperature and invisibility of ESR process,it is difficult to study it by hot state experiment.Therefore,it is a feasible method to study the electroslag remelting process by numerical simulation.In this paper,the steady-state multi-physical field model and the transient model of coupled slag skin are established and simulated by sequential coupling method.The distributions of multiphysical fields were calculated by the steady-state model,and then the steady-state results were taken as the initial conditions of the transient model to calculate the dynamic changes of molten pool structure,slag skin thickness,temperature field and flow field.Then,the effects of different voltage,current and secondary cooling intensity on multi-physical field,molten pool result and slag skin thickness were studied.The results show that:(1)In the initial stage of smelting,the heat input into the slag pool increases,the temperature of the slag pool increases,and the thickness of the slag skin on both sides of the slag pool decreases;With the smelting process,the slag skin on both sides of the ingot is partially melted by the liquid metal in the molten pool,and the thickness of the slag skin on both sides of the ingot decreases.At 300 s,the slag skin thickness basically reaches equilibrium,and the slag skin thickness on both sides of slag pool and ingot does not change.(2)In the smelting process,the bottom shape of the metal molten pool gradually changes from straight to parabolic,and the depth of the molten pool increases;The slag pool temperature and ingot temperature gradually increased.(3)When the voltage increases,the depth of molten pool deepens and the thickness of slag shell on both sides of slag pool and ingot decreases.As the current increases,the depth of molten pool increases,and the thickness of slag shell on both sides of slag pool and ingot decreases.When the input power is constant and the secondary cooling intensity is increased,the depth of molten pool becomes shallow and the thickness of slag shell on both sides of ingot increases.