Study On Slag Resistance Of Zirconia Solid Electrolyte And MgO-C Brick Under Applied Voltage

“Reduction with controlled oxygen flow” is a kind of green eletrochemical metallugy technique.It can not only obtain metal in cathode from molten electrolyte?such as slags and salts?dissolved electroactive oxide,but also at the same time release oxygen in anode.In this technique the key component is the zirconia solid eletrolytes with selective permeability for oxigen ions.Whether electrolytic reduction can proceed smoothly or not depends on the corrosion resistance of zirconia solid electrolyte under the applied voltage.Therefore,a cell with controlled oxygen flow was built using oxygen ion-conductive solid electrolyte and the SiO₂-Ca O-Al₂O₃-MgO slag containing Fe O in this paper.By means of scannning electron microscopy and energy dispersive spectroscopy,the efffects of the applied voltage and the slag basicity on the slag resistance of solid electrolyte at 1450 ? were investigated and the corrosion mechanisms were analyzed.Based on that,a new electrochemical method was developed for increasing the slag resistance of MgO-C bricks.A MgO-C brick with low carbon content was used to prepare electrode rods and Ca O-SiO₂-Al₂O₃ molten slag was used as electrolyte.The experiments of the slag resistance for MgO-C rods as cathode and anode were conducted at 1500? under the condition of applied voltage.Effects of applied voltage,the basicity of slag and the content of Al₂O₃ on the slag resistance of MgO-C electrodes were investigated,so as to provide a new way to enhance the slag resistance of MgO-C bricks at slag line during steelmaking.In the process of electrolytic reduction with controlled oxygen flow,the results of the corrosion of zirconia solid electrolyte show that:?1?The applied voltage enhances the slag corrosion to zirconia solid eletrolyte.When the applied voltage is small,the effect of applied voltage on the slag corrosion to zirconia solid electrolytic is not obvious,but the large applied voltage will increase the porosity of zirconia solidelectrolyte and decrease the interfacial tension of the slag.The further slag penetration will induce leaching MgO stabilizer into the slag and result in the phase transformation of zirconia,even disaggregation of zirconia oraganization structure.?2?The higher basicity will enhance the corrosion of zirconia membrane by the molten slag.When the basicity of molten slag increases,the viscosity of slag will decrease.This will lead to the increase of the amount of zirconia dissolved in the slag and the aggravation of the slag penetration.In severe cases,the zirconia grain can be broken off the interface and the inner membrane of zirconia can be destroyed.The study of the slag resistance of MgO-C electrodes show at applied voltage that:?1?Refractory magnesia-alumina spinel will form at the interface between slag and MgO-C electrode.The applied voltage will increase the amount of the spinel around cathode eletrode,while little iron also deposited around the cathode.All those will increase the viscosity of the slag near cathode and reduce the corrosion of slag to cathode MgO-C eletrode.?2?The basicity of slag can effect the viscosity of slag and change the distribution of refractory spinel at the interface.The lower the basicity of slag,the closer the spinel is to the interface between slag and cathode and the corrosion of MgO-C cathode is lesser.?3?The content of Al₂O₃ in molten slag directly effects the formation of spinel at the interface between slag and MgO-C cathode.When the content of Al₂O₃ is relatively high?over 15%?,spinel forms at the interface between slag and MgO-C cathode.The spinel will increase the viscosity of molten slag at the interface and reduce the corrosion of slag to MgO-C cathode.More Al₂O₃ in molten slag,more spinel will be found at the interface and less corrosion will attain.