Determination Of Electrical Conductivity Of Electroslag Remelting Slag System Based On Electrochemical Method

The physicochemical properties of slag determine the thermodynamic and kinetic behavior of slag in the electroslag remelting process,among which the conductivity of slag is one of the most important physical properties.In the process of electroslag remelting,slag as a heat source resistance body,its conductivity directly affects the temperature of slag,the power consumption of electric furnace,and also directly affects the productivity and economy of products.In the electroslag remelting process,the slag pool is part of the circuit and should have sufficient conductivity to keep the current flowing through it.At the same time,the slag tank separates the two metallic conductors,the consumable electrode and the remelted ingot.The resistance of the slag tank prevents short circuits and generates enough Joule heat to melt the electrodes.In this thesis,the AC four-probe method based on electrochemistry was used to measure the conductivity of slag,and the influence law of slag composition,temperature and w（CaO）/w（Al₂O₃）（C/A）values on the conductivity was determined.This thesis explains the change rule of electrical conductivity of slag system containing Ce,and essentially explains the influence mechanism of composition,temperature（1380℃,1450℃,1500℃,1550℃）and C/A value on the electrical conductivity of slag.The main conclusions of the thesis are as follows:（1）The influence of temperature on conductivity obeys Arrhenius law;The conductivity of CaF₂-CaO-Al₂O₃-SiO₂-Mg O-CeO₂ slag system is 0.532～1.503 S/cm when the temperature is 1380℃～1550℃.（2）When the content of CeO₂ in slag is 3%,with the increase of w（CaO）/w（Al₂O₃）from 1.70 to 1.84,the overall conductivity increases.The influence of C/A value on the conductivity can be summarized into four aspects:The change of oxygen type（bridge-oxygen becomes non-bridge-oxygen）,the charge compensation of basic oxide metal cations(Ca²⁺and Mg²⁺destroy the aluminosilicate structure),the change of slag melting temperature（1380℃～1392℃）and the phase change in the crystallization process（formation of calcium and aluminum compounds,etc.）.（3）With the increase of w（CeO₂）,the conductivity of CaF₂-CaO-Al₂O₃-SiO₂-Mg O-CeO₂ slag firstly increases and then decreases;When the content of CeO₂ is 6%,the conductivity of slag is the highest.When w（CeO₂）=0～12%,the conductivity of slag system ranges from 1.294～1.578 S/cm.CeO₂ used in slag mixing will be converted to Ce₂O₃ after slag melting,and the influence factors of slag composition on the conductivity can be summarized into four aspects:The change of melting temperature of slag system（1376℃～1405℃）,the change of crystalline phase（Mg SiO₃ becomes CeSiO₄）,the influence of the change of w（CaO）/w（Al₂O₃）on the activity of Ce₂O₃（increase of w（CaO）/w（Al₂O₃）reduces the activity of Ce₂O₃）and the decrease of network formation（SiO₂ and Al₂O₃ activity decreases）.（4）The thermodynamic analysis and XRD results show that:taking w（CeO₂）<3%as the limit,when w（CeO₂）<3%,the main rare earth compound in the slag is CeAl O3,and when w（CeO₂）>3%,the generated material changes into Ce₂O₃·SiO₂.