Study On Electrical Conductivity And Microstructure Of Low Reactivity Mold Slags For High-Mn And High-Al Steels

High-manganese high-aluminum steel is widely used in automotive,military and other fields due to its excellent microstructure and mechanical properties.The TWIP and TRIP steels with ultra-high strength and plasticity developed in recent years have become the darlings of domestic and foreign steel companies vying for chasing and researching.However,at present,there is still a lack of mold slag suitable for continuous casting of high-manganese and high-aluminum steel at home and abroad and its supporting continuous casting process,which results in the production process of high-manganese and high-aluminum steel continuous casting is unstable,and serious surface crack defects and leakage frequently occur.Steel accidents could not achieve continuous casting of multiple furnaces.Therefore,the development of low-reactivity mold slag has become a hot topic at home and abroad.On the basis of experimentally testing the electrical conductivity of low-reactive mold slag,this paper analyzes the relationship between the conductivity of the mold slag and the reactivity from the perspective of the electrochemical nature of steel slag reaction.At the same time,the glass slag samples quenched by high temperature slag were used to study the microstructure of low-reactive mold slag by infrared and Raman spectroscopy,and explore the characteristics of the microstructure of low-reactive mold slag system.The influence of Al₂O₃ inclusions,temperature and typical components on the microstructure of the mold slag was analyzed to provide a theoretical basis for the research and optimization of low-reactive mold slag.The main findings of the paper are as follows:(1)The effect of temperature on the conductivity of low-reactive mold slag meets the Arrhenius formula.As the temperature increases,the electrical conductivity gradually increases;in the low-reactive mold slag system,Al₂O₃ gradually replaces SiO₂ and BaO replaces CaO.The electrical conductivity showed a downward trend;with the increase of B₂O₃,F,Na₂O,Li₂O content,the electrical conductivity showed an upward trend.(2)The quantitative relationship between the conductivity and viscosity of the low-reactive mold slag was established according to the Arrhenius formula:ln?=-1.21ln?-0.69.From the perspective of the electrochemical nature of the steel slag reaction,the relationship between the conductivity of the slag and the reactivity is analyzed.When the degree of polymerization of the melt network structure decreases,the ion migration ability increases,and the conductivity of the slag rises.The electrical conductivity increases,the diffusion ability ofRAlO₄^4-andSiO₄^4-increases,and the reaction kinetics condition of the steel slag is improved so that the reaction rate of the electrode increases,resulting in the increased reactivity.(3)The microstructure of the low-reactive slag system was studied by infrared and Raman spectroscopy.The results showed that the low-reactive mold slag mainly consisted of Q_n-based silicate structure and Al-O-Al-based aluminate.The salt structures are interconnected to form a spatial network structure.F^-ions,O^2-ions,and free cations exist as ion clusters.Although the glass slag sample obtained by quenching the high-temperature slag has maintained the microstructure in the high-temperature liquid state,it cannot characterize the slag microstructure at a specific temperature.(4)With the increase of the content of Al₂O₃ inclusions in the mold slag,the content of Al-O-Al and aluminate-related structures in the melt gradually increases,the silicate structure content gradually decreases and tends to polymerize,and the mold slag melt structure gradually Transition to aluminate structure.When Al₂O₃ is used to replace SiO₂,the content of Al-O-Al and aluminate-related structures in the melt increases,and the aluminate structure develops in the direction of polymerization.The silicate structure content decreases and the degree of polymerization decreases.When BaO replaces CaO,the content of Al-O-Al in the melt gradually increases and the[AlO₆]content decreases,the aluminate structure in the melt tends to polymerize,and the decrease in free O^2-in the melt results in an increase in the degree of polymerization of the silicate structure.(5)As the content of B₂O₃ increases,the content of Al-O-Al in the melt decreases,the aluminate structure depolymerizes,and B₂O₃ forms[BO₃]to participates in network formation,resulting in a decrease in the symmetry of the melt network structure and a simpler melt network structure.With the increase of the F content,the Al-F and[AlO₆]content in the melt increase greatly,which makes the melt structure simpler and the degree of polymerization decreased.When the content of Li₂O and Na₂O increases,the amount of free O^2-in the melt increases,and the silicate and aluminate structures in the melt disintegrate,and the melt structure becomes simple.