Wetting Behaviors Of Calcium Ferrite Based Slag On Cristobalite And Rutile

In our country’s iron and steel production,the long-process ironmaking production process,dominated by blast furnaces,still occupies a dominant position in steel production.At the same time,most of the blast furnaces are based on sinter ore,with a small amount of pellets and lump ore as the charge materials.Therefore,it is particularly important to improve the quality of sinter in order to ensure the smooth operation of the blast furnace and reduce resources as well as energy consumption.After nearly a hundred years of development,the current iron ore sintering process is mainly based on high-basicity sintering process.The high-basicity sintere with calcium ferrite of silica and alumina（SFCA）as the main binding phase has high strength,good reducibility,low temperature reduction,low differentiation rate and low sintering temperature.However,at present,China’s iron and steel enterprises are facing problems such as overcapacity,comprehensive utilization of resources and environmental pollution.The domestic steel enterprises have to use domestic low-grade ore for sintering production,and various iron-containing raw materials are also widely used in the sintering process.At the same time,a large amount of vanadium-titanium magnetite is contained in the Panxi area of China.The quality of the sinter of vanadium-titanium magnetite has not been solved.Therefore,it is a difficult problem to improve the quality of sinter under complex raw material conditions.This subject comes from the National Natural Science Fund for Young Scientists-"Study on the Influence of Complex Materials on the Formation and Crystallization Behavior of Calcium Ferrate Melts during the Sintering Process"（No.51104192）and the Excellent Youth Fund Project"Mineral Processing and Extractive Metallurgy"（No51522403）.The purpose is to explore the assimilation behavior between calcium ferrite melt and SiO₂,TiO₂.The wettability of calcium ferrite melts on SiO₂ and TiO₂,the interfacial reaction of calcium ferrite melts with solid phase SiO₂ and TiO₂ and the mechanism of microstructure formation were explored through the design of wetting experiments.The wetting of calcium ferrite on SiO₂ is of dissolutive wetting system and SiO₂ has a large solubility in calcium ferrite slag.During the wetting process,SiO₂ continuously dissolves into the slag.After wetting,a large corrosion pit was formed below the droplet.The initial apparent contact angle is 30°-40°,and the equilibrium apparent contact angle is less than 10°,indicating that the calcium ferrite has good wettability on the cristobalite surface.The entire wetting process can be divided into three stages according to the change of normalized droplet diameter,rapid spreading stage,continuous decreasing rate of spreading rate and spreading equilibrium stage.The addition of a certain amount of Al₂O₃,MgO,SiO₂,and TiO₂ to the slag leads to an increase inη/γ,the spreading rate has a linear relationship withη/γand decreases with increasingη/γ.After wetting,the bulk SiO₂,Fe₂O₃ solid solution precipitated in the residual slag.The spreading of calcium ferrite on TiO₂ is of reactive wetting system.TiO₂ reacts with calcium ferrite to form CaTiO₃,Fe₂O₃ precipitates in the slag.The initial contact angle is between 30°-50°,the final equilibrium contact angle is less than 20°,and the wetting duration is between 70s and 180s.The wetting process is divided into four dynamic stages:physical spreading,first linear spreading,second linear spreading,and spreading balance.After wetting,the three-layer structure containing CaTiO₃,Fe₂O₃ and Fe₂TiO₅ was formed in the CF and CF-2M samples according to the product and the liquid residue density,but the three-layer structure was not obvious in other samples.The addition of a certain amount of TiO₂ in the calcium ferrite slag leads to the formation of a perovskite-containing dense layer at the solid-liquid interface,preventing the diffusion of TiO₂ into the slag,leaving unreacted calcium ferrite remaining in the slag.