Study On The Rheological Properties And Conductivity Of Heterogeneous Phase Titanium-Bearing Metallurgical Slag

Pan-Xi region is the most enriched region of vanadium and titanium resources in China. The prospective reserves of vanadic titanomagnetite are over10billion tons. As a kind of special metallurgical resources, vanadic titanomagnetite is a typical low-grade and multi-element isomorphous ore, which is difficult to select, smelt and separate, so the difficulty for its comprehensive utilization is also great. On the condition of strong reducing and high temperature, some titanium compounds are reduced to high melting point materials TiCxOy and TiCxNy, forming a complex heterogeneous slag system of gas-solid-liquid phase, which will cause a series of special issues in the blast furnance process. Currently, more theoretical studies have been carried out on the formation and evolution law of Titanium-bearing slag, but they are lack of system, in-depth and continuity, especially the research on the characterization of titanium-bearing slag’s rheological behavior is still not enough.On the base of chemical compositions of Pan-steel Titanium-bearing BF slag, slag samples of CaO-SiO2-Al2O3-MgO-TiO2are prepared in laboratory. By adding different content of TiC and TiN, we simulate the process of smelting vanadic titanomagnetite by BF to generate titanium-bearing slag, and study the rheological behavior of titanium-bearing slag with rheological principles and methods. By studying the viscosity and free running temperature changes of heterogeneous titanium-bearing slag containing different content of TiC and TiN, we analyze the impact of TiC and TiN on the viscosity and free running temperature; By building constitutive equations of titanium-bearing slag under different conditions, we identify and analyze its types of non-Newtonian fluid; By studying viscosity changes of slag samples under different electric field strength and shear rates, we characterize the electrorheological behavior of titanium-bearing slag via SEM; By an a.c. impedance technique, we measure the conductivity of slag samples containing different TiC content. The results are shown as follows:(1) The existence of TiC and TiN is the main reason for the thickening of titanium-bearing BF slag. With the increasing of TiC and TiN, the initial viscosity of the slag gradually increases, and the viscosity increases dramatically when the TiC content reaches4%and the TiN reaches8%; the free running temperature of the slag is not only related with the content of solid phase particles TiC and TiN, but also related with the content of other components such as TiO2; the effect of TiN on the viscosity and free running temperature is less than that of TiC.(2) Heterogeneous titanium-bearing slag containing solid phase particles TiC and TiN mostly belong to non-Newtonian fluid in this study. The titanium-bearing slag shows the shear-thickening tendency with the increasing of shear rate; all the rheological index n in constitutive equations are greater than1:the slag with TiC is close to dilatant fluid and the slag with TiN is close to plastic dilatant fluid, which shows the results are consistent with the shear-thickening behavior.(3) Research on the electrorheological behavior of titanium-bearing slag shows that:at1500℃, with the increasing of electric field strength, the viscosity of all slag samples with different TiC content increases in every shear rate, and all samples show a positive electrorheological effect. The regularity of the electrorheological effect of samples with different TiN content is not very obvious:When the TiN content is low(<2%), with the increasing of electric field strength, the viscosity of slag samples tends to decrease, showing a negative electrorheological effect; with the increasing of TiN content, slag samples gradually show a positive electrorheological effect.(4) SEM characterizations of slag samples with TiC show that:with the increasing of electric field strength, the distribution of solid conductive particles such as TiC and TiN changes from dispersed to chain or clustered distribution; distribution of perovskite changes from dispersed distribution to aggregation, and the grains are coarsened with the changes of electric field intensity. Regular changes of TiC and TiN, as well as the the behavior (including distribution and grain size) of perovskite formed under the high temperature, influence the the electrorheological behavior together. (5) Research on the conductivity of titanium-bearing slag shows that:the existence of TiC decreases the diffusion activation energy of slag. With the increasing of TiC content, the diffusion activation energy increases; TiC particles are charge carriers and decrease the conductivity of the slag.The slag containing2%TiC has the lowest conductivity in this study, while with the increasing of TiC content, the conductivity of slag increases.