In view of the fact that Ti–bearing blast furnace primary slag has been explored limitedly and its viscosity–structural property is not fully understood, the phase compositions, viscosity and structure of CaO–8%MgO–Al2O3–SiO2–TiO2–5%FeO slag are investigated by X-ray diffractometer, rotating cylinder method, Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy respectively, considering the effect of Al2O3 and TiO2. The critical temperature that is defined as the temperature below which the viscosity of slag increases quickly, could be explained by the relative amount of perovskite to melilite from phase compositions analysis. The slag viscosity first increases with increasing Al2O3 content from 10 to 15 mass%, and then decreases with the further increase of Al2O3 to 18 mass%. Increasing TiO2 content continuously lowers the viscosity. FTIR and Raman spectra results show that increasing Al2O3 or decreasing TiO2 content leads to complex Si–O and Ti–O networks structure, corresponding to the slag viscosity variation. The effect of weak linkages of Si–O–Al is more dominant when Al2O3exceeds 15 mass%, which results in the decrease of viscosity.

Because the behaviours of MgO and Al 2 O 3 during slag formation of high basicity sinter are not clearly understood, the effects of MgO and Al 2 O 3 on softening-melting properties are always arguable. In this paper, four kinds of sinter containing different MgO and Al 2 O 3 content are investigated. Some observations are obtained. The mechanism of the influence of MgO and Al 2 O 3 on softening properties of sinter are different. Al 2 O 3 has priority over MgO to enter into slag phase and forms low-melting point phase while MgO remains unslagged state and mainly exists in wustite as FeO-MgO solid solution. When sinter melts, the viscosity of the slag generated from sinter containing high MgO and Al 2 O 3 content is low, which could result in low pressure drop. As MgO and Al 2 O 3 content increase, the main minerals of residual slag change from 2CaO•SiO 2 to merwinte and melilite. The changes of the minerals in slag phase can well explain the trend of softening-melting characteristic temperatures.

No abstract

No abstract

This research provides fundamental insight into the roles of MgO and Al 2 O 3 on the viscous and structural behaviors of CaO−SiO 2 −MgO−Al 2 O 3 −10 mass% TiO 2 −5 mass% FeO (CaO/SiO 2 = 1.3) system primary blast furnace slag. The slag viscosity is measured by the rotating cylinder method, which is essential to the efficient and stable operation of a blast furnace. The network structure characterization of the quenched vitreous samples was conducted using Fourier Transformation Infrared (FTIR) and Raman spectroscopy. Usual viscous behaviors (that the slag viscosity and the activation energy decrease or increase with increasing MgO or Al 2 O 3 content) were observed, corresponding to changes in the network structure certified by FTIR and Raman analyses. It seems that the addition of MgO and Al 2 O 3 prefers to modify the Si−O and Ti−O network in the present slag. When the slag composition reaches 10% MgO and 12% Al 2 O 3 , unexpected viscous behaviors (that MgO increases viscosity and Al 2 O 3 decreases viscosity) are discovered. The roles of MgO and Al 2 O 3 could be interpreted by changes in the arrangement structure of ions in liquid, corresponding to changes in the primary equilibrium phase region determined in phase diagrams and variation in the difference between the experimental and liquidus temperature, respectively.