Effect of Oxygen to Silicon Ratio on the Viscosity of Metallurgical Slags

Abstract

Viscosity is an important physical property, which influences the performance of slags, in metallurgical processes such as iron making, steelmaking and continuous casting. Viscosity of slags is strongly influenced by the chemical composition and the temperature. Experimental measurement of slag viscosity requires high temperature equipment and is time consuming. Empirical relations/calculations using certain chemical parameters have been attempted to predict the viscosity, which may then be used for controlling metallurgical processes. Metallurgical slags used in the steel industry are made up of different oxides and fluorides, and may often be treated as silicates. The presence of silica, an inorganic polymer, in slags, has a major impact on "viscosity". It is convenient to describe the silicate slag structure in terms of the network character of silicates-either the Oxygen to Silicon ratio (O/Si ratio) or the Non Bridging Oxygen (NBO).The effect of O/Si ratio (and temperature) on the viscosity of slags has been studied theoretically in this work. Data on composition and viscosities were taken from the literature and the trends have been analyzed in terms of Oxygen to Silicon ratio. Data on four different slag systems, consisting of 33 slags, covering a range of temperatures, have been used. In all cases, irrespective of the system and the temperature, the viscosity was found to decrease steadily with increasing Oxygen to Silicon ratio. This is due to the increased breaking of the silicate network. The suitability of this parameter for assessment of slags (viscosities) has been demonstrated. KEY WORDS: slags; viscosity; chemical composition; oxygen to silicon ratio; silicate structure.

Viscosity measurement of mould fluxes using inclined plane test and development of mathematical model

“…If IPT is taken as a measure of viscosity, O/Si ratio generally shows a slightly better correlation with the mould powder viscosities than the other two ratios. This agrees with the investigation by Santhy et al,9 who observed a steady correlation between O/Si ratio and viscosities for simple slag chemistries.In the work of Santhy et al,9 a growing need of a viscosity characterisation model for the iron-and steelmaking fluxes and slags was identified. In order to further understand the gap in mould flux characterisation, the authors progress one step further by developing the following relationships which can predict the IPT ribbon lengths from the mould flux chemistry based on O/Si ratio for both CaO and CaF 2 classes of mould fluxes…”

Structural characterization of the near‐surface region of soda–lime–silica glass by X‐ray photoelectron spectroscopy

“…The experimental data point corresponding to 0 min of sputtering associated with the top surface consisted of the highest O total /Si ratio of 3.74, which was theoretically logical, owing to the high abundance of silanol groups and associated hydrogen-bonded water molecules on the surface. [27][28][29] However, the concentration of BO was experimentally found to be the highest at this point in depth. This unexpected outcome was confirmed to be true for the second category of SLS glass that was investigated separately, represented in Figure S3.…”

“…It is graphically portrayed in Figure 6. A high O/Si ratio is generally indicative of a depolymerized silicate network 27 . The presence of NBOs associated with network modifiers and hydrous species (SiOH/H 2 O) in the subsurface network of SLS glass increases the atomic ratio of O total /Si from the otherwise known value of 2.0 for fused silica (SiO 2 ) consisting of all Q 4 entities (four BOs without any NBO per silica tetrahedron).…”

“…A high O/Si ratio is generally indicative of a depolymerized silicate network. 27 The presence of NBOs associated with network modifiers and hydrous species (SiOH/H 2 O) in the subsurface network of SLS glass increases the atomic ratio of O total /Si from the otherwise known value of 2.0 for fused silica (SiO 2 ) consisting of all Q 4 entities (four BOs without any NBO per silica tetrahedron). The experimental data point corresponding to 0 min of sputtering associated with the top surface consisted of the highest O total /Si ratio of 3.74, which was theoretically logical, owing to the high abundance of silanol groups and associated hydrogen-bonded water molecules on the surface.…”

Cold Simulation of momentum transfer of a metal droplet falling through slag systems possessing net-work structured fluids

“…Although the use of thermodynamic data allows for the calculation of viscosity for wide composition range, the feature of the silicate melts are not directly considered in their models. Santhy et al (2005) analyzed the trends of viscosities of slags in terms of O/Si ratio. In all cases, irrespective of the system and the temperature, the viscosity was found to decrease steadily with increasing oxygen to silicon ratio.…”