A Study on the Effect of Na₂O on the Viscosity for Ironmaking Slags

Abstract

The viscosities of CaO-SiO 2 -10wt%MgO-20wt%Al 2 O 3 -Na 2 O slags (CaO/SiO 2 ¼ 0.8-1.2, wt%Na 2 O ¼ 0-10) were measured to estimate the effect of Na 2 O on the viscous behavior at elevated temperatures. The slag viscosity at 1773 K decreased with increasing Na 2 O contents, which is observed in a basic oxide component. However, the FT-IR spectroscopic analysis of the slag structure seemed to verify that [AlO 4 ]-tetrahedra depolymerized more readily than [SiO 4 ]-tetrahedra due to ionic charge compensation which has a tendency to be more effective on [AlO 4 ]-tetrahedra. Hence, for the present slag system, the viscosity decreased with additions of Na 2 O by providing network breaking O 2ions, and the charge balance by Na þ ions independently contributed to the depolymerization of the network structure of the molten slag. In addition, Na 2 O also lowered the critical temperature (T CR ) resulting in a larger temperature difference between the operating temperature (T OP ) and T CR , which can enhance operational stability.

Modeling Physicochemical Properties of Mold Slag

“…Research conducted by [2] confirms that the presence of Na 2 O lowers mold slag viscosity. Sodium oxide provides O 2− free ions, which react with the bridged O 0 and causes depolymerization of highly crystalline network (Fig.…”

“…Slag viscosity influences also high temperature reactions in inter-phase region between molten slag and liquid steel [1]. Studies of molten slag structure [2] show that the oxide systems are made of chains and rings of silicate type: [Si 3 4− (monomer), which form as a result of addition of structure modifiers [2].…”

“…1. Effect of CaF 2 addition on the structure of silicates [2] [Si 3 [6]. Heyeashi [7] observed that the addition of CaF 2 causes polymerization of silicates it by the formation of complex anions CaF − , this result is a consequence of the presence of Na 2 O in the slag.…”

“…Heyeashi [7] observed that the addition of CaF 2 causes polymerization of silicates it by the formation of complex anions CaF − , this result is a consequence of the presence of Na 2 O in the slag. The different behavior of calcium fluoride is due to the chemical composition of the oxide under consideration, mainly the basicity of the slag and the presence of other structure modifiers: Na 2 …”

“…2. Effect of Na 2 O addition on the structure of silicates [2] Presence of considerable fraction of Na 2 O causes the following changes in the silicates crystal lattice:…”