The Ability of Slags to Absorb Solid Oxide Inclusions

Abstract

The capture rate of solid oxide-inclusion particles from molten steel by molten slag depends on the rate of steel film drainage (which occurs at certain particle velocities), interfacial separation, and dissolution into the slag. In this study the capture of common oxide inclusions of sizes 2.5-200 mm and with velocities ranging from their terminal velocities to 0.3 m · s Ϫ1 approaching the interface between molten iron and slags with chemistries corresponding to ladle, tundish and mold slags are investigated. Calculations, based on a model available in literature, show that film drainage (when applicable) is rapid enough to be ignored. A sensitivity analysis based on the slag properties show that the interfacial energy between slag and inclusion is the most pertinent property that could hinder interfacial separation. However, the interfacial tension needed to achieve this has to be a minimum of 0.41 N/m which is unreasonable for the case of common oxide inclusions such as Al 2 O 3 , MgO, ZrO 2 and MgAl 2 O 4 . The final step of dissolution was found based on studies with Confocal Scanning Laser Microscope experiments, to be significantly slower than the other steps. For a 100 mm particle, in the slags/inclusions investigated a correlation between slag viscosity, h

Control of MgO·Al2O3 Spinel Inclusions in Stainless Steels

“…81) The total dissolution time of MgAl 2 O 4 inclusion particle into the CaO-SiO 2 -21wt%Al 2 O 3 slag (C/Sϭ0.9) was almost identical to that of MgO inclusion (approximately 200 s for a 150 mm diameter at 1 773 K), which was measured by employing the confocal scanning laser microscope (CSLM). 81,82) This phenomenon was explained by the formation of MgAl 2 O 4 reaction layer on the surface of MgO particle during dissolution.…”

“…81) The total dissolution time of MgAl 2 O 4 inclusion particle into the CaO-SiO 2 -21wt%Al 2 O 3 slag (C/Sϭ0.9) was almost identical to that of MgO inclusion (approximately 200 s for a 150 mm diameter at 1 773 K), which was measured by employing the confocal scanning laser microscope (CSLM). 81,82) This phenomenon was explained by the formation of MgAl 2 O 4 reaction layer on the surface of MgO particle during dissolution. [81][82][83][84] The total dissolution time (t) of inclusion particles are strongly dependent on the ratio of viscosity (h) to concentration difference of dissolving species between the particle and the slag (DC) based on the boundary layer diffusion mechanism.…”

“…81,82) This phenomenon was explained by the formation of MgAl 2 O 4 reaction layer on the surface of MgO particle during dissolution. [81][82][83][84] The total dissolution time (t) of inclusion particles are strongly dependent on the ratio of viscosity (h) to concentration difference of dissolving species between the particle and the slag (DC) based on the boundary layer diffusion mechanism. This can be expressed as Eq.…”

Dissolution Behavior of Al2O3 in Refining Slags Containing Ce2O3

“…They reported that increasing temperature, and rotating speed of the rod can accelerate the dissolution rate of alumina. Yi et al 3) researched the dissolution time of Al 2 O 3 and MgO inclusion in synthetic CaO-Al 2 O 3 -MgO in situ by a confocal scanning laser microscope (CSLM) and Valdez et al 4) study the ability of slags to absorb oxide inclusions. Cho et al 5) determinate the dissolution behavior of alumina particles in CaO-Al 2 O 3 and CaO-SiO 2 -Al 2 O 3 slags at the temperature between 1 793 K and 1 853 K using optical and electron microscopes.…”

Structure-Viscosity Relationship of Low-silica Calcium Aluminosilicate Melts

“…(i) flotation of inclusions to the steel melt-slag interface, (ii) separation into the slag phase and (iii) dissolution into the slag phase, among which the final step was reported to be a rate controlling process for the removal of inclusions. 1) When the dissolution process is controlled by diffusion, the total dissolution time (τ) will be: where R o is the inclusion radius, ρ is the inclusion density, k is the Boltzmann constant, T is the temperature, a is the ionic diameter, ΔC is the driving force for the dissolution and η is the viscosity of the slag. Therefore, the viscosity of the slag is an important factor affecting the dissolution time of the inclusions into the slag phase.…”