2001 Volume 41 Issue 4 Pages 317-324
The foaming index was measured for CaO–SiO2–FeO–Al2O3 and CaO–SiO2–FeO–MgOsatd–X (X = Al2O3, MnO, P2O5, and CaF2) slags to understand the foaming behavior. The foaming index of the CaO–SiO2–FeO–10Al2O3 slags (C/S = 0.93 and 1.2) decreases with increasing content of FeO up to 20 % and is almost constant for FeO content through 20 to 40 %. The viscosity of slags could be considered as the major contributor to foaming behavior. The addition of Al2O3 into the silicate slags results in an increase of foaming index due to an increase of slag viscosity; this could be explained by the structural role of Al2O3 in aluminosilicateslags. In the MgO-saturated and Al2O3-containing slags, FeO behaves as an acidic oxide, because slag melts would be more basic than MgO-saturated and non-Al2O3slags, where FeO behaves as a basic oxide, due to Al2O3 enhances the dissolution of MgO into the slags. The addition of MnO into the MgO-saturated slags decreases foaming index, simply due to a decrease of slag viscosity. However, the addition of CaF2 and P2O5 into the slags results in the complex foaming behavior of slags; this is probably due to the Marangoni effect. The relationships between foaming index and the physical properties of slags can be obtained from the dimensional analysis as follows:
Σ = 214(μ/√ρσ) (for the CaO-based slags)
Σ = 999(μ/√ρσ) (for the MgO-saturated slags)
The foam height is predicted as a function of decarburization rate from the molten iron and the contribution of slag foaming in EAF process was discussed as a function of decarburization rate.