Slag foamability is as critical a parameter as CO gas generation in order to obtain foam. Foamability is controlled by the slag phase physical properties viscosity, surface tension and density. These properties vary with slag composition.

Due to the nature of the EAF – with large variations in temperature and composition in different locations of the furnace – the slag is likely to be partly solid at some positions during some stages of the operation. A slag that is not fully liquid, but contains some solid material such as undissolved lime, also influences the foamability, since there is a change in the apparent viscosity:

Equation: eta = eta_0 × (1 - af)^-n

where:

η = apparent viscosity of the solid-containing melt

η0 = viscosity of the solid-free melt

f = volume fraction of solid particles in the melt

a and n are constants.



Viscosities of Al2O3-CaO-SiO2 slag compositions (mole fractions) at 1550 °C / Pa s

Surface tension of Al2O3-CaO-SiO2 slag compositions (mass %) at 1600 °C / mN m-1

References

  • VDEh, Veslag Stahleisen GmbH,  Slag Atlas, VDEh, Veslag Stahleisen GmbH, 3-514-000457-9 Book icon