Dephosphorization of High Carbon Ferrochromium Particle by Na₂CO₃, Na₂SO₄ and K₂CO₃ Fluxes

Abstract

High carbon ferrochromium particles weighing 3 g were tested for dephosphorization by sodium carbonate, sodium sulfate, potassium carbonate and their mixtures in the temperature range 730 to 1 200°C in a nickel crucible. 60% of phosphorus was removed from the samples with 0.3 mm in diameter using the flux of 0.5 to 0.8 g.
Diffusion of phosphorus in the solid metal was found to be rate-determining. The carbonates and sulfate oxidized, pulverized ferrochromium particles and enhanced dephosphorization. The optimum temperatrue was 1 000 to 1 100°C, but rephosphorization occured at higher temperatures following the initial dephosphorization due to the vaporization and the decomposition of the fluxes. The dephosphorization capability was in the order of sodium sulfate, potassium carbonate and sodium carbonate. Phosphorus in the fluxes was water-soluble and recovered completely. Inert atmosphere prevented ferrochromium from oxidation.