EFFECTS OF FLUX COMPOSITION AND OXIDIZING CONDITIONS ON DEPHOSPHORIZATION OF CHROMIUM-CONTAINING HOT METAL BY USING CAO-CAF2-BASED FLUXES

Removal of phosphorous from chromium-containing hot metal by using CaO-CaF2-based fluxes was investigated at 1480 +/- 20-degrees-C. Experiments were carried out using a 300 kg induction furnace in which the fluxes were injected into the metal by using a gas mixture of O2 + Ar. Experimental results showed that the optimum ratios of CaO/CaF2 and O2/(CaO + CaF2) for dephosphorization were approximately 1/1 and 40 Nl/kg, respectively. Under these conditions, about 50 per cent of phosphorous was removed by using 70 kg/ton of the flux from the metal containing approximately 6 mass% of carbon and 28 approximately 29 mass% of chromium. The contents of Cr2O3 of the slag after the treatment were as low as 1 approximately 2 mass%. When the ratio of O2/(CaO + CaF2) was increased to more than 40 Nl/kg, the loss of chromium by oxidation was increased without any favorable effect on the degree of dephosphorization. In addition, when chromium contents are more than 17 mass%, the observed value of L(P) ((mass% P)/[mass% P]) was good agreement with the calculated one on the assumption that the oxygen potential is determined by the reaction of CaO.Cr2O3 formation.