Effects of Flux Composition and Oxidizing Conditions on Dephosphorization of Chromium-containing Hot Metal by Using CaO-CaF₂-based Fluxes

Abstract

Removal of phosphorous from chromium-containing hot metal by using CaO-CaF₂-based fluxes was investigated at 1480 ± 20°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 6 mass% of carbon and 28 29 mass% of chromium. The contents of Cr₂O₃ of the slag after the treatment were as low as 12 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.