Dephosphorisation of hot metal containing moderate amounts of chromium with CaO–FeO x –Cr 2 O 3 –CaF 2 slag

Abstract

With the extensive use of low-grade Cr-containing ore, the dephosphorisation issue of hot metal containing moderate amounts (0.2%-1%) of chromium is gaining more and more attention. To achieve dephosphorisation and chromium retention, a series of experiments on the dephosphorisation of hot metal containing moderate amounts of chromium were carried out at 1723 K. In the experiments, the crystallisation performance of the slag with various CaO/Fe₂O₃ ratio and Cr₂O₃ content, as well as the transfer of phosphorus and chromium between slag and hot metal at 1723 K were investigated. The results show that the dephosphorisation process goes through four stages: melting and precipitation, dissolution of refractory, continual oxidation, and phase transition. With the increase of CaO/Fe₂O₃ ratio, the chromium loss decreases while the dephosphorisation ratio first increases and then decreases. The addition of Cr₂O₃ promotes the precipitation of Fe(Cr,Al)₂O₄, which inhibits the dephosphorisation and chromium loss.