Dephosphorisation of hot metal containing moderate amounts of chromium with CaO–FeO_x–Cr₂O₃–CaF₂ 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.

KEYWORDS:

• Dephosphorisation
• chromium loss
• solute transfer reactions
• crystallinity
• Cr-containing ore
• Fe(Cr,Al)₂O₄
• microstructure of slag
• phosphorus recovery

Acknowledgements

This work was supported by the National Natural Science Foundation of China and Steel Joint Research Fund of China BaoWu Steel Group Co., LTD (No. U1960110, 1660116, and U1560109).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by National Natural Science Foundation of China: [grant number 1660116]; National Natural Science Foundation of China: [grant number U1960110]; Steel Joint Research Fund of China BaoWu Steel Group Co., LTD: [grant number U1560109].