LAUSR

Abstract To achieve reuse of converter slag, the influence of the P2O5 content on the component activity of dephosphorization slag, the basicity of the slag, and the phosphorus content in liquid steel were studied and the influence of temperature on the end phosphorus content in liquid steel was analyzed. The results show that the slag remaining in the last heat still exhibited strong dephosphorization ability. Six heats of industrial basic oxygen furnace trials with a 100t-scale top–bottom combined blown converter were carried out using slag-remaining technology. The phases of dephosphorization slag were analyzed by scanning electron microscopy– energy dispersive X-ray spectroscopy and X-ray diffraction. The decomposition reaction of RO phase (a solid-solution composed of some divalent metal oxides, such as FeO, MgO, MnO, CaO, etc.) was relatively complete in slag with a high CaO/SiO2 ratio but was not complete in the slag with a low CaO/SiO2 ratio. Euhedral crystals of 2CaO· SiO2 with certain amount of 3CaO· P2O5 were formed, resulting in a solid-solution phase of 2CaO· SiO2–3CaO· P2O5. The liquid phase was present in greater amount and was mainly composed of calcium ferrite. The enrichment of SiO2 and P2O5 was easier with increasing recycling times of the converter slag. To maintain a higher efficiency of dephosphorization, the P2O5 content in the slag should be maintained below 3% and the CaO/SiO2 ratio of slag should be maintained above 3.