Estimation of Oxygen Potential at Slag/Metal Interface and Effect of Initial Slag Condition on Hot Metal Dephosphorization

Hot metal dephosphorization experiments at the small size scale furnace were performed for the purpose of estimating the interfacial oxygen potential of dephosphorization reaction between slag and metal, and investigating the influence of initial slag condition on dephosphorization behavior and the formation of solid phase. The results are summarized as follows; (1) Interfacial oxygen potential was estimated from phosphorous distribution ratio and Slag composition at the turning point from dephosphorization to re-phosphorization, It exists between oxygen potential of slag bulk and oxygen potential of metal bulk at every slag composition. Furthermore, as slag basicity becomes low, interfacial oxygen potential increases and fends to approach the oxygen potential of slag bulk. (2) In the case of initial lump-sum addition of iron oxide to slag, it was possible to increase the reaction rate of dephosphorization and decrease the final [%P] Value. By means of enhancing (FeO) content in slag composition, slag can be controlled to have low melting point and dephosphorization between liquid phase of slag and metal proceeds efficiently. This slag control at the early stage of dephosphorization makes it possible to crystallize C,S phase from liquid phase efficiently and concentrate phosphorous in C2S phase at the late stage. Oil the other hand, in the case of divided addition of iron oxide, the stagnation of dephosphorization was observed. In this case, C2S phase was crystallized at file early stage while dephosphorization between liquid phase and metal didn't proceed sufficiently, Therefore, crystallization of C2S phase at the early stage retard the transport of phosphorous to C2S phase at the late stage.