Thermodynamic models for predicting dephosphorisation ability and potential of CaO–FeO–Fe₂O₃–Al₂O₃–P₂O₅slags during secondary refining process of molten steel based on ion and molecule coexistence theory

Abstract

Thermodynamic models for predicting phosphorus distribution ratio P and phosphate capacity C PO 32 4 of CaO-FeO-Fe 2 O 3 -Al 2 O 3 -P 2 O 5 slags during secondary refining process of molten steel, according to the ion and molecule coexistence theory (IMCT), i.e. IMCT2 P and IMCT2C PO 32 4 4 against the aforementioned parameters can be observed for the slags in the higher temperature range from 1918 to 1927 K. The influences of the aforementioned parameters on dephosphorisation ability are significantly different from those on dephosphorisation potential of the slags.

Critical Evaluation of Prediction Models for Phosphorus Partition between CaO-based Slags and Iron-based Melts during Dephosphorization Processes

“…Thus, it is necessary to distinguish the dephosphorization mechanism between hot metal and molten steel by a fixed CaO-based slag system before evaluating the collected 16 models in the next section. CaO-based slags Taking the secondary refining process [83] as an example for molten steel dephosphorization, greater oxygen potential of molten steel or slags can be maintained through the [C]-[O] equilibrium in molten steel or by the (Fe t O)-[O] equilibrium at the slag-metal interface as displayed in Figure 1(b). Moreover, a high content of CaO in slags can easily be realized by adding a reasonable amount of slag-forming agents.…”

“…As thermodynamic models, the collected 16 models of k P or L P were established under the condition of the slag-metal equilibrium over various temperature ranges. Only several models among the collected 16 models of k P or L P , rather than the entire 16 models, had primarily been evaluated by Yang et al [81][82][83] based on the experimental data of L P for molten steel dephosphorization by the CaO-based slags. In this contribution, the collected 16 models of k P or L P from the literature [2,3,10,13,19,20,21,23,26,33,37,40,55,57,65,67,69,70,74] have critically been evaluated based on the measured [84] results of hot metal dephosphorization at a commercial-scale hot metal pretreatment station as well as the recently proposed dephosphorization mechanism [84] of hot metal by CaO slags.…”

“…Thus, dephosphorization reactions of hot metal during the dephosphorization pretreatment process [84] can be described by the same chemical reactions in Eqs. [1] and [2] as those of molten [84] (Mass pct) log L P;measured (-) log L IMCT P;calculated [84] (-) CaO SiO 2 MgO FeO Fe steel during the secondary refining process [83] by the same CaO-based slags.…”

“…Finally, a general method for developing the prediction model of k P or L P with ideal accuracy from the reported models has been suggested or provided through revising the collected models for the assigned slags equilibrated with molten steel or hot metals. In addition, the developed L P model [84] based on the ion and molecule coexistence theory (IMCT) [81][82][83][84][85][86][87][88][89][90][91][92][93][94] for slags, i.e., the IMCT-L P model, [84] for hot metal dephosphorization by CaObased slags has also been assessed through comparison with the predicted results by the revised models from the literature.…”

“…For instance, many researchers such as Schu¨rmann and Fischer, [55] Ide and Fruehan, [69] and Basu et al [75] briefly reviewed or critically evaluated the related literature on prediction models of L P between steelmaking slags and molten steel prior to 1991, 2000, and 2007, respectively. In addition, Yang et al [81][82][83] also tabulated and assessed some models of L P between steelmaking slags and molten steel. However, the detailed literature survey on prediction models of L P between various slags and molten steel or hot metal was not carried out by researchers.…”