A Further Evaluation of the Coupling Relationship between Dephosphorization and Desulfurization Abilities or Potentials for CaO-based Slags: Influence of Slag Chemical Composition

Abstract

The coupling relationships between dephosphorization and desulfurization abilities or potentials for CaO–FeO–Fe2O3–Al2O3–P2O5 slags over a large variation range of slag oxidization ability during the secondary refining process of molten steel have been proposed by the present authors as logLp + 5logLs or logCpo3-4 + logCs2- in the reducing zone and as logLp + logLs - 5logNFetO or logCPO3-4 + logCs2- in the oxidizing zone based on the ion and molecule coexistence theory (IMCT). In order to further verify the validation and feasibility of the proposed coupling relationships, the effects of chemical composition of the CaO-based slags are provided. The chemical composition of slags was described by three group parameters including reaction abilities of components represented by the mass action concentrations Ni , two kinds of slag basicity as simplified complex basicity and optical basicity , and the comprehensive effect of iron oxides FetO and basic oxide CaO. Comparing with the strong effects of chemical composition of the CaO-based slags on dephosphorization and desulfurization abilities or potentials, the proposed coupling relationships have been confirmed to not only be independent of slag oxidization ability as expected but also irrelevant to the aforementioned three groups of parameters for representing the chemical composition of the CaO-based slags. Increasing temperature from 1811 to 1927 K (1538 to 1654 °C) can result in a decreasing tendency of the proposed coupling relationships. In terms of the proposed coupling relationships, chemical composition of slags or fluxes with assigned dephosphorization ability or potential can be theoretically designed or optimized from its desulfurization ability or potential, and vice versa. Considering the large difference of magnitude between phosphate capacity CPO3-4 and sulfide capacity CS2- , the proposed coupling relationships between dephosphorization and desulfurization abilities for CaO-based slags are recommended to design or optimize chemical composition of slags.

Titanium Distribution Ratio Model of Ladle Furnace Slags for Tire Cord Steel Production Based on the Ion–Molecule Coexistence Theory at 1853 K

“…It is quite essential to establish a thermodynamic model for calculating the titanium distribution ratio between steel and slag. The ion-molecule coexistence theory (IMCT) has been efficaciously applied to describe phosphate capacity, manganese distribution, sulfide capacity, and so on, as shown in Table 1 [10][11][12][13][14][15][16][17][18][19][20][21][22][23]. In the IMCT, the defined mass action-concentration (MAC) is consistent with the classical concept of activity in the slag.…”

Generation Mechanism of MgO and Al2O3 Inclusions in 51CrV4 Spring Steel Based on the Ion–Molecule Coexistence Theory

“…However, it is difficult to determine the activity of each constituent in a complex refining slag. The IMCT provides an effective way to obtain the activity of a complicated slag [41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56]. In the IMCT, the defined mass action-concentration (MAC) is consistent with the classical concept of activity in the slag.…”

Effect of various components on the distribution of phosphorus in CaO–FeO–MgO–SiO2–MnO–TiO2–V2O5–P2O5 slag based on IMCT

“…The reaction capacity or activity of the component in the slag is characterized by the mass action concentration of the component (N i ), which is defined as the mole fraction under the equilibrium condition of the slag system. Based on the IMCT, Yang et al [17][18][19][20][21][22][23][24] had successfully developed a thermodynamic model for predicting L P between molten steel and CaO-SiO 2 -MgO-FeO-Fe 2 O 3 -MnO-Al 2 O 3 -P 2 O 5 slags during top-bottom combined blown converter steelmaking process, and a thermodynamic model for predicting the phosphate capacity of CaO-SiO 2 -MgO-FeO-Fe 2 O 3 -MnO-Al 2 O 3 -P 2 O 5 slags at the steelmaking endpoint during an 80-ton top-bottom combined blown converter steelmaking process, simultaneously proposed the coupling relationships between dephosphorization and desulphurization abilities or potentials for CaO-FeO-Fe 2 O 3 -Al 2 O 3 -P 2 O 5 slags over a large variation range of slag oxidization ability during the secondary refining process of molten steel. The aforementioned models can be valid for predicting dephosphorization ability of CaO-based slags between hot metal and molten steel, respectively.…”