No abstract

slags reported by different researchers, a total of 200 industrial measurements with large compositional variations and predicted results by summarised five L Mn models and two C Mn models. The developed thermodynamic model for calculating manganese distribution ratio can determine quantitatively the respective manganese distribution ratio L Mn,i and the respective manganese capacity C Mn,i of four demanganisation products as MnO, MnO • SiO 2 , 2MnO • SiO 2 and MnO • Al 2 O 3 . A significant difference of demanganisation abilities among FeO, FeO + Al 2 O 3 and FeO + SiO 2 can be found as 98, 1.8 and 0.2%. By comparing binary and complex basicity, the optical basicity is recommended to describe the relationship between basicity and manganese distribution ratio. With the aid of the current model, the co-effects of the N FeO /N MnO ratio and optical basicity on the L Mn and C Mn of CaO-SiO 2 -FeO-MgO-MnO-Al 2 O 3 slags are investigated.

In the current study, the thermodynamics of the slag-metal equilibrium reaction between Inconel 718 Ni-based alloy and CaF2-CaO-Al2O3-MgO-TiO2 electroslag remelting (ESR)-type slags were systematically investigated in the temperature range from 1773 to 1973 K (1500 to 1700 °C). The equilibrium Al content increased with increasing temperature, whereas the equilibrium Ti content decreased with increasing temperature at a fixed slag composition. The important factors for controlling the oxidation of Al and Ti in the Inconel 718 superalloy were TiO2 > Al2O3 > CaO > CaF2 > MgO in ESR-type slag and Al > Ti in a consumable electrode. The conventional method of sampling by means of a quartz tube could result in contamination of the molten metal and changes in the size of the “special reaction interface”. Therefore, a novel method was used in the present study to investigate the slag-metal reaction kinetics to accurately obtain the kinetic parameters. The mass transfer coefficient was determined by coupling with the kinetic model derived from the assumption that the reaction rate ([Al] + (TiO2) = [Ti] + (Al2O3)) was controlled by the mass transfer of [Ti], [Al], (TiO2) and (Al2O3) in the boundary layer, respectively.

A thermodynamic model (IMCT-L Mn ) for calculating manganese distribution ratio between CaO-SiO 2 -MgO-FeO-MnO-Al 2 O 3 -TiO 2 -CaF 2 slags and carbon saturated liquid iron have been developed based on the ion and molecule coexistence theory. The predicted manganese distribution ratio shows a reliable agreement with the measured ones. With the aid of the IMCT-L Mn model, the respective manganese distribution ratio of (and 2MnO•TiO 2 are investigated. The results indicate that the structural units SiO 2 + FeO play a key role in CaO-SiO 2 -MgO-FeO-MnO-Al 2 O 3 -TiO 2 -CaF 2 slags in demanganisation process in the course of hot metal treatment at 1673 K. The manganese distribution ratio at a given binary basicity range increases with CaF 2 content, while that decreases with TiO 2 content at different binary basicity scopes, which demonstrate that high Mn in the metal is favoured by TiO 2 content. In the present study, various critical experiments are carried out in an effort to clarify the effect of temperature on demanganisation ability, indicating that the lower temperature of molten metal is, the faster the rate of demanganisation reaction is and the shorter the thermodynamic equilibrium time is and the lower end-point Mn content is. It can be deduced from the obtained experimental results that the greater oxygen potential of slags or iron-based melts, lower content of basic oxides in slags, and lower temperature at reaction region is benefit for demanganisation reaction.

A thermodynamic model for predicting the phosphorus distribution ratio L P of CaO-SiO 2 -MgO-FeO-Fe 2 O 3 -Al 2 O 3 -P 2 O 5 slags was developed by considering the mass action concentration of ion couples or structural units in slags based on the ion-molecule coexistence theory (IMCT) and is referred to as the IMCT-L P model. Compared with the equilibrium mole number or mass percentage of the slag components, the mass action concentration for structural units of CaO-SiO 2 -MgO-FeO-Fe 2 O 3 -Al 2 O 3 -P 2 O 5 slags used in HIsmelt smelting reduction ironmaking can characterize the reaction ability of the components. The mass action concentration of the iron oxides N Fet O may characterize the oxidizing ability of the slag. The dephosphorization reactions in the HIsmelt smelting reduction vessel are jointly controlled by basic oxides and the oxidizing ability of the slag. The IMCT model can not only accurately predict the total phosphorus distribution ratio of metallurgical slags but also forecast the respective phosphorus distribution ratio of basic oxides in the slag, i.e. the dephosphorization contribution rates of 3CaO•P 2 O 5 , 4CaO•P 2 O 5 and 2CaO•P 2 O 5 were 99.7%, 0.227% and 0.033%, respectively. Moreover, to more conveniently predict the phosphorus distribution ratio, the empirical formulas of the phosphorus distribution ratio considering slag composition and temperature were determined by mathematical regression.