Тhe Study of the Process of Metal-Thermal Reduction of Boron from the Slag of the System CaO-SiO2-MgO-Al2O3-B2O3

Abstract

The results of thermodynamic modeling of the effect of aluminum (0.005–0.1%), contained in the metal at constant silicon concentrations (0.2%) and carbon (0.1%) on the boron reduction process from the slag of the system CaO-SiO2-MgO-Al2O3-B2O3 basicity (CaO)/(SiO2) equal to 5 in the temperature range 1400–1700 °C, in steps of 50 °C are presented. For modeling, the software complex HSC Chemistry 6.12 developed by Outokumpu Research Oy (Finland) was used. The calculations using the Equilibrium Compositions module at a gas-phase pressure of 1 atm, containing 2.24 m3 of N2 (gas) as a neutral additive were performed. The obtained simulation results indicate the thermodynamic possibility of boron reduction from the slag of the CaO-SiO2-MgO-Al2O3-B2O3 system by silicon and aluminum, whose concentration in the metal is insignificant – 0.2 and 0.005–0.1%, respectively. It was found that an increase in the initial aluminum content in the steel promotes an increase in the concentration of reduced boron in the metal with a content of 4% B2O3 and a given temperature. Thus, at a process temperature of 1650 °C, an increase in the initial aluminum content from 0.005 to 0.1% made it possible to increase the boron concentration in the metal by 28.5%. The results of thermodynamic modeling characterizing the effect of temperature on the degree of boron reduction at different aluminum contents are presented. Experiments on the inter-phase distribution of boron between the slag of the CaO-SiO2-MgO-Al2O3-B2O3 system and the metal were carried out in a high-temperature Tamman resistance furnace. Low-carbon steel containing 0.005% Al was used. It was shown that aging of the metal under the slag containing 4.3% of B2O3 is accompanied by reduction of boron, the amount of which in the finished steel is 0.0089%. The coefficient of boron assimilation (KB) is 5.8%, which is in principle correlated with the results of thermodynamic modeling. The obtained results of thermodynamic modeling and experimental data showed that it is possible in principle to directly microlite boron steel by reducing it with aluminum and silicon contained in the metal.