EQUILIBRIUM DISTRIBUTION OF BORON BETWEEN METAL OF Fe – C – Si – Al SYSTEM AND BORON SLAG

Using the HSC 6.1 Chemistry software package (Outokumpu)  and simplex-lattice planning, the thermodynamic modeling of the  boron equilibrium distribution between iron containing 0.2  % of C,  0.35  % of Si, 0.028  % of Al (in the terms and hereinafter indicated  mass.  %) and slag of the system СаО – SiO2 – Аl2O3 – 8  %  МgO – 4  % В2O3 was carried out in a wide range of chemical composition and at  temperatures of 1550  °С and 1600  °С. Adequate mathematical models in the form of III degree polynomial obtained for each temperature, describes the equilibrium distribution of boron between slag and  metal depending on the slag composition. Mathematical modeling  results are presented graphically in the form of diagrams of composition – boron equilibrium distribution. It is shown that slag basicity  affects on the boron distribution coefficient. Thus, increasing the slag  basicity from 5 to 8 at temperature of 1550  °С reduces the boron distribution coefficient from 160 to 120 and, as a consequence, increase  the boron content in the metal from 0.021  % at LB  =  159 to 0.026  %  at LB  =  121, that is, growth slag basicity is beneficial to the development of boron reco very process. The positive effect of the slag basicity on boron recovery process in the researched range of the chemical  composition can be explained according to the slag phase composition and thermodyna mics of boron reduction reactions. The temperature growth of the metal negatively affects the boron recovery.  Equilibrium boron distribution coefficient increases by an average of  10 units with an increase in temperature to 1600  °C. The diagrams  contain marked field of slag chemical composition with 53  –  58  % of  CaO, 8.5  –  10.5  % of SiO2 and 20  –  27  % of Al2O3 , providing boron  distribution coefficients at level of 140  –  170 at temperature range of  1550  –  1600  °C and allowing to expect boron concentration in the  metal at the level of 0.020  % at LB  =  168  % and 0.023  % at LB = 139  at the 4  % of B2O3 in the slag initial.

boron,  metal,  slag,  phase distribution,  design of experiments,   thermodynamic modeling,  structure-property diagrams

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