Molecular–Dynamic Simulation of the Melt of an Industrial Oxide–Fluoride Mold Flux

Abstract

Abstract—The paper discusses the results of molecular–dynamic simulation of a melt of the multicomponent oxide–fluoride CaO–SiO2–Al2O3–MgO–Na2O–K2O–CaF2–FeO system that corresponds to the composition of an industrial mold flux (MF) used in steel casting for slag targeting in the mold of a continuous casting machine as: (wt %) 35.35% SiO2, 30.79% CaO, 8.58% Al2O3, 1.26% MgO, 13.73% CaF2, 7.57% Na2O, 0.88% K2O, and 1.82% FeO. These concentrations were converted to mole fractions and the number of ions was calculated for each of the components in the model. An eight-component oxide–fluoride melt containing 2003 ions in the main cube with an edge length of 31.01 A was simulated under periodic boundary conditions at an experimentally determined solidification onset temperature of 1257 K at a constant volume. The Coulomb interaction was considered by the Ewald–Hansen method. The time step was 0.05t0, where t0 = 7.608 × 10–14 s is the internal unit of time. The melt density was taken as 3.04 g/cm3 based on experimental data obtained by the authors. The interparticle interaction potentials were chosen in the Born–Mayer form. Based on the simulation results, the structure of subcrystalline groups of atoms present in the melt at the temperature of solidification onset was determined. A discussion of the simulation results and their comparison with the literature data was held. It is shown that the computer model allows one to obtain a fairly realistic picture of the atomic structure of the slag melt, which indicates that the basic structural component of all silicate systems is silicon–oxygen tetrahedron. Tetrahedra in silicates either are in the form of structural units isolated from each other or, being connected together through vertices, form complex anions, which is consistent with the theory of slag melts. Molecular–dynamic simulation allows one to obtain adequate information on the structure of a melt of a certain chemical composition.