Studium vybraných fyzikálně-chemických vlastností anorganických tavenin

Abstract

Molten inorganic oxide melts play an important role in a wide range of metallurgical applications. Oxide systems form the basis of casting powders and metallurgical slags. The role of these systems consists namely in the refining effect on the metal, in protection of metal surface against oxidation effects of furnace atmosphere, and in thermal insulation of the liquid metal level. Function of oxide (slag) systems depends on their physical-chemical properties, which are determined mainly by their composition and temperature. The dissertation focuses on investigation of surface tension, interfacial tension and viscosity of molten inorganic systems, especially oxide systems. For the actual experimental research of these selected physical-chemical properties the casting powder system was chosen, which in terms of its chemical composition represents the system used in technological practice for continuous casting of steel. This system contains, besides the dominant components, which are SiO2, CaO, Al2O3 and MgO also a number of accompanying impurities, such as Fe2O3, TiO2 and Na2O. For this system six components and ternary systems containing equivalent proportions of the components present in majority in the original casting powder were prepared. Furthermore concentration series with addition of SiO2 both for real and synthetic systems was prepared. As representative of metallic phase three iron based systems with an increasing carbon contents were chosen for the experimental investigation of interfacial tension at the interface metallic phase/oxide system. Due to the relatively high temperatures of measurement and the nature of oxide system the sessile drop technique was chosen as optimum method for obtaining the experimental data of the surface and interfacial tension. Temperature dependencies and concentration dependencies of surface and interfacial tensions of the created concentration series of real and six-component system were observed using this method. Experimental research of dynamic viscosity was carried out on a rotational high temperature viscometer Anton Paar. The temperature and concentration dependences of viscosity of the ternary system CaO- Al2O3-SiO2 was observed. As part of this work mathematical modelling of surface tension and viscosity were carried out. Functionality of selected models for calculation of these properties was for simplification verified only on the concentration series of the ternary system CaO- Al2O3-SiO2. For calculation of the temperature dependence of surface tension empirical model of regular solution, semi-empirical model based on Butler's equation and geometric Chou model were chosen. Temperature dependence of the viscosity was calculated with use of the Iida model based on the Arrhenius equation, Urbain model based on the Weymann-Frenkel equation and NPL model working on the basis of optical basicity. The results obtained by mathematical modelling were compared with the experimental data.