Interfacial tension at the interface of a system of molten oxide and molten steel

This paper is focused on a study of the interfacial tension between selected oxide and metal phases. The experimental research on the interfacial tension was performed in a horizontal resistive graphite Tamman furnace using an original method of measuring. This method consists of fixing both liquid phases in a horizontal position using a mandrel made of tungsten wire in a corundum cover. In this work the influence of the carbon content in the steel on the interfacial tension was studied. For this purpose a steel with 0.411 % of mass fraction of carbon and a steel with 2.64 % of carbon were used. Because of the wide variety of oxide systems used in industry, a characteristic system of casting powder was chosen for this study. This system contains dominant components, i.e., SiO2, CaO, Al2O3 and MgO, as well as a range of attendant mixtures, e.g., Fe2O3, TiO2 and Na2O. Simultaneously, the influence of SiO2 on the temperature dependence of the interfacial tension was observed. For this reason a concentration series with gradual additions of SiO2 was created. It was found that an increasing content of carbon in the steel significantly decreases the interfacial tension between the oxide system and the steel. The interfacial tension was found to decrease slightly with an increase in the content of SiO2 in the oxide system.Web of Science48341841

Comprehensive study of rheological and surface properties of the selected slag system in the context of its internal structure

Rheological (dynamic viscosity, flow curves) and surface properties (surface tension) of real slag system were experimentally investigated. Measurements of dynamic viscosity were performed with use of the high-temperature viscometer Anton Paar FRS 1 600. The method of sessile drop was used for measurement of surface tension. Surface tension and dynamic viscosity were measured in the temperature interval from 1 200 to 1 600 °C. The structural characteristics of the selected samples were determined by X-ray diffraction (XRD). The samples for given analysis were prepared by quench cooling. Experimentally determined values of dynamic viscosity and surface tension were compared with the results of X-ray diffraction phase analysis.Web of Science55470069

Effect of CaO/ SiO2 ratio on viscosity and structure of slag

The objective of this work is experimental determination of temperature dependences of viscosity of the molten CaO - Al2O3 - SiO2 system and assessment of impact of CaO/SiO2 ratio on viscosity and structure of this system. Experimental measurements of viscosity were performed with use of the high-temperature viscometer Anton Paar FRS 1 600. Viscosity was measured in a rotational mode during heating at the rate of 3,3 °C/min in the temperature interval from 1 673 to 1 873 K. Viscosity in the molten oxide system is determined by the internal structure. Exact clarification of the change of structure of the oxide system caused by the increased content of CaO was performed by Fourier transform infrared spectroscopy.Web of Science54345845

Wetting of refractory ceramics with high-manganese and structural steel and description of interfacial interaction

This work aims to describe the interfacial interaction at the interface between refractory material and high-manganese (XT 720) and structural (11 523) steel using a wetting test up to 1600 degrees C. The contact angles were determined through the sessile drop method, and the results were put into context through degradation testing and the characterization of the interfacial interface by Energy Dispersive X-Ray (EDX), X-Ray Diffraction (XRD) analyses, and Scanning Electron Microscopy (SEM). The lowest resistance to molten steel was observed for chamotte materials, while the highest was observed for materials based on electrofused corundum. High-manganese steel was strongly erosive to the materials tested, with the wetting angle decreasing significantly from 10 to 103 degrees with decreasing Al2O3 content (an increase of 2.4 to 59.4% corundum) in the refractories. Structural steel showed wetting angles from 103 to 127 degrees for identical refractories. These results were consistent with the average erosion depth for Mn steel (0.2-7.8 mm) and structural steel (0-2.4 mm).Web of Science1212art. no. 178

Effect of chemical composition and temperature on viscosity and structure of molten CaO-Al2O3-SiO2 system

The effects of the change of chemical composition and temperature on the viscosity of CaO-Al2O3-SiO2 oxide system with basicity from 0.78 to 1.63 were investigated in this paper. Experimental measurements of viscosity were performed with use of the high-temperature viscometer Anton Paar FRS 1600. Viscosity was measured in a rotational mode during heating at the rate of 2.2 K/min in the temperature interval from 1673 to 1873 K. Viscosity is often sensitive to the structural changes in molten oxide systems, which implies that the analysis of viscosity is an effective way to understand the structure of molten oxide systems. Exact clarification of the change of structure of the oxide system caused by increased content of CaO was performed by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and X-ray diffraction (XRD).Web of Science6042878287

Study of Choses Pyhsical-Chemical Properties of Inorganic Melts

Import 21/10/2013V širokém spektru metalurgických aplikací mají roztavené anorganické oxidické taveniny významnou roli. Oxidické systémy tvoří základ licích prášků a metalurgických strusek. Úloha těchto systému spočívá především v rafinačním působení na kov, ochraně hladiny kovu před oxidačním působením pecní atmosféry a tepelné izolace hladiny kovu. Funkce oxidických (struskových) systémů závisí na jejich fyzikálně-chemických vlastnostech, které jsou určeny především jejich složením a teplotou. Disertační práce je zaměřena na studium povrchového napětí, mezifázového napětí a viskozity roztavených anorganických, zejména oxidických systémů. Pro vlastní experimentální výzkumu těchto vybraných fyzikálně-chemických vlastností byl vybrán systém licího prášku, který z hlediska chemického složení představuje soustavu používanou v technologické praxi pro plynulé odlévání oceli. Tento systém obsahuje kromě dominantních složek, kterými jsou SiO2, CaO, Al2O3 a MgO řadu doprovodných příměsí, jako například Fe2O3, TiO2 a Na2O. K tomuto systému byly současně připraveny syntetická šestisložková soustava a ternární soustava obsahující pouze majoritně zastoupené složky v ekvivalentních poměrech původního licího prášku. Dále byly sestaveny koncentrační řady s přídavky SiO2 jak pro reálnou, tak pro syntetické soustavy. Pro experimentální výzkum mezifázového napětí na rozhraní kovová fáze/ oxidický systém, byly jako zástupce kovové fáze vybrány tři systémy na bázi železa s narůstajícím obsahem uhlíku. Pro získání experimentálních dat povrchového a mezifázového napětí byla vzhledem k relativně vysokým teplotám měření a charakteru oxidických soustav zvolena jako optimální metoda ležící kapky. Pomocí této metody byly sledovány změny teplotních koncentračních závislostí povrchového a mezifázového napětí, vytvořených koncentračních řad reálného a šestisložkového systému. Experimentální výzkum dynamické viskozity byl proveden na rotačním vysokoteplotním viskozimetru Anton Paar. Sledovány byly teplotní a koncentrační závislosti viskozity ternárního systému CaO-Al2O3-SiO2. V rámci této práce bylo dále provedeno matematické modelování povrchového napětí a viskozity. Funkčnost vybraných modelů pro výpočet těchto vlastností byla pro zjednodušení ověřována pouze na koncentrační řadě ternárního systému CaO-Al2O3-SiO2. Pro výpočet teplotní závislosti povrchového napětí byly vybrány empirický model regulárního roztoku, poloempirický model vycházející z Butlerovy rovnice a geometrický Chou model. Teplotní závislost viskozity byla vypočítána pomocí Iida modelu vycházejícího z Arrheniovy rovnice, Urbain modelu vycházejícího z Weymann-Frenkelovy rovnice a NPL modelu pracujícího na základě optické bazicity. Získané výsledky matematického modelování byly porovnávány s experimentálními daty.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.Prezenční619 - Katedra fyzikální chemie a teorie technologických pochodůvyhově

Influence of temperature and chemical composition on phase transformations of selected oxide melts

The paper deals with structural changes of solid phase of selected oxide systems during their transition into liquid state. Analyses concerned poly-component systems forming basis of casting powders for CCM mould. Industrially used oxide system with prevailing contents of CaO–Al2O3–SiO2 components and with numerous accompanying admixtures was tested. Investigation was focused on temperatures, during which individual phases disappear and precipitate, as well as on infl uence of CaO content on phase composition at selected temperatures. The experiments were realised with use of original methodology consisting of shock cooling of the tested melt in liquid nitrogen. Thus obtained samples were further investigated by X-ray diff raction phase analyses at ambient temperatures. The obtained results provide additional data on physical-chemical properties of oxide systems, such as surface tension, viscosity, sintering intervals, etc., which can be used in technological practice for appropriate lubrication eff ect of casting powders in the mould.Web of Science52330029

Registration of rheological properties of liquids by electromagnetic levitation

The presented paper is focused on possibilities of research of rheological properties of liquids with use of the device based on the principle of electromagnetic levitation. The device works on the principle of damping of the levitated body vibrations by the liquid. Levitation is ensured by feedback control of the magnetic field using an optical barrier. Vibrations are excited by controlled interruptions of electromagnetic field. Thanks to this principle it is possible to investigate the liquid of non-Newtonian character, as well as liquids susceptible to clinging on spindles of rotational viscometers. The equipment was calibrated using silicate oil standards and its performance was compared with commercially used models of viscometers Anton Paar FRS1600 (viscosity range 3 mPa s–20 Pa s, precision 0.5%, temperature range 300–1600°C) and Brookfield DV-III Ultra (viscosity range 1.4 mPa s–20 Pa s, precision 1%, temperature range 100–1600°C).Web of Science59115514

Verification of mathematical models for calculation of viscosity of molten oxide systems

The subject of this work is the comparison of numerically obtained values of dynamic viscosity using different types of mathematical models and experimentally measured data of viscosity of oxide systems. The ternary system of SiO2-CaO-Al2O3, which presents simplified base of the casting powders used in technological process, was submitted to the experiment. Experimental research of dynamic viscosity is highly limited by its complexity. That’s why model studies play such an important role in this field. For mathematic calculation of viscosity the NPL model, Iida model and Urbain model were chosen. The results of simulation were compared with the experimentally obtained values of viscosity.Web of Science53338237

Rheological Characteristics of Fe–C–Cr(Ni) Alloys

The principal objective of this project was to investigate the rheological properties of Fe–C–Cr and Fe–C–Ni-based low-alloy steels using an Anton Paar high-temperature rotational viscometer up to 1550 °C. The emphasis was placed on determining the liquidus temperatures and evaluating the flow and viscosity curves and the temperature dependence of dynamic viscosity. All were studied depending on the change in the content of chromium (0.010–4.863 wt%), nickel (0.001–4.495 wt%), and carbon (0.043–1.563 wt%). It was shown that the dynamic viscosity decreases with increasing nickel content and increases with increasing carbon and chromium content. The experimental data of the flow curves were fitted using the Herschel–Bulkley model with a good agreement between the measured and calculated values. Characterization of the internal structure was performed by SEM and EDX analyses, confirming non-significant changes in the microstructure of the original and remelted samples. The phase composition of the selected samples was also determined using JMatPro 12.0 simulation software (Sente Software Ltd., Guildford, UK)