A significant number of welding fluxes and industrial ceramics are produced in the Ukraine. The production of these materials is sufficient for both domestic needs and significant export. It is assumed that the ternary CaO-Al 2 O 3-SiO 2 system may become the basis for the development of agglomerated welding fluxes and technical ceramics. Three samples of ternary CaO-Al 2 O 3-SiO 2 system were studied by means of high-temperature X-ray diffraction above the melting point: 23.3CaO-14.7Al 2 O 3-62.0SiO 2 wt. % (sample 1, eutectic), 9.8CaO-19.8Al 2 O 3-70.4SiO 2 wt. % (sample 2, eutectic), 15.6 CaO-36.5Al 2 O 3-47.9SiO 2 wt. % (sample 3). Experimental scattering intensity curves, structure factors and the radial distribution function of atoms were obtained. The structural parameters of short-range order were calculated using melt structure models obtained by Reverse Monte Carlo method. The existence of microparticle associates of the mullite or sillimanite type immersed in the slag matrix is assumed. It is assumed that the calcium ions coordinated aroundthese associates are surrounded by oxygen melt anions. Such a structure can be considered as a colloidal solution. The microparticle of mullite is the core of the aggregate that is surrounded by calcium and oxygen ions from the molten medium.

The ceramic flux for submerged arc-surfacing with main component composition MgO (10.0 wt. %)-Al2O3 (25.0 wt. %)-SiO2 (40.0 wt. %)-CaF2 (25.0 wt. %) was prepared in a disk dryer-granulator using a sodium/potassium silicate solution as a binder. X-ray powder diffraction (XRPD) collected at r.t. identified α- phase of quartz, Al2O3, MgO and CaF2 of the initial components in the samples taken after granulation and subsequent annealing at 600 °C. In contrast to the low temperature annealing, anorthite (CaAl2Si2O8) is the main phase in the composition of the samples remelted at 1500 °C and quenched subsequently. Chemical analysis performed by means of scanning electron microscopy with energy-dispersive X-ray spectroscopy analysis (SEM/EDX) detects that the grains of the remelted samples possess the same Ca : Al : Si elemental ratio as anorthite. High temperature X-ray diffraction (HTXRD) was used to examine structural transformation in the solid at 600 °C < T < 1200 °C and stages of thermal evolution of ceramic flux were determined. The ceramic flux melts completely at the temperature above 1350 °C. The intensity pattern of the flux melt was obtained by X-ray diffraction of scattered X-rays at 1450 °C. After calculating the structure factor (SF), the radial distribution function (RDF) was evaluated and used to calculate the structural basicity of the flux melt

The expert evaluation of literature data was carried out and methods of calculation of thermodynamic properties of melts of the CaO-Al2O3 system in the whole concentration range were offered. Thermodynamic activities of aluminium oxide at 0.74 < x Al 2 O 3 < 1 were calculated from the coordinates of the liquidus line of constitution diagram of the system CaO-Al2O3, determined by different authors. Using calculation and experimental data on thermodynamic activity of Al2O3, the evaluation of thermodynamic activities of calcium oxide was carried out by integration of Gibbs-Duhem equation. It was established that they reveal great negative deviations from thermodynamic properties of perfect solutions. Basing on the established values of thermodynamic activity of calcium oxide, the liquidus line of constitution diagram of the system CaO-Al2O3 was plotted on the side of calcium oxide. The obtained values of activity of components and liquidus temperature of the system CaO-Al2O3 allow evaluating the thermodynamic properties of corresponding three-and four-component systems, predicting processes of interaction in the metal-slag-gaz system and creating new consumables for welding and electroslag remelting. 28 Ref., 2 Tables, 4 Figures.

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At Company «Zaporozhstekloflyus» the technology of two-stage melting of flux (duplex-process) was mastered, where firstly the charge is melted in separate melting unit, and then the melt is finally melted in another unit. This allowed decreasing the content of harmful impurities in melt: oxides of iron and sulphur by 2-3 times, phosphorus -by 4-6 times, and, thus, improving the flux quality. In addition, raw base for production of fused fluxes was widened that is extremely important under conditions of deterioration of raw material quality. Due to the double refining of melt of fluxes the duplex-process solved in principle the problem of utilization of slag crust, formed in submerged-arc welding. Production of fused semi-products designed for application in charge of welding consumables (covered electrodes, flux-cored wires and agglomerated fluxes) was mastered. Submerged-arc welding is the leading technological process in manufacture of large-size welded metal structures. Among four components of this process, such as welding equipment, base metal, welding wire and flux, a high quality of the latter and its welding-technological capabilities provide a user with required technical and economical characteristics of welding, and remain a decisive factor for a manufacturer of fluxes in sale of the own products.However, the traditional technologies of manufacture of welding fused fluxes, i.e. melting in open gas or electric arc furnaces can already scarcely deal with this problem. The reasons are not only in deterioration of quality of traditional raw materials and growth of requirements to the quality of welded metal structures, but also in the technologies themselves, as each transition in flux melting from one grade to another or change in quality of charge consumables determine the efficiency of flux melting furnaces, influences the life of lining, predetermine the volume of consumption of power carriers, and result, as a rule, in additional production costs.In the last years the requirements to restriction of content of harmful impurities in steels of critical welded structures were rapidly increased [1,2]. To provide the required characteristics of quality of welded joints, it is necessary to restrict the content of these impurities in fluxes. Thermodynamic analysis of pyrometallurgical processes, running in flux melting furnaces, showed complications of simultaneous decrease in sulphur and phosphorus in the melt [3].Appearance of two-stage flux melting (duplex-process) [4], at which the charge is melted at the separate melting unit and then at the second one its refining is performed, allows not only decreasing the content of oxides of iron, sulphur and phosphorus in the melt and thus improving the quality of flux, but also extending the source of raw materials for production of fused fluxes, which is extremely important under the conditions of deterioration of quality of raw materials. Besides, due to double refining of melt of fluxes the duplex process almost solved the problem of utilization of slag crust...