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<p> </p><p><span style="font-family: Times New Roman; font-size: small;">MgO-C based refractory materials are used in steel metallurgy to a large extent. Magnesia-carbon bricks are tested for basic physical-mechanical parameters in as supplied state, for carbon content, and chemical analysis of magnesium component. According to the type of their usage, they are subjected to tests at higher temperatures, carbonization firing, and after firing, the physical-mechanical parameters are determined at specified temperatures. One of the most tested properties of these materials is their resistance to oxidation. The methodology for such testing is not yet defined in ISO, EN and ASTM test procedures, therefore the methodology used in other countries is being applied. In conditions of U. S. Steel, Košice, s.r.o., the MgO-C bricks intended for the working lining of slag zones of steel ladles are tested by oxidation resistance test (oxidizing area procedure). </span><span style="font-family: Times New Roman; font-size: small;">The described test method was developed at U. S. Steel Research and Technology Center in Munhall and has been used for more than 15 years to evaluate various carbon containing bricks. Test specimens in the shape of a cube are heated in an oxidizing atmosphere to a temperature of 1482</span><span style="font-family: Times New Roman; font-size: small;">°C with holding time of 5 hours. After cutting of the test specimens, the percentage of oxidized area is calculated. This test is used for selecting the appropriate type of lining material for the working lining of slag zone of the steel ladle in the steelmaking secondary metallurgy process and for the building of database of different types of MgO-C bricks.</span></p><p> </p>

The presented paper is oriented to the processing of the results obtained from the measurement of the physical and chemical properties of the synthetic melts of the system FeO-SiO 2 -Fe 2 O 3 . On the basis of these results and knowledge obtained from the literature, we present an image of these melt structures. The structure of the system FeO-SiO 2 -Fe 2 O 3 may be characterized as an amorphous solidified melt. The basic structural component of such sets is the chemical compound fayalite (2FeO • SiO 2 ), which is ionized in cation Fe 2+ and anion complex SiO 4 4-. In the course of melting, the components are ionized, and formed are simple cations (e.g., Fe 2+ , FeO + , and Fe 3+ ), anion complexes (e.g., SiO 4 4-, FeO 2 -, Fe 2 O 5 4-, SiFeO 7 7-, FeO 3 3-, etc.) and, clusters, the composition of which corresponds to the present chemical components (for example: wu ¨stite, magnetite, fayalite). Tetrahedral SiO 4 4is a principal structural unit of the silicate melts. When increasing its content in the system, polymerization occurs with the formation of more complex anions (e.g., Si 2 O 7 6-, Si 3 O 10 8-, Si 3 O 9 6-, Si 2 O 6 4-, etc.). Knowledge about the non-negligible effect of iron upon the properties of these melts was obtained from analysis of the physical and chemical properties of the fayalite melt. Ferrous oxide behaves in these systems as the donor of the oxygen anions. The gradual transfer of the ferrite-oxygen complexes from tetrahedral to octahedral co-ordination depends on the reduction in the number of oxygen anions in the system. Existence of the individual ferrito-oxygen and silico-oxygen complexes is reflected in the physical properties of the fayalite melts.

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The aim of this study was to realize and evaluate laboratory corrosion tests for a solution of problems such as wear of refractory materials at processing of aluminum, for example. The static crucible corrosion tests were carried out in laboratory resistive furnace at 850 °C during 2 h air atmosphere. Two standards of alumina-silica shaped refractory bricks were used as a corroding material. Pure sodium chloride and potassium chloride were applied as a corrosive media. The results of tests were evaluated by macroscopic, microscopic, chemical and semiquantitative EDX analysis. Sodium chloride shows more significant penetration and chemical interaction in penetrated area. EDX analysis confirms creation of the reaction layer between chlorides and elements of refractory lining. The products of reactions penetrate more deeply into A lining. K ions penetrate into the grains of the lining more intense than Na ions.

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