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The results of mineralogical-petrographic analysis of Ankerharth magnesian-dolomite refractory mixtures used in the hearths of steel-melting furnaces are described. The regularities of changes in their phase and chemical compositions are identified and the mechanism of their wear in service at the Omutninskii Metallurgical Works is considered.Refractory materials have a very significant role in ensuring reliable and safe performance of metallurgical plants and influence the quality and production cost of steel. Recently, steel-melting furnaces in the nonferrous sector have tended to grow in sizes and their service temperatures have increased; consequently, requirements imposed on the quality of melting have grown as well. Therefore, the significance of high-grade non-molded refractories has also grown, since they have to satisfy more severe operating conditions. The main properties of a refractory ramming mixture are the constancy of its volume at high temperatures, corrosion resistance, and wear resistance. Correct ramming of a furnace hearth increases the efficiency of the steel-melting furnace and extends the service life of its working chamber. Identification of negative factors affecting the service life of refractories, studying the mechanism of their wear, and selecting refractories with optimal properties remain topical issues. In this context, we have performed a comparative study of the wear mechanism of open-hearth furnace bottoms rammed by magnesian-dolomite mixtures of the Ankerharth and Jehearth grades supplied by foreign producers. The results of these studies are summarized in two papers. The first paper describes the study of the wear mechanism of Ankerharth materials produced by RHI AG (Austria) sampled after their service in furnaces at the Omutninskii Metallurgical Works.The main line of our research was studying chemical corrosion of refractories, which is one of the most significant factors influencing their resistance. The latter depends not only on the chemical and mineral composition of rammed lining and the composition of metallurgical melts, but also on the method and quality of ramming the furnace chamber and the location of refractories in the furnace hearth.The main purpose of this study was to investigate diffusion zonality arising in ramming mixtures when they react with molten metal and slag and to analyze the effect of changes in the chemical and mineralogical compositions of refractory materials in service on their resistance. To solve this problem we analyzed the chemical and phase composition, texture, and structure of samples taken from an openhearth furnace bottom before and after service correlated to different zones formed in the samples in the course of reactions between refractory materials and molten metal and slag. Our study was based on the principles of the metasomatic zonality theory developed by D. S. Korzhinskii [1] for natural processes and on our own studies of reactions between periclase-chromite refractories and nickel converter matte [2] and between mineral r...

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The results of mineralogical-petrographic analysis of Jehearth magnesian-dolomite refractory mixture used in the hearths of steel-melting furnaces are described. The variation regularities of its phase and chemical composition are identified and the mechanism of its wear in service at the metallurgical works in Russia is considered.The present study is the continuation of the preceding paper [1] and focuses on the refractory material Jehearth produced by the Slovakian Magnesite Works and used in the hearths of open-hearth furnaces at the Vyksunskii Metallurgical Works. We have also investigated the initial material, namely magnesian-dolomite mixture of grade Jehearth 30BA. Materials were studied using the methods of optical and electron microscopy, microprobe, silicate, and x-ray phase analysis described in [1]. RESULTS OF INVESTIGATION AND DISCUSSIONThe initial refractory mixture Jehearth 30 BA (sample M22) used in the post-blow zone of an open-hearth furnace has the form of a gray powder with a yellowish tint and prevailing particle size < 0.5 mm; the lateral size of 0.5 -1.5 mm is observed in less than 30% particles. Around 7% of the mixture is represented by aggregate fragments or "lumps" of rounded or slightly elongated shape and size up to 10 mm. The largest of these fragments have a flattened shape resembling shingle. Petrographic analysis identifies these fragments as a typical granoblastic structure formed by isometric periclase grains of size ranging from 0.04 to 0.2 mm with rare pores of length 0.1 mm. The periclase grains have a hexagonal section with slightly rounded angles. According to the probe analysis data, periclase contains 4% wustite component with traces of Si, Al, Mn, Ca, K, and P. The interstices contain bands of size up to 0.1 -0.3 mm identified as bicalcium silicate and a spinel-like phase whose composition is close to calcium ferrite.The chemical composition of the initial refractory differs from its specifications [2] by a higher content (within 0.5 -2 wt.%) of SiO 2 , Al 2 O 3 , and CaO and a lower content of MgO and FeO + Fe 2 O 3 (Table 1). Iron exists in the initial refractory mainly as the trivalent form. The CaO/SiO ratio found by silicate analysis is 1.7 times lower than the specifications data, due to a higher content of SiO 2 .According to the norm (Table 1) of the initial material, the quantitative ratio of its phases is as follows (mol.%): periclase 90.5, bicalcium silicate 2.1, bicalcium ferrite 5.4, and CaO 2.0.Variations occurring in refractory Jehearth 30BA in service were studied on the basis of two samples taken from different parts of the furnace hearth: from the front bank at the level of the slag belt near the middle blow zone (M34) and from the back bank (M2).Sample M34 of size 100´80´60 mm is monolithic and has a zonal structure. The sintered part of the sample, which is the remotest from the site of contact with molten metal and slag (over 55 mm), which is classified as the least altered zone 1, has a light gray color with a yellowish shade and a brecciated struc...

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