Thermal Stability of Fused Corundum

Perepelitsyn, V. A.; Kormina, I. V.; Karpets, L. A.; Zubov, A. S.

doi:10.1023/b:refr.0000029621.47335.ba

Cited by 6 publications

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“…The latter under the working conditions (usually normal oxygen partial pressure) are unstable and tend to decay and break up. This in turn leads to a complete loss of strength.One can check for the presence of filler having elevated potential energy either petrographically (from the change in refractive index) or else by using the method proposed by the Engineering Center at the Pervoural'sk Dinas Plant Company [2].We compared the thermal properties of several species of fused high-alumina filler as regards thermal resistance and loss of strength after thermal loading. The fillers were sieved and washed from specimens supplied by metallurgical organizations in the Ural as dry concrete mixtures or else specimens received from producers as lump material of grain size 30 -100 mm.…”

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confidence: 99%

“…One can check for the presence of filler having elevated potential energy either petrographically (from the change in refractive index) or else by using the method proposed by the Engineering Center at the Pervoural'sk Dinas Plant Company [2].…”

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“…The thermal resistance was determined by the method described in [2]. The grain strength before and after heating was estimated in accordance with GOST 8269.0 -97 "Stone rubble and grits from hard rocks and industrial products wastes from building work.…”

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A study of coarse refractory filling

Kashcheev¹,

Zemlyanoi²

2009

Refract Ind Ceram

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A study has been made on the role of the coarse-filler strength characteristics in refractory materials. Measurements have been made on the mechanical properties of several fillers (corundum, and spinel), and the effects of heat treatment on the mechanical properties.Much attention is being given to the matrix part of refractory materials and items, which are finely ground components producing a continuous medium. It is correctly considered that this determines virtually all the basic working characteristics: strength, creep, porosity, thermal resistance, corrosion resistance, and so on. However, one should not forget the role of the granular filler. Coarse dense filler produces a framework in the item or the material that substantially influences the compressive strength and the thermal resistance of the item or lining, while having less effect on the rheological properties: pressability, mobility, and water uptake of the concrete mixture. The medium-grained and fine-grained filler on the other hand has a considerable effect on the rheological behavior and has less effect on the strength (within some best limits).It is considered a priori that the use of a granular filler (sintered or melted) in producing a refractory has the maximum possible best effects on the properties such as the strength, porosity, and so on, and shows least changes during the operation of the refractory. On the other hand, resistance measurements made on various refractory materials and items in the last 3 -5 years have led to an increasing frequency of premature failure because of inadequate strength and heat resistance of the coarse melted filler. This applies not only to items (in particular, periclase-carbon items for lining ferrous metallurgy converters) and to concrete-type materials (for lining channels in blast furnaces, or a working and reinforcement lining of steel-pouring ladles, and so on).A feature common to all cases of premature failure lies in the state of the coarse filler. On the one hand, it completely corresponds to the requirements as regards chemical and grain-size compositions, while on the other hand, in the preparation of specimens for petrographic examination (surface polishing) the filler grains have elevated brittleness (the grains break in polishing), which indicates that the grains have excess energy, which during service is consumed as a rule in failure of the grains, i.e., during the service of the item or material, there may be fracturing of the grains with subsequent impregnation of the lining by liquid directly in the filler grains, but not in the matrix.Excess potential energy arises in the grains of coarse fused filler, which may evidently occur during cooling of the molten material (too rapid forced cooling [1]) or melting in a reducing medium in a melting system, which favors transition of impurity transitional oxides into a reduced state and predetermines the volume changes in the filler grains under oxidizing conditions.Reductive melting at a reduced oxygen partial pressure causes the material to a...

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A study of coarse refractory filling

Kashcheev¹,

Zemlyanoi²

2009

Refract Ind Ceram

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“…Petrography is used in the enterprise to monitor carefully the chemical composition and structure of melted refractory materials, and their thermal stability is determined by an original plant procedure on samples of crushed grit [1].…”

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Production of melted refractory materials in joint stock company (OAO) Dinur

Gorokhovskii¹,

Karpets²,

Perepelitsyn³

et al. 2007

Refract Ind Ceram

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Information is provided about melted refractory materials described by the system MgO-Al 2 O 3 -SiO 2 whose large series production is organized in the OAO Pervoural Dinas Brick Plant. Characteristics are given for the material composition and properties of melted white corundum, alloyed corundum, spinels and silica glass.Currently in all technically developed countries and in Russia production of highly wear-resistant oxide-carbonaceous refractories is based on using high quality synthetic and enriched natural mineral starting material. Artificial refractory starting materials are obtained by three main methods: chemical, solid-phase high-temperature sintering and melting. Inorganic products of chemical synthesis [1 -5] have the dispersed size of crystals (from fractions to several microns) and a developed specific surface. The size of crystals in sintered materials is as a rule two to three orders of magnitude larger than that of similar products of chemical synthesis. Melted materials are characterized by a coarsely crystalline structure (apart from glassy silica) with a crystal size from fractions to several centimetres, i.e. exceeding sintered sizes by two to three orders of magnitude, and with low porosity.It is well known that about 60 -70% of refractories in service fail as a result of chemical reaction with liquid, gaseous, and solid substances. Since the rate of dissolution, evaporation and chemical reaction of refractories with corrosive media is inversely proportional to the crystal size, the most corrosion-resistant are dense coarsely crystalline melted materials. On the basis of many comparative industrial tests in service it has been established that the corrosion resistance of melted materials is higher by 30 -60% than for sintered materials.In accordance with the development program a plant in OAO Dinur is carrying out continuous expansion of the range and an increase in the volume of output for contemporary refractories using melted materials of in-house production. In OAO Pervoural Dinas Brick Plant physicochemical bases have been developed for the technology and commercial production has been organized for a whole series of melted refractory materials of the system MgO-Al 2 O 3 -SiO 2 ( Table 1).Production of silica glass is carried out in plasma reactors PR-420 by the method of oxidation melting in a unit. Starting materials for the production are enriched silica sand, that is fed into the high-temperature chamber, where under the

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“…όπου V i και V f είναι ο όγκος των δειγμάτων πριν και μετά την έψηση, αντιστοίχως. Παρατηρείται ότι για το βωξίτη η κυρίαρχη φάση είναι το α-κορούνδιο, ένα ορυκτό οξείδιο το οποίο εμφανίζει μεγάλη σκληρότητα και είναι ιδιαίτερα σταθερό σε θερμοκρασιακές μεταβολές [84]. Το κορούνδιο αποκτά αυτή την κρυσταλλική δομή μετά από τη διάσπαση συνήθως του γκιψίτη, Al(OH) 3 , και του βοεμίτη, γ-AlO(OH), ορυκτά που περιέχονται στην πρώτη ύλη του βωξίτη πριν αυτός υποστεί την πρώτη θερμική κατεργασία, μετά την παραλαβή του από το αντίστοιχο πέτρωμα.…”

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Thermal Stability of Fused Corundum

Cited by 6 publications

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A study of coarse refractory filling

A study of coarse refractory filling

Production of melted refractory materials in joint stock company (OAO) Dinur

Επίδραση Των Συνθηκών Παραγωγής Στις Ιδιότητες Πυρίμαχων Υλικών

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