Reaction of periclase-spinel refractories with oxygen-converter slags

Conclusions Chemical and petrographical studies showed that the zonal structure of periclase-spinel refractories formed during service in converters is a result of the active reaction between refractories and slag. In the working zone of the brick we detected a number of new mineral compounds, the most fusible of which are calcium oxychromite and eutectic mixtures of calcium oxychromites and calcium silicates.Translated from Ogneupory, No.6, pp. 28–32, June, 1970.     

High-temperature abrasion of refractories

Conclusions The most rapid abrasion in dinas refractories occurs in the 700–900°C range; periclase 800–1000°C; mullite-corundum articles exhibit a smooth increase in abrasion with rise in temperature. The abrasion of refractory concretes is much higher than for bricks.It is possible by determining the abrasion resistance to carry out quality control of the firing process, and also to check the quality of linings made from concretes.Translated from Ogneupory, No. 1, pp. 13–14, January, 1991.     

Destructive mechanism for periclase-spinel and magnesite-chromite refractories in oxygen converter linings

Conclusions The greatest wear of magnesite-chrome and periclase-spinel linings was observed in the cylindrical part of the converter in the places showing intense movement of metal and slag and maximum heat load. In these sections of the structure we get a predominant erosion by fusion, but the share of the erosion due to scaling is substantial.In the throat, wear of the lining occurs mainly due to scaling as a result of frequent changes in temperature and air.The wear of the lining of the bottom is slight compared with sections located above and takes place mainly as a result of erosion developed during intensive movement of the metal in the blow period.PS refractories are more resistant in the linings of the converter than MC refractories, which is explained by the difference in the mechanism of their wear.To increase the resistance of refractories PS against the action of converter slags it is necessary to make them from enriched chromitic ores and magnesite with the use of high-temperature firing, which will ensure better development of the direct bond of the grains of periclase with the chrome-spinel and more complete mineral formation (with maximum yield of secondary spinel).Translated from Ogneupory, No. 1, pp.32–38, January, 1967.     

High-temperature fatigue of magnesia refractories

Conclusions A study was made of the fatigue of refractory MKhS and PShS at high temperatures. From the test results fatigue curves were constructed. It was found that with a reduction in the maximum stress there is an increase in the durability of the refractories.To characterize the refractories with respect to the fatigue curve it is desirable to determine the tentative limiting fatigue which in this case at 1000 cycles for refractories MKhS equals 0.44–0.68 of _comp. With an increase in the test temperature both the absolute and the relative limits of fatigue are reduced. The fatigue test results show that to increase the cyclic durability of refractory products it in necessary to reduce the acting cyclic stress. The data obtained enable us to predict the resistance of products working in conditions of controlled high temperatures and cyclic loading.Translated from Ogneupory, No. 8, pp. 51–54, August, 1972.     

Some results of the installation of a technology for periclase-spinel refractories

The characteristics of periclase-spinel refractories and mixtures with an additive of synthesized spinel produced by the Magnezit Company are presented. The best refractories are produced from spinel synthesized by block melting and casting into molds and by sintering caustic magnesite and aluminum-containing slag. The possibility of manufacturing spinel-containing mixtures using waste periclase-spinel refractories is considered. Replacement of part of the mixture by a spinel-containing material improves considerably the physicomechanical parameters of the mixture.Translated from Ogneupory i Tekhnicheskaya Keramika, No. 9, pp. 31 – 33, September, 1996.     

Wear of high-fired periclase-spinel refractories in the roof of a double-bath steel-melting furnace

Conclusions Periclase-spinel products prepared from magnesite powders which are pure in chemical composition and beneficiated Kempirsaisk chromite possess an increased resistance (30% higher than in ordinary periclase-spinel brick) during service in the roof of a double-bath steel-melting furnace, operating with oxygen blow in the bath. Their wear in general occurs as a result of the fusion of the working surface. The mechanism of this wear is explained by the metasomatic processes which lead almost to complete replacement of the periclase and chrome-spinel by ferritic spinels.The increase in the resistance of the experimental periclase—spinel refractories is helped by the structure with the direct bond between the grains which retards the access of silicates and slags inside the textural elements. This exerts a favorable influence on the change in structure of the refractory during service, especially in the transition zone in which additional sintering and crack formation leading to scaling of the experimental refractory hardly develops.On the basis of the results of the research we recommend that refractory enterprises set up various technological production lines for making periclase-spinel products from pure Satkinsk magnesite powders (94–96% magnesium oxide) and beneficiated Kempirsaisk chromite (59–60% chromium oxide) using high-temperature firing in a tunnel klin. The use of high fired periclase-spinel products with a direct bond between the grains would increase the resistance of the roofs of metallurgical furnaces operating with the use of oxygen and increasing their outputs.Translated from Ogneupory, No. 5, pp. 28–33, May, 1973.     

Effect of some technical factors on the spalling resistance of periclase-spinel refractories

Conclusions The thermal-shock resistance (spalling resistance) of periclase-spinel refractories increases 1.6–2.0 times when the chromite and finely milled magnesite are added separately to the batch. The main technical factor leading to an increase in the stable spalling resistance of the products is the application of a layer of ground chromite to the coarse grained part of the magnesite in the batch and its bonding. The strength and apparent density of the articles under these conditions are somewhat diminished, and there is roughly a 1% increase in porosity.The increased spalling resistance of periclase-spinel refractories when the chromite is added separately to the batch is due to the formation of a special submicrocracked structure, ensuring a reduction in the thermal expansion and elastic characteristics, an increase in the deformation prior to destruction (/E) and a damping decrement () of the material, and restriction and retarding of the rate of capillary liquid suction by the products.Translated from Ogneupory, No. 5, pp. 31–39, May, 1968.     

含ZrO2添加剂对方镁石-尖晶石耐火材料力学性能的影响

在方镁石 -尖晶石耐火材料中 ,加入三种不同类型的含ZrO2 添加剂 ,均能明显提高材料的力学性能。经XRD、偏光显微镜及电子探针分析 ,认为改善性能的机理在于 :引入ZrO2 改善了材料的显微组织结构 ,并产生了适量微裂纹 ,强化了基质 ,从而提高了材料的力学性能     

Wear of periclase-spinel refractories in the roof of a 900-ton open-hearth furnace

Conclusions The wear of the roof of a 900-ton open-hearth furnace working with oxygen blow in the bath occurs mainly by scaling.Splashing of the slag falling on the roof accelerates mass-exchange between the bath and the roof as a result of which the period of forming the zonal structure in the roof refractories is reduced. Raising the roof by 500 mm and increasing the central angle of the roof by up to 95° contributes to an increase in the service life of the roof without markedly impairing the furnace operation.Translated from Ogneupory, No.6, pp. 25–28, June, 1970.     

含ZrO2添加剂对方镁石-尖晶石耐火材料力学性能的影响

在方镁石-尖晶石耐火材料中,加入三种不同类型的含ZrO2添加剂,均能明显提高材料的力学性能。经XBD、偏光显微镜及电子探针分析,认为改善性能的机理在于引入ZrO2改善了材料的显微组织结构,并产生了适量微裂纹,强化了基质,从而提高了材料的力学性能。     

Phase relationships and properties of the phase composition periclase-spinel

Conclusions We investigated the phase composition and properties of the compositions periclase-spinel bond in the system MgO-Mg (Al_1–xCr_x)₂O₄, where x=0–1, using spinel-phase concentrations of from 5 to 30% by weight.The essential feature of the phase inversions consists in the development and decomposition of solid solutions of spinel constituent in the periclase. With an increase in the content of magnesiochromite in the spinels, their absorption by the periclase increases. After cooling, the concentration of spinel phase in the solid solution with the periclase is about 5%.An increase in the concentration of the spinel phase from 5 to 30%, and also change in its composition in the direction from magnesio-alumina spinel to magnesiochromite (x1) impairs the thermalshock resistance, strength and porosity.To improve the properties of magnesite articles, it is desirable to use 5–15% by weight of magnesio-alumina spinel as the bond, or chromitic ore, the spinel of which contains a large quantity of magnesia-alumina constituent (MgAl₂O₄).Translated from Ogneupory, No. 5, pp. 42–50, May, 1967.     

Effect of reaction of periclase and iron-chrome spinel on the properties of periclase-spinel refractories

Conclusions Using a typical composition of the type MgO-Mg(Al_1–x–yCr_xFe_y)₂O₄ a study was made of the effect of the processes involved in the processing and decomposition of solid solutions of periclase and spinels on the technical properties of the fired products.During cooling from 1600–1750°C decomposition occurs in the solid solutions of periclase and spinel; the crystals of spinel separating under these conditions are able to grow to large sizes which inevitably should lead to the development of stresses inside the periclase grains.The decomposition of the solid solution of periclase and spinel adversely affects the strength and thermal-shock resistance of the fired specimens.The best technical properties are possessed by combinations of periclase with small (up to 15%) quantities of high-alumina (x=0.16 and 0.46) spinels.The use of compositions of periclase with high-alumina spinels of the type x=0.16 and 0.46 enables us to obtain denser and more thermal-shock resistant refractories.Translated from Ogneupory, No.6, pp. 44–47, June, 1970.     

The phase conversions and properties of refractories based on the MgO-Al2O3-Cr2O3system

Conclusions An investigation of the phase conversions in the MgO-Al₂O₃-Cr₂O₃ system at a below-unity ratio MgO/R₂O₃ and varied content of sesquioxides showed that the magnesiochromite initially being formed in all mixtures interacts with the Al₂O₃ at temperatures above 1000°C with the result that two kinds of solid solutions are formed, viz., a spinel one Mg(Cr_xAl)_1–x)₂O₄ and (Al_xCr_1–x)₂O₃. The predominance of a given component in the original composition remains preserved in both phases.The presence was established of a solid solution of Al₂O₃ in the spinel phase which contained a signficant amount of MgAl₂O₄. No solid solutions of R₂O₃ are formed in the spinel when the chromite component predominates in both phases.The changes in the properties of the specimens correspond to the phase conversions. After high-temperature firing materials of the type Mg(Al, Cr)₂O₄-(Al, Cr)₂O₃ possess adequate property indices.The analysis is concerned with that part of the system for which MgO/(Al₂O₃ + Cr₂O₃) is less than unity.Translated from Ogneupory, No. 8, pp. 48–53, August, 1976.     

High-temperature tunnel furnace for drying and firing spinel-containing refractories

The participants of the development, construction, and start-up of a tunnel furnace are mentioned. The concept of a tunnel furnace as a thermotechnological complex is defined, where the main component is the drying-and-firing chamber acting as a reactor in product treatment. The design of the drying-and-firing chamber and the furnace in general is described. Design parameters and data on the industrial performance of the furnace in drying and firing spinel-containing refractories are given. __________ Translated from Novye Ogneupory, No. 8, pp. 25–28, August, 2006.