Periclase-spinel refractories from beneficiated materials

Conclusions Magnesite and magnesite-chromite powders obtained on the basis of beneficiated Satkinsk magnesite using the flotation method can be employed for making periclase-spinel refractories similar in quality to products of grade PShSO and PShSP. For such refractories there is typically an increased refractoriness under load of 2 kg/cm², which on average equals 1640–1670°C.The periclase-spinel products made from beneficiated materials contain 4–5% silicates instead of 8–12% in the refractories obtained from ordinary powders. In the high-temperature fired periclase-spinel refractories made from beneficiated materials we note the formation of high-quality structures containing about 50% direct intergranular bonds between the highly refractory minerals. In the structural elements of such refractories there is a predominance of intergranular bond of the type periclase-secondary spinel-periclase.Translated from Ogneupory, No. 2, pp. 10–14, February, 1973.     

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.     

Improved technology for producing certain magnesite refractories and a statistical method for evaluating their properties

Conclusions As a result of improving the technology for manufacturing certain magnesite refractories we improved their quality and reduced the loss. Comparatively good qualitative factors and enhanced wear resistance in service are possessed by roof products made by a combined periclase-spinel and magnesite-chromite technology, incorporating in the batch both granular chromite and chromite milled together with magnesite powder.The comparatively low loss and the excellent property factors are typical for steel casting nozzles made on the basis of magnesite powder obtained by burning magnesite in shaft furnaces. Mathematical statistical techniques were used to determine the distribution and mutual relationships between the property factors of some magnesite products. The marked mutual relationship between the quality factors indicates the possibility of using statistical methods for evaluating some properties of these products.Translated from Ogneupory, No. 5, pp. 8–14, May, 1973.     

Periclase —spinel products from magnesite powder with high alumina content

Conclusions Periclase-spinel articles with low contents of chromite made from magnesite powder containing magnesia-alumina spinel have a high range of physicochemical properties (except spalling resistance) and completely satisfy the requirements in service for the roofs of open-hearth and walls of electric steel-melting furnaces.With an increase in the content of magnesite in the fine constituent, it is possible to obtain products of the same quality from magnesite powder with a high porosity (up to 20–23%).The change in ratio of chrome spinel and magnesia-aluminous spinel in the periclase-spinel articles toward a certain increase in the latter is worthy of attention and requires further investigation.Translated from Ogneupory, No. 2, pp. 11–15, February, 1966.     

Slag and hot-slag resistance of basic refractories

Conclusions Using the instrument described, which has been improved in design for testing refractory materials for slag and hot slag resistance, we investigated the properties of magnesite, magnesite-chromite, and chrome-magnesite specimens. It was established that their life is determined by the resistance of the refractory bond. The best resistance is possessed by periclase-spinel specimens. An increase in the content of calcium oxide in the slags reduces the slag resistance of all periclase-spinel refractories that were tested. Impregnating the magnesite products with a saturated solution of chromium acetate and firing them after impregnation at 400–500°C markedly increases their slag resistance.Translated from Ogneupory, No. 7, pp. 47–52, July, 1968.     

Production technology of high-density periclase-spinel roof materials

Conclusions High-density periclase-spinel refractories can be produced from a body of magnesite powder containing 94–96% magnesium oxide and Kempirsai chromite by high-pressure molding and high-temperature firing in a tunnel kiln. The product is strong with good thermal stability and high onset temperature of deformation under a load. The structure of the refractory is improved as a result of the formation of a large proportion of direct intergranular bonds between the periclase and spinel.It is planned to produce experimental industrial-scale batches of periclase-spinel roof refractories and to subject them to trials in the roof of open-hearth furnaces in continuous operation.Translated from Ogneupory, No. 8, pp. 39–44, August, 1973.     

Testing porous periclase — Spinel products in the lining of a rotary kiln burning magnesite

Conclusions The life of porous periclase-spinel products in the most badly worn section of the sintering zones of rotary kilns used for firing caustic dust is 50–100% greater than the average life of the lining in this zone made from chrome-magnesite and magnesite-chromite products.The increased wear resistance of the experimental periclase-spinel products is probably explained by the reduction in the rates of zone formation owing to the features of the phase composition and the structure of the refractories, and also the appreciable strength and comparatively low thermal conductivity.It is desirable to use perous periclase-spinel products for lining the sintering zones of rotary kilns used for firing magnesite, mainly in the most badly worn sections having a temporary fused area (skin).Translated from Ogneupory, No. 1, pp. 30–35, January, 1973.     

Periglase-spinel refractories based on magnesite powder from caustic dust

Conclusions Periclase-spinel products in whose batch ordinary magnesite powder of fractions 3-1 mm is replaced with powder of the same fraction but obtained by burning caustic magnesite without sintering additives are satisfactory as regards all factors except thermal-shock resistance, and meet the requirements of GOST 10888-64.The resistance and wear of the experimental periclase-spinel products in the roof of an open-hearth furnace are about the same as for ordinary roof magnesite-chromite refractories.Translated from Ogneupory, No.5, pp. 12–13, May, 1970.     

Service of chrome — Forsterite products in the vertical channels and roofs of slaggers and regenerators of open-hearth furnaces

Conclusions Following industrial testing of thermal-shock resistant chrome -forsterite refractories in 400 ton open-hearth furnaces we established that it is possible to use them completely for replacing magnesite — chromite products in the roofs of slaggers and regenerators, and chrome — magnesite products in the structure of vertical channels.The use of chrome-forsterite products in the structure of the roofs and the walls of the lower structure of open-hearth furnaces would reduce the consumption of magnesite — chromite and chrome — magnesite products and have a substantial saving effect.Translated from Ogneupory, No. 2, pp. 22–31, February, 1970.     

Production and service-testing of refractories based on flotation-concentrated magnesite

Conclusions Flotation-concentrated magnesite and pure and concentrated chromite were used for producing high-temperature fired magnesite, magnesite-chromite, and periclase-spinel refractories which, compared with ordinary types, contained less silicates and, more direct bonds between the high-refractoriness minerals so that their refractoriness under a load and their thermal strength were higher.In the lining of 100-ton converters for steel, the durability of the experimental magnesite refractory produced from concentrated magnesite and tar-impregnated was 19% better than that of ordinary tarbonded magnesite brick.In the lining of the tuyere zone and of the zone above it in 20-ton and 30-ton converters for copper and nickel, the durability of the experimental magnesite-chromite and periclase-spinel refractories produced from concentrated magnesite and concentrated and pure chromite was 30–35% better than that of ordinary MKhS and PShS type refractories.Translated from Ogneupory, No. 1, pp. 11–15, January, 1976.     

The effect of additives,fineness and firing temperature on the sintering of caustic magnesite

Summary Caustic dust obtained by calcining magnesite in rotary or shaft furnaces working with mazut sinters much more weakly than that obtained by calcining with coal dust. Increasing the temperature of calcination from 1600 to 1700° C is inadequate for a marked improvement in the sintering of the dust.Sintering can be strengthened by dispersing the dust very thoroughly or by making sintering additions.Oxides of iron effectively influence the sintering of caustic dust obtained in furnaces with coal heating, and very slightly affect sintering of dust obtained from oil-fired furnaces.There is a substantial increase in the sintering of dust from furnaces heated with oil with the addition of commercial titania, titano-magnetite concentrate or titano-alumina slag.It is most effective to add titano-alumina slag in amounts of 7–9% as a densifying agent.The addition of titano-alumina slag may be one of the ways of densifying magnesite powders during the calcination of caustic dust with the sludge process or by means of preliminary briquetting it (before burning).The microstructure of the specimens of caustic dust proves the effectiveness of titanium additions on the recrystallization of periclase and reducing the number and sizes of the pores.     

Magnesite-chromite products from high purity magnesite and chromite

Conclusions Products made from magnesite and chromite with low-impurity oxide concentrations possess better thermal factors than ordinary periclase-spinel refractories: refractoriness under load: 1700°C and above; bending strength at 1300°C 2.5–3 times greater; deformation 3–4 times; and the rate of deformation at steady-state creep is about a half.The periclase-spinel products with low quantities of impurities have an increased thermal-shock resistance, which is achieved by adding small quantities of chromite to the granular part of the batch in combination with the additions made to the dispersed constituent.The products develop a direct bond between the crystals of periclase, i. e., periclase-spinel, in which two types of direct bond exist between the periclase and the spinels: the contact between crystal and crystal, and the contacts in the form of shells and edgings of spinels around the crystals of periclase. In the latter case, the development of a direct bond between the crystals is more complete which is contributed to by the replacement in the silicate part of monticellite by dicalcium silicate.Translated from Ogneupory, No. 2, pp. 32–37, February, 1971.     

Lining steel tapping apertures of oxygen converters

Conclusions The use of blocks for lining steel discharge apertures substantially reduces the number of repairs, and cuts their work content.The resistance of periclase-spinel blocks and blocks made from brine magnesia is 80–81 heats.The maximum resistance (132 heats) was achieved by using blocks made from fused magnesite.Translated from Ogneupory, No. 7, pp. 5–9, July, 1970.     

Firing caustic magnesite dust

Conclusions Six experimental batches of magnesite powder were obtained for preparing magnesia products by firing caustic dust in a rotary furnace. To improve the sintering, chromite or titanomagnetite was added to the dust. The final conclusions on the optimum cycle for the production of dense magnesite powders from caustic dust will be made after we have obtained data on the stability in service of products made from these powders.Translated from Ogneupory, No.2, pp.5–14, February, 1967.     

Magnesia roof refractories with fused spinel in the batch

Conclusions Dense highly fired roof refractories based on sintered magnesite powder and electrofused aluminomagnesia spinel are characterized by high volume constancy and a 30–50% lower wear compared with ordinary periclase — spinel products in comparative tests in the roofs of 600 ton open-hearth furnaces working with the use of oxygen.The wear of magnesite — spinel refractories containing 20, 30, and 40% electrofused spinel in the batch during service in the roofs of open-hearth furnaces occurs by fusion.Translated from Ogneupory, No. 1, pp. 24–28, January, 1971.     

Effect of the properties of magnesite powders on the quality of spinel-bonded magnesite products

Conclusions Magnesite powders have different chemical compositions, density, and structures.The properties of magnesite powders substantially affect the factors, particularly thermal shock resistance, (spalling resistance) of magnesite powders with a spinel bond.The production of highly thermal shock resistant products is governed by the formation of a heterogeneous and irregular crystalline microstructure in the products which is guaranteed by the use in them of granular constituent, chemically pure, dense, strong, and inert (with respect to secondary recrystallization) magnesite powders.The chief structural features of magnesite products based on spinel bonds can be evaluated as a first approximation by the coefficient of irregular granularity and the secondary recrystallization of periclase.Translated from Ogneupory, No. 7, pp. 9–15, July, 1969.     

Dynamic method for determining the coefficient of transverse deformation of refractories at high temperatures

Conclusions We developed a direct dynamic method and constructed apparatus for determining the coefficient of transverse deformation of refractory materials.We studied the temperature dependence of the coefficient of transverse deformation of magnesite, dinas, periclase-spinel and high-alumina refractories.Translated from Ogneupory, No. 7, pp. 47–50, July, 1969.     

Laboratory-scale technological studies on periclase refractories

Conclusions Laboratory-scale technological studies were carried out for developing the technology of periclase products based on different magnesite powders. Our studies showed the possibility of producing periclase refractories meeting the property specifications of GOST 4689-74 from certain imported powders.Translated from Ogneupory, No. 7, pp. 13–16, July, 1988.     

Dead burning magnesite in shaft furnaces with natural gas

Conclusions The dead burning of raw magnesite in pieces of 40–250 mm size has been achieved in shaft furnaces heated by natural gas. The quality of the burned magnesite and the economics of the furnace working were improved in comparison with those obtained when using fuel oil.Translated from Ogneupory, No. 3, pp. 16–18, March, 1969.     

Effect of composition of metallurgical powder on the slopes and hearths of electric arc furnaces

Summary To reduce the sliding of fettling powders from the slopes of electric furnaces, it is desirable to use powders with not more than 10% of the fraction finer than 0.088 mm, and the SiO₂ content should be about 4.5–6%. Addition to the magnesite powder of coarse dolomite fraction 15-0.5 mm, and also 6–7% coal tar pitch, reduces the mobility of the powders.The rational composition of metallurgical powders used for fettling slopes and hearths of electric arc furnaces largely depends on the grade of steel being melted.The increase in the life of the slopes and hearths of an electric furnace in which stainless steel was being melted, fettled with MPMZ powder, was due to the increase in the content of periclase bonded with melilite and mervinite in the slopes and melilite and forsterite in the hearths.During the melting of steel of changing sorts, the increase in the life of the slopes and hearths, fettling with magnesite-dolomite powders is due to the presence of crystals of periclase bonded mainly with highly refractory dicalcium silicate.When fettling is done with MPMZ powder the structure of the slopes and hearths is identical. The use of chromemagnesite, magnesite-chromite and magnesite-dolomite powders give rise to the formation of a heterogeneous structure in the slopes and hearths which leads to their irregular wearing away.To prolong the service of the hearths and slopes of electric furnaces it is necessary to continue investigating the wear resistance of fettling materials in furnaces of different capacities, where steels of different types are being melted, typifying the life of the powders by the consumption per ton of steel melted, the burn-out profile of the lining, the interrepair periods and other factors.