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.     

Sighting tubes for temperature measurements in open-hearth roofs

Conclusions Service tests of sighting tubes made from corundum and magnesia spinel showed that a gas permeability of 0.0009–0.00006 liter·m/m²·h·mm water guarantees the measurement of temperature with optical pyrometers without interference from the gaseous atmosphere.The maximum life of sighting tubes placed in the roof of open-hearth furnaces is obtained only when the articles are fixed at a distance not exceeding 40–50 mm in front of the roof surface; the minimum life is possessed by those products protruding into the furnace space by a magnitude equal to 3 diameters. The greatest resistance is shown by articles made from magnesia spinel.The sighting spinel, thin-walled tubes can be used for short control temperature checks of the roof of open-hearth furnaces; corundum and spinel tubes can be used for automatic measurements of temperatures in periodic kilns for firing refractories.Translated from Ogneupory No. 6, pp. 7–10, June, 1968.     

The wear of magnesia refractories in electric furnaces for melting cast iron

Conclusions The wear of magnesia refractories, i. e., magnesite, perictase — spinel, and magnesite — chromite bricks and magnesite — phosphate mortar, in the walls of electric furnaces for melting cast iron is the result of the solution predominantly of the periclase crystals and to a lesser extent of the spinel in the lowbasicity ferrosilicate slag melt. Brick of the PShS type proved to be the most durable refractory. The use of high-alumina brick in the roof of the furnaces accelerates the wear of the magnesia bricks in the walls.To increase the durability of the lining of these furnaces trials should be carried out with an all-basic wall lining constructed of high-density PShSP-type brick on MF-1-type magnesite — phosphate mortar and a roof lining constructed of MKhS brick and the same mortar.Translated from Ogneupory, No. 4, pp. 44–49, April, 1976.     

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.     

Refractories of a fused periclase-chromite material for the wall lining of 100-ton arc furnaces

Conclusions The durability of a wall lining in 100-ton arc furnaces of MKhVP type refractories based on fused periclase—chromite material is 20–30% higher than that of a lining constructed of periclase—spinel brick produced from sintered magnesite and chromite ore.The chemical inertness, high resistance to attack by corrosive media, and the low content of low-melting silicates in the MKhVP refractories ensure that the rate of zone formation in the bricks is slow and the durability of the lining high.Bricks of fused periclase—chromite can be recommended as refractories for the wall lining of the arc furnaces of the Oskolsk Metallurgical Combine now being constructed.These refractories should also be subjected to testing in the roof lining of arc furnaces.Translated from Ogneupory, No. 7, pp. 26–30, July, 1978.     

Obtaining fused magnesia-alumina spinel and using it to produce magnesite-spinel roof refractories

Conclusions A method was developed for producing fused spinel which, when used in place of chromite as a component of the charge for basic refractories, yields roof products characterized by enhanced refractoriness under load, and also by low creep at elevated temperatures. This ensures high factors for the other properties. The preliminary testing of the refractories in the roofs of electric-steel melting furnaces demonstrated an increase in their wear resistance by 26–33% compared with the resistance of the currently supplied periclase-spinel refractories, which are used normally in these conditions.Translated from Ogneupory, No. 4, pp. 12–17, April, 1973.     

Highly spalling resistant periclase-spinel brick (A Discussion)

Conclusions We established in principle the possibility of manufacturing in production conditions roof periclasespinel brick with a high spalling resistance by introducing ground chromite into the coarse grained part of the batch.Incorporating 18% coarse chromite into the granular part of the batch before mixing it with the finely milled magnesite powder increases the average spalling resistance of periclase-spinel refractories by a factor of 1.4. However, the existing production scheme is responsible for serious variations in spalling resistance. The other factors (with the exception of the refractoriness under load, which is reduced by 60°) correspond to the levels for ordinary PShSO products.Although comparative testing in the roof of an oscillating open-hearth furnace showed that spallingresistant periclase-spinel brick is highly wear resistant in such conditions, supplementary investigations of the industrial factors are required in order to obtain the special structure which increases the thermal shock resistance and makes it stable, and also slows down the melt saturation of the products.Translated from Ogneupory, No. 8, pp. 13–19, August, 1967.     

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.     

Unfired chemically bonded magnesia products for open-hearth roofs

Conclusions An experimental batch of unfired reinforced products having a chemical bond was produced and tested in the roof of a small open-hearth furnace. The wear intensity of these refractories is 30–60% less than the wear of ordinary fired roof products produced by enterprises in the Ogneuporerud Trust. The properties of the unfired products are improved by using better raw materials.Translated from Ogneupory, No. 8, pp. 9–17, August, 1972.     

The production and service testing of magnesia wares from Rapna magnesia

Conclusions Magnesite refractories from Rapna magnesia are of high quality.Tests on periclase — spinel wares from Rapna magnesia in the crowns of Marten's furnaces working under intensified conditions showed that their wear was 15 to 17% lower than that of regular periclase — spinel bricks.It was shown that, by the use of periclase — spinel bricks from Rapna magnesia in the crown of a Marten's furnace working with an oxygen jet, it will be possible to lengthen the run of the furnace by 16–21%.Translated from Ogneupory, No. 7, pp. 1–6, July, 1969.     

Main causes of refractory wear in the shaft of a blast furnace and means of improving the resistance

Conclusions During service, refractories in a blast furnace shaft are saturated by components of the batch, change their properties and phase composition, and acquire a zoned structure which reduces the resistance to the complex action of the physicochemical and thermomechanical destructive factors.The wear of the shaft is a maultistaged cyclic process, including the saturation of the refractories through the pores, joints, and cracks by liquid and gaseous components of the batch and the gaseous medium, the decomposition of mullite and the formation of new compounds and glass — mainly potassium phyllitic and nepheline compounds — solution and reduction of the new compounds, and abrasion of the reaction products by the batch materials.We recommended for the lining of the shaft shoulders and the bottom and upper parts of the hearth the use of dense kaolin refractories containing 41–42% Al₂O₃ and with an open porosity of 8–12%, the technology for which is being introduced at the Chasov-Yar Refractories Combine.Translated from Ogneupory, No. 4, pp. 41–45, April, 1980.     

Making electrofused magnesia-alumina spinel for producing high-grade refractories

Conclusions The basic technical parameters for melting and producing magnesia-alumina spinel in an electric arc furnace OKB-514 were evaluated and specified. A study was made of the properties of certain compositions of spinel, the melting of an experimental batch of spinel, and using this as a basis, high-qualityroof products were made.Translated from Ogneupory, No. 4, pp. 41–45, April, 1972.     

Service of basic refractories with additions of fused aluminomagnesia spinel in open hearth roofs

Conclusions We developed the basic technical parameters for making high-quality roof refractories, using electrofused spinel.Tests carried out in the roofs of large tonnage open-hearth furnaces, working with the use of oxygen, showed that the wear resistance of these refractories is 30% greater than that of ordinary periclase-spinel.Refractories containing 30% nonchromite spinel should be considered as the most promising.It would be desirable to produce and test large batches of these refractories in service.Translated from Ogneupory, No. 5, pp. 22–27, May, 1968.     

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.     

Spinel-bonded magnesite brick for high-tonnage electric arc furnaces

Conclusions The manufacture of an experimental batch of spalling resistant magnesite-chrome brick with a spinel binder has made it possible to improve the technological norms for the production of these parts and has shown the possibility of making them at the new shop at the Magnezit Plant.The parts produced show good characteristics: refractoriness-under-load of 2 kg/cm² — 1650–1720°; additional shrinkage during heating to 1650° with subsequent holding for three hours –0.1%; spalling resistance 7–13 water-heating-cooling cycles (heating to 1300°); apparent porosity 15–17%; compressive strength 620 kg/cm².To obtain parts with good physical-chemical properties it is essential to use MK magnesite powder; to add at least 6–8% industrial alumina to the charge (in terms of Al₂O₃); to make certain the magnesite-alumina mixture is highly dispersed so that it helps to complete the spinel formation reaction during the firing; to use a mixture of the following grain composition: not less than 20% fraction 3–1 mm; 55–60% finer than 0.5 mm, including 30–35% finer than 0.06 mm; to press the parts at 1200–1500 kg/cm²; to fire the parts at a temperature not less than 1600°, batching them far apart so as to avoid the formation of an uneven structure.The use of magnesite brick with a spinel binder for the walls of high-tonnage electric arc furnaces used to melt transformer steel ensures satisfactory strength of the walls in the slag belt and prevents the steel becoming contaminated with chromium.     

Production of roof refractories using magnesite chromite clinker

Conclusions A method for producing roof products using magnesite-chromite clinker from caustic magnesite and Kimpersai chromite was developed and tested on an industrial scale. The dry method of producing the clinker from 20–25% chromite and 75–80% magnesite powder is the best.Roof refractories made with the use of magnesite-chromite clinker satisfy the requirements of GOST for all factors except spalling resistance.Translated from Ogneupory, No. 7, pp. 9–14, July, 1967.     

Experience with the use of mullite-corundum refractories in the roofs of electric-steel furnaces

Conclusions The resistance of mullite-corundum roof articles, as for periclase chromite, is due to the absorption of melt products from the working region of the furnace and the action of one-sided, high-temperature heating, but in view of the considerable difference in the physicochemical properties the use of the first in the central zone of the roof, subjected to the most severe working conditions, is more desirable than the second.The use of mullite corundum roof bricks, structurally reinforced with nonisometric grains of fused mullite, instead of periclase-chromite refractories will provide an increased roof life, both during the melting of stainless and ballbearing steels, without a change in the structure design; the increase amounts to 25–35%.Translated from Ogneupory, No. 4, pp. 43–46, April, 1986.     

Magnesite-spinel roof products with sintered magnesia-alumina spinel in the batch

Conclusions The basic production parameters were determined for magnesite-spinel refractories using sintered spinel. At the Experimental Factory of the Ukrainian Scientific-Research Institute of Refractories products were prepared having an open porosity of 9.3–12.5%, a compressive strength of 550–820 kg/cm², and a thermal shock resistance of more than 15 water-heat cycles.Petrographic studies established that a typical feature for magnesite-spinel refractories is the irregular granular structure and the development in large quantities of dense contacts between the grains and sections of the spinel and periclase bond, sometimes with partial (mutual) intergrowths. These features apparently determine the high ceramic and service properties of these refractories.Translated from Ogneupory, No. 7, pp. 40–46, July, 1972.     

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 magnesite-chromite products in the roofs of open-hearth furnaces

Conclusions There is a relationship between the firing temperature, the degree of recrystailization of periclase and also the rate of erosion of the bricks in service.With high-temperature firing (1650–1750°C) and use of chromite and magnesite enriched with highly refractory oxides, a high resistance is possessed by roof bricks MKhS, RPShS and periclase-spinelide brick with additions of chromemagnesite clinker.Results of our work show the absence of a connection between the rate of wear of products and property factors provided for in standards for testing. The exception to a certain degree is thermal shock resistance (spalling resistance) and then only in the case of low values (a batch of dense products made of chromemagnesite clinker).In connection with this it is desirable to develop a method of determining those properties in the goods which directly or indirectly would influence their erosion (wear) resistance during use. These properties include in particular the dimensions of the crystals of periclase and the degree of the density of their reciprocal arrangement, which fundamentally characterize their specific surface.For more detailed study of the influence of the crystals of chromespinelides on the behavior of roof bricks in service, it is desirable to make additional tests of trial batches of brick in comparative service conditions.