The development of new technological p r o c e s s e s in the power, metallurgical, engineering, p e t r ochemical, and other industries r e q u i r e s the creation of lightweight m a t e r i a l s capable of withstanding the action of carbon-containing reducing media and possessing good heat-insulating properties. Outside the Soviet Union, anorthite lightweight artifacts obtained by casting from kaolin--gypsumlike m a s s e s are used for service at 1100-1260~ [1, 2]. The low iron oxide content of these artifacts (0.28-0.62%)* is due to the use of pore initial m a t e r i a l for their manufacture. The relatively simple technology, which lends itself to mechanization, the use of cheap raw m a t e r i a l , and the high heat-insulating p r o p e r t i e s of anorthite lightweight r e f r a c t o r i e s were the basis for development of their production.It is known [3] that artifacts with an apparent density of 0.60-0.65 g / c m 3 and a c o m p r e s s i v e strength of up to 1.5 MPa are obtainable on the basis of secondary kaolins and builder's gypsum with added sawdust which s e r v e s a burning additive. The service t e m p e r a t u r e of the artifacts is 1150-1200~ This article gives the r e s u l t s of preparation in the laboratory of anorthite lightweight r e f r a c t o r i e s with an apparent density of less than 0.5 g / c m 3, a high strength, low t h e r m a l conductivity, and a m a x i m u m service t e m p e r a t u r e of 1300~Recently, various h i g h -m o l e c u l a r synthetic compounds --polyethylene, polystyrene, polyvinyl, e t c . -have been used extensively as r o c k -f o r m i n g additives [4][5][6]. To obtain r e f r a c t o r i e s with a low apparent density, PSV foaming polystyrene suspension was used. Its incorporation into the paste p e r m i t s the preparation of artifacts with an open porosity of 85% [7]. Thanks to the spherical shape of the polystyrene grains the p o r e s in the m a t e r i a l are spherical with smooth walls; as in the case of cellular c e r a m i c , this * H e r e and below we give the percentages by weight.

Lightweight chamotte refractories are produced by plastic forming and semidry pressing, with use of burning-off additions, sawdust and coke, respectively. More effective is semidry pressing in which strong carbon-containing materials, pitch, petroleum, and metallurgical coke, are most suitable. However, lightweight parts produced with coke are distinguished by low strength, caused by the coarse-grained loose structure of the fragments as the result of burning off of the carbon and the irregular form of the coke grains. In addition coke is an energy-consuming material in short supply. Abroad there are produced similar types of lightweight refractories the strength of which is significantly (by about three times) higher than of domestic ones as the result of use as the burning-off additions of polymer materials with a spherical form.These investigations were devoted to establishment of the possibility of use as the burning-off addition of chemical production wastes for production of lightweight parts not inferior in properties to the requirements for type ShKL-1.3 parts to GOST 5040-78.As the original materials KV-2 Vladimirovka kaolin, ShKV-2 chamotte from this kaolin, wastes of the production of polyethylene wax (TU 6-05-361-16-83) not previously used, and wastes from the production of synthetic rubber -crumb rubber from the wastes of type A BS-P rubber (TU 38.103524-87) -were used.The production wastes of polyethylene wax (subsequently wax) are a solid substance with a melting point of 85-100~ and a flash point of about 300~ The crumb rubber from rubber waste, yellowish brown spherical particles, has a specific odor, a flash point of 315~ a spontaneous combustion temperature of 355~ and an ash content of 13.8%. The characteristics of crumb rubber from rubber waste are given in Table 1.The chemical composition of the ash of the crumb rubber from the production waste is (wt. %) 51.2 SiO 2, 0.32 AI203 , 7.08 Fe203, 0.66 TiO2, 7.8 CaO, 17.1 MgO, 0.17 Na20 , 0.31 K20, 2.77 SO3, and Amealc 2.60.The influence of the maximum particle size of the burning-off addition and of the quantity of it and also of the pressing, drying, and firing parameters on the properties of the lightweight specimens was investigated. Cubes with an edge of 50 mm were pressed and on them were determined the apparent density, compressive strength, and shrinkage. The physicomechanical and thermal insulation properties were determined on standard specimens prepared from a normal size brick.The mixture was prepared by mixing of the burning-off addition moistened with commercial lignosulfonate with the refractory material. It should be noted that certain difficulties related to breakup and sifting of the necessary fraction of wax arose. The mechanical action caused softening of it, as the result of which the wax particles stuck to the screens. Therefore for the purpose of hardening the wax it was treated with liquid nitrogen, as the result of which the wax was prepared normally. Investigation of the maximum particle size of burning-off additions show...

Oxide fibers with a polycrystalline structure are synthesized by forming the fibers from r spinning solutions which have precisely defined properties, followed by heat treatment.Studies carried out in the Ukrainian Scientific-Research Institute of Refractories led to the development of a method for obtaining alumina fibers from viscous spinning compositions, the basis of which are inorganic sols of the oxychloride type, with additions of organic polymers to boost the fiber-forming properties of the solutions.The fibers formed in the shaping process are subjected to heat treatment, during which a microcrystalline structure is developed, ensuring that the oxide fibers are strong.This article deals with a study of the processes that occur in the fiber when it is heated in service to 1400~ and the effect of various reinforcing, stabilizing, and modifying additives on the crystallization of the alumina in the fiber. To assess the degree of calcination of the A1203 fiber, we selected the important factor of the shrinkage of roll fibrous material, which for thermal-insulation and compensation materials is of such great importance in service.The fiber raw material obtained in the form of fibrous roll on the receiver conveyor was used to prepare rectangular specimens whose length and width were measured across the center. The linear shrinkage Al of the specimens was calculated from the equationwhere lo is the dimension before firing, mm, and 11 is the dimension after firing, mm.We also measured and calculated the weight loss of the fiber during calcination. Figure 1 shows the relationships of the linear shrinkage and the weight loss of the alumina fibers to the firing temperature.The rise in temperature was effected at a single rate (200~ for all the temperatures studied. It was established that a gradual increase in shrinkage from 31 to 33% is observed with a rise in temperature from 900 to 1200~ in the range 1200-1400~ there is a more rapid increase in the shrinkage, and its value at 1400~ reaches 37%0 The weight loss of the fiber at 1200~ equals 57.5%.To assess the thermal stability of the fiber in service, the specimens, after production firing, were subjected to repeat heating at 1400~ with a soak of i0 h; the after-contraction was then determined.Clearly, the higher the temperature at which the fiber had been preliminarily fired, the more it tends to preserve its dimensions during repeat heating.Thus, AI20a fiber prefired at 1400~ had an after-contraction of 2.3%.During prolonged soaking of the alumina fibers at high temperatures, modification inversions occur in the Al2Os, and there is an increase in the size of the corundum crystals, which is accompanied by a reduction in the elasticity and strength of the fibers.In order to stabilize the crystal structure of the y-A1203 and preserve the strength of the fiber, various additives were made, e.g., Si02, Cr203, MgO, Li20, B203,. We studied the influence of certain additives on the thermal stability of the fibers and the crystallization of A1203oIt was established that...

It is known [I-4] that additions of SiO2, Cr203, MgO, NiO, Li20, and others are capable of altering the temperature characteristics of the phase inversions of A1203, which in some cases makes it possible to retard the conversion of the metastable modifications of AIzO 3 into the stable o-form.For aluminum oxide fibers this fact is important since the conversion into the o-form markedly impairs their elastic and strength characteristics [5].Polycrystalline alumina fibers with additions of Si02, MgO, and Cr203 obtained with the technology described in [2] were fired in air at 600-1200~ (6h) and 1300~ (3h).The phase composition of the fired specimens was checked on the DRON-I.5 diffractometer (in Cu K~-radiation).The x-ray investigation of the degree of conversion of AIzO 3 into the o-form in these fibers without additives and with an addition of SiO 2 was done on specimentablets I0 mm in diameter and 2 mm thick.The specimens were pressed from alumina fibers and fired at 800~and then calcined in air, holding them for different times at 1200-1300~The electron-microscopic studies of the polycrystalline fibers were done on the EVM-100 AKmicroscope using the suspension method, and also diffraction and microdiffraction methods. Analysis of the phase composition showed that all the specimens fired at 600~ were x-ray amorphous.The appearance of the a-Al20 s in specimens of fiber without additives is noted starting from IO00=C.The process is actively developed at 12000C, and is complete at 1300-=C. The main transition phase to the ~-form is 7-A1203.Traces of the G-phase (Fig. i) were noted among the other intermediate forms.The electron-microscopic studies show that at 800~ the fibers have a tangled granular structure with separate grains having dimensions of about 6 i~m and less. Well formed crystals measuring 0.I • 6 ~m were rarely encountered (Fig. 2a). The electronographic studies show the presence of 7-and 8-A1203. At 12000C the granular-network structure of the fibers takes the place of the densely layered mass without visible boundaries between the phases. The fibers consist mainly of ~-AI203.When 2, 5, and 10%* SiO z are added to the alumina fibers starting at 800~ in addition to 7-AI2Os, the transition 6-and 8-forms are developed, whose region of existence extends with increase in the concentration of the SiO 2 addition (Fig. 3). On the diffractograms of the specimens fired at 1200~ together with reflexes for the transition 6-and #-phases, we note the presence of lines for ~-A1203, and moreover, their intensity is markedly weakened with increase in the concentration of SiO 2 in the samples.The lines for mullite for the various concentrations of SiO 2 were fixed starting at 1200-1300~ their intensity increased with increase in the firing temperature and increase in the concentration of added SiO 2.The fibers with the addition of 2% SiO 2 had sections with a different morphology.We noted a network-granular structure with the dimensions of separate grains equal to 6-7 nm, and also layered, platelike sections without ...

Types MKRR-130, MKRV-200, MKRP-340, MKRF-100, MKRPG, and MKRV-340 fiber materials to GOST 23619-79 are produced by Northern Dolomite Combine, Sukhoi Log Refractory Material Plant, and Pervoural'sk Dinas Plant. Individual experimental production lots of similar materials are produced to specification.According to an estimate made by the Ukrainian S cientific-Research Institute for Refractories, 43.5 % of all production is due to the share of steel industry plants using fiber materials, 18 % to assembly and construction administrations for the repair of heating equipment, 6.5 % to the energy and electrical industry, 5.9 % to the construction material industry, 3.4 % to chemistry and petrochemistry, 1.5% to the automobile industry, 2.4% to other machine building industries, and 1.2% is exported.Fiber materials are used most widely in the steel industi~ in blast furnace production for insulation of the walls and domes of hot blast stoves and the tops of blast furnaces, in compensation gaps, etc.In steel melting in teeming of certain types of steels inserts type MKRV-340 muUite-silica inserts are used for heating the top portion of the ingot, and MKRF-100 thin high-grade felt for sealing the joints between molds and hot tops (Taganrog Pipe Plant, Omutninsk Metallurgical Plant, Dnepr Special Steel).A promising direction is use of thermal insulation plates for the "cold lining" of continuous casting machine tundishes. This makes it possible to reduce the heat flow through the lining, increase its life, and eliminate preliminary heating of the ladle.Mechanized hoods are used for slow cooling of billets. The hoods are lined with MKRV-200 fiber. With a thickness of 60 mm cooling of billets from 770 to 200~ in 50 h is provided.Fiber refractories are widely used in roiling mill furnaces for insulating the vertical transverse and longitudinal hearth tubes of continuous furnaces and also in the thermal insulation layer of the linings of walls, hearths, and roofs of continuous furnaces and soaking pits.One of the rational places for use of fiber refractory materials is the lining of the walls and roofs of bell furnaces. According to the data of the State Union Institute for Design of Steel Casting and Rolling Production Equipment for Ferrous Metallurgy the use of fiber refractories makes it possible to: reduce the heat flow through the walls and roof, the shell temperature, and fuel consumption; reduce the heat content of the lining, which leads to an increase in productivity as the result of decreasing the time for heating and cooling; increase the size of the charge, which also increases productivity; reduce the labor requirement for installation of the lining as the result of use of mechanized methods. At present hundreds of bell furnaces with fiber linings are operating at Magnitogorsk and Krivoi Rog Metallurgical Combines and Novolipetsk, Chelyabinsk, Konstantinovka, and other plants.