The working layers of furnace linings are being increasingly made of refractory fibrous materials [i]. Various types of materials require different methods of attaching the refractories to the support structures.Tiles are attached with cements [2], or on the faces with T-shaped anchors; roll materials are attached to metallic rods that are welded onto the wall or boundary armatures, followed by securement.At temperatures up to 800-I150~ fixing is done with gaskets made of heat-resistant alloys; and at higher temperaturesceramic anchors of different configuration.In our country for the imported furnaces used in mineral fertilizer production, metallurgy and petrochemical industries, they are using ceramic anchors produced by foreign firms, mainly of two types.They consist of hollow, thin-walled nozzles in the form of a truncated cone with poles on the expanded section.The anchors of mullite-silica composition are 60 mm high and are designed for use at temperatures up to 1350~anchors of mullite-corundum composition (two parts) are 90 mm high, porous, and they can be used to 1550-1600~The USSR is not producing any ceramic anchors except for small batches of experimental chamotte units.Their technical development has been undertaken by the Institute. Both types of anchor are of the rather complex, thin-walled variety, and so investigations were done to choose a batch composition and a method of pressing them.Kaolin chamotte was used to obtain mullite-silica anchors together with clay an kaolin. They were pressed by the plastic method, as this is the most convenient in production.After firing at 1350~ the anchors made of chamotte and clay were free of defects and deformations.Their apparent density was 1.96-1.98 g/cm 3, open porosity 18-19%, and tensile strength 0.30-0.44 N/mm 2.The low tensile strength, the high labor content of the task, and the low productivity made it necessary to resort to the dry pressing method.Chamotte grades ShGR and ShKN fractions <2 and <0.5 mm were used, and the bond consisted of DNI clay and KN-I kaolin~ It is known that the reinforcement of materials with refractory fiber enhances their tensile strength [3, 4]. Chamotte anchors with additions of mullite-silica fibers were therefore tested in this work.To obtain uniform distribution of the fiber in the dry body it was milled to produce a material with a predominant size of 0.16-0.25 and 0.3-0.5 wm. The fiber was dry mixed with the chamotte, moistened, and then the clay was added.Cubes were pressed with edges of 50 mm, which were used to determine the compressive strength, since it indirectly characterizes the tensile strength [5]. The composition and properties of the laboratory specimens fired at 1370~ are shown in Table I.The articles made from ShGR chamotte and Druzhkov clay had a refractoriness under load (RUL) at 0.2 N/mm 2 of 1280~ while the maximum service temperature of the anchors is 1350~ Replacing the ShGR chamotte with ShKN boosted the RUL to 1330~Adding milled fiber to the body, regardless of the grain-size composition, did no...
In the manufacture of lightweight artifacts coke, sawdust, mixtures of sawdust and lignin [1][2][3], and thermoplastic resins are used as combustible additives. Foreign manufacturers of lightweight artifacts use expanded polystyrene [4]. In the Soviet Union research is being carried out on the use of expanded polystyrene in the manufacture of high-alumina lightweight artifacts from self-packing masses or by vibrocompaction [5,6].We have developed a procedure for obtaining chamotte lightweight artifacts with an apparent density ranging from 0.3 to 0.7 g/cm 3 by casting. The starting materials were Druzhkov clay and chamotte from Novoselki kaolin; the combustible additive was PSV-S polystyrene with a grain size less than 0.4 mm. The polystyrene was expanded in boiling water, dried, and sifted into fractions.The masses for casting (they had the consistency of thick sour cream) were prepared in a propeller mixer. Artifacts of normal size were cast in metal molds on metal hearths, dried, and roasted in a gaschamber kiln at 1300~To select the optimal ratio of clay to chamotte in the charge, we made artifacts of three compositions (Nos.
To increase the effectiveness and economy of production operations it is necessary to develop refractory materials operating at high temperatures in aggressive media. Their use makes it possible to improve the thermal insulation properties of linings, to reduce heat losses and the weight of structures, to increase operating temperatures, and to provide purity of the controlled atmosphere in the working space of furnaces as the result of high resistance to the action of a reducing atmosphere.The most effective materials for service under such conditions are corundum ones. Industry produces lightweight corundum parts but the lightest of them has an apparent density of i.i g/cm 3 and a compressive strength at room temperature of 2.5 N/mm 2.This article is devoted to development of a method of production of ultralight corundum parts with increased mechanical strength.Since the mechanical properties of oxide materials are structurally sensitive characteristics, the mechanical properties of ultralight corundum material were investigated in relation to its phase composition. To vibroground alumina were added CaO, MgO, and SiO 2 in a stoichiometric ratio providing synthesis of the minerals gehlenite, anorthite, cordierite, monticellite, and diopside, the melting points of which are significantly below the melting point of corundum. Belgorod chalk, quartz sand, and magnesium chloride hexahydrate served as the additions. The parts were prepared by slip casting and expanded polystyrene of the finer than 1 mm fraction was used as the pore forming addition.It was established that additions corresponding to the stoichiometric composition of gehlenite with a 3% content of it provided the greatest increasein mechanical strength of the ultralight material.Using the method developed the Experimental Plant of Ukrainian Scientific-Research Institute for Refractories produced experimental lots of ultralight corundum parts which were characterized by 97 wt.% A1203, an apparent density of 0.4-0.5 g/cm 3, a compressive strength at room temperature of 2.0-4.5 N/mm 2, a thermal conductivity at an average temperature of 350~ of 0.37 W/(m'K) and of 600~ of 0.45 W/(m.K), a temperature of the start of softening under a load of 0.2 N/mm 2 of 1260-1300~ and the absence of additional contraction at 1550~The parts were intended for service in heating equipment with a controlled atmosphere and a maximum temperature of 1550~ Figure i shows the temperature relationship of the compressive strength of specimens of ultralight corundum material with an apparent density of 0.4 g/cm 3. The presence of a maximum at a temperature of about 800~ when the strength reaches 90% of its value at room temperature, and a reduction in compressive strength in the temperature area above 900-I000~ in connection with formation of a liquid phase caused by the presence in the composition of lower melting gehlenite are characteristic.It should be noted that with an increase in temperature from room to 900~ the reduction in strength of the corundum material does not exceed 2...
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