Some properties of refractories based on clinkers with various concentrations of calcium oxide

Conclusions We have studied the properties of the refractories prepared from periclase-lime clinkers with a CaO concentration of 2 to 60%. It is established that as the concentration of CaO is increased, the rate also increased at 1500–1650°C; the degree of dissolution of the refractories in slag is reduced; and in connection with this, their wear resistance is also lowered when tested under conditions simulating, in a first approximation, normal production conditions.The wear-resistance of the fired, pitch-impregnated refractories is higher than for the resin-bonded refractories of the same composition; this is the result of their greater density and strength at the test temperatures. The stability of the resin-bonded refractories made from synthetic clinker with 20% CaO is roughly 20% higher and that of the pitchimpregnated fired refractory 40–50% higher than the resistance of the resin-magnesite refractories normally used in production.Translated from Ogneupory, No. 5, pp. 43–48, May, 1981.     

Deformation characteristics of silicon carbide and chamotte refractories

Conclusions It was established that silicon-carbide refractories with bonds of silicon nitride and oxynitride, and also self-bonded silicon carbide articles possess 2–3 times higher elasticity moduli compared with chamotte (firebrick) refractories.The anisotropy of the elasticity modulus determined in the longitudinal and transverse directions of the refractories is markedly higher (anisotropy coefficient n=2.28–2.49) than for chamotte refractories (n=1.22).In high-temperature conditions (1600–1650°C) the compressive strength of SiC refractories is about 28 N/mm², and the tensile strength 2.1 N/mm², i.e., the compressive strength is about 10 times higher than the tensile.At room temperature the strength of SiC refractories is double that of chamotte, while at 1200–1400°C this difference increases to 10 times.Silicon carbide self-bonded articles at high temperatures possess the highest strength properties, which confirms the effectiveness of using them in service under the action of abrasive forces.A new method was developed for determining the deformation and strength characteristics of refractories on the UITS-0.5/2.5 test machine.A method was developed for obtaining tension and compression diagrams from the results of tests for pure and longitudinal-transverse bending.Translated from Ogneupory, No. 7, pp. 8–13, July, 1989.     

Effect of boron nitride addition on some properties of aluminosilicate refractories

Conclusions An addition of 10–60 wt.% of boron nitride significantly alters the thermal conductivity, thermal expansion, and the elastic modulus of aluminosilicate refractories.As the boron nitride content is increased from 1–60% the strength of specimens heated in a nitrogen atmosphere with an oxygen content of 0.02% decreases.During cyclic heat treatment in an oxidizing atmosphere between 900 and 20°C additional bonds develop between the particles of the aluminosilicate and the oxygen-free additive. As a result the strength of the specimen increases.The thermal shock resistance of the specimens increases with an increase in the amount of boron nitride addition. Specimens with 40–50% boron nitride addition are in practice insensitive to temperature drops in the range 20–2400°C.Aluminosilicate refractories with the addition of 30–40 wt.% of boron nitride can be used as lining material in high temperature systems with brief nonsteady or cyclic work schedules.Translated from Ogneupory, No. 4, pp. 36–39, April, 1968.     

Strength of forsterite refractories at high temperatures

Conclusions The compressive strength of forsterite refractories is higher with the use of prefired dunite. The noncontinuous grading does not always produce high-strength products.The strength of forsterite refractories in the 100–200°C range drops 20–40%, then increases; at 1000°C it exceeds the original strength by 20–45%, after which it drops continuously.The strength of single-phase monomineral forsterite specimens (MgSiO₄) does not alter with temperature rise to 1100°C.     

Use of silicoorganic polymers in alumina-refractory technology

Conclusions Using alumina refractories as an example, it is shown that the newly developed silicoorganic bonding containing an ethyl silicate base and polymethylphenylsiloxane resin dispersed in it, provides a sufficiently strong crock; a significant increase in the strength of the articles after heat treatment at 350–1000°C; and helps to improve the thermal-block resistance, density and the strength of the refractories and reduces shrinkage on firing.Translated from Ogneupory, No. 8, pp. 51–55, August, 1980.     

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.     

Vibro-cast periclase refractories of a grainy structure and some of their properties

Conclusions We have studied the process of obtaining vibro-cast periclase refractories based on fine- and coarse-grained molding systems using a low-concentration solution of HCl as the binder.Using a combined experimental and calculation method based on the use of a cone, we have carried out studies to optimize the production parameters of the vibro-casting process.The materials obtained in the initial (unfired) state are characterized by fairly high strength (_comp=12–30 MPa) and can be used as refractory concretes.The process of sintering the materials was studied and it is shown that their properties are comparable with the normal periclase refractories of a grainy structure. After firing at 1550–1600°C the refractories show virtually no additional shrinkage and their true porosity is 19–23%, ultimate compressive strength 30–60 MPa, and ultimate bend strength 12–26 MPa.The results were proved industrially. Large details of the smelting unit of induction furnaces were manufactured and successfully tested.Translated from Ogneupory, No. 8, pp. 9–15, August, 1986.     

Investigation of the heat treatment processes of resin-bonded refractories in an atmosphere consisting of the products of sublimation and decomposition of the binder

Conclusions Heat treatment of the resin-bonded refractories in an atmosphere consisting of the products of sublimation and decomposition of the binder leads to a significant improvement in the properties of the specimens (in particular, in the coked condition). The increase in the content of the residual carbon, the mechanical strength of the specimens, and their hydration resistance are determined by the heat treatment temperature. The highest levels of the physical and the technological properties are obtained after heat treating the specimens in the 400–600°C range. In this case, the most significant effect is observed in the lime-periclase refractories and the minimum effect is obtained in the resin-periclase refractories.The increased hydration resistance of the resin-bonded refractories containing free calcium oxide (the lime-periclase and the periclase-lime refractories) owes mainly to fixing up of CaO during the heat treatment process and to the formation of the protective calcium carbonate films at the surface of the fired dolomite grains.Translated from Ogneupory, No. 2, pp. 10–13, February, 1992.     

Generalized diagrams and creep limits of dinas refractories for coke furnaces

Conclusions Creep in dinas refractories may be described in the framework of an elastoplastic model, facilitating the construction of generalized creep diagrams. With their aid we can obtain predictions of the values of long-term strength (creep limits) for dinas for periods of upto 12 years. It is shown that the creep limit of dinas after 15–25 years' service in coke ovens is 1.5–2.5 times higher than in the original refractories of contemporary production.Translated from Ogneupory, No. 5, pp. 16–21, May, 1989.     

Determining the resistance of refractories in a slag stream

Conclusions A method is proposed for testing refractories for slag resistance at 1500–1600°C. The results of investigation into high-grade refractories showed that their resistance is variable, and in the main is extremely low. Only silicon carbide, nitride-bonded silicon carbide, and carbon specimens will resist convective slag at 1500–1550°C. The other refractories were destroyed in varying degrees by the slag.Destruction of oxide refractories with an increase in the basicity of the slag is markedly increased, In these conditions nonoxide materials have about the same degree of destruction.Translated from Ogneupory, No. 8, pp. 53–58, August, 1967.     

Lightweight refractories semidry-molded from Borovich clay

Conclusions It was shown in a laboratory investigation that in the production of lightweight chamotte refractories by semidry molding it is difficult to achieve the strength specified by the relevant All-Union State Standard. The strength depends mainly on the chemical and mineral composition and the properties of the binder clay and on the ash content of the burn-out additive.With high-sintering, semirefractory Lyubytin clay as binder and petroleum coke with an ash content below 1% as burn-out additive the finished refractory product had an apparent density of 1 g/cm³ and a cold-crushing strength of 7–17 kg/cm². The strength of the refractory was increased by adding a substance containing alkali or CaO to the batch, more particularly expanded perlite.An experimental batch of lightweight chamotte refractories of apparent density 1 g/cm³ was produced from Borovich plastic clay from the Ust'-Brynkino Sector and coal coke fines from a UDSC. Without added sintering substances the cold-crushing strength was 24–38 kg/cm² (i.e., 30 kg/cm² on average).Translated from Ogneupory, No. 6, pp. 9–15, June, 1976.     

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.     

Study of the strength of ultralightweight refractories

Conclusions A design for equipment and a test method were developed for studying ultralightweight refractories. We obtained temperature relationships with the tensile, bending, and compressive strengths of refractories ShLB-0.4 and ShLB-0.6. A considerable increase in the strength of these refractories was noted at 900°C.Deceased.Translated from Ogneupory, No.6, pp.43–47, June, 1972.     

Unfired refractories bonded with coal tar pitch

Conclusions Medium-temperature coal tar pitches are effective bonds for making unfired dolomite and dolomite —magnesite refractories by pressing bodies heated to 100–120°C. The features of the refractories with a pitch bond are the higher contents of carbon resistant to oxidation (about 4%), and the higher compressive strength (400–500 kg/cm²), and finally the higher hydration resistance (10 days).Refractories bonded with pitch are much better than products containing tar, and accordingly offer a greater resistance when used in oxygen converter linings.Translated from Ogneupory, No. 3, pp. 6–15, March, 1971.     

Aluminophosphate bonded refractory mortars

Conclusions Chamotte mortars containing aluminophosphate bonds considerably improve the strength of the joint between firebrick refractories after heating to 400–800°C compared with mortars based on Portland cement and water glass. The highest strength for the mortar-firebrick bond is provided with a phosphoric acid density of 1.42–1.43 g/cm³ (60% phosphoric acid), and incorporating 20% bond in the mortar.It is possible to increase the strength of the chamotte mortar containing aluminophosphate bond during air setting and during heating, and also to increase the strength with time, by adding active materials to the mortar.Aluminophosphate-bonded mortar markedly increases the strength of the refractory-metal bonding, which is very important in building linings which are subject to movement during operation for example, in rotary kilns. It is desirable to test mortars containing aluminophosphate bonds in rotary kilns, and also in similar plant in the refractories, ceramic, and cement industries.Translated from Ogneupory No. 1, pp. 37–42, January, 1971.     

Forsterite refractories from the dunites of the Kytlym deposits

Conclusions Kytlym dunites consist mainly of olivine. Their calcination loss is low and their density and strength after firing are adequate.The physicochemical properties of the refractories produced from dunite not fired beforehand are better than those of the refractories produced from fired dunite.All refractories produced from Kytlym dunites satisfy the requirements of GOST 14832-69.Translated from Ogneupory, No. 5, pp. 27–32, May, 1977.     

Thermomechanical and deformation properties of periclase and magnesia-spinel refractories

Conclusions The strength of periclase and magnesia-spinel refractories at normal temperatures varies in wide limits and is determined by the quantity, shape, dimensions, and distribution of the pores and microcracks. At high temperatures the degree of influence of the pores and microcracks on the strength is reduced.In the region of medium temperatures (600–1200°C) there is a temporary strengthening and an increase in E_d of the magnesia-spinel refractories, due to the internal stresses caused by the difference in the coefficient of linear thermal expansion of the spinels and periclase.With further increase in temperature the articles' strength and E_d are reduced as a result of the softening of the silicate bond. The abradability of the refractories depends slightly on the porosity but strongly on the compressive strength.The least creep is typical of refractories made of fused materials (PKhVP) with a comparatively low concentration of silicate phase, the viscous flow of which at temperatures above 1450°C determines the plastic deformation of the periclase and magnesia-spinel articles made industrially.Periclase refractories containing 2.5–3% silicates in the form of montichellite are brittle up to 1400°C and above this temperature they are elastoplastic, while articles and tiles containing up to 0.5% silicates in the form of Ca₂SiO₄ may be brittle up to 1600°C. They possess high thermomechanical properties and wear resistance in service in gate valves for steel ladles.The wear under friction of periclase tiles at various temperatures is determined by the crystal structure, the change in strength of the materials, and the state of the rubbing surfaces, and also by the adhesion and deformation reactions.Translated from Ogneupory, No. 1, pp. 7–14, January, 1983.     

Properties of refractories produced from synthetic magnesia

Conclusions The sinterability, open porosity, and cold-crushing strength of magnesite and magnesite-chromite specimens processed from magnesia powders (96–97% MgO) are improved with a decrease in the size of the periclase grains in the powder and with an increase in the firing temperature and do not depend on the percent and composition of the silicates and on the B₂O₃ content of the magnesia powder.The high-temperature bending strength of both types of refractories increases with a decrease in the B₂O₃ content of the magnesia powder. The creep resistance of the magnesite specimens increases with the ratio CaO/SiO₂ in the magnesia powder while the creep resistance of the magnesite — chromite specimens does not depend on this index.The indices of the open porosity and strength of the magnesite and magnesite — chromite specimens were optimal when they were produced with magnesia obtained by the bicarbonate method from dolomite.To produce dense and strong magnesite refractories from magnesia, they should be fired at a temperature not below 1700°C. The firing temperature of magnesite — chromite refractories should not be below 1750°C.Translated from Ogneupory, No. 6, pp. 53–57, June, 1978.     

Silicone polymers in oxide refractories technology

Conclusions We developed a method for obtaining silicone bonds for refractory materials based on nonhydrolyzed ethyl silicate, silicone resins, and organic adhesive component.Using corundum and periclase refractories as examples we demonstrated that use of the new bonds contributes to a significant strengthening of the materials in the range 20–900°C, and they are therefore prospective for preparing unfired refractories. The use of bond ensures densification and strengthening of corundum refractories, while simultaneously reducing the shrinkage, and leads to an increase in the stabilization of the high-temperature strength of the articles and a reduction in their wettability by molten steel. It is shown that the new oxide materials may be obtained in the production of tiles for the gate valves of steel-casting ladles.Translated from Ogneupory, No. 3, pp. 13–16, March, 1984.     

Obtaining aluminosilicate refractories by the hydrothermal method

Conclusions On the basis of aluminosilicate bond made from heat-processed hydrated alumina and quartz sand in the molecular ratio of Al₂O₃: SiO₂=32, in conditions of autoclave processing at 800–1000 kg/cm² in a period of 8–12 h, it is possible to obtain unfired aluminosilicate refractories with quite high physico-chemical factors.During the heating of the specimen after autoclave processing to the temperature of sintering, their strength diminishes to a small extent, which makes it possible to use these refractories directly in structures.The high strength of aluminosilicate refractories after autoclave processing is due to the formation of a gel-like hydrated aluminosilicate upon the interaction of Al(OH)₃ with SiO₂.The technology developed for the production of unfired autoclave firebrick and high-alumina refractories permits us to obtain large products which make it possible to industrialize their transportation and laying, and to reduce the number of joints in the lining.Translated from Ogneupory, No.1, pp.15–19, January, 1967.