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.     

Development of a method of production of porous fillers from refractory clays and kaolins

Conclusions The basic production parameters were developed for production of chamotte porous fillers with an apparent density of 0.35–1.3 g/cm³ by expansion of refractory clays and kaolins in the 1500–1700°C range.It was established that DN2 clay expands sufficiently effectively with a heating rate of not less than 20°C/min and KV-2 kaolin with a rate of 60°C/min.The specified apparent density of the filler is obtained by varying the temperature, the hold, and the expanding addition content. At 1500–1700°C the maximum expansion effect is observed in the first 1–5 min. The optimum time for obtaining a constant volume filler is determined by the form of the clay raw material, the sulfate addition content, and the expansion temperature.A necessary condition for high-quality production of a porous filler is conformance of the hold and the size of granulated material to the selected expansion temperature.Testing of the method developed in small rotating kilns showed the possibility of production of a porous refractory filler with an apparent density of 1.2–1.3 g/cm³.Translated from Ogneupory, No. 7, pp. 32–36, July, 1985.     

Mastering the production of dense kaolin refractories for blast furnaces

Conclusions The Ukrainian Institute of Refractories has developed a technology, and the Chasov-Yar Factory is mastering the manufacturing methods, for dense kaolin refractories with a porosity of not more than 12% for blast furnaces. The bricks are made with high-fired chamotte using Novoselitsk and Polozhe kaolins. Firing is done in tunnel kilns with a setting height of 1.95 m.The increase in apparent density to 2.35–2.36 g/cm³ in the green brick due to rational use of kaolin chamotte and the improvement in body processing facilitate the regular production of goods with a porosity of not more than 12%, using existing SM-1085 toggle presses and tunnel kilns with a high setting.Translated from Ogneupory, No. 5, pp. 6–12, May, 1979.     

Sintering boron nitride by hot pressing and its properties at high temperatures

Conclusions During hot pressing only powders of BN synthesized at low temperatures are sintered. The high dispersion of the powder, and the imperfect structure of the crystals lead to its recrystallization and sintering at high temperatures.The optimum conditions for hot pressings BN are: temperature 1800C, soak 10 min, pressure 300 kg/cm². The apparent porosity of the specimens obtained under these conditions is 0–0.1%, apparent density 2.06–2.08 g/cm³.In the hot-pressed specimens we detected substantial growth of the crystals of BN.The properties of the hot-pressed articles made from low-temperature BN suggest that they can be considered as constructional refractory materials capable of operating at high temperatures.Translated from Ogneupory, No. 3, pp. 48–54, March, 1967.     

Porous materials based on corundum and aluminophosphate bond

Conclusions Highly porous corundum products obtained by using fluoroplastics have a relatively high strength in the green state (7 kg/cm² with an apparent density of 0.4 g/cm³), and a low apparent density after firing (0.23 g/cm³).The incorporation of aluminophosphate bond sharply increases the strength of the products after combustion of the organic part, and reduces the total shrinkage during heat processing from 30 to 4–5%.The use of electrofused corundum in place of commercial alumina reduces the concentration of organic constituent in the body to 18%; under these conditions the additional shrinkage at 1600°C of specimens fixed at 1000°C drops to 0.5–1%.Translated from Ogneupory,No.5, pp.46–50, May, 1972.     

Role of sintering additives in the production of lime refractories

Conclusions A production technology is proposed for lime refractories covering the preparation of high-density lime clinker, followed by crushing, batching, adding waterproof bond, pressing the goods, and firing at 2020 K.The technology for obtaining high-density lime clinker resistant to atmospheric hydrolysis, includes milling CaCO₃ to a particle size of 100–150 m with simultaneous incorporation of sintering additives (2–6% TiO₂ or 2–4% titanium ferrites), and the use of water solutions of sulfite lye as bond; pelletizing and firing at 2020 K. The lime clinker has an apparent density of 2.75–3.03 g/cm³, and an open pelletizing and firing at 2020 K. The lime clinker has an apparent density of 2.75–3.03 g/cm³, and an open porosity of 3.4–9.8%.The lime products have an apparent density of 2.65–2.97 g/cm³, open porosity 4.4–16.4%, compressive strength 60–140 N/mm², and refractoriness under load 1610–1700°C and above.Translated from Ogneupory, No. 2, pp. 13–16, February, 1992.     

Chamotte-kaolin insulating bricks with an apparent density of 0.8–0.9 g/c m3

Conclusions Using sandy kaolin raw materials at the Velikoanadaol'sk refractories combine we made lightweight insulants with an apparent density of 0.8 and 0.9 g/cm³, using coke fractions <3 and 5 mm, respectively. In both cases the articles had a relatively high strength and low thermal conductivity.Translated from Ogneupory, No. 1, pp. 15–17, January, 1982.     

Thermophysical parameters of high-performance corundum insulation at 500–2100 K

Conclusions Measurements have been made on the thermal conductivity and thermal diffusivity for corundum refractories based on hollow granules having apparent densities of 0.3–0.6 g/cm³, as well as foam corundum ones at about 0.5 g/cm³, which cover the range 200–1700°C. A conduction model has been devised that gives a qualitative explanation of the temperature and porosity effects.Translated from Ogneupory, No. 5, pp. 33–38, May, 1988.     

Rheological and technological properties of cassiterite suspensions and of the casts made from them

Conclusions The rheological and technological properties of cassiterite suspensions, as of the casts made from them, have been studied as a function of their pH. It is established that the optimum intervals correspond to pH 1–3 and 11–12.4. At these values of pH, cassiterite products were obtained with an open porosity of 1.5–4.0%, apparent density of 5.97–6.27 g/cm³, and an ultimate bend strength of 750–900 kgf/cm². The alkali slips for the casting of thick-walled articles cannot reasonably be used because of their slow setting rate.Translated from Ogneupory, No. 2, pp. 45–49, February, 1979.     

Methods of intensifying the sintering of kaolinitic clay

Conclusions We studied how combined additives improve the sintering of Kirov kaolinite clay. An addition of surface-active agent in the form HAlA still pot residue, and SAlA still pot residue, increased the densification during pressing and more intensively improved the sintering of Kirov kaolinite clay with combined incorporation with talc-magnesite.Incorporating 0.1–0.15% (as MgO) talc-magnesite and 0.3% mixture of still pot residues SAlA and HAlA (in the ratio 1:2) and 0.3% kerosene increases the apparent density from 2.30 to 2.47 g/cm³, and reduces the water absorption of the specimens made from Kirov clay from 6.6 to 3.8%.A high degree of sintering (apparent density 2.44 g/cm³ and water absorption 4.6%) is achieved by the combined use of talc-magnesite and water-soluble still pot residues HAlA.Translated from Ogneupory, No. 4, pp. 59–63, April, 1970.     

Monolithic lining of ladles for out-of-furnace treatment of steels

Conclusions We studied the effect of the additives (silicon carbide, boron nitride, and chromite) on the physical and mechanical properties of a high-alumina ramming body, It was established that chromite additions significantly improve the properties of the body.The optimum composition of the high-alumina body based on the ÉB-50 electrocorundum (73%) and the ShMK-77,5 mullite-corundum chamotte (27.0%) containing 10% chromite additive was developed using orthophosphoric acid as a binder. The body has the following properties: apparent density 2.4 g/cm³; open porosity 23.8%; and the ultimate compressive strength 135.5 N/mm².The developed body composition is recommended for preparing rammed lining of the ladles used for the vacuum treatment of steels.Translated from Ogneupory, No. 3, pp. 5–7, March, 1988.     

Magnesia foamed ceramics

Conclusions We determined the conditions for which hydration of magnesium oxide is diminished so much that it is possible to make porous articles measuring 200×120×50 mm and with an apparent density of 0.5–2.0 g/cm³, or higher, using the foam method and water suspensions.The porous ceramics made from magnesium oxide by the foam method with the same apparent density are distinguished by the much greater compressive strength compared with ceramics made by combustible additive methods.With increase in apparent density of the porous articles made from magnesium oxide, the thermal shock resistance is also increased.Translated from Ogneupory, No. 2, pp. 50–53, February, 1968.     

Properties of fired dolomite refractories with tar bond

Conclusions The laboratory specimens made of tar-bonded fired dolomite showed an apparent porosity of 8 to 18%; slightly better porosity was shown by specimens made with more fully sintered dolomite.The tar barely permeates the dolomite grains.When they are stored, the porosity is increased and the bulk density and strength of the specimens are reduced. This is less obvious after coke firing.Bricks made of all the tested dolomites with the addition of 8 and 6% tar at a pressure of 500 kg/cm² showed a bulk density of 2.6 g/cm² or more. Similar results are obtained when making the bricks by pneumatic tamping.For tests in the lining of converters we recommend blocks made of freshly fired dolomite with an apparent porosity of 5–10 and 15–20 and a grain composition lower than 15–10 mm. As a bond, 6 to 8% tar containing 65–70% medium coaltar pitch and 35–30% anthracite oil should be added. The blocks have to be pressed at at least 500 kg/cm².     

Sintering high purity,magnesia with additions of hafnium dioxide

Conclusions The introduction of hafnium dioxide into high-purity active magnesia accelerates its sintering and with 0.1–0.3 mol % HfO₂ a ceramic with an apparent density of 99–100% of the theoretical (3.56–3.63 g/cm³) can be obtained after firing at 1300–1400°C. The optimum quantity of HfO₂ additive is close to 0.25 mol %.The calcination temperature of the mixture of magnesium hydroxide and additive obtained by precipitation from a solution of MgCl₂ and Hf(SO₄)₂ with ammonia, and the fabrication pressure do not greatly affect the final density of the ceramics.Sintering of spectrally pure MgO containing 0.25 mol. % HfO₂ begins at 950°C, then the apparent density grows rapidly with rise in firing temperature, approaching 3.40 g/cm² at 1100°C. Selective recrystallization at these low temperatures is slow and sintering is not accompanied by a substantial grain growth. At 1300°C and higher firing temperatures densification of the ceramics approaches the limit in several minutes.The mechanism of the transfer of substance during the sintering of these specimens is volume self-diffusion from the grain boundaries to the surfaces of the bridges formed between them. The energy of activation of this process [3.9 eV (6.2 × 10^–16 J) in the 1000–1300°C range] and the coefficient of self-diffusion for MgO calculated in accordance with this (6 × 10^–14 cm²/sec at 1100°C) correspond to existing data on the diffusion of magnesium into MgO.With the incorporation of 0.25 mol. % HfO₂ in less pure magnesia obtained from chemically pure MgCl₂, sintering is little different from the sintering of spectrally pure MgO, but the limiting apparent density of the ceramics in this case is somewhat lower-of the order of 99% of the theoretical.     

Investigating sintering of magnesia obtained by chemical beneficiation

Conclusions A study was made of the sintering behavior of samples of magnesium oxide obtained by chemical purification. The magnesia obtained by the nitrate method is a low sinter-active material. The density of the material after firing at up to 2400°C equals about 3.0 g/cm³. Partial hydration of the material improves the sintering results. The magnesia obtained by the ammonium-sulfate technology is an active material which when fired yields a densely sintered product with a density of 3.3–3.4 g/cm³.Translated from 0gneupory, No. 5, pp. 25–33, May, 1991.     

Dependence of the properties of chamotte on the firing regime of the briquette

Conclusions The physicomechanical properties and phase composition of chamotte depends on the composition of the gas medium, the firing temperature, and the cooling regime. In the briquettes fired at 1500°C in an oxidizing medium with the cooling temperature lowered from 1500 to 1200°C, the apparent density increases and the porosity decreases. In the briquettes fired in a reducing medium with the cooling temperature lowered from 1500 to 1300°C, there is a reduction in the apparent density and an increase in the porosity but with a further reduction of the cooling temperature to 1200°C, these properties change in the opposite direction.The apparent density of chamotte and its concentration of mullite is increased with a reduction in the cooling rate. The apparent density of the chamotte from the Polozhsk kaolin under analogous cooling conditions increases more rapidly than that from the Novoselitsk kaolin chamotte.The temperature interval in which the cooling rate effectively increases the apparent density of the chamotte fired in an oxidizing medium is 1500–1300°C. In a reducing medium this interval is shifted 100°C toward lower temperatures.The experiments have shown that an increase in the cooling rate of the fired briquettes at temperatures below 1200°C has only a very slight effect on the apparent density and porosity of the Novoselitsk kaolin chamotte. When the chamotte has been obtained from Polozhsk kaolin, a reduction in the cooling rate at temperatures below 1200°C, and particularly in a reducing medium, has a quite perceptible effect on the increase in apparent density and reduction of porosity of the material.Translated from Ogneupory, No. 3, pp. 22–26, March, 1982.     

The optimum apparent density of steel casting plugs made by semidry pressing

Conclusions A method was developed for classifying plugs into groups which were distinguishable by their apparent density and porosity. The plugs are classified by weighing them and measuring their height.Testing the plugs in service after they have been classified with this method made it possible to determine the optimum range for apparent density and porosity.For large ladles the optimum plugs are those classed in group II and III with apparent densities of 1.97–2.00 g/cm³ (apparent porosity 15–20%).For small ladles the best resistance was shown by plugs in group I and II with an apparent density of 1.94–2.00 g/cm³ (apparent porosity 17–22%).Nomograms were developed, together with calculating scales and a device which ensure the production of plugs with the predetermined apparent density.As a result of the work, owing to the strict observation of the technology and the measures completed in the open-hearth department, it was possible to improve the life of the plugs.Participants in the work included V. S. Turchaninov, A. M. Timofeev, R. A. Musikhina, S. A. Perezolova, V. F. Shutkin, N. A. Voipalina, M. F. Lepskii, P. F. Serebrii, S. D. Gamzikova and V. S. Firfarov.     

Anorthite lightweight refractories for service in carbon-containing media

Conclusions The authors have developed a procedure for making anorthite lightweight artifacts with an apparent density of 0.5 g/cm³ and a low iron oxide content, permitting their service in carbon-containing reducing media up to 1300°C.Translated from Ogneupory, No. 7, pp. 40–42, July, 1980.     

Gas-flame guniting of the lining of intermediate continuous steel-casting ladles

Conclusions As a result of laboratory investigations and rig testing of the flame guniting of intermediate ladles for continuous steel-casting plant we recommend the following bodies: 90% corundum, 10% sodium tripolyphosphate; 80–90% corundum, 20–10% chamotte; 80–90% high-alumina chamotte, 20–10% chamotte. The particle size of the corundum body is <0.088 mm, high-alumina <0.25 mm.The optimum guniting cycle is: consumption of natural gas 60 m³/h, oxygen 100 m³/h, gunite body 150–200 kg/h, guniting distance 450–550 mm, rate of moving the burner 1.0 m/min.In the case of chamotte, the coefficient of gunite body utilization equals 0.75, for high-alumina 0.70, and for corundum 0.40, with an open porosity in the gunite coating of 10–15, 8–10,and 4–6%, respectively.Using the experimental equipment the body made from 90% corundum and 10% sodium tripolyphosphate was used to gunite the side surface of the lining of an intermediate ladle. The wear of the gunite section of the lining was 1.3–2.5 mm per heat.Translated from Ogneupory, No. 4, pp. 37–42, April, 1973.     

A Study of Refractories from Baddeleyite Stabilized with Magnesium Oxide

It is shown that refractory articles can be produced from ZrO₂ on a forsterite binder based on natural baddeleyite with native grain composition. The articles have a high density (4.71 – 4.72 g/cm³), ultimate compressive strength (257.6 MPa), heat resistance (6 – 8 water heat cycles from 1300°C), and a low porosity (12.2%).