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A technology for producing forming mixtures for casting molds based on various refractory fillers and a gypsum binder is developed. An optimum composition is suggested that includes 35% powdered KP-3 quartz calcined at 900°C, 35% fly ash, and 30% gypsum plus additions regulating the casting properties of the forming mixtures. The introduction of the developed composition and the technological process for the production of molds made it possible to decrease the thickness of aluminum-base castings by a factor of 2–3, the mass of cast parts by 30–50%, and the labor intensity by a factor of 2–3.

The corrosion resistance of refractories depends on their structure, on the size and nature of the pore distribution in the articles, which determine the depth and mechanism of reaction between refractory and corroding agents from metallurgical production, and also on the presence of active, highly refractory materials in the capillaries of the refractory, capable of reacting with the penetrating melt to form infusible compounds or solid solution.

In order to develop a reliable protective coating, it is necessary to take a number of factors into account (the granulometric and chemical compositions, their relationship (ratio), the kinetics of the physicochemical processes-occurring at the phase boundaries etc.). When the composition of the protective coating is selected properly, penetration of the metal does not take place.

A silicon carbide powder has been fabricated from worked-out articles of grade KN. The properties of a mortar based on it for the lining of a multisection heating furnace of a TPA 30–102 mill are described. Specifications TU 1521-001-02069208-94 for silicon carbide mortar of grade MKK-70 have been developed for optimum compositions.

Phase diagrams of the system Al2O3 - SiO2 as presented in the domestic and foreign literature are analyzed. The congruent and incongruent states of mullite, liquation in the solid phase, and the structures of mullite and sillimanite are discussed.

The operation of linings of sections of heating furnaces of old and new designs is considered. Specifications for periclase-chromite mortar produced by the Pervoural'sk New Pipe Plant are worked out. The behavior and structural transformation of the heated mortar are investigated.

It is established that the amount of mullite and the value of the open porosity of specimens increase in the sequence α-Al2O3→(γ+α)-Al2O3→γ-Al2O3→Al2O3 · 3H2O. The apparent density and the ultimate compressive strength increase in the reverse direction. Active modifications of alumina (hydrargillite, γ-Al2O3) stimulate mullite formation, which is accompanied by an increase in the open porosity to 40% and a decrease of the mechanical strength to 8−12.5 MPa, and high (up to 12%) linear shrinkage. High-quality, dense, strong refractories can be produced in a single firing from coarse-grained quartzite and finely disperse corundum and alumina in the form of α-Al2O3.

The effect of neodymium, cerium, lanthanum, and yttrium chromites, added in amounts of not more than 8%, on the sintering of magnesia in air and in vacuum has been studied. On addition of rare-earth chromites, the initial magnesia is sintered to a density of 0.98. By their sintering action, these chromites fall into the following sequence: neodymium chromite — lanthanum chromite — yttrium chromite — cerium chromite. The highest density (0.98 – 0.99) and the lowest porosity (1–2%) are obtained on addition of 2% of neodymium chromite to magnesia. The process of sintering of magnesia is accompanied by an increase in the size of periclase crystals from 12 to 38–56 µm.

It is shown that with an increase in the diffusion factor, the yield of synthesis products for solid-phase reactions increases, and for the Al2O3-SiO2 system is determined mainly by the fineness of the alumina.

A study was carried out of the corrosion of mullite ceramics of varied porosity. The degree of corrosion varies with the original density of the ceramic. When the porosity is reduced by half the corrosion is also halved.

Additions in the form of TiO2 or ZrO2 are recommended in order to obtain effective sintering of the chemically synthesized composite MgO + MgCr2O4, obtained from the thermal decomposition of magnesium chromate. The articles prepared in accordance with the new process based on dense-sintered clinker have excellent physicochemical properties. The experimental tap hole blocks made using the clinker process showed 1.5 times greater resistance than that of fused periclase blocks when tested at the Nizhnetagilsk Metallurgical Combine.

It was established that depending on the type of original beryllium raw material (hydroxide or basic carbonate of beryllium) and the temperature of processing there are changes in the volumes of the pores and the nature of their distribution with respect to sizes.

The protection of refractories must be given specified organizational forms. In our view, the chief refractory engineer of large metallurgical plants should function on the same footing as the deputy chief engineer (like the chief rolling-mill engineer or the chief steel-smelter), with the required staffing arrangements.

An investigation of the sintering process of neodymia in vacuo and in air showed that using industrial grade neodymia powder and firing the specimens in vacuo at 1800–1850°C gives a well sintered ceramic of relative density 0.96–0.98 for a true porosity of 1–1.5%.

Tar-bonded unfired type MDTBS-70 and MDTBS-75 parts produced by Chelyabinsk Metallurgical Combine were tested under the conditions of the South Ural Nickel Combine in nickel production converters. The life of the refractories in the tuyere belt and in the wall above the tuyeres was the same as for the KhPT parts and the rate of wear was 3-5 mm/h. The primary factor influencing the wear rate of the refractories is the chemical reaction of the calcium oxide and the dolomite with the high-iron slags.

In chemical composition the experimental chrome-spinel-periclase refractories are characterized by a high degree of purity. The total content of impurity oxides of silicon, calcium, and iron does not exceed 2%. The parts possess increased density, porosity, and slag resistance but a lower heat resistance than the imported refractories with a silica content of 0.5%.

It is recommended that the mullite-silica products made from polydispersed mixtures of alumina and silica in the presence of oxide additives be fired at a temperature of 1380–1410°C according to the firing regime of the dinas refractories. We obtained products containing a mixture of iron and calcium oxides (maintaining their total content not exceeding 3% and a 2∶1 ratio). Oxide additions exceeding 3.5% have a negative effect on the technological effectivenesss and the properties of the products.

The influence was investigated of finely dispersed additives in the form of the decomposition products of magnesium chromite, aluminum nitride, etc., on the sintering of periclase bodies.

We investigated the kinetics of spinel-formation in the MgO-FeO (Fe2O3)-Al2O3-Cr2O3 system using a petrographic method for determining the width of a layer of interaction products. The magnitude of the apparent activation energy of the process of spinellide formation was 327.99 kJ/mole.

The authors investigate the mechanism and kinetics of formation of the protective coating of the refractory lining of copper-smelting converters. The use of alumina-containing materials to create the protective coating permits an increase in the campaign time of the converter between repairs by a factor of 1.5–2 (in comparison with a magnetite coating), a decrease in the coating deposition time from 5.5–6 to 2–2.5 h, and a decrease in the rate of wear of the coating from 14.5–16.2 to 5.5–6.6 mm/day.

Carbon exerts a significant influence on the microstructure of beryllium ceramics. With the introduction of activated carbon into the composition of the ceramic its microstructure undergoes changes. Even small amounts of carbon (about 0.1%) lead to the development of pores. With increase in carbon concentration there is an increase in the amount of large pores. The distribution of pores over the specimen's cross section is irregular.

The processes of capillary penetration of FeO into refractory porous materials at 1400–1550°C have been studied. It is established that in the initial stages the capillary penetration is slowed down by the wetting of the walls of the capillary by the melt. The processes of oxidation of a medium-carbon steel in a medium of water vapor at 1550°C have also been studied. It is shown that the penetration by FeO into the layer of refractory coating is determined not by the rate of capillary penetration but by the rate of formation of these products. The tendency to form a metallized burn on the surface of large steel casts with the use of antiburn coatings is a function of the oxidation rate of the liquid steel, taking into account the interaction between the oxidation products and the refractory filler of the coating.

The authors have investigated aluminosilicate fiber with organosilicon binder. They show that a rise in pressing pressure from 5 to 50 kPa, a rise in temperature from 300 to 500°C, and a rise in treatment time from 15 to 60 min enables us to obtain products with apparent densities from 0.4 to 0.65 g/cm3.

We studied the relationships between the average sizes of the crystallites, the specific surface and the nature of the porosity and the composition and temperature of synthesizing powdered materials in the system MgCr2O4-MgAl2O4 and also the linear shrinkage during sintering of specimen prepared from the materials. It is shown that the relationships are nonlinear and their extremes correspond to the compositions close to MgCrAlO4.

On etudie la cinetique de l'interaction et du frittage de melanges mullite-silice a base de quartzite a grain grossier, de verre de quartz et de chamotte avec de l'alumine finement dispersee pour differentes temperatures de cuisson

The authors examine two possible modes of oxygen migration in the oxide refractory steel interface region at high temperatures which are tentatively designated as the physical and chemical modes. Oxygen distribution is of great significance in the interaction processes of molten steel with oxide refractories. The partial pressure of oxygen P /SUB O2/ over the oxides ThO/sub 2/, Y/sub 2/O/sub 3/, ZrO/sub 2/, Al/sub 2/O/sub 3/, BeO, CaO, Cr/sub 2/O/sub 3/, MgO TiO/sub 2/ and SiO/sub 2/ are presented. Equations are explained which make it possible to evaluate the oxygen distribution between the steel and the slag. For solving certain practical problems, the oxygen distribution constant can be assigned the same value for all the oxide refractories.

We have studied the sintering qualities of masses based on EB-50 electrocorundum and mixtures of MgO+MgCr2O4 and MgCr2O4+MgAl2O4. The masses expand during firing. The most stable compositions are those containing from 40 to 80% electrocorundum. In this case the ultimate compressive strength of the specimens was 20–30 MPa and the open porosity, 32–36%. The addition of 40% iron oxide does not reduce the volume changes in the masses based on MgO+MgCr2O4 containing more than 40% electrocorundum.

It is established that in the PUE-116 and Radex R-60 articles there is significant development of the plastic deformation compared with BPGE articles. This is connected with the form of the technical periclase selected as the starting material. Therefore, it can be assumed that the use of PUE-116 articles is preferable in construction-stressed linings, and articles BPGE in the slag belt. The use of Radex R-60 articles in the construction-stressed linings is more desirable than Soviet made MKhS and PShS articles [2], which is explained by the lower residual stress values developing at elevated temperatures in the Tadex R-60.

Using the instrument described, which has been improved in design for testing refractory materials for slag and hot slag resistance, we investigated the properties of magnesite, magnesite-chromite, and chrome-magnesite specimens. It was established that their life is determined by the resistance of the refractory bond. The best resistance is possessed by periclase-spinel specimens. An increase in the content of calcium oxide in the slags reduces the slag resistance of all periclase-spinel refractories that were tested. Impregnating the magnesite products with a saturated solution of chromium acetate and firing them after impregnation at 400–500°C markedly increases their slag resistance.

We prepared and tested in service crucibles of fused magnesium oxide with special additions, having a considerably higher resistance in induction-furnace conditions at temperatures of about 2000°C. The additives guaranteed the necessary sintering of the working zone in the crucible, and helped to form a direct bond between the crystals of periclase.

A new method is proposed for determining the slag resistance of refractories with lever apparatus which is qualitative. The new technique permits the specific features of the destruction of refractories by slags to be determined, and explains the mechanism of this process by mineralogical analysis and by describing the external appearance of the changed specimens. Data on the changes in the specimens during tests and the compositions of the zones will be given in the next article. Data obtained by the new method show that the slag destruction of refractories accelerates with time.

A study was made of the impregnating rate and wetting of magnesia with molten fayalite in isothermal conditions after preliminary processing of the specimens with soluble chromium salt. The application on the surface of magnesia of a thin film of chromium oxide greatly reduces the rate of impregnation, and almost halves the degree of wetting.

The effect of the metallic additives (Al, Cr, and FeSi) on the properties of unfired periclase-carbon products was studied. It was shown that their presence decreases the degree of oxidation of graphite without decreasing the strength properties of the refractory. When heat treating the periclase-carbon specimens up to 1000°C, the effectiveness of the additives decreases in the following order: Al, Cr, FeSi. At 1400°C, the effectiveness of all the additives is virtually identical.