Effects of some factors on centrifugal casting of oxide ceramics

Conclusions It is shown that in technically suitable conditions for shaping blanks by centrifugal casting, the deposition of the particles occurs with a streamline schedule, and the coarse fractions are deposited during acceleration of the rotation of the mold. The main factor influencing the density of the finely dispersed blanks is the duration of rotation, and for systems containing coarse filler, centrifugal acceleration. Regulating the dimensions (wall thickness) of the blank is possible by altering the concentration of solid phase in the slip and the degree of filling of the mold with it.Translated from Ogneupory, No. 1, pp. 22–24, January, 1992.     

A freeze method of obtaining ceramic based on fused quartz

Conclusions The technology of producing materials based on fused quartz by freezing the blank in a liquid nitrogen medium has been studied.The advantages of this method over slip casting in porous molds are: a reduction in the molding time; the production of articles with a large variety of wall thicknesses and complexity of surface; the possibility of firing the blanks immediately after molding; the production of strong articles with a porosity of 40-0%; the possibility of making articles with specified dimensions without mechanical treatment; and the simplicity of the process.Assistance was given in the manufacture of the molds and the molding of the specimen material.Translated from Ogneupory, No. 7, pp. 49–52, July, 1980.     

Refractories for continuous casting of low carbon rimmed steel

Conclusions The compound proportioning device designed by the All-Union Institute of Refractories from an aluminous nozzle containing 80–82% alumina with a porosity of 18–23% and a corundum insert containing 97% alumina with a porosity of not more than 18% satisfies the requirements of continuous casting of low-carbon rimmed steel of the type 05–08KP.Investigations led to the determination of a range of refractories for steel casting and intermediate ladles permitting satisfactory casting in continuous casting plant of low carbon rimmed steel of the type 05–08KP from 140-ton ladles in four shanks with a casting time of about 1.5 h.Translated from Ogneupory, No. 8, pp.4–12, August, 1967.     

Multichannel devices produced from a refractory material

Conclusions Ceramic blanks with open channels of varied cross section were produced from a refractory material by the ceramics technology.Translated from Ogneupory, No. 2, pp. 9–11, February, 1978.     

Dense zircon insert-batchers for intermediate ladles on continuous steel casting plant

Conclusions A technology was developed for making dense zircon insert-batchers with an open porosity of up to 10%. The insert wear is less than 1 mm during the hot time. They satisfy the property requirements for continuous casting of killed carbon steel deoxidized with aluminum in amounts of up to 300 g/ton.Translated from Ogneupory, No. 3, pp. 11–13, March. 1973.     

Sintering and recrystallization of high-purity magnesia-alumina spinel during hot pressing

Conclusions A study was made of the densification and recrystallization of magnesia — alumina spinel of high dispersion during hot pressing in the temperature range 1200–1600°C, a pressure of 60–300 cm², and a holding time of 10–30 min.The relative density of 92–98% theoretical was achieved at 1300–1400°C, a pressure of 300 kg/cm², and a soaking of 10 min. The spinel of theoretical density with a finely crystalline homogeneous structure was obtained by hot pressing at 1450–1600°C.Intensive recrystallization of the spinels during hot pressing occurs in the temperature range ensuring maximum rate of densification (1450–1600°C).The rate of recrystallization of the spinel grains during hot pressing at 1400°C and a pressure of 300 kg/cm² and soakings of 10 and 30 min, has the order of 10^–6 cm/sec and the maximum for the grains of diameter from 2 to 6.Report read at a symposium on pure oxide sintering, Khar'kov, 1968.Deceased.Translated from Ogneupory, No.6, pp. 32–36, June, 1970.     

Continuous hot pressurized fluids extraction of isoflavones and soyasaponins from defatted soybean flakes

This work examined the effect of pressure (413–4410 kPa), temperature (333–393 K), solvent flow rate (10–25 mL/min), ethanol-to-water ratio (0–95%) and the feed loading (80–450 g) on hot pressurized fluids extraction of isoflavones and soyasaponins from defatted soybean flakes. A four-factor Taguchi experimental design was employed to optimize operational conditions of these extractions. Experimental results indicated that 95% of isoflavones and 76% soyasaponins were recovered from defatted soybean flakes by using hot pressurized 80% ethanol extraction at 383 K, 551 kPa and 25 mL/min with a 80 g feed loading. The recovered isoflavones were further purified by a solid–liquid column packed with Amberlite XAD 16-HP resin. The content of isoflavones in the collected fraction could be enhanced from 1 to 58% by weight.     

Slip casting combined with colloidal spray coating in fabrication of tubular anode-supported solid oxide fuel cells

A simple and cost-effective slip casting technique was successfully developed to fabricate NiO–YSZ anode substrates for tubular anode-supported single SOFCs. An YSZ electrolyte film was coated on the anode substrates by colloidal spray coating technique. A single cell, NiO–YSZ/YSZ (20 μm)/LSM–YSZ, using the tubular anode supports with YSZ coating, was assembled and tested to demonstrate the feasibility of the techniques applied. Using humidified hydrogen (75 ml/min) as fuel and ambient air as oxidant, the maximum power densities of the cell were 760 mW/cm² and 907 mW/cm² at 800 °C and 850 °C, respectively. The observed OCV was closed to the theoretical value and the SEM results revealed that the microstructure of the anode fabricated by slip casting is porous while the electrolyte film coated by colloidal spray coating is dense.     

Experience gained in increasing the durability of steel-teeming ladle linings at the West Siberian Metallurgical Works

Conclusions The use of 70–75% of silica artifacts to line steel-teeming ladles, accompanied by routine hot patchings, has permitted an increase in the lining durability by from four to five melts.With an increase in the ladle throughput from 1–2 to 6–7 melts per day, accompanied by hot patchings, the maximal lining durability was 37 melts (average 28 melts) and the refractory consumption was reduced by 2.1 kg/ton of steel.The saving obtained by the use of a silica lining was 332,200 rubles.Translated from Ogneupory, No. 7, pp. 33–35, July, 1980.     

Preparation of alkaline PVA-based polymer electrolytes for Ni–MH and Zn–air batteries

Alkaline PVA polymer electrolyte with high ionic conductivity of about 0.047 S cm^–1 at room temperature was obtained by a solution casting method. The PVA polymer electrolytes, blended with KOH and H₂O, were studied by DSC, TGA, cyclic voltammetric and a.c. impedance methods. The PVA polymer electrolytes show good mechanical strength and high ionic conductivity. The electrochemical stability window at the metal–electrolyte interface is ±1.2 V for stainless steel. Ni–MH and Zn–air batteries with PVA polymer electrolytes were assembled and tested. Experimental results show good electrochemical performances of the PVA-based Ni–MH and Zn–air batteries.     

Development of a technology for producing molds on gypsum binder

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.Translated from Ogneupory, No. 6, pp. 16–20, June, 1995.     

Rheological and technological properties of chromic oxide slips and castings

Conclusions An investigation of the rheological properties of chromic oxide slips showed that their optimum casting interval lies in an acid medium at pH not above 3. In this case the zeta potential is at maximum, the viscosity at minimum, and the building-up rate and density of the casting high.Firing in a mild reducing medium gave chromic oxide specimens of porosity 14–16% and a cold-crushing strength of 1300–1700 kg/cm².Translated from Ogneupory, No. 2, pp. 42–46, February, 1976.     

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.     

Possibility of using cake from refractories production

Conclusions The use of the materials obtained as refractory heat-insulating articles is rational with minimum mechanical loading, that is, not exceeding 0.2 N/mm², and working temperatures above 1300°C. The use of the material is possible as a protective heat insulating material in slightly oxidizing and oxidizing conditions.Granulated calcined material, apparently, is also useable as heat-insulating filler for the hot tops in steel casting in ingots, which can be confirmed by appropriate testing,Translated from Ogneupory, No. 7, pp. 25–28, July, 1988.     

Differentiated use of refractories in blast-furnace hot blast stoves

Conclusions In the service of blast furnace hot blast stoves the lining and checkerwork fail in individual zones as the result of deformation of the refractories, formation of cracks, and chemical corrosion of the lining under the action of low-melting dust at high temperatures.It was shown that the deformation of aluminosilicate refractories depends not only upon temperature, load, and hold but also to a large degree upon the physicochemical properties of the parts, especially upon the composition and quantity of impurities.On the basis of an analysis of the service of refractories in hot blast stoves recommendations were developed on differentiated use of refractories in the different zones of the lining and checkerwork.For lining of the walls and the checkerwork of high-temperature hot blast stoves operating with a blast temperature up to 1300°C (temperature under the crown 1500–1550°C) the use of the following forms of refractories (GOST 20901-75) is recommended: 1550–1200°C temperature zone — type DV dinas parts; 1200–1100°C temperature zone — type MKV-72 mullite-corundum parts; 1100–900°C temperature zone — type ShV-42 chamotte parts; 900–700°C temperature zone — type ShV-37 chamotte parts; 700–400°C temperature zone — type ShV-28 chamotte parts.To line the lower portion of the combustion chamber mullite-corundum parts of types MK-80 to Technical Specification 14-8-405-82 or MKV-72 must be used.Lining of the crown, the inner wall of the combustion chamber, the hot blast lines, and the gas burners must be done with mortars corresponding to the types of refractories used (dinas and VT-1) with the addition of 10–12% orthophosphoric acid.Type MKRP-340 mullite-silica fiber parts to GOST 23619-79 and other fiber materials are recommended for use as the compensation gap filler up to temperatures of not higher than 1150°C, and asbestos-vermiculite plates to GOST 13450-68 in the up to 600°C temperature zone.The shell of the hot blast stove in the high temperature zone must be covered with thermal-insulation gunited concrete.Translated from Ogneupory, No. 7, pp. 44–50, July, 1986.     

Densification of RO2 type oxides during hot pressing

Conclusions The optimal conditions for obtaining high-density products by the hot pressing of pure oxides of the type RO₂ were established. In order to prepare high-density samples with simultaneous hot pressing and stabilization of the zirconium and hafnium dioxide the heating must be slowed down in the polymorphic interval (800–1200°C) to generate the necessary number of vacancies which ensure significant densification. The amount of stabilizer (calcium or magnesium oxide) should not be less than 7% (by weight). Prestabilized zirconium and hafnium dioxide can be sintered by hot pressing with heating without holding in the interval 800–1200°C to a relative density of 0.98–0.99 under a pressure of 160 kg/cm², and also with a holding time of 10 min and a temperature of 1700–1800°C (zirconium dioxide) and 2100–2200°C (hafnium dioxide).Fused quartz can be sintered by hot pressing to zero water absorption and a relative density of about 1.0 at 1400°C, a pressure of 200 kg/cm², and a holding time of 10 min.Deceased.Translated from Ogneupory, No. 2, pp. 36–40, February, 1969.     

Service of elongated composite nozzle batchers and nozzles under the batcher insert for continuous steel casting

Conclusions High-alumina composite elongated batcher nozzles containing 62–64% A1₂O₃ satisfy the requirements of casting killed steel. They are being introduced in the continuous steel casting plant of the electric steel casting shop of the Novolipets Metallurgical Factory.The casting of metal in a crystallizer needs to be done through elongated batching devices under a cover, with the maximum degree of sealing and proximity of the metal surface to the tapping hole of the nozzle.Prolonged casting of the unkilled steels type ST2KP and 3KP should be done through elongated high-alumina nozzles containing 80–82% A1₂O₃ with corundum batcher inserts.The following took part in the project: S. A. Krulevetskii, E. I. Ermolaeva, V. V. Parfent'eva, L. N. Baskakova, T. K. Chirkina, N. T. Nikokoshev, Yu. A. Kravchenko, and G. B. Lesokhin.Translated from Ogneupory, No. 2, pp. 21–24, February, 1969.     

Experimental casting of multichamotte refractories from slip

Conclusions The possibility of casting refractories from multichamotte slip with a maximum moisture content of 15% has been investigated; a preliminary treatment of the slip under vacuum is recommended as well as a brief vibration of the gypsum molds within a certain period after pouring.The high rate of moisture loss and solidification of multichamotte slip castings allow production on an industrial scale.Multichamotte kaolin mixtures yield castings up to 100 × 80 × 80 mm which acquire the following properties after firing at 1470° C: bulk density –2.17–2.26 g/cm³; porosity –12 to 18%; compressive strength –420 to 800 kg/cm²; loss on ignition –2. 7 to 4. 3; total shrinkage in relation to the size of gypsum molds –4 to 5%.The casting process is of practical value for the manufacture of multichamotte products (including high-alumina refractories) since molding the latter by means of pressing is either impossible or extremely difficult.Industrial tests are conducted for the verification and more accurate determination of technological parameters and the technical and economic effectiveness of the method.     

High-temperature rheological properties of clay bodies and bodies plasticized with clay

Conclusions We determined the rheological properties of clay materials at elevated temperatures. With an increase in the temperature and pressure the structural-mechanical constants diminish, and the plasticity increases. The total proportion of elastic and plastic deformations reaches significant values (92–95%) in kaolins at 1450°C, and in Chasov-Yar clay at 1200–1250°C. It is in these conditions precisely that we obtain the densest thermal-pressed products.With optimum thermoplastic pressing temperatures the various clay materials have the closest viscosity and maximum yield point values.The best natural raw material for thermoplasticizing is Chasov-Yar clay, but it is possible to use other clay materials. It is possible to regulate the rheological properties of bodies by varying the compositions (filler + thermoplasticizer) of the bodies, the pressing temperature, and pressure.The rheological properties of mixtures of zircon and thermoplasticizer (10% Chasov-Yar clay) at 1450–1480°C facilitate the production of especially dense products for continuous steel casting. Tests carried out on continuous casting plant were successful.Translated from Ogneupory, No. 6, pp. 43–51, June, 1973.     

Casting of products from aqueous acid alumina slips in gypsum molds

Conclusions An investigation was carried out of the pH of slips of commercial alumina GA85 fired together with 0.1% MgO and 1.5% H₃BO₃ (on 100%) at 1300°C and ground to particles of 1–3 as a factor in the growth rate, density, and moisture content of the castings and in the process of water elimination to the gypsum mold.The added MgO and B₂O₃ narrow the pH range for casting to 2–3 from the 2.5–4.5 for all-alumina slips.The process of water elimination from the slip to the gypsum mold depends not only on the density of the casting but also on the form of bond of the water with the solid phase which depends in turn on the pH.Translated from Ogneupory, No. 3, pp. 50–52, March, 1978.