Effective refractory materials for lining the hearths of tunnel furnace cars were developed at Petrokast Silika Co. The cars lined with such refractories have been successfully operating for more than 2.5 years in various enterprises.Petrokast Silika Co. (previous "Riostal'") supplies refractory articles and dry finished refractory mixtures (concretes) for the country's metallurgical concerns. In addition, the cumulative experience in selecting refractory materials for extreme conditions of use in metallurgical aggregates allowed obtaining refractories highly recommended as lining for hearths of tunnel furnace cars in roasting of building brick.This material, brand VCF (vibratory casting fireclay), was supplied to several firms in the construction industry such as Pobeda, Kudinovsk Ceramics Combine, Lenstroikeramika, Petrokeramika, Zvezda Factory, Neva Ceramics Factory, etc. For a relatively low price, it ensured stability of the car lining at the level of 70 -80 cycles.Since the stability of the lining is also a function of its design to a significant degree, the experiments conducted in this area allowed proposing refractories with several design variants. One such design is shown in Fig. 1. Its advantages include: minimum articles of standard sizes used (total of four), i.e., simplicity of assembling the car hearth;ensuring uniform loading of all constituent elements; relaxation of the significant localized stresses that arise; simple and inexpensive maintenance of the car; accessible and effective heat insulation in the assembly. It should be noted that Petrokast Silika Co. has also manufactured linings for cars for Unimoranda, Serik, and Burton at different times. The molds were designed and manufactured independently.The mineral composition of refractories for car linings was optimized with x-ray, petrographic, and thermogravimetric methods of investigation. Several brands of finished articles for lining cars or dry mixtures for making these items on site are now offered to building brick manufacturers.The properties of the proposed refractory materials for lining cars and the properties of materials based on hydraulic binders or liquid glass are reported in Table 1.With respect to the thermomechanical properties, the proposed refractories are much better than traditional materials and allow a longer operating cycle of the car hearth.The thermal stability was determined at the same furnace temperature (1000°C) for all samples, and the samples were cooled in water. It should be noted that carefully selecting the grain composition of the fillers ensures much lower water requirements and consequently optimum final porosity of the articles, which are functionally correlated with the strength and thermal stability of the proposed materials.Using the optimized composition of VCF refractory guarantees a minimum of 120 cycles for the car hearth, and the quality is due to the continuous regular backbone of silica tetrahedrons and a glass phase of stable composition in the ceramic binder. The material does not tend t...

In recent years, extensive studies have been carried out on the synthesis of amorphous metals and alloys having improved physicochemical properties. Centrifugal-casting units are used for maintaining the melt in its amorphous state during the course of its solidifcation. Their operation is based on rotating a bowl at a speed of approximately i0,000 rpm and continuously feeding a thin jet of the molten material having a temperature of 1500-1600~ onto its bottom portion.The melt comes into contact with the bottom of the bowl and forms a film having a thickness up to 200 ~m under the action of the centrifugal force. This film is driven upwards to the edge of the bowl and is separated from it to form granules having a size of approximately 200 zm. The bowl is cooled using liquid nitrogen (T = 173 K) so as to ensure retention of the amorphous state of the granules during their fall and to avoid ~heir crystallization.Until recently, graphite bowls or water-cooled copper bowls have been used for carryin g out atomization of the melts. However, the extent of their corrosion under the action of the melt is so significant that they can not be reused after the very first melting. Furthermore, the molten metal is contaminated with the material of the bowl. Bowls made from fused quartz are also not being used widely because of cristobalitization and cracking during the course of cooling.This paper deals with a study of the possibility of replacing such bowls and other products used under the conditions involving the action of aggressive chemical media and temperature gradients with ceramic components. When developing the components, it was borne in mind that they must possess the following set of properties simultaneously: a high thermal shock resistance (heating internally up to 1550-1600~ and cooling from the outside up to 100~ nonwettability with the melts; ability to retain mechanical strength under the conditions involving prolonged action of temperature gradients along (across) the wall of the bowl; and sufficient mechanical strength for withstanding the stresses develped in the edge of the bowl under the action of significant centrifugal loads and the shear stresses developed during the operation.The accumulated experimental and the theoretical data show that some of the properties (for example, refractoriness and the limits of temperature compatibility of the products) are controlled by the physicochemical nature of the compact ceramic materials. However, their mechanical strength and corrosion resistance can be improved using different technological routes and new heterophase materials having a specific structure [i].In view of the fact that the structure consists of an aggregate of pores and a solid region containing crystals, a glass, and an amorphous phase, one can develop materials having the required service characteristics by changing the quantitative and the qualitative ratios of the structural elements and establishing the structure--property relationships.It is known that the nature of the pore structure of ...

666.762.62;[669o!84o In view of the high cost of the refractories and expenses of relining of the converters, it is necessary to carry out studies for improving the service life of the linings of the metallurgical units according to the method of torch (flame) guniting. In the absence of abundant resources of magnesite, lime gains in importance as a refractory component of the gunite powders [I].In order to improve the coating technology and to optimize the properties, we studied the structure of the calcareous gunite coatings in the original condition and after their exposure to a lime-fayalite melt during the converter steelmaking process.The experimental specimens included fragments of an already used gunite-coated lining of a converter belonging to the Zapadno-Sibirsk Steel Plant (ZS~) after completing the industrial cm~ipaign using torch guniting and, also, blocks (bars) that were specially obtained by guniting the periclase-carbon bricks located in the taphole of the converter.A mixture of blast furnace slag (7-12%*), coke (28-30%), and lime (remainder) was used as a gunite powder. T he as-received granular materials having a moisture content of not more than 1% were milled in a ball mill until the content of the minus 0.088 nm~ fraction amounted to not less than 90%; mixing with predetermined quantities of the finely dispersed additives (that were obtained in advance) was carried out simultaneously. Guniting was carried out maintaining the following parameters: temperature of the flame approximately 1600~ consumption of oxygen 350-500 m3/min, and consumption of the powder 1000-1300 kg/min. The duration of guniting did not exceed 20 min. The thickness of the coating amounted to 20-30 nm~.

The wastes from this treatment (trapped dust and fine fractions) were found by test to be a valuable material for agricultural use, as is evident also from foreign experience [3], so the method can be operated without any waste at all.Material purified to a residual calcium oxide content of below 1.7% with either oven has been used in producing electrotechnical periclase at the Ogneupory Cooperative with the existing techniques to make only the first class of electrotechnical periclase.Material treated in the rotating oven without leaching and having a residual calcium oxide content less than 2.1% has given electrotechnical periclase of classes 2 and 3 with yields correspondingly of 80 and 20%.At the Eastern Refractories Institute, we have developed a technology for making dense sintered periclase clinker from thermochemically treated brucite for making high-grade refractories containing over 96% of the main substance.