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The level of the physical and mechanical properties of steels and alloys can be improved by decreasing the degree of their contamination with nonmetallic inclusions. Among the methods and the technological routes available for solving this problem, the filter-refining method appears to be promising. This method involves passing a molten metal through a filtering unit in which the particles of the nonmetallic phase are separated out and are arrested at the developed surface of the filter. This concept is not new; in the Soviet literature, the process is known as the "Firam-process." This method reduces the extent of contamination due to nonmetallic inclusions during the process of pouring molten metals into the ingot molds and the molds used for continuous casting or in foundry.At the present time, a large volume of experimental data is available on this subject. Systematization of these data is required mainly for evaluating the prospects of application of this method for refining steels and alloys under the conditions of mass-scale production.A filter element (filter-assembly) forms the main technological component of any filtering unit. Under industrial conditions, two basically different designs of the filter elements have been tried out. The first design includes a refining chamber having a granular (lump) sorbent. The sorbent granules are obtained by fragmenting (dispersing) large lumps of a refractory ceramic. A ceramic filter element forms the main component of the second design. Different methods are used for producing it (in particular, compaction, slip casting, extrusion of a refractory body, compaction of ceramic granules into a single block containing a developed system of pore channels, and braiding of glass fibers or the fibers of a plastic ceramic material). In recent years, the so-called 'foam' filter elements have gained in importance. They are obtained by impregnating foamed polyurethane with a ceramic suspension, squeezing out the excess suspension, drying, and firing. The filter elements are located in the intermediate spaces during top-pouring of steels [i, 9], in the channels of the bottom-pouring lines [13], in the intermediate ladles [2, 6-8, I0, 14], in the channels of the immersible nozzles (downtubes) used during continuous casting [15], in the short pipes (nozzles) of the RH and DH installations [16], and in the casting equipment [17]. Figure 1 shows the dispositioning of the filter elements during top and bottom pouring and continuous casting.The method proved to be highly effective when refining the plain-carbon steels that were deoxidized (killed) using A1 [5,8,12,14] The maximum weight of the alloy being refined amounted to 250 tons [6] at a pouring rate of 2.5 ton/min [14].The effectiveness of the filter-refining process is indicated by the decrease in the contamination due to nonmetallic inclusions [5,8,9] and the total oxygen content in the alloy [i, 2, 5, 18] and, in a number of cases, by the decrease in the sulfur content [ii]. All et al. [5] and Fukudo [7] observed a decrea...

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The refractories produced using phenol-formaldehyde based binders are widely employed for lining oxygen converters, electrical steelmaking furnaces, steel refining units, and other metallurgical installations.As a result of carbonization of the phenol-formaldehyde resins, a binding (bonding) carbonaceous network (skeleton) forms within the components. The physicoceramic and the service properties of the refractories depend on it to a large extent. The formation of the network occurs through curing (setting/hardening) of the resin by polycondensation of the oligomers with subsequent carbonization of the developed polymer.The earlier investigations [i, 2] showed that there is a significant effect of the refractory filler on the carbonization process of the phenol-formaldehyde binder; loosening of the polymer network, loss of resistance of the polymer skeleton to oxidation, and reduction of the coke residue during its carbonization are observed. The effect increases with increasing dispersion and basicity of the filler.We studied the carbonization process of a phenol-formaldehyde binder in a system (composition) containing a periclase filler by analyzing the volatile products formed during their heat treatment.Resol phenol-formaldehyde resin was used as a binder and finely milled periclase (finer than 0.088 mm) was used as a filler.The system consisting of the binder and the filler was prepared by mixing the periclase powder with the resin with subsequent curing of the resin at 200~ in a drier. The system contained 30% hardened polymer. The volatile substances formed during the high-temperature heat treatment of the "periclase-phenol-formaldehyde polymer" system were analyzed by comparison with the volatile substances liberated during destruction of pure polymer. Figure 1 shows the schematic of the apparatus used for carrying out pyrolysis of the specimens. It consists of a quartz test tube 1 in which a platinum boat 2 containing the specimen is placed, a heating furnace 3, a vacuum pump 4, a sampler 5, vacuum cocks (valves) 6, and valve-dispensers (feeders) 7.Before carrying out pyrolysis, the specimens were subjected to evacuation up to a residual pressure of 1.3 Pa at a temperature of 220~ for 30 min for removing the sorbed gases. Thereafter the test tube containing the specimen was disconnected from the sampler system and was heated successively up to 300, 400, 500, 800, and 1000~ maintaining a 60-min dwell at these temperatures. Then, samples were drawn for analysis by connecting the evacuated sampler system to the test tube containing the specimen. After equalization of pressure, the test tube was disconnected from the sampler system. Using the valve-dispensers, the gas existi~R in the samples was fed to a LKhM-8MD chromatograph for analysis. The columns of one of the chromatographs were filled with the 'Polisorb-I' sorbent; this made it possible to analyze CO2, C2H 2 and H20. The columns of the second chromatograph were filled with zeolite for determining the contents of H 2, CH 4, CO, 02 and N 2. Oxygen and...