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...

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The service of refractories in the lining of the VP-130 and ~SPTs vacuum degassers of Orsk-Khalilovo Metallurgical Combine is characterized by severe conditions of the aggressive action of slag containing 2-4% YeO, 3-5% TiO2, 4-7% A1203, 16-22% MgO, 1-3% Cr203, 27-36% CaO, and 18-28% SiO 2. The metal is superheated in the electric furance to 1750~ as the result of its subsequent teeming in a continuous casting machine [I]. The slag basicity of 1.6-1.9 favors the formation in it of dicalcium silicate which, as is known, penetrates into the pores of the refractory and destroys it as the result of expansion of the volume in the polymorphic transformation during cooling [2][3][4].In accordance with the normally used method for reducing the corrosive action of slag on the lining it is neutralized during treatment in the vacuum degasser by supplying a slag neutralizer to the vacuum chamber.A corundum slag neutralizer to Technical Specification 14-8-489-85 and also a ramming compound to Technical Specification 14-8-359-80 are used as the slag neutralizer in Orsk-Khalilovo Metallurgical Combine.However, these materials do not influence the polymorphic transformation of dicalcium silicate.At the same time a number of elements (boron, phosphorus, etc.) stabilizing the high-temperature phase of dicalcium silicate at low temperatures are known [2].Orsk-Khalilovo Metallurgical Combine and the All-Union Institute for Refractories have developed a corundum slag neutralizer containing oxides of boron and phosphorous which neutralizes the slag and stabilizes the high-temperature phase of dicalcium silicate in it. Aluminoborophosphate concentrate, which contains these elements, is simultaneously the binder for the mixture.Commercial-grade alumina to GOST 6972-74, Kumak clay to Technical Specification 14-8-338-80, and aluminoborophosphate concentrate to Technical Specification 113-08-10-17-84 were used for the production of this slag neutralizer.The alumina is supplied to Orsk-Khalilovo Metallurgical Combine in the form of a fine powder (with a residue on a No. 0088 sieve of not more than 30%) and it is not additionally treated.Clay from the existing production line in the form of powder with passage through a No. 054 sieve of not less than 65% was used.The aluminoborophosphate concentrate was used in the form of an aqueous solution with a density of 1.5-1.6 g/cm 3.First laboratory tests were made of four compositions of slag neutralizer on cylindrical specimens with a diameter of 36 m~n and a height of 50 mm formed on a hyraulic press. A mixture with a moisture content of 22-24% was prepared in a laboratory mill.The clay was added in the form of a slip. The compositions differed in the content of clay and aluminoborophosphate concentrate.The specimens of each form were dried in a drying chamber at 100~ and heat treated at 120, 700, and 1350~In determination of the physicomechanical properties the best results were obtained after heat treatment of the specimens of composition 4 at 1350~ (Table i). This composition was recommended f...

Determining the properties of the graphite-bearing refractories is of considerable importance in view of the wide application of these refractories and the stringent specifications on their properties [I].This paper presents the test results on the strength and the thermal shock resistance of the corundum-graphite refractories used in continuous preform casting machines. The tests were carried out on the laboratory specimens made from the industrial (No. i) and the experimental (Nos. 2-6) hatches that are used for producing submerged nozzles and monoblock stoppers. Table i gives the composition of the specimens under study.The laboratory specimens were made on a hydraulic press at a pressure of i00 MPa, and were fired at 1620-1670~ in a coke-powder charge.The high-temperature strength and the compressive creep were determined in argon atmosphere. The heating elements, the loading pads, and the protective screens of the heating chamber of the test set-up were made from graphite [2]. For determining the ultimate compressive strength, cylindrical specimens measuring 50 mm in height and 36 mm in diameter were heated at a rate of 180~ up to 1470~ at a rate of 720-900~ in the 1470-1770~ range, and at a rate of 120-180~ up to 18200K; at a given test temperature, the isothermal holding period amounted to 0.5 h. Table 2 shows the test results along with the data on the ultimate tensile strength obtained using the radial (diametric) compression method [3]. For all the specimens the temperature of strain initiation under load (determined according to GOST 4070-83) was above 2020~For the purpose of comparison, we measured the high-temperature strength of the specimens cut out from an imported monoblock stopper. It was equal to 8.4 MPa at 1820~ Almost all the experimental specimens, except specimen No. 6 having combined (alloyed) graphite, were found to be inferior to the specimens of the monoblock stopper with respect to strength. The temperature dependence of the ultimate compressive strength was determined in the 1720-1870~ range for the specimens of the batch No. i used for producing submersible nozzles. Composi~ tion number