V. G. Borisov

Reaction thermodynamics in the SiO2-SiC system

ConclusionsThermodynamic analysis showed that in the SiO2-SiC system the following reaction may occur prior to 1950°K: 2 SiO2 (solid-liquid)+SiC (solid)=3 SiO (gas)+CO (gas). In the 1950–2800°K range the reaction between SiO2 and SiC may be expressed by two combined reactions 1) 2 SiO2 (solid-liquid)+SiC (solid)=SiO (gas)+CO (gas). 2) SiO2 (solid-liquid)+2 SiC (solid)=3 Si (liquid)+2 CO (gas). With temperature rise, the degree of occurrence of the process following reaction 2 increases, and that following reaction 1 diminishes. The results of the thermodynamic analysis agree well with experimental data.

Thermodynamic analysis of dissociative volatilization of silicon carbide

ConclusionsWe made a thermodynamic analysis of the dissociative evaporation or volatilization of silicon carbide in the range 2500–3150°K. Up to 2540°K dissociation of silicon carbide occurs only in the gaseous phase. Above 2540°K silicon carbide dissociates in the gaseous and condensed phases. At a temperature above 3150°K silicon carbide does not exist in the condensed phase.On the basis of the results of our thermodynamic analysis, we established the composition of the equilibrium gaseous phase over silicon carbide and the degree of the progress of reactions of dissociation and volatilization of SiC.

Thermophysical properties of tar-bonded refractories

ConclusionsAn investigation was carried out of the thermal diffusivity of as-molded, heat-treated, and coked dolomite, magnesite and dolomite-magnesite tar-bonded refractories by the even-rate heating of flat specimens to 200–1600°C in an inert medium.The relation was determined between the thermal diffusivity and the heat-treatment conditions and composition of the specimens; it was established that the disturbance of the monotonic temperature dependence of the thermal diffusivity arises primarily from Ca(OH)2 dehydration; it was shown that the thermal diffusivity is a function not only of the temperature but also of the rate of heating.The thermal capacity was determined by a known method for 1000–1900°C and calculated from the additivity of the thermal capacity of coked tar-dolomite refractories. The determined and calculated values differed by not more than 5–10%.The thermal conductivity of tar-bonded refractories was determined from the data relating to the thermal diffusivity and thermal capacity and compared with published findings. Up to 1000–1400°C the results obtained in this investigation lie within the spread of the published data.

Thermal diffusivity of resin-bonded refractories over a wide temperature range

Results are shown of thermal diffusivity measurements made on resin-bonded refractories of various compositions and structures.

Increasing the resistance of oxygen converter linings

ConclusionsWe developed a. differentiated construction for converter linings using tarred dolomite and periclase — spinel refractories in sites most prone to erosion: the throat, the neck, and the upper cylindrical parts on the pivot sides. Taking into account the topography of the wear we selected a rational profile for the working layer of the lining with which we obtained a higher and more uniform resistance.We developed and introduced a production technology for tarred dolomite refractories by pressingbodies cooled to 35–45°C, using tar with an increased coke residue and a viscosity of C1040=40-50 sec as the bond.We also improved the order of feeding in the batch materials, introduced slag and blow cycles for converter melting, ensuring rapid finishing of the high-basic slag in the blow process, reducing the melting time and the number of heats produced with the blow, etc.As a result of improving the quality of the tarred dolomite refractories, the introduction of the differentiated (with respect to thickness and types of refractories used) constructions for the linings, the use of rational firing cycles for the linings, improvements and stabilization in the quality of the batch materials, and improvements in the converter melting technology, the average life of the converter linings increased to 612 heats and the total consumption of refractories dropped to 2.95 kg/ton of steel; the maximum resistance reached 646 heats.The increase in the life of the linings ensured regular operation of the converter shop and provided a substantial increase in steel output.

Investigation of the heat treatment processes of resin-bonded refractories in an atmosphere consisting of the products of sublimation and decomposition of the binder

ConclusionsHeat treatment of the resin-bonded refractories in an atmosphere consisting of the products of sublimation and decomposition of the binder leads to a significant improvement in the properties of the specimens (in particular, in the coked condition). The increase in the content of the residual carbon, the mechanical strength of the specimens, and their hydration resistance are determined by the heat treatment temperature. The highest levels of the physical and the technological properties are obtained after heat treating the specimens in the 400–600°C range. In this case, the most significant effect is observed in the lime-periclase refractories and the minimum effect is obtained in the resin-periclase refractories.The increased hydration resistance of the resin-bonded refractories containing free calcium oxide (the lime-periclase and the periclase-lime refractories) owes mainly to fixing up of CaO during the heat treatment process and to the formation of the protective calcium carbonate films at the surface of the fired dolomite grains.

Improvement and introduction of the lining of a gas-oxygen refining vessel

ConclusionsA design of lining differentiated by thickness and form of refractories used has been developed and introduced in Dnepr Special Steel Plant for the first time in the USSR for a vessel for gas-oxygen refining of low-carbon and corrosion-resistant types of steel specifying use in the working layer of the lining of:type BPGK periclase-carbon refractories in the bottom (920 mm);type PShPKh periclase-spinellide refractories with addition of fused chrome-alumina-spinellide in combination with PKhK refractories in the housing (690 mm) and throat (460 mm). The average life of such a lining is 63 heats and the maximum 73 heats under unfavorable operating conditions of the vessel.With an increase in the melting of low-carbon types of steel a thicker design of lining with a variable lining thickness in the cylindrical housing of the vessel (from 690 to 920 mm) with an increase in the power of its drive mechanisms is recommended for introduction. In the experimental campaigns the maximum life of the thickened lining reached 80 heats. For the purpose of further increasing the gas-oxygen refining vessel life it is primarily necessary to improve its operating conditions, for which there are very signifcant reserves, and also to accelerate work on introduction of torch guniting.

Structure evolution in periclase-carbon refractories at elevated temperatures

ConclusionsAt high temperatures, periclase-carbon systems exhibit a significant change in their phase composition and spatial distribution of the oxide and the carbonaceous components. The structure evolution of the periclase-carbon refractories occurs due to sintering of the mineralogical filler under the conditions involving a change in the volumetric proportions of the oxide and the carbonaceous phases because of the oxidation-reduction reactions.

Development of a resistant differentiated lining for steel teeming ladles

ConclusionsA differentiated steel teeming ladle lining with the use in the walls of tar- or pitchbonded heat-treated periclase-chromite refractories has been developed.The life of the ladles with the experimental linings in the shops of Novolipetsk Metallurgical Combine is three and more times greater than the life of the normally used chamotte or rammed quartz-clay ladle linings.The life of lime-periclase linings may be significantly increased the use of measures eliminating skull formation on the refractory lining in service including heating and covering of the ladles with covers during the periods between teemings, the use of special magnesia mortars, etc.

Comparative tests of refractories in the tuyere zones of a converter with bottom oxygen blowing

For the purpose of investigation of highly resistant refractories for use in the tuyere zones of the bottoms of converters with bottom oxygen blowing after semiproduction tests, comparative tests were made of different domestic refractories under production conditions. Tuyere refractories in the form of 280x225x190 mm blocks with a center channel under the 30 mm diameter tuyere were produced for the investigation at Magnesite Combine in TsMI-2. Blocks of the type PKhK periclase-chromite composition, type PShGP periclase with a spinel binder, type KhM chromite-periclase, KhPT, and type MKhVP periclasechromite were produced. The chemical compositions of the mixtures for production of the parts are given. Vanadium iron was blown and the bottom fuel-oxygen blowing of the vanadium iron was done using two variations. The amount of wear of the blocks and tuyeres is presented and a chemical analysis of the samples of parts after service is shown. Under the conditions of the investigation conducted, KhM chromite-periclase refractories showed the greatest resistance.