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At present MKN corundum hydraulically hardening compound produced by Borovichi Refractory Combine to TU 14-8-359-80 is used for the outer lining of the nozzles of batch and circulating steel vacuum degassing vessels [I, 2].Wear of nozzle lining of this compound during serive is observed in areas in contact with slag and metal. The basic reasons for wear are penetration and attack of the lining by slag, penetration by metal, erosion action of the moving flows of metal and slag, and sharp thermal shocks at the start and end of vacuum degassing. To increase the life of the lining it is desirable to decrease its porosity and increase the strength and slag resistance.According to [3][4][5][6][7][8] one of the directions in improvement of corundum refractories is addition to the charge of zirconium dioxide. Taking this into consideration, addition of baddeleyite to MKN corundum hydraulically hardening compound to improve the above properties was tested.In conducting the investigations the following original materials were used: fused corundum powder to TU 14-8-384-81 produced by Kazakh Refractory Plant; type PB-2 baddeleyite powder to TU 14-8-393-82; high-alumina cement produced in the experimental Technology Section of All-Union Refractory:Institute meeting the requirments for type Talyum high-alumina cement to TU 6-03-339-78.The chemical analyses* of the original materials are shown in Table i.To obtain comparable results under the same conditions laboratory specimens of concretes were prepared** from corundum hydrauiicaily hardening compounds with additions of 6 and 16%% finely found baddeleyite and also from standard production MKN corundum compound.For all of the compounds s maximum grain size of the fused corundum was 7 mm. in preparation of the specimens the mixtures were moistened with 10% water. The moistened compounds were tamped in split metal molds and held in a humid atmospehre. The hardened specimens had the form of cubes with an edge length of 30 mm. Specimens in the form of 80 mm diameter 35 mm thick disks were prepared for determination of thermal conductivity.The compressive strengths of the specimens after hardening for 3 and 7 days had comparable values for the compound with addition of 6% baddeleyite and MKN compound (21.4 and 25.6 N/mm =, respectively, after 3 days and 30.9 and 26.9 N/mm: after 7 days). With an increase in baddeleyite content in the corundum compound to 16% the compressive strength of the specimens dropped to 17 N/mm 2 after 3 days and to 21N/mm = after 7 days of hardening.The hardened concrete specimens were fired in a batch kiln at 1600~ the service temperature of the lining. The properties of the fired specimens are given in Table 2. An analysis of this data showed that specimens of the corundum compound with addition of 6% baddeleyite possess the best combination of properties (lowest porosity, greatest strength, *The chemical analyses of the materials and the physicotechnical properties of the specimens were determined in the Laboratory for investigation of Refractory Propert...

To increase the service life of vaccum degasser linings abroad hot repairs by guniting are widely used [i-7]. The introduction of guniting of vacutun degasser linings in domestic plants is being delayed primarily by the lack of guniting equipment for these units.Taking into consideration foreign experience the circulation vacutm~ degasser in the No. 1 Oxygen Converter Shop at Novolipetsk Metallurgical Combine was installed with a guniting machine designed for semidry hot guniting of the outer and inner linings of the intake and discharge legs. In connection with this the necessity arose of developing compounds making it possible to hot gunite vacuum degasser linings, which was the purpose of this work.In development of the guniting compounds fused corundum to TU 14-8-384-81 and sintered type PPM-85 periclase to GOST 24862-81 were used as the refractory filler. The binder was Talyum high-alumina cement to TU 6-03-339-78 made in the experimental technology area of AllUnion Refractory Institute. Taking into consideration the recommendations of [8] a plasticizing addition, Druzhkovka Deposit clay, was added to the guniting compounds.In the initial stage of the work laboratory specimens of corundum-and magnesia-type guniting compounds, the chemical and grain size compositions of which are shown in Table i, were prepared. The MKTG-I corundum compound differs from the MKG-I compound in the presence of a sintered titanium-containing addition. In comparison with MPKhBG compound, MPK magnesia compound was characterized by a higher aluminum oxide content.For investigation of the physicotechnical properties concrete specimens in the form of cubes with an edge of 30 mm were prepared from the compounds. In preparation of the specimens the compounds were moistened with water to a plastic consistency and were rammed in split metal molds lubricated with machine oil. The specimens were removed from the molds after hardening for 1 day~ The hardened specimens were fired in a batch kiln at 1600~ with a hold of 4 h. The results of investigation of their physicotechnical properties are given in Table i.Of the corundum composition compounds the specimens of MKTG-I compound with a titaniumcontaining addition had the higher mechanical strength (43.6 N/mm 2) and lower porosity (32.9%). However, MKG-I corundum compound without such an addition is of interest from the point of view of obtaining a heat-resistant gunited coating (15 thermal cycles) and decreasing the changes in linear dimensions in heat treatment (0.13-0.67% growth)~ In the group of magnesia specimens, specimens of MPK compound with an increased aluminum oxide content had the lower open porosity (27.9%) and higher heat resistance (5 thermal cycles). Specimens of MPK and MPKhBG magnesia compounds were characterized by close values of mechanical strength.

In circulating and batch vacuum degassers for steel the outer linings of the intake and return nozzles made of MKN-94 corundum hydraulically hardening compound produced by Borovichi Refractory Compound [i] are subjected to significant wear in service.In [2] a corundum hydraulically hardening compound with addition of baddeleyite making it possible to increase the mechanical strength of the outer lining of the nozzles, to reduce its open porosity, and reduce the rate of wear in service is described.According to [i] the increase in mechanical strength and decrease in open porosity of concrete of corundum hydraulically hardening compound may also be obtained by addition to its composition of titanium dioxide, which promotes sintering of the concrete at the service temperature (1600 ~ but at the same time significant linear shrinkage (1.7%) is observed. The use in preparation of the corundum compound of baddeleyite and titanium dioxide additions leads to an increase in cost of it.Taking this into consideration in this work to improve the physicotechnical characteristics of corundum compound, addition to its composition as the titanium-containing addition of titanium slag, the cost of which does not exceed the cost of fused corundum, in place of a portion of which it is added in preparation of the compound, was tested. The high titanium dioxide content in the titanium slag (more than 80%) provided a basis for expecting that addition of it to the corundum compound will promote an increase in mechanical strength and a reduction in porosity of the concrete in heat treatment, and the presence in the titanium slag of impurities increasing in volume at high temperatures made it possible to expect less shrinkage of the concrete in service than with the addition of pure titanium dioxide.In conducting the investigations fused corundum to TU 14-8-384-81, Talyum high-alumina cement to TU 6-03-339-78 produced in the experimental technology area of All-Union Refractory Institute, and titanium slag to TU 48-10-31-78 were used as the original materials. The chemical analyses of the fused corundum and the high-alumina cement are similar to those described in [2]. The chemical analysis of the titanium slag is* 84.5 TiO=, 4.8 FeO, 5.9 SiO=, 2.1 AI=03, 0.3 MgO, 1.0 Cr=03, and 0.5 MnO and the growth in firing 2.2.For the laboratory investigations specimens were prepared of corundum hydraulically hardening compound (particle size 7-0 ~Lm) with additions of 2 and 5% finely ground titanium slag. For comparison concrete specimens of MKN-94 production compound were also prepared under the same conditions. To prepare the specimens the components of the compounds were mixed, moistened with 10% water, rammed into split metal dies, and held in a humid atmosphere. The concrete specimens had the shapes of cubes with 30-mm edges and of 36-mm-diameter 50-mmhigh cylinders.After hardening for 3 days from the moment of mixing the compressive strengths of the specimens were determined. A portion of the specimens of each composition was fired in a batch...

The linings of equipment for out-of-furnace vacuum treatment of steel, of the circulation, batching, and jet types, in Soviet enterprises, are made of periclass-chromite refractories PKhP, as specified by TU-14-8-368-81; these are made of fired periclase-chromite and periclase, the proportions of which in the batch are approximately 87% [1-4]. Obtaining fused materials is connected with considerable energy expenditure.Satisfying the increasing demands for these refractories in the out-of-furnace treatment of steel at present is being held up mainly by the lack of capacity for electric melting of magnesia and chromiumcontaining materials.Reducing the proportion of fused materials in the production of refractories for vacuum treatment of steel is an important problem.One approach is the use of differentiated linings for the vacuum units, using refractories made of sintered materials in the less demanding sections, e.g. in the walls.