Compounds for semidry hot repair of the lining of the legs of a circulation vacuum degasser

Abstract

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.