At present the method of semidry guniting of the lining of steel teeming ladles, which makes it possible to increase their life by an average of 20-30% and to reduce material and labor costs in lining work, has been introduced into domestic metallurgy. The extent of introduction of guniting of steel teeming ladles based on steel poured is more than 40 million tons and is gradually increasing.Despite the results obtained, work is being done in the direction of torch guniting of the lining of steel teeming ladles [i]. This apparently is related to the fact that the torch method of guniting makes itpossible to obtain more dense coatings in comparison with similar coatings obtained by the traditional method of semidry guniting.This article presents the results of investigation of the properties of torch gunited coatings based on quartz Sand, chamotte, alumina, magnesite, and dolomite and also of production tests of torch guniting of the lining of steel teeming ladles with chamotte com ~ pounds.The coatings were applied under stand conditions in the flame of a gas--oxygen torch with consumptions% of 50 m3/h of natural gas, I00 m3/h of oxygen, and 50-60 kg/h of powder.The material compositions of the charges for torch guniting are given in Table i and the chemical compositions of the original components in Table 2.The charges were prepared by mixing the original components in a ball mill. This method makes it possible to obtain conglomerates of particles in the case of multicomponent compositions.The powders based on quartz sand, chamotte, and alumina were applied to chamotte brick and the powders based on magnesite and dolomite to periclase-chromite brick. The coating thickness was 20-120 n~n. The losses of powder in application of the coatings were 20-30%. Before application of the coating the surface of the brick was heated by a torch to 800-1000=C. As the result of chemical interaction and structural transformations of the charge components in the flame and directly in the coating its phase composition differs from the phase composition of the original charge (Table 3). Interaction of quartz with corundum with the formation of mullite and transformation of quartz into silica glassy phase occur. Aluminum oxide forms solid solutions with chrome oxide. Microscopic investigations showed that the quartz sand-base coating consists of silica glass with N = 1.46 and quartz grains. The pores are isolated round ones with a size of 0.02-0.6 mm. The chamotte-base coating consists of coarse crystals of mullite up to 0.3 m~n long, glassy phase, and rare grains of quartz with a size up to 0.25 mm. In immersion two glassy phases with N = 1.46 and N = 1.52 are observed. The pores are primarily isolated round ones with a size of 0.01-0.03 mm.The alumina-base coating has a light gray color and consists of angular corundum grains with a size of 0.02-0.05 mm. In immersion the corundum grains are colorless with N = 1.767. The pores are fine isolated ones of irregular form with a size of 0.01-0.03 ram.In application of the alumina and qu...
Investigations have been made to ascertain the feasibility of using dust, trapped during roasting of kaolin to chamotte, to make aluminosilicate guniting compounds. It was postulated that incorporation of highly dispersed dust into the charge would increase the density of the gunite coating and that the carbon introduced into its composition would reduce the wettability of the coating by metal and slags.The initial refractory materials for this investigation were ShKN-2 kaolin chamotte, Pologi kaolin, and dust collected by electrostatic precipitators and cyclones downstream of the furnace, during roasting of kaolin. Table 1 shows the chemical composition of the initial materials. The binder was sodium water glass (density 1.2 g/cm~ with ratio SiO2/Na20 = 2. The initial components were separately ground in a ball mill with metal balls. After grinding the kaolin chamotte contained 5?o of the + 2 mm fraction, 45?o of the 2-0.5 nun fraction, and 50% of the 0.5-0.09 mm one; the grain size of the kaolin and the dust particles was less than 0.09 ram.Using mechanical mixing, from the initial materials we obtain five guniting compounds containing 90?o of kaolin chamotte and 107o of kaolin, without dust and containing from 10 to 40% of dust (above 100%). The amount of binder introduced was 10% (above 100%).From the resulting guniting compounds, under a pressure of 100 kgf/cm 2 we molded cylindrical specimens (diameter and height 25 mm) and roasted them at 1600~176 i 8 9 10 . 1t 2, Fig. I. Diagram of gunlting sector: 1) ladle; 2) rotating arm; 3) manipulator; 4) pulverizer; 5) control disk; 6) guniting machine; 7) feed hopper; 8) belt conveyer; 9) tank with bubbler; 10) vessel for binder; 11) bin for powder. The guniting powder is fed to the bin from the working platform of the furnace.All-Union Institute of Refractories. Zaporozhe Refractory Factory. Zaporozhstal' Factory.
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