A discussion: Problems of the use of torch guniting for repair of the linings of thermal equipment and production of block refractory parts. Influence of refractory structure on the indices of torch guniting

Abstract

It is obvious that under otherwise equal conditions (lining temperature, type of refractory, guniting compound composition, etc.) the coating quality depends significantly upon the condition of the surface to which the coating is applied and the character of interaction of the guniting compound with the surface layer of the lining. The condition and structure of the lining surface layer are determined by the service conditions of the refractories in equipment [i, 2]. Therefore this investigation was divided into two portions, an investigation of the structure and properties of the worn refractories of actual equipment and an investigation of the character of change in the structure of the same refractories after torch guniting.To conduct the investigations samples of refractories were taken from the tuyere belt of the converters of the copper and nickel plants of the Norilsk Mining and Metallurgical Combine.An attempt to study the change in structure of the refractory and particularly the change in composition of its structural constituents in interaction with the molten materials was made in investigation of the service conditions of refractories in the reaction mixture in melting of sulfide raw material in the suspended condition [2, 3]. The methods of investigation of refractories used in these works (optical microscopy and x-ray spectral mlcroanalysls) were also used in our investigation.As is known, the original chromium and magnesium oxide-base refractories used for lining of the tuyere belt of the Norilsk Mining and Metallurgical Combine converters have a base of granules of periclase-spinellides and chromites and the binder is monticellite-type silicate (Ca, Mg) SiO~ [3]. The parts differ by types in the ratio of magnesite and chromite [4].From the equipment there were taken 15 most characteristic samples of refractories, which were conditionally separated by degree of wear into four groups. Earlier [2, 3] it was established that in the first stage of interaction with the molten material penetration of the refractory occurs and then formation on the hot surface of the lining slag, the composition of which is determined by the composition of the molten materials. In the subsequent stages interaction of the lining slag with the adjoining portion of the refractory occurs with the formation of transition zones. In investigation of the refractories of horizontal converters it was established that the majority of the specimens have an identical structure (Fig. i). The specimens differ in the thickness of the zones, the lining slag, the working zone with penetration or without it, and the zone of unchanged refractory. In addition differences in the depth and composition of penetration and in the composition and structure of the lining slag were noted.The thickness of the lining slag varies from 0.5 to i0 mm depending upon the degree of wear of the part.In the majority of cases the lining slag was magnetite with a variable content of nonferrous meteals up to ferrites containing inclusions (veins) of iron silicat...