One of the most important means of increasing labor productivity, economy, and rational utilization of material and labor resources in modern metallurgy is reducing the time for repair of the worn linings of metallurgical equipment, mechanization and automation of this process, and economy in refractory materials.In recent years it has become obvious that one of the promising methods in this direction is [I] the torch guniting method. The effectiveness of the guniting process is determined to a large degree by the occurrence of the components of its heat-and mass-exchange processes, in particular the heating of the refractory material particles in the jet and heating of the lining.The wide introduction of torch guniting in metallurgy provides a tremendous saving and therefore at present metallurgists of many countries of the World are displaying active interest in it. However, until now the theory of the guniting process has been developed very weakly and in essence has a fragmentary character. The many publications on torch guniting contain essentially a presentation of specific production experience and descriptions of narrowly specific results of experimental production investigations, the basis of which is practical experience and experience in the study, including theoretical, of similar or related phenomena and processes and also intuitive concepts of the rules of torch guniting. Some publications have been devoted to theoretical investigations but as a rule they consider only individual particular problems in a simplified setting.The need for development of the theory of guniting and, in particular, of the theory of the heat-and mass-exchange processes composing the essence and determining the effectiveness of torch guniting has been maturing for a long time. An experimental solution of these problems is difficult because of the difficulty and complexity in the development and use of a large flame stand (with a flame carrying the solid phase) and also the large variety of technological, geometric, and other characteristics of metallurgical equipment causing in turn wide variation in the conditions of repair of points of wear of the lining.In connection with this, in the State Institute for the Design of Nickel Industry Plants and the All-Union Institute for Refractories an attempt has been made to develop a universal physicomathematical model and software for the common system computer for calculation of a combination of complex heat and mass exchange processes which are the basis of torch guniting of metallurgical equipment. Below is given a brief description of the model developed and individual practical significant results obtained during computer experiments with it.The general model consists of three particular physicomathematical models. The first describes the temperature and velocity field of the gaseous and solid (polydisperse) phases of the guniting flame, the second the conditions of heat exchange of the portion of the lining being gunited with the external in relation to it medium, and the thi...

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...

Successful experience accumulated in the steel industry on the introduction and use of torch guniting as a method of hot repair of metallurgical equipment linings and above all else of steel melting converters has created good experience for its use in nonferrous metallurgy.However, the first experience in the use of torch guniting for repair of the tuyere belt of horizontal converters at South Ural Nickel Plant did not provide positive results [i]. This indicates that direct transfer of experience in the steel industry without taking into consideration the specific operating conditions of nonferrous metallurgical equipment is not promising.The basic reason for the low effectiveness of torch guniting of nickel industry converters was the relatively low temperature of the converter process of nickel mattes (< 1500~ and consequently the low lining temperature before application of the coating, which is approximately 400~ lower than the temperature of a steel melting converter after pouring of the metal.By operating conditions and applicability of torch guniting copper and nickel production equipment may be conditionally divided into a number of basic groups.The first group includes the 30-ton vertical converters for processing of ferronickel at Pobyzhskoe and Buruktal'sk Nickel Plants. They are almost completely similar to steel melting converters and consequently guniting methods developed in the steel industry may be applied to them. However, as calculations showed, as the result of the low scale of production and the relatively long life of the lining in these units the use of torch guniting for repair of them is economically undesirable.Another group of equipment is electric arc furnaces for melting of anodic mickel or copper, which are similar to steel melting electric furnaces. For these furnaces local wear of the lining as the result of nonuniform distribution of power between the electrodes is most characteristic. The possibility of repairing local wear of their lining involves the necessity of development of a method of directed torch guniting and the appropriate equipment, Vertical converters for melting of sulfide copper and copper-nickel concentrates are the third group and are similar to vertical steel melting converters in their operating characteristics (batch process) and temperature of the production operation (above 1700~The difference is in the properties of the molten materials processed in them. In particular, molten sulfides at above 1700~ possess a high penetrating capicity and quite easily fill cracks, irregularities, and voids in the refractory lining. The influence of this factor on the effectiveness of guniting and the adhesion strength of the gunited layer with the lining have not been studied and the problem includes evaluation of the effectiveness of preliminary treatment of the surface to be repaired with a high temperature flame for the purpose of melting out of the sulfides, removal of the slag crust from the surface, and heating of the lining before application of the coating.