Flame guniting is based on the principle of interaction of the high-temperature refractory particles with the surface of the lining, the temperature of which is significantly lower than the temperature of the particles being applied and the gunited coating being formed. In such a process the temperature state of the coating--lining system satisfies the inequality to<~

The method of torch guniting is based on the creation of a high-temperature flame in the cavity of the converter in jet mixing and combustion of coke fines in a flow of oxygen. However, in such a method of combustion complete mixing of the components does not occur in the flame, as the result of which the guniting flow does not contain a stoichiometric mixture of fuel and oxygen.To provide complete combustion of the fuel, it is necessary to add an additional quantity of oxygen.Determination of the necessary quantity of oxygen to maintain rational guniting conditions in relation to the capacity of the guniting equipment, the chemical compositions of the guniting mixture and the coke fines, and the ratio of the initial velocities of the coke fines and oxygen is a complex and pressing problem.

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At the Karaganda Metallurgical Combine wide use is made of flame guniting of oxygen converter linings [i].Taking into consideration positive experience in the use of this method, the combine together with the Donets Scientific-Research Institute for Ferrous Metallurgy has developed for the first time in world practice a combination of equipment and method for flame guniting of open-hearth roof linings.Experimental guniting of the roofs of 600-ton open hearths was started in the second half of 1980.The gunite mixture and the basic equipment used were similar to that used in guniting converter linings.However, during development of the method and taking into consideration the character of furnace roof lining wear, substantial changes in the design of the guniting lance were introduced.Since the portion of the lining from the center portion of the roof to the rear wall is subject s the greatest wear, the guniting nozzles were located in a fan shape, that is, in such a manner that in the working position the axis of each nozzle is directed perpendicular to the roof surface.At the same time, the flame covers the arc of the roof from the center portion to the rear wall.Experience in guniting converter linings [2] has shown that the effectiveness of its use depends to a significant degree upon the parameters of the process, including the consumption of Gunite mixture, of oxygen and air for pneumatic movement, the rates of flow of the components, their ratio, etc.However, the guniting conditions for open-hearth roofs and converter linings have basic differences.The primary of them is the presence in the furnace working space of the fuel flame.To this it must be added that one side of the furnace is under suction, the configuration of the working space is less convenient for the creation of identical conditions in guniting all portions of the roof, the strength characteristics of a holdup-holddown roof are lower than of a converter lining enclosed in a metal shell, and the capabilities of an open-hearth shop for providing the guniting equipment with oxygen are less than of a converter shop.The parameters of guniting the furnace roofs were selected taking all of these features into consideration.To eliminate furnace stoppages it was desirable to combine guniting with some production period in melting.Heating, melting, and finishing may be this period. Naturally guniting during the melting or finishing period is possible with poured sills.Therefore, the design of the head and the nozzles is based on the condition that the guniting nozzle in the working position is located 0.7-0.9 m above the level of the working door sills. In the transverse cross section of the furnace the nozzle is located in such a manner that its front edge is at a distance of 1.3 m from the rear wall.The distance between the slits of the nozzles located in the 1.25-m-long portion of the lance and the surface of the roof changed from the first to the last nozzle within limits of 3.0-3.6 m.The oxygen consumption for guniting in one of the furnaces durin...