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The operating conditions of refractoriesin billet continuous casting machine tundishes are constantly becoming more severe as the result of the increase in the chemical and erosion action of the molten metal, which is related to the increase in the time of its contact with the lining in pouring by the "heat after heat" method, the high temperature (up to 1670~ of the metal, and the presence of alloys and oxides of manganese and iron forming low-melting eutectics with the oxides of the refractories.In the Converter Shop of the Azovstal' Zhdanov Metallurgical Combine KShU-37, KShU-38, and KShU-39 ladle brick (GOST 5341-69) are used to line the 23-ton tundishes.The reinforcing layer is 40 mm thick and the working layer I00 mm thick.The average life of the lining is 4.8 heats.In repair of the lining after teeming as the result of penetration of the metal into the joints of the lining, welding of it and the slag to the bricks, and erosion failure at the point of impact of the stream up to 80-90% of the refractory parts are replaced.A traditional lining of refractory parts [i, 2] does not possess sufficient life, which restricts improvement in continuous teeming and influences the stability and economy of billet continuous casting machine operation.In addition, the use of individual piece refractories for the lining of tundishes involves large expenditures of low productivity manual labor and is practically impossible to mechanize.As domestic and foreign experience shows [3][4][5], an effective solution of the composite problem of increasing the life and mechanization of the preparation and repair of tundish linings is the use of monolithic protective refractory coatings.The All-Union Scientific-Research Institute for Mechanization in Ferrous Metallurgy together with Azovstal' Metallurgical Combine has developed and approved compositions of magnesia--spinellide coatings (Table i) for protection of billet continuous casting machine tundish linings.The ratios of the components of the coatings were determined on the basis of the results of laboratory tests.The choice of magnesia--spinellide coatings was the result of their adequate chemical and mechanical resistance during teeming and the peculiarity of their softening in the 800-I000~ range ( Table 2). The latter property guaranteed a decrease in failure of the brick lining in removal from the tundish of the residues of steel and slag in comparison with the possible failure in tundishes with silica and aluminosilicate mixtures [7, 8]. For example, in heating of magnesia--spinellide materials in the 800-I000~ range a reduction in their ~comp occurs.This reduction leads to failure of the concrete lining in the given case particularly in the zone where the coating adjoins the base brick lining of the tundish.The basic physicomechanical properties of the coating are presented in Table 3.To determine the thickness of the magnesia--spinellide monolithic protective coating its thermal loss of strength in a tundish was studied.For this purpose samples prepared from mixtures of t...

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