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An analysis was carried out of certain aspects of the zone-forming process in the roof brick of open-hearth furnaces.

High-density periclase-spinel refractories can be produced from a body of magnesite powder containing 94–96% magnesium oxide and Kempirsai chromite by high-pressure molding and high-temperature firing in a tunnel kiln. The product is strong with good thermal stability and high onset temperature of deformation under a load. The structure of the refractory is improved as a result of the formation of a large proportion of direct intergranular bonds between the periclase and spinel. It is planned to produce experimental industrial-scale batches of periclase-spinel roof refractories and to subject them to trials in the roof of open-hearth furnaces in continuous operation.

High-density strong blocks for the lining of the pouring apertures of converters and open-hearth furnaces were produced from periclase-spinel bodies and from fused periclase. The life of the periclase-spinel blocks in the pouring apertures of 100-ton and 400-ton open-hearth furnaces equals 50–60 and 27–41 melts and in the apertures of 100-ton and 250-ton converters 80–145 and 35–70 melts respectively. The life of the blocks molded from fused periclase equals 115–200 and 45–74 melts in the apertures of 100-ton and 250-ton converters respectively and 80–128 melts in the aperture of 100-ton open-hearth furnaces. The durability of these lining blocks is two to five times greater than that of individual refractory bricks and rammed compounds so that the number and labor intensity of the repair jobs decrease sharply. The wear of the blocks takes the form primarily of corrosion and erosion by the metal melt during its flow from the converter and open-hearth furnace.

Periclase-spinel products prepared from magnesite powders which are pure in chemical composition and beneficiated Kempirsaisk chromite possess an increased resistance (30% higher than in ordinary periclase-spinel brick) during service in the roof of a double-bath steel-melting furnace, operating with oxygen blow in the bath. Their wear in general occurs as a result of the fusion of the working surface. The mechanism of this wear is explained by the metasomatic processes which lead almost to complete replacement of the periclase and chrome-spinel by ferritic spinels.