REFRACTORIES UDC 666.762.3Periclase--chromite (magnesite-chromite) roof refractories are made from a mixture of magnesite and coarse-grained chromite (MKhS articles) [1] or finely milled chromite (PShS articles) [2]. The latter have a high density and strength, and the former have a high thermal-shock resistance.A combination method has been developed for obtaining periclase--chromite refractories featuring the simultaneous incorporation in the batch of granular and finely milled chromite.Using the combination method the Magnezit Combine and the Nikitovsk Dolomite Factory {NDF) prepared and tested in service, including trials at the Magnitogorsk Metallurgical Combine (MMC), experimental batches of periclase-chromite goods which had a high density, strength, and thermal-shock resistance simultaneously. The batch composition included 45-55% granular magnesite powder, 10-17% granular chromite, and 30-40% finely milled mixture of chromite and magnesite, which itself contained 10-20% chromite.At NDF the granular magnesite powder was added as fractions --3 mm at the Magnezit Combine in compounds TsMI-1 in fractions --2 mm, and in TsMI-2 in two fractions: 3-1 and --1 ram. The goods were also pressed at NDF into TsMI-1 on 1000-ton UZTM hydraulic presses, and into TsMI-2 on 1500-ton PR-7 presses, and then fired in high-temperature tunnel kilns with a setting height of 1.1 m (in TsMI-2 also with a low setting).With a certain similarity between the grain-size compositions and production equipment (pressing, firing) we noted higher densities and strengths in the products made at the Magnezit Combine. This may be due, beside the technological factors, to the use at NDF of the harder-sintering magnesite used in the granular part of the batch.The main structural elements of the goods made by the combination method are the aggregates of periclase grains, the coarse grains of chrome spinel, and the bonding mas~ of periclase--spinel composition.

No abstract

No abstract

No abstract

No abstract