Phase transformations in periclase-spinel roofs of open-hearth furnaces with blowing through of the bath by compressed air

Conclusions The crystallochemical properties of the periclase and the spinels of the periclase-spinel bricks were radically changed during service in open-hearth furncces with blowing through of the bath with compressed air; new types of ferrite spinels and their solid solutions in periclase were formed. Periclase forms magnesiowüstite and magnesioferrite with ferric oxides resulting in a lowering of the melting point from 2800 to 1600°C. This type of transformation of periclase is one of the main causes of wear of periclase-spinel roofs by fusion.Under the service conditions chrome spinel is transformed into magnesioferrite and magnetite, with a lowering of the melting point from 2100 to 1750°C.In the working zone the lattice parameters of the solid solutions in periclase (magnesiowüstite) increased from 4.204 to 4.218 Å, indicating a considerable amount of divalent iron and manganese cations in the periclase crystal lattice.In the periclase-spinel bricks we identified independent types of spinel, represented by inverted (magnetite), almost inverted (magnesioferrite), partially inverted (chrompicotite) and ordinary (magnesiospinel) structures. In the spinels the cations are variously distributed at tetrahedral and octohedral lattice sites. In the working zone ferrite spinels (up to 90%) — magnesioferrite and magnetite — predominated; they have an inverted structure and low melting points. The content of easily fusible ferrite spinels increased with increasing intensity of blowing of air through the bath. The formation of a large amount of ferrite spinels is one of the main causes of the fusion and rapid wear of periclase-spinel roofs of open-hearth furnaces.Translated from Ogneupory, No. 2, pp. 25–31, February, 1969.     

The formation of minerals in a chromite-periclase refractory produced from fused materials and its wear in the roof of an open-hearth furnace

Refractories and Industrial Ceramics - An analysis was carried out of certain aspects of the zone-forming process in the roof brick of open-hearth furnaces. It was established that three fissure...     

Magnesia products from powders containing more than 94% MgO

Conclusions Using magnesite powders with large contents of magnesium oxide we obtained high-quality magnesite and periclase-spinel products. Periclase-spinel products obtained from the above powders satisfy the requirements of GOST for the PShSP type of product for the roofs of open-hearth furnaces and electric steel furnaces. Their thermal shock resistance is 7–15 water-heat cycles, compared with 5–7 heat cycles for ordinary periclase-spinel products, which is due to their structural features.Translated from Ogneupory, No. 1, pp. 54–58, January, 1969.     

Wear of high-fired periclase-spinel refractories in the roof of a double-bath steel-melting furnace

Conclusions 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.The increase in the resistance of the experimental periclase—spinel refractories is helped by the structure with the direct bond between the grains which retards the access of silicates and slags inside the textural elements. This exerts a favorable influence on the change in structure of the refractory during service, especially in the transition zone in which additional sintering and crack formation leading to scaling of the experimental refractory hardly develops.On the basis of the results of the research we recommend that refractory enterprises set up various technological production lines for making periclase-spinel products from pure Satkinsk magnesite powders (94–96% magnesium oxide) and beneficiated Kempirsaisk chromite (59–60% chromium oxide) using high-temperature firing in a tunnel klin. The use of high fired periclase-spinel products with a direct bond between the grains would increase the resistance of the roofs of metallurgical furnaces operating with the use of oxygen and increasing their outputs.Translated from Ogneupory, No. 5, pp. 28–33, May, 1973.