Testing sprayers for guncreting roofs of open-hearth furnaces

Conclusions Experiments were done with nozzles and sprayers of various types. The best adhesion of the applied concrete layer was achieved in the case of fine dispersion of the slurry to form separate droplets, and a moderate rate of output. The guncreting of open-hearth furnace roofs should be done with sprayers designed with connecting pipes, or with a slot.Translated from Ogneupory, No. 6, pp. 12–16, June, 1971.     

Unfired chemically bonded magnesia products for open-hearth roofs

Conclusions An experimental batch of unfired reinforced products having a chemical bond was produced and tested in the roof of a small open-hearth furnace. The wear intensity of these refractories is 30–60% less than the wear of ordinary fired roof products produced by enterprises in the Ogneuporerud Trust. The properties of the unfired products are improved by using better raw materials.Translated from Ogneupory, No. 8, pp. 9–17, August, 1972.     

Increasing the life of open-hearth roofs

Conclusions Test were done in triple-channel open-hearth furnaces of capacity 400 tons, and we introduced a design for a longitudinal-ribbed roof with reinforced suspension, for which the refractories division of the Combine developed the production of MKhS brick, 520 mm long. The contribution of the reinforced suspension in increasing the life of the roofs was approximately eight heats. The greatest resistance was noted in roofs fitted before removing the shuttering. Rigid fitting of the roof in the cold state in combination with weakening of the ramming at one lock permitted more uniform distribution of the mechanical load which rises during heating, and enabled us to reduce the roof rise by 18–20 mm during preheating and service. At the Nizhne-Tagil Metallurgical Combine we are strengthening our control over the quality of the structure and fitting of the roof.The life of open-hearth roofs resulting from the introduction of the above measures increased in the first half of 1967 by 18 heats compared with 1966.Translated from Ogneupory, No. 1, pp 31–35, January, 1969.     

Testing magnesite-chromite products in the roofs of open-hearth furnaces

Conclusions There is a relationship between the firing temperature, the degree of recrystailization of periclase and also the rate of erosion of the bricks in service.With high-temperature firing (1650–1750°C) and use of chromite and magnesite enriched with highly refractory oxides, a high resistance is possessed by roof bricks MKhS, RPShS and periclase-spinelide brick with additions of chromemagnesite clinker.Results of our work show the absence of a connection between the rate of wear of products and property factors provided for in standards for testing. The exception to a certain degree is thermal shock resistance (spalling resistance) and then only in the case of low values (a batch of dense products made of chromemagnesite clinker).In connection with this it is desirable to develop a method of determining those properties in the goods which directly or indirectly would influence their erosion (wear) resistance during use. These properties include in particular the dimensions of the crystals of periclase and the degree of the density of their reciprocal arrangement, which fundamentally characterize their specific surface.For more detailed study of the influence of the crystals of chromespinelides on the behavior of roof bricks in service, it is desirable to make additional tests of trial batches of brick in comparative service conditions.     

Testing periclase-spinel brick in the roofs of open-hearth furnaces

Conclusions Special periclase-spinel brick OPShS with a high content of finely ground Kimpersai chromite and no magnesite in the finely ground part of the batch, used in roofs of large open-hearth furnaces, working in oxygen fed into the flame and into the bath, showed greater wear than PShS brick and about the same wear as MKhS.Rational periclase-spinel roof brick RPShS tested for the first time at MTMK showed encouraging results in regard to wear resistance.Roofs of periclase-spinel brick made in one case from Saranov and in the other from Kimpersai chromite, in identical conditions of production and service, did not reveal great differences in resistance.N. N. Baranova, E. K. Kozhevnikova, A. P. Kukushkin, and E. A. Sagatulina took part in the work.     

Service of forsterite refractories in regenerator roofs of open-hearth furnaces

Conclusions The Panteleimonov Refractories Plant produced a large industrial batch of forsterite roof brick for the lower structure of open-hearth furnaces. Tests carried out at the Donetsk Metallurgical Factory showed that it is desirable to use these forsterite refractories: the life of the regenerator roofs was four campaigns in the main roof with an adequately large residual thickness.Investigations established that the changes in the forsterite brick during service in the roof of regenerators are similar to the changes in bricks during service in other structural elements, but the destruction processes occur much more slowly.Translated from Ogneupory, No. 8, pp. 31–38, August, 1968.     

Mathematical statistical models for predicting the wearability of roofs of open-hearth furnaces

Models are constructed for computing the wearability of the roof of an open-hearth furnace with allowance for operating conditions and properties of the parts. For the case of incomplete information model corrections to the mean wearability are suggested, depending on the main properties of the parts. The computed data on the wearability and the gain in wearability of 250-ton furnaces as function of the properties of the parts are presented for operating parameters equal to the base variant.Translated from Ogneupory, No. 10, pp. 24 – 28, October, 1994.     

Experience in using periclase-chromite refractories in roofs of tilting open-hearth furnaces

The workers of the Azovsta’ integrated iron-and-steel works have determined the causes of early wear of main roofs of open-hearth furnaces. They have resorted to lining the main roofs by periclase-chromite refractories of grade LIIIV produced in Slovakia. The use of refractories of grade LIIIV has increased the endurance of the main roofs of open-hearth furnaces by 100 heats. A petrographic study has shown that the high operating properties of articles made of LIIIV are due to their composition and structure, obtained as a result of the use of high-quality initial materials (chromite ore and magnesite powder) and a modern manufacturing process. Introduction of the developed manufacturing process has increased substantially the endurance of the linings and reduced the number of cold repairs of the open-hearth furnaces and the consumption of refractories. Translated from Ogneupory i Tekhnicheskaya Keramika, No. 6, pp. 34–38, June, 1997.     

On the question of the life of magnesite-chromite roofs for open-hearth furnaces

Summary The wear of magnesite—chromite roofs in open-hearth furnaces is affected considerably by the method of assembling the roof, the shape and dimensions of the roof, and the service conditions.In planning open-hearth furnaces it is necessary to aim at getting a reduction in the span of the roof. The design of the roof should be such that the thrust load is transferred to the cold rings of bricks.The life of the roof is more correctly determined not only by the number of heats, but by the length of the campaign in terms of the number of hot days.     

Use in open-hearth roofs of periclase-chromite parts made from electrofused periclase-chromite

Conclusions A production test was made in the roof of a 180-ton open hearth of periclase-chromite parts produced by the Magnesite Combine from electrofused periclase-chromite.The life of the roof of experimental parts was an average of two campaigns of 690 heats, which is three times longer than the life of PKhS refractories produced by the Nizhnii Tagil Metallurgical Combine.The difference in the life of the two forms of refractories may be explained by features of their phase composition, structure, and failure mechanism.It was shown that the main improvement in the quality of the refractories is a significant reserve for increasing the life of open hearth roofs. The use in open hearth roofs of parts of electrofused periclase-chromite makes it possible to decrease the refractory consumption by 3.36 kg per ton of steel and to reduce the cost of a ton of steel by 0.05 rubles.It is necessary to continue work in the direction of production and use of refractories of pure sintered and fused original materials, especially in the local areas subject to the maximum wear of the roofs of open hearths in which high quality steel is melted.Translated from Ogneupory, No. 7, pp. 45–50, July, 1985.     

Intensity of wear and tear of magnesite-chrome refractories in open-hearth roofs

Conclusions When magnesite-chrome brick wears out, the temperature gradient through the open-hearth furnace roof is increased; hence the dimensions of the spalling working part of the brick are reduced and the time interval between spalling during the run is increased.The increased wear resistance of dense, high-fired magnesite-chrome roof refractories in service in the roofs of rocking furnaces was due to reduction in the size of the spalling working part and a longer period between spalling as a result of delayed migration of the melts and the associated rate of formation of zones in the brick.It is possible to bring about a considerable reduction in the intensity of the wear and tear in magnesite-chrome roof refractories during service in open hearth furnaces by increasing the temperature gradient (t/) through the thickness of the roof, by intensive cooling of the outer surface of smooth roofs during the first half of the run, and also by using dense magnesite-chrome refractories.