Guniting the roof of open-hearth furnaces during intermediate overhaul

Refractories and Industrial Ceramics -     

Guniting slag belt in copper-refining furnaces

Conclusions A gunite mixture with a chrome-magnesite face base can be successfully applied and welded to the chrome-magnesite brickwork of the slag belt in copper-refining furnaces.Guniting the slag-belt lining is a reliable and effective method of prolonging its life and increasing the amount of time in between repairs.     

Guniting the lining of heating furnaces of rolling mills

Conclusions Guniting mass compositions and a procedure for guniting worn brickwork of continuous heating furnaces of rolling mills have been developed. At a number of metallurgical factories the worn brickwork of eight continuous heating furnaces of rolling mills have been repaired by guniting. The use of guniting enables the period between furnace lining repairs to be doubled (from 1 to 2 years), the volume of brickwork repair and the length of the repair work to be reduced, and a saving of 5000 rubles per annum per furnace to be obtained (merely by reducing the amount of repair work).Using IR spectroscopy the authors have investigated hydration and dehydration in alumina and high-alumina cements and aluminosilicate guniting masses with additives of these cements. They have shown that during guniting by the semidry method, hydration of the cements included in the composition of the gunite coatings does not go to completion and ends in the stage of formation of CaO·Al₂O₃·10H₂O; dehydration of the gunite coatings is completed below 300°C.Translated from Ogneupory, No. 5, pp. 30–35, May, 1980.     

Guncreting refractory structures in open-hearth furnaces

Conclusions As a result of the use of guncreting for repairing refractory structures in open hearths at the Izhorsk plant, the consumption of fettling materials for repairing the back walls has dropped from 2.8–2.9 kg/t of steel to 1 kg. On account of the saving of refractories in three 50-t open-hearth furnaces, according to preliminary estimates, the saving should be about 16,000 rubles.The use of the guncreting method for back walls of open-hearth furnaces in combination with ramming, using a guncrete body, will substantially increase the life of these areas and save a large amount of magnesite brick.Refractory materials for guncreting should be prepared in specialist refractory concerns.The work on guncreting methods for roofs should be continued.Translated from Ogneupory, No. 2, pp. 35–36, February, 1966.     

Guniting of the lining of furnaces for heating of steel billets

Conclusions A method of guniting of the rolling mill heating furnaces during shutdown for cold repairs and with a lining surface temperature of 900–1200°C was developed with the use of guniting powders produced by industry of aluminosilicate and basic compositions with hydraulic and silicate binders. The introduction of composite guniting of the lining in the cold and hot conditions makes it possible to reduce the volume of lining repair work by 10–15 m³ per furnace and the consumption of brick refractories by 0.1 kg per ton of steel rolled and to increase the life of the lining by 1.5–2.0 times.Translated from Ogneupory, No. 4, pp. 48–51, April, 1988.     

Use of magnesite concrete in open-hearth furnaces

Conclusions Many years practical experience with the use of refractory magnesite concretes in open-hearth furnaces at the KMZ confirmed that it is rational to use them even for preparing concretes and blocks on the working sites of open-hearth shops, and it also confirmed the unacceptability of open-hearth furnace structures for placing the concretes.A project for a furnace framework should be developed bearing in mind the use of blocks of maximum sizes which will accelerate repairs.Simultaneously with the increase in the output of chrome-magnesite mixture for the production of concrete it is necessary to produce this mixture with greater fineness for the wash materials.Translated from Ogneupory, No. 6, pp.31–35, June, 1972.     

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.     

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.