Use of magnesian-dolomite mixtures in steel-melting furnace hearths and the mechanism of their wear in service. 1. Study of Jehearth refractory mixture

The results of mineralogical-petrographic analysis of Jehearth magnesian-dolomite refractory mixture used in the hearths of steel-melting furnaces are described. The variation regularities of its phase and chemical composition are identified and the mechanism of its wear in service at the metallurgical works in Russia is considered. __________ Translated from Novye Ogneupory, No. 12, pp. 31–41, December, 2006.     

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.     

Study of service conditions and nature of wear of refractories in 15-ton rotary steel-smelting furnace

Conclusions Magnesite and periclase-spinel parts are subjected during service to the unilateral action of slag, metal and melt dust, and operate under conditions of high temperature and a variable gas medium.The intensified wear of the lining with rammed mixture leads to the formation of a high-magnesite slag which hampers the processes of desulfurization and dephosphorization during oxygen blasting of the bath.The layer of rammed mixture between rows 15–20 mm thick prevents the metal seeping into the second row, which makes it possible to repair the linings without replacing it.Spent parts show clearly marked zonal structure; the working zones are strongly saturated with oxides of iron, silicon and calcium, the percentage of magnesium oxide being low.The zones are represented by complex spinels cemented by dicalcium silicate, monticellite and glass; this leads to impairment of their flame properties.     

Tests of mullite-corundum refractories based on fused mullite in the roof of an electric steel-melting furnace

Mullite-corundum refractories based on 63 – 90% fused mullite have been produced and tested in the roof of a 50-ton electric arc furnace. It has been established that their wear resistance is no worse than that of heat-resistant mullite-corundum bricks of grade MK-80 produced according to TU 14-80405-82. The tested refractories were worn due to their saturation with oxides from the molten products and the interaction of the latter with the structural components of the refractory. This promoted the decomposition of mullite into corundum and a glass phase with aftercompaction ands spalling of the refractory.Translated from Ogneupory i Tekhnicheskaya Keramika, No. 12, pp. 31 – 35, December, 1996.     

Forsterite refractories made with olivinite from Khabozerskiy deposit and their service in open-hearth furnace regenerator checkers

Conclusions Forsterite parts made of Khabozerskiy olivinite possess increased density, durability and stability at elevated temperatures.In open-hearth regenerator checkers forsterite brick possesses adequate wear resistance in service and melt dust resistance. The best results were obtained when this brick was used in air regenerator checkers.     

Analysis of magnesite — Spinel refractories after service in the roof of an open-hearth furnace

Conclusions Macroscopic and microscopic investigations of MShS refractories after service and direct observations of their behavior in the roof of open-hearth furnaces fired with oxygen-enriched fuel showed that MShS bricks containing 20 and 30% fused spinel are eroded by the sweating of the working surface.An increase in the spinel content of the mix for MShS refractories from 30 to 60% produces a tendency to erosion by spalling, the explanation being the reduced volumetric stability of the brick which manifests itself in aftershrinkage and distension as a result of the action of iron oxides.Translated from Ogneupory, No. 4, pp. 26–33, April, 1977.     

Life of refractories in service in a furnace for melting in a molten bath

Conclusions As the result of laboratory and production tests it was established that the periclase-chromite refractories produced from fused material show the greatest life in the lining of furnaces for melting in a molten bath.A method of production of fused chromite-periclase used for the production of fused periclase-chromite refactories to Technical Specification (TU) 14-8-368-81 was developed.A design of combined lining of a furnace for melting in a molten bath with the use of highly resistant refractories was developed.Translated from Ogneupory, No. 1, pp. 56–60, January, 1986.     

Developing alkali-resistant refractories and their service in furnaces calcining sodium adipates

Conclusions A furnace used for burning alkali stocks at the Shchekinsk Chemical Combine was used to test a refractory lining in the walls and bottom of the receiver, and also the walls, roof, and bottom of the gas duct made with spinel-containing refractories developed by the Ukrainian Refractories Research Institute. The tests showed that the refractories had a high resistance to alkali flux at service temperatures of 1100°C.The specially developed high-density refractory based on magnesia spinel is a promising material for use under the intensive chemical action of alkali compounds.Translated from Ogneupory, No. 4, pp. 35–39, April, 1972.     

Erosion mechanism of refractories in a pyro-processing furnace for recycling lithium-ion secondary batteries

The refractory lining in a furnace is always damaged and peels off when spent lithium-ion secondary batteries (LIB) are pyro-processed in a rotary kiln. To develop highly durable refractories and to elucidate the erosion behavior, various analyses such as scanning electron microscopy/energy dispersive X-ray spectroscopy, laser-induced breakdown spectroscopy, inductively coupled plasma atomic emission spectroscopy, ion chromatography, and X-ray diffraction were performed on the linings sampled from different sections of a refractory. Our results suggested the following mechanisms in Al₂O₃–SiO₂–CaO refractory damage during pyro-processing of spent LIB packs. First, Li₂O, P₂O₅, LiF, and HF were formed by thermal decomposition of electrolyte constituents of the lithium-ion secondary batteries. When HF reacts with SiO₂, Al₂O₃, and CaO on the surface of the refractory, each fluoride that forms vaporizes and melts. When Li₂O and P₂O₅ (as well as LiF) react with the Al₂O₃–SiO₂ refractory, an Li₂O–Al₂O₃–SiO₂–P₂O₅(-LiF) phase with a low melting point forms and penetrates into the refractory through pores, grain boundaries, and cracks, resulting in peeling off.