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Jiao K.X.,University of Science and Technology Beijing | Zhanga J.L.,University of Science and Technology Beijing | Liua Z.J.,University of Science and Technology Beijing | Zhao Y.G.,Henan Winna Industrial group Co. | Houa X.M.,University of Science and Technology Beijing
Journal of Mining and Metallurgy, Section B: Metallurgy | Year: 2015

A type of carbon composite brick was produced via the microporous technique using natural flack graphite, α-Al2O3 and high-quality bauxite chamotte (Al2O3≥87 mass%) as raw materials with fine silicon powder as additive. The composition and microstructure of the obtained carbon composite were characterized using chemical analysis, XRD and SEM with EDS. The high temperature properties of thermal conductivity, oxidization and corrosion by molten slag and hot metal of the composite were analyzed. Based on these, the type of carbon composite brick worked in a blast furnace hearth for six years was further sampled at different positions. The protective layer was found and its chemical composition and microscopic morphology were investigated. It is found that the carbon composite brick combines the good properties of both the conventional carbon block and ceramic cup refractory. The protective layer near the hot face consists of two separated sublayers, i.e. the slag layer and the carbon layer. A certain amount of slag phase is contained in the carbon layer, which is caused by the reaction of coke ash with the refractory. No obvious change in the chemical composition of the protective layer along the depth of the sidewall is found. This work provides a useful guidance for the extension of the lifetime of blast furnace hearths. Source


Zuo H.,University of Science and Technology Beijing | Wang C.,University of Science and Technology Beijing | Zhang J.,University of Science and Technology Beijing | Zhao Y.,Henan Winna Industrial group Co. | Jiao K.,University of Science and Technology Beijing
Ceramics International | Year: 2015

Al2O3-SiC-SiO2-C composites are widely used in ironmaking operations due to their favorable erosion-resistance. In the present paper, the oxidation behavior and kinetics of Al2O3-SiC-SiO2-C composites in air are investigated in terms of a theoretical analysis associated with the experimental data. Furthermore, the effects of temperature on the oxidation reaction are discussed. The results show that the oxidation of Al2O3-SiC-SiO2-C composites is mainly caused by atmospheric oxygen reacting with C and SiC in the materials. At 1200 °C, a protective layer can be found on the material surface due to the formation of the mullite phase. Predictions from the Chou model are in agreement with the experimental data. The characteristic oxidation time which indicates anti-oxidation properties for Al2O3-SiC-SiO2-C composites at 1000 °C and 1200 °C are 142.41 min and 264.89 min, respectively, indicating that the material at 1200 °C is more resistant to oxidation due to the formation of a protective layer on the surface. © 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Source


Zuo H.,University of Science and Technology Beijing | Wang C.,University of Science and Technology Beijing | Zhang J.,University of Science and Technology Beijing | Zhao Y.,Henan Winna Industrial group Co. | Jiao K.,University of Science and Technology Beijing
TMS Annual Meeting | Year: 2015

Traditional refractory materials for blast furnace hearth lining are mainly composed of carbon bricks and the ceramic cup. However, these materials can't meet the demands for long service life design of blast furnaces. In this paper, a new refractory called carbon composite brick (CCB) was introduced, which combined the advantages of carbon bricks and the ceramic cup. In this case, the resistance of the CCB against corrosion was equal to the ceramic cup and the thermal conductivity of the CCB was equal to carbon bricks. From the results of more than 20 blast furnaces, the CCB could be well used in small blast furnaces and large blast furnaces. In the bad condition of low grade burden and high smelting intensity, the CCB gave full play to the role of cooling system, and effectively resisted the erosion of hot metal to improve the service life of blast furnaces. Source


Zuo H.,University of Science and Technology Beijing | Wang C.,University of Science and Technology Beijing | Zhang J.,University of Science and Technology Beijing | Jiao K.,University of Science and Technology Beijing | Zhao Y.,Henan Winna Industrial group Co.
TMS Annual Meeting | Year: 2015

The carbon composite brick is a new refractory used in blast furnace hearth and bottom. It caused wide attention due to its high thermal conductivity and low erosion by molten iron. In this paper, chemical constituents, SEM-EDS and X-ray diffraction were carried out in order to understand reaction mechanisms. A series of experiments of oxidation resistance characteristics were made. The oxidation mechanisms of carbon composite bricks in the presence of air were analyzed. According to the analysis on many experimental results, the oxidation process of carbon composite bricks under different temperatures were controlled by different mechanisms. In the condition of high temperature, SiO2 as oxidation product hindered the diffusion of O2, and reduced the oxidation loss of graphite in the internal. Source


Zuo H.,University of Science and Technology Beijing | Wang C.,University of Science and Technology Beijing | Zhang J.,University of Science and Technology Beijing | Zhao Y.,Henan Winna Industrial group Co. | And 2 more authors.
Kuei Suan Jen Hsueh Pao/Journal of the Chinese Ceramic Society | Year: 2015

The oxidation behaviors and kinetics of carbon bricks used in blast furnace hearth were investigated based on the thermodynamic analysis and the oxidation resistance experimental results. The results show that the mass loss of carbon bricks is due to the loss of carbon. The mass loss increases with increasing temperature and holding time. The oxidation process of carbon bricks belongs to the model of continuous oxidation rather than the model of protective oxidation. At 800-1200 ℃, the rate-controlled step of oxidation process is the C-O reaction and the activation energy is 5586.76 J/mol. The oxidation layer is formed in the internal carbon bricks due to the loss of carbon. The area of oxidation layer increases with increasing temperature and holding time, thus decreasing the strength and the density of the materials. ©, 2015, Chinese Ceramic Society. All right reserved. Source

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