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General Index for China's Refractories Volume 14,2005

Vol. 14. No.1, 2005

Rheology of Alumina-Based Graphite-Containing Castables

Ye Fangbao, M.Rigaud, Liu Xinhong and Zhong Xiangchong (1) 3
Abstract
In this work, the rheological behavior of ultra-low cement alumina-based castables with addition of flake graphite and extruded graphite pellets has been investigated by using IBB rheometer. Emphasis has been laid on the influence of the type and amount of carbon addition on rheological properties of the alumina-based castables and the results are compared with corresponding alumina castable samples without any carbon addition. It is found that alumina-based castables with extruded graphite pellets have good rheological behavior and flowability with lower water demand (< 6.3%) and no segregation during the shearing of castable.
 

Thermal Shock Resistance of Bauxite-based ¦Â-sialon/Al2O3/SiO2 Mixtures in Flowing Nitrogen at High temperatures

Liu Zhanjie, Zhang Haijun and Zhong Xiangchong (1) 9
Abstract
Thermal shock resistant properties of reaction sintered bauxite-based ¦Â-Sialon bonded corundum have been investigated, and the results are compared with those of Al2O3 based counterpart. It is found they all have very good thermal shock resistance. Their residual strength ratios after one thermal shock cycle at ¦¡èT=1200ºC and ¦¡èT=1350ºC are 61%~73% and 53%~65% respectively. Their critical temperature difference (TSR) is 600ºC~800ºC. TSR parameters are calculated based on thermal expansion, modulus of elasticity, and fracture toughness determined. The reasons for improving TSR of these composite materials are discussed.

Reaction Sintering of ¦¦Â-sialon /Al2O3/SiO2 Mixtures in Flowing Nitrogen at High temperatures

Jin Shengli, Li Yawei and Li Nan (1) 13
Abstract
¦Â-sialon/alumina/silica mixtures were sintered in flowing nitrogen at 1 500¡æ and 1 600¡æ respectively. The sintering properties and morphology of samples were investigated by SEM, EDS and XRD. Results show that sintered properties of the samples are influenced by soaking temperatures and compositions. Bulk densities of samples are increased with the increase of the soaking temperature, whereas the apparent porosities are decreased. Mass loss of the sintered samples at 1 500¡æ is lower than that at 1 600¡æ, but all the mass loss remains approximately constant with the increase of sialon content. From the point of thermodynamic analysis, Complex chemical reactions take place in samples during sintering process and the volatile of SiO (g) is responsible for the mass loss of samples. Compared to cross section microstructure of ¦¦Â-sialon/Al2O3/SiO2 mixtures sintered in coke powder bed consisting of the dense center with well-developed column of sialon phase, the transitional part with needle like grain nitrogen-containing phase and the loose part with short granular Al2O3 phase, those of mixtures sintered in flowing nitrogen is made of well-developed sialon in dense center and slightly loose part with sialon debris. 
Key words: Reaction sintering, Sialon, Alumina, Silica, Mixture
 

Investigation on the Properties of Fe-Si3N4 Bonded SiC Composite

Zhang Yong, Feng Di and Peng Dayan (1) 18
Abstract
The mechanical properties of pressureless sintering Fe-Si3N4 bonded SiC and Si3N4 bonded SiC with same manufacture process have been compared in this paper. The oxidizing mechanism of Fe-Si3N4 bonded SiC ceramic matrix composite was been investigated especially through TG-DSC (thermo gravimetric analysis-differential scanning calorimeter) experiment. During oxidation procedure the main reaction is the oxidation of SiC and Si3N4, SiO2 which form protecting film to prevent further oxidizing. And residual iron in the samples become Fe2O3 and Fe3O4, the oxidation kinetics at 1 100¡«1 300¡æ of Fe-Si3N4 bonded SiC is has been studied especially. The weight gain per unit area at initial stage changes according to beeline rule, in the middle according to conic, and in the last oxidation period follows parabola rule. 
Key words: Fe-Si3N4 bonded SiC, Composite, Oxidation£¬Iron-silicide
 

Prospect of Refractory for Hot Metal Pretreatment

Li Bozhi, Cao Feng (1) 23
Abstract
The paper investigates the recent developing situation and the latest research achievements of refractory for hot metal pretreatment. The relationship among desiliconization, dephosphorization and desulphurization techniques and the main corrosion reactions by various treating agents is analyzed. Some improving measures of several problems in practice are put forward while we anticipate the future developing direction of refractory for hot metal pretreatment.
Key words: hot metal pretreatment, refractory, desiliconization, dephosphorization, desulphurization
 

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