Articles
All articles | Recent articles
Microstructure and Phase Evolution of Cement-Bonded High-Alumina Refractory Castables for Porous Purging Plugs
Q. Wang, Y. Li, N. Xu, R. Xiang, S. Li
The State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology (WUST), Wuhan 430081, China
received June 25, 2017, received in revised form August 15, 2017, accepted September 6, 2017
Vol. 9, No. 1, Pages 1-6 DOI: 10.4416/JCST2017-00044
Abstract
This work addresses the microstructure and phase evolution of four designed high-alumina refractory castables (containing ρ-Al2O3 or calcium aluminate cement as a binder source and 0 or 1 wt% microsilica). Various experimental tests (air permeability, linear change rate, apparent porosity, cold modulus of rupture, cold crushing strength, hot modulus of rupture, pore size distribution, X-ray diffraction and scanning electron microscopy) were conducted to characterize the castables. The results show that using cement as the binder has a significant effect on the properties of the refractory castables. The cement-bonded castables exhibited a lower linear shrinkage rate, apparent porosity and air permeability, higher cold modulus of rupture and cold crushing strength, as well as a smaller mean pore size than that of the ρ-Al2O3-bonded castables. The results were attributed to the formation of calcium hexaluminate. Some CA6 was detected inside the pores, which occupied space in the pores and prevented the formation of interconnected pores, while some CA6 existed outside the pores, which enhanced the densification of the structure and reduced the size of pores. Moreover, the addition of microsilica can facilitate interconnected pore formation in cement-bonded castables, but lower the hot modulus of rupture owing to the formation of low-melting-temperature phase (C2AS).
Download Full Article (PDF)
Keywords
Cement, porous purging plug, microstructure, phase evolution, pore size distribution
References
1 Primachenko, V.V., Martynenko, V.V., Ustichenko, V.A.: The manufacturing experience and an application in the Ukraine mullite-corundum purging plugs for the blowing of steel in the ladles. In: Proceedings of UNITECR'01. Cancun, Mexico, 2001.
2 Kimura, M., Ohuchi, T., Tsuzuki, T., et al.: Development and application of porous type gas purging plug with high bubbling reliability and durability. In: Proceedings of UNITECR'01, Cancun, Mexico, 2001.
3 Li, Z.G., Ye, F.B., Zhang, Y.: Effects of nano calcium carbonate on strength and microstructure of Corundum-based castables, China Refract., 19, 1 – 6, (2010).
4 Auvray, J.M., Gault, C., Huger, M.: Evolution of elastic properties and microstructural changes versus temperature in bonding phases of alumina and alumina-magnesia refractory castables, J. Eur. Ceram. Soc., 27, 3489 – 3496, (2007).
5 Braulio, M.A.L., Milanez, D.H., Sako, E.Y., Bittencourt, L.R.M., Pandolfelli, V.C.: Expansion behavior of cement bonded alumina-magnesia refractory castables, Am. Ceram. Soc. Bull., 86, 9201 – 9206, (2007).
6 Ide, K., Suzuki, T., Asano, K., Nishi, T., Isobe, T., Ichikawa, H.: Expansion behavior of alumina-magnesia castables, J. Tech. Assoc. Refract., 25, 202 – 208, (2005).
7 Ko, Y.C., Lay, J.T.: Thermal expansion characteristics of alumina-magnesia and alumina-spinel castables in the temperature range 800°– 1650 °C, J. Am. Ceram. Soc., 83, 2872 – 74, (2000).
8 Myhre, B.: Microsilica in refractory castables – how does microsilica quality influence performance? In: Proceedings of Unified International Conference on Refractories, Orlando, USA, 191 – 195, (2005).
9 Liu, G., Jin, X., Qiu. W., et al.: The effect of microsilica on the oxidation resistance of Al2O3-SiC-SiO2-C castables with Si and B4C additives, Ceram. Int., 42, 251 – 262, (2016).
10 Wang, Q., Ye, G., Wang, Y., et al.: Effect of micro-sized calcium carbonate addition on volumetric stability and strength of corundum-based castables, Int. J. Appl. Ceram. Technol., 12, E166 – E171, (2015).
11 Auvray, J.M., Gault, C., Huger, M.: Microstructural changes and evolutions of elastic properties versus temperature of alumina and alumina-magnesia refractory castables, J. Eur. Ceram. Soc., 28, 1953 – 1960, (2008).
12 Fuhrer, M., Hey, A., Lee, W.E.: Microstructural evolution in self-forming spinel/calcium aluminate-bonded castable refractories, J. Eur. Ceram. Soc., 18, 813 – 820, (1998).
13 Díaz, L.A., Torrecillas, R.: Hot bending strength and creep behavior at 1000 – 1400 °C of high alumina refractory castables with spinel, periclase and dolomite additions, J. Eur. Ceram. Soc., 29, 53 – 58, (2009).
14 Wang, Y., Li, X., Zhu, B., et al.: Microstructure evolution during the heating process and its effect on the elastic properties of CAC-bonded alumina castables, Ceram. Int., 42, 11355 – 11362, (2016).
15 Lee, W.E., Vieira, W., Zhang, S., Ahari, K.G., Sarpoolaky, H., Parr, C.: Castable refractory concretes, Int. Mater. Rev., 46, 145 – 167, (2001).
16 Braulio, M.A.L., et al.: Microsilica effects on cement bonded alumina-magnesia refractory castables, Refract., 62, 543 – 549, (2010).
17 Sandberg, B., Myhre, B.: Castables in the System MgO-A12O3-SiO2. In: Proceedings of UNITECR'95, Kyoto, Japan, 1995.
18 Braulio, M.A.L., Rigaud, M., Buhr, A., Parr, C., Pandolfelli, V.C.: Spinel-containing alumina-based refractory castables, Ceram. Int., 37, 1705 – 1724, (2011).
19 Zhang, S., Lee, W. E.: Refractories Handbook. Marcel Dekker lnc., USA., 2004.
20 Criado, E., Estrada, D.A., DeAza, S.: Dilatometric study of the formation of CA2 and CA6 in cements and refractory concretes, Bull. Span. Ceram. Glass Soc., 15, 319 – 321, (1976).
21 Criado, E., Caballero, A., Pena, P.: Microstructural and mechanical properties of alumina-calcium hexaluminate composites. In: The World Congress on High Tech Ceramics. Milan, Italy, 1986.
22 Wang, Q.H., Li, Y.B., Li, S.J. et al.: Effects of critical particle size on properties and microstructure of porous purging materials, Mater. Lett., 197, 48 – 51, (2017).
23 Li, S., Li, N.: Effects of composition and temperature on porosity and pore size distribution of porous ceramics prepared from Al(OH) 3, and kaolinite gangue, Ceram. Int., 33, 551 – 556, (2007).
24 Rice, R.W.: Comparison of stress concentration versus minimum solid area based mechanical property-porosity relations, J. Mater. Sci., 28, 2187 – 2190, (1993).
25 Souza, T.M., Luz, A.P., Brito, M.A.M. et al.: In situ elastic modulus evaluation of Al2O3-MgO refractory castables, Ceram. Int., 40, 1699 – 1707, (2014).
Copyright
Göller Verlag GmbH
