The Understanding of the Microstructural Changes of Refractory Castables after Thermal Shocks through Damping Measurements

Rainer Telle, Nicolas Traon, Thorsten Tonnesen

GHI/RWTH-Aachen Institute of Mineral Engineering – Department of Ceramics and Refractory Materials 52062 Aachen/Germany

Revision 06.10.2011, 24.10.2011

Volume 4, Issue 2, Pages 121 - 126

Abstract

The work herein correlates the damping measurements and the microstructural modifications of refractory castables after thermal shocks at air. According to DIN EN 993-11, thermal shocks at air at different temperatures (750, 850, 950 and 1050 °C) were progressively conducted on refractory samples based on tabular alumina with addition of partially stabilized zirconia (PSZ). The same thermal shocks were carried out at 950 °C on white fused alumina samples as well. The thermal shock damage evaluation of high-alumina refractory castables was based on dynamic Young’s modulus and damping characterization data obtained via the impulse excitation technique (IET), according to the ASTM E1876-07. Scanning electron microscopy (SEM) completes this survey so as to understand the elastic changes of these refractory formulations. The results show that the damping increase in PSZ castables may be explained by crack nucleation and propagation while such phenomena do not occur in WFA castable.

Keywords

thermal shock, impulse, excitation technique, partially stabilized, zirconia, Young’s modulus, damping

References

[1] Tonnesen, T.; Telle, R.: Thermal shock damage in castables: Microstructural changes and evaluation by a damping method. cfi/Ber. DKG 84 (2007) [9] E132–136.

 

2] Mielczarek, A.; Fischer, H.; Riehemann, W.: Amplitude- dependant damping of PSZ with sinter defects. Mater. Sci. Engin. A 442 (2006) 488–491

 

3] Pereira, H.A.; Nascimento, R.C.; Rodrigues, J. de A.: Effect of non linearity on Young’s modulus and damping characterisation of high alumina refractory castables through the impulse excitation technique. 53rd Int. Coll. on Refractories (2010) Aachen, Germany, Proc. 90–93

 

4] Johnson, P.A.; Zinszner, B.; Rasolofosaon, N.J.: Resonance and elastic nonlinear phenomena in rock. J. Geophys. Res. 101 (1996) [B5] 11553– 11564

 

5] Abeele, K.V.D.; Visscherb, J.: Damage assessment in reinforced concrete using spectral and temporal nonlinear vibration techniques. Cement and Concrete Res. 30 (2000) 1453–1464.

 

6] Braulio, M.A.L.; et al.: Aggregate effects on the thermal shock resistance of spinel-forming refractory castables. Refractories Worldforum (2010) [2] 102–106

 

7] Primachenko, V.; et al.: The influence of sintered or fused MgO-stabilized ZrO2 on properties of zirconia products. Proc. UNITECR 2007 (2007) 268–271

 

8] Schickle, B.; Telle, R.; Tonnesen, T.: Changes of the mechanical and elastic properties of castables as a function of thermal shock cycles. 53rd Int. Coll. on Refractories (2010) Aachen, Germany, Proc. 86–89

 

9] DIN EN 993-11: Determination of resistance to thermal shock, German version CEN/TS 993/11 (2003)

 

10] ASTM 1876-07: Standard test method for dynamic Young’s modulus, shear modulus, and Poisson’s ratio by impulse excitation of vibration. ASTM International (2007) 15

 

11] Pereira, H.A.; et al.: Elastic moduli, damping and modulus of rupture changes in a refractory castable due to thermal shock damage. 52nd Int. Coll. on Refractories (2009) Aachen, Germany, Proc. 20–23

 

12] Hasselman, D.P.H: Rolle der Bruchzähigkeit bei der Temperaturwechselbeständigkeit feuerfester Erzeugnisse. Ber. DKG 54 (1954) 195–201  

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