Engineering the Microstructural Parameters of Erosion Resistant High Alumina Castables
1 Federal University of São Carlos, Materials Engineering Department, São Carlos, SP, 13565-905/Brazil
2 Petrobras, Rio de Janeiro, RJ, 21941-915, Brazil
Revision 30.01.2018, 05.05.2018
Volume 10, Issue 3, Pages 84 - 92
Abstract
Different parameters (i.e., particle size distribution and packing, size and amount of coarse grains, and other features of the resulting microstructure) can affect the erosion resistance of refractory castables. In this sense, this work investigated the performance of high-alumina castable compositions containing: (i) different amounts of calcium aluminate cement (CAC) as binder, (ii) white or brown-fused alumina as coarse grains, (iii) distinct maximum particle size and distribution modulus of the formulations, and (iv) sodium borosilicate (0–5 mass-%) as a sintering additive, during erosion measurements. Besides the determination of the eroded volume of samples fred at distinct temperatures (600–1200 °C), apparent porosity and hot modulus of rupture of the designed formulations were also analysed. The obtained results indicated that the most promising evaluated composition comprised 10 mass-% of CAC as, specimens with lower cement amounts resulted in high eroded volume or even full erosion. No signifcant changes in the measured eroded volume could be detected for the refractory formulations containing white or brown-fused alumina aggregates and coarse grains with different particle size, as the matrix fraction (fine components) is the main area of the castables to be worn due to the SiC particles’ impact. The addition of sodium borosilicate to the castables helped to improve their erosion resistance (due to the generation of a boron-rich liquid phase and its further interaction with the other available oxides), when pre-fring the samples at intermediate temperatures (800 °C, 1000 °C or 1200 °C for 5 h).
Keywords
erosion, particle size distribution, calcium aluminate cement, refractory castables
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