Fracture Process Zone in Refractory Castables after High-Temperature Thermal Shock
1 RWTH Aachen University, Institute of Mineral Engineering, 52070 Aachen/Germany
2 KTH Royal Institute of Technology, 10044 Stockholm/Sweden
Revision 01.12.2015, 11.01.2016
Volume 8, Issue 2, Pages 74 - 80
Abstract
Thermal shock damage is an important issue for the refractories industry. To understand the microstructural behaviour and with it the thermoelastic properties during thermal shock treatment are key topics for high performance refractory materials and their development. Most ceramic materials exhibit a critical temperature difference (ΔTc) as a minimum temperature required for fracture initiation. Refractories exhibit within their heterogeneous structure already pores, aggregates of different size and cracks. To understand the influence of the temperature difference (ΔT) and the temperature level, a new high temperature thermal shock furnace was designed and constructed. Unlike standard thermal shock tests with compressed air or water, the new furnace’s two separately heatable and interconnected chambers enable the transfer of samples between two high temperatures without exposing them to the surrounding atmosphere at room temperature. To understand the effect of rapid temperature changes, the natural aggregate andalusite and the synthetic aggregates Al2O3–ZrO2–SiO2 and Al2O3–ZrO2 are incorporated in a model low cement castable formulation based on tabular alumina. The influence of these aggregates on the elastic and thermomechanical properties is examined and correlated to the microstructure.
Keywords
Refractories, high temperature thermal shock, eutectic aggregates, liquid phase bridging
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