Experimental analysis of the evolution of thermal shock damage using transit time measurement of ultrasonic waves

Thermal shock is a principal cause of catastrophic wear of the refractory lining of high temperature installations in metal making processes. To investigate thermal shock experimentally with realistic and reproducible heat transfer conditions, chamotte and corund refractory samples of ambient temperature were subjected to surface contact with molten aluminium followed by passive cooling in ambient air. The evolution of damage was characterized by measuring the transit time of ultrasonic longitudinal waves at various sample locations after each test cycle. The mechanical validity of transit time measurement was confirmed in independent experiments. The single test cycle performed with chamotte material indicated the reproducibility and reliability of the experimental set-up and damage characterization method. Multiple test cycles performed with corund material yielded a reliable set of data, to be used for model validation purposes. Both non-uniform damage due to temperature gradients as well as uniform damage due to exposure to a uniform temperature were determined experimentally. The interaction between both damage mechanisms requires further investigation as well as the possible shielding of heat transport by damage.