Development of a Novel Thermal Shock test for isostatically Pressed Carbon-Bonded Refractories

In refractory engineering, assessing thermal shock resistance is crucial for flow-control components such as ladle shrouds, tundish nozzles, and slide gates. Chemical, mechanical, and thermal degradation of these parts can produce severe safety, environmental and economic consequences in steel plants. Standardized tests, however, may not fully characterize the damage evolution and failure modes that occur under real service conditions. To address this gap, we developed a novel thermal-shock test that simulates progressively increasing thermal severity, typical of service. The study proceeded in two phases. In the first phase we demonstrated the feasibility of induction heating to produce ascending thermal shock and to quantify resulting damage in Alumina-Carbon-based mixes. This preliminary phase established that the test protocol can record strain evolution and the onset of cracking as function of time and temperature. Specimen geometries were designed to be representative of service pieces. In the second phase, we applied comprehensive in situ monitoring to several isostatically pressed carbon-oxide materials that differ in brittleness at failure. An infrared temperature measurement, contact extensometers, as well as non-contact techniques, such as digital image correlation (DIC) and laser Doppler vibrometry (LDV), were employed. Because of the novelty of Laser Doppler Vibrometry for refractories damage assessment, the outputs of this method were validated against acoustic-emission signals recorded during stress-strain cycles in separate mechanical tests; damage metrics were examined in both time and frequency domains. During thermal shock tests, materials of different brittleness exhibited varied failure behaviors, including abrupt cracking throughout the sample thickness, gradual crack growth, and distributed damage formation without pronounced crack localization. These observed modes correlated with rankings from standardized thermal-shock indices. In-situ non-destructive tests proved particularly valuable for the analysis of non-brittle failure. Micro-structural inspection of tested specimens provides to further understanding of the material behavior under thermal shock and supports better prediction of component performance in steel-making operations.