Thermal Shock and Thermo-Mechanical Behavior of Carbon-Reduced and Carbon-Free Refractories

The thermal shock behaviour of novel carbon-reduced refractories with maximum grain size of 1 mm was investigated. A wedge splitting test for small specimen geometries (max. 40 × 40 × 20 mm 3 ) was successfully implemented with different loading configurations to determine “work of fracture” and thermal shock parameters. Additionally, heating-up thermal shock tests were performed with an electron beam facility. The addition of 2.5 wt% ZrO 2 and TiO 2 to Al 2 O 3 refractories appears to improve their thermal shock resistance due to microstructural changes that reduce brittleness and inhibit critical crack growth. However, a phase transition of ZrO 2 affects the properties at elevated temperature. For another pure alumina refractory, no geometry-independent value for the work of fracture could be obtained for the sample geometry used, which is probably related to the formation of a large interaction zone of the fracture surfaces. Al 2 O 3 -C materials with addition of semi-conductive Si and nanoparticles revealed a strong effect of the pressing direction on the work of fracture. However, the thermal shock parameter R’’’’ was hardly affected by the different additives. Furthermore, thermal shock tests using the electron beam facility JUDITH 1 did not indicate any significant differences in the damage pattern of the different Al 2 O 3 -C materials.