Authors:
Dr. Erwan Brochen | Forschungsgemeinschaft Feuerfest e. V. at the European Centre for Refractories | Germany
Tim Waldstädt | Forschungsgemeinschaft Feuerfest e. V. at the European Centre for Refractories | Germany
Michael Kaminski | Forschungsgemeinschaft Feuerfest e. V. at the European Centre for Refractories | Germany
Dr. Christian Dannert | Forschungsgemeinschaft Feuerfest e. V. at the European Centre for Refractories | Germany
In service refractories undergo thermal shocks, which magnitudes and ranges of temperature highly depend on the processes they are used in. The suitability of refractory products to a given process, and more especially their ability to sustain thermal shocks, is, however, still widely established by using standardised testing methods that display little compliance with their actual service conditions. This may lead to the selection of products that are not the best fit for an application. A product could perform well at medium temperatures, even when faced with thermal shocks of high magnitude, but completely fail at higher temperatures despite experiencing thermal shocks of smaller magnitude.
A new testing system for TSR was used to assess the response of typical refractories to different thermal cycling conditions. Especially different temperature ranges (moderate or high temperatures), different magnitudes of thermal shocks and different thermal shock modalities (ascending/descending) were investigated. The resulting damaging was assessed with ultrasonic measurements. For shaped products (high alumina, andalusite and fused silica bricks), the damaging was found to be more severe for thermal cycling applied at high temperature (above 900°C) than at moderate temperature (below 900°C) despite having the same magnitude (ΔT of at least 580 K). The investigated unshaped refractory (high alumina castable) displayed a more complex TSR, potentially improving at high temperature.
Practice-oriented investigations, promoting experimental thermal loading close to their service conditions, lead to more relevant claims about the TSR of refractory products and better prediction of the lifetime of refractory linings achieved.