Al2O3-C refractories are extensively used as functional components in continuous casting of steel. These high-duty Al2O3-C products -like submerged entry nozzles, ladle shrouds and monoblock stoppers- contain up to 30 wt.-% carbon and present excellent mechanical, thermal and chemical properties, enabling the cost- and quality effective implementation of the continuous casting process.
Ceramic glazes are externally applied on Al2O3-C flow control refractory products to protect carbon from oxidation. These glazes are typically boron-containing. However, the increasing requirements for clean steel technology along to environmetal- and health issues associated with boron compounds will make the utilization of boron-free glazes a necessity in the upcoming years.
New boron-free self-glazing Al2O3-C formulations with wollastonite, magnesia, sodium carbonate and/or calcium magnesium aluminate additives were developed with the assistance of the FactSage software tool. These compositions presented a softening point in the range of 1000 – 1100 °C for self-glaze formation, which is the typical preheating temperature range for Al2O3-C functional refractory products. In addition, the influence of particle packing on their oxidation resistance was investigated, based on established and newly developed particle size distribution models with distribution moduli in the range of 0,28 – 0,8.