Authors:
Robert Świerszcz | Zakłady Magnezytowe "ROPCZYCE" S.A. | Poland
Zbigniew Czapka | Zakłady Magnezytowe "ROPCZYCE" S.A. | Poland
Prof. Dr. Jacek Szczerba | AGH University of Science and Technology | Poland
Dr. Ilona Jastrzębska | AGH University of Science and Technology | Poland
Functional additives and firing procedures determine the properties of alumina-carbon (Al2O3-C) refractory materials used as flow control element in the continuous steel casting process. In this work, we compare the physicochemical and mechanical properties of Al2O3-C refractory materials produced using Al or Si as functional additives, and fired at different temperature conditions, 800, 1000, 1200 and 1400°C. The samples were heat-treated in the carbon bed to limit the oxygen access. Simulations of predominance diagrams Al-C-N-O and Si-C-N-O, showed that depending on the partial pressure of CO and N2, the oxide, carbide and nitride phases can appear in the Al2O3-C material. XRD results revealed that aluminium carbide (Al4C3) is formed in the material containing Al addition after heat treatment as low as 800°C, while silicon carbide (SiC) generates for Si addition only above 1000°C. Samples with Al addition are susceptible to hydration which was confirmed by FTIR measurements. This is the result of reaction between Al4C3 from refractory and H2O from the air producing amorphous AlOOH.
In summary, the conducted studies show that depending on the additive used, to obtain a material with the desired properties, microstructure and durability, the amount of this additive and the heat treatment temperature play a key role and shall be properly selected.
The research was conducted and funded by the Research and Development Centre of Ceramics Material in Zaklady Magnezytowe “ROPCZYCE S.A.” in cooperation with the Faculty of Material Science and Ceramics AGH University of Science and Technology, Poland.