Thermal shock- and corrosion-resistant heat-insulating composites based on renewable raw materials for application in steel ingot casting

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The aim of the project is to investigate an innovative materials concept for refractory hollowware, such as runner bricks, that is applied in steel ingot casting, especially in bottom pouring. A heat-insulating refractory based on the renewable raw material rice husk ash is combined with an alumina or alumina-rich coating prepared by flame spraying in order to provide both excellent thermal insulating properties and a high resistance to chemical interactions with the steel melt. Thanks to the minimized heat transfer to the novel insulating material used instead of common hollowware refractories, a reduction of segregations in the steel is expected. Furthermore, the material made from rice hush ash provides great ecological and economic advantages. However, for the production of high alloy steels the reactivity of free silica towards alloying elements such as manganese or chrome would be problematical. Therefore, the chemically inert coating on the silica-rich substrate is essential to ensure a high purity of the steel. Flame spraying has been chosen as coating technique because the lamellar structures typically obtained by this technique are beneficial for the thermal shock resistance.