Interactions between Carbon‐Bonded Alumina Filters and Molten Steel: Impact of a Titania‐Doped Filter Coating

Herein, the influence of adding titania to the carbonaceous alumina coating of Al₂O₃–C filters on the interactions with molten steel is investigated. Therefore, coated filters are immersed for 30 s in molten steel (42CrMo4) at 1580 °C. Mainly by microstructural and chemical analyses, the immersed filters as well as the solidified steel are characterized. Due to the reducing atmosphere of the heat treatment during sample manufacturing, the formation of aluminum titanate phases in the coating is not observed. During immersion, on the one hand, titania acts as the sintering agent for alumina within the coating and for precipitated alumina inclusions from the melt. On the other hand, dissolved titanium in the melt decreases the surface tension and thus increases wetting of the steel melt on the filter surface. The results indicate that more but smaller alumina inclusions remain in the solidified steel if titania is added to the coating. Thus, the modification of alumina inclusions by adding titania to the filter coating presents a way to tailor these inclusions depending on the product's application.