Identifikation der Quelle von Calciumaluminat-Einschlüssen hochkohliger Stähle mittels Schlackentracings

In metallurgy, the steel cleanness is crucial for determining the mechanical properties and overall quality of the final product. Monitoring and reducing non-metallic inclusions (NMI), particularly calcium aluminate (CA) inclusions, are key aspects in the steel production process, especially in the production of medium-carbon steels. Slag tracing allows for the investigation of the origins and behavior of these inclusions during the melting process. This master's thesis focuses on the origins and properties of CA inclusions in high-carbon steel, with the experimental melts conducted at voestalpine Linz GmbH. BaCO3 is added during the tapping process to trace the ladle slag, and a slag mixture containing SrCO3 is fed into the tundish of the continuous casting plant. Furthermore, the effect of ladle glazing on inclusion formation is investigated. Analytical methods employed include scanning electron microscopy, X-ray radiographic measurements, and rare earth elements fingerprint analysis. The results show that the addition of Ca-containing auxiliaries such as CaC2 and CaSi significantly influences the formation and modification of the NMI. Furthermore, Ba- and Sr-marked inclusions are examined, and their formation history is discussed. The REE fingerprint analysis confirms Ca treatment as an inclusion source for the examined NMIs. Additionally, ladle glazing was identified as an exogenous source in the following heat.