Study on the Influence of FeTi‐Addition on the Inclusion Population in Ti‐Stabilized ULC Steels and Its Consequences for SEN‐Clogging

Abstract

During the continuous casting of Ti‐stabilized ULC/IF steel grades clogging of the submerged entry nozzle (SEN) is frequently observed. A new statistical evaluation indicates that increasing Ti/Al‐ratios in these steels lead to an increase in the occurrence of clogging and its intensity. Investigations of samples of two TiULC heats, taken at the RH‐degasser, show a remarkable increase of inclusions due to FeTi‐addition. The presence of Ti‐bearing alumina particles contrary to the thermodynamical expectations, indicate that their formation takes place as a consequence of FeTi‐addition. Laboratory‐scale experiments confirm the formation of alumina inclusions containing traces of Ti. Their size is found to be significantly smaller compared to pure alumina inclusions. Rising numbers of small inclusions within the steel are suspected to accelerate the buildup of clogging deposits. Two mechanisms are proposed to explain the formation of these particles. On the one hand ferrotitanium acts as a source of oxygen, resulting in the formation of new inclusions during dissolution. On the other hand, the modification of preexisting deoxidation products in regions with high Ti‐contents may play a role.