Abrupt Casting Failures Due to Sub Entry Nozzle Clogging in Calcium Treated Aluminum Killed Steel.

Clogging of sub entry nozzle is a recurrent problem during continuous casting of low carbon aluminum deoxidized steel. Newly modernized SMS shop, producing mainly low carbon aluminum deoxidized steel through BOF-Twin LF-CC route was facing a major issue of nozzle clogging leading to abrupt abortion of sequence casting. The incidences of SEN clogging were very high leading to loss of shop productivity. Within a span of one month around 28 cases of casting abortion were reported due SEN clogging. Casting was getting stopped in 3–4 heat sequence even after calcium treatment practice was adopted in each heat. The process of steelmaking was studied in detail to find out the root cause of nozzle clogging. It was found that dendritic clusters of alumina originating as a result of deoxidation of steel and reoxidation of aluminum during secondary refining was probably causing SEN clogging. It was also found that optimization of Ca treatment practice was required for successful continuous casting of an aluminum-killed steel. The paper elaborates the technical issues faced related to clogging of SEN in a newly installed high speed single strand slab caster during continuous casting of low carbon steel deoxidized with aluminum. The paper covers the essential steps required to identify the root cause of nozzle clogging and various process interventions essential to eliminate the SEN clogging issues and streamline the production of low carbon aluminum-killed steel in higher sequence lengths. [ABSTRACT FROM AUTHOR]