SUBMERGED ENTRY NOZZLE CLOGGING DURING CONTINUOUS CASTING OF Al-KILLED STEEL

F. Tehovnik, J. Burja, B. Arh, Institute of metals and technology, Ljubljana, Slovenia, M. Knap, University of Ljubljana, Faculty of Natural Sciences and Engineering, Ljubljana, Slovenia Nozzle clogging is a common problem in the production of continuously cast Al-killed steels. Clogging occurs when there are solid inclusions in molten steel at casting temperatures. SENs (Submerged entry nozzles) from continuous casting of Al-killed low alloy steel grades with increased content of sulfur (0,020 to 0,035 % S) were examined. The examinations revealed that the deposits are mainly alumina based, with spinel and sulfur inclusions and some entrapped steel melt. It was concluded that the process of clogging begins when the steel melt infiltrates the refractory and removes the protective zirconia surface, thus allowing the adhesion of fine solid aluminates, which form the deposits.