Nozzle clogging during the continuous casting of aluminum-killed steel

Nozzle clogging during the continuous casting of aluminum-killed steel hinders productivity and quality during steelmaking. The objective of this research was to gain a better understanding of the mechanisms and factors affecting nozzle clogging so that practices can be implemented in industry to reduce the impact of this problem.; A dynamic continuous casting simulation was built that allows for the flow of steel through small simulation nozzles and provides a quantitative method to measure the effect of different factors on the rate of nozzle clogging. The simulator was demonstrated to produce accretions similar to those observed in industrial nozzles. Accretions were shown to consist mostly of alumina with some solidified steel. In addition, products of steel-refractory interactions such as CA₆, commonly found in industrial nozzle accretions, were observed in the laboratory nozzles.; Experiments were performed to examine whether differences in clogging performance occurs with the following nozzle materials: alumina, magnesia, zirconia, zirconia-graphite, and alumina-graphite. No differences in clogging performance were found between the alumina, magnesia, zirconia, and zirconia-graphite nozzle materials. However, industrial alumina-graphite nozzle materials were shown to clog at a faster rate. Nozzles made of industrial alumina-graphite had strong thermochemical interactions with the steel that increased the rate of nozzle clogging. No significant steel-refractory interactions were observed in the pure oxide or zirconia-graphite nozzles.; A factorial experiment was performed to determine the metallurgical and refractory factors that are most significant to nozzle clogging. The factors tested were: carbon, soluble aluminum, and titanium contents of steel, superheat, and graphite and silica content of alumina-based nozzles. The metallurgical factors were determined to be most significant in this study. The primary factors found to have the strongest effect on nozzle clogging were: carbon, soluble aluminum, and titanium content of the steel and superheat. Strong evidence was found that pointed to reoxidation and inclusion deposition as significant mechanisms for nozzle clogging.