Investigation the causes of corrosion and failure of the submerged entry nozzle for continuous casting of steel

At present, Continuous casting is the most important method of producing ingot in the world. The controlling parts of melts are shroud, stopper and submerged entry nozzle (SEN), which are special refractories. Among the special refractory components, SEN is very important. The duty of SEN is pouring the liquid steel from tundish to crystallizator. The aim of this study was to investigate the causes of corrosion and failure of the soundless SEN that used in continuous casting of Saba Steel Company. At the beginning, different sections of a sound and soundless SEN were prepared. Bulk density, apparent porosity, XRD, XRF and scanning electron microscopy was performed in this research. The results showed that unsuitable coating applied on the surface of SEN and less graphite content of zirconia graphite body of SEN are the major causes of failure so that the soundless and sound nozzle has 8 and 10 graphite percent, which leading to decreased resistance to thermal shock and corrosion.