Abstract: The formation mechanism of nozzle clogging in the submerged entry nozzle (SEN) used for AISI321 stainless steel was analyzed by means of scanning electron microscope (SEM) and FactSage software. The results showed that the deposit was mainly classified into three parts. The first part was composed of frozen steel at the surface of refractory. The formation of frozen steel was resulted from TiO₂ which was formed due to the oxidation of TiN or the reduction of SiO₂ in refractory by Ti in steel. For the second part, it was a dendritic materials, which was consisted of complex inclusions of CaO·TiO₂-MgO·Al₂O₃ containing rich CaO·TiO₂. The accumulation of the complex inclusions in steel resulted in the formation of second layer. There was massive frozen steel closed to molten steel at the third part, which was consisted of TiN with a core of MgO·Al₂O₃  and frozen steel. The precipitation of TiN induced by MgO·Al₂O₃  promoted the freeze of steel and formation of complex TiN inclusions. In order to solve the problem of nozzle clogging, the following measures were proposed: reducing the carbon and nitrogen content in steel and the additive amount of titanium alloy; reducing the SiO₂ content in the refractory of submersed nozzle; improving the cleanliness of steel, especially promoting the removal of CaO·TiO₂ inclusions; modifying the CaO·TiO₂ inclusions to liquid particles by aluminum control and calcium treatment during refining process.

Key words: stainless steel, continuous casting, inclusions, nozzle clogging