Study on the nozzle clogging mechanism of composite rare earth steel

Through microstructure characterisation and industrial experiments, combined with thermodynamic analysis, the formation mechanism composite rare earth steel nozzle nodules were discussed in this paper. The results showed that the nodules could be divided into a reaction layer, a calcium aluminate layer and a rare earth aluminate layer from the inner wall of nozzle towards the centre. The main phases of the reaction layer were refractory compounds such as Al 2 O 3 , CaO▪6Al 2 O 3 and CaO▪2Al 2 O 3 , the main components of the calcium aluminate layer were CaO▪2Al 2 O 3 , CaO▪Al 2 O 3 and (La,Ce)AlO 3 , the rare earth aluminate layer was dominated by (La,Ce)AlO 3 and a small amount of calcium aluminate. Finally, the process optimisation measures were implemented, such as adjusting LF refining slag, feeding pure Ca wire and decreasing the oxygen content in steel. The nozzle clogging situation was improved, and the number of continuous casting furnaces was increased from less than four to five.