Cause and Mechanism of Casting Nozzle Clogging During Aluminum Continuous Casting and Rolling

The temperature field and velocity field of molten aluminum flowing through the casting nozzle during continuous casting and rolling were simulated by establishing a simulation model. The morphology and composition of the casting nozzle materials after reaction with molten aluminum at different temperatures (850, 900, 950℃) for different times (2,4,6,8,10 h) were studied by experiments. The mechanism of the casting nozzle clogging was analyzed. The results show that during the molten aluminum flowing, the temperature gradient of the casting nozzle at the fixed position of an iron plate was higher than that of other regions. The uneven velocity distribution of molten aluminum resulted in uneven temperature distribution, and the temperature of the molten aluminum in contact with the nozzle wall was relatively low, which led to slag hanging easily. Al₂O₃ slag inclusions and silicon were formed by displacement reaction of high temperature molten aluminum with SiO₂ in the nozzle materials. The produced Al₂O₃ would increase the surface roughness of the nozzle wall, and also it would enter the molten aluminum to increase the viscosity and slow down the flow velocity; therefore the slag inclusions on the nozzle wall could not be washed away in time. The slag inclusions on the nozzle wall then continued to increase, and eventually caused the nozzle clogging.