Effect of Nozzle Clogging on the Fluid Flow Pattern in a Billet Mold with Particle Image Velocimetry Technology

The flow pattern of molten steel in a mold of continuous casting affects the temperature distribution and initially solidifies the shell thickness homogeneity, inclusion transport, and liquid slag entrapment. Alumina inclusions in Al-killed steel tend to adhere to the inner wall of the nozzle, which changes the nozzle geometry structures and affects the molten steel flow pattern in the mold. In this study, two different clog shapes—the hemispherical clog and tube clog—were identified based on the clogged straight-nozzle dissection results. The hydraulic straight-nozzle casting model with different clog situations was designed to investigate the effect of the clog status on the fluid flow in the mold using particle image velocimetry (PIV) technology. The results show that a tail stream with a length of 80 mm forms near the nozzle wall in the fluid flow direction when the hemispherical clog sticks to the nozzle and the jet stream deflects to the clogged side after the jet stream and tail stream mix. However, when the hemispherical clog sticks to the nozzle outlet, the jet stream deflects to the nonclogged side. The increase in the tube clog thickness causes an increase in the jet stream velocity magnitude near the nozzle outlet.