The Role of Submerged Entry Nozzle Port Shape on Fluid Flow Turbulence in a Slab Mold

The fluid flow of liquid steel in a wide slab mold (1880 x 230 mm) influenced by two different submerged entry nozzle (SEN) designs (bifurcated nozzles with rectangular, SEN-R, vs square, SEN-S, ports) and immersion depths of 115 and 185 mm was studied using a 1:1 scale water model. To analyze the fluid dynamics, particle image velocimetry and video recording techniques were used. The fluid-flow dynamics indicate that the discharging jets using either SEN design suffer strong wandering and raveling effects that enhance turbulence in the meniscus region. The preceding results show the existence of velocity spikes (defined as velocities with magnitudes that exceed the standard deviation of the average velocity) in the submeniscus region. Using the SEN-R ports yields more velocity spikes per minute with larger magnitudes than using the SEN-S, which could be the main cause of the detrimental quality of steel. The capability of slag entrainment by the flow developed by a nozzle was the criterion employed to evaluate quantitatively the merits of one nozzle over the other. This criterion is based on the capillary number, which gives the ratio between viscous-inertial and surface forces at the metal-slag interface.