Numerical study of internal SEN design effects on jet oscillations in a funnel thin slab caster

Abstract

The understanding of the jets oscillations inside the funnel thin slab mould is essential to ensure constant molten steel delivery, better flow patterns control and consequently increase the shop productivity and quality of the final product. To achieve this, a particular numerical study of the internal nozzle design effects on the mould fluidynamics is carried out trying to determinate the origin of the jets oscillations, for this, a mathematical model was developed including the fundamental equations, the RSM turbulence model and the VOF multiphase model. The governing equations are discretised and solved thought the implicit segregated-iterative method embedded in FLUENT ®. The results show that even for SEN designs with stable operational behaviour, the jet oscillations remain present and became more intense for higher casting speeds and deeper immersions. The nozzle analysis shows that the internal geometry promotes flow perturbations at the zone where the internal transversal areas start changing, generating high and low dynamic pressures encouraging a tendency for the molten steel to leave in preference for one of the ports. In addition, a delicate micro-scale force balance was found on the internal bifurcation tip of the nozzle, this balance is related to the fluctuant velocities and the ferrostatic pressure. If this balance is broken the oscillations are more intense, promoting permanent variations of the mass flow rate from one port to the other. Consequently, it is concluded that the jets oscillations have their origin inside the SEN. © 2014 ISIJ.