On Modelling Parasitic Solidification Due to Heat Loss at Submerged Entry Nozzle Region of Continuous Casting Mold

Abstract

Continuous casting (CC) is one of the most important processes of steel production; it features a high production rate and close to the net shape. The quality improvement of final CC products is an important goal of scientific research. One of the defining issues of this goal is the stability of the casting process. The clogging of submerged entry nozzles (SENs) typically results in asymmetric mold flow, uneven solidification, meniscus fluctuations, and possible slag entrapment. Analyses of retained SENs have evidenced the solidification of entrapped melt inside clog material. The experimental study of these phenomena has significant difficulties that make numerical simulation a perfect investigation tool. In the present study, verified 2D simulations were performed with an advanced multi-material model based on a newly presented single mesh approach for the liquid and solid regions. Implemented as an in-house code using the OpenFOAM finite volume method libraries, it aggregated the liquid melt flow, solidification of the steel, and heat transfer through the refractory SENs, copper mold plates, and the slag layer, including its convection. The introduced novel technique dynamically couples the momentum at the steel/slag interface without complex multi-phase interface tracking. The following scenarios were studied: (i) SEN with proper fiber insulation, (ii) partial damage of SEN insulation, and (iii) complete damage of SEN insulation. A uniform 12 mm clog layer with 45% entrapped liquid steel was additionally considered. The simulations showed that parasitic solidification occurred inside an SEN bore with partially or completely absent insulation. SEN clogging was found to promote the solidification of the entrapped melt; without SEN insulation, it could overgrow the clogged region. The jet flow was shown to be accelerated due to the combined effect of the clogging and parasitic solidification; simultaneously, the superheat transport was impaired inside the mold cavity.

On modelling conjugated heat transfer in the thin slab CC mold and solid shell formation under the applied EMBr

“…The details of the MHD model implementation considering the shell conductivity can be found elsewhere [8,9]. The damping source refers to a single mesh approach restricting motion to the melt region only [12].…”

“…However, they become computationally demanding and, to overcome such a bottle neck, are reduced to the 2Dslice or even 1D models where the turbulent melt flow is over-simplified. In the presented study, a single mesh approach is applied to simulate the turbulent flow together with the solidification, thermal resistance of a slag skin and the air gap, and with the heat transfer in the water cooled copper mold [12]. The electric potential method was used to tackle the magnetohydrodynamics effects [13].…”

Numerical Modeling of Metallurgical Processes: Continuous Casting and Electroslag Remelting

“…Hua et al [3] adopted an LES model coupled with the volume of fraction (VOF) to simulate the steel-slag interface's interaction behavior, and the increase of block rates under nozzle clogging on the flow vortex distribution in the mold was well predicted. Alexander et al [4] studied the heat transfer in an SEN through an advanced multi-material model based on a newly presented single mesh approach. Results show that parasitic solidification occurred inside an SEN bore with partially or completely absent insulation, and the clogging of SEN was found to promote the solidification of the entrapped melt.…”

Influence of the adjustable EMBr on the asymmetric flow in a thin slab caster with a misaligned SEN

“…The influence of the applied magnetic field on the asymmetric flow inside a TSC mold due to the partial SEN blockage was recently presented by the authors including effects on the solidification profiles [18]. The SEN clogging can occur during deposition of the non-metallic inclusions [19,20] or due to the combined effect with the parasitic solidification inside the SEN bore because of the heat losses [21,22]. A large eddy simulation was performed to investigate the transient asymmetric fluid flow, solidification, and inclusion transport in a slab CC under different EMBr power by Lu et al [23].…”