Abstract
Slab molds receive liquid steel from the tundish through bifurcated submerged entry nozzles (SEN) using a slide valve as throughput control. Due to the off-centering position of the three plates’ orifices that conform to the valve to control the steel passage, the flow inside the nozzle and mold is inherently biased toward the valve opening side. In the practical casting, a biased flow induces inhomogeneous heat fluxes through the mold copper plates. The nozzle design itself is also a challenge, and has direct consequences on the quality of the product. A diagnosis of the casting process regarding the internal and external flows, performed through experimental and mathematical simulation tools, made it possible to reach concrete results. The mathematical simulations predicted the flow dynamics, and the topography and levels variations of the meniscus characterized through a full-scale water model. The flows are biased, and the meniscus level fluctuations indicated that the current nozzle is not reliable to cast at the two extremes of the casting speeds of 0.9 m/min and 1.65 m/min, due to the danger of mold flux entrainment. A redesign of the nozzle is recommended, based on the experimental and mathematical results presented here.
Highlights
The steel slab defects such as oscillation marks, hook cracks, laminations, slivers, depressions, mold slag entrainment, and heat transfer are related to the fluid flow of liquid steel in the mold [1,2,3,4,5].Simultaneously, the flow of liquid steel inside the nozzle fixes the flow patterns in the mold
The tip contacts on a seating brick; the rod is controlled by a servomechanism providing up and down motions permitting higher or lower steel flows passing through the slit left between the tip and seating brick
The present work studies flow of liquid steel in a slab mold fed through an slide valve (SV) device under current use in a caster in the USA, emphasizing time-dependent flows using water modeling and computer fluid dynamics (CFD) simulations
Summary
The steel slab defects such as oscillation marks, hook cracks, laminations, slivers, depressions, mold slag entrainment, and heat transfer are related to the fluid flow of liquid steel in the mold [1,2,3,4,5]. The liquid steel descends faster than the steel descending on the opposite side Researchers reported this effect on one, and two-phase flows using numerical approaches in the nozzle, verifying the original hypothesis, that biased flows in the mold are due to the slide valve [5,6,7,8,9,10]. The present work studies flow of liquid steel in a slab mold fed through an SV device under current use in a caster in the USA, emphasizing time-dependent flows using water modeling and computer fluid dynamics (CFD) simulations. The study aims at a process diagnosis, which should be useful to clarify the mechanisms of momentum transfer and their possible implications on slab quality, leading to recommendations and conclusions Another goal is to clarify if further efforts are necessary on the way to modify the present design
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