Abstract
Particles in molten steel, including argon-gas bubbles, slag droplets, and non-metallic inclusions, are removed into the surface-slag layer or captured by the solidifying steel-shell during continuous steel casting. Captured particles often become serious defects in the final steel product, so understanding particle-capture mechanisms is important for steel quality. Slab casters often have a straight mold and upper-strand prior to a curved lower-strand. The present work investigates particle capture in such a caster using computational modeling with a standard k-ε model for molten-steel flow, a discrete phase model for inclusion transport, and an advanced capture criterion for inclusion entrapment and engulfment into the steel shell. A new postprocessing methodology is presented and applied to predict inclusion-capture rates in commercial cast product. The locations and size distributions of particles captured into the shell, and actual capture rates are quantified. The model predictions are validated with ultrasonic-test plant measurements of the locations of large particles captured in a steel slab. The results reveal how large-inclusion capture accumulates in the beginning of the curved strand, leading to a capture band in the slab inside radius. Finally, the capture fractions and locations due to all capture mechanisms are compared for different inclusion sizes, and the implications are discussed.
Highlights
The sink terms to account for steel solidification [25] and the advanced capture formed on as-cast steel slabs, produced during steady casting conditions while inclusions criterion modeling methodology [17] are implemented with separate C-code based Usercontinuously flow in into the mold strand regions through the nozzleisfrom the upstream
The removal percentage of these inclusions increases greatly with inclusion size. Within this critical size range, 60–80% of inclusions with diameters of 200 μm to 300 μm are captured into the steel shell and show an accumulation band near the beginning of the curved part of the strand, 4–6 m below the meniscus
Primary Dendrite Arm Spacing (PDAS) is very important for the capture of large inclusions deep into the strand region, as well as the local steel flow velocity across the solidification which controls the drag, 19 ofand the other forces which push the inclusions towards the steel shell front and thereby lessen the chance of rotation
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Static-electromagnetic braking systems were shown to reduce the penetration depth of the jet, leading to less bubbles sent down the narrow face deep into the strand, and less particle capture [22] These previous works used continuous particle injection to predict particle distributions in the cast product. The present work applies the advanced particle-capture criterion [17,18] with a standard k-ε turbulent fluid-flow model and a particle transport model, to investigate the transport and capture of large inclusion particles during continuous casting of steel slabs in a commercial caster with a vertical mold and upper section and a curved lower strand, using a 9.5 m-long strand domain. The capture fractions and mechanisms of inclusion capture including both entrapment and engulfment are quantified according to inclusion size, considering molten steel velocity, inclusion velocity and PDAS
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