Steel flow dominated by inertial and buoyancy flows under gas bubbling and thermal stratification conditions, in a one-strand tundish, was studied using a 2/5 scale water model. The use of a turbulence inhibitor yields plug flow volume fractions well above 40 pct for a casting rate of 3.12 tons/min under isothermal conditions. Small flow rates of gas injection (246 cm 3 /min), through a gas curtain, improved the fluid flow by enhancing the plug flow volume fraction. Higher flow rates originated an increase of back-mixing flow, thus forming recirculating flows in both sides of this curtain.Step inputs of hot water drove streams of this fluid toward the bath surface due to buoyancy forces. A rise in gas flow rate led to a thermal homogenization in two separated cells of flow located at each side of the gas curtain.Step inputs of cold water drove streams of fluid along the tundish bottom. Use of the gas curtain homogenized the lower part of the tundish as well as the upper part of the bath at the left side of the curtain. However, temperature at the top corner of the tundish, in the outlet box, remained very different than the rest of the temperatures inside this tundish. High gas flow rates (912 cm 3 /min) were required to homogenize the bath after times as long as twice the mean residence time of the fluid. Particle image velocimetry (PIV) measurements corroborated the formation of recirculating flows at both sides of the gas curtain.

In the current research study, a mathematical model was developed to study the dissipation phenomena inside a new design of ladle shroud and its effects on flow patterns and inclusion removal rate. The New Ladle Shroud performance is evaluated in a conventional slab tundish, and the results are compared to different flow control arrangements. The velocity of the entry jet is decreased and the bulk flow is well controlled, the inclusion removal rate is improved, and compared to those arrangements where turbulence inhibitors are used.

Temperature control of liquid steel by plasma heating is physically and mathematically modeled. A dimensionless plasma heating number is employed for scaling up of heating operations between a steam jet for water model and a plasma prototype. Overall responses of step-input temperatures in steel are fairly well predicted by the physical model. Fluid-flow structure and thermal fields, in terms of dimensionless temperatures, of steel are different from those of water. Two positions of plasma in a tundish were studied, centered and off-centered. The second position decreased the heating response of a plasma, although a more homogeneous thermal field was obtained in regard to the first position. Consequently, a centered position offered a faster thermal response than the off-centered one. Flow controllers decreased the efficiency of plasma due to the formation of stagnant zones located in their proximity, which were not active enough to exchange momentum and heat with the bulk flow.

Simple changes on tundish geometry may lead to significant improvements of transport phenomena of liquid steel in tundishes. In the present case steel flow in a six-strand billet trough type tundish is mathematically simulated. Numerical results indicate the existence of a high fluid turbulence in the pouring zone and recirculating flows. Steel temperatures in the strands are also different, which from practice it would mean different qualities of billet among the strands.A simple change of design by widening the pouring box improves all the steel flow characteristics. First the turbulence in the pouring box is decreased, the recirculating flows are eliminated and steel temperatures in the six strands become closer to each other. Using a computational technique known as volume of fluid, surface topography of bath including the covering slag was simulated for both types of tundishes. These simulations predicted an open eye of the slag layer for the first tundish while in the second this phenomena was avoided. Thus, it was demonstrated the original hypothesis that small changes in tundish design may lead to a more controlled steel flow. Mathematische Modellierung der Geometrie eines Tundishs fOr mehradrige StranggieBanlagen und ihr EinfluB auf die Stahlstromung. Einfache Anderungen in der Tundishgeometrie konnten zu betrachtlichen Verbesserungen der Transportphanomens flOssigen Stahls im GieBverteiler fOhren. Gegenstand dieser Untersuchung ist daher die Ausbildung der Stahlstromunq in einem Tundish, der eine 6-adrige StranggieBanlage speist. Numerische Ergebnisse der entsprechenden mathematischen Simulation weisen auf die Existenz einer groBen Turbulenz in der GieBzone und auf ROckstromungen hin. AuBerdem differierte die Stahltemperatur in den einzelnen Stranqen, was aus Sicht der Praxis auf unterschiedliche Knuppelqualltat deutet. Eine leichte Veranderunq der Bauart durch Aufweiten des GieBkastens verbessert aile Eigenschaften der Stahlstrornunq, Zunachst verringert sich die Turbulenz, dann gbit es keine ROckstromungen mehr und schlieBlich gleicht sich auch die Stahltemperatur in den 6 Strangen an. Mit einer Berechnungstechnik, bekannt als FIOssigkeitssvolumen, wurde die Badtopographie an der Obertlache zusammen mit der deckenden Schlackenschicht fOr beide Tundishvarianten simuliert. FOr den einen GieBverteiler wies die Schlacke ein offenes Auge auf, im anderen Fall wurde dieses Phanomen vermieden. So lieB sich die Ausgangshypothese, daB kleine Anderungen der Tundishbauart zu einer besser regelbaren Stahlstrornunq fOhren konnsn, belegen.

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