The demand for higher quality steel and higher production rates in the production of steel slabs is ever increasing. These slabs are produced using a continuous casting process. The molten steel flow patterns inside the components of the caster play an important role in the quality of these products. A simple yet effective design method that yields optimum designs is required to design the systems influencing the flow patterns in the caster. The tundish is one of these systems. Traditionally, experimental methods were used in the design of these tundishes, making use of plant trials or water modelling. These methods are both costly and time consuming. More recently, Computational Fluid Dynamics (CFD) has established itself as a viable alternative to reduce the number of experimentation required, resulting in a reduction in the time scales and cost of the design process. Furthermore, CFD provides more insight into the flow process that is not available through experimentation only. The CFD process is usually based on a trial-and-error basis and relies heavily on the insight and experience of the designer to improve designs. Even an experienced designer will only be able to improve the design and does not necessarily guarantee optimum results. In this thesis, a more efficient design methodology is proposed. This methodology involves the combination of a mathematical optimiser with CFD to automate the design process. The methodology is tested on a four different industrial test cases. The first case involves the optimisation of a simple dam-weir configuration of a single strand caster. The position of the dam and weir relative to inlet region is optimised to reduce the dead volume and increase the inclusion removal. The second case involves the optimisation of a pouring box and baffle of a two-strand caster. In this case, the pouring box and baffle geometry is optimised to maximise the minimum residence time at operating level and a typical transition level. The third case deals with the geometry optimisation of an impact pad to reduce the surface turbulence that should result in a reduction in the particle entrainment from the slag layer. The last case continues from the third case where a dam position and height is optimised in conjunction with the optimised impact pad to maximise the inclusion removal on the slag layer. The cases studies show that a mathematical optimiser combined with CFD is a superior alternative compared to traditional design methods, in that it yields optimum designs for a tundish in a continuous casting system. / Thesis (PhD (Mechanical Engineering))--University of Pretoria, 2006. / Mechanical and Aeronautical Engineering / unrestricted

A importância de um escoamento adequado em distribuidores de lingotamento contínuo, quando o objetivo é produzir aços limpos (clean steels), vem sendo largamente discutida e estudada nas últimas décadas. Esses estudos usualmente são realizados em modelos físicos e/ou numéricos, visto que em unidades industriais são de difícil execução. Nos modelos físicos, os estudos como a simulação da remoção de inclusões para diferentes condições de escoamento tem se mostrado bastante importante para o entendimento do escoamento no distribuidor e seus respectivos artifícios favorecedores de flotação de inclusões. Este trabalho tem como objetivo estudar o comportamento da remoção de inclusões em um modelo físico do distribuidor de lingotamento contínuo de tarugos frente à modificação de escoamento no distribuidor. O ensaio proposto para quantificar a remoção de inclusões envolve a utilização de micropartículas de polietileno para simulação das inclusões sólidas de alumina e peneira metálica como método de captura de inclusões passantes pelo veio do distribuidor. Para fornecer suporte a este estudo, foram realizados estudos de qualificação do escoamento por meio do ensaio de linhas de fluxo e de quantificação dos tempos de residência e frações de volumes característicos por meio do ensaio de distribuição de tempos de residência. A técnica utilizada se mostrou confiável sob o ponto de vista experimental. Como resultados do comportamento da remoção de inclusões frente aos parâmetros estudados, têm-se especificamente para o distribuidor estudado que: o aumento da velocidade de lingotamento, em média, aumentou o porcentual de inclusões passantes de 11,61 (1,8 m/min) para 17,45% (2,6 m/min); a presença do tubo longo, em média, aumentou o porcentual de inclusões passantes de 2,79 (sem tubo longo) para 27,03% (com tubo longo); a presença das barreiras, em média, diminuiu o porcentual de inclusões passantes de 16,16 (sem barreiras) para 13,65% (com barreiras). / When the objective is to produce clean steels, the appropriated melt flow in the tundish is very important. It has been widely discussed and studied by researchers in the lasts decades. Physical and/or mathematical models are used to perform these studies because is very difficult to do it in industrial plants. In the physical models, the studies as the simulation of inclusion removal to different conditions of fluid flow have showed to be very important to understand the tundish and its respective tools to improve the inclusion removal. This work aims to study the behavior of inclusion flotation in a physical model of continuous casting tundish of steel billets in different kinds of fluid flow. The method proposed to quantify the inclusion removal involves the utilization of microparticles of polyethylene to simulate solid alumina inclusion and a metallic sieve in the strand as a method to catch the non-floated inclusions. The quantification of inclusion removal has the support of two others experiments to qualify de flow pattern by visual observation using dye tracer and quantify the residence time distribution of the model using acid tracer. The method used in this work to quantify inclusion removal showed to be reliable from an experimental point of view. As results of the behavior of the inclusion removal, the speed of ingoting increased the non-floated inclusions from 11.61 (1.8 m/min) to 17.45% (2.6 m/min), the presence of the submerged inlet shroud increased the non-floated inclusions from 2.79 (without) to 27.03% (with) and the presence of the dams the non-floated inclusions decreased from 16.16 (without) to 13.65% (with).

A importância de um escoamento adequado em distribuidores de lingotamento contínuo, quando o objetivo é produzir aços limpos (clean steels), vem sendo largamente discutida e estudada nas últimas décadas. Esses estudos usualmente são realizados em modelos físicos e/ou numéricos, visto que em unidades industriais são de difícil execução. Nos modelos físicos, os estudos como a simulação da remoção de inclusões para diferentes condições de escoamento tem se mostrado bastante importante para o entendimento do escoamento no distribuidor e seus respectivos artifícios favorecedores de flotação de inclusões. Este trabalho tem como objetivo estudar o comportamento da remoção de inclusões em um modelo físico do distribuidor de lingotamento contínuo de tarugos frente à modificação de escoamento no distribuidor. O ensaio proposto para quantificar a remoção de inclusões envolve a utilização de micropartículas de polietileno para simulação das inclusões sólidas de alumina e peneira metálica como método de captura de inclusões passantes pelo veio do distribuidor. Para fornecer suporte a este estudo, foram realizados estudos de qualificação do escoamento por meio do ensaio de linhas de fluxo e de quantificação dos tempos de residência e frações de volumes característicos por meio do ensaio de distribuição de tempos de residência. A técnica utilizada se mostrou confiável sob o ponto de vista experimental. Como resultados do comportamento da remoção de inclusões frente aos parâmetros estudados, têm-se especificamente para o distribuidor estudado que: o aumento da velocidade de lingotamento, em média, aumentou o porcentual de inclusões passantes de 11,61 (1,8 m/min) para 17,45% (2,6 m/min); a presença do tubo longo, em média, aumentou o porcentual de inclusões passantes de 2,79 (sem tubo longo) para 27,03% (com tubo longo); a presença das barreiras, em média, diminuiu o porcentual de inclusões passantes de 16,16 (sem barreiras) para 13,65% (com barreiras). / When the objective is to produce clean steels, the appropriated melt flow in the tundish is very important. It has been widely discussed and studied by researchers in the lasts decades. Physical and/or mathematical models are used to perform these studies because is very difficult to do it in industrial plants. In the physical models, the studies as the simulation of inclusion removal to different conditions of fluid flow have showed to be very important to understand the tundish and its respective tools to improve the inclusion removal. This work aims to study the behavior of inclusion flotation in a physical model of continuous casting tundish of steel billets in different kinds of fluid flow. The method proposed to quantify the inclusion removal involves the utilization of microparticles of polyethylene to simulate solid alumina inclusion and a metallic sieve in the strand as a method to catch the non-floated inclusions. The quantification of inclusion removal has the support of two others experiments to qualify de flow pattern by visual observation using dye tracer and quantify the residence time distribution of the model using acid tracer. The method used in this work to quantify inclusion removal showed to be reliable from an experimental point of view. As results of the behavior of the inclusion removal, the speed of ingoting increased the non-floated inclusions from 11.61 (1.8 m/min) to 17.45% (2.6 m/min), the presence of the submerged inlet shroud increased the non-floated inclusions from 2.79 (without) to 27.03% (with) and the presence of the dams the non-floated inclusions decreased from 16.16 (without) to 13.65% (with).

A importância de um escoamento adequado em distribuidores de lingotamento contínuo, quando o objetivo é produzir aços limpos (clean steels), vem sendo largamente discutida e estudada nas últimas décadas. Esses estudos usualmente são realizados em modelos físicos e/ou numéricos, visto que em unidades industriais são de difícil execução. Nos modelos físicos, os estudos como a simulação da remoção de inclusões para diferentes condições de escoamento tem se mostrado bastante importante para o entendimento do escoamento no distribuidor e seus respectivos artifícios favorecedores de flotação de inclusões. Este trabalho tem como objetivo estudar o comportamento da remoção de inclusões em um modelo físico do distribuidor de lingotamento contínuo de tarugos frente à modificação de escoamento no distribuidor. O ensaio proposto para quantificar a remoção de inclusões envolve a utilização de micropartículas de polietileno para simulação das inclusões sólidas de alumina e peneira metálica como método de captura de inclusões passantes pelo veio do distribuidor. Para fornecer suporte a este estudo, foram realizados estudos de qualificação do escoamento por meio do ensaio de linhas de fluxo e de quantificação dos tempos de residência e frações de volumes característicos por meio do ensaio de distribuição de tempos de residência. A técnica utilizada se mostrou confiável sob o ponto de vista experimental. Como resultados do comportamento da remoção de inclusões frente aos parâmetros estudados, têm-se especificamente para o distribuidor estudado que: o aumento da velocidade de lingotamento, em média, aumentou o porcentual de inclusões passantes de 11,61 (1,8 m/min) para 17,45% (2,6 m/min); a presença do tubo longo, em média, aumentou o porcentual de inclusões passantes de 2,79 (sem tubo longo) para 27,03% (com tubo longo); a presença das barreiras, em média, diminuiu o porcentual de inclusões passantes de 16,16 (sem barreiras) para 13,65% (com barreiras). / When the objective is to produce clean steels, the appropriated melt flow in the tundish is very important. It has been widely discussed and studied by researchers in the lasts decades. Physical and/or mathematical models are used to perform these studies because is very difficult to do it in industrial plants. In the physical models, the studies as the simulation of inclusion removal to different conditions of fluid flow have showed to be very important to understand the tundish and its respective tools to improve the inclusion removal. This work aims to study the behavior of inclusion flotation in a physical model of continuous casting tundish of steel billets in different kinds of fluid flow. The method proposed to quantify the inclusion removal involves the utilization of microparticles of polyethylene to simulate solid alumina inclusion and a metallic sieve in the strand as a method to catch the non-floated inclusions. The quantification of inclusion removal has the support of two others experiments to qualify de flow pattern by visual observation using dye tracer and quantify the residence time distribution of the model using acid tracer. The method used in this work to quantify inclusion removal showed to be reliable from an experimental point of view. As results of the behavior of the inclusion removal, the speed of ingoting increased the non-floated inclusions from 11.61 (1.8 m/min) to 17.45% (2.6 m/min), the presence of the submerged inlet shroud increased the non-floated inclusions from 2.79 (without) to 27.03% (with) and the presence of the dams the non-floated inclusions decreased from 16.16 (without) to 13.65% (with).

Thesis (MEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: In modern steelmaking a tundish serves as an important metallurgical reactor to remove inclusions and maintain thermal and chemical homogeneity in the product. In this study the flow behaviour in a four strand tundish was investigated by means of a 1/2 scale water model, based on Froude number similarity, as well as by using numerical modelling. Both the numerical study and physical model were used to characterise residence time distribution (RTD) in the vessel and to calculate properties pertaining to the tundish flow regime. The three different tundish configurations investigated in this study are: a bare tundish with no flow control devices, a tundish with a turbulence inhibitor and a tundish using a turbulence inhibitor with holes in combination with dams. Preliminary investigations focussed on the framework for obtaining an accurate numerical solution within reasonable computational times. The effect of assuming symmetry and dynamically steady flow in the numerical model was shown to be small relative to the effect of grid size and justifiable by the savings in computational time. The grid independence study indicated the importance of using a finer mesh in areas of high velocity gradients to obtain realistic results and also to limit the number of computational cells. A procedure using gradient adaptation was used to refine the mesh automatically in the required regions for different tundish geometries. Results also showed that the inlet boundary of the numerical model should be selected at the ladle outlet, since assuming a flat velocity profile at the nozzle port resulted in significant changes in the RTD response. Comparison of the results obtained using the numerical model with those from physical experiments yielded an average error of less than 10%. This was assumed to be a good prediction, considering the assumptions employed in the numerical model. Both the physical and numerical models showed that a tundish without flow control devices was prone to significant short circuiting. The addition of a turbulence inhibitor was shown to be successful in preventing short circuiting and provided surface directed flow, which is thought to aid inclusion removal in the slag. Additionally, the minimum, peak and mean residence times and plug flow volume fraction were increased significantly, while the dead volume fraction decreased. However, using a turbulence inhibitor with holes in combination with dams showed that this configuration may cause increased refractory wear together with increased risk of slag entrainment due to flow patterns with increased surface turbulence. It also showed that the short-circuiting might not be eliminated completely. This indicates that certain design changes to tundish flow control systems can introduce problems that outweigh the benefits of the altered flow patterns. Furthermore, the numerical method, which was based on the water model, was modified to simulate the high temperature steel process. A very good match was obtained between the results using the two different numerical models. This serves as additional evidence that tundish water modelling based on Froude number similarity provides a good representation of the actual industrial process. Using the numerical model based on the high temperature steel process the effect of turbulence inhibitor shape was studied for four different turbulence inhibitor designs. Results showed the best performance, based on flow characteristic properties and surface turbulence values, was achieved for the design using a rectangular box-like shape with flanges at the top. However, the comparison emphasized the effect of the turbulence inhibitor shape on the flow behaviour, as each design yielded completely different flow patterns. It was also observed that a good turbulence inhibitor provided an optimum amount of turbulent suppression. Insufficient suppression would cause fast flows, which will result in insufficient residence time for inclusion flotation and high surface turbulence values, which may cause slag entrainment. On the other hand, too much suppression may increase the variation between strands. / AFRIKAANSE OPSOMMING: Die verdeeltrog speel ‘n belangrike rol in die moderne staalvervaardigingsproses deur inklusies te verwyder en termiese en chemiese homogeniteit in die produk te verseker. In hierdie studie is die vloeigedrag in ‘n verdeeltrog met vier uitlate bestudeer deur middel van ‘n 1:2-skaal watermodel, gebaseer op Froude-getal gelykheid, sowel as deur numeriese modellering. Beide die numeriese en watermodel is gebruik om die verblyftyd-distribusie in die trog te karakteriseer en om waardes te bereken wat die vloeigedrag in die verdeeltrog beskryf. Drie verskillende verdeeltrog-opstellings is in hierdie studie bestudeer, naamlik: ‘n leë verdeeltrog met geen vloeibeheertoestelle nie, ‘n verdeeltrog met ‘n turbulensie- inhibeerder en ‘n verdeeltrog wat gebruik maak van ‘n turbulensie-inhibeerder met gate, gekombineer met lae damwalle. Vroeë ondersoeke het gefokus op ‘n metode om akkurate numeriese resultate binne aanvaarbare tye te verkry. Die invloed van die aannames van simmetrie en dinamiese gestadigde vloei op die resultate is bepaal om klein te wees teenoor dié van die roostergrootte. Die gebruik van die aannames is dus geregverdig deur die afname in berekeningstyd wat dit meebring. Die roosteronafhanklikheidstudie het getoon dat dit belangrik is om die vloeivergelykings oor klein volume-eenhede op te los in areas van hoë snelheidsgradiënte, beide om realistiese resultate te verseker en om die aantal volume-eenhede te beperk. ‘n Prosedure wat gebruik maak van gradiëntaanpassing is gebruik om die roostergrootte outomaties te verklein in die areas met hoë snelheidsgradiënte vir verskillende verdeeltrog-opstellings. Resultate het ook getoon dat dit belangrik is om die inlaatgrens van die numeriese model by die smeltpot se uitlaat te kies, aangesien noemenswaardige verskille in die verblyftyd-distribusie waargeneem is wanneer ‘n uniforme snelheidsprofiel aanvaar is waar die metaal die verdeeltrog binnegaan. Daar is gevind dat die resultate by die numeriese en watermodelle verskil met ‘n gemiddelde fout van ongeveer 10%. Dit word beskou as ‘n goeie ooreenstemming, as die aannames wat in die numeriese model gebruik word in ag geneem word. Beide die numeriese en watermodelle het getoon dat die metaalvloei in die leë verdeeltrog geneig is om die kortste roete na die uitlate te kies. Deur van ‘n turbulensie inhibeerder gebruik te maak word hierdie probleem opgelos deur die metaalvloei opwaarts te forseer. In die proses neem die minimum-, piek- en gemiddelde verblyftye, sowel as die propvloei volumefraksie, toe, terwyl die dooievloei fraksie afneem. Die turbulensie inhibeerder met die gate en die lae damwalle is egter meer geneig tot erosie van die vuurvaste materiaal en kan ook vloeipatrone veroorsaak wat metaalskuimdruppels in die metaal kan opneem. Verder volg ‘n klein fraksie van die vloei steeds ‘n kortpad na die uitlaat. Hierdie resultate toon dat sekere veranderings aan verdeeltrog vloeibeerheerstelsels nadelige gevolge kan hê wat enige positiewe gevolge uitkanselleer. Verder is die numeriese metode wat tot dusver op die watersisteem gebaseer is, aangepas om die vloei in die hoëtemperatuur staalproses te simuleer. ‘n Baie goeie vergelyking is verkry tussen die resultate wat die twee numeriese modelle voorspel. Hierdie dien as ‘n verdere bewys dat ‘n watermodel, wat op Froude-getal gelykheid gebaseer is, die industriële proses akkuraat kan simuleer. Deur gebruik te maak van die numeriese model van die hoë temperatuur staalproses, is die effek van die turbulensie-inhibeerder se vorm vir vier verskillende ontwerpe bestudeer. Die studie het getoon dat die beste resultate vir vloeikarakteriserende eienskappe en oppervlak- turbulensie verkry is met ‘n reghoekige ontwerp. Die resultate beklemtoon egter die belangrikheid van die invloed van die turbulensie-inhibeerder se vorm op die vloeigedrag in die verdeeltrog, aangesien elke vorm noemenswaardige verskillende vloeipatrone opgelewer het. Daar is opgemerk dat ‘n goeie turbulensie-inhibeerder ‘n optimale hoeveelheid turbulensie onderdrukking veroorsaak. In die geval van te min onderdrukking is die verblyftye te kort en die oppervlak turbulensie te hoog. Te veel onderdrukking kan egter lei tot groot variasie in die eienskappe van die metaal by die verskillende uitlate.

<p>This thesis work aimed to provide a better knowledge of inclusion behavior at the steel-slag interface. All results are based on mathematical modeling of liquid and solid inclusion separation to the slag. The model descriptions of the inclusion transfer are based on the equation of motion at the system. It is assumed that the inclusion transfer is governed by four forces acting on the inclusion as it has reached the steel-slag interface. These are the buoyancy force, the added mass force, the drag force and the rebound force. The models assume two cases of inclusion separation depending on the inclusion Reynolds number. In the case where Reynolds number is larger or equal to unity, Re≥1, a steel film is formed between the inclusion and the slag. This steel film must first be drained before the inclusion can separate to the slag. If Reynolds number, Re<1, then no steel film is formed and the inclusion will be in direct contact with the slag. The mathematical models also propose three types of inclusion behavior as the inclusion crosses the steel-slag interface. The inclusion can either, pass and separate to the slag, oscillate at the interface with the possibility of reentering the steel bath with the steel flow or it can remain at the interface not completely separated to the slag. A parameter study for 20 μm inclusions showed that the most important parameters controlling the inclusion behavior at the steel-slag interface are the slag viscosity and the interfacial tensions between the phases. For 100μm inclusions also the inclusion density affects the inclusion behavior. The models were applied to ladle and tundish conditions. Since the slags in the chosen industrial conditions have not been studied experimentally before, estimations of the important physical property parameters were made. Future measurements will therefore be needed in order to make predictions of inclusion transfer behavior at the steel-slag interface which are more relevant for the industry. The main conclusion is that useful plots can be made in order to illustrate the tendency for the inclusion transfer and how to manipulate the physical property parameters in order to increase the inclusion separation in ladles and tundishes.</p>

This thesis work aimed to provide a better knowledge of inclusion behavior at the steel-slag interface. All results are based on mathematical modeling of liquid and solid inclusion separation to the slag. The model descriptions of the inclusion transfer are based on the equation of motion at the system. It is assumed that the inclusion transfer is governed by four forces acting on the inclusion as it has reached the steel-slag interface. These are the buoyancy force, the added mass force, the drag force and the rebound force. The models assume two cases of inclusion separation depending on the inclusion Reynolds number. In the case where Reynolds number is larger or equal to unity, Re≥1, a steel film is formed between the inclusion and the slag. This steel film must first be drained before the inclusion can separate to the slag. If Reynolds number, Re&lt;1, then no steel film is formed and the inclusion will be in direct contact with the slag. The mathematical models also propose three types of inclusion behavior as the inclusion crosses the steel-slag interface. The inclusion can either, pass and separate to the slag, oscillate at the interface with the possibility of reentering the steel bath with the steel flow or it can remain at the interface not completely separated to the slag. A parameter study for 20 μm inclusions showed that the most important parameters controlling the inclusion behavior at the steel-slag interface are the slag viscosity and the interfacial tensions between the phases. For 100μm inclusions also the inclusion density affects the inclusion behavior. The models were applied to ladle and tundish conditions. Since the slags in the chosen industrial conditions have not been studied experimentally before, estimations of the important physical property parameters were made. Future measurements will therefore be needed in order to make predictions of inclusion transfer behavior at the steel-slag interface which are more relevant for the industry. The main conclusion is that useful plots can be made in order to illustrate the tendency for the inclusion transfer and how to manipulate the physical property parameters in order to increase the inclusion separation in ladles and tundishes. / QC 20101221

In this study, the goal is to optimize the process and to reduce the clogging tendency during the continuous casting process. The focus is on clogging when the refractory base material (RBM) in the SEN is in contact with the liquid steel. It is difficult or impossible to avoid non-metallic inclusions in the liquid steel, but by a selection of a good RBM in the SEN clogging can be reduced.   Different process steps were evaluated during the casting process in order to reduce the clogging tendency. First, the preheating of the SEN was studied. The results showed that the SEN can be decarburized during the preheating process. In addition, decarburization of SEN causes a larger risk for clogging. Two types of plasma coatings were implemented to protect the RBM, to prevent reactions with the RBM, and to reduce the clogging tendency. Calcium titanate (CaTiO3) mixed with yttria stabilized zirconia (YSZ) plasma coatings were tested in laboratory and pilot plant trials, for casting of aluminium-killed low-carbon steels. For casting of cerium alloyed stainless steels, YSZ plasma coatings were tested in laboratory, pilot plant and industrial trials. The results showed that the clogging tendency was reduced when implementing both coating materials.   It is also of importance to produce clean steel in order to reduce clogging. Therefore, the steel cleanliness in the tundish was studied experimentally. The result showed that inclusions originated from the slag, deoxidation products and tundish refractory and that they were present in the tundish as well as in the final steel product. / <p>QC 20170227</p> / VINNOVA

The aim of this thesis work is to increase the knowledge of inclusion behavior at the steel-slag interface by mathematical modeling and in-situ Confocal Scanning Laser Microscope experiments. Mathematical models based on the equation of motion predicting liquid and solid inclusion behavior was first investigated. Four main forces, the buoyancy force, the added mass force, the rebound force and the drag force, act on the inclusion as it crosses the interface. There are three types of behavior an inclusion at the steel-slag interface can adopt. These are a) pass, which means that the inclusion is separated to the slag, b) remain, where the inclusion stays at the interface without being fully transferred to the slag or c) oscillate, and the inclusion rises and descends at the interface until the motion is dampened out by the interfacial forces. The studies showed the importance of accurate experimental physical property data. Application of the models to industrial conditions illustrated that useful plots could be made showing the industry how to optimize their interfacial properties in the ladle and tundish to obtain maximum inclusion separation. In-situ Confocal Scanning Laser Microscope (CSLM) experiments were carried out in order to study agglomeration of liquid and semi liquid inclusions at the steel-gas and steel-slag interfaces and in the slag. Liquid-liquid inclusion agglomeration at steel-gas and steel-slag interfaces was seen to not occur without using force. However, when already transferred to the slag the inclusions agglomerated freely due to a higher free energy force. Comparison of experimental and theoretical agglomeration force showed good agreement between experiments and theory. The main conclusion of this work is that inclusion separation is a complex field of study and there exist no model that takes everything into account. Here the tendency for inclusion transfer and how to manipulate the physical properties for inclusion separation together with agglomeration experiments have been studied. For the future maybe coupling of models for computational fluid dynamics, agglomeration, inclusion separation, dissolution and slag entrainment in addition with experimental physical property data can provide a better overview and understanding. / QC 20100823

The strand similarity and inclusion removal capability are two critical parameters to measure the performance of multi-strand tundish in clean steel production. In this work, the effect of two flow regulators, i.e., Flow Control Devices (FCD) and Electromagnetic Stirring (EMS) on eight-strand tundish performance have been investigated by establishing a water model and conducting numerical simulations of water model. The water model was focused on revealing the effect of stirring while the simulation was employed to investigate the effect of two FCDs, namely baffle wall and turbo-stopper. The analysis of strand similarity and inclusion removal were conducted by analyzing flow characteristics derived from Combined Model of Residence Time Distribution (RTD) curve and observing the flow movement in the tundish model. In addition, the tundish capability to remove inclusions was also studied by injecting inclusion particles using Discrete Phase Model (DPM) in ANSYS Fluent. Experiment results cause the Combined Model needs to be modified. This modification was employed when analyzing tundish configuration involving stirring. By using the modified Combined Model, the stirring can significantly increase the well-mix volume to almost 100% as it annihilates dead zone. The stirring also increases the similarity between strands and makes the RTD curve more similar to ideal mixing curve.  However, the problem of short-circuiting flow need to be solved and care should be taken into consideration regarding the selection of stirring direction as well as bath surface condition when implementing EMS in reality. The simulation results show that the addition of baffle wall and turbo-stopper are beneficial to improve mixing as well as to avoid the short-circuiting flow. Furthermore, compared to individual FCD, the combination of baffle wall and turbo-stopper results in the best performance to remove inclusions by providing surface-directed flow and generating a higher plug flow.