Tundish Configuration Research Articles

Understanding of baffle effect of inserting a filter within a tundish via a water model experiment and numerical simulation

The baffle effect of inserting a filter within a tundish was investigated using a combination of water model experiments and numerical simulations. The filter, which is a cost-effective device used to enhance the quality of molten steel by removing inclusions, was studied for its impact on the removal rate of inclusions. In the water model experiments, a scaled-down model of the tundish system was created with a geometric ratio of 1:4. Polyethylene particles of varying sizes were used to simulate the inclusions. Additionally, a three-dimensional numerical model of the water model was developed to validate the experimental findings, provide supplementary data for analysis, and propose an optimized tundish configuration by moving the weir away from the filter by 50, 100, and 150 mm. The flow patterns were also thoroughly examined. The results revealed that the presence of the filter increased the flow resistance within the tundish, leading to changes in the residence time distribution. This resulted in the formation of a ‘dead zone’ with a significantly prolonged residence time. The higher flow resistance hindered the entry and exit of particles from the last chamber of the tundish. As a result, the distribution of particles in the last chamber became more dispersed, reducing the detrimental effects of inclusions in the steel. The removal efficiency of the seven types of particles was improved by 2–7%. Furthermore, by moving the weir away from the filter by 50 mm, the removal ratio could be further increased by approximately 2%.

Comparison of Fluid Flow and Temperature Distribution in a Single-Strand Tundish with Different Flow Control Devices

The effects of flow control devices (FCD) in a single-strand tundish, including weir, dam, turbulence inhibitor and gas curtain, have been investigated using water model experiments and CFD simulations. A scaled-down water model was built up to visualize flow pattern and measure the residence-time distribution (RTD) of different tundish configurations. A CFD model was applied to calculate the fluid flow, heat transfer and RTD curves in the prototype tundish under the nonisothermal conditions. The Eulerian–Lagrangian approach was applied to investigate the bubble flow in the system. The results show that each FCD has its own unique function to control the flow. It is important to evaluate the combined effects of FCD based on their installations. The molten steel flow in the tundish could be improved if these flow control devices were arranged properly.

Fluid Flow Characterization of Single-Strand Tundish with Flow Modifiers through Physical Water Model (PWM) and CFD Simulation

The flow behavior in the continuous casting tundish dominates the quality and cleanliness of steel production. In this research, the single strand tundish's fluid flow behavior with different flow modifiers is investigated through numerical and experimental simulation. The numerical; simulation is performed in ANSYS FLUENT 19.2 (commercial package) and experimental through physical water model technique. The flow behaviors of bare tundish and tundish with three different flow modifiers are investigated. The three different flow modifiers deployed are the dam, baffle, and turbulence inhibiter (TI). Fluid flow performance is examined through residence time distribution (RTD) curves, which are derived from the measurement of the tracer concentration at the outlet. Good agreement between the CFD simulation and physical water model experiments is discovered. The results show there is an improvement in residence time and fluid flow (also improved inclusion removal) after the deployment of flow modifiers. There is a 20% improvement in peak and minimum residence time of RTD curves due to flow modifiers application. It is also discovered that the tundish configuration in this research, the tundish with turbulence inhibiter, provides optimal flow characteristics and eventually intended to promote a better level of inclusion removal.

Mathematical Modelling of Multiphase Flow and Inclusion Behavior in a Single-Strand Tundish

A mathematical model was developed to study the effects of the flow control devices and the gas curtain on the steel cleanness in a single-strand tundish. The Eulerian–Lagrangian approach was applied to investigate the bubble flow and the behavior of the non-metallic inclusions in the system. Two modelling approaches were considered: (i) one-way coupling, where the influence of the micro-inclusion on the molten steel flow is neglected; and (ii) two-way coupling, where the momentum exchange between the molten steel and the bubbles is modelled. The model verification and validation (V&V) were carried out in order to establish confidence in the model predictions. Four different tundish configurations and the effect of various parameters, such as the inclusion size, the inclusion density and the gas flow rate, were investigated at the normal casting conditions. The results show that the flow control devices and the gas curtain reduce the extent of the dead volumes in the tundish and thus enhance the removal efficiency of the inclusions. Controlling the gas stirring intensity is important for tundish operation with the aim of removing the inclusions. Theoretical analysis suggests that small bubbles are preferable to increase the inclusion removal rate in industrial operations.

Numerical Simulation of Metal Melt Flow in a One-Strand Tundish Regarding Active Filtration and Reactive Cleaning

In the paper, two different cleaning strategies for nonmetallic inclusions in steel melts, active filtration and reactive cleaning, are examined in a prototype tundish configuration. In active filtration, nonmetallic inclusions are deposited at the filter surfaces. In reactive cleaning, nonmetallic inclusions stick to the filter surfaces, too. In addition, they are floated by the action of carbon monoxide bubbles, which are generated by reaction between carbon and oxygen in the steel melt. In order to compare the performance of both strategies, numerical simulations of the two-phase flows of steel melt and dispersed nonmetallic inclusions are performed. Turbulence is resolved with implicit large eddy simulation. If necessary, species transports of dissolved carbon in the melt and reaction with oxygen are employed. Cleaning efficiencies are deduced from the simulations which demonstrate that reactive cleaning is much more efficient than active filtration.

Optimization of flow control devices in a ten-strand billet caster tundish

The physical model of a ten-strand billet caster tundish was established to study the effects of various flow control devices on the melt flow. Before and after the optimization of the melt flow, the inclusion removal in the tundish was evaluated by plant trials. The physical modeling results show that when combined with a baffle, the turbulence inhibitor, instead of the impact pad, can significantly improve the melt flow. A turbulence inhibitor with a longer length of inner cavity and without an extending lip at the top of the sidewall seems to be efficient in the improvement of the melt flow. Various types and designs of baffles all influence the flow characteristics significantly. The “V” type baffles are better than the straight baffles for flow control. The “V” type baffle with four inclined holes at the sidewall away from the stopper rods is better in melt flow control than the one with one inclined hole at each sidewall. The combination of a well-designed turbulence inhibitor and an appropriate baffle shows high efficiency on improving the melt flow and an optimal proposal was presented. Plant trials indicate that, compared with the original tundish configuration in prototype, the inclusions reduce by 42% and the inclusion distribution of individual strands is more similar with the optimal one. The optimal tundish configuration effectively improves the melt flow in the ten-strand billet caster tundish.

Optimization of flow control devices for a T-type five-strand billet caster tundish: water modeling and numerical simulation

The optimization of flow control devices (FCDs) for a T-type five-strand billet caster tundish was carried out by water modeling and numerical simulation. In water modeling experiments, flow characteristics of the bare tundish and tundish configurations with designed U-type baffles and a round turbulence inhibitor were analyzed using residence time distribution (RTD) curves. Mathematical models for liquid steel in the real plant tundish were established using the fluid dynamics software package Fluent. The flow field, the temperature field, and the RTD curves of liquid steel in the proposed tundish configurations were obtained. The results of numerical simulation and water modeling were validated with each other by the predicted and experimental RTD curves. The results of flow field and temperature field were used to reflect the actual state of a real plant tundish and to choose the optimal FCD. Finally, from the whole performance of the multi-strand tundish, the optimal scheme was determined by combining the results of water modeling and numerical simulation. With the optimal tundish equipped with U-type baffle with deflector holes and round turbulence inhibitor, not only was the flow characteristic of each strand improved, but also the difference of flow characteristics between multiple strands was smaller.

Numerical study of effects of pour box design on tundish flow characteristics

In the paper, the effects of special pour box design on tundish flow characteristics are investigated with the help of computational fluid dynamics. The numerical model is based on an Eulerian–Lagrangian approach for melt flow and non-metallic inclusion behaviour, respectively. For a prototypical twin strand tundish configuration, basic features of the mean tundish flow, residence time distributions and parameters of the melt history are discussed. It is shown that the pour box design is not only of importance for the tundish flow field but also of significance for processes of secondary metallurgy.

Molten Steel Flow in a Slab Continuous-casting Tundish

Fields of fluid flow and temperature, and residence time distribution (RTD) curves were investigated by mathematical simulation in a one-strand tundish for continuous casting. It was known from the investigation that a big “spring uprush” formed on surface around the long shroud when molten steel flowed into a turbulence inhibitor (TI) with extending lips and rushed up reversely out of the TI, while four small “spring uprushes” existed on surface when a TI without extending lips because the liquid steel flowed mainly out of the 4 corners of the TI. The flow of liquid steel in the former tundish configuration was not reasonable and the height of an area where temperature was less than 1819 K was about half of liquid surface height on the right side of the stopper, which meant that big dead zone existed in the former tundish configuration. In the optimal one, the height of such area was only seventh of the liquid surface height. The RTD curves obtained from the mathematical simulation basically agreed with those from the physical modeling and the flow characteristics obtained from these two methods agreed with each other.

Experimental and Numerical Investigations on Non-metallic Inclusions Distribution in Billets Casted at a Multi-strand Continuous Casting Tundish

Modern tundishes plays an important role of refining treatments to improve the quality and purity of casted steel. Purity of steel is defined by the non-metallic inclusions in the steel product, including their size, quantity, distribution, chemical composition and mineralogy. The aim of presented studies was to investigate the number and distribution of non-metallic inclusion in individual billets casted in a six-strand tundish. The industrial measurements, performed during stable production conditions at the continuous steel casting (CSC) plant, were performed for different tundish working space configurations. Analysis of the size and number of non-metallic inclusions has been done on the metallographic samples using light microscope. Experimental studies were supported with numerical simulations using large eddy simulations (LES) method. A modified boundary condition describing inclusion separation at the liquid steel surface was implemented in commercial code AnsysFluent. Experimental results concern size distribution of inclusions in billets for current tundish configuration showed big differences between casted ingots. Numerical results shown the domination in the number of inclusions occurring in the nozzles number 3 and 4 (for basic tundish configuration) and in the nozzles number 2 and 5 (for tundish with turbulence inhibitor). The reason for that is the change in configuration tundish working space, that has an impact on the flow field inside the tundish. Experimental measurements performed for proposed modified tundish configuration (with turbulence inhibitor) shown that those differences are much smaller, which in consequence has an influence in higher quality of continuously casted ingots for individual strand of CSC.

Optimization of a Six-Strand Continuous Casting Tundish: Industrial Measurements and Numerical Investigation of the Tundish Modifications

Abstract The main differences in the transient zone extent between the individual strands for the former industrial six-strand tundish configuration is the basis for undertaking this study. The aim this study was to improve the casting conditions by proposing the optimal equipment of the tundish working space. For economic reasons, only the variants with different baffles configurations were considered. It was also dictated by the simplicity of construction and the possibility of its implementation by the base operating steel mill. In the current study, industrial plant measurements and mathematical modeling were used. Industrial experimental data were used to diagnose the current state of the industrial tundish and then validate the numerical simulations. After this, the influence of different baffle configurations installed in the tundish on the steel flow characteristic was modeled mathematically. Residence time distribution (RTD) curves are plotted, and individual flow shares for the investigated tundish were estimated based on the curves. Finally, the industrial plant was rebuilt according to the numerical results and additional plant measurements were performed. A result of the appearance of the baffles in the tundish working space was the reduction of the transient zone extent. The results indicate the increasing share of the dispersed plug flow and a decreasing share of the dead volume flow, with a practically unchanging share of well-mixed volume flow in the modified tundish.

Optimization of flow control devices in a single-strand slab continuous casting tundish

The optimization of flow control devices in a single-slab continuous casting tundish was carried out by physical modeling, and the optimized scheme was presented. With the optimal tundish configuration, the minimum residence time of liquid steel was increased by 1.4 times, the peak concentration time was increased by 97%, and the dead volume fraction was decreased by 72%. A mathematical model for molten steel in the tundish was established by using the fluid dynamics package Fluent. The velocity field, concentration field, and the residence time distribution (RTD) curves of molten steel flow before and after optimization were obtained. Experimental results showed that the reasonable configuration with flow control devices can improve the fluid flow characteristics in the tundish. The results of industrial application show that the nonmetallic inclusion area ratio in casting slabs is decreased by 32% with the optimal tundish configuration.

Numerical Investigation of the Fluid Flow in Continuous Casting Tundish Using Analysis of RTD Curves

A detailed mathematical procedure of the optimization of the fluid flow in a tundish water model with and without flow control devices (weir and dam) was carried out using the commercial CFD code FLUENT 6. 0. The (k-ɛ) two-equation model was used to model turbulence. The residence time distribution (RTD) curves were used to analyze the behavior of the flow in tundish. The location of flow control devices in the tundish was studied. The results show that the flow modifiers play an important role in promoting the floatation of nonmetallic inclusions in steel. Comparing the three geometric configurations that are considered (bare tundish, weir, weir + dam), the tundish equipped with the arrangement (weir+dam) is a best and optimal geometric configuration of tundish.

Modeling of Fluid Flow and Residence Time Distribution in a Four-strand Tundish for Enhancing Inclusion Removal

The introduction of the appropriate size and precise location of flow control devices such as dam, turbulence inhibitor, etc., helps to modify the flow pattern and minimizing short circuiting and dead zone. Beside this, these also create the surface directed flow and maximize the residence time available for the flotation of inclusions and assimilation of the reaction products from the molten steel into the slag phase. These can be products of deoxidation, reoxidation, precipitation, emulsification and/or entrainment of refractory components into the melt and thus encompass both indigenous and exogenous inclusions. To this end, both the numerical and physical simulations were carried out mainly for three cases: a) in absence of flow control devices (i.e., bare tundish), b) in the presence of a dam, and c) with the application of turbulence inhibiting device (TID) and dam combination in the existing tundish configuration. The commercial CFD (computational fluid dynamics) package FLUENT® was used to predict the flow field prevalent in the water model tundish at steady state, whereas in the experimental program, both Particle Image Velocimetry (PIV) techniques for flow measurements and tracer dispersion experiments for concentration measurements were applied in the present study. Among all types of configurations applied in the present study, a combination of TID with holes+a dam work reasonably found to be an optimum configuration of the four-strand tundish regarding inclusion floatation. A superior strand similarity is also achieved in this configuration. Also the predicted time averaged horizontal and vertical components agreed within ±10% with the experimentally derived ones.

Fluid Flow in A Four-strand Bloom Continuous Casting Tundish with Different Flow Modifiers

Fluid flows in a four-strand tundish for bloom continuous casting have been investigated with physical modeling and mathematical simulation methods. The liquid steel flow velocity fields in the former tundish and the optimal one with a turbulence inhibitor and newly-designed baffles were numerically calculated and the flow characteristics in the two cases and other tundish configurations were measured in the physical modeling. The results in the physical modeling experiments showed that large difference in the Residence Time Distribution (RTD) curves of two outlets in one side of the former configuration tundish existed. It was found from the numerical calculation of the velocity fields in the tundishes that with the former tundish configuration velocities and turbulent degree of the liquid steel flow in the impact zone of the tundish were large due to the high velocities of liquid steel from the long shroud of the ladle, which caused in lining corrosion and slag entrapment due to the surface eddies. Asymmetric velocity field in the tundish with the former baffles formed and short circuit flow existed in one side of the four-strand tundish. For the optimal configuration of the tundish with a turbulence inhibitor and newly-designed baffles, very similar RTD curves of the two outlets in the same side of the tundish were achieved. The velocities and turbulent degree in the impacting zone of the tundish were depressed and quiet and symmetric molten steel flow was obtained. Eddies on surface and short circuit flow in the optimal tundish disappeared. Such improvement of liquid steel flow in the tundish would increase the ability of inclusion removal. Turbulence inhibitors should be used with other well-designed flow control devices for effective improvement to fluid flow characteristics in tundishes.

Numerical simulation of flow phenomena and optimum operation of tundish

To enhance the quality of grade 20 carbon-steel on the continuous casting production line, the mechanism of forming blowholes and non-metallic inclusions in billets and numerical simulation of flow phenomena about liquid steel in tundish were studied. The results show that the configuration and operation of tundish play an important part in quality assurance of grade 20 carbon-steel products. By optimizing the configuration of the tundish, the depth of liquid bath in tundish is enhanced, the impact of liquid steel is decreased, and the residence time of liquid steel is lengthened, which is useful for eliminating inclusions and blowholes and improving the service life of tundish. Improving the pouring and tapping operation of liquid steel can avoid the contact of liquid steel with air, and decrease re-oxidation. Strict control of the superheat degree of casting liquid steel can decrease the non-metallic inclusion content of the re-oxidation in billets and reduce the erosion of tundish. The inclusions and blowholes in the continuous casting grade 20 steel billets are reduced to a great extent and qualification rate is enhanced from 60% to 80%.

Modelling of flow behaviour in continuous casting tundish

One of the steel plants of Steel Authority of India Ltd (SAIL) is considering a proposal to increase the capacity of tundish from the present level of 17 tonne to a targeted level of 25 tonne. As a step towards designing a larger tundish, the flow profile of steel in various alternate tundish configurations considered have been characterized using a 3‐D steady‐state mathematical simulation under assumption of both isothermal and non‐isothermal conditions. Apart from generation of flow profiles of steel inside the tundish, the Residence Time Distribution curves have been predicted for analysis of flow behaviour inside the tundish. Based on the above analysis, the optimum tundish configuration was chosen for further development.

Mathematical modelling of flows and discrete phase behaviour in a V-shaped tundish

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Mathematical Modeling of Iron and Steel Making Processes. Design Optimization of a Single-strand Continuous Caster Tundish Using Residence Time Distribution Data.

This paper contains the results of a design optimization study performed on the steady-casting operation of the Columbus Stainless single-strand stainless steel caster tundish. Residence Time Distribution (RTD) data such as minimum residence time (or plug flow volume fraction) and dead volume are used as objective functions in the mathematical optimization process. Water is used in the first two case studies as modeling fluid to allow for comparison with water model results. Liquid steel is used in the last case study to investigate the effect of temperature and buoyancy on the resulting flow patterns and the optimum design. Two separate tundish configurations are considered. The first has one dam and one weir, while the second comprises a baffle with angled holes and an impact pad. Significant improvements of up to 34% in minimum residence time are obtained for the second configuration.

A numerical simulation for mini-mill Tundish design —effects of FC pad on tundish flow characteristics

A numerical analysis of fluid flow in a mini-mill continuous casting tundish has been carried out. The major concern has been focussed on validating the possibility of the use of an FC (Flow Control) pad under the ladle shroud in the tundish. For this purpose, steady state modeling to find flow patterns and non-steady state approaches calculating residence time distribution (RTD) curves for different tundish configurations have been chosen in the present study. Both calculated flow fields and predictions of tracer dispersion have been compared with the results of water model experiments.