Physical Water Model Research Articles

Continuous Casting Slab Mold: Key Role of Nozzle Immersion Depth.

Based on a physical water model with a scaling factor of 0.5 and a coupled flow-heat transfer-solidification numerical model, this study investigates the influence of the submerged entry nozzle (SEN) depth on the mold surface behavior, slag entrapment, internal flow field, temperature distribution, and initial solidification behavior in slab casting. The results indicate that when the SEN depth is too shallow (80 mm), the slag layer on the narrow face is thin, leading to slag entrapment. Within a certain range of SEN depths (less than 170 mm), increasing the SEN depth reduces the impact on the mold walls, shortening the "plateau period" of stagnated growth on the narrow face shell. This allows the upper recirculation flow to develop more fully, resulting in an increase in the surface flow velocity and an expansion in the high-temperature region near the meniscus, which promotes uniform slag melting but also heightens the risk of slag entrainment due to shear stress at the liquid surface (with 110 mm being the most stable condition). As the SEN depth continues to increase, the surface flow velocity gradually decreases, and the maximum fluctuation in the liquid surface diminishes, while the full development of the upper recirculation zone leads to a higher and more uniform meniscus temperature. This suggests that in practical production, it is advisable to avoid this critical SEN depth. Instead, the immersion depth should be controlled at a slightly shallower position (around 110 mm) or a deeper position (around 190 mm).

Thermodynamic and Kinetic Behavior Study of Gas Bubbles in High‐Temperature Steel Melts

This study provides an exhaustive exploration of the thermal expansion of low‐temperature argon bubbles in high‐temperature molten steel and the resulting dynamic effects. The energy equation of compressible fluid simultaneously with the volume of fluid model under the Euler framework is solved. The generation and rising behavior of bubbles are validated through rigorous physical water model experiments. Findings reveal that, within a heating time of 0.2–0.45 ms, gas bubbles already complete 65–90% of their internal energy increase. The total heat transfer time and heat transfer coefficient of bubbles exhibit distinctive patterns influenced by the initial diameter and temperature of the bubbles. Specifically, under the conditions studied, bubbles exhibit a total heat transfer time of ≈20–60 ms, accompanied by a heat transfer coefficient ranging from 500 to 2600 W (m2 * K)−1. During the thermal expansion process, gas bubbles experience energy transfer and conversion within the two‐phase flow. This article establishes a dynamic model describing bubble thermal expansion in steel melts based on underwater bubble dynamics’ first principles. The model provides a quantitative depiction of instantaneous changes in bubble size, velocity, and kinetic energy under specific conditions.

Continuous casting tundish quality study by mathematical & physical simulations, economics with plant result justifications

A combination of physical modeling, computational fluid dynamics modeling, and economics with plant trial studies was performed for quality improvement of Special Bar Quality (SBQ) and Oil Country Tubular Goods (OCTG) grade tundish steels. The present study consists of operating parameters like inert gas shrouding, non-isothermal conditions, and flow control devices (FCD) used on the billet product and slab quality. This work uses mathematical modeling using the fluid volume and discrete phase method (DPM) and the standard k-ε turbulence model validated with one-third scale physical water model experiments. A strong correlation between the physical model and computational simulation was found with rejection ratio and inclusion counts. Data about customer demands correlated with operating parameters for proper plant insights with an economic study to predict the cost-related issue. With the incorporation of FCD, the weight of the tundish skull was reduced by 6–10 M USD/year with a simulation studies expenditure of around 200 K. FCD also reduced the customer complaint index (CCI).

Experimental and Simulation Analysis of Physical Water Model through Tracer Injection under Various Baffles and Turbulence Inhibitor Conditions for Developing the Fluid Flow Parameters and Inclusion Removal Rates in Tundish

Tundish is a critical part involved in the continuous casting process, which ensures the constant flow of liquid metal and with performing different functions. In odd-numbered multistrand tundish, the confirmation consistency of the fluid flow among all the strands is one of major concerns. In this study, five-strand tundish with a set of weirs and a baffle is utilized for investigation concerning fluid flow parameters and inclusion removal analysis. The simulation is carried out in ANSYS FLUENT 19.2 software through the defined numerical model, and the experimental analysis is performed on a scaled physical water model through tracer injection. Four different baffles are designed along with two different types of turbulence inhibiter for the tundish to enhance the fluid flow parameters and inclusion removal rates. The inclusion sizes were varied from 10 to 100 µm with a difference of 20 µm respectively for studying the inclusion removal rate concerning inclusion sizes. From the outcomes obtained like the residence time distribution (RTD) curves and others, it was concluded that the fourth baffle version with the first turbulence inhibiter, which are equipped in tundish version TV8 is the most beneficial tundish version for the enhancement in fluid flow and inclusion removal rates as compared to other tundish versions in this study.

Water Modeling on Circulating Flow and Mixing Time in a Ruhrstahl–Heraeus Vacuum Degasser

A physical water model based on the similarity principle is established to investigate the fluid flow and mixing phenomena during the Ruhrstahl–Heraeus (RH) steel refining process. The velocity distribution and the turbulent features on the center section are obtained using particle image velocimetry (PIV) measurement. Two vortexes between the down‐leg snorkel and the ladle sidewall are observed. The effects of the number of gas‐injection nozzles and the liquid levels in the vacuum chamber on the fluid phenomena are performed. More injected nozzles and a higher liquid level in the vacuum chamber generate larger velocity in the ladle. Twenty monitors in the ladle are used to monitor the variation of the conductivity to obtain the mixing time, indicating that the mixing time varies much with locations. The distribution of the mixing time on the vertical center section of the ladle is obtained. Moreover, the relationship between the circulation rate and the mixing time is obtained, indicating that the mixing time decreases with increasing circulation rate, and the slope of their relationship is −0.35.

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.

Numerical study of influence of casting speed on fluid flow characteristics in the four strand tundish

Steel maker companies attempt to achieve high production quality and decrease production costs due to high competition of the global steel industry. Steel cleanliness plays a significant role in the steel quality which is the key success factor for the steelmaker. In order to optimize the steel cleanliness in the continuous casting process, flow characteristics were studied to enhance the inclusion removal efficiency in four strand tundish. The purpose of this research is to study the effect of casting speed on the flow characteristics of molten steel inside a four-strand tundish. The investigation was carried out by using the commercial computational fluid dynamic (CFD) software ANSYS 18.2. A 1:3 water model tundish based on process parameters from Millcon Steel PLC were employed in this study. The simulation results were validated with the physical water model. The residence time distribution (RTD) curves were applied to analyze the flow characteristics of the tundish. The results of this study show the different casting speeds have an effect on the flow characteristics inside the tundish. The start point of RTD curve of the flow in the tundish with casting speed of 3.0 m/min is the shortest amongst all casting speeds used (1.7, 2.0, 2.3 and 3.0 m/min). A short time period of the start point of RTD curve increases the chance of inclusion contamination in the casting mould and leads to low quality products. Furthermore, the outlet positions affect the minimum residence time of RTD curves and the tracer concentration directly. The RTD start point of the middle outlet located close to the inlet position is faster than that of the far outlet located far from the inlet. The results obtained from the study contributes to the optimization of productivity and quality of the example plant.

Physical water model and CFD studies of fluid flow in a single strand tundish

Flow characteristics in a continuous casting tundish is one of the key parameters producing a high quality clean steel. In this study, the fluid flow analyses of a single-strand tundish model were carried out using the commercial CFD software ANSYS FLUENT 14.0 and experimentally verified by physical water model. The realizable k-ɛ equation was utilized to model turbulent phenomenon. The behavior and performance of the flow in tundish with and without flow modifiers were investigated by the residence time distribution (RTD) curves which were obtained from the tracer concentration measurement at the outlet. The results from CFD are in agreement with the experiment results. The results show that the flow modifier plays an important role in increasing residence time and enhancing flow performance which could feasibly promote the inclusion removal potentials in the tundish process. The peak and the minimum residence time of RTD curves of the tundish model with flow modifiers were improved for more than 20%. With the comparison of the four flow modifier configurations (bare tundish, dam, baffle and turbostop) in the current tundish model, it could be concluded that the turbostop could provide the optimal flow characteristic in which could improve the level of inclusion removable.

A vertical continuous casting machine for large blooms

ABSTRACTThe Zhong Yuan Special Steel Company installed a vertical continuous casting machine to achieve higher productivity and product yield while retaining world-leading product quality. The vertical continuous casting machine was commissioned by Voestalpine Stahl in 2015. Zhong Yuan Special Steel required a special design for quality and size, comprising a special tundish, mould, secondary cooling system, and vertical roll layout. Other advanced technology packages included stopper rod controls, hydraulic oscillator, online solidification model, and online breakout prevention system. The new machine not only improved casting billet quality, but also improved production efficiency and reduced costs compared with tradition ingot casting. The tundish and electromagnetic mixing were optimised by extensive computational fluid dynamics simulations. The tundish design was optimised by physical water model experiments.

Numerical And Physical Simulation Of Liquid Steel Behaviour In One Strand Tundish With Subflux Turbulence Controller

AbstractThis paper presents the results of computer simulations (Ansys-Fluent) and laboratory experiments (physical water model) carried out to describe the motion of steel flow in the tundish. The facility under investigation is a single-nozzle slab tundish. The internal geometry of consider object was changed by flow control device i.e. subflux turbulence controller (STC). In order to obtain a complete hydrodynamic picture in the tundish furniture variants tested, the computer simulations were performed for both isothermal and non-isothermal conditions. From the performed computer simulations and laboratory experiments (physical modeling) it can be found that, the non-isothermal conditions occurring during continuous steel casting will definitely influence the hydrodynamic pattern forming in the tundishes with STC.

Numerical, Physical, and Industrial Studies of Liquid Steel Chemical Homogenization in One Strand Tundish with Subflux Turbulence Controller

Chemical homogenization of liquid steel is one of the basic parameters defining quality of final products. The 95% chemical homogenization level is a required minimum that defines the effective dissolution of all the components introduced to the liquid steel. The object of investigation was a one‐strand wedge‐type tundish designed for casting slabs. For the set zone of alloy feeding, numerical simulations, laboratory experiments (with a isothermal physical water model) and industrial experiments were carried out. During the research project, a method for the hybrid introduction of an alloy addition to liquid steel has been developed, which combines the pulse and the step methods. From the performed computational fluid dynamics (CFD) computations, laboratory and industrial trials, fields of liquid steel flow, maps of water motion, behavior of non‐metallic inclusions during industrial alloying process, mixing curves and time mixing characterize influence of using subflux turbulence controller (STC) on alloying process in the tundish have been obtained. In the tundishes with STC and a low dam, a reduction in mixing time was noted.

The Influence of the Shape of Turbulence Inhibitors on the Hydrodynamic Conditions Occuring in a Tundish

Abstract The article presents results of the research that was carried out taking into account the influence of the (impact pads) turbulence inhibitor geometry and its equipment of the working space on the hydrodynamic conditions occurring in T-type tundish. Four different turbulence inhibitors were discussed. They differ in shape and configuration of external walls. The research was conducted basing on the numerical simulations as well as on tests performed on physical water model. As a result of calculations the velocity field distribution, turbulence field and marker concentration distribution in the liquid steel for the tested geometrical variants of turbulence inhibitors were obtained. Worked out RTD curves (Residence Time Distribution) allowed to determine the kinetics of steel mixing (the range of transient zone was estimated), and the percentage participation of the particular flow zones. The test carried out on the water model concerned one of the tested turbulence inhibitors. Research was done to verify the parameter settings of the numerical model applied in calculations. Obtained results gave valuable information about the work of the object after applying different turbulence inhibitors.

Numerical model for the minimization of intermixed round bars in a four line continuous caster

The grade transition process in a four line round billets continuous caster was analyzed. A numerical model was developed to determine, quickly and accurately, the length and location of intermixed steel in the bar. The model is based on “tank in series” or “volumes” mathematical models and was calibrated with physical water model measurements and full three-dimensional (3-D) turbulent numerical calculations. Comparison of the model with measurements performed on intermixed steel bars is also presented. The good agreement between these plant measurements and the numerical results validated the model. The model was implemented on PCs with a visual interface that allowed the easy input and output of data, and the program is operated in a steel shop. Finally, the code was employed to evaluate different strategies to fill the tundish during grade transitions. The “double dilution” process, which consists of filling the tundish in two steps, proved to be useful to reduce the amount of downgraded steel.

Turbulent flow through bifurcated nozzles

AbstractA finite‐element model has been used to study steady‐state turbulent flow through bifurcated submerged‐entry nozzles with oversized ports typical of those used in the continuous casting of steel. Both 2D and 3D simulations have been performed with the commercial code FIDAP, using the standard K–ϵ turbulence model. Predicted velocities from 3D simulations compare reasonably with experimental measurements using a hot‐wire anemometer conducted in a physical water model, where severe turbulent fluctuations are present. Results show that a 2D simulation can also capture the main flow characteristics of the jet existing the nozzle and requires two orders of magnitude less computer time than the 3D simulation. A model combining the nozzle and mould was set up to study the effect of the outlet boundary conditions of the nozzle on the jet characteristics. This modelling technique will assist in the design of submerged‐entry nozzles, especially as applied to enhance steel quality in the continuous casting process. Further, the model will provide appropriate inlet boundary conditions for a separate numerical model of the mould.