Molten Steel Flow Research Articles

Mathematical Modeling on Optimization of Submerged Entry Nozzle for an Ultra-Thick Slab Continuous Casting Mold

To optimize the submerged entry nozzle (SEN) for an ultra-thick slab mold, a mathematical model has been established. The molten steel flow and solidification, inclusion transports, and meniscus fluctuation have been investigated through the model. Compared with the concave-bottom SEN cases, the convex-bottom SEN decreases the imping depth of the jet flow and increases the horizontal velocity and temperature on the meniscus. However, the remelting of the solidified shell is dramatic for the convex-bottom case. The well depth of the concave-bottom SEN and the SEN’s submerged depth have little influence on molten steel flow and solidification. The effects of SEN port shape and port angle on the molten steel flow are significant. As the port shape changes from rectangle to square or the port downward angle decreases, the imping depth of jet flow decreases, the horizontal velocity and the temperature on the mold free surface increase. For the ultra-thick mold, a square-shaped-port SEN with a −10° downward angle is more beneficial by comprehensive consideration of molten steel flow and solidification, inclusion removal, and mold powder melting. The optimized SEN has been applied to the actual caster and its performance has been assessed, indicating that the SEN optimization is efficient.

Effect of EMBr on Flow in Slab Continuous Casting Mold and Industrial Experiment of Nail Dipping Measurement

In this study, a funnel mold (FM) model of a multi-mode electromagnetic braking (EMBr) device was developed, and the magnetic flux density at different currents was obtained by MAXWELL software. By using the magnetohydrodynamics (MHD) module of FLUENT software, the volume of fluid binomial flow turbulence model and the EMBr mathematical model of the steel/slag flow field were coupled, and the characteristics of the molten steel flow and the liquid-level fluctuation in the 1520 mm × 90 mm FM with the casting speed of 6 m/min were calculated under the effect of the electromagnetic field. The FM liquid-level characteristic information under production conditions was obtained in a nail board industrial experiment and compared with the magnetic-fluid coupling model. The results show that the EMBr can significantly change the flow behavior of molten steel. When the magnetic pole current is not less than 800-600 A, the maximum liquid-level fluctuation height decreases from 18 mm without EMBr to less than 5 mm, and the liquid-level cannot easily entrap slag. Considering the EMBr effect and production cost, the reasonable magnetic pole current should be 800-600 A. The reliability of numerical simulation was also verified by the industrial test results of the nail board.

Modeling study of EMBr effects on molten steel flow, heat transfer and solidification in a continuous casting mold

During continuous casting process, the internal molten steel flow pattern of the mold is one of the important factors affecting the quality of slab products. The application of electromagnetic braking (EMBr) technology in the slab caster provides an effective solution to improve the molten steel flow pattern in the mold. In the current research, one of the commonly used EMBr technology is studied, namely the Ruler-EMBr technology. In detail, the effect of magnetic flux density on the behavior of the molten steel jet flow, heat transfer, and solidification in a 1450 mm × 230 mm slab mold is numerically simulated through a Reynolds-averaged Navier-Stokes (RANS) turbulence model together with an enthalpy-porosity approach. The simulation results indicate that the electromagnetic force generated by the Ruler-EMBr can significantly suppress the diffusion of the impinging jet to the narrow face of the mold with the increase of magnetic flux density. By that, the impact of the upward backflow on the meniscus region in the mold is suppressed. Correspondingly, the uniformity of the temperature distribution in the mold is effectively improved. The parametric studies suggest that the optimized magnetic flux density is 0.3 T to ensure the improvement of steel quality with a casting speed of 1.6 m/min. By applying the magnetic flux density of 0.3 T, the Ruler-EMBr has a better capability to reduce the maximum amplitude of the surface velocity by 24.5% and increase the average surface temperature of the molten steel by 0.25% when compared to the case of No-EMBr. With this electromagnetic parameter, the Ruler-EMBr technology can well prevent the mold flux entrapment and promote solidified shell uniform growth along the casting direction.

Influences of the Braking Effect of Ruler EMBr on Molten Steel Flow and Steel–Slag Interface Fluctuation in a Continuous Casting Mold

Electromagnetic braking (EMBr) technology, as one of the most effective technologies in the continuous casting process, provides an effective tool for improving the internal and external defects of steel products. Specifically, the EMBr technology takes the benefit of the generation of Lorentz force to decrease flow instability, mold powder entrapment, and surface defects, if applied properly. For this purpose, to gain a clear understanding of the effect of EMBr technology on the continuous casting process, a commonly used EMBr technology, namely ruler EMBr technology, is applied in the current work to investigate the dynamic behaviors of molten steel flow and steel–slag interface fluctuation inside a slab mold. Furthermore, to obtain a desirable braking effect of the ruler EMBr technology, operational parameters including the magnetic flux density, submerged entry nozzle (SEN) depth, and magnetic pole location are numerically investigated. The results demonstrate that the braking effect exerted by the ruler EMBr device is favorable for suppressing the impact of upward stream on the steel–slag interface with the magnetic flux density exceeding 0.3 T. For the influence of the SEN depth and magnetic pole location on the effect of ruler EMBr mold, the results show that a steady jet flow pattern can be obtained through the adjustment of a location between the ruler EMBr device and the SEN depth. For instance, when the ruler EMBr device installation position of 225 mm corresponds to the SEN depth of 150 mm, the upward deflection of jet stream is suppressed and a stable interface fluctuation profile is formed. With this adjustment, the possibility of mold flux entrapment is decreased.

Numerical Investigation for Effects of Polydisperse Argon Bubbles on Molten Steel Flow and Liquid Slag Entrapment in a Slab Continuous Casting Mold

Numerical Investigation for Effects of Polydisperse Argon Bubbles on Molten Steel Flow and Liquid Slag Entrapment in a Slab Continuous Casting Mold

Optimization of the Liquid Steel Flow Behavior in the Tundish through Water Model Experiment, Numerical Simulation and Industrial Trial

A reasonable tundish flow behavior could improve liquid steel cleanliness by promoting floating and removal of the inclusions. The flow behaviors of the tundish could be obtained by water model experiments and numerical simulations, respectively. However, the difference in density between the tracer and water in the experiment can contribute to notable errors. A new type of tracer, which is a mixture of potassium chloride (KCl) and ethanol, was proposed in this study to reduce the errors. The numerical simulation model was validated by the experimental data and its error was below 2%. By comparing the flow behaviors in seven tundishes with different inner structures obtained by simulation, it is found that the C1 can significantly reduce the dead volume ratio and C4 can improve the uniformity of liquid steel charged though each outlet. The structural strength of the baffle in C1 scheme was not considered, resulting in a crack of the baffle in the industrial trial. Industrial trials of the molten steel flow in the C4-based tundish were conducted and reported a reduction of 43.81% in the inclusions over the prototype.

Analysis of fluid flow characteristics of RH reactor with different bottom-blowing arrangements

ABSTRACT A numerical model of RH reactor with bottom-blowing is developed and used to analyse the influence of bottom-blowing position and gas flow rate on the fluid flow of molten steel, shear stress and slag layer. The results show that the flow difference caused by bottom-blowing positions is mainly due to the different movement behaviour of bubbles. When blowing directly below the up-snorkel, the bubble flow is more concentrated. With the increase in the flow rate, the offset of bubbles towards the up-snorkel direction increases, and it is easier to enter the gap between the up-snorkel and the ladle wall to form slag eye, and increase of shear stress on the ladle and the snorkels. When the position is under the up-snorkel which offset towards the centre of the ladle, the wall shear stress is weaker under the same flow rate, and the flow rate allows larger before slag eye forming.

Effect of the wear of supersonic oxygen lance on the stirring characteristics and metallurgical effects in the converter steelmaking process

ABSTRACT Studying the variation in jet characteristics of an oxygen lance nozzle is of great significance for the converter smelting process. A full-size geometric model of a 120-t converter was established and the effects of a worn oxygen lance nozzle exit on the gas jet, stirring characteristics, and molten bath velocity distribution were studied. An increasing wear angle increases the nozzle exit velocity, increases the jet velocity attenuation, decreases the area of the longitudinal high-velocity zone of the molten bath, increases the area of the low-velocity and dead zones, worsens the molten steel flow, and decelerates the reaction rate. Then, industrial tests were conducted using a 120-t converter. When the wear angle increased from 0 to 20°, the phosphorus content, carbon–oxygen equilibrium, and TFe content in the slag increased from 0.029%, 0.0023, and 12.92% to 0.032%, 0.0028, and 14.58%, respectively. This study has important implications for optimizing the oxygen supply in converters.

Numerical study on mechanical erosion behaviour of the burning-free Al2O3–C bottom nozzle during casting

The burning-free bottom nozzle is a novel component for accurately controlling the molten steel flow during the casting steel process. The effect of the thermal mechanical behaviour of burning-free Al2O3–C bottom nozzle materials under extreme temperatures during casting on the thermally induced failure was investigated. First, the high-temperature dynamic Young's modulus and thermal expansion of the bottom nozzle materials were tested in the temperature range of 300–1473 K. A composite material constitutive model, a thermal conductive model and the concrete damage plasticity model (CDP) were adopted to examine the mechanical erosion behaviour of the Al2O3–C bottom nozzle in the casting process based on Finite Element Method (FEM). Results shown that the area near the core of the bottom nozzle was at a high temperature and under tensile stress conditions, whereas the edge area restricted by the external steel shell was mainly under compressive stress conditions. Then, the cracking tendency was evaluated, and an optimised bottom nozzle with a composite structure was proposed. The burning-free Al2O3–C bottom nozzle with a composite structure has an advantage in reducing the risks of cracking and extending the service life compared with the nozzle made of homogeneous materials. This work can make a significant contribution to the design of high performance bottom nozzles.

Effect of nozzle clogging on flow and inclusion transport in GCr15 steel casting process

Nozzle clogging affects molten steel flow, inclusion transport and slab quality. In this paper, a numerical simulation model for the nozzle clogging and the effect of the relevant parameters on the nozzle clogging simulation is studied. The nozzle clogging impact on the flow, inclusion transport and the nozzle clogging formation process are studied. The numerical simulation of the flow in the mold and nozzle is verified by particle image velocimetry measurement of the mold. The obtained simulation results of the clogged nozzle are verified by industrial experiments. The nozzle clog growth rate increases when the higher inclusion magnification factor is used. However, the nozzle clogging simulation results show that a hole exists in the nozzle clog. The deviation between the nozzle clog thickness obtained by the simulation results and those obtained from the experiments increase when the inclusion magnification factor increases from 1 to 20. The increase of the random walk model parameter increases the randomness of the inclusion transport. It is beneficial to increase the homogeneous simulation results of the nozzle clog thickness. The nozzle clogs that are initially formed in the upper section of the nozzle and extend then to the nozzle port. The nozzle clogs change the inner shape of the nozzle and result in the jet stream disperse, and the impact depth of the jet stream decreases when the solution time increases. The solid shell captures more inclusions, and the solid shell cleanliness decreases when the solution time increases.

Fluid Flow and Heat Transfer Behaviors under Non-Isothermal Conditions in a Four-Strand Tundish

In the continuous casting process, the fluid flow of molten steel in the tundish is in a non-isothermal state. Because of the geometric shape and process parameters of a multi-strand tundish, the fluid flow behavior of each strand is quite inhomogeneous, and the difference in temperature, composition and inclusion content between each strand is great, which directly affects the quality of the steel products. In this paper, the fluid flow, heat transfer phenomena and inclusion trajectories in a four-strand tundish with and without flow-control devices (FCDs) are investigated using a water model and numerical simulation in isothermal and non-isothermal conditions. The results show that natural convection has a significant influence on the flow pattern and temperature distributions of molten steel in the tundish. Without FCDs, the average residence times of the molten steel in the tundish obtained by the isothermal water model, non-isothermal water model and non-isothermal mathematical model were 251.2 s, 263.3 s and 266.0 s, respectively, and the dead zone volumes were 21.51%, 29.26% and 28.21%, respectively. With FCDs, the average residence times of the molten steel obtained by the isothermal water model, non-isothermal water model and non-isothermal mathematical model were 293.0 s, 304.0 s and 305.2 s, respectively, and the dead zone volumes were 43.98%, 50.23% and 52.78%, respectively. The flow characteristics of the molten steel in the tundish were different between the isothermal and non-isothermal conditions. Compared with isothermal conditions, the numerical simulation results were closer to the water model results in non-isothermal conditions. The trial results showed that the fluid flow in a tundish has a non-isothermal characteristic, and the results in non-isothermal conditions can better reflect the actual fluid flow and heat transfer behaviors of molten steel in a tundish.

Distribution of Nonmetallic Inclusions in Slab for Tinplate

Tinplate is widely used in food packaging and chemical packaging. Industrial production continues to reduce the thickness of tinplate steel, which puts higher requirements on the control of inclusions. In this study, compared with traditional detection methods, the Ultrasonic Detection method can analyze the distribution of nonmetallic inclusions in larger size samples, which is closer to the actual production process. The numerical simulation model is established to analyze the flow, heat transfer and solidification behavior of molten steel. The results show: There are two nonmetallic inclusion bands in the sample at the edge of the slab, one is the inner and outer arc side of the sample, and the other is the 1/8 to 1/4 slab thickness region of the inner arc side in the sample. The inclusions in the thickness direction of the slab edge within the range of 1/8 to 1/4 are captured in areas 800 mm to 1400 mm below the meniscus. The solidification of the inner and outer arcs is not symmetrical, which leads to the asymmetrical distribution of inclusions in the inner and outer arcs. This study can provide a reference for improving the tinplate production process.

Prediction of molten steel flow in a tundish with water model data using a generative neural network with different clip sizes

Prediction of molten steel flow in a tundish with water model data using a generative neural network with different clip sizes

Numerical simulation of flow field of molten steel in the caster mould

In order to analyse the molten steel flow in the mould, a 2D model including the mould and the SENwas established. The fluctuation of molten steel on the meniscus of the mould and the steel flow velocity field in the mould and nozzle were analyzed. The calculation results show that: (1) the steel flow velocity field in the mouldwas the highest in the nozzle area. When liquid steel flows out of the SEN, its flow velocity decreases gradually. (2) There were three regions flow in the mould. There were two reflux areas outside the nozzle, the dividing line is the free surface, and the other reflux area is 0.2 m∼0.9 m. The liquid steel within 0.9 m∼1.5 m flows vertically downward. (3) The free surface near the nozzle is high, while the free surface away from the nozzle is low. The free surface is the lowest at 0.1 m and the highest at 0.06 m.

Correction to: Influence of the Vertical Pole Parameters on Molten Steel Flow and Meniscus Behavior in a FAC-EMBr Controlled Mold

Correction to: Influence of the Vertical Pole Parameters on Molten Steel Flow and Meniscus Behavior in a FAC-EMBr Controlled Mold

Simulation study on multiphase behavior of gas-metal-slag in the 260t converter

Taking the 260t BOF steelmaking process as the research object, it is of great significance to study the Gas-metal-slag interaction with oxygen lance. In this paper, a 3D mathematical model is established by using fluent. Through changing some physical parameters of lance height and slag, the impact depth, impact cavity area and energy transfer and flow are analyzed. The numerical results show that with the increase of lance height, the diameter of impact cavity in molten steel becomes larger, but the impact depth decreases. When the lance height is 32de, the area of high speed zone in the molten steel pool is the largest, the energy in oxygen jet is mostly dissipated in the process of reaching the slag level, and the kinetic energy obtained by the slag is only about 14% of the kinetic energy of molten steel. With the increase of slag thickness, the depth and area of the cavity decrease, and the flow of molten steel is restrained. The change of slag viscosity and slag density has little effect on the flow velocity. This study can provide reference and guidance for the regulation and control of the process parameters of converter refining.

A Simulation-Based Digital Design Methodology for Studying Conjugate Heat Transfer in Tundish

The successful design of refractory lining for a tundish is critical due to the demand of superheat control, improvement of steel cleanliness and reduction in material cost during continuous casting. A design of experiment analysis, namely, the Taguchi method, was employed to analyze two-dimensional heat transfer through refractory linings of a single-strand tundish, with the consideration of the thickness and the thermal conductivity of lining materials. In addition, a three-dimensional conjugate heat transfer model was applied in the tundish, taking in account the molten steel flow and heat conduction in the linings. A special focus of this study was to demonstrate the analysis methodology of combining Taguchi and CFD modelling to explore lining design in terms of thickness and thermal conductivity for the given process conditions during tundish operations.

Effect of Top‐Swirling Turbulence Inhibitor on Multiphase Flow in a Single‐Strand Tundish During Transient Casting

The turbulence and multiphase flows in a single‐strand slab casting tundish during the start‐up operation, steady‐state casting, and the ladle changeover process without a turbulence inhibitor (TI), with an ordinary TI, and with a top‐swirling TI are numerically investigated and compared to assess the metallurgical advantages of a top‐swirling TI. The results show that the designed top‐swirling TI has no negative effect on the turbulence flow of molten steel during steady‐state casting, as the swirling flow may enhance the inclusion removal rate, and erosion of the guide vanes is relatively weak. During start‐up operation, the use of a top‐swirling TI effectively alleviated level fluctuations in the impact zone, which decreased from 38.75 mm at 90 s to 12.5 mm at the start‐up tonnage, then decreased to zero within 180 s. During ladle changeover, the second stage of steel exposure could be eliminated by the top‐swirling TI, while the areas of steel exposure remaine around 1550 and 750 cm2 without a TI and with an ordinary TI after 60 s of refilling time. The top‐swirling TI could effectively improve the turbulence flow of molten steel, avoiding secondary oxidation and slag entrapment, making it suitable for widespread application and popularization.

Collision-coalescence among inclusions with bubble attachment and transport in molten steel of RH

Inclusions can lead to various defects in the final steel products, and RH vacuum refining is an effective and vital technology to remove inclusions from molten steel. By the computational fluid dynamics (CFD) method, the inclusion mass/population conservation model is developed to have a deep insight into the inclusion transfer behavior in the argon molten steel flow of RH. Particularly, the argon slip velocity is introduced into the inclusion convection velocity in the mathematical model, and the inclusions attached by argon bubbles can return to the molten steel when bubbles escape from the free surface of the vacuum chamber. The numerical results of the fluid flow and the inclusion transfer behavior are validated by the measured data in the actual experiment. The argon bubbles significantly enhance the inclusion transport and collision-coalescence process. Besides, the variations of the inclusion volume concentration and the inclusion number density in the up snorkel are about 2 times those in the down snorkel. The number of inclusions with diameters less than 10 μm decreases with the vacuum treatment time, while the number of inclusions with diameters greater than 10 μm increases first and then decreases gradually. Near the free surface of the ladle, there are the greatest inclusion volume concentration, the greatest inclusion number density and the lowest inclusion characteristic radius.

Molten Steel Flow, Heat Transfer and Inclusion Distribution in a Single-Strand Continuous Casting Tundish with Induction Heating

The electrical magnetic field plays an important role in controlling the molten steel flow, heat transfer and migration of inclusions. However, industrial tests for inclusion distribution in a single-strand tundish under the electromagnetic field have never been reported before. The distribution of non-metallic inclusions in steel is still uncertain in an induction-heating (IH) tundish. In the present study, therefore, using numerical simulation methods, we simulate the flow and heat transfer characteristics of molten steel in the channel-type IH tundish, especially in the channel. At the same time, industrial trials were carried out on the channel-type IH tundish, and the temperature distribution of the tundish with or without IH under different pouring ladle furnace was analyzed. The method of scanning electron microscopy was employed to obtain the distribution of inclusions on different channel sections. The flow characteristics of molten steel in the channel change with flow time, and the single vortex and double vortex alternately occur under the electromagnetic field. The heat loss of molten steel can be compensated in a tundish with IH. As heating for 145 s, the temperature of the molten steel in the channel increases by 31.8 K. It demonstrates that the temperature of the molten steel in the tundish can be kept at the target value of around 1813 K, fluctuating up and down 3 K after using electromagnetic IH. In the IH channel, the large inclusions with diameters greater than 9 μm are more concentrated at the edge of the channel, and the effect of IH on the inclusion with diameters less than 9 μm has little effect.