Steel Slag Interface Research Articles

Numerical study on the effects of strands consistency on metallurgical transport behaviours of low-carbon steel in tundish–submerged entry nozzle–mould systems

In this study, the innovative tundish–submerged entry nozzle (SEN)–mould systems that enabled data transmission between the tundish and the mould were constructed to investigate the effect of strands consistency on the metallurgical transport behaviours of low-carbon steel. The velocity magnitude near stopper-rod A and T-outlet A was notably low. Owing to inactive flow regions and temperature variations near the stopper-rods, the maximum temperature difference between T-outlet A and T-outlet B was approximately 2.8 K. In case 2, a vortex occurred near the right narrow face of the steel–slag interface, while no vortex was present near the left narrow face. In cases 3, 5 and 6, some streamlines existed approximately perpendicular to the steel–slag interface. These phenomena increased the possibility of slag entrainment via the upward flow mechanism and shear layer instability. Cases belonging to strand A featured a higher temperature gradient than cases belonging to strand B, and this trend was related to the temperature difference between T-outlet A and T-outlet B. The extreme differences in temperature gradient were 0.067 K/mm for case 3 and 0.056 K/mm for case 4. At an SEN port angle of 15°, strands consistency had the greatest influence on the uniformity of the temperature gradient. Different solutes exhibited similar distribution patterns, and solute segregation was closely related to the partition coefficient. Various velocity components and SEN structures determined the position of the impact point, thereby influencing fluid flow and temperature distribution in the mould. The concentration distribution of solutes was closely related to the velocity at T-outlet A/B. The thickness of the solidified shell and mushy zone closely depended on the temperature at T-outlet A/B. Strands consistency impacted metallurgical transport behaviours in the mould and the quality of the bloom.

Effect of Refining Slag Composition on the Cleanliness of Oriented Silicon Steel

To improve the cleanliness of oriented silicon steel, industrial experiments are performed under different refining slag composition conditions. The results show that the use of medium‐basicity refining slag (w(CaO)/w(SiO2) = 2.3–2.6, w(CaO)/w(Al2O3) = 2.3–2.6) results in higher steel cleanliness with lower Al2O3 volume fraction, and smaller inclusions. In addition, the thermodynamic equilibrium between the oriented silicon steel slag and the molten steel is investigated at a temperature of 1873 K (1600 °C) to understand the effect of different slag compositions on the oxygen content and Al2O3 absorption capacity. Furthermore, a mathematical model is introduced to describe the behavior of inclusions at the steel–slag interface as well as to predict the removal of oxide inclusions during the slag‐refining process. The experimental and predicted results for inclusion removal after slag refining are in good agreement.

Multi-Scale Study on the Effect of Snowmelt Salt on the Interface Adhesion of Rubberized Asphalt–Steel Slag

To explore the effect of snowmelt agent on the adhesion of the rubberized asphalt–steel slag interface, the adhesion of the rubberized asphalt–steel slag interface under different concentrations of snowmelt agent was studied. The macroscopic fracture characteristics of the steel slag-rubberized asphalt mixture under different concentrations of snowmelt salt were studied. The surface energy of steel slag and rubberized asphalt after the action of different concentrations of snowmelt salt was tested at the microscopic scale, and then their adhesion was calculated. It was used to study the microscopic surface interaction under the action of snowmelt agents. At the molecular scale, the interface models of rubberized asphalt–NaCl solution–Ca3SiO5 were constructed, and the interaction between steel slag and asphalt under different concentrations of snowmelt agent was studied. The results show the following: when the concentration of snowmelt agent is 8%–12%, the fracture of the rubberized asphalt–steel slag mixture is more inclined to brittle fracture, and the failure speed is faster; the adhesion of steel slag-rubberized asphalt is weakened under the action of the snowmelt agent, but it can still maintain good adhesion; before the concentration of snowmelt agent reached saturation, the adhesion property of steel slag-rubberized asphalt decreases with the increase of snowmelt agent concentration; when the concentration of snowmelt agent reached saturation, NaCl precipitates and adheres to the molecular surface of steel slag, which enhances the interaction between steel slag and rubberized asphalt; the inflection point with salt concentration is related to the solvent precipitated from the solution.

Analysis of the influence of electrode rotation on the desulfurization behavior during electroslag remelting process

A transient multi-physics coupling mathematical model is developed to investigate the influence of electrode rotation on desulfurization in the electroslag remelting (ESR) process. This model incorporates a thermodynamic and kinetic model to calculate the sulfur transfer rate from steel to slag, while simultaneously including the magnetohydrodynamic flow, heat transfer, and species transport. The volume of fluid (VOF) approach is employed to track the slag-steel interface. Experimental validation is conducted to ensure the reliability of the model. Sulfur in steel is primarily removed at the slag-electrode interface and the slag-droplet interface, but the slag-metal pool interface contributes very little to desulfurization. The electrode rotation disperses the molten droplets and enhances the heat convection, resulting in a reduction of the total amount of Joule heat and the temperature within the mold. At the electrode tip, rotating the electrode achieves a higher removal of sulfur, more than 10 % compared to the static electrode. The final removal ratios of sulfur are 78.79 %, 82.01 %, 84.90 %, and 80.81 % with the electrode rotating at 0, 20, 40, and 60 rpm, respectively. The optimal desulfurization is achieved at the rotating speed of 40 rpm, due to the refined droplets, the faster renewal rate of the slag-steel interface, the elevated temperature of the interface, and the longer residence time for droplets passing through the slag layer.

Mathematical Modeling of Transient Submerged Entry Nozzle Clogging and Its Effect on Flow Field, Bubble Distribution and Interface Fluctuation in Slab Continuous Casting Mold

Submerged entry nozzle (SEN) clogging will affect the production efficiency and product quality in the continuous casting process. In this work, the transient SEN clogging model is developed by coupling the porous media model defined by the user-defined function (UDF) and the discrete phase model (DPM). The effects of the transient SEN clogging process on the flow field, the distribution of argon gas bubbles and the fluctuation of the interface between steel and slag in the concave bottom SEN in the continuous casting slab mold with a cross-section of 1500 mm × 230 mm are studied by coupling transient SEN clogging model, DPM and volume of fluid (VOF) model. The results show that the actual morphology and thicknesses of SEN clogging are in good agreement with the numerical simulation results. The measurement result of the surface velocity is consistent with the numerical simulation result. With increasing the simulation time, the degree of SEN clogging increases. The flow velocities of molten steel flowing from the outlet of the side hole increase, because the flow space is occupied with the clogging inclusions, which leads to the increased number of argon gas bubbles near the narrow wall. The steel–slag interface fluctuation near the narrow walls also increases, resulting in the increased risk of slag entrapment.

Physical Model of Inclusions Removal at Static Steel-Slag Interface.

Inclusions are one of the important factors affecting the cleanliness of molten steel. The current optimization of inclusion removal methods mainly focuses on promoting inclusions to float to the slag-steel interface so that the inclusions can be absorbed and removed by the refining slag. However, the research on the floating removal of inclusions cannot be carried out directly in the ladle, so methods such as mathematical models and physical models were developed. This article uses silicone oil to simulate the slag layer; polypropylene particles; and aluminum oxide particles to simulate inclusions to establish a water model experiment. By changing the viscosity of silicone oil and the diameter of particles, the factors affecting the movement of inclusions at the slag-steel interface were explored. Based on the water model, a mathematical model of the floating behavior of inclusions at the slag-steel interface was constructed, and parameters such as particle diameter and interfacial tension in the water model experiment were studied by the mathematical model for calculation. Both the mathematical model and the water model experimental results show that after the viscosity of silicone oil increases from 0.048 Pa·s to 0.096 Pa·s, the dimensionless displacement and terminal velocity of the particles decreases. When the diameter of the same particle increases, the dimensionless displacement and terminal velocity increases. The dimensionless displacement of polypropylene particles of the same diameter is larger than that of aluminum oxide particles, and the terminal velocity is smaller than that of aluminum oxide particles. This is attributed to the better overall three-phase wettability of polypropylene particle. When the liquid level increases, the dimensionless displacement and terminal velocity of particles under the same conditions show only slight differences (less than 10%).

Numerical Simulation on the Motion Behavior of Micro-inclusions at the Steel–Slag Interface

Numerical Simulation on the Motion Behavior of Micro-inclusions at the Steel–Slag Interface

Analysis of metallurgical defects in enamel steel castings

Abstract The relevant experiments and studies were conducted to address the metallurgical defects such as subcutaneous bubbles and slag inclusions occurring during the enamel steel continuous casting process. According to the high-temperature experimental results, calculations were made to determine the changes in viscosity and tension due to the steel reaction with the slag. Based on the experimental findings, there was a notable variation in the content of SiO2 and Al2O3 in the slag before and after the reaction. The concentration of the element Al in the steel melt significantly decreased, whereas the concentration of Ti showed a minimal change. These observations indicate that the reduction of SiO2 at the slag–steel interface is predominantly attributed to the role of Al. The calculation results showed that at 300 s of reaction time, the viscosity rapidly increased from 0.108 to 0.133 Pa·s and then slowly increased to 0.155 Pa·s; The interfacial tension rapidly decreased from its initial value of 1,380 mJ·m−2 to a minimum of 1,320 mJ·m−2, and it then slowly increased to an equilibrium state. Therefore, the main cause of the occurrence of porosity defects in the enamel steel continuous casting process is the reduction of interfacial tension between slag, steel, and gas caused by the reaction between the slag and steel, as well as the foaming of the slag.

Numerical Simulation of Mold Slag Entrapment Behavior in Nonoriented Silicon Steel Production Process

This paper is based on the surface defects of casting billets in the production process of nonoriented silicon steel plates at a steel plant in North China. Taking the parameters of a slab mold in the nonoriented silicon steel production process as a prototype, the flow field characteristics of the mold under the same section, different drawing speed and immersion depth were systematically studied by using a LES (large eddy simulation) and VOF (volume of fluid) coupling algorithm. The results show that under the current conditions, when the critical slag entrapment speed increases from 1.0 m/min to 1.2 m/min, the nozzle insertion depth increases linearly with the critical slag entrapment speed, while when the nozzle insertion depth exceeds 130 mm, the increasing effect of further increasing the nozzle insertion depth on the critical slag entrapment speed begins to decrease. When the drawing speed of continuous casting is kept constant at 1.4 m/min, the abnormal fluctuation height of the steel slag interface is significantly improved when the angle of the water nozzle is increased from 15° to 20°, and the proportion of slag entrapment is also reduced from 0.376% to 0.015%. When the nozzle angle is 25°, the slag entrapment ratio is reduced to 0%, and the steel slag interface also ensures a certain activity. The numerical simulation results were applied to the industrial site, and the slag inclusion rate and crack rate of the billet in the continuous casting process of nonoriented silicon steel were obviously improved after the optimization process.

Modeling of Motion of Inclusions in Argon‐Stirred Steel Ladles

A 3D discrete phase model (DPM)‐ and volume of fluid–coupled model is developed to investigate the multiphase flow in a 260 ton argon‐stirred ladle. The flow field and interfacial behavior in the argon‐stirred ladle are accurately predicted. Then, the Lagrangian DPM is used to trace the motion of inclusions in the liquid steel. Residence time maps, which provided the residence time required for inclusions travelling from the bulk liquid steel to the steel–slag interface, are proposed and plotted as functions of inclusion diameter and percentage of inclusions. For inclusions smaller than 10 μm, the average residence time is size‐independent but decreases from 175 to 93 s with an increment in the gas flow rate from 50 to 400 NL min−1. With increasing the inclusion size, the average residence time is dependent on both gas flow rate and inclusion diameter. When the inclusion diameter increases to 1000 μm, the average residence time is almost independent of the gas flow rate. The current model overestimates the inclusion removal rate. However, this overestimation indicates that only appropriately considering the behavior of inclusions at the steel–slag interface can accurately predict the removal of inclusions in argon‐stirred ladles.

Numerical Analysis of Slag–Steel–Air Four-Phase Flow in Steel Continuous Casting Model Using CFD-DBM-VOF Model

Argon injection is usually applied in the continuous casting mold to prevent submerged entry nozzle (SEN) clogging. However, the stability of the slag–steel interface is affected by the injected gas, even leading to the formation of the slag eye. A computational fluid dynamics–discrete bubble model–volume of fluid (CFD-DBM-VOF) model is established to predict the argon–slag–steel–air four-phase flow in the continuous casting mold. The bubble behavior is treated with the Lagrangian approach considering bubble coalescence and breakup. The movement behavior of the slag–steel interface is analyzed with and without argon blowing, validated with the water model. The results show that the large bubble tends to float up into the slag–steel interface near the SEN with argon injection, resulting in fluctuations in the slag–steel interface near the SEN. The bubble distribution, flow field, fluctuation height of the slag–steel interface and configuration of the slag eye in the mold are analyzed. Furthermore, the effect on the casting speed, gas flow rate and thickness of the slag layer is obtained based on the result. The mathematical prediction results showcase a combination of well-established phenomena and newly generated predictions.

Motion behaviour of solid inclusions at the steel–slag interface in high-Al steel

ABSTRACT In the steelmaking process of high-Al steel, solid inclusions will accumulate in the slag phase near the steel–slag interface, and it is crucial to eliminate the residual Al-containing inclusions in molten steel. In the present study, the film-rupture and drainage models were applied to clarify the characteristics of the inclusion detachment motion. The analysis of parameters was carried out and their impact on the inclusion motion was further discussed. It was found that the micro-size inclusions are prone to remain at the interface or rebound back into the steel. According to the models, the motion of the solid inclusion in the drainage stage is solely influenced by the steel density and the interfacial tension between steel and slag. The decrease of the steel–slag interfacial tension is beneficial to the transfer of the inclusions, while the low-density of the high-Al steel will promote the rebound of the inclusions.

Optimization of Port Angle for Narrow‐Width Mold Flow Field under High Casting Speed Based on Large Eddy Simulation and High‐Temperature Measurement of Velocity

Herein, the flow field of the mold through numerical simulation and high‐temperature measurement is studied, and discussed the effects of casting speed and port angle on the flow field of the 880 mm wide mold. The velocities near the mold surface of the numerical simulation are in good agreement with those of the high‐temperature measurement. As the casting speed continues to increase, the surface flow velocity of the mold also increases. When the casting speed increases to 1.8 m min−1, the flow pattern of the mold exhibits a strong double‐roll flow, the strong jet increases the risk of argon bubbles being captured by the solidification front inside the mold. As the port angle of the submerged entry nozzle (SEN) gradually increases, the surface flow velocity of the mold gradually decreases. By appropriately increasing the port angle of the SEN to 20°, the surface flow velocity of the mold decreases, and the stability of the molten steel–slag interface improves. At the same time, there is no significant change in the distribution of argon bubbles, and the removal rate of inclusions is the highest.

A Computational Fluid Dynamics‐Thermodynamics Coupled Approach to Simulate Desulfurization in Ladle Furnace Based on Interface Equilibrium Assumption

This study proposes a coupled computational fluid dynamics and thermodynamics model based on the assumption of interface equilibrium at the steel–slag interface to simulate the desulfurization process in a ladle furnace. The species transport equation is solved to analyze the kinetic behavior and chemical content variation in the melt. The sulfur distribution ratio is calculated based on the slag sulfide capacity and oxygen activity. Subsequently, the solutions are coupled by introducing the species transfer and source terms generated by comparing the initial and predicted thermodynamic equilibrium states at the steel–slag interface cell. The model is validated by experimentally comparing the sulfur content. Furthermore, the model is applied under different kinetics and thermodynamics conditions. With an increase in the gas flow rate, the in‐phase effective diffusion coefficient increases, but the number of interface cells involved in the sulfur transfer process decreases. The complex relationship between the desulfurization process and the gas flow rate results from the mutual antagonism between these two factors. Moreover, the study findings demonstrate that a higher slag basicity enhances the calculated sulfur distribution ratio and final desulfurization ratio.

Numerical Simulation of the Flow Field in an Ultrahigh-Speed Continuous Casting Billet Mold

Ultrahigh-speed continuous casting is a critical element in achieving high-efficiency continuous casting. In the present work, a three-dimensional model of a 160 mm × 160 mm billet ultrahigh-speed continuous casting mold was developed for use in studying the influences of different casting parameters on molten steel flow. The results showed that the flow pattern in the mold was not associated with its casting speeds, submerged entry nozzle (SEN) immersion depths, or inner diameters. Variation in casting speeds significantly affected the liquid level of the steel–slag interface. Its liquid level fluctuation was reasonable at an SEN immersion depth of 80 mm. Its impact depth reached the shallowest point, which was conducive to upward movement within high-velocity and high-temperature regions, and accelerated the floating of non-metallic inclusions. Expanding the inner diameter of the SEN could effectively weaken the initial kinetic energy of the jet. However, it may cause a deeper impact depth and a degree of upward movement in the raceway, which exhibited the shallowest impact depth in the jet and the most reasonable behavior of molten steel at a liquid level for which the inner diameter of the SEN was 40 mm.

Research Status of Numerical Simulation of Nonmetallic Inclusions Interfacial Removal

The removal of inclusions in liquid steel has always been the focus of research, and the removal of inclusions is mainly through the process of the inclusion through the slag–steel interface. The inclusion removal process can be subdivided into inclusions in molten steel grew up rise, in steel–slag interface through separation, adsorb dissolved in molten slag 3 steps. Based on the microscopic process of three steps, this article summarizes and discusses the mathematical model, fluid mechanics model, and experimental verification method of inclusion removal process, analyzes limiting and influencing factors of inclusion removal process, and comprehensively describes the numerical simulation research progress of inclusion removal process. With the development of numerical simulation techniques and experimental equipment, some progress has been made in the study of interfacial removal of inclusions. The inclusion interface removal behavior can be analyzed semiquantitatively based on dynamic force model. The computational fluid dynamics model has advantages in studying the phenomena of the inclusion interface, and the phase‐field method is often used to simulate the removal process of the inclusion interface. The combination of water model and numerical simulation, high‐temperature laser confocal method, and other methods is of great help to explore the interface behavior of inclusions.

A boundary layer model for capture of inclusions by steel–slag interface in a turbulent flow

A boundary layer model for capture of inclusions by steel–slag interface in a turbulent flow

Investigation of Inclusion Removal at Steel–Slag Interface toward a Small‐Scale Criterion for Particle Separation

Interactions between inclusion particles and the steel–slag interface directly affect the inclusion removal efficiency and thus influence steel cleanliness. Herein, the three‐phase interactions are resolved using the volume of fluid (VOF) method coupled with a dynamic overset mesh. The simulation is able to capture the instantaneous interface deformation and predict the particle motion driven by capillary force. The model validity is first demonstrated by comparison with analytical results. Then, a parameter study is conducted to examine the most influential factors governing the separation process. The results show that the system's wetting condition and the slag viscosity have a decisive effect on particle behavior at the interface (separation or entrapment). From an energy perspective, a better wetting condition generates more energy sources, and the interfacial energy is efficiently transformed into the particle's kinetic energy within a less viscous environment, thus leading to better separation. Besides, a criterion for predicting particle behavior is developed based on a modified Reynolds number (, relevant to fluid properties) and a quantity related to particle dynamics (ζ). The current work brings insights into the interfacial phenomenon during inclusion removal, which can be incorporated into large‐scale simulations to estimate the removal efficiency more accurately.

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.

Study on the Motion Behavior of Inclusion Clusters at the Steel–Slag Interface

Study on the Motion Behavior of Inclusion Clusters at the Steel–Slag Interface