Influence of electromagnetic stirring on the flow field and argon bubble distribution in the continuous casting mold of slab based on high-temperature online measurement of flow velocity near the mold surface

PurposeThe purpose of this article is to numerically investigate the effect of casting speed on the fluid flow, solidification and inclusion motion under the influence of electromagnetic stirring (EMS) in the bloom caster mold with bifurcated submerged entry nozzle (SEN).Design/methodology/approachThe electromagnetic field obtained by solving Maxwell’s equation is coupled with the fluid flow, solidification and discrete phase model using the in-house user-defined functions. An enthalpy porosity approach and Lagrangian approach are applied for the solidification analysis and non-metallic inclusions motion tracking, respectively.FindingsInvestigation shows that the casting speed and EMS significantly affect the steel flow, solidification and inclusion behavior inside the mold. Investigations are being conducted into the complex interplay between the induced flow and the SEN’s inertial impinging jet. In low and medium casting speeds, the application of EMS significantly increases the inclusion removal rate. Inclusion removal is studied for its different size and density and further effect of EMS is also reported on cluster formation and distribution of inclusion in the domain.Practical implicationsThe model may be used to optimize the process parameter (casting speed and EMS) to improve the casting quality of steel by removing the impurities.Originality/valueThe effect of casting speed on the solidification and inclusion behavior under the influence of time-varying EMS in bloom caster mold with bifurcated nozzle has not been investigated yet. The findings may assist the steelmakers in improving the casting quality.

PurposeThe purpose of this study is to explore how a time-varying electromagnetic stirring (EMS) affects the fluid flow and solidification behavior in a slab caster continuous casting mold. Further, the study of inclusion movements in the mold is carried out under the effect of a time-varying electromagnetic field.Design/methodology/approachA three-dimensional coupled numerical model of solidification and magnetohydrodynamics has been developed for slab caster mold to investigate the inclusions transport by discrete phase model with the use of user-defined functions. Enthalpy porosity and the Lagrangian approach are applied to analyze the behavior of solidification and inclusion.FindingsThe study shows that the magnetic field density distribution has a radial symmetry in relation to the stirrer’s center. As the EMS current intensity increases, the strength of the lower recirculation zone gradually decreases and nearly disappears at higher intensities. Additionally, the area of localized remelting zone expands in the solidification front with rising current intensity. The morphology of inclusions and EMS current intensity have a significant impact on the behavior and movement of inclusions within the molten steel.Practical implicationsBy using the model, one can optimize the EMS parameter to enhance the quality of steel casting through the elimination of impurities and by improving the microstructure of cast that mainly depend on solidification and flow patterns of molten steel.Originality/valueUntil now, the use of time-varying EMS in the slab caster mold to study solidification and inclusion behavior has not been explored.

Effect of non-deformable and deformable bubbles on static yield stress of cement mortar

Mold electromagnetic stirring (M-EMS) is a technique that enhances the quality of the billet by promoting the equiaxed grain formation. In the present study, a 3D numerical model coupled with M-EMS is established to investigate the effect of current density and frequency on flow pattern, solidification and interface behaivour in billet continuous casting of steel. Volume of fluid (VOF) model is adopted to study the behaivour of the slag-metal interface. The results reveal that the current density of EMS mainly determines the strength of stirring. On increasing the current density, the intensity of stirring increases. It leads to an increase in the uniformity of temperature distribution in the billet. However, at a very high current density (>=800 A), M-EMS inhibits the solidification growth below the center of the stirrer and increases the interface fluctuation. Frequency plays little role in affecting flow behavior, thus affecting heat transfer and solidification. Furthermore, no appreciable change is seen in the interface fluctuations on changing the frequency of EMS.

Segregation behavior and precipitated phases of super-austenitic stainless steel influenced by electromagnetic stirring

Simulation of electromagnetic field and its effect during electromagnetic stirring in continuous casting mold

Rheology of bubble-bearing magmas

A few reports have been made on the influence of electromagnetic stirring on weld zone, from the point of minimization of crystal grain and acceleration of blowhole decrease, in the case of TIG and MIG welding for titanium alloy or aluminium alloy.But the application for Submerged-arc welding has not been experimented. Therefore, in the former report, the authors investigated, how the electromagnetic stirring made influence on its bead shape, penetration and solidification structure of D.C.submerged-arc welding of mild steel. From this study the authors made it clear that the shape of penetration showed very peculiar change and that the primary crystals of weld metal were minimized.In this cotinuous report, the authors investigted how electromagnetic stirring hardness distribution and notch toughness of Submerge-arcd weld zone changed.The authors measured the hardness distribution by micro-Vickers Hardness tester, and the notch toughness by V-notch Charpy impact test. From these studies the authors have found out the following results.1) The hardness increases by electromagnetic stirring.2) As to the notch toughness, the authors made the transition curves of absorbed energy and fracture phase from the impact test, and from them, obtained the transition temperature of both 15ft-lb and fracture phase.As the result it became clear that both of the transition temperatures moved to the lower temperature side by 20 degrees C. The author also made the micro observation of fracture phases of impact test pieces with electron microscope and considered the changes of shape of the destructive phase caused by electromagentic stirring.

In thin slab continuous casting, argon injection is commonly employed to prevent nozzle clogging. However, the bubbles significantly influence the flow field, interface fluctuations, and slag entrainment within the mold. Notably, bubble entrapment at the solidification front may induce quality defects in cast slabs. In this study, a numerical model combining Large Eddy Simulation (LES), Volume of Fluid (VOF), and two-way coupled Discrete Phase Model (DPM) was established, along with a force balance model-based bubble capture criterion, to investigate the internal transient multiphase flow behavior under varying argon injection rates. The results reveal that argon bubbles form vortical structures near the Submerged Entry Nozzle (SEN), constraining flow space in the upper recirculation zone. In the lower recirculation zone, small bubbles generate multiple small vortices through alternating buoyancy and drag forces. While increased argon flow rate elevates absolute bubble entrapment quantity, the relative proportion remains unaffected. Furthermore, argon flow rate substantially impacts interface fluctuation amplitude and slag entrainment. Crucially, the analysis demonstrates that 99% of bubbles and all entrapped slag inclusions are concentrated within 23 and 17 mm below the slab surface, respectively, with argon flow rate exhibiting negligible impact on inclusion entrainment depth. This study enhances understanding of multiphase interaction about molten steel, slag, and argon bubbles, while providing data-driven insights for optimizing trimming strategies in industrial production and a recommended upper limit for argon injection flow rate.

The paper presents the research results of horizontal continuous casting of ingots of aluminium alloy containing 2% wt. silicon (AlSi2). Together with the casting velocity (velocity of ingot movement) we considered the influence of electromagnetic stirring in the area of the continuous casting mould on refinement of the ingot’s primary structure and their selected mechanical properties, i.e. tensile strength, yield strength, hardness and elongation. The effect of primary structure refinement and mechanical properties obtained by electromagnetic stirring was compared with refinement obtained by using traditional inoculation, which consists in introducing additives, i.e. Ti, B and Sr, to the metal bath. On the basis of the obtained results we confirmed that inoculation done by electromagnetic stirring in the range of the continuous casting mould guarantees improved mechanical properties and also decreases the negative influence of casting velocity, thus increasing the structure of AlSi2 continuous ingots.

Numerical and experimental investigation of thermo-fluid flow and element transport in electromagnetic stirring enhanced wire feed laser beam welding

Recent developments of an advanced numerical model for Continuous Casting of steel unveiled at the previous 2010 CSSCR Conference in Sapporo, Japan are presented. These include coupling of the existing multiphase, heat transfer and solidification model to argon injection for tracking bubble trajectories in the SEN, metal bulk and across the slag bed after passing through the metal surface. Hence, description of a method for adding gas injection in combination with a multiphase model for tracking metal/slag interfaces (Discrete Phase Model + Volume Of Fluid, DPM+VOF) is given.Validation is supported by tests on a revamped Continuous Casting Simulator (CCS-1) based on a low melting point alloy, which can realistically replicate the flow conditions in the caster. Metal-slag-argon flow predictions were compared to observations in the physical model showing good agreement on features such as discharging jets, rolls, standing waves and argon distribution measured through a variety of techniques such as ultrasound, electromagnetic probes and video sequences.Ultimately, the model makes possible the prediction of stable or unstable flows within the mould as a function of different argon flow-rates and bubble sizes. Application to industrial practice is an ongoing task and preliminary results are illustrated. The robustness of the model combined with direct observations in CCS-1 make possible the description of phenomena difficult to observe in the caster (e.g. argon injection and metal flow), but critical for the stability of the process and the quality of cast products.

Solution of three-dimensional temperature and turbulent velocity field in continuously cast steel billets with electromagnetic stirring by a meshless method

Submerged entry nozzle (SEN) clogging is a troublesome phenomenon in the continuous casting process that can induce the asymmetric mold flow, and thus, lowering the steel product quality. In this paper, a mathematical model coupling the electromagnetic and flow fields, was developed to investigate the influence of the SEN clogging rate on the flow field and the influence of electromagnetic stirring (EMS) on the asymmetric mold flow. Slag entrapment index Rc was introduced to quantify the possibility of slag entrapment, and symmetric index S was introduced to quantify the symmetry of the flow field. The results show that as the SEN clogging rate increased, the slag entrapment index Rc increased, while the symmetric index S decreased. EMS can greatly improve the symmetry of the flow field with SEN clogging, but it cannot remove the asymmetric phenomenon completely because the stirring intensity should be controlled below the safe level to avoid slag entrapment.

At some locations along the length of open sewers and drains, sediment particles get deposited on the bottom bed, reducing hydraulic efficiency. A sediment invert trap (SIT) can be implemented on the bottom of open sewers and drains to trap sediment particles moving on the bed surface. Several investigators have conducted experimental and computational studies to understand the particle trapping behavior of invert traps of various shapes and depths under varying sediment and flow parameters. In experimental studies, previous investigators have used actual and artificial sediment particles; in computational analyses, spherical particles have been considered. The current study investigated the particle trapping behavior of an irregular hexagonal sediment invert trap (SIT) through experiments and two-dimensional (2D) numerical modeling. Seventy-two experiments were performed using actual sewage solid particles in an open rectangular channel with a bottom-fitted invert trap with multiple depths. Sixty numerical simulations were performed using ANSYS Fluent 2020 R1 computational fluid dynamics (CFD) software, considering spherical and nonspherical sewage solid particles. The velocity field was predicted using the volume of fluid (VOF) model combined with the realizable k-ϵ turbulence model. Particle trap efficiency was predicted using a stochastic discrete phase model (DPM). Trap efficiency varied significantly with depth of flow, invert trap depth, slot aperture size, and particle size and shape. Analysis of the simulated flow field showed that variation of turbulent kinetic energy above the trap’s slot aperture was also responsible for variations in trap efficiency values. Fluent simulations considering particles as nonspherical (using shape factors) agreed well with experimentally measured trap efficiency, with mean absolute percentage errors (MAPE) of 6.23%, 8.79%, and 13.77% for particle size ranges SS1, SS2, and SS3, respectively, with both slot apertures at all flow depths. The 2D-CFD study consistently overpredicted trap efficiencies compared to the experimental findings. With a fixed length and width of 0.32 and 0.15 m, respectively, the optimal depth of the irregular hexagonal SIT was found to be 0.65 m with slot aperture sizes of 0.15 and 0.03 m, whereas with slot aperture size of 0.15 m only, invert trap depths equal to 0.58, 0.43, and 0.38 m was found as optimum.