Application Of Electromagnetic Stirring Research Articles

A review of electromagnetic stirring on solidification characteristics of molten metal in continuous casting

The solidification of molten metal represents a pivotal phase in the preparation and shaping of metallic materials. Continuous casting, as a crucial juncture in the solidification of molten metal, occupies a position of paramount significance. Nevertheless, during the process of continuous casting, challenges emerge, including uneven temperature field distribution, non-uniform solidification microstructures, and the presence of impurities, leading to defects such as segregation and shrinkage in the castings. Researchers have devoted decades to addressing these issues, culminating in the discovery that the application of electromagnetic stirring during continuous casting can expedite the flow of molten metal, enhance solute diffusion, thereby achieving uniform temperature and flow field distributions, refining solidification microstructures, and ameliorating macrosegregation, among other benefits. This article provides an overview of the recent research achievements and advancements in the utilization of electromagnetic stirring during the continuous casting process. It primarily elucidates various stirring devices commonly employed in continuous casting and expounds upon the influence of electromagnetic stirring on solidification characteristics. And the current problems and future development trends in the application of electromagnetic stirring were discussed.

Effect of Electromagnetic Stirring on Shape of β-Al<sub>9</sub>Fe<sub>2</sub>Si<sub>2</sub> Intermetallic Compounds Formed During Solidification of Al–Si–Fe Alloys

A rotating magnetic field was applied during the solidification of Al–Si–Fe alloys (Si = 5 mass% or 10 mass% and Fe = 0.5 mass% or 1 mass%) and the effect of electromagnetic stirring on the area and shape of the intermetallic compounds was studied. The phases formed during solidification of the alloys were not influenced by electromagnetic stirring. The alloys consisted of α-Al, Si and intermetallic β-Al9Fe2Si2. At coil current frequencies above 10 Hz, electromagnetic stirring induced fragmentation of dendritic α-Al, giving rise to coarsening of the β-Al9Fe2Si2 present between the fragmented α-Al grains. The application of electromagnetic stirring at coil current frequencies above 80 Hz decreased the aspect ratio of β-Al9Fe2Si2 in Al–10 mass%Si–1 mass%Fe, while no such decrease was identified in Al–5 mass%Si–0.5 mass%Fe, Al–5 mass%Si–1 mass%Fe or Al–10 mass%Si–0.5 mass%Fe. It was found that the shape of the β-Al9Fe2Si2 phase formed under forced flow of the melt depended significantly on the stirring intensity and the solid fraction of the melt at which intermetallic compounds were formed.

Predicting Grain Structure in Continuously-Cast Stainless Steel Slab

Macrostructural features in continuously-cast stainless steel slabs such as the distribution of equiaxed and columnar grains, and microporosity, are crucial to the post-processes, and the mechanical properties of the final steel products. Among the methods for controlling grain structure during the continuous casting process, the application of electromagnetic stirring (EMS) during casting is known to alter the grain structure of the slab. In this study, we predicted macrostructural features in a continuous-cast stainless steel slab using computer simulation. We approximated the heat transfer system as a one-dimensional heat conduction model with solidification. The effect of EMS was investigated by introducing an effective thermal conductivity of the melt. We assumed that EMS caused turbulent flow, and enhanced the thermal conductivity. Columnar-to-equiaxed transition (CET) and microporosity were estimated with the models proposed by Hunt and Niyama, respectively. The effect of EMS on microporosity was negligible, and microporosity was inevitable in the centerline of the slab. EMS made a second equiaxed region between the outer wall and the center of the slab. Because the effective thermal conductivity was high due to EMS, the temperature field in the slab was distorted, and the Hunt criterion for CET was satisfied in the region. The CET results were compared and verified with cellular automata simulation. Various process parameters including casting speed, superheating, and the position of the EMS module, were examined to predict the macrostructure of the slab.

Effect of casting speed on solidification and inclusion motions in bloom mold caster under the influence of in-mold electromagnetic stirring

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.

Effect of electromagnetic stirring frequency on tribological performance and corrosion resistance of Al-Sn bearing alloy

The Al-Sn bearing alloy was prepared by electromagnetic stirring (EMS) technique, and the effect of stirring frequency on tribological performance and corrosion resistance of Al-Sn bearing alloy was studied. The samples were subjected to tribological experiments and electrochemical tests. The microstructure of the sample was observed by an optical microscope, the wear surface and corrosion morphology were observed by a scanning electron microscope(SEM), the 3D morphology and wear volume of the wear mark were measured by a white light interference microscope, and the composition of corrosion product film was analyzed by X-ray photoelectron spectroscopy(XPS). The microstructure shows that when the stirring current is 60 A and the stirring frequency is 30 Hz, the electromagnetic force has a strong refining effect, and the crystal grains are fine and uniformly distributed throughout the sample. With the increase of the stirring frequency, the wear surface becomes smoother, and more wear debris adhesion phenomenon appears, showing better friction performance. The application of EMS changes the alloy microstructure, which in turn improves the distribution of Sn and enhances the tribological properties. At the same time, the sample with EMS generates a dense corrosion product film in the later stage of immersion, which has good corrosion resistance.

The mechanism of columnar-to-equiaxed transition during electromagnetic centrifugal solidification

Abstract A series of Hastelloy C tubes were solidified under a centrifugal field with various conditions of bulk liquid flow obtained with a controllable electromagnetic field. Their macrostructures show that the columnar-to-equiaxed transition was promoted both by increasing electromagnetic stirring and by increasing the superheat, and the application of electromagnetic stirring at different times can also influence the percentage of the total area occupied by the equiaxed region. Mechanical damage of dendrites is the most probable mechanism for the promotion of the columnar-to-equiaxed transition with high velocity flows. The detachment of the nuclei originated in the chill zone can also promote the columnar-to-equiaxed transition.

The Weld Microstructure and Mechanical Properties of the Alloy 52 and Its Variants with Applied Electromagnetic Stirring during Welding

This study investigated the impact of electromagnetic stirring (EMS) on nickel-base alloy welds prepared with the gas tungsten arc welding process. Alloy 52 and its variants, Alloy 52M and Alloy 52MSS, were carefully evaluated with their weld microstructure and mechanical properties. The results showed that the welds exhibited a typical microstructure of dendrites, and that the dendrites could be refined by electromagnetic stirring. Meanwhile, with an application of EMS, the precipitates became smaller and more evenly distributed in the inter-dendritic areas. Ti(N,C)s, Nb/(Nb,Si)Cs, and large-scale Laves phase with (Nb,Mo,Ti)Cs were the precipitates present in the Alloy 52, Alloy 52M, and Alloy 52MSS welds, respectively. With the refined microstructure, both Alloy 52 and Alloy 52M welds were observed to have an increase in their tensile strength, with a decrease in their elongations. Comparatively, for the Alloy 52MSS weld, the tensile strength was enhanced along with a slight increase in elongation. Deep and dense dimples were a dominant feature of low-Nb-additions welds, and dendrite-like features were found prevalent among the Alloy 52MSS welds. With EMS, the dimples of Alloy 52 welds and the dendrite-like features of Alloy 52MSS welds became finer, while the dimples of Alloy 52M welds grew coarser.

Evolutions of the Micro- and Macrostructure and Tensile Property of Cu-15Ni-8Sn Alloy During Electromagnetic Stirring-Assisted Horizontal Continuous Casting

The present study investigates the evolution of the micro- and macrostructure and tensile property of the Cu-15Ni-8Sn (weight percent) alloy prepared by horizontal continuous casting and electromagnetic stirring (EMS). The results show that the application of EMS is beneficial for grain refinement and for microstructure transformation from the dendrite to the rosette structure and that it leads to a significant improvement in the tensile property. The forced flow induced by EMS homogenizes the temperature field ahead of the solid-liquid interface, disturbing the heat flow direction and resulting in the columnar to equiaxed transition. The grain refinement under different electromagnetic stirring frequencies is mainly derived from the homogenization of the temperature and the remelting of dendritic arms. In addition, the evolution of the tensile property with and without EMS is discussed from the perspective of fracture mode and fine-grain strengthening.

Effect of Electromagnetic Stirring on the Microstructure and Properties of Fe-Cr-Co Steel.

High chromium steel has been synthesized by an induction furnace adopting electromagnetic stirring (EMS). Varying amounts of cobalt was added to obtain 3, 6, and 12% Co in the steel. The melt was allowed to solidify with or without EMS in a rotary magnetic field. The effects of the varying cobalt content and the stirring have been characterized by the microstructural evolution and the consequent improvement in mechanical properties. The application of a rotary EMS during solidification has shown a significant effect on the grain refining, the reduction of element segregation, the promotion of eutectic volume fraction, and the consequent improvement of mechanical properties, including hardness and high-temperature strength. The formation mechanism of the eutectic structure and the precipitation of M7C3 and M23C6 carbides was discussed according to the calculated phase diagram. The increment of cobalt content improved the eutectic volume fraction. Cobalt addition also enhanced the hardness and the yield tensile strength, provided that the ingot structure was homogenized by the EMS.

Influence of electromagnetic stirring (EMS) on the microstructure and mechanical property of Incoloy825 superalloy

We experimentally investigate the influence of the electromagnetic stirring (EMS) on the microstructure and the mechanical properties of Incoloy825 superalloy. Three trails of experiments with different values of the EMS alternating current (I=0, 150 and 300A, respectively), however with identical EMS frequency (f=5Hz), were conducted. We figure out that the equiaxed grain region is increased and the average grain size is decreased whilst EMS is applied. The application of EMS can also decrease the total number of TiN, especially for the inclusion in large scales (>2μm). The values of the yield strength, the ultimate tensile strength and the elongation of Incoloy825 superalloy specimens are also increased whilst EMS is applied.

Grain Refinement and Elimination of Hot Cracks due to Application of Electromagnetic Stirring in Commercial Aluminum Alloy Welds

. In this work the physical effects of electromagnetic stirring (EMS) during welding on the microstructure of some commercial 6xxx and 7xxx series of aluminum alloys are investigated. Experiments are carried out with standard GTA equipment in combination with a current carrying coil providing an axial magnetic field. In order to achieve the maximum grain refining effect, a range of optimal stirring parameters is established. It is then demonstrated that the optimal parameters are in the frequency range of 2 to 15 Hz and the corresponding magnetic field intensities of 10 to 25 mT. These parameters are then applied to reduce susceptibility of these alloys to hot cracking. This paper concludes that by application of EMS to GTA welding of aluminum alloys it is possible to refine the grain structure and reduce the hot cracking susceptibility of these alloys, especially those employed in the aerospace and automotive industries.

Mechanical Properties and Microstructure of Thin Plates of A6061 Wrought Aluminum Alloy Using Rheology Forging Process with Electromagnetic Stirring

We propose the possibility of fabricating A6061 thin plates using the rheology forging process. Electromagnetic stirring (EMS) is used to fabricate a semi-solid slurry. A thin plate is formed by injecting the slurry into the forging die. When the punch speed used to compress the slurry is low, turbulent flow occurs. When the punch speed is high, laminar flow occurs, and the solid and liquid phases move simultaneously. For a pressure of 150 MPa or below, incomplete filling behavior and cracks occur. For a pressure of 200 MPa or above, a durable formed product can be obtained. However, the differences between the mechanical properties according to the application of EMS and pressure are slight. The microstructure of the slurry without EMS has an unclear distinction between the liquid phase and solid phase. However, the microstructure of the thin plates formed by using this slurry has a clear distinction between the liquid and solid with respect to the spheroid shapes. The tensile strength and elongation for a thin plate formed with a punch speed of 300 mm/s and pressure of 250 MPa with EMS slurry are 169 MPa and 11.0 pct, respectively. After T6 heat treatment, the tensile strength improves to 305 MPa.

Mathematical modelling of billet casting with secondary cooling zone electromagnetic stirrer

A three-dimensional unsteady coupled mathematical model has been applied to analyse the turbulent flow, temperature fields and macroscopic solidification of molten steel in billet continuous casting with electromagnetic stirring (EMS). Induction currents caused by fluid flow and the stirrer end effect have been investigated. The Lorentz force and Joule heat caused by induction currents have also been taken into account. The application of EMS in the secondary cooling zone results in significant changes in molten steel flow and temperature distribution, and the flow patterns on the horizontal cross-section agree well with the results in other references. Joule heat and Lorentz force are mainly located at the surface layer of the billet and decrease rapidly with penetration depth. The degree of superheat is reduced or eliminated rapidly when molten steel is stirred by EMS, hence is beneficial to generate more equiaxed grains. Stirring intensity is highest in the regions near the two ends of the stirrer. The Joule heat produced by induction has limited influence and can be ignored. The industrial trials showed that the EMS can effectively suppress the central shrinkage cavity and the centre C segregation to improve product quality.

Effects of electromagnetic stirring and rare earth compounds on the microstructure and mechanical properties of hypereutectic Al–Si alloys

In this paper, the effects of rare earth addition and electromagnetic stirring on the microstructure and the mechanical properties of hypereutectic Al–Si alloys have been reported. Hypereutectic Al–Si alloy was prepared using liquid metallurgy route and modified with the addition of cerium oxide. To control the structure, slurry of hypereutectic Al–Si alloy was subjected to electromagnetic stirring before pouring into the mould. It was observed that the addition of cerium oxide (0.2 wt.%) refined the primary silicon particles and modified the eutectic silicon particles. Further, the electromagnetic stirring of the hypereutectic Al–Si alloy reduced the average size of primary silicon particles, from 152 ± 9 to 120 ± 6 μm, and the length of β-intermetallic compounds decreased from 314 ± 12 to 234 ± 10 μm. Similarly, the application of electromagnetic stirring on cerium oxide-modified hypereutectic Al–Si alloy also reduced the average size of primary silicon particles from 98 ± 5 to 76 ± 4 μm and the average length of β-intermetallic compounds from 225 ± 7 to 203 ± 5 μm. Mechanical properties namely tensile strength, ductility and hardness of the alloys were improved with electromagnetic stirring and addition of cerium oxide appreciably.

Numerical Simulation and Application of Electromagnetic Stirring in Ansteel

The numerical simulation and application experiment are used to research the electromagnetic stirring (EMS) in Angang steel company limited. The results show that the stirring effect in side to side position of EMS rolls is better than that in face to face position. And the stirring effect in triples zero patterns are better than that in the double butterfly patterns. The application effect of EMS in Ansteel is obvious. The equiaxed zone in different steel grade such as low carbon aluminum killed steel, pipe steel, silicon steel and high carbon steel is improved 12-25% with EMS. And the slab center segregation has an obvious decreased after using EMS.

Effects of electromagnetic stirring and superheat on the microstructural characteristics of Al–Si–Fe alloy

Semisolid metal (SSM) processing is getting momentum to be the preferred fabrication route for near or net-shaped castings. For SSM processing of Al–Si alloys, there are two important microstructural features which influence the properties of finished products. These are the size and morphology of the primary α-Al phase and the eutectic matrix which consists of silicon, aluminum, and intermetallic phases. The presence of iron is beneficial to reduce the soldering effects in permanent mold castings, but it is unfavorable due to formation of a range of intermetallic phases. The casting parameters play an important role in avoiding the segregation of thin platelets of Fe-intermetallic, which is detrimental to mechanical properties. In this context, it is of particular interest to see the effects of melt stirring on the formation of eutectic silicon flakes and iron-based intermetallics during SSM processing. The effects of process parameters such as cooling rate and superheat are investigated on the morphology and size distribution of eutectic silicon and iron-based intermetallics during application of electromagnetic stirring (EMS). It is concluded that melt stirring not only alters the morphology of α-Al phase to rosette or globule shape, but also refines the eutectic silicon and iron-intermetallics.

A scaling analysis of alloy solidification in presence of electromagnetic stirring

Application of electromagnetic stirring (EMS) during continuous casting shears off the dendrites from the solidification front to produce billets with a non-dendritic microstructure. In the present study, a systematic approach to the scaling analysis of momentum, energy and species conservation equations pertaining to the case of the solidification of a binary alloy in the presence of EMS is outlined. With suitable choices of non-dimensionalizing parameters, the governing equations coupled with appropriate boundary conditions are first scaled, and then the relative significance of various terms appearing in them are analysed. In the physical domain two regions are identified, one where the electromagnetic forces play a dominant role in the momentum equations, and the other where the inertia and viscous effects play major roles. Using the scaling predictions, the influence of various processing parameters on the system variables can be utilized for the selection of appropriate electromagnetic forces to shear off the dendrites from the solidification area. For the sake of assessment of the scaling analysis, the predictions are validated against corresponding computational results.

Recent Topics of Research and Development in Continuous Casting

Three major issues in continuous casting are nonmetallic inclusions, cracking and segregation. By the application of electromagnetic stirring (EMS) in mold the inclusion entrapment by the growing initial solid shell is hindered and the number of inclusions near the surface of slabs is much reduced. By the application of level magnetic field (LMF) the downward liquid flow induced by the exit flow from submerged entry nozzle is much decelerated and the entrapment of large size inclusions inside the slabs is eliminated, which otherwise cause inner defects. Electromagnetic casting (EMC) prevents from the formation of oscillation mark and hook mark, concomitantly eliminates the entrapment of inclusions and bubbles at the hook mark and also prevents from the formation of surface depression and longitudinal surface cracking in hypo-peritectic steels. Resonance-like unsteady bulging with oscillation of molten metal level in mold causes internal cracking and can be prevented by unequally spaced support rolls. Macrosegregation can be reduced by the proper reduction of casting thickness or, in the case of bloom, the minimization of the size of equiaxed solids, which can be realized by the application of EMS.

Semiconductor Crystal Growth by Modified Vertical Gradient Freezing with Electromagnetic Stirring

This paper presents a numerical model for the unsteady transport of a dopant during the VGF process by submerge d heater growth with a steady axial magnetic field and a steady radial electric current. Electromagnetic (EM) stirring can be induced in the gallium antimonide melt just above the crystal growth interface by applying a small radial electric current in the melt together with an axial magnetic field. The application of EM stirring provides a significant convective dopant transport in the melt so that the crystal solidifies with relatively good radial homogeneity. Dopant distributions in the crystal and in th e melt at several different stages during growth are presented.

The mechanism of columnar-to-equiaxed transition during electromagnetic centrifugal solidification

Abstract A series of Hastelloy C tubes were solidified under a centrifugal field with various conditions of bulk liquid flow obtained with a controllable electromagnetic field. Their macrostructures show that the columnar-to-equiaxed transition was promoted both by increasing electromagnetic stirring and by increasing the superheat, and the application of electromagnetic stirring at different times can also influence the percentage of the total area occupied by the equiaxed region. Mechanical damage of dendrites is the most probable mechanism for the promotion of the columnar-to-equiaxed transition with high velocity flows. The detachment of the nuclei originated in the chill zone can also promote the columnar-to-equiaxed transition.