Electromagnetic Stirring Research Articles

Simulation and Experimental Study of Fluid Flow and Solidification Behavior in Thin Slabs Continuous Casting Process under Secondary Electromagnetic Stirring

During the thin slab continuous casting process of silicon steel, electromagnetic stirring (EMS) can control the flow, heat transfer, and solidification of molten steel through electromagnetic force. Herein, a 3D mathematical model coupling the fluid flow, heat transfer, solidification, and the electromagnetic field is built. The effects of varied current intensities on the flow, heat transfer, and solidification of molten steel in the thin slab under secondary EMS are explored based on applying the electromagnetic brake in the mold region. In the findings, it is demonstrated that increasing the current intensity increases the flow rate and vorticity of the molten steel in the second cooling zone, eliminating the superheating phenomenon and improving the uniformity of the molten steel's temperature distribution. Meanwhile, based on the nucleation and growth parameters determined from thermal simulation experiments, the cellular automation finite‐element model is used to simulate the microstructure evolution during the solidification of thin slab. In the results, it is shown that the stirring energy increases when the current intensity increases, potentially promoting equiaxed crystal growth and grain refinement. Compared to the production sample, a reasonable qualitative agreement is achieved for the grain morphology, equiaxed crystal ratio, and columnar to equiaxed transition.

X-ray Imaging of Two-Phase Flow Regimes in a Liquid Metal Swirling Downward Flow With Side Wall Gas Injection

The formation and behavior of gas bubbles is experimentally investigated in a liquid metal downward pipe flow, a configuration that largely corresponds to the situation in a submerged entry nozzle (SEN) in the continuous casting process in steel making. The experimental mockup is operated at room temperature using the ternary alloy GaInSn as model fluid. Argon gas is injected through an orifice located in the SEN wall. The gas distribution in the pipe is visualized by means of the X-ray radiography. The set-up is completed by an electromagnetic stirrer, which is used to create a swirling flow in the tube. Depending on the volume flow rates of the gas and the liquid metal, as well as the intensity of the swirl flow generated by the stirrer, 4 flow regimes are observed: (1) the formation of an almost stationary gas pocket in the region below the injection point without any electromagnetic stirring, (2) a twisted void zone along the side wall, (3) a straight void zone in the center of the pipe, and (4) a bubble chain in the core of the pipe flow. The experiments reveal that the wetting conditions at the inner SEN wall have a decisive influence on the resulting flow regime.

Numerical simulation of macrosegregation phenomenon in Cu-6wt%Ag alloy ingots fabricated by electromagnetic stirring

The development and research of high strength and conductivity materials are essential for the advancement of high-field magnets, including pulsed magnets. This study investigates the effect of electromagnetic fields on the solidification casting of binary Cu-6wt%Ag alloy ingots with diameters of 40 and 160 mm. A 3D numerical simulation is performed utilizing the continuum model with conservation of total momentum, mass, energy, and species. The results indicate that applying electromagnetic stirring (EMS) to small cross-section ingots can cause many randomly distributed small regions with higher segregation degrees inside the ingot, which is not conducive to improving the macrosegregation inside the ingot. For large cross-section ingots without EMS, compared to small cross-section ingots, there is more severe macrosegregation inside the ingot, especially the extreme center segregation with a maximum segregation degree of about 414%. EMS can effectively control macrosegregation within a specific range and eliminate center segregation. When the linear EMS's magnetic induction intensity is set to 0.06 T, the maximum segregation degree near the ingot center can be reduced to less than 260%. Simultaneously, the EMS induced forced convection is also instability, leading to numerous haphazard solute accumulations and depletions, which explains many small segregation regions in the ingot. In terms of improving macrosegregation in large cross-section ingots, Linear EMS has a definite advantage over rotary EMS. It is possible to keep the entire segregation degree in the ingot below 100% when the linear EMS's magnetic induction intensity is set to 0.036 T and the stirring frequency is 4 Hz. The ideal stirring parameters range for linear EMS is to maintain the magnetic induction intensity at around 0.036 T and the stirring frequency in the range of 4–8 Hz.

Numerical and Experimental Study on Carbon Segregation in Shaped Billet of Medium Carbon Steel with Combined Electromagnetic Stirring

Carbon segregation is the major and classical internal defect in the continuous casting process of carbon steel. Based on the combined electromagnetic stirring equipment for new billet in a steel plant, China, the influence of combined electromagnetic stirring (M-EMS + F-EMS) on the carbon segregation of 300 mm × 340 mm special-shaped billet was studied via numerical simulation and on-site industrialization tests. The Lorentz force and carbon solute distribution were simulated under different EMS parameters. The formation mechanism of the carbon segregation of medium carbon steel with different combined electromagnetic stirring processes was analyzed. The results show that: (1) with the combined action of “solute flushing” effect and gravity, the carbon concentration in the loose side of the medium carbon steel casting billet is gradually lower than the fixed side, while the carbon concentration on the fixed side gradually accumulates more; and (2) under the action of combined electromagnetic stirring, the segregation index of casting billet could be controlled to remain between 0.96–1.05 and shows an increasing change in solidification from the skin to the center. When the current and frequency of M-EMS are 250 A and 2.0 Hz and the F-EMS are 180 A and 8.0 Hz, the carbon segregation defects in the special-shaped (300 mm × 340 mm) casting billet can be significantly improved.

Effect of Alternating Magnetic Field on the Organization and Corrosion Resistance of 2205 Duplex Stainless Steel Narrow-Gap Laser-MIG Hybrid Weld Head

In this study, an alternating magnetic field is applied in the narrow-gap laser-MIG hybrid welding of 2205 duplex stainless steel with a thickness of 25 mm to achieve the purpose of balancing the ration of the two phases, refining the grains and improving the corrosion resistance. With the help of OM, EBSD, TEM, and other microstructural analysis methods, the organization evolution of a 2205 duplex stainless steel narrow-gap laser arc hybrid weld under the effect of alternating magnetic field is revealed. The corrosion resistance of the welded joints is investigated by electrochemical tests. The results show that the use of a 40 mT applied alternating magnetic field can not only effectively inhibit the generation of porosity and unfused defects in the weld, but also that the addition of an alternating magnetic field improves the ratio of austenite to ferrite in the weld, and the ratio of the two phases is increased from 0.657 without a magnetic field to 0.850. The weld grain preferential orientation is affected by the magnetic field, and the weld austenite grains are shifted from the Goss texture to the Copper texture. Under the electromagnetic stirring effect of the applied magnetic field, the average austenite grain size decreased from 4.15 μm to 3.82 μm, and the average ferrite grain size decreased from 4.99 μm to 4.08 μm. In addition, the effect of the alternating magnetic field increases the density of twins in the organization. Electrochemical test results show that the addition of an alternating magnetic field increases the corrosion potential by 75.2 mV and the pitting potential by 134.5 mV, which indicates that the corrosion resistance of the cover-welded specimens is improved by the effect of an alternating magnetic field. The improvement in corrosion resistance mainly depends on the austenite grain refinement and the increase in the austenite content.

Multi-physical fields distribution in billet during helical electromagnetic stirring: A numerical simulation research

Multi-physical fields distribution in billet during helical electromagnetic stirring: A numerical simulation research

Improving Weldability of Press Hardened Steel Through Combining Stepped Current Pulse and Magnetically Assisted Resistance Spot Welding Process

Abstract Press-hardened steel (PHS), characterized by its extremely high strength, has wide applications in vehicle body manufacturing as an innovative lightweight material. Nevertheless, the poor weldability of PHS results in poor weld toughness and a high risk of interfacial fracture (IF), posing challenges to the resistance spot welding (RSW) process. Introducing an external magnetic field in the welding process to perform electromagnetic stirring (EMS), the magnetically assisted RSW (MA-RSW) process has been proven an effective method to improve the weld toughness of high-strength steel, but it may increase the risk of expulsion. In response to these challenges, this study introduces a new process called SPMA-RSW to improve the weldability of PHS by combining MA-RSW and the stepped-current pulses (SP) technique, which can enlarge the weld lobe. Nugget appearance, microstructure, microhardness, and mechanical properties were systematically investigated by comparing traditional RSW, MA-RSW, SP-RSW, and SPMA-RSW. The result showed that the SPMA-RSW process would significantly increase the nugget size, inhibit the shrinkage voids, finer the grain size of PHS welds, and harden the nugget region. This increased the lap-shear strength and changed the fracture mode from brittle IF mode to ductile plug fracture (PF) mode at the same heat input. Specifically, the peak load and energy absorption were increased by 32.3% and 84.2%, respectively. Then, an analytical model was developed to reveal the mechanism of the effect of EMS on the fracture mode transition and was verified by experiment. This work can help improve the weld quality and thermal efficiency of the RSW process for PHS.

Multiphase Solidification Modeling of Solidification Structure Evolution and Macrosegregation of Round Bloom Continuous Casting Process with Mold Electromagnetic Stirring and Final Electromagnetic Stirring

Based on Eulerian–Eulerian method, a 3D/2D multiphase solidification model, which takes into consideration the heat transfer and fluid flow with grains nucleation and crystal growth, is developed to predict the macrostructure evolution and macrosegregation in continuously cast round bloom. The results show that the mold electromagnetic stirring (M‐EMS) can accelerate superheat dissipation and promote grain nucleation, but the horizontal swirl induced by M‐EMS has a strong washing effect on the solidification front and leads to subsurface negative segregation. When the M‐EMS current intensity increases from 200 to 300 A, the subsurface negative segregation ratio decreases from 0.935 to 0.875. The final electromagnetic stirring (F‐EMS) not only improves the center segregation, but also leads to the formation of negative segregation zone near the round bloom center due to the enhancement of solute washing induced by F‐EMS. As the F‐EMS current intensity increases from 150 to 300 A, the center segregation ratio decreases from 1.148 to 1.075, and the negative segregation ratio near the strand center decreases from 0.985 to 0.977. Another phenomenon is found that the nucleation of equiaxed grain ahead of columnar tips restrains the solute diffusion and leads to a local macrosegregation in columnar‐to‐equiaxed transition zone.

The effect of electromagnetic stirring on processes of alloy crystallization and the macro- and microstructure of continuously cast billets for production of pipes which are resistant to hydrogen sulfide

The effect of electromagnetic stirring on processes of alloy crystallization and the macro- and microstructure of continuously cast billets for production of pipes which are resistant to hydrogen sulfide

Effect of electromagnetic stirring current on the mechanical properties of Cu-15Ni-8Sn alloy and its mechanism of inducing dendrite refinement and Sn distribution homogenization

A Cu-15Ni-8Sn alloy was prepared by electromagnetic stirring (EMS) based on the traditional melting casting method. The effects of electromagnetic stirring current on the dendrite structure characteristics, Sn element distribution, tensile strength, and elongation of the Cu-15Ni-8Sn alloy were studied, and appropriate electromagnetic stirring current parameters were selected. The relationship between the characteristics of the precipitated phase and the orientation of the matrix under the electromagnetic stirring current was analyzed, and the mechanism of fine crystal strengthening induced by the electromagnetic field was discussed. The results showed that EMS was beneficial for dendrite thinning. As the stirring current increased from 0 A to 140 A, the dendrite structure gradually changed to a rosette structure. When the stirring current was 30 A, the minimum secondary dendrite spacing was approximately 35.18 µm, and the grain boundary width was reduced to approximately 10 µm, The Sn element fluctuation range in the matrix was also the smallest, and the precipitate phase was dominated by the CuNi2Sn phase, which had a coherent relationship with the matrix. At this time, the tensile strength and elongation of the alloy were 520.82 MPa and 9.72 %, respectively. The forced flow caused by EMS promoted the temperature field in the melt to become uniform and inhibited the growth of dendrites. The flow of high-temperature molten liquid led to the remelting of dendrite arms, which produced a large number of dendrite fragments, refined the dendrites, and significantly improved the mechanical properties of the alloy.

Phase-field simulation of the dendrite growth in aluminum alloy AA5754 during alternating current electromagnetic stirring laser beam welding

Electromagnetic stirring is known to promote material flow, reduce porosity, uniform elements distribution, and refine grain in laser beam welding (LBW), which enhances the applicability of LBW in various industries. In this study, a phase-field model of dendrite growth in AA5754 Al alloy electromagnetic stirring laser beam welding was established. The model considered the thermal electromagnetic Lorentz force resulting from the interaction between the electric field generated by the Seebeck effect and the magnetic field, as well as the temperature gradient and solidification rate of the solidification interface obtained from the computational fluid dynamics electromagnetic stirring LBW model. The variation rules of dendrite growth with different magnetic parameters and effects are analyzed. Comprehensively, the magnetic field promotes the solidification rate, thus promoting interfacial instability and a large magnetic flux density leads to a faster interface instability. The solidification rate as well as the temperature gradient affect the growth rate, and the accelerated growth caused by the solidification rate with a high frequency and a large magnetic flux density effectively inhibits the slow growth caused by the temperature gradient. The thermal electromagnetic Lorentz force is the main factor for the branch increment at low frequencies, while both thermal electromagnetic Lorentz force and temperature gradient increase the number of branches at high frequencies. The calculated average branch numbers considering various factors in the stable stage under different magnetic parameters were consistent with the results of the scanning electron microscope tests.

Effect of electromagnetic stirrer centered outside the mold on steel flow field of bloom continuous casting

Effect of electromagnetic stirrer centered outside the mold on steel flow field of bloom continuous casting

Effect of magnetic field assisted thermal diffusion on microstructure and properties of titanium alloy laser cladding coating

Ti–Al composite coating was prepared on the surface of a titanium alloy by the laser cladding technology and coaxial powder feeding under argon protection. The cladding material was AlSi10Mg aluminum alloy powder. The intermediate sample was thermally diffused at high temperature for 6 h and then placed in a certain intensity of the alternating electromagnetic field until completely cooled. The alloy substrate and coating solidified under the action of the alternating electromagnetic field, and the surface coating of a high strength titanium alloy was obtained. The morphology and microstructure of the composite coating were analyzed by SEM, XRD, and energy dispersive spectroscopy (EDS), and the hardness of the coating was measured. The results showed that the high temperature thermal diffusion promoted the interatomic diffusion; repaired some defects, such as cracks and pores; and eliminated the elemental metals that did not participate in the reaction, and the surface hardness of the coating joint reached the maximum. The electromagnetic stirring makes the titanium alloy coating and substrate bond well, the joint is relatively straight, the number of cracks and pores is obviously reduced, and the comprehensive performance of the coating is improved.

Study on Stirring Effect of Spiral Magnetic Field in Continuous Casting of Round Blooms

Herein, for the continuous casting of round blooms with strand electromagnetic stirring, the effects of rotating magnetic field (RMF) and spiral magnetic field (SMF) on the electromagnetic, fluid flow, heat transfer, solidification, and macrostructure are investigated by numerical simulation and industrial experiments, respectively. The results show that the molten steel flows in a spiral shape along the casting direction with the RMF and SMF. Due to the influence of secondary flow caused by electromagnetic stirring (EMS), and the zone of high velocity of molten steel accounts for 13.7% of the whole stirring range with the RMF. The SMF has a strong stirring effect in the whole range of secondary flow, the zone of high velocity of molten steel accounts for 49.1% of the whole stirring range, and the liquid fraction of the SMF at the liquid core is also lower. The results of the industrial experiments prove that the SMF has a wider stirring depth than the RMF, and the center crack range is significantly reduced.

Effect of magnetic alternate stirring on solidification structure of the round billet

ABSTRACT In this study, a permanent magnet stirrer was constructed for the implementation of experiments on different magnetic field stirring modes. Through experiments, it can be observed that when the fixed speed of 200 rpm and the alternate stirring mode of magnetic field was adopted, the loose area in the core of ingots was reduced from about 72 mm2 to 21 mm2, which significantly improved the density and element uniformity of the ingot. A Φ220 mm SAE1527 round billet was selected as industrial trial steel. When the stirring current and frequency was 350 A and 3 HZ, the electromagnetic stirring of the mold was adjusted from continuous stirring to alternate stirring mode. The solidification structure of the billet has been improved to a certain extent. Furthermore, the number of spot segregation larger than 0.5mm2 was reduced from 43 to 26, thereby improving the uniformity of internal elements in the billet.

Effect of Final Electromagnetic Stirring on Internal Thermal Stress, Strain and Cracking of Continuous Casting Bloom

Effect of Final Electromagnetic Stirring on Internal Thermal Stress, Strain and Cracking of Continuous Casting Bloom

Effect of electromagnetic stirring on the transient flow, solidification and inclusion movements in the continuous casting slab mold

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.

Numerical and Experimental Study on Carbon Segregation in Square Billet Continuous Casting with M-EMS.

Electromagnetic stirring (M-EMS) has been extensively applied in continuous casting production to reduce the quality defects of casting billets. To investigate the effect of continuous casting electromagnetic stirring on billet segregation, a 3D multi-physics coupling model was established to simulate the internal heat, momentum, and solute transfer behavior, to identify the effect of M-EMS on the carbon segregation of a continuous casting square billet of 200 mm × 200 mm. The results show that M-EMS can move the high-temperature zone upward, which is favorable for the rapid solidification of the billet, and can promote the rotational flow of the molten steel in the horizontal direction. When the electromagnetic stirring current is varied in the range of 0-500 A, the degree of carbon segregation first decreases and then increases, with the best control of segregation at 300 A. In the frequency range of 3-5 Hz, the degree of carbon segregation degree increases with frequency. Meanwhile, the simulation and experimental results show that 3 Hz + 300 A is the best electromagnetic stirring parameter for improving the carbon segregation of casting billets with a size of 200 mm × 200 mm. So, a reasonable choice of the M-EMS parameters is crucial for the quality of the billet.

Influence Of External Magnetic Field On Mechanical And Metallurgical Properties Of Pressure Vessel Steel (Sa 516 Grade 70) Welds Using Gas Tungsten Arc Welding

Abstract The mechanical and metallurgical properties of weld play the most important role in the performance of welds which needs to be enhanced. The superimposing external magnetic field to the welding arc provided wonderful and favourable results for improving the shape and properties of weld. In this research, different configurations of specially designed electromagnets were used to investigate their effects on weld characteristics of SA 516 grade 70 welds. It is observed that 0-0-S-N configuration yielded maximum penetration (3.92 mm) compared with other configurations as well as the conventional gas tungsten arc welding (GTAW) process. Tensile test, Charpy impact test and microhardness were performed to investigate the mechanical properties and microstructure analysis was used to determine the metallurgical properties of the weld joints. The result shows that the tensile strength, impact strength, and microhardness of magnetically controlled GTAW (MCGTAW) weld was 620MPa, 275J and 198HV respectively which is 3.16%, 22.76%, and 1.51% higher than weld produced by GTAW process. It has also been observed that electromagnetic stirring refined the microstructure of the weld pool. The average grain size of MCGTAW weld was 31.035µm whereas 42.558µm average grain was obtained in conventional GTAW weld. The electromagnetic stirring enhanced the weld cooling rate resulting formation of more acicular ferrite which is desirable.

Effect of Stroke Length (50 mm and 100 mm) on the Dry Reciprocating Wear Characteristics of Refined and Unrefined A390 Alloy

The present work reports the influence of stroke lengths viz. 50 mm and 100 mm on the reciprocating wear characteristics of refined and unrefined hyper eutectic aluminium silicon alloy (A390). The refined A390 alloy was prepared through the electromagnetic stirring process along with the addition of 0.1 wt.% Al–5Ti–B grain refiner. The wear tests were performed in an indigenously developed pin on reciprocating plate tribometer conforming to ASTM G 133-05 standard. The microstructure had shown the refinement of eutectic silicon and decrease in size of polyhedral primary silicon particles due to the combined action of grain refiner addition and electromagnetic stirring. Refined and unrefined A390 alloys were heat treated under T6 condition. Hardness of the refined A390 alloy (107 BHN) was higher than that of unrefined A390 alloy (89 BHN). Reciprocating wear tests were conducted at two stroke lengths with contact loads varied from 15 N to 60 N and the linear velocity from 0.2 m/s to 1.0 m/s for a constant sliding distance of 350 m. During the wear tests it was observed that as the velocity varied from 0.2 m/s to 0.4 m/s the wear loss was found to decrease at both stroke lengths tested for refined and unrefined samples, further increase in velocity increases the wear rate. As the stroke length varied from 50 mm to 100 mm the wear loss was found to decrease for both refined and unrefined alloys. This reduction in wear loss with increase in stroke length was due to the reduced reversals of load happening at larger stroke length (100 mm) also the frequency of reciprocation is high at 50 mm stroke length compared to that at 100 mm for the similar sliding conditions tested.