Rotational Electromagnetic Field Research Articles

Direct chill casting with reversing rotational electromagnetic field

In order to achieve higher qualities of aluminum metal products, fine grain structures of materials are required. It is well known that agitation of a liquid metal during solidification process is effective to promote grain size refinement. In this research, the reversing RMF, i.e., the RMF that reverses rotation direction of an electromagnetic field at regular intervals, was applied to a molten metal pool in a cylindrical container of a round billet of DC casting. Electromagnetic fields generated by the reversing RMF stirrer were measured and compared with simulation results of electromagnetic analysis. The molten metal in the pool caused a clockwise and a counter-clockwise flow by applying the reversing RMF, and the flow field was simulated by a CFD calculation. It was found that the liquid metal was effectively stirred with the reversing RMF, resulting a higher turbulent intensity of the liquid metal. Grain sizes of a billet were measured and a relation between the flows and the sizes were investigated.

Numerical modelling of fluid flows in square billet moulds, using a new nozzle orientation in the presence of an in-mould rotary electromagnetic stirrer

ABSTRACTAn electromagnetic field simulation along with a fluid flow analysis model were developed, to study the effect of the submerged entry nozzle’s (SEN) angle of rotation, together with a rotational electromagnetic field, on the turbulent liquid steel flow within a curved, square mould of a billet continuous caster. The Realisable-k-ϵ turbulence model and the volume of fluid multiphase model were implemented, so as to simulate the effect of turbulent fluid flow on the shape of the top liquid steel meniscus. Similarly, the magnetic induction method was employed for simulating the effects of rotating magnetic fields on the flow patterns developed within the mould region. The predicted magnetic field and fluid flows were validated against previous experimental work. Predicted results demonstrated that fluid flows and the shape of the liquid steel meniscus could be significantly modified by changing the orientation of the SEN’s ports in the presence of a low-frequency rotating magnetic field.

Solidification refining of MG-Si by Al-Si alloy under rotating electromagnetic field with varying frequencies

Abstract Aiming to develop an effective solidification purification process by Al-Si alloy refining method, experiments under rotating electromagnetic field (REMF) with varying frequencies have been carried out. High B/P removal rates under REMF can be confirmed. A primary Si-rich layer formed near the side surface of the sample, while the interior of the sample is mainly eutectic Si/Al. Effect of varying frequency of REMF on alloy structure, size of the primary Si flakes and B/P contents in the primary Si flakes are studied. An apparent segregation coefficient is introduced to describe refining process. The apparent segregation coefficients of B and P are determined to be 0.12 and 0.06 respectively when the frequency of REMF and the cooling rate are10 Hz and 50 mK s −1 respectively.

Influence of lower frequency electromagnetic field on dendritic crystal growth in special alloys

Based on a new developed chemical etching method to special alloys (e.g. Incoloy800H superalloy, GCr15 bearing steel and 1Cr13 stainless steel), the morphology of dendritic crystal growth and its transition to equiaxed crystal in the solidification structure with lower frequency electromagnetic fields were observed and investigated to understand the action mechanism of electromagnetic fields on the solidification of the special alloys. By applying a rotating electromagnetic field (REMF) in the casting of special alloys, the growth condition of dendritic crystals, such as the temperature gradient and concentration of elements in the front of dendritic crystals, have been changed by the forced convection of melt and bring the columnar dendrites to equiaxed dendrites. These phenomena are proved in the morphology observation of the Incoloy800H superalloy, GCr15 steel and 1Cr13 steel by the new developed chemical etching method, and the tips of dendritic crystals are changed from sharp to round. Meanwhile, with the application of REMF, the growing dendrites are broken in the front of dendritic crystals by the forced melt flow. Some of the dendrite fragments are partially remelted to become effective nuclei, and some of them are survived during the solidification process. Finally, a criterion for the dendrite fragmentation under REMF is derived based on the dendrite fragmentation theory of Campanella et al.

Crystal orientation and corrosion resistance of CuNi10Fe1Mn alloy billet under rotating electromagnetic field

CuNi10Fe1Mn alloy billet under rotating electromagnetic field (REF) was characterized in this work. The change of the crystal orientation was first explored by X-ray diffraction (XRD) and scanning election microscope (SEM); the corrosion resistance was done by three electrodes system, and the natural sea water was used as corrosion medium. The results demonstrate that the strongest crystal orientation is transformed from crystal plane (200) to (111); moreover, the crystal plane (111) whose intensity is the strongest on the cross section and vertical section with REF causes the tubes be rolled easily, and the corrosion resistance of the billet is increasing with REF. As a result, properties of CuNi10Fe1Mn alloy tubes can be improved by REF.

Effect of Rotating Electromagnetic Field on Corrosion Behavior of CuNi<sub>10</sub>Fe<sub>1</sub>Mn Alloy Tube Billet

The effects of the rotating electromagnetic field (REF) on the corrosion behavior of the CuNi10Fe1Mn alloy tube billets were investigated by immersion test and electrochemical measurements. It is found that the imposing REF can be used to improve the resulting microstructures which affect the corrosion behavior of the CuNi10Fe1Mn alloy tube billet. The REF could induce the microstructure changes of the CuNi10Fe1Mn alloy tube billets and result in the gains refinement and the preferred orientation on the crystal plane. The improvement of the corrosion behavior is contributed to the change of microstructures of BFe10-1-1 alloy tube billets. The electrochemical measurements and immersion test show that the CuNi10Fe1Mn alloy tube billets with REF increase the corrosion resistance compared with the CuNi10Fe1Mn alloy tube billets without REF. Therefore all these observations suggested a nobler corrosion behavior of the CuNi10Fe1Mn alloy tube billets with the REF.

Effects of Rotating Electromagnetic Field on Solidification Microstructure of ZA27 Alloy

In the present, by using rotating electromagnetic field (REMF) equipment, the effects of REMF for crystal growth processes in cast ZA27 alloy were investigated. It was found that the growth of the primary and secondary dendrites was restrained by alternative REMF and solidification microstructure transformed from dendrite to non-dendrite and globular crystal. The grain refinement effects were further improved with increasing of voltage.

Numerical simulation on electromagnetic field, flow field and temperature field in semisolid slurry preparation by A-EMS

A two-dimensional computational model coupling an annular electromagnetic stirring (A-EMS) with a macroscopic heat and fluid flow analysis in Al-alloys semisolid slurry preparation was developed. The dynamic evolutions of the electromagnetic field, flow field, and temperature field were presented successfully by commercial software ANSYS 10.0 with corresponding experimental verification. A horizontally rotational electromagnetic field and, thereby, a more intensive velocity field were uniformly distributed in the stirred melt even at commercial frequency, and thus, a lower temperature difference in the stirred melt and subsequent uniformly fine microstructures were obtained compared with the normal electromagnetic stirring. The simulation results were in good agreement with experimental ones.

Rotational electromagnetic-field-aided false twisting of metallic filaments

In the present research, a novel method based on previous work is improved to exert false twist of metallic filaments on the basis of a rotational electromagnetic field. Primarily, the effect of the rotational force of a single-phase induction stator on current-carrying conductive filaments is studied. Thereafter, the prototype of the proposed system is designed and tested. The analytical and experimental results prove the capability of the method in false twisting of conductive (metallic) filaments. The proposed method can be employed as a false-twisting box for polymeric conductive and magnetic filaments.

Defect Visualization for Alternating Current Field Measurement Based on the Double U-shape Inducer Array

To meet the demand for defect visualization in alternating current field measurement(ACFM) technique,a double U-shape orthogonal inducer array is introduced.This excitation method induces a rotational electromagnetic field,which effectively avoids the influence of defect orientation on detection and provides sufficient signal data for defect visualization.The inversion methods of surface shape and cross section shape of defect are proposed on the basis of the rotational electromagnetic field.The results of FEM simulation analysis show that the average relative errors of these inversion methods are less than 10%.Verification tests are carried out for these inversion methods by using the ACFM testing system built in the laboratory,and the results prove that these methods are simple and feasible,and can effectively realize real-time defect visualization for ACFM.

Sur la Propagation d’ondes Electromagnétiquesdans un Plasma Froid dans un Champ Electromagnétique enRotation

In a previous paper we presented a calculation of theexpression of the dielectric tensor of a plasma in a rotatingelectromagnetic field. In this paper, by means of the expression ofdielectric tensor, the dispersion relation of a cold plasma ispresented, discussed and compared with the one obtained byKlimontovich for a constant magnetic field.

Quantum theory of electron motion in a cyclic resonant accelerator

The motion of a relativistic electron in a constant focusing magnetic field and a high-frequency rotational electromagnetic field, used to offset the radiative energy loss, is studied on the basis of the Klein-Gordon equation. The solutions found may be used to construct a theory for electron storage rings, in which quantum fluctuations are particularly important.