Electromagnetic processing of materials is newly proposed to be considered as one of the engineering fields where functions of electromagnetism are utilized for processing electrically conducting materials, such as liquid metals, electrolytes and plasmas. The background requiring this processing, the engineering characteristics supporting it and details of the birth of electromagnetic processing of materials are described. The applicable functions of electromagnetism to material processing are revealed in the cases adopting direct magnetic field, high frequency alternating one and traveling one, respectively. The existing processes and the proposed ones are classified into utilized functions and engineering applications are discussed.
Closed form solutions as well as Finite Element, Volume Integral and Boundary Integral numerical methods are reviewed from the viewpoint of electromagnetic confinement system analysis. Particular attention is given to the use of Boundary Integral methods to obtain a self-consistent solution of the electromagnetic field equations when the conducting body is molten metal with a free surface. The application of Finite Element and Volume Integral methods to confinement problems involving an assumed free surface contour is reviewed. Closed form solutions that conveniently yield upper bound estimates of confinement and stirring forces are discussed. A 2-D electromagnetic casting system is used to focus the discussion of the various methods. Numerical methods (e. g., Fast Fourier Transform, eigenvalue decomposition, Preconditioned Conjugate Gradients) that are useful in the analysis of confinement problems are discussed. Free surface profiles for several 2-D applications are presented. Suitable methods for 3-D confinement problems are briefly discussed. A substantial reference list is included in the paper.
2) MADYLAM, E. N. S. H. M. G., Institut National Polytechnique de Grenoble, 38402, Saint-Martin-d'Heres CEDEX, France. A theoretical analysis has been made to clarify the stability condition of Horizontal ElectroMagnetic Casting (HEMC) by means of the linear stability theory. The stabilities of thin plates and round rods of molten metal are analyzed when infinitesimal perturbations are added on the free surface of the levitated metal. Anisotropic influence of imposed magnetic field on the stabilization of perturbated surfaces is confirmed. A critical wave length which distinguishes stable condition from unstable one is 0.02 m for molten steel with the applied current density of 106 A/m2. This length practically limits the distance between a metal supply nozzle and the solidified part of the metal.
In this paper, a modeling methodology is described which permits the computation of the cross-sectional geometry of a two dimensional column of perfectly conducting liquid in the presence of a magnetic field imposed by specified configurations of source conductors. The description is self-consistent in the sense that the column geometry results from a magnetic pressure corresponding to a magnetic field determined by the column geometry. Solutions are obained by iteratively calculating the magnetic field structure for a given column geometry and source conductors, and then calculating a new column geometry based on the magnetic stresses, surface tension, and pressure jump at the liquid-air interface. This loop is continued until a self-consistent solution is obtained. A quadrupole source magnetic shaping problem solved by Shercliff ushing conformal mapping is duplicated using the methodology described in this paper. The results obtained are in good agreement with those published by Shercliff. In addition, results are shown for arbitrary shaping problems, including levitation of horizontal columns, that are too complex for analytic solutions.
In twin roll casting process, two difficulties must be conquered. One is the formation of a wide molten metal film and the other is the controlling and stabilizing of flow between two rolls. Regarding the first problem, application of an alternating magnetic field on molten metal film is proposed. In order to confirm this idea, the effect of a high frequency magnetic field on suppression of film shrinkage is calculated by use of a mathematical model. This model based on water model experiments has been developed to take into account the magnetic pressure acting on molten metal films. The second problem is tackled with imposing a direct magnetic field. It is found that the surface wave on the molten metal puddle between two rolls causes a saw edge shape and that magnetic field can suppress the saw edge shape by experiments using tin. The effect of magnetic field intensity on suppression of saw edge shape is evaluated.
A mathematical representation has been developed to describe the three-dimensional velocity and temperature fields in shallow tundishes to be used in novel continuous casting systems. Particular attention has been paid to the effect of externally imposed magnetic fields in modifying the flow. It was found that the imposition of vertical or horizontal fields may play an important role in minimizing flow non-uniformities and hence variations in the temperature of the stream entering the mold of the caster. In the absence of (magnetic) flow control arrangements, serious flow and temperature maldistribution may occur, especially in the production of wide strip or thin slabs. The effect of magnetic fields on inclusion removal has also been investigated, but the inclusion removal efficiency of shallow tundishes is thought to be low in any case.
The magnetohydrodynamic (MHD) behaviours of liquid metal located in AC magnetic field are studied both by the simulation experiments using mercury and by the numerical analyses. By imposing AC magnetic field on a mercury pool, (i) the meniscus shapes convexity, (ii) the characteristic flow pattern is generated, and (iii) the ferrostatic pressure gradient decreases below the meniscus. Based on the results of this fundamental study, a novel application of electromagnetic field has been proposed to control the early solidification phenomena in the continuous casting mold for steel. The simulation experiments of continuous casting of billet, in which Sn-10%Pb alloy is continuously cast with a stearic acid substituting for a mold flux, has been conducted by using the same type of electromagnetic field as above at the early solidification region. Consequently the depth of oscillation marks on the surface of billet is reduced remarkably. In addition to this, the change of morphology of the cast structure from columner to equiaxed has been observed.
The paper summarizes the develo0ment of a two-dimensional (axisymmetric) and a three-dimensional mathematical model for electromagnetic casters of the two types used in the aluminum industry, which may soon be applied to other metals. A physical model where liquid metal is simulated by Wood's alloy is described and measurements of magnetic field, electric field, meniscus deformation and melt velocity reported. Some of the measurements are compared to the predictions of the 2D model and found to yield approximate agreement.
Conducting downward longitudinal stirring by the use of linear-motor type In-mold Electromagnetic Stirrer (M-EMS), it was possible to control the molten steel flow within the mold and to reduce inclusions and pinholes at the inside t/8 accumulation zone of the curved-type slab continuous caster. The reason have proved from the investigation of flow pattern in the mold and three-dimensional flow analysis; that is the M-EMS downward longitudinal stirring reduces the penetration depth of outlet molten steel flow from the nozzle and decelerates the flow-rates at the meniscus.
A three-dimensional mathematical model has been developed to analyze the heat transfer and the fluid flow in the continuous casting mold with electromagnetic brake. For verification of the mathematical model, the comparison of the flow field between the experimentally measured and computed results has been done under the isothermal condition. The theoretical predictions of the temperature field and heat transfer phenomena are compared and discussed with experimental results.
In continuous casing of steel, control of the teeming rate of steel from the tundish to the mold is carried out by changing the cross-sectional area of the flow channel by means of a stopper or slide gate. However, nozzle clogging or air suction occasionally occur in the controlled section, and this interferes with the degree of control of the teeming rate of steel or deteriorates the cleanness of the steel. To improve this conventional method, some methods using a linear motor-type electromagnetic stirrer were proposed or tested, though, these methods are not yet practicable because of the difficulty of using a linear motor-type stirrer for control of the teeming rate of steel. In contrast, a rotary type stirrer is considered to be more suitable to the control of the teeming rate molten steel, because a higher intensity of stirring can be obtained through shorter affected zone by the rotary-type stirrer than by a linear motor-type stirrer. On the basis of this idea, an electromagnetic valve using rotary-type stirrer was devised, and a series of experiments using low melting-temperature metal and molten steel were carried out to investigate the characteristics of the control and to improve the design of the electromagnetic valve. By increasing the rotational speed, the flow rate was reduced to about half of that of non-stirring when the depth of the molten steel in the tundish is 500 mm. The response of control was quick enough to apply it to steel or another high melting-temperature metal teeming as a non-contact control method.