EMS(electromagnetic stirrer)

ELECTROMAGNETIC STIRRING IN CONTINUOUS CASTING PROCESS The application of electromagnetic stirring (EMS) technique promotes the formation of an equiaxed crystallic zone in the strand. It causes the refinement of the solidification structure, the reduction in the content of inclusions and improvement in the quality of the surface, sub surface and the inner structure of the cast product. Principle of electromagnetic stirring It is well known that an alternating magnetic field (B) (either single phase, two phase or three phase) applied to a conductor, whether solid or fluid, will induce electric current (j) in the conductor, and hence there is a force (F = j x B). This force is known as Lorentz force. Due to the Lorentz force there is a generation of a torque that gives the liquid steel a rotational movement. The generated torque depends on the following factors. Intensity of supply current Number of windings forming a coil Frequency System geometry These parameters change depending on the stirrer type. Thus the magnetic field acts as a non intrusive stirring device and it can, in principle, be engineered to provide any desired pattern of stirring. The stirrer design, size and position etc. depend on the continuous casting machine data, the steel grades to be produced and the casting parameters. Electromagnetic melt stirring systems create a rotating magnetic induction field with an induction of B, which induces eddy current j in a direction perpendicular to B, whose velocity is v. Induction B and current j create the electromagnetic force, which works on every unit of volume of steel and bring about a stirring motion in the liquid steel. The vector product (v x B) demonstrate a connection between the electromagnetic field and the flow of the liquid steel. The speeds of th