Study on the Regulation of Electromagnetic Stirring of Liquid Metal.

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The high frequency induction furnace is often used for fundamental studies concerning the molten metals, but it is impossible to change the stirring intensity widely under a constant temperature. This limitation prevents the advancement of the metallurgical kinetic studies. The present study proposes two methods to provide a means of regulating the flow intensity widely based on a conventional induction furnace. The characteristics of the flow regulation have been checked experimentally and theoretically.1. Flow Regulation by Electrically Conductive Rings(1) Method : A ring made from graphite or molybdenum is located between a crucible and a heating coil to absorb a part of the magnetic fluxes which penetrate in a liquid iron and generate the stirring forces. The fraction of absorption can be regulated by the apparent resistivity which is changed by the shape of the ring.(2) Experiments : The measurements of the magnetic flux densities in the furnace and the experiment on dissolution o … More f a graphite rod in a liquid iron have been made. The distributions of the magnetic flux densities and local mass transfer coefficients have been found to change extremely with the change in the resistivity of the ring. From these results, it is concluded that the flow regulation is enabled by using the ring. However it seems difficult to connect the ring to a variable resistance for more convenient operation.2. Flow Regulation by a Secondary Coil(1) Method : A water cooled copper coil (secondary coil) which is connected to an external coil, variable turn numbers, is located out of a crucible near the free surface of liquid iron. The magnetic fluxes near the secondary coil can be changed by changing the turn numbers of the external coil.(2) Experiments : The same experiments as the above ones have been made and the flow regulation by changing the turn numbers of the external coil connected to the secondary coil has been realized experimentally.3. Theoretical StudyThe mutual inductance model is applied to the electromagnetic field in the furnace. The computed results on the magnetic flux densities agree well with the observed ones. The fluid flow and mass transfer in liquid iron have been analyzed numerically on the basis of the Navier-Stokes equation and the conservation equation of carbon in liquid iron. The computed results have supported the capability of the secondary coil methods. Less