Continuous Casting of Round Bloom Strands with Mould-Electromagnetic Stirring; Numerical Simulations with A Full Coupling Method

In the continuous casting of round bloom strands electromagnetic mould–stirrers (M‑EMS) are often employed to enhance the flow inside the strand. It is well known, that the flow in the liquid core of the strand strongly influences the quality of the end product. With M‑EMS optimal velocities at the solidification front can be achieved. These velocities further the transition from columnar to equiaxed solidification as well as reducing the number of surface and sub-surface defects among other benefits. Therefore M-EMS is used at the steel plant of voestalpine Stahl Donawitz GmbH & Co KG for the majority of products. In the present work the electromagnetic stirring is studied by means of numerical simulations. Due to the harsh environment at the steel plant measurements are difficult to perform. Physical 1:1 scaled models of the casting process can not be used because the conductivity of water is too low. If liquid metals are used, measurements are getting rather complicated due to the opacity or the required treatment of the metals. Thus numerical simulations are very important to gain a better understanding of the whole process. The presented numerical model considers the full coupling between the flow field and the magnetic field. Each part of this multiphysic problem is simulated with an optimal solver. While the flow field is calculated with FLUENT, a commercial finite volume CFD code, the electromagnetic field is calculated with ANSYS EMAG, a commercial finite element solver. This approach enables the study of various parameters and their influence on the flow field and solidification structure. It will be shown how variations of the stirring frequency and stirring strength affect the flow inside the liquid core. With the help of numerical simulations the knowledge about the continuous casting process with electromagnetic stirring can be deepened and optimizations of the process found.