Introduction

Continuous casting is one of the most significant developments in the technology of steelmaking. A ladle containing 300 tons of molten steel at 1600^oC can be cast into approximately 60 minutes in a semi-finished product like bloom, billet and slab. It reduces energy consumption, material handling and as a result lead to increase in plant productivity. In addition continuous casting offers the possibility to integrate the hot strip or blooming mill by direct hot charging. In recent years considerable developments have taken place both in conventional continuous casting to improve the product quality and to develop new technology to produce nearly finished products. Some of the developments are briefly described.

Electromagnetic Stirring(EMS)


EMS is an electric method of inducing motion in liquid steel without using any mechanical device. In continuous casting EMS can be applied in mold and secondary cooling zone to

• Decrease segregation and porosity
• Improve steel cleanliness by forcing inclusions to float on the surface where they can be absorbed by a slag
• Improve the steel quality in terms of reducing the defects

Stirring induced by EMS modifies the flow pattern of molten steel of the solidifying strand. Improved stirring reduces segregation. Because of the imposed stirring, the superheat of the melt can be quickly dissipated which results in modification of structure of the solidifying strand from columnar to equiaxed and then to globular structure.

EMS allows to increase the casting speed which increases productivity of the caster.

An inductive electromagnetic stirrer is the stator of an asynchronomous motor, the rotor of which is the liquid core of the solidifying strand. This stator produces either a rotating or travelling magnetic field B, which induces eddy current J, perpendicular to B and its velocity vector. B and J combine together to create an electromagnetic force which causes stirring in the bath. The mains frequency is usually used for stirring billets or small blooms beneath the mold . In secondary cooling zone low frequency (1 to 20Hz0 is required to electromagnetically stir the liquid steel of the solidifying strand because the thick solid steel shell shields the magnetic flux.