Influence of Modified Casting Practice on Steel Cleanliness

Consistently high level of cleanliness needs to be ensured, particularly in grades of steel used for critical applications. In addition, preventing the formation of alumina rich non-deformable inclusions is important in high carbon steels for the deep drawing applications. In the present work, influence of billet caster up-gradation on the overall cleanliness of high carbon steel has been investigated, mechanical characteristics of oxide inclusions evaluated and assessment of the existing deoxidation practice have been done. In general, there has been improvement in the overall level of steel cleanliness due to increasing tundish capacity, submerge pouring of liquid steel and application of in-mold EMS. These measures have effectively controlled the inclusions originating from reoxidation of liquid steel. However, the characteristics of the oxide inclusions generated during the deoxidation process in ladle remained same even after the caster up-gradation. The conventional deoxidation practice was found to generate mostly inclusions of variable compositions and alumina rich non-deformable inclusions, which makes the steel less suitable for very fine wire drawing applications. Appropriate measures have been proposed for further improvement in the inclusion characteristics while processing those grades of steels during the secondary steelmaking.