Improving productivity and quality in thick slab casting by direct control of FC mould

Abstract

An Electromagnetic Brake (EMBR) makes it possible to increase the casting speed while maintaining or even improving the product quality. For conventional slabs, the FC mould is most appropriate while for thin slabs, the ruler type EMBR is the preferred solution. The FC mould features two independently controlled static magnetic fields, one at meniscus level and another at the bottom of the mould. The upper field controls the speed flow at meniscus to prevent mould powder entrapments and the lower field reduces the penetration of the steel jets from the casting nozzle, to facilitate flotation of inclusions. The FC mould is the only equipment capable of controlling these parameters independently. It affords effective solutions to reduce pinholes, cracks and surface or subsurface inclusions. A new closed loop control of the FC mould, the EM Control, has also been developed, based upon the input of two meniscus level signals that simulate the meniscus speed. Through 3D transient modelling of the caster performance, temperatures, steel speed, meniscus level are made available. The two static fields are then adapted on-line to achieve both low penetration and a constant meniscus speed.