SIMETAL 3D Sprays allow a flexible adjustment of the cooling nozzles during the entire casting process. The nozzle positioning is carried out in such a manner that the slab center is adequately sprayed and cooled. Furthermore the system determines the best nozzle distance to the slab corner to avoid overcooling of the corners. Thus a uniform temperature profile over the entire slab is achieved even by adjusting of the slab width.
Drive and nozzle arrangement
Continuous casting must satisfy strict dimensional and quality criteria to enable subsequent processing for the foreseen product applications. The challenge is to achieve a uniform water distribution and thus a homogeneous temperature profile over the slab width. The casting of variable slab widths complicates the cooling process when a conventional spray-nozzle arrangement is used. Conventional systems are characterized by rigid nozzle positions and by two separate nozzle-control loops – this means a reduced water flow at the slab margins compared with the slab center and an inhomogeneous temperature profile and varying mechanical properties of the slab may result. Such systems are therefore always a compromise between the ability to control the slab corner and slab center temperatures. Furthermore, since the nozzle positions are fixed, only a step-wise cooling control is possible. The formation of transverse corner cracks during continuous casting frequently occurs as a result of overcooling in the strand-corner areas where the heat transfer is two dimensional.
Siemens VAI has developed a moveable nozzle arrangement which allows the nozzle position in relationship to the slab width to be adjusted. This is accomplished by raising or lowering the nozzle arrangement in a slanted direction according to the spray angle. The nozzle positioning is carried out in such a way that the slab center is adequately sprayed and cooled and that a defined distance to the slab corner is maintained to avoid overcooling of the corners. Each strand segment is controlled by its own spray width adjustment controller. The SIMETAL 3D Sprays are linked with the SIMETAL Dynacs secondary cooling model which enables an online determination of the strand temperature. Since the spray area is no more constant with SIMETAL 3D Sprays an optimum combination between casting width and speed can be found in order to optimize total spray water and air consumption. An optimized heat removal from the strand is a key issue in the continuous casting process. Using SIMETAL 3D Sprays an even temperature profile over the whole slab width can be achieved. The first industrial application took place in July 2006 at a newly commissioned slab caster for a Korean steel producer.