For decades, Primetals Technologies has been refining the roll geometry of continuous casting machines, leading in an increasingly stable mold level during the casting process. The most recent development is a promosing model for establishing the ideal caster roll geometry already at the design stage.
Casting at higher speeds
This solution gives a preview of how the caster will perform during operation, as it simulates both the unsteady bulging effect and mold level fluctuations created by the phenomenon of bulging.
The model enables steel producers to set up new or revamped casters that are made to minimize mold level fluctuations during production. Therefore, they will be able to cast at higher speeds while producing slabs of high metallurgical level.
A steady process during continuous casting is important to produce high-quality products. Bulging is common and occurs as liquid steel at the core of the hot strand pushes against the shell of the slab as the strand moves between two rolls.
During this process, heavy fluctuations in the mold level can emerge, which might cause surface defects, or, in a worst-case scenario, a breakout, in which liquid steel pours out of the shell. Intensified bulging often leads to operators having to reduce the casting speed.
Greater stability and product quality
Unsteady bulging is a complicated problem involving, among other factors, mold level deviations, solidification in the mold, and shell growth in the secondary cooling zone. The newly developed model is designed to consider all these parameters. Utilizing Fourier transform, an advanced mathematical method, Primetals Technologies’ new software tool is capable of including a wide spectrum of parameters such as targeted steel grade, section size, and casting speed in its calculations. In this way, it identifies just the right frequency spectrum needed to set the optimal roll geometry.
Thanks to these simulations, it is possible to improve the distance and diameter of the rolls before installing the equipment. Roll pitches are one of the main aspects causing unsteady bulging, and by optimizing roll geometry, unsteady bulging is reduced by about 50 percent. Over the last months, this achievement was accomplished repeatedly at several steel plants where this solution is already in work.
There are more benefits to be had with the new software model. Minimizing the occurrence of unstable bulging increases the caster’s range to include peritectic and ferritic steel grades, as no reduction in casting speed is necessary. Moreover, smoother strand shells and increased slab-surface quality are garanteed. The optimization of the rolls can be executed also for existing casters implemented by other plant builders.
