Brno Dynamic Solidification Models

Utilization of Nonlinear Model Predictive Control to Secondary Cooling during Dynamic Variations

In the continuous casting of steel, there is a variety of dynamic situations, both planned and unplanned. The planned simulations include decreasing the temperature of the steel in the tundish or changing the steel grade. Unplanned situations can be breakout system interventions, equipment failure, etc. These situations can be optimally controlled by means of a modern type of controller-based, fuzzy-based predictive control algorithm by using the 3D non-linear transient temperature field model of the strand. A very fast dynamic solidification model was developed for the purpose to calculate these regulation models it real time. Software implementation and integration to the Level 2 automatization system is presented. Finally, advantages and disadvantages of this method of regulation are shown to the modeling of non-standard situations on a modern slab caster with 17 cooling loops in the secondary cooling zone...

Operational experiences with the secondary cooling modification of continuous slab casting

The surface temperature on the small radius surface in positions of straightening is an important parameter that can influence the surface quality of continuously cast steel slabs. Based on the detailed analysis the replacement of cooling nozzles pertaining to the small radius surface in the secondary cooling was performed on the caster in Evraz Vitkovice Steel due to the requirement on the increase of surface temperatures on the small radius surface of cast slabs. The results and experiences obtained after the replacement of cooling nozzles are compared to long-time operational data for the preceding setup of cooling nozzles that are used on the caster since 1995. The comparison is performed with the use of data acquired from the dynamic solidification model and with the use of the statistical operational data. The optimization of cooling nozzles setup is also discussed in the paper...

CHALLENGES IN NUMERICAL MODELLING OF CONTINUOUS STEEL CASTING – VERY FAST GPU DYNAMIC SOLIDIFICATION MODEL AND ITS USE IN CONTINUOUS CASTING control

Dynamic solidification models of continuous casting are very demanding from the computational point of view. The extensive progress of parallel computing on graphics processing units (GPUs) in last years serves a great opportunity to use GPUs for computing of dynamic solidification models of continuous casting. A GPU, which is usually equipped with several hundred processors, can enable a substantial speed-up of solidification models due to high parallelism. The paper describes the development of the parallel GPU dynamic solidification model with the use of CUDA computing architecture and NVIDIA Tesla GPU. Its computing performance is then compared with commonly used non-parallel models. Consequently, the GPU model is used for model-based predictive control with an emphasis on violent changes in the casting speed. This approach utilizes the GPU model for real-time prediction of the temperature field for various control strategies. The proper control strategy is then chosen according to the evaluation of the thermal behaviour of cast blank and other criteria. The results show that parallel computing and GPUs are great tools to enhance the computing performance of dynamic solidification models. Due to the significant speed up in order of tens, new opportunities for real-time control of casting have become available...

Transient simulation temperature field for continuous casting steel billet and slab

The presented models are valuable computational tools and accurate simulators for investigating transient phenomena in billet and slab caster operations, and for developing control methods, the choice of an optimum cooling strategy to meet all quality requirements, and an assessment of the heat-energy content required for direct rolling. The numerical models of temperature field in the continuous casting are determined via the transient 3D enthalpy balance equation with the Finite Differences Method. The transient simulation is undergoing a non-stop trial run in one operation because steel billets/slabs are produced 24 hours per day. The numerical computation has to take place simultaneously with the data acquisition – not only to confront it with the actual numerical model, but also to make it more accurate throughout the process. It enables a multiple increase in the speed with which the temperature field of the continuous casting is computed – both with the application of more sophisticated software as well as hardware. As a result of this, it will be possible to monitor the formation of the temperature field – in real time – within the mould, the secondary- and maybe even the tertiary-cooling zones, and also to utilize this information for the optimization of the control of the caster as a whole as well as its individual parts. There are examples of the application of the models on the temperature field of a real concast billet and slab on Trinecke zelezarny and Evraz Vitkovice Steel...

New Challenges in Modelling and Secondary Cooling Control of Continuous Steel Casting

In recent years, there is a dominant trend for the utilization of dynamic solidification models in process and quality control of continuous steel casting. A significant effort has been done in case of control of secondary cooling where water and air-mist nozzles are used. Both simple and sophisticated control and regulation methods are nowadays used for the optimal control of secondary cooling. The paper presents our recent development of advanced control methods based on the fuzzy logic and model predictive control approach. Cooling control by means of the cooling curves and of the PID regulator was implemented in order to evaluate the control capabilities of developed tools. The presented control solution represents a combination of a transient multidimensional numerical model of temperature fields for continuous steel casting and advanced control algorithms. The study case with a temporary drop of the casting speed, which is typical in case of the intervention of the breakout prediction system, was used to evaluate control capabilities of presented algorithms. The results show that our control and regulation algorithms are very efficient tool for the continuous casting control. Applicability of the developed algorithms was tested in a Level 2 implementation of ASM Automation Company, which is our sole implementation partner, and robust control behaviour was observed....

Numerical Models of Solidification and their Application in Metal and Ceramic Technology

Solidification (crystallization) phenomena play a major role in such diverse operations as casting, crystal growth, and welding. Solidification proceeds at various rates, which are sometimes far from equilibrium. Thus, the micro-structure obtained is generally not homogeneous and gives rise to variations in composition with position at both small and large scales, which is known as segregation. Solute segregation is important because it leads to non-equilibrium phases, cracks, and other problems, which lower the mechanical properties of the final product. Segregation is classified, according to its scale, as macro-segregation or micro-segregation...

Latest Articles