# Measurement and Model-Based Control of Solidification in Continuous Casting of Steel Billets
## 4 Discussion  
The ConSolCast project dealt in detail with the topic of strand breakouts and surface defects and developed measurement techniques and model-based tools to minimise such casting anomalies. At ESF, this led to the installation of a new operator information and advisory system with an appropriately extended HMI. This approach for online monitoring and control of the billet casting process was focused on the real-time visualisation of  
* Measured casting parameters;
* Simulated 3D temperature field, shell thickness along the strand length and actual crater end position;
* Traffic lights regarding possibly critical or dangerous values for selected casting parameters, shell thickness and crater end position;
* Suggested casting speed and spray water flow rates to adjust a given target crater end position.  
A disadvantage of the implemented traffic light procedure is that a strand may be closed, where a breakout would not occur in each case. However, the advantages of this procedure outweigh the disadvantages, because a real breakout could damage plant components or cause longer downtimes. Thus, avoidance of such possible breakouts or preventing casting failures improves the casting process in terms of  
* Higher machine availability, i.e., productivity;
* Higher safety;
* Lower maintenance costs.  
With the introduction of the traffic light system in combination with the DynSolidCC model-based monitoring and control functions, the breakout rate could be decreased from about 2-3% (which is typical for the industry) to values of about 1-1.5%.  
The recording of the temperatures within the mould could successfully provide measurement data, which were used as a basis for the validation and adaptation of the DynSolidCC mould boundary condition submodel. Additional measurements of strand surface temperatures with an infrared camera allowed adjusting the boundary condition model parameters for the spray water and radiation cooling zones of the caster. Moreover, the measurement campaigns with the laser vibrometer revealed that the simulated evolution of the crater end position fits well with the measured footprint of a completely solidified strand in the recorded vibrational spectra. This finding shall be investigated in the future also for other casting formats and qualities in order to establish a new measurement technique for assessment of the solidification state in a strand during continuous casting processes.  
Conceptualisation, M.S., M.G. and P.F.; Data curation, R.S. and J.B.; Funding acquisition, M.S., M.G. and P.F.; Methodology, M.S., M.K. and W.K.; Project administration, M.S., M.G. and P.F.; Resources, M.S., M.G. and P.F.; Software, M.S., W.K. and J.B.; Supervision, M.S., M.G. and P.F.; Validation, M.G. and R.S.; Writing--original draft, M.S.; Writing--review and editing, M.K., W.K., M.G., R.S., J.B. and P.F. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Research Fund for Coal and Steel under grant agreement no. 799295.  
Not applicable.  
The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.