Salzgitter Flachstahl GmbH is the first company in the world to use the new “Mould Screen” software from S&B Industrial Minerals GmbH for modelling the behaviour of the flux film in the continuous casting mould. Mould Screen recognizes unfavourable conditions in the mould that may lead to poor quality or disruptions to the casting process, for example through breakouts. It alerts the operators to critical operating conditions, enabling them to take timely and objective action.
Mould Screen calculates the behaviour of the flux film between the strand surface and the mould plates – which so far had not been measurable in any way – and displays it graphically on a screen.
First tests performed at Salzgitter at the end of 2011 and in spring 2012 had convinced the operators that Mould Screen would be able to visualize the behaviour of the flux film in an unprecedented, reliable manner. In a test phase, it is now being investigated how Mould Screen can be used under real production conditions. The system was installed on one of Salzgitter”s continuous casters at the end of October 2012 and has been in 24/7 operation ever since. The tests are being accompanied by the Technical University RWTH Aachen within the framework of a diploma thesis.
For the tests, Salzgitter Flachstahl GmbH integrated the Mould Screen computer into the PLC system of its continuous casting line No. 4 and into the existing software environment. Mould Screen receives the measured data online, processes them and displays the results in real time.
Mould Screen answers questions like “What happens when the casting speed, cooling water rate, the supply pressure or temperature change?” on the spot. For example, by objectively setting the conditions for casting flux infiltration at the meniscus, Mould Screen can improve the efficiency of breakout prediction systems and help avoid the resulting damage. First investigations have shown that Mould Screen can, for example, reduce the number of false sticker alarms.
Furthermore, the model can provide new, so far unavailable information on strand shell formation, which may serve as a basis for further optimization of existing models.
The user can choose between a display of the current state of operation or the simulation of various operating scenarios computed by the “Modify” tool. Additionally, it offers the possibility of reviewing and explaining unclear phenomena from the past by evaluating historical data.
Mould Screen displays all process-relevant variables, such as strand shell thickness, the temperature field in the strand shell and, by this, the strand surface temperature, the local and integral heat flux, heat transfer resistance in the flux film and the flux film thickness (liquid and solid), the water temperature in the cooling channels as well as the surface temperature of the copper plates. In the computation, Mould Screen considers aspects such as fluid mechanics, heat dissipation from the inside out, phase transformations, temperature-dependent material properties of the steel, as well as the properties of the casting flux. On top of that, machine parameters, the temperature, pressure and quantity of the cooling water as well as mould oscillation are taken into account in the calculation.
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