With MouldScreen, the Continuous Casting Fluxes Division of the S&B Group has introduced a software programme for modelling the properties of the flux film in the continuous casting mould. The software identifies and visualizes critical conditions in the mould that may lead to cracking, breakouts and other quality problems and enables countermeasures to be taken at an early stage.
With MouldScreen it is possible to make retrospect analyses of unclear phenomena, monitor present operating conditions and forecast possible scenarios. The software displays all process-relevant variables, such as shell thickness, temperature field in the strand shell and, by this, the strand surface temperature, local and integral heat flux, heat transfer resistance in the flux film and its thickness (liquid and solid), water temperature in the cooling channels and copper skin temperature.
Unlike other models and calculation methods, the MouldScreen algorithm provides as a direct result the heat transfer resistance (the ratio of flux film thickness vs. its thermal conductivity measured in m²K/W) in the gap. The advantage over other methods is that the heat transfer resistance does not require to be pre-selected by more or less well-founded assumptions.
With MouldScreen it is now possible to immediately assess how the casting process changes in case of varying casting powder properties or changing operating parameters. The results can be retrieved in graphical form immediately upon entry of the process parameters (casting speed, cooling water quantity, mould geometry, casting powder, steel analysis, etc.). The question „What happens when the casting speed, cooling water supply pressure or temperature change?“ will be answered while casting is on-going- i.e. online. Thus it is possible to detect – at a very early stage – critical conditions in the mould and take effective countermeasures.
MouldScreen was originally developed to visualize the behaviour of the flux film between the strand shell and the copper plate. The behaviour of the flux film has major production and quality relevance but is not measureable. On top of that, MouldScreen provides the possibility to couple the thermal model with a mechanical strand shell model. Thus stresses and strains due to thermo-mechanical loading of the strand shell during casting become calculable and more effective and targeted countermeasures can be taken to avoid cracking or breakouts.
As it allows to objectively set the conditions for casting powder infiltration at the meniscus, MouldScreen can avoid breakouts more reliably and help make breakout prediction systems more effective.
A great advantage of the MouldScreen algorithm is that it can be conveniently used for parameter studies and inverse modelling. The „Modify“ tool can either display the current operating state or a variant computed by the tool. It is possible at any time to switch between the modified and the current casting situation by mouse click.
„Modify“ can analyze different operating scenarios for a given mould and display the results in graphical form. Thus the casting process can be immediately assessed in case of variation of powder/slag properties, casting speed, water quantity or even mould design. This information, in addition to the characteristic slag temperatures, makes it possible to determine the solid and liquid fractions in the flux film – a novelty in monitoring the continuous casting process.
For studying different parameter settings, a slide button is provided for varying parameters such as the casting speed – the results will immediately pop up on the screen.
MouldScreen considers aspects such as fluid mechanics, heat dissipation from the inside out, phase transitions, temperature-dependent material properties of the steel, the mould powder or the casting slag. On top of that, machine parameters, temperature, cooling water pressure and quantity, mould oscillation and the formation of oscillation marks are taken into account in the calculation.
For assessing the effect of different design features and operating modes of continuous casting moulds – for example, the material and thickness of the copper plates, casting speed, water quantity – on the behaviour of the flux film, Stollberg developed the „Modify“ tool. For mould powder information, the programme refers to the comprehensive Stollberg internal database.
Background: Computer algebra
MouldScreen is based on an algorithm developed by computer algebra methods. With the help of this new development tool, Stollberg has implemented previously hard to control mathematical approaches to modelling the continuous casting process into an application programme.
This methodology – which is at the interface between mathematics and computer science – is dedicated among others to the development of efficient computing methods. The origin of computer algebra goes back almost 175 years and, since the development of PC technology, it has been increasingly applied to industrial phenomena.
Time-consuming numerical computation loops, adaptive grid definitions, convergence problems and large data amounts are obsolete, providing a reasonable ratio between the programming effort and the overall development effort. This is also reflected in the memory requirements and computation times of the software, both of which are smaller by an order of magnitude compared to common numerics.
The successes achieved in describing the conditions in the area of the meniscus show that computer algebra is a suitable tool to tackle previously hardly controllable formalisms.
About Stollberg of the S&B Group
The Continuous Casting Fluxes Division, part of the S&B Group, provides, through its Stollberg products, full support to the steel industry with a range of products and services covering all aspects of liquid steel casting. It is present around the globe with seven manufacturing facilities and competence centers in Europe, USA, Brazil, India, Korea and China and offers the international steelmaking industry high value added solutions, from process optimization to efficiency improvement during the daily production routine.
Pursuing a holistic approach for the entire process, from tundish and ladle metallurgy via casting of liquid steel in all kinds of techniques all the way through to the cast sections, Stollberg solutions range from high-grade products to complex service and consulting, offering each individual customer a special product or service tailor-made to his particular needs.
Through continuous product development the Stollberg product and service portfolio enhances its position as the leading supplier of casting fluxes, metallurgical slags and covering compounds worldwide. Long-standing cooperation with reputable Universities and Institutes all over Europe, North and South America, and Asia allows Stollberg to stay abreast of industry developments.
Amongst its long-lasting customers: the Arcelor-Mittal-Group, POSCO, TATA-Corus-Group, ThyssenKrupp Steel, Hüttenwerke Krupp Mannesmann, Salzgitter Stahl and voestalpine Stahl. For more information please visit www.sandb.de.
S&B is an international Group of companies with extensive mining, processing and distribution operations and around 2,000 employees in more than 20 countries worldwide and well known products brands like Stollberg, IKO, Otavi, IBECO. S&B develops and transforms natural resources into value-creating industrial solutions for a wide range of applications, i.e. for foundries, the iron and steel industry, construction and civil engineering, environmental applications.
For more information please visit www.sandb.com
S&B Industrial Minerals GmbH, Stollberg Division
Anke Fischer-Lohrengel
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+49 (208) 85005-86
www.stollberg.com
stollberg@sandb.com
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