Introduction: The Future of Casting Simulation with THERCAST®
In modern steelmaking and foundry engineering, numerical simulation has become an essential tool for developing and optimizing casting technologies. European steel companies are currently facing increasingly aggressive competition on their own markets, while several key industrial sectors, such as the automotive industry, are experiencing significant slowdowns that reduce production volumes. In this context, although various support and protection measures are being implemented at the European level (tax adjustments, industrial aid, etc.), a decisive strategy remains the optimization of existing processes. Innovation and the reduction of development and time-to-market cycles for new steel grades are crucial.
Simulation represents a powerful means to achieve these goals, as it allows engineers to virtually explore and optimize complex casting operations that are difficult to observe directly (for instance, temperature gradients, defects, bubble formation, or solidified shell thickness in continuous casting). By enabling virtual design before physical trials, simulation reduces development errors, costs, and lead times while helping identify the origins of defects that are often invisible in real conditions.
THERCAST®, developed by Transvalor, is a leading 3D simulation software for casting processes. Using the finite element method, it models the thermomechanical phenomena occurring during mold filling, cooling, and solidification. The software provides detailed insights into metal temperature evolution, mold and core interactions, flow velocities, pressures, as well as stresses and deformations that determine the final shape and integrity of the cast piece.
Recent developments in THERCAST® further enhance its predictive capabilities for the steelmaking industry. A new coupled inclusion model now accounts for the real interactions between liquid metal flow and inclusions, improving the understanding of their transport and accumulation during solidification. In addition, improved modelling of segregation and solidification strengthens the software’s ability to simulate complex metallurgical behaviours across steels and other industrial alloys.
New Inclusion and Particle Model: Smarter, More Accurate Physics
The inclusion and particle model in THERCAST® has been completely redesigned to provide a realistic representation of particles, bubbles, and inclusions in molten metal flows. These enhancements address critical challenges in continuous casting and ingot processes, where powders, exothermic cushions, or refractory particles can detach and be carried by the liquid metal, generating defects that compromise product quality.
Key improvements:
- Advanced physical equations: lift (volume and wall), drag, virtual mass, viscous, gravity, and pressure/stress gradient forces.
- Accurate across laminar and turbulent flows, covering a wide Reynolds number range.
- Sophisticated particle interactions: fluid-particle, gas-particle, inter-particle, agglomeration, and clogging.
- Modernized Analysis mode improves workflow, providing intuitive particle and sensor management.
Inclusion Tracking:
The new version introduces a coupled model that accounts for the mutual interaction between liquid metal flow and inclusions. This improvement allows realistic tracking of inclusions during filling, solidification, and cooling, enabling assessment of their movement, final position, and criticality for the product based on the finishing process sequence (chutes, non-destructive testing, etc.). Users can define sensors for inclusion density and diameter and perform exploratory studies by releasing inclusions at various locations, times, and with different properties to extract detailed process insights (see Figure 1).
Figure 1: Visualization of inclusion tracking and automatic air bubble creation in a THERCAST® simulation.
Automatic Air Bubble Creation and Monitoring:
In continuous casting and ingot production, high metal flow rates can generate turbulence, which under certain conditions may lead to the formation of air bubbles. To address this, the new version of THERCAST® introduces a criterion that defines the conditions under which bubbles are created. The approach relies on a sensor-based methodology: the user specifies only the minimum bubble size to be studied, and the software automatically generates the required number of sensors (see Figure 2). During the casting simulation, the movement of these sensors can be visualized in real time and exported in VTFX format, providing detailed information on bubble volume, position, and temperature for comprehensive analysis (see Figure 3).
Figure 2: Air bubble generation tool in the new version of THERCAST®.
Figure 3: Animation showing agitated fluid–particle coupling and particle agglomeration.
These upgrades allow engineers to simulate the formation, transport, and interaction of inclusions and bubbles with unprecedented precision. By linking particle behaviour to process parameters, THERCAST® now enables better defect prediction, process optimization, and control of final product quality
Electromagnetic Stirring Simulation: Controlling Flow for Quality
A key advancement in THERCAST® is its enhanced Electromagnetic Stirring (EMS) simulation, enabling precise control of molten metal flow during continuous casting. By influencing turbulence and flow patterns, EMS plays a critical role in homogenizing temperature, reducing segregation, and optimizing grain structure, directly affecting the mechanical properties and quality of the final product.
THERCAST® now supports full 3D turbulent VMS (Volume of Metal Stirring) simulations, allowing engineers to analyse the complex interactions between electromagnetic fields and molten metal movement in detail. The software provides two complementary approaches:
- Defining complete electromagnetic stirrers (see Figure 4) and running fully coupled, semi-coupled, or decoupled simulations, evaluating the resulting electromagnetic force fields on the melt. Specialized meshing tools ensure accurate representation of the stirrer geometry and its influence on local flow.
Figure 4: Design of a Stirrer: Inspired by a real stirrer with arbitrary shape and current parameters, featuring 6 coils in 3 pairs with 120° phase shift, a core to concentrate the electromagnetic field, 20 turns per coil, 1000 A RMS current, and 10 Hz frequency.
- Direct application of an analytical electromagnetic force field to the mesh as a boundary condition (see Figure 5), providing flexible yet accurate modelling of stirring effects without detailed hardware specifications.
Figure 5: Direct application of a force field to the mesh as a boundary condition in the form of an adaptable analytical law.
Simulation results illustrated in Figure 6 below, demonstrate that EMS significantly improves flow uniformity, minimizes macro- and micro-segregation, and promotes homogeneous solidification. By enabling prediction of interactions between flow, nucleation, and grain growth, engineers can better control final grain size and microstructure, improving product consistency and reducing defect rates.
Figure 6: Casting results: Comparison of flow with (left panel) and without stirring (right panel), showing the velocity field magnitude and corresponding iso-surfaces.
Improved Segregation Model with CET Integration
Segregation, the uneven distribution of alloying elements during solidification, remains one of the most critical challenges in casting. It arises from factors such as temperature gradients, local chemistry, cooling rates, and solidification paths. Accurately predicting both micro- and macro-segregation is essential for controlling final alloy properties and preventing defects.
The new Columnar-to-Equiaxed Transition (CET) model in THERCAST® addresses these challenges by providing advanced predictive capabilities for grain structure evolution and solute redistribution.
Highlights of the CET model:
- Grain transport and CET transitions: Predicts columnar-to-equiaxed transitions, grain movement, and sedimentation based on local solidification conditions.
- Enhanced mechanical and viscosity models: Temperature- and solid-fraction-dependent formulations improve representation of the mushy zone (see Figure 7) and solid–liquid interactions.
Figure 7: Variation of viscosity across the mushy zone as a function of secondary dendrite arm solid fraction (tip of the dendrites where liquid flow is hindered) and coherency solid fraction (base of the dendrites where stress transfer begins). Different viscosity curves illustrate the effect of interdendritic morphology on material behaviour and segregation.
- Multi-phase coupling: Simulates solid, liquid, and mushy zones for greater physical realism.
- Flexible solidification paths: Supports no enrichment, extra-dendritic enrichment, and combined inter- and extra-dendritic enrichment, enabling precise solute distribution modelling.
- Industrial validation: Tested on ingots up to 10 tons and benchmark cases from IJL, CEMEF, and other partners, confirming accurate CET position predictions and macrosegregation mapping (see Figure 8).
Figure 8: Prediction of Columnar-to-Equiaxed Transition (CET) position: comparison of experimental results [Gandin, 1999] (left) and current TSV simulation (right) for the fully solidified ingot. Simulation completed in 2.4 hours using 12 processors.
These capabilities are complemented by THERCAST®’s high-performance 3D parallel computing, which allows simulations of multi-ton ingots and continuous casting setups to be completed in just a few CPU hours. This makes the software suitable for both academic studies and industrial applications, providing reliable predictions across a wide range of alloys and casting conditions. Together, these advancements establish THERCAST® as a robust predictive tool for controlling segregation, optimizing grain structure, and improving overall product quality.
Conclusion
THERCAST® has advanced significantly as a simulation platform for casting processes. With its upgraded inclusion and particle model, enhanced segregation and Columnar-to-Equiaxed Transition (CET) predictions, and realistic electromagnetic stirring simulations, the software provides engineers with tools to better visualize, predict, and control molten metal behaviour, supporting improved quality control, defect reduction, and process optimization across a variety of alloys and casting configurations.
Looking ahead, the roadmap for THERCAST® introduces new capabilities, including gas bubble and inclusion pump modelling, argon injection simulations for continuous casting, automated particle inoculation and random particle generation, extension of the CET model to multicomponent alloys, and integrated simulation of filling and cooling stages in large-scale ingot processes. It will also feature detachment models addressing interactions between slag, refractories, sand molds, and liquid metal, further enhancing predictive accuracy and industrial relevance.
In upcoming articles, the continued evolution of the macrosegregation model in THERCAST® will be addressed in greater detail, offering further insights into its predictive capabilities. Stay tuned for further updates!
