Transvalor is delighted to announce the release of the THERCAST® NxT 3.0 : a new version of our solidification and casting software which will boost the digitalization of the casting processes in the steelmaking industry and revolutionize the approach to plant design.
This has been achieved with a twofold strategy: on one hand more physics included, for technically precise description of the phenomena; on the other hand, an improved user experience with increased informative content and clarity, stronger orientation to business and ergonomic interaction.
For us in Transvalor the technical precision of THERCAST® NxT 3.0 is the keystone of the digital twin of industrial casting processes
For this reason, the effort of our development team focused on key physical aspects to be included or enhanced in the THERCAST® NxT 3.0 solver.
New electromagnetic solver. THERCAST® NxT 3.0 can now solve the electromagnetic equations necessary to simulate the onset of a rotating or traveling magnetic field in the liquid metal and the consequent action of the Lorentz force field, to simulate an important aspect of the continuous casting process: the action of electromagnetic devices for the stirring of the fluid flow [1]. Simulation of M-EMS, S-EMS and F-EMS can be addressed at various levels of detail: with a full description of the EM devices and computing the Lorentz forces, with an analytical Lorentz force field depending on space and time, or with a force computed on a structured grid with an external tool. It provides full insights on the interaction of the magnetic field with the fluid flow and its effect of the formation of the solid skin, temperature distribution and related defects.
Figure 1 Mould EMS Setup in THERCAST® NxT 3.0 of a conventional slab casting
Figure 2 Mould EMS Setup in THERCAST® NxT 3.0: computed Lorentz Force
Figure 3 Liquid metal velocity field in slab casting without (left) and with EMS (right)
Figure 4 Layout of a simulation inspired by the Aphrodite experiment described in [2]
Figure 5 Temperature and flow pattern with different stirring parameters during solidification of a Sn-Pb binary alloy
Figure 6 Effect of EMS on segregation of Pb in a Sn-Pb binary alloy at the end of solidification
Physical model of the surface tension. Surface tension plays an important role in the flow of the liquid metal, and it is critical e.g. in continuous casting, where the behavior of the meniscus and its interaction with the liquid slag directly affects the surface quality of the cast products and in the filling phases of foundry processes. Some alloys are more sensitive than others, such as aluminum alloys, whose oxidation kinetics facilitate the creation of an alumina layer that impacts the flow. In version 3.0 of THERCAST® NxT, the surface tension force (STF) has been introduced into the Navier-Stokes equation for incompressible fluids, using a semi-implicit formulation [3-5]. The wettability effect has also been implemented considering the description of the wetting angle proposed by Bellet's work [6]. These different implementations now make it possible to consider the Marangoni effects (convection loops related to the surface tension gradient). The Marangoni force has been implemented simply as an explicit force, dependent on the variability of the surface tension with temperature. It is now possible to activate the computation of these forces directly via the interface, in the same way as it is done for the Darcy's law.
Simulation of lost foam process. In this process, the cavity is initially filled with a polystyrene part (the blank) which is gradually replaced by the metal during filling. The filling is done from the top and takes hydrostatic pressure into account. The filling phase is critical for the good quality of the cast product and occurs in a longer time than gravity casting. THERCAST® NxT 3.0 has been equipped with innovative technology that allows us to provide detailed information on this stage of the process. The input data to simulate this process is very simple: we have introduced the concept of cavity properties, which makes it possible to replace the air properties (generally filling any cavity) with the properties of the blank in a very simple way. It is possible to change the properties of your polystyrene blank using the well-known option in the interface.
Enhanced microsegregation model. A dynamic computation of the solidification path is now possible with version 3.0 of THERCAST® NxT, together with a more realistic description of the mushy zone both from the perspective of the thermal behavior (latent heat release as a function of the solidification path) and of the interdendritic flow. It is possible to compute the solidification path as a function of the local chemical composition determined by the solute partition and interdendritic enrichment. The permeability of the mushy zone is computed as a function of the secondary dendrite arm spacing and has an impact on the pressure drop and liquid flow. All these features are essential for a realistic simulation of the segregation phenomena which are important both for ingot casting and continuous casting.
Inclusions/bubble tracking. It is possible to track the trajectory of any inclusions or gas bubbles in the liquid metal, during any phase of any process: in the tundish, in the primary cooling zone and at the nozzle level in continuous casting, in ingot casting in top or bottom filling configuration and in foundry. A density and dimension can be assigned to the particles and several groups of particles can be released in the liquid metal, choosing the location and time of appearance. Gas bubbles are automatically generated by the full description of the liquid free surface behavior. We are already working on the next step, which is to generate inclusions with tear-off models, whether with powders, ceramics, sand or refractory mould elements. This will provide an indication of possible product pollution after solidification but also make it possible to evaluate the wear of the moulding or casting elements during production.
Whether THERCAST® NxT 3.0 is used for research, design or production, the full deployment of its technical potential is only achieved through an excellent user experience
Two main novelties characterize the THERCAST® NxT 3.0: a fully integrated optimization module and the Phyton console for limitless use of scripting at all stages of the simulation process. The effort of our team of programmers is now ready to become a breakthrough tool in the hands of our users. This has been accompanied by a very accurate and detailed work based on the collected feedback from our users on how to improve at all levels the interaction with THERCAST® NxT 3.0: major and minor changes have been done to achieve an important general improvement in terms of stability, comfort and efficiency.
Optimization module: give up trial-and-error and explore your design space efficiently. The automatic optimization module is integrated into the graphical interface, and it is an essential tool to optimize your processes, improve the quality of your products and reduce your costs. The main application is of course for design variables and process parameters, but the module can be also used to optimize the mesh or to execute complex experimental data fittings (e.g. thermocouple measurements), without any needs for onerous reverse engineering techniques. Moreover, it allows to establish interactions between parameters (notion of order or analytic law).
The graphical user interface of THERCAST® NxT 3.0 has a section dedicated to optimization, designed to take full advantage of this module. There is a space for analyzing the results: it provides new graphical tools to visualize the cost function, the relevance of parameters or to validate compliance with constraints. The ranking of the individuals with respect to the cost function is easily accessible and any individual simulation in the DOE can be exported as a new simulation project, together with its results.
For an efficient use of the computation resources, it is possible to enable parallel launch of individual simulations to optimize CPU time.
Python API: automate, customize, create! We developed a Python scripting module fully integrated with THERCAST® NxT 3.0. The broad list of variables and actions we provide gives you access to all the simulation features in a simplified and highly efficient way. Python scripts can be used in THERCAST® NxT 3.0 to create projects, run calculations, and analyze results with maximum automation. The user interface has a Python console to run the scripts, but it is also possible to launch them without accessing it. You will be able to create your custom process, manage objects, import and generate meshes, define all types of parameters, automatically generate calculation variants, display only the results you need in the optimal configuration, export results and much more. Moreover, and very important, Python scripting allows you to interconnect THERCAST® NxT 3.0 with other digital tools for a full automation of your entire workflow. But there is more: the API now allows you to invent and execute actions that have not yet been implemented! Let's take as an example the multiple loading of STL geometries. This feature doesn't exist in THERCAST® NxT 3.0 user interface, but thanks to the Multi_STL_files_loading.py file, you can now do it. Our API has almost no limitations, whether in set-up or analysis mode, you can create the scripts you need, simply load them into the Python console, and run them. THERCAST® NxT 3.0 script store provides examples to show you the power and flexibility you have in this new release.
Discover the new features of the Graphical User Interface
A renovated Material Data Tool: be in complete control of your material properties. This tool has been completely renewed and it has now become a powerful means to design your material file. A material file for the specific application can be generated: continuous casting, ingot casting or foundry. Existing material files can be easily edited, to add or modify properties and verify data. All material properties can be visualized in plots, including the flow stress curves, the parameters of the microsegregation model and of the CAFE method for the grain nucleation and growth. A procedure for verifying the data before starting a calculation has been added.
A new concept for the Setup Status panel: go straight to the perfect setup. Not only an informative checklist, now this panel is effectively usable in the simulation setup process. Not only it is possible to visualize the messages showing errors in the setup and (where applicable) the parameter values, but it is now possible to reach the specific setting/action with a double click on the error message. In other words, the setup status panel is now a functional map leading the user through the sequence of actions to be taken to fix the setup errors.
Categorized and customizable result menu: efficient selection of scalars, vectors and tensors. The result variables have been reorganized in several context-relevant groups, to make it easier for the user to select the one of interest. The groups are: Process, Thermal, Deformation, Constraints, Kinematics, Material properties, Numerical parameters. These groups can be customized by the user, by modifying the html file to organize scalars and vectors according to the specific needs of the analysis. The variables can be hidden or made visible according to user criteria and arranged in different categories.
Python API Store: unleash your creativity. Check THERCAST® NxT 3.0 Python API store, to see how to automatize result analysis and much more, with many of the scripts we prepared for you.
References
[1] Marioni, L. (2017), Computational Modelling and Electromagnetic-CFD Coupling inCasting Processes, PhD Thesis, Université Paris sciences et lettres
[2] Hachani, L. (2015). Experimental study of the solidification of Sn–10 wt.%Pb alloy under different forced convection in benchmark experiment. International Journal of Heat and Mass Transfer, 85, 438-454.
[3] Hysing, S. (2006). A new implicit surface tension implementation for interfacial flows. International Journal for Numerical Methods in Fluids, 51(6), 659-672.
[4] Khalloufi, M. (2017). Multiphase flows with phase change and boiling in quenching processes (Doctoral dissertation, Université Paris sciences et lettres).
[5] Chen, Q. (2018). Thermomechanical numerical modelling of additive manufacturing by selective laser melting of powder bed: Application to ceramic materials (Doctoral dissertation, Université Paris sciences et lettres).
[6] Bellet, M. (2001). Implementation of surface tension with wall adhesion effects in a three‐dimensional finite element model for fluid flow. Communications in numerical methods in engineering, 17(8), 563-579.
