Drivetrain electrification is essential to reduce environmental impact from road transportation. One critical step is the production of higher-performing drivetrain components with tighter tolerances to reduce energy consumption and waste. This study focuses on replacing traditional gas-fired furnaces with sustainable low-pressure carburizing (LPC) and gas cooling methods. The project leverages advanced computational tools for predicting quenching outcomes (e.g., cooling rates, material properties, and distortions) to enable sustainable and efficient production. The approach involves CFD modelling of the chamber, splitting it into a 2D/3D sub model for the heat exchanger and a 3D model for the entire chamber. Parametric studies are conducted to optimize turbine RPM settings for uniform cooling and minimal distortions, providing detailed velocity profiles and cross-sectional flow insights. Components with all their design details are added for running a series of parametric studies to predict velocity and heat transfer characteristics in the chamber. The results highlight optimal turbine RPM settings for a more even cooling which would reduce distortion, marking significant progress toward predictive accuracy in gas cooling processes.

Stopper systems are widely used in the Continuous Casting (CC) process to control the steel flow from the tundish to the mould during casting of high-quality grades. The flow regulation region is subjected to severe under-pressures and generation of pressure fluctuations, especially around the narrowest gap and the tip of the stopper. This can lead to issues with air infiltration through the refractory materials, adverse flow regimes or even cavitation, which can lead to inclusions and level instabilities in the mould. Acquiring knowledge of such pressure distribution requires data from measurements which are difficult to conduct in the hostile high-temperature and corrosive environment of liquid steel in the plants. In this work, the pressure distribution is investigated in a Continuous Casting Simulator (CCS) based on a eutectic Bismuth-Tin alloy (Bi 58%-Sn 42%) with a low melting point (137 degrees C) equipped with a stainless-steel stopper rod. The pressure distribution is investigated through direct pressure measurements at two different points; a) Direct pressure measurement by sensor installed flush at the stopper-tip side and b) Indirect pressure measurements of back-pressure in the stopper argon line. The argon flow varied between 0 to 6 l/min, while casting speed varied between 0.6 to 1 m/min for a 1200 x 220 mm mould size. Results show that considerable under-pressures take place in the flow regulation region, reaching levels as low as 6.6 and 80 mbar absolute pressure at the stopper tip side and argon line. There was a detectable difference in pressure between the direct pressure measurements and additional argon line measurements. Ultimately, it could be concluded that the argon line pressure measurements; often used as industrial standard for ensuring positive pressures in the casting system, generally overpredicts the pressure in the system. This could lead to inappropriate argon settings for a caster, generation of unwanted inclusions and mould level instabilities. It was additionally possible to acoustically detect the onset of cavitation in the liquid metal.

This manuscript describes the methodology to optimise casting practices using SWERIM's digital twins. The process starts by compiling process data such as machine layout, steel grade and slag compositions to build a Library with detailed models of slag/steel properties, mould oscillation, product withdrawal, Electro-magnetic stirring, etc. Then, A 3D virtual geometry is constructed including the mould, SEN and 1-1.5 m length of slab/billet after the mould exit. These geometries are imported into Ansys-Fluent® v16.0 to solve for flow, heat transfer and solidification in a parallel cluster. Two reference cases for slab/billet casters are modelled showing an excellent agreement to map existing practices based on validation with flow measurements, solidification frames and temperatures in the casters. Subsequently, a matrix of parametric study cases is setup based on possible operational windows discussed with partners. The results of this analysis are imported into statistical analysis software to generate a set of guidelines to optimize process parameters such as shell thickness, temperature, etc. This allows finding “Sweet spots” to enhance the operating range of the casters and improve the quality of the final products.

Stopper controls see considerable use in Continuous Casting (CC) throughput control. The flow regulation results in a narrow gap between the stopper and the SEN throat which can result in considerable under-pressures. Large pressure gradients across the refractory material lead to air infiltration through joints and porous refractory material which result in oxidation and corresponding issues such as inclusions, clogging, with adverse effect on product quality. Improving the CC process makes it necessary to understand how the pressure evolves in the continuous caster. Swerim and SSAB investigated the pressure in the argon line of a ceramic stopper for different casting conditions in a liquid metal continuous casting simulator. The results showed a narrow operational region for positive pressures in stopper and an occurrence of considerably low pressures at levels down to -741 mbar relative pressure. At these under-pressures the risk for air infiltration, and thus product issues, is considerable.

A holistic approach to diagnose the occurrence of cracking on HSLA steel slabs and propose counter-measures to prevent them is presented. The approach consisted on plant monitoring, including direct temperature measurements in the strand with pyrometers. Extensive characterization was performed via thermo-mechanical tests and microscopy techniques which revealed combination of Widmanstatten ferrite, acicular ferrite and secondary phases that promote embrittlement during casting with a minimum ductility between 700 degrees C-800 degrees C (+/- 50 degrees C) which is responsible for cracking in this steel. Finally, 1D and 3D numerical models were developed to test possible cooling strategies which proved that reductions in water flowrate can have a positive effect in slab quality by avoiding the low ductility zone. Corrective actions included decreasing cooling to increase the overall temperature of the strand before the straightener to increase the overall temperature. Yet, some slabs still observed the presence of cracks which points at secondary factors such as high tundish temperatures > 1 530 degrees C producing cracking. Other secondary factors include strong temperature variations up to +/- 250 degrees C during measurements which would send the strand corners into the low ductility range producing cracking despite having a hot slab centre. Although these optimization strategies are particular to each caster and steel grade, a similar approach could be applied to address secondary cooling issues during continuous casting. The models presented are an ideal toolkit to analyse the influence of product size and operation parameters in combination with plant monitoring and extensive microstructure characterization to improve the quality and productivity of the process.

Continuous casting of steel in an industrial billet caster is modeled numerically including multiphase turbulent flow, mold electromagnetic stirring (M-EMS), heat transfer, and solidification. Two different steel grades (case-hardening and micro-alloyed steel) and casting powders are considered in the study to evaluate the castability and powder performance. Existing models to estimate thermophysical properties of casting powders are reviewed and compared to measurement data. Complex mold taper design is considered by constructing a digital twin and applying a corresponding velocity for the solidified shell in 3D. Slag infiltration is simulated from the beginning of casting to steady operation as a function of shell solidification and resulting heat transfer between liquid steel and oscillating mold wall. Additionally, the model predicts air gap size, excessive taper, and mold friction through a quasi-thermomechanical analysis. This includes a new approach to estimate mold friction based on Lubrication Index (LI) and Contact Index (CI) concepts. The resulting shell thickness, cooling water temperature, nail-dipping measurement, and mold friction are compared to plant data and literature for validation. This novel modeling approach can address phenomena difficult to analyze on real casters such as slag entrainment and infiltration, corresponding thermal response, and contact conditions between shell, slag, and mold.

The ductility drop and decrease in strength that lead to crack formation during continuous casting of steel is typically investigated by means of the hot ductility test. In this study, hot ductility tests are performed by using a thereto-mechanical Gleeble system to simulate the deformation of steels at high temperatures and low deformation rates similar to those during continuous casting. Thus, temperature was varied between 600 and 1000 degrees C while strain rates covered a range from 0.001 to 0.1 s(-1). Tests are carried out to identify the temperature range at which the steel is susceptible to crack formation as well as the effect of strain rate. Characterization of fractured surfaces and phase transformation after thermo-mechanical tests are conducted in the SEM and Optical Microscope. The combination of these techniques makes possible to formulate cracking mechanisms during hot processing which show critical strain for failure at temperatures between 700 and 900 degrees C based on the convergence of three different criteria: I) Reduction of area, II) True fracture strength-ductility and III) True total energy. This approach provides a better understanding of crack formation in steels at the high temperatures experienced during continuous casting. This information is key to productivity losses and avoid defect formation in the final cast products.

The findings in this work enhance the understanding of oxidation mechanisms and scale growth at high temperatures of a high strength low alloy (HSLA) steel for improving surface quality during continuous casting. The oxidation phenomenon was investigated under dry air and water vapor atmospheres by heating specimens at 1000, 1100, and 1200 degrees C at different holding times. Temperature and time had great effects on the kinetics, where faster (i.e., parabolic) oxidation rates were present under water vapor when compared with the dry air condition. Temperature strongly influenced the number of defects, such as pores, voids, gaps and micro-cracks, formed in the oxide scale. A phase analysis confirmed the presence of FeO as the first phase formed at the steel surface, Fe(3)O(4)as the middle and thicker phase, and Fe(2)O(3)as the last phase formed in the oxide/air interface. The micromechanics of the oxides demonstrated that a combination of phases with high (wustite) and low plasticity (magnetite and hematite) could also have been the reason for the uneven cooling during Continuous Casting (CC) that resulted in the undesired surface quality of the steel slabs. This work gives a good look at the oxide scale effect on the surface quality of steel slabs through an understanding the kinetics during oxidation.

The present research addresses the effect of surface condition on oxide scale formation at high temperatures such as those experienced during secondary cooling in Continuous Casting. Tests were carried out in clean, as-cast and surfaces covered with casting powder to replicate the oxidation/re-oxidation after the mould. Specimens oxidized at 1000, 1100 and 1200 degrees C under dry air and water-vapour conditions revealed that the oxide scale formation is strongly influenced by temperature, environmental and surface conditions. The oxide scale thickness increases with temperature alterations in the surface (e.g., as-cast and covered with powder) where oxides and carbonates from the casting powder accelerate oxidation kinetics leading to thick and unstable scales. A high amount of carbon is present on surfaces covered with casting powder where it diffuses through the oxide scale forming CO and CO2 which lead to stress accumulation that makes scales prone to defects such as pores, voids and micro-cracks. Ultimately, if wustite remains attached to the steel surface or inside oscillation marks, it may disturb heat transfer during secondary cooling which has deep industrial implications for crack formation and overall casting yield. Therefore, accurate insights on scale type and growth mechanisms could lead to accurate control of its formation during casting.

Continuous casting accounts for 96% of the total crude steel production in the world equivalent to 1689 million tons in 2017 [1]. This has been a driving force to generate research to increase production and quality to meet the global demands for steel. Increasing throughput (i.e. increasing casting speed) is an alternative to increase productivity; however, higher speeds often lead to lower quality since the process becomes unpredictable and harder to control. This could lead to non-uniform solidification resulting in distortion, cracks; and in the worst-case scenario, to breakouts [2]. In order to improve the as cast product quality, Electro-Magnetic Stirring (EMS), Electromagnetic Breaking (EMBr) and a combination of both has been previously used to improve the flow of molten steel and to facilitate the growth equiaxed structures during casting [3]. The introduction of in-mould electromagnetic stirring also provides heat circulation throughout the melt to avoid meniscus freezing. A numerical model has been developed to understand the effect of in-mould electromagnetic stirrer (M-EMS) on the flow and the solidification of the shell during the casting process of a 240 x 240 bloom of micro-alloyed steel. The paper focuses on flow pattern at the meniscus and at various height regions along with the shell formation within the mould. The paper also focuses on the limitations and challenges arising from the application of EMS in combination with flow, heat transfer and solidification occurring simultaneously during the bloom casting process.