Application of a multi-field model for controlling segregation in low-alloyed steel by twin-roll casting

Compared with conventional production routes, so-called twin-roll casting (TRC) significantly reduces manufacturing costs, energy consumption, and waste emissions. However, solute segregation during the TRC severely degrades the resultant product quality, and moreover, this critical challenge seems difficult to be eliminated during subsequent rolling and heat treatment processes, thus drastically deteriorating the final product's properties. As is known, the TRC can be considered as complicated process coupling multi-fields due to flow, thermal, and solute concentration, which makes traditional experimental approaches not only laborious but also unavailable for in situ monitoring. Combined with a volume-averaged method, hence, a numerical model by synergy of thermodynamics and kinetics (thermo-kinetic synergy) is herein proposed to simulate the TRC process, where, it can be found, with increasing the casting speed, the vortex region contracts and the cooling rate increases, in contrast with the expansion with enhancing the heat transfer coefficients and reducing the cooling rates. Following the model prediction, one will see, the increased casting speed alleviates the center segregation by enhancing the thermodynamic driving force, while the enhanced heat transfer coefficient suppressed the edge segregation by increasing the kinetic energy barrier. As such, the optimized processing parameters can be determined, so that both segregation phenomena were simultaneously mitigated, designed by a “high thermodynamic driving force - high generalized stability” strategy. Taking low-alloyed steel as studied target under these optimal conditions, an enhanced strength-ductility synergy in the strip results finally.