Effect of process parameters variation on CC mould hydrodynamics and inclusions behaviour

Elimination of inclusions in the continuous casting mould is essential to elaborate clean steel. Considering the large number of phases, phenomena occurring in the CC mould are rather complex and a good description is the key factor for reliable prediction of the steel cleanliness in mould, thus of the final products quality. The hydrodynamics in mould, depending on the process parameters such as the casting velocity, the argon flow rate, the mould dimensions, the Submerged Entry Nozzle (SEN) design, the SEN immersion depth, can be represented by the liquid steel flow and its turbulence. These parameters directly control the inclusions behaviour in the liquid steel in mould. Numerical results are reported on the impact of the process parameters on fluid flow patterns generated in the mould and on the inclusions behaviour with their entrapment by the slab solidifying shell. Numerical simulations based on the use of the CFD Fluent software show that the liquid steel flows in the mould are mainly unsteady flows. The numerical results show that the argon flow rate and the SEN immersion depth can have a real effect on the stability of the liquid steel flows in mould. The design of the nozzle and its clogging state can also completely modify flows in the CC mould and gas bubbles and inclusions behaviour as well. These results are confirmed by an industrial analysis expressed as an index of surface defects on the final products.