Optimisation of degradation strategy of transition steel slabs in continuous casting of thin size automotive panel

Pressing crack defects in automotive panels are frequently linked to steel coils rolled from transition steel slabs produced during ladle change-over operation in continuous casting. To address this, a dynamic control strategy for transition slabs downgrading was developed. Numerical simulations of molten steel mixing inside the tundish during ladle change were investigated and the calculation results were validated by industrial measurements. The continuous casting steel slabs at the stage when the mass fraction of molten steel in the subsequent heat at the tundish outlet reached 20% and 85% were the starting and ending points for the transition slabs cutting, respectively. The coupling relationships of the length division of the transition slabs with different steel throughputs were obtained based on the numerical calculation. This knowledge was embedded into a novel cutting model to dynamically optimise the transition slab length. The downgrade amount of the transition slabs was reduced by 33%, and the incidence of the pressing crack defects of tracking automotive panel client did not increase.