Numerical study on the characteristics of solute distribution and the formation of centerline segregation in continuous casting (CC) slab

To reveal the characteristics of solute distribution and the formation of centerline segregation in continuous casting (CC) slab, a 3D simulation model for the prediction of centerline segregation during a slab CC process was developed. Experiments including the morphology of strand transverse section obtained by acid etch and the segregation degree of C tested by chemical analyzer were carried out to verify the accuracy of the numerical model. The maximum deviation between the calculated and experimented results reaches as low as 3.22%. In the turbulent flow region, the solute distribution in the liquid pool is relatively uniform and its distribution pattern is similar to that of flow pattern. In the final stage of solidification during a slab CC process, the solidification of molten steel in the centerline region is not simultaneous and the pattern of solute distribution is highly depended on the shape of liquid pool. The final solidification and serious segregation occur at a position roughly 595 mm from the slab center. Moreover, the quantitative relations between the position of solidification front and the solute concentration on the centerline were studied. The results show that solute redistribution and the solidification front moving continuously toward centerline lead to the formation of centerline segregation in CC slab. The central segregation degree of solutes in steel Q345 arranged in weakening order is S, C, P, Si, and Mn.