Influence of Superheat on Macrosegregation in Continuously Cast Steel Billet from Statistical Maximum Viewpoint

The statistics of extreme values (SEV) and the generalized Pareto distribution (GPD) are introduced to obtain the predicted maximum carbon content and represent the macrosegregation degree along the casting direction in continuous casting billets (represented by 82B cord steel). Subsequently, the influence mechanism of the superheat on macrosegregation has been investigated. It's found that the SEV and the GPD methods can correctly obtain the predicted maximum carbon content and the results obtained by the SEV method increase linearly with the return period, while the GPD method can calculate the upper limit value of carbon content. The stochastic mathematical methods can get rid of the limitations of the sampling length and analysis area. During the exploration of the superheat influence mechanism based on the results obtained by these two methods, lower superheat can increase the secondary dendritic arm spacing (SDAS) and make the enriched carbon element easier concentrating on the centerline, resulting in centerline segregation and the increase of the corresponding result in the centerline. Under higher superheat condition, the segregation will be mainly represented as V-shaped segregation due to the decrease of the SDAS, leading to the increase of corresponding result in the off-center position.