Study on the control of macro/semi-macro segregation in unevenly solidified slabs through optimizing soft reduction process

In recent years, concerns have been raising about issues such as poor soft reduction effect and severe center segregation caused by uneven solidification during slab continuous casting. In view of this, a transient heat transfer-solidification model has been employed to reveal the effects of both water flux distribution uniformity and casting speed on uneven solidification morphology together with experimental observation. The industrial trials demonstrate severe segregation near the 1/8 width position of the slab castings. Nevertheless, both the macrosegregation ratio and distribution region markedly decrease by adjusting the soft reduction segments and/or casting speed to align the central solid fraction at the inlet and outlet of the segments with the optimized soft reduction zone. Given the uneven solidification of the slab castings, it's necessary to broaden the soft reduction zone. Additionally, the dimensionless perimeter L of semi-macro segregation was first introduced to characterize the morphological complexity. The optimized soft reduction parameters decrease the size and dimensionless perimeter L of semi-macro segregation, which is beneficial to the minimization of macro/semi-macro segregation.