Quantification of macrosegregation in continuously cast steel structures

Abstract

Macrosegregation was investigated in longitudinal sections of continuously cast, experimental slabs of austenitic stainless steel and carbon‐manganese steel. The macro‐mapping technique was applied to investigate austenitic stainless steel slab sections. The method was based on electron probe microanalysis that was applied in a step‐point mode to locally investigate segregation areas. The same stainless steel specimens and carbon‐manganese steel specimens were etched to reveal the segregation structure. The macrosegregation in three carbon‐manganese steel slabs was represented by etch‐prints. The quantitative investigation of structure was performed directly on the macroetched specimens and on the etch‐prints. The morphology of macrostructure was characterised by new parameters: segregation factor M, width of a segregation band W0.5, centreline segregation intensity C and the heterogeneity index H. The segregation factor M was proportional to the inhomogeneity in segregate size distribution and to the segregate area fraction. W0.5 was defined as the area where the segregate area fraction is greater or equal to half of the maximum value of measured area fractions. Parameter C equal to a ratio Mmax/W0.5, represented the intensity of centreline segregation. The heterogeneity index H was based on the measurements of mean size of segregates and the mean free path within segregate areas. For a homogeneous structure the heterogeneity index is zero and it increases with growing inhomogeneity of a macrostructure.