QUANTIFICATION OF MACROSEGREGATION IN CONTINUOUSLY CAST STEEL STRUCTURES

Macrosegregation was investigated in longitudinal sections of continuo usly cast, experimental slabs of austenitic stainless steel and carbon -manganese steel. The macro-mapping technique was applied to investiga te austenitic stainless steel slab sections. The method was based on e lectron probe microanalysis that was applied in a step-point mode to l ocally investigate segregation areas. The same stainless steel specime ns and carbon-manganese steel specimens were etched to reveal the segr egation structure. The macrosegregation in three carbon-manganese stee l 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 W-0.5, centreline segregation intensity C and the heterogeneity index H. The segregation factor M was proportional to the inhomogeneity in s egregate size distribution and to the segregate area fraction. W0.5 wa s defined as the area where the segregate area fraction is greater or equal to half of the maximum value of measured area fractions. Paramet er C equal to a ratio M-max/W-0.5, represented the intensity of centre line segregation. The heterogeneity index H was based on the measureme nts of mean size of segregates and the mean free path within segregate areas. For a homogeneous structure the heterogeneity index is zero an d it increases with growing inhomogeneity of a macrostructure.