Quantitative Assessment Of Segregation By Video Image Processing

Continuously cast steel often exhibits a nonhomogeneous composition resulting from elemental segregation during solidification. Concentrated regions of phosphorus, carbon, sulfur, manganese and other elements can have detrimental effects on properties. At present, measurement of segregation is by subjective assessment of sulfur prints or chemical analysis of drillings. Detailed elemental distribution measurements require expensive and time consuming measurements using x-ray mapping facilities. This paper outlines a newly developed technique in which segregation patterns are determined by applying an etchant to produce selective darkening of phosphorus rich regions. A CCD video camera and computer are used to assess the etched sample and construct an approximate phosphorus distribution map. X-ray maps of phosphorus produced by a computer controlled electron microprobe are used to check the accuracy of the technique. Further processing techniques are applied to x-ray and etch maps to obtain measures of segregation.