Quantitative examination of segregation in slabs for the production of sour service linepipe

Abstract

Segregation is a major problem to be overcome by producers of HIC resistant steels. Primary segregation is an inherent and unavoidable feature of the solidification process. The constitutive relationship between solid and liquid stage determines microsegregation and it is influenced by the chemical composition of the steel and its cooling rate. Macrosegregation occurs when microsegregated liquids collect and shift through liquid flow. Oregon Steel Mills has conducted systematic measurements on pressure-cast slabs using a computer assisted micro analyzer. This microprobe measures element concentrations over a large area of the specimen. A statistical evaluation based on the frequency distribution of the concentrations forms the basis of a quantitative analysis. From this, characteristic parameters such as the segregation factor and maximum concentration can be derived. This paper discussed the influence of carbon on segregation structure and on segregation properties of manganese, and compares the results with those of continuously cast slabs.