Assessment of pearlite banding using automatic image analysis: application to hydrogen-induced cracking

Abstract

Methods to quantify ferrite-pearlite banding using automatic image analysis have been proposed and tested, for example, in relation to classical banding charts. The method that is found to have the most general applicability is based on the measurement of the Feret's diameter distributions in two directions parallel and perpendicular to the rolling direction. The quantity related to banding is the ratio between the slopes of the cumulative frequency distribution curves. Structural steels with banded ferritic-pearlitic structures were investigated with regard to hydrogen-induced cracking (HIC) in previous work. The results show that the development of HIC depends on microstructural heterogeneities such as pearlife banding and inclusions. In the present work, the quantitative relationship between HIC parameters and banding is investigated. Banding quantification was used to interpret results of HIC tests. It was found that there is a significant correlation between banding and HIC in the National Association of Corrosion Engineers solution. No corresponding correlation was observed for the less acidic British Petroleum solution.