Microstructural Analysis of Separations Occurring during Charpy Impact Test of Linepipe Steels

摘要

In this study, microstructural investigation was conducted on separations occurring during Charpy impact tests of linepipe steels. Particular emphasis was placed on roles of microstructural phases such as acicular ferrite, bainite, and hard secondary phases. The detailed microstructural analysis of fractured impact specimens revealed that the band structure of bainite elongated along the rolling direction worked as prior initiation sites for separations, and that the number and length of separations increased with increasing volume fraction of bainite.