Significance of separations occurring in mechanical testing of thermomechanical rolled pipeline steels

Abstract

In this study, the origin of separations is investigated in modern high strength pipeline steels. In-depth microstructure characterization and property correlation is used to demonstrate that preferred crystallographic planes are responsible for the generation of separations in thermomechanical rolled steels with high cleanliness. Further insights on the influence of crystallographic orientation are obtained by performing different types of standard and non-standard tests with specific specimen and notch orientations and evaluating the related crack propagation path. Finally, special texture components are identified, which determine whether in-plane fracture, splitting or deflection of the cleavage parts take place. This study assists in understanding the separation phenomenon in modern high strength pipeline steels across the different test methods. Furthermore, it amplifies that the separations in thermomechanical rolled steels with high steel cleanliness are inherently linked to the orientation of specific crystallographic planes and are not necessarily an indication of a poor material behavior.

Keywords

• Separations
• Crack propagation
• Crack tip opening displacement
• Texture