Influences of microstructure and texture on crack propagation path of X70 acicular ferrite pipeline steel

The aspects of two pipeline steels with different technologies were investigated by using transmission electron microscopy (TEM) and electron back-scattered diffraction (EBSD). The microstructure presents a typical acicular ferrite characteristic with fine particles of martensite/austenite (M/A) constituent, which distributes in grains and at grain boundaries. The bulk textures of the pipeline steel plate are 112<110> and <111> fibers, respectively, and the 112<110> component is the favorable texture benefiting for drop weight tear test. Moreover, low angle boundaries and low coincidence site lattice boundaries are inactive and more resistant to fracture than high energy random boundaries.