Effect of microstructure on the mechanical properties and texture in high strength 560 MPa linepipe steels

The study described here is aimed at understanding microstructure–texture relationship in conjunction with impact toughness, in two high strength 560 MPa (X80) linepipe steels characterized by ferrite–bainite and predominantly bainitic microstructure, respectively. The common textures in both the steels were identified to be (a) {665)〈110〉 of the α-fiber and (b) {111}〈110〉 and {111}“〈011〉 components of the γ-fiber, with the intensity of the γ-fiber components being similar in both the steels. On the other hand, the major differences in texture were (a) absence of {001}〈110〉 and {332}〈110〉 and presence of desired {332}〈113〉 and {554}〈225〉 texture in bainitic steel and (b) near absence of ε-fiber and presence of high intensity of {001}〈110〉 texture in ferrite–bainite steel. These differences in texture contributed to variation in mechanical properties in the two steels, particularly, toughness.