Texture engineered high toughness pipeline steel for arctic environment

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The safety and security of systems used for transportation and distribution of natural oil and gas are of major concern to the Canadian government. Pipelines used in arctic areas and the north of Canada face many challenges, such as ice scouring, permafrost and fault crossings. The pipes served in such environments must have high strength and high fracture toughness. It is known that in ferritic steels the {001}<110> (rotated cube) texture can lead to a significant reduction in toughness; and conversely, the crystallographic texture with {110}, {111}, {332} and {112} planes produce better toughness characteristics. Therefore, reducing rotated cube texture can be an effective way of enhancing the fracture toughness. At present, grain refinement and precipitation strengthening are the strategies to pursue a good combination of strength and toughness. However, these strategies are not sufficiently effective. For a further increase in the low-temperature toughness, a novel approach is required for the steel manufacturing process. Although the texture evolution was discussed by several researchers and our team in the past decade, the relationship between crystallographic texture, low-temperature toughness, tensile properties, phase composition and grain size in API X70 pipeline steels need to be investigated in details. In this project, we will collaborate with the manufacturer of pipeline steels - EVRAZ Inc. and CanmetMATERIALS laboratory, and develop novel thermo-mechanical processing to improve properties of X70 steels in arctic environment by texture modification and grain-size refinement. The texture-based design offers an original approach towards the ultimate objective of enhancing the strength and the low-temperature toughness of pipeline steels.