Texture engineered high toughness pipeline steel for arctic environment

加拿大政府主要关注天然石油和天然气运输和分配系统的安全性。在北极地区和加拿大北部使用的管道面临着许多挑战，如冰冲刷，永久冻土和断层交叉。在这种环境中使用的管道必须具有高强度和高断裂韧性。众所周知，在铁素体钢中，{001}<110>（旋转立方体）织构可导致韧性显著降低;相反，具有{110}、{111}、{332}和{112}面的晶体织构产生更好的韧性特性。因此，降低旋转立方织构是提高断裂韧性的有效途径。目前，晶粒细化和沉淀强化是追求良好强韧性结合的策略。然而，这些策略并不足够有效。为了进一步提高低温韧性，钢的制造工艺需要一种新的方法。虽然在过去的十年中，许多研究人员和我们的团队讨论了织构的演变，但API X70管线钢的晶体织构、低温韧性、拉伸性能、相组成和晶粒尺寸之间的关系需要详细研究。在这个项目中，我们将与管线钢制造商- EVRAZ Inc.合作。和CanmetMATERIALS实验室，开发新的热机械加工，以提高性能的X70钢在北极环境中的织构改性和晶粒细化。基于织构的设计为提高管线钢的强度和低温韧性的最终目标提供了一种新颖的方法。

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.