Texture engineered high toughness pipeline steel for arctic environment

用于运输和分配天然气的系统的安全性是加拿大政府主要关注的问题。在北极地区和加拿大北部使用的管道面临许多挑战，如冰冲刷、永久冻土和断层穿越。在这种环境下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）织构会导致韧性显著降低；相反，{110}、{111}、{332}和{112}面的晶体织构具有更好的韧性特性。因此，减少旋转立方织构是提高断裂韧性的有效途径。目前，晶粒细化和析出强化是追求强度与韧性良好结合的策略。然而，这些策略还不够有效。为了进一步提高低温韧性，需要在钢的制造工艺中寻找新的方法。虽然在过去的十年里，一些研究者和我们的团队对织构演变进行了讨论，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进行详细的研究。在这个项目中，我们将与管道钢制造商EVRAZ Inc.和CanmetMATERIALS实验室合作，开发新的热机械加工方法，通过组织改性和晶粒细化来改善X70钢在北极环境中的性能。基于织构的设计为提高管道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.