Improving low-temperature weld seam toughness of electric resistance welded X70 line pipe

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In response to the increased public expectations on safety, security, and environmental protection, the pipeline industry is targeting pipelines with zero material defects through develop and implement new technologies. Electric resistance welded (ERW) linepipe in the 70KSI yield strength (X70) range holds great promise to meet the technical requirements for strain based design and high toughness at extremely low temperatures. It meets current regulatory demand that proven, safe, and reliable technology (instead of a higher strength grade, for instance) should be used in order to minimize any environmental risks. The quality of ERW linepipe depends on the performance of its longitudinal bondline, which in current X70 linepipe can exhibit excellent toughness at -5 degree C, but can exhibit an inconsistently low toughness at lower temperatures. Toughness is a measurement of steel's capability to resist fracture, therefore, it is a key mechanical property to ensure the safety of a pipeline. The research objectives of this CRD project are, (1) to determine the key microstructure features and low-temperature toughness of the bondline of ERW X70 linepipe as influenced by how the welding is done, and (2) to fundamentally understand the welding process by mathematical modeling the temperature and deformation during ERW of X70. The anticipated value for Evraz from the project involves economic benefits from higher quality and lower costs in products and applications, and improved competitiveness. In addition, this project will contribute highly qualified personnel to the Canadian workforce.