Evaluation of the in-service weldability of vintage and modern pipeline steels

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Maintaining the integrity of the oil and gas pipeline network is essential to the energy transport system inCanada. Much of this depends on the ability to weld many of the aging pipeline steels, which may be well over50 years in service. However, over this time steel making practices have changed, along with the weldingprocesses which have tended to favour higher welding speeds and cooling rates for more rapid fabrication andlower costs. The current proposal will build a relationship between the University of Waterloo and StantecConsulting Ltd. The goal will be to develop processing practices and identify the weldability limits for vintagepipeline steels such as X70. Since it is necessary to avoid excessive cooling rates during welding which maylead to formation of hard phases, it is vital to understand what welding parameters will produce weldmicrostructures with good integrity and high toughness. This will be determined by developing continuouscooling transformation diagrams for both vintage and modern X70 pipeline steels. Thermal cycling will beapplied to the steels using a state-of-the-art Gleeble thermo-mechanical testing system to simulate variouswelding thermal cycles and cooling conditions, and correlate these with hardness and toughness. This willprovide key insights in what limiting welding parameters for can be applied in the field to ensure integrity afterin-service repair.