The tensile properties and toughness of microstructures relevant to the HAZ of X80 linepipe steel girth welds ...

• Main Author: Gaudet, Michael J.
• Format: Text
• Language: English
• Published: University of British Columbia 2015
• Subjects: Arctic
• Online Access: https://dx.doi.org/10.14288/1.0166539; https://doi.library.ubc.ca/10.14288/1.0166539

In the transportation of oil and gas products from and over remote locations, such as Canada's Arctic environment, pipelines are used. Girth welding to join sections of steel pipelines creates a substantial heat affected zone (HAZ) within the base pipeline steel. While there is significant concern as to the fracture and mechanical properties of the HAZ as whole, detailed knowledge about the mechanical properties of the microstructural constituents is lacking. For this research, measurements of the temperature time profile in the HAZ of single and dual torch welds were made. This was then used to guide heat treatments of X80 steel in a Gleeble simulator to create samples of 8 different bulk microstructures with differing amounts and morphologies of bainite, ferrite and martensite-retained austenite (MA). From the heat treated samples tensile and Kahn tear test specimens were made for testing at ambient, -20⁰C, and -60⁰C. The highest strength microstructure proved to be the finest, lower bainitic ...