Charpy Impact Toughness and Transition Temperature for API 5L X52 Seamless Pipeline

This work presents the Charpy energy values (CVN) in the ductile-to-brittle transition (DBT) temperature zone for different directions with respect to the longitudinal direction of API 5L X52 seamless pipeline steel. The material-processing directions were L-T, T-L, S-T, T-S, L-S, S-L, and 45°. At the same time, the temperature variation was –100, 0, 25, 50, and 100°C. Charpy impact specimens were machined in accordance with the ASTM E23 standard, with dimensions of 10×10×55 mm. In addition, the microstructures and fracture surfaces were examined using scanning electron microscopy. The energy values for all directions show lower shelf behavior at –100°C, a transition zone from –100 to 50°C, and an upper shelf behavior above 50°C as the characteristics of this type of grade pipeline.