Abstract : As a consequence to reduction of gas transportation costs, pressure inside pipe will tend to increase. To achieve it, ferritic-bainitic steel with high strength, such as X100 (yield strength above 100 ksi, or 690 MPa) were developed. Girth welds of modern line pipe steel X100, issued from a pulsed automatic gas metal arc welding, were tested to check their performance in artic temperature conditions. It is shown that an impact specimen at -20 °C with a notch placed in the middle of the fusion line could break at low energy (<40 J). The brittle zone is located in the coarse-grained heat-affected zone of the weld. The reproduction of two heat-affected zones with a thermal-mechanical simulator, Gleeble 1500, allows determining the mechanical behavior of representative microstructures of the welded joint. Tension tests with or without notch, bend tests and impact tests are performed between -196°C and 20 °C. This experimental database is used to fit materials constitutive equations which are used in a finite element code to predict the fracture of the welded joint. Results obtained by local approach are compared with those obtained by the usual dimensioning rules used by exploiters (Failure Assessment Diagrams).