Characterization of fiber laser welds in X100 pipeline steel

Recent developments in steel grades for pipeline applications have lead to new high strength grades, such as API5L-X100. Higher strength enables the use of thinner walled pipe, with greater operating pressures and reduced overall costs. The base material presents good toughness values; however there are still limitations regarding the weldability of this material. Research is needed to develop appropriate welding procedures, avoiding typical problems like: cold cracking and toughness reduction in the weld area, and to achieve high productivity and economical feasibility. In the present paper an X100 steel grade welded by high power fiber lasers and TIG is studied and the microstructures developed are analysed aiming to contribute to a better understanding of the transformations induced in this material by the thermal cycle associated with fusion welding.