Mechanical Characterization of Welded API X70 Steel Exposed to Air and Seawater: A review

A review of the mechanical characterization carried out on welded API X70 steel, and other related steels are presented in this paper. The major problems facing pipeline network are failures demonstrated in form of leaks, ageing, ruptures and explosions. However, corrosion-induced failure also occurs in pipelines that are installed in harsh environments such as seawater. The research works under review considered the welded joints of the API X70 pipelines to be a more critical region than the base metal. The mechanical properties of the welds examined include tensile strength, hardness, and Charpy impact absorbed energy. The experimental methods used to characterize the work that are reviewed include scanning electron microscope (SEM), X-ray diffraction and electron backscatter diffraction (EBSD) and ThermoARL optical emission spectroscopic analysis. Welding technique such as submerged arc welding (SAW) and Manual metal arc (MMA) and parameters used in producing welds are also discussed briefly. Discussion of seawater environment is also presented. It is important to mention that most of the works reported in the literature are those that considered weldments that are exposed to ambient air while just a few considered welds exposed to the corrosive environment such as seawater. Therefore, this review concludes with the need for more research to determine more empirical data on the effect of seawater on mechanical properties of welded API X70. (paper)