Analysis of Weld Defects in Offshore Structural H Beams

H beam welds along rolling and transverse direction were investigated with nondestructive testing, mechanical testing and microstructural analysis. Crack and fracture occurred, during guided bend testing, in the specimens welded along rolling direction between flanges of the H beams with higher S content although no defect was detected prior to the bend test. The fracture seemed to be lamellar tearing because of step-like fracture propagation and terrace and wall fracture appearance of the ruptured bend test specimen. On top of this, lamellar tear was already created in the base metal area near the HAZ before the bend test in microstructural analysis on the welds. It seems that lamellar tearing occurred in the specimens welded along rolling direction between flanges of the H beams with higher S content as cracks were formed and propagated into a ferrite phase region in α-γ band structure in combination with low ductility in transverse direction due to MnS inclusions elongated along rolling direction.