Fracture-Toughness Evaluation in Submerged Arc-Welding Seam Welds in Nonstandard Curved SE(B) Specimens in the Short Radial Direction of API 5L Steel Pipe

摘要

Plane-strain fracture toughness of submerged arc-welding seams of an API 5L steel pipe in the short radial direction was evaluated using nonstandard curved SE(B) test specimens. These specimens are directly cut from the pipe and require no machining other than the crack starter notch. The stress intensity factor function for the nonstandard curved SE(B) specimen was calibrated for three-point bending loading. The initiating notch was aligned to make the crack propagate through the weld-deposited metal zone. The measured fracture-toughness value was 56.3 ± 2.9 MPai √m. A fractographic study of the tested specimens showed that the deposited metal fracture consists of a mixture of ductile tearing and cleavage that corresponds to the ferrite and the dendritic grains, respectively. The dendritic grains behave in a brittle way, thus being the main contributions to the relatively low fracture-toughness values obtained from the tests.