Tensile properties of welded joints with delayed hydride crack

Abstract

In this work, a procedure for producing tensile coupon specimens with naturally delayed hydride cracks was proposed, and the tensile properties of the specimens were studied. Firstly, a delayed hydride crack was prefabricated on the welded plate according to the relevant specification, and the crack type was determined by microstructure and macrostructure observation and analysis. Secondly, the tensile coupon specimens of welded joints with or without delayed hydride cracks were cut from the welded plate. Finally, tensile tests of welded joints were carried out, and the strain and displacement were monitored by a digital image correlation system. The test phenomena, fracture mode and the tensile properties of the welded joint were analysed according to the stress-strain curve, the strain cloud map and the tensile property parameters. When the specimen fractured at the base metal, the effect of delayed hydride crack on the strength and deformation of the welded joints was insignificant. The cracked area ratio was relatively small (e.g. 1.91% to 22.5%). When the specimen fractured at the cracked region, the cracked area ratio was relatively large (e.g. 16.77% to 39.62%). The fracture modes could be divided into two types: the full-sectional yield fracture and the low stress fracture. The remaining ultimate strength, yield-to-tensile ratio and elongation of low stress fracture specimens showed a linear decline with the increase of cracked area ratio. For specimens with cracked area ratio between 16.77% and 22.5%, the differences in fracture locations might be caused by the pattern and angles of the crack.