Tensile Behavior and Fracture Properties of X80 Line Pipe Steel

摘要

The welding of steel line pipe results in a heat affected zone with a graded microstructure where fracture and yielding is of significant concern. In this study, X80 steel is subjected to heat treatments in a Gleeble simulator to produce samples containing different amounts and morphologies of bainite, ferrite and martensite-retained austenite (MA). These microstructures were then subjected to tensile and fracture testing. The results showed that there was good correlation between the microstructures and properties measured from the tensile tests. Fracture testing used the Kahn tear test which is a thin-sheet, slow strain rate fracture test. This test showed that the predominantly ferrite sample had the lowest tear strength and unit propagation energy while the sample with the bainitic/MA microstructure had the highest tear strength and unit propagation energy.