Application of nondestructive magnetic flux leakage method in characterization of mechanical properties of API X65 steel

In this paper, the capability of non-destructive method of magnetic flux leakage in characterizing the microstructure and mechanical properties of API X65 steel has been evaluated. Magnetic flux leakage method is a popular non-destructive inspection method for oil and gas pipelines based on the detection of magnetic flux leakage from the surface of the part. This test is widely used to identify all discontinuities including surface and subsurface cracks as well as thickness changes due to latent corrosion in the inner wall of pipelines. In this study, four different microstructures subjected to four different types of heat treatment have been used. The results show that changes in microstructural characteristics, including morphology of the ferrite phase (polyhedral or needle) as well as the size of the ferrite grains, affect the density of magnetic flux lines emitted inside the part and the amount of magnetic flux leaked from the surface. Therefore, one can use the magnetic flux leakage test to efficiently determine the type of microstructure as well as the mechanical properties of the part.