Study of Stress-Corrosion Cracks, Physical and Mechanical Properties of Steel After Hydrostatic Re-Testing

Abstract

The hydrostatic re-testing of pipelines is one of the general methods of determination of service reliability of pipes in the zones characterized by high risk of stress corrosion. The detailed complex metal-physics studies of structural and stress-strain state of steel, as well as topography of stress-corrosion cracks, hydrogenation in fragments of pipes damaged at various stages of loading during re-testing were carried out due to the idea of “damage” of steel caused by harmful effect of increased pipes deformation. Templates of pipes having fractures and zones with or without stress-corrosion defects were cut out for studies. It has been shown that no deterioration of mechanical and ductility properties occurs in the parts of pipes without stress-corrosion defects. No considerable changes of character and degree of cracking as well as cracks topography have been detected during various stages of re-testing.