Improvement of Low-Alloy Pipe Steel Sulfide Stress Cracking Resistance

The influence of sheet microstructure formed by various thermomechanical processing schedules on sulfide stress cracking (SSC) resistance under uniaxial tension for low-alloy pipe steels grades X42–X65 is studied. A favorable role is established for substitution of a ferritic-pearlitic by a ferritic-bainitic microstructure and improvement of structural component dispersion is established. The favorable effect is facilitated by using high intensity post-deformation cooling from the austenite region. It is shown that segregation bands and non-metallic inclusions in a sheet axial zone do not affect the duration of specimens withstanding SSC, but they can lead to formation of hydrogen cracks (HIC) on a specimen surface that is a defective feature. In order to prevent crack formation in a specimen surface and premature failure it is necessary to lay down high specifications for specimen gauge length and fillet surface quality.