Anisotropy of B+F Dual-phase X80 Pipeline Steel under Slow Strain Tension in Simulated Seawater

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    Anisotropy of dual-phase pipeline steel is an important factor affecting the safe service of pipeline steel. In this paper, the slow strain tension and polarization behaviors in simulated seawater of hot rolled ferrite + bainite dual-phase X80 pipeline steel at different angles (0, 45 and 90°) with rolling direction were studied. The microstructures, tensile curves, scanning electron microscopy and polarization curves were analyzed. The results show that X80 pipeline steel is composed of polygonal ferrite and lath bainite, the content ratio of which is about 1:1. The yield strength of X80 pipeline steel with different rolling direction in simulated seawater environment are decreased significantly, which indicates that X80 pipeline steel is obviously corroded under stress. For the dual-phase pipeline steel parallel to the rolling direction (0°), the stress-strain curve presents dome shape. The yield strength and tensile strength are the highest, the yield strength ratio is 0.81, yet the ductility is relatively low. Dual-phase pipeline steel perpendicular to the rolling direction (90°) has lower strength, smallest fracture radiation area and the best ductility. However its corrosion resistance to seawater is the worst. The self-corrosion potential of dual-phase pipeline steel at 45° with rolling direction in simulated seawater is the most positive showing that the corrosion resistance is best.

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  • Received:July 22,2020
  • Revised:July 22,2020
  • Adopted:April 26,2022
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