Journal of Hebei University of Science and Technology (Oct 2020)
Study on anisotropy of B+F dual-phase X80 pipeline steel under slow strain tensile in simulated seawater
Abstract
In order to study the effect of anisotropy on the safe service of B+F dual-phase X80 pipeline steel, the slow strain tensile and polarization behaviors of hot rolled ferrite + bainite dual-phase X80 pipeline steel at three angles(0°, 45° and 90°) with rolling direction were analyzed by metallography, scanning electron microscopy, slow strain tensile test and electrochemical polarization method in simulated seawater. The result shows that the dual-phase X80 pipeline steel is composed of polygonal ferrite and lath bainite, and the content ratio of ferrite and bainite is about 1∶1. The slow tension yield strength of X80 pipeline steel with different angles from rolling direction decreases significantly with the increase of sampling angle in simulated seawater environment, which indicates that seawater has obvious stress corrosion to X80 pipeline steel; the slow strain tensile stress-strain curve of B+F dual-phase X80 pipeline steel parallel to rolling direction(0°) shows dome shape, the yield strength and tensile strength are the highest, the yield strength ratio is 0.81, and the uniform elongation is 13.4%, which can meet the application requirement; the self-corrosion potential of B+F dual-phase X80 pipeline steel perpendicular to the rolling direction(90°) is the most negative and the self-corrosion current is the largest, which indicates the seawater corrosion resistance is the worst; the corrosion resistance of dual-phase pipeline steel in the direction of 45° from the rolling direction in simulated seawater is the best due to the most positive self-corrosion potential. The research on the slow strain tensile anisotropy of B+F dual-phase X80 pipeline steel in simulated seawater environment can improve its safe service, and has some reference value for the actual production of large deformation pipeline steel.
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