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Deformation and Fracture Behavior of Large Deformation Pipeline Steel

Date:2018-04-09    keywords:pipeline steel
Large-deformation pipeline steel is a new type of pipeline structural material that is suitable for the long-distance transmission pipelines in geological complex areas (landslides, earthquakes, frozen soils, etc.), in order to reduce the formation damage caused by the movement of the pipeline. The typical structure of this new type of pipeline steel is composed of a two-phase structure consisting of a soft matrix phase and a hard phase. It is characterized by a high deformation-enhancement index (>0.1) on the basis of high strength and toughness. Elongation (>8%) and lower yield ratio (<0.8) give the ultimate deformation ability to resist buckling, destabilization, and ductile fracture in a large strain environment to meet the demand for large deformation. Therefore, it has the ultimate deformation ability to resist buckling, destabilization and ductile fracture in the large-strain environment and meets the requirement of large deformation.

1) In the bainite and ferrite dual-phase large deformation pipeline steel, plastic deformation is preferentially carried out in ferrite. With the development of plastic deformation, the morphology of the two-phase microstructure gradually shows an azimuthal distribution.
2) The nucleation of ferrite and bainite two-phase large deformation pipeline steel usually has three typical methods: nucleation of inclusions, nucleation of phase interfaces, nucleation in ferrite or bainite matrix;
3) In the bainitic and ferritic two-phase large-deformation pipeline steel, cracks mainly propagate through ferrite. When cracks pass through ferrite, the cracks usually pass straight through, indicating that ferrite does little to prevent cracks. When the crack and bainite meet, the cracks usually curve back, indicating that bainite has a greater role in preventing cracks. ;
4) The fracture model of ferrite + bainite large deformation pipeline steel was established.

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