Abstract
In this paper, X80 grade test steel was trial-produced in the laboratory, the mechanical properties, microstructure and precipitate morphology of the trial-produced test steel were analyzed and studied, and the precipitation law of Nb element in high-grade pipeline steel was studied by thermal simulation method. The results show that the X80 grade test steel has excellent mechanical properties, yield strength of 660 MPa, tensile strength of 720MPa and yield ratio of 0.91. The impact energy is greater than 295 under -20°C test conditions and the cross-section rate of the DWTT fiber reached 90% under -15°C test conditions, and the test results completely meet the API.5L standard requirements. By the thermal simulation experiment, it is found that the precipitation process of Nb particles in the test steel is the nucleation growth process of controlled by diffusion. The tip temperature of the PTT curve is about 900°C, and the Nb element in the test steel is found at 810°C by solid solubility calculation can be completely precipitated.
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