A pipeline steel with HIC resistance and large deformation resistance and its manufacturing method

Abstract

The invention relates to a pipeline steel with HIC resistance and large deformation resistance. The alloy composition is C: 0.03-0.039%, Si: 0.15-0.35%, Mn: 1.6-1.9%, S: ≤0.002% , P: ≤0.012%, Al: 0.02~0.045%, Cr: 0.15~0.35%, 0.05≤Nb+V+Ti≤0.1%, Nb, V, Ti are not 0, Ni: 0.15~0.50%, Cu : 0.01~0.25%, Ca: ≤0.002%, N: ≤0.0046%, Mo: 0.01~0.20%, the balance is Fe and unavoidable impurity elements, with bainite single-phase structure, and bainite crystal The particle size is above 11.5 grade. The transverse yield strength ratio of the product is Rt0.5 / Rm≤0.78, Charpy impact energy at -20°C is greater than or equal to 350J, and the drop hammer shear area SA% at -20°C is greater than or equal to 90%; Ratio≤0.77; Longitudinal stress ratio Rt1.5 / Rt0.5≥1.18, Rt2.0 / Rt1.0≥1.1; HIC resistance: Soak in NACE TM0284‑2004A solution for 96 hours, crack length rate%: 0, crack Width ratio %: 0, crack sensitivity ratio %: 0.

Description

technical field [0001] The invention belongs to the technical field of iron-based alloys, and in particular relates to a pipeline steel. Background technique [0002] Pipeline transportation is the most economical and reasonable transportation method for oil and natural gas. Long transmission pipelines not only need to pass through different temperature regions, but also need to pass through areas of stratum movement caused by natural disasters such as earthquake permafrost, debris flow, and landslides. High resistance to large deformation can adapt to the transmission geological environment. [0003] Large-deformation-resistant pipeline steel is one of the most challenging research fields in the development of pipeline steel, and pipeline steel is required to have higher resistance to compression and tensile strain. A large number of studies have proved that in addition to the basic strong plasticity to measure performance parameters, such as yield strength, tensile stren...

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Problems solved by technology

[0004] In response to the requirement of "resistance to large deformation", the pipeline steels disclosed in patent documents such as CN2009100760066.8, CN201210327206, and CN2009100760066.8 all involve the use of methods such as relaxation to obtain a dual-phase structure of ferrite + bainite, which has a relatively Good anti-large deformation properties, but because the organization is a two-phase organization, see figure 2 , and the two-phase structure has an obvious band shape along the rolling direction, so the anti-HIC performance is not ideal. There is a state where hydrogen is easy to accumulate in the two-phase structure, and the band structure can also induce the accumulation of hydrogen

For pipeline steel with a dual-phase structure of ferrite + bainite, the HIC resistance performance test is carried out according to the corresponding standards of NACE. The steel plate has many HIC cracks along different directions of thickness, and the HIC resistance performance is not ideal.

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