A kind of hydrogen sulfide corrosion-resistant X70 pipeline steel for straight seam welded pipe and its production method

Abstract

An X70 pipeline steel with hydrogen sulfide corrosion resistance for a longitudinal welded pipe comprises the following components in percentage by weight: 0.030-0.060% of C, 0.15-0.30% of Si, 0.55-0.95% of Mn, less than or equal to 0.010% of P, less than or equal to 0.0010% of S, 0.10-0.30% of Cr, 0.05-0.15% of Mo, 0.015-0.065% of Nb, 0.02-0.05% of V, 0.01-0.02% of Ti and less than or equal to 0.004% of N. The X70 pipeline steel is produced through the following production steps: smelting, casting all components into a blank, and heating the blank; performing hot rolling; performing laminar cooling; and rolling. The X70 pipeline steel has the advantages as follows: the yield strength Rt0.5 is 500-545 MPa, the tensile strength Rm is 600-660 MPa, the yield-strength ratio (Rt0.5) / Rm is less than or equal to 0.86, the elongation A50mm is larger than or equal to 35%, the impact energy KV2 at 20 DEG C below zero is larger than or equal to 290 J, the DWTT cross section shear rate SA at 15 DEG C below zero is larger than or equal to 95%, and the hardness number HV10 is less than or equal to 225. According to the NACE TM 0284 standard, HIC inspection is carried out in an A solution, the CLR value, the CTR value and the CSR value of a cross section of an X70 pipeline steel sample are

Description

technical field [0001] The invention relates to a pipeline steel and a production method, in particular to a hydrogen sulfide corrosion-resistant X70 pipeline steel for straight seam welded pipes and a production method. Background technique [0002] Oil and natural gas are important energy sources for the development of the national economy, and their proportions in energy consumption are increasing day by day. At present, pipeline transportation is still the most economical, safe and efficient long-distance transportation method for oil and natural gas. However, with the depletion of easy-to-exploit oil and natural gas resources, the development of natural gas with high hydrogen sulfide content is increasing to ensure the supply of subsequent energy. [0003] Hydrogen sulfide is one of the most corrosive and harmful media in oil and gas. When natural gas contains a high proportion of H 2 When S and moisture, due to the effect of electrochemical corrosion, H 2 The hydro...

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Problems solved by technology

[0005] After retrieval, before the present invention, the X70MS steels involved in the patent application numbers CN201110331254.8, CN201310198848.5, and CN201310275095.3 all used the Cu+Cr+Ni system, and more precious metals Cu and Ni were added, resulting in The production cost of raw materials increases, and Cu and Ni elements do not have corrosion protection in the acidic environment with pH ≤ 3.5, so they are not suitable for H 2 S corrosive environment

The patent application numbers are CN201310275095.3. The content of Mn element in the patent is relatively high, which is easy to cause band segregation, reduce the uniformity of structure, and increase the risk of hydrogen-induced cracking in pipeline steel, and the examples of this patent also show that hydrogen-induced cracking does occur Cracking (CLR even reaches 18.2%), which seriously affects its safety in actual working conditions

The patent application numbers CN201310469618.8 and CN201310470450.2 also use the higher-cost Cu+Cr+Ni system, and the chemical composition of the Mn element (≤1.2wt%) has no lower limit requirement, which does not meet the actual process production , because when the Mn content is less than 0.55wt%, the austenite zone of the steel will shrink excessively and lead to a large amount of pro-eutectoid ferrite, and the steel with this structure type cannot reach the strength level of X70 both theoretically and practically

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