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High strength seamless steel pipe excellent in hydrogen-induced cracking resistance and its production method

A hydrogen-induced cracking resistance, seamless steel pipe technology, applied in the field of pipeline steel pipes, can solve the problem that the resistance to HIC may not be improved.

Active Publication Date: 2005-10-26
NIPPON STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Therefore, even if the HIC-resistant steel suggested in the above-mentioned Japanese Patent Application Laid-Open S53-106318 and the like is applied to high-strength steel, the HIC resistance does not necessarily improve

Method used

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  • High strength seamless steel pipe excellent in hydrogen-induced cracking resistance and its production method
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  • High strength seamless steel pipe excellent in hydrogen-induced cracking resistance and its production method

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0069] Some kinds of steels having the chemical composition shown in Table 1 were melted by a converter. The billet produced by continuous casting is heated to 1100°C or higher, and then a hollow billet is obtained by using a turning roll piercer. These hollow tube blanks are finished rolled into steel pipes through a mandrel mill and a sizing mill. Then, when the steel pipe is not cooled to Ar 3 Point or lower, these steel pipes are uniformly heated at 950°C, quenched and tempered to produce seamless steel pipes. Steel pipe dimensions and heat treatment conditions are shown in Table 2. In this case, the cooling rate was set at 30°C / sec.

[0070] From the obtained steel pipes, JIS 12 tensile test samples were prepared for tensile testing, and tensile strength (TS) and yield strength (YS) were measured. Note that the tensile test was performed in accordance with JIS Z 2241.

[0071] In addition, samples with a thickness of 12-20 mm, a width of 20 mm, and a length of 100 mm...

Embodiment 2

[0083] In order to confirm the effect of heat treatment conditions, steel No. 3 in Table 1 was melted by a converter, and the slab produced by continuous casting was heated to 1100° C. or higher, and then a hollow billet was obtained by using a skew rolling mill. The hollow tube blank is finished rolled into a steel tube through a mandrel type seamless tube rolling mill and a sizing mill. Then the steel pipe is cooled in the range of 920°C to 20°C, and a seamless steel pipe is produced by changing the cooling start temperature, cooling rate and tempering temperature. The dimensions and heat treatment conditions of the produced steel pipes are shown in Table 3. In this case, No. 3 tested the Ar of the steel 3 point is 768°C, while its Ac 1 The point is 745°C.

[0084] As in Example 1, JIS 12 tensile test samples were prepared for tensile testing, and tensile strength (TS) and yield strength (YS) were measured.

[0085] In addition, the HIC resistance test was performed unde...

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Abstract

The present invention relates to a high strength seamless steel pipe excellent in hydrogen-induced cracking resistance, characterized by consisting of, by mass %, C: 0.03 - 0.11 %, Si: 0.05 - 0.5 %, Mn: 0.8 - 1.6 %, P: 0.025 % or less, S: 0.003 % or less, Ti: 0.002 - 0.017 %, Al: 0.001 - 0.10 %, Cr: 0.05 - 0.5 %, Mo: 0.02 - 0.3 %, V: 0.02 - 0.20 %, Ca: 0.0005 - 0.005 %, N: 0.008 % or less and O (Oxygen): 0.004 % or less, and the balance Fe and impurities, and also characterized in that the microstructure of the steel is bainite and / or martensite, ferrite is precipitated at grain boundaries and yield stress is 483 MPa or more. Further, to ensure high strength of the steel, the seamless steel pipe preferably contains, by mass %, at least one of Cu: 0.05 - 0.5 % and Ni: 0.05 - 0.5 %. To produce the above-mentioned steel pipe, it is desirable to limit a starting temperature of quenching after rolling, a cooling rate and a tempering temperature. By this configuration a seamless steel pipe having an yield stress of 483 MPa or more and excellent HIC resistance, which is suitable for a pipeline, can be provided.

Description

technical field [0001] The present invention relates to a seamless steel pipe having excellent hydrogen-induced cracking resistance (hereinafter referred to as "HIC resistance"), which is used as a steel pipe having a grade of 5L-X70 or higher than the American Petroleum Institute (API) standard grades of pipeline steel pipe. Background technique [0002] In recent years, well conditions in oil wells for crude oil and gas wells for natural gas (hereinafter collectively referred to as "oil wells, etc.") have become increasingly severe and transportation of crude oil and natural gas is performed under harsh environments. Well conditions in oil wells etc. tend to contain CO as water depth increases 2 、H 2 S, Cl - and other substances in the environment, and crude oil and natural gas often contain H 2 S. [0003] When the oil well is on the seabed, as the water depth increases, the offshore pipeline steel pipe requires high strength and thick wall thickness to support the w...

Claims

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Application Information

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IPC IPC(8): C21D8/10
Inventor 村尾畅俊久宗信之大迫一近藤邦夫
Owner NIPPON STEEL CORP