WO2024071358A1 - Matériau d'acier pour tuyau de conduite à haute résistance présentant une excellente ténacité à la rupture dans l'hydrogène, son procédé de fabrication, tube d'acier pour tuyaux de conduite à haute résistance et son procédé de fabrication - Google Patents

Matériau d'acier pour tuyau de conduite à haute résistance présentant une excellente ténacité à la rupture dans l'hydrogène, son procédé de fabrication, tube d'acier pour tuyaux de conduite à haute résistance et son procédé de fabrication Download PDF

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WO2024071358A1
WO2024071358A1 PCT/JP2023/035560 JP2023035560W WO2024071358A1 WO 2024071358 A1 WO2024071358 A1 WO 2024071358A1 JP 2023035560 W JP2023035560 W JP 2023035560W WO 2024071358 A1 WO2024071358 A1 WO 2024071358A1
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hydrogen
temperature
steel
content
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PCT/JP2023/035560
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Japanese (ja)
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佳宏 西原
拓史 岡野
奈穂 井上
大地 泉
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Ｊｆｅスチール株式会社
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Publication of WO2024071358A1 publication Critical patent/WO2024071358A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/10—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur

Definitions

  • the present invention relates to a high-strength line pipe steel material that has excellent fracture toughness in hydrogen in a high-pressure hydrogen gas environment of 1 MPa or more, and is suitable for applications such as line pipes for transporting hydrogen gas, a manufacturing method thereof, and a high-strength line pipe steel pipe and a manufacturing method thereof.
  • Austenitic stainless steels such as SUS316L, which exhibit fracture toughness in hydrogen, are used for steel structures used in high-pressure hydrogen gas environments.
  • the steel has low strength, and when designed to withstand high hydrogen pressure, the wall thickness becomes thicker and the line pipe becomes very expensive, making it unsuitable for pipeline construction. For this reason, there has been a demand for steel materials for hydrogen line pipes that are lower cost and can withstand high-pressure hydrogen gas environments.
  • Patent Document 3 proposes an austenitic steel material with a high Mn content.
  • the technology described in Patent Document 3 makes it possible to provide a steel material that is less expensive than austenitic stainless steel, but because it is austenitic, it is more expensive than low-alloy steel.
  • no consideration is given to suppressing pitting corrosion, which is the starting point of hydrogen-induced cracking, such as HIC resistance and SSCC resistance.
  • the limit of fatigue failure of a steel structure used in a high-pressure hydrogen gas environment corresponds to the critical crack length calculated from the operating conditions of the pipeline and the hydrogen-induced crack propagation lower limit K IH , which corresponds to the fracture toughness value of the steel in hydrogen gas. From the viewpoint of extending the life and improving the safety of hydrogen structures, increasing the K IH of the steel is considered to be one effective guideline.
  • Patent Document 4 proposes a manufacturing method for steel materials with excellent K IH , but does not mention the characteristics of the welds. In general, welds are more susceptible to property deterioration due to hydrogen than base materials. Therefore, it is important to improve K IH , including welds.
  • the present invention has been made to solve the above-mentioned problems of the prior art, and aims to provide a high-strength line pipe steel material with excellent fracture toughness in hydrogen in a high-pressure hydrogen gas environment, suitable for steel structures used in a high-pressure hydrogen gas environment, such as line pipes for 100% hydrogen gas or natural gas (natural gas is a gas whose main components are hydrocarbons such as methane and ethane) containing hydrogen at a hydrogen partial pressure of 1 MPa or more, a manufacturing method thereof, and a high-strength line pipe steel pipe and a manufacturing method thereof.
  • the high-pressure hydrogen gas environment is assumed to be high-pressure hydrogen gas of 1 MPa or more, or an environment containing 0.2% or more hydrogen gas.
  • the term "excellent fracture toughness in hydrogen under high pressure hydrogen gas environment” refers to a case where the hydrogen-induced crack propagation lower limit K IH is 80 MPa ⁇ m 1/2 or more, which is determined by conducting a fracture toughness test under both environments of room temperature (20 ⁇ 10 °C), hydrogen gas at a pressure of 1 MPa or more, or a mixed atmosphere of natural gas (mainly composed of hydrocarbons such as methane and ethane) containing hydrogen at a hydrogen partial pressure of 1 MPa or more.
  • the fracture toughness value refers to a value determined by conducting a fracture toughness test in accordance with ASTM E399, ASTM E1820, and ASTM E1681.
  • Natural gas containing hydrogen at a hydrogen partial pressure of 1 MPa or more refers to, for example, a gas having a hydrogen concentration of 30% or less by volume fraction and a total gas pressure of 30 MPa or less.
  • steel here includes thin steel plates, thick steel plates, seamless steel pipes, electric resistance welded steel pipes, steel sections, steel bars, etc.
  • the present inventors conducted technical studies on the conditions that should be satisfied by a steel material for obtaining a high-strength linepipe steel material and a high-strength linepipe steel pipe having excellent fracture toughness in hydrogen under a high-pressure hydrogen gas environment, with the aim of suppressing hydrogen absorption into the steel material, which is the root cause of hydrogen embrittlement.
  • the hydrogen-induced crack propagation lower limit K IH of the steel material and the steel pipe is improved in a metal structure in which the number of inclusions having an aspect ratio of 2.0 or more and a length of 10 ⁇ m or more is 15 pieces/100 mm2 or less, and the maximum grain size of the bainite in the range from the surface of the steel material and the steel pipe to the center of the plate thickness is 25 ⁇ m or less.
  • the hydrogen-induced crack propagation lower limit K IH of the steel material is further improved if the area fraction of the retained austenite is 0 to 3%, and the area fraction of the bainite in the range from the surface of the steel material and the steel pipe to the center of the plate thickness is 90% or more.
  • high strength refers to a tensile strength of 520 MPa or more.
  • the gist of the present invention is as follows. [1] In mass%, C: 0.02 to 0.15%, Si: 0.01 to 2.0%, Mn: 0.5 to 1.5%, P: 0.0001 to 0.015%, S: 0.0002 to 0.0015%, Al: 0.005 to 0.15%, O: 0.01% or less, N: 0.010% or less, Nb: 0.10% or less, H: 0.02 ppm or less, Or even more so: Ca: 0 to 0.005%, Ni: 0 to 2.0%, Ti: 0 to 0.1%, Cu: 0 to 1.0%, Cr: 0 to 1.0%, Mo: 0 to 0.60%, W: 0 to 1.0%, V: 0 to 0.10%, Zr: 0 to 0.050%, Mg: 0 to 0.01%, REM: 0 to 0.01%, B: 0 to 0.0020%, Ta: 0 to 0.2%, Hf: 0 to 0.2%, Re: 0 to 0.005%, Sn: 0
  • the chemical composition comprises, in mass%, Ca: 0.0001 to 0.005%, Ni: 0.01 to 2.0%, Ti: 0.005 to 0.1%, Cu: 0.01 to 1.0%, Cr: 0.01 to 1.0%, Mo: 0.01 to 0.60%, W: 0.01 to 1.0%, V: 0.01 to 0.10%, Zr: 0.0001 to 0.050%, Mg: 0.0001 to 0.01%, REM: 0.0001 to 0.01%, B: 0.0001 to 0.0020%, Ta: 0.0001 to 0.2%, Hf: 0.0001 to 0.2%, Re: 0.0001 to 0.005%, Sn: 0.0001 to 0.3%,
  • a steel material for high-strength linepipes having excellent fracture toughness in hydrogen according to [1] or [2], wherein the area fraction of retained austenite is 0 to 3%, and the area fraction of the bainite in the range from the steel material surface to the center of the plate thickness is 90% or more.
  • the present invention relates to a method for producing a high-strength steel material for line pipes having excellent fracture toughness in hydrogen.
  • the chemical composition comprises, in mass%, Ca: 0.0001 to 0.005%, Ni: 0.01 to 2.0%, Ti: 0.005 to 0.1%, Cu: 0.01 to 1.0%, Cr: 0.01 to 1.0%, Mo: 0.01 to 0.60%, W: 0.01 to 1.0%, V: 0.01 to 0.10%, Zr: 0.0001 to 0.050%, Mg: 0.0001 to 0.01%, REM: 0.0001 to 0.01%, B: 0.0001 to 0.0020%, Ta: 0.0001 to 0.2%, Hf: 0.0001 to 0.2%, Re: 0.0001 to 0.005%, Sn: 0.0001 to 0.3%,
  • steel materials with extremely improved fracture toughness in hydrogen under high-pressure hydrogen gas environments can be easily and simply manufactured, which is of great industrial benefit.
  • the hydrogen absorption resistance characteristics of steel structures such as high-pressure hydrogen gas line pipes can be significantly improved, which also has the effect of greatly contributing to improving the safety of steel structures.
  • a steel material will be specifically described, then as a second embodiment, a UOE steel pipe, which is an example of a steel pipe of the present invention, will be specifically described, and as a third embodiment, an electric resistance welded steel pipe, which is an example of a steel pipe of the present invention, will be specifically described.
  • C 0.02 to 0.15%
  • the C content is set to 0.02% or more.
  • the C content is 0.03% or more. More preferably, the C content is 0.035% or more. Even more preferably, the C content is 0.04% or more.
  • the C content exceeds 0.15%, the weldability decreases. For this reason, the C content is limited to 0.15% or less.
  • the C content is 0.10% or less.
  • the C content exceeds 0.08%, the hardness of the surface layer and the central segregation increases during controlled cooling, so that the SSCC resistance and HIC resistance may deteriorate. Furthermore, the toughness also deteriorates. For this reason, the C content is more preferably 0.08% or less. Even more preferably, the C content is 0.06% or less.
  • Si 0.01 to 2.0% Si is contained for deoxidation, but if the content is less than 0.01%, the deoxidation effect is insufficient, so the Si content is set to 0.01% or more.
  • the Si content is preferably 0.02% or more. More preferably, the Si content is 0.05% or more. Even more preferably, the Si content is 0.08% or more. Since the above effect is observed up to 2.0%, the Si content is set to 2.0% or less.
  • the Si content is preferably 1.8% or less, more preferably 1.5% or less. Even more preferably, the Si content is 1.0% or less. However, if the Si content exceeds 0.5%, toughness and weldability may be deteriorated, so the Si content is most preferably 0.5% or less.
  • Mn 0.5 to 1.5% Mn effectively contributes to improving strength and toughness, but if the content is less than 0.5%, the effect of inclusion is poor, so the Mn content is set to 0.5% or more.
  • the Mn content is 0.6% or more, more preferably 0.8% or more. More preferably, the Mn content is 1.0% or more.
  • the Mn content is limited to 1.5% or less.
  • the Mn content is 1.4% or less. More preferably, the Mn content is 1.3% or less, and even more preferably, the Mn content is 1.2% or less.
  • P 0.0001 to 0.015%
  • P is an inevitable impurity element that deteriorates weldability and increases the hardness of the central segregation, thereby deteriorating HIC resistance. Since this tendency becomes significant when the P content exceeds 0.015%, the P content is limited to 0.015% or less.
  • the P content is preferably 0.012% or less, and more preferably 0.010% or less. More preferably, the P content is 0.008% or less. The lower the content, the better, but from the viewpoint of refining costs, the P content is set to 0.0001% or more.
  • S 0.0002 to 0.0015%
  • S is an inevitable impurity element, and since it becomes MnS inclusions in steel and deteriorates HIC resistance, it is preferable that the S content is small, but up to 0.0015% is permissible. Therefore, the S content is set to 0.0015% or less.
  • the S content is preferably 0.0010% or less, and more preferably 0.0008% or less. The lower the content, the better, but from the viewpoint of refining costs, it is set to 0.0002% or more.
  • Al 0.005 to 0.15%
  • Al is added as a deoxidizer, but if it is less than 0.005%, there is no effect, so the Al content is 0.005% or more. On the other hand, if it exceeds 0.15%, the cleanliness of the steel decreases and the toughness deteriorates, so the Al content is set to 0.15% or less.
  • the Al content is preferably 0.12% or less, more preferably 0.10% or less. More preferably, the Al content is 0.08% or less.
  • O 0.01% or less O is a cause of oxide inclusions, so the less the better. This effect does not become a problem if the O content is 0.01% or less, so the O content is set to 0.01% or less.
  • the O content is preferably 0.0080% or less. More preferably, the O content is less than 0.0030%.
  • the lower limit is not particularly limited, but may be 0.0005% or more.
  • N 0.010% or less N effectively contributes to improving strength, but if the content exceeds 0.010%, the hardness increases during controlled cooling, resulting in deterioration of toughness. For this reason, the N content is set to 0.010% or less.
  • the N content is preferably set to 0.008% or less, more preferably set to 0.006% or less, and even more preferably set to 0.004% or less.
  • the content is preferably set to 0.00001% or more. More preferably, the N content is 0.002% or more.
  • Nb 0.10% or less
  • Nb is an element effective for increasing the strength and toughness of steel. If the content is less than 0.001%, the effect of the content is poor, so 0.001% or more is preferable. On the other hand, if the content exceeds 0.10%, the toughness of the welded part deteriorates, so the Nb content is set to 0.10% or less.
  • the Nb content is preferably set to 0.095% or less.
  • the Nb content is more preferably set to 0.090% or less, and even more preferably set to 0.085% or less.
  • the Nb content is most preferably set to 0.080% or less.
  • H 0.02 ppm or less H may be introduced into the steel material in various processes during manufacturing, and if the amount introduced is large, the risk of cracking after solidification increases and the K IH may be significantly reduced. These effects are not a problem if the amount is 0.02 ppm or less, so the H content is set to 0.02 ppm or less.
  • the H content is preferably 0.015 ppm or less, more preferably 0.008 ppm or less.
  • the H content is further preferably 0.005 ppm or less, and most preferably less than 0.002 ppm.
  • the lower limit is not particularly limited, but is preferably 0.0008 ppm or more for reasons of manufacturing costs.
  • the H content is more preferably 0.001 ppm or more.
  • the amount of hydrogen is the amount of hydrogen remaining after forming of steel material, steel pipe, UOE, etc.
  • the chemical composition disclosed herein may further contain one or more elements selected from Ca, Ni, Ti, Cu, Cr, Mo, W, V, Zr, Mg, REM, B, Ta, Hf, Re, Sn, and Sb in the following ranges:
  • Ca 0 to 0.005% Since Ca is an element effective in improving HIC resistance by controlling the morphology of sulfide-based inclusions, when Ca is contained, the Ca content may be 0% or more, but if it is less than 0.0001%, the effect of adding it is insufficient. Therefore, when Ca is contained, the Ca content is preferably 0.0001% or more. More preferably, it is 0.0005% or more. On the other hand, if it exceeds 0.005%, not only the effect is saturated, but also the HIC resistance is deteriorated due to the decrease in the cleanliness of the steel, so when Ca is contained, the Ca content is limited to 0.005% or less. The Ca content is preferably 0.004% or less. The Ca content is more preferably 0.002% or less, and even more preferably 0.0008% or less.
  • Ni 0 to 2.0%
  • Ni is an element effective in improving toughness and increasing strength, and when Ni is contained, the Ni content may be 0% or more, but to obtain this effect, it is preferable to contain 0.01% or more.
  • the Ni content is more preferably 0.1% or more.
  • the Ni content is 2.0% or less.
  • the Ni content is preferably 1.8% or less.
  • the Ni content is more preferably 1.4% or less, and even more preferably 0.8% or less.
  • Ti 0 to 0.1% Since Ti contributes to increasing the strength of the steel material, when Ti is contained, the Ti content may be 0% or more. In order to obtain the above effect, when Ti is contained, the content is preferably 0.005% or more. More preferably, it is 0.008% or more. On the other hand, when the content exceeds 0.1%, the effect is saturated and becomes a factor of increasing costs, so when Ti is contained, the Ti content is 0.1% or less.
  • the Ti content is preferably 0.08% or less, and more preferably 0.06% or less. In order to suppress costs, the Ti content is further preferably 0.05% or less. The Ti content is most preferably 0.04% or less.
  • Cu 0 to 1.0%
  • Cu is an element effective in improving toughness and increasing strength, and when Cu is contained, the Cu content may be 0% or more, but to obtain this effect, it is preferable to contain 0.01% or more. It is more preferable to make it 0.05% or more.
  • the Cu content is 1.0% or less.
  • the Cu content is preferably 0.95% or less, and more preferably 0.9% or less. More preferably, the Cu content is 0.85% or less. Most preferably, the Cu content is 0.5% or less.
  • Cr 0 to 1.0% Like Mn, Cr is an effective element for obtaining sufficient strength even with low C.
  • the Cr content may be 0% or more, but to obtain this effect, it is preferable to contain 0.01% or more. It is more preferable to make it 0.05% or more.
  • the content is too high, the hardenability becomes excessive, so that the SSCC resistance deteriorates. In addition, the weldability also deteriorates. Therefore, when Cr is contained, it is 1.0% or less.
  • the Cr content is preferably 0.95% or less.
  • the Cr content is more preferably 0.9% or less, and even more preferably 0.85% or less.
  • Mo 0 to 0.60%
  • Mo is an element effective in improving toughness and increasing strength, and is an element effective in improving SSCC resistance and HIC resistance.
  • the Mo content may be 0% or more, but to obtain this effect, it is preferable to contain 0.01% or more. It is more preferable to contain 0.10% or more.
  • the Mo content is 0.60% or less.
  • the Mo content is preferably 0.50% or less. More preferably, it is 0.40% or less. Further preferably, it is 0.35% or less.
  • W 0 to 1.0% W contributes to increasing the strength of the steel material.
  • the W content may be 0% or more, but in order to obtain the above effect, when W is contained, the content is preferably 0.01% or more.
  • the W content exceeds 1.0%, the effect is saturated and becomes a factor of increasing costs, so when W is contained, the W content is 1.0% or less.
  • the W content is preferably 0.9% or less, and more preferably 0.8% or less. In order to suppress costs, it is even more preferable to make it 0.5% or less.
  • V is an element that can be optionally contained to increase the strength and toughness of the steel material.
  • the V content may be 0% or more, but if the content is less than 0.01%, the effect of the inclusion is poor, so the V content is preferably 0.01% or more.
  • the V content is more preferably 0.03% or more.
  • the toughness of the weld deteriorates, so if it is contained, it is preferably 0.10% or less.
  • the V content is preferably 0.09% or less.
  • the V content is more preferably 0.07% or less, and even more preferably 0.06% or less.
  • Zr, Mg and REM are elements that can be added at will to improve toughness through grain refinement and crack resistance through control of inclusion properties.
  • the content may be 0% or more, but since the effect of containing them is poor when the content is less than 0.0001%, the content is preferably 0.0001% or more. More preferably, it is 0.0005% or more.
  • the Zr content is preferably 0.0001% or more.
  • the Zr content is more preferably 0.0005% or more.
  • the REM content is preferably 0.0001% or more.
  • the REM content is more preferably 0.0005% or more.
  • the Mg content is preferably 0.0001% or more.
  • the Mg content is more preferably 0.0005% or more.
  • the Zr content should be 0.050% or less. It is preferable that the Zr content be 0.040% or less. It is more preferable that the Zr content be 0.020% or less. If they are contained, the REM content should be 0.01% or less. It is preferable that the REM content be 0.009% or less. It is more preferable that the REM content be 0.008% or less. If they are contained, the Mg content should be 0.01% or less. It is preferable that the Mg content be 0.009% or less. It is more preferable that the Mg content be 0.008% or less.
  • B 0 to 0.0020%
  • B is an element that improves hardenability, contributes to increasing the strength of the steel material, inhibits the coarsening of prior austenite grains, and improves various properties of the material.
  • the B content may be 0% or more, but in order to obtain the above effect, the content is preferably 0.0001% or more. More preferably, it is 0.0008% or more.
  • the B content exceeds 0.0020%, the effect is saturated and becomes a factor of increasing costs, so when B is contained, the B content is 0.0020% or less.
  • the B content is preferably 0.0014% or less.
  • the B content is more preferably 0.0012% or less. In order to suppress costs, it is even more preferably 0.0010% or less.
  • Ta 0 to 0.2%
  • Ta is an element that forms carbides and nitrides and contributes to improving strength.
  • the Ta content may be 0% or more, but in order to obtain the above effect, it is preferable that the Ta content is 0.0001% or more. More preferably, the Ta content is 0.0008% or more.
  • the content exceeds 0.2%, it may cause a decrease in toughness, so when Ta is contained, the Ta content is 0.2% or less. It is preferable that Ta is 0.16% or less. It is more preferable that Ta is 0.12% or less, and even more preferable that Ta is 0.10% or less.
  • Hf 0 to 0.2%
  • Re 0 to 0.005%
  • the contents of these elements are preferably 0.0001% or more.
  • they are 0.0010% or more. That is, when these elements are contained, the Hf content is preferably 0.0001% or more.
  • the Hf content is more preferably 0.0010% or more.
  • the Re content is preferably 0.0001% or more.
  • the Re content is preferably 0.001% or more.
  • Hf when these elements are contained, if the content of Hf exceeds 0.2% and the content of Re exceeds 0.005%, oxides increase and, if they aggregate, hydrogen resistance properties are impaired, so Hf is 0.2% or less and the Re content is 0.005% or less. That is, when these elements are contained, the Hf content is 0.2% or less.
  • the Hf content is preferably 0.18% or less, and more preferably 0.12% or less.
  • the Re content is 0.005% or less.
  • the Re content is preferably 0.004% or less, and more preferably 0.003% or less.
  • Sn and Sb 0 to 0.3%
  • Sn and Sb contents may be 0% or more, but in order to obtain the above effects, it is preferable that the contents are each 0.0001% or more. Preferably, they are 0.001% or more. That is, when Sn is contained, the Sn content may be 0% or more, but it is preferable that the Sn content is 0.0001% or more. It is more preferable that the Sn content is 0.001% or more. When Sb is contained, the Sb content may be 0% or more, but it is preferable that the Sb content is 0.0001% or more.
  • the Sb content is 0.001% or more.
  • the Sn content is 0.3% or less. It is preferable to make the Sn content 0.2% or less. It is more preferable to make the Sn content 0.1% or less. It is even more preferable to make the Sn content 0.01% or less.
  • Sb is contained, the Sb content is 0.3% or less. It is preferable to make the Sb content 0.2% or less. It is more preferable to make the Sb content 0.1% or less. It is even more preferable to make the Sb content 0.01% or less.
  • the Sb content is 0.3% or less. It is preferable to make the Sb content 0.2% or less. It is more preferable to make the Sb content 0.1% or less. It is even more preferable to make the Sb content 0.01% or less.
  • the remainder other than the above-mentioned components consists of Fe and unavoidable impurity elements.
  • the metal structure of the steel material of the present invention is described below.
  • Metal structure 15 inclusions/ 100 mm2 or less with an aspect ratio of 2.0 or more and a length of 10 ⁇ m or more
  • inclusions in the material include elongated MnS and cementite. These act as hydrogen accumulation sources, leading to a significant decrease in HIC resistance and causing a decrease in the hydrogen-induced crack propagation limit K IH .
  • the number of inclusions with an aspect ratio of 2.0 or more and a length of 10 ⁇ m or more is set to 15 inclusions/100 mm2 or less.
  • the number density of the inclusions is preferably 10 inclusions/100 mm2 or less.
  • the lower limit is not particularly limited, and may be 0 inclusions/100 mm2 .
  • Retained austenite is 0-3% (preferable) When retained austenite remains in the steel structure, it acts as a hydrogen trap site, increasing the amount of hydrogen in the steel and increasing the hydrogen embrittlement susceptibility. Furthermore, when a steel material or steel pipe is used as a steel structure, if the retained austenite transforms into martensite due to stress load during use, the martensite is very hard and may become a source or propagation path of HIC, significantly decreasing K IH . In the present invention, the retained austenite is set to 3% or less to improve K IH . For this reason, the retained austenite is preferably set to 3% or less. The retained austenite is more preferably set to 2% or less. More preferably, it is set to 1% or less. The retained austenite may be 0%.
  • the area fraction of bainite in the range from the steel surface (in the case of steel pipes, the surface of the steel pipe inner surface) to the center of the plate thickness is 90% or more (preferred).
  • the steel material In order to achieve a high strength of tensile strength of 520 MPa or more as a material suitable for line pipes, the steel material must have a bainite structure.
  • the bainite structure includes bainitic ferrite or granular bainite that transforms during or after accelerated cooling, which contributes to transformation strengthening, and also includes tempered bainite.
  • bainite structure includes heterogeneous structures such as ferrite, martensite, pearlite, island martensite, and retained austenite, the strength decreases, and the normal (atmospheric) toughness and K IH deteriorate. Furthermore, the presence of steel structures with different hardnesses causes stress distribution in the steel material when stress is applied during use, and acts as a hydrogen accumulation source due to stress-induced diffusion, thereby degrading HIC resistance. For this reason, it is preferable that bainite is 90% or more in area fraction. It is more preferable that bainite is 92% or more in area fraction, and even more preferable that bainite is 95% or more in area fraction. There is no particular upper limit, but it may be 100%.
  • the maximum grain size in the range from the steel surface (the surface of the steel pipe inner surface in the case of a steel pipe) to the center of the plate thickness is 25 ⁇ m or less.
  • grains with a maximum grain size of more than 25 ⁇ m from the surface of the inner steel material to the center of the plate thickness tend to accumulate strain around the grains, which easily become the starting point and propagation path of hydrogen cracks, and therefore the K IH is significantly deteriorated. Therefore, it is necessary to make the maximum grain size from the inner surface of the steel material to the center of the plate thickness 25 ⁇ m or less.
  • the maximum grain size from the inner surface of the steel material to the center of the plate thickness is preferably 24 ⁇ m or less, more preferably 22 ⁇ m or less, and even more preferably 20 ⁇ m or less. Although the lower limit is not particularly limited, the maximum grain size is preferably 4 ⁇ m or more.
  • the measurement range of the crystal grain size is 1 mm ⁇ 1 mm, and the crystal grain size is defined as the area grain size (weighted average when the boundary with an orientation difference of 15° or more is defined as the grain boundary).
  • the hydrogen-induced crack propagation threshold K IH in a high-pressure hydrogen gas environment of 1 MPa or more is 80 MPa ⁇ m 1/2 or more.
  • the high-strength steel material of the present disclosure has a hydrogen-induced crack propagation threshold K IH of 80 MPa ⁇ m 1/2 or more in a high-pressure hydrogen gas environment of 1 MPa or more.
  • the upper limit is not particularly limited, it is preferable that the hydrogen-induced crack propagation threshold K IH of the steel material is 120 MPa ⁇ m 1/2 or less, and more preferably 100 Pa ⁇ m 1/2 or less.
  • the hydrogen-induced crack propagation threshold K IH refers to the plane strain fracture toughness K IC or its provisional value obtained in a high-pressure hydrogen gas of 1 MPa or more in accordance with ASTM E399 or ASTM E1820, or the crack propagation threshold or its provisional value obtained in accordance with ASTM E1681.
  • the thickness of the steel plate is not particularly limited, but it is preferable that the thickness be 5 mm or more. It is preferable that the thickness be 30 mm or less.
  • the present invention by having the above-mentioned chemical composition and metal structure, can obtain an excellent hydrogen-induced cracking threshold K IH in high-pressure hydrogen gas, and can be applied to hydrogen line pipes.
  • the high-strength steel for line pipes according to the present invention can be obtained by limiting the manufacturing conditions shown below, and the manufacturing method and conditions are specifically explained below.
  • molten steel process Average cooling rate of molten steel: 50° C./min or more (preferred conditions)
  • the inclusions defined in the present invention aggregate during the cooling process of the molten steel, it is also effective to increase the average cooling rate of the molten steel.
  • Heating process [heating temperature of cast piece: 1000 to 1250°C] If the heating temperature of the billet or slab is less than 1000°C, the diffusion of micro-segregated impurity elements such as C, P, and S is insufficient, and a homogeneous material cannot be obtained, which causes an increase in the number of inclusions and non-uniform precipitation, thereby reducing toughness. Therefore, the heating temperature of the billet is set to 1000°C or higher.
  • the heating temperature of the billet is preferably set to 1050°C or higher, and more preferably set to 1100°C or higher.
  • the heating temperature of the billet is set to 1250°C or lower.
  • the heating temperature of the billet is preferably set to 1200°C or lower, and more preferably set to 1150°C or lower.
  • Total rolling reduction in the recrystallization temperature range after heating of the slab 35% to 55%
  • the total reduction in the recrystallization temperature range is set to 35% or more.
  • the total reduction in the recrystallization temperature range is more preferably set to 40% or more, and even more preferably set to 43% or more.
  • the total reduction in the recrystallization temperature range is set to 55% or less. Preferably, it is set to 52% or less.
  • the total reduction in the recrystallization temperature range is more preferably set to 50% or less, and even more preferably set to 48% or less.
  • the lower limit temperature Tnr of recrystallization can be calculated, for example, from the components of the steel by the following formula.
  • the surface temperature of the steel sheet can be measured by a radiation thermometer, etc.
  • [%X] indicates the content (mass%) of the X element in the steel.
  • the reduction in the final rolling pass in the recrystallization temperature range is preferably 11% or more.
  • the reduction in the final rolling pass in the recrystallization temperature range is more preferably 13% or more, and even more preferably 15% or more.
  • the reduction ratio of the final rolling pass at (recrystallization temperature - 80°C) or higher is set to 15% or more.
  • the reduction ratio of the final rolling pass at (recrystallization temperature - 80°C) or higher is preferably set to 16% or more.
  • the reduction ratio of the final rolling pass at (recrystallization temperature - 80°C) or higher is more preferably 18% or more, and even more preferably 20% or more.
  • Rolling at a temperature lower than (recrystallization temperature - 80°C) is more effective at refining the grains because more strain is introduced at lower temperatures. For this reason, it is preferable to roll at low temperatures within the range where the cooling start temperature for controlled cooling can be observed.
  • the lower the rolling end temperature the better.
  • the Ar 3 point means the ferrite transformation start temperature during cooling, and can be calculated, for example, from the composition of the steel by the following formula.
  • the surface temperature of the hot-rolled steel sheet can be measured by a radiation thermometer or the like.
  • Ar3 (°C) 910-310[%C]-80[%Mn]-20[%Cu]-15[%Cr]-55[%Ni]-80[%Mo]
  • [%X] indicates the content (mass%) of the X element in the steel.
  • Controlled cooling start temperature Surface temperature of hot-rolled steel sheet above Ar3 transformation point
  • Ar3 point Ar3 transformation point
  • ferrite is generated before controlled cooling, and the strength is greatly reduced. Therefore, the surface temperature of the hot-rolled steel sheet at the start of cooling is set to be equal to or higher than the Ar3 transformation point.
  • the surface temperature of the hot-rolled steel sheet at the start of cooling is preferably equal to or higher than the Ar3 transformation point + 20°C, and more preferably equal to or higher than the Ar3 transformation point + 50°C.
  • the surface temperature of the hot-rolled steel sheet at the start of cooling is the temperature of the tail end of the hot-rolled steel sheet, where the cooling start temperature is the lowest.
  • the surface temperature of the hot-rolled steel sheet at the start of cooling is preferably equal to or lower than the Ar3 transformation point + 120°C, and more preferably equal to or lower than the Ar3 transformation point + 80°C.
  • the cooling start time difference between the leading end and the tail end of the hot-rolled steel sheet is set to 50 seconds or less.
  • the cooling start time difference is preferably set to 45 seconds or less.
  • the cooling start time difference is more preferably set to 40 seconds or less, and further preferably set to 32 seconds or less. Although it is possible to shorten the cooling start time difference by shortening the length of the hot-rolled steel sheet, this reduces manufacturability, so it is preferable to shorten the cooling start time difference by increasing the hot-rolled steel sheet conveying speed.
  • the cooling start time difference may be 0 seconds, but from the viewpoint of manufacturability, it is preferable to set it to 20 seconds or more.
  • Average cooling rate from 750 ° C to 550 ° C at the center of plate thickness 15 to 50 ° C / s If the average cooling rate from 750°C to 550°C at the center of the plate thickness is less than 15°C/s, the specified bainite structure including granular bainite cannot be obtained, and strength is reduced. For this reason, the average cooling rate at the center of the plate thickness is set to 15°C/s or more. From the viewpoint of suppressing the variation in the structure, the average cooling rate at the center of the plate thickness is preferably set to 17°C/s or more.
  • the average cooling rate at the center of the plate thickness is preferably set to 20°C/s or more, and more preferably set to 25°C/s or more.
  • the average cooling rate is set to 50°C/s or less.
  • the average cooling rate is preferably set to 48°C/s or less, and more preferably set to 45°C/s or less.
  • the average cooling rate is more preferably set to 42°C/s or less, and most preferably set to 38°C/s or less.
  • the cooling to 550°C or less at the hot-rolled steel plate temperature at the center of the plate thickness is not particularly limited, but from the viewpoint of suppressing the variation in the structure and grain size, the average cooling rate is preferably set to 15°C/s or more and 50°C/s or less. That is, for cooling to 550°C or less, the average cooling rate is preferably 15°C/s or more. The average cooling rate is more preferably 30°C/s or more, and even more preferably 35°C/s or more. For cooling to 550°C or less, the average cooling rate is preferably 50°C/s or less. The average cooling rate is more preferably 48°C/s or less, and even more preferably 42°C/s or less. The average cooling rate for 550°C or less is the average value of the cooling rates from 550°C to 250°C.
  • the cooling stop temperature at the center of the thickness after hot rolling exceeds 650°C, the material strength is significantly reduced, and from the viewpoint of obtaining a uniform bainite structure, the cooling stop temperature at the center of the thickness is set to 650°C or less.
  • the cooling stop temperature at the center of the thickness is preferably set to 620°C or less, more preferably set to 615°C or less, and even more preferably set to 600°C or less.
  • the cooling stop temperature at the center of the thickness is less than 250°C, quench cracks are likely to occur during cooling.
  • the cooling stop temperature is set to 250°C or more.
  • the cooling stop temperature at the center of the thickness is preferably set to 300°C or more, more preferably set to 350°C or more, and even more preferably set to 380°C or more.
  • the cooling stop temperature needs to be set to a predetermined temperature or more. Specifically, hydrogen present in the steel gradually escapes during cooling, and the higher the temperature, the greater the effect, but if the cooling stop temperature is too low, the steel will be overcooled and hydrogen will remain in the steel. Furthermore, if the cooling stop temperature is too low, it is easy to form retained austenite, which rapidly increases hydrogen in a large amount compared to other phases. Therefore, in order to reduce the amount of hydrogen in the steel, the cooling stop temperature needs to be 250°C or higher. Although it is acceptable to allow the steel to cool after cooling is stopped, it is more preferable to cool it slowly until the temperature drops by about 50°C from the cooling stop temperature in order to promote the formation of bainite.
  • Dehydrogenation treatment (optimal conditions) If hydrogen is present in steel to begin with, the acceleration of fatigue crack growth increases, and the fatigue life decreases. Therefore, it is preferable to use a dehydrogenation process to release the hydrogen remaining after manufacturing. Dehydrogenation can reduce the amount of hydrogen in steel by holding the product at high temperature for a certain period of time before use. Hydrogen can also be dehydrogenated by holding it at room temperature for a long time. When holding it at room temperature, the holding time is long, so the holding time is preferably 96 hours or more. Furthermore, since scale on the steel surface inhibits dehydrogenation, it is preferable to remove the scale before dehydrogenation.
  • the holding time R (sec) is preferably calculated from the plate thickness and pipe thickness t (mm) of the steel plate and steel pipe, and the hydrogen diffusion coefficient D (mm ⁇ sec ⁇ 1 ) in steel at room temperature, as shown in the following formula (A).
  • R ⁇ t2 /D (A) The hydrogen diffusion coefficient varies depending on the contained components and metal structure, but for example, the hydrogen diffusion coefficient may be 1 ⁇ 10 ⁇ 5 to 5 ⁇ 10 ⁇ 3 mm 2 /s, and more preferably 5 ⁇ 10 ⁇ 4 mm 2 /s or less.
  • the dehydrogenation process is carried out before pipe making or welding to connect steel pipes. It is preferable to carry out the dehydrogenation process at a high temperature because the hydrogen diffusion coefficient D at high temperatures becomes small and hydrogen is quickly removed.
  • the diffusion coefficient D' (diffusion coefficient at each temperature) at which the value of D in the above formula (A) is maintained may be used for calculation.
  • the dehydrogenation temperature is preferably 550°C or less. It is more preferable that the dehydrogenation temperature T is 500°C or less. It is even more preferable that the dehydrogenation temperature T is 400°C or less, and most preferably 300°C or less.
  • the dehydrogenation temperature T is room temperature or higher.
  • the dehydrogenation temperature T is 50°C or higher. It is more preferable that the dehydrogenation temperature T is 100°C or higher, and most preferably 150°C or higher.
  • the dehydrogenation temperature T mentioned here is the temperature of the atmosphere in the dehydrogenation process. Room temperature means 20 ⁇ 10°C.
  • the temperature Tc at the dehydrogenation temperature T (atmospheric temperature) for R (sec) or more as specified by formula (A), and it is even more preferable to hold the temperature Tc for the above-mentioned holding time R (sec) or more after it reaches the target dehydrogenation temperature T.
  • at least the former can appropriately control the amount of hydrogen in the surface layer of the steel material and steel pipe, and by implementing the latter, the amount of hydrogen in the steel material from the surface layer to the center of the thickness of the steel material and steel pipe can be appropriately controlled.
  • the thickness temperature, or the center temperature Tc can be measured using a thermocouple or the like, or can be predicted using the finite element method or the like.
  • the time and temperature of the dehydrogenation process may include the temperature and time applied when heating in the pipe-making process for electric resistance welded pipes, UOE, etc., as described below.
  • scale on the steel surface inhibits dehydrogenation, it is preferable to remove the scale before carrying out the dehydrogenation process.
  • the removal method There is no restriction on the removal method, but it may be physical cleaning using a high-pressure cleaner, for example, or a chemical method using a scale remover. The effect of scale removal can be obtained if a thickness of about 100 ⁇ m is removed.
  • a UOE steel pipe which is an example of a steel pipe for high strength line pipe, can be obtained by limiting the manufacturing conditions shown below, and the manufacturing method and conditions will be specifically described.
  • the chemical composition, metal structure, and hydrogen-induced crack propagation lower limit K IH of the UOE steel pipe are the same as those described for the steel plate of the first embodiment, and as for the manufacturing method, the molten steel process, heating process, hot rolling process, controlled cooling process after hot rolling, and dehydrogenation process are performed in the same manner as those described for the steel material.
  • the pipe-making process after rolling will be specifically described below.
  • UOE steel pipes are manufactured by bending hot-rolled steel sheets, specifically by groove-forming the ends of the hot-rolled steel sheets, and forming them into a steel pipe shape using a C press, a U press, and an O press, then seam-welding the butt joints using internal and external welding, and then expanding the pipe as necessary.
  • Any welding method may be used as long as it provides sufficient joint strength and joint toughness, but it is preferable to use submerged arc welding from the viewpoint of excellent welding quality and manufacturing efficiency.
  • Pipe expansion can also be performed on steel pipes that have been formed into a tubular shape by press bending and then have seam-welded butt joints.
  • the average cooling rate of the welded steel pipe in the temperature range from 1500°C to 1000°C to 50°C/min or more.
  • the average cooling rate is more preferably 55° C./min or more, and even more preferably 60° C./min or more. Although there is no particular upper limit, the average cooling rate is preferably 100° C./min or less.
  • an example of a steel pipe for high strength line pipe according to the present invention is an electric resistance welded steel pipe, which can be obtained by limiting the manufacturing conditions shown below, and the manufacturing method and conditions will be specifically described below.
  • the composition, metal structure, and hydrogen induced crack propagation lower limit K IH of the steel material are the same as those described for the steel material of the first embodiment, and as for the manufacturing method, the steps other than the cooling step after rolling and the pipe making step (melting step, heating step, hot rolling step, dehydrogenation treatment step) are performed in the same manner as those described for the steel material.
  • Cooling process after rolling (controlled cooling process)
  • the cooling start temperature and the average cooling rate of the controlled cooling are the same as those described in the first embodiment.
  • the cooling stop temperature at the center of the thickness after hot rolling exceeds 650°C, the material strength is significantly reduced, and from the viewpoint of obtaining a uniform bainite structure, the cooling stop temperature at the center of the thickness is set to 650°C or less.
  • the cooling stop temperature at the center of the thickness is preferably set to 620°C or less, more preferably set to 615°C or less, and even more preferably set to 600°C or less.
  • the cooling stop temperature at the center of the thickness is set to 250°C or more.
  • the cooling stop temperature at the center of the thickness is preferably set to 300°C or more, more preferably set to 350°C or more, and even more preferably set to 380°C or more.
  • the cooling stop temperature at the center of the thickness is most preferably 450°C or more. After cooling is stopped, it is sufficient to allow the steel to cool, but in order to promote the generation of bainite, it is more preferable to slowly cool the steel until the temperature drops by about 50°C from the cooling stop temperature.
  • the winding temperature is preferably 650°C or less.
  • the winding temperature is more preferably 620°C or less, more preferably 615°C or less, and even more preferably 600°C or less.
  • the winding temperature is preferably 250°C or more, more preferably 300°C or more, more preferably 350°C or more, and most preferably 380°C or more.
  • the electric resistance welded steel pipe given as an example of the present invention is manufactured by forming the pipe into a cylindrical shape by cold roll forming, and then butting and welding both circumferential ends of the cylindrical shape together. Furthermore, the electric resistance welded steel pipe may be manufactured by forming the pipe into an electric resistance welded steel pipe material (electric resistance welded steel pipe) using a sizing roll that satisfies the following formula (1) (sizing process), and applying an internal pressure p (MPa) that satisfies the following formula (2) to the inner surface of the electric resistance welded steel pipe material (internal pressure application process).
  • the cylindrical shape means that the circumferential cross section of the tube is in a "C" shape.
  • the plate thickness of the hot-rolled steel plate means the plate thickness of the hot-rolled steel plate before the sizing process is performed.
  • X thickness of electric welded steel pipe material (mm) / radius of electric welded steel pipe material (mm)) ⁇ yield strength of electric welded steel pipe material (MPa)
  • MPa yield strength of electric welded steel pipe material
  • the thickness of the electric welded steel pipe material given as an example of the steel pipe of the present invention is preferably 5 mm or more.
  • the thickness of the electric welded steel pipe material is preferably 30 mm or less.
  • the radius of the electric welded pipe material is preferably 400 mm or less.
  • the radius of the electric welded pipe material is preferably 200 mm or more.
  • the yield strength of the electric welded steel pipe material is preferably 480 MPa or more in order to withstand the gas pressure of pipeline operation. A yield strength of 500 MPa or more is more preferable.
  • the yield strength is preferably 560 MPa or less.
  • a yield strength of 550 MPa or less is more preferable.
  • the diameter of the sizing roll is set to satisfy the above formula (1) in order to reduce the absolute value of the residual stress in the axial direction of the tube. If the diameter of the sizing roll is less than the right side of the formula (1), the intended residual shear stress of the present invention cannot be obtained.
  • the diameter of the sizing roll is preferably 2000 mm or less.
  • the electric resistance welded steel pipe material is expanded to generate tensile stress in the circumferential direction of the pipe, thereby reducing the absolute value of the residual stress in the circumferential direction of the pipe.
  • the left side (X) of the above equation (2) corresponds to the internal pressure p when the tensile stress generated in the circumferential direction of the pipe is equal to the yield stress of the electric resistance welded steel pipe material.
  • the internal pressure p is set to a value greater than the left side (X) of equation (2) and the electric resistance welded steel pipe material is expanded to the plastic region.
  • the high-strength steel material disclosed herein can be formed into a tube by press bending, roll forming, UOE forming, or the like, and then the butt joints can be welded to produce high-strength steel pipes for sour-resistant line pipes (UOE steel pipes, electric resistance welded steel pipes, spiral steel pipes, etc.) with excellent material uniformity within the steel plate, suitable for transporting crude oil or natural gas.
  • sour-resistant line pipes UOE steel pipes, electric resistance welded steel pipes, spiral steel pipes, etc.
  • steel pipes with excellent HISC resistance can be produced, even if there is a high hardness region in the weld.
  • the above-mentioned observation surface was etched using a 3 vol% nital solution, and a scanning electron microscope photograph was taken at an appropriate magnification between 1000 and 5000 times to observe bainite.
  • Bainite was judged visually by comparison with the structure photograph in Non-Patent Document 1, and the structure fraction was determined by binarizing the bainite and other regions in the SEM photograph based on the above judgment, and determining the fraction by image analysis, which was taken as the area fraction of bainite.
  • Samples for metal structure observation were taken from the center of the plate width in the longitudinal center of the steel material and steel pipe obtained as described above, and the cross section of this sample parallel to the rolling direction was used as the observation surface.
  • the observation surface was mirror-polished and then etched with colloidal silica, and observation was performed with a scanning electron microscope (SEM) at the center of the sample in a field of view of 10 mm x 10 mm. The observation was performed at a magnification of 2000 to 5000 times, and the average of three fields of view was used as the number density of inclusions.
  • SEM scanning electron microscope
  • Temperature-programmed hydrogen analysis The amount of hydrogen remaining in the steel was measured using a temperature-programmed desorption analysis method, using a low-temperature temperature-programmed hydrogen analyzer (gas chromatograph type) (JTF-20AL). Temperature-programmed desorption analysis was performed in the temperature range from room temperature to 400°C at a heating rate of 200°C/h, and the sum of the measurements was taken as the amount of hydrogen.
  • the test specimens were cylindrical, 30 mm long in the longitudinal direction of the steel pipe, at a 1/4 position of the plate thickness of the steel material and a 1/4 position from the inner surface of the steel pipe, and had a diameter of 7 ⁇ . This amount of hydrogen was measured before the steel was subjected to the high-pressure hydrogen fatigue test described in the aging section below, and is the amount of H shown in Tables 1-1 and 1-2.
  • Fracture toughness test in high pressure hydrogen gas The test was carried out in accordance with ASTM E1820 at room temperature (20 ⁇ 10°C), in hydrogen gas (containing 100% hydrogen) at a pressure of 25 MPa, or in a mixed atmosphere of natural gas (mainly hydrocarbons such as methane and ethane) containing hydrogen with a partial pressure of 1 MPa or more at the above temperature and pressure.
  • CT test pieces (plate thickness 12.7 mm, plate width 25.4 mm) were used as test pieces, and were taken in a direction in which the machine notch introduction direction and the rolling direction of the steel material were parallel. Fatigue pre-cracks were introduced in the atmosphere under the conditions of frequency: 1 Hz, repeated load waveform: sine wave, control method: K value control, and stress ratio R: 0.1.
  • the test was carried out in hydrogen gas or a mixed atmosphere of hydrogen gas and natural gas.
  • the fracture toughness test was carried out by the unloading-elastic compliance method using a single test piece.
  • the crosshead displacement speed during loading was 0.002 mm/sec.
  • Example 1 The dehydrogenation treatment of steel pipes No. 2, 4, 8, 14, 22, and 33 carried out in Example 1 was carried out at the dehydrogenation treatment temperature T (ambient temperature) and time shown in Tables 2-1 and 2-2, which correspond to the dehydrogenation holding time t in Table 4 being Y and the holding time tc at the plate thickness center temperature Tc being N, respectively.
  • the dehydrogenation temperature T was set to the temperature shown in Table 4, and the holding time tc after the center temperature Tc reached the dehydrogenation temperature T shown in Table 4 was set to satisfy formula (A).
  • the dehydrogenation temperature T is the temperature shown in Table 4, but the holding time t of the ambient temperature and the holding time tc after the temperature at the center of the plate thickness Tc reaches the above-mentioned dehydrogenation temperature T do not satisfy the above-mentioned formula (A).
  • dehydrogenation holding time t is Y
  • dehydrogenation temperature T ambient temperature
  • holding time t satisfies formula (A)
  • dehydrogenation holding time t is N
  • dehydrogenation temperature T ambient temperature
  • holding time tc at steel center temperature Tc is Y means that the holding time tc after the plate thickness center temperature Tc reaches a predetermined temperature satisfies formula (A), and "holding time tc at steel center temperature Tc is N” means that the plate thickness center temperature Tc reaches a predetermined temperature, but the holding time tc after Tc reaches the predetermined temperature does not satisfy formula (A).
  • All of the inventive examples of the present invention satisfied the conditions of a hydrogen-induced crack propagation threshold K IH of 80 MPa ⁇ m 1/2 or more and a tensile strength of 520 MPa or more.
  • the examples in which the dehydrogenation treatment was performed under more suitable conditions had superior fracture toughness in hydrogen.

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Abstract

La présente invention concerne un matériau d'acier pour tuyau de conduite à haute résistance présentant une excellente ténacité à la rupture dans l'hydrogène dans un environnement d'hydrogène gazeux à haute pression, et qui convient pour être utilisé pour une structure d'acier utilisée dans un environnement d'hydrogène gazeux à haute pression, tel qu'un tuyau de conduite destinée à l'hydrogène gazeux 100 % ou au gaz naturel (le gaz naturel étant un gaz contenant un hydrocarbure tel que le méthane et l'éthane en tant que composant principal) contenant de l'hydrogène à une pression partielle d'hydrogène d'au moins 1 MPa ; un procédé de fabrication du matériau d'acier ; un tube en acier pour tuyaux de conduite à haute résistance ; et un procédé de fabrication du tube en acier. Ce matériau d'acier pour tuyau de conduite à haute résistance présentant une excellente ténacité à la rupture dans l'hydrogène est caractérisé en ce qu'il comporte une composition spécifique et une structure spécifique, une résistance à la traction d'au moins 520 MPa et une limite inférieure de propagation de fissure induite par l'hydrogène d'au moins KIH of 80 MPa·m1/2 dans un environnement d'hydrogène gazeux à haute pression d'au moins 1 MPa.
PCT/JP2023/035560 2022-09-29 2023-09-28 Matériau d'acier pour tuyau de conduite à haute résistance présentant une excellente ténacité à la rupture dans l'hydrogène, son procédé de fabrication, tube d'acier pour tuyaux de conduite à haute résistance et son procédé de fabrication WO2024071358A1 (fr)

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Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2012122103A (ja) * 2010-12-09 2012-06-28 Sumitomo Metal Ind Ltd 耐水素誘起割れ性、脆性亀裂伝播停止特性および耐食性に優れた厚鋼板
WO2014156187A1 (fr) * 2013-03-29 2014-10-02 Ｊｆｅスチール株式会社 Matériau d'acier et récipient d'hydrogène et procédés de fabrication de celui-ci
JP2018012855A (ja) * 2016-07-20 2018-01-25 新日鐵住金株式会社 低合金鋼材、低合金鋼管および容器、ならびにその容器の製造方法
WO2020137812A1 (fr) * 2018-12-26 2020-07-02 Ｊｆｅスチール株式会社 Acier pour environnements à hydrogène gazeux à haute pression, structure en acier pour environnements à hydrogène gazeux à haute pression et procédé de production d'acier pour environnements à hydrogène gazeux à haute pression
WO2022030818A1 (fr) * 2020-08-07 2022-02-10 주식회사 포스코 Plaque d'acier présentant une excellente résistance à la fragilisation par l'hydrogène et une excellente ténacité et son procédé de fabrication
JP2022068942A (ja) * 2020-10-23 2022-05-11 Ｊｆｅスチール株式会社 高圧水素ガス環境用鋼材およびその製造方法
WO2022209896A1 (fr) * 2021-03-30 2022-10-06 Ｊｆｅスチール株式会社 Tuyau en acier pour de l'hydrogène haute pression, récipient pour de l'hydrogène haute pression, et procédé permettant de fabriquer ledit tuyau en acier

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2012122103A (ja) * 2010-12-09 2012-06-28 Sumitomo Metal Ind Ltd 耐水素誘起割れ性、脆性亀裂伝播停止特性および耐食性に優れた厚鋼板
WO2014156187A1 (fr) * 2013-03-29 2014-10-02 Ｊｆｅスチール株式会社 Matériau d'acier et récipient d'hydrogène et procédés de fabrication de celui-ci
JP2018012855A (ja) * 2016-07-20 2018-01-25 新日鐵住金株式会社 低合金鋼材、低合金鋼管および容器、ならびにその容器の製造方法
WO2020137812A1 (fr) * 2018-12-26 2020-07-02 Ｊｆｅスチール株式会社 Acier pour environnements à hydrogène gazeux à haute pression, structure en acier pour environnements à hydrogène gazeux à haute pression et procédé de production d'acier pour environnements à hydrogène gazeux à haute pression
WO2022030818A1 (fr) * 2020-08-07 2022-02-10 주식회사 포스코 Plaque d'acier présentant une excellente résistance à la fragilisation par l'hydrogène et une excellente ténacité et son procédé de fabrication
JP2022068942A (ja) * 2020-10-23 2022-05-11 Ｊｆｅスチール株式会社 高圧水素ガス環境用鋼材およびその製造方法
WO2022209896A1 (fr) * 2021-03-30 2022-10-06 Ｊｆｅスチール株式会社 Tuyau en acier pour de l'hydrogène haute pression, récipient pour de l'hydrogène haute pression, et procédé permettant de fabriquer ledit tuyau en acier

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