JP2018012856A - Low alloy steel material, low alloy steel tube and container and method for producing the container - Google Patents

Low alloy steel material, low alloy steel tube and container and method for producing the container Download PDF

Info

Publication number
JP2018012856A
JP2018012856A JP2016142206A JP2016142206A JP2018012856A JP 2018012856 A JP2018012856 A JP 2018012856A JP 2016142206 A JP2016142206 A JP 2016142206A JP 2016142206 A JP2016142206 A JP 2016142206A JP 2018012856 A JP2018012856 A JP 2018012856A
Authority
JP
Japan
Prior art keywords
pressure hydrogen
alloy steel
content
hydrogen gas
container
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
JP2016142206A
Other languages
Japanese (ja)
Other versions
JP6648647B2 (en
Inventor
大村　朋彦
Tomohiko Omura
朋彦 大村
潤 中村
Jun Nakamura
潤 中村
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nippon Steel Corp
Original Assignee
Nippon Steel and Sumitomo Metal Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Family has litigation
First worldwide family litigation filed litigation Critical https://patents.darts-ip.com/?family=61019965&utm_source=google_patent&utm_medium=platform_link&utm_campaign=public_patent_search&patent=JP2018012856(A) "Global patent litigation dataset” by Darts-ip is licensed under a Creative Commons Attribution 4.0 International License.
Application filed by Nippon Steel and Sumitomo Metal Corp filed Critical Nippon Steel and Sumitomo Metal Corp
Priority to JP2016142206A priority Critical patent/JP6648647B2/en
Publication of JP2018012856A publication Critical patent/JP2018012856A/en
Application granted granted Critical
Publication of JP6648647B2 publication Critical patent/JP6648647B2/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/32—Hydrogen storage
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

Landscapes

  • Filling Or Discharging Of Gas Storage Vessels (AREA)
  • Heat Treatment Of Articles (AREA)
  • Fuel Cell (AREA)

Abstract

PROBLEM TO BE SOLVED: To provide a low alloy steel material for high pressure hydrogen containers, which allows a life design based on the endurance ratio under a high-pressure hydrogen gas environment, has a high strength and has excellent fatigue resistance under a high-pressure hydrogen gas environment, and good hydrogen gas embrittlement resistance.SOLUTION: There is provided a low alloy steel material for high pressure hydrogen having a chemical composition which comprises, by mass%, 0.20 to 0.60% of C, 0.05 to 1.0% of Si, 0.35 to 3.0% of Mn, 0.025% or less of P, 0.010% or less of S, 0.005 to 0.10% of Al, 0.0003 to 0.01% of B, 0 to 0.5% of Ti, 0 to 1.0% of Zr, 0 to 2.0% of Hf, 0.005% or less of O, 0.008% or less of N, satisfies the following expressions: 0.008≤Ti+0.5Zr+0.25Hf≤0.05 and 0.0003≤B-(11/14)N+(11/48)Ti+(11/91)Zr+(11/178)Hf and comprises, if necessary, one or more selected from Cr, Mo, V, W, Nb, Ta, Ni, Cu, Co, Ca, Mg and REM in a specific amount.SELECTED DRAWING: Figure 1

Description

本発明は、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に関する。詳しくは、本発明は、高圧水素環境下での特性に優れる高圧水素用の、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に関する。   The present invention relates to a low alloy steel material, a low alloy steel pipe and a container, and a method for manufacturing the container. More specifically, the present invention relates to a low alloy steel material, a low alloy steel pipe and a container, and a method for producing the container, for high pressure hydrogen having excellent characteristics in a high pressure hydrogen environment.

近年、水素を燃料として走行する燃料電池自動車の開発および燃料電池自動車に水素を供給する水素ステーションの実用化研究が進められている。低合金鋼はこれまで主として水素ステーションに設置される水素を貯蔵する蓄圧器（以下、後述の「タンク」と纏めて「容器」ともいう。）に用いられている。従来の４５ＭＰａ級の水素ステーションには主としてＣｒおよびＭｏを含有するＪＩＳ ＳＣＭ４３５鋼が用いられ、特に、大型厚肉容器には、ＣｒとＭｏに加えて１．６〜２．０質量％のＮｉも含有するＳＮＣＭ４３９鋼が一般に用いられている。   In recent years, development of a fuel cell vehicle that runs on hydrogen as a fuel and research into practical use of a hydrogen station that supplies hydrogen to the fuel cell vehicle have been advanced. Until now, low alloy steel has been mainly used in pressure accumulators (hereinafter referred to as “tanks”, which will be described later, also referred to as “containers”) for storing hydrogen, which are mainly installed in hydrogen stations. JIS SCM435 steel mainly containing Cr and Mo is used for the conventional 45 MPa class hydrogen station, and in particular, a large thick container also contains 1.6 to 2.0 mass% Ni in addition to Cr and Mo. The SNCM439 steel it contains is generally used.

高圧水素ガス環境において優れた機械的特性や耐疲労特性を有する低合金鋼として、特許文献１には、０．１０〜０．２０質量％のＣに加え、Ｃｒ、ＭｏおよびＶを含有する引張強さが９００〜９５０ＭＰａの低合金鋼が開示されている。特許文献２には、特許文献１に開示された低合金鋼にさらにＮｉを含有させた引張強さが９００〜９５０ＭＰａの低合金鋼が開示されている。特許文献３には、０．１５〜０．６０質量％のＣに加え、ＭｏとＶを含有する引張強さが９００ＭＰａ以上の低合金鋼が開示されている。特許文献４には、０．０５〜０．１２質量％のＣを含有する、また、特許文献５には、０．０５〜０．１５質量％のＣを含有する、ベイナイト組織を主体とした低合金鋼材が開示されている。特許文献６には、特定量のＭｎ、Ｃｒ、ＭｏおよびＶを含有し引張強さが９００ＭＰａ以上である、厚さが１２ｍｍを超える厚肉容器にも好適な低合金鋼が開示されている。特許文献７には、Ｍｎ、Ｔｉ、ＮｂおよびＶ等を含有する、高圧水素環境中での耐疲労き裂進展特性に優れる鋼材が開示されている。   As a low alloy steel having excellent mechanical properties and fatigue resistance in a high-pressure hydrogen gas environment, Patent Document 1 describes a tensile material containing Cr, Mo, and V in addition to 0.10 to 0.20 mass% of C. A low alloy steel having a strength of 900 to 950 MPa is disclosed. Patent Document 2 discloses a low alloy steel having a tensile strength of 900 to 950 MPa in which Ni is further added to the low alloy steel disclosed in Patent Document 1. Patent Document 3 discloses a low alloy steel containing Mo and V in addition to 0.15 to 0.60 mass% C and having a tensile strength of 900 MPa or more. Patent Document 4 contains 0.05 to 0.12% by mass of C, and Patent Document 5 mainly contains a bainite structure containing 0.05 to 0.15% by mass of C. A low alloy steel is disclosed. Patent Document 6 discloses a low alloy steel that contains a specific amount of Mn, Cr, Mo, and V, has a tensile strength of 900 MPa or more, and is suitable for a thick container having a thickness exceeding 12 mm. Patent Document 7 discloses a steel material containing Mn, Ti, Nb, V, and the like and having excellent fatigue crack growth resistance in a high-pressure hydrogen environment.

特開２００９−４６７３７号公報JP 2009-46737 A 特開２００９−２７５２４９号公報JP 2009-275249 A 特開２００９−７４１２２号公報JP 2009-74122 A 特開２０１２−１０７３３２号公報JP 2012-107332 A 特開２０１２−１０７３３３号公報JP 2012-107333 A 特開２０１４−１７３１６０号公報JP 2014-173160 A 国際公開第２０１４／１５６１８７号International Publication No. 2014/156187

商用化が進められている燃料電池自動車としては、ガソリン車と同等の航続距離を確保するために、例えば、これまでの４５ＭＰａよりも高圧である７０ＭＰａの水素を充填可能なタンクを搭載した自動車（以下、「７０ＭＰａ級燃料電池自動車」という。）が要求される。そして、７０ＭＰａ級燃料電池自動車に水素を供給する水素ステーションには、上記水素タンクよりも高圧の水素を貯蔵可能なことが要求される。   As fuel cell vehicles being commercialized, in order to secure a cruising distance equivalent to that of a gasoline vehicle, for example, a vehicle equipped with a tank capable of filling hydrogen of 70 MPa, which is higher than the conventional 45 MPa ( Hereinafter, “70 MPa class fuel cell vehicle” is required. A hydrogen station that supplies hydrogen to a 70 MPa class fuel cell vehicle is required to store hydrogen at a higher pressure than the hydrogen tank.

ところで、高圧容器は以下の４タイプに分類される。
・Ｔｙｐｅ Ｉ：金属容器
・Ｔｙｐｅ ＩＩ：金属ライナー・フープ巻き容器
・Ｔｙｐｅ ＩＩＩ：金属ライナー・全周巻き容器
・Ｔｙｐｅ ＩＶ：非金属ライナー・全周巻き容器 By the way, high-pressure containers are classified into the following four types.
-Type I: Metal container-Type II: Metal liner-Hoop-wrapped container-Type III: Metal liner-All-around container-Type IV: Non-metal liner-All-around container

７０ＭＰａ級燃料電池自動車およびそれに対応するために水素ステーションに設置される容器には、強度および高圧水素ガスによる脆化（以下「水素ガス脆化」という。）に対する耐久性の観点から、Ｔｙｐｅ ＩＩＩの複合容器であって内面の金属ライナーを炭素繊維で強化したもの、またはＴｙｐｅ ＩＶの複合容器であって内面のプラスチックライナーを炭素繊維で強化したもの、が使用されている。なお、上記Ｔｙｐｅ ＩＩＩの複合容器の内面金属ライナーには、オーステナイト系ステンレス鋼（ＳＵＳ３１６系）またはアルミニウム合金が使用される。   From the viewpoint of strength and durability against embrittlement due to high-pressure hydrogen gas (hereinafter referred to as “hydrogen gas embrittlement”), a 70 MPa class fuel cell vehicle and a container installed in a hydrogen station to cope with the 70 MPa class fuel cell vehicle A composite container in which an inner metal liner is reinforced with carbon fibers or a Type IV composite container in which an inner plastic liner is reinforced with carbon fibers is used. Note that austenitic stainless steel (SUS316 series) or aluminum alloy is used for the inner metal liner of the Type III composite container.

しかし、Ｔｙｐｅ ＩＩＩおよびＴｙｐｅ ＩＶの複合容器は非常に高価である。このため、７０ＭＰａ級の高圧水素用容器として、上記複合容器と比較して安価なＴｙｐｅ Ｉの金属容器であって、特に低合金鋼からなるものが望まれている。   However, Type III and Type IV composite containers are very expensive. For this reason, as a 70 MPa class high-pressure hydrogen container, a type I metal container that is inexpensive compared with the composite container, and particularly made of low alloy steel is desired.

耐水素ガス脆化特性に優れた低合金鋼、低合金鋼材およびこのような低合金鋼製の容器は、特許文献１〜７に開示されている。特に、特許文献６に開示されているような厚肉の容器では、焼入れ性の向上に有効であるＢ（ボロン）を微量含有させた鋼を用いるのが有効である。ただし、これらの低合金鋼製容器を水素ステーションおよび燃料電池自動車に適用する際には、疲労寿命に基づいた寿命設計を行う必要があるため、良好かつ安定した耐疲労特性が求められる。   Patent Documents 1 to 7 disclose low-alloy steels, low-alloy steel materials, and containers made of such low-alloy steels that are excellent in hydrogen gas embrittlement resistance. In particular, in a thick container as disclosed in Patent Document 6, it is effective to use a steel containing a small amount of B (boron), which is effective in improving hardenability. However, when these low alloy steel containers are applied to a hydrogen station and a fuel cell vehicle, it is necessary to design a life based on the fatigue life, so that good and stable fatigue resistance is required.

通常の大気中の疲労試験では、個々の材料は、固有の疲労限度（無限の疲労寿命を示す応力（すなわち、疲労破壊を起こさない応力）の上限値。通常、繰返し応力の最大応力と最小応力との差の１／２である「応力振幅」で表される。）を有する。疲労試験における「疲労限度」および「応力振幅」にはそれぞれ、「σW」および「σa」の記号が用いられる。多くの場合、上記の疲労限度（σW）を材料の引張強さ（σB）で除した商である「耐久比」に基づいて使用応力条件が設定される。 In normal atmospheric fatigue tests, each material has its own fatigue limit (the upper limit of stress that exhibits an infinite fatigue life (ie, stress that does not cause fatigue failure). Usually, the maximum and minimum stresses of cyclic stress. It is expressed by “stress amplitude” which is ½ of the difference between Symbols “σ W ” and “σ a ” are used for “fatigue limit” and “stress amplitude” in the fatigue test, respectively. In many cases, the use stress condition is set based on the “durability ratio” which is a quotient obtained by dividing the fatigue limit (σ W ) by the tensile strength (σ B ) of the material.

低合金鋼の場合、耐久比（σW／σB）は、通常は０．４〜０．５程度である。一方、後述のように、本発明者らの詳細な検討によって、高圧水素ガス環境下では、耐久比以下の応力条件でも疲労寿命が極端に低下する場合のあることが初めて明らかになった。このため、高圧水素ガス環境下で低合金鋼を用いる場合、耐久比に基づく寿命設計が極めて難しかった。 In the case of low alloy steel, the durability ratio (σ W / σ B ) is usually about 0.4 to 0.5. On the other hand, as described later, the inventors' detailed examination revealed for the first time that, under a high-pressure hydrogen gas environment, the fatigue life may be extremely reduced even under a stress condition below the durability ratio. For this reason, when low alloy steel is used in a high-pressure hydrogen gas environment, life design based on the durability ratio is extremely difficult.

本発明は、高圧水素ガス環境下での耐久比に基づく寿命設計が可能であり、引張強さで８５０ＭＰａ以上の高い強度と０．４５以上の耐久比を有し、高圧水素ガス環境下での耐疲労特性に優れるとともに良好な耐水素ガス脆化特性を備える高圧水素用容器、該容器の素材として用いるのに好適な高圧水素用低合金鋼材および高圧水素用低合金鋼管、ならびに該容器の製造方法を提供することを目的とする。   The present invention can design a life based on a durability ratio under a high-pressure hydrogen gas environment, and has a high tensile strength of 850 MPa or more and a durability ratio of 0.45 or more under a high-pressure hydrogen gas environment. High-pressure hydrogen container having excellent fatigue resistance and good hydrogen gas embrittlement characteristics, low-alloy steel material for high-pressure hydrogen and low-alloy steel pipe for high-pressure hydrogen suitable for use as a material for the container, and production of the container It aims to provide a method.

本発明は、上記の課題を解決するために完成されたものであり、その要旨は、下記に示すいずれも高圧水素用の、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にある。   The present invention has been completed to solve the above-mentioned problems, and the gist of the present invention is a low alloy steel material, a low alloy steel pipe and a container for high pressure hydrogen, and a method for producing the container. is there.

（１）質量％で、
Ｃ：０．２０〜０．６０％、
Ｓｉ：０．０５〜１．０％、
Ｍｎ：０．３５〜３．０％、
Ｐ：０．０２５％以下、
Ｓ：０．０１０％以下、
Ａｌ：０．００５〜０．１０％、
Ｂ：０．０００３〜０．０１％、
Ｔｉ：０〜０．５％、
Ｚｒ：０〜１．０％、
Ｈｆ：０〜２．０％、
Ｏ：０．００５％以下、
Ｎ：０．００８％以下
Ｃｒ：０〜５．０％、
Ｍｏ：０〜１．５％、
Ｖ：０〜１．０％、
Ｗ：０〜３．０％、
Ｎｂ：０〜０．１％、
Ｔａ：０〜０．２％、
Ｎｉ：０〜５．０％、
Ｃｕ：０〜３．０％、
Ｃｏ：０〜３．０％、
Ｃａ：０〜０．０１％、
Ｍｇ：０〜０．０１％、
ＲＥＭ：０〜０．５０％、
残部：Ｆｅおよび不純物であり、かつ、
下記の式[1]で表されるＦｎ１が０．００８〜０．０５、および、
下記の式[2]で表されるＦｎ２が、０．０００３以上である、
化学組成を有し、
粒径１０μｍ以上の炭窒化物系介在物の個数が断面観察で１０個／１００ｍｍ2以下であり、
耐久比が０．４５以上である、
高圧水素用低合金鋼材。
Ｆｎ１＝Ｔｉ＋０．５Ｚｒ＋０．２５Ｈｆ・・・[1]
Ｆｎ２＝Ｂ−（１１／１４）Ｎ＋（１１／４８）Ｔｉ＋（１１／９１）Ｚｒ＋（１１／１７８）Ｈｆ・・・[2]
ただし、上記式中のＴｉ、Ｚｒ、Ｈｆ、ＢおよびＮは、それぞれの元素の鋼中含有量（質量％）を意味し、Ｔｉ、ＺｒおよびＨｆは、含有されない場合はゼロとする。 (1) In mass%,
C: 0.20 to 0.60%,
Si: 0.05 to 1.0%,
Mn: 0.35 to 3.0%,
P: 0.025% or less,
S: 0.010% or less,
Al: 0.005 to 0.10%,
B: 0.0003 to 0.01%,
Ti: 0 to 0.5%,
Zr: 0 to 1.0%,
Hf: 0 to 2.0%,
O: 0.005% or less,
N: 0.008% or less Cr: 0 to 5.0%,
Mo: 0 to 1.5%,
V: 0 to 1.0%
W: 0 to 3.0%
Nb: 0 to 0.1%,
Ta: 0 to 0.2%,
Ni: 0 to 5.0%,
Cu: 0 to 3.0%,
Co: 0 to 3.0%,
Ca: 0 to 0.01%,
Mg: 0 to 0.01%,
REM: 0 to 0.50%,
Balance: Fe and impurities, and
Fn1 represented by the following formula [1] is 0.008 to 0.05, and
Fn2 represented by the following formula [2] is 0.0003 or more.
Has a chemical composition,
The number of carbonitride inclusions having a particle size of 10 μm or more is 10/100 mm 2 or less by cross-sectional observation,
The durability ratio is 0.45 or more,
Low alloy steel for high pressure hydrogen.
Fn1 = Ti + 0.5Zr + 0.25Hf [1]
Fn2 = B- (11/14) N + (11/48) Ti + (11/91) Zr + (11/178) Hf [2]
However, Ti, Zr, Hf, B, and N in the above formula mean the contents (mass%) of each element in steel, and Ti, Zr, and Hf are zero when not contained.

（２）前記化学組成が、質量％で、
Ｃｒ：０．１〜５．０％、
Ｍｏ：０．１〜１．５％、
Ｖ：０．０１〜１．０％、
Ｗ：０．０１〜３．０％、
Ｎｂ：０．００１〜０．１％、
Ｔａ：０．００１〜０．２％、
Ｎｉ：０．１〜５．０％、
Ｃｕ：０．１〜３．０％、
Ｃｏ：０．１〜３．０％、
Ｃａ：０．０００１〜０．０１％、
Ｍｇ：０．０００１〜０．０１％、および、
ＲＥＭ：０．０００１〜０．５０％、
から選択される１種以上を含有する、上記（１）に記載の高圧水素用低合金鋼材。 (2) The chemical composition is mass%,
Cr: 0.1 to 5.0%,
Mo: 0.1 to 1.5%,
V: 0.01-1.0%
W: 0.01-3.0%
Nb: 0.001 to 0.1%,
Ta: 0.001 to 0.2%,
Ni: 0.1 to 5.0%,
Cu: 0.1 to 3.0%,
Co: 0.1-3.0%
Ca: 0.0001 to 0.01%,
Mg: 0.0001 to 0.01%, and
REM: 0.0001 to 0.50%,
The low alloy steel for high pressure hydrogen according to (1) above, which contains one or more selected from the above.

（３）旧オーステナイト結晶粒がＡＳＴＭ粒度番号９．０以上である、
上記（１）または（２）に記載の高圧水素用低合金鋼材。 (3) The prior austenite crystal grains are ASTM grain size number 9.0 or more,
The low alloy steel for high pressure hydrogen according to (1) or (2) above.

（４）上記（１）から（３）までのいずれかに記載の高圧水素用低合金鋼材からなる、
高圧水素用低合金鋼管。 (4) The high-pressure hydrogen low alloy steel material according to any one of (1) to (3) above,
Low alloy steel pipe for high pressure hydrogen.

（５）上記（４）に記載の高圧水素用低合金鋼管からなり、
引張強さが８５０ＭＰａ以上である、
高圧水素用容器。 (5) The low-alloy steel pipe for high-pressure hydrogen described in (4) above,
The tensile strength is 850 MPa or more,
High pressure hydrogen container.

（６）上記（５）に記載の高圧水素用容器を製造する方法であって、
前記高圧水素用低合金鋼管を所定の形状に成形加工した後、８８０〜９５０℃に加熱・保持してから、８００〜５００℃の温度域における平均冷却速度を２℃／秒以上として焼入れし、次いで、焼戻しする、
高圧水素用容器の製造方法。 (6) A method for producing the high-pressure hydrogen container according to (5) above,
After forming and processing the low-alloy steel pipe for high-pressure hydrogen into a predetermined shape, after heating and holding at 880 to 950 ° C., quenching with an average cooling rate in the temperature range of 800 to 500 ° C. being 2 ° C./second or more, Then temper,
A method for producing a container for high pressure hydrogen.

本発明によれば、高圧水素ガス環境下での耐久比に基づく寿命設計が可能であり、引張強さで８５０ＭＰａ以上の高い強度を有し、高圧水素ガス環境下での耐疲労特性に優れるとともに良好な耐水素ガス脆化特性を備える高圧水素用容器、該容器の素材として用いるのに好適な高圧水素用低合金鋼材および高圧水素用低合金鋼管を得ることができる。また、本発明の方法によれば、このような高圧水素用容器を安定して得ることができる。   According to the present invention, the life design based on the durability ratio under a high-pressure hydrogen gas environment is possible, the tensile strength is as high as 850 MPa or more, and the fatigue resistance under a high-pressure hydrogen gas environment is excellent. A high-pressure hydrogen container having good hydrogen gas embrittlement characteristics, a low-pressure steel material for high-pressure hydrogen and a low-alloy steel pipe for high-pressure hydrogen that are suitable for use as a material for the container can be obtained. Moreover, according to the method of the present invention, such a high-pressure hydrogen container can be obtained stably.

実施例に記載の鋼Ａおよび鋼Ｗを用いて、常温大気中での疲労試験および常温９０ＭＰａの高圧水素ガス中での疲労試験を行い、横軸に疲労寿命（単位：回）を、縦軸に応力振幅（σa）（単位：ＭＰａ）と引張強さ（σB）（単位：ＭＰａ）との比「σa／σB」をとって、高圧水素ガス環境下、耐久比（σW／σB）となる応力条件で疲労寿命が極端に低下する例を示す図である。なお、鋼Ａのデータが白丸印と白三角印であり、鋼Ｗのデータが黒三角印である。Using the steel A and the steel W described in the examples, a fatigue test in a normal temperature atmosphere and a fatigue test in a high-pressure hydrogen gas at a normal temperature of 90 MPa are performed, the horizontal axis indicates the fatigue life (unit: times), and the vertical axis The ratio “σ a / σ B ” between the stress amplitude (σ a ) (unit: MPa) and the tensile strength (σ B ) (unit: MPa) is used to determine the durability ratio (σ W It is a figure which shows the example which fatigue life falls extremely on the stress conditions used as / (sigma) B ). In addition, the data of the steel A are white circle marks and white triangle marks, and the data of the steel W is black triangle marks.

本発明者らは、種々の低合金鋼材を用いて、応力振幅（σa）を種々に変化させて引張強さ（σB）との比である「σa／σB」が、常温において、大気中および高圧水素ガス環境下で疲労寿命（疲労破壊を生じるまでの応力の繰返しの回数で、「Ｎf」の記号が用いられる。）に及ぼす影響について検討した。その結果、高圧水素ガス環境下では、耐久比（σW／σB）以下の応力条件でも疲労寿命（Ｎf）が極端に低下する場合のあることが明らかになった。 The inventors of the present invention use various low alloy steel materials, change the stress amplitude (σ a ) variously, and change the ratio of the tensile strength (σ B ) to “σ a / σ B ” at room temperature. The effect on fatigue life (the number of repetitions of stress until fatigue failure occurs and the symbol “N f ” is used) in the atmosphere and in a high-pressure hydrogen gas environment was examined. As a result, it has been clarified that under a high-pressure hydrogen gas environment, the fatigue life (N f ) may be extremely reduced even under a stress condition less than the durability ratio (σ W / σ B ).

図１に、高圧水素ガス環境下、耐久比（σW／σB）となる応力条件で疲労寿命（Ｎf）が極端に低下する場合の一例を示す。図１において、白丸印の「大気中」および白三角印の「水素中」のプロットは、後述の実施例中の鋼Ａを用いた試験番号１の詳細データであり、また、黒三角印の「水素中（介在物）」のプロットは、実施例中の鋼Ｗを用いた試験番号２３のデータである（実施例の表１および表２参照。）。 FIG. 1 shows an example of a case where the fatigue life (N f ) is extremely reduced under a stress condition that results in a durability ratio (σ W / σ B ) in a high-pressure hydrogen gas environment. In FIG. 1, the plots of “in the atmosphere” with white circles and “in hydrogen” with white triangles are detailed data of test number 1 using steel A in the examples described later. The plot of “in hydrogen (inclusions)” is data of test number 23 using steel W in the examples (see Tables 1 and 2 in the examples).

図１において、横軸は疲労寿命（Ｎf）（単位：回）で、縦軸は応力振幅（σa）（単位：ＭＰａ）と引張強さ（σB）（単位：ＭＰａ）との比「σa／σB」である。 In FIG. 1, the horizontal axis is fatigue life (N f ) (unit: times), and the vertical axis is the ratio of stress amplitude (σ a ) (unit: MPa) to tensile strength (σ B ) (unit: MPa). “Σ a / σ B ”.

白丸印で示すように、大気中の疲労試験では、横軸の疲労寿命（Ｎf）は縦軸の「σa／σB」に応じて変化するが、所定の「σa／σB」以下では疲労破壊が起こらなくなり、無限の疲労寿命（以下、「無限寿命」という。）となる。図１の例では、１０7回で試験を中断しており、１０7回耐久した条件を「無限寿命」と解釈した。そして、無限寿命となる応力振幅（σa）の上限値が疲労限度（σW）で、その（σW）と引張強さ（σB）との比「σW／σB」が耐久比になる。低合金鋼の耐久比は、通常は０．４〜０．５程度の値となり、図１の場合は、０．５である。 As indicated by white circles, in the fatigue test in the atmosphere, the fatigue life (N f ) on the horizontal axis changes according to “σ a / σ B ” on the vertical axis, but the predetermined “σ a / σ B ” In the following, fatigue failure does not occur, and the fatigue life is infinite (hereinafter referred to as “infinite life”). In the example of FIG. 1, it has been abort the test 107 times, was interpreted as "infinite life" 10 7 times endurance criteria. The upper limit of the stress amplitude (σ a ) that gives an infinite life is the fatigue limit (σ W ), and the ratio (σ W / σ B ) between the (σ W ) and tensile strength (σ B ) is the durability ratio. become. The durability ratio of the low alloy steel is usually about 0.4 to 0.5, and is 0.5 in the case of FIG.

一方、白三角印で示すように、高圧水素ガス中の疲労試験では、応力振幅（σa）が疲労限度（σW）より大きい応力条件では、水素の影響により、大気中での疲労試験に比べて、疲労寿命（Ｎf）は低下する。ただし、耐久比に及ぼす水素の影響はほとんど無く、図１の場合では、大気中と同様に耐久比は０．５となる。従って、高圧水素ガス環境下においても、耐久比以下の応力条件で部材の設計を行えば、大気中と同様の寿命設計が可能なはずである。しかし、黒三角印で示すように、高圧水素ガス中の疲労試験では、耐久比以下の応力条件でも、極端な短寿命で疲労破壊が起こることがある。 On the other hand, as shown by white triangle marks, in fatigue tests in high-pressure hydrogen gas, under stress conditions where the stress amplitude (σ a ) is greater than the fatigue limit (σ W ), the fatigue test in the atmosphere is caused by the influence of hydrogen. In comparison, the fatigue life (N f ) decreases. However, there is almost no influence of hydrogen on the durability ratio, and in the case of FIG. 1, the durability ratio is 0.5 as in the atmosphere. Therefore, even in a high-pressure hydrogen gas environment, if a member is designed under a stress condition below the durability ratio, it should be possible to design a life similar to that in the atmosphere. However, as indicated by the black triangle mark, in a fatigue test in high-pressure hydrogen gas, fatigue failure may occur with an extremely short life even under stress conditions below the durability ratio.

本発明者らは、図１中の黒三角印で示すような、低合金鋼の高圧水素ガス環境における耐久比以下の応力条件での疲労寿命（Ｎf）の低下の原因について調査した。その結果、炭窒化物系介在物を起点とした疲労破壊による現象であることが明らかになった。 The inventors investigated the cause of the decrease in fatigue life (N f ) under stress conditions below the durability ratio in a high-pressure hydrogen gas environment of low alloy steel, as indicated by the black triangles in FIG. As a result, it became clear that this phenomenon was caused by fatigue fracture starting from carbonitride inclusions.

そこでさらに、詳細な調査を行った結果、次の重要な知見が得られた。   As a result of further detailed investigation, the following important findings were obtained.

耐久比以下の応力条件で疲労破壊の起点として作用し、疲労寿命（Ｎf）の大きな低下の原因となる炭窒化物系介在物はその粒径が１０μｍ以上である。しかし、粒径が１０μｍ以上の粗大な炭窒化物系介在物の個数が、断面観察で１０個／１００ｍｍ2以下であれば、図１中の黒三角印の場合のような、疲労寿命のイレギュラーな低下が生じないので、良好な疲労寿命を確保できる。上記介在物の「粒径」とは、各介在物の最長となる寸法を長径ａ（μｍ）、その長径に対して垂直な方向を幅とし、その幅の最長値を短径ｂ（μｍ）とした場合に、（ａ×ｂ）0.5の値を指す。 Carbonitride-based inclusions that act as a starting point for fatigue fracture under stress conditions below the durability ratio and cause a significant decrease in fatigue life (N f ) have a particle size of 10 μm or more. However, if the number of coarse carbonitride inclusions having a particle size of 10 μm or more is 10/100 mm 2 or less in cross-sectional observation, the fatigue life is reduced as in the case of the black triangle mark in FIG. Since a regular drop does not occur, a good fatigue life can be secured. The “particle size” of the inclusions is the longest dimension a (μm) of the longest dimension of each inclusion, the width perpendicular to the major axis is the width, and the longest value of the width is the minor axis b (μm). In this case, the value is (a × b) 0.5 .

なお、軸受鋼等で問題となる高サイクル条件下では、介在物を起点とした疲労破壊が起こることは広く知られている。しかし、高圧水素用材料としての使用を想定した低サイクル条件下の場合、大気中では上記のような介在物起点の疲労破壊は起こらない。従って、上記の粗大な炭窒化物系介在物を起点とした疲労破壊は、高圧水素ガス環境下において特有の現象であり、介在物周囲にトラップされた水素の影響と、介在物自身の大きさ（応力集中）が重畳した破壊現象と考えられる。通常の鋼の場合には、粗大な炭窒化物系介在物が生成することは少ない。しかし、焼入れ性向上のためＢを含有させる鋼の場合には、Ｂ窒化物（ＢＮ）の生成を抑制し固溶Ｂを確保するために窒化物生成能の強いＴｉ、ＺｒやＨｆを含有させる必要があり、このＴｉ、ＺｒやＨｆが粗大な炭窒化物系介在物（以下、「Ｔｉ−Ｚｒ−Ｈｆの炭窒化物系介在物」ということがある。）を形成する。   It is well known that fatigue fracture occurs starting from inclusions under high cycle conditions that are problematic for bearing steels and the like. However, in the case of low cycle conditions assuming use as a high-pressure hydrogen material, the above-described fatigue starting from inclusions does not occur in the atmosphere. Therefore, fatigue fracture starting from the above coarse carbonitride inclusions is a unique phenomenon in a high-pressure hydrogen gas environment, and the influence of hydrogen trapped around the inclusions and the size of the inclusions themselves. This is considered to be a fracture phenomenon in which (stress concentration) is superimposed. In the case of ordinary steel, coarse carbonitride inclusions are rarely generated. However, in the case of steel containing B in order to improve hardenability, Ti, Zr and Hf having a strong nitride-forming ability are contained in order to suppress the formation of B nitride (BN) and ensure solid solution B. The Ti, Zr, and Hf need to form coarse carbonitride inclusions (hereinafter, sometimes referred to as “Ti—Zr—Hf carbonitride inclusions”).

また、耐久比（σW／σB）を、換言すれば、疲労限度（σW）を極力大きくすることによって、より高応力の条件で部材が使用できるメリットが生まれる。耐久比には基地組織の均質性が強く影響する。この観点から、高圧水素用材料の場合にも、旧オーステナイト結晶粒の微細化が耐久比の向上に有効であって、望ましい旧オーステナイト結晶粒はＡＳＴＭ粒度番号で９．０番以上であることが判明した。さらに、焼入れ−焼戻し処理による製造の場合には、マルテンサイト相の分率（以下、単に「マルテンサイト率」という。）が高いほど均質組織となり、耐久比が向上するので、８０％以上のマルテンサイト率を確保することが望ましいことも確認できた。 Further, by increasing the durability ratio (σ W / σ B ), in other words, the fatigue limit (σ W ) as much as possible, there is an advantage that the member can be used under higher stress conditions. The durability ratio is strongly influenced by the homogeneity of the base tissue. From this point of view, also in the case of high-pressure hydrogen materials, refinement of the prior austenite crystal grains is effective in improving the durability ratio, and the desirable prior austenite crystal grains are ASTM grain size numbers of 9.0 or more. found. Furthermore, in the case of manufacturing by quenching and tempering treatment, the higher the fraction of martensite phase (hereinafter simply referred to as “martensite ratio”), the more homogeneous the structure and the durability ratio is improved. It was also confirmed that it is desirable to secure the site rate.

本発明は、上記の内容に基づいて完成されたものである。以下、本発明の各要件について詳しく説明する。   The present invention has been completed based on the above contents. Hereinafter, each requirement of the present invention will be described in detail.

１．化学組成：
本発明に係る高圧水素用低合金鋼材、高圧水素用低合金鋼管および高圧水素用容器の化学組成の限定理由は次のとおりである。以下の説明において、各元素の含有量についての「％」は、「質量％」を意味する。 1. Chemical composition:
The reasons for limiting the chemical composition of the low alloy steel for high pressure hydrogen, the low alloy steel pipe for high pressure hydrogen, and the container for high pressure hydrogen according to the present invention are as follows. In the following description, “%” for the content of each element means “mass%”.

Ｃ：０．２０〜０．６０％
Ｃは、鋼の焼入れ性を高めるのに有効な元素であり、０．２０％以上含有させる必要がある。一方、０．６０％を超えて過剰にＣを含有させてもその効果は飽和し、また。焼入れ時の焼割れの危険性が増す。このため、Ｃの含有量は０．２０〜０．６０％とする。Ｃ含有量の好ましい下限は０．２５％であり、より好ましい下限は０．３０％である。Ｃ含有量の好ましい上限は０．５０％であり、より好ましい上限は０．４０％である。 C: 0.20 to 0.60%
C is an element effective for enhancing the hardenability of steel, and needs to be contained by 0.20% or more. On the other hand, the effect is saturated even if C is contained excessively exceeding 0.60%. Increased risk of cracking during quenching. For this reason, the C content is set to 0.20 to 0.60%. The minimum with preferable C content is 0.25%, and a more preferable minimum is 0.30%. The upper limit with preferable C content is 0.50%, and a more preferable upper limit is 0.40%.

Ｓｉ：０．０５〜１．０％
Ｓｉは、鋼の脱酸に有効な元素である。脱酸効果を得るには、Ｓｉ含有量を０．０５％以上とする必要がある。一方、Ｓｉ含有量が１．０％を超えると、軟質相であるフェライト相の析出を促進して、靱性等の機械的特性を低下させる。このため、Ｓｉの含有量は０．０５〜１．０％とする。Ｓｉ含有量の好ましい下限は０．１０％であり、より好ましい下限は０．１５％である。Ｓｉ含有量の好ましい上限は０．８０％であり、より好ましい上限は０．６０％である。 Si: 0.05-1.0%
Si is an element effective for deoxidation of steel. In order to obtain a deoxidation effect, the Si content needs to be 0.05% or more. On the other hand, when the Si content exceeds 1.0%, precipitation of the ferrite phase, which is a soft phase, is promoted, and mechanical properties such as toughness are deteriorated. For this reason, content of Si shall be 0.05-1.0%. The minimum with preferable Si content is 0.10%, and a more preferable minimum is 0.15%. The upper limit with preferable Si content is 0.80%, and a more preferable upper limit is 0.60%.

Ｍｎ：０．３５〜３．０％
Ｍｎは、鋼の焼入れ性を向上させるのに有効な元素である。この効果を得るには、少なくとも０．３５％のＭｎを含有させる必要がある。一方、３．０％を超えてＭｎを含有させてもその効果は飽和する。このため、Ｍｎの含有量は０．３５〜３．０％とする。Ｍｎ含有量の好ましい下限は０．４０％であり、より好ましい下限は０．５０％である。Ｍｎ含有量の好ましい上限は２．０％であり、より好ましい上限は１．５％である。 Mn: 0.35 to 3.0%
Mn is an element effective for improving the hardenability of steel. In order to obtain this effect, it is necessary to contain at least 0.35% of Mn. On the other hand, the effect is saturated even if Mn is contained exceeding 3.0%. For this reason, content of Mn shall be 0.35-3.0%. The minimum with preferable Mn content is 0.40%, and a more preferable minimum is 0.50%. The upper limit with preferable Mn content is 2.0%, and a more preferable upper limit is 1.5%.

Ｐ：０．０２５％以下
Ｐは、結晶粒界に偏析し、靱性および耐水素ガス脆化特性を低下させる。このため、Ｐ含有量は０．０２５％以下に制限する必要がある。Ｐ含有量はできるだけ少ないことが望ましい。 P: 0.025% or less P segregates at the crystal grain boundary and lowers toughness and hydrogen gas embrittlement resistance. For this reason, P content needs to be limited to 0.025% or less. It is desirable that the P content is as low as possible.

Ｓ：０．０１％以下
ＳもＰと同様に粒界に偏析し、靱性および耐水素ガス脆化特性を低下させる。さらに、Ｓは、硫化物系介在物を生成し、高圧水素ガス環境における疲労寿命を低下させる。このため、Ｓ含有量は０．０１％以下とする必要がある。Ｓ含有量はできるだけ少ないことが好ましく、含有量の上限は望ましくは０．００５％、さらに望ましくは０．００３％である。 S: 0.01% or less S, like P, segregates at the grain boundaries, reducing toughness and hydrogen gas embrittlement resistance. Furthermore, S produces sulfide inclusions and reduces the fatigue life in a high-pressure hydrogen gas environment. For this reason, S content needs to be 0.01% or less. The S content is preferably as small as possible, and the upper limit of the content is desirably 0.005%, and more desirably 0.003%.

Ａｌ：０．００５〜０．１０％
Ａｌは、鋼の脱酸に有効な元素である。その効果は、Ａｌの含有量が０．００５％未満では得られない。一方、０．１０％を超えてＡｌを含有させてもその効果は飽和する。このため、Ａｌの含有量は０．００５〜０．１０％とする。Ａｌ含有量の好ましい下限は０．０１％であり、より好ましい下限は０．０２％である。Ａｌ含有量の好ましい上限は０．０７％であり、より好ましい上限は０．０５％である。なお、本発明のＡｌ含有量とは、酸可溶Ａｌ（「Ｓｏｌ．Ａｌ」）での含有量を指す。 Al: 0.005-0.10%
Al is an element effective for deoxidation of steel. The effect cannot be obtained when the Al content is less than 0.005%. On the other hand, the effect is saturated even if Al is contained exceeding 0.10%. For this reason, the content of Al is set to 0.005 to 0.10%. A preferable lower limit of the Al content is 0.01%, and a more preferable lower limit is 0.02%. The upper limit with preferable Al content is 0.07%, and a more preferable upper limit is 0.05%. In addition, Al content of this invention points out content in acid-soluble Al ("Sol.Al").

Ｂ：０．０００３〜０．０１％
Ｂは、微量の含有で鋼の焼入れ性を高め、マルテンサイト率を高めて大気中および水素中の耐久比を向上させるのに有効な元素であって、焼入性を確保するために、０．０００３％以上含有させる必要がある。一方、０．０１％を超える量のＢを含有させても上記の効果が飽和する。このため、Ｂ含有量は０．０００３〜０．０１％とする。ただし、Ｂの含有量は、十分な焼入性を確保するために、焼入れ性に有効に働く固溶Ｂの指標となる前記の式[2]で表されるＦｎ２が０．０００３以上も満たす量でなければならない。 B: 0.0003 to 0.01%
B is an element effective for improving the hardenability of steel with a small amount of content, increasing the martensite ratio, and improving the durability ratio in the atmosphere and in hydrogen, and is 0 for ensuring hardenability. It is necessary to contain 0003% or more. On the other hand, the above effect is saturated even if B is contained in an amount exceeding 0.01%. For this reason, B content shall be 0.0003-0.01%. However, in order to ensure sufficient hardenability, the content of B satisfies that Fn2 represented by the above formula [2] serving as an index of solid solution B that effectively works on hardenability is 0.0003 or more. Must be quantity.

Ｔｉ：０〜０．５％
Ｔｉは、ＺｒおよびＨｆと同様に、炭窒化物生成能が強い元素の１つであり、鋼中のＮ（窒素）およびＣと結びついて、炭窒化物を形成する。Ｔｉ、ＺｒやＨｆの次に窒化物生成能が強い元素はＢであるため、固溶Ｎが残っている場合には、Ｂが窒化物（ＢＮ）を形成し、焼入れに有効に働く固溶Ｂ量が減少してしまう。従って、ＢＮの形成を防止するために、Ｔｉを含有させるが、０．５％を超える量のＴｉを含有させても上記の効果が飽和して材料コストの上昇を招く。このため、Ｔｉ含有量の上限を０．５％とする。なお、Ｔｉの含有量は、Ｂの焼入れ性向上効果を十分確保させるために、前記の式[1]および式[2]で表されるＦｎ１およびＦｎ２がそれぞれ、０．００８以上および０．０００３以上も満たす量でなければならない。さらに、Ｔｉの含有量は、高圧水素ガス環境下での疲労破壊の起点となる粗大な炭窒化物系介在物の多量の生成を抑止するために、前記の式[1]で表されるＦｎ１が０．０５以下も満たす量でなければならない。 Ti: 0 to 0.5%
Ti, like Zr and Hf, is one of the elements having a strong carbonitride-forming ability and is combined with N (nitrogen) and C in steel to form carbonitride. The element having the strongest nitride forming ability next to Ti, Zr and Hf is B. Therefore, when solid solution N remains, B forms a nitride (BN) and is a solid solution that works effectively for quenching. B amount will decrease. Therefore, in order to prevent the formation of BN, Ti is contained. However, even if Ti is contained in an amount exceeding 0.5%, the above effect is saturated and the material cost is increased. For this reason, the upper limit of the Ti content is set to 0.5%. Note that the Ti content is such that Fn1 and Fn2 represented by the above formulas [1] and [2] are 0.008 or more and 0.0003, respectively, in order to sufficiently secure the effect of improving the hardenability of B. The amount must also satisfy the above. Furthermore, the content of Ti is Fn1 represented by the above formula [1] in order to suppress the generation of a large amount of coarse carbonitride inclusions that are the starting points of fatigue fracture in a high-pressure hydrogen gas environment. The amount must satisfy 0.05 or less.

Ｚｒ：０〜１．０％
Ｚｒは、ＴｉおよびＨｆと同様に、炭窒化物生成能が強い元素の１つであり、鋼中のＮおよびＣと結びついて、炭窒化物を形成する。Ｔｉ、ＺｒやＨｆの次に窒化物生成能が強い元素はＢであるため、固溶Ｎが残っている場合には、Ｂが窒化物（ＢＮ）を形成し、焼入れに有効に働く固溶Ｂ量が減少してしまう。従って、ＢＮの形成を防止するために、Ｚｒを含有させるが、１．０％を超える量のＺｒを含有させても上記の効果が飽和して材料コストの上昇を招く。このため、Ｚｒ含有量の上限を１．０％とする。なお、Ｚｒの含有量は、Ｂの焼入れ性向上効果を十分確保させるために、前記の式[1]および式[2]で表されるＦｎ１およびＦｎ２がそれぞれ、０．００８以上および０．０００３以上も満たす量でなければならない。さらに、Ｚｒの含有量は、高圧水素ガス環境下での疲労破壊の起点となる粗大な炭窒化物系介在物の多量の生成を抑止するために、前記の式[1]で表されるＦｎ１が０．０５以下も満たす量でなければならない。 Zr: 0 to 1.0%
Zr, like Ti and Hf, is one of the elements having a strong carbonitride-forming ability, and forms carbonitride by combining with N and C in steel. The element having the strongest nitride forming ability next to Ti, Zr and Hf is B. Therefore, when solid solution N remains, B forms a nitride (BN) and is a solid solution that works effectively for quenching. B amount will decrease. Therefore, in order to prevent the formation of BN, Zr is contained. However, even if Zr is contained in an amount exceeding 1.0%, the above effect is saturated and the material cost is increased. For this reason, the upper limit of the Zr content is set to 1.0%. Note that the content of Zr is such that Fn1 and Fn2 represented by the above formulas [1] and [2] are 0.008 or more and 0.0003, respectively, in order to sufficiently ensure the effect of improving the hardenability of B. The amount must also satisfy the above. Furthermore, the content of Zr is Fn1 represented by the above formula [1] in order to suppress the formation of a large amount of coarse carbonitride inclusions that are the starting points of fatigue fracture in a high-pressure hydrogen gas environment. The amount must satisfy 0.05 or less.

Ｈｆ：０〜２．０％
Ｈｆも、ＴｉおよびＺｒと同様に、炭窒化物生成能が強い元素の１つであり、鋼中のＮおよびＣと結びついて、炭窒化物を形成する。Ｔｉ、ＺｒやＨｆの次に窒化物生成能が強い元素はＢであるため、固溶Ｎが残っている場合には、Ｂが窒化物（ＢＮ）を形成し、焼入れに有効に働く固溶Ｂ量が減少してしまう。従って、ＢＮの形成を防止するために、Ｈｆを含有させるが、２．０％を超える量のＨｆを含有させても上記の効果が飽和して材料コストの上昇を招く。このため、Ｈｆ含有量の上限を１．０％とする。なお、Ｈｆの含有量は、Ｂの焼入れ性向上効果を十分確保させるために、前記の式[1]および式[2]で表されるＦｎ１およびＦｎ２がそれぞれ、０．００８以上および０．０００３以上も満たす量でなければならない。さらに、Ｈｆの含有量は、高圧水素ガス環境下での疲労破壊の起点となる粗大な炭窒化物系介在物の多量の生成を抑止するために、前記の式[1]で表されるＦｎ１が０．０５以下も満たす量でなければならない。 Hf: 0 to 2.0%
Hf, like Ti and Zr, is one of the elements having a strong carbonitride-forming ability and is combined with N and C in steel to form carbonitride. The element having the strongest nitride forming ability next to Ti, Zr and Hf is B. Therefore, when solid solution N remains, B forms a nitride (BN) and is a solid solution that works effectively for quenching. B amount will decrease. Therefore, in order to prevent the formation of BN, Hf is contained. However, even if Hf in an amount exceeding 2.0% is contained, the above effects are saturated and the material cost is increased. For this reason, the upper limit of the Hf content is 1.0%. Note that the content of Hf is such that Fn1 and Fn2 represented by the above formulas [1] and [2] are 0.008 or more and 0.0003, respectively, in order to sufficiently ensure the effect of improving the hardenability of B. The amount must also satisfy the above. Further, the content of Hf is Fn1 represented by the above formula [1] in order to suppress the generation of a large amount of coarse carbonitride inclusions that are the starting points of fatigue fracture in a high-pressure hydrogen gas environment. The amount must satisfy 0.05 or less.

上記のＴｉ、ＺｒおよびＨｆは、前記の式[1]で表されるＦｎ１が、０．００８〜０．０５を満たし、かつ、前記の式[2]で表されるＦｎ２が、０．０００３以上を満たせば、２種以上を複合して含有させる必要はなく、単独で含有させても良い。   In the above Ti, Zr, and Hf, Fn1 represented by the formula [1] satisfies 0.008 to 0.05, and Fn2 represented by the formula [2] is 0.0003. If the above is satisfied, it is not necessary to combine two or more kinds, and they may be contained alone.

Ｏ（酸素）：０．００５％以下
Ｏは、不純物として鋼中に存在し、含有量が０．００５％を超えると粗大な酸化物を形成して、靱性等の機械的特性および高圧水素ガス環境における疲労寿命を低下させる。このため、Ｏ含有量は０．００５％以下とする。Ｏ含有量はできるだけ少ないことが好ましく、含有量の上限は望ましくは０．００４％、さらに望ましくは０．００３％である。 O (oxygen): 0.005% or less O is present in steel as an impurity, and when the content exceeds 0.005%, a coarse oxide is formed, mechanical properties such as toughness, and high-pressure hydrogen gas. Reduces fatigue life in the environment. For this reason, the O content is set to 0.005% or less. The O content is preferably as small as possible, and the upper limit of the content is desirably 0.004%, and more desirably 0.003%.

Ｎ（窒素）：０．００８％以下
Ｎは不純物として鋼中に存在し、含有量が０．００８％を超えると粗大な窒化物を形成して、靱性等の機械的特性および高圧水素ガス環境における疲労寿命を低下させる。さらに、多量のＮは、ＢＮを形成し、Ｂの焼入れ性向上効果を低下させてしまう。このため、Ｎ含有量は０．００８％以下とする。Ｎ含有量はできるだけ低い方が好ましく、含有量の上限は望ましくは０．００６％、さらに望ましくは０．００５％である。 N (nitrogen): 0.008% or less N is present in steel as an impurity, and when the content exceeds 0.008%, coarse nitrides are formed, mechanical properties such as toughness and high-pressure hydrogen gas environment Reduces fatigue life. Further, a large amount of N forms BN and reduces the effect of improving the hardenability of B. For this reason, N content shall be 0.008% or less. The N content is preferably as low as possible, and the upper limit of the content is desirably 0.006%, and more desirably 0.005%.

Ｃｒ：０〜５．０％
Ｃｒは、焼入れ時に未固溶の微細な炭化物を生成し、結晶粒を微細化させて高圧水素ガス中の耐久比（換言すれば、疲労限度）を向上させる作用を有する。また、Ｃｒは、鋼の焼入れ性を向上させる作用も有する。このため、必要に応じてＣｒを含有させてもよい。しかし、５．０％を超える量のＣｒを含有させても上記の効果が飽和して材料コストの上昇を招く。従って、含有させる場合のＣｒ含有量の上限を５．０％とする。Ｃｒ含有量の上限は、３．０％であることが好ましく、１．２％であることがさらに好ましい。なお、前記の効果を安定して得るためには、Ｃｒ含有量の下限は、０．１％であることが好ましく、０．３％であることがさらに好ましい。 Cr: 0 to 5.0%
Cr has the effect | action which produces | generates the fine carbide | carbonized_material which does not dissolve at the time of hardening, refines | miniaturizes a crystal grain, and improves the durability ratio (in other words, fatigue limit) in high pressure hydrogen gas. Moreover, Cr also has the effect | action which improves the hardenability of steel. For this reason, you may contain Cr as needed. However, even if Cr is contained in an amount exceeding 5.0%, the above effect is saturated and the material cost is increased. Therefore, the upper limit of the Cr content when contained is 5.0%. The upper limit of the Cr content is preferably 3.0%, and more preferably 1.2%. In addition, in order to acquire the said effect stably, it is preferable that the minimum of Cr content is 0.1%, and it is further more preferable that it is 0.3%.

Ｍｏ：０〜１．５％
Ｍｏは、焼入れ時に未固溶の微細な炭化物を生成し、結晶粒を微細化させて高圧水素ガス中の耐久比を向上させる作用を有する。また、Ｍｏは、鋼の焼入れ性を向上させる作用も有する。このため、必要に応じてＭｏを含有させてもよい。しかし、１．５％を超える量のＭｏを含有させても上記の効果が飽和して材料コストの上昇を招く。従って、含有させる場合のＭｏ含有量の上限を１．５％とする。Ｍｏ含有量の上限は、１．０％であることが好ましく、０．８％であることがさらに好ましい。なお、前記の効果を安定して得るためには、Ｍｏ含有量の下限は、０．１％であることが好ましく、０．２％であることがさらに好ましい。 Mo: 0 to 1.5%
Mo has the effect | action which produces | generates the fine carbide | carbonized_material undissolved at the time of quenching, refines | miniaturizes a crystal grain, and improves the durable ratio in high pressure hydrogen gas. Moreover, Mo also has the effect | action which improves the hardenability of steel. For this reason, you may contain Mo as needed. However, even if Mo is contained in an amount exceeding 1.5%, the above effect is saturated and the material cost is increased. Therefore, the upper limit of the Mo content when contained is 1.5%. The upper limit of the Mo content is preferably 1.0%, and more preferably 0.8%. In addition, in order to acquire the said effect stably, it is preferable that the minimum of Mo content is 0.1%, and it is further more preferable that it is 0.2%.

Ｖ：０〜１．０％
Ｖは、焼入れ時に未固溶の微細な炭化物を生成し、結晶粒を微細化させて高圧水素ガス中の耐久比を向上させる作用を有する。また、Ｖは、鋼の焼入れ性を向上させる作用も有する。このため、必要に応じてＶを含有させてもよい。しかし、１．０％を超える量のＶを含有させても上記の効果が飽和して材料コストの上昇を招く。従って、含有させる場合のＶ含有量の上限を１．０％とする。Ｖ含有量の上限は、０．７％であることが好ましく、０．５％であることがさらに好ましい。なお、前記の効果を安定して得るためには、Ｖ含有量の下限は、０．０１％であることが好ましく、０．０３％であることがさらに好ましい。 V: 0 to 1.0%
V has the effect | action which produces | generates the fine carbide | carbonized_material which does not dissolve at the time of quenching, refines | miniaturizes a crystal grain, and improves the durable ratio in high pressure hydrogen gas. Moreover, V also has the effect | action which improves the hardenability of steel. For this reason, you may contain V as needed. However, even if V is contained in an amount exceeding 1.0%, the above effect is saturated and the material cost is increased. Therefore, the upper limit of the V content when contained is 1.0%. The upper limit of V content is preferably 0.7%, and more preferably 0.5%. In addition, in order to acquire the said effect stably, it is preferable that the minimum of V content is 0.01%, and it is further more preferable that it is 0.03%.

Ｗ：０〜３．０％
Ｗは、焼入れ時に未固溶の微細な炭化物を生成し、結晶粒を微細化させて高圧水素ガス中の耐久比を向上させる作用を有する。また、Ｗは、鋼の焼入れ性を向上させる作用も有する。このため、必要に応じてＷを含有させてもよい。しかし、３．０％を超える量のＶを含有させても上記の効果が飽和して材料コストの上昇を招く。従って、含有させる場合のＷ含有量の上限を３．０％とする。Ｗ含有量の上限は、２．０％であることが好ましく、１．５％であることがさらに好ましい。なお、前記の効果を安定して得るためには、Ｗ含有量の下限は、０．０１％であることが好ましく、０．１％であることがさらに好ましい。 W: 0 to 3.0%
W has the effect | action which produces | generates the fine carbide | carbonized_material which does not dissolve at the time of hardening, refines | miniaturizes a crystal grain, and improves the durable ratio in a high pressure hydrogen gas. W also has the effect of improving the hardenability of steel. For this reason, you may contain W as needed. However, even if V is contained in an amount exceeding 3.0%, the above effect is saturated and the material cost is increased. Therefore, the upper limit of the W content when contained is 3.0%. The upper limit of the W content is preferably 2.0%, and more preferably 1.5%. In addition, in order to acquire the said effect stably, it is preferable that the minimum of W content is 0.01%, and it is further more preferable that it is 0.1%.

上記のＣｒ、Ｍｏ、ＶおよびＷから選ばれる２種以上を複合して含有させる場合の合計量は、５．０％以下であることが好ましい。   The total amount in the case where two or more selected from Cr, Mo, V and W are combined and contained is preferably 5.0% or less.

Ｎｂ：０〜０．１％
Ｎｂは、焼入れ時に未固溶の微細な炭化物を生成し、結晶粒を微細化させ、高圧水素ガス中の耐久比を向上させる作用を有する。また、ＮｂはＴｉ、ＺｒやＨｆと結び付き、炭窒化物を形成するのでＮの固定に有効であり、Ｂの焼入れ性向上作用に寄与する。このため、必要に応じてＮｂを含有させてもよい。しかし、０．１％を超える量のＮｂを含有させても上記の効果が飽和して材料コストの上昇を招く。従って、含有させる場合のＮｂ含有量の上限を０．１％とする。Ｎｂ含有量の上限は、０．０８％であることが好ましく、０．０５％であることがさらに好ましい。なお、前記の効果を安定して得るためには、Ｎｂ含有量の下限は、０．００１％であることが好ましく、０．００５％であることがさらに好ましい。 Nb: 0 to 0.1%
Nb has the effect | action which produces | generates the insoluble fine carbide | carbonized_material at the time of hardening, refines | miniaturizes a crystal grain, and improves the durable ratio in a high pressure hydrogen gas. Further, Nb is combined with Ti, Zr and Hf to form carbonitride, so that it is effective for fixing N and contributes to the effect of improving the hardenability of B. For this reason, you may contain Nb as needed. However, even if Nb in an amount exceeding 0.1% is contained, the above effect is saturated and the material cost is increased. Therefore, the upper limit of Nb content in the case of making it contain shall be 0.1%. The upper limit of the Nb content is preferably 0.08%, more preferably 0.05%. In order to stably obtain the above effect, the lower limit of the Nb content is preferably 0.001%, and more preferably 0.005%.

Ｔａ：０〜０．２％
Ｔａは、焼入れ時に未固溶の微細な炭化物を生成し、結晶粒を微細化させ、高圧水素ガス中の耐久比を向上させる作用を有する。また、ＴａはＴｉ、ＺｒやＨｆと結び付き、炭窒化物を形成するのでＮの固定に有効であり、Ｂの焼入れ性向上作用に寄与する。このため、必要に応じてＴａを含有させてもよい。しかし、０．２％を超える量のＴａを含有させても上記の効果が飽和して材料コストの上昇を招く。従って、含有させる場合のＴａ含有量の上限を０．２％とする。Ｔａ含有量の上限は、０．１％であることが好ましく、０．０５％であることがさらに好ましい。なお、前記の効果を安定して得るためには、Ｔａ含有量の下限は、０．００１％であることが好ましく、０．００５％であることがさらに好ましい。 Ta: 0 to 0.2%
Ta has a function of generating insoluble fine carbides during quenching, refining crystal grains, and improving the durability ratio in high-pressure hydrogen gas. Further, Ta is effective for fixing N because it is combined with Ti, Zr, and Hf to form carbonitrides, and contributes to the effect of improving the hardenability of B. For this reason, you may contain Ta as needed. However, even if Ta is contained in an amount exceeding 0.2%, the above effect is saturated and the material cost is increased. Therefore, the upper limit of the Ta content when contained is 0.2%. The upper limit of the Ta content is preferably 0.1%, and more preferably 0.05%. In order to obtain the above effect stably, the lower limit of the Ta content is preferably 0.001%, and more preferably 0.005%.

上記のＮｂおよびＴａを複合して含有させる場合の合計量は、０．２％以下であることが好ましい。   The total amount in the case where Nb and Ta are combined and contained is preferably 0.2% or less.

Ｎｉ：０〜５．０％
Ｎｉは、鋼の焼入れ性を向上させる元素である。このため、必要に応じてＮｉを含有させてもよい。しかし、Ｎｉの含有量が５．０％を超えると、製造コストが大きく嵩む。このため、含有させる場合のＮｉ含有量の上限を５．０％とする。Ｎｉ含有量の上限は、３．０％であることが好ましく、１．０％であることがさらに好ましい。なお、前記の効果を安定して得るためには、Ｎｉ含有量の下限は、０．１％であることが好ましく、０．３％であることがさらに好ましい。 Ni: 0 to 5.0%
Ni is an element that improves the hardenability of steel. For this reason, you may contain Ni as needed. However, if the Ni content exceeds 5.0%, the manufacturing cost increases greatly. For this reason, the upper limit of Ni content in the case of making it contain shall be 5.0%. The upper limit of the Ni content is preferably 3.0%, and more preferably 1.0%. In order to obtain the above effect stably, the lower limit of the Ni content is preferably 0.1%, and more preferably 0.3%.

Ｃｕ：０〜３．０％
Ｃｕは、鋼の焼入れ性を向上させる元素である。このため、必要に応じてＣｕを含有させてもよい。しかし、Ｃｕの含有量が３．０％を超えると、製熱間加工性が低下する。このため、含有させる場合のＣｕ含有量の上限を３．０％とする。Ｃｕ含有量の上限は、２．０％であることが好ましく、１．０％であることがさらに好ましい。なお、前記の効果を安定して得るためには、Ｃｕ含有量の下限は、０．１％であることが好ましく、０．３％であることがさらに好ましい。 Cu: 0 to 3.0%
Cu is an element that improves the hardenability of steel. For this reason, you may contain Cu as needed. However, when the Cu content exceeds 3.0%, the hot-working processability is lowered. For this reason, when making it contain, the upper limit of Cu content shall be 3.0%. The upper limit of the Cu content is preferably 2.0%, and more preferably 1.0%. In addition, in order to acquire the said effect stably, it is preferable that the minimum of Cu content is 0.1%, and it is further more preferable that it is 0.3%.

Ｃｏ：０〜３．０％
Ｃｏは、鋼の焼入れ性を向上させる元素である。このため、必要に応じてＣｏを含有させてもよい。しかし、Ｃｏの含有量が３．０％を超えると、製造コストが大きく嵩む。このため、含有させる場合のＣｏ含有量の上限を３．０％とする。Ｃｏ含有量の上限は、２．０％であることが好ましく、１．０％であることがさらに好ましい。なお、前記の効果を安定して得るためには、Ｃｏ含有量の下限は、０．１％であることが好ましく、０．３％であることがさらに好ましい。 Co: 0 to 3.0%
Co is an element that improves the hardenability of steel. For this reason, you may contain Co as needed. However, if the Co content exceeds 3.0%, the manufacturing cost increases greatly. For this reason, the upper limit of Co content in the case of making it contain shall be 3.0%. The upper limit of the Co content is preferably 2.0%, and more preferably 1.0%. In order to obtain the above effect stably, the lower limit of the Co content is preferably 0.1%, and more preferably 0.3%.

上記のＮｉ、ＣｕおよびＣｏから選ばれる２種以上を複合して含有させる場合の合計量は、５．０％以下であることが好ましい。   The total amount when two or more selected from the above-mentioned Ni, Cu and Co are combined is preferably 5.0% or less.

Ｃａ：０〜０．０１％
Ｃａは、鋼中のＳと結合して硫化物を形成し、介在物の形状を改善して靱性等の機械的特性を向上させる効果を有する。このため、必要に応じてＣａを含有させてもよい。しかし、Ｃａを０．０１％を超えて含有させてもこうした効果が飽和する。このため、含有させる場合のＣａ含有量の上限を０．０１％とする。Ｃａ含有量の上限は、０．００５％であることが好ましく、０．００３％であることがさらに好ましい。なお、前記の効果を安定して得るためには、Ｃａ含有量の下限は、０．０００１％であることが好ましく、０．０００３％であることがさらに好ましい。 Ca: 0 to 0.01%
Ca combines with S in steel to form sulfides, and has the effect of improving the shape of inclusions and improving mechanical properties such as toughness. For this reason, you may contain Ca as needed. However, such effects are saturated even if Ca is contained in excess of 0.01%. For this reason, the upper limit of Ca content in the case of making it contain shall be 0.01%. The upper limit of the Ca content is preferably 0.005%, and more preferably 0.003%. In addition, in order to acquire the said effect stably, it is preferable that the minimum of Ca content is 0.0001%, and it is further more preferable that it is 0.0003%.

Ｍｇ：０〜０．０１％
Ｍｇは、鋼中のＳと結合して硫化物を形成し、介在物の形状を改善して靱性等の機械的特性を向上させる効果を有する。このため、必要に応じてＭｇを含有させてもよい。しかし、Ｍｇを０．０１％を超えて含有させてもこうした効果が飽和する。このため、含有させる場合のＭｇ含有量の上限を０．０１％とする。Ｍｇ含有量の上限は、０．００５％であることが好ましく、０．００３％であることがさらに好ましい。なお、前記の効果を安定して得るためには、Ｍｇ含有量の下限は、０．０００１％であることが好ましく、０．０００３％であることがさらに好ましい。 Mg: 0 to 0.01%
Mg combines with S in steel to form sulfides, and has an effect of improving the shape of inclusions and improving mechanical properties such as toughness. For this reason, you may contain Mg as needed. However, these effects are saturated even if Mg is contained in excess of 0.01%. For this reason, the upper limit of Mg content in the case of making it contain shall be 0.01%. The upper limit of the Mg content is preferably 0.005%, and more preferably 0.003%. In order to obtain the above effect stably, the lower limit of the Mg content is preferably 0.0001%, and more preferably 0.0003%.

ＲＥＭ：０〜０．５０％
ＲＥＭは、鋼中のＳと結合して硫化物を形成し、介在物の形状を改善して靱性等の機械的特性を向上させる効果を有する。このため、必要に応じてＲＥＭを含有させてもよい。しかし、ＲＥＭを０．５０％を超えて含有させてもこうした効果が飽和する。このため、含有させる場合のＲＥＭ含有量の上限を０．５０％とする。ＲＥＭ含有量の上限は、０．４０％であることが好ましく、０．３０％であることがさらに好ましい。なお、前記の効果を安定して得るためには、ＲＥＭ含有量の下限は、０．０００１％であることが好ましく、０．０００５％であることがさらに好ましい。 REM: 0 to 0.50%
REM combines with S in steel to form sulfides, and has the effect of improving the shape of inclusions and improving mechanical properties such as toughness. For this reason, you may contain REM as needed. However, even if REM is contained in excess of 0.50%, such an effect is saturated. For this reason, the upper limit of REM content in the case of making it contain shall be 0.50%. The upper limit of the REM content is preferably 0.40%, and more preferably 0.30%. In addition, in order to acquire the said effect stably, it is preferable that the minimum of REM content is 0.0001%, and it is further more preferable that it is 0.0005%.

本発明において「ＲＥＭ」とは、Ｓｃ、Ｙ、およびランタノイドの合計１７元素を指し、「ＲＥＭの含有量」とは、ＲＥＭが１種の場合はその含有量、２種以上の場合はそれらの合計含有量を指す。また、ＲＥＭは一般的には複数種のＲＥＭの合金であるミッシュメタルとしても供給されている。このため、個別の元素を１種または２種以上添加してＲＥＭの量が上記の範囲となるように含有させてもよいし、例えば、ミッシュメタルの形で添加して、ＲＥＭの量が上記の範囲となるように含有させてもよい。   In the present invention, “REM” refers to a total of 17 elements of Sc, Y, and lanthanoid, and “REM content” refers to the content when REM is 1 type, and the content thereof when 2 or more types are included. Refers to the total content. REM is also supplied as misch metal, which is generally an alloy of a plurality of types of REM. For this reason, one or more individual elements may be added and contained so that the amount of REM is in the above range. For example, the amount of REM may be added in the form of misch metal. You may make it contain so that it may become this range.

上記のＣａ、ＭｇおよびＲＥＭから選ばれる２種以上を複合して含有させる場合の合計量は、０．５０％以下であることが好ましい。   The total amount when two or more selected from the above-mentioned Ca, Mg, and REM are combined is preferably 0.50% or less.

本発明に係る高圧水素用低合金鋼材、高圧水素用低合金鋼管および高圧水素用容器は、上述の各元素と、残部がＦｅおよび不純物であり、かつ、前記の式[1]で表されるＦｎ１が０．００８〜０．０５、および、前記の式[2]で表されるＦｎ２が０．０００３以上である、化学組成を有する。   The low-alloy steel material for high-pressure hydrogen, the low-alloy steel pipe for high-pressure hydrogen, and the high-pressure hydrogen container according to the present invention are each of the above-described elements, the balance being Fe and impurities, and represented by the above formula [1] It has a chemical composition in which Fn1 is 0.008 to 0.05, and Fn2 represented by the above formula [2] is 0.0003 or more.

ここで「不純物」とは、鉄鋼材料を工業的に製造する際に、鉱石、スクラップ等の原料、製造工程の種々の要因によって混入する成分であって、本発明に悪影響を与えない範囲で許容されるものを意味する。   Here, “impurities” are components mixed in due to various factors of raw materials such as ores and scraps and manufacturing processes when industrially producing steel materials, and are permitted within a range that does not adversely affect the present invention. Means what will be done.

Ｆｎ１：０．００８以上で０．０５以下
本発明に係る高圧水素用低合金鋼材、高圧水素用低合金鋼管および高圧水素用容器は、下記の式[1]で表されるＦｎ１が０．００８以上で０．０５以下であるものである。
Ｆｎ１＝Ｔｉ＋０．５Ｚｒ＋０．２５Ｈｆ・・・[1]
ただし、式[1]中のＴｉ、ＺｒおよびＨｆは、それぞれの元素の鋼中含有量（質量％）を意味し、含有されない場合はゼロとする。 Fn1: 0.008 or more and 0.05 or less The low alloy steel for high pressure hydrogen, the low alloy steel pipe for high pressure hydrogen and the container for high pressure hydrogen according to the present invention have an Fn1 represented by the following formula [1] of 0.008. The above is 0.05 or less.
Fn1 = Ti + 0.5Zr + 0.25Hf [1]
However, Ti, Zr, and Hf in the formula [1] mean the contents (mass%) of each element in steel, and are zero when not contained.

Ｆｎ１が０．００８未満の場合には、鋼中に固溶Ｎが残って、Ｂが窒化物（ＢＮ）を形成し、焼入れに有効に働く固溶Ｂ量が減少して、Ｂの焼入れ性向上効果が十分に得られないことがある。一方、Ｆｎ１で０．０５を超える量のＴｉ、ＺｒおよびＨｆを含有させても、Ｂの焼入れ性向上効果が飽和するし、高圧水素ガス環境下での疲労破壊の起点となる粗大なＴｉ−Ｚｒ−Ｈｆの炭窒化物系介在物の多量の生成を招くため、耐疲労特性が低下する。Ｆｎ１の好ましい下限は０．０１であり、より好ましい下限は０．０１２である。Ｆｎ１の好ましい上限は０．０３であり、より好ましい上限は０．０２である。   When Fn1 is less than 0.008, solid solution N remains in the steel, B forms a nitride (BN), and the amount of solid solution B that effectively works for quenching is reduced. The improvement effect may not be sufficiently obtained. On the other hand, even when Ti, Zr, and Hf in an amount exceeding 0.05 are contained in Fn1, the effect of improving the hardenability of B is saturated, and coarse Ti− that becomes a starting point of fatigue fracture in a high-pressure hydrogen gas environment Since a large amount of Zr—Hf carbonitride inclusions is generated, the fatigue resistance is deteriorated. A preferable lower limit of Fn1 is 0.01, and a more preferable lower limit is 0.012. The upper limit with preferable Fn1 is 0.03, and a more preferable upper limit is 0.02.

Ｆｎ２：０．０００３以上
本発明に係る高圧水素用低合金鋼材、高圧水素用低合金鋼管および高圧水素用容器は、下記の式[2]で表されるＦｎ２が０．０００３以上であるものである。
Ｆｎ２＝Ｂ−（１１／１４）Ｎ＋（１１／４８）Ｔｉ＋（１１／９１）Ｚｒ＋（１１／１７８）Ｈｆ・・・[2]
ただし、式[2]中のＢ、Ｎ、Ｔｉ、ＺｒおよびＨｆは、それぞれの元素の鋼中含有量（質量％）を意味し、Ｔｉ、ＺｒおよびＨｆは、含有されない場合はゼロとする。 Fn2: 0.0003 or more The low alloy steel for high pressure hydrogen, the low alloy steel pipe for high pressure hydrogen and the container for high pressure hydrogen according to the present invention have Fn2 represented by the following formula [2] of 0.0003 or more. is there.
Fn2 = B- (11/14) N + (11/48) Ti + (11/91) Zr + (11/178) Hf [2]
However, B, N, Ti, Zr and Hf in the formula [2] mean the content (mass%) of each element in steel, and Ti, Zr and Hf are zero when not contained.

Ｆｎ２は、十分な焼入性を確保するための、焼入れ性に有効に働く固溶Ｂの指標であり、この値が０．０００３以上の場合に、上記Ｆｎ１と相俟って良好な焼入れ性を具備できる。Ｆｎ２の好ましい下限は０．０００５であり、より好ましい下限は０．００１である。Ｆｎ２の好ましい上限は０．００２である。   Fn2 is an indicator of solid solution B that effectively works on hardenability to ensure sufficient hardenability. When this value is 0.0003 or more, good hardenability is combined with Fn1. Can be provided. A preferred lower limit of Fn2 is 0.0005, and a more preferred lower limit is 0.001. A preferable upper limit of Fn2 is 0.002.

２．介在物：
高圧水素ガス中の疲労寿命には、炭窒化物系介在物が強く影響する。特に、耐久比以下の応力条件で、粒径が１０μｍ以上である炭窒化物系介在物は、疲労破壊の起点として作用し、高圧水素ガス環境における疲労寿命の大きな低下の原因となる。しかし、粒径が１０μｍ以上の粗大な炭窒化物系介在物の個数が、断面観察で１０個／１００ｍｍ2以下であれば、疲労寿命のイレギュラーな低下が生じない。このため、本発明に係る高圧水素用低合金鋼材、高圧水素用低合金鋼管および高圧水素用容器は、粒径１０μｍ以上の炭窒化物系介在物の個数を断面観察で１０個／１００ｍｍ2以下とする。粒径１０μｍ以上の炭窒化物系介在物の個数は断面観察で、８個／１００ｍｍ2以下であることが好ましく、５個／１００ｍｍ2以下であればより好ましい。 2. Inclusions:
The fatigue life in high-pressure hydrogen gas is strongly influenced by carbonitride inclusions. In particular, carbonitride-based inclusions having a particle size of 10 μm or more under a stress condition of a durability ratio or less act as a starting point for fatigue failure and cause a significant decrease in fatigue life in a high-pressure hydrogen gas environment. However, if the number of coarse carbonitride inclusions having a particle size of 10 μm or more is 10/100 mm 2 or less in cross-sectional observation, the fatigue life is not irregularly reduced. For this reason, the low alloy steel material for high pressure hydrogen, the low alloy steel tube for high pressure hydrogen, and the container for high pressure hydrogen according to the present invention are 10/100 mm 2 or less in the number of carbonitride inclusions having a particle size of 10 μm or more by cross-sectional observation. And The number of carbonitride inclusions having a particle size of 10 μm or more is preferably 8 pieces / 100 mm 2 or less, more preferably 5 pieces / 100 mm 2 or less in cross-sectional observation.

なお、上記の炭窒化物系介在物の「粒径」とは、各介在物の最長となる寸法を長径ａ（μｍ）、その長径に対して垂直な方向を幅とし、その幅の最長値を短径ｂ（μｍ）とした場合に、（ａ×ｂ）0.5の値を指す。 The “particle size” of the carbonitride inclusions is the longest dimension of each inclusion, the major axis a (μm), the direction perpendicular to the major axis as the width, and the longest value of the width. Indicates a value of (a × b) 0.5 where B is a minor axis b (μm).

上記粒径が１０μｍ以上である炭窒化物系介在物の個数条件は、疲労破壊が問題となる高応力が負荷される部位で満足すれば良いが、より安全側で評価をする場合は、該介在物が粗大化し易い、インゴットまたは連続鋳造された鋳片の、最終凝固位置に対応する部位（例えば、厚板素材の板厚の中央部、継目無鋼管の内面近傍等）で介在物の計測を行えば良い。一方、上記介在物個数を過度に低減することは製鋼コストの上昇につながる。よって、製鋼コストの上昇を抑えるため、粒径１０μｍ以上の炭窒化物系介在物の個数は、断面観察で３個／１００ｍｍ2以上であっても良い。 The number condition of the carbonitride inclusions having a particle size of 10 μm or more may be satisfied at a site where high stress that causes fatigue failure is applied. Inclusion measurement at the part corresponding to the final solidification position of the ingot or continuous cast slab where the inclusion is likely to become coarse (for example, the central part of the plate thickness of the thick plate material, the inner surface of the seamless steel pipe, etc.) Just do it. On the other hand, excessively reducing the number of inclusions leads to an increase in steelmaking costs. Therefore, in order to suppress an increase in steelmaking cost, the number of carbonitride inclusions having a particle size of 10 μm or more may be 3/100 mm 2 or more by cross-sectional observation.

粗大な炭窒化物系介在物の低減には、Ｎの含有量を低減することも有効である。さらに、溶鋼の冷却過程で該介在物は凝集・粗大化するため、溶鋼の冷却速度を速くすることも有効である。望ましくは、１５００〜１０００℃の温度域における平均冷却速度を５０℃／分以上とするのが良い。また、これ以外にも製鋼時に粗大介在物を浮揚除去する種々の製鋼方法、例えば、タンディッシュヒーター等の活用も有効である。   Reducing the N content is also effective for reducing coarse carbonitride inclusions. Furthermore, since the inclusions agglomerate and become coarse during the cooling process of the molten steel, it is also effective to increase the cooling rate of the molten steel. Desirably, the average cooling rate in the temperature range of 1500 to 1000 ° C. should be 50 ° C./min or more. In addition to this, it is also effective to use various steelmaking methods for levitating and removing coarse inclusions during steelmaking, such as tundish heaters.

炭窒化物系介在物の同定には、光学顕微鏡で観察された粒径１０μｍ以上の非金属介在物を走査型電子顕微鏡（以下、「ＳＥＭ」という。）観察時に、付属するエネルギー分散型Ｘ線分析装置にて、軽元素（Ｓ、Ｏ、Ｎ、ＢおよびＣ）以外のＦｅを含む各金属元素の含有量（質量比）を求めれば良い。本発明では、この方法で、Ｔｉ、Ｚｒ、Ｈｆ、ＮｂおよびＴａを合計で８０質量％以上含有する介在物を炭窒化物系介在物として同定した。   For identification of carbonitride inclusions, an energy dispersive X-ray attached to a non-metallic inclusion having a particle diameter of 10 μm or more observed with an optical microscope at the time of observation with a scanning electron microscope (hereinafter referred to as “SEM”). What is necessary is just to obtain | require content (mass ratio) of each metal element containing Fe other than a light element (S, O, N, B, and C) in an analyzer. In the present invention, by this method, inclusions containing at least 80% by mass of Ti, Zr, Hf, Nb and Ta were identified as carbonitride inclusions.

３．耐久比：
低合金鋼を高圧水素ガス環境下で用いた場合に、疲労寿命のイレギュラーな低下が生じなければ、耐久比が高いほど、使用応力条件の設定を安定かつ確実に行うことができる。従って、本発明に係る高圧水素用低合金鋼材、高圧水素用低合金鋼管および高圧水素用容器は、耐久比が０．４５以上とする。 3. Durability ratio:
When the low alloy steel is used in a high-pressure hydrogen gas environment, unless the fatigue life is irregularly reduced, the higher the durability ratio, the more stable and reliable the setting of the operating stress conditions can be made. Therefore, the durability ratio of the low alloy steel for high pressure hydrogen, the low alloy steel pipe for high pressure hydrogen and the container for high pressure hydrogen according to the present invention is 0.45 or more.

４．旧オーステナイト結晶粒：
高圧水素ガス中の耐久比（σW／σB）の向上、換言すれば、疲労限度（σW）の向上には、鋼材の結晶粒度が影響する。０．４５以上の高い耐久比を確保して、より高応力の条件で部材を使用するために、本発明に係る高圧水素用低合金鋼材、高圧水素用低合金鋼管および高圧水素用容器は、旧オーステナイト結晶粒のＡＳＴＭ粒度番号が９．０番以上であることが望ましい。なお、工業的な製造工程では該粒度番号の上限は１２．０程度である。 4). Old austenite grains:
The improvement of the durability ratio (σ W / σ B ) in high-pressure hydrogen gas, in other words, the improvement of the fatigue limit (σ W ), is influenced by the crystal grain size of the steel material. In order to ensure a high durability ratio of 0.45 or more and use the member under higher stress conditions, the low alloy steel for high pressure hydrogen, the low alloy steel pipe for high pressure hydrogen and the high pressure hydrogen container according to the present invention are: It is desirable that the prior austenite crystal grains have an ASTM grain size number of 9.0 or more. In an industrial production process, the upper limit of the particle size number is about 12.0.

ＡＳＴＭ粒度番号は、鋼材から採取した試料を樹脂に埋めて断面を鏡面研磨した後、例えば、界面活性剤を添加したピクリン酸飽和水溶液によって腐食（エッチング）し、光学顕微鏡によって観察することにより測定することができる。なお、電子線後方散乱回折法（Electron Back Scatter Diffraction、ＥＢＳＤ）を用いて得られた、マルテンサイト組織の結晶方位図から、マルテンサイト変態前の旧オーステナイト粒の結晶方位をマルテンサイト変態時にマルテンサイトとオーステナイトが持つ特定の結晶方位関係（例えば、Ｋｕｒｄｊｕｍｏｖ−Ｓａｃｈｓの関係）を用いて再構築することで、旧オーステナイト結晶粒のＡＳＴＭ粒度番号を求めることもできる。   The ASTM particle size number is measured by burying a sample collected from a steel material in a resin and mirror-polishing the cross section, then corroding (etching) with a saturated aqueous solution of picric acid to which a surfactant is added, and observing with an optical microscope. be able to. The crystal orientation of the prior austenite grains before the martensitic transformation was determined from the martensitic crystal orientation diagram obtained using the electron backscatter diffraction (EBSD) martensite transformation. It is also possible to obtain the ASTM grain number of the prior austenite crystal grains by restructuring using a specific crystal orientation relationship (for example, Kurdjumov-Sachs relationship) possessed by and austenite.

高圧水素ガス中の耐久比には、基地組織の均質性も強く影響する。０．４５以上の高い耐久比を確保するには、鋼材の組織が焼戻しマルテンサイト相が主体の組織からなることが望ましい。焼戻し後の組織からマルテンサイト率を測定することは難しいが、マルテンサイト率は焼入れままの鋼材の硬さに反映される。高圧水素ガス環境における耐久比を低下させないためのマルテンサイト率は８０％以上であり、これを確保するためには、焼入れままの硬さが、ロックウェルＣスケール硬さ（以下、「ＨＲＣ」という。）で「５０Ｃ＋２６（ただし、「Ｃ」はＣの鋼中含有量（質量％）を表す。）」以上であることが望ましい。   The durability ratio in high-pressure hydrogen gas is also strongly influenced by the homogeneity of the base structure. In order to secure a high durability ratio of 0.45 or more, it is desirable that the steel material has a structure mainly composed of a tempered martensite phase. Although it is difficult to measure the martensite ratio from the structure after tempering, the martensite ratio is reflected in the hardness of the as-quenched steel material. The martensite ratio in order not to lower the durability ratio in the high-pressure hydrogen gas environment is 80% or more, and in order to ensure this, the hardness as quenched is referred to as Rockwell C scale hardness (hereinafter referred to as “HRC”). )), “50C + 26 (where“ C ”represents the content (mass%) of C in steel)” or more is desirable.

５．引張強さ：
本発明の高圧水素用容器は、引張強さが８５０ＭＰａ以上である。この引張強さであれば、７０ＭＰａ級の高圧水素用容器として安定して用いることができる。なお、上記引張強さの上限は十分な耐水素ガス脆化特性を確保する観点から１０００ＭＰａ程度である。 5. Tensile strength:
The high-pressure hydrogen container of the present invention has a tensile strength of 850 MPa or more. With this tensile strength, it can be stably used as a 70 MPa class high-pressure hydrogen container. The upper limit of the tensile strength is about 1000 MPa from the viewpoint of securing sufficient hydrogen gas embrittlement resistance.

６．製造方法：
本発明の高圧水素用容器は、例えば、以下の方法により製造することができるが、この方法には限定されない。 6). Production method:
The high-pressure hydrogen container of the present invention can be produced, for example, by the following method, but is not limited to this method.

上記で説明した化学組成を有する低合金鋼を、溶製した後、鋳造によりインゴットまたは鋳片とする。継目無鋼管を製造する場合には、いわゆる「ラウンドＣＣ」法によって、製管用の円形ビレット形状を有する鋳片にしてもよい。なお、粗大な炭窒化物系介在物の低減のために、溶鋼の１５００〜１０００℃の温度域における平均冷却速度を５０℃／分以上とするのが良い。また、製鋼時に粗大介在物を浮揚除去する種々の製鋼方法、例えば、タンディッシュヒーター等を活用することも有効である。   After melting the low alloy steel having the chemical composition described above, it is cast into an ingot or slab. When a seamless steel pipe is manufactured, a slab having a circular billet shape for pipe making may be formed by a so-called “round CC” method. In order to reduce coarse carbonitride inclusions, the average cooling rate in the temperature range of 1500 to 1000 ° C. of molten steel is preferably 50 ° C./min or more. It is also effective to utilize various steelmaking methods for levitating and removing coarse inclusions during steelmaking, such as tundish heaters.

次の工程として、鋳造されたインゴットまたは鋳片に、分塊圧延、熱間圧延、熱間押出、熱間鍛造等の熱間加工を施して厚板、継目無鋼管等を製造し、これらを素材に用いて所定の高圧水素用容器形状に成形加工する。   As the next step, cast ingots or slabs are subjected to hot working such as block rolling, hot rolling, hot extrusion, hot forging, etc. to produce thick plates, seamless steel pipes, etc. The material is molded into a predetermined high-pressure hydrogen container shape.

上記の成形加工後、焼入れ−焼戻し処理を行う。望ましい焼入れの加熱温度は８８０〜９５０℃である。焼入れの加熱温度が８８０℃未満では、焼入れが不十分となり、マルテンサイト率が低下して、大気中および高圧水素ガス中での耐久比が低下することがある。焼入れの加熱温度が９５０℃を超えると、旧オーステナイト結晶粒が粗大化してＡＳＴＭ粒度番号９．０を下回って、大気中および高圧水素ガス中で耐久比が低下することがある。なお、上記温度域での保持時間は、高圧水素用容器のサイズや形状にもよるが、５〜９０分とすることが好ましく、１５〜６０分とすることがより好ましい。   A quenching-tempering process is performed after said shaping | molding process. A desirable quenching heating temperature is 880-950 ° C. When the heating temperature for quenching is less than 880 ° C., quenching becomes insufficient, the martensite ratio is lowered, and the durability ratio in the atmosphere and high-pressure hydrogen gas may be lowered. When the heating temperature for quenching exceeds 950 ° C., the prior austenite crystal grains become coarse and fall below the ASTM grain size number 9.0, and the durability ratio may decrease in the atmosphere and in high-pressure hydrogen gas. The holding time in the temperature range is preferably 5 to 90 minutes, more preferably 15 to 60 minutes, although it depends on the size and shape of the high-pressure hydrogen container.

上記の加熱・保持後の焼入れは、８０％以上のマルテンサイト率を確保するために、例えば、水焼入れ、油焼入れ等によって、８００〜５００℃の温度域における平均冷却速度が２℃／秒以上となるように行うことが望ましい。なお、冷却設備には、浸漬設備、ミスト冷却設備、シャワー冷却設備等、適宜の設備を用いれば良い。焼入れ時の冷却速度は、高圧水素用容器形状にした成形加工材の最も冷却が遅い部位（両面焼入れの場合には板厚や肉厚の中央部、片面焼入れの場合には焼入れ側と反対面の表面）にＫタイプシース熱電対を取り付け、実測した温度履歴から算出すれば良い。   In order to ensure a martensite ratio of 80% or higher, the quenching after the heating and holding is performed by, for example, water quenching, oil quenching, or the like, and the average cooling rate in the temperature range of 800 to 500 ° C is 2 ° C / second or more. It is desirable to do so. In addition, what is necessary is just to use appropriate equipments, such as an immersion equipment, a mist cooling equipment, a shower cooling equipment, for a cooling equipment. The cooling rate during quenching is the slowest part of the molded material in the shape of a high-pressure hydrogen container (in the case of double-sided quenching, the center of the plate thickness or wall thickness, in the case of single-sided quenching, the opposite side from the quenching side A K-type sheathed thermocouple may be attached to the surface) and calculated from the actually measured temperature history.

焼入れに次いで焼戻し処理を行うが、その温度はＡｃ1点未満とし、かつ、８５０ＭＰａ以上の引張強さが得られる極力高い温度であることが望ましい。焼戻し処理の時間は特に限定されないが、容器全体を均質に熱処理する観点から、１０〜１２０分とすることが望ましい。 Tempering is performed after quenching, and the temperature is preferably less than Ac 1 point, and is preferably as high as possible to obtain a tensile strength of 850 MPa or more. The tempering time is not particularly limited, but is preferably 10 to 120 minutes from the viewpoint of uniformly heat-treating the entire container.

以下、実施例によって本発明をより具体的に説明するが、本発明はこれらの実施例に限定されるものではない。   EXAMPLES Hereinafter, although an Example demonstrates this invention more concretely, this invention is not limited to these Examples.

表１に示す化学組成を有する低合金鋼Ａ〜Ｗをそれぞれ、１．５〜３トン溶製した後、鋳造によりインゴットとした。なお、鋼Ａ〜Ｖでは、溶製後の１５００〜１０００℃の温度域における平均冷却速度は、全て５０℃／分以上であった。鋼Ｗについては、溶製後に保温処置を行って冷却速度を意図的に小さくしたので、１５００〜１０００℃の温度域における平均冷却速度は、２０℃／分であった。   Low alloy steels A to W having chemical compositions shown in Table 1 were melted by 1.5 to 3 tons, respectively, and then made into ingots by casting. In steels A to V, the average cooling rate in the temperature range of 1500 to 1000 ° C. after melting was 50 ° C./min or more. About steel W, since the heat retention treatment was performed after melting and the cooling rate was intentionally reduced, the average cooling rate in the temperature range of 1500 to 1000 ° C. was 20 ° C./min.

表１における鋼Ａ〜Ｑおよび鋼Ｗは、化学組成が本発明で規定する範囲内にある鋼である。一方、鋼Ｒ〜Ｖは、化学組成が本発明で規定する条件から外れた鋼である。表１中には各鋼について、下記の式で表されるＡｃ1点の計算値も併記した。なお、式中の各元素記号は、それぞれの元素の含有量（質量％）を示す。
Ａｃ1（℃）＝７５１−１６．３Ｃ＋３４．９Ｓｉ−２７．５Ｍｎ−５．５Ｃｕ−１５．９Ｎｉ＋１２．７Ｃｒ＋３．４Ｍｏ Steels A to Q and Steel W in Table 1 are steels whose chemical compositions are within the range defined by the present invention. On the other hand, the steels R to V are steels whose chemical compositions deviate from the conditions specified in the present invention. In Table 1, the calculated value of Ac 1 point represented by the following formula is also shown for each steel. In addition, each element symbol in a formula shows content (mass%) of each element.
Ac 1 (° C.) = 751-16.3C + 34.9Si-27.5Mn-5.5Cu-15.9Ni + 12.7Cr + 3.4Mo

Figure 2018012856
Figure 2018012856

上記の各インゴットに熱間鍛造および熱間圧延を施して、厚さ１５〜６０ｍｍの板材に仕上げた。   Each ingot was subjected to hot forging and hot rolling to finish a plate material having a thickness of 15 to 60 mm.

次いで、表２に示す条件で、各厚さの板材を焼入れした。なお、焼入れは、焼入れ媒体とその攪拌条件を種々変えて行い、焼入れ時の冷却速度は、板厚中央部にＫタイプシース熱電対を挿入し計測した。   Next, the plate material of each thickness was quenched under the conditions shown in Table 2. The quenching was performed by changing the quenching medium and the stirring conditions in various ways, and the cooling rate during quenching was measured by inserting a K-type sheath thermocouple at the center of the plate thickness.

各鋼について、焼入れままの各厚さの板材から、旧オーステナイト結晶粒のＡＳＴＭ粒度番号測定用試験片および板厚中心部のＨＲＣ測定用試験片を採取した。   For each steel, a specimen for ASTM grain number measurement of prior austenite crystal grains and a specimen for HRC measurement at the center of the plate thickness were collected from the as-quenched sheet material.

すなわち、焼入れままの板材の圧延方向に直角の方向から試験片を採取し、圧延方向に直角の断面が観察面になるように樹脂埋めし、鏡面研磨した後、界面活性剤を添加したピクリン酸飽和水溶液によって腐食（エッチング）し、光学顕微鏡観察して、旧オーステナイト結晶粒（以下、「旧オーステナイト粒」という。）のＡＳＴＭ粒度番号を測定した。   That is, a test piece was taken from the direction perpendicular to the rolling direction of the as-quenched plate material, resin-filled so that the cross section perpendicular to the rolling direction was the observation surface, mirror-polished, and then added with a surfactant. Corrosion (etching) with a saturated aqueous solution was performed, and the ASTM grain size number of the prior austenite crystal grains (hereinafter referred to as “old austenite grains”) was measured under an optical microscope.

また、焼入れままの板材から、各板厚まま×２０ｍｍ×２０ｍｍの寸法の試験片を採取し、板厚中心部のＨＲＣを測定し、マルテンサイト率が８０％以上となる指標である前述の「５０Ｃ＋２６」の値と比較した。   Further, from the as-quenched plate material, test pieces having dimensions of 20 mm × 20 mm are collected as they are, and the HRC at the center portion of the plate thickness is measured, and the martensite ratio is 80% or more. 50C + 26 "value.

さらに、各鋼について、各厚さの焼入れままの残りの板材に、表２に示す条件で焼戻しを行い、介在物測定用試験片、引張試験片および疲労試験片を採取した。   Furthermore, each steel was tempered under the conditions shown in Table 2 on the remaining as-quenched plate materials of each thickness, and inclusion test specimens, tensile test specimens, and fatigue test specimens were collected.

すなわち、各鋼について、焼戻し後の板材の板厚中心部から、１０ｍｍ×１０ｍｍ×１０ｍｍの寸法の介在物測定用の試験片を採取し、板の圧延方向に対して長手方向となる面（いわゆる、「Ｌ断面」）が観察面になるように樹脂埋めし、鏡面研磨した後、光学顕微鏡観察して１０ｍｍ×１０ｍｍの面積（１００ｍｍ2）における粒径１０μｍ以上の炭窒化物系介在物の個数を測定した。 That is, for each steel, a specimen for measuring inclusions having a size of 10 mm × 10 mm × 10 mm is taken from the center part of the thickness of the plate after tempering, and a surface that is in the longitudinal direction with respect to the rolling direction of the plate (so-called The number of carbon nitride-based inclusions having a particle size of 10 μm or more in an area of 10 mm × 10 mm (100 mm 2 ) was observed with an optical microscope after resin embedding so that the “L cross section” becomes the observation surface and mirror polishing. Was measured.

介在物の粒径は、各介在物の最長となる寸法を長径ａ（μｍ）、その長径に対して垂直な方向を幅とし、その幅の最長値を短径ｂ（μｍ）とした場合に、（ａ×ｂ）0.5の値とした。なお、介在物測定用試験片は各試験番号について１０個ずつ採取し、この１０個の試験片を用いて上記のようにして計測した粒径１０μｍ以上の炭窒化物系介在物の個数を算術平均して、その試験番号の介在物個数とした。 The particle size of the inclusions is determined when the longest dimension of each inclusion is the major axis a (μm), the direction perpendicular to the major axis is the width, and the longest width is the minor axis b (μm). , (A × b) 0.5 . In addition, ten test pieces for inclusion measurement were collected for each test number, and the number of carbonitride inclusions having a particle size of 10 μm or more measured using the ten test pieces as described above was arithmetically calculated. On average, the number of inclusions of the test number was used.

既に述べたように、炭窒化物系介在物の同定には、光学顕微鏡で観察された粒径１０μｍ以上の非金属介在物を再度ＳＥＭでの観察時に、付属するエネルギー分散型Ｘ線分析装置（本体、検出器とも日本電子（株）製ＪＸＡ−８５３０Ｆ）にて軽元素（Ｓ、Ｏ、Ｎ、ＢおよびＣ）以外のＦｅを含む各金属元素の含有量（質量比）を求めれば良い。このため、本実施例では、Ｔｉ、Ｚｒ、Ｈｆ、ＮｂおよびＴａを合計で８０質量％以上含有する介在物を炭窒化物系介在物と同定した。なお、試料表面は鏡面研磨、分析時の倍率は３０００倍、加速電圧は１５ｋＶ、照射電流は５ｎＡ、試料室真空度は２×１０-4Ｐａの条件で測定した。スペクトラム処理は、バックグラウンド処理有り、ＺＡＦ補正有り、で行った。 As already described, for the identification of carbonitride inclusions, an attached energy dispersive X-ray analyzer (non-metallic inclusions with a particle size of 10 μm or more observed with an optical microscope is again observed with an SEM ( What is necessary is just to obtain | require content (mass ratio) of each metal element containing Fe other than a light element (S, O, N, B, and C) in JXA-8530F by JEOL Ltd. for a main body and a detector. For this reason, in this example, inclusions containing at least 80 mass% of Ti, Zr, Hf, Nb, and Ta were identified as carbonitride inclusions. The sample surface was mirror-polished, the analysis magnification was 3000 times, the acceleration voltage was 15 kV, the irradiation current was 5 nA, and the sample chamber vacuum was 2 × 10 −4 Pa. Spectrum processing was performed with background processing and with ZAF correction.

また、焼戻し後の板材の板厚中心部から、圧延方向に平行な方向に、平行部直径が６ｍｍの丸棒引張試験片を採取し、常温で引張試験を行って引張強さ（σB）（単位：ＭＰａ）を求めた。 In addition, a round bar tensile test piece having a parallel part diameter of 6 mm is taken from the center part of the thickness of the plate after tempering in a direction parallel to the rolling direction, and subjected to a tensile test at room temperature to obtain a tensile strength (σ B ). (Unit: MPa) was determined.

さらに、焼戻し後の板材の板厚中心部から、圧延方向に平行な方向に、円形断面の棒状疲労試験片を採取し、常温の大気中および９０ＭＰａの高圧水素ガス環境で応力比（最小応力の最大応力に対する比で、「Ｒ」の記号が用いられる。）が−１（すなわち両振り）の条件で、単軸の引張圧縮の疲労試験を行った。この際、周波数は１Ｈｚとし、応力振幅（σa）（単位：ＭＰａ）を種々に変化させて試験を行い、疲労寿命（Ｎf）、つまり、疲労破壊が起こるまでの応力の繰返し回数を測定した。各鋼について、上記応力振幅（σa）と引張試験で求めた引張強さ（σB）との比「σa／σB」を求めた。 Furthermore, a rod-shaped fatigue test piece having a circular cross section was collected from the center of the thickness of the plate after tempering in a direction parallel to the rolling direction, and the stress ratio (minimum stress) was obtained in a normal temperature atmosphere and a high pressure hydrogen gas environment of 90 MPa. The ratio of maximum stress to the symbol “R” is used.) A uniaxial tensile and compression fatigue test was performed under the condition of −1 (ie, double swing). At this time, the frequency is set to 1 Hz, the test is performed by variously changing the stress amplitude (σ a ) (unit: MPa), and the fatigue life (N f ), that is, the number of times the stress is repeated until fatigue failure occurs is measured. did. For each steel, the ratio “σ a / σ B ” between the stress amplitude (σ a ) and the tensile strength (σ B ) determined in the tensile test was determined.

上記の大気中および高圧水素ガス中ともに、疲労試験は最大１０7回まで行い、１０7回耐久した条件を「無限寿命」とした。無限寿命となる応力振幅（σa）の上限値が疲労限度（σW）で、その（σW）と引張強さ（σB）との比「σW／σB」が耐久比になる。この耐久比となる応力条件（応力振幅条件）下で、各鋼について、棒状疲労試験片を５本ずつ用いて、さらに上記の高圧水素ガス中での疲労試験を行って、疲労寿命を求めた。 Both in the above atmosphere and a high-pressure hydrogen gas, fatigue test was carried out up to 10 7 times to 10 7 times endurance criteria as "infinite life". The upper limit of the stress amplitude (σ a ) that gives an infinite life is the fatigue limit (σ W ), and the ratio (σ W / σ B ) between that (σ W ) and tensile strength (σ B ) is the durability ratio . Under the stress condition (stress amplitude condition) at which the durability ratio is obtained, the fatigue life was obtained by performing a fatigue test in the above-described high-pressure hydrogen gas using five rod-shaped fatigue test pieces for each steel. .

表２に、上記の各試験結果を併せて示す。なお、表２では、耐久比となる応力条件下、高圧水素ガス中で行った疲労試験の結果について、最も短かった疲労寿命の値を「疲労寿命」として記載した。すなわち、耐久比となる応力条件の下に高圧水素ガス中で行った疲労試験の場合には、５本全ての試験片についてイレギュラーな疲労寿命の低下が認められなかった場合の疲労寿命は「１０7回以上（表中の記載では≧１×１０7）」となり、イレギュラーな結果が出た場合の疲労寿命は「１０7回未満」の具体的な回数となる。また、図１として、高圧水素ガス環境における耐久比（σW／σB）となる応力条件で、疲労寿命（Ｎf）が極端に低下する場合の一例として、鋼Ａを用いた試験番号１のデータ（白丸印と白三角印で、それぞれ「大気中」および「水素中」でのデータである。）と比較した場合の鋼Ｗを用いた試験番号２３の「水素中」でのデータ（黒三角印）を示す。 Table 2 also shows the results of the above tests. In Table 2, the fatigue life value that was the shortest was described as “fatigue life” for the result of the fatigue test conducted in high-pressure hydrogen gas under the stress condition that is the durability ratio. That is, in the case of a fatigue test conducted in high-pressure hydrogen gas under the stress condition that is the durability ratio, the fatigue life when no irregular fatigue life reduction is observed for all five test pieces is “ 10 7 times or more (in the table, ≧ 1 × 10 7 ) ”, and the fatigue life when an irregular result is obtained is a specific number of times“ less than 10 7 times ”. Further, as shown in FIG. 1, as an example of the case where the fatigue life (N f ) is extremely reduced under the stress condition that is the durability ratio (σ W / σ B ) in the high-pressure hydrogen gas environment, test number 1 using steel A (Data in “in hydrogen” of test number 23 using steel W when compared with the data (white circles and white triangles, respectively, “in air” and “in hydrogen”) (Black triangle mark).

Figure 2018012856
Figure 2018012856

表２から、本発明で規定する条件を満たす試験番号１〜１７は、大気中および高圧水素ガス中の耐久比となる応力条件における疲労寿命が１０7回以上（１０7回で破断無し）であり、良好な耐疲労特性を備えていることが明らかである。さらに、上記本発明例の試験番号１〜１７は、旧オーステナイト粒のＡＳＴＭ粒度番号が９．０以上で、かつ焼入れままのＨＲＣが前記「５０Ｃ＋２６」の値よりも十分大きくマルテンサイト率が高いため、大気中および高圧水素ガス中で０．４５以上の高い耐久比が得られている。 From Table 2, Test Nos. 1 to 17 satisfying the conditions specified in the present invention have a fatigue life of 10 7 times or more (no breakage at 10 7 times) under the stress condition that is the durability ratio in the atmosphere and high-pressure hydrogen gas. It is clear that it has good fatigue resistance. Furthermore, the test numbers 1 to 17 of the present invention examples are because the ASTM austenite grain size number is 9.0 or more and the as-quenched HRC is sufficiently larger than the value of “50C + 26” and the martensite ratio is high. In addition, a high durability ratio of 0.45 or more is obtained in the atmosphere and high-pressure hydrogen gas.

これに対して、比較例の試験番号１８〜２６は、高圧水素ガス中の耐久比となる応力条件における疲労寿命が短くて耐疲労特性に劣っているか、大気中および高圧水素ガス中の耐久比が低く、０．４５に満たなかった。   On the other hand, the test numbers 18 to 26 of the comparative examples show that the fatigue life is short and the fatigue resistance is inferior in the stress condition that is the durability ratio in the high-pressure hydrogen gas, or the durability ratio in the atmosphere and in the high-pressure hydrogen gas. Was low, less than 0.45.

試験番号１８は、大気中および高圧水素ガス中の耐久比となる応力条件における疲労寿命が１０7回以上である。しかし、用いた鋼ＲのＢ含有量が０．０００１％と低く、焼入れままのＨＲＣが前記「５０Ｃ＋２６」の値よりも小さくマルテンサイト率が低いため、大気中および高圧水素ガス中とも耐久比が０．３５であった。 Test No. 18 has a fatigue life of 10 7 times or more under a stress condition that provides a durability ratio in the atmosphere and high-pressure hydrogen gas. However, since the B content of the steel R used is as low as 0.0001% and the as-quenched HRC is smaller than the value of “50C + 26” and the martensite ratio is low, the durability ratio is high in the atmosphere and in high-pressure hydrogen gas. It was 0.35.

試験番号１９も、大気中および高圧水素ガス中の耐久比となる応力条件における疲労寿命が１０7回以上である。しかし、用いた鋼ＳのＦｎ２の値が「−０．０００５」であり、ＮがＢと結びついてＢＮを形成し、焼入れに有効な固溶Ｂ量が確保できず、焼入れままのＨＲＣが前記「５０Ｃ＋２６」の値よりも小さくマルテンサイト率が低いため、大気中および高圧水素ガス中とも耐久比が０．４であった。 Test No. 19 also has a fatigue life of 10 7 times or more under a stress condition that provides a durability ratio in the atmosphere and high-pressure hydrogen gas. However, the value of Fn2 of the used steel S is “−0.0005”, N is combined with B to form BN, and the amount of solute B effective for quenching cannot be secured, and the as-quenched HRC is Since the martensite ratio was smaller than the value of “50C + 26”, the durability ratio was 0.4 in the air and high-pressure hydrogen gas.

試験番号２０は、大気中および高圧水素ガス中とも耐久比は０．５であるし、大気中では耐久比となる応力条件における疲労寿命は１０7回以上で、良好な耐疲労特性が得られている。しかし、用いた鋼ＴのＴｉ含有量およびＦｎ１の値が本発明で規定する条件から外れるため、粗大な炭窒化物系介在物が多く生成した。このため、高圧水素ガス中での疲労破壊の起点となる、面積１００ｍｍ2中に存在した粒径１０μｍ以上の炭窒化物系介在物の個数が本発明で規定する条件から外れ、高圧水素ガス中の耐久比となる応力条件における疲労寿命は５．１×１０4回と短く、耐疲労特性に劣っている。 Test No. 20 has an endurance ratio of 0.5 in the atmosphere and in high-pressure hydrogen gas, and has a fatigue life of 10 7 times or more under the stress condition that is the endurance ratio in the atmosphere. ing. However, since the Ti content of the steel T used and the value of Fn1 deviated from the conditions defined in the present invention, many coarse carbonitride inclusions were generated. For this reason, the number of carbonitride inclusions having a particle size of 10 μm or more present in an area of 100 mm 2 , which is the starting point of fatigue fracture in high-pressure hydrogen gas, deviates from the conditions specified in the present invention. The fatigue life under the stress condition of the durability ratio is as short as 5.1 × 10 4 times and is inferior in fatigue resistance.

試験番号２１は、大気中および高圧水素ガス中とも耐久比は０．５であるし、大気中では耐久比となる応力条件における疲労寿命は１０7回以上で、良好な耐疲労特性が得られている。しかし、用いた鋼ＵのＺｒ含有量およびＦｎ１の値が本発明で規定する条件から外れるため、粗大な炭窒化物系介在物が多く生成した。このため、高圧水素ガス中での疲労破壊の起点となる、面積１００ｍｍ2中に存在した粒径１０μｍ以上の炭窒化物系介在物の個数が本発明で規定する条件から外れ、高圧水素ガス中の耐久比となる応力条件における疲労寿命は１．５×１０4回と短く、耐疲労特性に劣っている。 Test No. 21 has an endurance ratio of 0.5 in the atmosphere and in high-pressure hydrogen gas, and has a fatigue life of 10 7 times or more under the stress condition that is the endurance ratio in the atmosphere. ing. However, since the Zr content of the steel U used and the value of Fn1 deviated from the conditions defined in the present invention, many coarse carbonitride inclusions were generated. For this reason, the number of carbonitride inclusions having a particle size of 10 μm or more present in an area of 100 mm 2 , which is the starting point of fatigue fracture in high-pressure hydrogen gas, deviates from the conditions specified in the present invention. The fatigue life under the stress condition that gives the durability ratio is as short as 1.5 × 10 4 times and is inferior in fatigue resistance.

試験番号２２は、大気中および高圧水素ガス中とも耐久比は０．５であるし、大気中では耐久比となる応力条件における疲労寿命は１０7回以上で、良好な耐疲労特性が得られている。しかし、用いた鋼ＶのＮ含有量が本発明で規定する条件から外れて高いので、粗大な炭窒化物系介在物が多く生成した。このため、高圧水素ガス中での疲労破壊の起点となる、面積１００ｍｍ2中に存在した粒径１０μｍ以上の炭窒化物系介在物の個数が本発明で規定する条件から外れ、高圧水素ガス中の耐久比となる応力条件における疲労寿命は６．０×１０4回と短く、耐疲労特性に劣っている。 Test No. 22 has an endurance ratio of 0.5 in the atmosphere and in high-pressure hydrogen gas, and has a fatigue life of 10 7 times or more under the stress condition that is the endurance ratio in the atmosphere. ing. However, since the N content of the steel V used was high outside the conditions specified in the present invention, a large amount of coarse carbonitride inclusions were produced. For this reason, the number of carbonitride inclusions having a particle size of 10 μm or more present in an area of 100 mm 2 , which is the starting point of fatigue fracture in high-pressure hydrogen gas, deviates from the conditions specified in the present invention. The fatigue life under the stress condition of the durability ratio is as short as 6.0 × 10 4 times and is inferior in fatigue resistance.

化学組成が本発明で規定する範囲内にある鋼Ｗを用いた試験番号２３は、大気中および高圧水素ガス中とも耐久比は０．５であるし、大気中では耐久比となる応力条件における疲労寿命は１０7回以上で、良好な耐疲労特性が得られている。しかし、鋼Ｗを溶製直後の冷却速度が遅かったため、溶鋼の冷却過程で炭窒化物が粗大化し、面積１００ｍｍ2中に存在した粒径１０μｍ以上の炭窒化物系介在物の個数が本発明で規定する条件から外れ、高圧水素ガス中の耐久比となる応力条件における疲労寿命は３．１×１０4回と短く、耐疲労特性に劣っている。 Test No. 23 using steel W having a chemical composition within the range specified in the present invention has an endurance ratio of 0.5 in the atmosphere and in high-pressure hydrogen gas. The fatigue life is 10 7 times or more, and good fatigue resistance characteristics are obtained. However, since the cooling rate immediately after melting the steel W was slow, the carbonitride was coarsened during the cooling process of the molten steel, and the number of carbonitride inclusions having a particle size of 10 μm or more present in an area of 100 mm 2 was the present invention. The fatigue life under the stress condition that is the durability ratio in the high-pressure hydrogen gas is as short as 3.1 × 10 4 times and is inferior in fatigue resistance.

化学組成が本発明で規定する範囲内にある鋼Ａを用い、面積１００ｍｍ2中に存在した粒径１０μｍ以上の炭窒化物系介在物の個数も本発明で規定する条件を満たす試験番号２４は、大気中および高圧水素ガス中の耐久比となる応力条件における疲労寿命が１０7回以上である。しかし、焼入れの加熱温度が１０００℃であり、旧オーステナイト結晶粒が粗大化してＡＳＴＭ粒度番号９．０を下回るため、大気中および高圧水素ガス中高圧水素ガス中とも耐久比が０．４であった。 Using steel A having a chemical composition within the range specified in the present invention, the number of carbonitride inclusions having a particle size of 10 μm or more existing in an area of 100 mm 2 also satisfies the test number 24 satisfying the conditions specified in the present invention. In addition, the fatigue life is 10 7 times or more under the stress condition that is the durability ratio in the atmosphere and in the high-pressure hydrogen gas. However, since the heating temperature for quenching is 1000 ° C. and the prior austenite crystal grains become coarser and fall below ASTM grain size number 9.0, the durability ratio is 0.4 in the atmosphere and in the high-pressure hydrogen gas in the high-pressure hydrogen gas. It was.

化学組成が本発明で規定する範囲内にある鋼Ａを用い、面積１００ｍｍ2中に存在した粒径１０μｍ以上の炭窒化物系介在物の個数も本発明で規定する条件を満たす試験番号２５も、大気中および高圧水素ガス中の耐久比となる応力条件における疲労寿命が１０7回以上である。しかし、焼入れの加熱温度が８５０℃であり、焼入れままのＨＲＣが前記「５０Ｃ＋２６」の値よりも小さくマルテンサイト率が低いため、大気中および高圧水素ガス中とも耐久比が０．３５であった。 Using steel A having a chemical composition within the range specified by the present invention, the number of carbonitride inclusions having a particle size of 10 μm or more present in an area of 100 mm 2 is also the test number 25 satisfying the conditions specified by the present invention. In addition, the fatigue life is 10 7 times or more under the stress condition that is the durability ratio in the atmosphere and in the high-pressure hydrogen gas. However, the heating temperature for quenching was 850 ° C., and the as-quenched HRC was smaller than the value of “50C + 26” and the martensite ratio was low, so the durability ratio was 0.35 in the atmosphere and in high-pressure hydrogen gas. .

同様に、化学組成が本発明で規定する範囲内にある鋼Ａを用い、面積１００ｍｍ2中に存在した粒径１０μｍ以上の炭窒化物系介在物の個数も本発明で規定する条件を満たす試験番号２６も、大気中および高圧水素ガス中の耐久比となる応力条件における疲労寿命が１０7回以上である。しかし、焼入れの際の８００〜５００℃の温度域における平均冷却速度が１０℃／秒であり焼入れままのＨＲＣが前記「５０Ｃ＋２６」の値よりも小さくマルテンサイト率が低いため、大気中および高圧水素ガス中とも耐久比が０．４であった。 Similarly, the test using the steel A having a chemical composition within the range defined by the present invention and the number of carbonitride inclusions having a particle size of 10 μm or more present in an area of 100 mm 2 satisfies the conditions defined by the present invention. No. 26 also has a fatigue life of 10 7 times or more under a stress condition that provides a durability ratio in the atmosphere and high-pressure hydrogen gas. However, since the average cooling rate in the temperature range of 800 to 500 ° C. during quenching is 10 ° C./second and the as-quenched HRC is smaller than the value of “50C + 26” and the martensite ratio is low, The durability ratio in the gas was 0.4.

大気中および高圧水素ガス中の耐久比がいずれも０．４５以上であり、しかも、その耐久比となる応力条件における疲労寿命が１０7回以上で、良好な耐疲労特性が得られた上記の試験番号１〜１７で作製した焼戻し後の板材を用いて、次に、耐水素ガス脆化特性を調査した。その結果、いずれの場合も耐水素ガス脆化特性にも優れることが確認できた。 Both the durability ratio in the atmosphere and high-pressure hydrogen gas is 0.45 or more, and the fatigue life under the stress condition that is the durability ratio is 10 7 times or more, and good fatigue resistance characteristics are obtained. Next, using the tempered plate material prepared in Test Nos. 1 to 17, hydrogen gas embrittlement resistance was investigated. As a result, it was confirmed that in both cases, the hydrogen gas embrittlement resistance was also excellent.

本発明によれば、高圧水素ガス環境下での耐久比に基づく寿命設計が可能であり、引張強さで８５０ＭＰａ以上の高い強度を有し、高圧水素ガス環境下での耐疲労特性に優れるとともに良好な耐水素ガス脆化特性を備える高圧水素用容器、該容器の素材として用いるのに好適な高圧水素用低合金鋼材および高圧水素用低合金鋼管を得ることができる。また、本発明の方法によれば、このような高圧水素用容器を安定して得ることができる。

According to the present invention, the life design based on the durability ratio under a high-pressure hydrogen gas environment is possible, the tensile strength is as high as 850 MPa or more, and the fatigue resistance under a high-pressure hydrogen gas environment is excellent. A high-pressure hydrogen container having good hydrogen gas embrittlement resistance, a low-pressure steel material for high-pressure hydrogen and a low-alloy steel pipe for high-pressure hydrogen that are suitable for use as a material for the container can be obtained. Moreover, according to the method of the present invention, such a high-pressure hydrogen container can be obtained stably.

Claims (6)

質量％で、
Ｃ：０．２０〜０．６０％、
Ｓｉ：０．０５〜１．０％、
Ｍｎ：０．３５〜３．０％、
Ｐ：０．０２５％以下、
Ｓ：０．０１０％以下、
Ａｌ：０．００５〜０．１０％、
Ｂ：０．０００３〜０．０１％、
Ｔｉ：０〜０．５％、
Ｚｒ：０〜１．０％、
Ｈｆ：０〜２．０％、
Ｏ：０．００５％以下、
Ｎ：０．００８％以下
Ｃｒ：０〜５．０％、
Ｍｏ：０〜１．５％、
Ｖ：０〜１．０％、
Ｗ：０〜３．０％、
Ｎｂ：０〜０．１％、
Ｔａ：０〜０．２％、
Ｎｉ：０〜５．０％、
Ｃｕ：０〜３．０％、
Ｃｏ：０〜３．０％、
Ｃａ：０〜０．０１％、
Ｍｇ：０〜０．０１％、
ＲＥＭ：０〜０．５０％、
残部：Ｆｅおよび不純物であり、かつ、
下記の式[1]で表されるＦｎ１が０．００８〜０．０５、および、
下記の式[2]で表されるＦｎ２が、０．０００３以上である、
化学組成を有し、
粒径１０μｍ以上の炭窒化物系介在物の個数が断面観察で１０個／１００ｍｍ2以下であり、
耐久比が０．４５以上である、
高圧水素用低合金鋼材。
Ｆｎ１＝Ｔｉ＋０．５Ｚｒ＋０．２５Ｈｆ・・・[1]
Ｆｎ２＝Ｂ−（１１／１４）Ｎ＋（１１／４８）Ｔｉ＋（１１／９１）Ｚｒ＋（１１／１７８）Ｈｆ・・・[2]
ただし、上記式中のＴｉ、Ｚｒ、Ｈｆ、ＢおよびＮは、それぞれの元素の鋼中含有量（質量％）を意味し、Ｔｉ、ＺｒおよびＨｆは、含有されない場合はゼロとする。 % By mass
C: 0.20 to 0.60%,
Si: 0.05 to 1.0%,
Mn: 0.35 to 3.0%,
P: 0.025% or less,
S: 0.010% or less,
Al: 0.005 to 0.10%,
B: 0.0003 to 0.01%,
Ti: 0 to 0.5%,
Zr: 0 to 1.0%,
Hf: 0 to 2.0%,
O: 0.005% or less,
N: 0.008% or less Cr: 0 to 5.0%,
Mo: 0 to 1.5%,
V: 0 to 1.0%
W: 0 to 3.0%
Nb: 0 to 0.1%,
Ta: 0 to 0.2%,
Ni: 0 to 5.0%,
Cu: 0 to 3.0%,
Co: 0 to 3.0%,
Ca: 0 to 0.01%,
Mg: 0 to 0.01%,
REM: 0 to 0.50%,
Balance: Fe and impurities, and
Fn1 represented by the following formula [1] is 0.008 to 0.05, and
Fn2 represented by the following formula [2] is 0.0003 or more.
Has a chemical composition,
The number of carbonitride inclusions having a particle size of 10 μm or more is 10/100 mm 2 or less by cross-sectional observation,
The durability ratio is 0.45 or more,
Low alloy steel for high pressure hydrogen.
Fn1 = Ti + 0.5Zr + 0.25Hf [1]
Fn2 = B- (11/14) N + (11/48) Ti + (11/91) Zr + (11/178) Hf [2]
However, Ti, Zr, Hf, B, and N in the above formula mean the contents (mass%) of each element in steel, and Ti, Zr, and Hf are zero when not contained. 前記化学組成が、質量％で、
Ｃｒ：０．１〜５．０％、
Ｍｏ：０．１〜１．５％、
Ｖ：０．０１〜１．０％、
Ｗ：０．０１〜３．０％、
Ｎｂ：０．００１〜０．１％、
Ｔａ：０．００１〜０．２％、
Ｎｉ：０．１〜５．０％、
Ｃｕ：０．１〜３．０％、
Ｃｏ：０．１〜３．０％、
Ｃａ：０．０００１〜０．０１％、
Ｍｇ：０．０００１〜０．０１％、および、
ＲＥＭ：０．０００１〜０．５０％、
から選択される１種以上を含有する、請求項１に記載の高圧水素用低合金鋼材。 The chemical composition is mass%,
Cr: 0.1 to 5.0%,
Mo: 0.1 to 1.5%,
V: 0.01-1.0%
W: 0.01-3.0%
Nb: 0.001 to 0.1%,
Ta: 0.001 to 0.2%,
Ni: 0.1 to 5.0%,
Cu: 0.1 to 3.0%,
Co: 0.1-3.0%
Ca: 0.0001 to 0.01%,
Mg: 0.0001 to 0.01%, and
REM: 0.0001 to 0.50%,
The low alloy steel for high pressure hydrogen according to claim 1, comprising at least one selected from 旧オーステナイト結晶粒がＡＳＴＭ粒度番号９．０以上である、
請求項１または２に記載の高圧水素用低合金鋼材。 Prior austenite grains are ASTM grain size number 9.0 or higher,
The low alloy steel material for high pressure hydrogen according to claim 1 or 2. 請求項１から３までのいずれかに記載の高圧水素用低合金鋼材からなる、
高圧水素用低合金鋼管。 It consists of the low alloy steel for high pressure hydrogen according to any one of claims 1 to 3.
Low alloy steel pipe for high pressure hydrogen. 請求項４に記載の高圧水素用低合金鋼管からなり、
引張強さが８５０ＭＰａ以上である、
高圧水素用容器。 The low-alloy steel pipe for high-pressure hydrogen according to claim 4,
The tensile strength is 850 MPa or more,
High pressure hydrogen container. 請求項５に記載の高圧水素用容器を製造する方法であって、
前記高圧水素用低合金鋼管を所定の形状に成形加工した後、８８０〜９５０℃に加熱・保持してから、８００〜５００℃の温度域における平均冷却速度を２℃／秒以上として焼入れし、次いで、焼戻しする、
高圧水素用容器の製造方法。

A method for producing the high-pressure hydrogen container according to claim 5,
After forming and processing the low-alloy steel pipe for high-pressure hydrogen into a predetermined shape, after heating and holding at 880 to 950 ° C., quenching with an average cooling rate in the temperature range of 800 to 500 ° C. being 2 ° C./second or more, Then temper,
A method for producing a container for high pressure hydrogen.

JP2016142206A 2016-07-20 2016-07-20 Low alloy steel material, low alloy steel pipe and container, and method of manufacturing the container Active JP6648647B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP2016142206A JP6648647B2 (en) 2016-07-20 2016-07-20 Low alloy steel material, low alloy steel pipe and container, and method of manufacturing the container

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP2016142206A JP6648647B2 (en) 2016-07-20 2016-07-20 Low alloy steel material, low alloy steel pipe and container, and method of manufacturing the container

Publications (2)

Publication Number Publication Date
JP2018012856A true JP2018012856A (en) 2018-01-25
JP6648647B2 JP6648647B2 (en) 2020-02-14

Family

ID=61019965

Family Applications (1)

Application Number Title Priority Date Filing Date
JP2016142206A Active JP6648647B2 (en) 2016-07-20 2016-07-20 Low alloy steel material, low alloy steel pipe and container, and method of manufacturing the container

Country Status (1)

Country Link
JP (1) JP6648647B2 (en)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2019183218A (en) * 2018-04-06 2019-10-24 日本製鉄株式会社 High pressure hydrogen container, and steel material for high pressure hydrogen
CN112442629A (en) * 2019-08-28 2021-03-05 宝山钢铁股份有限公司 Medium-carbon steel for mechanical structure and manufacturing method thereof
CN113930664A (en) * 2020-06-29 2022-01-14 宝山钢铁股份有限公司 High-purity battery case steel and manufacturing method thereof
EP4032999A1 (en) * 2021-01-20 2022-07-27 Poppe & Potthoff GmbH Low weight hydrogen distribution system and components
CN115433884A (en) * 2022-06-17 2022-12-06 攀钢集团攀枝花钢铁研究院有限公司 Hydrogen energy long-distance conveying pipeline alloy, pipeline and preparation method of pipeline
CN115647733A (en) * 2022-10-11 2023-01-31 中国核动力研究设计院 Hafnium standard substance and preparation method thereof
US11767572B1 (en) * 2022-06-15 2023-09-26 Hyundai Motor Company Alloy steel having excellent hydrogen embrittlement resistance and strength and method of manufacturing same

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0617122A (en) * 1992-06-30 1994-01-25 Aichi Steel Works Ltd Production of non-heattreated steel excellent in durability ratio
JP2007113063A (en) * 2005-10-20 2007-05-10 Sumitomo Metal Ind Ltd Hot-forged parts
JP2008007841A (en) * 2006-06-30 2008-01-17 Sumitomo Metal Ind Ltd Continuously cast ingot for thick steel plate, its manufacturing method, and thick steel plate
JP2009057620A (en) * 2007-09-03 2009-03-19 Sumitomo Metal Ind Ltd Seam welded pipe for hydroform and its raw material steel sheet, and manufacturing methods therefor
JP2009074122A (en) * 2007-09-19 2009-04-09 Sumitomo Metal Ind Ltd Low alloy steel for high pressure hydrogen gas environment, and vessel for high pressure hydrogen
JP2011063840A (en) * 2009-09-16 2011-03-31 Sumitomo Metal Ind Ltd Steel sheet having excellent hic resistance and uoe steel pipe
JP2014173160A (en) * 2013-03-12 2014-09-22 Nippon Steel & Sumitomo Metal Low alloy steel for high pressure hydrogen gas and accumulator for high pressure hydrogen
WO2014156187A1 (en) * 2013-03-29 2014-10-02 Ｊｆｅスチール株式会社 Steel material and hydrogen container as well as manufacturing methods therefor

Patent Citations (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0617122A (en) * 1992-06-30 1994-01-25 Aichi Steel Works Ltd Production of non-heattreated steel excellent in durability ratio
JP2007113063A (en) * 2005-10-20 2007-05-10 Sumitomo Metal Ind Ltd Hot-forged parts
JP2008007841A (en) * 2006-06-30 2008-01-17 Sumitomo Metal Ind Ltd Continuously cast ingot for thick steel plate, its manufacturing method, and thick steel plate
JP2009057620A (en) * 2007-09-03 2009-03-19 Sumitomo Metal Ind Ltd Seam welded pipe for hydroform and its raw material steel sheet, and manufacturing methods therefor
JP2009074122A (en) * 2007-09-19 2009-04-09 Sumitomo Metal Ind Ltd Low alloy steel for high pressure hydrogen gas environment, and vessel for high pressure hydrogen
US20090285713A1 (en) * 2007-09-19 2009-11-19 Sumitomo Metal Industries, Ltd. Low alloy steel for high-pressure hydrogen gas environment and container for high-pressure hydrogen
KR20100046052A (en) * 2007-09-19 2010-05-04 수미도모 메탈 인더스트리즈, 리미티드 Low alloy steel for high-pressure hydrogen gas environment, and container for high-pressure hydrogen
JP2011063840A (en) * 2009-09-16 2011-03-31 Sumitomo Metal Ind Ltd Steel sheet having excellent hic resistance and uoe steel pipe
JP2014173160A (en) * 2013-03-12 2014-09-22 Nippon Steel & Sumitomo Metal Low alloy steel for high pressure hydrogen gas and accumulator for high pressure hydrogen
WO2014156187A1 (en) * 2013-03-29 2014-10-02 Ｊｆｅスチール株式会社 Steel material and hydrogen container as well as manufacturing methods therefor
KR20150119952A (en) * 2013-03-29 2015-10-26 제이에프이 스틸 가부시키가이샤 Steel material and hydrogen container as well as manufacturing methods therefor
US20160053355A1 (en) * 2013-03-29 2016-02-25 Jfe Steel Corporation Steel material, hydrogen container, method for producing the steel material, and method for producing the hydrogen container (as amended)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2019183218A (en) * 2018-04-06 2019-10-24 日本製鉄株式会社 High pressure hydrogen container, and steel material for high pressure hydrogen
CN112442629A (en) * 2019-08-28 2021-03-05 宝山钢铁股份有限公司 Medium-carbon steel for mechanical structure and manufacturing method thereof
CN113930664A (en) * 2020-06-29 2022-01-14 宝山钢铁股份有限公司 High-purity battery case steel and manufacturing method thereof
EP4032999A1 (en) * 2021-01-20 2022-07-27 Poppe & Potthoff GmbH Low weight hydrogen distribution system and components
WO2022157247A1 (en) * 2021-01-20 2022-07-28 Poppe + Potthoff Gmbh Hydrogen distribution system and components having low weight
US11767572B1 (en) * 2022-06-15 2023-09-26 Hyundai Motor Company Alloy steel having excellent hydrogen embrittlement resistance and strength and method of manufacturing same
CN115433884A (en) * 2022-06-17 2022-12-06 攀钢集团攀枝花钢铁研究院有限公司 Hydrogen energy long-distance conveying pipeline alloy, pipeline and preparation method of pipeline
CN115647733A (en) * 2022-10-11 2023-01-31 中国核动力研究设计院 Hafnium standard substance and preparation method thereof

Also Published As

Publication number Publication date
JP6648647B2 (en) 2020-02-14

Similar Documents

Publication Publication Date Title
JP6648646B2 (en) Low alloy steel material, low alloy steel pipe and container, and method of manufacturing the container
CA2963770C (en) Austenitic stainless steel and method of manufacturing the same
JP6648647B2 (en) Low alloy steel material, low alloy steel pipe and container, and method of manufacturing the container
JP6451545B2 (en) High Mn steel for high-pressure hydrogen gas, method for producing the same, and piping, container, valve and joint made of the steel
KR101842825B1 (en) Austenitic stainless steel and method for producing same
AU2014245634B2 (en) Abrasion resistant steel plate having excellent low-temperature toughness and hydrogen embrittlement resistance and method for manufacturing the same
JP4251229B1 (en) Low alloy steel for high pressure hydrogen gas environment and container for high pressure hydrogen
US20090098403A1 (en) Low alloy steel for oil country tubular goods and seamless steel pipe
JP6179977B2 (en) High-strength steel with excellent high-pressure hydrogen environment embrittlement resistance and method for producing the same
CN105102657A (en) Steel material and hydrogen container as well as manufacturing methods therefor
JP6554844B2 (en) Manufacturing method of high-pressure hydrogen container
KR20180038024A (en) Steel structure for hydrogen excellent in hydrogen embrittlement resistance in high-pressure hydrogen gas and manufacturing method thereof
CN102628145A (en) High strength steel pipe with excellent toughness at low temperature and good sulfide stress corrosion cracking resistance
CN105102653A (en) Steel structure for hydrogen, and method for manufacturing pressure accumulator for hydrogen and line pipe for hydrogen
EP3395991A1 (en) High strength seamless stainless steel pipe for oil wells and manufacturing method therefor
TW201741473A (en) Austenitic stainless steel material
AU2015325557A1 (en) High-strength steel material for oil well and oil country tubular goods
JP6583532B2 (en) Steel and oil well steel pipes
JPWO2020138458A1 (en) Carburized nitride bearing parts
JP6149435B2 (en) Low alloy steel for high pressure hydrogen gas and pressure accumulator for high pressure hydrogen
CN106319362A (en) X52 seamless pipeline steel pipe with sour corrosion resistance and manufacturing method of X52 seamless pipeline steel pipe
JP7370992B2 (en) High tensile strength steel and high toughness steel
JP2005314810A (en) Steel for induction hardening
JPWO2020138432A1 (en) Steel material
RU2785314C2 (en) Steels with high tensile strength and high impact viscosity

Legal Events

Date Code Title Description
A621 Written request for application examination

Free format text: JAPANESE INTERMEDIATE CODE: A621

Effective date: 20190306

A977 Report on retrieval

Free format text: JAPANESE INTERMEDIATE CODE: A971007

Effective date: 20191108

TRDD Decision of grant or rejection written
A01 Written decision to grant a patent or to grant a registration (utility model)

Free format text: JAPANESE INTERMEDIATE CODE: A01

Effective date: 20191217

A61 First payment of annual fees (during grant procedure)

Free format text: JAPANESE INTERMEDIATE CODE: A61

Effective date: 20191230

R151 Written notification of patent or utility model registration

Ref document number: 6648647

Country of ref document: JP

Free format text: JAPANESE INTERMEDIATE CODE: R151