JP2004324800A - Tank for high pressure hydrogen gas, and piping - Google Patents

Tank for high pressure hydrogen gas, and piping Download PDF

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Publication number
JP2004324800A
JP2004324800A JP2003122131A JP2003122131A JP2004324800A JP 2004324800 A JP2004324800 A JP 2004324800A JP 2003122131 A JP2003122131 A JP 2003122131A JP 2003122131 A JP2003122131 A JP 2003122131A JP 2004324800 A JP2004324800 A JP 2004324800A
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hydrogen gas
pressure
pressure hydrogen
aluminum
stainless steel
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JP4700263B2 (en
Inventor
Hidetaka Kimura
英隆 木村
Hideki Fujii
秀樹 藤井
Masao Kurosaki
将夫 黒崎
Tetsuo Takeshita
哲郎 竹下
Naoki Okumura
直樹 奥村
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Nippon Steel Corp
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Nippon Steel Corp
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    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02EREDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30Hydrogen technology
    • Y02E60/32Hydrogen storage

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Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-pressure hydrogen gas tank for storing high-pressure hydrogen gas at a pressure of 0.1-80 MPa for a long time, repeating to be filled with high-pressure hydrogen gas to the maximum 80 MPa and to discharge hydrogen gas to the minimum 0.1 MPa, and to restrict intrusion of hydrogen into high-pressure hydrogen gas piping for transproting high-pressure hydrogen gas, of which the pressure fluctuates within a range at 0.1-80 MPa. <P>SOLUTION: As a material for this high-pressure hydrogen gas tank and the high-pressure hydrogen gas piping, a stainless steel containing an appropriate quantity of C, Si, P, S, Mn, Ni, Cr and N is used, and this stainless steel has an aluminum layer formed from aluminum or an aluminum alloy and having a thickness of 100 nm to 10 mm in a surface to be brought in contact with hydrogen gas. This stainless steel can, furthermore, contain one or two kinds or more of Mo, Nb, Ti and B. The high-pressure hydrogen gas tank or outside of the high-pressure hydrogen gas piping is desirably formed with a reinforced layer of carbon fibers. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【0001】
【発明の属する技術分野】
本発明は、圧力が0.1〜80MPaの高圧水素ガスを長期間貯蔵し、最大80MPaの高圧水素ガスの充填と、最小0.1MPaまでの水素ガスの放出とを繰り返す、定置式大型水素タンク、車載用水素タンクなどに好適な高圧水素ガス用タンク及び圧力が0.1〜80MPaの範囲内で変動する高圧水素ガスを輸送する高圧水素ガス用配管に関する。
【0002】
【従来の技術】
近年、地球温暖化の問題から、温室効果ガスの排出を抑制するために、水素をエネルギーとして利用する技術が注目されている。従来、水素を高圧水素ガスとして貯蔵する際には、厚肉のCr−Mo鋼製の高圧ボンベに圧力40MPa程度までの水素ガスを充填していた。しかし、このようなCr−Mo鋼製のボンベは、高圧水素の充填と放出を繰り返すことによって、内圧の変動と水素の侵入により疲労強度が低下するため、肉厚を30mm程度にする必要があり、重量がかさむ。
【0003】
一方、特許文献1には、樹脂からなる容器の内側に合成ゴムを内側にライニングし、外側を炭素繊維によって補強した、水素を燃料とする自動車に搭載する高圧水素タンクが開示されている。しかし、この高圧水素タンクは軽量であるが、材質が樹脂であるために、水素ガスの透過が問題であり、また、経年劣化が懸念される。
【0004】
また、水素に限らず、高圧ガス容器として、耐食性に優れるアルミニウム、ステンレス鋼を素材として用いる技術が特許文献2及び特許文献3に開示されている。特許文献2は、アルミニウム製の高圧ガス容器の内面にアルミナ層を生成させたものであり、高純度ガス中への不純物ガス成分の放出を抑制したものである。しかし、アルミニウムは強度が低いため、高圧水素ガスの充填と放出の繰り返しに伴う0.1〜80MPaの範囲内の内圧の変動に対する疲労寿命に問題がある。
【0005】
特許文献3には、オーステナイト系ステレス鋼板を加工し、溶接後に還元雰囲気で熱処理を行う高圧ガス容器の製造方法が開示されているが、最大80MPaの水素ガスを長期間貯蔵する際には、10ppm超の水素が侵入して機械的性質を損なう可能性がある。
【0006】
また、特許文献4〜6には、Alめっきを施したステンレス鋼が開示されている。しかし、これらには、高圧水素ガス中で使用するものではなく、Alめっきによる水素侵入の抑制を示唆するものではない。
【0007】
【特許文献1】
特開2002−188794号公報
【特許文献2】
特開平11−257593号公報
【特許文献3】
特開平9−166290号公報
【特許文献4】
特開平5−295513号公報
【特許文献5】
特開平8−134595号公報
【特許文献6】
特開2002−12954号公報
【0008】
【発明が解決しようとする課題】
本発明は、圧力が0.1〜80MPaの高圧水素ガスを長期間貯蔵し、最大80MPaの高圧水素ガスの充填と、最小0.1MPaまでの水素ガスの放出とを繰り返す高圧水素ガス用タンク及び圧力が0.1〜80MPaの範囲内で変動する高圧水素ガスを輸送する高圧水素ガス用配管への水素侵入の抑制を課題とする。
【0009】
【課題を解決するための手段】
本発明は、ステンレス鋼の表面をアルミニウム又はアルミニウム合金で被覆することにより、水素侵入を大幅に抑制できるという知見に基づき、更に、高圧水素タンク又は配管の材質をオーステナイト系又は二相系ステンレス鋼とすることにより、水素侵入による靭性、引張強度、延性、疲労強度等の機械的性質の劣化の抑制を図ったものであり、その要旨は以下のとおりである。
【0010】
(1) 圧力が0.1〜80MPaの水素ガスを貯蔵する高圧水素ガス用タンクにおいて、前記高圧水素ガス用タンクの材質が、質量%で、
C :0.002〜0.08%、 Si:0.01〜3.0%、
P :0.005〜0.04%、 S :0.0001〜0.01%、
Mn:0.1〜2.0%、 Ni:3.0〜28.0%、
Cr:15.0〜28.0%、 N :0.02〜0.40%
を含有し、残部Fe及び不可避的不純物からなるステンレス鋼であり、水素ガスと接する面にアルミニウム又はアルミニウム合金からなる厚さ100nm〜10mmのアルミ層を有することを特徴とする高圧水素ガス用タンク。
【0011】
(2) 高圧水素ガス用タンクの材質が、更に、質量%で、
Mo:0.01〜7.0%、 Nb:0.005〜1.0%、
Ti:0.005〜1.0%、 B :0.0003〜0.003%
の1種又は2種以上を含有するステンレス鋼であることを特徴とする(1)に記載の高圧水素ガス用タンク。
【0012】
(3) (1)又は(2)記載の高圧水素ガス用タンクの外側に高強度繊維材料からなる補強層を形成したことを特徴とする高圧水素ガス用タンク。
【0013】
(4) 圧力が0.1〜80MPaの水素ガスを輸送する高圧水素ガス用配管において、前記高圧水素ガス用配管の材質が、質量%で、
C :0.002〜0.08%、 Si:0.01〜3.0%、
P :0.005〜0.04%、 S :0.0001〜0.01%、
Mn:0.1〜2.0%、 Ni:3.0〜28.0%、
Cr:15.0〜28.0%、 N :0.02〜0.40%
を含有し、残部Fe及び不可避的不純物からなるステンレス鋼であり、水素ガスと接する面にアルミニウム又はアルミニウム合金からなる厚さ100nm〜10mmのアルミ層を有することを特徴とする高圧水素ガス用配管。
【0014】
(5) 前記高圧水素ガス用配管の材質が、更に、質量%で、
Mo:0.01〜7.0%、 Nb:0.005〜1.0%、
Ti:0.005〜1.0%、 B :0.0003〜0.003%
の1種又は2種以上を含有するステンレス鋼であることを特徴とする(4)記載の高圧水素ガス用配管。
【0015】
(6) (4)または(5)記載の高圧水素ガス用配管の外側に高強度繊維材料からなる補強層を形成したことを特徴とする高圧水素ガス用配管。
【0016】
【発明の実施の形態】
本発明者は、ステンレス鋼にアルミニウム又はアルミニウム合金を被覆することにより、水素の鋼への侵入を防止する方法を指向し、以下の検討を行った。
【0017】
直径が5mm、長さが30mmのSUS304及びSUS316の棒鋼の表面を機械研削し、端部を半球状に加工した。次に、SUS304の棒鋼にアルミニウムを、SUS316の棒鋼にAl−10%Mg−1%Ca−7%Siからなるアルミニウム合金を溶融めっきした。
【0018】
SUS304及びSUS316の棒鋼の機械研削ままの試料、アルミニウムめっき試料及びアルミニウム合金めっき試料を、それぞれ3本ずつ、内径20mm、肉厚50mmのNi合金製の容器の中に入れ、銅リングをシール材としてNi合金製の蓋をボルトで固定し、気密性を保持した。Ni合金製の蓋に予め取り付けた高圧コックから、容器内を真空引きし、水素ガスを入れ、再び真空に引く操作を数回繰り返した後、78MPaの高圧水素ガスを注入し、コックを閉じ、更にコックがついた鋼管の端を溶接で閉じた。このNi合金製の容器ごと80℃に保持されたシリコンオイル恒温槽に浸し、10000時間保持した。この後、試料を取り出した。
【0019】
SUS304及びSUS316ともに、機械研削ままの試料、機械研削後に高圧水素ガス中に保持した試料、アルミニウムめっき試料、アルミニウム合金めっき試料を、それぞれ3本ずつの水素量を分析し、各3本の平均値を求めた。各試料の水素量は、不活性ガス融解法によるガス抽出と熱伝導度法による分析で求めた。なお、アルミニウムめっき試料、アルミニウム合金めっき試料を軸方向に垂直に切断し、断面のアルミ層の厚さを光学顕微鏡で測定した結果、何れも5〜10μmであった。
【0020】
各試料の水素量の平均値を図1に示す。図1において、SUS304及びSUS316のアルミ被覆材は、それぞれ、アルミニウムを溶融めっきしたSUS304の棒鋼及びAl−10%Mg−1%Ca−7%Siからなるアルミニウム合金を溶融めっきしたSUS316の棒鋼である。図1から、アルミニウムめっき又はアルミニウム合金めっきを施すと高圧水素中におけるステンレス鋼への水素侵入を防止できることがわかる。
【0021】
80℃で10000時間保持した際の、アルミニウム中における水素の拡散距離を拡散係数から計算すると、10〜30mm程度であり、アルミ層の厚さである5〜10μmを上回る。即ち、アルミ層によるステンレス鋼への水素侵入の抑制の原因は、アルミ層中での水素の拡散の抑制ではないと考えられる。ステンレス鋼をアルミ層で被覆することにより、水素侵入が抑制される機構については、アルミ層の表面の酸化層による水素侵入の抑制、酸化層の表面における水素分子の水素原子への乖離反応の抑制、アルミ層とステンレス鋼の界面での水素トラップなどが考えられる。
【0022】
以下、本発明について詳細に説明する。まず、ステンレス鋼の化学成分を規定した理由について述べる。
【0023】
Cは、固溶状態ではステンレス鋼の強化やオーステナイト相の安定化に有効であるが、この効果はC量が0.002%未満では不十分である。一方、0.08%を超えると粒界に炭化物が析出して鋭敏化により耐食性が劣化し、また延性、靭性が低下する。したがってC量を0.002〜0.08%とした。
【0024】
Siは、脱酸元素として有効であり、0.01%以上添加が必要である。一方、Si量が3.0%超では、材料の延性、靭性が劣化するため、上限を3.0%以下とした。
【0025】
Pは、不純物であり、耐食性を劣化させるので0.04%以下とする必要がある。一方、P量を、0.005%未満とするには精錬コストが増大するため、下限を0.005%以上とした。
【0026】
Sも、不純物であり、耐食性や熱間加工性を劣化させるので0.01%以下とする必要がある。一方S量を、0.0001%未満とするには精錬コストが増大するため、下限を0.0001%以上とした。
【0027】
Mnは、Sを固定し、Nの固溶限を上げる効果を有し、熱間加工性を改善するため、0.1%以上の添加が必要である。一方、Mn量が2.0%を超えると製造工程での加熱中に異常酸化を生じるため、上限を2.0%以下とした。
【0028】
Niは、オーステナイト相を安定化し、靭性を高める元素であり、3.0%以上の添加が必要である。一方、Ni量を28.0%超としても効果が飽和し、またコストが高くなる。したがってNi量を3.0〜28.0%の範囲とした。
【0029】
Crは、ステンレス鋼の表面に不働態皮膜を生成させ、耐食性を向上させる重要な元素である。また、Crは、Niと共存してオーステナイト相の安定化に寄与する。しかし、この効果はCr量が15.0%未満では不十分であり、28.0%を超えると製造性を損ない、コストが高くなる。したがって、Cr量を15.0〜28.0%の範囲とした。
【0030】
Nは、耐孔食性及び強度を向上させる効果を有し、またオーステナイト相の安定化に寄与する。しかし、その効果を発揮するには0.02%以上のNの添加が必要である。一方、N量が0.40%を超えると窒化物を生成して延性、靭性、更には製造性も損なう。したがって、N量を0.02〜0.40%の範囲とした。
【0031】
更に、Mo、Nb、Ti、Bの1種又は2種以上を含有しても良い。
【0032】
Moは、不働態皮膜の補修に有効に働き、耐食性を向上させるが、この効果はMo量が0.01%未満ではやや不十分であり、7.0%を超えると製造性を損なうことがある。したがってMo量は、0.01〜7.0%とすることが好ましい。
【0033】
Nbは、強度を向上させ、鋭敏化を抑制する効果を有する元素であり、0.005%以上の添加が好ましい。一方、この効果はNb量が1.0%を超えると飽和するため、上限を1.0%以下とすることが好ましい。
【0034】
Tiも、強度を向上させ、鋭敏化を抑制する効果を有する元素であり、0.005%以上の添加が好ましい。一方、この効果は、Ti量が1.0%を超えると飽和するため、上限を1.0%以下とすることが好ましい。
【0035】
Bは、結晶粒界を強化し、熱間加工性、冷間加工性を向上させる元素であり、この効果を得るには0.0003%以上の添加が好ましい。一方、Bを0.003%超添加すると硼化物を生じ、熱間加工性を劣化させることがあるため、上限を0.003%以下とすることが好ましい。
【0036】
ステンレス鋼は、オーステナイト相を40体積%以上含有すると、10ppm程度の水素侵入による材料の延性、靭性などの機械的性質の劣化が小さいため好ましい。オーステナイト相の残部は、主にフェライト相、マルテンサイト相である。オーステナイト相は100体積%でも良い。オーステナイト相の体積%は、強磁性体であるフェライト相及びマルテンサイト相の体積%を電磁誘導法によって測定し、残部をオーステナイト相として求めることができる。
【0037】
ステンレス鋼のフェライト相及びマルテンサイト相の体積%は、例えばフィッシャーインストルメンツ社製のフェライト含有量測定器を用いて測定すれば良いが、この際には、試料のサイズに注意する必要があり、板厚が3mm以上の場合は圧延方向に平行な板厚断面の鏡面研磨試料を用いて板厚中心部で、また、板厚が3mm未満の場合は板を複数枚重ね、その厚さ合計が3mm以上となるようにして圧延面で測定すれば良い。
【0038】
ステンレス鋼の水素と接する面には、アルミニウム又はアルミニウム合金からなるアルミ層を形成する。アルミ層には、それぞれ0.2%以下のFe、Cr、Mn等を不可避的不純物として含有することが許容される。アルミニウム合金は、Al量が50%以上であることが必要であり、0.1〜20%のMg、0.1〜20%のCa、0.1〜20%のSiの1種以上を添加しても良い。Si量は5〜11%であることが好ましい。
【0039】
アルミ層の厚さは、100nm未満では、厚さを均一にすることが難しくなり、また欠陥を生じ、母材のステンレス鋼を露出し易くなる。一方、アルミ層の厚さを10mm超とするには材料コストや製造コストが増大する。したがって、ステンレス鋼の表面のアルミ層の厚さを100nm〜10mmとした。
【0040】
なお、アルミ層の厚みの好ましい範囲は、アルミ層の形成方法によって異なる。アルミ層を蒸着によって形成させる際には100nm〜10μmであることが好ましい。また、溶融めっきによりアルミ層を形成する際には、1μm〜1mmであることが好ましい。また、ステンレス鋼の表面をアルミ層で被覆したクラッド材とする際には、表面のアルミ層が溶損し、母相のステンレス鋼の露出を防止するために、1mm〜10mmであることが好ましい。
【0041】
本発明の高圧水素ガス用タンクの胴体部、配管は、ステンレス鋼板を筒状に成形して端部同士を突き合わせて溶接しても良く、ステンレス鋼管を用いても良い。ステンレス鋼の水素と接する面にアルミ層を形成させる方法としては、真空中でアルミニウム又はアルミニウム合金を蒸着する方法、アルミニウム又はアルミニウム合金の溶融めっき浴に浸漬して溶融めっきする方法がある。高圧水素ガス用タンクは胴体部に蓋部を溶接するが、蓋部の水素ガスに接する面にアルミ層を形成することが必要である。
【0042】
また、大型構造物である高圧水素ガス用タンクを製造する場合は、アルミニウム又はアルミニウム合金とステンレス鋼のクラッド板を用いて、アルミ層を摩擦攪拌接合(riction tir elding、FSWという)又はタングステン電極不活性ガスアーク溶接(ungsten nert as welding、TIGという)を用いて接合し、ステンレス鋼部はアルミ層とは別にFSW又はTIGで接合すれば良い。
【0043】
本発明の高圧水素ガス用タンク及び配管を輸送機器の燃料系、例えば自動車の車載用として使用する際には軽量化が重要である。そのため、高圧水素ガス用タンク及び配管の材質であるステンレス鋼の板厚を薄くすることが必要になる。これには、ステンレス鋼からなる高圧水素ガス用タンク及び配管の外側に、高強度繊維材からなる補強層を形成し、高圧水素ガスの圧力による応力を負担することが有効である。
【0044】
補強層は、軽量で高強度の炭素繊維であることが好ましい。炭素繊維は、ポリアクリロニトリル系でもピッチ系でも良い。また、補強層は、炭素繊維を高圧水素ガス用タンク及び配管の外側に巻き付け、樹脂で固めることによって形成することが好ましい。炭素繊維は、タンクの円周方向又は軸方向に巻くことが好ましいが、形状によっては任意の方向に巻いても良く、たるみを残さず、張力を保った状態でタンク、配管に巻き付けることが好ましい。また、炭素繊維を複数回巻き付ける際には、すでに巻いてある炭素繊維上に密着させて巻き付けることが好ましい。炭素繊維を巻き付けた後、炭素繊維がずれないようにナイロン、ポリカーボネートなどの熱可塑性樹脂又はビニルエステル樹脂、エポキシ樹脂などの熱硬化性樹脂で固めることが好ましい。
【0045】
なお、本発明の高圧水素ガス用タンク及び配管を大型構造物である貯蔵施設に適用する際にも、水素ガスの圧力が高いため、外側に炭素繊維からなる補強層を形成し、内圧に起因する応力を配分する構造としても良い。
【0046】
【実施例】
(実施例1)
表1に示した化学成分からなる鋼A、Bを溶解、鋳造、熱延、溶体化熱処理、酸化スケール除去により板厚25mmの鋼板とした。フィッシャーインストルメンツ社製のフェライト含有量測定器を用いて、板厚断面の中央部でオーステナイト相の体積%を測定した。
【0047】
鋼板を成形、溶接し、内径100mm、軸方向長さ400mmの円筒形の高圧水素ガス用タンク(以下、タンクA、Bという)を製作した。タンクA、Bの両底面には直径50mmの穴をあけ、片方には高圧コックが付いたステンレス鋼管を溶接した。もう片方には枝管に圧力計が付いたステンレス鋼管を溶接し、タンク内部にニクロム線を熱源とする加熱装置と純アルミニウムを入れたポットを挿入した。加熱装置及びポットを通電配線とともに冶具によって固定し、冶具と鋼管の隙間をゴム製の円形リングでシールした。
【0048】
高圧コックから真空ポンプでタンクA、B内部を1×10−2Pa以下に減圧し、高圧コックを閉じた。次に純アルミニウムを入れたポットを加熱し、純アルミニウムが溶融してから5分間放置した後、ポットの加熱を停止し、タンクA、B内面にアルミニウムを蒸着した。この後、2時間放置して高圧コックを開き、空気を導入した。更に、純アルミニウムを入れたポットの軸方向の位置を変えて、再び真空ポンプで減圧し、純アルミニウムを入れたポットを加熱して、アルミニウムをタンクA、Bの内面に蒸着する操作を数回繰り返し、アルミ層を形成した。
【0049】
純アルミニウムを入れたポット、加熱装置、冶具をタンクA、Bから取り出して、鋼A、Bから採取した直径が5mm、長さが30mmの棒鋼を挿入し、鋼管の端部にステンレス鋼製の蓋を溶接した。更に室温下で、高圧コック側から真空ポンプにより、タンクA、B内を減圧してから、水素ガスを導入し、再び真空引く操作を数回繰り返した。その後、水素ガスをタンクA、Bの内に導入し、水素ガス用コンプレッサーで水素ガスの圧力を常温で29.9MPaとした。最後に高圧コックを閉じ、このタンクA、Bを赤外線照射器で80℃に保たれた恒温室に入れ、1000時間放置した後、常温に冷却した。
【0050】
高圧コックを水素放散用スタックにつないで開放し、内部の水素を大気圧まで放散した。更に、高圧コックからタンクA、B内部に0.12MPaのNガスを10分間注入し、タンクA、B内部の水素を窒素で置換した。この操作の後、タンクA、Bを周方向に切断し、タンクA、B内部を目視し、アルミ層で被覆されていることを確認した。更にタンクA、Bの円筒部の軸方向の中央部より、周方向の肉厚断面を観察面とし、周方向の長さが20mmの試料を5個採取し、機械研磨した。走査電子顕微鏡で最大3000倍に拡大し、各試料3視野の写真を撮影し、それぞれの写真で任意の5箇所でアルミ層の厚さを測定した。アルミ層の厚さは、約0.6〜3μmであり、観察した全ての視野において、ステンレス鋼の表面を被覆していた。
【0051】
更に、タンクA、Bの胴部より試料を採取し、鋼A、Bの水素量を分析した。比較のために、タンクA、Bの素材である鋼板の水素量、タンクA、Bに封入した棒鋼の水素量を測定した。各試料の水素量は、不活性ガス融解法によるガス抽出と熱伝導度法による分析で求めた。その結果を表2に示す。アルミ層を形成したタンクA、Bの水素量は約3ppmであり、試験前とほぼ同等であったのに対し、棒鋼A、Bの水素量は約6ppmに増加していた。なお、水素量の分析精度は1ppm以内である。
(実施例2)
表1に示した鋼C、D、E、Fを実施例1と同様にして板厚25mmの鋼板とし、オーステナイト相の体積%を測定し、内径100mm、軸方向長さ400mmの円筒形の高圧水素ガス用タンク(以下、タンクC、D、E、Fという)を製作した。タンクC、D、E、Fの両底面に直径50mmの穴をあけ、全体をアルミニウム溶融槽に浸漬して、溶融アルミニウムめっきした。
【0052】
室温まで冷却した後、両底面にあけた直径50mmの穴のうち片方には高圧コックが付いたステンレス鋼管を溶接した。もう片方には枝管に圧力計が付いたステンレス鋼管を溶接し、鋼C、D、E、Fから採取した直径が5mm、長さが30mmの棒鋼を挿入し、ステンレス鋼管の外側に蓋を溶接した。なお、それぞれ両底面の穴にステンレス鋼管を溶接する際は、溶接に支障ないように、予め溶接部のアルミニウムを研削して除去した。実施例1と同様に、タンクC、D、E、F内部に室温で29.9MPaの水素ガスを充填し、80℃にして1000時間放置し、常温に冷却した。
【0053】
この後、実施例1と同様に、内部の水素を放散し、窒素で置換して、タンクC、D、E、Fを周方向に切断して内部を目視し、アルミ層で被覆されていることを確認した。更にタンクC、D、E、Fの円筒部の軸方向の中央部より、周方向の肉厚断面を観察面とし、周方向の長さが20mmの試料を各鋼種3個計12個採取し、機械研磨した。走査電子顕微鏡で最大1000倍に拡大し、各試料3視野の写真を撮影し、それぞれの写真で任意の5箇所でアルミ層の厚さを測定した。アルミ層の厚さは、約5〜30μmであり、全ての観察視野において、ステンレス鋼表面を被覆していた。
【0054】
更に、タンクC、D、E、Fの胴部より試料を採取し、ステンレス鋼の水素量を分析した。比較のために、タンクC、D、E、Fの素材である鋼板の水素量、タンクC、D、E、Fに封入した棒鋼の水素量を測定した。各試料の水素量は、不活性ガス融解法によるガス抽出と熱伝導度法による分析で求めた。その結果を表3に示す。アルミ層を形成したタンクC、D、E、Fは、水素量が約3ppmであり、試験前とほぼ同等であったのに対し、棒鋼C、D、E、Fの水素量は約6ppmに増加していた。なお、水素量の分析精度は1ppm以内である。
(実施例3)
実施例1と同様にして製造した鋼Aをさらに熱間圧延、溶体化熱処理、冷間圧延、溶体化熱処理、酸化スケール除去を実施し、厚さ3mmの板とした。フィッシャーインストルメンツ社製のフェライト含有量測定器を用いて、板断面中央部においてオーステナイト相の体積%を測定した。この鋼板を成形、溶接し、内径30mm、長さ200mmの円筒を2つ製造し、それぞれ片側端部を板厚25mmの鋼Aで溶接して塞いだ。この状態で2つの円筒を溶融アルミニウム槽に浸漬してめっきを行い、円筒内外表面にアルミ層を形成した。さらに、円筒開口部側に高圧コックが付いたステンレス鋼管をそれぞれ溶接し、高圧水素ガス用タンクとした。なお、この溶接の際は溶接部のアルミ層は研削で取り除いた。
【0055】
1つの高圧水素ガス用タンクの外側には、圧力に起因する応力を配分するため、補強層を形成した。補強層は、高圧水素ガス用タンクの外側に、炭素繊維を強度設計上十分な量巻いた上、合成樹脂で固めることにより形成した。
【0056】
これらの高圧水素ガス用タンクを用いて、高圧水素の充填及び放出を模擬した内圧疲労試験を以下のようにして実施した。まず、実施例1と同様に、高圧水素ガス用タンクの内部に室温で29.9MPaの水素ガスを充填し、80℃にして1000時間放置し、常温に冷却することにより、高圧水素ガスの充填による水素侵入を模擬した。更に、高圧コックより圧力70.9MPaの窒素ガスを導入し、0.1MPaまで減圧し、再び70.9MPaの窒素ガスを導入する操作を繰り返した。
【0057】
外側に炭素繊維からなる補強層を形成しなかった高圧水素ガス用タンクは、内圧疲労試験として、内圧を70.9MPaに上昇させて、0.1MPaに減圧する操作を2786回繰り返した後、破損して圧力が上昇しなくなった。これに対し、外側に炭素繊維からなる補強層を形成した高圧水素ガス用タンクは、30000回の内圧疲労試験後も破損しなかった。
【0058】
【表1】

Figure 2004324800
【0059】
【表2】
Figure 2004324800
【0060】
【表3】
Figure 2004324800
【0061】
【発明の効果】
本発明により、高圧水素ガスの充填と放出を繰り返し、また長期間貯蔵する高圧水素ガス用タンク及び高圧水素ガスを輸送する高圧水素ガス用配管への水素侵入の抑制が可能になり、水素脆化を抑制し、長寿命化が期待できるなど、産業上の貢献が極めて顕著である。
【図面の簡単な説明】
【図1】ステンレス鋼の水素侵入特性に及ぼすアルミ層の効果を示す図である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention provides a stationary large-sized hydrogen tank that stores high-pressure hydrogen gas having a pressure of 0.1 to 80 MPa for a long period of time and repeats filling of a high-pressure hydrogen gas of a maximum of 80 MPa and discharge of a hydrogen gas of a minimum of 0.1 MPa. The present invention relates to a high-pressure hydrogen gas tank suitable for an in-vehicle hydrogen tank and the like, and a high-pressure hydrogen gas pipe for transporting a high-pressure hydrogen gas whose pressure varies within a range of 0.1 to 80 MPa.
[0002]
[Prior art]
In recent years, due to the problem of global warming, attention has been paid to a technology that uses hydrogen as energy in order to suppress emission of greenhouse gases. Conventionally, when hydrogen is stored as high-pressure hydrogen gas, a thick-walled high-pressure Cr-Mo steel cylinder is filled with hydrogen gas up to a pressure of about 40 MPa. However, since the Cr-Mo steel cylinder repeatedly fills and releases high-pressure hydrogen, the internal pressure fluctuates and the penetration of hydrogen lowers the fatigue strength, so the wall thickness must be reduced to about 30 mm. , Weight increases.
[0003]
On the other hand, Patent Literature 1 discloses a high-pressure hydrogen tank mounted on an automobile using hydrogen as a fuel, in which a synthetic rubber is lined inside a container made of resin and the outside is reinforced with carbon fibers. However, although this high-pressure hydrogen tank is lightweight, since the material is resin, there is a problem of permeation of hydrogen gas, and there is a concern about deterioration over time.
[0004]
In addition, Patent Literature 2 and Patent Literature 3 disclose techniques using not only hydrogen but also aluminum and stainless steel having excellent corrosion resistance as high-pressure gas containers as raw materials. Patent Literature 2 discloses a method in which an alumina layer is formed on an inner surface of a high-pressure gas container made of aluminum, and suppresses emission of an impurity gas component into a high-purity gas. However, since aluminum has low strength, there is a problem in the fatigue life with respect to the fluctuation of the internal pressure in the range of 0.1 to 80 MPa due to the repetition of charging and discharging of high-pressure hydrogen gas.
[0005]
Patent Document 3 discloses a method for manufacturing a high-pressure gas container in which an austenitic stainless steel plate is processed and heat-treated in a reducing atmosphere after welding. However, when hydrogen gas at a maximum of 80 MPa is stored for a long time, 10 ppm is used. Excessive hydrogen can enter and impair mechanical properties.
[0006]
Patent Literatures 4 to 6 disclose stainless steel plated with Al. However, these are not used in high-pressure hydrogen gas and do not suggest suppression of hydrogen intrusion by Al plating.
[0007]
[Patent Document 1]
JP 2002-188794 A [Patent Document 2]
JP-A-11-257593 [Patent Document 3]
JP-A-9-166290 [Patent Document 4]
JP-A-5-295513 [Patent Document 5]
JP-A-8-134595 [Patent Document 6]
JP-A-2002-12954
[Problems to be solved by the invention]
The present invention provides a high-pressure hydrogen gas tank that stores a high-pressure hydrogen gas having a pressure of 0.1 to 80 MPa for a long period of time, repeats filling of a high-pressure hydrogen gas of a maximum of 80 MPa, and discharge of a hydrogen gas to a minimum of 0.1 MPa. It is an object to suppress the intrusion of hydrogen into a high-pressure hydrogen gas pipe for transporting a high-pressure hydrogen gas whose pressure fluctuates within a range of 0.1 to 80 MPa.
[0009]
[Means for Solving the Problems]
The present invention is based on the finding that, by coating the surface of stainless steel with aluminum or an aluminum alloy, hydrogen intrusion can be greatly suppressed, and furthermore, the material of the high-pressure hydrogen tank or piping is made of austenitic or duplex stainless steel. By doing so, the deterioration of mechanical properties such as toughness, tensile strength, ductility, and fatigue strength due to hydrogen intrusion is suppressed, and the gist is as follows.
[0010]
(1) In a high-pressure hydrogen gas tank storing a hydrogen gas having a pressure of 0.1 to 80 MPa, the material of the high-pressure hydrogen gas tank is
C: 0.002 to 0.08%, Si: 0.01 to 3.0%,
P: 0.005 to 0.04%, S: 0.0001 to 0.01%,
Mn: 0.1 to 2.0%, Ni: 3.0 to 28.0%,
Cr: 15.0 to 28.0%, N: 0.02 to 0.40%
A high-pressure hydrogen gas tank, comprising stainless steel containing Fe and the unavoidable impurities, and having an aluminum layer made of aluminum or an aluminum alloy and having a thickness of 100 nm to 10 mm on a surface in contact with hydrogen gas.
[0011]
(2) The material of the high-pressure hydrogen gas tank is further
Mo: 0.01 to 7.0%, Nb: 0.005 to 1.0%,
Ti: 0.005 to 1.0%, B: 0.0003 to 0.003%
The high-pressure hydrogen gas tank according to (1), which is a stainless steel containing one or more of the following.
[0012]
(3) A high-pressure hydrogen gas tank, wherein a reinforcing layer made of a high-strength fiber material is formed outside the high-pressure hydrogen gas tank according to (1) or (2).
[0013]
(4) In a high-pressure hydrogen gas pipe for transporting a hydrogen gas having a pressure of 0.1 to 80 MPa, the material of the high-pressure hydrogen gas pipe is mass%.
C: 0.002 to 0.08%, Si: 0.01 to 3.0%,
P: 0.005 to 0.04%, S: 0.0001 to 0.01%,
Mn: 0.1 to 2.0%, Ni: 3.0 to 28.0%,
Cr: 15.0 to 28.0%, N: 0.02 to 0.40%
A high-pressure hydrogen gas pipe, comprising stainless steel containing Fe and the unavoidable impurities, and having an aluminum layer made of aluminum or an aluminum alloy and having a thickness of 100 nm to 10 mm on a surface in contact with the hydrogen gas.
[0014]
(5) The material of the high-pressure hydrogen gas pipe further includes
Mo: 0.01 to 7.0%, Nb: 0.005 to 1.0%,
Ti: 0.005 to 1.0%, B: 0.0003 to 0.003%
(4) The high-pressure hydrogen gas pipe according to (4), which is a stainless steel containing one or more of the following.
[0015]
(6) A high-pressure hydrogen gas pipe comprising a high-strength fiber material reinforcing layer formed outside the high-pressure hydrogen gas pipe according to (4) or (5).
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
The inventor of the present invention aimed at a method for preventing intrusion of hydrogen into steel by coating stainless steel with aluminum or an aluminum alloy, and made the following studies.
[0017]
The surface of a SUS304 or SUS316 steel bar having a diameter of 5 mm and a length of 30 mm was mechanically ground and the end was processed into a hemispherical shape. Next, aluminum was hot-dip plated on a SUS304 bar and an aluminum alloy made of Al-10% Mg-1% Ca-7% Si on a SUS316 bar.
[0018]
SUS304 and SUS316 steel bar samples, as-machined, aluminum-plated samples, and aluminum-alloy-plated samples were each placed in a Ni-alloy container having an inner diameter of 20 mm and a wall thickness of 50 mm. The Ni alloy lid was fixed with bolts to maintain airtightness. From the high-pressure cock attached in advance to the Ni alloy lid, the inside of the container is evacuated, hydrogen gas is charged, and the operation of evacuating again is repeated several times, then 78 MPa high-pressure hydrogen gas is injected, and the cock is closed. Furthermore, the end of the steel pipe with the cock was closed by welding. The entire container made of Ni alloy was immersed in a silicon oil thermostat kept at 80 ° C. and kept for 10,000 hours. Thereafter, the sample was taken out.
[0019]
For both SUS304 and SUS316, the amount of hydrogen was analyzed for each of the as-machined samples, the samples held in high-pressure hydrogen gas after mechanical grinding, the aluminum plating samples, and the aluminum alloy plating samples, and the average value of each of the three samples was analyzed. I asked. The amount of hydrogen in each sample was determined by gas extraction by an inert gas melting method and analysis by a thermal conductivity method. The aluminum plating sample and the aluminum alloy plating sample were cut perpendicular to the axial direction, and the thickness of the aluminum layer in the cross section was measured with an optical microscope.
[0020]
FIG. 1 shows the average value of the hydrogen content of each sample. In FIG. 1, the aluminum coating materials of SUS304 and SUS316 are a SUS304 steel bar hot-dip coated with aluminum and a SUS316 steel bar hot-dip coated with an aluminum alloy made of Al-10% Mg-1% Ca-7% Si, respectively. . From FIG. 1, it can be seen that aluminum plating or aluminum alloy plating can prevent intrusion of hydrogen into stainless steel in high-pressure hydrogen.
[0021]
When the diffusion distance of hydrogen in aluminum when held at 80 ° C. for 10,000 hours is calculated from the diffusion coefficient, it is about 10 to 30 mm, which exceeds the aluminum layer thickness of 5 to 10 μm. That is, it is considered that the cause of the suppression of the intrusion of hydrogen into stainless steel by the aluminum layer is not the suppression of the diffusion of hydrogen in the aluminum layer. The mechanism by which hydrogen intrusion is suppressed by coating stainless steel with an aluminum layer is to suppress the intrusion of hydrogen by the oxide layer on the surface of the aluminum layer, and to suppress the dissociation reaction of hydrogen molecules to hydrogen atoms on the surface of the oxide layer. A hydrogen trap at the interface between the aluminum layer and the stainless steel may be considered.
[0022]
Hereinafter, the present invention will be described in detail. First, the reasons for defining the chemical components of stainless steel will be described.
[0023]
C is effective in strengthening stainless steel and stabilizing the austenite phase in a solid solution state, but this effect is insufficient when the amount of C is less than 0.002%. On the other hand, if the content exceeds 0.08%, carbides precipitate at the grain boundaries, and the corrosion resistance is deteriorated due to sensitization, and the ductility and toughness are reduced. Therefore, the C content was set to 0.002 to 0.08%.
[0024]
Si is effective as a deoxidizing element and needs to be added in an amount of 0.01% or more. On the other hand, if the Si content exceeds 3.0%, the ductility and toughness of the material deteriorate, so the upper limit is set to 3.0% or less.
[0025]
P is an impurity and degrades corrosion resistance, so it must be 0.04% or less. On the other hand, if the P content is less than 0.005%, the refining cost increases, so the lower limit is made 0.005% or more.
[0026]
S is also an impurity and degrades corrosion resistance and hot workability, so it needs to be 0.01% or less. On the other hand, if the S content is less than 0.0001%, the refining cost increases, so the lower limit is made 0.0001% or more.
[0027]
Mn has the effect of fixing S and increasing the solid solubility limit of N, and requires 0.1% or more of Mn to improve hot workability. On the other hand, if the Mn content exceeds 2.0%, abnormal oxidation occurs during heating in the production process, so the upper limit was made 2.0% or less.
[0028]
Ni is an element that stabilizes the austenite phase and increases the toughness, and it is necessary to add 3.0% or more. On the other hand, even if the Ni content exceeds 28.0%, the effect is saturated and the cost is increased. Therefore, the Ni content is set in the range of 3.0 to 28.0%.
[0029]
Cr is an important element that forms a passivation film on the surface of stainless steel and improves corrosion resistance. Further, Cr coexists with Ni and contributes to stabilization of the austenite phase. However, this effect is insufficient when the Cr content is less than 15.0%, and when it exceeds 28.0%, the productivity is impaired and the cost increases. Therefore, the Cr content is set in the range of 15.0 to 28.0%.
[0030]
N has an effect of improving pitting corrosion resistance and strength, and contributes to stabilization of the austenite phase. However, it is necessary to add 0.02% or more of N to exhibit the effect. On the other hand, if the N content exceeds 0.40%, nitrides are formed and ductility, toughness, and productivity are impaired. Therefore, the N content is set in the range of 0.02 to 0.40%.
[0031]
Further, one or more of Mo, Nb, Ti and B may be contained.
[0032]
Mo works effectively in repairing a passive film and improves corrosion resistance, but this effect is slightly insufficient when the amount of Mo is less than 0.01%, and may impair manufacturability when the amount of Mo exceeds 7.0%. is there. Therefore, the Mo content is preferably set to 0.01 to 7.0%.
[0033]
Nb is an element having the effect of improving strength and suppressing sensitization, and is preferably added at 0.005% or more. On the other hand, since this effect is saturated when the Nb content exceeds 1.0%, the upper limit is preferably set to 1.0% or less.
[0034]
Ti is also an element having the effect of improving strength and suppressing sensitization, and is preferably added at 0.005% or more. On the other hand, this effect saturates when the Ti content exceeds 1.0%, so the upper limit is preferably set to 1.0% or less.
[0035]
B is an element that strengthens crystal grain boundaries and improves hot workability and cold workability. To obtain this effect, 0.0003% or more is preferable. On the other hand, if B is added in excess of 0.003%, borides are formed and hot workability may be degraded, so the upper limit is preferably made 0.003% or less.
[0036]
It is preferable that the stainless steel contains 40% by volume or more of an austenite phase because deterioration of mechanical properties such as ductility and toughness of the material due to intrusion of about 10 ppm of hydrogen is small. The remainder of the austenite phase is mainly a ferrite phase and a martensite phase. The austenite phase may be 100% by volume. The volume% of the austenite phase can be determined by measuring the volume% of the ferrite phase and the martensite phase, which are ferromagnetic materials, by an electromagnetic induction method, and determining the remainder as the austenite phase.
[0037]
The volume% of the ferrite phase and the martensite phase of the stainless steel may be measured using, for example, a ferrite content measuring device manufactured by Fischer Instruments, but in this case, it is necessary to pay attention to the size of the sample, When the plate thickness is 3 mm or more, a mirror-polished sample of a plate thickness section parallel to the rolling direction is used at the center of the plate thickness, and when the plate thickness is less than 3 mm, a plurality of plates are stacked, and the total thickness is What is necessary is just to measure on a rolling surface so that it may be set to 3 mm or more.
[0038]
An aluminum layer made of aluminum or an aluminum alloy is formed on the surface of the stainless steel that comes into contact with hydrogen. The aluminum layer is allowed to contain 0.2% or less of Fe, Cr, Mn, or the like as inevitable impurities. The aluminum alloy must have an Al content of 50% or more, and add at least one of 0.1 to 20% Mg, 0.1 to 20% Ca, and 0.1 to 20% Si. You may. The amount of Si is preferably 5 to 11%.
[0039]
When the thickness of the aluminum layer is less than 100 nm, it is difficult to make the thickness uniform, and a defect is generated, so that the base material stainless steel is easily exposed. On the other hand, if the thickness of the aluminum layer exceeds 10 mm, material costs and manufacturing costs increase. Therefore, the thickness of the aluminum layer on the surface of the stainless steel was set to 100 nm to 10 mm.
[0040]
The preferred range of the thickness of the aluminum layer varies depending on the method of forming the aluminum layer. When the aluminum layer is formed by vapor deposition, the thickness is preferably 100 nm to 10 μm. When the aluminum layer is formed by hot-dip plating, the thickness is preferably 1 μm to 1 mm. When the surface of the stainless steel is made of a clad material coated with an aluminum layer, the thickness is preferably 1 mm to 10 mm in order to prevent the aluminum layer on the surface from being melted and exposing the stainless steel of the matrix.
[0041]
The body and piping of the tank for high-pressure hydrogen gas of the present invention may be formed by forming a stainless steel plate into a cylindrical shape and welding the ends by abutting each other, or a stainless steel pipe. As a method of forming an aluminum layer on the surface of stainless steel in contact with hydrogen, there are a method of evaporating aluminum or an aluminum alloy in a vacuum and a method of immersion in a hot-dip plating bath of aluminum or an aluminum alloy for hot-dip plating. The high-pressure hydrogen gas tank has a lid welded to the body, but it is necessary to form an aluminum layer on the surface of the lid that contacts the hydrogen gas.
[0042]
In the production of a high-pressure hydrogen gas tank is a large structure, using a clad plate of aluminum or an aluminum alloy and stainless steel, the friction stir welding an aluminum layer (F riction S tir W elding, that FSW) or tungsten electrode inert gas arc welding (T ungsten I nert G as welding , that TIG) were bonded using a stainless steel section may be joined separately by FSW or TIG the aluminum layer.
[0043]
When the high-pressure hydrogen gas tank and piping of the present invention are used for a fuel system of transportation equipment, for example, for use in a vehicle, reduction in weight is important. Therefore, it is necessary to reduce the thickness of stainless steel, which is a material for the high-pressure hydrogen gas tank and the piping. For this purpose, it is effective to form a reinforcing layer made of a high-strength fiber material outside the high-pressure hydrogen gas tank and the pipe made of stainless steel, and to bear the stress caused by the pressure of the high-pressure hydrogen gas.
[0044]
The reinforcing layer is preferably a lightweight and high-strength carbon fiber. The carbon fibers may be polyacrylonitrile-based or pitch-based. The reinforcing layer is preferably formed by wrapping carbon fibers around the outside of the high-pressure hydrogen gas tank and the piping and hardening the resin with a resin. The carbon fiber is preferably wound in the circumferential direction or axial direction of the tank, but may be wound in any direction depending on the shape, leaving no slack, and is preferably wound around the tank and pipe while maintaining tension. . Further, when winding the carbon fiber a plurality of times, it is preferable that the carbon fiber be wound in close contact with the already wound carbon fiber. After the carbon fiber is wound, it is preferable to solidify with a thermoplastic resin such as nylon or polycarbonate or a thermosetting resin such as a vinyl ester resin or an epoxy resin so that the carbon fiber does not shift.
[0045]
When applying the high-pressure hydrogen gas tank and piping of the present invention to a storage facility that is a large-sized structure, since the pressure of hydrogen gas is high, a reinforcing layer made of carbon fibers is formed on the outside, and the It is good also as a structure which distributes the stress which performs.
[0046]
【Example】
(Example 1)
Steels A and B composed of the chemical components shown in Table 1 were melted, cast, hot rolled, solution heat treated, and oxidized scale removed to obtain steel sheets having a thickness of 25 mm. The volume% of the austenite phase was measured at the center of the cross section of the plate thickness using a ferrite content measuring device manufactured by Fischer Instruments.
[0047]
A steel plate was formed and welded to produce a cylindrical high-pressure hydrogen gas tank (hereinafter, tanks A and B) having an inner diameter of 100 mm and an axial length of 400 mm. Holes having a diameter of 50 mm were formed on both bottom surfaces of the tanks A and B, and a stainless steel tube having a high-pressure cock was welded to one of the holes. On the other side, a stainless steel pipe with a pressure gauge was welded to the branch pipe, and a heating device using a nichrome wire as a heat source and a pot containing pure aluminum were inserted into the tank. The heating device and the pot were fixed together with the energizing wiring by a jig, and the gap between the jig and the steel pipe was sealed with a rubber circular ring.
[0048]
The pressure inside the tanks A and B was reduced to 1 × 10 −2 Pa or less by a vacuum pump from the high pressure cock, and the high pressure cock was closed. Next, the pot containing the pure aluminum was heated and left for 5 minutes after the pure aluminum was melted. Then, the heating of the pot was stopped, and aluminum was deposited on the inner surfaces of the tanks A and B. Thereafter, the high-pressure cock was left open for 2 hours, and air was introduced. Further, the axial position of the pot containing pure aluminum was changed, the pressure was again reduced by the vacuum pump, the pot containing pure aluminum was heated, and the operation of depositing aluminum on the inner surfaces of tanks A and B was repeated several times. An aluminum layer was repeatedly formed.
[0049]
The pot, the heating device, and the jig containing pure aluminum were taken out of the tanks A and B, and a steel bar having a diameter of 5 mm and a length of 30 mm collected from the steels A and B was inserted into the end of the steel pipe. The lid was welded. Further, the operation of reducing the pressure in the tanks A and B with a vacuum pump from the high pressure cock side at room temperature and then introducing hydrogen gas and evacuating again was repeated several times. Thereafter, hydrogen gas was introduced into the tanks A and B, and the pressure of the hydrogen gas was adjusted to 29.9 MPa at room temperature by a hydrogen gas compressor. Finally, the high-pressure cocks were closed, and the tanks A and B were placed in a constant temperature room maintained at 80 ° C. by an infrared irradiator, left for 1000 hours, and then cooled to room temperature.
[0050]
The high-pressure cock was connected to the hydrogen diffusion stack and opened, and the hydrogen inside was released to atmospheric pressure. Further, 0.12 MPa N 2 gas was injected into the tanks A and B from the high pressure cocks for 10 minutes, and the hydrogen inside the tanks A and B was replaced with nitrogen. After this operation, the tanks A and B were cut in the circumferential direction, the insides of the tanks A and B were visually observed, and it was confirmed that the tanks A and B were covered with the aluminum layer. Furthermore, five samples having a circumferential length of 20 mm were collected from the central portion in the axial direction of the cylindrical portions of the tanks A and B, and five samples having a circumferential length of 20 mm were taken and mechanically polished. The specimen was magnified 3000 times at the maximum with a scanning electron microscope, and photographs of three visual fields of each sample were taken, and the thickness of the aluminum layer was measured at any five places in each photograph. The thickness of the aluminum layer was about 0.6 to 3 μm, and covered the surface of the stainless steel in all the visual fields observed.
[0051]
Further, samples were taken from the trunks of tanks A and B, and the amounts of hydrogen in steels A and B were analyzed. For comparison, the hydrogen content of the steel plate as the material of the tanks A and B and the hydrogen content of the steel bars sealed in the tanks A and B were measured. The amount of hydrogen in each sample was determined by gas extraction by an inert gas melting method and analysis by a thermal conductivity method. Table 2 shows the results. The hydrogen content of the tanks A and B on which the aluminum layers were formed was about 3 ppm, which was almost the same as before the test, whereas the hydrogen content of the steel bars A and B increased to about 6 ppm. The analysis accuracy of the amount of hydrogen is within 1 ppm.
(Example 2)
Steels C, D, E and F shown in Table 1 were made into steel plates having a thickness of 25 mm in the same manner as in Example 1, and the volume% of the austenite phase was measured. Hydrogen gas tanks (hereinafter referred to as tanks C, D, E, and F) were manufactured. Holes having a diameter of 50 mm were made in both bottom surfaces of the tanks C, D, E, and F, and the whole was immersed in an aluminum melting tank, and was subjected to hot-dip aluminum plating.
[0052]
After cooling to room temperature, a stainless steel tube with a high-pressure cock was welded to one of the 50 mm diameter holes drilled on both bottom surfaces. On the other side, a stainless steel pipe with a pressure gauge was welded to the branch pipe, a steel bar with a diameter of 5 mm and a length of 30 mm sampled from steel C, D, E, F was inserted, and a lid was placed on the outside of the stainless steel pipe. Welded. When welding the stainless steel pipes to the holes on both bottom surfaces, the aluminum at the welded portion was removed by grinding in advance so as not to hinder the welding. As in Example 1, the insides of the tanks C, D, E, and F were filled with hydrogen gas at 29.9 MPa at room temperature, left at 80 ° C. for 1000 hours, and cooled to room temperature.
[0053]
Thereafter, as in Example 1, the inside hydrogen is diffused, replaced with nitrogen, and the tanks C, D, E, and F are cut in the circumferential direction, and the inside is visually observed and covered with an aluminum layer. It was confirmed. Further, from the central portion in the axial direction of the cylindrical portion of each of the tanks C, D, E, and F, a thick section in the circumferential direction is used as an observation surface, and a total of twelve samples of each steel type having a length of 20 mm in the circumferential direction are collected. , Mechanically polished. The specimen was magnified up to 1000 times with a scanning electron microscope, and photographs of three visual fields of each sample were taken. The thickness of the aluminum layer was measured at any five points in each photograph. The thickness of the aluminum layer was about 5 to 30 μm, and covered the stainless steel surface in all observation fields.
[0054]
Furthermore, samples were taken from the trunks of tanks C, D, E, and F, and the amount of hydrogen in the stainless steel was analyzed. For comparison, the hydrogen amounts of the steel plates as the raw materials of the tanks C, D, E, and F, and the hydrogen amounts of the steel bars sealed in the tanks C, D, E, and F were measured. The amount of hydrogen in each sample was determined by gas extraction by an inert gas melting method and analysis by a thermal conductivity method. Table 3 shows the results. The tanks C, D, E, and F on which the aluminum layer was formed had a hydrogen content of about 3 ppm, which was almost the same as before the test, whereas the bar steels C, D, E, and F had a hydrogen content of about 6 ppm. Was increasing. The analysis accuracy of the amount of hydrogen is within 1 ppm.
(Example 3)
The steel A produced in the same manner as in Example 1 was further subjected to hot rolling, solution heat treatment, cold rolling, solution heat treatment, and oxide scale removal to obtain a plate having a thickness of 3 mm. The volume% of the austenite phase was measured at the center of the plate cross section using a ferrite content measuring device manufactured by Fischer Instruments. This steel plate was formed and welded to produce two cylinders having an inner diameter of 30 mm and a length of 200 mm, and one end was welded and closed with steel A having a plate thickness of 25 mm. In this state, the two cylinders were immersed in a molten aluminum bath to perform plating, and aluminum layers were formed on the inner and outer surfaces of the cylinders. Further, a stainless steel pipe having a high-pressure cock on the side of the cylindrical opening was welded to form a high-pressure hydrogen gas tank. At the time of this welding, the aluminum layer at the welded portion was removed by grinding.
[0055]
A reinforcing layer was formed outside one high-pressure hydrogen gas tank to distribute stress caused by pressure. The reinforcing layer was formed by winding a sufficient amount of carbon fiber on the outside of the high-pressure hydrogen gas tank in terms of strength design and then solidifying it with a synthetic resin.
[0056]
Using these high-pressure hydrogen gas tanks, an internal pressure fatigue test simulating the filling and release of high-pressure hydrogen was performed as follows. First, as in Example 1, the inside of the high-pressure hydrogen gas tank was filled with hydrogen gas at 29.9 MPa at room temperature, left at 80 ° C. for 1000 hours, and cooled to room temperature to fill the high-pressure hydrogen gas. Simulated hydrogen intrusion. Further, the operation of introducing nitrogen gas at a pressure of 70.9 MPa from a high pressure cock, reducing the pressure to 0.1 MPa, and introducing nitrogen gas at 70.9 MPa again was repeated.
[0057]
The tank for high-pressure hydrogen gas, which did not have a reinforcing layer made of carbon fiber on the outside, was broken after repeating the operation of increasing the internal pressure to 70.9 MPa and reducing the pressure to 0.1 MPa as an internal pressure fatigue test, 2786 times. Then the pressure stopped rising. On the other hand, the high-pressure hydrogen gas tank in which the reinforcing layer made of carbon fibers was formed on the outside did not break even after 30,000 times of the internal pressure fatigue test.
[0058]
[Table 1]
Figure 2004324800
[0059]
[Table 2]
Figure 2004324800
[0060]
[Table 3]
Figure 2004324800
[0061]
【The invention's effect】
The present invention makes it possible to suppress the intrusion of hydrogen into a high-pressure hydrogen gas tank that repeatedly fills and discharges high-pressure hydrogen gas and that stores high-pressure hydrogen gas for long-term storage and a high-pressure hydrogen gas pipe that transports high-pressure hydrogen gas. The industrial contribution is extremely remarkable, for example, it can be expected to prolong the service life.
[Brief description of the drawings]
FIG. 1 is a diagram showing the effect of an aluminum layer on the hydrogen penetration characteristics of stainless steel.

Claims (6)

圧力が0.1〜80MPaの水素ガスを貯蔵する高圧水素ガス用タンクにおいて、前記高圧水素ガス用タンクの材質が、質量%で、
C :0.002〜0.08%、
Si:0.01〜3.0%、
P :0.005〜0.04%、
S :0.0001〜0.01%、
Mn:0.1〜2.0%、
Ni:3.0〜28.0%、
Cr:15.0〜28.0%、
N :0.02〜0.40%
を含有し、残部Fe及び不可避的不純物からなるステンレス鋼であり、水素ガスと接する面にアルミニウム又はアルミニウム合金からなる厚さ100nm〜10mmのアルミ層を有することを特徴とする高圧水素ガス用タンク。
In a high-pressure hydrogen gas tank storing a hydrogen gas having a pressure of 0.1 to 80 MPa, the material of the high-pressure hydrogen gas tank is mass%,
C: 0.002 to 0.08%,
Si: 0.01 to 3.0%,
P: 0.005 to 0.04%,
S: 0.0001 to 0.01%,
Mn: 0.1 to 2.0%,
Ni: 3.0 to 28.0%,
Cr: 15.0 to 28.0%,
N: 0.02 to 0.40%
A high-pressure hydrogen gas tank, comprising stainless steel containing Fe and the unavoidable impurities, and having an aluminum layer made of aluminum or an aluminum alloy and having a thickness of 100 nm to 10 mm on a surface in contact with hydrogen gas.
高圧水素ガス用タンクの材質が、更に、質量%で、
Mo:0.01〜7.0%、
Nb:0.005〜1.0%、
Ti:0.005〜1.0%、
B :0.0003〜0.003%
の1種又は2種以上を含有するステンレス鋼であることを特徴とする請求項1に記載の高圧水素ガス用タンク。
The material of the high-pressure hydrogen gas tank is further
Mo: 0.01 to 7.0%,
Nb: 0.005 to 1.0%,
Ti: 0.005 to 1.0%,
B: 0.0003-0.003%
The high-pressure hydrogen gas tank according to claim 1, wherein the tank is a stainless steel containing one or more of the following.
請求項1又は2記載の高圧水素ガス用タンクの外側に高強度繊維材料からなる補強層を形成したことを特徴とする高圧水素ガス用タンク。3. A high-pressure hydrogen gas tank comprising a high-strength fiber material reinforcing layer formed outside the high-pressure hydrogen gas tank according to claim 1 or 2. 圧力が0.1〜80MPaの水素ガスを輸送する高圧水素ガス用配管において、前記高圧水素ガス用配管の材質が、質量%で、
C :0.002〜0.08%、
Si:0.01〜3.0%、
P :0.005〜0.04%、
S :0.0001〜0.01%、
Mn:0.1〜2.0%、
Ni:3.0〜28.0%、
Cr:15.0〜28.0%、
N :0.02〜0.40%
を含有し、残部Fe及び不可避的不純物からなるステンレス鋼であり、水素ガスと接する面にアルミニウム又はアルミニウム合金からなる厚さ100nm〜10mmのアルミ層を有することを特徴とする高圧水素ガス用配管。
In a high-pressure hydrogen gas pipe for transporting a hydrogen gas having a pressure of 0.1 to 80 MPa, the material of the high-pressure hydrogen gas pipe is mass%,
C: 0.002 to 0.08%,
Si: 0.01 to 3.0%,
P: 0.005 to 0.04%,
S: 0.0001 to 0.01%,
Mn: 0.1 to 2.0%,
Ni: 3.0 to 28.0%,
Cr: 15.0 to 28.0%,
N: 0.02 to 0.40%
A high-pressure hydrogen gas pipe, comprising stainless steel containing Fe and the unavoidable impurities, and having an aluminum layer made of aluminum or an aluminum alloy and having a thickness of 100 nm to 10 mm on a surface in contact with the hydrogen gas.
高圧水素ガス用配管の材質が、更に、質量%で、
Mo:0.01〜7.0%、
Nb:0.005〜1.0%、
Ti:0.005〜1.0%、
B :0.0003〜0.003%
の1種又は2種以上を含有するステンレス鋼であることを特徴とする請求項4記載の高圧水素ガス用配管。
The material of the high pressure hydrogen gas piping is further
Mo: 0.01 to 7.0%,
Nb: 0.005 to 1.0%,
Ti: 0.005 to 1.0%,
B: 0.0003-0.003%
The high-pressure hydrogen gas pipe according to claim 4, wherein the pipe is a stainless steel containing one or more of the following.
請求項4または5記載の高圧水素ガス用配管の外側に高強度繊維材料からなる補強層を形成したことを特徴とする高圧水素ガス用配管。A high-pressure hydrogen gas pipe comprising a high-strength fiber material reinforcing layer formed outside the high-pressure hydrogen gas pipe according to claim 4.
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KR20210092292A (en) 2018-12-21 2021-07-23 닛테츠 스테인레스 가부시키가이샤 Cr-based stainless steel sheet with excellent hydrogen embrittlement resistance
WO2023178842A1 (en) * 2022-03-22 2023-09-28 于善广 Hydrogen transportation pipelines and small movable iron and steel plants

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