JP4496750B2 - Stainless steel for polymer electrolyte fuel cell separator and polymer electrolyte fuel cell using the stainless steel - Google Patents

Stainless steel for polymer electrolyte fuel cell separator and polymer electrolyte fuel cell using the stainless steel Download PDF

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JP4496750B2
JP4496750B2 JP2003348772A JP2003348772A JP4496750B2 JP 4496750 B2 JP4496750 B2 JP 4496750B2 JP 2003348772 A JP2003348772 A JP 2003348772A JP 2003348772 A JP2003348772 A JP 2003348772A JP 4496750 B2 JP4496750 B2 JP 4496750B2
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JP2004149920A (en
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伸 石川
國夫 福田
康 加藤
古君  修
研治 高尾
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JFE Steel Corp
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    • CCHEMISTRY; METALLURGY
    • C23COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
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Description

本発明は、耐久性に優れるとともに接触抵抗値の小さい固体高分子型燃料電池セパレータ用ステンレス鋼とそのステンレス鋼製セパレータを用いた固体高分子型燃料電池に関するものである。 The present invention relates to a polymer electrolyte fuel cell using the stainless steel separators of stainless steel and its use smaller solid polymer fuel cell separator having a contact resistance value with excellent durability.

近年、地球環境保全の観点から、発電効率に優れ、CO2 を排出しない燃料電池の開発が進められている。この燃料電池はH2 とO2 を反応させて電気を発生させるものであり、使用される電解質の種類により、リン酸型燃料電池,溶融炭酸塩型燃料電池,固体電解質型燃料電池,アルカリ型燃料電池,固体高分子型燃料電池等が開発されている。 In recent years, from the viewpoint of global environmental conservation, development of fuel cells that are excellent in power generation efficiency and do not emit CO 2 has been underway. This fuel cell generates electricity by reacting H 2 and O 2. Depending on the type of electrolyte used, the phosphoric acid fuel cell, molten carbonate fuel cell, solid electrolyte fuel cell, alkaline type Fuel cells, polymer electrolyte fuel cells, and the like have been developed.

これらの燃料電池のうち、固体高分子型燃料電池は、他の燃料電池に比べて、
(a) 発電温度が80℃程度であり、格段に低い温度で発電できる、
(b) 燃料電池本体の軽量化,小型化が可能である、
(c) 短時間で立上げできる、
等の利点を有している。このため、固体高分子型燃料電池は、電気自動車の搭載用電源,家庭用の定置型発電機,携帯用の小型発電機として利用するべく、今日もっとも注目されている燃料電池である。
Among these fuel cells, the polymer electrolyte fuel cell is compared with other fuel cells,
(a) The power generation temperature is about 80 ° C, and power can be generated at a significantly lower temperature.
(b) The fuel cell body can be reduced in weight and size.
(c) Start up in a short time,
And so on. For this reason, the polymer electrolyte fuel cell is the fuel cell that is attracting the most attention today for use as a power source for mounting an electric vehicle, a stationary generator for home use, and a small portable generator.

固体高分子型燃料電池は、高分子膜を介してH2 とO2 から電気を取り出すものであり、図1に示すように、ガス拡散層2,3(たとえばカーボンペーパ等)およびセパレータ4,5によって膜−電極接合体1を挟み込み、これを単一の構成要素(いわゆる単セル)とし、セパレータ4とセパレータ5との間に起電力を生じさせるものである。 The polymer electrolyte fuel cell takes out electricity from H 2 and O 2 through a polymer membrane. As shown in FIG. 1, gas diffusion layers 2 and 3 (for example, carbon paper) and separators 4 and 4 are used. The membrane-electrode assembly 1 is sandwiched by 5 to form a single component (so-called single cell), and an electromotive force is generated between the separator 4 and the separator 5.

なお膜−電極接合体1は、MEA(すなわち Membrance-Electrode Assembly )と呼ばれており、高分子膜とその膜の表裏面に白金系触媒を担持したカーボンブラック等の電極材料を一体化したものであり、厚さは数10μm〜数100 μmである。ガス拡散層2,3は、膜−電極接合体1と一体化される場合も多い。   The membrane-electrode assembly 1 is called MEA (that is, Membrance-Electrode Assembly), and is an integration of a polymer membrane and an electrode material such as carbon black carrying a platinum-based catalyst on the front and back surfaces of the membrane. The thickness is several tens of μm to several hundreds of μm. In many cases, the gas diffusion layers 2 and 3 are integrated with the membrane-electrode assembly 1.

固体高分子型燃料電池を上記した用途に適用する場合は、このような単セルを直列に数十〜数百個つないで燃料電池スタックを構成して使用している。   When the polymer electrolyte fuel cell is applied to the above-described use, a fuel cell stack is formed by connecting several tens to several hundreds of such single cells in series.

セパレータ4,5には、
(A) 単セル間を隔てる隔壁
としての役割に加え、
(B) 発生した電子を運ぶ導電体、
(C) O2 (すなわち空気)とH2 が流れる空気流路,水素流路、
(D) 生成した水やガスを排出する排出路
としての機能が求められる。さらに固体高分子型燃料電池を実用に供するためには、耐久性や電気伝導性に優れたセパレータ4,5を使用する必要がある。
For separators 4 and 5,
(A) In addition to serving as a partition wall that separates single cells,
(B) a conductor that carries the generated electrons,
(C) an air flow path, a hydrogen flow path through which O 2 (ie air) and H 2 flow,
(D) A function as a discharge path for discharging generated water and gas is required. Furthermore, in order to put the polymer electrolyte fuel cell into practical use, it is necessary to use separators 4 and 5 having excellent durability and electrical conductivity.

耐久性に関しては、電気自動車の搭載用電源として使用される場合は、約5000時間と想定されている。あるいは家庭用の定置型発電機等として使用される場合は、約 40000時間と想定されている。したがってセパレータ4,5には、長時間の発電に耐えられる耐食性等の特性が要求される。   In terms of durability, when used as a power source for mounting on an electric vehicle, it is assumed to be about 5000 hours. Or, if it is used as a home-use generator, it is assumed that it is about 40,000 hours. Therefore, the separators 4 and 5 are required to have characteristics such as corrosion resistance that can withstand long-time power generation.

また電気伝導性に関しては、セパレータ4,5とガス拡散層2,3との接触抵抗は極力低いことが望まれる。 その理由は、セパレータ4,5とガス拡散層2,3との接触抵抗が増大すると、固体高分子型燃料電池の発電効率が低下するからである。つまり、接触抵抗が小さいほど、電気伝導性が優れている。   Regarding electrical conductivity, it is desirable that the contact resistance between the separators 4 and 5 and the gas diffusion layers 2 and 3 is as low as possible. The reason is that as the contact resistance between the separators 4 and 5 and the gas diffusion layers 2 and 3 increases, the power generation efficiency of the polymer electrolyte fuel cell decreases. That is, the smaller the contact resistance, the better the electrical conductivity.

現在までに、セパレータ4,5としてグラファイトを用いた固体高分子型燃料電池が実用化されている。このグラファイトからなるセパレータ4,5は、接触抵抗が比較的低く、しかも腐食しないという利点がある。しかしながら衝撃によって破損しやすいので、小型化が困難であり、しかも空気流路6,水素流路7を形成するための加工コストが高いという欠点がある。グラファイトからなるセパレータ4,5が有するこれらの欠点は、固体高分子型燃料電池の普及を妨げる原因になっている。   To date, polymer electrolyte fuel cells using graphite as separators 4 and 5 have been put into practical use. The separators 4 and 5 made of graphite have an advantage that they have a relatively low contact resistance and do not corrode. However, since it is easily damaged by an impact, it is difficult to reduce the size and the processing cost for forming the air channel 6 and the hydrogen channel 7 is high. These disadvantages of the separators 4 and 5 made of graphite are factors that hinder the spread of solid polymer fuel cells.

そこでセパレータ4,5の素材として、グラファイトに替えて金属素材を適用する試みがなされている。特に、耐久性向上の観点から、ステンレス鋼を素材としたセパレータ4,5の実用化に向けて、種々の検討がなされている。   Therefore, an attempt is made to apply a metal material instead of graphite as a material for the separators 4 and 5. In particular, from the viewpoint of improving durability, various studies have been made toward practical application of separators 4 and 5 made of stainless steel.

たとえば特開平8-180883号公報には、不働態皮膜を形成しやすい金属をセパレータとして用いる技術が開示されている。しかし不働態皮膜の形成は、接触抵抗の上昇を招くことになり、発電効率の低下につながる。このため、これらの金属素材は、カーボン素材と比べて接触抵抗が大きく、しかも耐食性が劣る等の改善すべき問題点が指摘されていた。   For example, Japanese Patent Application Laid-Open No. 8-180883 discloses a technique that uses a metal that easily forms a passive film as a separator. However, the formation of a passive film causes an increase in contact resistance, leading to a decrease in power generation efficiency. For this reason, it has been pointed out that these metal materials have problems to be improved such as a contact resistance larger than that of the carbon material and inferior in corrosion resistance.

また特開平10-228914 号公報には、SUS304等の金属セパレータの表面に金めっきを施すことにより、接触抵抗を低減し、高出力を確保する技術が開示されている。しかし、薄い金めっきではピンホールの発生防止が困難であり、逆に厚い金めっきではコストの問題が残る。   Japanese Patent Application Laid-Open No. 10-228914 discloses a technique for reducing contact resistance and ensuring high output by performing gold plating on the surface of a metal separator such as SUS304. However, it is difficult to prevent pinholes with thin gold plating, and conversely with thick gold plating, the problem of cost remains.

また特開2000-277133 号公報には、フェライト系ステンレス鋼基材にカーボン粉末を分散させて、電気伝導性を改善したセパレータを得る方法が開示されている。しかしながらカーボン粉末を用いた場合も、セパレータの表面処理には相応のコストがかかることから、依然としてコストの問題が残っている。 また、表面処理を施したセパレータは、組立て時にキズ等が生じた場合に、耐食性が著しく低下するという問題点も指摘されている。   Japanese Patent Application Laid-Open No. 2000-277133 discloses a method of obtaining a separator having improved electrical conductivity by dispersing carbon powder in a ferritic stainless steel substrate. However, even when carbon powder is used, a cost problem still remains because the surface treatment of the separator requires a corresponding cost. Further, it has been pointed out that the separator subjected to the surface treatment has a problem that the corrosion resistance is remarkably lowered when scratches or the like are generated during assembly.

さらに、ステンレス鋼に表面処理を施さず、そのままセパレータに適用しようとする試みがなされている。たとえば特開2000-239806 号公報や特開2000-294255 号公報には、Cu,Niを積極的に添加した上で、S,P,N等の不純物元素を低減し、かつC+N≦0.03質量%,10.5質量%≦Cr+3×Mo≦43質量%を満足するセパレータ用フェライト系ステンレス鋼が開示されている。特開2000-265248 号公報や特開2000-294256 号公報には、Cu,Niを 0.2質量%以下に制限して金属イオンの溶出を抑えた上で、S,P,N等の不純物元素を低減し、かつC+N≦0.03質量%,10.5質量%≦Cr+3×Mo≦43質量%を満足するセパレータ用フェライト系ステンレス鋼が開示されている。   Furthermore, an attempt has been made to apply stainless steel as it is to the separator without subjecting it to surface treatment. For example, in Japanese Patent Laid-Open Nos. 2000-239806 and 2000-294255, Cu, Ni are positively added, impurity elements such as S, P, and N are reduced, and C + N ≦ 0.03 mass%. , 10.5% by mass ≦ Cr + 3 × Mo ≦ 43% by mass is disclosed. In JP 2000-265248 A and JP 2000-294256 A, Cu and Ni are limited to 0.2% by mass or less to suppress elution of metal ions, and impurity elements such as S, P, and N are added. A ferritic stainless steel for a separator that is reduced and satisfies C + N ≦ 0.03% by mass, 10.5% by mass ≦ Cr + 3 × Mo ≦ 43% by mass is disclosed.

しかし、これらの発明は、いずれもステンレス鋼の成分を所定の範囲に規定して、不働態皮膜を強固にすることによって、表面処理を施さず、そのまま使用しても溶出金属イオンによる電極担持触媒の触媒能の劣化を低減し、腐食生成物による電極との接触抵抗の増加を抑制しようとする思想に基づいている。したがって、ステンレス鋼自体の接触抵抗を低下させようとするものではない。また数万時間の発電に耐える耐久性(すなわち耐出力電圧低下)を確保できるものでもない。
特開平8-180883号公報 特開平10-228914 号公報 特開2000-277133 号公報 特開2000-239806 号公報 特開2000-294255 号公報 特開2000-265248 号公報 特開2000-294256 号公報
However, all of these inventions define the components of stainless steel within a predetermined range and strengthen the passive film, so that the surface treatment is not performed and the electrode-supported catalyst based on the eluted metal ions can be used as it is. This is based on the idea of reducing the deterioration of the catalytic ability of the steel and suppressing an increase in contact resistance with the electrode due to corrosion products. Therefore, it does not attempt to reduce the contact resistance of the stainless steel itself. Further, it is not possible to ensure durability (that is, output voltage reduction) that can withstand power generation for tens of thousands of hours.
Japanese Patent Laid-Open No. 8-180883 Japanese Patent Laid-Open No. 10-228914 JP 2000-277133 A JP 2000-239806 JP JP 2000-294255 A JP 2000-265248 A JP 2000-294256 A

本発明は、従来の技術が抱えている上記のような問題点に鑑み、耐食性が良好であると同時に、接触抵抗が小さい(すなわち電気伝導性に優れる)固体高分子型燃料電池セパレータ用ステンレス鋼、およびそれを用いた固体高分子型燃料電池を提供することを目的とする。   In view of the above-mentioned problems of the prior art, the present invention is a stainless steel for a polymer electrolyte fuel cell separator having good corrosion resistance and low contact resistance (that is, excellent electrical conductivity). And a polymer electrolyte fuel cell using the same.

すなわち本発明は、素材となるステンレス鋼の成分のみならず表面に存在する不働態皮膜の成分を所定の範囲に規定することにより、表面処理を施さなくても接触抵抗が小さく、発電効率が優れ、かつステンレス鋼自体の耐食性が高い固体高分子型燃料電池セパレータ用ステンレス鋼、およびそれを用いた固体高分子型燃料電池を提供することを目的とする。   That is, the present invention regulates not only the component of stainless steel as a raw material but also the component of the passive film existing on the surface within a predetermined range, so that the contact resistance is small and the power generation efficiency is excellent even without surface treatment. Another object of the present invention is to provide stainless steel for a polymer electrolyte fuel cell separator having high corrosion resistance of stainless steel itself, and a polymer electrolyte fuel cell using the same.

本発明者は、接触抵抗を低く抑えた上で、高い耐食性を発揮するためのステンレス鋼製セパレータについて、ステンレス鋼の成分,不働態皮膜の成分の観点から鋭意研究を行なった。その結果、Moを含有した高純度フェライト系ステンレス鋼を素材として、その表面に生成する不働態皮膜の成分を調整することによって接触抵抗が大幅に低減されることを見出した。   The present inventor conducted intensive research on stainless steel separators for exhibiting high corrosion resistance while keeping contact resistance low, from the viewpoints of stainless steel components and passive film components. As a result, it has been found that contact resistance is greatly reduced by adjusting the components of the passive film formed on the surface of Mo-containing high purity ferritic stainless steel.

まず本発明を想到するにいたった実験結果について説明する。   First, the experimental results for conceiving the present invention will be described.

実験では、C: 0.004質量%,N: 0.007質量%,Si: 0.1質量%,Mn: 0.1質量%,Cr:30.5質量%,Mo:1.85質量%,P:0.03質量%,S: 0.005質量%を含有し、冷間圧延を施したフェライト系ステンレス鋼(板厚0.5mm )を素材とした。一部の素材には大気中で焼鈍( 950℃,2分間)を行なった後、湿式で 600番研磨を行なった。また、他の素材には、露点−60℃の75体積%H2 +25体積%N2 雰囲気中で焼鈍( 950℃,2分間)を行ない、いわゆるBA仕上げとした。さらに、硝酸を10質量%,塩酸を50質量%,ピクリン酸を1質量%含む酸性水溶液を用いて、これらの素材に種々の温度,時間でエッチング処理を行なった後、純水洗浄,冷風乾燥して、接触抵抗の測定に供した。 In the experiment, C: 0.004 mass%, N: 0.007 mass%, Si: 0.1 mass%, Mn: 0.1 mass%, Cr: 30.5 mass%, Mo: 1.85 mass%, P: 0.03 mass%, S: 0.005 mass% A ferritic stainless steel (thickness 0.5 mm) that contains cold rolled steel was used as a material. Some materials were annealed in the atmosphere (950 ° C., 2 minutes) and then wet-coated No. 600. The other materials were annealed (950 ° C., 2 minutes) in a 75 volume% H 2 +25 volume% N 2 atmosphere with a dew point of −60 ° C. to obtain a so-called BA finish. In addition, these materials were etched at various temperatures and times using an acidic aqueous solution containing 10% by mass nitric acid, 50% by mass hydrochloric acid and 1% by mass picric acid, followed by pure water cleaning and cold air drying. The contact resistance was measured.

接触抵抗の測定は、同一条件でエッチング処理した試験片(50mm×50mm)を4枚準備して、図2に示すように2枚の試験片8を、その両側から同じ大きさの3枚のカーボンペーパ(東レ製 TGP-H-120)9で交互に挟み、さらに銅板に金めっきを施した電極10を接触させ、単位面積あたり 137.2N/cm2 (すなわち 14kgf/cm2 )の圧力をかけて試験片8間の抵抗を測定した。その測定値に接触面の面積を乗じ、さらに接触面の数(=2)で除した値を接触抵抗値とした。 For the measurement of contact resistance, four test pieces (50 mm × 50 mm) etched under the same conditions were prepared, and two test pieces 8 as shown in FIG. Carbon paper (Toray TGP-H-120) 9 is alternately sandwiched, and the copper plate is contacted with gold-plated electrodes 10, and a pressure of 137.2 N / cm 2 (ie, 14 kgf / cm 2 ) is applied per unit area. The resistance between the test pieces 8 was measured. The value obtained by multiplying the measured value by the area of the contact surface and further dividing by the number of contact surfaces (= 2) was taken as the contact resistance value.

なお接触抵抗値は、2枚1組の試験片8を交換しながら6回測定した測定値に基づいてそれぞれ算出し、その平均値を表1に示す。   The contact resistance values were calculated based on the measurement values measured six times while exchanging a set of two test pieces 8, and the average values are shown in Table 1.

参考例として、表面に金めっき(厚さ約 0.1μm)を施したステンレス鋼板(厚さ0.3mm ,SUS304相当)およびグラファイト板(厚さ5mm)についても、同様の測定を行ない、接触抵抗値を算出した。その結果を表1に併せて示す。   As a reference example, the same measurement was performed on a stainless steel plate (thickness 0.3 mm, equivalent to SUS304) and a graphite plate (thickness 5 mm) with gold plating (thickness approx. 0.1 μm) on the surface, and the contact resistance value was calculated. Calculated. The results are also shown in Table 1.

またエッチング処理を施した後の不働体皮膜を光電子分光法によって測定し、ピーク分離法により不働体皮膜中(すなわち酸化状態)のFe,Cr,Alのスペクトル強度を算出し、このスペクトル強度からCr含有量,Fe含有量,Al含有量を求めた。さらにそのCr含有量,Fe含有量からCr,Feの原子数を算出してCr/Fe比を原子数の比で算出した。またCr含有量,Fe含有量,Al含有量からCr,Fe,Alの原子数を算出してAl/(Cr+Fe)比を原子数の比で算出した。その結果を表1に示す。   In addition, the passive film after etching is measured by photoelectron spectroscopy, and the spectral intensity of Fe, Cr, and Al in the passive film (that is, the oxidized state) is calculated by the peak separation method. Content, Fe content, and Al content were determined. Furthermore, the Cr / Fe ratio was calculated from the Cr content and the Fe content to calculate the Cr / Fe ratio. The number of Cr, Fe, and Al atoms was calculated from the Cr content, Fe content, and Al content, and the Al / (Cr + Fe) ratio was calculated as the ratio of the number of atoms. The results are shown in Table 1.

不働態皮膜に含有されるO(酸素)のうち、金属酸化物の状態で存在する酸素(以下、O(M) という)と、金属水酸化物の状態で存在する酸素(以下、O(H) という)をピーク分離してそれぞれのスペクトル強度を算出し、O(M) とO(H) の原子数を算出してO(M) /O(H) 比を原子数の比で算出した。その結果を表1に示す。   Of the O (oxygen) contained in the passive film, oxygen present in the metal oxide state (hereinafter referred to as O (M)) and oxygen present in the metal hydroxide state (hereinafter referred to as O (H) ))) And the respective spectrum intensities were calculated, the number of O (M) and O (H) atoms was calculated, and the O (M) / O (H) ratio was calculated as the number of atoms. . The results are shown in Table 1.

Figure 0004496750
Figure 0004496750

表1から明らかなように、ステンレス鋼板をエッチング処理することによって接触抵抗値は低下する。特に、不働態皮膜のCr/Fe比が原子数比で1以上であれば、ステンレス鋼板の接触抵抗値は10mΩ・cm2 以下となる。またO(M) /O(H) 比が原子数比で 0.9以下では、接触抵抗値がさらに低減して8mΩ・cm2 以下となる。 As is apparent from Table 1, the contact resistance value is lowered by etching the stainless steel plate. In particular, when the Cr / Fe ratio of the passive film is 1 or more in terms of the number of atoms, the contact resistance value of the stainless steel plate is 10 mΩ · cm 2 or less. If the O (M) / O (H) ratio is 0.9 or less in terms of the number of atoms, the contact resistance value is further reduced to 8 mΩ · cm 2 or less.

さらにBA仕上げとしたステンレス鋼では、不働態皮膜中にAlが含まれているが、エッチング処理によってAl含有量を低下させると、接触抵抗値も低下する。このとき、不働態皮膜を構成する主要な金属元素であるCr,Fe,Alのそれぞれの含有量から算出されるAl/(Cr+Fe)比が原子数比で0.05未満であれば、BA仕上げとしたステンレス鋼板の接触抵抗値は10mΩ・cm2 以下となる。 Further, in the stainless steel with BA finish, Al is contained in the passive film, but when the Al content is reduced by the etching treatment, the contact resistance value also decreases. At this time, if the Al / (Cr + Fe) ratio calculated from the respective contents of Cr, Fe, and Al, which are the main metal elements constituting the passive film, is less than 0.05 in terms of the atomic ratio, the BA finish is used. The contact resistance value of stainless steel sheet is 10 mΩ · cm 2 or less.

接触抵抗値が10mΩ・cm2 以下であれば、燃料電池の特性にほとんど悪影響を及ぼさない。 If the contact resistance value is 10 mΩ · cm 2 or less, the fuel cell characteristics are hardly adversely affected.

これまで耐食性の観点から不働態皮膜のCr/Fe比の影響が調査された例はあるが、この実験によって、不働態皮膜の成分を調整すれば接触抵抗値を大幅に低減できるという従来にない知見を得た。この知見に基づいて完成された本発明は下記の通りである。   There has been an example in which the influence of the Cr / Fe ratio of the passive film has been investigated from the viewpoint of corrosion resistance, but it has never been possible to significantly reduce the contact resistance value by adjusting the components of the passive film by this experiment. Obtained knowledge. The present invention completed based on this finding is as follows.

1.Cを0.03質量%以下、Nを0.03質量%以下、Crを20〜45質量%、Moを 0.1〜5.0 質量%、Siを 1.0質量%以下、Mnを 1.0質量%以下、Alを0.001〜0.2 質量%以下含有し、かつC含有量とN含有量の合計が0.03質量%以下を満足し、さらにTiまたはNbを0.01〜0.5 質量%、あるいはTiおよびNbを合計0.01〜0.5 質量%を含有し、残部がFeおよび不可避的不純物からなる組成を有するステンレス鋼であって、かつ前記ステンレス鋼の表面の不働態皮膜に含有されるCr含有量とFe含有量から算出されるCr/Fe比が原子数比で1以上であり、前記不働態皮膜に含有されるAlの含有量、Crの含有量およびFeの含有量から算出されるAl/(Cr+Fe)比が、原子数比で0.05未満であり、かつ前記不働態皮膜に含有される酸素のうち、金属酸化物の状態で存在する酸素:O(M) の含有量と、金属水酸化物の状態で存在する酸素:O(H) の含有量から算出されるO(M) /O(H) 比が、原子数比で0.9以下であることを特徴とする固体高分子型燃料電池セパレータ用ステンレス鋼。 1. C is 0.03% by mass or less, N is 0.03% by mass or less, Cr is 20 to 45% by mass, Mo is 0.1 to 5.0% by mass , Si is 1.0% by mass or less, Mn is 1.0% by mass or less, and Al is 0.001 to 0.2% by mass. %, And the total of C content and N content satisfies 0.03% by mass or less, and further contains 0.01 to 0.5% by mass of Ti or Nb, or 0.01 to 0.5% by mass of Ti and Nb , The balance is stainless steel having a composition composed of Fe and inevitable impurities, and the Cr / Fe ratio calculated from the Fe content and the Cr content in the passive film on the surface of the stainless steel is the number of atoms. The Al / (Cr + Fe) ratio calculated from the Al content, the Cr content and the Fe content contained in the passive film is less than 0.05 in atomic ratio, Of the oxygen contained in the passive film, the content of oxygen: O (M) present in the form of a metal oxide and metal water Solid polymer fuel characterized in that the O (M) / O (H) ratio calculated from the content of oxygen: O (H) present in the oxide state is 0.9 or less in terms of the number of atoms Stainless steel for battery separator.

.固体高分子膜、電極およびセパレータとからなる固体高分子型燃料電池であって、前記セパレータとして上記1に記載の固体高分子型燃料電池セパレータ用ステンレス鋼を用いることを特徴とする固体高分子型燃料電池。 2 . A solid polymer type fuel cell comprising a solid polymer membrane, an electrode and a separator, wherein the separator is the stainless steel for a solid polymer type fuel cell separator as described in 1 above. Fuel cell.

以上に説明したように本発明によれば、接触抵抗値が低く、かつ耐食性に優れた固体高分子型燃料電池セパレータ用ステンレス鋼が得られる。 したがって、従来は耐久性の問題から高価なグラファイト製セパレータを使用していた固体高分子型燃料電池に、安価なステンレス鋼製セパレータを提供することが可能となった。   As described above, according to the present invention, a stainless steel for a polymer electrolyte fuel cell separator having a low contact resistance value and excellent corrosion resistance can be obtained. Accordingly, it has become possible to provide an inexpensive stainless steel separator for a polymer electrolyte fuel cell that has conventionally used an expensive graphite separator due to durability problems.

なお、本発明は、固体高分子型燃料電池セパレータに限らず、電気伝導性を有するステレンス鋼製電気部品としても広く利用できる。   The present invention is not limited to the polymer electrolyte fuel cell separator, but can be widely used as an electrical component made of stainless steel having electrical conductivity.

まず、本発明に係るセパレータ用ステンレス鋼の成分の限定理由を説明する。   First, the reasons for limiting the components of the separator stainless steel according to the present invention will be described.

C:0.03質量%以下,N:0.03質量%以下,C+N:0.03質量%以下
CおよびNは、ともにステンレス鋼中のCrと反応し、粒界にCr炭窒化物として析出するので、耐食性の低下をもたらす。したがってC,Nは、いずれも含有量が小さいほど好ましく、C:0.03質量%以下,N:0.03質量%以下であれば、耐食性を著しく低下させることはない。また、C含有量とN含有量の合計(以下、C+Nという)が0.03質量%を超えると、セパレータをプレス加工する際に生じる割れが著しく増加する。したがってC+Nは、0.03質量%以下とする。好ましくは、C: 0.015質量%以下,N: 0.015質量%以下,C+N:0.02質量%以下である。
C: 0.03% by mass or less, N: 0.03% by mass or less, C + N: 0.03% by mass or less C and N both react with Cr in stainless steel and precipitate as Cr carbonitrides at grain boundaries, resulting in reduced corrosion resistance Bring. Therefore, the smaller the content of C and N, the better. If C: 0.03% by mass or less and N: 0.03% by mass or less, the corrosion resistance will not be significantly reduced. On the other hand, if the total of the C content and the N content (hereinafter referred to as C + N) exceeds 0.03% by mass, cracks generated when the separator is pressed are remarkably increased. Therefore, C + N is 0.03% by mass or less. Preferably, C: 0.015 mass% or less, N: 0.015 mass% or less, and C + N: 0.02 mass% or less.

Cr:20〜45質量%
Crは、ステンレス鋼板の耐食性を確保するために必要な元素であり、Cr含有量が20質量%未満では、セパレータとして長時間の使用に耐えられない。また、Cr含有量が20質量%未満では、不働態皮膜のCr/Fe比を1以上に調整して、接触抵抗値を10mΩ・cm2 以下とすることが困難である。一方、Cr含有量が45質量%を超えると、σ相の析出によって靭性が低下する。したがってCr含有量は、20〜45質量%とした。好ましくは22〜35質量%である。
Cr: 20 to 45 mass%
Cr is an element necessary for ensuring the corrosion resistance of the stainless steel plate. If the Cr content is less than 20% by mass, it cannot be used for a long time as a separator. On the other hand, if the Cr content is less than 20% by mass, it is difficult to adjust the Cr / Fe ratio of the passive film to 1 or more and make the contact resistance value 10 mΩ · cm 2 or less. On the other hand, if the Cr content exceeds 45% by mass, the toughness decreases due to the precipitation of the σ phase. Therefore, the Cr content is set to 20 to 45% by mass. Preferably it is 22-35 mass%.

Mo: 0.1〜5.0 質量%
Moは、ステンレス鋼板の耐隙間腐食性を改善するのに有効な元素である。この効果を発揮するためには、 0.1質量%以上含有させる必要がある。一方、 5.0質量%を超えて添加すると、ステンレス鋼が著しく脆化して生産が困難になる。したがってMo含有量は、 0.1〜5.0 質量%とした。好ましくは 0.5〜3.0 質量%である。
Mo: 0.1-5.0 mass%
Mo is an element effective for improving the crevice corrosion resistance of the stainless steel plate. In order to exert this effect, it is necessary to contain 0.1% by mass or more. On the other hand, if added over 5.0% by mass, the stainless steel becomes extremely brittle and production becomes difficult. Therefore, the Mo content is set to 0.1 to 5.0 mass%. Preferably it is 0.5-3.0 mass%.

本発明に係るセバレータ用ステンレス鋼は、上記した組成に加えて、次の成分を含有する。 Sebareta stainless steel according to the present invention, in addition to the above-described composition, containing the following Ingredients.

Si: 1.0質量%以下
Siは、脱酸のために有効な元素であり、ステンレス鋼の溶製段階で添加される。しかし過度に含有させるとステンレス鋼板が硬質化し、しかも延性が低下する。したがってSi含有量の上限を 1.0質量%とする。さらに好ましくは0.01〜0.6 質量%である。
Si: 1.0 mass% or less
Si is an effective element for deoxidation, and is added at the melting stage of stainless steel. However, if it is contained excessively, the stainless steel plate becomes hard and the ductility decreases. Thus the upper limit of the Si content shall be the 1.0 wt%. More preferably, it is 0.01-0.6 mass%.

Mn: 1.0質量%以下
Mnは、Sと結合し、ステンレス鋼に固溶したSを低減する効果を有するので、Sの粒界偏析を抑制し、熱間圧延時の割れを防止するのに有効な元素である。Mn含有量が 1.0質量%以下であれば、この効果を十分に発揮する。好ましくは 0.001〜0.8 質量%である。
Mn: 1.0 mass% or less
Mn combines with S and has the effect of reducing S dissolved in the stainless steel, so it is an effective element for suppressing grain boundary segregation of S and preventing cracking during hot rolling. If the Mn content is 1.0% by mass or less, this effect is sufficiently exhibited. Preferably it is 0.001-0.8 mass%.

Al: 0.001〜0.2 質量%
Alは、製鋼工程における脱酸に有効な元素であり、その効果を得るためには 0.001質量%以上が必要である。一方、 0.2 質量%を超えて添加しても、その効果は飽和し、コストアップとなる。したがってAl含有量は、 0.001〜0.2 質量%とする。
Al: 0.001 to 0.2 mass%
Al is an element effective for deoxidation in the steelmaking process, and 0.001% by mass or more is necessary to obtain the effect. On the other hand, even if added over 0.2% by mass, the effect is saturated and the cost increases. Therefore the Al content shall be the 0.001 wt%.

Tiを0.01〜0.5 質量%またはNbを0.01〜0.5 質量%,あるいはTiおよびNbを合計0.01〜0.5 質量%
TiおよびNbは、ステンレス鋼中のC,Nを炭窒化物として固定し、プレス成形性を改善するのに有効な元素である。C含有量とN含有量が上記した範囲を満足し、TiまたはNbを添加する場合は、Ti含有量が0.01質量%以上またはNb含有量が0.01質量%以上でその効果が発揮される。またTiおよびNbを添加する場合は、TiおよびNbを合計0.01質量%以上含有すると、その効果が発揮される。一方、TiまたはNbを添加する場合に、Ti含有量が 0.5質量%またはNb:含有量が 0.5質量%を超えると、その効果は飽和する。またTiおよびNbを添加する場合は、TiおよびNbが合計 0.5質量%を超えると、その効果は飽和する。したがってTiまたはNbを添加する場合は、Tiを0.01〜0.5 質量%またはNbを0.01〜0.5 質量%含有させ、TiおよびNbを添加する場合は、TiおよびNbを合計0.01〜0.5 質量%させる。
0.01 to 0.5% by mass of Ti or 0.01 to 0.5% by mass of Nb or 0.01 to 0.5% by mass of Ti and Nb
Ti and Nb are effective elements for fixing C and N in stainless steel as carbonitrides and improving press formability. When the C content and the N content satisfy the above range and Ti or Nb is added, the effect is exhibited when the Ti content is 0.01% by mass or more or the Nb content is 0.01% by mass or more. Moreover, when adding Ti and Nb, the effect will be exhibited, if Ti and Nb are contained 0.01 mass% or more in total. On the other hand, when Ti or Nb is added, if the Ti content exceeds 0.5% by mass or the Nb: content exceeds 0.5% by mass, the effect is saturated. In addition, when Ti and Nb are added, if Ti and Nb exceed 0.5 mass% in total, the effect is saturated. Therefore, when adding Ti or Nb is Ti was contained 0.01 to 0.5 wt% or Nb 0.01 to 0.5 wt%, when adding Ti and Nb are Ti and Nb Ru is total 0.01 to 0.5 wt%.

本発明では、セパレータの素材となるステンレス鋼板の熱間加工性を向上するために上記した元素の他に、Ca,Mg, REM(すなわち希土類元素),Bをそれぞれ 0.1質量%以下、 あるいはステンレス鋼板の靭性向上の目的でNi:1質量%以下を添加しても良い。また、接触抵抗値を低減するために、Ag:1質量%以下,Cu:5質量%以下を添加し、さらにAgを微細に分散させる目的でV: 0.5質量%以下を添加しても良い。   In the present invention, in order to improve the hot workability of the stainless steel plate as the material of the separator, in addition to the above elements, Ca, Mg, REM (ie, rare earth element) and B are each 0.1% by mass or less, or the stainless steel plate For the purpose of improving toughness, Ni: 1% by mass or less may be added. In order to reduce the contact resistance value, Ag: 1 mass% or less, Cu: 5 mass% or less may be added, and V: 0.5 mass% or less may be added for the purpose of finely dispersing Ag.

その他の元素は、残部Feおよび不可避的不純物である。   Other elements are the balance Fe and inevitable impurities.

次に、本発明に係るセパレータ用ステンレス鋼が具備すべき特性について説明する。   Next, the characteristics that the stainless steel for separators according to the present invention should have will be described.

ステンレス鋼板表面の不働態皮膜のCr/Fe比:原子数比で1以上
不働態皮膜の成分は接触抵抗値を低減する上で重要な要因であり、接触抵抗値を低くするためには、不働態皮膜のCr含有量とFe含有量から算出されるCr/Fe比を高くする必要がある。前記した実験結果で説明した通り、 10mΩ・cm2 以下の接触抵抗値を得るためには、Cr/Fe比を原子数比で1以上とする必要がある。
The Cr / Fe ratio of the passive film on the stainless steel plate surface is 1 or more in terms of atomic ratio. The components of the passive film are an important factor in reducing the contact resistance value. It is necessary to increase the Cr / Fe ratio calculated from the Cr content and the Fe content of the active film. As explained in the above experimental results, in order to obtain a contact resistance value of 10 mΩ · cm 2 or less, the Cr / Fe ratio needs to be 1 or more in terms of the number of atoms.

ステンレス鋼板表面の不働態皮膜のO(M) /O(H) 比:原子数比で 0.9以下
不働態皮膜に含有されるO(酸素)の結合状態も、接触抵抗値を低減する上で重要な因子である。接触抵抗値を低減するためには、金属酸化物の状態で存在する酸素(すなわちO(M) )と金属水酸化物の状態で存在する酸素(すなわちO(H) )から算出されるO(M) /O(H) 比を低くするのが有効である。前記した実験結果で説明した通り、O(M) /O(H) 比を原子数比で 0.9以下とすれば、8mΩ・cm2 以下の接触抵抗値が得られる。
O (M) / O (H) ratio of passive film on stainless steel sheet surface: 0.9 or less in atomic ratio The bonding state of O (oxygen) contained in the passive film is also important in reducing the contact resistance value. It is a serious factor. In order to reduce the contact resistance value, oxygen (that is, O (M)) present in the metal oxide state and oxygen (that is, O (H)) present in the metal hydroxide state is calculated from O ( It is effective to lower the M) / O (H) ratio. As explained in the above experimental results, when the O (M) / O (H) ratio is 0.9 or less in terms of the number of atoms, a contact resistance value of 8 mΩ · cm 2 or less can be obtained.

ステンレス鋼板表面の不働態皮膜のAl/(Cr+Fe)比:原子数比で0.05未満
不働態皮膜にAl酸化物が含まれると、接触抵抗値が増加する。酸洗仕上げや研磨仕上げのステンレス鋼板に比べて、BA仕上げのステンレス鋼板では不働態皮膜に含まれるAlが多い。したがってBA仕上げのステンレス鋼板の接触抵抗値を低減するためには、不働態皮膜中のAl量を減少させる必要がある。前記した実験結果で説明した通り、不働態皮膜のCr含有量,Fe含有量,Al含有量から算出されるAl/(Cr+Fe)比を原子数比で0.05未満とすれば、BA仕上げのステンレス鋼板においても10mΩ・cm2 以下の接触抵抗値が得られる。
Al / (Cr + Fe) ratio of passive film on stainless steel plate surface: atomic ratio is less than 0.05. If Al oxide is contained in the passive film, the contact resistance value increases. Compared to pickled and polished stainless steel plates, BA-finished stainless steel plates contain more Al in the passive film. Therefore, in order to reduce the contact resistance value of the BA-finished stainless steel plate, it is necessary to reduce the amount of Al in the passive film. As explained in the above experimental results, if the Al / (Cr + Fe) ratio calculated from the Cr content, the Fe content, and the Al content of the passive film is less than 0.05 in terms of the atomic ratio, the BA-finished stainless steel plate Also, a contact resistance value of 10 mΩ · cm 2 or less is obtained.

このように不働態皮膜のCr含有量,Fe含有量,Al含有量およびO(酸素)の結合状態を調整するためには、酸を用いたエッチング,酸性水溶液への浸漬,電解エッチング等の手法を用いることができる。   Thus, in order to adjust the Cr content, Fe content, Al content and O (oxygen) bonding state of the passive film, etching using acid, immersion in acidic aqueous solution, electrolytic etching, etc. Can be used.

このような不働態皮膜の組成の調整は、ステンレス鋼板をセパレータに加工する前に行なっても良いし、あるいはセパレータに加工した後で行なっても良い。ただし、Cr/Fe比,O(M) /O(H) 比,Al/(Cr+Fe)比を所定の範囲に安定して維持するためには、セパレータに加工した後で酸洗処理を行なうのが好ましい。   Such adjustment of the composition of the passive film may be performed before the stainless steel plate is processed into a separator, or may be performed after the stainless steel plate is processed into a separator. However, in order to stably maintain the Cr / Fe ratio, O (M) / O (H) ratio, and Al / (Cr + Fe) ratio within the predetermined ranges, the pickling process is performed after the separator is processed. Is preferred.

このようにして作製したステンレス鋼製セパレータを用いて固体高分子型燃料電池を製造すると、接触抵抗値が低く、発電効率が優れ、かつ耐食性が高い固体高分子型燃料電池が製造できる。   When a polymer electrolyte fuel cell is produced using the stainless steel separator thus produced, a polymer electrolyte fuel cell having a low contact resistance value, excellent power generation efficiency, and high corrosion resistance can be produced.

〔実施例1〕
転炉および強攪拌真空酸素脱炭処理法(SS−VOD)によって表2に示す成分のステンレス鋼を溶製し、さらに連続鋳造法によって厚さ200mm のスラブとした。このスラブを1250℃に加熱した後、熱間圧延によって厚さ4mmの熱延ステンレス鋼板とし、さらに焼鈍( 850〜1100℃)および酸洗処理を施した。次いで、冷間圧延によって厚さ0.3mm とし、さらに焼鈍( 850〜1100℃)および酸洗処理の後、調質圧延を行ない、いわゆる2B仕上げの冷延ステンレス鋼板とした。
[Example 1]
Stainless steel having the components shown in Table 2 was melted by a converter and a strong stirring vacuum oxygen decarburization treatment method (SS-VOD), and further a 200 mm thick slab was formed by a continuous casting method. This slab was heated to 1250 ° C., and then hot rolled into a hot-rolled stainless steel plate having a thickness of 4 mm, and further subjected to annealing (850 to 1100 ° C.) and pickling treatment. Next, the thickness was reduced to 0.3 mm by cold rolling, and after annealing (850 to 1100 ° C.) and pickling treatment, temper rolling was performed to obtain a cold rolled stainless steel sheet having a so-called 2B finish.

Figure 0004496750
Figure 0004496750

得られた冷延ステンレス鋼板の板幅方向中央部かつ長手方向中央部から 200mm×200mm の試験片を4枚ずつ切り出した。鋼番号1〜9の冷延ステンレス鋼板から各々切り出した4枚の試験片にプレス加工を施して、所定の形状を有するセパレータとした。その後、各鋼番号毎に一部のセパレータに不働態皮膜の組成調整処理を施してCr/Fe比を調整した。ここで不働態皮膜の組成調整処理を行なう際には、A:硝酸を10質量%と塩酸を50質量%とピクリン酸を1質量%含む溶液(50℃,120 秒)あるいはB:硝酸を5質量%とフッ酸を20質量%含む溶液(50℃,300秒)を用いた。   Four test pieces each having a size of 200 mm × 200 mm were cut out from the central portion in the plate width direction and the central portion in the longitudinal direction of the obtained cold-rolled stainless steel plate. Four test pieces cut out from each of the cold-rolled stainless steel plates of steel numbers 1 to 9 were subjected to press working to obtain a separator having a predetermined shape. Then, the composition adjustment process of the passive film was performed to some separators for every steel number, and Cr / Fe ratio was adjusted. Here, when performing the composition adjustment treatment of the passive film, A: a solution containing 10% by mass of nitric acid, 50% by mass of hydrochloric acid and 1% by mass of picric acid (50 ° C., 120 seconds) or B: 5% nitric acid A solution containing 50% by mass and 20% by mass of hydrofluoric acid (50 ° C., 300 seconds) was used.

また、不働態皮膜の組成調整処理を行なわなかった場合はプレス加工後に、不働態皮膜のCr含有量,Fe含有量,Al含有量,金属酸化物として存在するO含有量,金属水酸化物として存在するO含有量を測定し、さらに各元素の原子数を算出した上で、Cr/Fe比,O(M) /O(H) 比,Al/(Cr+Fe)比を算出した。不働態皮膜の組成調整処理を行なった場合はプレス加工後さらに、不働態皮膜の組成調整処理を施した後に、不働態皮膜のCr含有量,Fe含有量,Al含有量,金属酸化物として存在するO含有量,金属水酸化物として存在するO含有量を測定し、さらに各元素の原子数を算出した上で、Cr/Fe比,O(M) /O(H) 比,Al/(Cr+Fe)比を算出した。なお、それぞれの元素の含有量は、光電子分光法を用いてスペクトル強度をピーク分離して求めた。   In addition, in the case where the composition adjustment treatment of the passive film was not performed, the Cr content, the Fe content, the Al content, the O content existing as a metal oxide, and the metal hydroxide after the press working After measuring the O content present and calculating the number of atoms of each element, the Cr / Fe ratio, O (M) / O (H) ratio, and Al / (Cr + Fe) ratio were calculated. Passive coating composition adjustment treatment is performed after pressing, and after passivation coating composition adjustment treatment, the passive coating Cr content, Fe content, Al content, and metal oxide are present. After measuring the O content present as a metal hydroxide and calculating the number of atoms of each element, the Cr / Fe ratio, O (M) / O (H) ratio, Al / ( Cr + Fe) ratio was calculated. In addition, content of each element was calculated | required by carrying out peak separation of the spectral intensity using photoelectron spectroscopy.

こうして不働態皮膜の組成調整処理を行なったセパレータと処理を行なわなかったセパレータを用いて、それぞれ発電特性を調査した。発電特性の評価のために、高分子膜と電極、さらにガス拡散層2,3が一体化された有効面積50cm2 の膜−電極接合体1(エレクトロケム社製 FC50-MEA )を用いて、図1に示す形状の単セルを作成した。単セルの空気流路6と水素流路7は、いずれも高さ1mm,幅2mmの矩形とし、全体で17列配置した。カソード側には空気を流し、アノード側には超高純度水素(純度 99.9999体積%)を80±1℃に保持したバブラにより加湿した後供給して、電流密度 0.4A/cm2 (条件1)および0.7A/cm2(条件2)の出力電圧を測定した。 Thus, the power generation characteristics were investigated using the separator that had been subjected to the composition adjustment treatment of the passive film and the separator that had not been subjected to the treatment. For evaluation of power generation characteristics, a membrane-electrode assembly 1 (FC50-MEA manufactured by Electrochem Co., Ltd.) having an effective area of 50 cm 2 in which a polymer membrane and an electrode and gas diffusion layers 2 and 3 are integrated is used. A single cell having the shape shown in FIG. 1 was prepared. The single cell air flow path 6 and hydrogen flow path 7 were both rectangular with a height of 1 mm and a width of 2 mm, and were arranged in 17 rows in total. Air is allowed to flow on the cathode side, and ultrahigh purity hydrogen (purity 99.9999 vol%) is supplied to the anode side after being humidified by a bubbler maintained at 80 ± 1 ° C and supplied with a current density of 0.4 A / cm 2 (Condition 1) And an output voltage of 0.7 A / cm 2 (condition 2) was measured.

また電流密度0.4A/cm2の条件で2000時間にわたって連続して稼動させた後、条件1および条件2の出力電圧を測定した。この単セルの発電実験の期間中は、単セル本体の温度は80±1℃に保持した。また膜−電極接合体1,カーボンペーパ9等は試験片を替えるたびに新品に取り替えた。 Moreover, after operating continuously for 2000 hours on the conditions of 0.4 A / cm < 2 > current density, the output voltage of the conditions 1 and 2 was measured. During the period of the power generation experiment of this single cell, the temperature of the single cell main body was maintained at 80 ± 1 ° C. The membrane-electrode assembly 1, carbon paper 9 and the like were replaced with new ones every time the test piece was changed.

参考例として、ステンレス鋼板(SUS304相当)を上記の鋼番号1〜9と同様の形状に加工した後、表面に金めっき(厚さ約 0.1μm)を施したセパレータ、および厚さ3mmのグラファイト板の片面に幅2mm,高さ1mmの溝を2mm間隔で17列配置したセパレータを用いて、電流密度 0.4A/cm2 および0.7A/cm2の出力電圧を測定した。出力電圧の測定方法は、上記の鋼番号1〜9と同じである。 As a reference example, a stainless steel plate (equivalent to SUS304) was processed into the same shape as steel numbers 1 to 9 above, and then a gold plated (thickness of about 0.1 μm) surface was applied to the separator, and a graphite plate with a thickness of 3 mm. Using a separator in which 17 rows of grooves having a width of 2 mm and a height of 1 mm were arranged on one side of the substrate at 2 mm intervals, output voltages of current densities of 0.4 A / cm 2 and 0.7 A / cm 2 were measured. The method for measuring the output voltage is the same as the steel numbers 1 to 9 described above.

その結果を表3に示す。   The results are shown in Table 3.

Figure 0004496750
Figure 0004496750

表3から明らかなように、本発明の成分範囲を満足するステンレス鋼(すなわち鋼番号3〜6および9)にAまたはBの液を用いて処理を行ない、不働態皮膜の成分を調整しCr/Fe比を1以上としたセパレータを用いた単セルは、初期の出力電圧および2000時間経過後の出力電圧ともに、金めっきを施したセパレータやグラファイト板のセパレータと同等の出力電圧が得られ、十分に実用に耐え得るレベルであった。   As is apparent from Table 3, stainless steel (ie, steel numbers 3 to 6 and 9) satisfying the component range of the present invention is treated with the A or B solution to adjust the passive film components and Cr. A single cell using a separator with a / Fe ratio of 1 or more can obtain an output voltage equivalent to that of a gold plated separator or a graphite plate separator, both of the initial output voltage and the output voltage after 2000 hours. It was a level that could sufficiently withstand practical use.

さらに、O(M) /O(H) 比が 0.9以下のセパレータを用いた単セルは、性能が一層向上し、初期の出力電圧および2000時間経過後の出力電圧ともに、金めっきを施したセパレータやグラファイト板のセパレータと同等の出力電圧が得られた。   Furthermore, the single cell using the separator having an O (M) / O (H) ratio of 0.9 or less has further improved performance, and both the initial output voltage and the output voltage after 2000 hours have been subjected to gold plating. And an output voltage equivalent to that of a graphite plate separator.

一方、 本発明の成分範囲を外れるステンレス鋼(すなわち鋼番号1,2,7,8)では、不働態皮膜の組成調整処理の有無に関わらず、初期の出力電圧および2000時間経過後の出力電圧は、いずれも金めっきを施したセパレータやグラファイト板のセパレータに比べて低下した。   On the other hand, in the case of stainless steel (ie, steel numbers 1, 2, 7, and 8) that falls outside the component range of the present invention, the initial output voltage and the output voltage after 2000 hours are passed regardless of the composition adjustment treatment of the passive film. Were lower than those of gold-plated separators or graphite plate separators.

また、本発明の成分範囲を満足するステンレス鋼(すなわち鋼番号3〜6および9)であっても不働態皮膜の組成調整処理を行なわなかった場合、不働態皮膜のCr/Fe比が低く、初期の出力電圧は、金めっきを施したセパレータやグラファイト板のセパレータに比べて低下した。   Further, even when stainless steel (ie, steel numbers 3 to 6 and 9) satisfying the component range of the present invention is not subjected to the composition adjustment treatment of the passive film, the Cr / Fe ratio of the passive film is low, The initial output voltage was lower than that of gold plated separators or graphite plate separators.

〔実施例2〕
実施例1で用いた熱延ステンレス鋼板を、冷間圧延によって厚さ0.2mm とし、さらに露点−60℃のアンモニア分解ガス中で焼鈍( 850〜1050℃)を施し、いわゆるBA仕上げの冷延ステンレス鋼板とした。
[Example 2]
The hot-rolled stainless steel plate used in Example 1 was made into a thickness of 0.2 mm by cold rolling and further annealed (850 to 1050 ° C.) in ammonia decomposition gas having a dew point of −60 ° C. A steel plate was used.

得られた冷延ステンレス鋼板から、実施例1と同じ方法で試験片を採取し、所定の形状を有するセパレータとした。さらに、このセパレータの不働態皮膜のCr/Fe比,O(M) /O(H) 比,Al/(Cr+Fe)比を算出した。なお、セパレータの形状や成形方法,不働態皮膜の組成調整処理,各元素の含有量の測定方法は実施例1と同じであるから説明を省略する。   A test piece was collected from the obtained cold-rolled stainless steel plate by the same method as in Example 1 to obtain a separator having a predetermined shape. Further, the Cr / Fe ratio, O (M) / O (H) ratio, and Al / (Cr + Fe) ratio of the passive film of this separator were calculated. In addition, since the shape of a separator, a shaping | molding method, the composition adjustment process of a passive film, and the measuring method of content of each element are the same as Example 1, description is abbreviate | omitted.

さらに実施例1と同様に、セパレータの発電特性を調査した。それらの結果を表4に示す。   Furthermore, as in Example 1, the power generation characteristics of the separator were investigated. The results are shown in Table 4.

Figure 0004496750
Figure 0004496750

表4から明らかなように、BA仕上げとしたステンレス鋼板においても、本発明の成分範囲を満足するステンレス鋼(すなわち鋼番号3〜6および9)にAまたはBの液を用いて処理を行ない、不働態皮膜の成分を調整しCr/Fe比を1以上としたセパレータを用いた単セルは、初期の出力電圧および2000時間経過後の出力電圧ともに、金めっきを施したセパレータやグラファイト板のセパレータと同等の出力電圧が得られ、十分に実用に耐え得るレベルであった。   As is apparent from Table 4, even in the stainless steel plate finished with BA, the stainless steel (that is, steel numbers 3 to 6 and 9) satisfying the component range of the present invention is processed using the liquid A or B. Single cells using separators with a passive film component adjusted to a Cr / Fe ratio of 1 or more are gold plated separators and graphite plate separators for both the initial output voltage and the output voltage after 2000 hours. An output voltage equivalent to the above was obtained, and it was at a level that could sufficiently withstand practical use.

O(M)/O(H)比が0.9以下のセパレータ、またはさらに、Al/(Cr+Fe)比が0.05未満のセパレータを用いた単セルは、性能が一層向上し、初期の出力電圧および2000時間経過後の出力電圧ともに、金めっきを施したセパレータやグラファイト板のセパレータと同等の出力電圧が得られた。   A single cell using a separator with an O (M) / O (H) ratio of 0.9 or less, or a separator with an Al / (Cr + Fe) ratio of less than 0.05, has further improved performance, initial output voltage and 2000 hours. Both the output voltage after the lapse of time and the output voltage equivalent to the gold plated separator and the graphite plate separator were obtained.

一方、 本発明の成分範囲を外れるステンレス鋼(すなわち鋼番号1,2,7,8)では、不働態皮膜の組成調整処理の有無に関わらず、初期の出力電圧および2000時間経過後の出力電圧は、いずれも金めっきを施したセパレータやグラファイト板のセパレータに比べて低下した。   On the other hand, in the case of stainless steel (ie, steel numbers 1, 2, 7, and 8) that falls outside the component range of the present invention, the initial output voltage and the output voltage after 2000 hours are passed regardless of the composition adjustment treatment of the passive film. Were lower than those of gold-plated separators or graphite plate separators.

固体高分子型燃料電池の例を模式的に示す斜視図である。It is a perspective view which shows the example of a solid polymer type fuel cell typically. 接触抵抗の測定に用いた試料を模式的に示す断面図である。It is sectional drawing which shows typically the sample used for the measurement of contact resistance.

符号の説明Explanation of symbols

1 膜−電極接合体
2 ガス拡散層
3 ガス拡散層
4 セパレータ
5 セパレータ
6 空気流路
7 水素流路
8 試験片
9 カーボンペーパ
10 電極
DESCRIPTION OF SYMBOLS 1 Membrane-electrode assembly 2 Gas diffusion layer 3 Gas diffusion layer 4 Separator 5 Separator 6 Air flow path 7 Hydrogen flow path 8 Test piece 9 Carbon paper
10 electrodes

Claims (2)

Cを0.03質量%以下、Nを0.03質量%以下、Crを20〜45質量%、Moを 0.1〜5.0 質量%、Siを 1.0質量%以下、Mnを 1.0質量%以下、Alを 0.001〜0.2 質量%以下含有し、かつC含有量とN含有量の合計が0.03質量%以下を満足し、さらにTiまたはNbを0.01〜0.5 質量%、あるいはTiおよびNbを合計0.01〜0.5 質量%を含有し、残部がFeおよび不可避的不純物からなる組成を有するステンレス鋼であって、かつ前記ステンレス鋼の表面の不働態皮膜に含有されるCr含有量とFe含有量から算出されるCr/Fe比が原子数比で1以上であり、前記不働態皮膜に含有されるAlの含有量、Crの含有量およびFeの含有量から算出されるAl/(Cr+Fe)比が、原子数比で0.05未満であり、かつ前記不働態皮膜に含有される酸素のうち、金属酸化物の状態で存在する酸素:O(M) の含有量と、金属水酸化物の状態で存在する酸素:O(H) の含有量から算出されるO(M) /O(H) 比が、原子数比で0.9以下であることを特徴とする固体高分子型燃料電池セパレータ用ステンレス鋼 C is 0.03% by mass or less, N is 0.03% by mass or less, Cr is 20 to 45% by mass, Mo is 0.1 to 5.0% by mass , Si is 1.0% by mass or less, Mn is 1.0% by mass or less, and Al is 0.001 to 0.2% by mass. %, And the total of C content and N content satisfies 0.03% by mass or less, and further contains 0.01 to 0.5% by mass of Ti or Nb, or 0.01 to 0.5% by mass of Ti and Nb , The balance is stainless steel having a composition consisting of Fe and inevitable impurities, and the Cr / Fe ratio calculated from the Fe content and the Cr content contained in the passive film on the surface of the stainless steel is the number of atoms. The Al / (Cr + Fe) ratio calculated from the Al content, the Cr content and the Fe content contained in the passive film is less than 0.05 in atomic ratio, Of the oxygen contained in the passive film, the oxygen: O (M) content present in the form of a metal oxide and the metal Solid polymer fuel characterized in that the O (M) / O (H) ratio calculated from the content of oxygen: O (H) present in the oxide state is 0.9 or less in terms of the number of atoms Stainless steel for battery separator . 固体高分子膜、電極およびセパレータとからなる固体高分子型燃料電池であって、前記セパレータとして請求項1に記載の固体高分子型燃料電池セパレータ用ステンレス鋼を用いることを特徴とする固体高分子型燃料電池 A solid polymer fuel cell comprising a solid polymer membrane, an electrode and a separator, wherein the stainless polymer for a polymer electrolyte fuel cell separator according to claim 1 is used as the separator. Type fuel cell .
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JP2000294256A (en) * 1999-04-09 2000-10-20 Sumitomo Metal Ind Ltd Solid high polymer fuel cell
WO2002038828A1 (en) * 2000-11-10 2002-05-16 Honda Giken Kogyo Kabushiki Kaisha Method of surface treatment for stainless steel product for fuel cell
JP2002270196A (en) * 2001-03-07 2002-09-20 Matsushita Electric Ind Co Ltd High molecular electrolyte type fuel cell and operating method thereof
JP2003223904A (en) * 2001-02-22 2003-08-08 Jfe Steel Kk Separator for fuel cell, its manufacturing method, and polymer electrolyte fuel cell

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH09157801A (en) * 1995-10-05 1997-06-17 Hitachi Metals Ltd Steel for separator of solid electrolytic fuel cell
JP2000294256A (en) * 1999-04-09 2000-10-20 Sumitomo Metal Ind Ltd Solid high polymer fuel cell
WO2002038828A1 (en) * 2000-11-10 2002-05-16 Honda Giken Kogyo Kabushiki Kaisha Method of surface treatment for stainless steel product for fuel cell
JP2003223904A (en) * 2001-02-22 2003-08-08 Jfe Steel Kk Separator for fuel cell, its manufacturing method, and polymer electrolyte fuel cell
JP2002270196A (en) * 2001-03-07 2002-09-20 Matsushita Electric Ind Co Ltd High molecular electrolyte type fuel cell and operating method thereof

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