WO2016052622A1 - フェライト系ステンレス鋼材と、これを用いる固体高分子形燃料電池用セパレータおよび固体高分子形燃料電池 - Google Patents
フェライト系ステンレス鋼材と、これを用いる固体高分子形燃料電池用セパレータおよび固体高分子形燃料電池 Download PDFInfo
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- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/02—Details
- H01M8/0202—Collectors; Separators, e.g. bipolar separators; Interconnectors
- H01M8/0204—Non-porous and characterised by the material
- H01M8/0206—Metals or alloys
- H01M8/0208—Alloys
- H01M8/021—Alloys based on iron
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- C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
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- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
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- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
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- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
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- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
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- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
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- C22C38/004—Very low carbon steels, i.e. having a carbon content of less than 0,01%
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- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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- C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/10—Fuel cells with solid electrolytes
- H01M8/1016—Fuel cells with solid electrolytes characterised by the electrolyte material
- H01M8/1018—Polymeric electrolyte materials
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- C21D2211/00—Microstructure comprising significant phases
- C21D2211/004—Dispersions; Precipitations
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- C21—METALLURGY OF IRON
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- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/10—Fuel cells with solid electrolytes
- H01M2008/1095—Fuel cells with polymeric electrolytes
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/50—Fuel cells
Definitions
- the present invention relates to a ferritic stainless steel material, a separator for a polymer electrolyte fuel cell using the same, and a polymer electrolyte fuel cell.
- the separator here is sometimes called a bipolar plate.
- Fuel cells are cells that generate direct current using hydrogen and oxygen, and are roughly classified into solid electrolyte type, molten carbonate type, phosphoric acid type, and solid polymer type. Each type is derived from the constituent material of the electrolyte part constituting the basic part of the fuel cell.
- fuel cells that have reached the commercial stage include a phosphoric acid type that operates near 200 ° C. and a molten carbonate type that operates near 650 ° C.
- solid polymer type that operates near room temperature
- solid electrolyte type that operates at 700 ° C. or more are attracting attention as compact power supplies for automobiles or home use.
- FIG. 1 is an explanatory view showing the structure of a polymer electrolyte fuel cell
- FIG. 1 (a) is an exploded view of a fuel cell (single cell)
- FIG. 1 (b) is a perspective view of the whole fuel cell. is there.
- the fuel cell 1 is an assembly of single cells.
- a fuel electrode membrane (anode) 3 is laminated on one surface of a solid polymer electrolyte membrane 2, and an oxidant electrode membrane (cathode) 4 is laminated on the other surface.
- the separators 5a and 5b are stacked.
- a fluorine ion exchange resin membrane having a hydrogen ion (proton) exchange group As a typical solid polymer electrolyte membrane 2, there is a fluorine ion exchange resin membrane having a hydrogen ion (proton) exchange group.
- the fuel electrode film 3 and the oxidant electrode film 4 include a fluorine resin having particulate platinum catalyst, graphite powder, and hydrogen ion (proton) exchange groups on the surface of a diffusion layer made of carbon paper or carbon cloth made of carbon fiber.
- the catalyst layer which consists of is contacted with the fuel gas or oxidizing gas which permeate
- a fuel gas (hydrogen or hydrogen-containing gas) A is flowed from a flow path 6 a provided in the separator 5 a and hydrogen is supplied to the fuel electrode film 3. Further, an oxidizing gas B such as air is flowed from the flow path 6b provided in the separator 5b, and oxygen is supplied. The supply of these gases causes an electrochemical reaction to generate DC power.
- the functions required of the polymer electrolyte fuel cell separator are (1) a function as a “flow path” for uniformly supplying fuel gas in the surface on the fuel electrode side, and (2) water generated on the cathode side as fuel. Function as a “flow path” that efficiently discharges the battery together with a carrier gas such as air and oxygen after reaction from the battery, and (3) between single cells that maintain low electrical resistance and good electrical conductivity as electrodes over a long period of time A function as an electrical “connector”, and (4) a function as “a partition wall” between an anode chamber of one cell and a cathode chamber of an adjacent cell in adjacent cells.
- the thermally expansive graphite processed product is remarkably inexpensive, and is thus attracting the most attention as a material for polymer electrolyte fuel cell separators.
- the thermally expansive graphite processed product is remarkably inexpensive, and is thus attracting the most attention as a material for polymer electrolyte fuel cell separators.
- to deal with stricter dimensional accuracy deterioration of organic resin over time, which occurs during fuel cell application, carbon corrosion that progresses under the influence of battery operating conditions, and during fuel cell assembly and use Unexpected cracking accidents that occur are left as issues to be solved in the future.
- Patent Document 1 discloses a fuel cell separator which is made of a metal member and directly gold-plated on a contact surface with an electrode of a unit cell.
- the metal member include stainless steel, aluminum, and a Ni-iron alloy, and SUS304 is used as the stainless steel.
- the separator is gold-plated, the contact resistance between the separator and the electrode is reduced, and the conduction of electrons from the separator to the electrode is improved, so that the output voltage of the fuel cell is increased. Yes.
- Patent Document 2 discloses a polymer electrolyte fuel cell in which a separator made of a metal material in which a passive film formed on the surface is easily generated by the atmosphere is used. Stainless steel and titanium alloy are mentioned as metal materials. In the present invention, there is always a passive film on the surface of the metal used for the separator, and the degree to which the water generated in the fuel cell is ionized because the metal surface is hardly chemically attacked. It is said that it is reduced and the fall of the electrochemical reactivity of a fuel cell is suppressed. In addition, it is said that the electrical contact resistance value is reduced by removing the passive film at the portion in contact with the electrode film of the separator and forming a noble metal layer.
- the steel does not contain B, and M 23 C 6 type, M 4 C type, M 2 C type, MC type carbide-based metal inclusions and M 2 B type boron as metal precipitates in the steel. No solid inclusions precipitate, and the amount of C in steel is 0.012% or less (in this specification, “%” relating to chemical composition means “% by mass” unless otherwise specified)
- Ferritic stainless steel for fuel cell separators is disclosed.
- Patent Documents 4 and 5 disclose polymer electrolyte fuel cells in which ferritic stainless steel in which such metal precipitates are not deposited is applied as a separator.
- Patent Document 6 discloses a ferrite for a separator of a polymer electrolyte fuel cell in which B is not contained in steel but 0.01 to 0.15% C is contained in steel, and only Cr-based carbides are precipitated. Stainless steel and a polymer electrolyte fuel cell to which it is applied are shown.
- Patent Document 7 discloses that a solid polymer that does not contain B in steel, contains 0.015 to 0.2% C in the steel, and contains 7 to 50% Ni and precipitates Cr-based carbides. An austenitic stainless steel for a separator of a fuel cell is shown.
- Patent Document 8 discloses that among M 23 C 6 type, M 4 C type, M 2 C type, MC type carbide metal inclusions and M 2 B type boride inclusions having conductivity on a stainless steel surface.
- 1 shows a stainless steel for a separator of a polymer electrolyte fuel cell in which one or more of these are dispersed and exposed, C: 0.15% or less, Si: 0.01 to 1.5%, Mn: 0 0.01 to 1.5%, P: 0.04% or less, S: 0.01% or less, Cr: 15 to 36%, Al: 0.001 to 6%, N: 0.035% or less
- a ferritic stainless steel is described in which the Cr, Mo, and B contents satisfy 17% ⁇ Cr + 3 ⁇ Mo ⁇ 2.5 ⁇ B, and the balance is Fe and inevitable impurities.
- Patent Document 9 discloses that M 23 C 6 type, M 4 C type, M 2 C type, MC type carbide-based metal inclusions and M having a surface of a stainless steel material corroded with an acidic aqueous solution and having conductivity on the surface. 2 A method for producing a stainless steel material for a separator of a polymer electrolyte fuel cell in which one or more of B-type boride-based metal inclusions are exposed is shown: C: 0.15% or less; Si: 0.
- Patent Document 10 discloses that when an M 2 B type boride-based metal compound is exposed on the surface and the anode area and the cathode area are each 1, the area where the anode is in direct contact with the separator, and the cathode A solid polymer fuel cell is shown in which all of the areas in direct contact with the separator are in the ratio of 0.3 to 0.7, and M 23 C 6 type having conductivity on the stainless steel surface, M Stainless steel is shown in which one or more of 4 C type, M 2 C type, MC type carbide metal inclusions and M 2 B type boride inclusions are exposed.
- the stainless steel constituting the separator is C: 0.15% or less, Si: 0.01 to 1.5%, Mn: 0.01 to 1.5%, P: 0.04% or less, S: 0.01% or less, Cr: 15 to 36%, Al: 0.2% or less, B: 3.5% or less (excluding 0%), N: 0.035% or less, Ni: 5% or less, Mo: 7% or less, W: 4% or less, V: 0.2% or less, Cu: 1% or less, Ti: 25 ⁇ (C% + N%) or less, Nb: 25 ⁇ (C% + N%) or less.
- a ferritic stainless steel material in which the content of Cr, Mo and B satisfies 17% ⁇ Cr + 3 ⁇ Mo ⁇ 2.5 ⁇ B is shown.
- Patent Documents 11 to 15 disclose an austenitic stainless clad steel material in which M 2 B type boride metal precipitates are exposed on the surface, and a method for producing the same.
- Patent Document 16 discloses a fuel cell including a ferritic stainless steel in which B in the steel is precipitated as an M 2 B type boride and a separator made of the steel.
- the ferritic stainless steel is, by mass%, C: 0.08% or less, Si: 0.01 to 1.5%, Mn: 0.01 to 1.5%, P: 0.035% or less, S : 0.01% or less, Cr: 17 to 36%, Al: 0.001 to 0.2%, B: 0.0005 to 3.5%, N: 0.035% or less, if necessary, Ni, Mo, It contains Cu, and the contents of Cr, Mo, and B satisfy 17% ⁇ Cr + 3Mo ⁇ 2.5B, and the balance is Fe and inevitable impurities.
- Patent Document 17 discloses a stainless steel material for a separator of a polymer electrolyte fuel cell including a conductive substance made of M 2 B type boride-based metal inclusions.
- a conductive substance made of M 2 B type boride-based metal inclusions for example, as austenitic stainless steel, by mass%, C: 0.2% or less, Si: 2% or less, Mn: 3% or less, Al: 0.001% or more and 6% or less, P: 0.06% or less S: 0.03% or less, N: 0.4% or less, Cr: 15% or more and 30% or less, Ni: 6% or more and 50% or less, B: 0.1% or more and 3.5% or less, balance Fe And stainless steel containing impurities.
- Patent Document 18 discloses a ferritic stainless steel sheet on which an oxide film having good electrical conductivity at a high temperature is formed.
- the ferritic stainless steel sheet is, in mass%, C: 0.02% or less, Si: 0.15% or less, Mn: 0.3 to 1%, P: 0.04% or less, S: 0.003 %: Cr: 20-25%, Mo: 0.5-2%, Al: 0.1% or less, N: 0.02% or less, Nb: 0.001-0.5%, the balance being Fe and It consists of inevitable impurities and satisfies 2.5 ⁇ Mn / (Si + Al) ⁇ 8.0.
- the ferritic stainless steel sheet is further, in mass%, Ti: 0.5% or less, V: 0.5% or less, Ni: 2% or less, Cu: 1% or less, Sn: 1% or less, B: 0 0.005% or less, Mg: 0.005% or less, Ca: 0.005% or less, W: 1% or less, Co: 1% or less, and Sb: 0.5% or less. Yes.
- Patent Document 19 discloses a ferritic stainless steel sheet in which a small amount of Sn is added to improve oxidation resistance and high-temperature strength.
- the ferritic stainless steel sheet is, by mass%, C: 0.001 to 0.03%, Si: 0.01 to 2%, Mn: 0.01 to 1.5%, P: 0.005 to 0 0.05%, S: 0.0001 to 0.01%, Cr: 16 to 30%, N: 0.001 to 0.03%, Al: more than 0.8% to 3%, Sn: 0.01 to 1%, the balance consists of Fe and inevitable impurities.
- Patent Document 20 discloses ferritic stainless steel in which the passive film is modified by adding Sn to improve the corrosion resistance.
- the ferritic stainless steel is, by mass%, C: 0.01% or less, Si: 0.01 to 0.20%, Mn: 0.01 to 0.30%, P: 0.04% or less, S : 0.01% or less, Cr: 13 to 22%, N: 0.001 to 0.020%, Ti: 0.05 to 0.35%, Al: 0.005 to 0.050%, Sn: 0 0.001 to 1%, the balance being Fe and inevitable impurities.
- Japanese Patent Laid-Open No. 10-228914 Japanese Patent Laid-Open No. 8-180883 JP 2000-239806 A JP 2000-294255 A JP 2000-294256 A JP 2000-303151 A JP 2000-309854 A JP 2003-193206 A JP 2001-214286 A JP 2002-151111 A JP 2004-071319 A JP 2004-156132 A JP 2004-306128 A JP 2007-1118025 A JP 2009-215655 A JP 2000-328205 A JP 2010-140886 A JP 2014-031572 A JP 2012-172160 A JP 2009-174036 A
- An object of the present invention is to provide a ferritic stainless steel material having excellent corrosion resistance in the environment inside the solid molecular fuel cell and having a contact electric resistance equivalent to that of a gold plating material, and a solid polymer fuel cell comprising the stainless steel material Separator, and a polymer electrolyte fuel cell to which the separator is applied.
- the present inventor has found that MEA composed of a diffusion layer, a polymer membrane, and a catalyst layer has very little metal elution from the surface of the metal separator even when used as a separator for a polymer electrolyte fuel cell for a long time.
- the present invention is listed below.
- the chemical composition is mass%, C: 0.001 to less than 0.020%, Si: 0.01 to 1.5%, Mn: 0.01 to 1.5%, P: 0.035% or less, S: 0.01% or less, Cr: 22.5 to 35%, Mo: 0.01 to 6%, Ni: 0.01-6%, Cu: 0.01 to 1%, N: 0.035% or less, V: 0.01 to 0.35%, B: 0.5 to 1.0%, Al: 0.001 to 6.0%, Sn: 0.02 to 2.50%, Rare earth elements: 0-0.1%, Nb: 0 to 0.35%, Ti: 0 to 0.35%, and Balance: Fe and impurities, and
- the value calculated as ⁇ Cr content (mass%) + 3 ⁇ Mo content (mass%) ⁇ 2.5 ⁇ B content (mass%) ⁇ is 20 to 45%
- a ferritic stainless steel material in which M 2 B-type boride-based metal precipitates are dispersed in a parent phase consisting only of a
- the chemical composition is mass%, Nb: 0.001 to 0.35%, and Ti: 0.001 to 0.35%, Containing one or more selected from, and 3 ⁇ Nb / C ⁇ 25, 3 ⁇ Ti / (C + N) ⁇ 25,
- a separator for a polymer electrolyte fuel cell comprising the ferritic stainless steel material for a polymer electrolyte fuel cell separator according to any one of (1) to (3) above.
- a polymer electrolyte fuel cell comprising the ferritic stainless steel material for a polymer electrolyte fuel cell separator according to any one of (1) to (3) above.
- M in M 2 B and M 23 C 6 represents a metal element, but not a specific metal element, but a metal element having a strong chemical affinity with Cr or B.
- M is mainly composed of Cr and Fe and contains a small amount of Ni and Mo because of the relationship with coexisting elements in steel.
- M 2 B type boride-based metal precipitates include Cr 2 B, (Cr, Fe) 2 B, (Cr, Fe, Ni) 2 B, (Cr, Fe, Mo) 2 B, (Cr, Fe, Ni, Mo) 2 B, Cr 1.2 Fe 0.76 Ni 0.04 B, and the like.
- B also has an action as “M”.
- Examples of the M 23 C 6 type include Cr 23 C 6 and (Cr, Fe) 23 C 6 .
- M 23 (C, B) 6 type carbide metal in which a part of C is substituted with B in any of the above M 2 B type borate metal precipitate and M 23 C 6 type carbide metal precipitate
- Metal deposits such as precipitates or M 2 (C, B) type boride metal deposits may also be deposited.
- the above notation includes these. Basically, similar performance is expected for metal-based dispersions with good electrical conductivity.
- the subscript index “ 2 ” in the “M 2 B” type notation is “a metal element in a boride, such as Cr, Fe, Mo, Ni, X (where X is Cr, Fe, Mo, Ni).
- a metal element in a boride such as Cr, Fe, Mo, Ni, X (where X is Cr, Fe, Mo, Ni).
- B content “(Cr mass% / Cr atomic mass + Fe mass% / Fe atomic mass + Mo mass% / Mo atomic mass + Ni mass% / Ni atomic mass + X mass% / X atomic mass) / ( This means that a stoichiometric relationship in which (B mass% / B atomic weight) is approximately 2 is established.
- This notation is not a special one but a very general notation.
- the present invention it is possible to reduce the contact resistance of the surface, and without performing expensive surface treatment such as expensive gold plating, it has excellent anti-eluting metal ion characteristics. That is, it is possible to obtain a ferritic stainless steel material that is remarkably excellent in corrosion resistance in the environment within the solid molecular fuel cell and that has a contact electric resistance equivalent to that of a gold plating material.
- This stainless steel material is suitable for a separator of a polymer electrolyte fuel cell. For full-scale spread of polymer electrolyte fuel cells, it is extremely important to reduce the cost of the fuel cell body, particularly the separator cost.
- the present invention is expected to accelerate the full-scale spread of polymer electrolyte fuel cells using metal separators.
- FIG. 1 is an explanatory view showing the structure of a polymer electrolyte fuel cell
- FIG. 1 (a) is an exploded view of a fuel cell (single cell)
- FIG. 1 (b) is a perspective view of the whole fuel cell. is there.
- FIG. 2 is a photograph showing the shape of the separator manufactured in Example 3.
- M 2 B boride-type metal precipitate M 2 B contains 60% or more of Cr, and is more excellent in corrosion resistance than the parent phase. Since the Cr concentration is higher than that of the parent phase, the passive film formed on the surface is also thinner than the parent phase, and the conductivity (electrical contact resistance performance) is excellent.
- the exposure means that the M 2 B type boride-based metal precipitate protrudes to the outer surface without being covered with the passive film formed on the surface of the parent phase of stainless steel.
- M 2 B-type boride-based metal deposit is to function as electrical path (bypass), lowering the electrical contact resistance of the surface significantly Has an effect.
- the M 2 B type boride metal precipitate exposed on the surface may drop off, the M 2 B boride metal precipitate is a metal precipitate and is thus metal-bonded to the parent phase. , None fall out.
- the M 2 B-type boride-based metal precipitate is precipitated by a eutectic reaction that proceeds at the end of solidification, the M 2 B-type boride metal precipitate has characteristics that the composition is substantially uniform and is extremely stable thermally. Due to the thermal history in the manufacturing process of the steel material, there is no re-dissolution, re-precipitation, or component change. Further, the M 2 B type boride metal precipitate is a very hard precipitate. It is mechanically crushed in each process of hot forging, hot rolling, and cold rolling and finely and uniformly dispersed.
- Metal tin and tin oxide Sn are dissolved in the parent phase by adding them as alloy elements in the molten steel stage.
- pickling is performed to expose M 2 B in the steel located in the vicinity of the steel surface to the surface and reduce the electrical contact resistance of the steel surface.
- the tin dissolved in the mother phase is concentrated not only on the surface of the mother phase but also on the M 2 B surface as metal tin or tin oxide as the mother phase is dissolved (corrosion) by pickling. .
- the gradual metal elution proceeds according to the environment in the fuel cell, and the passive film changes.
- the tin in the steel further concentrates not only on the surface of the parent phase, but also on the M 2 B surface, resulting in a behavior that becomes a surface enriched state suitable for securing desired characteristics.
- Both metallic tin and tin oxide are excellent in electrical conductivity and work to lower the electrical contact resistance on the surface of the mother phase in the fuel cell.
- Chemical composition (3-1) C 0.001 to less than 0.020% C is an impurity in the present invention. If the current scouring technique is applied, it can be made less than 0.001%, but the scouring time becomes longer and the scouring cost increases. Therefore, the C content is 0.001% or more. On the other hand, when the C content is 0.020% or more, corrosion resistance is lowered due to sensitization, and room temperature toughness is lowered and productivity is lowered. Therefore, the C content is less than 0.020%.
- the C content is preferably 0.0015% or more, and preferably less than 0.010%.
- Si 0.01 to 1.5%
- Si is a deoxidizing element that is as effective as Al in mass-produced steel. If the Si content is less than 0.01%, deoxidation is insufficient. Therefore, the Si content is 0.01% or more. On the other hand, if the Si content exceeds 1.5%, the moldability deteriorates. Therefore, the Si content is 1.5% or less.
- the Si content is preferably 0.05% or more, and more preferably 0.1% or more. Moreover, it is preferable that Si content is 1.2% or less, and it is more preferable that it is 1.0% or less.
- Mn 0.01 to 1.5%
- Mn has an effect of fixing S in steel as a Mn-based sulfide, and has an effect of improving hot workability.
- Mn content shall be 0.01% or more.
- the Mn content is 1.5% or less.
- the Mn content is preferably 0.05% or more, and more preferably 0.1% or more. Further, the Mn content is preferably 1.2% or less, and more preferably 1.0% or less.
- P in steel is the most harmful impurity along with S, so its content is 0.035% or less. The lower the P content, the better.
- S in steel is the most harmful impurity along with P, so its content is 0.01% or less. The lower the S content, the better.
- S is a Mn-based sulfide, Cr-based sulfide, Fe-based sulfide, or a composite non-metallic precipitate with these composite sulfides and oxides depending on the coexisting elements in the steel and the S content in the steel. Most of them are deposited. Further, S may form a rare earth element-based sulfide that is added as necessary.
- non-metallic deposits of any composition can act as a starting point of corrosion to varying degrees, which is detrimental to maintaining a passive film and suppressing metal ion elution. It is.
- the amount of S in steel of ordinary mass-produced steel is more than 0.005% and around 0.008%, but is preferably reduced to 0.004% or less in order to prevent the above-mentioned harmful effects.
- the more preferable S content in steel is 0.002% or less, and the most preferable S content level in steel is less than 0.001%. The lower it is, the better. If it is less than 0.001% at the industrial mass production level, with the current refining technology, the increase in manufacturing cost is slight and there is no problem.
- (3-6) Cr: 22.5 to 35.0% Cr is a very important basic alloy element for securing the corrosion resistance of the base material, and the higher the Cr content, the better the corrosion resistance. In ferritic stainless steel, if the Cr content exceeds 35.0%, production on a mass production scale becomes difficult. On the other hand, if the Cr content is less than 22.5%, the corrosion resistance necessary for a polymer electrolyte fuel cell separator cannot be secured even if other elements are changed, and the M 2 B type boride metal precipitate By precipitation, the amount of Cr in the parent phase that contributes to improvement in corrosion resistance may be lower than the amount of Cr in the molten steel, and the corrosion resistance of the base material may deteriorate.
- M 23 C 6 type carbide metal precipitates may react with C in the steel to form M 23 C 6 type carbide metal precipitates.
- the M 23 C 6 type carbide metal precipitate is a metal precipitate having excellent conductivity, but causes a decrease in corrosion resistance due to sensitization. By exposing the M 2 B type boride-based metal precipitate to the surface, the electrical surface contact resistance value can be reduced.
- the amount of Cr is required so that the calculated value is 20 to 45%.
- the Cr content is preferably 23.0% or more, and preferably 34.0% or less.
- Mo 0.01 to 6.0% Mo has the effect of improving the corrosion resistance in a small amount as compared with Cr. In order to effectively exhibit corrosion resistance, the Mo content is set to 0.01% or more. On the other hand, if the Mo content exceeds 6.0%, precipitation of intermetallic compounds such as a sigma phase cannot be avoided during the production, and production becomes difficult due to the problem of embrittlement of steel. For this reason, the upper limit of the Mo content is set to 6.0%. Further, Mo has a feature that even if Mo in steel is eluted due to corrosion inside the polymer electrolyte fuel cell, the influence on MEA performance is relatively small.
- Mo does not exist as a metal cation but exists as a molybdate ion, which is an anion, so that the influence on the cation conductivity of a fluorine-based ion exchange resin film having a hydrogen ion (proton) exchange group is small. Because. Mo is an extremely important element for maintaining corrosion resistance, and is calculated as ⁇ Cr content (% by mass) + 3 ⁇ Mo content (% by mass) ⁇ 2.5 ⁇ B content (% by mass) ⁇ . It is necessary that the amount of Mo in steel is 20 to 45%.
- the Mo content is preferably 0.05% or more, and preferably 5.0% or less.
- Ni 0.01 to 6.0% Ni has the effect of improving corrosion resistance and toughness.
- the upper limit of the Ni content is 6.0%. If the Ni content exceeds 6.0%, it becomes difficult to obtain a ferrite-based single phase structure even if heat treatment is applied industrially.
- the lower limit of the Ni content is 0.01%.
- the lower limit of the Ni content is the amount of impurities mixed in when manufactured industrially.
- the Ni content is preferably 0.03% or more, and preferably 5.0% or less.
- Cu 0.01 to 1.0%
- Cu contains 0.01% or more and 1.0% or less. If the Cu content exceeds 1.0%, hot workability will be reduced, and it will be difficult to ensure mass productivity. On the other hand, when the Cu content is less than 0.01%, the corrosion resistance in the polymer electrolyte fuel cell is lowered.
- Cu exists in a solid solution state. When it is deposited as a Cu-based precipitate, it becomes a Cu elution starting point in the battery, and the fuel cell performance is lowered.
- the Cu content is preferably 0.02% or more, and preferably 0.8% or less.
- N in ferritic stainless steel is an impurity. Since N deteriorates room temperature toughness, the upper limit of the N content is set to 0.035%. The lower the better. Industrially, the N content is most preferably 0.007% or less. However, excessive reduction of the N content leads to an increase in melting cost, so the N content is preferably 0.001% or more, and more preferably 0.002% or more.
- V 0.01 to 0.35%
- V is not an additive element added intentionally, but is unavoidably contained in a Cr source added as a melting raw material used in mass production.
- V content shall be 0.01% or more and 0.35% or less.
- V has an effect of improving the room temperature toughness although it is slight.
- the V content is preferably 0.03% or more, and preferably 0.30% or less.
- B 0.5 to 1.0%
- B is an important additive element in the present invention.
- all B in the steel is precipitated as an M 2 B type boride-based metal precipitate by a eutectic reaction.
- B is a metal precipitate which is extremely stable thermally.
- the M 2 B type boride-based metal deposit exposed on the surface has a function of significantly reducing the electrical surface contact resistance. If the B content is less than 0.5%, the amount of precipitation is insufficient to obtain the desired performance. On the other hand, when the B content exceeds 1.0%, it is difficult to stably mass-produce and manufacture. For this reason, B content shall be 0.5% or more and 1.0% or less.
- the B content is preferably 0.55% or more, and preferably 0.8% or less.
- Al 0.001 to 6.0%
- B contained in the stainless steel according to the present invention is an element having a strong binding force with oxygen in the molten steel, it is necessary to lower the oxygen concentration by Al deoxidation. Therefore, it is preferable to contain Al in the range of 0.001% to 6.0%.
- Non-metal oxides are formed as deoxidation products in steel, but the remainder is in solid solution.
- the Al content is preferably 0.01% or more, and preferably 5.5% or less.
- Sn 0.02 to 2.50%
- Sn is a very important additive element.
- Sn dissolved in the matrix is not only the surface of the matrix in the polymer electrolyte fuel cell, but also M 2 Concentration as metal tin or tin oxide also on the B surface significantly suppresses the elution of metal ions from the mother phase and M 2 B, which progresses slightly, while reducing the surface contact resistance of the mother phase.
- M 2 Concentration as metal tin or tin oxide also on the B surface significantly suppresses the elution of metal ions from the mother phase and M 2 B, which progresses slightly, while reducing the surface contact resistance of the mother phase.
- M 2 B Concentration as metal tin or tin oxide also on the B surface significantly suppresses the elution of metal ions from the mother phase and M 2 B, which progresses slightly, while reducing the surface contact resistance of the mother phase.
- the electrical contact resistance performance of M 2 B can be stabilized and improved to the same level as the
- Sn content is less than 0.02%, such an effect cannot be obtained, and if it exceeds 2.50%, the productivity decreases. For this reason, Sn content shall be 0.02% or more and 2.50% or less.
- the Sn content is preferably 0.05% or more, and preferably 2.40% or less.
- Rare earth elements 0 to 0.1%
- the rare earth element is an optional additive element and is added as misch metal.
- Rare earth elements have the effect of improving hot manufacturability. For this reason, a rare earth element may be contained up to 0.1%.
- the rare earth element content is preferably 0.005% or more, and more preferably 0.05% or less.
- Nb 0 to 0.35%
- Ti 0 to 0.35%
- Nb and Ti are both optional elements in the present invention and are stabilizing elements for C and N in steel. Carbides and nitrides form in steel. For this reason, the contents of Ti and Nb are both set to 0.35% or less.
- the content of Nb and Ti is preferably 0.001% or more, and preferably 0.30% or less.
- Nb is contained so that the (Nb / C) value is 3 or more and 25 or less
- Ti is contained so that the ⁇ Ti / (C + N) ⁇ value is 3 or more and 25 or less.
- Steel materials 1 to 17 having the chemical composition shown in Table 1 were melted in a 180 kg vacuum melting furnace and formed into a flat ingot having a maximum thickness of 80 mm.
- Steel materials 1 to 11 are examples of the present invention, and steel materials 12 to 17 are comparative examples.
- the surface temperature of the steel ingot is 60 mm thick and 430 mm wide in a temperature range of 1170 ° C. to 930 ° C. after being heated and held in a city gas heating furnace heated to 1170 ° C. Forged into slab for hot rolling.
- the hot-rolling slab was recharged in a city gas heating furnace heated to 1170 ° C with a surface temperature of 800 ° C or higher, reheated and held soaked, and then 30 mm thick by an upper and lower two-roll hot rolling mill. And then gradually cooled to room temperature.
- the surface and end surfaces are cleaned by machining, they are heated and held again in a city gas heating furnace heated to 1170 ° C., and then hot-rolled to a thickness of 1.8 mm, with a coil width of 400 to 410 mm and a unit weight of 100 A coil of ⁇ 120 kg was used.
- the final annealing was performed in a bright annealing furnace in a 75 volume% H 2 -25 volume% N 2 atmosphere with a dew point adjusted to ⁇ 50 to ⁇ 53 ° C.
- the annealing temperature is 1060 ° C.
- the structure is a single phase of ferrite.
- the added B is precipitated as M 2 B in the steel, and M 2 B is about 1 ⁇ m for the small one and about 7 ⁇ m for the large one. It was confirmed that it was finely crushed to the size of and uniformly dispersed macroscopically including the thickness direction.
- the bright annealed film on the surface was removed by polishing with No. 600 emery paper and washed, and the intergranular corrosion resistance was evaluated by a sulfuric acid-copper sulfate test method according to JIS-G-0575.
- the steel material 17 in Table 2 is an austenitic stainless steel commercial steel equivalent material, and the steel material 18 is the gold plating material.
- a 0.116 mm thick, 340 mm wide, 300 mm long cut plate is collected from steel materials 1 to 18, and spray etching treatment with a ferric chloride aqueous solution at 35 ° C. and 43 ° Baume is performed simultaneously on the entire upper and lower surfaces of the cut plate. It was.
- the etching processing time by spraying is 40 seconds.
- the amount of cutting was 8 ⁇ m on one side.
- a 60 mm square sample collected separately from steel materials 1 to 18 was immersed in an aqueous solution of sulfuric acid having a pH of 3 containing 80 ppm F 2 - ions simulating the inside of a solid polymer fuel cell for 1000 hours, and subjected to a fuel cell. It was set as the material II for electrical surface contact resistance measurement which simulated the environment under application.
- Table 2 summarizes the results of electrical contact resistance measurement and the amount of iron ions dissolved in a pH 3 sulfuric acid aqueous solution simulating the battery environment.
- Cr ions, Mo ions and others are also quantified at the same time, but since they are very small, the behavior was shown by comparison with the amount of Fe ions with the largest amount of elution.
- the steel material 18 is a material obtained by subjecting the surface contact resistance measurement materials I and II of the steel material 17 to gold plating treatment with an average thickness of 50 nm, and the gold plating treatment material is the most excellent electrical surface. It is said to be an ideal material with contact resistance performance. For this reason, the steel material 18 is shown collectively as a reference example.
- M 2 B is precipitated and dispersed, and further contains Sn, so that the electrical surface contact resistance is stably equal to that of the gold plating material, and the eluted iron ions are also equal to that of the gold plating material. It was. Except for steel materials 12 to 15 and 17 to which Sn is not added, a fuel cell using an electric surface contact resistance measurement material I after spray etching treatment using ferric chloride aqueous solution and a pH 3 sulfuric acid aqueous solution The presence of metallic tin and tin oxide was confirmed on the surface of the material II simulating the environment under application.
- the metal ion elution suppression effect by adding Sn is clear.
- membrane which is excellent in corrosion resistance that the steel material 17 which is a gold plating material is favorable. It can be determined that the steel materials 1 to 11 as examples of the present invention are equivalent to gold plating, and accordingly, it is determined that a surface covering effect equivalent to gold plating in a fuel cell can be expected for metal tin and tin oxide.
- Example 2 Using the coil material prepared in Example 1, a separator having the shape shown in the photograph in FIG. 2 was press-molded, and the fuel cell application evaluation was actually performed.
- the separator has a channel area of 100 cm 2 .
- the fuel cell operation setting evaluation condition is a constant current operation evaluation at a current density of 0.1 A / cm 2 , and is one of the operating environments of a home stationary fuel cell.
- the utilization rate of hydrogen and oxygen was constant at 40%.
- the evaluation time is 500 hours.
Abstract
Description
(1)化学組成が、質量%で、
C:0.001~0.020%未満、
Si:0.01~1.5%、
Mn:0.01~1.5%、
P:0.035%以下、
S:0.01%以下、
Cr:22.5~35%、
Mo:0.01~6%、
Ni:0.01~6%、
Cu:0.01~1%、
N:0.035%以下、
V:0.01~0.35%、
B:0.5~1.0%、
Al:0.001~6.0%、
Sn:0.02~2.50%、
希土類元素:0~0.1%、
Nb:0~0.35%、
Ti:0~0.35%、および、
残部:Feおよび不純物であり、かつ、
{Cr含有量(質量%)+3×Mo含有量(質量%)-2.5×B含有量(質量%)}として算出される値が20~45%であるとともに、
フェライト相のみからなる母相中にM2B型硼化物系金属析出物が分散し、かつ、表面に露出している、フェライトステンレス鋼材。
希土類元素:0.005~0.1%を、
含有する、上記(1)に記載のフェライトステンレス鋼材。
Nb:0.001~0.35%、および、
Ti:0.001~0.35%、
から選択される1種以上を含有し、かつ、
3≦Nb/C≦25、
3≦Ti/(C+N)≦25、
を満足する、上記(1)または(2)に記載のフェライトステンレス鋼材。
M2Bは、60%以上のCrを含有しており、母相よりも耐食性に優れる。Cr濃度が母相よりも高いことにより、表面に生成する不動態皮膜も母相に比較して薄くなり導電性(電気的な接触抵抗性能)が優れる。
Snは、溶鋼段階で合金元素として添加することにより母相中に固溶している。固体高分子形燃料電池セパレータとして適用するに際して、鋼表面近傍に位置している鋼中のM2Bを表面に露出させて鋼表面の電気的な接触抵抗を下げるために酸洗する。このとき、母相中に固溶しているスズは、酸洗による母相溶解(腐食)に伴い母相の表面のみならず、M2B表面にも金属スズ、または酸化スズとして濃化する。さらに、固体高分子形燃料電池セパレータとして適用開始した直後に燃料電池内環境に応じて緩やかな金属溶出が進行して不動態皮膜が変化する。その過程における母相の溶出に伴ってさらに鋼中のスズが母相の表面のみならず、M2B表面にも濃化し、所望の特性を確保するに好適な表面濃化状態となる挙動を有している。金属スズ、酸化スズともに導電性に優れ、燃料電池内での母相表面の電気的な接触抵抗を下げる働きをする。
(3-1)C:0.001~0.020%未満
Cは、本発明においては不純物である。現状の精練技術を適用すれば0.001%未満とすることも可能であるが、精練時間が長くなり精練コストが嵩む。そのため、C含有量は、0.001%以上とする。一方、C含有量が0.020%以上であると、鋭敏化による耐食性低下を起こしやすくなるとともに、常温靭性が低下し、製造性が低下する。そのため、C含有量は、0.020%未満とする。C含有量は、0.0015%以上であることが好ましく、0.010%未満であることが好ましい。
Siは、量産鋼において、Alと同様に有効な脱酸元素である。Si含有量が0.01%未満であると、脱酸が不十分となる。そのため、Si含有量は、0.01%以上とする。一方、Si含有量が1.5%を超えると、成形性が低下する。そのため、Si含有量は、1.5%以下とする。Si含有量は、0.05%以上であることが好ましく、0.1%以上であることがより好ましい。また、Si含有量は、1.2%以下であることが好ましく、1.0%以下であることがより好ましい。
Mnは、鋼中のSをMn系硫化物として固定する作用があり、熱間加工性を改善する効果がある。上記効果を効果的に発揮させるため、Mn含有量は0.01%以上とする。一方、Mn含有量が1.5%を超えると、製造時における加熱時に、表面に生成する高温酸化スケールの密着性が低下することにより、表面肌荒れの原因となるスケール剥離を起こしやすくなる。そのため、Mn含有量は、1.5%以下とする。Mn含有量は、0.05%以上であることが好ましく、0.1%以上であることがより好ましい。また、Mn含有量は、1.2%以下であることが好ましく、1.0%以下であることがより好ましい。
本発明においては、鋼中のPは、Sと並んで最も有害な不純物であるので、その含有量は0.035%以下とする。P含有量は低ければ低い程好ましい。
本発明において、鋼中のSは、Pと並んで最も有害な不純物であるので、その含有量は0.01%以下とする。S含有量は低ければ低いほど好ましい。Sは、鋼中共存元素および鋼中のS含有量に応じて、Mn系硫化物、Cr系硫化物、Fe系硫化物、または、これらの複合硫化物および酸化物との複合非金属析出物としてその殆どが析出する。また、Sは、必要に応じて添加する希土類元素系の硫化物を形成することもある。しかしながら、固体高分子形燃料電池のセパレータ環境においては、いずれの組成の非金属析出物も、程度の差はあるものの腐食の起点として作用するので、不動態皮膜の維持、金属イオン溶出抑制に有害である。通常の量産鋼の鋼中S量は、0.005%超0.008%前後であるが、上記の有害な影響を防止するためには0.004%以下に低減することが好ましい。より好ましい鋼中S量は0.002%以下であり、最も好ましい鋼中S量レベルは、0.001%未満である。低ければ低い程、望ましい。工業的量産レベルで0.001%未満とすることは、現状の精錬技術をもってすれば製造コストの上昇もわずかであり、問題ない。
Crは、母材の耐食性を確保する上で極めて重要な基本合金元素であり、Cr含有量は高いほど優れた耐食性を奏する。フェライト系ステンレス鋼においてはCr含有量が35.0%を超えると量産規模での生産が難しくなる。一方、Cr含有量が22.5%未満であると、その他の元素を変化させても固体高分子形燃料電池セパレータとして必要な耐食性を確保できないとともに、M2B型硼化物系金属析出物として析出することにより、耐食性向上に寄与する母相中のCr量が溶鋼のCr量に比べて低下して母材の耐食性が劣化する場合がある。また、Crは鋼中のCと反応してM23C6型炭化物系金属析出物を形成する場合がある。M23C6型炭化物系金属析出物は導電性に優れる金属析出物であるが、鋭敏化による耐食性低下の原因となる。M2B型硼化物系金属析出物を表面に露出させることにより、電気的な表面接触抵抗値を低減することができる。固体高分子形燃料電池内部での耐食性を確保するためには、少なくとも、{Cr含有量(質量%)+3×Mo含有量(質量%)-2.5×B含有量(質量%)}として算出される値を20~45%とするCr量が必要である。Cr含有量は、23.0%以上であることが好ましく、34.0%以下であることが好ましい。
Moは、Crに比べて、少量で耐食性を改善する効果がある。耐食性を効果的に発揮させるため、Mo含有量は、0.01%以上とする。一方、6.0%を超えてMoを含有すると、製造途中でシグマ相等の金属間化合物の析出を回避できなくなり、鋼の脆化の問題から生産が困難となる。このため、Mo含有量の上限を6.0%とする。また、Moは、固体高分子形燃料電池の内部で、仮に腐食により鋼中Moの溶出が起こったとしても、MEA性能に対する影響は比較的軽微であるという特徴を有する。この理由は、Moが金属陽イオンとして存在せずに陰イオンであるモリブデン酸イオンとして存在するため、水素イオン(プロトン)交換基を有するフッ素系イオン交換樹脂膜の陽イオン伝導度に対する影響が小さいためである。Moは、耐食性を維持するために極めて重要な元素であり、{Cr含有量(質量%)+3×Mo含有量(質量%)-2.5×B含有量(質量%)}として算出される値を20~45%とする鋼中Mo量であることが必要である。Mo含有量は、0.05%以上であることが好ましく、5.0%以下であることが好ましい。
Niは、耐食性および靭性を改善する効果を有する。Ni含有量の上限は6.0%とする。Ni含有量が6.0%を超えると、工業的に熱処理を施してもフェライト系単相組織とすることが困難となる。一方、Ni含有量の下限は0.01%とする。Ni含有量の下限は工業的に製造した場合に混入してくる不純物量である。Ni含有量は、0.03%以上であることが好ましく、5.0%以下であることが好ましい。
Cuは、0.01%以上、1.0%以下含有する。Cu含有量が1.0%を超えると、熱間での加工性を低下することになり、量産性の確保が難しくなる。一方、Cu含有量が0.01%未満であると、固体高分子形燃料電池中での耐食性が低下する。本発明に係るステンレス鋼においては、Cuは固溶状態で存在する。Cu系析出物として析出させると、電池内でのCu溶出起点となり燃料電池性能を低下させるようになる。Cu含有量は、0.02%以上であることが好ましく、0.8%以下であることが好ましい。
フェライト系ステンレス鋼におけるNは不純物である。Nは常温靭性を劣化させるのでN含有量の上限を0.035%とする。低ければ低い程望ましい。工業的に、N含有量は、0.007%以下とすることが最も望ましい。しかし、N含有量の過剰な低下は溶製コストの上昇をもたらすので、N含有量は0.001%以上とすることが好ましく、0.002%以上であることがより好ましい。
Vは、意図的に添加する添加元素ではないが、量産時に用いる溶解原料として添加するCr源中に不可避的に含有されている。V含有量は、0.01%以上0.35%以下とする。Vは、わずかではあるが常温靭性を改善する効果を有する。V含有量は、0.03%以上であることが好ましく、0.30%以下であることが好ましい。
Bは、本発明においては重要な添加元素である。溶鋼を造塊するに際して、すべての鋼中BがM2B型硼化物系金属析出物として共晶反応により析出する。Bは熱的に極めて安定な金属析出物である。表面に露出したM2B型硼化物系金属析出物は電気的な表面接触抵抗を顕著に下げる働きを有する。B含有量が0.5%未満では、析出量が所望の性能を得るには不十分である。一方、B含有量が1.0%を超えると安定して量産製造することが難しくなる。このため、B含有量は0.5%以上1.0%以下とする。B含有量は、0.55%以上であることが好ましく、0.8%以下であることが好ましい。
Alは、脱酸元素として溶鋼段階で添加する。本発明に係るステンレス鋼が含有するBは溶鋼中酸素との結合力が強い元素であるので、Al脱酸により酸素濃度を下げておく必要がある。そのため、Alを0.001%以上6.0%以下の範囲で含有させるのがよい。鋼中では脱酸生成として非金属酸化物を形成するが、残余は固溶している。Al含有量は、0.01%以上であることが好ましく、5.5%以下であることが好ましい。
本発明においては、Snは極めて重要な添加元素である。鋼中にSnを0.02%から2.50%の範囲で含有することにより、母相中に固溶しているSnが固体高分子形燃料電池内では母相の表面のみならず、M2B表面にも金属スズまたは酸化スズとして濃化することにより母相ならびにわずかといえども進行するM2Bからの金属イオンの溶出を顕著に抑制するとともに、母相の表面接触抵抗を低減し、さらにM2B表面に金属スズまたは酸化スズとして濃化することにより、M2Bの電気的な接触抵抗性能も安定して金めっき素材並みに改善される。Sn含有量が、0.02%未満ではこのような効果が得られず、2.50%を超えると製造性が低下する。このため、Sn含有量は、0.02%以上2.50%以下とする。Sn含有量は、0.05%以上であることが好ましく、2.40%以下であることが好ましい。
本発明においては、希土類元素は任意添加元素であり、ミッシュメタルとして添加される。希土類元素は、熱間製造性を改善する効果がある。このため、希土類元素を、0.1%を上限として含有してもよい。希土類元素の含有量は、0.005%以上であることが好ましく、0.05%以下であることが好ましい。
この値は、M2B型硼化物系金属析出物が析出したフェライト系ステンレス鋼の耐食挙動を示す目安となる指数である。この値は20%以上45%以下とする。この値が20%未満であると固体高分子形燃料電池内での耐食性が十分確保できず金属イオン溶出量が多くなる。一方、この値が45%超では量産性が著しく悪くなる。
NbおよびTiは、いずれも、本発明においては任意添加元素であり、鋼中のCおよびNの安定化元素である。鋼中では炭化物および窒化物を形成する。このため、TiおよびNbの含有量は、いずれも、0.35%以下とする。NbおよびTiの含有量は、0.001%以上であることが好ましく、0.30%以下であることが好ましい。Nbは(Nb/C)値が3以上25以下となるように、Tiは{Ti/(C+N)}値が3以上25以下となるように、含有する。
次に、本発明の効果を、実施例を参照しながら具体的に説明する。
2 固体高分子電解質膜
3 燃料電極膜(アノード)
4 酸化剤電極膜(カソード)
5a,5b セパレータ
6a,6b 流路
Claims (5)
- 化学組成が、質量%で、
C:0.001~0.020%未満、
Si:0.01~1.5%、
Mn:0.01~1.5%、
P:0.035%以下、
S:0.01%以下、
Cr:22.5~35.0%、
Mo:0.01~6%、
Ni:0.01~6%、
Cu:0.01~1%、
N:0.035%以下、
V:0.01~0.35%、
B:0.5~1.0%、
Al:0.001~6.0%、
Sn:0.02~2.50%、
希土類元素:0~0.1%、
Nb:0~0.35%、
Ti:0~0.35%、および、
残部:Feおよび不純物であり、かつ、
{Cr含有量(質量%)+3×Mo含有量(質量%)-2.5×B含有量(質量%)}として算出される値が20~45%であるとともに、
フェライト相のみからなる母相中にM2B型硼化物系金属析出物が分散し、かつ、表面に露出している、フェライトステンレス鋼材。 - 前記化学組成が、質量%で、
希土類元素:0.005~0.1%を、
含有する、請求項1に記載のフェライトステンレス鋼材。 - 前記化学組成が、質量%で、
Nb:0.001~0.35%、および、
Ti:0.001~0.35%、
から選択される1種以上を含有し、かつ、
3≦Nb/C≦25、
3≦Ti/(C+N)≦25、
を満足する、請求項1または請求項2に記載のフェライトステンレス鋼材。 - 請求項1から請求項3までのいずれか1項に記載の固体高分子形燃料電池セパレータ用フェライト系ステンレス鋼材により構成される、固体高分子形燃料電池用セパレータ。
- 請求項1から請求項3までのいずれか1項に記載の固体高分子形燃料電池セパレータ用フェライト系ステンレス鋼材により構成される、固体高分子形燃料電池。
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KR1020177011771A KR20170063900A (ko) | 2014-10-01 | 2015-09-30 | 페라이트계 스테인리스강재와, 이것을 이용하는 고체 고분자형 연료 전지용 세퍼레이터 및 고체 고분자형 연료 전지 |
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JP6278172B1 (ja) * | 2016-08-30 | 2018-02-14 | 新日鐵住金株式会社 | フェライト系ステンレス鋼材、セパレーター、セルおよび燃料電池 |
WO2018043285A1 (ja) * | 2016-08-30 | 2018-03-08 | 新日鐵住金株式会社 | フェライト系ステンレス鋼材、セパレーター、セルおよび燃料電池 |
US20190267640A1 (en) * | 2018-02-28 | 2019-08-29 | Toyota Jidosha Kabushiki Kaisha | Stainless steel substrate, fuel cell separator, and fuel cell |
JP2020152949A (ja) * | 2019-03-19 | 2020-09-24 | 日鉄ステンレス株式会社 | ステンレス鋼板およびステンレス鋼板の製造方法 |
US10833335B2 (en) | 2018-02-28 | 2020-11-10 | Toyota Jidosha Kabushiki Kaisha | Stainless steel substrate |
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CN111876661A (zh) * | 2020-06-17 | 2020-11-03 | 宁波宝新不锈钢有限公司 | 一种燃料电池用高耐蚀铁素体不锈钢及其制造方法 |
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