Stainless steel material for alkaline water electrolysis apparatus, member for alkaline water electrolysis apparatus and method for producing the same, and alkaline water electrolysis treatment apparatus

Abstract

To provide a Ni-saving stainless steel material for an alkaline water electrolysis apparatus, which yields a member for an alkaline water electrolysis apparatus while ensuring durability (resistance to metal elution) in alkaline water electrolysis, even without pretreatment.SOLUTION: A stainless steel material for an alkaline water electrolysis apparatus contains, on a mass basis, C: 0.100% or less, Si: 1.00% or less, Mn: 3.00 to 12.00%, Ni: 7.00 to 9.00%, P: 0.0030% or less, S: 0.0030% or less, Cr: 10.0 to 18.0%, N: 0.01 to 0.25%, Cu: 0.01 to 1.00%, Mo: 0.01 to 1.00%, Al: 0.005 to 0.080%, B: 0.0001 to 0.0100%, Ca: 0.0005 to 0.0100%, and O: 0.0100% or less, with the balance consisting of Fe and impurities.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a stainless steel material for an alkaline water electrolysis device, a member for an alkaline water electrolysis device, a method for manufacturing the same, and an alkaline water electrolysis treatment device.

Background Art

[0002] Measures against global warming have become a global issue, and as one of the measures, the use of renewable energy that does not generate CO2 is being promoted. However, since renewable energy uses natural energy, there is a problem that it is difficult to match the power generation amount with the demands from people's lifestyles. For example, solar power generation cannot generate electricity during bad weather or at night when electricity is needed in daily life. Also, in climate conditions where the daytime temperature is mild, the power generated by solar power generation may become surplus in consideration of other power generation methods, and in some power transmission systems, the surplus power may have an adverse effect on the power transmission system. Therefore, there may also occur a contradiction that the generated power cannot be utilized even on sunny days. Although there is a method of storing surplus power in a storage battery, currently, a large-sized storage battery is required and it is expensive, so there are many problems in its application to large-scale power generation.

[0003] As a means of effectively utilizing this surplus power, a method of producing hydrogen generated by electrolytic decomposition of water has been studied. If hydrogen can be produced and stored, stable supply of carbon-free renewable energy power is expected by generating electricity using a fuel cell with hydrogen at night or during bad weather. Also, it is possible to produce methane from the hydrogen generated above to make a fuel that is easier to store and more environmentally friendly than hydrogen.

[0004] The method of electrolyzing water is generally classified into each method of alkaline water electrolysis, solid polymer type water electrolysis, and high-temperature water electrolysis. Among these, alkaline water electrolysis is expected to be promising in industrial applications that require strict cost-effectiveness because it may be possible to use low-cost materials such as iron-based materials.

[0005] Some parts of the water electrolysis device have already been put into practical use. For example, an example of a water electrolysis device is described in FIGS. 1 and 2 of Patent Document 1. In the water electrolysis device described in Patent Document 1, a diaphragm is installed between electrodes installed in water to electrolyze water, generating oxygen on the anode side and hydrogen on the cathode side, and extracting hydrogen.

[0006] In Patent Document 1, it is described that nickel electrodes are used because stainless steel has no durability (resistance to metal elution) in an alkaline water electrolysis environment. However, nickel is a rare metal, which is not only expensive but also limited in production countries, and there are geopolitical risks. In addition, the problem is also that the raw material prices fluctuate wildly in a speculative manner.

[0007] Stainless steel materials are widely known as corrosion-resistant materials cheaper than nickel. As an example of applying stainless steel materials to alkaline electrolysis, Patent Document 2 describes a stainless steel anode characterized by being immersed in a corrosive agent solution mainly composed of an aqueous potassium hydroxide solution and electrolyzed before being used in an alkaline water electrolysis cell. According to Patent Document 2, it is described that the corrosion resistance of the stainless steel material is improved compared to the untreated one by electrolysis treatment in the corrosive agent solution. However, the evaluation time is a short period of about 160 hours, and since there is no long-term evaluation record, it is unclear whether the long-term durability (resistance to metal elution) is sufficient.

[0008] Patent Document 3 describes a hydrogen and oxygen generation device composed of a stainless steel material having an iron-based passive film formed on the surface by heat treatment after purification treatment by electrolytic polishing. However, the device described in Patent Document 3 is a hydrogen and oxygen generation device in pure water, and its durability (resistance to metal elution) in alkaline water has not been evaluated.

[0009] On the one hand, as a means for improving the corrosion resistance of stainless steel materials, Patent Document 4 describes a method of forming a boron-containing or boron- and fluorine-containing or their oxygen-based coating layer on the surface. In Patent Document 4, it is stated that by electrolyzing a stainless steel material with a boric acid aqueous solution alone or a mixed aqueous solution obtained by adding hydrofluoric acid to boric acid, the corrosion resistance of the film formed on the surface of the stainless steel material is improved. The electrolytic solution used for the electrolytic treatment is mainly composed of boric acid, and it is an electrolytic method under an acidic solution. Therefore, the formed film mainly consists of boron. This formed film is characterized by excellent stress corrosion cracking resistance in a neutral or acidic solution containing chlorides, but the durability (metal elution resistance) when electrolyzed in an alkaline aqueous solution has not been evaluated.

[0010] Therefore, in order to solve the above problems, the applicant of the present application proposed, in Patent Document 5, a stainless steel material for an alkaline electrolytic treatment apparatus including a base material made of stainless steel and a film formed on the surface of the base material, with fluorine contained in the film. This stainless steel material is manufactured by subjecting it to an anodic electrolytic treatment in an alkaline aqueous solution after either an immersion treatment of immersing the stainless steel material in an aqueous solution containing hydrofluoric acid or an inorganic compound containing fluorine, or an electrolytic treatment of electrolyzing the stainless steel material in the aqueous solution.

[0011] In addition, the applicant of the present application proposed, in Patent Document 6, a stainless steel material for an electrolytic treatment apparatus including a base material made of stainless steel and a film formed on the surface of the base material, with at least Ni present in the film, and the Ni concentration, Fe concentration, and Cr concentration in the film satisfying a predetermined relational expression. This stainless steel material is manufactured by subjecting it to an anodic electrolytic treatment in an alkaline aqueous solution, but it is described that before this treatment, either an immersion treatment of immersing the stainless steel material in an aqueous solution containing hydrofluoric acid or an inorganic compound containing fluorine, or one or both of the electrolytic treatments of electrolyzing the stainless steel material in the aqueous solution may be performed.

Prior Art Documents

Patent Documents

[0012] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-122255 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-45205 [Patent Document 3] Japanese Patent Application Laid-Open No. 9-302492 [Patent Document 4] Japanese Patent Application Laid-Open No. 2010-189666 [Patent Document 5] Japanese Patent Application Laid-Open No. 2020-164915 [Patent Document 6] Japanese Patent Application Laid-Open No. 2021-161482 [Summary of the Invention] [Problems to be Solved by the Invention]

[0013] Ni contained in stainless steel materials is advantageous for improving the durability (resistance to metal elution) during alkaline electrolysis because it can form a film containing Ni on the surface of the stainless steel materials. On the other hand, since Ni is an expensive metal, considering the cost aspect, a Ni-saving type of inexpensive stainless steel material is required. In addition, for Ni-saving type stainless steel materials, if pretreatment is not performed before anodic electrolysis treatment in an alkaline aqueous solution, the durability (resistance to metal elution) during alkaline electrolysis cannot often be ensured. Therefore, there is also a problem that the cost and labor required for pretreatment are high. Note that SUS301S etc. are examples of stainless steel materials that can ensure the durability (resistance to metal elution) during alkaline electrolysis without performing pretreatment, but this stainless steel material has a high Ni content.

[0014] The present invention has been made to solve the above problems, and an object thereof is to provide a Ni-saving type of stainless steel material for an alkaline electrolysis device that can provide a member for an alkaline electrolysis device capable of ensuring the durability (resistance to metal elution) during alkaline electrolysis without performing pretreatment. Another object of the present invention is to provide a member for an alkaline water electrolysis apparatus and a method for manufacturing the same, which can ensure durability (resistance to metal elution) during alkaline water electrolysis without performing pretreatment. Furthermore, an object of the present invention is to provide an alkaline water electrolysis treatment apparatus including a stainless steel material for an alkaline water electrolysis apparatus or a member for an alkaline water electrolysis apparatus having the above characteristics.

Means for Solving the Problems

[0015] As a result of intensive research on stainless steel materials for alkaline water electrolysis apparatuses to solve the above problems, the present inventors have found that by reducing the Ni content while increasing the Mn content, a Ni-concentrated film is formed on the surface during alkaline water electrolysis without performing pretreatment, ensuring durability (resistance to metal elution), and thus completing the present invention.

[0016] That is, the present invention relates to a stainless steel material for an alkaline water electrolysis apparatus containing, by mass, C: 0.100% or less, Si: 1.00% or less, Mn: 3.00 to 12.00%, Ni: 7.00 to 9.00%, P: 0.0030% or less, S: 0.0030% or less, Cr: 10.0 to 18.0%, N: 0.01 to 0.25%, Cu: 0.01 to 1.00%, Mo: 0.01 to 1.00%, Al: 0.005 to 0.080%, B: 0.0001 to 0.0100%, Ca: 0.0005 to 0.0100%, and O: 0.0100% or less, with the balance being Fe and impurities.

[0017] The present invention also relates to a member for an alkaline water electrolysis apparatus including a base material made of the above stainless steel material for an alkaline water electrolysis apparatus and a Ni-concentrated film formed on the surface of the base material.

[0018] The present invention also relates to a method for manufacturing a member for an alkaline water electrolysis apparatus, in which a base material made of the above stainless steel material for an alkaline water electrolysis apparatus is disposed in an alkaline water electrolysis apparatus and electrolysis treatment is performed.

[0019] Furthermore, the present invention relates to a stainless steel material for an alkaline water electrolysis device or an alkaline water electrolysis treatment device including the member for an alkaline water electrolysis device.

Effects of the Invention

[0020] According to the present invention, it is possible to provide a Ni-saving type stainless steel material for an alkaline water electrolysis device that gives a member for an alkaline water electrolysis device capable of ensuring durability (resistance to metal elution) during alkaline water electrolysis without performing pretreatment. Moreover, according to the present invention, it is possible to provide a member for an alkaline water electrolysis device capable of ensuring durability (resistance to metal elution) during alkaline water electrolysis without performing pretreatment and a method for manufacturing the same. Furthermore, according to the present invention, it is possible to provide an alkaline water electrolysis treatment device including the stainless steel material for an alkaline water electrolysis device or the member for an alkaline water electrolysis device having the above characteristics.

Embodiments for Carrying Out the Invention

[0021] Hereinafter, embodiments of the present invention will be specifically described. It should be understood that the present invention is not limited to the following embodiments, and modifications and improvements to the following embodiments based on ordinary knowledge of those skilled in the art within the scope not departing from the gist of the present invention also fall within the scope of the present invention. In addition, in this specification, the “%” display regarding components means “mass %” unless otherwise specified.

[0022] <Stainless Steel Material for Alkaline Water Electrolysis Device> The stainless steel material for an alkaline water electrolysis device according to an embodiment of the present invention (hereinafter sometimes abbreviated as "stainless steel material") contains C: 0.100% or less, Si: 1.00% or less, Mn: 3.00 to 12.00%, Ni: 7.00 to 9.00%, P: 0.0030% or less, S: 0.0030% or less, Cr: 10.0 to 18.0%, N: 0.01 to 0.25%, Cu: 0.01 to 1.00%, Mo: 0.01 to 1.00%, Al: 0.005 to 0.080%, B: 0.0001 to 0.0100%, Ca: 0.0005 to 0.0100%, and O: 0.0100% or less, and the balance consists of Fe and impurities.

[0023] Here, in this specification, the "alkaline water electrolysis device" means a device for producing hydrogen and oxygen in an alkaline solution. The alkaline solution used in the alkaline water electrolysis device is not particularly limited, and a solution having a pH greater than 7, for example, a strong alkaline solution (pH 14 or higher) or a weak alkaline solution (pH 11 to 12) can be used. Specific examples of the alkaline solution include a KOH solution, an NaOH solution, and a K2CO3 solution.

[0024] Also, in this specification, the "stainless steel material" means a material formed from stainless steel, and its material form is not particularly limited. Examples of the material form include a plate shape (including a strip shape), a rod shape, and a tubular shape. Further, various shaped steels having a T-shaped or I-shaped cross-sectional shape may also be used. Also, in this specification, the "impurities" mean components that are mixed in due to raw materials such as ores and scraps and various factors in the manufacturing process when the stainless steel material is industrially manufactured, and are allowed within a range that does not adversely affect the present invention. For example, the impurities include inevitable impurities. Regarding the content of each element, including "xx% or less" means that it is xx% or less but includes an amount exceeding 0% (especially exceeding the impurity level).

[0025] The stainless steel material according to an embodiment of the present invention may further contain one or more selected from Nb: 0.50% or less, Ti: 0.50% or less, Mg: 0.0050% or less, Zr: 0.50% or less, Co: 0.50% or less, V: 0.50% or less, W: 0.50% or less, REM: 0.100% or less, and Sn: 0.100% or less, as required. Hereinafter, each component will be described in detail.

[0026] <C: 0.100% or less> C is an element effective for stabilizing the austenite phase. However, since C promotes the precipitation of Cr carbides, if the C content is too high, intergranular corrosion occurs and the durability (resistance to metal elution) during alkaline electrolysis decreases. Therefore, the C content is 0.100% or less, preferably 0.095% or less, more preferably 0.090% or less, still more preferably 0.085% or less, and particularly preferably 0.080% or less. On the other hand, the lower limit value of the C content is not particularly limited, but is 0.001% from the viewpoint of obtaining the above effects of C.

[0027] <Si: 1.00% or less> Si is an element effective for deoxidation and improving oxidation resistance. However, if the Si content is too high, the stainless steel material hardens, and the workability and toughness (particularly, the toughness of the welded part when welded) decrease. Therefore, the Si content is 1.00% or less, preferably 0.95% or less, more preferably 0.90% or less, still more preferably 0.85% or less, and particularly preferably 0.80% or less. On the other hand, the lower limit value of the Si content is not particularly limited, but is 0.01% from the viewpoint of obtaining the above effects of Si.

[0028] <Mn: 3.00 to 12.00%> Mn is an element necessary for forming a Ni-enriched film on the surface of stainless steel materials during alkaline water electrolysis. To ensure this effect, the Mn content should be 3.00% or more, preferably 3.20% or more, more preferably 3.50% or more, still more preferably 3.80% or more, and particularly preferably 4.00% or more. However, if the Mn content is too high, the corrosion resistance will decrease. Therefore, the Mn content should be 12.00% or less, preferably 11.80% or less, more preferably 11.50% or less, still more preferably 11.30% or less, and particularly preferably 11.00% or less.

[0029] <Ni: 7.00~9.00%> Ni is an element effective for improving the durability (resistance to metal elution) during alkaline water electrolysis. To ensure this effect, the Ni content should be 7.00% or more, preferably 7.10% or more, more preferably 7.20% or more, and still more preferably 7.30% or more. However, if the Ni content is too high, the cost will increase. Therefore, the Ni content should be 9.00% or less, preferably 8.90% or less, more preferably 8.70% or less, and still more preferably 8.50% or less.

[0030] <P: 0.0030% or less> P is an element contained in various raw materials. If the P content is too high, the weldability and workability will decrease. Therefore, the P content should be 0.0030% or less, preferably 0.0028% or less, and more preferably 0.0025% or less. On the other hand, the lower limit of the P content is not particularly limited, but removing P requires a very high cost for refining. Therefore, considering economic efficiency, the P content can be 0.0001% or more.

[0031] <S: 0.0030% or less> S is an element contained in various raw materials. If the S content is too high, the toughness (especially the toughness of the welded part when welded) decreases, and inclusions that serve as corrosion initiation points are likely to be generated. Therefore, the S content is 0.0030% or less, preferably 0.0028% or less, more preferably 0.0025% or less. On the other hand, the lower limit of the S content is not particularly limited, but removing S requires a very large cost for refining. Therefore, considering economic efficiency, the S content can be 0.0001% or more.

[0032] <Cr: 10.0~18.0%> Cr is an element effective for ensuring corrosion resistance. To ensure this effect, the Cr content is 10.0% or more, preferably 10.5% or more, more preferably 11.0% or more. However, if the Cr content is too high, the cost increases. Therefore, the Cr content is 18.0% or less, preferably 17.5% or less, more preferably 17.0% or less.

[0033] <N: 0.01~0.25%> N is an element effective for cost reduction. Also, N is an element that dissolves in the austenite phase to increase strength and corrosion resistance and contributes to alloy reduction. To ensure these effects, the N content is 0.01% or more, preferably 0.02% or more, more preferably 0.03% or more, still more preferably 0.05% or more. However, if the N content is too high, bubbles are likely to occur in the stainless steel material. Therefore, the N content is 0.25% or less, preferably 0.23% or less, more preferably 0.20% or less.

[0034] <Cu: 0.01~1.00%> Cu is an element effective for desulfurization and deoxidation. Also, Cu contributes to the improvement of corrosion resistance. To ensure these effects, the Cu content is 0.01% or more, preferably 0.03% or more, more preferably 0.05% or more, still more preferably 0.10% or more. However, if the Cu content is too high, the cost increases. Therefore, the Cu content is 1.00% or less, preferably 0.95% or less, more preferably 0.90% or less.

[0035] <Mo: 0.01~1.00%> Mo is an element effective in improving corrosion resistance. To ensure this effect, the Mo content should be 0.01% or more, preferably 0.05% or more, more preferably 0.10% or more, and still more preferably 0.15% or more. However, if the Mo content is too high, the cost will increase. Therefore, the Mo content should be 1.00% or less, preferably 0.95% or less, and more preferably 0.90% or less.

[0036] <Al: 0.005~0.080%> Al is an element effective in improving oxidation resistance, deoxidation property, and workability. To ensure these effects, the Al content should be 0.005% or more, preferably 0.008% or more, and more preferably 0.010% or more. However, if the Al content is too high, the oxidation resistance and deoxidation property will conversely decrease, and inclusions are likely to occur. Therefore, the Al content should be 0.080% or less, preferably 0.075% or less, and more preferably 0.070% or less.

[0037] <B: 0.0001~0.0100%> B is an element effective in improving hot workability. To ensure this effect, the B content should be 0.0001% or more, preferably 0.0003% or more, and more preferably 0.0005% or more. However, if the B content is too high, the corrosion resistance will decrease. Therefore, the B content should be 0.0100% or less, preferably 0.0095% or less, and more preferably 0.0090% or less.

[0038] <Ca: 0.0005~0.0100%> Ca is an element effective in suppressing the formation of inclusions and improving corrosion resistance. To ensure this effect, the Ca content should be 0.0005% or more, preferably 0.0008% or more, and more preferably 0.0010% or more. However, if the Ca content is too high, the hot workability will decrease. Therefore, the Ca content should be 0.0100% or less, preferably 0.0095% or less, and more preferably 0.0090% or less.

[0039] <O: Below 0.0100%> O is an element that affects hot workability. Therefore, the O content should be 0.0100% or less, preferably 0.0095%, more preferably 0.0090% or less. On the other hand, the lower limit of the O content is not particularly limited, but is typically 0.0001%.

[0040] <Nb: 0.50% or less, Ti: 0.50% or less> Nb and Ti are elements effective in suppressing sensitization and improving intergranular corrosion resistance. However, if the contents of Nb and Ti are too high, workability will decrease and costs will increase. Therefore, the contents of Nb and Ti are each 0.50% or less, preferably 0.45% or less, more preferably 0.40% or less. On the other hand, the lower limit of the contents of Nb and Ti is not particularly limited, but in order to ensure the above effects, it can be 0.0001% or more, 0.0003% or more, or 0.0005% or more.

[0041] <Mg: 0.0050% or less> Mg is an element effective in improving manufacturability. However, if the Mg content is too high, costs will increase. Therefore, the Mg content is 0.0050% or less, preferably 0.0045% or less, more preferably 0.0040% or less. On the other hand, the lower limit of the Mg content is not particularly limited, but in order to ensure the above effects, it can be 0.0001%, 0.0003%, or 0.0005%.

[0042] <Zr: 0.50% or less, Co: 0.50% or less, V: 0.50% or less, W: 0.50% or less> Zr, Co, V, and W are elements effective for improving oxidation resistance. However, if the contents of Zr, Co, V, and W are too high, the workability and toughness will decrease and the cost will also increase. Therefore, the contents of Zr, Co, V, and W are each 0.50% or less, preferably 0.45% or less, more preferably 0.40% or less. On the other hand, the lower limit of the contents of Zr, Co, V, and W is not particularly limited, but in order to ensure the above effects, it can be 0.0001% or more, 0.0002% or more, or 0.0003% or more.

[0043] <REM:0.100% or less> REM (rare earth elements) are elements effective for improving oxidation resistance. However, if the REM content is too high, the manufacturability will be impaired and the cost will also increase. Therefore, the REM content is 0.100% or less, preferably 0.095% or less, more preferably 0.090% or less. On the other hand, the lower limit of the REM content is not particularly limited, but in order to ensure the above effects, it can be 0.001% or more, 0.005% or more, or 0.010% or more. Note that REM is a general term for a total of 17 elements including Sc, Y, and 15 elements (lanthanoids) from La to Lu, and the REM content means the total content of these elements. These elements can be used alone or in combination of two or more. Also, lanthanoids are industrially added in the form of mischmetal.

[0044] <Sn:0.100% or less> Sn is an element effective for improving oxidation resistance. However, if the Sn content is too high, the hot workability will decrease. Therefore, the Sn content is 0.100% or less, preferably 0.090% or less, more preferably 0.080% or less. On the other hand, the lower limit of the Sn content is not particularly limited, but in order to ensure the above effects, it can be 0.001% or more, 0.005% or more, or 0.010% or more.

[0045] The stainless steel material according to the embodiment of the present invention has an austenitic metal structure. Here, in this specification, "austenitic" means that the metallographic structure is mainly the austenite phase at room temperature. Therefore, "austenitic" includes those that slightly contain phases other than the austenite phase (for example, ferrite phase, martensite phase, etc.). However, "austenitic" does not include a duplex structure of ferrite phase and austenite phase, a duplex structure of ferrite phase and martensite phase, and a duplex structure of ferrite phase, austenite phase, and martensite phase.

[0046] The stainless steel material according to an embodiment of the present invention preferably has an arithmetic mean height Sa of the surface of 0.70 μm or less, and more preferably 0.65 μm or less. By controlling the arithmetic mean height Sa of the surface within this range, a Ni-enriched film is uniformly formed on the surface during alkaline electrolysis, so that the durability (resistance to metal elution) during alkaline electrolysis can be improved. The lower limit of the arithmetic mean height Sa of the surface is not particularly limited because the lower the value, the easier it is to obtain the effect. For example, it is 0.01 μm. Here, in this specification, the "arithmetic mean height Sa of the surface" can be obtained by measuring and analyzing the surface shape in accordance with ISO 25178-2:2012.

[0047] The stainless steel material according to an embodiment of the present invention preferably has a Ni enrichment rate index represented by the following formula (1) of 6.5 or more. Ni enrichment rate index = (R A -R B ) / 4 ···(1) In the formula, R A is the concentration (atomic %) of Ni with respect to the total of Fe, Cr, Ni, and Mn at a depth of 1 nm from the surface after immersing the stainless steel material in a 0.1 M KOH aqueous solution at 60°C and electrolyzing it at a potential of 1.2 V (vs. SHE) for 4 hours, and R B is the concentration (atomic %) of Ni with respect to the total of Fe, Cr, Ni, and Mn at a depth of 1 nm from the surface before electrolysis.

[0048] Here, the Ni concentration rate index is an index representing the formation rate of the Ni concentration film during alkaline electrolysis. If the Ni concentration rate index is 6.5 or more, it can be said that the formation rate of the Ni concentration film is high during alkaline electrolysis. From the viewpoint of stably ensuring this effect, the Ni concentration rate index is preferably 6.6 or more, more preferably 6.7 or more. The upper limit of the Ni concentration rate index is not particularly limited, but for example, it is 15.0 or less, 13.0 or less, or 10.0 or less. In addition, the concentration of each element at a depth of 1 nm from the surface can be calculated by measuring the elemental depth profile from the surface by FE-AES (field emission type Auger electron spectroscopy). The elements to be measured in this elemental analysis are C, O, Fe, Cr, Ni, and Mn, and the concentration of each element can be calculated from the measured amounts of these elements. The concentration (atomic %) of Ni with respect to the total of Fe, Cr, Ni, and Mn is the percentage of the amount of Ni when the total amount of the remaining elements excluding C and O among the elements to be measured is 100.

[0049] The method for manufacturing a stainless steel material according to an embodiment of the present invention is not particularly limited as long as it is a method capable of manufacturing a stainless steel material having the above characteristics. Hereinafter, an example of the method for manufacturing a stainless steel material according to an embodiment of the present invention will be described. First, the steel adjusted to the above chemical composition is melted and cast by a conventional method to obtain a steel slab (slab) to be subjected to hot rolling. Subsequently, hot rolling is performed by a conventional method. The conditions during hot rolling are not particularly limited, but usually, the heating temperature of the steel slab is preferably 1050 to 1250°C. After hot rolling, annealing and pickling may be performed as necessary. The annealing temperature at this time is not particularly limited, but for example, it may be in the range of 1050 to 1100°C.

[0050] Subsequently, cold rolling and annealing are performed. Note that the annealing immediately before the final finish cold rolling is referred to as solution treatment, and the solution treatment is also performed in the same manner. Further, pickling is performed as necessary. The conditions for cold rolling are not particularly limited, but the annealing after cold rolling is preferably performed at 1000 to 1150°C with isothermal holding for 1 to 600 seconds. Cold rolling, annealing, and pickling may be repeated a plurality of times for the purpose of finally obtaining a stainless steel material with the required thickness.

[0051] Solution treatment is performed immediately before the final finish cold rolling for work hardening. In the solution treatment, it is preferable to perform heat treatment under the conditions of isothermal holding at 1000 to 1150°C for 1 to 600 seconds. If the solution treatment temperature is less than 1000°C, recrystallization is insufficient, and twinning deformation cannot be sufficiently performed during finish cold rolling. For this reason, the solution treatment temperature is preferably 1000°C or higher. On the other hand, if the solution treatment temperature exceeds 1150°C, the crystal grains become coarsened (exceeding 0.1 mm) and the strength decreases. For this reason, the solution treatment temperature is preferably 1150°C or lower.

[0052] After the final finish cold rolling, in order to control the surface roughness of the stainless steel material (particularly, the arithmetic mean height Sa of the surface to 0.70 μm or less), the surface of the steel material may be mechanically polished or electropolished. Mechanical polishing is preferably performed in the range of up to 10 μm in the thickness direction of the stainless steel material from the surface. Mechanical polishing may be performed using abrasive paper or abrasive stones, etc., and solid abrasive agents may also be used. Further, for electropolishing, a commercially available electropolishing solution may be used. The electropolishing treatment is preferably performed at 40 to 60°C. As other conditions for electropolishing, the current density is 1 to 20 dm 2 and the time is desirably in the range of 1 to 10 minutes.

[0053] <Member for Alkaline Water Electrolysis Device and Method for Manufacturing the Same> The member for an alkaline water electrolysis device according to an embodiment of the present invention includes a base material made of the above stainless steel material and a Ni-enriched film formed on the surface of the base material. By adopting such a configuration, the member for an alkaline water electrolysis device according to an embodiment of the present invention can ensure durability (resistance to metal elution) during alkaline water electrolysis by means of the Ni-enriched film formed on the surface of the base material.

[0054] Here, in this specification, the "member for an alkaline water electrolysis device" means a member (part) used for alkaline water electrolysis treatment. Examples of the member for an alkaline water electrolysis device include an anode electrode, an electrolytic cell, and other related members used in the alkaline water electrolysis device. Among these, the member for an alkaline water electrolysis device is preferably an anode electrode.

[0055] In the Ni-enriched film, the concentration of Ni with respect to the total of Fe, Ni, and Cr is preferably 20 atomic% or more, more preferably 30 atomic% or more, and still more preferably 35 atomic% or more. By controlling the concentration of Ni in the Ni-enriched film within such a range, the durability (resistance to metal elution) during alkaline water electrolysis can be stably enhanced. The upper limit of the concentration of Ni in the Ni-enriched film is not particularly limited, but is typically 60 atomic% or less. Here, the concentration of Ni in the Ni-enriched film can be measured in the same manner as the method described above. Here, the measurement position of the concentration of Ni in the Ni-enriched film is set at a position 1 nm deep from the surface.

[0056] The thickness of the Ni-enriched film is not particularly limited, but is preferably 1 to 300 nm. If the thickness of the Ni-enriched film is too small, the durability (resistance to metal elution) may decrease when the member for an alkaline water electrolysis device is used as the anode electrode of the alkaline water electrolysis device.

[0057] The member for an alkaline water electrolysis device according to an embodiment of the present invention can be manufactured by disposing the base material made of the above stainless steel material in an alkaline water electrolysis device and performing electrolysis treatment. Specifically, the base material made of the above stainless steel material may be immersed in an alkaline aqueous solution and electrolysis treatment may be performed. The member for an alkaline water electrolysis device according to an embodiment of the present invention can form a Ni-enriched film only by being arranged in the alkaline water electrolysis device and subjected to electrolysis treatment, so that the durability (resistance to metal elution) during alkaline water electrolysis can be ensured without performing pretreatment.

[0058] The electrolysis potential for the electrolysis treatment may be adjusted according to the type of stainless steel material and is not particularly limited. For example, the electrolysis potential for the electrolysis treatment can be the electrolysis potential when the alkaline water electrolysis device actually operates, and is generally 1.0 to 1.8 V (vs. SHE). Note that this electrolysis potential is a potential based on the standard hydrogen electrode (SHE). The electrolysis time for the electrolysis treatment is not particularly limited, but is typically 10 hours or more, for example, 24 to 100 hours. An inorganic compound as a pH adjustment reagent may be added to the alkaline aqueous solution to control the pH of the alkaline aqueous solution. Examples of the inorganic compound include KOH, NaOH, Ca(OH)2, K2CO3, Na2CO3, CaCO3, etc. These can be used alone or in combination. Also, the temperature of the alkaline aqueous solution is not particularly limited, but from the viewpoint of the formation rate of the Ni-enriched film, it is preferably 20 to 90 °C, more preferably 30 to 80 °C.

[0059] <Alkaline water electrolysis treatment device> The alkaline water electrolysis treatment device according to an embodiment of the present invention includes the above stainless steel material or the above member for an alkaline water electrolysis device. By having such a configuration, the alkaline water electrolysis treatment device according to an embodiment of the present invention can ensure the durability (resistance to metal elution) during alkaline water electrolysis because a Ni-enriched film is formed on the surface of the stainless steel material during alkaline water electrolysis treatment, or a Ni-enriched film is pre-formed on the surface of the stainless steel material (base material).

[0060] The alkaline water electrolysis treatment apparatus according to the embodiment of the present invention is not particularly limited in other configurations as long as it has the above configuration. For example, the alkaline water electrolysis treatment apparatus according to the embodiment of the present invention includes an electrolytic cell, an anode electrode, and a cathode electrode. Among these, it is preferable that the electrolytic cell and the anode electrode are composed of the above stainless steel material or the above member for an alkaline water electrolysis apparatus, and it is more preferable that the anode electrode is composed of the above stainless steel material or the above member for an alkaline water electrolysis apparatus.

Example

[0061] Hereinafter, the content of the present invention will be described in detail with reference to examples, but the present invention is not construed as being limited thereto.

[0062] (Examples 1 to 15 and Comparative Examples 1 to 5) A stainless steel plate was produced according to the following procedure. A slab having the composition shown in Table 1 was melted, heated to 1100 °C, and then hot-rolled into a hot-rolled plate with a thickness of 15 mm. Next, the hot-rolled plate was annealed at 1070 °C, pickled, and then cold-rolled into a cold-rolled plate with a thickness of 2 mm. Next, the cold-rolled plate was annealed by isothermal holding at 1070 °C for 300 seconds. Next, the obtained annealed plate was subjected to a solution treatment by isothermal holding at 1100 °C for 300 seconds. Next, the obtained solution-treated plate was finally finish cold-rolled to obtain a finally finished cold-rolled plate with a thickness of 1 mm. Next, the finally finished cold-rolled plate was subjected to mechanical polishing by wet polishing using a #600 grit stone. Note that mechanical polishing was not performed for Comparative Example 3.

[0063]

Table 1

[0064] The following evaluations were performed on the stainless steel plate obtained as described above.

[0065] <Arithmetic mean height Sa of the surface> The arithmetic mean height Sa of the surface of the stainless steel plate was measured in accordance with ISO 25178-2:2012. A laser microscope (VK-X3000 manufactured by Keyence Corporation) was used as the surface roughness measuring device. In the measurement, the surface of the stainless steel plate was observed in one field of view using a 50x objective lens. Five regions of 50 μm × 50 μm were selected from the observed one field of view, and the arithmetic mean height Sa in each region was calculated. The average value of the arithmetic mean height Sa of the five calculated regions was taken as the evaluation result.

[0066] <Ni Concentration Rate Index> A test piece of 50 mm (rolling direction) × 10 mm (width direction) × 2 mm (thickness direction) was taken from the stainless steel plate. Next, regarding the surface of the taken test piece, using FE-AES (JUMP-9510F manufactured by JEOL Ltd.), the depth profile of the elements from the surface was measured. Then, at a position 1 nm deep from the surface, the concentration R of Ni with respect to the total of the remaining elements (Fe, Cr, Ni, and Mn) excluding C and O among the elements to be measured (C, O, Fe, Cr, Ni, and Mn) B was calculated. Next, an alkaline-resistant tape was wound around the taken test piece, and an electrolytic sample was prepared so that only the lower 2 cm of the test piece was electrolyzed. The prepared electrolytic sample was immersed in a 0.1 M KOH aqueous solution at 60 °C, and constant potential electrolysis was performed for 4 hours with the electrolytic potential set at 1.2 V (vs. SHE). Regarding the surface of the sample thus electrolyzed, the depth profile of the elements from the surface was measured in the same manner as above, and the concentration R of Ni with respect to the total of Fe, Cr, Ni, and Mn at a position 1 nm deep from the surface A was calculated. Next, the Ni concentration R A and R B obtained above were used to calculate the Ni concentration rate index according to the above formula (1).

[0067] <Alkaline Electrolysis Test> A test piece of 50 mm (rolling direction) × 10 mm (width direction) × 2 mm (thickness direction) was taken from a stainless steel plate. Next, an alkali-resistant tape was wound around the taken test piece, and an electrolysis sample was prepared so that only the lower 2 cm of the test piece was electrolyzed. The prepared electrolysis sample was immersed in a 0.1 M KOH aqueous solution at 60 °C, and a potentiostatic electrolysis test was conducted under the conditions of the electrolysis potential and electrolysis time shown in Table 2, assuming the actual environment. Next, after the potentiostatic electrolysis test, the KOH aqueous solution was sampled, and the amount of metal elution was measured by ICP-OES (inductively coupled plasma optical emission spectrometry). For ICP-OES, ICPS-8100 manufactured by Shimadzu Corporation was used, the metals to be measured were Fe, Cr, Ni, and Mn, and the total amount of elution of these metals [μg] was divided by the volume [L] and electrolysis time [h] of the KOH aqueous solution to obtain the metal elution amount [μg / (L·h)]. In this evaluation, if the metal elution amount is 1.50 [μg / L·h] or less, it can be determined that the amount of metal elution is small and the durability (metal elution resistance) during alkaline water electrolysis is good. Also, regarding the surface of the sample after the alkaline water electrolysis test, the depth profile of the elements from the surface was measured in the same manner as above, and the concentration of Ni with respect to the total of Fe, Cr, Ni, and Mn in the Ni-enriched film (at a position 1 nm deep from the surface) was calculated. The above evaluation results are shown in Table 2.

[0068]

Table 2

[0069] As shown in Table 2, since Examples 1 to 15 have a predetermined composition, the amount of metal elution is small, and the durability (metal elution resistance) during alkaline water electrolysis could be ensured. On the other hand, in Comparative Example 1, since the Ni content was too low, the Ni enrichment rate index was low, and an appropriate Ni-enriched film was not formed, so the amount of metal elution increased. In Comparative Example 2, since the Mn content was too low, the Ni enrichment rate index was low, and an appropriate Ni-enriched film was not formed, so the amount of metal elution increased. In Comparative Example 3, since the Cr content was too low, corrosion resistance could not be ensured, resulting in an increase in the amount of metal elution. In Comparative Example 4, since the Ca content was too low, deoxidation became insufficient and inclusions increased, resulting in an increase in the amount of metal elution. In Comparative Example 5, since the S content was too high, a large number of inclusions were generated and a uniform Ni-enriched film was not formed, resulting in an increase in the amount of metal elution.

[0070] As can be seen from the above results, according to the present invention, it is possible to provide a Ni-saving stainless steel material for an alkaline water electrolysis device that can provide a member for an alkaline water electrolysis device capable of ensuring durability (resistance to metal elution) during alkaline water electrolysis without performing pretreatment. Further, according to the present invention, it is possible to provide a member for an alkaline water electrolysis device capable of ensuring durability (resistance to metal elution) during alkaline water electrolysis without performing pretreatment and a method for manufacturing the same. Furthermore, according to the present invention, it is possible to provide an alkaline water electrolysis treatment device including the stainless steel material for an alkaline water electrolysis device or the member for an alkaline water electrolysis device having the above characteristics.

Claims

1. A stainless steel material for an alkaline water electrolysis device, containing, by mass, C: 0.100% or less, Si: 1.00% or less, Mn: 3.00 - 12.00%, Ni: 7.00 - 9.00%, P: 0.0030% or less, S: 0.0030% or less, Cr: 10.0 - 18.0%, N: 0.01 - 0.25%, Cu: 0.01 - 1.00%, Mo: 0.01 - 1.00%, Al: 0.005 - 0.080%, B: 0.0001 - 0.0100%, Ca: 0.0005 - 0.0100%, and O: 0.0100% or less, with the balance being Fe and impurities.

2. The stainless steel material for an alkaline water electrolysis device according to Claim 1, further containing one or more selected from Nb: 0.50% or less, Ti: 0.50% or less, Mg: 0.0050% or less, Zr: 0.50% or less, Co: 0.50% or less, V: 0.50% or less, W: 0.50% or less, REM: 0.100% or less, and Sn: 0.100% or less.

3. The stainless steel material for an alkaline water electrolysis device according to Claim 1 or 2, wherein the arithmetic mean height Sa of the surface is 0.70 μm or less.

4. The stainless steel material for an alkaline water electrolysis device according to Claim 1 or 2, wherein the Ni concentration rate index represented by the following formula (1) is 6.5 or more. Ni concentration rate index = (R A - R B ) / 4... (1) In the formula, R A is the concentration (atomic %) of Ni with respect to the total of Fe, Cr, Ni, and Mn at a depth of 1 nm from the surface after immersing the stainless steel material for the alkaline water electrolysis device in a 0.1 M KOH aqueous solution at 60°C and electrolyzing it at a potential of 1.2 V (vs. SHE) for 4 hours, and R B is the concentration (atomic %) of Ni with respect to the total of Fe, Cr, Ni, and Mn at a depth of 1 nm from the surface before the electrolysis.

5. A member for an alkaline water electrolysis device, comprising a base material made of the stainless steel material for an alkaline water electrolysis device according to Claim 1 or 2, and a Ni-enriched film formed on the surface of the base material.

6. The member for an alkaline water electrolysis device according to Claim 5, wherein the Ni concentration in the Ni-enriched film is 20 atomic% or more with respect to the total of Fe, Ni, and Cr.

7. A method for manufacturing a member for an alkaline water electrolysis device, comprising disposing a base material made of the stainless steel material for an alkaline water electrolysis device according to Claim 1 or 2 in an alkaline water electrolysis device and performing electrolysis treatment.

8. An alkaline water electrolysis treatment device comprising the stainless steel material for an alkaline water electrolysis device according to Claim 1 or 2, or the member for an alkaline water electrolysis device according to Claim 5.

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