JP7589098B2 - Fuel cell separator and fuel cell - Google Patents

Description

The present invention relates to a fuel cell separator and a fuel cell.

Fuel cells are used as an energy source for a variety of applications, including household use, automobiles, and mobile devices, because they generate electricity efficiently and emit almost no harmful exhaust gases. Fuel cells can be classified according to the type of electrolyte, and known types include phosphoric acid fuel cells (PAFCs), molten carbonate fuel cells (MCFCs), solid oxide fuel cells (SOFCs), and polymer electrolyte fuel cells (PEFCs). Among these, polymer electrolyte fuel cells can be operated at low temperatures of around 80°C, making them easier to handle than other fuel cells, and they also have the advantage of having a high output density.

In a polymer electrolyte fuel cell, a proton-conductive polymer membrane is usually used as the electrolyte. A pair of electrodes, the fuel electrode and the oxygen electrode, are attached to both sides of the electrolyte and integrated to form an electrode assembly. The electrode assembly is sandwiched between separators to form a single cell. A polymer electrolyte fuel cell comprises a cell stack in which these single cells are connected in series. By supplying a fuel gas such as hydrogen or hydrocarbon to the fuel electrode and an oxidant gas such as oxygen or air to the oxygen electrode, an electrochemical reaction is caused to proceed at the three-phase interface between the gas, electrolyte, and electrode, and electricity can be extracted.

Because separators are required to function as a conductor for transporting generated electrons and as a flow path for gas in addition to functioning as a barrier between single cells, materials such as graphite and titanium alloys have been used as separator materials. However, separators made of carbon have the disadvantages of being easily damaged by impact, being difficult to make compact, and requiring high processing costs to form the flow paths. Separators made of titanium alloys also have the disadvantage of being expensive. In particular, the issue of cost can be the biggest obstacle to the widespread use of fuel cells. Therefore, the use of stainless steel as a separator material is being considered.

On the other hand, the polymer membrane used as an electrolyte has proton conductivity when it contains water. In order to maintain the proton conductivity of the polymer membrane, the fuel gas and the oxidant gas are generally supplied to the electrodes after being humidified with humidifying water. In addition, water is generated by an electrochemical reaction at the oxygen electrode. Thus, water is always present inside the solid polymer fuel cell, and the water moves between the two electrodes by electroosmosis and diffusion. Therefore, if stainless steel is used as the material for the separator, when the solid polymer fuel cell is operated for a long period of time, metal ions may be eluted from the stainless steel into the humidifying water or the generated water, causing corrosion of the stainless steel. The eluted metal ions exchange with protons of the functional groups (e.g., sulfonic acid groups) of the polymer membrane. As a result, the proton conductivity of the polymer membrane is inhibited, which may lead to a decrease in battery performance, such as an increase in the internal resistance of the battery and a decrease in voltage. In addition, the eluted metal ions may be reduced at the fuel electrode and precipitate as metal ions, or may become hydroxides or oxides and precipitate at the oxygen electrode. If metals or other substances are deposited on these electrodes, the electrode area will decrease and the electrochemical reaction will be inhibited, resulting in a decrease in battery performance.

Thus, Patent Document 1 proposes a stainless steel for fuel cells that has excellent corrosion resistance and can be used in fuel cells. The stainless steel contains 16% by mass or more of Cr and has a coating obtained by subjecting the surface of the stainless steel to anodic electrolysis in an electrolyte solution containing sodium sulfate, the coating having an intensity ratio [(OO/OH)/(Cr/Fe)] of 1.0 or more as determined by X-ray photoelectron spectroscopy.
Patent Document 2 also describes a steel sheet containing, on a mass basis, C: 0.02 to 0.14%, Mn: 0.5 to 1.75%, Mo: 2.35 to 10%, Ni: 5.15 to 25%, and Cr: 23% or less, and the contents of Cr, Mo, and Ni are 10-0.3×([Cr%]+3×[Mo%]+0.05×[Ni%])≦4
There has been proposed a stainless steel for polymer electrolyte fuel cells, characterized in that the content of the elements is such that the balance consists of Fe and unavoidable impurities.

Patent No. 4811529 Patent No. 4276325

In recent years, with the demand for cost reduction of fuel cells, there has been a demand for improving the manufacturability (hot workability) and processability of stainless steels used as materials for separators. However, the manufacturability and processability of conventional stainless steels used in fuel cells cannot be said to be sufficient.
Furthermore, the elution of metal ions from stainless steel is affected by the concentration of fluoride ions ( ^F- ) and chloride ions ( ^Cl- ) contained in the humidified water and the generated water. For example, when components contained in the catalytic layer of the electrode (e.g., sulfurous acid, organic acids, ammonia, etc.) or components generated by thermal deterioration of the catalytic layer of the electrode or the electrolyte (e.g., hydrofluoric acid, sulfuric acid, etc.) dissolve in the humidified water or the generated water, the elution of metal ions is thought to be accelerated. The corrosion resistance of conventional stainless steels used in fuel cells in environments containing fluoride ions and chloride ions has not been fully studied, and it cannot be said that they have sufficient corrosion resistance.

The present invention has been made to solve the above problems, and aims to provide a fuel cell separator that is made from a material that is easy to manufacture and process, and that has good corrosion resistance even in an environment that contains fluoride ions and chloride ions, and a fuel cell that includes this fuel cell separator.

The present inventors have conducted intensive research focusing on austenitic stainless steel sheets as a material for fuel cell separators. In order to improve the manufacturability of austenitic stainless steel sheets, it is desirable to increase the content of the δ ferrite phase (hereinafter referred to as the "δ phase"), which has a high solid solubility of P and S in a solidified state. However, if the content of the δ phase increases, cracks are more likely to occur due to the difference in strength with the austenite phase (hereinafter referred to as the "γ phase"). Therefore, it is necessary to control the content of the δ phase within an appropriate range, but if the content of expensive Ni is reduced, the content of the δ phase increases. Therefore, in order to ensure a balance between the δ phase and the γ phase, it is necessary to add γ-generating elements (Mn, Cu, N, etc.). However, if the content of Mn or Cu is increased, the corrosion resistance decreases, and if the content of N is increased, the hardness increases and the workability decreases. In view of these points, the present inventors have optimized the composition of the austenitic stainless steel sheet, and have found that the above problems can be solved by making it a specific composition, and have completed the present invention.

That is, the present invention provides a fuel cell separator composed of an austenitic stainless steel plate containing, by mass, 0.060 to 0.080% C, 0.3 to 0.7% Si, 0.7 to 1.2% Mn, 0.035% or less P, 0.030% or less S, 7.0 to 9.0% Ni, 20.0 to 22.0% Cr, 0.5% or less Mo, 0.1 to 0.5% Cu, 0.02% or less Al, 0.100 to 0.160% N, with the balance being Fe and impurities, and having an A value, represented by the following formula (1), of -2 to 5.5.
A=3(Cr+Mo)+4.5Si-2.8Ni-1.4(Mn+Cu)-84(C+N)-19.8 (1)
In the formula, Cr, Mo, Si, Ni, Mn, Cu, C and N represent the content (mass%) of each element.

The present invention also relates to a fuel cell that includes the above fuel cell separator.

The present invention provides a fuel cell separator that is made of a material that is easy to manufacture and process, and has good corrosion resistance even in an environment that contains fluoride ions and chloride ions, and a fuel cell that includes this fuel cell separator.

The following is a detailed description of the embodiments of the present invention. The present invention is not limited to the following embodiments, and it should be understood that modifications and improvements to the following embodiments, which are made based on the ordinary knowledge of those skilled in the art, fall within the scope of the present invention, without departing from the spirit of the present invention.
In this specification, the "%" designation for components means "% by mass" unless otherwise specified.

A fuel cell separator according to an embodiment of the present invention is made of an austenitic stainless steel plate.
The structure of the fuel cell separator is not particularly limited and may be any structure known in the art. For example, the fuel cell separator may have flow paths (grooves) through which a fuel gas and an oxidant gas can flow.

The austenitic stainless steel plate, which is the material for fuel cell separators, contains C: 0.060-0.080%, Si: 0.3-0.7%, Mn: 0.7-1.2%, P: 0.035% or less, S: 0.030% or less, Ni: 7.0-9.0%, Cr: 20.0-22.0%, Mo: 0.5% or less, Cu: 0.1-0.5%, Al: 0.02% or less, N: 0.100-0.160%, and the balance being Fe and impurities.
In this specification, the term "impurities" refers to components that are mixed in due to various factors in raw materials such as ores and scraps and in the manufacturing process during industrial production of austenitic stainless steel sheet, and which are acceptable within a range that does not adversely affect the present invention.

The above austenitic stainless steel sheet may further contain B: 0.001 to 0.004%.
The above austenitic stainless steel sheet may further contain one or more selected from Ca: 0.0001 to 0.10%, Mg: 0.0001 to 0.1%, and REM: 0.0001 to 0.10%.
Furthermore, the above-mentioned austenitic stainless steel sheet may further contain one or more selected from Ti: 0.001 to 1.0%, Nb: 0.001 to 1.0%, V: 0.001 to 1.0%, and Zr: 0.001 to 1.0%.
Each component will be described in detail below.

<C: 0.060-0.080%>
If the C content is too high, the corrosion resistance of the austenitic stainless steel sheet is reduced. Therefore, the upper limit of the C content is set to 0.080%, preferably 0.078%, and more preferably 0.075%. %. On the other hand, if the C content is too low, it leads to an increase in refining costs. Therefore, the lower limit of the C content is 0.060%, preferably 0.065%, and more preferably 0.080%. It is controlled to 0.070%.
In this specification, the term "corrosion resistance" refers to corrosion resistance in the separator environment of a fuel cell, particularly in an environment containing fluoride ions and chloride ions. The concentrations of are not particularly limited, but their typical concentrations are 3 ppm and 20 ppm, respectively.

<Si: 0.3 to 0.7%>
If the Si content is too high, the workability of the austenitic stainless steel sheet decreases. Therefore, the upper limit of the Si content is set to 0.7%, preferably 0.68%, and more preferably 0. On the other hand, if the Si content is too low, the oxidation resistance of the austenitic stainless steel sheet may decrease. Therefore, the lower limit of the Si content is set to 0.3%, preferably 0.65%. is controlled to 0.32%, more preferably 0.35%.

<Mn: 0.7 to 1.2%>
Mn is an element that produces the austenite phase (γ phase). If the Mn content is too high, the corrosion resistance of the austenitic stainless steel sheet will decrease. Therefore, the upper limit of the Mn content is set to 1.2%. The Mn content is controlled to be preferably 1.18%, and more preferably 1.15%. On the other hand, if the Mn content is too low, the amount of γ phase decreases, so that it is necessary to ensure an appropriate balance between the δ phase and the γ phase. Therefore, the lower limit of the Mn content is controlled to 0.7%, preferably 0.75%, and more preferably 0.8%.

<P: 0.035% or less>
If the P content is too high, the workability of the austenitic stainless steel sheet is reduced. Therefore, the upper limit of the P content is set to 0.035%, preferably 0.034%, and more preferably 0. On the other hand, the lower limit of the P content is not particularly limited, but is preferably 0.001%, more preferably 0.005%, and further preferably 0.010%.

<S: 0.030% or less>
If the S content is too high, the manufacturability of the austenitic stainless steel sheet decreases. Therefore, the upper limit of the S content is set to 0.030%, preferably 0.025%, and more preferably 0. On the other hand, the lower limit of the S content is not particularly limited, but is preferably 0.0001%, more preferably 0.0003%, and further preferably 0.0005%.

<Ni: 7.0-9.0%>
Ni, like Mn, is an element that forms the austenite phase (γ phase). Since Ni is expensive, if the Ni content is too high, the manufacturing cost increases. Therefore, the upper limit of the Ni content is set to be The Ni content is controlled to 9.0%, preferably 8.9%, and more preferably 8.8%. On the other hand, if the Ni content is too low, the workability of the austenitic stainless steel sheet is reduced. The lower limit of the content is controlled to 7.0%, preferably 7.5%, and more preferably 7.8%.

<Cr:20.0-22.0%>
If the Cr content is too high, the formation of intermetallic compounds (σ phase) is promoted, which reduces the workability of the austenitic stainless steel sheet. Therefore, the upper limit of the Cr content is set to 22. The Cr content is controlled to 0%, preferably 21.8%, and more preferably 21.5%. On the other hand, if the Cr content is too low, sufficient corrosion resistance cannot be obtained. Therefore, the lower limit of the Cr content is is controlled to 20.0%, preferably 20.5%.

<Mo: 0.5% or less>
Since Mo is expensive, if the Mo content is too high, the manufacturing cost increases. Therefore, the upper limit of the Mo content is controlled to 0.5%, preferably 0.3%, and more preferably 0.15%. On the other hand, the lower limit of the Mo content is not particularly limited, but is preferably 0.001%, more preferably 0.002%, and further preferably 0.003%.

<Cu: 0.1 to 0.5%>
If the Cu content is too high, the corrosion resistance of the austenitic stainless steel sheet is reduced. Therefore, the upper limit of the Cu content is set to 0.5%, preferably 0.4%, and more preferably 0.3%. On the other hand, if the Cu content is too low, the workability of the austenitic stainless steel sheet is reduced. Therefore, the lower limit of Cu is set to 0.1%, preferably 0.12%, More preferably, it is controlled to 0.15%.

<Al: 0.02% or less>
If the Al content is too high, the amount of inclusions generated increases, degrading the quality. Therefore, the upper limit of the Al content is set to 0.02%, preferably 0.018%, and more preferably 0.02%. On the other hand, the lower limit of the Al content is not particularly limited, but is preferably 0.0001%, more preferably 0.0002%, and further preferably 0.0003%.

<N: 0.100-0.160%>
If the N content is too high, the workability of the austenitic stainless steel sheet is reduced. Therefore, the upper limit of the N content is controlled to 0.160%. If the N content is too low, the amount of γ phase will be reduced, making it difficult to ensure a proper balance between the δ phase and the γ phase, and the manufacturability of the austenitic stainless steel sheet will decrease. It is controlled to 100%, preferably 0.105%, and more preferably 0.110%.

<B: 0.001-0.004%>
If the B content is too high, the corrosion resistance of the austenitic stainless steel sheet is reduced. Therefore, the upper limit of the B content is controlled to 0.004%, preferably 0.003%. If the B content is too low, the manufacturability of the austenitic stainless steel sheet decreases, so the lower limit of the B content is controlled to 0.001%, preferably 0.002%.

<Ca: 0.0001-0.10%>
Ca is an element that is added as necessary to improve hot workability. From the viewpoint of obtaining the effect of Ca, the lower limit of the Ca content is 0.0001%, preferably 0.0005%. %, and more preferably 0.001%. If the Ca content is too high, the amount of inclusions produced increases, lowering the quality. Therefore, the upper limit of the Ca content is set to 0.001%. is controlled to 0.10%, preferably 0.05%, and more preferably 0.01%.

<Mg: 0.0001-0.1%>
Mg is an element that is added as necessary to improve hot workability. From the viewpoint of obtaining the effect of Mg, the lower limit of the Mg content is 0.0001%, preferably 0.0005%. %, and more preferably 0.001%. If the Mg content is too high, the amount of inclusions produced increases, lowering the quality. Therefore, the upper limit of the Mg content is set to 1. is controlled to 0.1%, preferably 0.05%, and more preferably 0.01%.

<REM: 0.0001-0.10%>
REM is an element that is added as necessary to improve hot workability. From the viewpoint of obtaining the effect of REM, the lower limit of the content of REM is 0.0001%, preferably 0.0005%. %, more preferably 0.001%. In addition, since REM is expensive, if the REM content is too high, the manufacturing cost increases. Therefore, the upper limit of the REM content is It is controlled to 0.10%, preferably 0.05%, and more preferably 0.01%.

<Ti: 0.001-1.0%>
Ti is an element that is added as necessary to fix C in the steel and improve intergranular corrosion resistance. From the viewpoint of obtaining the effect of Ti, the lower limit of the Ti content is 0. The Ti content is controlled to 0.001%, preferably 0.005%, and more preferably 0.010%. If the Ti content is too high, the workability of the austenitic stainless steel decreases. The upper limit of the content is controlled to 1.0%, preferably 0.8%, and more preferably 0.5%.

<Nb: 0.001 to 1.0%>
Nb is an element that is added as necessary to fix C in the steel and improve intergranular corrosion resistance. From the viewpoint of obtaining the effect of Nb, the lower limit of the Nb content is 0. The Nb content is controlled to 0.001%, preferably 0.005%, and more preferably 0.010%. If the Nb content is too high, the workability of the austenitic stainless steel decreases. The upper limit of the content is controlled to 1.0%, preferably 0.8%, and more preferably 0.5%.

<V: 0.001-1.0%>
V is an element that is added as necessary to fix C in the steel and improve intergranular corrosion resistance. From the viewpoint of obtaining the effect of V, the lower limit of the V content is 0. The V content is controlled to 0.001%, preferably 0.005%, and more preferably 0.010%. If the V content is too high, the workability of the austenitic stainless steel decreases. The upper limit of the content is controlled to 1.0%, preferably 0.8%, and more preferably 0.5%.

<Zr: 0.001 to 1.0%>
Zr is an element that is added as necessary to fix C in the steel and improve intergranular corrosion resistance. From the viewpoint of obtaining the effect of Zr, the lower limit of the Zr content is 0. The Zr content is controlled to 0.001%, preferably 0.005%, and more preferably 0.010%. If the Zr content is too high, the workability of the austenitic stainless steel is reduced. The upper limit of the content is controlled to 1.0%, preferably 0.8%, and more preferably 0.5%.

The austenitic stainless steel sheet has an A value, represented by the following formula (1), of -2 to 5.5, preferably -1.8 to 5.4, and more preferably -1.5 to 5.3.
A=3(Cr+Mo)+4.5Si-2.8Ni-1.4(Mn+Cu)-84(C+N)-19.8 (1)
In the formula, Cr, Mo, Si, Ni, Mn, Cu, C and N represent the content (mass%) of each element.
By controlling the A value within the above range, it is possible to achieve both manufacturability and workability of the austenitic stainless steel sheet. In particular, by setting the A value to -2 or more, oxidation of the grain boundaries can be suppressed, making it difficult for oxide scale to remain. Furthermore, by setting the A value to 5.5 or less, edge cuts during the production of the austenitic stainless steel sheet can be suppressed, and elongation that allows the austenitic stainless steel sheet to be processed into a separator shape can be ensured during processing.

The austenitic stainless steel sheet is a cold-rolled annealed sheet. This austenitic stainless steel sheet can be manufactured by using a method known in the art, except for melting stainless steel having the above composition. Specifically, it can be manufactured as follows. First, stainless steel having the above composition is melted and forged or cast, and then hot-rolled to obtain a hot-rolled sheet. Next, the hot-rolled sheet is appropriately annealed, pickled, and cold-rolled to obtain a cold-rolled sheet. Next, the cold-rolled sheet is appropriately annealed and pickled to obtain a cold-rolled annealed sheet.
The conditions for each step may be appropriately adjusted depending on the composition of the stainless steel, and are not particularly limited.

Austenitic stainless steel sheets with the above characteristics are not only easy to manufacture and process, but also have good corrosion resistance in environments containing fluoride ions and chloride ions, making them suitable for use as materials for fuel cell separators.

Fuel cell separators can be manufactured by using the above-mentioned austenitic stainless steel plate as a material and forming it into a desired shape by a known method such as press forming. For example, a fuel cell separator can be made by forming flow paths (grooves) through which fuel gas and oxidant gas can flow in the above-mentioned austenitic stainless steel plate using press forming.

A fuel cell according to an embodiment of the present invention includes a fuel cell separator using the above-mentioned austenitic stainless steel plate as its material.
The structure of the fuel cell is not particularly limited, and any structure known in the art can be applied. A typical fuel cell includes a unit cell composed of a polymer membrane, electrodes (fuel electrode and oxygen electrode) arranged on both sides of the polymer membrane, and fuel cell separators arranged on both sides of the electrodes. The fuel cell includes a cell stack in which the unit cells are connected in series.

In a fuel cell having the above structure, fuel gas such as hydrogen or hydrocarbon is passed through the flow path between the fuel cell separator and the fuel electrode, thereby supplying the fuel gas to the fuel electrode. In addition, oxidant gas such as oxygen or air is passed through the flow path between the fuel cell separator and the oxygen electrode, thereby supplying the oxidant to the oxygen electrode. By supplying these gases to each electrode, an electrochemical reaction occurs, generating a direct current between the fuel electrode and the oxygen electrode.

The present invention will be described in detail below with reference to examples, but the present invention should not be construed as being limited to these.

30 kg of stainless steel having the composition shown in Table 1 was vacuum melted, forged into a plate with a thickness of 30 mm, heated at 1230°C for 2 hours, and hot rolled to a thickness of 4 mm to obtain a hot-rolled plate. Next, the hot-rolled plate was annealed and pickled to obtain a hot-rolled annealed plate, and the hot-rolled annealed plate was cold rolled to obtain a cold-rolled plate. Next, the cold-rolled plate was annealed, water-cooled, and pickled to obtain a cold-rolled annealed plate (austenitic stainless steel plate). Note that Comparative Example 9 is a steel type equivalent to SUS316L, which contains a large amount of expensive Ni and Mo.

The following evaluations were carried out on the cold-rolled annealed sheet obtained above, as well as its intermediate materials, the hot-rolled sheet and the hot-rolled annealed sheet.

<Manufacturability>
The manufacturability was evaluated by measuring the maximum edge cut length of the hot-rolled sheet and observing the oxide scale on the surface of the hot-rolled and annealed sheet.
The maximum edge cut length of the hot-rolled sheet was determined by measuring the edge cut length of the hot-rolled sheet and taking the maximum value as the maximum edge cut length.
In addition, the surface of the hot-rolled and annealed sheet was scraped off by 20 μm in the thickness direction, and then the presence or absence of black oxide scale on the surface was evaluated.
In the evaluation of manufacturability, those in which the maximum edge cut length was 3 mm or less and no oxide scale was observed were rated as pass (◯), and those in which the maximum edge cut length exceeded 3 mm and/or oxide scale was observed were rated as fail (×).

<Processability>
The workability was evaluated using a cold-rolled annealed sheet obtained by cold rolling to a thickness of 0.3 mm, annealing, water cooling, and pickling. The workability was evaluated in accordance with the tensile test method specified in JIS Z2241:2011. Specifically, a No. 13B test piece was cut out from the center of the width direction of the cold-rolled annealed sheet, and a tensile test was performed at a tensile speed of 20 mm/min to measure the elongation (%). In this evaluation, a specimen that achieved 50% elongation that can be processed into a separator shape was evaluated as pass (◯), and a specimen that achieved less than 50% elongation was evaluated as fail (×).

<Corrosion resistance>
The corrosion resistance was evaluated using a cold-rolled annealed sheet obtained by cold rolling to a thickness of 1.0 mm, annealing, water cooling and pickling. The cold-rolled annealed sheet was cut into a test piece of 30 mm x 30 mm from the center in the width direction, and a hole with a diameter of 6.5 mm was drilled in the center. Next, after wet polishing with #600 on this test piece, a resin crevice forming material standardized in ASTM G78 was placed on both sides of the test piece, and the test piece was tightened with a torque of 1.0 N·m using bolts and nuts to obtain a crevice corrosion test piece. Next, the crevice corrosion test piece was immersed in a sulfuric acid solution (pH 3) at 90 ° C. containing 3 ppm fluoride ions and 20 ppm chloride ions, and electrolysis was performed at 0.9 V vs. SHE for 6 hours, and the total amount of electricity was measured. In this evaluation, if the amount of electricity was 2 C or less, it was considered that there were few eluted metal ions, and therefore it was judged as pass (◯), and if the amount of electricity exceeded 2 C, it was judged as fail (×).

The results of each of the above evaluations are shown in Table 2.

As shown in Table 2, the austenitic stainless steel sheets of Examples 1 to 4 satisfied the prescribed composition and A value, and therefore were excellent in manufacturability, workability, and corrosion resistance.
On the other hand, the austenitic stainless steel sheets of Comparative Examples 1 and 2 had insufficient manufacturability because the A value was outside the range. The austenitic stainless steel sheet of Comparative Example 3 had insufficient workability because the Cu content was too low. The austenitic stainless steel sheet of Comparative Example 4 had insufficient workability because the Cr and N contents were too high. The austenitic stainless steel sheet of Comparative Example 5 had insufficient corrosion resistance because the Cr content was too low. The austenitic stainless steel sheet of Comparative Example 6 had insufficient manufacturability and workability because not only the Ni, Cr, Al, and N contents but also the A value were too high. The austenitic stainless steel sheet of Comparative Example 7 had insufficient manufacturability and corrosion resistance because the Mn and Ni contents were too high, the Cr content was too low, and the A value was also too high. The austenitic stainless steel sheet of Comparative Example 8 had insufficient workability and corrosion resistance because the Ni and Cr contents were too low and the N content was too high. The austenitic stainless steel sheet of Comparative Example 9 is excellent in all respects of manufacturability, workability and corrosion resistance, but contains large amounts of expensive Ni and Mo, resulting in high manufacturing costs.

As can be seen from the above results, the present invention can provide a fuel cell separator that is made from a material that is easy to manufacture and process, and that has good corrosion resistance even in an environment that contains fluoride ions and chloride ions, as well as a fuel cell that includes this fuel cell separator.

Claims (5)

A separator for a fuel cell composed of an austenitic stainless steel plate containing, by mass, 0.060 to 0.080% C, 0.3 to 0.7% Si, 0.7 to 1.2% Mn, 0.035% or less P, 0.030% or less S, 7.0 to 9.0% Ni, 20.0 to 22.0% Cr, 0.5% or less Mo, 0.1 to 0.5% Cu, 0.02% or less Al, 0.100 to 0.160% N, with the balance being Fe and impurities, and having an A value, represented by the following formula (1), of -2 to 5.5.
A=3(Cr+Mo)+4.5Si-2.8Ni-1.4(Mn+Cu)-84(C+N)-19.8 (1)
In the formula, Cr, Mo, Si, Ni, Mn, Cu, C and N represent the content (mass%) of each element. The fuel cell separator according to claim 1, wherein the austenitic stainless steel plate further contains, by mass, 0.001 to 0.004% B. The fuel cell separator according to claim 1 or 2, wherein the austenitic stainless steel plate further contains, by mass, one or more selected from Ca: 0.0001-0.10%, Mg: 0.0001-0.1%, and REM: 0.0001-0.10%. The fuel cell separator according to any one of claims 1 to 3, wherein the austenitic stainless steel plate further contains, by mass, one or more selected from Ti: 0.001 to 1.0%, Nb: 0.001 to 1.0%, V: 0.001 to 1.0%, and Zr: 0.001 to 1.0%. A fuel cell comprising a fuel cell separator according to any one of claims 1 to 4.