JP4174722B2 - Ni-based alloy with extremely low ion elution in a polymer electrolyte fuel cell environment - Google Patents

Description

  The present invention relates to a Ni-based alloy having a remarkably small amount of ion elution in a polymer electrolyte fuel cell environment, and the present invention relates to a solid used for stacking and assembling unit cells of a polymer electrolyte fuel cell. The present invention relates to an assembly structure member for a solid polymer fuel cell made of a Ni-based alloy having a remarkably small amount of ion elution in a polymer fuel cell environment.

In recent years, a polymer electrolyte fuel cell that operates at a low temperature from room temperature to 80 ° C. is expected to be used for in-vehicle use and portable use because it can be made compact, and its development is being advanced rapidly. The structure of the polymer electrolyte fuel cell is shown in the schematic explanatory diagram of FIG. In FIG. 1, 1 is a hydrogen electrode, 2 is an oxygen electrode, 3 is a platinum catalyst, 4 is a solid electrolyte membrane, and 5 is a unit cell. The unit cell 5 is formed by providing platinum catalysts 3, 3 ′ on both surfaces of the solid electrolyte membrane 4, providing the hydrogen electrode 1 outside the platinum catalyst 3, and providing the oxygen electrode 2 outside the platinum catalyst 3 ′. The unit cells 5 are separated by a separator 6 to form a solid polymer fuel cell. In order to form a polymer electrolyte fuel cell by laminating a plurality of unit cells 5 separated by separators 6, the plurality of unit cells 5 are separated from each other by separators 6 using at least two support plates 7 and fastening tools 8 such as bolts and nuts. Laminated and fixed with a gap.

  The principle of power generation in the unit cell 5 of the polymer electrolyte fuel cell having such a structure is as follows. That is, when hydrogen obtained from natural gas or methanol is supplied to the hydrogen electrode 1, the supplied hydrogen is decomposed into hydrogen ions and electrons by the platinum catalyst 3 on the hydrogen electrode 1 side, and the electrons are taken out as electricity. The oxygen electrode 2 is reached through an external load circuit (not shown). On the other hand, hydrogen ions move to the oxygen electrode 2 side through the solid electrolyte membrane 4 made of a solid polymer ion exchange membrane that passes only hydrogen ions, and on the oxygen electrode 2 side, hydrogen ions and electrons are moved by the platinum catalyst 3 '. And oxygen react to produce water. The solid electrolyte membrane 4 has a role of allowing hydrogen gas to permeate as hydrogen ions. For this purpose, the solid electrolyte membrane 4 needs to be wet. On the oxygen electrode 2 side, hydrogen ions, electrons, and oxygen react to generate water, so that there is no problem with wet retention of the solid electrolyte membrane 4, but the hydrogen electrode 1 side separated by the solid electrolyte membrane 4 is As it is, it will dry because there is no water to be supplied. Therefore, in order to ensure the wetness of the solid electrolyte membrane on the hydrogen electrode 1 side, the water 9 discharged from the oxygen electrode 2 side is received by the manifold 10, passes through the pipe 11, and is pumped to the solid electrolyte membrane on the hydrogen electrode 1 side. 4 is supplied.

  As described above, the water 9 discharged from the oxygen electrode 2 side is received by the manifold 10 and supplied to the solid electrolyte membrane 4 on the hydrogen electrode 1 side by the pump 12 through the pipe 11, whereby the solid electrolyte on the hydrogen electrode 1 side is supplied. Although wetting of the membrane is ensured, the solid electrolyte membrane 4 normally used in the polymer electrolyte fuel cell is sulfonated, so that it is discharged from the oxygen electrode 2 side due to these. Since the water 9 is sulfuric acid acid and has a weak corrosivity, the manifold 10 and the pipe 11 that receive the water 9 need to have corrosion resistance.

Further, the solid electrolyte membrane used in the polymer electrolyte fuel cell may be subjected to fluorination treatment instead of sulfonation treatment, and as a result, water 9 discharged from the oxygen electrode 2 side is caused. Becomes hydrofluoric acid acidic, and the manifold 10 and the pipe 11 that receive the water 9 are similarly required to have corrosion resistance.
Further, the hydrogen electrode 1 and the oxygen electrode 2 are provided with through holes (not shown), and the sulfuric acid acid or hydrofluoric acid water 9 discharged from the oxygen electrode 2 side has the through holes (not shown). Through the contact with the separator 6, sulfuric acid or hydrofluoric acid water 9 discharged from the oxygen electrode 2 side and circulated to the hydrogen electrode 1 side also contacts the separator 6 through a through hole (not shown). To do. Therefore, the separator 6 is also required to have corrosion resistance.

Stainless steel such as SUS316L is generally used as a material for the manifold 10, pipe 11, separator 6, etc. that require such corrosion resistance, and the sulfuric acid acid or hydrofluoric acid acid water produced on the oxygen electrode 2 side is used as a support plate. 7. Stainless steel such as SUS316L is generally used for the support plate 7 and the fastening tools 8 such as bolts and nuts because they adhere to the fastening tools 8 such as bolts and nuts by being scattered and corroding them. ing. That is, the structural member excluding the unit cell 5 for assembling the solid polymer fuel cell, such as the support plate 7, the fastening tool 8, the manifold 10, the pipe 11, and the separator (hereinafter referred to as an assembly structural member for the polymer electrolyte fuel cell). ) Is known to use stainless steel such as SUS316L (see Patent Document 1, Patent Document 2, Patent Document 3, etc.).
JP 2001-6714 A JP 2000-299121 A JP 2000-331696 A

  In general, if the corrosion rate (mm / year) before and after the corrosion test is less than 0.1 mm / year, it is judged as excellent as an assembly structure member for a polymer electrolyte fuel cell, and the corrosion resistance of stainless steel is also judged as excellent. ing. However, stainless steel has a large amount of elution of metal ions, and the eluted metal ions cause the solid electrolyte membrane to be remarkably reduced because it degrades the solid electrolyte membrane. Therefore, the development of a metal material with a very small amount of metal ion elution has been demanded.

  Therefore, the present inventors have intensively studied to obtain a metal material with extremely little metal ion elution in a polymer electrolyte fuel cell environment. As a result, the Ni-based alloy containing Cr: 43% to 50% by mass% (hereinafter,% represents mass%) is Mo: 0.1-2%, Mg: 0.001-0.05% , N: 0.001 to 0.04%, Mn: 0.05 to 0.5%, Fe: 0.05 to 1.0% and Si: 0.01 to A Ni-based alloy having a composition containing 0.1% of one or two types, the balance being Ni and inevitable impurities, and adjusting C as an inevitable impurity to 0.05% or less is a solid polymer fuel Since the corrosion rate (mm / year) before and after the corrosion test in the battery environment is less than 0.1 mm / year and the ion elution amount is extremely small in the solid polymer fuel cell environment, this Ni-based alloy is a solid polymer. Stainless steel as an assembly structural member for fuel cell It was obtained a finding that has even more excellent effect.

This invention has been made based on such knowledge,
(1) Cr: more than 43-50%, Mo: 0.1-2%, Mg: 0.001-0.05%, N: 0.001-0.04%, Mn: 0.05-0. Ni base with a remarkably small amount of ion elution in a polymer electrolyte fuel cell environment having a composition comprising 5%, the balance being Ni and inevitable impurities, and the amount of C contained as inevitable impurities being adjusted to 0.05% or less Assembly structure member for polymer electrolyte fuel cell made of alloy,
(2) Cr: More than 43-50%, Mo: 0.1-2%, Mg: 0.001-0.05%, N: 0.001-0.04%, Mn: 0.05-0. Containing 5%, further containing one or two of Fe: 0.05-1.0% and Si: 0.01-0.1%, the balance consisting of Ni and inevitable impurities, An assembly structure member for a polymer electrolyte fuel cell comprising a Ni-based alloy having a remarkably small ion elution amount in a polymer electrolyte fuel cell environment having a composition in which the amount of C contained as an inevitable impurity is adjusted to 0.05% or less It has characteristics.

This Ni-based alloy has a remarkably small amount of ion elution in a polymer electrolyte fuel cell environment, so that a polymer electrolyte fuel cell such as a support plate 7, a clamp 8, a manifold 10, a pipe 11 and a separator 6 can be assembled. This is particularly effective as an assembly structure member for solid polymer fuel cells. Therefore, the present invention
( 3 ) A manifold member for a polymer electrolyte fuel cell comprising a Ni-based alloy having a remarkably small amount of ion elution in the polymer electrolyte fuel cell environment according to (1) or (2),
( 4 ) A piping member for a polymer electrolyte fuel cell made of a Ni-based alloy having a remarkably small amount of ion elution in the polymer electrolyte fuel cell environment according to (1) or (2),
( 5 ) A fastening member for a polymer electrolyte fuel cell made of a Ni-based alloy having a remarkably small amount of ion elution in the polymer electrolyte fuel cell environment according to (1) or (2),
( 6 ) A support plate member for a polymer electrolyte fuel cell made of a Ni-based alloy having a remarkably small amount of ion elution in the polymer electrolyte fuel cell environment according to (1) or (2),
( 7 ) The separator has a feature in a polymer electrolyte fuel cell separator member made of a Ni-based alloy having a remarkably small amount of ion elution in the polymer electrolyte fuel cell environment described in (1) or (2).

Next, the reason for limitation of each element in the alloy composition of the Ni-based alloy having a remarkably small amount of ion elution in the polymer electrolyte fuel cell environment of the present invention will be described in detail.
Cr:
In a polymer electrolyte fuel cell environment in which a small amount of sulfuric acid is mixed, Cr is effective in suppressing metal ion elution. In that case, it is necessary to contain more than 43%, but if it contains more than 50%, processing becomes difficult. Therefore, Cr contained in the Ni-based alloy of the present invention is determined to be more than 43-50%. More preferably, it is 43.1 to 47%.

Mo:
Mo has the effect of suppressing an increase in the amount of elution when the sulfuric acid concentration is increased particularly in a polymer electrolyte fuel cell environment containing a small amount of sulfuric acid. In that case, the effect is shown by containing 0.1% or more, but if it exceeds 2%, the phase stability is deteriorated and it becomes difficult to solidify the Cr-bcc phase. Since a microbattery was formed between the -fcc phase and the Cr-bcc phase, resulting in an increase in the elution amount of metal ions, the Mo content was determined to be 0.1 to 2%. More preferably, it is more than 0.1 to less than 0.5%.

N, Mn and Mg:
By making N, Mn, and Mg coexist, phase stability can be improved. That is, N, Mn, and Mg have the effect of stabilizing the Ni-fcc phase that is the parent phase, promoting the solid solution of Cr, and making the second phase difficult to precipitate. However, when the N content is less than 0.001%, there is no effect of phase stabilization. On the other hand, when the N content exceeds 0.04%, nitrides are formed and metal ions are eluted in the polymer electrolyte fuel cell environment. Therefore, the N content is set to 0.001 to 0.04% (more preferably 0.005 to 0.03%).
Similarly, if the Mn content is less than 0.05%, there is no effect of phase stabilization, while if it exceeds 0.5%, the elution amount of metal ions in the polymer electrolyte fuel cell environment increases. The Mn content is 0.05 to 0.5% (more preferably 0.1 to 0.4%).
Similarly, if the Mg content is less than 0.001%, there is no effect of phase stabilization. On the other hand, if it exceeds 0.05%, the elution amount of metal ions in the polymer electrolyte fuel cell environment increases. Therefore, the Mg content is set to 0.001 to 0.05% (more preferably 0.002% to 0.04%).

Fe and Si:
Fe and Si have the effect of improving the strength, so they are added as necessary. However, when Fe is contained in an amount of 0.05% or more, the content is more than 1%. In order to increase the elution amount of metal ions in the Fe, the Fe content was set to 0.05% to 1% (more preferably, less than 0.1 to 0.5%).
Similarly, if Si is contained in an amount of 0.01% or more, the effect is exhibited. However, if the content exceeds 0.1%, the elution amount of metal ions in the polymer electrolyte fuel cell environment increases. 0.01% to 0.1% (more preferably 0.02 to 0.05%).

C:
Although C is included as an inevitable impurity, C forms a carbide with Cr in the vicinity of the grain boundary, and the amount of elution of metal ions increases. Therefore, the lower the content of C, the better the content of C contained in the inevitable impurities. The upper limit of the amount was set to 0.05%.

  As described above, the Ni-based alloy of the present invention has a characteristic that the ion elution amount is remarkably small in the solid polymer fuel cell environment. By assembling, deterioration of the solid electrolyte membrane can be suppressed, so that a longer life polymer electrolyte fuel cell can be provided, and an excellent industrial effect can be achieved.

In each case, raw materials with a low C content were prepared, and these were melted and cast using a normal high-frequency melting furnace to prepare ingots having a thickness of 12 mm having the component compositions shown in Tables 1 to 3. The ingot was subjected to a homogenization heat treatment at 1230 ° C. for 10 hours, held within a range of 1000 to 1230 ° C., and reduced to 1 mm by one hot rolling, and finally made 5 mm thick. The present invention Ni-based alloy plates 1 to 20 having the composition shown in Tables 1 to 3 and comparative Ni are obtained by buffing the surface after solid solution treatment by holding at 1200 ° C. for 30 minutes and water quenching. Base alloy plates 1 to 10 were produced.
Similarly, a raw material having a low C content is melted and cast using a normal high-frequency melting furnace to produce a precision casting ingot having a component composition shown in Table 2 having a thickness of 5 mm, and this ingot is heated to 1230 ° C. The Ni-based alloy plate 21 of the present invention was produced by performing a homogenization heat treatment for 10 hours and then quenching with water.
Furthermore, a conventional alloy plate 1 made of a SUS304 stainless steel plate having a thickness of 5 mm and a conventional alloy plate 2 made of a SUS316L stainless steel plate were prepared.

  These Ni-base alloy plates 1 to 21, comparative Ni-base alloy plates 1 to 10 and conventional alloy plates 1 to 2 were cut into dimensions of 10 mm in length and 50 mm in width, respectively, to produce test pieces. After polishing the surface of the water-resistant emery paper # 400, it was degreased by being kept in an ultrasonic vibration state in acetone for 5 minutes.

Furthermore, prepared by 1000ppmH ₂ SO ₄ solution and 500ppmH ₂ SO ₄ solution regulates the fluid as a test solution simulating water sulfuric acid generated in the solid polymer fuel cell environment, further a polymer electrolyte fuel cell environment It was prepared by preparing a 500 ppm HF solution and a 50 ppm HF solution as a test solution simulating hydrofluoric acid acid water generated in Step 1. Furthermore, a test container made of polypropylene was prepared.
Test pieces made of the present invention Ni-base alloy plates 1 to 21, comparative Ni-base alloy plates 1 to 10 and conventional alloy plates 1 and 2 and the prepared test solution: 200 ml were put in polypropylene test containers, respectively, in a glove box The solution was degassed under reduced pressure and sealed by closing the upper lid in a hydrogen atmosphere. The sealed polypropylene test container is placed in a thermostat set at 80 ° C., held for 500 hours, and then the polypropylene test container is taken out, cooled, and quantitative analysis of the elements eluted in the H ₂ SO ₄ solution and the HF solution. Measure the total amount of metal ions eluted from the test piece (by ICP emission analysis), and calculate the amount of elution per unit area by dividing the total amount of metal ions eluted from the surface area of the test piece. Are shown in Tables 1-3.

From the results shown in Tables 1 to 3, it can be seen that the Ni-based alloy plates 1 to 21 of the present invention have a remarkably less elution amount of metal ions per unit area of the test piece than the conventional alloy plates 1 and 2. . However, the comparative Ni-base alloy plates 1 to 10 which are out of the present invention have a slightly large amount of metal ion elution or cracks in the middle of processing into a plate.

  The Ni-based alloy of the present invention is most effective when used in a polymer electrolyte fuel cell environment containing sulfuric acid or hydrofluoric acid as described above, but is not limited to this. Even in the molecular fuel cell environment, the elution amount of metal ions is extremely small. Therefore, it can be used not only as a polymer electrolyte fuel cell but also as a pharmaceutical production apparatus member that dislikes elution of metal ions.

It is a schematic explanatory drawing for demonstrating the structure of a polymer electrolyte fuel cell.

Explanation of symbols

1 Hydrogen electrode,
2 oxygen electrode,
3, 3 'platinum catalyst,
4 Solid electrolyte membrane,
5 unit cells,
6 separator,
7 Support plate,
8 Fasteners,
9 Water,
10 Manifold 10,
11 pipes,
12 Pump

Claims (7)

In mass%, Cr: more than 43-50%, Mo: 0.1-2%, Mg: 0.001-0.05%, N: 0.001-0.04%, Mn: 0.05-0 Ni having a remarkably small amount of ion elution in a polymer electrolyte fuel cell environment having a composition containing 0.5%, the balance being Ni and inevitable impurities, and the amount of C contained as inevitable impurities being adjusted to 0.05% or less An assembly structure member for a polymer electrolyte fuel cell comprising a base alloy . In mass%, Cr: more than 43-50%, Mo: 0.1-2%, Mg: 0.001-0.05%, N: 0.001-0.04%, Mn: 0.05-0 0.5%, and further containing one or two of Fe: 0.05 to 1.0% and Si: 0.01 to 0.1%, the balance being made of Ni and inevitable impurities , a polymer electrolyte fuel cell characterized by comprising a C content significantly less Ni based alloy ion elution amount in solid polymer fuel cell environment having a composition adjusted to 0.05% or less contained as unavoidable impurities Assembly structural member. 3. A manifold member for a polymer electrolyte fuel cell, comprising a Ni-based alloy having a remarkably small amount of ion elution in a polymer electrolyte fuel cell environment according to claim 1 or 2. 3. A solid polymer fuel cell piping member comprising a Ni-based alloy having a remarkably small amount of ion elution in a polymer electrolyte fuel cell environment according to claim 1 or 2. A fastening member for a solid polymer fuel cell, comprising a Ni-based alloy having a remarkably small amount of ion elution in a polymer electrolyte fuel cell environment according to claim 1 or 2. 3. A support plate member for a polymer electrolyte fuel cell, comprising a Ni-based alloy having a remarkably small amount of ion elution in a polymer electrolyte fuel cell environment according to claim 1 or 2. A separator member for a polymer electrolyte fuel cell, comprising a Ni-based alloy having a remarkably small amount of ion elution in a polymer electrolyte fuel cell environment according to claim 1 or 2.

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