JP2015086408A - Method for manufacturing metal component, metal component, separator for solid oxide fuel cell, and solid oxide fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a metal component that can efficiently manufacture a thin metal component while suppressing the generation of residual stress, to provide a metal component that is thin and has reduced residual stress, to provide a separator for a solid oxide fuel cell that is thin and has reduced residual stress and to provide a solid oxide fuel cell that has the separator for a solid oxide fuel cell.SOLUTION: The method for manufacturing a metal component is a method for manufacturing a metal component (a separator) composed of a heat-resistant metal material comprising as a main component Co or Cr and having a convexoconcave shape on the surface thereof and has a sheet-forming step of molding a slurry including a powder of a heat-resistant metal material and an organic binder into a sheet form to produce a sheet-like molded body 302, a molding step of pressing a molding tool 393 against the upper face of the sheet-like molded body 302, a molding tool 394 against the lower face thereof, respectively to form a convexoconcave shape and a calcination step of degreasing the sheet-like molded body 302 and calcinating the same to produce a metal component (a separator).

Description

  The present invention relates to a method for manufacturing a metal part, a metal part, a solid oxide fuel cell separator, and a solid oxide fuel cell.

A fuel cell is a power generation device that takes out electric energy by electrochemically reacting fuel and oxygen, and has high power generation efficiency and low generation amount of carbon dioxide, nitrogen oxide, sulfur oxide, etc. Research and development are underway as a power generation device that is friendly to the global environment.
Such fuel cells are classified into phosphoric acid type (PAFC), molten carbonate type (MCFC), solid polymer type (PEFC), and solid oxide type (SOFC) depending on the type of electrolyte used. Among these, a solid oxide fuel cell using ion conductive ceramics as an electrolyte is operated at a very high temperature, so that it is not necessary to use an expensive reaction catalyst such as platinum, which is advantageous in terms of cost. In addition, the internal reforming of fossil fuels is possible, so that various fuels can be applied, and since the constituent structure is solid, downsizing is relatively easy. .

  The solid oxide fuel cell constitutes one stack by connecting a plurality of unit cells (cells) composed of three layers of an electrolyte, a fuel electrode, and an air electrode in series. Moreover, a separator is inserted between the single cells. The separator electrically connects the single cells, and forms a flow path for supplying fuel gas to the fuel electrode and supplying oxidant gas to the air electrode. For this reason, the separator is required to have a function of maintaining airtightness with the unit cell as well as conductivity.

In addition, since the solid oxide fuel cell is operated at a high temperature of 700 to 1000 ° C., the separator needs to have sufficient heat resistance.
Conventionally, many separators made of conductive ceramics have been used as separators for solid oxide fuel cells, but in recent years, those made of metal have been developed and used in many cases.
For example, Patent Document 1 discloses a solid oxide fuel cell interconnector made of a pressed stainless steel material. In the press working, the shape of the mold is transferred to the surface of the workpiece, so that a separator having a desired shape can be obtained.

JP 2011-192546 A

However, residual stress due to processing is generated in the pressed workpiece. Although this residual stress relaxes with time, the separator gradually deforms accordingly. As a result, the airtightness between the separator and the unit cell is impaired, and there is a risk of leakage of fuel gas or oxidant gas supplied to the flow path.
In order to suppress such deformation over time, it is also considered to increase the thickness of the separator. However, as the thickness of the separator increases, the stack also increases in thickness, making it difficult to reduce the size of the fuel cell.
An object of the present invention is to provide a metal part manufacturing method capable of efficiently producing a thin metal part while suppressing the occurrence of residual stress, a metal part with little residual stress, and a thin solid oxide fuel cell with little residual stress. And a solid oxide fuel cell comprising such a solid oxide fuel cell separator.

The above object is achieved by the present invention described below.
The method for producing a metal part of the present invention is a method for producing a metal part having a concavo-convex shape on the surface, which is composed of a heat-resistant metal material mainly composed of Co or Cr,
Forming a slurry containing the powder of the heat-resistant metal material and an organic binder into a sheet, and forming a sheet-like molded body,
A molding step of forming the uneven shape on the surface of the sheet-shaped molded body;
After degreasing the sheet-like molded body, firing, firing step to obtain the metal parts,
It is characterized by having.
Thereby, since generation | occurrence | production of the residual stress at the time of shaping | molding is suppressed, a thin metal component can be manufactured efficiently.

In the metal part manufacturing method of the present invention, it is preferable to form the slurry into a sheet by a tape molding machine.
Thereby, a sheet-like molded object can be manufactured efficiently and inexpensively. For this reason, it is possible to reduce the manufacturing cost of metal parts and shorten the manufacturing period.
In the metal part manufacturing method of the present invention, it is preferable that in the forming step, the uneven shape is formed by transferring a forming die onto the surface of the sheet-like formed body.
Thereby, the uneven | corrugated shape with high dimensional accuracy can be formed reliably. Moreover, since the concavo-convex shape is formed along the concavo-convex surface of the mold, it is possible to prevent the surface of the concavo-convex shape from becoming rough.

In the metal part manufacturing method of the present invention, the ratio of the main component in the refractory metal material is preferably 50% by mass or more and 99.5% by mass or less.
Since such a material is a material having particularly high heat resistance and high conductivity, for example, a solid oxide fuel cell separator that achieves both excellent durability and high power generation characteristics (conductivity). (Metal parts) can be realized.

In the metal part manufacturing method of the present invention, the metal part is preferably a solid oxide fuel cell separator.
This makes it possible to easily manufacture a solid oxide fuel cell separator that achieves both excellent durability and high power generation characteristics.
The metal part of the present invention is composed of a sintered body of a heat-resistant metal material powder mainly composed of Co or Cr, has a Vickers hardness of 250 or more, an elongation of 40% or less, and has an uneven shape on the surface. It is characterized by that.
Thereby, since there is little residual stress and a shape change is suppressed, a metal component with high dimensional accuracy is obtained.

The separator for a solid oxide fuel cell according to the present invention includes the metal component according to the present invention.
As a result, a solid oxide fuel cell separator with high dimensional accuracy can be obtained.
The solid oxide fuel cell of the present invention includes the separator for a solid oxide fuel cell of the present invention.
Thereby, a solid oxide fuel cell with high reliability can be obtained.

1 is a perspective view showing an embodiment of a solid oxide fuel cell of the present invention. It is a disassembled perspective view which shows the cell shown in FIG. 1, and the separator (separator for solid oxide fuel cells of this invention) shown in FIG. It is a front view of the side surface of the separator shown in FIG. It is a figure for demonstrating the manufacturing method of the separator for solid oxide fuel cells to which embodiment of the manufacturing method of the metal component of this invention is applied. It is a figure for demonstrating the manufacturing method of the separator for solid oxide fuel cells to which embodiment of the manufacturing method of the metal component of this invention is applied. It is a figure for demonstrating the manufacturing method of the separator for solid oxide fuel cells to which embodiment of the manufacturing method of the metal component of this invention is applied.

Hereinafter, a metal part manufacturing method, a metal part, a solid oxide fuel cell separator and a solid oxide fuel cell of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.
[Solid oxide fuel cell]
First, an embodiment of the solid oxide fuel cell of the present invention will be described. Moreover, the separator contained in this solid oxide fuel cell is demonstrated as embodiment of the metal component of this invention.

FIG. 1 is a perspective view showing an embodiment of a solid oxide fuel cell of the present invention.
A solid oxide fuel cell 1 (hereinafter, also referred to as “fuel cell 1” for brevity) shown in FIG. 1 is a so-called flat plate type, and includes a large number of cells (unit cells) 2 and cells 2. A stack 4 formed by laminating a separator 3 (a separator for a solid oxide fuel cell according to the present invention) interposed between the upper plate, an upper presser plate 5 provided on the stack 4, and And a lower presser plate 6 provided.

Each cell 2 has the ability to generate electricity as a fuel cell. A sufficiently high voltage can be obtained by forming a stack 4 by connecting a plurality of such cells 2 in series.
The upper presser plate 5 and the lower presser plate 6 press the stack 4 from above and below so as to ensure close contact between the cell 2 and the separator 3. As a result, the electrical connectivity between the cells 2 via the separator 3 is enhanced, the contact resistance is reduced, the adhesion between the cells 2 and the separator 3 is enhanced, and the leakage of gas from the interlayer is suppressed. Can do.

Hereinafter, the cell 2 and the separator 3 will be described in more detail.
2 is an exploded perspective view showing the cell 2 shown in FIG. 1 and the separator (the separator for a solid oxide fuel cell of the present invention) 3 shown in FIG. FIG. 3 is a front view of the side surface of the separator shown in FIG.
The cell 2 shown in FIG. 2 includes a stacked body in which a fuel electrode (anode) 21, an electrolyte layer 22, and an air electrode (cathode) 23 are stacked in this order from below. Further, a lower separator (solid oxide fuel cell separator of the present invention) 31 is laminated below the cell 2 shown in FIG. 2, and an upper separator (present invention) is placed above the cell 2 shown in FIG. The solid oxide fuel cell separator 32) is laminated. The lower separator 31 and the upper separator 32 have the same structure.

Further, the lower separator 31 and the upper separator 32 are each composed of a plate-like body having the same shape as the cell 2 in plan view.
Among these, on the upper surface of the lower separator 31, that is, the surface facing the fuel electrode 21 of the cell 2 shown in FIG. The end portions in the longitudinal direction of the grooves 313 are opened to the side surface 311 (see FIG. 3A) of the lower separator 31 shown in FIG. 2 and the side surface 315 facing the side surface 311. It is configured. Thereby, each groove | channel 313 functions as a flow path which can flow this gas, when gas is supplied toward the side surface 311 or the side surface 315. FIG. As a result, the lower separator 31 can cause the fuel gas to reliably act on the fuel electrode 21 by flowing the fuel gas through the groove 313.

  On the other hand, a plurality of parallel grooves (concavo-convex shapes) 314 are formed on the lower surface of the lower separator 31, that is, the surface facing a cell (not shown) adjacent to the lower side of the cell 2 shown in FIG. The end portions in the longitudinal direction of the grooves 314 are opened to the side surface 312 (see FIG. 3B) of the lower separator 31 shown in FIG. 2 and the side surface 316 facing the side surface 312 respectively. It is configured. Thus, each groove 314 functions as a flow path through which the gas can flow when the gas is supplied toward the side surface 312 or the side surface 316. As a result, the lower separator 31 can cause the oxidant gas to reliably act on the air electrode adjacent to the lower side of the cell 2 by flowing the oxidant gas through the groove 314.

  In addition, a plurality of parallel grooves (uneven shape) 323 are formed on the upper surface of the upper separator 32, that is, the surface facing a cell (not shown) adjacent to the upper side of the cell 2 shown in FIG. The end portions in the longitudinal direction of the grooves 323 are configured to open to a side surface 321 of the upper separator 32 and a side surface 325 facing the side surface 321 shown in FIG. Thereby, each groove | channel 323 functions as a flow path which can flow this gas, when gas is supplied toward the side surface 321 or the side surface 325. FIG. As a result, the upper separator 32 can cause the fuel gas to reliably act on the fuel electrode adjacent above the cell 2 by flowing the fuel gas through the groove 323.

  On the other hand, on the lower surface of the upper separator 32, that is, the surface facing the air electrode 23 of the cell 2 shown in FIG. The end portions in the longitudinal direction of the grooves 324 are configured to open to the side surface 321 of the upper separator 32 and the side surface 325 facing the side surface 321 shown in FIG. Thus, each groove 324 functions as a flow path through which the gas can be flowed when the gas is supplied toward the side surface 322 or the side surface 326. As a result, the upper separator 32 can reliably cause the oxidant gas to act on the air electrode 23 by flowing the oxidant gas through the groove 324.

Here, the operation principle of the solid oxide fuel cell 1 will be described.
In order to operate the solid oxide fuel cell 1, a fuel gas and an oxidant gas are required. As the fuel gas, hydrogen gas, carbon monoxide gas, or the like is used. On the other hand, air or the like is used as the oxidant gas.
For example, when hydrogen gas is used as the fuel gas, the fuel electrode 21
H ₂ + O ²⁻ → H ₂ O + 2e ⁻
This reaction occurs.

On the other hand, the oxygen gas contained in the oxidant gas is
1 / 2O ₂ + 2e ⁻ → O ²⁻
It is subjected to the reaction.
Then, oxygen ions (O ²⁻ ) generated in the air electrode 23 pass through the electrolyte layer 22 and move to the fuel electrode 21. On the other hand, in the fuel electrode 21, the moved oxygen ions and hydrogen react to generate electrons. The electrons move to the air electrode 23 via an external circuit.
The fuel cell 1 can generate power as described above.

Note that the voltage that can be generated by this operating principle is usually about 0.3 V to 1.0 V per cell 2. Therefore, a sufficiently high voltage can be obtained by stacking a plurality of cells 2 in series.
Therefore, when a plurality of cells 2 are stacked to form a quadrangular prism-shaped stack 4, the flow path for supplying fuel gas in each cell 2 is all open on one of the four surfaces of the quadrangular prism. Therefore, if the fuel gas is supplied to the entire surface, the fuel gas can be distributed to each cell 2 with a simple configuration. Of the four surfaces, the fuel gas after reaction, such as water vapor, can be discharged from the surface facing the surface that supplies the fuel gas.

  Similarly, the flow path for supplying the oxidant gas in each cell 2 opens in a surface adjacent to the surface for supplying the fuel gas among the four surfaces of the quadrangular prism. For this reason, if oxidant gas is supplied to this whole surface, oxidant gas can be distributed to each cell 2 with a simple configuration. Of the four surfaces, the surface that faces the surface that supplies the oxidant gas can discharge the oxidant gas after the reaction, such as nitrogen.

  From the above, in the lower separator 31, since the groove 313 and the groove 314 intersect each other in plan view, the surface for supplying the fuel gas and the surface for supplying the oxidant gas can be naturally separated. The simple configuration described above can be easily realized. Similarly, in the upper separator 32, since the groove 323 and the groove 324 intersect each other in plan view, the above-described simple configuration can be easily realized.

Hereinafter, each part of the cell 2 will be described in more detail.
The fuel electrode 21, the electrolyte layer 22, and the air electrode 23 each have a plate shape having a square shape in plan view.
Examples of the constituent material of the fuel electrode 21 include zirconia to which a rare earth element and Ni are added, cerium oxide to which a rare earth element and Ni are added, and the like. The rare earth element is, for example, selected from the group consisting of Y, Lu (lutetium), Yb, Tm (thulium), Er (erbium), Ho (holmium), Dy (dysprosium), Gd, Sm, and Pr (praseodymium). These rare earth elements are added to the fuel electrode 21 as oxides. Specifically, an electrolyte is composed of a metal Ni such as nickel-added yttria stabilized zirconia (Ni-YSZ), nickel-added samaria stabilized zirconia (Ni-SSZ), nickel-added scandia stabilized zirconia (Ni-ScSZ). Examples thereof include a mixture with a material.

The average thickness of the fuel electrode 21 is not particularly limited, but is preferably about 5 μm to 800 μm, and more preferably about 10 μm to 500 μm. By setting the average thickness of the fuel electrode 21 within the above range, the durability of the fuel electrode 21 at high temperatures can be further increased while reducing the thickness of the fuel cell 1.
In addition, since the fuel electrode 21 needs to have gas permeability, its open porosity is preferably 15% or more, and more preferably 20% or more and 40% or less.

Examples of the constituent material of the electrolyte layer 22 include scandia-stabilized zirconia (ScSZ), yttria-stabilized zirconia (YSZ), samaria-stabilized zirconia (SSZ), and cobalt-added lanthanum gallate oxide (LSGMC).
The average thickness of the electrolyte layer 22 is not particularly limited, but is preferably about 5 μm or more and 800 μm or less, and more preferably about 10 μm or more and 500 μm or less. By setting the average thickness of the electrolyte layer 22 within the above range, the durability of the electrolyte layer 22 at high temperatures can be further increased while reducing the thickness of the fuel cell 1 and improving the passage efficiency of oxygen ions. .

The electrolyte layer 22 preferably has a relative density of 93% or more, and more preferably 95% or more, from the viewpoint of preventing gas permeation.
Examples of the constituent material of the air electrode 23 include lanthanum nickel ferrite (LNF), lanthanum manganate (LSM), lanthanum strontium cobaltite (LSC), lanthanum strontium cobaltite ferrite (LSCF), lanthanum strontium ferrite (LSF), samarium. Examples thereof include strontium cobaltite (SSC).

The average thickness of the air electrode 23 is not particularly limited, but is preferably about 5 μm to 800 μm, and more preferably about 10 μm to 500 μm. By setting the average thickness of the air electrode 23 within the above range, the durability of the air electrode 23 at high temperatures can be further increased while reducing the thickness of the fuel cell 1.
In addition, since the air electrode 23 needs to have gas permeability, the open porosity is preferably 20% or more, and more preferably 30% or more and 50% or less.
Further, the planar shape of the fuel electrode 21, the electrolyte layer 22, and the air electrode 23 is not limited to a quadrangle, but is a polygon such as a pentagon or a hexagon, a circle such as a perfect circle, an ellipse, or an ellipse. Also good.

Next, the lower separator 31 and the upper separator 32 will be further described in detail. In addition, since these are mutually the same structures, in the following description, only the lower separator 31 will be described, and the description of the upper separator 32 will be omitted.
The constituent material of the lower separator 31 is a refractory metal material mainly composed of Co or Cr.

  Such a refractory metal material refers to a material having the largest ratio (mass ratio) of Co or Cr among the contained elements. Since such a material is excellent in heat resistance such as corrosion resistance under high temperature and oxidation resistance under high temperature, the lower separator 31 is thin without impairing its function even during high temperature operation of the fuel cell 1. Is achieved. For this reason, the fuel cell 1 can be reduced in thickness and size.

  In the refractory metal material, the ratio of Co or Cr is preferably 50% by mass or more and 99.5% by mass or less, and more preferably 60% by mass or more and 98% by mass or less. Since such a material is a material having particularly high heat resistance and high conductivity, even when applied to the lower separator 31, the lower separator achieves both excellent durability and high power generation characteristics. 31 can be realized.

  The refractory metal material containing Co as a main component may be any material as long as it is a metal material containing Co as a main component. For example, as an additive element other than Co, B, C, Fe, Ni, Cr , Mo, W, Nb, Ta, Ti, Al, Zr, Re, Y, Hf, V, and the like, and one or more of these may be added in appropriate combination. The content of these additive elements is preferably such that the C content is about 0.03 to 0.9% by mass, and the Fe content is 0.5 to 20% by mass. The content of Ni is preferably about 3% by mass to 35% by mass, the content of Cr is preferably about 3% by mass to 40% by mass, and the content of Mo The rate is preferably about 3% by mass to 10% by mass, the W content is preferably about 3% by mass to 20% by mass, and the Nb content is 1% by mass to 5% by mass. The content of Ta is preferably about 2% by mass to 10% by mass, the content of Ti is preferably about 0.2% by mass to 2% by mass, Al Is about 0.2% by mass or more and 5% by mass or less. It is preferable to that.

The refractory metal material mainly composed of Cr may be any material as long as it is a metal material mainly composed of Cr. For example, as an additive element other than Cr, B, C, Fe, Ni, Cr, Mo, W, Nb, Ta, Ti, Al, Zr, Re, Y, Hf, V and the like may be mentioned, and one or more of these may be added in appropriate combination. The content of these additive elements is preferably such that the C content is about 0.001 to 1% by mass, and the Fe content is about 0.1 to 50% by mass. Preferably, the W content is preferably about 0.2% by mass to 15% by mass, the Ti content is preferably about 0.3% by mass to 5% by mass, Mo The content of is preferably about 1% by mass to 5% by mass, the content of Re is preferably about 0.1% by mass to 3% by mass, and the content of V is 0.1% by mass. % Or more and preferably about 3% by mass or less.
In addition to these additive elements, the refractory metal material may contain impurities inevitably mixed in the manufacturing process.

  The depths of the groove 313 and the groove 314 formed in the lower separator 31 are appropriately set according to the maximum thickness of the lower separator 31, but preferably about 5% to 40% of the maximum thickness. It is preferable that it is about 7% or more and 35% or less. By setting the depths of the groove 313 and the groove 314 within the above ranges, the flow resistance of the fuel gas and the oxidant gas can be sufficiently suppressed while sufficiently securing the mechanical strength of the lower separator 31. .

The thickness of the lower separator 31 is preferably about 10 μm or more and 1000 μm or less, and more preferably about 20 μm or more and 500 μm or less. The lower separator 31 having such a thickness can reduce the thickness and size of the fuel cell 1 while maintaining sufficient mechanical strength.
The area occupancy of the grooves 313 and 314 when the lower separator 31 is viewed in plan is preferably about 15% or more and 80% or less, and more preferably about 20% or more and 70% or less. . By setting the area occupancy rate of the grooves 313 and 314 within the above range, the contact area between the fuel gas and the fuel electrode 21 and the oxidant gas and air are ensured while sufficiently securing the mechanical strength of the lower separator 31. Since a sufficient contact area with the electrode 23 can be ensured, a thin fuel cell 1 with high power generation efficiency can be obtained.
In addition, the groove 313 illustrated in FIG. 2 is linear in a plan view, but the shape is not particularly limited, and may be bent or branched in the middle, or a plurality of grooves 313 may intersect each other. May be. Although not shown in FIG. 2, the groove 314 is the same as the groove 313.

  The Vickers hardness of the lower separator 31 is preferably 250 or more, and more preferably 300 or more and 1000 or less. The lower separator 31 having such a hardness is less likely to cause scratches on the surface thereof, and therefore, it is difficult to cause a gas leak or the like and has high reliability. Moreover, since it becomes excellent in abrasion resistance, even if the flow rate of fuel gas or oxidant gas is increased, wear of the lower separator 31 is suppressed, and the lower separator 31 having high durability over a long period of time can be obtained. . In addition, when the Vickers hardness of the lower separator 31 exceeds the upper limit value, the toughness of the lower separator 31 may be lowered. Therefore, the Vickers hardness is equal to or lower than the upper limit value from the viewpoint of improving the handleability and reliability. Is preferred.

The Vickers hardness of the lower separator 31 is measured in accordance with a test method defined in JIS Z 2244.
In addition, the elongation of the lower separator 31 is preferably 40% or less, and more preferably 2% or more and 30% or less. Since the lower separator 31 having such an extension is difficult to be deformed, it is difficult to cause problems such as gas leakage and contact failure, and the reliability becomes higher. In addition, since the toughness of the lower separator 31 may be lowered when the elongation of the lower separator 31 is less than the lower limit value, the elongation is not less than the lower limit value from the viewpoint of improving the handleability and reliability. preferable.
The elongation (breaking elongation) of the lower separator 31 is measured according to a test method defined in JIS Z 2241.

  In addition, according to this invention, since the lower side separator 31 is manufactured using a fine heat-resistant metal powder, the particle size of the metal crystal produced | generated in a sintered compact (lower side separator 31) becomes small. For this reason, the Vickers hardness of the lower separator 31 is higher than the conventional one, and the elongation is smaller than the conventional one. Therefore, according to the present invention, it is possible to obtain the lower separator 31 that is not easily deformed even at high temperatures. Therefore, it is possible to realize the fuel cell 1 that can stably generate power over a long period of time.

  As described above, the embodiment of the solid oxide fuel cell of the present invention, the embodiment of the metal component of the present invention, and the embodiment of the separator for the solid oxide fuel cell of the present invention have been described. It can also be applied to other than separators. Applicable metal parts of the present invention include, for example, turbine blades such as gas turbines and jet engines, engine intake and exhaust valves, rocker arms, turbocharger vanes, and the like.

[Manufacturing method of metal parts]
Next, an embodiment of a method for producing a metal part of the present invention will be described.
4-6 is a figure for demonstrating the manufacturing method of the separator for solid oxide fuel cells to which embodiment of the manufacturing method of the metal component of this invention is applied, respectively.
The method of manufacturing a metal part according to the present embodiment includes forming a sheet containing a heat-resistant metal material powder (heat-resistant metal powder) containing Co or Cr as a main component and an organic binder into a sheet, and then drying the sheet. A sheet forming step for obtaining a sheet-like formed body, a forming step for forming an uneven shape on the surface of the sheet-like formed body, and a firing step for degreasing the sheet-like formed body and then firing to obtain a metal part. Hereinafter, each process will be described sequentially.

[1] Sheeting process First, a heat-resistant metal powder used in the sheeting process is manufactured.
The heat-resistant metal powder is produced by various powdering methods such as an atomizing method (for example, a water atomizing method, a gas atomizing method, a high-speed rotating water atomizing method, etc.), a reduction method, a carbonyl method, and a pulverization method.

  Of these, those manufactured by the atomizing method are preferably used, and those manufactured by the water atomizing method or the high-speed rotating water atomizing method are more preferably used. The atomizing method is a method for producing a metal powder by causing molten metal (molten metal) to collide with a fluid (liquid or gas) jetted at high speed, thereby pulverizing and cooling the molten metal. By producing metal powder by such an atomizing method, extremely fine powder can be efficiently produced. Moreover, the particle shape of the obtained powder becomes close to a spherical shape due to the effect of surface tension. For this reason, when formed into a sheet in the sheet forming step, a sheet-like molded body having a high filling rate is obtained. As a result, it is possible to obtain a separator having excellent mechanical properties even if it is thin.

When the water atomizing method is used as the atomizing method, the pressure of water sprayed toward the molten metal (hereinafter referred to as “atomized water”) is not particularly limited, but is preferably 75 MPa or more and 120 MPa or less (750 kgf / cm ² or more and 1200 kgf / cm ² or less), more preferably 90 MPa or more and 120 MPa or less (900 kgf / cm ² or more and 1200 kgf / cm ² or less).

The temperature of the atomized water is not particularly limited, but is preferably about 1 ° C. or higher and 20 ° C. or lower.
Furthermore, atomized water is often sprayed in a conical shape having an apex on the molten metal drop path and the outer diameter gradually decreasing downward. In this case, the apex angle θ of the cone formed by the atomized water is preferably about 10 ° to 40 °, more preferably about 15 ° to 35 °. Thereby, the metal powder having the composition as described above can be reliably produced.

Moreover, according to the water atomization method (especially high-speed rotation water flow atomization method), a molten metal can be cooled especially rapidly. For this reason, the composition of each particle is made uniform and a homogeneous separator is obtained.
The cooling rate when the molten metal is cooled in the atomization method is preferably 1 × 10 ⁴ ° C./s or more, and more preferably 1 × 10 ⁵ ° C./s or more. By such rapid cooling, a metal powder capable of producing a separator having a particularly small particle size of metal crystals and excellent mechanical properties can be obtained.

Next, a slurry is prepared using the refractory metal powder.
The slurry is prepared by mixing a refractory metal powder, an organic binder, a solvent, and the like.
The average particle size of the refractory metal powder is not particularly limited, but is preferably about 0.5 μm to 30 μm, and more preferably about 1 μm to 20 μm. By using the heat-resistant metal powder having such a particle size, the separator 3 having sufficient mechanical properties can be obtained even when it is thinly formed.

Examples of the organic binder include various organic materials including methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, polyvinyl butyral, acrylic resin, emulsion, and the like.
The solvent is not particularly limited as long as it can dissolve or disperse the organic binder. In addition to water, organic solvents such as terpineol, butyl carbitol, acetone, and toluene are used.

Although the content rate of the organic binder in a slurry is suitably set according to the composition etc., it is preferable that it is about 1 mass% or more and 5 mass% or less. Moreover, although the content rate of the solvent in a slurry is suitably set according to the composition etc., it is preferable that it is about 10 mass% or more and 50 mass% or less.
Moreover, in addition to what was mentioned above, various additives, such as a dispersing agent, a plasticizer, antioxidant, and a rust inhibitor, may be added in the slurry. In this case, the total amount of these additives is preferably set to be 10% by mass or less in the slurry.
The viscosity of the slurry is not particularly limited, but is preferably 0.1 Pa · s or more and 100 Pa · s or less at room temperature.

Next, the prepared slurry is formed into a sheet shape to obtain a sheet-like formed body (green sheet) 301 shown in FIG.
For this forming, for example, various sheet forming methods such as a gravure coating method, a bar coating method, a screen printing method, a dip method, a spin coating method, a spray coating method, a reverse roll coating method, a doctor blade coating method, and the like are used.

Although the thickness of the obtained sheet-like molded object is suitably set according to the thickness of the separator 3 to be manufactured, it is preferably about 100 μm or more and about 10 mm or less as an example, and is about 300 μm or more and about 8 mm or less. Is more preferable.
In addition, the sheet-like molded object 301 shown to Fig.4 (a) becomes a long thing by shape | molding continuously. For this reason, it can be wound up in a roll shape and is suitable for storage, transportation and the like.

Moreover, it is preferable to use a tape molding machine for manufacture of the sheet-like molded body 301. By using a tape molding machine, the sheet-shaped molded body 301 can be manufactured efficiently and inexpensively. For this reason, reduction of the manufacturing cost of the separator 3 and shortening of a manufacturing construction period can be aimed at.
Next, the sheet-like molded body 301 shown in FIG. 4A is punched into a rectangular shape. Thereby, the rectangular sheet-like molded object 302 shown in FIG.4 (b) is obtained. The shape and size of the rectangular sheet-shaped molded body 302 are appropriately set according to the shape and size of the separator 3 to be manufactured. Therefore, the shape of the sheet-like molded body 302 is not limited to a rectangular shape.

[2] Forming Step Next, the groove 303 is formed on the upper surface of the obtained sheet-like molded body 302 and the groove 304 is formed on the lower surface. That is, an uneven shape is formed on the surface of the sheet-like molded body 302.
Any method can be used for this molding. Examples thereof include a method of transferring a molding die, a method of pouring a slurry into the molding die, and a method of removing unnecessary portions by machining or laser processing. Of these, the method of transferring the mold is preferably used. Specifically, as shown in FIG. 5, the mold 393 is pressed against the upper surface of the sheet-shaped molded body 302, and the mold 394 is pressed against the lower surface of the sheet-shaped molded body 302. As a result, the uneven shape of the mold 393 is transferred to the upper surface of the sheet-like molded body 302, and the uneven shape of the mold 394 is transferred to the lower surface of the sheet-like molded body 302. As a result, the separator molded body 30 shown in FIG. 6A is obtained. According to such a method, it is possible to reliably form an uneven shape with high dimensional accuracy. In addition, since the concavo-convex shape is formed along the concavo-convex surfaces of the molds 393 and 394, the surface of the concavo-convex shape can be prevented from becoming rough. As a result, finally, it is possible to obtain the separator 3 having a groove with a small gas flow resistance. In addition, when the surface roughness of the separator 3 becomes rough, there is a risk that cracks and breaks and the like starting from the surface may occur. However, according to the method described above, the separator 3 having high mechanical properties can be obtained.

In addition, about the sheet-like molded object 302, the dryness may be preset so that it may have plastic deformability. As an example of the drying conditions, the drying temperature is 50 ° C. or higher and 150 ° C. or lower, and the drying time is 1 minute or longer and 30 minutes or shorter.
Moreover, the shape retention property of an uneven | corrugated shape can be improved by drying on the drying condition with respect to the molded object 30 for separators after forming an uneven | corrugated shape.
Note that the mold 393 and the mold 394 are preferably pressed against the sheet-shaped molded body 302 at the same time. Thereby, even if it is a case where the thin molded object 30 for separators is formed especially, a thing with high dimensional accuracy can be formed efficiently.

[3] Firing step Next, the obtained separator molded body 30 is degreased.
As this degreasing process, the method of heating the molded object 30 for separators, the method of exposing the molded object 30 for separators to the gas which decomposes | disassembles an organic binder, etc. are mentioned, for example.
When the method of heating the molded body for separator 30 is used, the heating conditions of the molded body for separator 30 vary slightly depending on the composition and blending amount of the organic binder, but the temperature is 100 ° C. or higher and 750 ° C. or lower × 0.1 hour or longer and 20 hours or longer. The temperature is preferably about 150 ° C. or more and 600 ° C. or less × 0.5 hours or more and 15 hours or less. Thus, the separator molded body 30 can be degreased necessary and sufficiently without sintering the separator molded body 30. As a result, it is possible to reliably prevent a large amount of the organic binder component from remaining in the degreased body.
Further, the atmosphere when heating the separator molded body 30 is not particularly limited, and a reducing gas atmosphere such as hydrogen, an inert gas atmosphere such as nitrogen and argon, an oxidizing gas atmosphere such as air, or A reduced-pressure atmosphere obtained by reducing these atmospheres can be used.

On the other hand, examples of the gas that decomposes the organic binder include ozone gas.
In addition, such a degreasing process is divided into a plurality of steps (steps) having different degreasing conditions, so that the organic binder in the separator molded body 30 is not left in the separator molded body 30 more quickly. Can be disassembled and removed.
Moreover, you may make it perform machining, such as cutting, grinding | polishing, and cutting | disconnection with respect to a degreased body as needed. Since the degreased body is relatively low in hardness and relatively rich in plasticity, it can be easily machined while preventing the shape of the degreased body from collapsing. According to such machining, the separator 3 with high dimensional accuracy can be easily obtained finally.

Next, the obtained degreased body is fired to obtain a sintered body (separator 3) shown in FIG.
Due to this sintering, the heat-resistant metal powder is diffused at the interface between the particles, resulting in sintering. As a result, a dense sintered body can be obtained while maintaining the shape of the separator molded body 30.
The firing temperature varies depending on the composition, particle size, and the like of the heat-resistant metal powder used in the production of the separator molded body 30 and the degreased body. The temperature is preferably about 1050 ° C. or higher and 1260 ° C. or lower.

The firing time is 0.2 hours or more and 7 hours or less, and preferably 1 hour or more and 6 hours or less.
In the firing step, the sintering temperature or a firing atmosphere described later may be changed during the firing process.
By setting the firing conditions in such a range, the entire defatted body can be sufficiently sintered while preventing oversintering due to excessive progress of sintering and enlargement of the crystal structure. As a result, a sintered body having a high density and particularly excellent mechanical properties can be obtained.
In addition, the atmosphere at the time of firing is not particularly limited, but in consideration of preventing significant oxidation of the refractory metal powder, a reducing gas atmosphere such as hydrogen, an inert gas atmosphere such as argon, or these A reduced-pressure atmosphere or the like in which the atmosphere is reduced is preferably used.

  The separator 3 obtained as described above has a lower residual stress than those obtained by conventional press working and those obtained by machining such as cutting. That is, in the press working, plastic deformation is caused to the refractory metal material. Therefore, as described above, the stress accompanying the processing remains, and this relaxes with time, thereby causing the separator 3 to deform with time. In machining, stress remains in the machining area due to interference with the machining tool. On the other hand, according to the method described above, since the molding is performed on the relatively soft sheet-shaped molded body 302, stress hardly remains in the separator 3. Therefore, the separator 3 with little deformation with time can be obtained. Moreover, in the method mentioned above, since a deformation | transformation is suppressed, even the thinner separator 3 can be manufactured reliably.

On the other hand, a refractory metal material containing Co or Cr as a main component has a relatively high hardness and a relatively low ductility, so that it is difficult to increase the dimensional accuracy in press molding. In addition, since machinability is low, it is difficult to efficiently perform highly accurate machining.
On the other hand, according to the above-described method according to the present invention, the separator 3 having high dimensional accuracy can be efficiently manufactured even when such a refractory metal material is used. In other words, the uneven shape of the mold can be faithfully reproduced with respect to the sheet-shaped molded body without generating a significant residual stress regardless of the alloy composition of the refractory metal material. Dimensional change is suppressed.

  Furthermore, the separator 3 has different groove shapes on the upper surface and the lower surface. In such a case, the occurrence of residual stress becomes more prominent in the conventional press working and machining, but according to the present invention, even in such a case, the residual stress can be reliably suppressed and the time-dependent A separator 3 with little deformation can be obtained. Such a separator 3 has high adhesion to the cell 2 and can reliably suppress gas leakage even if it is thin. Therefore, by using the separator 3, a small and highly reliable fuel cell 1 can be obtained.

The relative density of the sintered body thus obtained is preferably 97% or more, and more preferably 98% or more. A sintered body having a relative density in such a range has a shape that is almost as close to the target shape as possible by using powder metallurgy technology. For this reason, the separator 3 having high mechanical characteristics and high dimensional accuracy can be obtained.
As mentioned above, although the manufacturing method of the metal component of this invention, the metal component, the separator for solid oxide fuel cells, and the solid oxide fuel cell were demonstrated based on suitable embodiment, this invention is limited to this. It is not a thing.

For example, in the separator according to the embodiment, the shape of the groove is different between the upper surface and the lower surface. However, the present invention is not limited to such a form, and the shape of the groove is the same between the upper surface and the lower surface. Good.
Moreover, you may make it give an additional process to the sintered compact after a baking process as needed. Examples of the additional process include a hot isostatic pressing process (HIP process).

Next, specific examples of the present invention will be described.
1. Production of solid oxide fuel cell separator (Example 1)
[1] First, the raw material was melted in a high-frequency induction furnace and pulverized by a high-speed rotating water stream atomization method (in each table, expressed as “rotating water”) to obtain a heat-resistant metal powder. Subsequently, classification was performed using a standard sieve having an opening of 150 μm. The alloy composition of the obtained refractory metal powder is as follows.
Fe: 20% by mass, Mo: 5% by mass or more, V: 0.5% by mass, Cr: balance For specifying the alloy composition, a solid emission spectroscopic analyzer (spark emission analyzer) manufactured by SPECTRO, model: SPECTROLAB, type: LAVMB08A was used.

[2] Next, the obtained heat-resistant metal powder and organic binder (polyvinyl butyral) were dissolved in toluene and ethanol (above, solvent) to prepare a slurry. The amount of the organic binder in the slurry was 3% by mass, and the amount of the solvent in the slurry was 30% by mass.
[3] Next, the slurry was formed into a sheet with a tape forming machine to obtain a long sheet-like formed body.
Subsequently, the sheet-like molded body was punched into a rectangular shape to obtain a rectangular sheet-shaped molded body.
[4] Next, as shown in FIG. 5, a molding die was pressed from above and below the sheet-like molded body to obtain a molded body for a separator.

[5] Next, this separator molded body was degreased under the following degreasing conditions to obtain a degreased body.
<Degreasing conditions>
・ Heating temperature: 470 ° C
・ Heating time: 1 hour ・ Heating atmosphere: Argon atmosphere

[6] Next, the obtained degreased body was fired under the following firing conditions to obtain a sintered body (separator).
<Baking conditions>
・ Heating temperature: 1100 ° C
-Heating time: 3 hours-Heating atmosphere: Argon atmosphere In addition, the obtained sintered compact is a plate-shaped body which makes a square by planar view and is 100 mm long x 100 mm wide x 3 mm in maximum thickness. Moreover, the groove | channel formed in the upper surface and the lower surface is a groove | channel of the shape shown in FIG. 2, The depth was 0.5 mm, the width | variety was 1 mm, and the space | interval of grooves was 1 mm.

(Example 2)
A sintered body was obtained in the same manner as in Example 1 except that the heat-resistant metal powder having the following alloy composition was used.
C: 0.1% by mass, Fe: 5% by mass, Cr: 28% by mass, Mo: 7% by mass, Co: remainder (Example 3)
A sintered body was obtained in the same manner as in Example 1 except that the heat-resistant metal powder having the following alloy composition was used.
Co: 15% by mass, Mo: 2% by mass, V: 0.5% by mass, Cr: balance (Example 4)
A sintered body was obtained in the same manner as in Example 1 except that the heat-resistant metal powder having the following alloy composition was used.
C: 0.05 mass%, Cr: 40 mass%, Mo: 6 mass%, Co: remainder

(Comparative Example 1)
First, a refractory metal material having the composition shown in Table 1 was prepared.
Next, the prepared melted material was pressed to obtain a separator having the same shape as in Example 1.
(Comparative Example 2)
First, a refractory metal material having the composition shown in Table 1 was prepared.
Next, the prepared melted material was cut using a milling machine to obtain a separator having the same shape as in Example 1.

(Comparative Example 3)
First, a refractory metal material having the composition shown in Table 1 was prepared.
Next, the prepared melted material was pressed to obtain a separator having the same shape as in Example 2.
(Comparative Example 4)
First, a refractory metal material having the composition shown in Table 1 was prepared.
Next, the prepared melted material was cut using a milling machine to obtain a separator having the same shape as in Example 2.

2. 2. Evaluation of Solid Oxide Fuel Cell Separator 2.1 Heat Resistance Test The heat resistance test was performed on the separators obtained in each Example and each Comparative Example under the following conditions.
<Conditions for heat test>
・ Heating temperature: 850 ° C
・ Heating time: 100 hours ・ Heating atmosphere: air (water vapor amount 20%)
Subsequently, about the separator after a test, the dimensional change (maximum curvature amount) from before a test was measured, and it evaluated in accordance with the following evaluation criteria.

<Evaluation criteria for dimensional change>
A: The maximum warpage amount is 1 to 1.25 times before the test. ○: The maximum warpage amount is 1.25 times to less than 1.5 times before the test. Δ: The maximum warpage amount is 1 before the test. It is 5 times or more and less than 2 times. X: The maximum warpage amount is 2 times or more before the test.

2.2 Measurement of Vickers Hardness Vickers hardness at room temperature was measured for the separators obtained in each Example and each Comparative Example according to the test method of Vickers hardness test specified in JIS Z 2244.
The measurement results are shown in Table 1.
2.3 Measurement of Elongation For the separators obtained in each Example and each Comparative Example, the elongation at room temperature was measured in accordance with the metal material tensile test method defined in JIS Z 2241.
The measurement results are shown in Table 1.

As is clear from Table 1, it was confirmed that the separators obtained in each example can keep the dimensional change small even after the heat resistance test.
On the other hand, the separator obtained in each comparative example was found to have a relatively large dimensional change by the heat resistance test.
Moreover, about the ingot of the heat-resistant metal material having the same composition as that of Example 1 as well as Comparative Examples 1 and 2, press working and cutting were performed to obtain a separator. The Vickers hardness was less than 750 and the elongation was 10 to 12%.

1 ... Solid oxide fuel cell 2 ... Cell 21 ... Fuel electrode 22 ... Electrolyte layer 23 ... Air electrode 3 ... Separator 31 ... Lower separator 311 ... Side 312 ... Side 313 ... Groove 314... Groove 315 .. side surface 316 .. side surface 32... Upper separator 321. ... sheet-like molded body 302 ... sheet-like molded body 303 ... groove 304 ... groove 393 ... mold 394 ... mold 4 ... stack 5 ... upper presser plate 6 ... lower presser plate

Claims (8)

A method of manufacturing a metal part having a concavo-convex shape on the surface, composed of a heat-resistant metal material mainly composed of Co or Cr,
Forming a slurry containing the powder of the heat-resistant metal material and an organic binder into a sheet, and forming a sheet-like molded body,
A molding step of forming the uneven shape on the surface of the sheet-shaped molded body;
After degreasing the sheet-like molded body, firing, firing step to obtain the metal parts,
A method for producing a metal part, comprising:   The method of manufacturing a metal part according to claim 1, wherein the slurry is formed into a sheet shape by a tape forming machine.   The metal part manufacturing method according to claim 1 or 2, wherein, in the forming step, the uneven shape is formed by transferring a forming die onto a surface of the sheet-like formed body.   The method for manufacturing a metal part according to any one of claims 1 to 3, wherein a ratio of the main component in the heat-resistant metal material is 50 mass% or more and 99.5 mass% or less.   The method for manufacturing a metal part according to any one of claims 1 to 4, wherein the metal part is a solid oxide fuel cell separator.   A metal part comprising a sintered body of a heat-resistant metal material powder containing Co or Cr as a main component, having a Vickers hardness of 250 or more, an elongation of 40% or less, and an uneven surface. .   A metal oxide separator according to claim 6, comprising a solid oxide fuel cell separator.   A solid oxide fuel cell comprising the separator for a solid oxide fuel cell according to claim 7.

Images