JPH0193062A - Manufacture of separator for fuel cell - Google Patents

Abstract

PURPOSE:To decrease deformation in a working process and to reduce cost by forming a separator with a nickel-stainless steel clad material, having a specified clading ratio, in which pure nickel or high nickel steel is formed to fuel gas side and chromium-nickel stainless steel is faced to oxidizing gas side. CONSTITUTION:A separator 5 is made of nickel stainless steel clad material having low nickel ratio, and its nickel side 5a is faced to an anode 7 and the stainless steel side 5b is faced to a cathode 10. The separator 5 is formed by the explosion bonding or welding of a nickel plate and a stainless steel plate and by rolling them to form a thin clad plate and by pressing. Although deformation arises by the difference of rolling property of each material, by limiting the clading ratio of nickel to stainless steel to 0.2-20%, deformation in rolling is decreased. The yield of the clad material is increased and in addition, cost is reduced by thinning the nickel plate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a molten carbonate fuel cell, and particularly to a method for manufacturing a fuel cell separator in which fuel cell bodies are laminated.

[Prior art] The principle of a fuel cell is the reverse reaction of water electrolysis, in which hydrogen in the fuel and oxygen in the air are chemically reacted to generate electricity and water at the same time. .

To explain this with reference to FIG. 2, the fuel cell body 1 includes a porous anode electrode (fuel electrode) 2 that reacts with fuel gas such as hydrogen, a cathode electrode (air electrode) 3 that reacts with oxidizing gas, and a porous anode electrode (fuel electrode) 2 that reacts with fuel gas such as hydrogen; It consists of an electrolyte 4 made of carbonate interposed between the picture electrodes 2 and 3, and as shown in the figure, fuel gas containing hydrogen is supplied to the anode electrode fi2, while oxidation gas containing oxygen and carbon dioxide is supplied to the cathode electrode 3. Gas is supplied, and a reaction occurs within each electrode 2, 3 as shown in the figure, hydrogen and oxygen react via carbonate ions (CO3-2) to generate electricity.

This fuel cell main body 1 is stacked in multiple stages using separators to obtain high output.

The separator is formed with a flow path for supplying fuel gas to the anode electrode 2 of one of the stacked battery bodies 1 and a flow passage for supplying oxidizing gas to the cathode electrode 3 side of the other battery body 1,
By stacking the battery bodies 1 with separators in between, flow paths for fuel gas and oxidizing gas are formed in each layer.

[Problems to be Solved by the Invention] By the way, since a molten carbonate fuel cell generates electricity by reacting water and oxygen in a high-temperature atmosphere of 600°C or higher,
Separators are exposed to high-temperature corrosive environments.

In other words, one side is in a reducing atmosphere (fuel gas) and the other side is in an oxidizing atmosphere (oxidizing gas), and the separator is exposed to oxidizing and reducing effects from both sides in a high-temperature atmosphere. No single metal has been found that can withstand this and is low in cost.Separators are made by laminating layers.
In order to connect the batteries above and below, it has a current collecting function and requires electronic conductivity, so it is best to form it with metal, but as mentioned above, no metal has been found that can withstand both environments. Based on basic corrosion tests, materials such as nickel for the fuel gas side and stainless steel or Alloy 800 for the oxidizing gas side are promising.

Therefore, it has been considered to construct the separator with a plating plate made of old plating, but there is a problem in that it is prone to peeling and cracking and does not exhibit sufficient corrosion resistance on the fuel side of the fuel cell (the side on which the nickel plating is applied).

The present invention was made in consideration of the above circumstances, and an object of the present invention is to provide a method for manufacturing a fuel cell separator that forms flow paths for fuel gas and oxidizing gas in a high-temperature atmosphere and has good corrosion resistance. do.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides fuel cells that are stacked between an anode electrode and a cathode electrode, and a fuel gas is provided on the anode side and oxidized on the cathode side. In a method for manufacturing a fuel cell separator that forms a gas flow path, the fuel gas side of the separator is made of pure nickel or high nickel steel, and the oxidizing gas side is made of chromium nickel steel, and the cladding ratio of the separator (Ni[ thickness/total plate thickness) is 0.2~
20%, and then a flow path is formed by press working.

[Function] According to the above configuration, N1 is thermodynamically stable on the anode side, and since it is old/SUS clad steel, there is little deformation during press working, and costs can be reduced.

[Example] A preferred example of the method for manufacturing a fuel cell separator of the present invention will be described below with reference to the accompanying drawings.

First, a molten carbonate fuel cell will be explained with reference to FIG.

FIG. 2 shows an exploded view, and in the figure, 5 is a separator of the present invention which will be described later, and wet seal frames 6a and 6b are superposed above and below the separator. In this upper fuel gas side wet seal frame 6a, an anode electrode 7 made of a porous plate is stacked on the separator 5, and an electrolyte tile 8 made of carbonate is polymerized on top of the anode electrode 7.

A cathode electrode 10 made of a porous plate is stacked with a punch plate 9 in between, and an electrolyte tile 8 is stacked in the wet seal frame 6b on the oxidizing gas side in the lower part. Further, an anode electrode 7 is stacked below the lower electrolyte tile 8, and a cathode electrode 10 is stacked above the upper electrolyte tile 8. Laminated.

The separator 5 has a corrugated groove 13 to form a fuel gas flow path 11 shown in solid lines in the upper part and an oxidant gas flow path 12 shown in dotted lines in the lower part.

The upper and lower wet seal frames 6a and 6b are formed with a U-shaped cross section, and their outer peripheries are joined to the separator 5 by seam welding or caulking by laser welding, and the flow paths 11 of the separator 5, 12 has holes 13a and 13b for supplying and discharging fuel gas and oxidizing gas. Also, electrolyte tiles 8, wet seal frames 6a, 6b
Holes 14 are formed at the four corners of the separator 5 for supplying and discharging fuel scum and oxidizing gas.

Now, the separator 5 is a clad Ni/S with a low Ni ratio.
O3 material is used, and as shown in FIG. 1, the first side 5a is the anode electrode 7 side, and the SUS side 5b is the cathode electrode 10
It is located on the side.

This separator 5 is made by making a thick slab by explosion bonding or welding one plate and an SUS plate, and then rolling this one after another.
This is a thin plate clad material that is pressed into the shape shown in the figure.

In this case, deformation occurs due to the difference in rolling characteristics between the Ni and SUS materials, and the yield when forming a thin plate of Ni/SUS clad material decreases. By setting the clad ratio of the Ni/SυS clad material to 0.2 to 20%, deformation during rolling is reduced, the yield of clad steel of the old/SUS material can be improved, and the Ni thickness is reduced. Ni/S
It is possible to reduce the cost of OS cladding materials.

This will be explained further.

When manufacturing SUS N1 single-sided clad steel,
The difficulty and economical efficiency of its production are largely related to the thickness ratio of Ni to the total thickness of the clad steel. There are two reasons for this. That is, (1) SUS and Ni have different coefficients of thermal expansion, and this difference in thermal expansion tends to cause deformation during heating and cooling during the manufacturing process of clad steel. For this reason, during hot rolling, it is often difficult for the rolls to bite, and the success rate of rolling decreases.

Further, during heat treatment, warping may easily cause troubles such as contact with the furnace wall or ceiling of the heating furnace.

■ There is a large difference in deformation resistance between SuS and Ni during hot and cold rolling, with Ni being easier to stretch.

This licking, warpage and bending due to rolling are likely to occur, and there is a high probability of misrolling during hot rolling. In cold rolling, it may become impossible to continue rolling due to deterioration of the rolled shape, and even if rolling is possible, it may become impossible to pass the sheet through the annealing and pickling line.

As a countermeasure against these problems, it is effective to reduce the thickness ratio of N1 to the total thickness. That is, if the thickness ratio of N1 is kept within a certain range, the influence of SuS becomes dominant on both the thermal expansion coefficient and plastic deformation, and the behavior becomes close to that of sUs alone.

Figure 3 shows the relationship between the Ni thickness ratio and the warpage height during annealing. The temperature in the furnace is set at 1150°C, and the change in warpage height is shown when the cladding ratio is changed.

As can be seen from FIG. 3, as the cladding ratio increases, the warpage height also increases, and when the cladding ratio exceeds about 30%, it hits the ceiling of the line annealing furnace.

Figure 4 shows the relationship between the radius of curvature of warpage and the rolling ratio during cold rolling.
This was obtained by changing the In this case, the total thickness of the material before rolling was 4.0 nn, and the rolling roll diameter was 50 ml. As can be seen from FIG. 4, as the rolling rate increases, the curvature also increases, and in particular, the higher the cladding ratio, the higher this tendency becomes. Figure 4 shows experimental values, but in actual rolling at manufacturing sites, if the warpage becomes large, rolling becomes impossible.
From these data, it is possible to manufacture it with the same degree of difficulty as SUS material, and the rad ratio is up to about 10%, and when it exceeds 20%, the number of steps increases and the difficulty of manufacturing increases rapidly.

There is no specific lower limit for the Ni thickness ratio in terms of manufacturing, but if the ratio is too small, there is a possibility that Ni oxidation loss or the underlying steel may be exposed during the eaves removal process in the manufacturing process. This results in unstable cladding quality. Therefore, for a plate having a thickness of 2+ nm or less, it is necessary to make the Ni thickness 0.2% or more of the total thickness.

As described above, the range of the Ni thickness ratio is set to 0.2 to 20% of the total thickness of the clad steel.

By using this 0.2 to 20% Ni/SUS cladding material as the material for the separator 5, there is no problem with rolling as described above, and press deformation during press working of the separator 5 is reduced, resulting in a flat surface. The separator 5 can be made with good quality.

Also, the radiused material with small warpage can be easily set into the mold during press processing.

This separator 5 was explained using an example using Ni/SOS clad material, but the SUS used is 311330.
4L, 31133161, 5US310S etc. are used. In addition, it may be made of 5O3) INC0LLOY825 or heat-resistant steel, in short, any nickel-chromium steel with low N1 may be used.

In addition to pure nickel, any material having a high nickel content can be used as Nill.

In addition, the explanation was given using an example in which old/SOS cladding material is rolled, and the cladding ratio in that case is set to 0.2 to 20%. They may be formed so as to be directly joined.

Note that the web I/seal frames 6a, 6b are formed by press working, and alloy 800 or SuS material is a promising material. Furthermore, since the contact portion with the electrolyte tile 8 will be wetted with molten carbonate, the surface is coated with a corrosion-resistant coating such as aluminizing treatment. Further, the cathode electrode 10 is formed of porous Ni, which becomes a semiconductor with oxidizing gas and carbonate, but if it is too thick, the electrical resistance increases, so it needs to be made thin. Therefore, when R mechanical strength is required, it is reinforced with the illustrated punch plate 9, but it is not necessarily necessary to provide this punch plate 9. Further, since the anode electrode 7 is porous and has a carbonate storage function, it is better to have a thicker plate.

In this case, it has sufficient mechanical strength, so reinforcement with punched plates or the like is not necessary. Further, by setting the picture electrode 7.10 and the electrolyte tile 8 in the upper and lower wet seal frames 6a and 6b, leakage of molten carbonate around the electrodes and cracks in the tiles can be prevented.

[Effects of the Invention] As is clear from the above explanation, the present invention exhibits the following excellent effects.

(1) The separator is made of a cladding material made of pure nickel (or high nickel) and austenitic chromium-nickel steel, and the nickel side is placed on the anode electrode side and the austenitic chromium-nickel steel side is placed on the cathode electrode side. , it can have good corrosion resistance even when exposed to fuel gas and oxidizing gas in a high-temperature atmosphere.

(2) By using a clad material as the separator, peeling and cracking on the N1 side will not occur.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of essential parts of a fuel cell using the separator of the present invention, FIG. 2 is an exploded view of FIG. 1, FIG. 3 is a diagram showing the relationship between warpage and cladding ratio in the present invention, and FIG. The figure is a diagram showing the relationship between curvature and rolling rate during cold rolling in the present invention, and FIG. 5 is a diagram showing the principle of a molten carbonate fuel cell. In the figure, 5 is a separator, 5a is a Ni side, 5b is a SUS side, 7 is an anode electrode, 8 is an electrolyte tile, and 10 is a cathode electrode. Patent Applicant: Ishikawajima-Harima Heavy Industries Co., Ltd. Japan Metal Industry Co., Ltd. Representative Patent Attorney: Nobuo Kinutani Figure 2: Ni/total thickness cladding ratio (%) Figure 3: Rolling ratio

Claims (1)

[Claims] A method for manufacturing a fuel cell separator, which is interposed between an anode electrode and a cathode electrode in order to stack fuel cells, and forms a flow path for fuel gas on the anode side and oxidant gas on the cathode side, The separator's cladding ratio (N
1. A method for producing a fuel cell separator, which comprises forming a separator to a ratio (i plate thickness/total plate thickness) of 0.2 to 20%, and then forming a flow path by press working.