JP2003272651A - Manufacturing method of metal separator for fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a metal separator for a fuel cell enabled to grind a surface rolling influenced layer of a base material and make a conductive intercalated materials protrude in one process. <P>SOLUTION: The manufacturing method of the metal separator for the fuel cell having a conductive intercalated materials in the metal texture is provided with a process of injecting liquid including two or more kinds of abrasives with different particle sizes on a material plate after the rolling. <P>COPYRIGHT: (C)2003,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a metal separator provided in a polymer electrolyte fuel cell. 2. Description of the Related Art A polymer electrolyte fuel cell has a unit structure in which separators are stacked on both sides of a plate-shaped electrode structure (MEA: Membrane Electrode Assembly).
A plurality of units are stacked to form a fuel cell stack. The electrode structure has a three-layer structure in which an electrolyte membrane made of an ion exchange resin or the like is interposed between a pair of gas diffusion electrodes constituting a positive electrode (cathode) and a negative electrode (anode). The gas diffusion electrode has a gas diffusion layer formed outside the electrode catalyst layer in contact with the electrolyte membrane. Further, the separator is laminated so as to be in contact with the gas diffusion electrode of the electrode structure, and a gas flow path and a refrigerant flow path for flowing gas between the separator and the gas diffusion electrode are formed. According to such a fuel cell, for example, hydrogen gas, which is a fuel, flows through the gas flow path facing the gas diffusion electrode on the negative electrode side, and oxidizes oxygen or air into the gas flow path facing the gas diffusion electrode on the positive electrode side. When an inert gas flows, an electrochemical reaction occurs to generate electricity. The separator supplies electrons generated by a catalytic reaction of hydrogen gas on the negative electrode side to an external circuit,
It is necessary to have a function of sending electrons from an external circuit to the positive electrode side. For this reason, conductive materials made of graphite or metal materials are used for the separator. Metallic materials, in particular, have excellent mechanical strength and can be made lighter and more compact by making them thinner. This is advantageous in that As a metallic separator, a stainless steel plate in which nonmetallic conductive inclusions forming conductive paths are dispersed in a metal structure is press-formed from the economical point of view. [0004] However, since the stainless steel sheet has a surface rolling affected layer, in the production of the separator as described above, the surface rolling affected layer is removed by grinding. A step of exposing sound conductive inclusions that are not affected by rolling on the surface and a step of projecting the exposed conductive inclusions to reduce contact resistance are required. However, there has been a problem that a natural oxide film is formed on the surface of the base material between the step of grinding and removing the surface rolling-affected layer and the step of projecting the conductive inclusions. Once the natural oxide film is formed on the surface of the base material, the effect of improving the conductivity by the conductive inclusion protruding process is sufficient due to the presence of the natural oxide film even if the conductive inclusion protruding process is performed thereafter. You won't get it. Therefore, in order to obtain sufficient conductivity, a more complicated process must be performed, and there has been a problem that the manufacturing cost is increased. Accordingly, the present invention provides a method of manufacturing a metal separator for a fuel cell, which can grind the surface rolling-affected layer of a base material and protrude conductive inclusions in one step. It is an object. [0006] A method of manufacturing a metal separator for a fuel cell according to the present invention is directed to a method of manufacturing a metal separator for a fuel cell having conductive inclusions in a metal structure. The method is characterized in that a step of injecting a liquid containing two or more types of abrasives having different particle diameters onto the material plate is provided. [0007] In the above-mentioned material plate of the metal separator, since a conductive inclusion having a hardness higher than that of the base material is present in the metal structure, a method of manufacturing a metal separator for a fuel cell is usually employed in the metal plate. In addition, a step of grinding and removing the base material surface for grinding not only the base phase but also the conductive inclusions and a step of projecting the conductive inclusions for grinding only the base material surface are required. A common means used in these steps includes a wet blast method. Generally, the wet blast method is a method in which a liquid containing one kind of abrasive is sprayed onto a workpiece from a slit-shaped injection port. Use a large-grain abrasive that can provide a large kinetic energy that can grind even conductive inclusions.In the process of projecting conductive inclusions, a small kinetic energy that can grind only the base metal surface is obtained. An abrasive having a small particle size is used. On the other hand, in the method for producing a metal separator for a fuel cell according to the present invention, two particles having different particle sizes are used.
The most characteristic feature is that a specific wet blast method in which a liquid containing more than one kind of abrasive is sprayed on the separator is used. Therefore, according to the present invention, not only the base phase but also the conductive inclusions are ground and removed by the abrasive having a large particle diameter, and at the same time, only the surface of the base material is ground by the abrasive having a small particle diameter. In a single step, it is possible to grind and remove the surface of the base material and project the conductive inclusions, prevent the formation of a natural oxide film on the surface of the base material, and obtain an excellent conductivity improving effect. Further, according to the present invention, since there is no need for a complicated process as in the related art, there is an effect that the manufacturing cost can be kept low. Further, in a fuel cell using this separator, an excellent power generation voltage can be exhibited. The step of injecting the liquid containing two or more types of abrasives having different particle diameters may be performed after the press forming of the separator material plate, or may be performed before the press forming. Further, in the production method of the present invention, it is preferable to passivate the surface of the separator material plate, and this passivation step can be performed at any stage after the above-mentioned wet blasting step. May go. Further, the passivation treatment liquid is not particularly limited as long as it can form a passivation film on the surface of the base material of the separator. The material of the separator according to the present invention includes:
An austenitic stainless steel sheet having conductive inclusions is exemplified. Specifically, each component shown in Table 1 and the balance contain Fe, B and unavoidable impurities, and Cr, Mo and B satisfy the following equation (1): B is an M ₂ B and MB type boride, M
₂₃ (C, B) _6- type borides are precipitated on the surface, and these borides are austenitic stainless steel sheets that are conductive inclusions that form conductive paths on the surface of the separator. Cr (wt%) + 3 × Mo (wt%) − 2.5 × B (wt%) ≧ 17 (1) Next, the effects of the present invention will be described in detail using embodiments of the present invention. A. Manufacture of Separator <Example> A 0.2 mm thick austenitic stainless steel sheet containing the components shown in Table 2 and the balance Fe and unavoidable impurities is cut into a square of 100 mm x 100 mm to form a separator material. I got a board. Then
23.3 types of alumina particles having a particle size of 60 μm and 180 μm are used as abrasive grains on both sides of the material plate at a weight ratio of 1: 1 to 33.3.
Tap water maintained at 30 ° C. mixed with a weight% was sprayed from a spray nozzle at a spray pressure of 1 kg / cm ² for 30 seconds to grind the mother phase by wet blasting and to project conductive inclusions. Next, after washing and drying the material plate,
Press forming was performed with a pressing load of 50 tons to obtain the separator of Example. [Table 2] <Comparative Example> On both surfaces of the same material plate of the separator as in the embodiment, tap water maintained at 30 ° C. mixed with 33.3% by weight of alumina particles having a particle size of 180 μm as abrasive particles was sprayed from a spray nozzle. 3 with a spray pressure of 1 kg / cm ²
Spraying was performed for 0 second, and grinding by wet blasting was performed. Next, on both surfaces of this material plate, tap water maintained at 30 ° C., which was obtained by mixing 33.3% by weight of alumina particles having a particle size of 60 μm as abrasive particles, was sprayed from a spray nozzle at a pressure of 1 kg.
/ Cm ² for 30 seconds to project the conductive inclusions by wet blasting. After that, the material plate was washed with water, dried, and then press-formed with a press load of 50 tons.
A separator of a comparative example was obtained. B. Time-dependent change in power generation voltage Using the separators of the examples and the comparative examples obtained as described above, one fuel cell unit in which separators are laminated on both sides of the electrode structure (MEA) is formed, and this unit is used for power generation. Then, the change in the generated voltage with the increase in the generated current density was measured. The result is shown in FIG. As is apparent from FIG. 1, in the fuel cell unit using the separator of the embodiment in which the grinding of the surface rolling affected layer and the projection of the conductive inclusions are simultaneously performed, the grinding of the surface rolling affected layer and the conductive intermediate are performed. In comparison with the fuel cell unit using the separator of the comparative example in which the protrusion of the object was sequentially performed, the decrease in the generated voltage due to the increase in the generated current density was extremely small. As described above, according to the present invention,
By using a special wet blast method that sprays a liquid containing two or more abrasives having different particle diameters onto a rolled material plate, grinding of the surface rolling affected layer of the base material and protrusion of conductive inclusions At the same time, the formation of a natural oxide film on the surface of the base material can be prevented, and an excellent conductivity improving effect can be obtained.In the fuel cell using this separator, an excellent power generation voltage is exhibited. be able to.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a relationship between a power generation current density and a power generation voltage in a fuel cell using a separator of the present invention or a comparative example.

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Koji Kotani             1-4-1, Chuo, Wako-shi, Saitama Stock Association             Inside the Honda Research Laboratory (72) Inventor Masao Utsunomiya             1-4-1, Chuo, Wako-shi, Saitama Stock Association             Inside the Honda Research Laboratory F term (reference) 5H026 AA06 BB00 BB02 EE02 EE08

Claims (1)

Claims: 1. A method for manufacturing a metal separator for a fuel cell having conductive inclusions in a metal structure, wherein two or more types of abrasives having different particle diameters are formed on a rolled material plate. A method for producing a metal separator for a fuel cell, comprising a step of injecting a liquid containing: