JP2021150207A - Coated steel material for solid oxide-type fuel cell member, solid oxide fuel cell member, and production method thereof - Google Patents

Abstract

To provide a solid oxide fuel cell member which has an excellent oxidation resistance and has suppressed Cr poisoning, and a production method thereof, and a steel material therefor.SOLUTION: A coated steel material for a solid oxide fuel cell member has a metal base material and a metal coating as a surface layer of the metal base material. The metal base material contains, by mass%, C: over 0 and 0.1% or less, Al: 0.2% or less, Si:0.2% or less, Mn: 0.1% or more and 1.0% or less, Cr: 20.0% or more and 26.0% or less, Ni: 0.1% or more and 1.0% or less, Cu: 0.3% or more and 4.0% or less, W: 1.0% or more and 3.0% or less, La: 0.02-0.12%, Zr: 0.01-0.5%, and La+Zr: 0.03% or more and 0.5% or less with the balance consisting of Fe and inevitable impurities. The metal coating has a Co layer of 0.5-5.0 μm in thickness. A solid oxide fuel cell member arranged by use of the coated steel material, and a production method thereof are also disclosed.SELECTED DRAWING: Figure 1

Description

The present invention relates to a coated steel material for a solid oxide fuel cell member, a solid oxide fuel cell member, and a method for manufacturing the same.

The solid oxide fuel cell has excellent features such as high power generation efficiency, low amount of SOx, NOx, and CO ₂ generated, good responsiveness to load fluctuations, and compactness. It is expected to be applied to a wide range of power generation systems such as large-scale centralized type as an alternative to thermal power generation, decentralized type in the suburbs of cities, and private power generation. In recent years, solid oxide fuel cells that operate at medium and high temperatures of about 700 to 900 ° C have been developed, and among them, the parts for solid oxide fuel cells such as separators, interconnectors, and current collectors are medium. Properties such as oxidation resistance at high temperatures, electrical conductivity, thermal expansion coefficient close to that of electrolytes and electrodes, low cost, and ease of processing are required. For this reason, a ferritic stainless steel, for example, a metal base material made of a Fe—Cr alloy is preferably used as the material. The applicant of the present application has also proposed ferrite-based stainless steel having excellent oxidation resistance as JP-A-2007-16297 (Patent Document 1), International Publication No. 2012/144600 (Patent Document 2), and the like.

When a Fe-Cr alloy is used for a separator, interconnector, current collector, etc., it is placed in a high-temperature oxidizing atmosphere with the operation of the solid oxide fuel cell, so that oxidation progresses on the metal surface and Cr _{An oxide film mainly composed of 2} O ₃ is formed, which acts as a protective film to ensure oxidation resistance. However, on the other hand, Cr or Cr compounds (hereinafter abbreviated as Cr) volatilize from the oxide film mainly composed of _{Cr 2} O _{3 and reprecipitate on the electrode, gradually deteriorating the electrode characteristics, so-called Cr poisoning.} There is a problem.
In order to solve this problem, separators, interconnectors, and current collectors are used in which a coating film having both oxidation resistance and conductivity is provided on the surface of a metal base material.

For example, Patent Document 3 discloses a solid oxide fuel cell containing a separator whose surface is coated with a Ni—Co alloy as a component. When a Ni—Co alloy coated at a predetermined ratio is surface-treated (oxidized) for a certain period of time, an oxide (NiCr ₂ O ₄ ) having a spinel-type structure having excellent conductivity is formed on the surface. It is also stated that the coating of Ni-Co alloy forms a _{double oxide layer in which an oxide film of chromium oxide (Cr 2} O ₃ ) is formed inside the coating, and the evaporation of chromium can be prevented by the coating layer of nickel cobalt. Has been done.

Further, Patent Document 4 discloses a method for manufacturing an interconnector for a fuel cell, which is formed by forming a film containing Co oxide as a main component on a base material containing stainless steel as a main component. After Co-plating the base material, the surface of the base material is converted into a coating of Co-oxide by performing an oxidation step of oxidizing the Co-plated layer in an oxidizing atmosphere. It is described that Cr evaporation can be suppressed when a Co oxide film is provided on the surface. On the other hand, when the reaction of diffusing the metal Co to the base material occurs preferentially, the oxidation resistance of the base material is lowered, so that the surface roughness (Ra) of the base material is 1.2 μm before Co plating. By performing the following polishing steps, it is difficult to reduce the oxidation resistance of the base material. It is generally known that the oxidized Co described in Patent Document 7 has a spinel-type structure.

Japanese Unexamined Patent Publication No. 2007-16297 International Publication No. 2012/144600 Japanese Unexamined Patent Publication No. 2012-119126 Japanese Unexamined Patent Publication No. 2011-192546

As described above, the surface of a metal base material made of an Fe—Cr alloy is coated with a metal Co or Ni—Co alloy, and the surface is oxidized by intentionally performing a preliminary oxidation treatment to oxidize the spinel. It is known that a Co film or a Ni—Co oxide film is formed and used as a separator, an interconnector, and a current collector.

When a metal film containing austenite stabilizing elements such as Ni and Mn is coated on a metal base material like the Ni-Co alloy described in Patent Document 3, Ni and Mn and the like diffuse to the metal base material side. Then, the ferrite structure on the surface of the metal base material is destabilized and the austenite structure is stabilized. When austenite is formed on the surface of the metal base material, the coefficient of thermal expansion increases significantly, causing delamination between the metal base material and the coating film, and the difference in thermal expansion between the electrodes and electrolytes that make up the cell increases, causing damage to the cell. There is a risk of causing. Further, it is necessary to perform surface treatment (oxidation treatment) for a certain period of time in order to form a Ni—Co oxide film.

The technique disclosed in Patent Document 4 is an interconnector for both improving the oxidation resistance of the metal base material of the interconnector and preventing adverse effects on the member connected to the interconnector represented by the volatilization of the chromium component. This is a method for producing a Co oxide film on the surface by reducing the surface roughness of the metal base material and performing a preliminary oxidation treatment so that Co in the Co plating layer does not diffuse to the metal base material. .. That is, the Co oxide film is composed of a pure Co oxide, and is characterized in that neither the diffusion of Co into the metal substrate nor the diffusion of the alloying element from the metal substrate into the Co plating layer is allowed. However, it cannot be said that the Co oxide film has sufficient denseness of the oxide film, and there is a possibility that the oxide film is peeled off, so that a sufficient effect of suppressing Cr poisoning may not be obtained. In addition, it is necessary to perform a preliminary oxidation treatment in order to form a Co-oxide film.

From the above, an object of the present invention is to provide a solid oxide fuel cell member having excellent oxidation resistance and suppressing Cr poisoning. Another object of the present invention is to provide a solid oxide fuel cell member and a method for manufacturing the same.

The present inventors examined the composition of the metal base material to which the Co coating is applied for the above purpose. As a result, in a metal base material made of an Fe—Cr-based ferrite alloy having an appropriate amount of Mn and Cu and having excellent oxidation resistance, the metal group is used during the production and / or high temperature holding during operation of the solid oxide fuel cell. By diffusing Mn and Cu from the material to the Co coating, _{a spinel-type oxide layer containing Mn and Cu (Co, Mn, Cu) 3} O ₄ is formed to suppress Cr evaporation, and the metal substrate and the metal substrate. (Co, Mn, Cu) on the boundary of the spinel-type oxide layer ₃ O ₄ is chromia-based oxide layer is formed, an oxide of two layers composed of spinel-type oxide layer and chromia-based oxide layer We have found that the layer improves the oxidation resistance and that the metal substrate maintains the ferrite structure even after long-term oxidation, and has reached the present invention.

That is, one aspect of the present invention is a coated steel material for a solid oxide fuel cell member having a metal coating on the surface layer of the metal base material, and the metal base material has a mass% of C: more than 0% and 0.1. % Or less, Al: 0.2% or less, Si: 0.2% or less, Mn: 0.1% or more and 1.0% or less, Cr: 20.0% or more and 26.0% or less, Ni: 0.1 % Or more and 1.0% or less, Cu: 0.3% or more and% 4.0% or less, W: 1.0% or more and 3.0% or less, La: 0.02% or more and 0.12% or less, Zr: It is composed of 0.01% or more and 0.5% or less, La + Zr: 0.03% or more and 0.52% or less, the balance Fe and unavoidable impurities, and the metal coating has a thickness of 0.5 μm or more and 5.0 μm or less. It is a coated steel material for a solid oxide fuel cell member, which is characterized by having a layer.
Preferably, the metal base material contains Mn: 0.1% or more and 0.5% or less, and Cu: 0.3% or more and 2.0% or less.
Preferably, the metal base material has a plate shape having a thickness of 1.5 mm or less.

Further, another aspect of the present invention is a solid oxide fuel cell member using the above-mentioned coated steel material for a solid oxide fuel cell member, and the solid oxide fuel cell member is the metal. The surface layer of the base material has an oxide film, and the oxide film is a spinel-type oxide layer formed directly above the A layer, which is a chromia-based oxide layer, and containing Co, Mn, and Cu. It is a member for a solid oxide fuel cell, characterized in that it is composed of a layer B, which is a solid oxide fuel cell.

Further, in another aspect of the present invention, the above-mentioned coated steel material for a solid oxide type fuel cell member is applied to a solid oxide type fuel cell, and the above solid oxide type fuel cell is used in an operating environment. The metal film formed on the coated steel material for the oxide type fuel cell member is changed into an oxide film to form a solid oxide type fuel cell member, and the above oxide film is the A layer which is a chromae-based oxide layer. This is a method for manufacturing a solid oxide type fuel cell member, which is formed directly above the A layer and is composed of a B layer which is a spinel type oxide layer containing Co, Mn and Cu.

According to the present invention, a highly reliable solid oxide fuel cell member that does not require special pre-oxidation treatment, has excellent current collecting characteristics for a long period of time, and suppresses Cr poisoning, and a method for manufacturing the same. Can be obtained. Then, a coated steel material for a solid oxide fuel cell member suitable for these can be obtained.

It is a cross-sectional micrograph of a solid oxide fuel cell coated steel material when not in use. It is a cross-sectional micrograph of a solid oxide fuel cell coated steel material after heating at 850 ° C. for 4000 hours. (A) It is an electron diffraction image of [001] incident obtained from a metal coating region when a solid oxide fuel cell coated steel material is not used. (B) It is an electron diffraction simulation image of [001] incident of a dense hexagonal structure. (A) It is an electron diffraction image of [111] incident obtained from a metal base material region after heating a coated steel material for a solid oxide fuel cell at 850 ° C. for 4000 hours. (B) It is an electron diffraction simulation image of [111] incident of ferrite. (A) [110] Incident electrons obtained from the oxide layer region located on the upper side of the two oxide layers after heating the coated steel material for a solid oxide fuel cell at 850 ° C. for 4000 hours. It is a diffraction image. (B) It is an electron diffraction simulation image of [110] incident of a spinel type structure. (A) A reflected electron image of a cross section of a solid oxide fuel cell coated steel material after being heated at 850 ° C. for 4000 hours. (B) It is the surface analysis result of Co by the electron probe microanalyzer. (C) It is the surface analysis result of Mn by the electron probe microanalyzer. (D) It is the surface analysis result of Cu by the electron probe microanalyzer.

The metal base material in the coated steel material for a solid oxide fuel cell member of the present invention will be described. The metal base material contains C: more than 0% and 0.1% or less in mass%, Al: 0.2% or less, Si: 0.2% or less, Mn: 0.1% or more and 1.0% or less, Cr: 20.0% or more and 26.0% or less, Ni: 0.1% or more and 1.0% or less, Cu: 0.3% or more and% 4.0% or less, W: 1.0% or more and 3.0% or less , La: 0.02 or more and 0.12% or less, Zr: 0.01 or more and 0.5% or less, La + Zr: 0.03% or more and 0.5% or less, and a metal material composed of the balance Fe and unavoidable impurities is used. ..
The Fe-Cr alloy having this composition is a ferrite alloy, and when it has a Co coating on the surface of the metal substrate, it is caused by the diffusion of Mn and Cu into the metal coating at the operating temperature of the solid oxide fuel cell. Co, Mn, Cu) It _{is possible to form a 3} O ₄ spinel type oxide layer to suppress the evaporation of Cr, improve the oxidation resistance, and suppress the deterioration of the performance of the fuel cell.
The reasons for defining the content of each element are as follows. The content of each element is described as% by mass.

<C: More than 0% and less than 0.1%>
C is an element that reduces the amount of Cr in the base material by combining with Cr and lowers the oxidation resistance. Therefore, in order to improve the oxidation resistance, it is effective to make C as low as possible, and in the present invention, it is limited to the range of 0.1% or less. The preferred upper limit of C is 0.04%.
However, in the case of the coated steel material for a solid oxide fuel cell member of the present invention containing Zr, C forms Zr carbide (Zr carbide if N is also present), but if C is too low, Zr carbide Even if Zr that does not form a solid solution is dissolved in the ferrite matrix, excess Zr may still remain. The excess Zr reacts with Fe to form an intermetallic compound such as the Laves phase and precipitates to reduce the oxidation resistance. Therefore, C needs to exceed 0%. The preferable lower limit of C is 0.001%.

<Al: 0.2% or less>
_{Al forms Al 2} O ₃ in the form of particles and needles in the metal structure near the chromium-based oxide at the operating temperature of the solid oxide fuel cell. The chromia-based oxide is an oxide mainly composed of chromia. As a result, the outward diffusion of Cr becomes non-uniform and the formation of a stable chromia-based oxide layer is hindered, thereby deteriorating the oxidation resistance. Therefore, in the present invention, the range is limited to 0.2% or less (including 0%).

<Si: 0.2% or less>
Si forms a _{SiO 2} film near the interface between the chromium-based oxide layer and the base material at the operating temperature of the solid oxide fuel cell. Since _{the electrical resistivity of SiO 2} is higher than that of the chromium-based oxide layer, the electrical conductivity is lowered. Further, _{similarly to the formation of Al 2} O ₃ described above, the oxidation resistance is deteriorated by hindering the formation of a stable chromia-based oxide layer. Therefore, in the present invention, the range is limited to 0.2% or less (including 0%).

<Mn: 0.1% or more and 1.0% or less>
Mn is an element that, when the metal base material has a Co coating on the surface, diffuses from the metal base material into the Co coating together with Cu at an operating temperature of about 700 ° C. to 900 ° C. to form a spinel-type oxide. The spinel-type oxide layer containing Co and Mn is formed on the outside (surface side) of the chromia-based oxide layer. In this spinel type oxide layer, Cr forming a composite oxide that is deposited on ceramic parts such as electrolytes and electrodes of the solid oxide fuel cell to deteriorate the performance of the fuel cell is a steel for the solid oxide fuel cell. It has a protective effect that prevents it from evaporating from. Therefore, a minimum of 0.1% is required.
On the other hand, if it is added excessively, the Mn content in the spinel-type oxide layer increases, the oxide film becomes thick, and the oxidation resistance and conductivity may deteriorate. Therefore, Mn has an upper limit of 1.0%. The preferred upper limit of Mn is 0.5%.

<Cr: 20.0% or more and 26.0% or less>
Cr is an element necessary for maintaining the ferrite structure of a metal substrate and for achieving excellent oxidation resistance by forming a dense chromium-based oxide layer at the operating temperature of a solid oxide fuel cell. Is. A minimum of 20.0% is required to obtain good oxidation resistance and electrical conductivity. The lower limit of Cr that is preferable is 22.0%, and the lower limit of Cr that is more preferable is 23.0%.
However, excessive addition is not so effective in improving the oxidation resistance and causes deterioration in workability, so the upper limit is limited to 26.0%. The preferred upper limit of Cr is 25.0%.

<Ni: 0.1% or more and 1.0% or less>
Ni is effective in improving toughness by adding a small amount. Further, since it has the effect of improving the hot workability of steel containing Cu, a minimum of 0.1% is required. On the other hand, Ni is an austenite-forming element, and when it is excessively contained, it tends to have a duplex structure of ferrite-austenite and increases the coefficient of thermal expansion. Further, when producing a ferrite-based stainless steel as in the present invention, for example, when a melting raw material of a recycled material is used, it may be inevitably mixed. If the Ni content is too high, there is a concern that the bondability may be lowered or the ceramic parts may be damaged due to the difference in thermal expansion with the ceramic parts, so that a large amount of addition or mixing is not preferable. Therefore, in the present invention, the upper limit of Ni is set to 1.0%.

<Cu: 0.3% or more and 4.0% or less>
When the metal substrate has a Co film on its surface, Cu diffuses from the metal substrate into the Co film at an operating temperature of about 700 ° C. to 900 ° C., and Co and Mn are formed on the chromium-based oxide layer. The spinel-type oxide containing is densified. This spinel-type oxide has the effect of suppressing the evaporation of Cr from the chromium-based oxide layer. Therefore, a minimum of 0.3% is required. On the other hand, when Cu is added excessively, the Cu phase is precipitated in the matrix phase, making it difficult to form a dense chromia-based oxide layer at the location of the Cu phase, resulting in a decrease in oxidation resistance and hot workability. The upper limit of Cu was set to 4.0% because there is a possibility that the amount of copper may decrease or the ferrite structure may become unstable. The upper limit of preferred Cu is 2.0% or less.

<La: 0.02% or more and 0.12% or less>
La is indispensable to be added because it exhibits good oxidation resistance by densifying the oxide film containing Cr mainly by adding a small amount and improving the adhesion. When La is added less than 0.02%, the effect of improving the denseness and adhesion of the oxide film is small, while when added more than 0.12%, inclusions such as oxides containing La increase and hot working. La is 0.02% or more and 0.12% or less because the property may deteriorate.

<Zr: 0.01% or more and 0.5% or less>
Zr also has the effect of significantly improving the oxidation resistance and the electrical conductivity of the oxide film by densifying the oxide film by adding a small amount and improving the adhesion of the oxide film. When Zr is less than 0.01%, the effect of improving the denseness and adhesion of the oxide film is small, while when it is added more than 0.5%, many coarse compounds containing Zr are formed, resulting in hot workability and hot workability. Cold workability may deteriorate. Further, since it reacts with Fe to form an intermetallic compound such as a Laves phase and precipitates to lower the oxidation resistance, Zr is set to 0.01% or more and 0.5% or less.

<La + Zr: 0.03% or more and 0.52% or less>
In the present invention, the above-mentioned La and Zr are all preferably combined because they have an excellent effect of improving the oxidation resistance at high temperature, but in that case, the total of La and Zr is less than 0.03%. On the other hand, if it is added in excess of 0.52%, a large amount of compounds containing La and Zr are produced, which may reduce hot workability and cold workability. Therefore, La and Zr are 0.03% or more and 0.52% or less in total.

<W: 1.0% or more and 3.0% or less>
Generally, Mo is known as an element that exerts the same action and effect as W on solid solution strengthening and the like. However, as compared with Mo, W has an effect of appropriately suppressing the outward diffusion of Cr in the metal base material of the Fe—Cr based ferrite alloy when oxidized at the operating temperature of the solid oxide fuel cell. It is effective in suppressing excessive growth of a dense chromia-based oxide layer and maintaining a stable protective action for a long period of time. Therefore, in the present invention, W is essentially added alone.
By adding W, it is possible to appropriately suppress the outward diffusion of Cr in the metal base material of the Fe—Cr-based ferrite alloy, thereby suppressing the decrease in the amount of Cr inside the alloy after the formation of the chromium-based oxide layer. .. As a result, the dense chromia-based oxide layer is maintained for a long time, so that abnormal oxidation of the alloy can be prevented and excellent oxidation resistance can be maintained for a long time. A minimum of 1.0% is required to exert this effect. However, if W is added in excess of 3.0%, the hot workability deteriorates, so the upper limit of W is 3.0.

In the present invention, Fe and unavoidable impurities other than the above-mentioned elements are used. Hereinafter, typical impurities and their preferable upper limits are described below. Since it is an impurity element, the preferable lower limit of each element is 0%.
<Mo: 0.2% or less>
Mo is not positively added because it lowers the oxidation resistance, but the content of 0.2% or less does not significantly affect the oxidation characteristics, so the content is limited to 0.2% or less.
<S: 0.015% or less>
S forms sulfide-based inclusions with rare earth elements to reduce the amount of effective rare earth elements that have an effect on oxidation resistance, which not only lowers the oxidation resistance, but also improves hot workability and surface skin. Since it deteriorates, it is preferable to make it 0.015% or less. Preferably, it is 0.008% or less.
<P: 0.04% or less>
P is an element that is more easily oxidized than Cr that forms an oxide film, and in order to deteriorate the oxidation resistance, it is preferable to limit it to 0.04% or less. It is preferably 0.03% or less, more preferably 0.02% or less, and further preferably 0.01% or less.
<B: 0.003% or less>
B increases the growth rate of the oxide film at a high temperature of about 700 ° C. or higher, and deteriorates the oxidation resistance. Further, the contact resistance is deteriorated by increasing the surface roughness of the oxide film and reducing the contact area between the oxide film and the electrode. Therefore, B should be limited to 0.003% or less, and should be reduced to 0% as much as possible. The upper limit is preferably 0.002% or less, more preferably less than 0.001%.
<H: 0.0003% or less>
If H is excessively present in the Fe—Cr-based ferrite matrix, it easily gathers at defective parts such as grain boundaries and may cause hydrogen embrittlement, which may cause cracks during production. Therefore, 0.0003 It is good to limit it to% or less. More preferably, 0.0002% or less is preferable.

Next, the metal coating formed on the surface layer of the metal base material in the coated steel material for the solid oxide fuel cell member of the present invention will be described.
The metal coating of the present invention comprises a Co layer, which is composed of Co and other unavoidable impurities. The coated steel material for a solid oxide fuel cell of the present invention having this metal coating forms a spinel-type oxide layer containing Co, Mn and Cu at an operating temperature of about 700 ° C. to 900 ° C. to form a fuel cell member. Contributes to Cr poisoning resistance and oxidation resistance.
Among the unavoidable impurities, when Ni, which is an austenite stabilizing element, diffuses toward the metal base material, an austenite phase is formed near the surface in the metal base material, the thermal expansion coefficient increases, and the metal base material and oxides. It is a harmful element because delamination of the film occurs. Therefore, Ni is preferably 0.2% or less, more preferably 0.1% or less. Mn is also an austenite stabilizing element, but it has a smaller influence than Ni, and although it can be contained in a small amount and is effective for forming spinel-type oxides containing Co and Mn, Mn is contained in the metal substrate. When Mn is contained, it is not necessary to contain Mn in the Co film, and the Co film containing no Mn has better manufacturability. Therefore, the Mn is preferably 0.5% or less, more preferably 0.1. % Or less is good.

As the method for forming the metal film, any method for forming a dense film having excellent adhesion to the metal substrate can be selected. Preferred film forming methods include electroplating and electroless plating because a thin film can be formed relatively easily.

The thickness of the metal coating is preferably 0.5 to 5.0 μm in a state where it is not used as a coating steel material for a solid oxide fuel cell. If it is less than 0.5 μm, the spinel-type oxide film becomes thin and the effect of suppressing Cr evaporation becomes insufficient. Therefore, the lower limit is set to 0.5 μm. The lower limit of the preferable metal film thickness is 1.0 μm, and the lower limit of the more preferable metal film thickness is 1.5 μm. On the other hand, if it exceeds 5.0 μm, not only the oxide film becomes thick and the conductivity decreases, but also the oxide layer may be peeled off due to the thermal cycle in the repeated operation of the solid oxide fuel cell. Therefore, the upper limit is set to 5.0 μm. A more preferable upper limit of the thickness of the metal coating is 4.5 μm.

Since the grain boundaries have a higher atomic diffusion rate than those in the crystal grains, the diffusion of Mn and Cu in the metal film on the metal substrate is promoted at the operating temperature of the solid oxide fuel cell. Therefore, when it is not used as a coated steel material for a solid oxide fuel cell, it is preferable that the crystal grains of the metal coating have grain boundaries in an orientation close to perpendicular to the surface of the metal base material. At this time, "having grain boundaries in an orientation close to perpendicular to the surface of the metal base material" means that the boundary between the metal base material and the metal coating in the coated steel material is enlarged with an electron microscope as shown in FIG. This means that the grain boundaries observed in the metal film are 0 ° to 45 ° with respect to the vertical direction of the interface between the metal base material and the metal film.

After the metal film is formed, the Co metal film has a dense hexagonal crystal structure at room temperature in a state where it is not used as a coating steel material for solid oxide fuel cells, and its (001) plane lattice constant is It is known to be about 0.25 nm. On the other hand, the closest atom-to-atom distance of the (110) plane of the Fe—Cr-based ferrite alloy having a body-centered cubic structure, which is a metal base material, is about 0.25 nm, which is good because it is very close to the lattice constant of Co. Film formation is possible with an orientation relationship. This is also advantageous for film adhesion and crystal orientation control. Since the lattice constant changes when a large amount of impurity elements and alloying elements are contained in the Co film, there is a concern that the adhesion to the metal substrate may change. Therefore, the Co film has a dense hexagonal crystal structure. It is preferable to do so.

Next, the reason for defining the range of plate thickness in the metal base material of the coated steel material for the solid oxide fuel cell member of the present invention will be described.
The metal substrate of the present invention is provided by rolling, and the plate thickness thereof is preferably 1.5 mm or less. It is known that the oxidation resistance of alloys generally used in a high temperature environment decreases as the plate thickness decreases, and more significantly reflects the properties of the alloy material. The present invention can improve the oxidation resistance especially in a thin plate by achieving the above-mentioned alloy composition. Therefore, the preferable upper limit of the plate thickness of the coated steel material for the solid oxide fuel cell of the present invention is set to 1.5 mm. Needless to say, even when the plate thickness is more than 1.5 mm, the oxidation resistance of the coated steel material for a solid oxide fuel cell can be improved by achieving the alloy composition of the present invention.

By using the coated steel material for the solid oxide fuel cell member of the present invention, Mn and Cu of the metal base material are Co. It diffuses to the coating side to form a spinel-type oxide layer having Co, Mn and Cu. In addition, a chromia-based oxide layer is formed at the boundary between the metal substrate and the spinel-type oxide layer. Due to the structure of this two-layer oxide film, excellent oxidation resistance and suppression of Cr poisoning are realized. In other words, by using the coated steel material for the solid oxide fuel cell member of the present invention, as shown in FIG. 2, it has two oxide coatings on the surface layer of the metal base material, and has excellent oxidation resistance and Cr. It is possible to obtain a solid oxide fuel cell member that suppresses poisoning. At this time, the oxide film is composed of a layer A, which is a chromia-based oxide layer, and a layer B, which is a spinel-type oxide layer formed directly above the layer A and containing Co, Mn, and Cu.
The B layer, which is a spinel-type oxide layer formed directly above the A layer, which is a chromia-based oxide layer, is an oxide layer containing Co as a main component. The spinel-type oxide layer composed of only Co does not have sufficient density and stability of the oxide film, and there is a concern that peeling or the like may occur when the thickness is about 1 μm or more. A spinel-type oxide layer containing Co, Mn and Cu by diffusing and oxidizing Mn and Cu in a Co metal film from a metal base material made of an Fe—Cr-based ferrite alloy containing Mn and Cu specified in the present invention. Is formed directly above the A layer, the adhesion, denseness, and stability of the spinel-type oxide layer are improved, and even if the thickness is increased, it is difficult to peel off, and the spinel-type oxide layer is formed by Mn and Cu. The conductivity of is also improved.

As described above, the solid oxide fuel cell member having an oxide film on the surface layer of the metal base material, the above-mentioned metal base material has a mass% of C: more than 0% and 0.1% or less, Al. : 0.2% or less, Si: 0.2% or less, Mn: 0.1% or more and 1.0% or less, Cr: 20.0% or more and 26.0% or less, Ni: 0.1% or more 1. 0% or less, Cu: 0.3% or more and 4.0% or less, W: 1.0% or more and 3.0% or less, La: 0.02% or more and 0.12% or less, Zr: 0.01% It is composed of 0.5% or less, La + Zr: 0.03% or more and 0.52% or less, the balance Fe and unavoidable impurities, and the above oxide film is an A layer which is a chromia oxide layer and this A layer. It can be a member for a solid oxide fuel cell formed directly above the solid oxide fuel cell and composed of a layer B which is a spinel type oxide layer containing Co, Mn and Cu.
Preferably, the Mn and Cu are Mn: 0.1% or more and 0.5% or less, and Cu: 0.3% or more and 2.0% or less in mass%. Further, preferably, the metal base material has a plate shape having a thickness of 1.5 mm or less.

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.
A steel ingot was produced from the metal substrate of the present invention using a vacuum induction furnace or a vacuum smelting furnace. During vacuum melting or vacuum refining, melting was performed under controlled operating conditions in order to keep C, Si, Al and impurity elements within the specified range. The operating conditions referred to here are, for example, operating conditions in which the raw materials are carefully selected, the vacuum atmosphere in the furnace is increased, Ar bubbling, etc. are used alone or in combination.
The obtained ingots in mass% were C: 0.02%, Al: 0.053%, Si: 0.08%, Mn: 0.27%, Cr: 24.05%, Ni: 0. 59%, Cu: 0.9%, W: 2.02%, Zr: 0.21%, La: 0.06%, balance Fe and unavoidable impurities. Among the unavoidable impurities, Mo, P, B and H were in the ranges of Mo ≦ 0.2%, P ≦ 0.04%, B <0.001%, and H ≦ 0.0003%, respectively.
Then, the ingot was processed into a size of 1 mm by plastic working such as hot forging, hot rolling, and cold rolling, and then annealed at 950 ° C. for several minutes to obtain an annealed material.

A 10 mm (w) × 10 mm (l) × 1 mm (t) plate-shaped test piece was cut out from the above-mentioned annealed material, and the surface of the plate-shaped test piece was polished to # 1000 using sandpaper. Then, the surface of the plate-shaped test piece was plated with a Co coating having a thickness of 0.5 μm, 1.0 μm, and 4.0 μm to obtain a coated steel material shown in Table 1. At this time, as a comparative example, a plate-shaped test piece without Co-plating was prepared.

Various tests were performed using the above plate-shaped test piece.
First, the plate-shaped test piece was heat-treated at 850 ° C. for 500 to 5000 hours in the air, and then the weight before and after oxidation was measured. Further, with respect to the test piece heated at 850 ° C. for 5000 hours, the presence or absence of peeling of the oxide film was visually observed.
Next, with respect to the test pieces shown in Table 1, the degree of suppression of Cr evaporation was confirmed by the following test method. _{An alumina ring is placed on the test piece, and La 1-} xSrxMnO ₃ (hereinafter referred to as LSM) powder, which is preferably used for the air electrode of a solid oxide fuel cell, is contained in the alumina ring, and the absolute humidity is 10%. The heating was carried out for 30 hours in an atmosphere in which the heating temperature was fixed at 850 ° C. Then, the amount of Cr contained in the LSM powder was measured by ICP analysis. Table 2 shows the amount of oxidation increase, the presence or absence of peeling of the oxide film, and the amount of Cr evaporation in the above measurements.

No. defined in the present invention. The coated steel materials for solid oxide fuel cell members 1 to 3 are No. 1 of Comparative Example. Compared to 4, the amount of oxidation increased in 500 hours. This is because the Co coating contained in the coated steel material at the initial stage of oxidation includes an increase in oxidation when it changes to a spinel-type oxide coating. In discussing the oxidation resistance of a steel material exposed to a high-temperature oxidation atmosphere for a long time in a solid oxide fuel cell, it is appropriate to ignore this oxidation increase at the initial stage of oxidation. Therefore, looking at the increase in oxidation up to 5000 hours based on the weight at 500 hours, No. The coated steel materials for solid oxide fuel cells 1 to 3 are No. 1 of Comparative Example. It can be seen that the amount of oxidation increase is smaller than that of No. 4 and the oxidation resistance is improved. In addition, no peeling of the oxide film was observed after the heat treatment in any of the test pieces. However, No. Among the coated steel materials 1 to 3, No. The Co-coated steel material having a thickness of 1.0 μm in No. 2 has the largest increase in oxidation after 5000 hours based on the time of 500 hours. This is No. Since the Co-coated layer of the 0.5 μm Co-coated steel material of No. 1 is thin, the increase in the amount of Oxidation of Co is small, while No. In the 4.0 μm Co-coated steel material of No. 3, since the Co-coated layer is thick, a spinel-type oxide layer having a stable thickness is formed at the initial stage, and the growth rate is slowed down. No. In the 1.0 μm Co-coated steel material of 2, a slightly thick spinel-type oxide layer is formed, but the thickness is insufficient to sufficiently reduce the growth rate, so that the amount of oxidation increase is large. it is conceivable that.

From Table 2, No. 2 specified in the present invention. The coated steel materials for solid oxide fuel cells 1 to 3 are No. 1 of Comparative Example. On the other hand, it is clear that the amount of chromium evaporation is significantly suppressed at the initial stage of oxidation and after high-temperature long-term oxidation. However, the thinnest 0.5 μm Co-coated steel material No. In No. 1, Cr evaporation was detected, albeit slightly. Among the coated steel materials 1 to 3, the result is slightly inferior in terms of suppressing Cr evaporation.
From the above results, the Co coating thickness is preferably 1.5 μm or more in order to achieve both oxidation resistance and Cr evaporation suppression at a high level.

No. in Table 1 A transmission electron microscope observation of a metal base material and a metal coating was performed on the test piece of No. 3. The obtained photograph is shown in FIG. The metal film has grain boundaries in the direction perpendicular to the metal substrate. Further, FIG. 3 shows an electron diffraction image of [001] incident obtained from the metal film region, and it can be seen from the agreement with the electron diffraction simulation image that the metal film has a dense hexagonal structure.

No. in Table 1 With respect to the test piece of No. 3, the metal substrate and the oxide film after heating at 850 ° C. × 4000 hours were observed with a transmission electron microscope. The obtained photograph is shown in FIG. By heating in the atmosphere, two oxide films, which are a chromia-based oxide layer and a spinel-type oxide layer, are formed in this order from the metal substrate side. At this time, FIG. 4 shows an electron diffraction image of [111] incident on the metal substrate which is the region of reference numeral 5 in FIG. 2. However, from the agreement with the electron diffraction simulation image, the metal substrate has a ferrite structure even after heating. You can see that it is holding. Further, the electron diffraction image of [110] incident obtained from the region of reference numeral 3 in FIG. 2 is shown in FIG. 5, and it can be confirmed from the agreement with the electron diffraction simulation image that the electron diffraction image has a spinel-type structure.

No. in Table 1 After heating the test piece 3 at 850 ° C. for 4000 hours, Ni plating was applied to prevent the oxide layer from peeling off due to processing, and the metal substrate and the oxide film were observed by scanning electron microscopy and Co, Mn by an electron probe microanalyzer. , Cu surface analysis was performed. The obtained photograph is shown in FIG. By comparing the reflected electron image with the surface analysis of each element, it can be confirmed that the region of the spinel-type oxide layer contains Mn and Cu in addition to Co.

1 Metal coating 2 Metal base material 3 Spinel type oxide layer 4 Chromia-based oxide layer 5 Metal base material 6 Ni plating

Claims (5)

A coated steel material for a solid oxide fuel cell member having a metal coating on the surface layer of a metal base material.
The metal base material contains C: more than 0% and 0.1% or less, Al: 0.2% or less, Si: 0.2% or less, Mn: 0.1% or more and 1.0% or less, Cr in mass%. : 20.0% or more and 26.0% or less, Ni: 0.1% or more and 1.0% or less, Cu: 0.3% or more and 4.0% or less, W: 1.0% or more and 3.0% Below, La: 0.02% or more and 0.12% or less, Zr: 0.01% or more and 0.5% or less, La + Zr: 0.03% or more and 0.52% or less, the balance Fe and unavoidable impurities.
The metal coating is a coated steel material for a solid oxide fuel cell member, which comprises a Co layer having a thickness of 0.5 μm or more and 5.0 μm or less. The solid oxide according to claim 1, wherein the Mn and Cu are Mn: 0.1% or more and 0.5% or less and Cu: 0.3% or more and 2.0% or less in mass%. Coated steel material for fuel cell members. The coated steel material for a solid oxide fuel cell member according to claim 1 or 2, wherein the metal base material has a plate shape having a thickness of 1.5 mm or less. A solid oxide fuel cell member using the coated steel material for the solid oxide fuel cell member according to claims 1 to 3.
The solid oxide fuel cell member has an oxide film on the surface layer of the metal base material.
The oxide film includes a layer A, which is a chromia-based oxide layer, and a layer A.
A member for a solid oxide fuel cell, which is formed directly above the layer A and is composed of a layer B, which is a spinel-type oxide layer containing Co, Mn, and Cu. The coated steel material for a solid oxide fuel cell member according to claims 1 to 3 is applied to a solid oxide fuel cell.
Under the operating environment of the solid oxide fuel cell, the metal film formed on the coated steel material for the solid oxide fuel cell member is changed to an oxide film to form a member for the solid oxide fuel cell.
The oxide film includes a layer A, which is a chromia-based oxide layer, and a layer A.
A method for producing a solid oxide fuel cell member, which is formed directly above the A layer and is composed of a B layer, which is a spinel-type oxide layer containing Co, Mn, and Cu.

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