Stainless steel with excellent conductivity, preparation method of stainless steel, interconnection board and preparation method of interconnection board

Abstract

The invention discloses stainless steel with excellent conductivity, a preparation method of the stainless steel, an interconnection plate and a preparation method of the interconnection plate. The technical problems that in the prior art, stainless steel is poor in conductivity and oxidation resistance in the working process of a fuel cell are solved. The stainless steel provided by the invention comprises the following chemical components in percentage by weight: 13%-30% of Cr, 0.002%-3.0% of Be, 0.05%-0.5% of Zr, 0.05%-1.0% of Sr, and Clt. And T.O is less than or equal to 20ppm. The stainless steel provided by the invention is good in conductivity in the working process of the fuel cell interconnection plate, and the service life of the fuel cell interconnection plate is prolonged.

Description

Technical Field

[0001] The present application belongs to the technical field of stainless steel, and specifically relates to stainless steel with excellent electrical conductivity and a preparation method, and an interconnection plate and a preparation method. Background Art

[0002] Solid oxide fuel cell (SOFC) is a highly efficient energy conversion device that directly converts the chemical energy of fuel into electrical energy without chemical reaction. It can directly use carbon-containing gases such as methane, natural gas and water gas as fuel. In recent years, improvements in material manufacturing processes and design technologies have enabled the operating temperature of SOFC to be reduced from over 1000°C to a medium temperature range of 600-900°C, which also makes it possible to use metal connector materials as connector materials. Metal connectors can meet basic requirements such as electrical conductivity, thermal expansion coefficient, thermal conductivity, and oxidation resistance at operating temperatures.

[0003] At present, the exploration of metal connectors is mainly focused on adding appropriate amounts of active elements (such as Nb, Ti, Ni, Mo, W, etc.) to the steel matrix of ferritic stainless steel (iron-chromium alloy) and forming a new alloy with stable performance through an alloying process. However, this new alloy cannot meet the conductivity requirements of SOFC cell stacks for long-term operation.

[0004] Therefore, there is an urgent need for an iron-chromium alloy with good electrical conductivity. Summary of the invention

[0005] In order to solve the current technical problem of low conductivity of iron-chromium alloy during long-term operation of fuel cells, the present application provides a stainless steel with excellent conductivity and a preparation method, an interconnection plate and a preparation method.

[0006] In a first aspect of the present application, a stainless steel having excellent electrical conductivity is provided, comprising the following chemical components in mass fraction:

[0007] Cr: 13% ~ 30%, Be: 0.002% ~ 1.0%, Zr: 0.05 ~ 0.5%, Sr: 0.05% ~ 4.0%, C < 0.05%, TO ≤ 20ppm.

[0008] In some embodiments, the mass fraction ratio of the Sr to the Cr is 0.05 to 0.15.

[0009] In some embodiments, the mass fraction of Cr and the mass fraction of Sr conform to the following rule:

[0010] When the mass fraction of Cr is 13%≤Cr≤21%, the mass fraction ratio of Sr to Cr is 0.05-0.1; when the mass fraction of Cr is 21%<Cr≤30%, the mass fraction ratio of Sr to Cr is 0.07-0.15.

[0011] In some embodiments, the mass fraction ratio of the Zr to the Be is 0.4 to 2.5.

[0012] In some embodiments, the following chemical components are further included in mass fractions: La: 0.005% to 0.2%, Sc: 0.002% to 0.1%.

[0013] In some embodiments, the Be, the Sc and the La comply with the following rule: Be / (1.02*%Sc+0.79*%La) is in the range of 1.8-10.

[0014] In a second aspect of the present application, a method for preparing the stainless steel of the first aspect is provided, comprising the following steps:

[0015] Vacuum refining the molten steel, and during the vacuum refining process, when TO of the molten steel is ≤20 ppm, adding an alloy containing Be, Zr, Sr, La and Sc to the molten steel to obtain an alloyed molten steel;

[0016] The alloyed steel liquid is poured to obtain a stainless steel ingot.

[0017] In some embodiments, an alloy containing Be, Zr, Sr, La and Sc is added to the molten steel when the vacuum refining time is 0.6*T to 0.8*T, wherein T is the vacuum refining cycle.

[0018] In a third aspect of the present application, a fuel cell interconnection plate is provided, which is made of the stainless steel according to the first aspect.

[0019] In a fourth aspect of the present application, a method for preparing a fuel cell interconnect plate is provided, comprising the following steps:

[0020] The stainless steel of the first aspect is subjected to rolling, press forming and aging treatment in sequence, wherein the aging treatment temperature is 500°C to 550°C.

[0021] In some embodiments, during the aging treatment, the holding time is 60 min to 90 min, and hydrogen spraying treatment is used.

[0022] According to the embodiment of the present application, the stainless steel with excellent electrical conductivity includes the following chemical components by mass fraction: Cr: 13% to 30%, Be: 0.002% to 1.0%, Zr: 0.05 to 0.5%, Sr: 0.05% to 4.0%, C < 0.05%, TO ≤ 20ppm, and the rest is Fe and unavoidable impurities. The Sr element is added in the present application, which can diffuse outward quickly under high temperature working conditions to form holes between the steel matrix and the Cr2O3 film, and at the same time form a continuous state of (Sr, Cr) 3O4 outside the Cr2O3 film, thereby improving the electrical conductivity of the outer wall of the Cr2O3 film. The Be element and the Zr element are added in the present application, and the two can form intermetallic compounds during the aging treatment process, and can move into the holes under high temperature working conditions of stainless steel, thereby improving the electrical conductivity of the inner wall of the Cr2O3 film; at the same time, the Be-containing intermetallic compound diffused to the inner wall of the Cr2O3 further inhibits the diffusion of Cr, slows down the growth rate of the oxide film, and improves the electrical conductivity, thereby improving the service life of the fuel cell interconnection plate. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The figure shows the process steps of the method for preparing stainless steel of the present application. DETAILED DESCRIPTION

[0024] In order to make the technical personnel in the technical field to which the present application belongs to understand the present application more clearly, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0025] The first embodiment of the present application provides a stainless steel with excellent electrical conductivity, which is used for a fuel cell interconnection plate and has good electrical conductivity and slow oxide film growth, thereby increasing the service life of the fuel cell.

[0026] The stainless steel provided in this application includes the following chemical components by mass fraction:

[0027] Cr: 13% ~ 30%, Be: 0.002% ~ 1.0%, Zr: 0.05 ~ 0.5%, Sr: 0.05% ~ 4.0%, C < 0.05%, TO ≤ 20ppm.

[0028] The functions of each element are as follows:

[0029] Cr: A basic element to ensure the oxidation resistance and thermal expansion performance of stainless steel. If the content is less than 13%, the oxidation resistance of the present invention cannot be achieved. If the content is higher than 30%, due to the solid solution effect of Cr, the lattice will be excessively distorted, which will cause excessive scattering of conductive electrons and reduce the conductivity of stainless steel.

[0030] Be: Be has good electrical conductivity and corrosion resistance in iron-based alloys. In addition, it is lightweight and high-strength. It can reduce the overall weight of the battery and save energy when used in fuel cell stacks. During the operation of stainless steel, Cr and Sr on the surface of the alloy overflow to form Cr2O3 and (Sr, Cr)3O4 films, resulting in the formation of Cr and Sr-poor areas on the surface of the steel matrix. The Be and Zr elements in the steel matrix will form Zr-Be intermetallic compounds (ZrBe2, ZrBe5, Zr2Be) during the aging treatment. 13 、Zr2Be 17 ), and diffuses to the Cr and Sr-poor area under high-temperature working conditions. The intermetallic compound at this position is located between the substrate and the Cr2O3 film. Since the intermetallic compound has good conductivity, the conductivity of the steel substrate and the oxide film is enhanced; since the intermetallic compound can form a nail wedge structure, the adhesion between the steel substrate and the oxide film is improved, making the oxide film difficult to fall off, thereby improving the oxidation resistance of the material. In addition, Be itself will diffuse out of the steel substrate, thereby forming a nail wedge structure between the Cr2O3 oxide film and the substrate, improving the adhesion between the Cr2O3 oxide film and the substrate, and the Cr2O3 oxide film is not easy to fall off, thereby improving the oxidation resistance of the material.

[0031] Zr: Zr has a strong desulfurization and deoxidation effect, purifies the grain boundary, and enhances the grain boundary strength at high temperature; in addition, Zr is introduced in the present invention, and Zr and Be elements in the steel matrix will form Zr-Be intermetallic compounds (ZrBe2, ZrBe5, Zr2Be) during the aging treatment process. 13 、Zr2Be 17 ), since Zr diffuses quickly in the steel matrix, the Zr-Be intermetallic compound can quickly diffuse into the Cr-poor and Sr-poor areas on the surface of the steel matrix to fill the vacancies. Since the intermetallic compound has good conductivity, the conductivity of the steel matrix and the oxide film is enhanced.

[0032] Sr: The effects of Sr include: first, the alkaline earth element Sr in the alloy can improve the oxidizability of the alloy; second, it can inhibit the growth rate of the ferrite matrix grains, increase the initial growth temperature of the ferrite grains, and inhibit solidification cracks caused by excessive grain growth. The effect of Sr addition below 0.05% is not significant, and above 1% causes the inclusion size to be too large. The optimal range is 0.05%-1.0%, which can increase the initial growth temperature of the ferrite grains to 750°C. Third, at the operating temperature of 600°C-900°C, the diffusion rate of Sr is greater than that of Cr, and the speed is very fast. (Sr, Cr)3O4 will be formed outside the Cr2O3 film. The rapid diffusion of Sr causes vacancies to form at the interface between the steel matrix and the Cr2O3 film, which are fine intermetallic compounds (ZrBe2, ZrBe5, Zr2Be) generated in the aging process. 13 、Zr2Be 17 ) provides holes, and tiny intermetallic compounds can quickly occupy the vacancies, so that intermetallic compounds with good conductivity are enriched at the interface between the steel matrix and the Cr2O3 film, enhancing the conductivity of the inner wall of the Cr2O3 film; at the same time, a continuous state of (Sr, Cr)3O4 is formed outside the Cr2O3 film, which improves the conductivity of the outer wall of the Cr2O3 film. If the Sr content is too little, the outermost (Sr, Cr)3O4 film will be discontinuous, and the effect of improving the conductivity of the oxide film will be poor. It will also reduce the number of holes to a certain extent, and the number of intermetallic compounds distributed at the interface between the steel matrix and the Cr2O3 film will be small, thereby reducing the conductivity of the matrix and the Cr2O3 film. If the Sr content is too much, the large-sized Sr-containing oxides in the steel matrix will increase to a certain extent, deteriorating the conductive properties of the steel matrix.

[0033] From the above content, it can be known that the addition of Sr element in this application can quickly diffuse outward under high-temperature working conditions to form holes between the steel substrate and the Cr2O3 film, and at the same time form a continuous state of (Sr, Cr)3O4 outside the Cr2O3 film, thereby improving the conductivity of the outer wall of the Cr2O3 film. The addition of Be element and Zr element can form intermetallic compounds during the aging treatment process, and can move into the holes under high-temperature working conditions of stainless steel, thereby improving the conductivity of the inner wall of the Cr2O3 film; at the same time, the intermetallic compounds moving into the holes can inhibit the diffusion of Cr, reduce the growth rate of the Cr2O3 film, and increase the service life of the fuel cell interconnection board; the Be element itself can also diffuse outward, thereby forming a nail wedge structure between the Cr2O3 oxide film and the substrate, thereby improving the adhesion between the Cr2O3 oxide film and the substrate, and the Cr2O3 oxide film is not easy to fall off, thereby improving the oxidation resistance of the material.

[0034] In some embodiments, the mass fraction ratio of the Sr to the Cr is 0.05 to 0.15. If the mass fraction ratio of Sr to Cr is too large, it means that the content of the Sr element is too high and the content of the Cr element is low, which will, to a certain extent, lead to the formation of large-sized Sr-containing oxides in the steel matrix, deteriorating the electrical conductivity of the steel matrix. If the mass fraction ratio of Sr to Cr is too small, the outermost (Sr, Cr)3O4 film is discontinuous, and the effect of improving the electrical conductivity of the outer wall of the Cr2O3 oxide film is poor.

[0035] In some embodiments, the mass fraction of Cr and the mass fraction of Sr conform to the following rule:

[0036] When the mass fraction of Cr is 13%≤Cr≤21%, the mass fraction ratio of Sr to Cr is 0.05-0.1; when the mass fraction of Cr is 21%<Cr≤30%, the mass fraction ratio of Sr to Cr is 0.06-0.15. That is to say, when the Cr content is low, the mass fraction ratio of Sr to Cr is small, and when the Cr content is high, the mass fraction ratio of Sr to Cr is large. This is because at an operating temperature of 550-950°C, when the Cr content is low, the initial Cr2O3 oxide film thickness is thinner, and a smaller mass fraction ratio of Sr to Cr can ensure that Sr diffuses to the outer layer of the Cr2O3 oxide film, thereby improving the conductivity of the outer wall of the Cr2O3 oxide film. When the Cr content is high, the initial Cr2O3 oxide film thickness is thicker, and a higher concentration of Sr atoms is required to participate in the diffusion to ensure that there is enough Sr element to diffuse to the outer layer of the Cr2O3 oxide film, thereby improving the conductivity of the outer wall of the Cr2O3 oxide film.

[0037] In some embodiments, the mass fraction ratio of Zr to Be is 0.4 to 2.5, and the mass fraction ratio of Zr to Be is controlled to be 0.4 to 2.5 to form typical intermetallic compounds (ZrBe2, ZrBe5, Zr2Be 13 、Zr2Be 17 ), if the ratio is too large or too small, it will not only increase the amount of intermetallic compounds to a certain extent, but may also cause waste.

[0038] In some embodiments, the stainless steel further comprises the following chemical components by mass fraction: La: 0.005% to 0.2%, Sc: 0.002% to 0.1%. Both La and Sc are rare earth elements. The rare earth elements are added to act as purifiers to reduce the harmful effects of oxygen and sulfur at the grain boundaries; secondly, as microalloying elements, they are concentrated at the grain boundaries to strengthen the grain boundaries; thirdly, during the working process at a temperature of 600-900°C, the La and Sc elements concentrated at the grain boundaries will inhibit the diffusion of chromium elements out of the steel matrix and reduce the generation rate of the Cr2O3 film. At the same time, the La and Sc concentrated at the grain boundaries will also accelerate the diffusion of oxygen into the steel matrix, thereby forming a nail wedge structure between the Cr2O3 oxide film and the matrix, improving the adhesion between the Cr2O3 oxide film and the matrix, and the Cr2O3 oxide film is not easy to fall off, thereby improving the oxidation resistance of the material. That is to say, the metal compounds between the Cr2O3 oxide film and the substrate, as well as the La and Sc elements concentrated at the grain boundaries will inhibit the diffusion of chromium into the steel substrate and reduce the growth rate of the Cr2O3 oxide film. The metal compounds as well as La and Sc will form a nail wedge structure between the Cr2O3 oxide film and the substrate, which will improve the adhesion of the Cr2O3 oxide film to the substrate and make it less likely to fall off, thereby improving the oxidation resistance of the interconnection board.

[0039] In some embodiments, the Be, Sc and La meet the following rule: 1.8*(1.02*%Sc+0.79*%La)≤%Be≤10*(1.02*%Sc+0.79*%La), Be replaces a part of the expensive rare earth elements La and Sc, and cooperates with a small amount of rare earth elements to form a nail wedge structure between the matrix and the intermetallic compound. Zr-Be intermetallic compounds (ZrBe2, ZrBe5, Zr2Be) diffused to the inner wall of the Cr2O3 oxide film 13 、Zr2Be 17 ) further inhibits the diffusion of Cr, slows down the growth rate of Cr2O3 oxide film, and the thinner oxide film cooperates with the pin-wedge structure formed by La and Sc at the grain boundary to enhance the adhesion between the substrate and the oxide film. If Be is lower than this range, it cannot replace the rare earth elements, and the adhesion of the oxide film is poor; if it is higher than this range, large-sized Be-containing oxides may be formed to a certain extent, which deteriorates the antioxidant and conductive properties of the substrate.

[0040] In some embodiments, the stainless steel also includes Mo, and the mass fraction of Mo is 1%-5%. Under medium-temperature oxidation conditions of 600°C-900°C, due to the outward diffusion of Cr, a large number of vacancies are formed between the matrix and the oxide, which are occupied by Fe-Mo intermetallic compounds, forming oxides located between the Cr oxide and the steel matrix, which can improve the conductivity of the inner wall.

[0041] An embodiment of the second aspect of the present application provides a method for preparing stainless steel according to any embodiment of the first aspect.

[0042] See also Figure 1 , the preparation method of the present application comprises the following steps:

[0043] S1. Vacuum refining the molten steel. During the vacuum refining process, when TO of the molten steel is ≤20 ppm, an alloy containing Cr, Be, Zr and Sr is added to the molten steel to obtain an alloyed molten steel;

[0044] S2. pouring the alloyed steel liquid to obtain stainless steel.

[0045] In step S1, when the alloy is added, TO in the molten steel is ≤20ppm. At this time, the molten steel has been completely deoxidized, which can reduce the risk of alloy oxidation and improve the alloy yield.

[0046] In some embodiments, when the vacuum refining time is 0.6*T to 0.8*T, an alloy containing Cr, Be, Zr, Sr, La and Sc is added to the molten steel, that is, before steel is tapped in the late refining stage, so that the yield of expensive rare earth elements can be improved. Wherein T is the vacuum refining cycle. If the alloy is added too early, the yield of the alloying elements will be reduced to a certain extent. If the alloy is added too late, it will cause the alloy to be uneven to a certain extent, and the conductivity and oxidation resistance of the product will be uneven.

[0047] The third embodiment of the present application provides a fuel cell interconnection plate, which is made of stainless steel of any embodiment of the first aspect. The interconnection plate has good oxidation resistance and conductivity during the operation of the fuel cell, thereby improving the service life of the fuel cell.

[0048] The fourth embodiment of the present application provides a method for preparing a fuel cell interconnection plate. The fuel cell interconnection plate is made of stainless steel according to any embodiment of the first aspect, and a large amount of intermetallic compounds can be formed to improve the conductivity of the interconnection plate during the working stage.

[0049] The preparation method comprises: stamping and aging the stainless steel of any embodiment of the first aspect in sequence, wherein the aging treatment temperature is 500°C to 550°C. 13 、Zr2Be 17) is above 500°C, so the lower limit of the aging treatment temperature is 500°C. Controlling the upper limit of the aging treatment temperature to 550°C can control the slower growth rate of the intermetallic compound, making it dispersed and distributed with a particle size less than 2nm. Nano-scale particles can diffuse to the holes at the interface between the substrate and the Cr2O3 oxide film at a faster rate during the oxidation process, thereby improving the conductivity of the Cr2O3 inner wall of the interconnecting plate.

[0050] In some embodiments, during the aging treatment, the holding time is 60 minutes to 90 minutes to allow the intermetallic compounds to precipitate and grow. If the holding time is too long, to a certain extent, the intermetallic compounds with too large particles will be formed, which will affect the diffusion rate and make it difficult to diffuse and aggregate in the cavities under oxidation conditions, thereby deteriorating the conductivity at the interface between the substrate and the Cr2O3 oxide film. If the holding time is too short, to a certain extent, the amount of intermetallic compounds will be reduced, thereby reducing the conductivity of the interconnection board.

[0051] In some embodiments, during the aging treatment, hydrogen spraying is used, and the amount of hydrogen spraying is ≥ 20m 3 / h to avoid oxidation of stainless steel during aging treatment.

[0052] The stainless steel and its preparation method, the interconnection plate and its preparation method provided in the present application will be further described below in conjunction with specific embodiments.

[0053] Example 1 to Example 6

[0054] Embodiments 1 to 6 provide a method for preparing an interconnection board, and the specific process is as follows:

[0055] Step 1: Add industrial pure iron, Cr alloy and C into a vacuum induction furnace for vacuum refining. The loading amount of the vacuum induction furnace is 3 tons. The vacuum refining time is 60 minutes. The vacuum refining temperature and the time when the alloy containing Be, Zr, Sr, La and Sc is added and the TO at that time are shown in Table 1. It should be noted that in Example 6, the alloy containing La and Sc is not added.

[0056] Step 2, pouring the molten steel in step 1 to obtain an alloy ingot as shown in Table 2 and Table 3, heating the alloy ingot at 1100° C., forging and tempering the alloy ingot for multiple passes to obtain a slab;

[0057] Step 3, hot rolling, annealing, softening, grinding and welding the flat slab to obtain a hot-rolled strip;

[0058] Step 4: performing blanking, cold rolling, intermediate grinding, edge trimming and solution treatment on the hot-rolled strip to obtain a strip.

[0059] The hot rolling temperature is 1100°C. The hot rolling includes: the first hot rolling, the second hot rolling and the third hot rolling. The first hot rolling deformation is 40%, the second hot rolling deformation is 30%, and the third hot rolling deformation is 30%. The final rolling temperature is 910°C. After rolling, the steel is water-cooled to room temperature.

[0060] The cold rolling includes: a first cold rolling, a second cold rolling and a third cold rolling, the deformation amount of the first cold rolling is 50%, the deformation amount of the second cold rolling is 40%, and the deformation amount of the third cold rolling is 10%.

[0061] Step 5, stamping: heat treatment to 300℃, hydrogen spraying rate 5m3 / h, heat preservation 20, stamping.

[0062] Step 6: Aging treatment of the steel plate after stamping in step S5: the aging treatment temperature, holding time and hydrogen injection amount are shown in Table 4.

[0063] Table 1

[0064] Table 2 serial number Cr / ％ Be / % Zr / ％ Sr / ％ La / % Sc / % C / ％ TO / % Mo / % Example 1 15 0.2 0.1 0.8 0.03 0.015 0.025 <![CDATA[15*10 -4 ]]> / Example 2 23 0.3 0.2 1.5 0.04 0.024 0.020 <![CDATA[16*10 -4 ]]> / Example 3 25 0.25 0.5 2 0.1 0.05 0.030 <![CDATA[14*10 -4 ]]> / Example 4 23 0.3 0.2 3 0.04 0.024 0.025 <![CDATA[15*10 -4 ]]> / Example 5 25 0.25 0.375 2 0.1 0.05 0.030 <![CDATA[14*10 -4 ]]> 5 Example 6 25 0.25 0.375 2 / / 0.030 <![CDATA[14*10 -4 ]]> / Comparative Example 1 15 0.2 0.1 0.3 0.03 0.015 0.025 <![CDATA[15*10 -4 ]]> / Comparative Example 2 23 0.3 0.2 0 0.03 0.015 0.025 <![CDATA[15*10 -4 ]]> / Comparative Example 3 23 0 0.2 1.5 0.04 0.024 0.020 <![CDATA[16*10 -4 ]]> / Comparative Example 4 25 0.25 0.5 0.4 0.01 0.01 0.030 <![CDATA[14*10 -4 ]]> / Comparative Example 5 22 0.25 0.5 3.74 0.04 0.024 0.025 <![CDATA[15*10 -4 ]]> / Comparative Example 6 25 0.25 0.5 2 0.1 0.05 0.030 <![CDATA[14*10 -4 ]]> / Comparative Example 7 23 0.3 0.2 3 0.04 0.024 0.025 <![CDATA[15*10 -4 ]]> /

[0065] Table 3

[0066] Table 4

[0067] The interconnection boards prepared in Examples 1 to 5 and Comparative Examples 1 to 7 were oxidized at 600°C-750°C for 30,000 h and 750°C-900°C for 30,000 h in an O2-H2O atmosphere, and the oxide film thickness and the resistance per unit area (ASR) of the oxide film were measured respectively. At the same time, the peeling of the oxide film on the substrate surface was observed. The results are shown in Table 5.

[0068] Table 5 Antioxidation and conductivity properties

[0069] From the data in Table 5, it can be seen that the interconnection board provided by Examples 1 to 6 of the present application has an oxide film thickness of 7 to 10 μm formed by oxidation at 600°C-750°C for 30,000 hours. The oxide film is thin and has good oxidation resistance. The ASR is 0.008 to 0.011 Ω·cm 2, small resistance per unit area, good conductivity. The oxide film thickness formed by oxidation at 750℃-900℃ for 30000h is 9-12μm, the oxide film is thin, the oxidation resistance is good, and the ASR is 0.009-0.012Ω·cm 2 , small resistance per unit area and good conductivity.

[0070] In Comparative Example 1, Sr / Cr is lower than 0.05, and the oxide film thickness formed by the interconnection board provided by oxidation at 600℃-750℃ for 30000h is 12μm. The oxide film thickness is thick, the oxidation resistance is poor, and the ASR is 0.015Ω·cm 2 , the resistance per unit area is large and the conductivity is poor. The thickness of the oxide film formed by oxidation at 750℃-900℃ for 30000h is 15μm. The oxide film is thick and the oxidation resistance is poor. The ASR is 0.018Ω·cm 2 , high resistance per unit area and poor conductivity.

[0071] Comparative Example 2 is a case where no Sr is added. The interconnection board provided is oxidized at 600°C-750°C for 30,000 hours, and the ASR is 0.022Ω·cm 2 , 750℃-900℃ oxidation for 30000h, ASR is 0.026Ω·cm 2 , poor conductivity.

[0072] In Comparative Example 3, Be was not added, and the oxide film was thickened and peeled off.

[0073] In Comparative Example 4, %Be / (1.02*%Sc+0.79*%La) is higher than 10, that is, the amount of rare earth elements added is relatively low, and the effect of enhancing the adhesion of the oxide film cannot be achieved, and the oxide film falls off.

[0074] In Comparative Example 5, Sr / Cr is higher than 0.17, that is, Sr is too high, and large-sized oxides are formed in the molten steel, resulting in deterioration of the conductive performance.

[0075] In Comparative Examples 6 and 7, the aging temperature and the aging time are relatively low, which affects the precipitation of intermetallic compounds, thereby deteriorating the oxidizability and oxidation resistance.

[0076] In the present application, Be and Zr elements are added, which can form intermetallic compounds during the aging treatment process and can move into the holes under high-temperature working conditions of stainless steel, thereby improving the conductivity of the inner wall of the Cr2O3 film; at the same time, the Be-containing intermetallic compounds diffused into the inner wall of Cr2O3 further inhibit the diffusion of Cr, slow down the growth rate of the oxide film, and increase the service life of the fuel cell interconnection plate.

[0077] The present application can also add La and Sc elements on the basis of adding Be and Zr elements to inhibit the diffusion of oxygen into the steel matrix, reduce the generation rate of Cr2O3 film, and improve oxidation resistance. At the same time, La can also form a nail wedge structure between the Cr2O3 oxide film and the matrix, thereby improving the adhesion between the Cr2O3 oxide film and the matrix, thereby improving the oxidation resistance of the material.

[0078] In the present application, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0079] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise" and "counterclockwise" indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0080] In this application, unless otherwise clearly specified and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0081] In addition, the descriptions of "first", "second", etc. in this application are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include one or more features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0082] Although the embodiments of the present application have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present application, and that the scope of the present application is defined by the claims and their equivalents.

Claims

1. A stainless steel with excellent electrical conductivity, characterized in that: The chemical components include the following mass fractions: Cr: 13% ~ 30%, Be: 0.002% ~ 1.0%, Zr: 0.05 ~ 0.5%, Sr: 0.05% ~ 4.0%, C < 0.05%, TO ≤ 20ppm.

2. The stainless steel according to claim 1, characterized in that The mass fraction ratio of the Sr to the Cr is 0.05 to 0.

15.

3. The stainless steel according to claim 2, characterized in that The mass fraction of Cr and the mass fraction of Sr conform to the following rules: When the mass fraction of Cr is 13%≤Cr≤21%, the mass fraction ratio of Sr to Cr is 0.05-0.1; when the mass fraction of Cr is 21%<Cr≤30%, the mass fraction ratio of Sr to Cr is 0.07-0.

15.

4. The stainless steel according to any one of claims 1 to 3, characterized in that: The mass fraction ratio of the Zr to the Be is 0.4 to 2.

5.

5. The stainless steel according to any one of claims 1 to 3, characterized in that: It also includes the following chemical components in mass fractions: La: 0.005% to 0.2%, Sc: 0.002% to 0.1%.

6. The stainless steel according to claim 5, characterized in that The Be, the Sc and the La comply with the following rule: the range of Be% / (1.02*%Sc+0.79*%La) is 1.8-10.

7. A method for preparing stainless steel according to any one of claims 1 to 6, characterized in that: The steps include: Vacuum refining the molten steel, and during the vacuum refining process, when TO of the molten steel is ≤20 ppm, adding an alloy containing Be, Zr, Sr, La and Sc to the molten steel to obtain an alloyed molten steel; The alloyed steel liquid is poured to obtain stainless steel.

8. The method for preparing stainless steel according to claim 7, characterized in that: When the vacuum refining time is 0.6*T to 0.8*T, an alloy containing Be, Zr and Sr is added to the molten steel, wherein T is the vacuum refining cycle.

9. A fuel cell interconnection plate, characterized in that: The stainless steel according to any one of claims 1 to 6 is used.

10. A method for preparing a fuel cell interconnection plate, characterized in that: The steps include: The stainless steel according to any one of claims 1 to 6 is sequentially rolled, stamped and aged, wherein the aging treatment temperature is 500° C. to 550° C., and the holding time is 60 min to 90 min.

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