Iron-chromium alloy for suppressing cr evaporation, fuel cell interconnect plate, and method of manufacture

Abstract

The application provides an iron-chromium alloy for inhibiting Cr volatilization, a fuel cell interconnection plate and a preparation method, and belongs to the alloy field. The iron-chromium alloy comprises the following chemical components: Cr: 13% to 22.5%, Cu: 0.7% to 4.0%, Zr: 0.3% to 1.0%, B: 0.015% to 0.45%, Ni: 1.0% to 1.2%, Mo: 1% to 3%, W: 0.1% to 3%, C+N: 0.010% or less, T.O: 0.002% or less, Si: 0.15% to 0.3%, Mn: 0.1% to 0.8%, Al: 0.15% to 0.4% and Fe. The application reasonably designs the chemical components of the iron-chromium alloy, adopts the Fe-based alloy, designs the high-Cr high-Cu low-Ni component system, and achieves the excellent oxidation resistance performance and the excellent Cr volatilization inhibition effect.

Description

Technical Field

[0001] This application relates to the field of alloy technology, and in particular to an iron-chromium alloy that inhibits Cr volatilization, a fuel cell interconnect plate, and a preparation method thereof. Background Technology

[0002] High-temperature solid oxide fuel cells (SOFCs) (800℃) are highly efficient energy conversion devices that directly convert the chemical energy of fuel into electrical energy without chemical reactions. They 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 SOFCs to operate at temperatures ranging from 1000℃ to the intermediate temperature range of 600-800℃. This has made it possible to use metal interconnects as interconnect materials. Metal interconnects can meet the basic requirements for electrical conductivity, coefficient of thermal expansion, thermal conductivity, and oxidation resistance at operating temperatures.

[0003] To date, four ferritic stainless steel connectors have been studied in considerable detail: Crofer 22APU, SUS430, X10CrAl18, and ZMG232. Representative ferritic Fe-Cr alloys include ZMG232 developed by Hitachi Metals and the Crofer22 APU alloy announced by ThyssenKrupp VDM in 2003. Later, ZMG232L and Crofer22H were further developed through optimization. ZMG232 is a ferritic Fe-Cr alloy mainly containing 22% Cr, 0.04% La, and 0.22% Zr. Although ZMG232 exhibits good oxidation resistance in the 650–800℃ range, some literature indicates that its electrical conductivity is still far from meeting practical application requirements. Although the aforementioned alloys exhibit superior performance, their commercial application still faces bottlenecks and cannot currently meet the requirements for long-term operation of SOFC battery stacks: Cr-containing alloys form volatile gaseous substances in oxidizing environments, which deposit on the cathode surface, severely damaging the electrochemical performance of SOFCs. Therefore, a nickel-based alloy with low Cr volatility is urgently needed. Summary of the Invention

[0004] This application provides an iron-chromium alloy for suppressing Cr volatilization, a fuel cell interconnect plate, and a preparation method thereof, in order to solve the following technical problem: how to suppress Cr volatilization in nickel-based alloys.

[0005] In a first aspect, this application provides an iron-chromium alloy for suppressing Cr volatilization, wherein the iron-chromium alloy comprises the following chemical composition by mass fraction: Cr: 13%–22.5%, Cu: 0.7%–4.0%, Zr: 0.3%–1.0%, B: 0.015%–0.45%, Ni: 1.0%–1.2%, Mo: 1%–3%, W: 0.1%–3%, C+N≤0.010%, TO≤0.002%, Si: 0.15%–0.3%, Mn: 0.1%–0.8%, Al: 0.15%–0.4%, rare earth elements: 0.001%–0.5%, and Fe; wherein the rare earth elements include one or more of La, Ce, Sc, and Y.

[0006] Optionally, the chemical components satisfy the following relationship:

[0007] [R]>0.06×[%Cu]+0.032×[%W]

[0008] In the formula, [R] represents the mass fraction of rare earth elements, [%Cu] represents the value before the mass fraction % of Cu, and [%W] represents the value before the mass fraction % of W.

[0009] Optionally, the chemical components satisfy the following relationship:

[0010] 0.4 ≤ [%Zr] + 1.1 [%B] ≤ 1.5

[0011] In the formula, [%Zr] represents the value preceding the mass fraction % of Zr, and [%B] represents the value preceding the mass fraction % of B. Optionally, the chemical composition satisfies the following relationship:

[0012] 1.5≤(0.22×[%Cr]+0.32×[%Cu]) / [Mo]≤3

[0013] In the formula, [%Cr] represents the value before the mass fraction % of Cr, [%Cu] represents the value before the mass fraction % of Cu, [Ni] represents the mass fraction of Ni, and [Mo] represents the mass fraction of Mo.

[0014] Secondly, this application provides a method for preparing the iron-chromium alloy according to any embodiment of the first aspect, the method comprising:

[0015] The molten steel is refined at high temperature, and the pressure of the high-temperature refining is adjusted according to the refining time to obtain alloyed molten steel.

[0016] The alloyed steel liquid is poured and crystallized to obtain the iron-chromium alloy.

[0017] Optionally, adjusting the pressure of the high-temperature refining according to the time of the high-temperature refining includes:

[0018] Adjusting the pressure of the high-temperature refining according to the time of the high-temperature refining;

[0019] When t < 0.2T, P is 1 Pa to 5 Pa;

[0020] When 0.2T < t < 0.6T, P is 0.1 Pa to 0.5 Pa;

[0021] When t > 0.6T, P is 1 Pa to 2 Pa;

[0022] Wherein, t represents the time of the high-temperature refining, P represents the pressure of the high-temperature refining, T represents the total time of the high-temperature refining, and T is 0.5 h to 0.7 h.

[0023] In a third aspect, the present application provides a fuel cell interconnector made of the ferrochromium alloy according to any one of the embodiments in the first aspect.

[0024] Optionally, the fuel cell interconnector satisfies at least one of the following performances:

[0025] At 900 °C, 400 mA / cm

[0028] ,

[0032] ,

[0031] ,

[0030] ,

[0029] , , , , , , The cathode deposition of Cr-containing substances for 4000 h of current polarization ≤ 0.05 mg / cm 2 ;

[0026] At 600 °C, 400 mA / cm 2 The cathode deposition of Cr-containing substances for 4000 h of current polarization ≤ 0.01 mg / cm 2 ;

[0027] At 900 °C, the creep strain under a load of 10 MPa for 2000 h ≤ 0.01%;

[0028] At 900 °C, the creep strain under a load of 10 MPa for 4000 h ≤ 0.03%.

[0029] In a fourth aspect, the present application provides a preparation method for the fuel cell interconnector according to the embodiment in the third aspect, and the method includes:

[0030] Successively heating, forging, and multi-pass tempering the ferrochromium alloy according to any one of the embodiments in the first aspect to obtain a flat blank;

[0031] Performing multi-pass hot rolling and annealing softening on the flat blank to obtain a hot-rolled strip blank;

[0032] Performing intermediate heat treatment, multi-pass cold rolling, and solution treatment on the hot-rolled strip blank to obtain a strip;

[0033] The strip is stamped and aged to obtain a fuel cell interconnect plate.

[0034] Optionally, the aging treatment includes the following parameters: temperature of 400℃~500℃, holding time of 60min~90min, and hydrogen injection rate ≥20m³. 3 / h.

[0035] The technical solutions provided in this application have the following advantages compared with the prior art:

[0036] This application provides an iron-chromium alloy that suppresses Cr volatilization. The chemical composition of the iron-chromium alloy is rationally designed, using an Fe-based alloy with a high-Cr, high-Cu, and low-Ni composition system, achieving excellent oxidation resistance while effectively suppressing Cr volatilization. The content of rare earth elements is rationally controlled to promote the dispersion strengthening effect of Cu and W elements in the alloy. Simultaneously, under medium-temperature oxidation conditions, rare earth elements promote the diffusion rate of Cu in the oxide film, thereby forming (Cr,Cu)3O4 on the outer layer of the Cr2O3 oxide film, inhibiting Cr diffusion. Oxidation at 600–900℃ results in a bilayer oxide film structure, with Cr2O3 adjacent to the substrate and (Cr,Cu)3O4 on the outer layer. Furthermore, the conductivity of (Cr,Cu)3O4 is 2–5 times that of Cr2O3, significantly enhancing the conductivity of the oxide film. The addition of Mo significantly reduces the thermal expansion coefficient of the nickel-based alloy, meeting the thermal expansion coefficient requirements of solid oxide fuel cells. Simultaneously, through the composition ratio of Mo, Cu, and Cr alloying elements, under medium-temperature oxidizing atmosphere conditions, the outward diffusion of Cr and Cu creates cavities between the matrix and the oxide film, promoting the diffusion of Mo into these cavities and reaching the critical formation conditions for Fe3Mo. This forms a conductive barrier between the matrix and the oxide film that inhibits Cr volatilization, preventing corrosion from extending into the matrix, enhancing the conductivity between the matrix and the oxide film, and extending battery life. This, in turn, suppresses Cr volatilization in nickel-based alloys. Attached Figure Description

[0037] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0038] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 A schematic flowchart illustrating a method for preparing an iron-chromium alloy provided in this application embodiment;

[0040] Figure 2 This is a schematic flowchart illustrating a method for fabricating a fuel cell interconnect plate according to an embodiment of this application. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0042] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0043] Furthermore, in the description of this application, the terms "comprising," "including," etc., mean "including but not limited to." In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this document, "and / or" describes the relationship between related objects, indicating that three relationships can exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. A and B can be singular or plural. In this document, "at least one" means one or more, and "more than" means two or more. "At least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c" or "at least one of a, b, and c" can both represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple. "Parts representation," such as parts by weight or parts by mass, indicates the proportional relationship between components. In the proportional relationships discussed in this article, parameters described by proportion should be understood as the first term of the proportion in the order of description, while the proportion figure should be understood as the second term. For example, if the mass ratio of substance A, substance B, and substance C is 1:2:3, then substances A, B, and C should correspond one-to-one with the proportion figure in the proportion in the order of description, i.e., the mass of substance A : the mass of substance B : the mass of substance C = 1:2:3.

[0044] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0045] This application provides an iron-chromium alloy for suppressing Cr volatilization. The iron-chromium alloy comprises the following chemical composition by mass fraction: Cr: 13%–22.5%, Cu: 0.7%–4.0%, Zr: 0.3%–1.0%, B: 0.015%–0.45%, Ni: 1.0%–1.2%, Mo: 1%–3%, W: 0.1%–3%, C+N≤0.010%, TO≤0.002%, Si: 0.15%–0.3%, Mn: 0.1%–0.8%, Al: 0.15%–0.4%, rare earth elements: 0.001%–0.5%, and Fe; wherein the rare earth elements include one or more of La, Ce, Sc, and Y.

[0046] The main functions of each component are as follows:

[0047] C and N: C forms carbides at the end of solidification and during heat treatment, which strengthen grain boundaries and delay the initiation, expansion, and merging of creep cavities in the alloy, thereby improving the alloy's high-temperature creep resistance. However, excessive carbon content negatively impacts corrosion resistance. Nitrogen content is a major cause of high-temperature brittleness in ferrite; therefore, the sum of C and N content should be controlled to no more than 0.010%. For example, the C+N content can be 0.004%, 0.005%, 0.006%, 0.007%, 0.008%, 0.009%, 0.010%, etc.

[0048] Cr: The main function of Cr is to improve the oxidation resistance of the alloy and it also has a certain solid solution strengthening effect. However, excessive Cr content will increase the coefficient of thermal expansion. In this application, considering both oxidation resistance and thermal expansion performance, the Cr content is controlled between 13% and 22.5%. For example, the Cr content can be 13%, 14%, 15%, 16%, 17%, 18%, 20%, 22.5%, etc.

[0049] Ni: Enhances the corrosion resistance of the alloy. However, excessive Ni content will form an austenitic structure, increasing the coefficient of thermal expansion and raising costs. For example, the Ni content can be 1.0%, 1.05%, 1.1%, 1.15%, 1.2%, etc.

[0050] Mo: Mo is a solid solution strengthening element. At medium and high temperatures, Fe can be formed in ferrite. 36 Cr 12 Mo 10 Intermetallic compounds, thereby improving the creep resistance of alloys at high temperatures. For example, the content of Mo can be 1%, 1.5%, 2%, 2.5%, 3%, etc.

[0051] Boron (B): The main function of boron is to reduce the aggregation of low-melting-point harmful elements by enriching small-radius boron at grain boundaries, thereby increasing the grain boundary bonding force of the ferrite matrix and improving the alloy's creep resistance and lifespan. Excessive boron content will affect hot working properties; the boron content should be controlled between 0.015% and 0.45%. For example, the boron content can be 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, etc.

[0052] Zr: Purifies grain boundaries; when combined with boron (B), it enhances grain boundary bonding and maintains high-temperature strength. It also provides antioxidant protection, improves oxide film structure, inhibits oxygen diffusion inward, and strengthens the bond between the oxide film and the iron-chromium alloy matrix. Excessive addition will deteriorate hot working properties. For example, the Zr content can be 0.3%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, etc.

[0053] Cu: a solid solution strengthening element; improves the oxide film structure and inhibits Cr volatilization. Under medium-temperature oxidation conditions, Y promotes the diffusion rate of Cu in the oxide film, thereby forming (Cr,Cu)3O4 on the outer layer of the Cr2O3 oxide film and inhibiting Cr diffusion. Oxidation at 600–900℃ results in a bilayer oxide film structure, with Cr2O3 adjacent to the substrate and (Cr,Cu)3O4 on the outer layer. Furthermore, the conductivity of (Cr,Cu)3O4 is 2–5 times that of Cr2O3, greatly enhancing the conductivity of the oxide film. For example, the Cu content can be 0.7%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4.0%, etc.

[0054] Rare earth elements: Adding rare earth elements to the alloy offsets the potential impact of high chromium (Cr) on plasticity. Because rare earth elements segregate at grain boundaries, they act as grain boundary strengtheners, delaying crack formation and propagation, thus significantly improving the alloy's creep resistance. For example, the content of rare earth elements can be 0.001%, 0.05%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, etc.

[0055] Si: A deoxidizer that improves the oxidation resistance and high-temperature strength of alloys. Excessive addition can lead to the formation of SiO2 on the alloy surface during oxidation, affecting electrical conductivity. For example, the Si content can be 0.15%, 0.2%, 0.25%, 0.3%, etc.

[0056] Mn: A deoxidizer that improves the oxidation resistance and high-temperature strength of alloys. Excessive addition will increase the coefficient of thermal expansion of the alloy. For example, the Mn content can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, etc.

[0057] Al: A strong deoxidizer that can improve the oxidation resistance and high-temperature strength of alloys. It can also reduce the density of alloys, achieving the advantages of lightweight materials and low cost. Excessive addition, however, affects tensile and weldability. For example, the Al content can be 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, etc.

[0058] It should be noted that TO represents the total oxygen content.

[0059] Fe is the matrix element. The specific content / range of Fe can be obtained by the formula for the upper and lower limits of the components. That is, the sum of the percentage content of each component in a composition should be equal to 100%. The content range of several components should meet the following conditions: the upper limit of a certain component + the lower limit of other components ≤ 100; the lower limit of a certain component + the upper limit of other components ≥ 100.

[0060] In some embodiments, the chemical components satisfy the following relationship:

[0061] [R]>0.06×[%Cu]+0.032×[%W]

[0062] In the formula, [R] represents the mass fraction of rare earth elements, [%Cu] represents the value before the mass fraction % of Cu, and [%W] represents the value before the mass fraction % of W.

[0063] By limiting the proportions of rare earth elements, Cu, and W, the dispersion strengthening effect of Cu in the alloy is promoted, effectively improving the alloy strength and increasing the service temperature to around 950℃. Under medium-temperature oxidation conditions, rare earth elements promote the diffusion rate of Cu in the oxide film, thereby forming (Cr,Cu)3O4 on the outer layer of the Cr2O3 oxide film and inhibiting the diffusion of Cr.

[0064] In some embodiments, the chemical components satisfy the following relationship:

[0065] 0.4 ≤ [%Zr] + 1.1 [%B] ≤ 1.5

[0066] In the formula, [%Zr] represents the value preceding the mass fraction % of Zr, and [%B] represents the value preceding the mass fraction % of B.

[0067] By limiting the elemental ratio of Zr and B, the composite addition of Zr and B enhances the grain boundary bonding force and maintains high-temperature strength. For example, the value of [%Zr]+1.1[%B] can be 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.5, etc.

[0068] In some embodiments, the chemical components satisfy the following relationship:

[0069] 1.5≤(0.22×[%Cr]+0.32×[%Cu]) / [Mo]≤3

[0070] In the formula, [%Cr] represents the value before the mass fraction % of Cr, [%Cu] represents the value before the mass fraction % of Cu, [Ni] represents the mass fraction of Ni, and [Mo] represents the mass fraction of Mo.

[0071] This application designs a high-Cr, high-Cu, and low-Ni composition system, achieving excellent antioxidant performance while also effectively suppressing Cr volatilization. Through the composition ratio of Mo, Cu, and Cr alloying elements, under medium-temperature oxidizing atmosphere conditions, the outward diffusion of Cr and Cu creates cavities between the substrate and the oxide film, promoting Mo diffusion into these cavities and reaching the critical formation conditions for Fe3Mo. This forms a conductive barrier between the substrate and the oxide film that inhibits Cr volatilization, preventing corrosion from extending into the substrate, enhancing the conductivity between the substrate and the oxide film, and extending battery life. For example, the value of (0.22 × [%Cr] + 0.32 × [%Cu] + [Ni]) / [Mo] can be 1.5, 1.7, 1.9, 2, 2.2, 2.4, 2.6, 2.8, 3, etc.

[0072] In summary, this application employs an Fe-based alloy with a high-Cr, high-Cu, and low-Ni composition system, achieving excellent antioxidant properties while effectively suppressing Cr volatilization. The rational control of rare earth element Y promotes the dispersion strengthening effect of Cu and W elements in the alloy. Simultaneously, under medium-temperature oxidation conditions, Y promotes the diffusion rate of Cu in the oxide film, thereby forming (Cr,Cu)3O4 on the outer layer of the Cr2O3 oxide film, inhibiting Cr diffusion. Oxidation at 600–900℃ results in a bilayer oxide film structure, with Cr2O3 adjacent to the substrate and (Cr,Cu)3O4 on the outer layer. Furthermore, the conductivity of (Cr,Cu)3O4 is 2–5 times that of Cr2O3, significantly enhancing the conductivity of the oxide film. The addition of Mo significantly reduces the coefficient of thermal expansion of the nickel-based alloy, meeting the requirements for the coefficient of thermal expansion in solid oxide fuel cells. Meanwhile, through the composition ratio of Mo, Cu, and Cr alloying elements, under medium-temperature oxidizing atmosphere conditions, due to the outward diffusion of Cr and Cu, cavities are formed between the substrate and the oxide film, which promotes the diffusion of Mo into the cavities and reaches the critical formation conditions of Fe3Mo. A conductive barrier that inhibits Cr volatilization is formed between the substrate and the oxide film, preventing corrosion from extending to the substrate, enhancing the conductivity between the substrate and the oxide film, and extending the battery life.

[0073] Figure 1 This is a schematic flowchart illustrating a method for preparing an iron-chromium alloy, as provided in an embodiment of this application.

[0074] Please see Figure 1 This application provides a method for preparing the iron-chromium alloy according to any embodiment of the first aspect, the method comprising:

[0075] S11. The molten steel is refined at high temperature, and the pressure of the high-temperature refining is adjusted according to the high-temperature refining time to obtain alloyed molten steel.

[0076] S12. The alloyed steel liquid is poured and crystallized to obtain the iron-chromium alloy.

[0077] In some embodiments, adjusting the pressure of the high-temperature refining according to the time of the high-temperature refining includes:

[0078] Adjusting the pressure of the high-temperature refining according to the time of the high-temperature refining;

[0079] When t < 0.2T, P is 1 Pa to 5 Pa;

[0080] When 0.2T < t < 0.6T, P is 0.1 Pa to 0.5 Pa;

[0081] When t > 0.6T, P is 1 Pa to 2 Pa;

[0082] Wherein, t represents the time of the high-temperature refining, P represents the pressure of the high-temperature refining, T represents the total time of the high-temperature refining, and T is 0.5 h to 0.7 h.

[0083] In the initial stage of refining (t < 0.2T), limiting P to 1 Pa to 5 Pa helps to promote the escape of gases (such as hydrogen, oxygen, etc.) in the molten steel, and also helps the rapid melting and uniform mixing of raw materials; in the middle stage of refining (0.2T < t < 0.6T), limiting P to 0.1 Pa to 0.5 Pa helps to reduce the gas content in the molten steel and further improve the purity of the molten steel. At the same time, the lower pressure is also beneficial to promoting the uniform distribution of alloy elements and the progress of chemical reactions; in the later stage of refining (t > 0.6T), limiting P to 1 Pa to 2 Pa ensures that T.O ≤ 20 ppm in the alloy, and helps to maintain the stability of the molten steel, preventing the splashing or spraying of the molten steel caused by too low pressure. At the same time, it also helps to control the further reaction and precipitation of alloy elements.

[0084] In some embodiments, the temperature of the vacuum refining is 1500 °C to 1600 °C.

[0085] The preparation product of the preparation method of the ferrochromium alloy is the above ferrochromium alloy. The chemical composition and microstructure of the ferrochromium alloy prepared by the preparation method of the ferrochromium alloy can refer to the above embodiments. Since the preparation method of the ferrochromium alloy adopts some or all of the technical solutions of the ferrochromium alloy embodiments, it at least has all the beneficial effects brought by the technical solutions of the ferrochromium alloy embodiments, and will not be elaborated here one by one.

[0086] Based on a general inventive concept, the present application also provides a fuel cell interconnector, and the fuel cell interconnector is made of the ferrochromium alloy described in any one of the above embodiments.

[0087] In some embodiments, the fuel cell interconnector satisfies at least one of the following performances:

[0088] 400 mA / cm at 900℃ 2 The cathode deposited with Cr content ≤0.05 mg / cm³ after 4000 h of current polarization 2 ;

[0089] 400 mA / cm at 600℃ 2 The cathode deposited with Cr content ≤0.01 mg / cm³ after 4000 h of current polarization 2 ;

[0090] The creep strain at 900℃ and 10MPa load for 2000h is ≤0.01%;

[0091] The creep strain at 900℃ and 10MPa load for 4000h is ≤0.03%.

[0092] This application thoroughly studies the effects of Cr and trace elements Cu, B, and Ni on the microstructure and oxide layer structure of the alloy. Using industrial pure iron as raw material, through reasonable element ratios and precise control of smelting and rolling processes, a long-life, chromium-resistant alloy interconnect is provided. It can be applied to batteries, electrolytic cells, connectors, separators, or sealing materials in the field of hydrogen energy, and is particularly suitable for connector materials of solid oxide fuel cells and hydrogen electrolytic cells.

[0093] Figure 2 This is a schematic flowchart illustrating a method for fabricating a fuel cell interconnect plate according to an embodiment of this application.

[0094] Please see Figure 2 This application provides a method for preparing the fuel cell interconnect plate described in the above embodiments, the method comprising:

[0095] S21. The iron-chromium alloy described in any of the above embodiments is sequentially heated, forged, and tempered in multiple passes to obtain a flat billet;

[0096] In some embodiments, the heating temperature is 1050°C to 1200°C.

[0097] S22. The flat billet is subjected to multiple hot rolling passes and annealing softening to obtain a hot-rolled strip billet;

[0098] In some embodiments, the temperature of the multi-pass hot rolling is 1000℃ to 1150℃. The multi-pass hot rolling includes a first hot rolling pass, a second hot rolling pass, and a third hot rolling pass. The deformation amount of the first hot rolling pass is 40% to 60%, the deformation amount of the second hot rolling pass is 30% to 50%, and the deformation amount of the third hot rolling pass is 30% to 40%. The final rolling temperature is above 900℃. After rolling, the material is water-cooled to room temperature.

[0099] S23. The hot-rolled strip is subjected to intermediate heat treatment, multiple cold rolling passes, and solution treatment to obtain strip material;

[0100] In some embodiments, the cold rolling includes: a first cold rolling, a second cold rolling, and a third cold rolling, wherein the deformation amount of the first cold rolling is 50% to 70%, the deformation amount of the second cold rolling is 40% to 60%, and the deformation amount of the third cold rolling is 30% to 60%.

[0101] In some embodiments, after step S23, the method further includes:

[0102] The strip is subjected to surface finishing, cleaning and shape correction in sequence. The specific process of surface finishing is as follows: rough polishing is performed using a polishing wheel with a grit size of 500-1000 mesh, followed by fine polishing using a polishing wheel with a grit size of 3000-4000 mesh.

[0103] S24. The strip is stamped and aged to obtain a fuel cell interconnect plate.

[0104] In some embodiments, the stamping process includes the following parameters: heating temperature of 200℃~400℃, and hydrogen injection volume ≥5m³. 3 / h, with a heat preservation time of 20min to 120min.

[0105] In some embodiments, the aging treatment includes the following parameters: temperature of 400℃~500℃, holding time of 60min~90min, and hydrogen injection rate ≥20m³. 3 / h.

[0106] In solution treatment, the temperature is limited to 400℃~500℃, and the holding time is 60min~90min, allowing the elements in the alloy to fully dissolve in the matrix and form a homogeneous solid solution. This helps improve the alloy's corrosion resistance, strength, and toughness. Hydrogen spraying is simultaneously employed during solution treatment to prevent oxidation of the ferrochromium alloy. For example, the solution treatment temperature can be 400℃, 420℃, 440℃, 460℃, 480℃, 490℃, 500℃, etc., the holding time can be 60min, 65min, 70min, 75min, 80min, 85min, 90min, etc., and the hydrogen spraying volume can be 20mg / L. 3 / h、22m 3 / h, 25m 3 / h、28m 3 / h, 30m 3 / h etc.

[0107] The product prepared by the preparation method of the fuel cell interconnect plate is the above-mentioned fuel cell interconnect plate. The chemical composition and microstructure of the fuel cell interconnect plate prepared by the preparation method of the fuel cell interconnect plate can refer to the above embodiments. Since the preparation method of the fuel cell interconnect plate adopts some or all of the technical solutions of the embodiments of the fuel cell interconnect plate, it has at least all the beneficial effects brought by the technical solutions of the embodiments of the fuel cell interconnect plate, which will not be elaborated here one by one.

[0108] The following further elaborates the present application in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present application and not to limit the scope of the present application. The experimental methods without specific conditions indicated in the following embodiments are usually measured according to industry standards. If there is no corresponding industry standard, they are carried out according to general international standards, conventional conditions, or the conditions recommended by the manufacturer.

[0109] This embodiment provides a preparation method of a fuel cell interconnect plate, which specifically includes the following steps:

[0110] Step 1: Vacuum melting, high-temperature refining, and pouring are carried out on the raw materials proportioned according to the ratio, and an iron-chromium alloy ingot with a set chemical composition is obtained after crystallization; among them, the pressure P of the high-temperature refining and the time t of the high-temperature refining satisfy the following relationship: when t < 0.2T, P varies within the range of 1 Pa to 5 Pa; when 0.2T < t < 0.6T, P varies within the range of 0.1 Pa to 0.5 Pa; when t > 0.6T, P varies within the range of 1 Pa to 2 Pa; the chemical composition of the iron-chromium alloy ingot is shown in Table 1, and the relationship between the chemical compositions of the nickel-based alloy ingots is shown in Table 2.

[0111] Step 2: The alloy ingot is heated, forged, and subjected to multiple tempering treatments to obtain a flat blank, and the heating temperature is 1100 °C.

[0112] Step 3: The flat blank is hot-rolled, annealed and softened, and grinded and welded to obtain a hot-rolled strip blank; 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 deformation amount of the first hot-rolling is 50%, the deformation amount of the second hot-rolling is 40%, and the deformation amount of the third hot-rolling is 30%. The final rolling temperature is higher than 900 °C. After rolling, it is water-cooled to room temperature.

[0113] Step 4: The hot-rolled strip blank is subjected to blooming, intermediate heat treatment, cold rolling, intermediate grinding, trimming, and solution treatment to obtain a strip; the cold rolling includes: the first cold rolling, the second cold rolling, and the third cold rolling. The deformation amount of the first cold rolling is 60%, the deformation amount of the second cold rolling is 50%, and the deformation amount of the third cold rolling is 40%.

[0114] Step 5: Perform surface finishing, cleaning, and shape correction on the strip. The specific process of surface finishing is as follows: first, use a 1000-mesh polishing wheel for coarse polishing, and then use a 3000-mesh polishing wheel for fine polishing.

[0115] Step 6: The strip is stamped and aged to obtain a fuel cell interconnect plate; the stamping includes the following parameters: heating temperature of 300℃, hydrogen injection rate of 5m³ / h. 3 The aging treatment includes the following parameters: temperature 450℃, holding time 60min, and hydrogen injection rate 20m³ / h. 3 / h.

[0116] Table 1. Chemical composition (wt, %) of iron-chromium alloy ingots, balance being Fe and unavoidable impurities.

[0117]

[0118]

[0119] Table 2 Relationship between the chemical compositions of iron-chromium alloy ingots

[0120] serial number 0.06 × [%Cu] + 0.032 × [%W] [%Zr]+1.1[%B] (0.22×[%Cr]+0.32×[%Cu]) / [Mo] Example 1 0.14 0.42 1.54 Example 2 0.09 0.61 2.41 Example 3 0.18 0.82 2.19 Example 4 0.24 1.13 2.68 Example 5 0.34 1.50 2.08 Comparative Example 1 0.34 1.50 2.08 Comparative Example 2 0.14 0.30 1.54 Comparative Example 3 0.14 0.42 3.08 Comparative Example 4 0.04 0.61 2.22

[0121] The fuel cell interconnect plates prepared in Examples 1 to 5 and Comparative Examples 1 to 4 were subjected to performance tests, and the results are shown in Table 3.

[0122] Table 3 Performance of Fuel Cell Interconnect Panel

[0123]

[0124]

[0125] As shown in Table 3, in Comparative Example 1, the amount of Y added is less than 0.06 × [%Cu] + 0.032 × [%W], which does not satisfy [Y] > 0.06 × [%Cu] + 0.032 × [%W], resulting in a low Cu diffusion rate and a higher Cr volatilization rate than in the Example. In Comparative Example 2, the amounts of Zr and B added are too low, failing to satisfy 0.4 ≤ [%Zr] + 1.1 [%B] ≤ 1.5, thus suppressing the effect of Zr and B composite addition in enhancing grain boundary bonding, and resulting in a higher high-temperature creep strain rate than in the Example. In Comparative Example 3, the amount of Mo added does not satisfy 1.5 ≤ (0.22 × [%Cr] + 0.32 × [%Cu]) / [Mo] ≤ 3, resulting in a lower Cr volatilization resistance than in the Example. In Comparative Example 4, the amount of Cu added is less than 0.7%, which is insufficient, resulting in a lower Cr volatilization resistance than in the Example.

[0126] Furthermore, one or more technical solutions in the embodiments of this application have at least the following technical effects or advantages:

[0127] In this embodiment, by designing reasonable alloy element additions and ratios, optimizing processes and processing techniques, and through reasonable element ratios and precise control of smelting and rolling processes, a long-life fuel cell interconnect plate with suppressed Cr volatilization is provided. This plate can be applied to batteries, electrolytic cells, connectors, separators, or sealing materials in the hydrogen energy field to solve the technical problems of low lifespan and severe Cr volatilization of existing alloys at 600℃~900℃.

[0128] In this embodiment, the target performance requirements are achieved through alloy composition design and smelting and processing techniques. Regarding the performance index for suppressing chromium volatilization, for alloy plates with a thickness of less than 2 mm, at 900°C, the performance index is 400 mA / cm². 2 After 4000 hours of current polarization, the Cr-containing material deposited at the cathode does not exceed 0.05 mg / cm³. 2 At 600℃ and under the same polarization conditions, the Cr-containing material deposited at the cathode does not exceed 0.01 mg / cm³. 2 Regarding creep resistance at 900℃, under a 10MPa load, the creep strain does not exceed 0.01% after 2000 hours and does not exceed 0.03% after 4000 hours.

[0129] In the embodiments of this application, the cost of the prepared iron-based material is lower, and the cost is reduced by more than 50% compared with that of general high-temperature nickel-based alloys.

[0130] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. An iron-chromium alloy for suppressing Cr evaporation, the iron-chromium alloy comprising, in terms of mass fraction, the following chemical components: Cr: 13% to 22.5%, Cu: 0.7% to 4.0%, Zr: 0.3% to 1.0%, B: 0.015% to 0.45%, Ni: 1.0% to 1.2%, Mo: 1% to 3%, W: 0.1% to 3%, C+N < 0.010%, T.O < 0.002%, Si: 0.15% to 0.3%, Mn: 0.1% to 0.8%, Al: 0.15% to 0.4%, rare earth elements: 0.001% to 0.5%, and Fe; wherein, The rare earth element is one or more of La, Ce, Sc and Y; The chemical composition satisfies the following relationship: [R] > 0.06 x [%Cu] + 0.032 x [%W]; 0.4 ≤ [%Zr] + 1.1 [%B] ≤ 1.5; 1.5 ≤ (0.22 x [%Cr] + 0.32 x [%Cu]) / [Mo] ≤ 3; In the formula, [R] represents the mass fraction of the rare earth element, the number before [%Cu] represents the mass fraction of Cu, the number before [%W] represents the mass fraction of W, the number before [%Zr] represents the mass fraction of Zr, the number before [%B] represents the mass fraction of B, the number before [%Cr] represents the mass fraction of Cr, and [Mo] represents the mass fraction of Mo.

2. A preparation method of the iron-chromium alloy of claim 1, the method comprising: high-temperature refining the molten steel, and adjusting the pressure of the high-temperature refining according to the time of the high-temperature refining to obtain an alloyed molten steel; when t < 0.2T, P is 1 Pa to 5 Pa; when 0.2T < t < 0.6T, P is 0.1 Pa to 0.5 Pa; when t > 0.6T, P is 1 Pa to 2 Pa; wherein t represents the time of the high-temperature refining, P represents the pressure of the high-temperature refining, and T represents the total time of the high-temperature refining, and T is 0.5 h to 0.7 h; casting and crystallizing the alloyed molten steel to obtain the iron-chromium alloy.

3. A fuel cell interconnection plate prepared from the iron-chromium alloy of claim 1.

4. The fuel cell interconnect plate of claim 3, wherein The fuel cell interconnection plate satisfies the following performances: Cathode deposition of Cr containing species < 0.05 mg / cm at 900 °C under 400 mA / cm 2 Cathode deposition of Cr containing species < 0.05 mg / cm at 900 °C under 400 mA / cm 2 ; Cathode deposition of Cr containing species < 0.01 mg / cm at 600 °C at 400 mA / cm 2 Cathode deposition of Cr containing species < 0.01 mg / cm at 600 °C at 400 mA / cm 2 ; creep strain ≤ 0.01% under 10 MPa load for 2000 h at 900°C; creep strain ≤ 0.03% under 10 MPa load for 4000 h at 900°C.

5. A preparation method of the fuel cell interconnection plate of claim 3 or 4, the method comprising: sequentially heating, forging and multi-pass tempering the iron-chromium alloy of claim 1 to obtain a flat billet; multi-pass hot rolling and annealing softening the flat billet to obtain a hot-rolled strip billet; intermediate heat treatment, multi-pass cold rolling and solid solution treatment of the hot-rolled strip billet to obtain a strip; punch forming and aging treatment of the strip to obtain a fuel cell interconnection plate; punch forming and aging treatment of the strip to obtain a fuel cell interconnection plate; The aging treatment includes the following parameters: temperature of 400-500 DEG C, holding time of 60-90 min and hydrogen spraying amount of >20 m 3 / h.

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