Iron-chromium alloy for inhibiting volatilization of Cr, fuel cell interconnection plate and preparation method

Abstract

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

Description

Technical Field

[0001] The present application relates to the technical field of alloys, and in particular to an iron-chromium alloy capable of inhibiting Cr volatilization, a fuel cell interconnection plate, and a preparation method thereof. Background Art

[0002] High-temperature solid oxide fuel cells (800°C) 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 the operating temperature of SOFC to be reduced from 1000°C to a medium temperature range of 600-800°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] So far, the four ferritic stainless steel connectors that have been studied in detail are Crofer 22APU, SUS430, X10CrAl18 and ZMG232. The more representative ferritic Fe-Cr alloys are ZMG232 developed by Hitachi Metals and Crofer22 APU alloy announced by ThyssenKrupp VDM in 2003. After optimization, ZMG232L and Crofer22H were further developed. ZMG232 is a ferritic Fe-Cr alloy mainly containing 22% Cr, 0.04% La and 0.22% Zr. Although ZMG232 has good oxidation resistance in the range of 650-800℃, some literature points out that the conductivity of ZMG232 is far from the level of practical application. Although the above alloys have excellent performance, there are still bottlenecks in their commercial use. Currently, they cannot meet the requirements of long-term operation of SOFC battery stacks: Cr-containing alloys form volatile gaseous substances in an oxidizing environment. These volatile substances will deposit on the cathode surface, seriously damaging the electrochemical performance of SOFC. Therefore, a nickel-based alloy with low Cr volatilization is urgently needed. Summary of the invention

[0004] The present application provides an iron-chromium alloy capable of suppressing Cr volatilization, a fuel cell interconnection plate and a preparation method thereof, so as to solve the following technical problem: how to suppress Cr volatilization in a nickel-based alloy.

[0005] In a first aspect, the present application provides an iron-chromium alloy for inhibiting Cr volatilization. The iron-chromium alloy includes the following chemical components, measured by mass fraction: 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%, TO≤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 elements include: one or more of La, Ce, Sc and Y.

[0006] Optionally, the chemical composition satisfies the following relationship:

[0007] [R]>0.06×[%Cu]+0.032×[%W]

[0008] In the formula, [R] represents the mass fraction of the rare earth element, [%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 composition satisfies the following relationship:

[0010] 0.4≤[%Zr]+1.1[%B]≤1.5

[0011] In the formula, [%Zr] represents the value before the mass fraction % of Zr, and [%B] represents the value before 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] In a second aspect, the present application provides a method for preparing the iron-chromium alloy according to any one embodiment of the first aspect, the method comprising:

[0015] The molten steel is subjected to high-temperature refining, and the pressure of the high-temperature refining is adjusted according to the time of the high-temperature refining 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, which is made of the ferrochromium alloy described in any one of the embodiments of the first aspect.

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

[0025] At 900 °C, the cathode deposition of Cr-containing substances with a current polarization of 400 mA / cm 2 for 4000 h is ≤ 0.05 mg / cm 2 ;

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

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

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

[0029] In a fourth aspect, the present application provides a method for preparing the fuel cell interconnector described in the embodiments of the third aspect, and the method includes:

[0030] Successively heating, forging, and performing multi-pass tempering on the ferrochromium alloy described in any one of the embodiments of 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 subjected to stamping and aging treatment to obtain a fuel cell interconnection plate.

[0034] Optionally, the aging treatment includes the following parameters: temperature of 400°C to 500°C, holding time of 60min to 90min, and hydrogen injection volume ≥ 20m 3 / h.

[0035] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0036] The present application provides an iron-chromium alloy that inhibits the volatilization of Cr. The chemical composition of the iron-chromium alloy is rationally designed. The Fe-based alloy is used to design a high Cr, high Cu and low Ni component system to achieve excellent antioxidant properties while having an excellent effect of inhibiting the volatilization of Cr. The content of rare earth elements is rationally controlled to promote the dispersion strengthening effect of Cu and W elements in the alloy. At the same time, rare earth elements promote the diffusion rate of Cu in the oxide film under medium-temperature oxidation conditions, thereby forming (Cr, Cu) 3O4 in the outer layer of the Cr2O3 oxide film to inhibit the diffusion of Cr. Oxidation under 600-900°C conditions has a double-layer structure, with Cr2O3 adjacent to the substrate and (Cr, Cu) 3O4 in the outer layer. And the conductivity of (Cr, Cu) 3O4 is 2-5 times that of Cr2O3, which greatly enhances the conductivity of the oxide film. Adding Mo significantly reduces the effect of the thermal expansion coefficient of the nickel-based alloy to meet the thermal expansion coefficient of the solid oxide fuel cell. At the same time, through the composition ratio of Mo, Cu, and Cr alloy elements, under the condition of medium-temperature oxidizing atmosphere, due to the external diffusion of Cr and Cu, holes are formed between the matrix and the oxide film, which promotes the diffusion of Mo into the holes and reaches the critical formation condition of Fe3Mo, forming a conductive barrier between the matrix and the oxide film that inhibits the volatilization of Cr, preventing the extension of corrosion to the matrix, enhancing the conductivity between the matrix and the oxide film, and extending the battery life. Thus, the volatilization of Cr in the nickel-based alloy is inhibited. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0038] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0039] Figure 1 A schematic flow chart of a method for preparing an iron-chromium alloy provided in an embodiment of the present application;

[0040] Figure 2 A schematic flow chart of a method for preparing a fuel cell interconnect plate provided in an embodiment of the present application. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution 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 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 this field without making creative work are within the scope of protection of this application.

[0042] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have 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., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0043] In addition, in the description of the specification of the present application, the terms "including", "comprising", etc. mean "including but not limited to". In this article, relational terms such as "first" and "second", etc. are only used 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 article, "and / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. Wherein A and B can be singular or plural. In this article, "at least one" means one or more, and "plurality" means two or more. "At least one", "the following at least one item (items)" or similar expressions refer to any combination of these items, including any combination of single items (items) or plural items (items). For example, "at least one of a, b, or c", or "at least one of a, b, and c", can all represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple. "Parts" such as parts by weight and parts by mass indicate the proportional relationship between the components. In the proportional relationship involved in this article, the parameters that need to be described by proportion should be understood as the first term of the proportional formula in the order of description, and the proportional numbers should be understood as the second term of the proportional formula. For example, the mass ratio of substance A, substance B, and substance C is 1:2:3, then substance A, substance B, and substance C should correspond one-to-one with the proportional numbers in the proportional formula in the order of description, that is, the mass of substance A: the mass of substance B: the mass of substance C = 1:2:3.

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

[0045] The present application provides an iron-chromium alloy for inhibiting Cr volatilization. The iron-chromium alloy includes the following chemical components, measured by mass fraction: 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%, TO≤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 elements include: one or more of La, Ce, Sc and Y.

[0046] The functions of each component are mainly reflected in:

[0047] C, N: C forms carbides at the end of solidification and during heat treatment, which plays a role in strengthening grain boundaries and can delay the initiation, expansion and merging of creep voids in the alloy, thereby improving the high-temperature creep resistance of the alloy. In addition, when the carbon content is too high, it has an adverse effect on corrosion resistance. Nitrogen content is the main cause of high-temperature brittleness of ferrite, so the sum of the contents of C and N should be controlled to not exceed 0.010%. Exemplarily, the content of C+N 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 has a certain solid solution strengthening effect, but too high Cr content will increase the thermal expansion coefficient. In this application, the Cr content is controlled at 13% to 22.5% in consideration of both oxidation resistance and thermal expansion performance. 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. If the Ni content is too high, austenite will be formed, the thermal expansion coefficient will increase, and the cost will increase. 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 the alloy at high temperatures. Exemplarily, the Mo content can be 1%, 1.5%, 2%, 2.5%, 3%, etc.

[0051] B: The role of B is mainly to enrich B at the grain boundary with a small radius, reduce the aggregation of harmful elements with low melting points, increase the grain boundary bonding force of the ferrite matrix, and thus improve the creep resistance and life of the alloy. If the content is too high, the hot working performance will be affected, and the B content should be controlled to 0.015% to 0.45%. For example, the B content can be 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, etc.

[0052] Zr: Purifies grain boundaries, and is added in combination with B to enhance grain boundary bonding and maintain high temperature strength. Anti-oxidation, improves oxide film structure, inhibits inward diffusion of oxygen, and enhances the bonding between oxide film and iron-chromium alloy matrix. Excessive addition will deteriorate hot working properties. Exemplarily, the Zr content can be 0.3%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, etc.

[0053] Cu: 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 in the outer layer of the Cr2O3 oxide film, inhibiting the diffusion of Cr. Oxidation under 600-900°C conditions has a double-layer structure, with Cr2O3 adjacent to the matrix and (Cr, Cu) 3O4 in the outer layer. And the conductivity of (Cr, Cu) 3O4 is 2 to 5 times that of Cr2O3, which greatly enhances the conductivity of the oxide film. Exemplarily, the Cu content can be 0.7%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4.0%, etc.

[0054] Rare earth elements: Rare earth elements are added to the alloy to offset the effect of high Cr on plasticity. Since rare earth elements are segregated at the grain boundaries, they play a role in grain boundary strengthening, delaying the formation and expansion of cracks, thereby significantly improving the durability of the alloy. 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: deoxidizer, can improve the oxidation resistance and high temperature strength of the alloy. Excessive addition will form SiO2 on the surface of the alloy during oxidation, affecting the conductivity. Exemplarily, the content of Si can be 0.15%, 0.2%, 0.25%, 0.3%, etc.

[0056] Mn: deoxidizer, can improve the oxidation resistance and high temperature strength of the alloy. Excessive addition will increase the thermal expansion coefficient of the alloy. Exemplarily, the content of Mn 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 the alloy. It can also reduce the density of the alloy, achieving the advantages of lightweight and low cost. Excessive addition affects the tensile and welding properties. 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 is the total oxygen content.

[0059] Fe is a matrix element. The specific content / content range of Fe can be obtained through the upper and lower limit formulas of the components, that is, the sum of the percentages of the contents of each component in a composition should be equal to 100%, and the content ranges of several components should meet the following conditions: the upper limit value of a component + the lower limit values ​​of other components ≤ 100; the lower limit value of a component + the upper limit values ​​of other components ≥ 100.

[0060] In some embodiments, the chemical composition satisfies the following relationship:

[0061] [R]>0.06×[%Cu]+0.032×[%W]

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

[0063] Limiting the ratio of rare earth elements, Cu, and W elements promotes the dispersion strengthening effect of Cu in the alloy, effectively improves the strength of the alloy, and increases the service temperature of the alloy to about 950°C. Under medium-temperature oxidation conditions, rare earth elements promote the diffusion rate of Cu in the oxide film, thereby forming (Cr, Cu)3O4 in the outer layer of the Cr2O3 oxide film, inhibiting the diffusion of Cr.

[0064] In some embodiments, the chemical composition satisfies the following relationship:

[0065] 0.4≤[%Zr]+1.1[%B]≤1.5

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

[0067] The element ratio of Zr and B is limited, and the composite addition of Zr and B enhances the grain boundary bonding and maintains the 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 composition satisfies 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] The present application designs a high Cr, high Cu, and low Ni component system to achieve excellent antioxidant properties while having an excellent effect of inhibiting Cr volatilization. Through the composition ratio of Mo, Cu, and Cr alloy elements, under medium-temperature oxidizing atmosphere conditions, due to the external diffusion of Cr and Cu, holes are formed between the matrix and the oxide film, which promotes the diffusion of Mo into the holes and reaches the critical formation conditions of Fe3Mo, forming a conductive barrier between the matrix and the oxide film that inhibits Cr volatilization, preventing corrosion from extending to the matrix, enhancing the conductivity between the matrix and the oxide film, and extending the battery life. Exemplarily, 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, the present application adopts Fe-based alloys and designs a high Cr, high Cu and low Ni composition system to achieve excellent antioxidant properties while having an excellent effect of inhibiting Cr volatilization. Reasonable control of rare earth element Y promotes the dispersion strengthening effect of Cu and W elements in the alloy. At the same time, under medium-temperature oxidation conditions, Y promotes the diffusion rate of Cu in the oxide film, thereby forming (Cr, Cu) 3O4 in the outer layer of the Cr2O3 oxide film, inhibiting the diffusion of Cr. Oxidation under 600-900°C conditions has a double-layer structure, with Cr2O3 adjacent to the substrate and (Cr, Cu) 3O4 in the outer layer. And the conductivity of (Cr, Cu) 3O4 is 2 to 5 times that of Cr2O3, which greatly enhances the conductivity of the oxide film. Adding Mo significantly reduces the effect of the thermal expansion coefficient of nickel-based alloys to meet the thermal expansion coefficient of solid oxide fuel cells. At the same time, through the composition ratio of Mo, Cu, and Cr alloy elements, under medium-temperature oxidizing atmosphere conditions, due to the external diffusion of Cr and Cu, holes are formed between the matrix and the oxide film, which promotes the diffusion of Mo into the holes and reaches the critical formation conditions of Fe3Mo. A barrier that is conductive and inhibits Cr volatilization is formed between the matrix and the oxide film, preventing corrosion from extending to the matrix, enhancing the conductivity between the matrix and the oxide film, and extending the battery life.

[0073] Figure 1 A schematic flow chart of a method for preparing an iron-chromium alloy provided in an embodiment of the present application.

[0074] See also Figure 1 The present application provides a method for preparing the iron-chromium alloy according to any one of the embodiments of the first aspect, the method comprising:

[0075] S11, subjecting the molten steel to high temperature refining, and adjusting the pressure of the high temperature refining according to the time of the high temperature refining, to obtain alloyed molten steel;

[0076] S12, pouring and crystallizing the alloyed steel liquid 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 the 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 alloying 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 alloying 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 has at least all the beneficial effects brought by the technical solutions of the ferrochromium alloy embodiments, which 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] 400mA / cm at 900℃ 2 The cathode deposited Cr content of the current polarization for 4000h is ≤0.05mg / cm 2 ;

[0089] 400mA / cm at 600℃ 2 The cathode deposited by current polarization for 4000h contains Cr substances ≤ 0.01mg / cm 2 ;

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

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

[0092] This application fully studies the influence of Cr and trace elements Cu, B, Ni on the alloy organization and oxide layer structure, takes industrial pure iron as raw material, and provides a long-life, chromium-volatile-resistant alloy interconnect through reasonable element ratio, precise control of smelting process and rolling process, and is applied to batteries, electrolytic cell 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 A schematic flow chart of a method for preparing a fuel cell interconnect plate provided in an embodiment of the present application.

[0094] See also Figure 2 The present application provides a method for preparing the fuel cell interconnection plate described in the above embodiment, the method comprising:

[0095] S21, sequentially heating, forging and multi-pass tempering the iron-chromium alloy described in any one of the above embodiments to obtain a slab;

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

[0097] S22, performing multiple hot rolling and annealing to soften the slab to obtain a hot-rolled strip;

[0098] In some embodiments, the temperature of the multiple hot rolling is 1000°C to 1150°C. The multiple hot rolling includes: a first hot rolling, a second hot rolling, and a third hot rolling. The first hot rolling deformation is 40% to 60%, the second hot rolling deformation is 30% to 50%, and the third hot rolling deformation is 30% to 40%. The final rolling temperature is higher than 900°C. After rolling, the steel is water-cooled to room temperature.

[0099] S23, subjecting the hot-rolled strip to intermediate heat treatment, multiple cold rolling and solution treatment to obtain a strip;

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

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

[0102] The strip is subjected to surface finishing, cleaning and plate shape correction in sequence. The specific process of the surface finishing is: rough polishing is performed using a polishing wheel with a particle size of 500-1000 meshes, and then fine polishing is performed using a polishing wheel with a particle size of 3000-4000 meshes.

[0103] S24, stamping and aging the strip to obtain a fuel cell interconnection plate.

[0104] In some embodiments, the stamping forming includes the following parameters: heating temperature is 200°C to 400°C, hydrogen injection volume is ≥ 5m 3 / h, the insulation time is 20min~120min.

[0105] In some embodiments, the aging treatment includes the following parameters: temperature of 400°C to 500°C, holding time of 60min to 90min, and hydrogen injection volume of ≥20m 3 / h.

[0106] In the solution treatment, the solution treatment temperature is limited to 400°C to 500°C, and the holding time is 60min to 90min, so that the elements in the alloy are fully dissolved in the matrix to form a uniform solid solution. This helps to improve the corrosion resistance, strength and toughness of the alloy. During the solution treatment process, hydrogen spraying is also used to prevent the iron-chromium alloy from oxidizing during the solution treatment process. Exemplarily, the solution treatment temperature can be 400°C, 420°C, 440°C, 460°C, 480°C, 490°C, 500°C, etc., the holding time can be 60min, 65min, 70min, 75min, 80min, 85min, 90min, etc., and the hydrogen spraying amount can be 20m 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 interconnector plate is the above fuel cell interconnector plate. The chemical composition and microstructure of the fuel cell interconnector plate prepared by the preparation method of the fuel cell interconnector plate can refer to the above embodiments. Since the preparation method of the fuel cell interconnector plate adopts some or all of the technical solutions of the embodiments of the fuel cell interconnector plate, it has at least all the beneficial effects brought by the technical solutions of the embodiments of the fuel cell interconnector plate, which will not be elaborated one by one here.

[0108] The following will further illustrate 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 determined 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 interconnector plate, which specifically includes the following steps:

[0110] Step 1: Vacuum melting, high-temperature refining, and pouring of the raw materials proportioned according to the ratio, and after crystallization, an iron-chromium alloy ingot with a set chemical composition is obtained; 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: Heating, forging, and multi-pass tempering of the alloy ingot to obtain a flat blank, and the heating temperature is 1100 °C.

[0112] Step 3: Hot rolling, annealing softening, and grinding and welding of the flat blank 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: Billet opening, intermediate heat treatment, cold rolling, intermediate grinding, trimming, and solution treatment of the hot-rolled strip blank 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, surface finishing, cleaning and plate shape correction of the strip, the specific process of the surface finishing is: firstly use a polishing wheel with a particle size of 1000 mesh for rough polishing, and then use a polishing wheel with a particle size of 3000 mesh for fine polishing.

[0115] Step 6: stamping and aging the strip to obtain a fuel cell interconnection plate; the stamping includes the following parameters: heating temperature is 300°C, hydrogen injection volume is 5m 3 / h, the holding time is 60min; the aging treatment includes the following parameters: temperature is 450℃, holding time is 60min and hydrogen injection volume is 20m 3 / h.

[0116] Table 1 Chemical composition of ferrochromium alloy ingot (wt, %), the balance is Fe and unavoidable impurities

[0117]

[0118]

[0119] Table 2 Relationship between the chemical compositions of ferrochromium 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 interconnection 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 interconnection board

[0123]

[0124]

[0125] As shown in Table 3, the amount of Y added in Comparative Example 1 is less than 0.06×[%Cu]+0.032×[%W], which does not satisfy [Y]>0.06×[%Cu]+0.032×[%W], the diffusion rate of Cu is low, and the amount of Cr volatilization is higher than that in the embodiment; the amount of Zr and B added in Comparative Example 2 is too low, which does not satisfy 0.4≤[%Zr]+1.1[%B]≤1.5, the effect of Zr and B composite addition to enhance the grain boundary bonding force is suppressed, and the high temperature creep strain rate is higher than that in the embodiment; the amount of Mo added in Comparative Example 3 does not satisfy 1.5≤(0.22×[%Cr]+0.32×[%Cu]) / [Mo]≤3, and the anti-Cr volatilization effect is lower than that in the embodiment. The amount of Cu added in Comparative Example 4 is less than 0.7%, the amount of addition is insufficient, and the anti-Cr volatilization effect is lower than that in the embodiment.

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

[0127] In the embodiments of the present application, by designing reasonable alloy element addition and ratio, optimizing process and processing preparation technology, and by reasonable element ratio, precise control of smelting process and rolling process, a fuel cell interconnection plate with long life and suppressed Cr volatilization is provided, and applied to batteries, electrolytic cell connectors, separators or sealing materials in the field of hydrogen energy, so as to solve the technical problems of low life and severe Cr volatilization of existing alloys at 600°C to 900°C.

[0128] In the embodiment of the present application, the target performance requirements are achieved through alloy composition design, smelting and processing technology. In terms of the performance index of inhibiting chromium volatilization, for alloy plates with a thickness of less than 2 mm at 900°C, 400 mA / cm 2 Current polarization for 4000h, cathode deposition of Cr-containing substances does not exceed 0.05mg / cm 2 ; At 600℃, under the same polarization conditions, the cathode deposited Cr-containing substances does not exceed 0.01mg / cm 2 In terms of creep resistance at 900℃, under a load of 10MPa, the creep strain does not exceed 0.01% in 2000 hours and does not exceed 0.03% in 4000 hours.

[0129] In the embodiments of the present application, the cost of the prepared iron-based material is relatively low, which is more than 50% lower than the cost of general high-temperature nickel-based alloys.

[0130] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. An iron-chromium alloy for inhibiting Cr volatilization, wherein the iron-chromium alloy comprises the following chemical components by mass fraction: 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%, TO≤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 elements include one or more of La, Ce, Sc, and Y.

2. The iron-chromium alloy according to claim 1, characterized in that The chemical composition satisfies the following relationship: [R] > 0.06×[%Cu] + 0.032×[%W] 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.

3. The iron-chromium alloy according to claim 1, characterized in that The chemical composition satisfies the following relationship: 0.4 ≤ [%Zr] + 1.1[%B] ≤ 1.5 In the formula, [%Zr] represents the value before the mass fraction % of Zr, and [%B] represents the value before the mass fraction % of B.

4. The iron-chromium alloy according to claim 1, characterized in that The chemical composition satisfies the following relationship: 1.5 ≤ (0.22×[%Cr] + 0.32×[%Cu]) / [Mo] ≤ 3 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.

5. A method for preparing an iron-chromium alloy according to any one of claims 1 to 4, the method comprising: Performing high-temperature refining on the molten steel and adjusting the pressure of the high-temperature refining according to the time of the high-temperature refining to obtain alloyed molten steel; Casting and crystallizing the alloyed molten steel to obtain the iron-chromium alloy.

6. The method according to claim 5, characterized in that The adjusting the pressure of the high-temperature refining according to the time of the high-temperature refining includes: Adjusting the pressure of the high-temperature refining according to the time of the high-temperature refining; 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.

7. A fuel cell interconnector, which is made of the iron-chromium alloy according to any one of claims 1 to 4.

8. The fuel cell interconnection plate according to claim 7, characterized in that: The fuel cell interconnector satisfies at least one of the following performances: 400mA / cm at 900℃ 2 The cathode deposited Cr content of the current polarization for 4000h is ≤0.05mg / cm 2 ; 400mA / cm at 600℃ 2 The cathode deposited by current polarization for 4000h contains Cr substances ≤ 0.01mg / cm 2 ; The creep strain at 900 °C under a load of 10 MPa for 2000 h ≤ 0.01%; The creep strain at 900 °C under a load of 10 MPa for 4000 h ≤ 0.03%.

9. A method for preparing a fuel cell interconnector according to claim 7 or 8, the method comprising: Successively heating, forging, and performing multi-pass tempering on the iron-chromium alloy according to any one of claims 1 to 4 to obtain a flat blank; Performing multi-pass hot rolling and annealing softening on the flat blank to obtain a hot-rolled strip blank; Performing intermediate heat treatment, multi-pass cold rolling, and solution treatment on the hot-rolled strip blank to obtain a strip; Performing stamping forming and aging treatment on the strip to obtain a fuel cell interconnector.

10. The method according to claim 9, characterized in that The aging treatment includes the following parameters: temperature of 400°C to 500°C, holding time of 60min to 90min, and hydrogen injection volume of ≥20m 3 / h.

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