A method for preparing stainless steel for solid oxide fuel cell connector

Abstract

The present invention relates to a method for preparing stainless steel for a solid oxide fuel cell connector, comprising the following steps: (1) mechanically ball-milling ferritic stainless steel pre-alloyed powder and nano-La2O3 powder to obtain a mechanically alloyed powder; (2) warm-pressing the mechanically alloyed powder to obtain a green body; and (3) sintering the green body to obtain stainless steel for a solid oxide fuel cell connector. The present invention selects a suitable mixed powder, and obtains high-performance stainless steel for a solid oxide fuel cell connector through mechanical ball milling, warm-pressing, and high-temperature sintering. This method not only improves material density but also achieves nano-oxide dispersion strengthening and metal element solid solution strengthening. Compared with traditional casting and rolling processes, this method improves material utilization, reduces machining, and achieves high production efficiency. Compared with the traditional hot isostatic pressing process for ODS steel, this method reduces material preparation costs, achieves high material utilization, and is more suitable for industrial-scale production.

Description

Technical Field

[0001] The invention belongs to the technical field of powder metallurgy materials, and in particular relates to a method for preparing stainless steel for a solid oxide fuel cell connector. Background Art

[0002] The world is facing increasingly severe environmental, population, and industrial challenges, and energy demand is constantly increasing. Solid oxide fuel cells (SOFCs) are energy conversion devices that can directly convert fuel into electricity without combustion. The interconnect is a key component of SOFCs, separating the fuel and oxidizing gases, providing electrical connections between cells, and distributing the reactant gases to the electrodes. Furthermore, the interconnect is exposed to both oxidizing and reducing atmospheres for extended periods of time. These harsh operating conditions dictate extremely stringent material requirements for the interconnect. In the early stages of SOFC system development, ceramic materials were widely used for interconnects, but manufacturing difficulties and high costs were the main obstacles to their application. In recent years, ferritic stainless steel has replaced expensive ceramics as the preferred interconnect material. Compared to ceramic interconnects, ferritic stainless steel offers advantages such as low material cost, good formability, enhanced mechanical and electrical properties, good oxidation resistance, and a thermal expansion coefficient similar to other SOFC components.

[0003] Stainless steel connectors are typically manufactured using a casting and rolling process, which is unable to form complex end-face airways in a single pass. Machining end-face airways presents drawbacks such as high processing difficulty and long production cycles. Furthermore, the casting process suffers from composition segregation, coarse grains, and low material utilization, making it difficult to achieve consistent production and engineered products. Consequently, large-scale production of connectors using the casting and rolling process is hampered by drawbacks such as high equipment investment, high manufacturing costs, difficulty improving high-temperature performance, and short service life.

[0004] Chinese patent application 201510195230.2 discloses a method for preparing a metal interconnect for a solid oxide fuel cell. The method involves rolling steel sheets, performing wire cutting to obtain the desired interconnect shape, and then sealing and splicing the metal interconnect. This interconnect preparation method involves multiple processing steps, a cumbersome operation, and low material utilization.

[0005] Chinese patent application 201610946958.9 discloses a self-sealing flat-plate solid oxide fuel cell connector and its preparation method. After preparing a metal connector, a gas passage and a groove are machined into the connector. This connector preparation method cannot be formed in one step, requiring subsequent processing to design the flow path.

[0006] Currently, Crofer22 APU material, produced by ThyssenKrupp in Germany, is the most widely used material for solid oxide fuel cell connectors. Its performance report shows that under 800°C tensile conditions, its yield strength is 30 MPa and its tensile strength is 30 MPa, indicating poor mechanical properties.

[0007] Chinese patent application 200910249062.5 discloses a solid oxide fuel cell connector material for fuel cells. The connector material prepared by the invention has an oxidation weight gain of 1.8×104 g / cm2 under 800°C / 20h oxidation conditions. 2 , high temperature oxidation resistance is poor.

[0008] Chinese patent application 200710300301.6 discloses a ferritic stainless steel containing the rare earth element yttrium for use in solid oxide fuel cells. The connector material prepared therefrom has an oxidation weight gain of 0.5 mg / cm3 under 800°C / 200h oxidation conditions. 2 , poor resistance to high temperature corrosion.

[0009] Chinese patent application 201711166855.1 discloses an aluminum-containing ferritic ODS steel and its preparation method. The multinary ferritic stainless steel is prepared by mixing Fe-Cr-Al-W pre-alloyed powder, Y2O3, and Zr powders, ball milling, and hot isostatic pressing (HIP) sintering. The ferritic stainless steel has a yield strength of 774 MPa and a tensile strength of 953 MPa, demonstrating excellent mechanical properties. However, the material utilization rate is low, the HIP process is costly, and the production efficiency is low, making it unsuitable for large-scale mass production of connectors.

[0010] Traditional solid oxide interconnector material preparation methods are characterized by complex steps, high subsequent processing costs, and low material utilization, limiting their large-scale industrial application. Furthermore, the resulting products exhibit insufficient mechanical properties and poor oxidation resistance, making them incapable of withstanding the high-temperature operating environments of solid oxide fuel cells. Therefore, developing interconnector materials and preparation methods that can withstand the extended operation of solid oxide fuel cells in high-temperature, oxidizing atmospheres and are suitable for large-scale industrial production is an urgent technical challenge in this field. Summary of the Invention

[0011] In response to the above problems, the present invention proposes a method for preparing stainless steel for solid oxide fuel cell connectors. By mechanically ball-milling ferritic stainless steel pre-alloyed powder and nano-La2O3 powder, and then subjecting them to warm pressing and high-temperature sintering, the material density is improved, and the effects of nano-oxide dispersion strengthening and metal element solid solution strengthening are achieved. The stainless steel for solid oxide fuel cell connectors is prepared with one-time net forming, inorganic processing, excellent high-temperature mechanical properties, and excellent high-temperature oxidation resistance.

[0012] The present invention specifically proposes a method for preparing stainless steel for a solid oxide fuel cell connector, comprising the following steps:

[0013] (1) mechanically ball milling ferritic stainless steel pre-alloyed powder and nano-La2O3 powder to obtain mechanically alloyed powder;

[0014] (2) performing warm pressing on the mechanically alloyed powder to obtain a green body;

[0015] (3) Sintering the green body to obtain stainless steel for a solid oxide fuel cell connector.

[0016] Furthermore, in step (1), the mass percentage of each element in the ferritic stainless steel pre-alloyed powder is: Cr: 16-30%, Si: 0-1.0%, Mn: 0-0.8%, Mo: 0-1.5%, Ni: 0-0.7%, Nb: 0.1-0.6%, Ti: 0.1-1%, V: 0.02-0.1%, and Fe: balance.

[0017] Furthermore, in step (1), the added mass accounts for 0.1-1.0% of the total mass of the powder, the particle size of the nano-La2O3 powder is ≤100nm, and the particle size of the ferritic stainless steel pre-alloyed powder is ≤300μm.

[0018] Furthermore, in step (1), the ball-to-material ratio of the mechanical ball milling is (5-20):1, the ball milling speed is 200-600 r / min, the ball milling time is 10-100 h, and the ball milling environment is a vacuum or argon environment.

[0019] Furthermore, in step (2), the warm pressing forming adopts a warm pressing forming device, which includes a warm pressing mold and a feeding system; wherein,

[0020] A warm-pressing mold, comprising a male mold and a female mold, wherein the male mold and the female mold cooperate to form a warm-pressing forming cavity;

[0021] A feeding system, comprising a hopper, a feeding box, and a feeding pipe connecting the hopper and the feeding box;

[0022] At least the material box in the feeding system is movable relative to the warm-pressing mold.

[0023] Furthermore, the hopper has a first semi-closed-loop heating and temperature control device and at least three first temperature sensors, so that the temperature difference between different points in the hopper does not exceed 10°C, the hopper set temperature is 60-150°C, and the difference between the measured temperature and the set temperature does not exceed 10°C; and / or

[0024] The material box has a second semi-closed-loop heating temperature control device and at least two second temperature sensors, so that the temperature difference at different points of the material box does not exceed 5°C. The set temperature of the material box is 60-150°C, and the difference between the actual measured temperature of the material box and the set temperature does not exceed 10°C.

[0025] Furthermore, the feeding pipe has an insulation layer, and the temperature of the mechanical alloying powder does not drop by more than 10° C. after flowing from the hopper through the feeding pipe to the feed box.

[0026] Furthermore, the length direction of the warm pressing mold is the moving direction of the material box, and the thickness direction of the green body is the pressing direction; the pressing pressure of the warm pressing is 600-1200 MPa, and the temperature is controlled at 60-150°C.

[0027] Furthermore, the male mold and / or female mold has a third semi-closed-loop heating temperature control device and at least three third temperature sensors, so that the temperature difference at different points of the male mold and / or female mold does not exceed 10°C.

[0028] Preferably, the present invention places the female mold at the bottom and uses a mobile feeding system to feed and fill the mold. Further exploration of the filling stability Fc of warm-pressing molding yields the following formula:

[0029]

[0030] Among them, the values of Fw and Fl satisfy:

[0031]

[0032]

[0033] The powder flow rate Sp is measured using GB / T 1482-2010 and characterizes the flow properties of the powder. Its physical meaning is the time (in seconds) required to discharge 50g of powder using a specific standard funnel. The smaller the value, the better the flowability, which is more beneficial for filling.

[0034] The powder column height Hp indicates the filling height of the powder. The higher the filling height, the deeper the negative mold cavity, which is more difficult to fill.

[0035] The width of the female mold cavity Wc refers to the width of the mold cavity. The width direction is perpendicular to the movement direction of the material box. The wider the female mold cavity, the more difficult it is to fill.

[0036] Box cavity bottom width W f , represents the width of the bottom of the material box cavity. The width direction is perpendicular to the movement direction of the material box. Increasing the width of the bottom of the material box cavity can improve the filling performance;

[0037] Filling width coefficient Fw, this value reflects the ratio of the bottom width of the material box cavity to the width of the mold cavity. When Fw = 1, it means that the bottom width of the material box cavity exceeds the width of the female mold cavity by more than 50%, that is, the bottom width of the material box cavity is at least 1.5 times the width of the female mold cavity. In actual production, the bottom width of the material box cavity can be designed to exceed the width of the female mold cavity by 50% or more (that is, the bottom width of the material box cavity is more than 1.5 times the width of the female mold cavity). However, experiments show that if the bottom width of the material box cavity is too large, there will be almost no further improvement in the filling performance. Therefore, when calculating the filling width coefficient Fw, it is necessary to calculate in sections to measure its influence on the filling stability Fc, that is:

[0038]

[0039] The length of the female mold cavity Lc refers to the length of the mold cavity. The length direction is parallel to the movement direction of the material box. The longer the mold cavity is, the more difficult it is to fill.

[0040] Length L of the bottom of the box cavity f , which indicates the length of the bottom of the material box cavity. The length direction is parallel to the direction of movement of the material box. Increasing the length of the bottom of the material box cavity can improve the filling performance.

[0041] Filling length factor F l , this value reflects the ratio of the bottom length of the material box cavity to the length of the mold cavity. l =1, it means that the length of the bottom of the material box cavity exceeds the length of the female mold cavity by more than 50%, that is, the length of the bottom of the material box cavity is at least 1.5 times the length of the female mold cavity. In actual production, the length of the bottom of the material box cavity can be designed to exceed the length of the female mold cavity by 50% or more (that is, the length of the bottom of the material box cavity is more than 1.5 times the length of the female mold cavity). However, experiments have shown that if the length of the bottom of the material box cavity is too large, there will be almost no further improvement in the filling performance. Therefore, when calculating the filling length coefficient Fl, it is necessary to calculate it in sections to measure its impact on the filling stability Fc, that is:

[0042]

[0043] Box filling speed S f , which indicates the speed at which the material box moves forward when performing the filling action. This value is negatively correlated with the filling performance.

[0044] The value of filling stability Fc measures the filling performance and filling stability during the pressing process, preferably 2.6-3.0, more preferably 2.6-2.8. When the value is above 2.6, it means that the filling performance can meet general needs. When the value exceeds 2.8, the filling speed S of the material box can be increased. fIn exchange for higher production efficiency. When it is lower than 2.6, a lower filling speed and / or a powder with better fluidity should be selected to improve the filling performance.

[0045] Furthermore, in the step (3), the sintering is performed in a vacuum or hydrogen or argon protective atmosphere, the sintering time is 0.5h to 3h, and the sintering temperature is 1350 to 1450°C.

[0046] Through the above preparation method, the present invention can also provide a stainless steel for solid oxide fuel cell connector, wherein the stainless steel has a yield strength of more than 30 MPa and a tensile strength of more than 50 MPa at 800 ° C, and an oxidation temperature of 800 ° C, an oxidation time of 200 h, and an oxidation atmosphere of air, and an oxidation weight gain of 0.85 mg / cm 2 the following.

[0047] The present invention has the advantages that:

[0048] (1) The present invention adopts powder metallurgy process to prepare stainless steel for solid oxide fuel cell connector. Compared with the traditional casting and rolling process, it improves material utilization, reduces subsequent processing steps, reduces processing difficulty, and significantly improves production efficiency; compared with the traditional hot isostatic pressing process of ODS steel, it greatly reduces the material preparation cost, has high material utilization, and is more suitable for industrial-scale production.

[0049] The present invention reduces the amount of forming lubricant added, improves the compressibility of the powder, increases the green density, significantly increases the density of the connected body after sintering, and thus improves the high-temperature mechanical properties of the connected body by adopting a warm pressing forming process and extending the sintering time.

[0050] (2) The present invention designs the mass ratio of Cr in the metal powder to be between 16% and 30%. As the Cr content increases, the corrosion resistance of the stainless steel increases, making the ferritic stainless steel connector more suitable for use in the operating environment of solid oxide fuel cells. The addition of metal elements such as Ti, Nb, and V to the ferritic stainless steel pre-alloyed powder achieves a solid solution strengthening effect, while simultaneously preventing grain growth and achieving a fine grain strengthening effect, effectively improving the mechanical properties of the connector.

[0051] The present invention mechanically ball-mills nano-La2O3 powder with ferritic stainless steel pre-alloyed powder. This process further refines the nano-oxide and disperses it throughout the matrix, achieving a dispersion-strengthening effect and effectively improving the high-temperature mechanical properties of the connector. The nano-oxide also exhibits excellent high-temperature stability, effectively enhancing the connector's high-temperature oxidation resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] The above and other objects, features and advantages of the exemplary embodiments of the present disclosure will become readily understood by reading the following detailed description with reference to the accompanying drawings, in which:

[0053] Figure 1 This is a schematic diagram of the process flow for preparing stainless steel for a solid oxide fuel cell connector according to the present invention;

[0054] Figure 2 The test results of the yield strength and tensile strength at 800°C of the stainless steel used for the solid oxide fuel cell interconnect in Examples 2, 6-8 of the present invention and Comparative Example 1 are as follows;

[0055] Figure 3 These are the test results of the high-temperature yield strength at 800°C and oxidation weight gain of the stainless steel used for the solid oxide fuel cell interconnect in Examples 1-5 of the present invention and Comparative Example 2. DETAILED DESCRIPTION

[0056] In order to make the objectives, technical solutions and advantages of the present invention more clear, the specific implementation methods and examples of the present invention will be further described in detail below.

[0057] A method for preparing stainless steel for a solid oxide fuel cell connector comprises the following steps:

[0058] (1) mechanically ball milling ferritic stainless steel pre-alloyed powder and nano-La2O3 powder to obtain mechanically alloyed powder;

[0059] The mass percentages of the elements in the ferritic stainless steel pre-alloyed powder are as follows: Cr: 16-30%, Si: 0-1.0%, Mn: 0-0.8%, Mo: 0-1.5%, Ni: 0-0.7%, Nb: 0.1-0.6%, Ti: 0.1-1%, V: 0.02-0.1%, and Fe: the balance; the added mass of the nano-La2O3 powder accounts for 0.1-1.0% of the total mass of the powder; the particle size of the nano-La2O3 powder is ≤100 nm, and the particle size of the ferritic stainless steel pre-alloyed powder is ≤300 μm;

[0060] The ball-to-material ratio of mechanical ball milling is (5-20):1, the ball milling speed is 200-600 r / min, the ball milling time is 10-100 h, and the ball milling environment is vacuum or argon environment;

[0061] (2) performing warm pressing on the mechanically alloyed powder to obtain a green body;

[0062] The warm-pressing forming adopts a warm-pressing forming device, which includes a warm-pressing mold and a feeding system; the warm-pressing mold includes a male mold and a female mold, and the male mold and the female mold cooperate to form a warm-pressing forming cavity; the feeding system includes a hopper, a material box, and a feeding pipe connecting the hopper and the material box; the material box in the feeding system can be moved relative to the warm-pressing mold, and the entire feeding system can also be configured to be movable relative to the warm-pressing mold when necessary;

[0063] The hopper has a first semi-closed-loop heating and temperature control device and at least three first temperature sensors, so that the temperature difference at different points in the hopper does not exceed 10°C, the hopper set temperature is 60-150°C, and the difference between the measured temperature and the set temperature does not exceed 10°C; and / or the material box has a second semi-closed-loop heating and temperature control device and at least two second temperature sensors, so that the temperature difference at different points in the material box does not exceed 5°C, the material box set temperature is 60-150°C, and the difference between the measured temperature and the set temperature does not exceed 10°C; and the feeding pipe has an insulation layer, and the temperature of the mechanical alloying powder after flowing from the hopper through the feeding pipe to the material box does not drop by more than 10°C;

[0064] The male mold and / or female mold are equipped with a third semi-closed-loop heating temperature control device and at least three third temperature sensors, so that the temperature difference between different points of the male mold and / or female mold does not exceed 10°C;

[0065] During warm pressing, the length direction of the warm pressing die is the moving direction of the material box. At the same time, the mechanical alloying powder flows from the hopper through the feeding pipe to the material box and is fed to the warm pressing die. The thickness direction of the green body is the pressing direction. The pressing pressure of warm pressing is 600-1200MPa, and the temperature is controlled at 60-150℃.

[0066] The filling stability Fc of warm pressing molding is expressed by the following formula:

[0067]

[0068] Among them, the values of Fw and Fl satisfy:

[0069]

[0070]

[0071] Among them, the powder flow rate Sp represents the flow performance of the powder; the powder column height Hp represents the filling height of the powder; the negative model cavity width Wc represents the width dimension of the mold cavity, and the width direction is perpendicular to the movement direction of the material box; the material box cavity bottom width Wf represents the width dimension of the material box cavity bottom, and the width direction is perpendicular to the movement direction of the material box; the filling width coefficient Fw reflects the ratio of the material box cavity bottom width to the mold cavity width.

[0072] The length of the female mold cavity Lc represents the length of the mold cavity, and the length direction is parallel to the direction of movement of the material box; the length of the bottom of the material box cavity L f , which indicates the length of the bottom of the box cavity, and the length direction is parallel to the direction of movement of the box; filling length coefficient F l , this value reflects the ratio of the bottom length of the material box cavity to the length of the mold cavity.

[0073] Box filling speed S f , which indicates the speed at which the material box moves forward when performing the filling action. This value is negatively correlated with the filling performance.

[0074] The value of filling stability Fc measures the filling performance and filling stability during the pressing process, preferably 2.6-3.0, more preferably 2.6-2.8. When the value is above 2.6, it means that the filling performance can meet general needs. When the value exceeds 2.8, the filling speed S of the material box can be increased. f In exchange for higher production efficiency. When it is lower than 2.6, a lower filling speed and / or a powder with better fluidity should be selected to improve the filling performance.

[0075] By strictly controlling the material selection, size, filling speed, hot pressing temperature, pressure and other conditions of the hot pressing mold and feeding system, the green body density and performance uniformity can be effectively guaranteed, thereby improving the performance of the final stainless steel product; avoiding large temperature differences in the storage, transportation, and mold loading processes is conducive to shortening the heating link and improving production efficiency.

[0076] (3) Sintering the green body to obtain stainless steel for a solid oxide fuel cell connector, wherein the sintering is performed in a vacuum or hydrogen or argon protective atmosphere, the sintering time is 0.5 h to 3 h, and the sintering temperature is 1350 to 1450°C.

[0077] Through the above preparation method, the stainless steel for the solid oxide fuel cell connector of the present invention has a yield strength of more than 30 MPa and a tensile strength of more than 50 MPa at 800°C, and an oxidation weight gain of less than 1 mg / cm when the oxidation temperature is 800°C, the oxidation time is 200 h, and the oxidation atmosphere is air. 2 Below, preferably 0.95 mg / cm 2 the following.

[0078] Embodiment 1:

[0079] The method for preparing stainless steel for a solid oxide fuel cell interconnector of this embodiment includes the following steps:

[0080] (1) Prepare ferritic stainless steel pre-alloyed powder and nano-La2O3 powder. The added mass of nano-La2O3 powder is 0.1% of the total mass of the ferritic stainless steel pre-alloyed powder and nano-La2O3 powder. The ferritic stainless steel pre-alloyed powder is prepared by water atomization. The main element composition of the pre-alloyed powder is as follows: Cr: 22%, Ti: 0.3%, Nb: 0.5%, V: 0.05%, and the balance is Fe.

[0081] (2) The above powders were placed in a high-energy mechanical ball mill for ball milling at a ball-to-material ratio of 15:1, a ball milling speed of 250 r / min, and a ball milling time of 20 h;

[0082] (3) The powder after ball milling is subjected to warm pressing molding, the powder flow rate Sp is 28.3 seconds / 50g, the powder column height Hp is 17.4mm, the bottom width of the material box cavity Wf: the width of the negative mold cavity Wc is 2, and the bottom length of the material box cavity L f The cavity length Lc of the female mold is 1.67, the filling speed Sf is 310 mm / s, and the filling capacity Fc is 2.65. The pressing pressure used is 700 MPa, the hopper temperature is 60°C, the temperature of the material box, male mold, and female mold is 65°C, and the compression ratio is 2:1. After pressing, the stainless steel green body is obtained, and the measured green body density is 6.35 g / cm 3 ;

[0083] (4) The green body is sintered in a hydrogen protective atmosphere for 1.5 hours at a sintering temperature of 1400° C. and cooled after sintering to obtain stainless steel for a solid oxide fuel cell connector.

[0084] (5) The stainless steel used for the solid oxide fuel cell interconnect prepared in this example was subjected to performance testing. In accordance with the requirements of the Chinese national standard GB / T 228.2-2015, "Tensile Test of Metallic Materials - High Temperature Test Method," a heating furnace was used to control the temperature at 800°C and a computer-controlled tensile testing machine was used to measure the tensile strength and yield strength. In accordance with the requirements of the Chinese national standard GB / T 230.1-2009, "Rockwell Hardness Test of Metallic Materials - Test Method," the sample was placed steadily on a rigid support with the axis of the indenter perpendicular to the sample surface. The indenter was pressed into the sample surface, holding the test force for 3 seconds before releasing the force. Each sample was tested four times on both sides, and the average value was obtained.

[0085] According to the requirements of the Chinese national standard GB / T 38430-2019 "Corrosion of metals and alloys - Isothermal exposure oxidation test method for metallic materials under high temperature corrosion conditions", the sample was placed in a crucible, the oxidizing atmosphere was air, the oxidation temperature was 800°C, the oxidation time was 200h, and the mass was measured by weight gain method after the sample was cooled.

[0086] The test results are: density 7.27g / cm3, hardness 76HRB, yield strength 31.2MPa at 800℃, tensile strength 58.59MPa; oxidation temperature 800℃, oxidation time 200h, oxidation weight gain 0.85mg / cm3 when the oxidation atmosphere is air 2 .

[0087] Example 2

[0088] The method for preparing stainless steel for a solid oxide fuel cell interconnector of this embodiment includes the following steps:

[0089] (1) Prepare ferritic stainless steel pre-alloyed powder and nano-La2O3 powder. The added mass of nano-La2O3 powder is 0.1% of the total mass of the ferritic stainless steel pre-alloyed powder and nano-La2O3 powder. The ferritic stainless steel pre-alloyed powder is prepared by water atomization. The main element composition of the pre-alloyed powder is as follows: Cr: 22%, Ti: 0.3%, Nb: 0.5%, V: 0.05%, and the balance is Fe.

[0090] (2) The above powders were placed in a high-energy mechanical ball mill for ball milling at a ball-to-material ratio of 15:1, a ball milling speed of 250 r / min, and a ball milling time of 20 h;

[0091] (3) The powder after ball milling is subjected to warm pressing molding, the powder flow rate Sp is 28.3 seconds / 50g, the powder column height Hp is 17.51mm, the bottom width of the material box cavity Wf: the width of the female mold cavity Wc is 2, and the bottom length of the material box cavity L f The cavity length Lc of the female mold is 1.67, the filling speed Sf is 310 mm / s, and the filling capacity Fc is 2.64. The pressing pressure used is 700 MPa, the hopper temperature is 75°C, the temperature of the material box, male mold, and female mold is 80°C, and the compression ratio is 2.01:1. After pressing, the stainless steel green body is obtained, and the measured green body density is 6.39 g / cm 3 ;

[0092] (4) The green body is sintered in a hydrogen protective atmosphere for 1.5 hours at a sintering temperature of 1400° C. and cooled after sintering to obtain stainless steel for a solid oxide fuel cell connector.

[0093] (5) The performance test of the stainless steel used for the solid oxide fuel cell connector prepared in this embodiment was carried out using the same test method as in Example 1. The test results were as follows: the density was 7.29 g / cm 3 The hardness is 78HRB; the yield strength at 800℃ is 32.06MPa; the tensile strength is 58.03MPa; the oxidation temperature is 800℃, the oxidation time is 200h, and the oxidation weight gain is 0.80mg / cm when the oxidation atmosphere is air. 2 .

[0094] Example 3

[0095] The method for preparing stainless steel for a solid oxide fuel cell interconnector of this embodiment includes the following steps:

[0096] (1) Prepare ferritic stainless steel pre-alloyed powder and nano-La2O3 powder. The added mass of nano-La2O3 powder is 0.1% of the total mass of ferritic stainless steel pre-alloyed powder and nano-La2O3 powder. The ferritic stainless steel pre-alloyed powder is prepared by water atomization method. The main element composition of the pre-alloyed powder is as follows: Cr: 22%, Si: 0.41%, Mn: 0.03%, Mo: 1.26%, Ni: 0.60%, Ti: 0.3%, Nb: 0.5%, V: 0.05%, and the balance is Fe;

[0097] (2) The above powders were placed in a high-energy mechanical ball mill for ball milling at a ball-to-material ratio of 15:1, a ball milling speed of 250 r / min, and a ball milling time of 20 h;

[0098] (3) The powder after ball milling is subjected to warm pressing molding, the powder flow rate Sp is 29.3 seconds / 50g, the powder column height Hp is 16.53mm, the bottom width of the material box cavity Wf: the width of the negative mold cavity Wc is 2, and the bottom length of the material box cavity L f The cavity length Lc of the female mold is 1.67, the filling speed Sf is 310 mm / s, and the filling capacity Fc is 2.67. The pressing pressure used is 700 MPa, the hopper temperature is 75°C, the temperature of the material box, male mold, and female mold is 80°C, and the compression ratio is 1.90:1. After pressing, the stainless steel green body is obtained, and the measured green body density is 6.26 g / cm 3 ;

[0099] (4) The green body is sintered in a hydrogen protective atmosphere for 1.5 hours at a sintering temperature of 1400° C. and cooled after sintering to obtain stainless steel for a solid oxide fuel cell connector.

[0100] (5) The performance test of the stainless steel used for the solid oxide fuel cell connector prepared in this embodiment was carried out using the same test method as in Example 1. The test results were as follows: the density was 7.2 g / cm 3 The hardness is 70HRB; the yield strength at 800℃ is 30.35MPa; the tensile strength is 52.98MPa; the oxidation temperature is 800℃, the oxidation time is 200h, and the oxidation weight gain is 0.9mg / cm when the oxidation atmosphere is air. 2 .

[0101] Example 4

[0102] The method for preparing stainless steel for a solid oxide fuel cell interconnector of this embodiment includes the following steps:

[0103] (1) Prepare ferritic stainless steel pre-alloyed powder and nano-La2O3 powder. The mass of nano-La2O3 powder added is 0.1% of the total mass of the ferritic stainless steel pre-alloyed powder and nano-La2O3 powder. The ferritic stainless steel pre-alloyed powder is prepared by water atomization. The main element composition of the pre-alloyed powder is as follows: Cr: 22%, Ti: 0.2%, Nb: 0.3%, V: 0.02%, and the balance is Fe.

[0104] (2) The above powders were placed in a high-energy mechanical ball mill for ball milling at a ball-to-material ratio of 15:1, a ball milling speed of 250 r / min, and a ball milling time of 20 h;

[0105] (3) The powder after ball milling is subjected to warm pressing molding, the powder flow rate Sp is 28.1 seconds / 50g, the powder column height Hp is 17.54mm, the bottom width of the material box cavity Wf: the width of the negative mold cavity Wc is 2, and the bottom length of the material box cavity L f The cavity length Lc of the female mold is 1.67, the filling speed Sf is 310 mm / s, and the filling capacity Fc is 2.64. The pressing pressure used is 700 MPa, the hopper temperature is 75°C, the temperature of the material box, male mold, and female mold is 80°C, and the compression ratio is 2.02:1. After pressing, the stainless steel green body is obtained, and the measured green body density is 6.4 g / cm 3 ;

[0106] (4) The green body is sintered in a hydrogen protective atmosphere for 1.5 hours at a sintering temperature of 1400° C. and cooled after sintering to obtain stainless steel for a solid oxide fuel cell connector.

[0107] (5) The performance test of the stainless steel used for the solid oxide fuel cell connector prepared in this embodiment was carried out using the same test method as in Example 1. The test results were as follows: the density was 7.3 g / cm 3 The hardness is 79HRB; the yield strength at 800℃ is 32.05MPa; the tensile strength is 58.4MPa; the oxidation temperature is 800℃, the oxidation time is 200h, and the oxidation weight gain is 0.78mg / cm when the oxidation atmosphere is air. 2 .

[0108] Example 5

[0109] The method for preparing stainless steel for a solid oxide fuel cell interconnector of this embodiment includes the following steps:

[0110] (1) Prepare ferritic stainless steel pre-alloyed powder and nano-La2O3 powder. The added mass of nano-La2O3 powder is 0.1% of the total mass of the ferritic stainless steel pre-alloyed powder and nano-La2O3 powder. The ferritic stainless steel pre-alloyed powder is prepared by water atomization. The main element composition of the pre-alloyed powder is as follows: Cr: 27%, Ti: 0.3%, Nb: 0.5%, V: 0.05%, and the balance is Fe.

[0111] (2) The above powders were placed in a high-energy mechanical ball mill for ball milling at a ball-to-material ratio of 15:1, a ball milling speed of 250 r / min, and a ball milling time of 20 h;

[0112] (3) The powder after ball milling is subjected to warm pressing molding, the powder flow rate Sp is 28.6 seconds / 50g, the powder column height Hp is 15.52mm, the bottom width of the material box cavity Wf: the width of the female mold cavity Wc is 2, and the bottom length of the material box cavity L f The cavity length Lc of the female mold is 1.67, the filling speed Sf is 310 mm / s, and the filling capacity Fc is 2.72. The pressing pressure used is 700 MPa, the hopper temperature is 75°C, the temperature of the material box, male mold, and female mold is 80°C, and the compression ratio is 1.78:1. After pressing, the stainless steel green body is obtained, and the measured green body density is 6.25 g / cm 3 ;

[0113] (4) The green body is sintered in a hydrogen protective atmosphere for 1.5 hours at a sintering temperature of 1400° C. and cooled after sintering to obtain stainless steel for a solid oxide fuel cell connector.

[0114] (5) The performance test of the stainless steel used for the solid oxide fuel cell connector prepared in this embodiment was carried out using the same test method as in Example 1. The test results were as follows: the density was 7.2 g / cm 3 The hardness is 70HRB; the yield strength at 800℃ is 31.63MPa; the tensile strength is 57.49MPa; the oxidation temperature is 800℃, the oxidation time is 200h, and the oxidation weight gain is 0.91mg / cm when the oxidation atmosphere is air. 2 .

[0115] Example 6

[0116] The method for preparing stainless steel for a solid oxide fuel cell interconnector of this embodiment includes the following steps:

[0117] (1) Prepare ferritic stainless steel pre-alloyed powder and nano-La2O3 powder. The added mass of nano-La2O3 powder is 0.4% of the total mass of the ferritic stainless steel pre-alloyed powder and nano-La2O3 powder. The ferritic stainless steel pre-alloyed powder is prepared by water atomization. The main element composition of the pre-alloyed powder is as follows: Cr: 22%, Ti: 0.3%, Nb: 0.5%, V: 0.05%, and the balance is Fe;

[0118] (2) The above powders were placed in a high-energy mechanical ball mill for ball milling at a ball-to-material ratio of 15:1, a ball milling speed of 250 r / min, and a ball milling time of 20 h;

[0119] (3) The powder after ball milling is subjected to warm pressing molding, the powder flow rate Sp is 28.3 seconds / 50g, the powder column height Hp is 17.35mm, the bottom width of the material box cavity Wf: the width of the female mold cavity Wc is 2, and the bottom length of the material box cavity L f The cavity length Lc of the female mold is 1.67, the filling speed Sf is 310 mm / s, and the filling capacity Fc is 2.65. The pressing pressure used is 700 MPa, the hopper temperature is 75°C, the temperature of the material box, male mold, and female mold is 80°C, and the compression ratio is 1.99:1. After pressing, the stainless steel green body is obtained, and the measured green body density is 6.33 g / cm 3 ;

[0120] (4) The green body is sintered in a hydrogen protective atmosphere for 1.5 hours at a sintering temperature of 1400° C. and cooled after sintering to obtain stainless steel for a solid oxide fuel cell connector.

[0121] (5) The performance test of the stainless steel used for the solid oxide fuel cell connector prepared in this embodiment was carried out using the same test method as in Example 1. The test results were as follows: the density was 7.25 g / cm 3 The hardness is 75HRB; the yield strength at 800℃ is 36.07MPa; the tensile strength is 64.52MPa; the oxidation temperature is 800℃, the oxidation time is 200h, and the oxidation weight gain is 0.65mg / cm when the oxidation atmosphere is air. 2 .

[0122] Example 7

[0123] The method for preparing stainless steel for a solid oxide fuel cell interconnector of this embodiment includes the following steps:

[0124] (1) Prepare ferritic stainless steel pre-alloyed powder and nano-La2O3 powder. The added mass of nano-La2O3 powder is 0.7% of the total mass of the ferritic stainless steel pre-alloyed powder and nano-La2O3 powder. The ferritic stainless steel pre-alloyed powder is prepared by water atomization. The main element composition of the pre-alloyed powder is as follows: Cr: 22%, Ti: 0.3%, Nb: 0.5%, V: 0.05%, and the balance is Fe;

[0125] (2) The above powders were placed in a high-energy mechanical ball mill for ball milling at a ball-to-material ratio of 15:1, a ball milling speed of 250 r / min, and a ball milling time of 20 h;

[0126] (3) The powder after ball milling is subjected to warm pressing molding, the powder flow rate Sp is 28.2 seconds / 50g, the powder column height Hp is 17.29mm, the bottom width of the material box cavity Wf: the width of the negative mold cavity Wc is 2, and the bottom length of the material box cavity L f The cavity length Lc of the female mold is 1.67, the filling speed Sf is 310 mm / s, and the filling capacity Fc is 2.65. The pressing pressure used is 700 MPa, the hopper temperature is 75°C, the temperature of the material box, male mold, and female mold is 80°C, and the compression ratio is 1.99:1. After pressing, the stainless steel green body is obtained, and the measured green body density is 6.31 g / cm 3 ;

[0127] (4) The green body is sintered in a hydrogen protective atmosphere for 1.5 hours at a sintering temperature of 1400° C. and cooled after sintering to obtain stainless steel for a solid oxide fuel cell connector.

[0128] (5) The solid oxide fuel cell connector made of stainless steel prepared in this embodiment was tested for performance. The test method was the same as in Example 1. The test results were: density was 7.24 g / cm 3 The hardness is 73HRB; the yield strength at 800℃ is 39.26MPa; the tensile strength is 64.60MPa; the oxidation temperature is 800℃, the oxidation time is 200h, and the oxidation weight gain is 0.24mg / cm when the oxidation atmosphere is air. 2 .

[0129] Example 8

[0130] The method for preparing stainless steel for a solid oxide fuel cell interconnector of this embodiment includes the following steps:

[0131] (1) Prepare ferritic stainless steel pre-alloyed powder and nano-La2O3 powder. The added mass of nano-La2O3 powder is 1.0% of the total mass of the ferritic stainless steel pre-alloyed powder and nano-La2O3 powder. The ferritic stainless steel pre-alloyed powder is prepared by water atomization. The main element composition of the pre-alloyed powder is as follows: Cr: 22%, Ti: 0.3%, Nb: 0.5%, V: 0.05%, and the balance is Fe;

[0132] (2) The above powders were placed in a high-energy mechanical ball mill for ball milling at a ball-to-material ratio of 15:1, a ball milling speed of 250 r / min, and a ball milling time of 20 h;

[0133] (3) The powder after ball milling is subjected to warm pressing molding, the powder flow rate Sp is 28.5 seconds / 50g, the powder column height Hp is 17.21mm, the bottom width of the material box cavity Wf: the width of the female mold cavity Wc is 2, and the bottom length of the material box cavity L f The cavity length Lc of the female mold is 1.67, the filling speed Sf is 310 mm / s, and the filling capacity Fc is 2.65. The pressing pressure used is 700 MPa, the hopper temperature is 75°C, the temperature of the material box, male mold, and female mold is 80°C, and the compression ratio is 1.98:1. After pressing, the stainless steel green body is obtained, and the measured green body density is 6.28 g / cm 3 ;

[0134] (4) The green body is sintered in a hydrogen protective atmosphere for 1.5 hours at a sintering temperature of 1400° C. and cooled after sintering to obtain stainless steel for a solid oxide fuel cell connector.

[0135] (5) The performance test of the stainless steel used for the solid oxide fuel cell connector prepared in this embodiment was carried out using the same test method as in Example 1. The test results were as follows: the density was 7.22 g / cm 3 The hardness is 72HRB; the yield strength at 800℃ is 34.73MPa; the tensile strength is 60.16MPa; the oxidation temperature is 800℃, the oxidation time is 200h, and the oxidation weight gain is 0.22mg / cm when the oxidation atmosphere is air. 2 .

[0136] Comparative Example 1

[0137] The method for preparing stainless steel for a solid oxide fuel cell interconnector of this comparative example comprises the following steps:

[0138] (1) Prepare ferritic stainless steel pre-alloyed powder and nano-La2O3 powder. The added mass of nano-La2O3 powder is 1.5% of the total mass of the ferritic stainless steel pre-alloyed powder and nano-La2O3 powder. The ferritic stainless steel pre-alloyed powder is prepared by water atomization. The main element composition of the pre-alloyed powder is as follows: Cr: 22%, Ti: 0.3%, Nb: 0.5%, V: 0.05%, and the balance is Fe;

[0139] (2) The above powders were placed in a high-energy mechanical ball mill for ball milling at a ball-to-material ratio of 15:1, a ball milling speed of 250 r / min, and a ball milling time of 20 h;

[0140] (3) The milled powder was subjected to warm pressing with a pressing pressure of 700 MPa, a hopper temperature of 75°C, a box, a male mold, and a female mold temperature of 80°C, and a compression ratio of 1.98:1. After pressing, a stainless steel green body was obtained, and the green body density was measured to be 6.22 g / cm 3 ;

[0141] (4) The green body is sintered in a hydrogen protective atmosphere for 1.5 hours at a sintering temperature of 1400° C. and cooled after sintering to obtain stainless steel for a solid oxide fuel cell connector.

[0142] (5) The performance test of the stainless steel used for the solid oxide fuel cell connector prepared in this embodiment was carried out using the same test method as in Example 1. The test results were as follows: the density was 7.18 g / cm 3 The hardness is 68HRB; the yield strength at 800℃ is 18.8MPa; the tensile strength is 37.35MPa; the oxidation temperature is 800℃, the oxidation time is 200h, and the oxidation atmosphere is air, and the oxidation weight gain is 0.19mg / cm 2 .

[0143] Comparative Example 2

[0144] The method for preparing stainless steel for a solid oxide fuel cell interconnector of this comparative example comprises the following steps:

[0145] (1) Prepare ferritic stainless steel pre-alloyed powder and nano-La2O3 powder. The added mass of nano-La2O3 powder is 0.1% of the total mass of the ferritic stainless steel pre-alloyed powder and nano-La2O3 powder. The ferritic stainless steel pre-alloyed powder is prepared by water atomization. The main element composition of the pre-alloyed powder is as follows: Cr: 22%, Ti: 0.3%, Nb: 0.5%, V: 0.05%, and the balance is Fe.

[0146] (2) The above powders were placed in a high-energy mechanical ball mill for ball milling at a ball-to-material ratio of 15:1, a ball milling speed of 250 r / min, and a ball milling time of 20 h;

[0147] (3) The milled powder was subjected to warm pressing with a pressing pressure of 700 MPa, a hopper temperature of 30°C, a box, a male mold, and a female mold temperature of 40°C, and a compression ratio of 1.97:1. After pressing, a stainless steel green body was obtained, and the green body density was measured to be 6.19 g / cm 3 ;

[0148] (4) The green body is sintered in a hydrogen protective atmosphere for 1.5 hours at a sintering temperature of 1400° C. and cooled after sintering to obtain stainless steel for a solid oxide fuel cell connector.

[0149] (5) The performance test of the stainless steel used for the solid oxide fuel cell connector prepared in this embodiment was carried out using the same test method as in Example 1. The test results were as follows: the density was 7.16 g / cm 3 The hardness is 67HRB; the yield strength at 800℃ is 29.24MPa; the tensile strength is 52.39MPa; the oxidation temperature is 800℃, the oxidation time is 200h, and the oxidation weight gain is 1.01mg / cm when the oxidation atmosphere is air. 2 .

[0150] Comparative Example 3

[0151] Comparative Example 3 is different from the above examples in terms of raw material composition and preparation method:

[0152] The ferritic stainless steel material provided in Comparative Example 3 contains the following elemental raw materials in the following mass ratios: Cr: 22%, Mn: 0.5%, Si: 0.25%, Ti: 0.1%, Cu: 0.25%, Al: 0.25%, and the balance is Fe. The production steps are as follows: Alloy raw materials are prepared according to the elemental ratios, and samples are obtained through smelting, casting, rolling, and machining.

[0153] In accordance with the requirements of China's national standard GB / T 228.2-2015 "Tensile test of metallic materials - High temperature test method", the sample of Comparative Example 3 was tested at a tensile temperature of 800°C. The test results showed that the yield strength was approximately 30 MPa and the tensile strength was approximately 30 MPa.

[0154] Comparative Example 4

[0155] Comparative Example 4 is different from the above examples in terms of raw material composition and preparation method:

[0156] The ferritic stainless steel material provided in Comparative Example 4 contains the following elemental raw materials in the following mass ratios: Cr: 21.8%, Mn: 0.46%, Si: 0.08%, Ni: 0.34%, Al: 0.05%, and the balance is Fe. The production steps are as follows: Alloy raw materials are prepared according to the elemental ratios, and samples are obtained through smelting, casting, rolling, and machining.

[0157] In accordance with the requirements of the Chinese national standard GB / T 228.2-2015 "Tensile Test of Metallic Materials - High Temperature Test Method", the ferritic stainless steel material of Comparative Example 4 was tested at a tensile temperature of 800°C. The test results showed that the yield strength was approximately 20 MPa and the tensile strength was approximately 30 MPa.

[0158] Comparative Example 5

[0159] The ferritic stainless steel material provided in Comparative Example 5 contains the following elemental raw materials in the following mass ratio: Cr: 20%, Mn: 0.03%, Si: 0.38%, Ni: 0.6%, Mo: 1.29%, and the balance is Fe. The production steps are as follows: pre-alloyed powder is prepared according to the proportions, the pre-alloyed powder is pressed at room temperature, and sintered at 1200°C for 1 hour to obtain a sample.

[0160] According to the requirements of the Chinese national standard GB / T 38430-2019 "Corrosion of metals and alloys - Isothermal exposure oxidation test method for metallic materials under high temperature corrosion conditions", the sample of comparative example 5 was subjected to high temperature oxidation performance test. The oxidation temperature was 800°C and the oxidation time was 200h. The test results showed that the oxidation weight gain was 1.04 mg / cm when the oxidizing atmosphere was air. 2 .

[0161] Comparative Example 6

[0162] The ferritic stainless steel material provided in Comparative Example 6 contains the following elemental raw materials in the following mass ratio: Cr: 18%, Mn: 0.1%, Si: 0.9%, Ni: 0.15%, Mo: 1%, and the balance is Fe. The production steps are as follows: pre-alloyed powder is first prepared according to the proportions, the pre-alloyed powder is pressed at room temperature, and sintered at 1200°C for 1 hour to obtain a sample.

[0163] According to the requirements of the Chinese national standard GB / T 38430-2019 "Corrosion of metals and alloys - Isothermal exposure oxidation test method for metallic materials under high temperature corrosion conditions", the high temperature oxidation performance test of the ferritic stainless steel material of comparative example 6 was carried out at an oxidation temperature of 800°C and an oxidation time of 200h. The test results showed that the oxidation weight gain was 1.3 mg / cm when the oxidizing atmosphere was air. 2 .

[0164] Comparative Example 7

[0165] The ferritic stainless steel material provided in Comparative Example 7 contains the following elemental raw materials in the following mass ratios: Cr: 13%, Mn: 0.2%, Si: 0.5%, Mo: 0.8%, Nb: 0.3%, and the balance is Fe. The production steps are as follows: first, pre-alloyed powder is prepared according to the proportion, the pre-alloyed powder is pressed at room temperature, and sintered at 1250°C for 1.5 hours to obtain a sample with a density of 7.25g / cm 3 .

[0166] According to the requirements of the Chinese national standard GB / T 38430-2019 "Corrosion of metals and alloys - Isothermal exposure oxidation test method for metallic materials under high temperature corrosion conditions", the high temperature oxidation performance test of the ferritic stainless steel material of comparative example 7 was carried out at an oxidation temperature of 800°C and an oxidation time of 200h. The test results showed that the oxidation weight gain was 1.5 mg / cm when the oxidizing atmosphere was air. 2 .

[0167] The powder compositions of Examples 1-8 and Comparative Examples 1-7 are shown in Table 1, and the performance test results are shown in Table 2:

[0168] Table 1 Powder composition of Examples 1-8 and Comparative Examples 1-7

[0169]

[0170] Table 2 Performance test results of Examples 1-8 and Comparative Examples 1-7

[0171]

[0172]

[0173] The above introduces the preferred embodiments of the present invention, which is intended to make the spirit of the present invention clearer and easier to understand, and is not intended to limit the present invention. Any modifications, replacements, and improvements made within the spirit and principles of the present invention should be included in the scope of protection outlined by the claims attached to the present invention.

Claims

1. A method for preparing stainless steel for a solid oxide fuel cell connector, characterized in that: The following steps are involved: (1) mechanically ball milling ferritic stainless steel pre-alloyed powder and nano-La2O3 powder to obtain mechanically alloyed powder; wherein the mass percentage of each element in the ferritic stainless steel pre-alloyed powder is: Cr: 22-30%, Si: 0-1.0%, Mn: 0-0.8%, Mo: 0-1.5%, Ni: 0-0.7%, Nb: 0.1-0.6%, Ti: 0.1-1%, V: 0.02-0.1%, Fe: balance; the added mass of the nano-La2O3 powder accounts for 0.1-1.0% of the total mass of the powder, and the particle size of the nano-La2O3 powder is ≤100 nm; (2) performing warm pressing on the mechanically alloyed powder to obtain a green body; wherein the pressing pressure of the warm pressing is 600 to 1200 MPa and the temperature is controlled at 60 to 80° C.; (3) sintering the green body to obtain stainless steel for a solid oxide fuel cell connector; wherein the sintering is performed in a vacuum or hydrogen or argon protective atmosphere, the sintering time is 0.5 h to 3 h, and the sintering temperature is 1400 to 1450° C.; The stainless steel used for the solid oxide fuel cell connector has a yield strength of more than 30 MPa and a tensile strength of more than 50 MPa at 800°C, and an oxidation weight gain of 0.85 mg / cm3 when the oxidation temperature is 800°C, the oxidation time is 200 h, and the oxidation atmosphere is air. 2 the following.

2. The preparation method according to claim 1, characterized in that In step (1), the mass percentage of each element in the ferritic stainless steel pre-alloyed powder is: Cr: 22-27%, Si: 0-1.0%, Mn: 0-0.8%, Mo: 0-1.5%, Ni: 0-0.7%, Nb: 0.1-0.6%, Ti: 0.1-0.3%, V: 0.02-0.1%, and Fe: balance.

3. The preparation method according to claim 1 or 2, characterized in that In step (1), the particle size of the ferritic stainless steel pre-alloyed powder is ≤300 μm.

4. The preparation method according to claim 3, characterized in that In step (1), the ball-to-material ratio of the mechanical ball milling is (5-20):1, the ball milling speed is 200-600 r / min, the ball milling time is 10-100 h, and the ball milling environment is a vacuum or argon environment.

5. The preparation method according to claim 3, characterized in that In step (2), the warm pressing forming adopts a warm pressing forming device, which includes a warm pressing mold and a feeding system; wherein, A warm-pressing mold, comprising a male mold and a female mold, wherein the male mold and the female mold cooperate to form a warm-pressing forming cavity; A feeding system, comprising a hopper, a feeding box, and a feeding pipe connecting the hopper and the feeding box; The material box in the feeding system is movable relative to the warm-pressing mold.

6. The preparation method according to claim 5, characterized in that The hopper has a first semi-closed-loop heating and temperature control device and at least three first temperature sensors, so that the temperature difference between different points in the hopper does not exceed 10°C, the hopper set temperature is 60-150°C, and the difference between the measured temperature and the set temperature does not exceed 10°C; and / or The material box has a second semi-closed-loop heating temperature control device and at least two second temperature sensors, so that the temperature difference at different points of the material box does not exceed 5°C. The set temperature of the material box is 60-150°C, and the difference between the actual measured temperature of the material box and the set temperature does not exceed 10°C.

7. The preparation method according to claim 5 or 6, characterized in that: The feeding pipe has an insulation layer, and the temperature of the mechanical alloying powder does not drop by more than 10°C after flowing from the hopper through the feeding pipe to the material box.

8. The preparation method according to claim 7, characterized in that The length direction of the warm pressing mold is the moving direction of the material box, and the thickness direction of the green body is the pressing direction.

9. The preparation method according to claim 8, characterized in that The male mold and / or female mold has a third semi-closed loop heating temperature control device and at least three third temperature measuring sensors, so that the temperature difference at different points of the male mold and / or female mold does not exceed 10°C.

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