Metal powder forming mold convenient to demold

Abstract

The metal powder forming mold comprises a top plate, an upper mold plate, a lower mold plate, an upper mold cavity plate, a lower mold cavity plate and a base, is equipped with a low-pressure pneumatic demolding assembly and comprises an ejector rod, a push plate and an air nozzle. The mold is used for preparing metal structural parts, and the formula comprises 40-50 parts of copper powder, 30-40 parts of 316L stainless steel powder, 20-30 parts of nickel powder, lithium stearate, carbon nanotubes and other additives. The preparation method comprises the steps of drying, fluorosilane coupling agent coating, ball milling, screening, pressing at 650-950 MPa and argon protection sintering at 950-1150 DEG C. An obtained part is high in breaking strength and few in demolding defects.

Description

Technical Field

[0001] The present invention relates to the technical field of forming dies, in particular to a metal powder forming die which is easy to demould. Background Art

[0002] The field of powder metallurgy has made significant progress in recent years, driven primarily by the growing demand for high-precision, complex-shaped metal parts in industries such as automotive, aerospace, and electronics. Metal powder forming, a core process in powder metallurgy, involves compacting metal powder into the desired shape under high pressure within a die, followed by sintering to achieve the desired mechanical properties. Innovations in die design, material selection, and manufacturing techniques have significantly improved the efficiency and quality of formed parts. For example, the development of advanced die materials such as high-strength tool steels and cemented carbides has enabled them to withstand the extreme pressure and wear generated by metal powder compaction. Furthermore, the application of computer-aided design (CAD) and finite element analysis (FEA) has enabled precise optimization of die geometry, improving powder compaction uniformity and reducing defects such as cracks or density gradients. The emergence of technologies such as isostatic pressing and additive manufacturing of dies has also provided greater flexibility in the production of complex parts. However, demolding—the removal of the compacted powder (green body) from the die—remains a key challenge, directly impacting production efficiency, die life, and part quality.

[0003] However, existing metal powder forming technologies have significant limitations in the demolding stage, and these shortcomings may undermine the advantages brought by advanced mold design. A major problem is the adhesion between the compacted powder and the mold surface, which is often exacerbated by high-pressure molding and the inherent surface roughness of metal powder. This adhesion often leads to difficulties in demolding, which in turn causes surface defects or insufficient dimensional accuracy of the green body, seriously affecting the quality of the final part. In addition, frequent adhesion will accelerate the wear of the mold surface, shorten the mold life, and increase maintenance costs during the production process. In the existing technology, commonly used solutions such as coating lubricants or optimizing mold surface treatment have alleviated the adhesion problem to a certain extent, but their effects are limited, especially in the production of high-precision or complex-shaped parts, and it is difficult to meet the requirements of efficient and stable demolding. These shortcomings highlight the need for new mold designs to achieve a smoother demolding process while maintaining the integrity of the green body and the long-term durability of the mold. Summary of the Invention

[0004] The present application provides a metal powder forming mold that is easy to demold, which includes, from top to bottom: a top plate, an upper mold plate, an upper cavity plate, a lower mold plate, a lower mold plate and a base. When the upper cavity plate and the lower cavity plate are combined, a molding cavity is formed. An injection port is provided on the top plate, and the injection port is connected to the molding cavity. A low-pressure pneumatic demolding component is provided at the lower end of the molding cavity.

[0005] As an optimal technical solution for a metal powder forming mold, the low-pressure pneumatic demolding assembly includes a push rod, a push plate and an air nozzle. The push plate is arranged on the upper end surface of the base, and several push rods are arranged between the push plate and the forming cavity. The air nozzle is arranged on the base.

[0006] As an optimal technical solution for a metal powder forming die, a support block is provided between the lower die plate and the base.

[0007] In addition, the present application also provides a metal structural part prepared by a forming mold, which includes, in parts by mass: 40 to 50 parts of Cu powder, 30 to 40 parts of 316L stainless steel powder, 20 to 30 parts of Ni powder, 0.6 to 1.2 parts of lithium stearate powder, 0.6 to 1.3 parts of polytetrafluoroethylene powder, 0.3 to 0.7 parts of nano-SiO2 powder, 0.5 to 1.0 parts of fluorinated silane coupling agent and 5.0 to 7.5 parts of carbon nanotubes.

[0008] It should be noted that Cu powder, as the main matrix material, provides good electrical conductivity and ductility, while promoting densification during the sintering process; 316L stainless steel powder enhances the corrosion resistance and mechanical strength of structural parts, especially the stability in harsh environments; Ni powder improves the toughness and oxidation resistance of the alloy, forming a uniform microstructure. The polar molecules of lithium stearate may form weak interactions with the non-polar surface of PTFE, promoting the uniform distribution of PTFE on the surface of powder particles, thereby enhancing the overall lubrication effect. Nano-SiO2 powder, as a reinforcing phase, significantly improves the hardness and wear resistance of the material, while optimizing the uniformity of the microstructure; fluorinated silane coupling agents improve the interfacial bonding between powder particles, promoting the compatibility and dispersibility of different components; carbon nanotubes, through their high strength and high toughness properties, significantly improve the tensile strength and fracture resistance of metal structural parts, while optimizing thermal conductivity.

[0009] Finally, this application provides a method for preparing a metal structural part, comprising the following technical steps: Step S1. Copper powder, 316L stainless steel powder, and nickel powder are dried separately in a vacuum drying oven. A 1.0%-1.5% solution of a fluorinated silane coupling agent is dissolved in ethanol and uniformly coated on the surfaces of the three metal powders by ultrasonic spraying. Step S2. The modified copper powder, 316L stainless steel powder and nickel powder are mixed in proportion, lithium stearate, PTFE powder and nano-silica are added to the mixed powder, and ball milled until the additives are evenly dispersed; Step S3. Add the carbon nanotubes to the mixed powder and mix them evenly. Sieve the mixed powder using a sieve to ensure that the powder particle size is within the range of 15-80 μm. Step S4. The powder is loaded into a forming mold and pressed at a pressure of 650-950 MPa to form a green body. A low-pressure pneumatic demolding assembly is used to assist demolding. After demolding, the green body is sintered at 950-1150°C for 1.5-2 hours under argon protection to obtain a sensor structure.

[0010] It should be noted that in step S1, Cu powder, 316L stainless steel powder and Ni powder are dried in a vacuum drying furnace to remove moisture and volatile impurities to prevent defects caused by gas release in subsequent molding; the fluorinated silane coupling agent is coated on the surface of the metal powder by ultrasonic spraying with a 1.0%-1.5% ethanol solution. The silane groups in its molecules react with the hydroxyl groups on the surface of the metal powder to form chemical bonds. At the same time, the fluorinated groups reduce the surface energy, improve the compatibility and dispersibility between the powders, and enhance the uniformity of subsequent mixing. In step S2, the modified metal powder is mixed with lithium stearate, PTFE micropowder, and nano-SiO2 through ball milling. The polar molecules of lithium stearate may form weak interactions with the non-polar surface of PTFE, promoting the uniform distribution of PTFE on the surface of the powder particles, thereby enhancing the overall lubrication effect and improving the release effect of the green body. At the same time, PTFE partially decomposes during high-temperature sintering, but its decomposition products (such as fluoride) may react with the surface of the metal powder to form a trace reinforcing phase, improving the flexural strength of the sintered body. Nano-SiO2 acts as a reinforcing phase to improve the mechanical properties and microstructural stability of the mixed powder. The ball milling process ensures the uniform dispersion of the additives and prevents agglomeration. In step S5, carbon nanotubes (CNTs) are added and the particle size is controlled by screening to 15-80μm. The high strength and high toughness of CNTs enhance the mechanical properties of the powder system, and their nanoscale structure promotes sintering densification. Screening ensures the consistency of the powder particle size, optimizing flowability and molding accuracy. In step S7, the powder is pressed and formed under a high pressure of 650-950 MPa. The high pressure promotes the close packing of particles and forms a green body. The low-pressure pneumatic demolding component uses airflow to assist in reducing mechanical stress during demolding and avoid damage to the green body. It is then sintered at 950-1150°C for 1.5-2 hours under argon protection. Argon prevents oxidation. The sintering process allows the metal particles to form a dense structure through diffusion and interface bonding. CNT and nano-SiO2 further enhance the grain boundary strength, ultimately forming a sensor structure with excellent mechanical properties and corrosion resistance.

[0011] As a preferred technical solution for a method for preparing a metal structural part, in step S1, the concentration of the fluorinated silane coupling agent is 1.2%-1.3%, and the spray rate of the ultrasonic spray method is controlled at 0.5-1.0 mL / min to ensure that a uniform nanoscale modified layer is formed on the surface of the metal powder, thereby improving the bonding strength between the powders and the subsequent sintering performance.

[0012] As a preferred technical solution for the preparation method of a metal structural part, in step S2, the ball milling process uses a planetary ball mill with a ball milling speed of 200-300 rpm, a ball-to-material ratio of 10:1, and a ball milling time of 4-6 hours to achieve uniform dispersion of the additive in the metal powder and avoid powder agglomeration.

[0013] As an optimal technical solution for the preparation method of a metal structural part, the mesh size of the sieve is 200-400 mesh, and the screening process is carried out under the protection of inert gas to avoid powder oxidation and ensure uniform powder particle size distribution, with the D50 value controlled at 30-50 μm.

[0014] As a preferred technical solution for the preparation method of a metal structural part, in step S7, the pressing process adopts a graded pressurization method, specifically: first pre-pressing at 300-400 MPa for 5-10 seconds, and then final pressing at 650-950 MPa for 10-15 seconds to improve the density and structural uniformity of the green body.

[0015] As a preferred technical solution for a method for preparing a metal structural part, in step S7, the air pressure of the low-pressure pneumatic demolding assembly is controlled at 0.2-0.5 MPa, and the demolding time is 2-5 seconds to reduce surface defects of the green body and improve demolding efficiency.

[0016] This invention provides a metal powder forming die equipped with a low-pressure pneumatic demolding assembly, significantly reducing demolding resistance (50-55 N) and demolding time (2-5 seconds), while controlling green body surface defects to 0.8%-1.0%. Metal structural parts prepared using a specific formula, including copper powder, 316L stainless steel powder, nickel powder, and additives such as polytetrafluoroethylene and carbon nanotubes, achieve a flexural strength of 545-589 MPa due to the formation of a dense Cu-Ni-Fe solid solution and strengthening phases such as metal fluorides. This preparation method ensures uniform powder dispersion, enhanced lubricity, and structural integrity, improving demolding efficiency, mold durability, and component performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the structure of the forming mold Figure 1 ; Figure 2 Schematic diagram of the structure of the forming mold Figure 2 ; Figure 3 The XRD pattern of the metal structure prepared in Example 2; Figure numerals: 10, top plate; 11, upper template; 12, upper cavity plate; 13, lower cavity plate; 14, lower template; 15, base; 16, ejector pin; 17, push plate; 18, air nozzle; 19, support block. DETAILED DESCRIPTION

[0018] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0019] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0020] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it constitute a separate or selective embodiment that is mutually exclusive with other embodiments.

[0021] Example 1

[0022] Please refer to Figure 1 and 2 As shown, this embodiment provides a metal powder forming mold that is easy to demold. Its structure includes, from top to bottom, a top plate, an upper mold plate, an upper cavity plate, a lower mold plate, a lower mold plate and a base, wherein the upper mold plate and the lower mold plate form a molding cavity for molding metal powder when the upper mold plate and the lower mold plate are molded together. An injection port is provided on the top plate, which is connected to the molding cavity and is used to inject a metal powder mixture. A low-pressure pneumatic demolding assembly is provided at the lower end of the molding cavity. The assembly includes a push rod, a push plate and an air nozzle. The push plate is provided on the upper end surface of the base. A number of push rods are provided between the push plate and the molding cavity. The air nozzle is installed on the base. The push rods are driven by low-pressure pneumatic means to assist in demolding the green body, thereby reducing damage to the green body and improving demolding efficiency. In addition, a support block is provided between the lower mold plate and the base to enhance the stability and durability of the mold structure.

[0023] Example 2

[0024] This embodiment provides a metal structural part prepared by a molding mold and a preparation method, wherein the metal structural part includes, in parts by mass: 50 parts of Cu powder, 35 parts of 316L stainless steel powder, 20 parts of Ni powder, 0.6 parts of lithium stearate powder, 1.2 parts of polytetrafluoroethylene powder, 0.3 parts of nano-SiO2 powder, 1.0 parts of fluorinated silane coupling agent and 5.0 parts of carbon nanotubes.

[0025] The method for preparing a metal structural part includes the following technical steps: Step S1. Copper powder, 316L stainless steel powder, and nickel powder were dried separately in a vacuum drying oven. A 1.2% solution of a fluorinated silane coupling agent was dissolved in ethanol and uniformly coated on the surfaces of the three metal powders by ultrasonic spraying at a spray rate of 0.5 mL / min. Step S2. The modified copper powder, 316L stainless steel powder, and nickel powder were mixed in proportion, lithium stearate, PTFE powder, and nano-silica were added to the mixed powder, and ball-milled until the additives were evenly dispersed. The ball milling process used a planetary ball mill at a ball milling speed of 200 rpm, a ball-to-powder ratio of 10:1, and a ball-to-powder ratio of 6 hours. Step S3. Adding carbon nanotubes to the mixed powder and mixing them evenly, sieving the mixed powder using a sieve with a mesh size of 400 mesh. The sieving process is performed under inert gas protection to ensure that the powder particle size is within the range of 15-80 μm; Step S4. The powder is loaded into a forming mold and pre-pressed at 400 MPa for 10 seconds, and then pressed at a final pressure of 650 MPa for 15 seconds to form a green body. A low-pressure pneumatic demolding assembly is used to assist in demolding. The air pressure is controlled at 0.5 MPa and the demolding time is 2 seconds. After demolding, the green body is sintered at 1150°C for 1.5 hours under argon protection.

[0026] Example 3

[0027] This embodiment provides a metal structural part prepared by a molding mold and a preparation method, wherein the metal structural part includes, in parts by mass: 45 parts of Cu powder, 30 parts of 316L stainless steel powder, 25 parts of Ni powder, 1.2 parts of lithium stearate powder, 0.6 parts of polytetrafluoroethylene powder, 0.7 parts of nano-SiO2 powder, 0.5 parts of fluorinated silane coupling agent and 6.0 parts of carbon nanotubes.

[0028] The method for preparing a metal structural part includes the following technical steps: Step S1. Copper powder, 316L stainless steel powder, and nickel powder were dried separately in a vacuum drying oven. A 1.0% solution of a fluorinated silane coupling agent was dissolved in ethanol and uniformly coated on the surfaces of the three metal powders by ultrasonic spraying at a spray rate of 0.8 mL / min. Step S2. The modified copper powder, 316L stainless steel powder, and nickel powder were mixed in proportion, lithium stearate, PTFE powder, and nano-silica were added to the mixed powder, and ball-milled until the additives were evenly dispersed. The ball milling process used a planetary ball mill at a ball milling speed of 300 rpm, a ball-to-powder ratio of 10:1, and a ball-to-powder ratio of 4 hours. Step S3. Adding carbon nanotubes to the mixed powder and mixing them evenly, sieving the mixed powder using a sieve with a mesh size of 200 mesh. The sieving process is performed under inert gas protection to ensure that the powder particle size is within the range of 15-80 μm; Step S4. The powder is loaded into a forming mold and pre-pressed at 350 MPa for 5 seconds, and then pressed at a final pressure of 950 MPa for 15 seconds to form a green body. A low-pressure pneumatic demolding assembly is used to assist in demolding. The air pressure is controlled at 0.2 MPa and the demolding time is 5 seconds. After demolding, the green body is sintered at 950°C for 2 hours under argon protection.

[0029] Example 4

[0030] This embodiment provides a metal structural part prepared by a molding mold and a preparation method, wherein the metal structural part includes, in parts by mass: 40 parts of Cu powder, 40 parts of 316L stainless steel powder, 30 parts of Ni powder, 0.8 parts of lithium stearate powder, 1.3 parts of polytetrafluoroethylene powder, 0.5 parts of nano-SiO2 powder, 0.7 parts of fluorinated silane coupling agent and 7.5 parts of carbon nanotubes.

[0031] The method for preparing a metal structural part includes the following technical steps: Step S1. Copper powder, 316L stainless steel powder, and nickel powder were dried separately in a vacuum drying oven. A 1.5% solution of a fluorinated silane coupling agent was dissolved in ethanol and uniformly coated on the surfaces of the three metal powders by ultrasonic spraying at a spray rate of 1.0 mL / min. Step S2. The modified copper powder, 316L stainless steel powder, and nickel powder were mixed in proportion, lithium stearate, PTFE powder, and nano-silica were added to the mixed powder, and ball-milled until the additives were evenly dispersed. The ball milling process used a planetary ball mill at a ball milling speed of 250 rpm, a ball-to-powder ratio of 10:1, and a ball-to-powder ratio of 5 hours. Step S3. Adding carbon nanotubes to the mixed powder and mixing them evenly, sieving the mixed powder using a sieve with a mesh size of 300 mesh. The sieving process is performed under inert gas protection to ensure that the powder particle size is within the range of 15-80 μm; Step S4. The powder is loaded into a forming mold and pre-pressed at 300 MPa for 8 seconds, followed by a final pressing at 950 MPa for 10 seconds to form a green body. A low-pressure pneumatic demolding assembly is used to assist in demolding. The air pressure is controlled at 0.3 MPa, and the demolding time is 5 seconds. After demolding, the green body is sintered at 950°C for 1 hour under argon protection.

[0032] Example 5

[0033] This embodiment provides a metal structural part prepared by a molding mold and a preparation method, wherein the metal structural part includes, in parts by mass: 45 parts of Cu powder, 40 parts of 316L stainless steel powder, 25 parts of Ni powder, 0.8 parts of lithium stearate powder, 0.5 parts of polytetrafluoroethylene powder, 0.5 parts of nano-SiO2 powder, 0.7 parts of fluorinated silane coupling agent and 6.0 parts of carbon nanotubes.

[0034] The method for preparing a metal structural part includes the following technical steps: Step S1. Copper powder, 316L stainless steel powder, and nickel powder were dried separately in a vacuum drying oven. A 1.5% solution of a fluorinated silane coupling agent was dissolved in ethanol and uniformly coated on the surfaces of the three metal powders by ultrasonic spraying at a spray rate of 1.0 mL / min. Step S2. The modified copper powder, 316L stainless steel powder, and nickel powder were mixed in proportion, lithium stearate, PTFE powder, and nano-silica were added to the mixed powder, and ball-milled until the additives were evenly dispersed. The ball milling process used a planetary ball mill at a ball milling speed of 250 rpm, a ball-to-powder ratio of 10:1, and a ball-to-powder ratio of 5 hours. Step S3. Adding carbon nanotubes to the mixed powder and mixing them evenly, sieving the mixed powder using a sieve with a mesh size of 300 mesh. The sieving process is performed under inert gas protection to ensure that the powder particle size is within the range of 15-80 μm; Step S4. The powder is loaded into a forming mold and pre-pressed at 350 MPa for 8 seconds, followed by a final pressing at 800 MPa for 10 seconds to form a green body. A low-pressure pneumatic demolding assembly is used to assist in demolding. The air pressure is controlled at 0.3 MPa, and the demolding time is 5 seconds. After demolding, the green body is sintered at 950°C for 1 hour under argon protection.

[0035] Control Example Comparative Example 1 The difference between this control example and Example 3 is that 1.2 parts of Cu powder is used instead of 1.2 parts of lithium stearate powder, and the preparation method is modified accordingly.

[0036] Comparative Example 2 The difference between this control example and Example 3 is that 0.6 parts of Cu powder is used instead of 0.6 parts of polytetrafluoroethylene powder, and the preparation method is modified accordingly.

[0037] Performance testing methods Demolding efficiency testing: Using a low-pressure pneumatic demolding device equipped with a force sensor (air pressure controlled at 0.2-0.5 MPa, as in Examples 2-4), record the peak thrust required for each demold (unit: N). Lower peak thrust indicates less demolding resistance and better demolding efficiency. Demolding time is recorded using a timer (unit: seconds) from the time the pneumatic device is activated until the green body is completely released from the mold. Shorter times indicate higher demolding efficiency. Green body surface quality is assessed using an optical microscope (100x magnification) to observe the number and size of surface defects (e.g., scratches and cracks). The defect area percentage (%) is quantified; a lower percentage indicates better surface quality.

[0038] Flexural strength: According to ASTM B528, a sintered metal structural specimen with a size of 40 mm × 10 mm × 5 mm was prepared. A universal material testing machine (loading rate 0.5 mm / min) was used to apply a load until the specimen broke. The maximum breaking load (unit: N) was recorded and the formula σ = (3FL) / (2bh 2 ) to calculate the flexural strength (unit: MPa), where F is the maximum load, L is the span (30 mm), and b and h are the width and thickness of the specimen, respectively. Five specimens were tested for each formulation, and the average value was taken to ensure data reliability.

[0039] Table 1

[0040] Combined with Example 2 and Figure 3 It can be seen that after sintering, the metal structure formed multiple crystalline phases, including Cu–Ni–Fe solid solution (FCC structure), γ-Fe, Ni, SiO2, and metal fluorides (such as CuF2 and NiF2). After sintering, the metal structure formed a multiphase structure dominated by Cu–Ni–Fe solid solution (FCC structure), accompanied by the formation of trace strengthening phases such as metal fluorides such as CuF2 and NiF2. Among them, the formation of Cu–Ni–Fe solid solution indicates that Cu, Ni, and Fe have undergone good mutual dissolution during the high-temperature sintering process, constructing a dense face-centered cubic lattice structure, effectively improving the material's microstructure uniformity and load transfer capacity, and significantly enhancing the overall mechanical properties. On the other hand, polytetrafluoroethylene (PTFE) partially decomposes at high temperatures, and its decomposition products, such as hydrogen fluoride or fluoride ions, may react with metal powder to form stable metal fluorides. These metal fluorides are distributed in the metal matrix as dispersed phases, which can not only refine the grains and inhibit grain boundary migration, but also hinder crack propagation at the microscopic level, thereby improving the flexural strength of the material.

[0041] Combining Examples 2 to 5 and Table 1, it can be seen that the demolding thrust of Examples 2 to 5 is between 50 and 55 N, the demolding time is 2 to 5 seconds, the surface defect area accounts for only 0.8% to 1.0%, and the flexural strength is as high as 545 to 589 MPa.

[0042] Combining Example 3, Comparative Example 1, Comparative Example 2, and Table 1, it can be seen that Example 3 has a demolding force of 55 N, a demolding time of 5 seconds, a surface defect area of ​​only 1.0%, and a flexural strength of 562 MPa. In comparison, Comparative Example 1 has a demolding force of 70 N, a demolding time of 8 seconds, a surface defect area of ​​2.5%, and a flexural strength of only 425 MPa. Comparative Example 2 has a higher demolding force of 81 N, a demolding time of 9 seconds, a surface defect area of ​​3.0%, and a flexural strength of 423 MPa. The polar molecules of lithium stearate may form a weak interaction with the nonpolar surface of PTFE, promoting the uniform distribution of PTFE on the surface of the powder particles, thereby enhancing the overall lubrication effect and improving the demolding effect of the green body. At the same time, PTFE partially decomposes during high-temperature sintering, but its decomposition products (such as fluoride) may react with the metal powder surface to form a trace reinforcing phase, improving the flexural strength of the sintered body.

[0043] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A metal powder forming die that is easy to demould, characterized in that: From top to bottom, it includes: a top plate, an upper template, an upper cavity plate, a lower cavity plate, a lower template and a base. When the upper cavity plate and the lower cavity plate are combined, a molding cavity is formed. An injection port is provided on the top plate, and the injection port is connected to the molding cavity. A low-pressure pneumatic demolding component is provided at the lower end of the molding cavity.

2. The metal powder forming die according to claim 1, characterized in that: The low-pressure pneumatic demoulding assembly includes a push rod, a push plate and an air nozzle. The push plate is arranged on the upper end surface of the base. Several push rods are arranged between the push plate and the molding cavity. The air nozzle is arranged on the base.

3. The metal powder forming die according to claim 2, characterized in that: A support block is provided between the lower template and the base.

4. A metal structural part prepared based on the forming die according to claim 1, characterized in that: In terms of mass, it includes: 40 to 50 parts of Cu powder, 30 to 40 parts of 316L stainless steel powder, 20 to 30 parts of Ni powder, 0.6 to 1.2 parts of lithium stearate powder, 0.6 to 1.3 parts of polytetrafluoroethylene powder, 0.3 to 0.7 parts of nano-SiO2 powder, 0.5 to 1.0 parts of fluorinated silane coupling agent and 5.0 to 7.5 parts of carbon nanotubes.

5. The method for preparing a metal structural part according to claim 4, characterized in that: The following technical steps are included: Step S1. Copper powder, 316L stainless steel powder, and nickel powder are dried separately in a vacuum drying oven. A 1.0%-1.5% solution of a fluorinated silane coupling agent is dissolved in ethanol and uniformly coated on the surfaces of the three metal powders by ultrasonic spraying. Step S2. The modified copper powder, 316L stainless steel powder and nickel powder are mixed in proportion, lithium stearate, PTFE powder and nano-silica are added to the mixed powder, and ball milled until the additives are evenly dispersed; Step S3. Add the carbon nanotubes to the mixed powder and mix them evenly. Sieve the mixed powder using a sieve to ensure that the powder particle size is within the range of 15-80 μm. Step S4. The powder is loaded into a forming mold and pressed at a pressure of 650-950 MPa to form a green body. A low-pressure pneumatic demoulding assembly is used to assist demoulding. After demoulding, the green body is sintered at 950-1150° C. for 1.5-2 hours under argon protection.

6. The method for preparing a metal structural part according to claim 5, characterized in that: In step S1, the spray rate of the ultrasonic spray method is controlled at 0.5-1.0 mL / min.

7. The method for preparing a metal structural part according to claim 5, characterized in that: In step S2, the ball milling process uses a planetary ball mill with a ball milling speed of 200-300 rpm, a ball-to-material ratio of 10:1, and a ball milling time of 4-6 hours.

8. The method for preparing a metal structural part according to claim 5, wherein: In step S3, the mesh size of the sieve is 200-400 mesh.

9. The method for preparing a metal structural part according to claim 5, characterized in that: In step S4, the pressing process adopts a graded pressurization method, specifically: first pre-pressing at 300-400 MPa for 5-10 seconds, and then final pressing at 650-950 MPa for 10-15 seconds.

10. The method for preparing a metal structural part according to claim 5, wherein: In step S7, the air pressure of the low-pressure pneumatic demoulding component is controlled at 0.2-0.5 MPa, and the demoulding time is 2-5 seconds.

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