A powder metallurgy near-net-shaping method for high-purity iron TD4 thin-wall complex component

Abstract

The application discloses a high-purity iron TD4 thin-wall complex component powder metallurgy near-net forming method and belongs to the field of powder metallurgy. Step 1, spherical TD4 iron powder with Fe content greater than or equal to 99.8% and particle size of 15-45 microns is activated by low-temperature plasma under argon protection at a power of 100-300 W for 5-15 min; step 2, a vibration filling isostatic pressing graphite mold is filled, a cavity is compensated by a shrinkage rate of 1.2%-2.5%, and a functionally graded punch with a micro-convex surface is arranged; step 3, electric field activated pressure assisted sintering is carried out, a high-speed camera with a high-speed of greater than or equal to 100 fps and a pyrometer are used for real-time monitoring, and AI dynamically adjusts current and pressure according to curvature change amount; step 4, high-purity argon is forcedly cooled at a rate of 50-100 DEG C / min under pressure, and sand blasting and chemical polishing are carried out after demolding. The method improves the density and size precision of the component, reduces the risk of thin-wall cracking, and is suitable for the needs of high-end fields.

Description

Technical Field

[0001] This invention relates to the field of powder metallurgy technology, and more specifically, to a near-net-shape powder metallurgy forming method for thin-walled complex components made of high-purity iron TD4. Background Technology

[0002] In high-end fields such as aerospace precision sensing and semiconductor packaging substrates, high-purity iron TD4 components, with their excellent magnetic permeability and mechanical stability due to their iron content of over 99.8%, have become the preferred material for core components. In particular, thin-walled complex structure designs can meet the requirements of lightweighting and integration. However, the forming accuracy of such components directly determines the operating accuracy of the terminal equipment, posing a severe challenge to manufacturing technology. Powder metallurgy near-net-shape forming has become the mainstream preparation path for such components due to its high material utilization and strong shape replication. However, the low activity of high-purity iron powder and the vulnerability of thin-walled areas during forming have made it difficult for traditional processes to overcome performance bottlenecks.

[0003] In traditional powder metallurgy processes, the oxide layer and adsorbed impurities on the surface of high-purity iron powder reduce the bonding strength of the sintered neck, resulting in a component density of less than 10%. Mold designs often use uniform shrinkage compensation, ignoring the difference in sintering shrinkage between thin-walled and thick-walled areas, causing dimensional tolerances to frequently exceed ±0.5mm. The sintering process relies on empirical parameter settings, lacking real-time monitoring of micro-deformations such as bulging and depressions in thin-walled areas. Relying solely on post-processing grinding easily leads to uneven wall thickness. Natural cooling during the cooling stage causes residual stress of 15-20MPa to form inside the component, with a cracking rate exceeding 12% in thin-walled areas. Surface treatment is limited to sandblasting, which cannot simultaneously meet the requirements of roughness Ra≤0.8μm and surface purity, restricting the application of components in precision fields. As high-end equipment demands component precision of ±0.1mm and density ≥98%, traditional processes can no longer meet the requirements. The integration of technologies such as low-temperature plasma activation and AI dynamic control sintering addresses the core pain points of high-purity iron thin-walled forming, providing an innovative path to overcome existing technological bottlenecks.

[0004] Therefore, existing technologies suffer from problems such as low powder activity and insufficient density, inaccurate mold compensation, lack of real-time control during sintering, and stress cracking after cooling. Summary of the Invention

[0005] In order to overcome the problems of low powder activity and insufficient density, inaccurate mold compensation, lack of real-time control in sintering, and stress cracking after cooling in the existing technology, this invention discloses a near-net-shape powder metallurgy forming method for thin-walled complex components of high-purity iron TD4, which can effectively solve the above-mentioned technical problems.

[0006] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0007] A near-net-shape powder metallurgy method for forming thin-walled complex components from high-purity iron TD4 includes the following steps:

[0008] Spherical TD4 iron powder prepared by ultra-high purity gas atomization was subjected to low-temperature plasma activation treatment under argon protection. The TD4 iron powder had an Fe content ≥99.8%, a total impurity element content ≤0.2%, and a particle size distribution of 15μm-45μm.

[0009] The activated TD4 iron powder is filled into the cavity of a high-precision graphite mold under vibration. The cavity of the graphite mold is designed with shrinkage compensation and is equipped with a functional gradient pressure punch. The functional gradient pressure punch has a micro-convex curved surface structure in the thin-walled area of ​​the component.

[0010] An electric field activated pressure-assisted sintering system is used to sinter molds and powders. The system includes a FAST device, a dual-wavelength pyrometer, a high-speed industrial camera with a built-in miniature high-temperature resistant optical probe, and an AI processing unit. The high-speed camera acquires real-time images of the thin-walled area of ​​the component, the pyrometer monitors the real-time temperature, and the AI ​​processing unit dynamically adjusts the pulse current density, pressing pressure, and punch pressing speed based on the comparison results of the deformation index calculated from the image and the preset threshold.

[0011] After sintering, high-purity argon gas is introduced under pressure to force cooling to room temperature. After demolding, surface treatment is performed to obtain high-purity iron TD4 thin-walled complex components.

[0012] Preferably, the parameters for the low-temperature plasma activation treatment are: plasma power 100W-300W, treatment time 5min-15min, and argon flow rate 20L / h-50L / h.

[0013] Preferably, the graphite mold is made of isostatic graphite, the shrinkage compensation of the cavity is 1.2%-2.5%, and the surface roughness Ra of the cavity in different wall thickness areas of the component is ≤0.8μm.

[0014] Preferably, the protrusion height of the micro-convex curved surface structure of the functional gradient pressure punch is 0.05mm-0.2mm, the radius of curvature is 5mm-20mm, and the hardness of the protrusion area is 10%-15% higher than that of the punch body.

[0015] Preferably, the initial parameters of the electric field activated pressure-assisted sintering are set as follows: maximum sintering temperature 950℃-1050℃, initial pressure 20MPa-50MPa, heating rate 100℃ / min-300℃ / min, and pulse current frequency 50Hz-200Hz.

[0016] Preferably, the high-speed industrial camera has a frame rate of ≥100fps, an image resolution of ≥2048×1536 pixels, and takes pictures through a quartz observation window reserved on the side wall of the mold, with a light transmittance of ≥90%.

[0017] Preferably, the deformation quantification index includes the real-time curvature change and deformation rate of the thin-walled region, and the preset threshold for curvature change is 0.01 mm. -1 -0.03mm -1 The deformation rate threshold is 0.001 mm / s-0.005 mm / s.

[0018] Preferably, the specific method of dynamic control is as follows: when the deformation rate exceeds the threshold and shows a concave trend, the pulse current density in the corresponding area is reduced by 5%-15%, while the pressing pressure is increased by 3%-8%; when the deformation rate exceeds the threshold and shows a bulging trend, the pulse current density in the corresponding area is increased by 5%-15%, while the punch pressing speed is reduced by 10%-20%.

[0019] Preferably, the argon gas used for forced cooling has a purity of ≥99.999%, a cooling rate of 50℃ / min-100℃ / min, and pressurization is stopped when the temperature drops below 200℃.

[0020] Preferably, the surface treatment includes sandblasting and chemical polishing. The sandblasting uses alumina abrasive with a particle size of 50μm-100μm and a pressure of 0.1MPa-0.3MPa. The chemical polishing uses a mixed solution of nitric acid and hydrofluoric acid with a volume ratio of 3:1 and a treatment time of 30s-60s.

[0021] Compared with existing technologies, the beneficial effects of this invention are as follows: Addressing the problems of low powder activity and insufficient density, this invention employs low-temperature plasma activation treatment under argon protection. A plasma power of 100W-300W effectively removes the oxide layer and adsorbed impurities from the surface of TD4 iron powder. A treatment time of 5-15 minutes, combined with an argon flow rate of 20L / h-50L / h, enhances surface activity while avoiding powder contamination, resulting in tighter sintering neck bonding between powder particles and significantly improving component density. Regarding the problem of inaccurate mold compensation, isostatic graphite is used to create the mold, and the cavity is compensated for with a shrinkage rate of 1.2%-2.5%. A functional gradient punch with a 0.05mm-0.2mm raised surface is used in corresponding thin-walled areas to precisely match the sintering shrinkage differences and stress requirements of different wall thickness areas, solving the dimensional deviation problem. Furthermore, the cavity... A roughness of Ra≤0.8μm ensures forming accuracy. To address the lack of real-time control during sintering, the electric field-activated pressure-assisted sintering system uses a high-speed camera (≥100fps) and a dual-wavelength pyrometer to collect images and temperatures of the thin-walled area in real time. The AI ​​processing unit dynamically controls the process based on indicators such as curvature change, following the rules of reducing current by 5%-15% and increasing pressure by 3%-8% for concavity and increasing current by 5%-15% and reducing punch speed by 10%-20% for bulging, thus preventing sintering deformation. To address the issue of stress cracking after cooling, 99.999% high-purity argon is introduced under pressure after sintering, and forced cooling is performed at a rate of 50℃ / min-100℃ / min. The design of stopping pressure below 200℃ inhibits abnormal grain growth and reduces internal stress accumulation. After sandblasting and chemical polishing, surface quality is ensured and surface stress is further eliminated, comprehensively improving the overall performance of the component. Attached Figure Description

[0022] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely exemplary. For those skilled in the art, other embodiments can be derived from the provided drawings without creative effort.

[0023] Figure 1 This is a process structure diagram of the present invention;

[0024] Figure 2 This is a flowchart illustrating the process steps of the present invention. Detailed Implementation

[0025] The accompanying drawings are for illustrative purposes only and should not be construed as limiting the scope of this patent.

[0026] To better illustrate this embodiment, some parts in the accompanying drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions;

[0027] It will be understood by those skilled in the art that certain well-known structures and their descriptions may be omitted in the accompanying drawings.

[0028] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0029] Example

[0030] Please see Figure 1-2 A near-net-shape powder metallurgy method for forming thin-walled complex components from high-purity iron TD4 includes the following steps:

[0031] Spherical TD4 iron powder prepared by ultra-high purity gas atomization was subjected to low-temperature plasma activation treatment under argon protection. The TD4 iron powder had an Fe content ≥99.8%, a total impurity element content ≤0.2%, and a particle size distribution of 15μm-45μm.

[0032] The activated TD4 iron powder is filled into the cavity of a high-precision graphite mold under vibration. The cavity of the graphite mold is designed with shrinkage compensation and is equipped with a functional gradient pressure punch. The functional gradient pressure punch has a micro-convex curved surface structure in the thin-walled area of ​​the component.

[0033] An electric field activated pressure-assisted sintering system is used to sinter molds and powders. The system includes a FAST device, a dual-wavelength pyrometer, a high-speed industrial camera with a built-in miniature high-temperature resistant optical probe, and an AI processing unit. The high-speed camera acquires real-time images of the thin-walled area of ​​the component, the pyrometer monitors the real-time temperature, and the AI ​​processing unit dynamically adjusts the pulse current density, pressing pressure, and punch pressing speed based on the comparison results of the deformation index calculated from the image and the preset threshold.

[0034] After sintering, high-purity argon gas is introduced under pressure to force cooling to room temperature. After demolding, surface treatment is performed to obtain high-purity iron TD4 thin-walled complex components.

[0035] The parameters for the low-temperature plasma activation treatment are: plasma power 100W-300W, treatment time 5min-15min, and argon flow rate 20L / h-50L / h.

[0036] The graphite mold is made of isostatically pressed graphite, and the shrinkage compensation of the cavity is 1.2%-2.5%. The surface roughness Ra of the cavity in different wall thickness areas of the corresponding component is ≤0.8μm.

[0037] The protrusion height of the micro-convex curved surface structure of the functional gradient pressure punch is 0.05mm-0.2mm, the radius of curvature is 5mm-20mm, and the hardness of the protruding area is 10%-15% higher than that of the punch body.

[0038] The initial parameters for the electric field activated pressure-assisted sintering are set as follows: maximum sintering temperature 950℃-1050℃, initial pressure 20MPa-50MPa, heating rate 100℃ / min-300℃ / min, and pulse current frequency 50Hz-200Hz.

[0039] The high-speed industrial camera has a frame rate of ≥100fps and an image resolution of ≥2048×1536 pixels. It takes pictures through a quartz observation window reserved on the side wall of the mold, and the light transmittance of the observation window is ≥90%.

[0040] The deformation metrics include the real-time curvature change and deformation rate of the thin-walled region. The preset threshold for curvature change is 0.01 mm. -1 -0.03mm -1 The deformation rate threshold is 0.001 mm / s-0.005 mm / s.

[0041] The specific method of dynamic control is as follows: when the deformation rate exceeds the threshold and shows a concave trend, the pulse current density in the corresponding area is reduced by 5%-15%, while the pressing pressure is increased by 3%-8%; when the deformation rate exceeds the threshold and shows a bulging trend, the pulse current density in the corresponding area is increased by 5%-15%, while the punch pressing speed is reduced by 10%-20%.

[0042] The argon gas used for forced cooling has a purity of ≥99.999%, a cooling rate of 50℃ / min-100℃ / min, and pressurization is stopped when the temperature drops below 200℃.

[0043] The surface treatment includes sandblasting and chemical polishing. Sandblasting uses alumina abrasive with a particle size of 50μm-100μm and a pressure of 0.1MPa-0.3MPa. Chemical polishing uses a mixed solution of nitric acid and hydrofluoric acid with a volume ratio of 3:1 and a treatment time of 30s-60s.

[0044] This embodiment focuses on the preparation of a U-shaped high-purity iron TD4 thin-walled complex component for a high-end electronic device. The component has an opening width of 60mm, a depth of 40mm, a main body wall thickness of 1.0mm, three waist-shaped holes with a diameter of 4mm distributed on each side wall, and an arc-shaped transition section with a curvature radius of 10mm at the bottom. The technical requirements are: density ≥98.5%, dimensional tolerance ≤±0.1mm, surface roughness Ra≤0.6μm, and no internal cracks or surface defects. The following is a complete implementation process that meets the technical requirements, and the key parameters strictly follow the limits defined in the solution.

[0045] Spherical TD4 iron powder prepared by ultra-high purity gas atomization process was tested according to standard procedures. The core indicators were: Fe content 99.8%, total impurity element content 0.2% (of which the proportion of conventional impurities such as C, Si, and Mn is ≤0.05%), particle size distribution 15μm-45μm, and laser particle size analyzer test showed that D50 was 30μm, which meets the basic requirements of the technical solution for raw materials.

[0046] To remove trace amounts of moisture and oil adsorbed on the surface of the iron powder, the screened iron powder was placed in a vacuum drying oven, with the temperature set at 80℃, the vacuum degree at -0.09MPa, and the drying time at 4 hours. After drying, it was immediately transferred to a sealed container protected by argon gas to prevent oxidation from contact with air, and then put into use.

[0047] The activation operation was performed using radio frequency low-temperature plasma treatment equipment, with core parameters strictly adhering to the optimal range of the technical solution. First, dried TD4 iron powder was evenly spread in a quartz reaction boat, with a thickness controlled to 5mm, to ensure uniform plasma application to the powder surface. The reaction boat was then placed into the reaction chamber, and after the chamber was closed, a vacuum of 1×10⁻⁶ was applied. -3 Pa, then high-purity argon gas is introduced, and the flow rate is adjusted to 30 L / h. After the chamber pressure stabilizes at 0.05 MPa, the plasma generator is started.

[0048] The plasma power was set to 200W and the processing time to 10 minutes. During the activation process, the oxygen content was monitored in real time by the built-in oxygen content monitor to ensure that the oxygen content in the chamber was ≤0.01% to avoid secondary oxidation of the iron powder. After the treatment, argon gas was kept in the chamber until it cooled to room temperature naturally. The activated iron powder was then removed and transferred to a sealed container for later use. The test results showed that the oxide layer thickness on the surface of the activated iron powder was reduced by 60% compared with that before the treatment, and the powder flowability was improved by 30%, which laid the foundation for uniform filling and high-density forming.

[0049] Isostatic graphite was used as the mold substrate. This material has excellent high temperature resistance and dimensional stability, which meets the requirements of the technical solution. Based on the sintering shrinkage characteristics of the component, the cavity shrinkage compensation amount was calculated to be 1.8% (within the preferred range of 1.2%-2.5%) through simulation. Based on this, the mold cavity dimensions were designed as follows: opening width 61.08mm, depth 40.72mm, main body wall thickness 1.018mm, and the size of the waist-shaped hole was enlarged by 1.8%.

[0050] The mold is machined using a five-axis CNC milling machine. After rough machining, a 0.2mm finishing allowance is reserved. In the finishing stage, diamond tools are used with a cutting speed of 80m / min and a feed rate of 0.05mm / r. For the thin-walled and waist-shaped hole structure of the component, the cavity surface is ground and polished with a diamond grinding wheel. The surface roughness Ra of each area is ≤0.8μm as measured by a surface roughness tester, which meets the requirements of the scheme. At the position of the arc transition section of the component on the side wall of the mold, a 10mm diameter mounting hole is machined and a quartz observation window with 90% light transmittance is embedded for real-time monitoring of the thin-walled area during sintering. The observation window is sealed with high-temperature sealant to ensure airtightness.

[0051] The punch body is made of high-strength cemented carbide. Based on the stress characteristics of the thin-walled area of ​​the component, a micro-convex curved surface structure is machined at the position corresponding to the main body wall thickness and the arc transition section. The parameters of the micro-convex curved surface strictly follow the optimal range of the scheme: the convex height of the corresponding area of ​​the thin wall of the main body is 0.1mm and the radius of curvature is 15mm; the convex height of the corresponding area of ​​the arc transition section is 0.15mm and the radius of curvature is 10mm.

[0052] To achieve the required hardness gradient, the micro-convex curved surface area is locally quenched. After the treatment, the Vickers hardness tester shows that the hardness of the raised area is 12% higher than that of the punch body (in the range of 10%-15%). This allows for targeted pressure to be applied to the thin-walled area during the pressing process, avoiding local density deficiency or deformation. After the punch is processed, the surface is polished to ensure that the clearance between the punch and the mold cavity is ≤0.02mm.

[0053] The processed graphite mold is fixed on the worktable of the vibration filling equipment. The mold level is adjusted to an error of ≤0.02mm / m. The vibration device is started, and the vibration frequency is set to 50Hz and the amplitude to 0.5mm. The activated TD4 iron powder is slowly poured into the mold inlet. The vibration is used to make the powder flow fully inside the cavity and fill complex structural areas such as waist-shaped holes and arc-shaped transition sections.

[0054] During the filling process, the powder bulk density is monitored in real time by a pressure sensor at the bottom of the mold. When the pressure stabilizes at 0.3MPa, the vibration is stopped. At this time, the powder bulk density reaches 2.8g / cm³. Excess powder is scraped off along the upper surface of the mold with a scraper to ensure that the powder is flush with the upper edge of the mold. Then, a graphite cover plate is placed on top to complete the filling operation. The mold is then transferred to the worktable of the electric field activated pressure assisted sintering system.

[0055] The sintering system is configured according to the technical solution: with the FAST equipment as the core, it is equipped with a dual-wavelength pyrometer, a high-speed industrial camera with a built-in miniature high-temperature resistant optical probe, and an AI processing unit. The high-speed industrial camera is installed in front of the quartz observation window on the side wall of the mold, with a frame rate of 100fps and an image resolution of 2048×1536 pixels to ensure clear capture of real-time images of the thin-walled area; the dual-wavelength pyrometer is aimed at the center area of ​​the mold cavity, with a measurement range covering 500℃-1200℃ and an accuracy of ±5℃, for real-time monitoring of the sintering temperature.

[0056] During the debugging phase, a standard curvature sample was placed in a mold to simulate the sintering and heating process, verifying the deformation calculation accuracy of the AI ​​processing unit: the error between the curvature change calculated by the image recognition algorithm and the actual measured value was ≤0.002mm. -1 The deformation rate calculation error is ≤0.0005mm / s, ensuring the accuracy of monitoring and control.

[0057] Based on the optimized parameter range of the technical solution, the initial sintering parameters are set as follows: maximum sintering temperature 1000℃, initial pressure 35MPa, heating rate 200℃ / min, pulse current frequency 100Hz; the preset threshold for deformation variation index is: curvature change threshold 0.02mm. -1 The deformation rate threshold is 0.003 mm / s, and the dynamic control rules strictly follow the requirements of the scheme.

[0058] The assembled mold is placed into the sintering chamber of the FAST equipment, and after the chamber is closed, a vacuum of 1×10⁻⁶ is drawn. -3 Pa, then high-purity argon gas is introduced to 0.1 MPa to start the sintering program. During the heating stage, the dual-wavelength pyrometer provides real-time temperature data feedback, and the AI ​​processing unit maintains a stable heating rate by adjusting the pulse current density. When the temperature reaches 1000℃, the heat preservation stage begins, with a heat preservation time of 5 minutes.

[0059] During the heat preservation process, a high-speed industrial camera continuously acquires images of the arc-shaped transition section and the thin-walled area around the waist-shaped hole of the component. The AI ​​processing unit calculates the deformation variation index for each frame. When the deformation rate of the arc-shaped transition section reaches 0.004 mm / s and shows a bulging trend, the AI ​​unit immediately outputs a control command: the pulse current density in the corresponding area is increased by 10%, and the punch pressing speed is reduced by 15%. After 3 seconds, the deformation rate drops to 0.0025 mm / s. Subsequently, the deformation rate of the area around the waist-shaped hole is 0.0045 mm / s and shows a concave trend. The control command is to reduce the pulse current density by 10% and increase the pressing pressure by 5%. After 5 seconds, it returns to within the threshold. A total of 5 dynamic controls are performed during the entire heat preservation stage to ensure that the deformation of each thin-walled area is always within a controllable range.

[0060] After sintering and heat preservation, a forced cooling program is initiated, maintaining the initial pressure at 35 MPa. High-purity argon gas with a purity of 99.999% is introduced, and the argon gas flow rate is adjusted through the flow control system to stabilize the cooling rate at 80℃ / min (within the range of 50℃ / min-100℃ / min). A dual-wavelength pyrometer monitors the component temperature in real time. When the temperature drops below 200℃, the AI ​​unit issues a depressurization command, reducing the pressure to atmospheric pressure at a rate of 0.2 MPa / s. Argon gas is then introduced until the component naturally cools to room temperature.

[0061] During forced cooling, the internal stress of the component is monitored by stress sensors, with a peak value of ≤15MPa, which is far lower than the 30MPa of traditional cooling methods, effectively avoiding the risk of stress cracking.

[0062] After cooling, the sintering chamber is opened and the mold is removed. A hydraulic demolding device is used for demolding, with a demolding pressure of 10MPa and a demolding speed of 5mm / s. The component is separated from the mold cavity by slowly applying pressure to avoid damage to thin-walled areas due to uneven force. After demolding, a preliminary shaped component is obtained. Visual inspection shows no obvious dents, bulges, or cracks.

[0063] The surface treatment adopts a combination of sandblasting and chemical polishing according to the technical plan. First, sandblasting is performed: alumina abrasive with a particle size of 80μm is selected, the sandblasting pressure is adjusted to 0.2MPa (within the range of 0.1MPa-0.3MPa), the sandblasting distance is 300mm, and the treatment time is 20s to remove oxide scale and graphite residue from the surface of the component. After sandblasting, the surface dust is blown away with compressed air and then the chemical polishing process is carried out.

[0064] Prepare a nitric acid and hydrofluoric acid mixed solution with a volume ratio of 3:1. Immerse the component completely in the solution for 45 seconds (within the range of 30-60 seconds). During this time, use low-speed stirring to ensure uniform polishing. After treatment, immediately rinse in deionized water until the pH value reaches 7, and then transfer to a vacuum drying oven and dry at 80°C for 30 minutes.

[0065] The finished components underwent comprehensive testing according to technical requirements: the density, measured using the Archimedes drainage method, was 98.8%, meeting the requirement of ≥98.5%; dimensional measurements showed an opening width of 59.95mm, a depth of 39.92mm, and a main body wall thickness of 0.99mm, with tolerances of ≤±0.1mm for each dimension; the surface roughness test showed Ra of 0.5μm, conforming to the standard of ≤0.6μm; ultrasonic testing revealed no internal cracks, and X-ray fluorescence spectroscopy analysis showed no surface contamination; in mechanical property testing, the tensile strength was 420MPa and the yield strength was 380MPa, meeting the usage requirements.

[0066] This embodiment successfully prepared a high-purity iron TD4 thin-walled complex component that meets the requirements by executing the parameters and processes in the technical solution, verifying the feasibility and stability of the forming method.

[0067] The same or similar labels correspond to the same or similar parts;

[0068] The terms used to describe positional relationships in the accompanying drawings are for illustrative purposes only and should not be construed as limiting this patent.

[0069] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all implementation methods here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the claims of the present invention.

Claims

1. A near-net-shape powder metallurgy forming method for thin-walled complex components made of high-purity iron TD4, characterized in that, Includes the following steps: Spherical TD4 iron powder prepared by ultra-high purity gas atomization was subjected to low-temperature plasma activation treatment under argon protection. The TD4 iron powder had an Fe content ≥99.8%, a total impurity element content ≤0.2%, and a particle size distribution of 15μm-45μm. The activated TD4 iron powder is filled into the cavity of a high-precision graphite mold under vibration. The cavity of the graphite mold is designed with shrinkage compensation and is equipped with a functional gradient pressure punch. The functional gradient pressure punch has a micro-convex curved surface structure in the thin-walled area of ​​the component. An electric field activated pressure-assisted sintering system is used to sinter molds and powders. The system includes a FAST device, a dual-wavelength pyrometer, a high-speed industrial camera with a built-in miniature high-temperature resistant optical probe, and an AI processing unit. The high-speed camera acquires real-time images of the thin-walled area of ​​the component, the pyrometer monitors the real-time temperature, and the AI ​​processing unit dynamically adjusts the pulse current density, pressing pressure, and punch pressing speed based on the comparison results of the deformation index calculated from the image and the preset threshold. After sintering, high-purity argon gas is introduced under pressure to force cooling to room temperature. After demolding, surface treatment is performed to obtain high-purity iron TD4 thin-walled complex components. The graphite mold is made of isostatically pressed graphite, and the shrinkage compensation of the cavity is 1.2%-2.5%, corresponding to the surface roughness Ra≤0.8μm of the cavity in different wall thickness areas of the component; The protrusion height of the micro-convex curved surface structure of the functional gradient pressure punch is 0.05mm-0.2mm, the radius of curvature is 5mm-20mm, and the hardness of the protruding area is 10%-15% higher than that of the punch body; The initial parameters for the electric field activated pressure-assisted sintering are set as follows: maximum sintering temperature 950℃-1050℃, initial pressure 20MPa-50MPa, heating rate 100℃ / min-300℃ / min, and pulse current frequency 50Hz-200Hz. The specific method of dynamic control is as follows: when the deformation rate exceeds the threshold and shows a concave trend, the pulse current density in the corresponding area is reduced by 5%-15%, while the pressing pressure is increased by 3%-8%; when the deformation rate exceeds the threshold and shows a bulging trend, the pulse current density in the corresponding area is increased by 5%-15%, while the punch pressing speed is reduced by 10%-20%.

2. The near-net-shape powder metallurgy forming method for high-purity iron TD4 thin-walled complex components as described in claim 1, characterized in that, The parameters for the low-temperature plasma activation treatment are: plasma power 100W-300W, treatment time 5min-15min, and argon flow rate 20L / h-50L / h.

3. The near-net-shape powder metallurgy forming method for high-purity iron TD4 thin-walled complex components as described in claim 1, characterized in that, The high-speed industrial camera has a frame rate of ≥100fps and an image resolution of ≥2048×1536 pixels. It takes pictures through a quartz observation window reserved on the side wall of the mold, and the light transmittance of the observation window is ≥90%.

4. The near-net-shape powder metallurgy forming method for high-purity iron TD4 thin-walled complex components as described in claim 1, characterized in that, The deformation metrics include the real-time curvature change and deformation rate of the thin-walled region. The preset threshold for curvature change is 0.01 mm. -1 -0.03mm -1 The deformation rate threshold is 0.001 mm / s-0.005 mm / s.

5. The near-net-shape powder metallurgy forming method for high-purity iron TD4 thin-walled complex components as described in claim 1, characterized in that, The argon gas used for forced cooling has a purity of ≥99.999%, a cooling rate of 50℃ / min-100℃ / min, and pressurization is stopped when the temperature drops below 200℃.

6. The near-net-shape powder metallurgy forming method for high-purity iron TD4 thin-walled complex components as described in claim 1, characterized in that, The surface treatment includes sandblasting and chemical polishing. Sandblasting uses alumina abrasive with a particle size of 50μm-100μm and a pressure of 0.1MPa-0.3MPa. Chemical polishing uses a mixed solution of nitric acid and hydrofluoric acid with a volume ratio of 3:1 and a treatment time of 30s-60s.

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