A powder metallurgy near-net shape blank preparation process based on green body sculpturing finishing

Abstract

The application belongs to the technical field of precious metal forging blank preparation, and particularly relates to a powder metallurgy near-net-shape blank preparation process based on blank body carving and finishing, which comprises the following steps: S1: obtaining hydrogenated metal by adopting a hydrogenation-dehydrogenation method; S2: processing the hydrogenated metal into hydrogenated metal powder by using crushing equipment; S3: placing the powder into a dehydrogenation furnace for heat preservation and dehydrogenation; S4: preparing a rubber mold with a corresponding size according to a design, and performing cold isostatic pressing in an argon protection glove box to obtain a size-regularized blank; S5: carving the blank into a shape required by final forging by using an automatic carving machine; S6: placing the carved blank into a vacuum sintering furnace for sintering; S7: recycling the carved and crushed particles; and S8: performing die forging and final forging processing on the carved blank. The application omits the die forging pre-blank link and corresponding molds, heating and processing costs, realizes one-step processing of special-shaped parts from blank preparation to final forging, and can complete one-step die forging forming of more complex special-shaped parts by combining powder metallurgy carving forming and die forging technology.

Description

Technical Field

[0001] This invention relates to the field of precious metal forging billet preparation technology, and in particular to a powder metallurgy near-net-shape billet preparation process based on billet carving and trimming. Background Technology

[0002] Free forging refers to a processing method that uses simple, general-purpose tools or applies external force directly to the billet between the upper and lower anvils of a forging machine, causing the billet to deform and obtain the desired geometric shape and internal quality. Forgings produced using the free forging method are called free forgings.

[0003] Free forging primarily focuses on producing small batches of forgings. It utilizes forging equipment such as forging hammers and hydraulic presses to shape and process raw materials into qualified forgings. The basic processes of free forging include upsetting, drawing, punching, cutting, bending, twisting, shifting, and forging welding. Free forging always employs hot forging methods.

[0004] Free forging processes include basic processes, auxiliary processes, and finishing processes. The basic processes of free forging include upsetting, drawing, punching, bending, cutting, twisting, misalignment, and forging joining, with upsetting, drawing, and punching being the most commonly used in actual production. Auxiliary processes are pre-deformation processes, such as pressing the jaws, pressing the ingot edges, and cutting shoulders. Finishing processes are processes that reduce surface defects in forgings, such as removing surface irregularities and shaping.

[0005] Advantages of free forging: It offers great forging flexibility, capable of producing small parts weighing less than 100kg as well as heavy parts weighing over 300t; the tools used are simple, general-purpose tools; the forging process involves gradually deforming the billet in sections, thus requiring much smaller forging equipment to produce the same forging compared to die forging; it has low precision requirements for the equipment; and it has a short production cycle.

[0006] Disadvantages and limitations of free forging: production efficiency is much lower than that of die forging; forgings have simple shapes, low dimensional accuracy, and rough surfaces; workers experience high labor intensity and require high technical skills; and it is not easy to achieve mechanization and automation.

[0007] Die forging refers to a forging method that uses dies to shape a blank on specialized forging equipment to obtain a forging. This method produces forgings with precise dimensions, small machining allowances, and relatively complex structures, resulting in high productivity. It can be classified according to the equipment used: hammer forging, crank press forging, flat forging machine forging, and friction press forging, etc. The most commonly used equipment for hammer forging includes steam-air forging hammers, anvilless hammers, and high-speed hammers. Based on their function, they can be divided into two main categories: forging die chambers and billet-forming die chambers.

[0008] Advantages of die forging: High production efficiency. During die forging, the metal deformation occurs within the die cavity, thus achieving the desired shape more quickly; it can forge complex shapes and allows for a more rational distribution of metal flow lines, improving the service life of parts; die forgings have more precise dimensions, better surface quality, and smaller machining allowances; it saves metal materials and reduces machining workload. With sufficient batch production, it can reduce part costs.

[0009] Disadvantages and limitations of die forging: The weight of die forgings is limited by the capacity of general die forging equipment, and is mostly below 70 kg; the manufacturing cycle of forging dies is long and the cost is high; the investment cost of die forging equipment is greater than that of free forging.

[0010] For the preparation of irregularly shaped forgings such as titanium alloys, traditional free forging or die forging methods are generally used. However, due to the complexity of the irregularly shaped parts, the complex structural parts cannot be forged into shape during the forging process. Instead, the complex structural parts are filled in and then machined after forging. Although the final product can achieve the desired effect, the material utilization rate is greatly reduced, reaching only 40%-60% in the forging process of irregularly shaped parts. While some irregularly shaped parts can be pre-formed through pre-forging, this requires the addition of pre-forging dies and multiple heating processes, significantly increasing forging costs. Summary of the Invention

[0011] 1. Technical problems to be solved

[0012] The purpose of this invention is to solve the problem that the existing technology requires the addition of pre-forging molds and multiple heating, which greatly increases the forging cost. Therefore, this invention proposes a powder metallurgy near-net-shape billet preparation process based on billet carving and trimming.

[0013] 2. Technical Solution

[0014] To achieve the above objectives, the present invention adopts the following technical solution:

[0015] In a first aspect, this application provides a powder metallurgy near-net-shape billet preparation process based on billet carving and trimming, comprising the following steps:

[0016] S1: Using the hydrogenation dehydrogenation method, sponge metal absorbs hydrogen in a hydrogen absorption furnace to form hydride metal;

[0017] S2: The sponge metal is prepared into hydride metal powder using crushing equipment;

[0018] S3: Place the hydride metal powder into the dehydrogenation furnace and perform heat preservation and dehydrogenation;

[0019] S4: According to the design requirements, prepare a rubber mold of the corresponding size, load the hydride metal powder into the rubber mold in an argon-protected glove box, and perform cold isostatic pressing with a pressure set at 180MPa to obtain a regular billet of the corresponding size.

[0020] S5: Argon gas is injected into a specially designed fully sealed engraving machine to protect the blank at the atmosphere. The automatic engraving machine is used to engrave the blank into the material shape required for final forging.

[0021] S6: Place the carved blank into a vacuum sintering furnace for vacuum sintering;

[0022] S7: The broken particles after carving are recycled and crushed back into powder. Since they are not exposed to air, carving waste can be reused.

[0023] S8: The engraved blank is forged using a die forging method for final forging.

[0024] In one possible implementation, the temperature inside the hydrogen absorption furnace in S1 is 500-550°C.

[0025] In one possible implementation, the particle size of the hydride metal powder in S2 is D50: 12 μm.

[0026] In one possible implementation, the heat preservation dehydrogenation in S3 is carried out at 580°C for 6 hours.

[0027] In one possible implementation, the mold shape in S4 is basically square, cylindrical, or annular blank.

[0028] In one possible implementation, the pressure of the cold isostatic pressing in S4 is set to 180 MPa.

[0029] In one possible implementation, vacuum sintering in S6 is performed at 1150°C for 11 hours.

[0030] In one possible implementation, the particle size of the powder in S7 is 12 μm.

[0031] In one possible implementation, the metal is Ti metal.

[0032] 3. Beneficial effects

[0033] Compared with the prior art, the advantages of this invention are:

[0034] (1) In this application, the powder metallurgy engraving forming technology realizes the one-step leap from blank making to die forging of irregular parts, omitting the pre-brush process in the die forging process, and also omitting the corresponding mold cost and heating and processing cost of the pre-brush process; in addition, the realization of powder metallurgy engraving forming technology can be combined with die forging technology to realize one-step die forging of more complex irregular parts.

[0035] (2) In this application, the blank produced by the powder metallurgy blank fully sealed gas-insulated engraving forming technology can achieve a significant increase in the material utilization rate of irregular forgings after die forging. The material utilization rate can reach more than 90%, the material cost of forgings is reduced by 33.5%-55%, and the processing cost of forgings is reduced by about 30%. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the process structure for preparing near-net-shape powder metallurgy billets based on billet carving and trimming, as proposed in this invention. Detailed Implementation

[0037] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0038] Example 1:

[0039] Reference Figure 1 A near-net-shape powder metallurgy billet preparation process based on billet carving and trimming includes the following steps:

[0040] S1: Using the hydrogenation dehydrogenation method, sponge metal is subjected to hydrogen absorption at 550°C in a hydrogen absorption furnace to form hydride metal.

[0041] S2: The sponge metal is prepared into hydride metal powder with a D50 of 12μm using crushing equipment.

[0042] S3: Place the hydride metal powder into a dehydrogenation furnace and dehydrogenate it at 580°C for 6 hours.

[0043] S4: According to the design requirements, prepare rubber molds of the corresponding size. The mold shape is basically square, cylindrical or ring-shaped blank. In an argon-protected glove box, put hydride metal powder into the rubber mold and perform cold isostatic pressing. The pressure is set to 180MPa to obtain a regular blank of the corresponding size.

[0044] S5: Argon gas is injected into a specially designed fully sealed engraving machine to protect the blank at the atmosphere. The automatic engraving machine is then used to engrave the blank into the material shape required for final forging.

[0045] S6: Place the carved blank into a vacuum sintering furnace and sinter it at 1150℃ for 11 hours.

[0046] S7: The broken particles after carving are recycled and crushed again into 12μm powder. Since they are not exposed to air, carving waste can be reused.

[0047] S8: The engraved blank is forged using a die forging method for final forging.

[0048] In the embodiments of this application, the powder metallurgy engraving forming technology realizes a one-step leap from blank preparation to final die forging of irregular parts, omitting the pre-blanking process in the die forging process, and also omitting the corresponding mold costs and heating and processing costs of the pre-blanking process; in addition, the realization of powder metallurgy engraving forming technology can be combined with die forging technology to realize one-step die forging forming of more complex irregular parts.

[0049] In the embodiments of this application, the billet produced by the fully sealed gas-insulated engraving forming technology of powder metallurgy billet can achieve a significant improvement in the material utilization rate of irregular-shaped forgings after die forging, with the material utilization rate reaching more than 90%, the material cost of forgings reduced by 33.5%-55%, and the processing cost of forgings reduced by about 30%.

[0050] Example 2:

[0051] In this embodiment of the application, a powder metallurgy near-net-shape billet preparation process based on billet carving and trimming includes the following steps:

[0052] S1: Taking titanium alloys as an example, the HDH hydrogenation dehydrogenation method for titanium alloys involves placing sponge titanium in a hydrogen absorption furnace and subjecting it to a full hydrogen absorption reaction at a specific temperature of 550℃. This process aims to chemically react the titanium element in the sponge titanium with hydrogen gas, successfully converting it into titanium hydride (TiH2). This step is a crucial foundation for subsequent powder preparation. By precisely controlling the hydrogen absorption temperature and time, it is ensured that the sponge titanium is completely converted into TiH2, providing qualified raw materials for subsequent dehydrogenation and powder metallurgy forming processes.

[0053] S2: Titanium hydride powder with a D50 of 12 μm is prepared from sponge titanium using crushing equipment. First, the titanium hydride (TiH2) lumps formed after a complete hydrogen absorption reaction are physically crushed using specialized crushing equipment. This crushing process aims to gradually refine the lumpy titanium hydride to achieve the predetermined particle size distribution, ultimately obtaining titanium hydride powder with a D50 particle size of approximately 12 micrometers. This particle size parameter (D50: 12 μm) is a key indicator in powder metallurgy, directly affecting the powder's filling density, flowability, and the uniformity of the billet during subsequent cold isostatic pressing. By precisely controlling the crushing process parameters, it is possible to ensure that the obtained titanium hydride powder has a uniform particle size and regular shape, laying an important material foundation for the subsequent preparation of regular, dense near-net-shape billets.

[0054] S3: Titanium hydride powder is placed in a dehydrogenation furnace and subjected to a continuous dehydrogenation treatment at a set temperature of 580℃ for 6 hours. This crucial step aims to fully and stably release hydrogen from the titanium hydride (TiH2) powder by precisely controlling the dehydrogenation temperature and time, thereby converting it into pure titanium (Ti) powder. The dehydrogenation temperature of 580℃ is an optimized process parameter based on the thermal decomposition characteristics of titanium hydride, ensuring both efficient dehydrogenation reaction and effectively preventing powder particle sintering or growth due to excessive temperature. The long holding time of 6 hours provides sufficient thermodynamic conditions for complete hydrogen removal, ensuring the completeness and consistency of dehydrogenation. The entire dehydrogenation process is carried out under an inert atmosphere to prevent oxidation of the titanium powder at high temperatures. The dehydrogenated titanium powder obtained after this step has well-controlled chemical composition, particle size distribution, and particle morphology, providing a crucial material precursor for subsequent cold isostatic pressing to prepare high-density, high-performance near-net-shape blanks.

[0055] S4: According to the design requirements, prepare a rubber mold of the corresponding size. The mold shape is basically square, cylindrical, or ring-shaped to meet the geometric feature requirements of different near-net-shape parts. In an argon-protected glove box, load the dehydrogenated titanium powder or other metal powder prepared in step S4 into the rubber mold, ensuring uniform and dense powder filling without air ingress. Subsequently, perform cold isostatic pressing at a pressure of 180 MPa. This pressure value has been optimized to ensure that the powder particles are fully densified under three-dimensional isotropic pressure, while avoiding mold breakage or internal defects in the blank due to excessive pressure. Through this step, a near-net-shape blank with accurate dimensions, regular shape, and uniform internal density is finally obtained, laying a solid foundation for subsequent carving and shaping.

[0056] S5: High-purity argon gas is injected into a specially designed, fully sealed engraving machine to provide full-process atmospheric protection for the blank, effectively isolating it from oxygen and nitrogen and preventing oxidation or nitriding of the blank surface during high-temperature engraving. Using this automated engraving machine, based on a preset 3D digital model and processing path, the regular blank is precisely engraved into the complex material shape and contour required for final forging. This process achieves digital and refined forming from simple geometric blanks to near-net-shape parts, significantly reducing the material allowance and machining workload in subsequent forging.

[0057] S6: Carefully place the sculpted and shaped near-net-shape blank into a vacuum sintering furnace for high-temperature vacuum sintering. The sintering process parameters are set as follows: sinter at 1150℃ for 11 hours. This long sintering process aims to completely eliminate the porosity inside the blank through atomic diffusion and particle neck growth, promote metallurgical bonding between particles, and thus significantly improve the overall density, mechanical properties, and uniformity of the microstructure of the blank.

[0058] S7: The system collects the broken particles and cutting waste generated during the engraving process. Since the entire engraving process is completed under argon protection, these waste materials are not exposed to air, avoiding oxidation pollution. Therefore, these clean waste materials can be directly fed back into the crushing equipment and processed into fine powder with a particle size of approximately 12μm. This closed-loop process achieves clean recycling and reuse of engraving waste, significantly improving the utilization rate of powder materials and aligning with the concepts of green manufacturing and sustainable development.

[0059] S8: Precision die forging is used to finally forge near-net-shape billets that have undergone vacuum sintering and performance optimization. Die forging is carried out under controlled temperature and pressure conditions to further densify the material, accurately shape the final geometric dimensions and surface details of the parts, and optimize their internal streamline structure, thereby obtaining powder metallurgy near-net-shape parts with excellent comprehensive mechanical properties.

[0060] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A powder metallurgy near-net-shape billet preparation process based on billet carving and trimming, characterized in that, Includes the following steps: S1: Using the hydrogenation dehydrogenation method, sponge metal absorbs hydrogen in a hydrogen absorption furnace to form hydride metal; S2: The sponge metal is prepared into hydride metal powder using crushing equipment; S3: Place the hydride metal powder into the dehydrogenation furnace and perform heat preservation and dehydrogenation; S4: According to the design requirements, prepare a rubber mold of the corresponding size, load the hydride metal powder into the rubber mold in an argon-protected glove box, and perform cold isostatic pressing with a pressure set at 180MPa to obtain a regular billet of the corresponding size. S5: Argon gas is injected into a specially designed fully sealed engraving machine to protect the blank at the atmosphere. The automatic engraving machine is used to engrave the blank into the material shape required for final forging. S6: Place the carved blank into a vacuum sintering furnace for vacuum sintering; S7: The broken particles after carving are recycled and crushed back into powder. Since they are not exposed to air, carving waste can be reused. S8: The engraved blank is forged using a die forging method for final forging.

2. The powder metallurgy near-net-shape billet preparation process based on billet carving and trimming according to claim 1, characterized in that, The temperature inside the hydrogen absorption furnace in S1 is 500-550℃.

3. The powder metallurgy near-net-shape billet preparation process based on billet carving and trimming according to claim 1, characterized in that, The particle size of the hydride metal powder in S2 is D50: 12μm.

4. The powder metallurgy near-net-shape billet preparation process based on billet carving and trimming according to claim 1, characterized in that, The dehydrogenation process in S3 is carried out at 580°C for 6 hours.

5. The powder metallurgy near-net-shape billet preparation process based on billet carving and trimming according to claim 1, characterized in that, The mold shape in S4 is basically square, cylindrical or ring-shaped blank.

6. The powder metallurgy near-net-shape billet preparation process based on billet carving and trimming according to claim 1, characterized in that, The pressure of the cold isostatic pressure in S4 is set to 180 MPa.

7. The powder metallurgy near-net-shape billet preparation process based on billet carving and trimming according to claim 1, characterized in that, In the S6 process, vacuum sintering is performed at 1150°C for 11 hours.

8. The powder metallurgy near-net-shape billet preparation process based on billet carving and trimming according to claim 1, characterized in that, The particle size of the powder in S7 is 12 μm.

9. A powder metallurgy near-net-shape billet preparation process based on billet carving and trimming according to any one of claims 1-8, characterized in that, The metal is Ti metal.

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