A pure tungsten material and a processing method and device thereof

Abstract

The application discloses a kind of pure tungsten material and its processing method, device, the device includes a sealed cavity, the cavity is equipped with upper and lower parallel conductive plate, carrier for supporting tungsten green body is equipped between two conductive plates;The carrier includes metal net, and the lifting fixture for adjusting the spacing between metal net and conductive plate;The cavity is connected with water inlet pipe, water outlet pipe, gas inlet pipe, gas outlet pipe;The conductive plate is connected with electrically conductive heating body.The device of the application utilizes current heating, and the form of heat conduction and heat radiation is used to heat tungsten green body, and sintering temperature can be reached in a few minutes, greatly simplifies sintering process and sintering time, reduces the size of tungsten grain, and improves the performance of tungsten product.

Description

Technical Field

[0001] This invention relates to the field of refractory metal material preparation technology, specifically a pure tungsten material and its processing method and apparatus. Background Technology

[0002] Tungsten is a refractory metal with a melting point of 3308℃. It possesses excellent properties such as high strength, high hardness, high thermal conductivity, and high corrosion resistance. These characteristics make tungsten the best material for use in high-temperature and high-pressure environments, especially in aerospace, energy and power, and medical devices, where it plays an important role in industrial production and development.

[0003] Currently, the main methods for preparing tungsten include powder metallurgy, laser rapid prototyping, and metal powder injection molding. Laser rapid prototyping generates instantaneous localized high temperatures, melting tungsten powder and creating a metallurgical bond. After cooling, a tungsten product is obtained. However, the forming process generates a large temperature gradient, leading to defects such as edge warping and cracking in the tungsten product. Metal powder injection molding involves sintering a degreased tungsten green blank. Due to the numerous pores within the degreased green blank, it is difficult to obtain a highly dense tungsten product. Traditional powder metallurgy can produce dense tungsten products, but prolonged high-temperature sintering (2000-2400℃) causes tungsten grain coarsening, severely affecting the performance of the tungsten product. Chinese patent CN109047780A discloses a method for preparing highly dense sintered tungsten products. This patent involves mixing near-spherical fine tungsten powder with a paraffin binder to obtain a mixture, which is then subjected to a first cold isostatic pressing, degreasing, a second cold isostatic pressing, and sintering to obtain a highly dense tungsten product. However, this method involves cumbersome steps, requires sophisticated equipment, is time-consuming, and consumes a lot of energy, which is not conducive to the large-scale production of tungsten products.

[0004] In summary, current methods and apparatus for preparing pure tungsten materials suffer from problems such as cumbersome steps, demanding equipment requirements, long processing times, and high energy consumption, resulting in low production efficiency and hindering large-scale production of tungsten products. Therefore, there is an urgent need to develop an energy-efficient, high-performance, and easy-to-operate apparatus for the rapid preparation of pure tungsten materials. Summary of the Invention

[0005] The purpose of this invention is to provide a pure tungsten material and its processing method and apparatus to solve the problems mentioned in the background art, enabling rapid and efficient processing of pure tungsten material, and with simple operation.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] This invention discloses a processing apparatus for pure tungsten material, comprising a sealed cavity, wherein the cavity is provided with vertically parallel conductive plates, and a carrier for supporting tungsten green blanks is provided between the two conductive plates; the carrier includes a metal mesh and a lifting clamp for adjusting the distance between the metal mesh and the conductive plates; the cavity is connected to a water inlet pipe, a water outlet pipe, an air inlet pipe, and an air outlet pipe; and the conductive plates are connected to an electrically conductive heat conductor.

[0008] As a further aspect of the present invention: the electrically conductive heat conductor includes a connecting electrode connected to the lower end of the lower conductive plate and a loading electrode connected to one end of the connecting electrode; both the connecting electrode and the loading electrode are made of graphite.

[0009] As a further aspect of the present invention, the metal mesh and the lifting clamp are made of tungsten.

[0010] As a further aspect of the present invention, the distance between the metal mesh and the two conductive plates is 1-5 mm.

[0011] As a further aspect of the present invention, the conductive plate is made of graphite.

[0012] The second aspect of this invention discloses a processing method for preparing pure tungsten material using the above-described processing apparatus, comprising the following steps:

[0013] Highly active fine tungsten powder is pressed into shape to obtain tungsten green wafers; the particle size of the highly active fine tungsten powder is 400-500 mesh, and the pressing pressure is 300-500 MPa;

[0014] Tungsten green wafers are sintered at high temperature and then cooled with water to obtain pure tungsten sintered bodies.

[0015] As a further aspect of the present invention: the high-temperature sintering specifically includes:

[0016] The tungsten green billet is placed on a metal mesh, and the air inside the cavity is extracted through the exhaust pipe. Then, a nitrogen-hydrogen mixture with a hydrogen volume fraction of 15% is introduced through the intake pipe, so that the cavity is filled with a flowing nitrogen-hydrogen mixture atmosphere.

[0017] Connect the processing device to the current, controlling the current magnitude to 100-200A, to heat the tungsten green billet to 2400-2600℃ at a heating rate of 1000℃ / min, and hold it at that temperature for at least 5 minutes. The high heating rate utilizes the thermal effect of electric current; the total heat is equal to the square of the current × the resistance of the conductive graphite plate × the time the current passes through.

[0018] The third aspect of this invention discloses a pure tungsten material obtained by the above-described processing method.

[0019] As a further aspect of the present invention, the density is 94.8% or higher; the tungsten grain size is 4.03 μm or higher.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] 1. The device of the present invention uses electric current heating to heat the tungsten green billet through heat conduction and heat radiation, and can reach the sintering temperature in a few minutes, which greatly simplifies the sintering process and sintering time, reduces the size of tungsten grains, and improves the performance of tungsten products.

[0022] 2. The device of the present invention uses two layers of conductive graphite plates for heating, and the distance between the plates and the tungsten green billet is adjustable, so that the tungsten green billet can be heated evenly and the sintering process is accelerated.

[0023] 3. The device of the present invention selects a tungsten mesh as a heating carrier. The tungsten green billet does not come into direct contact with the conductive graphite plate, and the current does not pass directly through the tungsten green billet, so that the heating rate and real-time temperature are controllable, which facilitates the determination of sintering process parameters.

[0024] 4. This device is easy to operate, energy-saving and consumption-reducing, has a short sintering time and high production efficiency. This method can be extended to the preparation of other refractory metals. Attached Figure Description

[0025] Figure 1 This is a top view of the processing device in this invention;

[0026] Figure 2 This is a front view of the processing device in this invention;

[0027] Figure 3 The image shows the SEM fracture surface of the pure tungsten material prepared in Example 1 of this invention.

[0028] Figure 4 The image shows the SEM fracture surface of the pure tungsten material prepared in Example 2 of this invention.

[0029] Figure 5 This is a SEM fracture image of the pure tungsten material prepared in Example 3 of the present invention.

[0030] In the diagram: 1-Conductive plate, 2-Cavity, 21-Inlet pipe, 22-Outlet pipe, 23-Inlet pipe, 24-Outlet pipe, 3-Carrier, 31-Metal mesh, 32-Lifting clamp, 4-Electrically conductive heat conductor, 41-Connecting electrode, 42-Loading electrode. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] In the description of this invention, it should be noted that the terms "upper," "lower," "left," "right," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of this invention is usually placed during use. They are only used to facilitate the description of this invention and to simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0033] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0034] Please see Figure 1-5 In this embodiment of the invention, a processing device for pure tungsten material includes a sealed cavity 2. The cavity 2 is provided with vertically parallel conductive plates 1, and a carrier 3 for supporting tungsten green blanks is provided between the two conductive plates 1. The carrier 3 includes a metal mesh 31 and a lifting clamp 32 for adjusting the distance between the metal mesh 31 and the conductive plates 1. The lifting clamp 32 is prior art and will not be described in detail here. The cavity 2 is connected to a water inlet pipe 21, a water outlet pipe 22, an air inlet pipe 23, and an air outlet pipe 24. Two electrically conductive heat conductors 4 are symmetrically connected to the conductive plates 1.

[0035] Furthermore, the electrically conductive heat conductor 4 includes a connecting electrode 41 connected to the lower end of the lower conductive plate 1 and a loading electrode 42 connected to one end of the connecting electrode 41; both the connecting electrode 41 and the loading electrode 42 are made of graphite. The two conductive plates 1 are fixedly connected by conductive bolts made of graphite. A mounting hole is provided on one side of the connecting electrode 41, and the loading electrode 42 is inserted into the mounting hole, and the two are connected together by bolts.

[0036] Furthermore, the metal mesh 31 and the lifting clamp 32 are made of tungsten. The graphite carrier allows the tungsten green billet to be heated evenly, accelerating the sintering process.

[0037] Furthermore, the distance between the metal mesh 31 and the two conductive plates 1 is 1-5 mm.

[0038] Furthermore, the conductive plate 1 is made of graphite.

[0039] Examples 1-3 below were processed using the aforementioned processing apparatus. For detailed implementation methods, please refer to the examples. The SEM fracture morphology of the pure tungsten materials obtained in Examples 2-3 is shown in [the provided text]. Figure 3-5 .

[0040] Example 1

[0041] Highly active fine tungsten powder with a particle size of 1-3μm was pressed into shape at a pressing pressure of 400MPa and a holding time of 1min to obtain a tungsten green blank disc with a diameter of 1cm and a thickness of 2mm.

[0042] The tungsten green blank is placed on the metal mesh 31 (i.e., the tungsten mesh), which is located 1 mm above the lower graphite conductive plate 1, and the upper surface of the tungsten green blank is located 1 mm below the upper graphite conductive plate 1. Then, the air inside the cavity 2 is extracted through the exhaust pipe 24, and then a nitrogen-hydrogen mixture with a hydrogen volume fraction of 15% is introduced through the intake pipe 23. This process is repeated twice to ensure that the air is completely purged. Then, the intake pipe 23 and the exhaust pipe 24 are opened simultaneously to fill the cavity 2 with a flowing nitrogen-hydrogen mixture atmosphere.

[0043] Connect the two ends of the device to the current, and heat the tungsten green billet to 2400℃ at a heating rate of 1000℃ / min by controlling the current magnitude. Hold the temperature for 5 minutes, and then reduce the current to zero. By opening the water inlet pipe 21 and the water outlet pipe 22, circulating water is introduced to cool the billet to room temperature for 10 minutes, thus obtaining the tungsten sintered body.

[0044] Example 2

[0045] Highly active fine tungsten powder with a particle size of 1-3μm was pressed into shape at a pressing pressure of 400MPa and a holding time of 1min to obtain a tungsten green blank disc with a diameter of 1cm and a thickness of 2mm.

[0046] The tungsten green blank is placed on a tungsten mesh, which is 1 mm above the lower graphite conductive plate 1. The upper surface of the tungsten green blank is 1 mm below the upper graphite conductive plate 1. Then, the air in the cavity 2 is extracted through the exhaust pipe 24, and a nitrogen-hydrogen mixture with a hydrogen volume fraction of 15% is introduced through the intake pipe 23. This process is repeated twice to ensure that the air is completely purged. Then, the intake pipe 23 and the exhaust pipe 24 are opened simultaneously to fill the cavity 2 with a flowing nitrogen-hydrogen mixture atmosphere.

[0047] Connect the two ends of the device to the current, and heat the tungsten green billet to 2500℃ at a heating rate of 1000℃ / min by controlling the current magnitude. Hold the temperature for 5 minutes, and then reduce the current to zero. By opening the water inlet pipe 21 and the water outlet pipe 22, circulating water is introduced to cool the billet to room temperature for 10 minutes, thus obtaining the tungsten sintered body.

[0048] Example 3

[0049] Highly active fine tungsten powder with a particle size of 1-3μm was pressed into shape at a pressing pressure of 400MPa and a holding time of 1min to obtain a tungsten green blank disc with a diameter of 1cm and a thickness of 2mm.

[0050] The tungsten green blank is placed on a tungsten mesh, which is 1 mm above the lower graphite conductive plate 1. The upper surface of the tungsten green blank is 1 mm below the upper graphite conductive plate 1. Then, the air inside the cavity 2 is extracted through the exhaust pipe 24. Then, a nitrogen-hydrogen mixture with a hydrogen volume fraction of 15% is introduced through the intake pipe 23. This process is repeated twice to ensure that the air is completely purged. Then, the intake pipe 23 and the exhaust pipe 24 are opened simultaneously to fill the cavity 2 with a flowing nitrogen-hydrogen mixture atmosphere.

[0051] Connect the two ends of the device to the current, and heat the tungsten green billet to 2600℃ at a heating rate of 1000℃ / min by controlling the current magnitude. Hold the temperature for 5 minutes, and then reduce the current to zero. Circulate water is introduced by opening the water inlet pipe 21 and the water outlet pipe 22 to cool the billet to room temperature for 10 minutes, thus obtaining the tungsten sintered body.

[0052] The tungsten sintered bodies obtained in Examples 1-3 were subjected to density tests. The density and grain size observed by SEM fracture images are recorded in Table 1. The density test procedure is as follows: The density of the tungsten sintered body was tested using the Archimedes displacement method. The mass m1 of the tungsten sintered body in air was recorded, followed by the mass m2 in deionized water. The density of the tungsten sintered body was calculated using the following formula.

[0053]

[0054] Then, by looking up the table, the theoretical density ρ of tungsten is obtained. 理 The density of tungsten sintered body is calculated using the following formula:

[0055]

[0056] Table 1

[0057] Example Sintering temperature (°C) Density (%) Grain size (μm) Example 1 2400 94.8 4.03 Example 2 2500 95.5 5.71 Example 3 2600 96.1 6.31

[0058] As shown in Table 1, under the same holding time, the density and grain size of the tungsten sintered body increase with increasing sintering temperature. This is because high temperature promotes diffusion between powder particles, which is conducive to interparticle bonding and increases the density of the sintered body. At the same time, the increase in sintering temperature promotes the movement of grain boundary atoms, reduces interfacial energy, intensifies the engulfment between grains, and causes spontaneous and rapid grain growth, leading to grain coarsening.

[0059] Although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0060] Therefore, the above description is only a preferred embodiment of this application and is not intended to limit the scope of this application; that is, all equivalent modifications made in accordance with the scope of the claims of this application shall be within the protection scope of the claims of this application.

Claims

1. A processing method for preparing pure tungsten material using a processing apparatus for pure tungsten material, the processing apparatus comprising: A sealed cavity contains two parallel conductive plates, with a carrier supporting a tungsten green billet positioned between them. The carrier includes a metal mesh and a lifting clamp for adjusting the distance between the metal mesh and the conductive plates. The cavity is connected to an inlet pipe, an outlet pipe, an air inlet pipe, and an outlet pipe. Each conductive plate is connected to a heat-conducting element. The heat-conducting element includes a connecting electrode connected to the lower end of the lower conductive plate and a loading electrode connected to one end of the connecting electrode. Both the connecting electrode and the loading electrode are made of graphite. The distance between the metal mesh and the two conductive plates is 1-5 mm. The cavity is characterized by the following steps: Highly active fine tungsten powder is pressed into shape to obtain tungsten green wafers; the particle size of the highly active fine tungsten powder is 400-500 mesh, and the pressing pressure is 300-500 MPa; Tungsten green wafers are sintered at high temperature and then cooled with water to obtain pure sintered tungsten bodies. The high-temperature sintering specifically includes: The tungsten green wafer is placed on a metal mesh. The air inside the cavity is extracted through the exhaust pipe, and then a nitrogen-hydrogen mixture with a hydrogen volume fraction of 15% is introduced through the intake pipe, so that the cavity is filled with a flowing nitrogen-hydrogen mixture atmosphere. The processing device is connected to the current, and the current is controlled to heat the tungsten green wafer to 2400-2600℃ at a heating rate of 1000℃ / min, and hold it at that temperature for more than 5 minutes.

2. The processing method according to claim 1, characterized in that, The metal mesh and lifting clamp are made of tungsten.

3. The processing method according to claim 1, characterized in that, The conductive plate is made of graphite.

4. A pure tungsten material, characterized in that, Obtained by the processing method according to any one of claims 1-3.

5. The pure tungsten material according to claim 4, characterized in that, Its density is above 94.8%; the tungsten grain size is above 4.03μm.

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