Medium-particle tungsten powder and preparation method thereof

Abstract

The invention belongs to the technical field of tungsten powder preparation, and particularly relates to medium-particle tungsten powder and a preparation method thereof.The preparation method comprises the following steps that tungsten trioxide powder with the Fisher particle size being 3-6 m, the specific surface area being 4.5-8.5 m < 2 > / g and the apparent density being 1.5-2.2 g / cm < 3 > is obtained; the method comprises the following steps: respectively reducing tungsten trioxide powder by adopting hydrogen at 650-700 DEG C, 800-850 DEG C and 1000-1050 DEG C, and sieving to obtain the medium-particle tungsten powder. According to the method, the low-apparent-density tungsten oxide powder is selected, and staged heating reduction is adopted, so that the hydrogen utilization rate can be increased, the oxygen content in tungsten oxide is reduced, and the tungsten oxide is reduced more thoroughly; by controlling the low hydrogen flow, the hydrogen return pressure and the dew point, it is ensured that tungsten oxide is thoroughly reduced, the volatilization deposition effect is remarkable, and the tungsten powder is complete in development, regular in shape and free of fine agglomerated particles which are not thoroughly reduced or high in oxygen content.

Description

Technical Field

[0001] This application belongs to the field of tungsten powder preparation technology, specifically a medium-particle tungsten powder and its preparation method. Background Technology

[0002] Medium-sized tungsten powder (typically referring to powder with a particle size ranging from a few micrometers to tens of micrometers) achieves a good balance between flowability and pressing performance, possesses good filling properties and moderate sintering activity, and is a core raw material for many conventional tungsten products. It is mainly used to prepare tungsten carbide powder, which is then used to produce various cemented carbide cutting tools, drilling tools, and wear-resistant parts. It is also widely used in the manufacture of tungsten-copper, tungsten-silver, and other electrical alloy contacts, as well as high-density alloy counterweights, armor-piercing projectile cores, and other military products. It is a key basic material supporting traditional manufacturing, the power and electrical industry, and the defense industry.

[0003] The core issues with the microstructure of medium-particle tungsten powder are the presence of irregularly shaped particles, a tendency to agglomerate, and the presence of fine agglomerates with incomplete reduction or high oxygen content. These problems significantly degrade the performance of subsequent tungsten products. Irregularly shaped or incompletely reduced / high oxygen-content fine agglomerates have poor flowability, making it difficult to fill evenly during molding or injection molding. This results in uneven density distribution in the compact, which easily leads to deformation, cracking, or internal porosity defects after sintering, directly affecting the dimensional accuracy, density, and mechanical strength of the product. Furthermore, powder agglomeration severely hinders its uniform mixing with other components such as carbon black and binders. For example, in cemented carbide production, uneven mixing can cause localized compositional abnormalities during carburization, generating harmful free carbon or brittle phases, ultimately weakening the product's wear resistance and service life. Therefore, optimizing the dispersibility of tungsten powder and producing medium-particle tungsten powder with complete reduction of tungsten oxide and low oxygen content are key to improving its processing performance and product quality. Summary of the Invention

[0004] To address the problems in the current industrial-scale preparation of granular tungsten powder, such as irregular particle shapes, tungsten oxide morphology, and the presence of fine agglomerated tungsten powder particles with incomplete reduction and high oxygen content, which adversely affect the performance of subsequent products, this application provides a medium-sized tungsten powder and its preparation method.

[0005] According to a first aspect of this application, this application provides a method for preparing medium-particle tungsten powder, comprising the following steps: S1. Obtain tungsten trioxide powder; The tungsten trioxide powder has a Fisher particle size of 3-6 µm and a specific surface area of ​​4.5-8.5 m². 2 / g, loose bulk density is 1.5~2.2g / cm³ 3 ; S2. In the reduction furnace, hydrogen is used to reduce the tungsten trioxide powder at a first temperature, a second temperature, and a third temperature to obtain crude tungsten powder. The flow rate of the hydrogen gas is 20~30m³. 3 / h, return hydrogen pressure is 2~3kPa, dew point is -50~-30℃; The first temperature is 650~700℃, the second temperature is 800~850℃, and the third temperature is 1000~1050℃; S3. The coarse tungsten powder is sieved to obtain medium-particle tungsten powder.

[0006] Furthermore, in step S2, the amount of tungsten trioxide powder loaded into the boat is 0.7~1.2 kg / boat.

[0007] Furthermore, in step S2, the time for reducing the tungsten trioxide powder at the first temperature is 50-70 minutes.

[0008] Furthermore, in step S2, the time for reducing the tungsten trioxide powder at the second temperature is 50-70 minutes.

[0009] Furthermore, in step S2, the time for reducing the tungsten trioxide powder at the third temperature is 50-70 minutes.

[0010] Furthermore, in step S3, the Fisher particle size of the medium-sized tungsten powder is 3.0~3.8μm.

[0011] Furthermore, in step S3, the oxygen content of the medium-sized tungsten powder is less than or equal to 0.025%.

[0012] According to a second aspect of this application, this application provides a medium-particle tungsten powder, which is prepared by the above-described method for preparing medium-particle tungsten powder.

[0013] This application proposes a medium-particle tungsten powder and its preparation method, which produces the following beneficial effects: by selecting tungsten oxide powder with low bulk density and adopting staged heating reduction, the hydrogen utilization rate can be improved, the oxygen content in tungsten oxide can be reduced, and its reduction can be more thorough; by controlling low hydrogen flow rate, return hydrogen pressure and dew point, the complete reduction of tungsten oxide and the significant volatilization deposition effect are ensured, resulting in tungsten powder with complete development, regular morphology, and no fine agglomerates of incompletely reduced / high oxygen content. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of this application or 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 only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0015] Figure 1 This is an electron microscope image of the medium-particle tungsten powder prepared in Example 1 of this application; Figure 2 This is an electron microscope image of the medium-particle tungsten powder prepared in Example 2 of this application; Figure 3 This is an electron microscope image of the medium-particle tungsten powder prepared in Example 3 of this application; Figure 4 This is an electron microscope image of the medium-particle tungsten powder prepared in Example 4 of this application; Figure 5 This is an electron microscope image of the medium-particle tungsten powder prepared in Comparative Example 1 of this application; Figure 6 Electron micrograph of medium-particle tungsten powder prepared in Comparative Example 2 of this application; Figure 7 This is an electron microscope image of the medium-particle tungsten powder prepared in Comparative Example 3 of this application; Figure 8 This is an electron microscope image of the medium-particle tungsten powder prepared in Comparative Example 4 of this application; Figure 9 This is an electron microscope image of the medium-particle tungsten powder prepared in Comparative Example 5 of this application.

[0016] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0017] The technical solutions in the embodiments will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0018] According to a first aspect of this application, this application provides a method for preparing medium-particle tungsten powder, comprising the following steps: S1. Obtain tungsten trioxide powder; The tungsten trioxide powder has a Fisher particle size of 3–6 µm and a specific surface area of ​​4.5–8.5 m². 2 / g, loose bulk density is 1.5~2.2g / cm³ 3 ; Specifically, the Fisher particle size of the tungsten trioxide powder can be any one of 3µm, 3.5µm, 4µm, 4.5µm, 5µm, 5.5µm, and 6µm, or any combination thereof, and the specific surface area can be 4.5m². 2 / g, 5.0m 2 / g, 5.5m 2 / g, 6.0m 2 / g, 6.5m 2 / g, 7.0m 2 / g, 7.5m 2 / g, 8.0m 2 / g, 8.5m 2 The loose bulk density can be 1.5 g / cm³, which is a range of any one or both of the values ​​in g. 3 1.6g / cm 3 1.7g / cm 3 1.8g / cm 3 1.9g / cm 3 2.0g / cm 3 2.1g / cm 3 2.2g / cm 3 The range between any one of them or any two of them.

[0019] Tungsten trioxide powder, characterized by its large specific surface area, low bulk density, and numerous interparticle pores, is advantageous in traditional tubular reduction furnaces during boat charging. The numerous pores facilitate the entry of hydrogen gas, allowing for a thorough reaction with the tungsten oxide particles and improving hydrogen utilization, resulting in completely reduced tungsten powder. Furthermore, under the same conditions, tungsten trioxide with its low bulk density allows for a larger charge (up to 30% in boat loading) without affecting product performance, thus significantly increasing production. However, tungsten trioxide powder, with its coarse particle size, small specific surface area, and high bulk density, is prone to producing incompletely reduced / high-oxygen-content fine agglomerates during large-scale boat reduction, affecting product quality. Therefore, it is necessary to control the properties of the tungsten trioxide powder within a suitable range. In some preferred embodiments of this application, a Fisher particle size of 16-20 µm and a specific surface area of ​​4-8 m² can be used. 2 / g of tungsten trioxide raw material is crushed by a crusher to obtain the tungsten trioxide powder; the Fisher particle size is 16~20µm and the specific surface area is 4~8m². 2 / g of tungsten trioxide raw material has high surface activity and is relatively loose, with weak interparticle bonding. Large agglomerates can be dispersed into individual small particles under low external force, which is beneficial for crushing and pretreatment. Using this type of tungsten trioxide as raw material to prepare tungsten trioxide with low Fisher particle size and low bulk density can greatly reduce costs.

[0020] S2. In the reduction furnace, hydrogen is used to reduce tungsten trioxide powder at the first temperature, the second temperature, and the third temperature to obtain crude tungsten powder. The flow rate of hydrogen is 20~30m³. 3 / h, return hydrogen pressure is 2~3kPa, dew point is -50~-30℃; The first temperature is 650~700℃, the second temperature is 800~850℃, and the third temperature is 1000~1050℃; Preferably, the amount of tungsten trioxide powder loaded into the boat is 0.7~1.2 kg / boat, and the reduction time at the first temperature, the second temperature, and the third temperature is 50~70 min. Specifically, the hydrogen flow rate can be 20m³. 3 / h、22m 3 / h、24m 3 / h、26m 3 / h、28m 3 / h, 30m 3 The range of / h can be any one or any two of the following: the return hydrogen pressure can be any one or any two of 2kPa, 2.2kPa, 2.4kPa, 2.6kPa, 2.8kPa, 3kPa; the dew point can be any one or any two of -50℃, -45℃, -40℃, -35℃, -30℃; the first temperature can be any one or any two of 650℃, 660℃, 670℃, 680℃, 690℃, 700℃; the second temperature can be any one or any two of 800℃, 810℃, 820℃, 830℃, 840℃, 850℃; and the third temperature can be any one or any two of 1000℃, 1010℃, 1020℃, 1030℃, 1040℃, 1050℃.

[0021] In the reduction process described above, the temperature is increased in stages. The first temperature is set below 700℃ to increase the content of low-oxygen index tungsten oxide, effectively suppress the volatilization and deposition effect of tungsten oxide, reduce the probability of tungsten oxide being encapsulated due to deposition, and increase the probability of contact with hydrogen, thereby promoting the complete reduction of tungsten oxide. If the second temperature is too low, deoxidation may be incomplete, resulting in a high oxygen content in the generated tungsten powder. If the third temperature is too high, the tungsten powder will sinter, resulting in many sintering necks, which is not conducive to obtaining tungsten powder with regular morphology, and also results in high energy consumption for ultrasound. If the hydrogen flow rate is too low, the reduction may be incomplete, while if it is too high, the generated tungsten powder will have a finer particle size and more tungsten powder particles that retain the morphology of tungsten oxide. If the return hydrogen pressure is too low, water vapor will be discharged too quickly, which is not conducive to consuming fine tungsten oxide particles and promoting the volatilization, deposition, and growth of tungsten powder particles. If the return hydrogen pressure is too high, the system airflow will be obstructed, which is not conducive to the stable control of hydrogen flow rate, resulting in large fluctuations in tungsten powder particle size. If the hydrogen dew point is too high, the product is prone to oxidation, while if the dew point is too low, it is not conducive to the volatilization, deposition, and growth of the product. If the reduction time is too long, energy consumption will be high and production efficiency will be low; if the reduction time is too short, the reaction will be incomplete.

[0022] S3. Sift the coarse tungsten powder to obtain medium-particle tungsten powder; Preferably, the coarse tungsten powder is passed through a 325-mesh sieve to obtain medium-sized tungsten powder with a Fisher particle size of 3.0~3.8μm and an oxygen content of less than or equal to 0.025%.

[0023] After obtaining the crude tungsten powder, it is necessary to remove the larger particles and mechanical inclusions by sieving. Since the particle size of medium-sized tungsten powder is generally in the range of a few micrometers to tens of micrometers, a sieve such as 325 mesh can be used for sieving to obtain tungsten powder with a more uniform particle size.

[0024] According to a second aspect of this application, this application provides a medium-particle tungsten powder, which is prepared by the above-described method for preparing medium-particle tungsten powder.

[0025] The technical solution of this application will be further described below with reference to specific embodiments.

[0026] Example 1 A method for preparing medium-sized tungsten powder includes the following steps: S1. Obtain a Fisher particle size of 3µm and a specific surface area of ​​8.5m². 2 / g, loose bulk density is 1.5g / cm³ 3 Tungsten trioxide powder; S2. In the reduction furnace, hydrogen is used to reduce tungsten trioxide powder for 70 minutes at a first temperature of 700℃, a second temperature of 850℃, and a third temperature of 1050℃ respectively to obtain crude tungsten powder. The flow rate of hydrogen is 20m³. 3 / h, return hydrogen pressure is 3kPa, dew point is -30℃, and the amount of tungsten trioxide powder loaded in the boat is 1.2kg / boat; S3. Pass the coarse tungsten powder through a 325-mesh sieve to obtain medium-particle tungsten powder, wherein the Fisher particle size of the medium-particle tungsten powder is 3.8µm and the oxygen content is 0.018%; The electron microscope image of the medium-particle tungsten powder prepared in this embodiment is as follows: Figure 1 As shown, its particles are relatively well-developed, with a relatively regular morphology, and no small agglomerated particles that are not completely reduced or have high oxygen content.

[0027] Example 2 A method for preparing medium-sized tungsten powder includes the following steps: S1. Obtain a Fisher particle size of 6µm and a specific surface area of ​​4.5m². 2 / g, loose bulk density is 2.2g / cm³ 3 Tungsten trioxide powder; S2. In the reduction furnace, hydrogen is used to reduce tungsten trioxide powder for 50 minutes at a first temperature of 650℃, a second temperature of 800℃, and a third temperature of 1000℃ respectively to obtain crude tungsten powder. The flow rate of hydrogen is 30m³. 3 / h, return hydrogen pressure is 2kPa, dew point is -50℃, and the amount of tungsten trioxide powder loaded into the boat is 0.7kg / boat; S3. Pass the coarse tungsten powder through a 325-mesh sieve to obtain medium-particle tungsten powder, wherein the Fisher particle size of the medium-particle tungsten powder is 3.0µm and the oxygen content is 0.025%; The electron microscope image of the medium-particle tungsten powder prepared in this embodiment is as follows: Figure 2 As shown, its particles are relatively well-developed, with a relatively regular morphology, and no small agglomerated particles that are not completely reduced or have high oxygen content.

[0028] Example 3 A method for preparing medium-sized tungsten powder includes the following steps: S1. Obtain a Fisher particle size of 5µm and a specific surface area of ​​6.5m². 2 / g, loose bulk density is 1.9g / cm³ 3 Tungsten trioxide powder; S2. In the reduction furnace, hydrogen is used to reduce tungsten trioxide powder for 60 minutes at a first temperature of 680℃, a second temperature of 830℃, and a third temperature of 1020℃ respectively to obtain crude tungsten powder. The flow rate of hydrogen is 25m³. 3 / h, return hydrogen pressure is 2.5kPa, dew point is -40℃, and the amount of tungsten trioxide powder loaded in the boat is 1.0kg / boat; S3. Pass the coarse tungsten powder through a 325-mesh sieve to obtain medium-particle tungsten powder, wherein the Fisher particle size of the medium-particle tungsten powder is 3.5µm and the oxygen content is 0.021%; The electron microscope image of the medium-particle tungsten powder prepared in this embodiment is as follows: Figure 3 As shown, its particles are relatively well-developed, with a relatively regular morphology, and no small agglomerated particles that are not completely reduced or have high oxygen content.

[0029] Example 4 A method for preparing medium-sized tungsten powder includes the following steps: S1. Obtain a Fisher particle size of 3µm and a specific surface area of ​​8.5m². 2 / g, loose bulk density is 1.5g / cm³ 3 Tungsten trioxide powder; S2. In the reduction furnace, hydrogen is used to reduce tungsten trioxide powder for 60 minutes at a first temperature of 650℃, a second temperature of 800℃, and a third temperature of 1050℃ respectively to obtain crude tungsten powder. The flow rate of hydrogen is 28m³. 3 / h, return hydrogen pressure is 3kPa, dew point is -40℃, and the amount of tungsten trioxide powder loaded into the boat is 1.0kg / boat; S3. Pass the coarse tungsten powder through a 325-mesh sieve to obtain medium-particle tungsten powder, wherein the Fisher particle size of the medium-particle tungsten powder is 3.3µm and the oxygen content is 0.015%; The electron microscope image of the medium-particle tungsten powder prepared in this embodiment is as follows: Figure 4 As shown, its particles are relatively well-developed, with a relatively regular morphology, and no small agglomerated particles that are not completely reduced or have high oxygen content.

[0030] Comparative Example 1 The only difference between this comparative example and Example 4 is that, in step S1, the Fisher particle size is 6µm and the specific surface area is 1.8m². 2 / g, loose bulk density is 2.8g / cm³ 3 The tungsten trioxide powder obtained in step S3 has a Fisher particle size of 4.3 µm and an oxygen content of 0.032%. Electron microscopy images of the medium-particle tungsten powder prepared in this comparative example are shown below. Figure 5 As shown, most of its particles are relatively well-developed and have a relatively regular morphology, but there are still small aggregated particles that are not completely reduced or have a high oxygen content.

[0031] Comparative Example 2 The only differences between this comparative example and Example 4 are: in step S2, the hydrogen return pressure is 3 kPa; and in step S3, the obtained medium-particle tungsten powder has a Fisher particle size of 2.8 µm and an oxygen content of 0.045%. Electron microscopy images of the medium-particle tungsten powder prepared in this comparative example are shown below. Figure 6 As shown, most of its particles are relatively well-developed and have a relatively regular morphology, but there are still small aggregated particles that are not completely reduced or have a high oxygen content.

[0032] Comparative Example 3 The only difference between this comparative example and Example 4 is that in step S2, the first temperature is 750°C; and in step S3, the obtained medium-particle tungsten powder has a Fisher particle size of 3.5µm and an oxygen content of 0.037%. Electron microscopy images of the medium-particle tungsten powder prepared in this comparative example are shown below. Figure 7 As shown, most of its particles are relatively well-developed and have a relatively regular morphology, but there are still small aggregated particles that are not completely reduced or have a high oxygen content.

[0033] Comparative Example 4 The only differences between this comparative example and Example 4 are: in step S2, the dew point of hydrogen is -75°C; and in step S3, the obtained medium-particle tungsten powder has a Fisher particle size of 2.9µm and an oxygen content of 0.043%. Electron microscopy images of the medium-particle tungsten powder prepared in this comparative example are shown below. Figure 8 As shown, most of its particles are relatively well-developed and have a relatively regular morphology, but there are still small aggregated particles that are not completely reduced or have a high oxygen content.

[0034] Comparative Example 5 The only difference between this comparative example and Example 4 is that, in step S2, the hydrogen flow rate is 16m³. 3 / h; In step S3, the medium-particle tungsten powder obtained has a Fisher particle size of 4.2µm and an oxygen content of 0.30%; Electron microscopy images of the medium-particle tungsten powder prepared in this comparative example are shown below. Figure 9 As shown, most of its particles are relatively well-developed and have a relatively regular morphology, but there are still small aggregated particles that are not completely reduced or have a high oxygen content.

[0035] This application proposes a medium-particle tungsten powder and its preparation method, which produces the following beneficial effects: by selecting tungsten oxide powder with low bulk density and adopting staged heating reduction, the hydrogen utilization rate can be improved, the oxygen content in tungsten oxide can be reduced, and its reduction can be more thorough; by controlling low hydrogen flow rate, return hydrogen pressure and dew point, the complete reduction of tungsten oxide and the significant volatilization deposition effect are ensured, resulting in tungsten powder with complete development, regular morphology, and no fine agglomerates of incompletely reduced / high oxygen content.

[0036] The above description is only a preferred embodiment of this application and does not limit the patent scope of this application. All equivalent structural transformations made using the content of this application's specification under the inventive concept of this application, or direct / indirect applications in other related technical fields, are included within the patent protection scope of this application.

Claims

1. A method for preparing medium-particle tungsten powder, characterized in that, Includes the following steps: S1. Obtain tungsten trioxide powder; The tungsten trioxide powder has a Fisher particle size of 3-6 µm and a specific surface area of ​​4.5-8.5 m². 2 / g, loose bulk density is 1.5~2.2g / cm³ 3 ; S2. In the reduction furnace, hydrogen is used to reduce the tungsten trioxide powder at a first temperature, a second temperature, and a third temperature to obtain crude tungsten powder. The flow rate of the hydrogen gas is 20~30m³. 3 / h, return hydrogen pressure is 2~3kPa, dew point is -50~-30℃; The first temperature is 650~700℃, the second temperature is 800~850℃, and the third temperature is 1000~1050℃; S3. The coarse tungsten powder is sieved to obtain medium-particle tungsten powder.

2. The method for preparing medium-particle tungsten powder according to claim 1, characterized in that, In step S2, the amount of tungsten trioxide powder loaded into the boat is 0.7~1.2 kg / boat.

3. The method for preparing medium-particle tungsten powder according to claim 1, characterized in that, In step S2, the time for reducing the tungsten trioxide powder at the first temperature is 50-70 minutes.

4. The method for preparing medium-particle tungsten powder according to claim 1, characterized in that, In step S2, the time for reducing the tungsten trioxide powder at the second temperature is 50-70 minutes.

5. The method for preparing medium-particle tungsten powder according to claim 1, characterized in that, In step S2, the time for reducing the tungsten trioxide powder at the third temperature is 50-70 minutes.

6. The method for preparing medium-particle tungsten powder according to claim 1, characterized in that, In step S3, the Fisher particle size of the medium-sized tungsten powder is 3.0~3.8μm.

7. The method for preparing medium-particle tungsten powder according to claim 1, characterized in that, In step S3, the oxygen content of the medium-sized tungsten powder is less than or equal to 0.025%.

8. A medium-particle tungsten powder, characterized in that, It is prepared by the method for preparing medium-particle tungsten powder according to any one of claims 1 to 7.

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