Superfine tungsten powder and preparation method thereof

Abstract

The invention belongs to the technical field of powder metallurgy production, and particularly relates to superfine tungsten powder and a preparation method thereof.The preparation method comprises the following steps that purple tungsten is obtained; the purple tungsten is reduced in a reactor in a hydrogen atmosphere, the reactor is sequentially provided with a heating section and a cooling section from a feeding end to a discharging end, the heating section is sequentially composed of a pre-reduction section, a main reduction section and a deoxidation section, the pre-reduction section adopts a first spiral conveying blade for raising materials, and the main reduction section adopts a second spiral conveying blade for deoxidation. The main reduction section adopts a second spiral conveying blade to lift materials, and the deoxidation section adopts a third spiral conveying blade to lift materials; and finally, the superfine tungsten powder which is narrow in particle size distribution, low in oxygen content and high in recovery rate is obtained through cooling of the cooling section.

Description

Technical Field

[0001] The present invention belongs to the technical field of powder smelting, and in particular relates to ultrafine tungsten powder and a preparation method thereof. Background Art

[0002] Tungsten is a key strategic resource in my country, widely used in key areas such as cemented carbide. Metal cutting tools, molds, wear-resistant parts, and other related products made of tungsten meet many of the needs of modern industrial development. With the advancement of industrialization and the development of precision high-end manufacturing, traditional cemented carbide is no longer sufficient to meet the needs of modern industry. This has led to the development of ultrafine cemented carbide, which exhibits superior performance in strength, hardness, and fracture toughness compared to conventional cemented carbide. It is widely used in the automotive, aerospace, and 3C industries as high-efficiency precision cutting tools, micro-drills, micro-milling machines, blades, and precision molds.

[0003] Ultrafine tungsten powder is one of the key raw materials for the production of ultrafine cemented carbide, and its performance directly impacts its development. Currently, the hydrogen reduction method is the primary method for industrially producing high-quality ultrafine tungsten powder. This method is characterized by simplicity, reliability, low cost, and ease of automated production. The main steps of this process are: tungsten oxide is reduced with hydrogen through heating to produce tungsten powder; this is then sieved and passivated to obtain the ultrafine tungsten powder.

[0004] In actual industrial production, multi-tube pusher boat furnaces, tubular pusher boat furnaces, or rotary kilns are often used. The reduction principle of multi-tube pusher boat furnaces is static reduction. This means that the raw tungsten oxide is loaded into an alloy boat, and the material layer in the boat is static relative to the hydrogen atmosphere. The thickness and flatness of the material layer in the boat directly affect the adequacy of tungsten powder reduction, the integrity of the crystallization, and the uniformity of the particle size distribution of the resulting ultrafine tungsten powder. Therefore, using multi-tube pusher boat furnaces makes it difficult to produce high-quality and stable ultrafine tungsten powder. Fully enclosed production is difficult, and the equipment suffers from low output, high energy consumption, and high costs.

[0005] The rotary kiln reduction method for preparing ultrafine tungsten powder is dynamic reduction, meaning the material is periodically turned within the furnace tube, resulting in more uniform heating of the material. This increases the contact between tungsten oxide and hydrogen, allowing the water vapor produced by the reaction to be quickly discharged from the material, reducing the volatilization and deposition growth of tungsten hydrates. This results in ultrafine tungsten powder with a more uniform particle size. The use of a rotary kiln to produce ultrafine tungsten powder is currently the most common method in actual production.

[0006] Traditional rotary furnaces also have certain structural flaws. For example, the lifting plates within the furnace tubes are typically a single structure running the entire length, which prevents targeted material processing during the pre-reduction, main reduction, and deoxidation stages. This results in low reaction efficiency and high energy consumption. Single-tube rotary furnaces also suffer from low tungsten powder recovery rates. Some rotary furnaces utilize a dual-tube design with lifting plates installed within the tubes. However, these plates are uniformly distributed throughout the tubes, failing to consider the process requirements of different reaction stages. This further results in a wide particle size distribution in the produced powder and incomplete deoxidation.

[0007] Therefore, there is an urgent need for a method for preparing ultrafine tungsten powder with narrow particle size distribution, low oxygen content and high recovery rate. Summary of the Invention

[0008] In order to obtain ultrafine tungsten powder with narrow particle size distribution, low oxygen content and high recovery rate, the present invention provides an ultrafine tungsten powder and a preparation method thereof. The preparation method comprises: obtaining purple tungsten; reducing the purple tungsten in a reactor with a hydrogen atmosphere, the reactor being sequentially composed of a heating section and a cooling section from a feed end to a discharge end, the heating section being sequentially composed of a pre-reduction section, a main reduction section and a deoxidation section, the pre-reduction section using a first spiral conveying blade for lifting material, the main reduction section using a second spiral conveying blade for lifting material, and the deoxidation section using a third spiral conveying blade for lifting material; and finally cooling through a cooling section to obtain ultrafine tungsten powder with narrow particle size distribution, low oxygen content and high recovery rate.

[0009] According to one aspect of the present invention, the present invention provides the following technical solutions: A method for preparing ultrafine tungsten powder comprises the following steps: S1, obtaining violet tungsten; S2. Reducing the violet tungsten in a reactor under a hydrogen atmosphere, wherein the reactor is sequentially composed of a heating section and a cooling section from a feed end to a discharge end, wherein the heating section is sequentially composed of a pre-reduction section, a main reduction section, and a deoxidation section, wherein the pre-reduction section uses a first spiral conveying blade to lift the material, the main reduction section uses a second spiral conveying blade to lift the material, and the deoxidation section uses a third spiral conveying blade to lift the material, to obtain a first tungsten powder; S3. The first tungsten powder is cooled in a cooling section to obtain a second tungsten powder, wherein the particle size distribution width of the second tungsten powder, that is, the span value is less than 0.90.

[0010] As a preferred embodiment of the method for preparing ultrafine tungsten powder described in the present invention, in step S2, the length ratio of the cooling section to the heating section is (3-4):(7-8), the pre-reduction section, the main reduction section and the deoxidation section are the same length; the pitch of the first spiral conveying blade is 60-100 mm, the first spiral conveying blade is evenly and discontinuously arranged along the spiral direction, and the proportion of the portion without spiral conveying blades is 20-40%; the pitch of the second spiral conveying blade is 100-140 mm, the second spiral conveying blade is evenly and discontinuously arranged along the spiral direction, and the proportion of the portion without spiral conveying blades is 45-55%; the pitch of the third spiral conveying blade is 180-220 mm, and the third spiral conveying blade is continuously arranged along the spiral direction.

[0011] As a preferred embodiment of the method for preparing ultrafine tungsten powder described in the present invention, in step S2, the reactor is a rotary kiln, and the purple tungsten is reduced by using the rotary kiln. The inclination angle of the furnace body of the rotary kiln is set to 2~6°, and the furnace tube speed of the rotary kiln is 4.5~7.2r / min.

[0012] As a preferred embodiment of the method for preparing ultrafine tungsten powder according to the present invention, in step S2, the heating temperature of the pre-reduction section is 480-560°C, and the heating time is 24-40 min; the heating temperature of the main reduction section is 650-790°C, and the heating time is 20-36 min; the heating temperature of the deoxidation section is 840-900°C, and the heating time is 15-30 min.

[0013] As a preferred embodiment of the method for preparing ultrafine tungsten powder according to the present invention, in step S2, the hydrogen is introduced in a forward and reverse bidirectional manner, the direction of the hydrogen introduction being the same as the flow direction of the purple tungsten is the forward direction, the direction of the hydrogen introduction being opposite to the flow direction of the purple tungsten is the reverse direction, the direction of the hydrogen introduction in the pre-reduction section and the main reduction section is the forward direction, the direction of the hydrogen introduction in the deoxidation section and the cooling section is the reverse direction, and the flow rate of the forward hydrogen is 310-390 m / s. 3 / h, the flow rate of the reverse hydrogen is 55~90m 3 / h.

[0014] As a preferred embodiment of the method for preparing ultrafine tungsten powder according to the present invention, in step S1, the particle size of the violet tungsten is 10-16 μm, and the specific surface area is 2-8 m 2 / g, feeding at a rate of 0.5~2.5kg / min.

[0015] As a preferred embodiment of the method for preparing ultrafine tungsten powder according to the present invention, step S2 further comprises: The particle size of the first tungsten powder is detected. If the particle size of the first tungsten powder is within a preset particle size range, step S3 is executed; otherwise, step S3 is stopped.

[0016] As a preferred embodiment of the method for preparing ultrafine tungsten powder according to the present invention, in step S4, the preset particle size range is , A1 is the lower limit of particle size, A2 is the upper limit of particle size, and B is the target particle size.

[0017] According to another embodiment of the present invention, the present invention provides the following technical solutions: An ultrafine tungsten powder is obtained by using the above-mentioned method for preparing the ultrafine tungsten powder.

[0018] As a preferred embodiment of the ultrafine tungsten powder of the present invention, the particle size distribution width of the ultrafine tungsten powder is less than 80 ppm, the oxygen content is less than 80 ppm, and the recovery rate is greater than 90%.

[0019] Beneficial effects: The present invention provides an ultrafine tungsten powder and a preparation method thereof. The preparation method comprises the following steps: obtaining violet tungsten; reducing the violet tungsten in a reactor in a hydrogen atmosphere, wherein the reactor is sequentially composed of a heating section and a cooling section from a feed end to a discharge end, wherein the heating section is sequentially composed of a pre-reduction section, a main reduction section and a deoxidation section, wherein the pre-reduction section adopts a first spiral conveying blade to lift the material, the main reduction section adopts a second spiral conveying blade to lift the material, and the deoxidation section adopts a third spiral conveying blade to lift the material, thereby improving the reduction efficiency by more than 40%; the pitch of the spiral conveying blade is reduced in the deoxidation section, and no spiral blade is provided in the cooling section, thereby reducing the rotation resistance and reducing the motor power consumption by 15%; and finally, cooling in the cooling section is performed to obtain ultrafine tungsten powder with a narrow particle size distribution, low oxygen content and high recovery rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0021] Figure 1 This is the SEM image of the ultrafine tungsten powder prepared in Example 5.

[0022] Figure 2 This is the SEM image of the ultrafine tungsten powder prepared in Comparative Example 1.

[0023] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0024] The following will be a clear and complete description of the technical solutions in the embodiments. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0025] The present invention provides an ultrafine tungsten powder and a preparation method thereof. The preparation method comprises: obtaining purple tungsten; reducing the purple tungsten in a reactor in a hydrogen atmosphere, wherein the reactor is sequentially composed of a heating section and a cooling section from a feed end to a discharge end, wherein the heating section is sequentially composed of a pre-reduction section, a main reduction section and a deoxidation section, wherein the pre-reduction section adopts a first spiral conveying blade to lift the material, the main reduction section adopts a second spiral conveying blade to lift the material, and the deoxidation section adopts a third spiral conveying blade to lift the material; and finally cooling the powder through a cooling section to obtain ultrafine tungsten powder with a narrow particle size distribution, a low oxygen content and a high recovery rate.

[0026] According to one aspect of the present invention, the present invention proposes the following technical solution: A method for preparing ultrafine tungsten powder comprises the following steps: S1, obtaining violet tungsten; S2. Reducing the violet tungsten in a reactor under a hydrogen atmosphere, wherein the reactor is sequentially composed of a heating section and a cooling section from a feed end to a discharge end, wherein the heating section is sequentially composed of a pre-reduction section, a main reduction section, and a deoxidation section, wherein the pre-reduction section uses a first spiral conveying blade to lift the material, the main reduction section uses a second spiral conveying blade to lift the material, and the deoxidation section uses a third spiral conveying blade to lift the material, to obtain a first tungsten powder; S3. The first tungsten powder is cooled in a cooling section to obtain a second tungsten powder, wherein the particle size distribution width of the second tungsten powder, that is, the span value is less than 0.90.

[0027] Preferably, in step S2, the length ratio of the cooling section to the heating section is (3-4):(7-8), and the lengths of the pre-reduction section, the main reduction section, and the deoxidation section are the same; the pitch of the first spiral conveying blade is 60-100 mm, the first spiral conveying blade is uniformly and intermittently arranged along the spiral direction, and the proportion of the portion without spiral conveying blades is 20-40% (that is, the length of the portion without blades of the first spiral conveying blade along the spiral direction accounts for 20-40% of the length of the first spiral conveying blade along the spiral direction, and the length of the first spiral conveying blade along the spiral direction is the sum of the length of the portion without blades of the first spiral conveying blade along the spiral direction and the length of the portion with blades of the first spiral conveying blade along the spiral direction); the pitch of the second spiral conveying blade is 100-140 mm, the second spiral conveying blade is uniformly and intermittently arranged along the spiral direction, and the proportion of the portion without spiral conveying blades is 45-55%; the pitch of the third spiral conveying blade is 180-220 mm, and the third spiral conveying blade is continuously arranged along the spiral direction.

[0028] Preferably, in step S2, the reactor is a rotary kiln, and the purple tungsten is reduced using the rotary kiln. The furnace body inclination angle of the rotary kiln is set to 2-6 degrees, and the furnace tube speed of the rotary kiln is 4.5-7.2 r / min. Specifically, the furnace body inclination angle can be, for example, but not limited to, any one of 2°, 3°, 4°, 5°, and 6°, or a range therebetween. The furnace tube speed can be, for example, but not limited to, any one of 4.5 r / min, 4.8 r / min, 5.2 r / min, 5.9 r / min, 6.3 r / min, 6.9 r / min, and 7.2 r / min, or a range therebetween.

[0029] Furthermore, the feed end of the rotary kiln is higher than the discharge end, that is, the rotary kiln is tilted downward, and the angle between the axis from the feed end to the discharge end and the horizontal plane is 2-6 degrees.

[0030] Furthermore, a structure capable of feeding and lifting materials is provided in the furnace body of the rotary kiln, and the structure is a spiral conveying blade, which is composed of a first spiral conveying blade provided in the pre-reduction section, a second spiral conveying blade provided in the main reduction section, and a third spiral conveying blade provided in the deoxidation section.

[0031] Preferably, in step S2, the heating temperature of the pre-reduction section is 480-560° C., the heating temperature of the main reduction section is 650-790° C., and the heating temperature of the deoxidation section is 840-900° C. Specifically, the heating temperature of the pre-reduction section may be, for example, but not limited to, any one of 480° C., 500° C., 520° C., 540° C., 560° C., or a range therebetween; the heating temperature of the main reduction section may be, for example, but not limited to, any one of 650° C., 680° C., 720° C., 750° C., 790° C., or a range therebetween; and the heating temperature of the deoxidation section may be, for example, but not limited to, any one of 840° C., 850° C., 870° C., 880° C., 900° C., or a range therebetween.

[0032] Furthermore, purple tungsten is preferentially reduced to WO2 in a low-temperature hydrogen environment, avoiding the generation of volatile WO3H X Compounds prevent particle coarsening. Temperatures below 480°C are too slow, resulting in incomplete reduction. Above 560°C, the subsequent reduction to W results in a wider particle size distribution. The reduction of WO2 to W requires a moderate temperature to balance reaction rate and particle size control. During this stage, the hydrogen atmosphere must be kept dry (dew point < -40°C) to prevent moisture from promoting particle growth. Temperatures below 650°C are insufficient for reaction kinetics. Above 790°C, tungsten powder begins to sinter (BET surface area plummets). High-temperature deoxidation in the deoxidation stage (840-900°C) completely removes residual oxygen from the tungsten powder (target < 50 ppm), while simultaneously removing moisture through a countercurrent flow of hydrogen. Temperatures below 840°C result in incomplete deoxidation (residual oxygen > 200 ppm). Above 900°C, the tungsten powder significantly grows.

[0033] Preferably, in step S2, the heating time of the pre-reduction section is 24 to 40 minutes, the heating time of the main reduction section is 20 to 36 minutes, and the heating time of the deoxidation section is 15 to 30 minutes. Specifically, the heating time of the pre-reduction section can be, for example, but not limited to, any one of 24 minutes, 28 minutes, 32 minutes, 36 minutes, or 40 minutes, or a range therebetween; the heating time of the main reduction section can be, for example, but not limited to, any one of 20 minutes, 24 minutes, 28 minutes, 32 minutes, or 36 minutes, or a range therebetween; and the heating time of the deoxidation section can be, for example, but not limited to, any one of 15 minutes, 20 minutes, 25 minutes, 27 minutes, or 30 minutes, or a range therebetween.

[0034] Preferably, in step S2, the hydrogen is introduced in a forward and reverse bidirectional manner. The direction of the hydrogen introduction is the same as the flow direction of the purple tungsten, which is the forward direction of hydrogen. The direction of the hydrogen introduction is opposite to the flow direction of the purple tungsten, which is the reverse direction of hydrogen. The direction of the hydrogen introduction in the pre-reduction section and the main reduction section is the forward direction of hydrogen, and the direction of the hydrogen introduction in the deoxidation section and the cooling section is the reverse direction of hydrogen. The flow rate of the forward hydrogen is 310~390m 3 / h, the flow rate of the reverse hydrogen is 55~90m 3 / h. Specifically, the flow rate of hydrogen can be, for example but not limited to, 310m 3 / h、330m 3 / h、360m 3 / h、370m 3 / h、390m 3 / h or any one of them or the range between them; the flow rate of reverse hydrogen can be, for example but not limited to, 55m 3 / h、65m 3 / h、75m 3 / h、85m 3 / h、90m 3 / h or the range between them.

[0035] Furthermore, the reverse hydrogen has a cooling effect on the tungsten powder, and at the same time it is heated after passing through the cooling section, reducing the electric heating load of the deoxidation section, further saving energy, and preventing the growth of the tungsten powder.

[0036] Furthermore, in the pre-reduction stage (hydrogenation): high flow rate hydrogen (310~390m³ / h) ensures that the water vapor (H2O) generated by the reaction is quickly taken away to prevent the accumulation of water vapor and the formation of WO3H X The main reduction stage (hydrogenation): Maintain a high flow rate to promote the reduction of WO2 to W while avoiding localized hydrogen shortages that can lead to uneven reduction. At the lower flow rate limit (<310 m³ / h), water vapor is trapped, the oxygen content of the powder increases (>100 ppm), and coarse particles are likely to form. At the upper flow rate limit (>390 m³ / h), hydrogen is wasted, energy consumption increases by 30%, and high-speed airflow may cause fine powder (<50 nm) to be carried out, reducing recovery.

[0037] Reverse hydrogen flow rate (55-90 m³ / h): Deoxidation stage (reverse hydrogen): Reverse hydrogen (55-90 m³ / h) enters from the high-temperature zone (840-900°C), removing residual oxygen and inhibiting particle growth. Lower flow rate limit (<55 m³ / h): Incomplete deoxidation (oxygen content >80 ppm) may result in localized sintering (widening of the particle size distribution). Upper flow rate limit (>90 m³ / h): Excessively high reverse hydrogen flow rate disrupts powder flow, increasing dust generation and reducing recovery rate (<85%).

[0038] Preferably, in step S1, the particle size of the purple tungsten is 10-16 μm, and the specific surface area is 2-8 m 2 / g. Specifically, the particle size of purple tungsten can be, for example but not limited to, any one of 10 μm, 11 μm, 12 μm, 14 μm, 16 μm, or a range between two thereof; the specific surface area of ​​purple tungsten can be, for example but not limited to, 2 m 2 / g、3m 2 / g、5m 2 / g、7m 2 / g、8m 2 / g or a range between them.

[0039] Preferably, in step S1, the purple tungsten is fed at a rate of 0.5 to 2.5 kg / min. Specifically, the feeding rate may be, for example but not limited to, any one of 0.5 kg / min, 1.0 kg / min, 1.5 kg / min, 2.0 kg / min, 2.5 kg / min, or a range therebetween.

[0040] Preferably, the step S2 further includes: The particle size of the first tungsten powder is detected. If the particle size of the first tungsten powder is within a preset particle size range, step S3 is executed; otherwise, step S3 is stopped.

[0041] Furthermore, the preset particle size range is , A1 is the lower limit of particle size, A2 is the upper limit of particle size, and B is the target particle size.

[0042] According to another aspect of the present invention, the present invention provides the following technical solutions: An ultrafine tungsten powder is obtained by using the above-mentioned method for preparing the ultrafine tungsten powder.

[0043] Preferably, the oxygen content of the ultrafine tungsten powder is less than 80 ppm, and the recovery rate is greater than 90%.

[0044] The technical solution of the present invention is further described below with reference to specific embodiments.

[0045] Example 1 A method for preparing ultrafine tungsten powder comprises the following steps: S1. Obtain purple tungsten with a particle size of 15.00 μm and a specific surface area of ​​3.5 m² / g. Set the furnace body inclination angle to 5°, the furnace tube speed to 6.0 r / min, and feed the purple tungsten at a rate of 1.2 kg / min. S2. The purple tungsten is reduced in a reactor in a hydrogen atmosphere. The reactor is composed of a heating section and a cooling section from the feed end to the discharge end. The heating section is composed of a pre-reduction section, a main reduction section and a deoxidation section in sequence. The length ratio of the cooling section to the heating section is 4:7. The lengths of the pre-reduction section, the main reduction section and the deoxidation section are the same. The pre-reduction section adopts a first spiral conveying blade with a pitch of 80 mm. The first spiral conveying blade is evenly and intermittently arranged along the spiral direction, and the portion without the spiral conveying blade accounts for 30%. The temperature is set to 510° C. and the reaction time is 30 min. The main reduction section adopts a first spiral conveying blade. The second spiral conveying blade has a pitch of 120 mm, and the second spiral conveying blade is evenly and intermittently arranged along the spiral direction. The portion without spiral conveying blades accounts for 50%, the temperature is set to 715 ° C, and the reaction time is 25 min; the deoxidation section adopts the third spiral conveying blade, the pitch of the spiral conveying blade is 200 mm, and the third spiral conveying blade is continuously arranged along the spiral direction. The temperature is set to 860 ° C, and the reaction time is 17 min; the direction of hydrogen introduced into the pre-reduction section and the main reduction section is the forward direction, and the direction of hydrogen introduced into the deoxidation section and the cooling section is the reverse direction. The forward hydrogen flow rate is 360 m 3 / h, reverse hydrogen flow rate is 70m 3 / h; Laser particle size online detector setting warning range: D50: , i.e. 330-470nm; S3. Cooling in a cooling section yields tungsten powder having an average grain size D50 of 352 nm, a span of 0.88, an oxygen content of 67 ppm, and a recovery rate of 93.60%.

[0046] Example 2 A method for preparing ultrafine tungsten powder comprises the following steps: S1. Obtain purple tungsten with a particle size of 10.20 μm and a specific surface area of ​​3.0 m² / g. Set the furnace inclination angle to 2° and the furnace tube speed to 4.5 rpm. Feed the purple tungsten at a rate of 2.5 kg / min. S2. The violet tungsten is reduced in a reactor under a hydrogen atmosphere. The reactor is composed of a heating section and a cooling section from the feed end to the discharge end. The heating section is composed of a pre-reduction section, a main reduction section and a deoxidation section in sequence. The length ratio of the cooling section to the heating section is 4:8, and the lengths of the pre-reduction section, the main reduction section and the deoxidation section are the same. The pre-reduction section adopts a first spiral conveying blade with a pitch of 60 mm. The first spiral conveying blade is evenly and intermittently arranged along the spiral direction, and the portion without the spiral conveying blade accounts for 20%. The temperature is set to 560° C. and the reaction time is 38 min. The main reduction section adopts a second The spiral conveying blade has a pitch of 100 mm, and the second spiral conveying blade is evenly and intermittently arranged along the spiral direction. The portion without spiral conveying blades accounts for 45%, the temperature is set to 790 ° C, and the reaction time is 34 min; the deoxidation section adopts the third spiral conveying blade, the pitch of the spiral conveying blade is 180 mm, and the third spiral conveying blade is continuously arranged along the spiral direction. The temperature is set to 900 ° C, and the reaction time is 28 min; the direction of hydrogen introduced into the pre-reduction section and the main reduction section is the forward direction, and the direction of hydrogen introduced into the deoxidation section and the cooling section is the reverse direction. The forward hydrogen flow rate is 390 m 3 / h, reverse hydrogen flow rate is 90m 3 / h; Laser particle size online detector setting warning range: D50: , i.e. 224~329nm; S3. Cooling in a cooling section yields tungsten powder having an average grain size D50 of 280 nm, a span of 0.88, an oxygen content of 75 ppm, and a recovery rate of 92.50%.

[0047] Example 3 A method for preparing ultrafine tungsten powder comprises the following steps: S1. Obtain purple tungsten with a particle size of 14.8 μm and a specific surface area of ​​4.0 m² / g. Set the furnace inclination angle to 6° and the furnace tube speed to 7.2 rpm. Feed the purple tungsten at a rate of 0.5 kg / min. S2. The violet tungsten is reduced in a reactor in a hydrogen atmosphere. The reactor is composed of a heating section and a cooling section from the feed end to the discharge end. The heating section is composed of a pre-reduction section, a main reduction section and a deoxidation section in sequence. The length ratio of the cooling section to the heating section is 3:7. The lengths of the pre-reduction section, the main reduction section and the deoxidation section are the same. The pre-reduction section adopts a first spiral conveying blade with a pitch of 100 mm. The first spiral conveying blade is evenly and intermittently arranged along the spiral direction, and the portion without the spiral conveying blade accounts for 40%. The temperature is set to 480° C. and the reaction time is 25 min. The main reduction section adopts a second The spiral conveying blade has a pitch of 140 mm, and the second spiral conveying blade is evenly and intermittently arranged along the spiral direction. The portion without spiral conveying blades accounts for 55%, the temperature is set to 650 ° C, and the reaction time is 22 min; the deoxidation section adopts the third spiral conveying blade, the pitch of the spiral conveying blade is 220 mm, and the third spiral conveying blade is continuously arranged along the spiral direction. The temperature is set to 840 ° C, and the reaction time is 17 min; the direction of hydrogen introduced into the pre-reduction section and the main reduction section is the forward direction, and the direction of hydrogen introduced into the deoxidation section and the cooling section is the reverse direction. The forward hydrogen flow rate is 310 m 3 / h, reverse hydrogen flow rate is 55m 3 / h; Laser particle size online detector setting warning range: D50: , i.e. 298~417nm; S3. Cooling in a cooling section yields tungsten powder having an average grain size D50 of 333 nm, a span of 0.85, an oxygen content of 70 ppm, and a recovery rate of 94.20%.

[0048] Example 4 A method for preparing ultrafine tungsten powder comprises the following steps: S1. Obtain purple tungsten with a particle size of 15.0 μm and a specific surface area of ​​3.5 m² / g. Set the furnace inclination angle to 6° and the furnace tube speed to 5.0 r / min. Feed the purple tungsten at a rate of 0.6 kg / min. S2. The violet tungsten is reduced in a reactor in a hydrogen atmosphere. The reactor is composed of a heating section and a cooling section from the feed end to the discharge end. The heating section is composed of a pre-reduction section, a main reduction section and a deoxidation section in sequence. The length ratio of the cooling section to the heating section is 3:7. The lengths of the pre-reduction section, the main reduction section and the deoxidation section are the same. The pre-reduction section adopts a first spiral conveying blade with a pitch of 70 mm. The first spiral conveying blade is evenly and intermittently arranged along the spiral direction, and the proportion of the portion without the spiral conveying blade is 25%. The temperature is set to 480° C. and the reaction time is 25 min. The main reduction section adopts a second The spiral conveying blade has a pitch of 100 mm, and the second spiral conveying blade is evenly and intermittently arranged along the spiral direction. The portion without spiral conveying blades accounts for 50%, the temperature is set to 650 ° C, and the reaction time is 23 min; the deoxidation section adopts the third spiral conveying blade, the pitch of the spiral conveying blade is 190 mm, and the third spiral conveying blade is continuously arranged along the spiral direction. The temperature is set to 840 ° C, and the reaction time is 16 min; the direction of hydrogen introduced into the pre-reduction section and the main reduction section is the forward direction, and the direction of hydrogen introduced into the deoxidation section and the cooling section is the reverse direction. The forward hydrogen flow rate is 390 m 3 / h, reverse hydrogen flow rate is 90m 3 / h; Laser particle size online detector setting warning range: D50: , i.e. 365~491nm; S3. Cooling in a cooling section yields tungsten powder having an average grain size D50 of 396 nm, a span of 0.81, an oxygen content of 76 ppm, and a recovery rate of 91.09%.

[0049] Example 5 A method for preparing ultrafine tungsten powder comprises the following steps: S1. Obtain purple tungsten with a particle size of 15.0 μm and a specific surface area of ​​3.5 m² / g. Set the furnace inclination angle to 3° and the furnace tube speed to 7.0 r / min. Feed the purple tungsten at a rate of 2.1 kg / min. S2. The violet tungsten is reduced in a reactor in a hydrogen atmosphere. The reactor is composed of a heating section and a cooling section from the feed end to the discharge end. The heating section is composed of a pre-reduction section, a main reduction section and a deoxidation section in sequence. The length ratio of the cooling section to the heating section is 3:8. The lengths of the pre-reduction section, the main reduction section and the deoxidation section are the same. The pre-reduction section adopts a first spiral conveying blade with a pitch of 90 mm. The first spiral conveying blade is evenly and intermittently arranged along the spiral direction, and the proportion of the portion without the spiral conveying blade is 35%. The temperature is set to 550° C. and the reaction time is 30 min. The main reduction section adopts a second The spiral conveying blade has a pitch of 140 mm, and the second spiral conveying blade is evenly and intermittently arranged along the spiral direction. The portion without spiral conveying blades accounts for 50%, the temperature is set to 775 ° C, and the reaction time is 28 min; the deoxidation section adopts the third spiral conveying blade, the pitch of the spiral conveying blade is 200 mm, and the third spiral conveying blade is continuously arranged along the spiral direction. The temperature is set to 900 ° C, and the reaction time is 22 min; the direction of hydrogen introduced into the pre-reduction section and the main reduction section is the forward direction, and the direction of hydrogen introduced into the deoxidation section and the cooling section is the reverse direction. The forward hydrogen flow rate is 390 m 3 / h, reverse hydrogen flow rate is 90m 3 / h; Laser particle size online detector setting warning range: D50: , i.e. 108~192nm; S3, cooling through the cooling section to obtain tungsten powder, the average grain size D50 of which is 144nm, span: 0.84, oxygen content: 77ppm, recovery rate: 92.95%, such as Figure 1 shown.

[0050] Comparative Example 1 A method for preparing ultrafine tungsten powder comprises the following steps: S1. Obtain purple tungsten with a particle size of 15.0 μm and a specific surface area of ​​3.5 m² / g. Set the furnace inclination angle to 5°, the furnace tube speed to 6.0 r / min, and feed the purple tungsten at a rate of 1.2 kg / min. S2. The violet tungsten is reduced in a reactor under a hydrogen atmosphere. The reactor is sequentially divided into a heating section and a cooling section from the feed end to the discharge end. The heating section is sequentially composed of a pre-reduction section, a main reduction section and a deoxidation section. The length ratio of the cooling section to the heating section is 4:7. The lengths of the pre-reduction section, the main reduction section and the deoxidation section are the same. The pre-reduction section adopts a first spiral conveying blade with a pitch of 80 mm. The first spiral conveying blades are continuously arranged along the spiral direction. The temperature is set to 510° C. and the reaction time is 30 min. The main reduction section adopts a second The spiral conveying blade has a pitch of 60 mm, the second spiral conveying blade is arranged continuously along the spiral direction, the temperature is set to 715 ° C, and the reaction time is 25 min; the deoxidation section adopts the third spiral conveying blade, the pitch of the spiral conveying blade is 150 mm, the third spiral conveying blade is arranged continuously along the spiral direction, the temperature is set to 800 ° C, and the reaction time is 17 min; the direction of hydrogen introduced into the pre-reduction section and the main reduction section is the forward direction, and the direction of hydrogen introduced into the deoxidation section and the cooling section is the reverse direction, and the forward hydrogen flow rate is 360m 3 / h, reverse hydrogen flow rate is 70m 3 / h; Laser particle size online detector setting warning range: D50: , i.e. 330-470nm; S3, cooling in the cooling section to obtain tungsten powder, the average grain size D50 of which is 869nm, span: 1.27, oxygen content: 105ppm, recovery rate: 90.28%; the electron microscope photo of the obtained tungsten powder is as follows Figure 2 As shown, the grains are coarse. (An early warning was issued, and the process was debugged, but the target particle size could not be achieved. Production was stopped after a small number of samples were taken. The product particle size was large and uneven).

[0051] Compared with Example 1, all the spiral conveying blades in each reaction section of Comparative Example 1 are arranged continuously along the spiral direction, that is, the proportion of the parts without spiral conveying blades is 0%. The tungsten powder finally obtained has coarse grains, a wide particle size distribution, a high oxygen content and incomplete deoxidation.

[0052] Comparative Example 2 A method for preparing ultrafine tungsten powder comprises the following steps: S1. Obtain purple tungsten with a particle size of 15.0 μm and a specific surface area of ​​3.5 m² / g. Set the furnace inclination angle to 5°, the furnace tube speed to 6.0 r / min, and feed the purple tungsten at a rate of 1.2 kg / min. S2. The violet tungsten is reduced in a reactor in a hydrogen atmosphere. The reactor is composed of a heating section and a cooling section from the feed end to the discharge end. The heating section is composed of a pre-reduction section, a main reduction section and a deoxidation section in sequence. The length ratio of the cooling section to the heating section is 4:7. The lengths of the pre-reduction section, the main reduction section and the deoxidation section are the same. The pre-reduction section adopts a first spiral conveying blade with a pitch of 80 mm. The first spiral conveying blade is evenly and intermittently arranged along the spiral direction, and the portion without the spiral conveying blade accounts for 30%. The temperature is set to 580°C and the reaction time is 30 min. The main reduction section adopts a second spiral conveying blade. The spiral conveying blade has a pitch of 60 mm, and the second spiral conveying blade is evenly and intermittently arranged along the spiral direction. The portion without spiral conveying blades accounts for 50%, the temperature is set to 810 ° C, and the reaction time is 25 min. The deoxidation section adopts the third spiral conveying blade, the pitch of the spiral conveying blade is 200 mm, and the third spiral conveying blade is continuously arranged along the spiral direction. The temperature is set to 1000 ° C, and the reaction time is 17 min. The direction of hydrogen introduced into the pre-reduction section and the main reduction section is the forward direction of hydrogen, and the direction of hydrogen introduced into the deoxidation section and the cooling section is the reverse direction of hydrogen. The forward hydrogen flow rate is: 450m 3 / h, reverse hydrogen flow rate is 120m 3 / h; Laser particle size online detector setting warning range: D50: , i.e. 330~470nm; S3. Cooling in a cooling section yields tungsten powder having an average grain size D50 of 434 nm, a span of 0.90, an oxygen content of 65 ppm, and a recovery rate of 81.60%.

[0053] Comparative Example 3 A method for preparing ultrafine tungsten powder comprises the following steps: S1. Obtain purple tungsten with a particle size of 15.0 μm and a specific surface area of ​​3.5 m² / g. Set the furnace inclination angle to 5°, the furnace tube speed to 6.0 r / min, and feed the purple tungsten at a rate of 1.2 kg / min. S2. Reduce the violet tungsten in a reactor with a hydrogen atmosphere. The reactor is divided into a heating section and a cooling section from the feed end to the discharge end. The heating section is composed of a pre-reduction section, a main reduction section and a deoxidation section in sequence. The length ratio of the cooling section to the heating section is 4:7. The lengths of the pre-reduction section, the main reduction section and the deoxidation section are the same. The pre-reduction section adopts a first spiral conveying blade with a pitch of 80 mm. The first spiral conveying blade is evenly and intermittently arranged along the spiral direction, and the portion without the spiral conveying blade accounts for 30%. The temperature is set to 400°C and the reaction time is 30 min. The main reduction section adopts a second spiral conveying blade. The spiral conveying blade has a pitch of 120 mm, and the second spiral conveying blade is evenly and intermittently arranged along the spiral direction. The portion without spiral conveying blades accounts for 50%, the temperature is set to 600 ° C, and the reaction time is 25 min. The deoxidation section adopts the third spiral conveying blade, the pitch of the spiral conveying blade is 200 mm, and the third spiral conveying blade is continuously arranged along the spiral direction. The temperature is set to 800 ° C, and the reaction time is 17 min. The direction of hydrogen introduced into the pre-reduction section and the main reduction section is the hydrogen direction, and the direction of hydrogen introduced into the deoxidation section and the cooling section is the reverse hydrogen direction. The hydrogen flow rate is: 200m 3 / h, reverse hydrogen flow rate is 40m 3 / h; Laser particle size online detector setting warning range: D50: , i.e. 330~470nm; S3. Cooling in a cooling section yields tungsten powder having an average grain size D50 of 481 nm, a span of 1.21, an oxygen content of 132 ppm, and a recovery rate of 91.9%.

[0054] Comparative Example 4 A method for preparing ultrafine tungsten powder comprises the following steps: The difference from Example 1 is that a single-tube rotary kiln in the prior art is used in step S2; the reverse hydrogen flow rate is 400m 3 / h, laser-free particle size online detector; Tungsten powder was obtained by cooling in the cooling section. The average grain size D50 of the obtained tungsten powder was 136 nm, span was 1.26, oxygen content was 233 ppm, and recovery rate was 80.31%.

[0055] Comparative Example 5 A method for preparing ultrafine tungsten powder comprises the following steps: The difference from Example 1 is that in step S2, a double-tube forward and reverse hydrogen rotary furnace in the prior art is used; there is no laser particle size online detector; Tungsten powder was obtained by cooling in the cooling section, with an average grain size D50 of 128 nm, a span of 1.12, an oxygen content of 205 ppm, and a recovery rate of 86.51%.

[0056] Comparative Example 6 A method for preparing ultrafine tungsten powder comprises the following steps: Different from Example 1, the pre-reduction stage temperature / main reduction stage temperature / deoxidation stage temperature were 620° C. / 800° C. / 930° C. respectively, and the laser particle size online detector was in alarm state, and normal production could not be achieved.

[0057] Comparative Example 7 A method for preparing ultrafine tungsten powder comprises the following steps: The difference from Example 1 is that the pre-reduction stage temperature / main reduction stage temperature / deoxidation stage temperature are 620° C. / 800° C. / 930° C. respectively, and the laser particle size online detector is turned off; Tungsten powder was obtained by cooling in the cooling section, with an average grain size D50 of 728 nm, a span of 1.18, an oxygen content of 95 ppm, and a recovery rate of 91.61%.

[0058] Comparative Example 8 A method for preparing ultrafine tungsten powder comprises the following steps: The difference from Example 1 is that the hydrogen flow rate is 420m 3 / h; and cooling in the cooling section to obtain tungsten powder, with an average grain size D50 of 340 nm, a span of 0.92, an oxygen content of 77 ppm, and a recovery rate of 85.40%.

[0059] The present invention provides an ultrafine tungsten powder and a preparation method thereof. The preparation method comprises the following steps: obtaining violet tungsten; reducing the violet tungsten in a reactor in a hydrogen atmosphere, wherein the reactor is sequentially composed of a heating section and a cooling section from a feed end to a discharge end, wherein the heating section is sequentially composed of a pre-reduction section, a main reduction section and a deoxidation section, wherein the pre-reduction section adopts a first spiral conveying blade to lift the material, the main reduction section adopts a second spiral conveying blade to lift the material, and the deoxidation section adopts a third spiral conveying blade to lift the material, thereby improving the reduction efficiency by more than 40%; the pitch of the spiral conveying blade is reduced in the deoxidation section, and no spiral blade is provided in the cooling section, thereby reducing the rotation resistance and reducing the motor power consumption by 15%; and finally, cooling in the cooling section is performed to obtain ultrafine tungsten powder with a narrow particle size distribution, low oxygen content and high recovery rate.

[0060] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made by using the contents of the present invention specification under the inventive concept of the present invention, or direct / indirect application in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for preparing ultrafine tungsten powder, characterized in that: The steps include: S1, obtaining violet tungsten; S2. Reducing the violet tungsten in a reactor under a hydrogen atmosphere, wherein the reactor comprises a heating section and a cooling section from the feed end to the discharge end, wherein the heating section comprises a pre-reduction section, a main reduction section, and a deoxidation section; the pre-reduction section employs a first spiral conveying blade for lifting the material, the main reduction section employs a second spiral conveying blade for lifting the material, and the deoxidation section employs a third spiral conveying blade for lifting the material, to obtain a first tungsten powder; S3. The first tungsten powder is cooled in a cooling section to obtain a second tungsten powder, wherein the particle size distribution width of the second tungsten powder, that is, the span value is less than 0.

90.

2. The method for preparing ultrafine tungsten powder according to claim 1, characterized in that: In step S2, the length ratio of the cooling section to the heating section is (3-4):(7-8), and the lengths of the pre-reduction section, the main reduction section, and the deoxidation section are the same; the pitch of the first spiral conveying blade is 60-100 mm, the first spiral conveying blade is evenly and discontinuously arranged along the spiral direction, and the proportion of the portion without spiral conveying blades is 20-40%; the pitch of the second spiral conveying blade is 100-140 mm, the second spiral conveying blade is evenly and discontinuously arranged along the spiral direction, and the proportion of the portion without spiral conveying blades is 45-55%; the pitch of the third spiral conveying blade is 180-220 mm, and the third spiral conveying blade is continuously arranged along the spiral direction.

3. The method for preparing ultrafine tungsten powder according to claim 1, wherein: In step S2, the reactor is a rotary kiln, and the purple tungsten is reduced by using the rotary kiln. The inclination angle of the furnace body of the rotary kiln is set to 2-6 degrees, and the furnace tube speed of the rotary kiln is 4.5-7.2 r / min.

4. The method for preparing ultrafine tungsten powder according to claim 1, wherein: In step S2, the heating temperature of the pre-reduction section is 480-560°C, and the heating time is 24-40 minutes; the heating temperature of the main reduction section is 650-790°C, and the heating time is 20-36 minutes; the heating temperature of the deoxidation section is 840-900°C, and the heating time is 15-30 minutes.

5. The method for preparing ultrafine tungsten powder according to claim 1, characterized in that: In step S2, the hydrogen is introduced in a forward and reverse bidirectional manner. The direction of the hydrogen introduction is the same as the flow direction of the purple tungsten, which is the forward direction. The direction of the hydrogen introduction is opposite to the flow direction of the purple tungsten, which is the reverse direction. The direction of the hydrogen introduction in the pre-reduction section and the main reduction section is the forward direction, and the direction of the hydrogen introduction in the deoxidation section and the cooling section is the reverse direction. The flow rate of the forward hydrogen is 310~390m 3 / h, the flow rate of the reverse hydrogen is 55~90m 3 / h.

6. The method for preparing ultrafine tungsten powder according to claim 1, characterized in that: In step S1, the particle size of the purple tungsten is 10-16 μm, and the specific surface area is 2-8 m 2 / g, feeding at a rate of 0.5~2.5kg / min.

7. The method for preparing ultrafine tungsten powder according to claim 1, characterized in that: The step S2 further includes: The particle size of the first tungsten powder is detected. If the particle size of the first tungsten powder is within a preset particle size range, step S3 is executed; otherwise, step S3 is stopped.

8. The method for preparing ultrafine tungsten powder according to claim 7, characterized in that: The preset particle size range is , A1 is the lower limit of particle size, A2 is the upper limit of particle size, and B is the target particle size.

9. An ultrafine tungsten powder, characterized in that: The ultrafine tungsten powder is obtained by using the preparation method of ultrafine tungsten powder according to any one of claims 1 to 8.

10. The ultrafine tungsten powder according to claim 9, characterized in that: The oxygen content of the ultrafine tungsten powder is less than 80 ppm, and the recovery rate is greater than 90%.

Images