An ultrafine tungsten powder and its preparation method

Abstract

This invention belongs to the field of powder metallurgy production technology, specifically relating to an ultrafine tungsten powder and its preparation method. The preparation method includes the following steps: obtaining purple tungsten; reducing the purple tungsten in a reactor under a hydrogen atmosphere, wherein the reactor consists 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; the pre-reduction section uses a first spiral conveyor blade for material lifting; the main reduction section uses a second spiral conveyor blade for material lifting; and the deoxidation section uses a third spiral conveyor blade for material lifting; finally, the powder is cooled in a cooling section to obtain ultrafine tungsten powder with narrow particle size distribution, low oxygen content, and high recovery rate.

Description

Technical Field

[0001] This invention belongs to the field of powder metallurgy technology, specifically an ultrafine tungsten powder and its preparation method. Background Technology

[0002] Tungsten is an important strategic resource in my country and has wide applications in key fields such as cemented carbide. Metal cutting tools, molds, and wear-resistant parts made from tungsten meet many of the demands 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. Therefore, ultrafine cemented carbide has been proposed, which exhibits superior performance in terms of strength, hardness, and fracture toughness compared to ordinary cemented carbide. It is widely used in the automotive, aerospace, and 3C industries as a high-efficiency precision tool, micro-drill, micro-milling machine, insert, and precision mold.

[0003] Ultrafine tungsten powder is one of the important raw materials for preparing ultrafine cemented carbide, and its performance directly affects the development of ultrafine cemented carbide. At present, the main method for industrial preparation of high-quality ultrafine tungsten powder is the hydrogen reduction method, which has the advantages of being simple, easy to implement, stable and reliable, low cost, and easy to automate. The main steps of this process are: reducing tungsten oxide with hydrogen by heating to obtain tungsten powder; and then obtaining ultrafine tungsten powder through sieving, passivation and other treatments.

[0004] In actual industrial production, multi-tube pusher boat furnaces, tubular pusher boat furnaces, or rotary furnaces are commonly used. The reduction principle of multi-tube pusher boat furnaces is static reduction, where tungsten oxide is loaded into an alloy boat. The material layer in the boat is static relative to the hydrogen gas. The thickness and flatness of this material layer directly affect the sufficiency of tungsten powder reduction, the integrity of crystallization, and the uniformity of the particle size distribution of ultrafine tungsten powder. Therefore, it is difficult to produce high-quality and stable ultrafine tungsten powder using multi-tube pusher boat reduction furnaces, it is difficult to achieve fully enclosed production, and the equipment has low output, high energy consumption, and high cost.

[0005] The rotary kiln reduction method for preparing ultrafine tungsten powder utilizes dynamic reduction, where the material is periodically tumbled within the furnace tubes. This results in more uniform heating, increases the contact between tungsten oxide and hydrogen, and allows the generated water vapor to be quickly expelled from the material, reducing the volatilization and deposition of tungsten hydrates. Consequently, ultrafine tungsten powder with more uniform particle size can be obtained. Using a rotary kiln to produce ultrafine tungsten powder is currently the most common method in actual production.

[0006] Traditional rotary kilns also have certain structural defects. For example, the lifting plates in the furnace tube are usually a single structure running the entire length, which makes it impossible to target materials during the pre-reduction, main reduction, and deoxidation stages, resulting in low reaction efficiency and high energy consumption. Single-tube rotary kilns also suffer from low tungsten powder yield. Some rotary kilns use a double-tube design with lifting plates arranged inside the furnace tube, but the lifting plates are uniformly distributed throughout the entire process without considering the process requirements of different reaction stages, which further leads to a wide particle size distribution in the produced powder and incomplete deoxidation.

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

[0008] To obtain ultrafine tungsten powder with narrow particle size distribution, low oxygen content, and high recovery rate, this invention provides an ultrafine tungsten powder and its preparation method. The preparation method includes: obtaining purple tungsten; reducing the purple tungsten in a reactor under a hydrogen atmosphere, wherein the reactor consists 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; the pre-reduction section uses a first spiral conveyor blade for material lifting; the main reduction section uses a second spiral conveyor blade for material lifting; and the deoxidation section uses a third spiral conveyor blade for material lifting; finally, the powder is cooled in 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 solution:

[0010] A method for preparing ultrafine tungsten powder includes the following steps:

[0011] S1. Obtain purple tungsten;

[0012] S2. The purple tungsten is reduced in a reactor under a hydrogen atmosphere. The reactor consists 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. The pre-reduction section uses a first spiral conveyor blade for material lifting, the main reduction section uses a second spiral conveyor blade for material lifting, and the deoxidation section uses a third spiral conveyor blade for material lifting, to obtain the first tungsten powder.

[0013] S3. The first tungsten powder is cooled in the cooling section to obtain the second tungsten powder, and the particle size distribution width of the second tungsten powder, i.e., the span value, is <0.90.

[0014] In a preferred embodiment of the method for preparing ultrafine tungsten powder according to the present invention, 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 60~100mm, and the first spiral conveying blade is uniformly and intermittently arranged along the spiral direction, with the proportion of the portion without spiral conveying blades being 20~40%; the pitch of the second spiral conveying blade is 100~140mm, and the second spiral conveying blade is uniformly and intermittently arranged along the spiral direction, with the proportion of the portion without spiral conveying blades being 45~55%; the pitch of the third spiral conveying blade is 180~220mm, and the third spiral conveying blade is continuously arranged along the spiral direction.

[0015] In a preferred embodiment of the method for preparing ultrafine tungsten powder according to the present invention, in step S2, the reactor is a rotary kiln, and the tungsten powder is reduced by the rotary kiln. The tilt angle of the rotary kiln body is set to 2~6°, and the rotation speed of the rotary kiln tube is 4.5~7.2 r / min.

[0016] In 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℃ and the heating time is 24~40min; the heating temperature of the main reduction section is 650~790℃ and the heating time is 20~36min; and the heating temperature of the deoxidation section is 840~900℃ and the heating time is 15~30min.

[0017] In a preferred embodiment of the method for preparing ultrafine tungsten powder according to the present invention, in step S2, the hydrogen gas is introduced in a bidirectional manner, with the hydrogen gas introduced in the same direction as the flow direction of the tungsten (forward hydrogen direction) and in the opposite direction (backward hydrogen direction). The hydrogen gas introduced in the pre-reduction section and the main reduction section is in the forward hydrogen direction, while the hydrogen gas introduced in the deoxidation section and the cooling section is in the backward hydrogen direction. The forward hydrogen flow rate is 310~390 m³ / h. 3 / h, the flow rate of the reverse hydrogen is 55~90m³ / h. 3 / h.

[0018] In a preferred embodiment of the method for preparing ultrafine tungsten powder according to the present invention, in step S1, the particle size of the purple tungsten is 10~16μm and the specific surface area is 2~8m². 2 / g, fed at a rate of 0.5~2.5kg / min.

[0019] In a preferred embodiment of the method for preparing ultrafine tungsten powder according to the present invention, step S2 further includes:

[0020] The particle size of the first tungsten powder is detected. If the particle size of the first tungsten powder is within the preset particle size range, then step S3 is executed; otherwise, step S3 is stopped.

[0021] In 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 [missing information]. A1 is the lower limit of particle size, A2 is the upper limit of particle size, and B is the target particle size.

[0022] According to another aspect of the present invention, the present invention provides the following technical solution:

[0023] An ultrafine tungsten powder is obtained by the above-mentioned method for preparing ultrafine tungsten powder.

[0024] As a preferred embodiment of the ultrafine tungsten powder described in this invention, the ultrafine tungsten powder has a particle size distribution width, oxygen content < 80 ppm, and recovery rate > 90%.

[0025] Beneficial effects:

[0026] This invention provides an ultrafine tungsten powder and its preparation method. The preparation method includes the following steps: obtaining purple tungsten; reducing the purple tungsten in a reactor under a hydrogen atmosphere, wherein the reactor consists 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; the pre-reduction section uses a first spiral conveyor blade for material lifting; the main reduction section uses a second spiral conveyor blade for material lifting; and the deoxidation section uses a third spiral conveyor blade for material lifting, thereby improving the reduction efficiency by more than 40%; the deoxidation section reduces the pitch of the spiral conveyor blades, and the cooling section does not have spiral blades, reducing rotational resistance and reducing motor power consumption by 15%; finally, the ultrafine tungsten powder with narrow particle size distribution, low oxygen content, and high recovery rate is obtained by cooling in the cooling section. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention 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 the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0028] Figure 1 This is a SEM image of the ultrafine tungsten powder prepared in Example 5.

[0029] Figure 2The image shows the SEM image of the ultrafine tungsten powder prepared in Comparative Example 1.

[0030] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0031] The technical solutions described below in conjunction with the embodiments will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the 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] This invention provides an ultrafine tungsten powder and its preparation method. The preparation method includes: obtaining purple tungsten; reducing the purple tungsten in a reactor under a hydrogen atmosphere, wherein the reactor consists 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; the pre-reduction section uses a first spiral conveyor blade for material lifting; the main reduction section uses a second spiral conveyor blade for material lifting; and the deoxidation section uses a third spiral conveyor blade for material lifting; finally, the powder is cooled in a cooling section to obtain ultrafine tungsten powder with narrow particle size distribution, low oxygen content, and high recovery rate.

[0033] According to one aspect of the present invention, the present invention proposes the following technical solution:

[0034] A method for preparing ultrafine tungsten powder includes the following steps:

[0035] S1. Obtain purple tungsten;

[0036] S2. The purple tungsten is reduced in a reactor under a hydrogen atmosphere. The reactor consists 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. The pre-reduction section uses a first spiral conveyor blade for material lifting, the main reduction section uses a second spiral conveyor blade for material lifting, and the deoxidation section uses a third spiral conveyor blade for material lifting, to obtain the first tungsten powder.

[0037] S3. The first tungsten powder is cooled in the cooling section to obtain the second tungsten powder, and the particle size distribution width of the second tungsten powder, i.e., the span value, is <0.90.

[0038] 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 60~100mm, the first spiral conveying blade is uniformly and intermittently arranged along the spiral direction, and the proportion of its part without spiral conveying blades is 20~40% (that is, the length of the part of the first spiral conveying blade without blades along the spiral direction accounts for 20~40% of the total 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 part of the first spiral conveying blade without blades along the spiral direction and the length of the part of the first spiral conveying blade with blades along the spiral direction); the pitch of the second spiral conveying blade is 100~140mm, the second spiral conveying blade is uniformly and intermittently arranged along the spiral direction, and the proportion of its part without spiral conveying blades is 45~55%; the pitch of the third spiral conveying blade is 180~220mm, and the third spiral conveying blade is continuously arranged along the spiral direction.

[0039] Preferably, in step S2, the reactor is a rotary kiln, which is used to reduce the tungsten oxide. The tilt angle of the rotary kiln is set to 2~6°, and the rotation speed of the furnace tube is 4.5~7.2 r / min. Specifically, the tilt angle of the furnace body can be, for example, but not limited to, any one of 2°, 3°, 4°, 5°, 6° or a range between two of them, and the rotation speed of the furnace tube 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, 7.2 r / min or a range between two of them.

[0040] Furthermore, the feed end of the rotary kiln is higher than the discharge end, that is, the rotary kiln is tilted downwards, and the angle between the axis from the feed end to the discharge end and the horizontal plane is 2~6°.

[0041] Furthermore, the rotary kiln is equipped with a structure inside the furnace that enables feeding and lifting of materials. The structure is a spiral conveying blade, which consists of a first spiral conveying blade in the pre-reduction section, a second spiral conveying blade in the main reduction section, and a third spiral conveying blade in the deoxidation section.

[0042] Preferably, in step S2, the heating temperature of the pre-reduction section is 480~560℃, the heating temperature of the main reduction section is 650~790℃, and the heating temperature of the deoxidation section is 840~900℃. Specifically, the heating temperature of the pre-reduction section can be, for example, but not limited to, any one or a range between 480℃, 500℃, 520℃, 540℃, and 560℃; the heating temperature of the main reduction section can be, for example, but not limited to, any one or a range between 650℃, 680℃, 720℃, 750℃, and 790℃; and the heating temperature of the deoxidation section can be, for example, but not limited to, any one or a range between 840℃, 850℃, 870℃, 880℃, and 900℃.

[0043] Furthermore, tungsten is preferentially reduced to WO2 in a low-temperature hydrogen environment, avoiding the formation of volatile WO3H. X Compounds are used to prevent particle coarsening. Below 480℃, the reaction rate is too low, leading to incomplete reduction; above 560℃, the particle size distribution widens during subsequent reduction to W; the reduction of WO2 to W requires a moderate temperature to balance the reaction rate and particle size control. During this stage, hydrogen must be kept dry (dew point < -40℃) to prevent moisture from promoting particle growth. Below 650℃, reaction kinetics are insufficient; above 790℃, tungsten powder begins to sinter (BET surface area drops sharply). The deoxidation stage (840~900℃) thoroughly removes residual oxygen from the tungsten powder (target <50ppm), while simultaneously removing moisture through a counter-current hydrogen flow. Below 840℃, deoxidation is incomplete (oxygen residue >200ppm); above 900℃, tungsten powder grows significantly.

[0044] Preferably, in step S2, the heating time of the pre-reduction section is 24-40 min, the heating time of the main reduction section is 20-36 min, and the heating time of the deoxygenation section is 15-30 min. Specifically, the heating time of the pre-reduction section can be, for example, but not limited to, any one or a range between 24 min, 28 min, 32 min, 36 min, and 40 min; the heating time of the main reduction section can be, for example, but not limited to, any one or a range between 20 min, 24 min, 28 min, 32 min, and 36 min; and the heating time of the deoxygenation section can be, for example, but not limited to, any one or a range between 15 min, 20 min, 25 min, 27 min, and 30 min.

[0045] Preferably, in step S2, the hydrogen is introduced in a bidirectional manner, with the hydrogen introduced in the same direction as the flow direction of the tungsten (forward hydrogen flow) and in the opposite direction (backward hydrogen flow). The hydrogen introduced into the pre-reduction section and the main reduction section is in the forward hydrogen flow direction, while the hydrogen introduced into the deoxidation section and the cooling section is in the backward hydrogen flow direction. The forward hydrogen flow rate is 310~390 m³ / h. 3 / h, the flow rate of the reverse hydrogen is 55~90m³ / h. 3 / h. Specifically, the flow rate of hydrogen can be, for example, but not limited to, 310 m³ / h. 3 / h、330m 3 / h、360m 3 / h、370m 3 / h、390m 3 The flow rate of reverse hydrogen can be any one or more of the following values ​​per hour, or a range between both: 55 m³ / h; 3 / h、65m 3 / h、75m 3 / h、85m 3 / h、90m 3 Any one or a range between / h.

[0046] Furthermore, the reverse hydrogen acts as a coolant for the tungsten powder, while it is heated after passing through the cooling section, reducing the electric heating load of the deoxidation section, further saving energy, and also preventing the tungsten powder from growing.

[0047] Furthermore, in the pre-reduction section (corresponding to hydrogen): a high flow rate of hydrogen (310~390 m³ / h) ensures rapid removal of the water vapor (H₂O) generated in the reaction, preventing water vapor accumulation and the formation of WO₃H. X Generation (coarse particles). Main reduction section (with hydrogen): Maintain a high flow rate to promote the reduction of WO2 to W, while avoiding uneven reduction due to insufficient local hydrogen. Lower flow rate limit (<310 m³ / h): Water vapor retention, increased oxygen content in powder (>100 ppm), and easy formation of coarse particles. Upper flow rate limit (>390 m³ / h): Hydrogen waste, 30% increase in energy consumption, and high-speed airflow may cause fine powder (<50 nm) to be carried out, reducing the recovery rate.

[0048] Reverse hydrogen flow rate (55~90 m³ / h): Deoxidation section (reverse hydrogen): Reverse hydrogen (55~90 m³ / h) enters from the high-temperature zone (840~900℃), carrying away residual oxygen and inhibiting particle growth. Lower flow rate limit (<55 m³ / h): Incomplete deoxidation (oxygen content >80 ppm) may lead to local sintering (widened particle size distribution). Upper flow rate limit (>90 m³ / h): Excessively high reverse hydrogen flow rate will disturb powder flow, leading to increased dust and decreased recovery rate (<85%).

[0049] Preferably, in step S1, the tungsten ore has a particle size of 10~16μm and a specific surface area of ​​2~8m². 2 / g. Specifically, the particle size of tungsten can be, for example, but not limited to, any one of 10μm, 11μm, 12μm, 14μm, 16μm or a range between two of them; the specific surface area of ​​tungsten can be, for example, but not limited to, 2m². 2 / g、3m 2 / g、5m 2 / g、7m 2 / g、8m 2 The range of any one or both of / g.

[0050] Preferably, in step S1, the tungsten is fed at a rate of 0.5 to 2.5 kg / min. Specifically, the feeding rate can 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 between two of them.

[0051] Preferably, step S2 further includes:

[0052] The particle size of the first tungsten powder is detected. If the particle size of the first tungsten powder is within the preset particle size range, then step S3 is executed; otherwise, step S3 is stopped.

[0053] 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.

[0054] According to another aspect of the present invention, the present invention provides the following technical solution:

[0055] An ultrafine tungsten powder is obtained by the above-mentioned method for preparing ultrafine tungsten powder.

[0056] Preferably, the oxygen content of the ultrafine tungsten powder is <80ppm and the recovery rate is >90%.

[0057] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0058] Example 1

[0059] A method for preparing ultrafine tungsten powder includes the following steps:

[0060] 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 tilt angle to 5°, the furnace tube rotation speed to 6.0 r / min, and feed the purple tungsten at a rate of 1.2 kg / min.

[0061] S2. The purple tungsten is reduced in a reactor under a hydrogen atmosphere. The reactor consists 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. The length ratio of the cooling section to the heating section is 4:7. The pre-reduction section, the main reduction section, and the deoxidation section are of the same length. The pre-reduction section uses 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 proportion of the part without the spiral conveying blade is 30%. The temperature is set to 510℃, and the reaction time is 30 min. The main reduction section uses a second spiral conveying blade. The second helical conveyor blade has a pitch of 120 mm and is evenly and intermittently arranged along the helical direction. The portion of the section without helical conveyor blades accounts for 50% of the total area. The temperature is set at 715℃, and the reaction time is 25 min. The deoxidation section uses a third helical conveyor blade with a pitch of 200 mm, continuously arranged along the helical direction. The temperature is set at 860℃, and the reaction time is 17 min. In the pre-reduction and main reduction sections, hydrogen is introduced in the forward direction, while in the deoxidation and cooling sections, hydrogen is introduced against the forward direction, with a forward flow rate of 360 m³ / h. 3 / h, reverse hydrogen flow rate is 70m³ / h 3 / h; Laser particle size online detector setting warning range:

[0062] D50: That is, 330-470nm;

[0063] S3. Tungsten powder was obtained by cooling in the cooling section. Its average grain size D50 was 352 nm, span was 0.88, oxygen content was 67 ppm, and recovery rate was 93.60%.

[0064] Example 2

[0065] A method for preparing ultrafine tungsten powder includes the following steps:

[0066] 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 body tilt angle to 2° and the furnace tube rotation speed to 4.5 r / min. Feed the purple tungsten at a rate of 2.5 kg / min.

[0067] S2. Tungsten oxide is reduced in a reactor under a hydrogen atmosphere. The reactor consists 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. The length ratio of the cooling section to the heating section is 4:8. The pre-reduction section, main reduction section, and deoxidation section are of equal length. The pre-reduction section uses a first spiral conveyor blade with a pitch of 60 mm. The first spiral conveyor blade is evenly and intermittently arranged along the spiral direction, and the portion of the pre-reduction section excluding the spiral conveyor blade accounts for 20%. The temperature is set at 560℃, and the reaction time is 38 min. The main reduction section uses a second... The first section uses spiral conveyor blades with a pitch of 100mm. The second spiral conveyor blades are evenly and intermittently arranged along the spiral direction, with 45% of the section excluding the spiral conveyor blades. The temperature is set at 790℃, and the reaction time is 34 minutes. The deoxidation section uses a third spiral conveyor blade with a pitch of 180mm, continuously arranged along the spiral direction. The temperature is set at 900℃, and the reaction time is 28 minutes. The hydrogen gas introduced into the pre-reduction and main reduction sections flows in the forward direction, while the hydrogen gas introduced into the deoxidation and cooling sections flows against the forward direction, with a forward hydrogen flow rate of 390 m³ / h. 3 / h, reverse hydrogen flow rate is 90m³ / h 3 / h; Laser particle size online detector setting warning range:

[0068] D50: That is, 224~329nm;

[0069] S3. Tungsten powder was obtained by cooling in the cooling section. Its average grain size D50 was 280 nm, span was 0.88, oxygen content was 75 ppm, and recovery rate was 92.50%.

[0070] Example 3

[0071] A method for preparing ultrafine tungsten powder includes the following steps:

[0072] 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 body tilt angle to 6° and the furnace tube rotation speed to 7.2 r / min. Feed the purple tungsten at a rate of 0.5 kg / min.

[0073] S2. Tungsten oxide is reduced in a reactor under a hydrogen atmosphere. The reactor consists 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. The length ratio of the cooling section to the heating section is 3:7. The pre-reduction section, main reduction section, and deoxidation section are of equal length. The pre-reduction section uses a first spiral conveyor blade with a pitch of 100 mm. The first spiral conveyor blade is evenly and intermittently arranged along the spiral direction, and the portion of the pre-reduction section excluding the spiral conveyor blade accounts for 40%. The temperature is set to 480℃, and the reaction time is 25 min. The main reduction section uses a second... The first section uses spiral conveyor blades with a pitch of 140 mm. The second spiral conveyor blades are evenly and intermittently arranged along the spiral direction, with 55% of the section excluding the spiral conveyor blades. The temperature is set at 650℃, and the reaction time is 22 min. The deoxidation section uses a third spiral conveyor blade with a pitch of 220 mm, continuously arranged along the spiral direction. The temperature is set at 840℃, and the reaction time is 17 min. The hydrogen gas introduced into the pre-reduction and main reduction sections flows in the forward direction, while the hydrogen gas introduced into the deoxidation and cooling sections flows against the forward direction, with a forward hydrogen flow rate of 310 m³ / h. 3 / h, reverse hydrogen flow rate is 55m³ / h 3 / h; Laser particle size online detector setting warning range:

[0074] D50: That is, 298~417nm;

[0075] S3. Tungsten powder was obtained by cooling in the cooling section. Its average grain size D50 was 333 nm, span was 0.85, oxygen content was 70 ppm, and recovery rate was 94.20%.

[0076] Example 4

[0077] A method for preparing ultrafine tungsten powder includes the following steps:

[0078] 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 body tilt angle to 6° and the furnace tube rotation speed to 5.0 r / min. Feed the purple tungsten at a rate of 0.6 kg / min.

[0079] S2. Tungsten oxide is reduced in a reactor under a hydrogen atmosphere. The reactor consists 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. The length ratio of the cooling section to the heating section is 3:7. The pre-reduction section, main reduction section, and deoxidation section are of equal length. The pre-reduction section uses a first spiral conveyor blade with a pitch of 70 mm. The first spiral conveyor blade is evenly and intermittently arranged along the spiral direction, and the proportion of its portion without spiral conveyor blades is 25%. The temperature is set at 480℃, and the reaction time is 25 min. The main reduction section uses a second... The first section uses spiral conveyor blades with a pitch of 100mm. The second spiral conveyor blades are evenly and intermittently arranged along the spiral direction, with 50% of the section excluding the spiral conveyor blades. The temperature is set at 650℃, and the reaction time is 23 minutes. The deoxidation section uses a third spiral conveyor blade with a pitch of 190mm, continuously arranged along the spiral direction. The temperature is set at 840℃, and the reaction time is 16 minutes. The hydrogen gas introduced into the pre-reduction and main reduction sections flows in the same direction as the hydrogen flow, while the hydrogen gas introduced into the deoxidation and cooling sections flows in the opposite direction, with a flow rate of 390 m³ / h. 3 / h, reverse hydrogen flow rate is 90m³ / h 3 / h; Laser particle size online detector setting warning range:

[0080] D50: That is, 365~491nm;

[0081] S3. Tungsten powder was obtained by cooling in the cooling section. Its average grain size D50 was 396 nm, span was 0.81, oxygen content was 76 ppm, and recovery rate was 91.09%.

[0082] Example 5

[0083] A method for preparing ultrafine tungsten powder includes the following steps:

[0084] 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 body tilt angle to 3° and the furnace tube rotation speed to 7.0 r / min. Feed the purple tungsten at a rate of 2.1 kg / min.

[0085] S2. Tungsten oxide is reduced in a reactor under a hydrogen atmosphere. The reactor consists 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. The length ratio of the cooling section to the heating section is 3:8. The pre-reduction section, main reduction section, and deoxidation section are of equal length. The pre-reduction section uses a first spiral conveyor blade with a pitch of 90 mm. The first spiral conveyor blade is evenly and intermittently arranged along the spiral direction, and the proportion of the portion without the spiral conveyor blade is 35%. The temperature is set at 550℃, and the reaction time is 30 min. The main reduction section uses a second... The first section uses spiral conveyor blades with a pitch of 140 mm. The second spiral conveyor blades are evenly and intermittently arranged along the spiral direction, with 50% of the section excluding the spiral conveyor blades. The temperature is set at 775℃, and the reaction time is 28 min. The deoxidation section uses a third spiral conveyor blade with a pitch of 200 mm, continuously arranged along the spiral direction. The temperature is set at 900℃, and the reaction time is 22 min. The hydrogen gas introduced into the pre-reduction and main reduction sections flows in the same direction as the hydrogen flow, while the hydrogen gas introduced into the deoxidation and cooling sections flows against the hydrogen flow, with a flow rate of 390 m³ / h. 3 / h, reverse hydrogen flow rate is 90m³ / h 3 / h; Laser particle size online detector setting warning range:

[0086] D50: That is, 108~192nm;

[0087] S3. Tungsten powder was obtained by cooling in the cooling section. Its average grain size D50 was 144 nm, span was 0.84, oxygen content was 77 ppm, and recovery rate was 92.95%. Figure 1 As shown.

[0088] Comparative Example 1

[0089] A method for preparing ultrafine tungsten powder includes the following steps:

[0090] 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 body tilt angle to 5°, the furnace tube rotation speed to 6.0 r / min, and feed the purple tungsten at a rate of 1.2 kg / min.

[0091] S2. Tungsten oxide is reduced in a reactor under a hydrogen atmosphere. The reactor consists of a heating section and a cooling section from the feed end to the discharge end. The heating section comprises 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 pre-reduction section, main reduction section, and deoxidation section are of equal length. The pre-reduction section uses a first spiral conveyor blade with a pitch of 80 mm. The first spiral conveyor blade is continuously arranged along the spiral direction. The temperature is set to 510℃, and the reaction time is 30 min. The main reduction section uses a second... The first section uses spiral conveyor blades with a pitch of 60 mm. The second spiral conveyor blade is continuously arranged along the spiral direction. The temperature is set at 715℃, and the reaction time is 25 min. The deoxidation section uses a third spiral conveyor blade with a pitch of 150 mm, continuously arranged along the spiral direction. The temperature is set at 800℃, and the reaction time is 17 min. The hydrogen gas introduced into the pre-reduction and main reduction sections flows in the same direction as the hydrogen flow, while the hydrogen gas introduced into the deoxidation and cooling sections flows against the hydrogen flow, with a flow rate of 360 m³ / h. 3 / h, reverse hydrogen flow rate is 70m³ / h 3 / h; Laser particle size online detector setting warning range:

[0092] D50: That is, 330-470nm;

[0093] S3. Tungsten powder was obtained by cooling in the cooling section. Its average grain size (D50) was 869 nm, span was 1.27, oxygen content was 105 ppm, and recovery rate was 90.28%. The electron micrograph of the obtained tungsten powder is shown below. Figure 2 As shown, the grains are coarse. (An early warning was issued, the process was adjusted, but the target particle size could not be achieved. Production was stopped after a small number of samples were taken. The product particle size is too large and uneven.)

[0094] Compared with Example 1, in Comparative Example 1, all spiral conveying blades in each reaction section are continuously arranged along the spiral direction, that is, the proportion of the part without spiral conveying blades is 0%. The resulting tungsten powder has large grains, wide particle size distribution, high oxygen content and incomplete deoxidation.

[0095] Comparative Example 2

[0096] A method for preparing ultrafine tungsten powder includes the following steps:

[0097] 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 body tilt angle to 5°, the furnace tube rotation speed to 6.0 r / min, and feed the purple tungsten at a rate of 1.2 kg / min.

[0098] S2. Tungsten oxide is reduced in a reactor under a hydrogen atmosphere. The reactor consists 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. The length ratio of the cooling section to the heating section is 4:7. The pre-reduction section, main reduction section, and deoxidation section are of equal length. The pre-reduction section uses a first spiral conveyor blade with a pitch of 80 mm. The first spiral conveyor blade is evenly and intermittently arranged along the spiral direction, and the portion of the pre-reduction section without spiral conveyor blades accounts for 30%. The temperature is set at 580℃, and the reaction time is 30 min. The main reduction section uses a second spiral conveyor blade. The first section uses spiral conveyor blades with a pitch of 60mm. The second spiral conveyor blades are evenly and intermittently arranged along the spiral direction, with 50% of the section excluding the spiral conveyor blades. The temperature is set at 810℃, and the reaction time is 25 minutes. The deoxidation section uses a third spiral conveyor blade with a pitch of 200mm, continuously arranged along the spiral direction. The temperature is set at 1000℃, and the reaction time is 17 minutes. The hydrogen gas introduced into the pre-reduction and main reduction sections flows in the forward direction, while the hydrogen gas introduced into the deoxidation and cooling sections flows against the forward direction, with a forward hydrogen flow rate of 450 m³ / h. 3 / h, reverse hydrogen flow rate is 120m³ 3 / h; Laser particle size online detector setting warning range:

[0099] D50: That is, 330~470nm;

[0100] S3. Tungsten powder was obtained by cooling in the cooling section. Its average grain size D50 was 434 nm, span was 0.90, oxygen content was 65 ppm, and recovery rate was 81.60%.

[0101] Comparative Example 3

[0102] A method for preparing ultrafine tungsten powder includes the following steps:

[0103] 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 body tilt angle to 5°, the furnace tube rotation speed to 6.0 r / min, and feed the purple tungsten at a rate of 1.2 kg / min.

[0104] S2. Tungsten oxide is reduced in a reactor under a hydrogen atmosphere. The reactor consists 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. The length ratio of the cooling section to the heating section is 4:7. The pre-reduction section, main reduction section, and deoxidation section are of equal length. The pre-reduction section uses a first spiral conveyor blade with a pitch of 80 mm. The first spiral conveyor blade is evenly and intermittently arranged along the spiral direction, and the proportion of the portion without the spiral conveyor blade is 30%. The temperature is set at 400℃, and the reaction time is 30 min. The main reduction section uses a second spiral... The first section uses spiral conveyor blades with a pitch of 120mm. The second spiral conveyor blades are evenly and intermittently arranged along the spiral direction, with 50% of the section excluding the spiral conveyor blades. The temperature is set at 600℃, and the reaction time is 25 minutes. The deoxidation section uses a third spiral conveyor blade with a pitch of 200mm, continuously arranged along the spiral direction. The temperature is set at 800℃, and the reaction time is 17 minutes. The hydrogen gas introduced into the pre-reduction and main reduction sections flows in the forward direction, while the hydrogen gas introduced into the deoxidation and cooling sections flows against the forward direction, with a forward flow rate of 200 m³ / h. 3 / h, reverse hydrogen flow rate is 40m³ / h 3 / h; Laser particle size online detector setting warning range:

[0105] D50: That is, 330~470nm;

[0106] S3. Tungsten powder was obtained by cooling in the cooling section. Its average grain size D50 was 481 nm, span was 1.21, oxygen content was 132 ppm, and recovery rate was 91.9%.

[0107] Comparative Example 4

[0108] A method for preparing ultrafine tungsten powder includes the following steps:

[0109] Unlike Example 1, step S2 uses a single-tube rotary kiln from the prior art; the reverse hydrogen flow rate is 400 m³ / s. 3 / h, laser-free online particle size analyzer;

[0110] 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%.

[0111] Comparative Example 5

[0112] A method for preparing ultrafine tungsten powder includes the following steps:

[0113] Unlike Example 1, step S2 uses a dual-tube forward and reverse hydrogen rotary kiln from the prior art; there is no laser particle size analyzer.

[0114] Tungsten powder was obtained by cooling in the cooling section. Its average grain size D50 was 128 nm, span was 1.12, oxygen content was 205 ppm, and recovery rate was 86.51%.

[0115] Comparative Example 6

[0116] A method for preparing ultrafine tungsten powder includes the following steps:

[0117] Unlike Example 1, the temperatures of the pre-reduction section, main reduction section, and deoxidation section were 620℃, 800℃, and 930℃, respectively. The laser particle size analyzer was in alarm mode and production could not proceed normally.

[0118] Comparative Example 7

[0119] A method for preparing ultrafine tungsten powder includes the following steps:

[0120] Unlike Example 1, the pre-reduction section temperature, main reduction section temperature, and deoxidation section temperature are 620℃, 800℃, and 930℃, respectively, and the laser particle size analyzer is turned off.

[0121] Tungsten powder was obtained by cooling in the cooling section. Its average grain size D50 was 728 nm, span was 1.18, oxygen content was 95 ppm, and recovery rate was 91.61%.

[0122] Comparative Example 8

[0123] A method for preparing ultrafine tungsten powder includes the following steps:

[0124] Unlike Example 1, the hydrogen flow rate was 420 m³ / h. 3 / h; Tungsten powder was obtained by cooling in the cooling section, with an average grain size D50 of 340nm, span of 0.92, oxygen content of 77ppm, and recovery rate of 85.40%.

[0125] This invention provides an ultrafine tungsten powder and its preparation method. The preparation method includes the following steps: obtaining purple tungsten; reducing the purple tungsten in a reactor under a hydrogen atmosphere, wherein the reactor consists 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; the pre-reduction section uses a first spiral conveyor blade for material lifting; the main reduction section uses a second spiral conveyor blade for material lifting; and the deoxidation section uses a third spiral conveyor blade for material lifting, thereby improving the reduction efficiency by more than 40%; the deoxidation section reduces the pitch of the spiral conveyor blades, and the cooling section does not have spiral blades, reducing rotational resistance and reducing motor power consumption by 15%; finally, the ultrafine tungsten powder with narrow particle size distribution, low oxygen content, and high recovery rate is obtained by cooling in the cooling section.

[0126] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for preparing ultrafine tungsten powder, characterized in that, Includes the following steps: S1. Obtain purple tungsten; S2. The purple tungsten is reduced in a reactor under a hydrogen atmosphere. The reactor consists 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. The pre-reduction section uses a first spiral conveyor blade for material lifting, the main reduction section uses a second spiral conveyor blade for material lifting, and the deoxidation section uses a third spiral conveyor blade for material lifting, to obtain the first tungsten powder. The length ratio of the cooling section to the heating section is (3~4):(7~8). The lengths of the first spiral conveying blades are the same; the pitch of the first spiral conveying blade is 60~100mm, and the first spiral conveying blade is evenly and intermittently arranged along the spiral direction, with the proportion of the part without spiral conveying blades being 20~40%; the pitch of the second spiral conveying blade is 100~140mm, and the second spiral conveying blade is evenly and intermittently arranged along the spiral direction, with the proportion of the part without spiral conveying blades being 45~55%; the pitch of the third spiral conveying blade is 180~220mm, and the third spiral conveying blade is continuously arranged along the spiral direction. S3. The first tungsten powder is cooled in the cooling section to obtain the second tungsten powder, and the particle size distribution width of the second tungsten powder, i.e., the span value, is <0.

90.

2. The method for preparing ultrafine tungsten powder according to claim 1, characterized in that, In step S2, the reactor is a rotary kiln, which is used to reduce the purple tungsten. The tilt angle of the rotary kiln body is set to 2~6°, and the rotation speed of the rotary kiln tube is 4.5~7.2 r / min.

3. The method for preparing ultrafine tungsten powder according to claim 1, characterized in that, In step S2, the heating temperature of the pre-reduction section is 480~560℃ and the heating time is 24~40min; the heating temperature of the main reduction section is 650~790℃ and the heating time is 20~36min; the heating temperature of the deoxygenation section is 840~900℃ and the heating time is 15~30min.

4. The method for preparing ultrafine tungsten powder according to claim 1, characterized in that, In step S2, the hydrogen is introduced in a bidirectional manner, with the hydrogen introduced in the same direction as the flow direction of the tungsten (forward hydrogen flow) and in the opposite direction (backward hydrogen flow). The hydrogen introduced into the pre-reduction section and the main reduction section is in the forward hydrogen flow direction, while the hydrogen introduced into the deoxidation section and the cooling section is in the backward hydrogen flow direction. The forward hydrogen flow rate is 310~390 m³ / h. 3 / h, the flow rate of the reverse hydrogen is 55~90m³ / h. 3 / h.

5. The method for preparing ultrafine tungsten powder according to claim 1, characterized in that, In step S1, the tungsten ore has a particle size of 10~16μm and a specific surface area of ​​2~8m². 2 / g, fed at a rate of 0.5~2.5kg / min.

6. The method for preparing ultrafine tungsten powder according to claim 1, characterized in that, 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 the preset particle size range, then step S3 is executed; otherwise, step S3 is stopped.

7. The method for preparing ultrafine tungsten powder according to claim 6, 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.

8. An ultrafine tungsten powder, characterized in that, The ultrafine tungsten powder is obtained by the preparation method of ultrafine tungsten powder as described in any one of claims 1 to 7.

9. The ultrafine tungsten powder according to claim 8, characterized in that, The oxygen content of the ultrafine tungsten powder is <80ppm, and the recovery rate is >90%.

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