CN114289722A - Preparation method of fine-grained spherical tungsten powder - Google Patents
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Abstract
A preparation method of fine-grained spherical tungsten powder, belonging to the technical field of powder metallurgy. Aiming at the problems of large particles, wide distribution of powder particle sizes and low yield in the spheroidization process caused by irregular shapes and easy agglomeration of the tungsten powder with fine particle sizes of the raw materials at present, the invention firstly adopts the fluidized bed to treat and improve the powder state of the tungsten powder, improves the dispersibility of the powder and changes the surface shape of the powder. And then sending the treated powder into a powder feeding device, applying pressure to form a plasma torch, and carrying out spheroidizing treatment on the powder. Finally, the spherical tungsten powder with smooth surface and high spheroidization rate is obtained. The invention adopts the combination of the convection dispersion technology and the plasma spheroidization technology to prepare the fine-grained spherical tungsten powder, and the spheroidized tungsten powder has low activity, no pollution, good sphericity, full spheroidization and high yield.
Description
Technical Field
The invention belongs to the technical field of powder metallurgy, and particularly relates to a preparation method of fine-grained spherical tungsten powder.
Background
Tungsten and its alloy have excellent properties such as high melting point, high-temperature strength, good heat resistance and corrosion resistance, and are widely applied to the fields of aerospace, nuclear power, medical treatment and the like. The traditional powder metallurgy method is difficult to prepare tungsten and tungsten alloy products with complex structures. With the continuous development of material forming technology, 3D printing and powder injection forming technology become effective methods for preparing small tungsten and its alloy products. As a raw material for preparing tungsten product parts with complex structures by 3D printing and powder injection molding, the preparation of spherical tungsten powder is an important link for developing novel tungsten and alloy products thereof. Various methods for preparing spherical tungsten powder, such as halogenation method, rotating electrode method, partial preferential oxidation alkaline washing, ammonium paratungstate cyclic oxidation reduction method, spray drying method, etc., have various disadvantages, and industrialization cannot be realized. Therefore, it is necessary to develop a simple and low-cost preparation process of spherical tungsten powder.
The plasma spheroidization has the advantages of high energy density, high heating strength, no pollution and the like, has good effect on the treatment of refractory metal powder such as tungsten and the like, and can obtain spherical powder with good sphericity, high spheroidization rate and high purity. Because the commercial fine-grained tungsten powder is seriously agglomerated, the granularity and the granularity distribution of the powder obtained after the radio frequency plasma spheroidization are mainly determined by the granularity and the granularity distribution of the feeding powder, the spheroidization rate of the powder is improved by improving the power under the condition, the fine-grained spherical tungsten powder is gasified and disappears in the process, the median diameter of the powder is increased, and the powder obtained by the plasma spheroidization is wide in granularity distribution and easy to agglomerate and grow. The fluidization dispersion treatment can realize deagglomeration, crushing and refining and surface shaping of the powder, improve loose packing, tap density and the like of the powder, and has the advantages of low energy consumption, small abrasion and the like. Chinese patent (CN104070173B) discloses a method for preparing spherical tungsten powder, which comprises the steps of feeding tungsten powder with the particle size of 5-27 mu m into an air flow mill, grinding, and spheroidizing by an argon plasma torch to obtain the spherical tungsten powder, wherein the spheroidized powder has larger particle size, uneven distribution and low spheroidization rate of aggregates. Chinese patent (CN104174862B) discloses a preparation method of spherical tungsten powder with low cost, easy mass production and easy parameter control, but the prepared powder has uneven granularity, poor sphericity and easy pollution, and fine spherical tungsten powder is difficult to obtain. Therefore, the invention adopts the combination of the convection dispersion technology and the plasma spheroidization technology to prepare the fine-grained spherical tungsten powder, and the spheroidized tungsten powder has low activity, no pollution, good sphericity, full spheroidization and high yield.
Disclosure of Invention
The invention aims to solve the problems of large particles, wide distribution of powder particle sizes and low yield after spheroidization in the spheroidization process due to the fact that the existing tungsten powder with fine particle size is irregular and easy to agglomerate, and the spherical tungsten powder is prepared by combining a fluidization dispersion technology and a plasma spheroidization technology.
A preparation method of spherical tungsten powder is characterized in that a counter-jet type airflow milling dispersion technology is combined with a plasma spheroidization technology to prepare the spherical tungsten powder;
the method comprises the following specific steps:
1) the raw material powder is tungsten powder with the purity of more than 99.9 percent and the granularity of less than 3 mu m;
2) adding raw material powder into a fluidized bed, filling high-purity inert gas into equipment from bottom to top to remove air before dispersion treatment, providing a gas protection environment for the powder, and performing gas-filled cleaning on the equipment; after the air in the fluidized bed cavity is exhausted, transferring the air into a heating device, continuously introducing high-purity hydrogen gas with stable flow in the fluidized bed treatment process, and carrying out fluidization treatment for a certain time at constant current and constant temperature;
3) after the fluidized bed is subjected to dispersion treatment, the cavity of the fluidized bed is removed from the heating device, high-purity inert protective gas is continuously introduced, and after the fluidized bed is cooled to room temperature, the introduction of the protective gas is stopped, so that treated powder is obtained;
4) under the protection atmosphere of high-purity hydrogen with the purity of more than 99.9 percent, carrying out one or more times of calcination treatment on the powder treated in the step 3) at the temperature of 200-450 ℃;
5) sending the treated powder into a powder feeding device, applying pressure to form a plasma torch by taking argon as working gas, and carrying out spheroidizing treatment on the powder;
6) and cooling and collecting the powder after the plasma spheroidization to obtain the treated powder.
Further, the flow rate of the hydrogen gas flow in the step 2) is 1.5-5L/min, the heating temperature is 150-280 ℃, and the fluidization treatment is carried out for 100-360 min under constant flow and constant temperature.
Further, the calcination treatment process in the step 4) comprises the following steps: the heating rate is 1-2 ℃/min, the heat preservation time is 60-300 min, and the cooling rate is 2-5 ℃/min.
Further, in the spheroidizing treatment in the step 5), the powder feeding rate is 10-18 g/min, the treatment power is 10-35 kw, the powder feeding air flow is 8-15L/min, the middle gas flow is 35-50L/min, and the side gas flow is 30-75L/min.
The invention has the advantages that:
(1) the fluidization treatment is carried out under the atmosphere of high-purity inert gas and hydrogen, and due to the action of air flow, collision and friction occur between the powder and the inner wall of the cavity of the fluidized bed, so that the agglomeration among particles is opened, the surface appearance of the particles is changed, and no pollution is caused;
(2) after fluidization and dispersion treatment, the tungsten powder is agglomerated and opened, the fluidity becomes good, and the loose-packed tap density is improved;
(3) after the powder after fluidization treatment is calcined, the internal stress generated in the fluidization process can be eliminated, the powder activity is reduced, and the particle growth can be avoided in the subsequent plasma spheroidization process;
(4) the energy density in the plasma spheroidization process is high, the heating strength is high, the purity of the obtained powder is high, the spheroidization rate is high, the sphericity is good, and the method is suitable for treating refractory metal powder;
(5) the tungsten powder after fluidization and dispersion treatment is spheroidized by radio frequency plasma, and the tungsten powder has better fluidity, so that aggregation and growth of aggregate particles can be effectively avoided, and the spheroidized tungsten powder has good sphericity, sufficient spheroidization and high yield.
Drawings
FIG. 1 is an XRD pattern of tungsten powder before and after fluidization-plasma spheroidization.
Detailed Description
Example 1
1) The raw material powder is commercially available tungsten powder, the granularity is 2 mu m, and the purity is more than 99.9 percent;
2) adding raw material powder into a fluidized bed, filling high-purity inert gas into equipment from bottom to top to remove air before dispersion treatment, providing a gas protection environment for the powder, and performing gas-filled cleaning on the equipment; after the air in the cavity of the fluidized bed is exhausted, transferring the air into a heating device, and continuously introducing high-purity inert gas with stable flow in the fluidized bed treatment process, wherein the flow rate of the gas flow is 5L/min, the heating temperature is 250 ℃, and the fluidized treatment is carried out for 180min under constant flow and constant temperature;
3) after the fluidized bed is subjected to dispersion treatment, the cavity of the fluidized bed is removed from the heating device, high-purity inert protective gas is continuously introduced, and after the fluidized bed is cooled to room temperature, the introduction of the protective gas is stopped, so that treated powder is obtained;
4) under the protective atmosphere of high-purity hydrogen with the purity of more than 99.9 percent, heating the fluidized powder to 400 ℃ at the speed of 1 ℃/min, and preserving the heat for 60min to carry out two-time calcination treatment, wherein the cooling rate is 3 ℃/min;
5) sending the treated powder into a powder feeding device, using argon as working gas, applying pressure to form a plasma torch, and carrying out spheroidizing treatment on the powder, wherein the powder feeding speed is 15g/min, the treatment power is 30kw, the powder feeding gas flow is 15L/min, the middle gas flow is 50L/min, and the side gas flow is 75L/min;
6) and cooling and collecting the powder after plasma ionization to obtain spherical tungsten powder with particle size distribution concentrated about 2 microns, spheroidization rate close to 100% and good sphericity.
Example 2
1) The raw material powder is commercially available tungsten powder, the granularity is 1 mu m, and the purity is more than 99.9 percent;
2) adding raw material powder into a fluidized bed, filling high-purity inert gas into equipment from bottom to top to remove air before dispersion treatment, providing a gas protection environment for the powder, and performing gas-filled cleaning on the equipment; after the air in the cavity of the fluidized bed is exhausted, transferring the air into a heating device, and continuously introducing high-purity hydrogen gas with stable flow in the fluidized bed treatment process, wherein the flow rate of the gas flow is 4L/min, the heating temperature is 200 ℃, and the fluidization treatment is carried out for 120min at constant current and constant temperature;
3) and after fluidization dispersion treatment, removing the cavity of the fluidized bed from the heating device, continuously introducing high-purity inert protective gas, and after cooling to room temperature, stopping introducing the protective gas to obtain treated powder.
4) Under the protective atmosphere of high-purity hydrogen with the purity of more than 99.9 percent, heating the fluidized powder to 300 ℃ at the speed of 2 ℃/min, and preserving the heat for 90min to carry out primary calcination treatment, wherein the cooling rate is 4 ℃/min;
5) sending the treated powder into a powder feeding device, using argon as working gas, applying pressure to form a plasma torch, and carrying out spheroidizing treatment on the powder, wherein the powder feeding speed is 12g/min, the treatment power is 25kw, the powder feeding gas flow is 10L/min, the middle gas flow is 45L/min, and the side gas flow is 65L/min;
6) and cooling and collecting the powder after plasma spheroidization to obtain the spherical tungsten powder with the particle size distribution concentrated about 1 mu m, the spheroidization rate close to 100 percent and good sphericity.
Example 3
1) The raw material powder is commercially available tungsten powder, the granularity is 0.8 mu m, and the purity is more than 99.9 percent;
2) adding raw material powder into a fluidized bed, filling high-purity inert gas into equipment from bottom to top to remove air before dispersion treatment, providing a gas protection environment for the powder, and performing gas-filled cleaning on the equipment; after the air in the fluidized bed cavity is exhausted, transferring the air into a heating device, continuously introducing high-purity hydrogen gas with stable flow in the fluidized bed treatment process, wherein the flow rate of the gas flow is 3L/min, the heating temperature is 180 ℃, and performing fluidization treatment for 100min under constant flow and constant temperature.
3) And after fluidization dispersion treatment, removing the cavity of the fluidized bed from the heating device, continuously introducing high-purity inert protective gas, and after cooling to room temperature, stopping introducing the protective gas to obtain treated powder.
4) Under the protective atmosphere of high-purity hydrogen with the purity of more than 99.9 percent, heating the fluidized powder to 250 ℃ at the speed of 1 ℃/min, and preserving the heat for 120min to carry out primary calcination treatment, wherein the cooling rate is 2 ℃/min;
5) sending the treated powder into a powder feeding device, using argon as working gas, applying pressure to form a plasma torch, and carrying out spheroidizing treatment on the powder, wherein the powder feeding speed is 10g/min, the treatment power is 25kw, the powder feeding gas flow is 8L/min, the middle gas flow is 40L/min, and the side gas flow is 60L/min;
6) after spheroidizing treatment: and cooling and collecting the powder after plasma spheroidization to obtain the spherical tungsten powder with the particle size distribution concentrated about 0.8 mu m, the spheroidization rate close to 100 percent and good sphericity.
Although the present invention has been described with reference to a preferred embodiment, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (4)
1. A preparation method of spherical tungsten powder is characterized in that a counter-jet type airflow milling dispersion technology is combined with a plasma spheroidization technology to prepare the spherical tungsten powder;
the method comprises the following specific steps:
1) the raw material powder is tungsten powder with the purity of more than 99.9 percent and the granularity of less than 3 mu m;
2) adding raw material powder into a fluidized bed, filling high-purity inert gas into equipment from bottom to top to remove air before dispersion treatment, providing a gas protection environment for the powder, and performing gas-filled cleaning on the equipment; after the air in the fluidized bed cavity is exhausted, transferring the air into a heating device, continuously introducing high-purity hydrogen gas with stable flow in the fluidized bed treatment process, and carrying out fluidization treatment for a certain time at constant current and constant temperature;
3) after the fluidized bed is subjected to dispersion treatment, the cavity of the fluidized bed is removed from the heating device, high-purity inert protective gas is continuously introduced, and after the fluidized bed is cooled to room temperature, the introduction of the protective gas is stopped, so that treated powder is obtained;
4) under the protection atmosphere of high-purity hydrogen with the purity of more than 99.9 percent, carrying out one or more times of calcination treatment on the powder treated in the step 3) at the temperature of 200-450 ℃;
5) sending the treated powder into a powder feeding device, applying pressure to form a plasma torch by taking argon as working gas, and carrying out spheroidizing treatment on the powder;
6) and cooling and collecting the powder after the plasma spheroidization to obtain the treated powder.
2. The method for preparing spherical tungsten powder according to claim 1, wherein the flow rate of the hydrogen gas flow in the step 2) is 1.5 to 5L/min, the heating temperature is 150 to 280 ℃, and the fluidization treatment is carried out for 100 to 360min under constant flow and constant temperature.
3. The method for preparing spherical tungsten powder according to claim 1, wherein the calcination treatment process in the step 4) is: the heating rate is 1-2 ℃/min, the heat preservation time is 60-300 min, and the cooling rate is 2-5 ℃/min.
4. The method for producing spherical tungsten powder according to claim 1, wherein the spheroidization in the step 5) is performed at a powder feeding rate of 10 to 18g/min, a treatment power of 10 to 35kw, a powder feeding flow rate of 8 to 15L/min, a middle gas flow rate of 35 to 50L/min, and a side gas flow rate of 30 to 75L/min.
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| CN117000993A (en) * | 2023-08-04 | 2023-11-07 | 湖南宏承新材料科技有限公司 | Preparation method of tantalum powder for metal additive manufacturing |
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