CN1260123C - Prepn process of nano level tungsten powder and WC powder - Google Patents
Prepn process of nano level tungsten powder and WC powder Download PDFInfo
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Abstract
The present invention provides a preparation method of nano-grade tungsten powder and tungsten carbide powder. In the method, nano-grade WO3 powder is prepared by a supersonic spraying thermal conversion method at the high temperature of 250 to 300 DEG C and high pressure of 2.5 to 3.5MPa, the powder is reduced into nano WO<2.9> blue tungsten powder by H2, superhigh speed interlayer shear breaking is carried out, simultaneously, an isolating agent is added to coat the nano-grade blue tungsten particles, and then rotary liquid particle grading, continuous centrifugal sedimentation and baking are carried out to prepare nano blue tungsten powder coated with films; the powder is put in an air-extraction water-discharge reducing furnace with H2 led into both ends for heat preservation at the low temperature of 700 to 750 DEG C for 60 to 90 minutes, tungsten powder with the average particle size of no more than 80 nm is reduced, then the nano-grade tungsten powder and nano-grade carbon black powder are mixed, an organic substance isolating agent is added, after centrifugation and drying, heat preservation at the temperature of 980 to 1000 DEG C for 60 to 80 minutes and carbonization are carried out, nano-grade WC powder is prepared, bridging granules are broken by a superhigh speed interlayer shear machine, and through rotary liquid grading, centrifugal sedimentation and drying, the WC powder with the average particle size of no more than 90 nm is prepared.
Description
Technical Field
The invention belongs to the technical field of preparation of high-melting-point metal tungsten powder and tungsten carbide powder thereof, and particularly provides a preparation method of nano-grade superfine tungsten powder and nano-grade tungsten carbide powder, which is suitable for industrial production of nano-grade tungsten powder and nano-grade tungsten carbide powder.
Background
The melting point of tungsten metal is as high as 3410 ℃, and the highest position in all the metals is more noble, the boiling point is 5527 ℃, the evaporation heat is 799.4(J/ml), and any metal is not comparable. This characteristic determines that the metal tungsten can be the best material for use under high temperature and ultra-high temperature conditions, so the metal tungsten is widely used to makevarious electric incandescent filaments, ultra-high temperature electrothermal bodies, ultra-high temperature heat-resistant parts, etc., such as various electric filaments, thermionic emission filaments and cathodes, ultra-high temperature electrothermal elements, heat shields, etc.
The domestic demand of only illuminating filaments is up to 450 tons every year. The tungsten electric heating element (plate) year is about 150 tons, and the blunt tungsten ingot blank and large-scale products are about 170 tons. In recent years, with the development of high and new technologies, the demand for high-performance tungsten plates, especially wide (more than 700mm) large-area thin plates, ultrathin foil strips with high-performance long-life anti-seismic tungsten filaments and the like is increased rapidly, for example, the annual demand for high-quality tungsten sheets for DVD disks nickel-plated tungsten boats exceeds 70 tons, and the annual demand for military products exceeds 50 tons. In recent years, tungsten alloy has been used as a substrate, a heat slug, a packaging connector and a heat dissipation element in large-scale integrated circuits and high-power microwave devices due to its excellent electrical conductivity, heat dissipation characteristics, controllable expansion coefficient and other characteristics. The tungsten-copper alloy has high heat conductivity and heat resistance, greatly improves the use power of microelectronic devices, can miniaturize the devices, and has expansion coefficient which can be well matched with semiconductor materials such as silicon chips, gallium arsenide and the like in the microelectronic devices and ceramic materials for tube seats, so the tungsten-copper alloy is an ideal packaging material. According to the incomplete statistics in 2000, only the tungsten powder is required for 200-250 tons in China, and the research and development work of the metal tungsten powder has important significance in national economic development and modernhigh-tech development.
China is a large tungsten-producing country, more than 2 ten thousand tons of crude tungsten products are exported every year, 50 percent of tungsten used by large countries in all industries in the world is provided by China, the yield of pure tungsten metal products in China is about 1000-1200 tons, the yield is also top in the world, but China hardly exists in recent years on the production technology and intellectual property rights of high-quality tungsten materials. The development of new technology is slower, but the development of high and new technology has higher and higher requirements on pure tungsten and alloy materials thereof, and the requirements on tungsten wires, plates, foils or other alloy materials (such as tungsten-copper electrical alloy, tungsten-nickel-iron high-specific gravity alloy and the like) taking tungsten as a matrix are provided for uniform structure, ultra-fine grain and good plasticity. But the prior production technology is difficult to meet the development requirement of modern high technology. The long-term production experience shows that the tungsten material is manufactured, and the intermediate product is obtained by adopting a powder metallurgy process in the early stage, wherein the process mainly comprises the following steps: preparing raw powder, forming, sintering and the like. Then, the final used product can be obtained by further hot processing and the like according to the product performance requirements. Research shows that the quality of the original tungsten powder, particularly the granularity of the tungsten powder, has a determining effect on the powder metallurgy process and the material performance of the tungsten product.
As known from about 15 years of relevant literature retrieval and analysis, tungsten powder with the particle size of 2-5 microns is adopted in production or development work of various countries at present, the tungsten powder is rapidly aggregated, recrystallized and grown from 800 ℃ to about 2000 ℃, and crystal grains grow from (2-5) microns to (200-400) microns and are about 60-80 times of original tungsten crystal grains. The coarse tungsten grains obviously reduce the mechanical property, the physical property and the pressure processing property of the pure tungsten material. If the tungsten particles can be made finer, the tungsten billet will have excellent properties. Therefore, in recent years, it has been a focus of much attention of domestic and foreign scholars to adopt tungsten powder with nanometer ultrafine particles (less than or equal to 100nm) in production, prepare tungsten blanks with ultrafine grains by a powder metallurgy process, and study the comprehensive mechanical properties of the tungsten blanks.
The WC tungsten carbide powder is the main raw material of hard alloy, the annual output of the hard alloy in China is 7600 tons, and the annual WC needs about 6000 tons, and the recent material science progress reveals that when the WC particle size is less than or equal to 100nm, the ultra-fine grain hard alloy with the WC average grain size less than or equal to 0.5 mu m can be obtained, the bending strength of the alloy is up to 4300MPa which is twice higher than that of the conventional alloy and exceeds the bending strength of high-speed steel. Has wide application prospect in the development of modern high-tech and new materials, so the preparation technology of the nano tungsten carbide powder is a competitive hot spot of various industry strong countries.
Disclosure of Invention
The invention aims to provide a preparation method of nano-grade superfine tungsten powder and tungsten carbide powder, which is suitable for industrial production.
The invention adopts a supersonic spray thermal conversion methodwith the high temperature of 250-300 ℃ and the high pressure of 2.5-3.5 MPa to prepare the nanoscale WO3Powder of H2Reducing the gas into WO at the temperature of 420-500 DEG C2.9Blue tungsten powder, use of And (2) phase change stress crushing effect, namely preparing loose and porous nano blue tungsten powder, further crushing blue tungsten particles by using an ultrahigh-speed interlaminar shear crusher, performing particle size classification by using a high-speed hydrocyclone classifier, settling and separating the nano blue tungsten particle slurry by using a continuous centrifuge, and returning the large blue tungsten powder to the ultrahigh-speed interlaminar shear to continue shearing and crushing. Adding phenolic resin in the shearing and crushing process to coat a layer of separant on the surfaces of the nano blue tungsten particles to prevent new tungsten particles from gathering, recrystallizing and growing in the reduction process, and feeding H at two ends2And reducing the tungsten powder at the low temperature of 700-750 ℃ in a reducing furnace with air exhaust and drainage at the middle section to prepare a first product, namely nano tungsten powder, mixing the nano tungsten powder with nano carbon black powder and industrial alcohol, simultaneously adding phenolic resin, and preparing carbonized mixed slurry in a high-speed interlaminar shear crusher. Centrifugally drying, carbonizing at 980-1000 deg.C, discharging, crushing with high-speed interlaminar shearing machine, grading, centrifuging, separating alcohol, oven drying, sieving with 15 μm sieve, and making into flat productWC powder with the average grain diameter less than or equal to 90nm, and the shape of the grains is spherical. The specific preparation process of the invention comprises the following steps:
1. preparation of nanoscale WO3Powder of
Preparation of nano WO by high-temperature high-pressure supersonic spray thermal conversion method3Powder: the atomized solution is directly prepared from high-concentration ammonium tungstate solution, WO thereof3The content is 350-370 g/L, the newly designed supersonic atomizing nozzle with ring gap airflow resonant short focal length F of 13mm and nozzle spray angle α of 45 degrees is used for spraying, the compressed air pressure is 2.5-3.5 MPa, and the air jet speed is 650-700 m.s-1. The liquid flow conveying speed is 280-320 ml/min, the hot air temperature is 250-350 ℃, reverse air supply is adopted, and the obtained nano WO3The water content of the powder was reduced to 15%, and the obtained WO3The average particle size of the powder is less than or equal to 50 nm.
2. By H2Preparation of loose and porous blue tungsten powder particles by low-temperature reduction
By H2Low temperature (420-500 deg.C), H2Gas cross section flow rate of 20ml/cm2Preparing loose and porous blue tungsten by reduction at 60-80 min (WO)2.9) Powder particles. Following WO3To WO2.9When in use, WO3The crystal system of (A) is not changed and is a monoclinic system, but the lattice constants of a-axis and c-axis are respectively represented by a1＝0.7304，c10.3844(nm) expansion to alpha of blue tungsten21.205(nm) (about 1.65 times) c22.359(nm) (about 6.14 times) and b-axis b10.7514nm, reduction to b2About 2 times of 0.3767nm, the huge shearing deformation of crystal lattice causes a great deal of cracks and pores in the blue tungsten particles, and most of WO is in the process of forming blue tungsten3The particles have fragmented into small particles of blue tungsten, with all the blueThe small tungsten particles are formed into loose and porous fragile particles, and provide favorable conditions for further crushing the blue tungsten particles. The average particle size of the loose and porous nano blue tungsten particles is less than or equal to 40 nm.
3. Ultra-high-speed interlaminar shear crushing of langtung particles
An ultrahigh-speed interlaminar shearing crusher is characterized in that a plurality of porous moving plates rotating at a high speed (10000-20000 rpm) and a plurality of porous fixed plates with the same number relatively move at a high speed to generate an interlaminar high-energy shearing effect, so that nano brittle particles can be further crushed, and loose nano blue-tungsten particles can be further crushed. Preparing slurry from loose and porous blue tungsten powder according to the mass ratio of blue tungsten to industrial alcohol of 1: 5, putting the slurry into a shearing machine, and circularly shearing the slurry according to 40 min/kg. Separating coarse micron-sized particles and blue tungsten particles larger than 40nm from the slurry by a high-speed rotary liquid type nano-particle grader, returning the slurry to a shearing machine for continuous shearing, and suspending the fine nano blue tungsten particles smaller than or equal to 40nm in industrial alcohol to form suspension. After the blue tungsten is crushed by an ultra-high-speed interlaminar shearing machine, the blue tungsten particles are all less than or equal to 40nm, the particle size distribution is narrow, and micron-sized blue tungsten particles are not generated.
4. Nano blue tungsten particles coated by phenolic resin
Adding phenolic resin powder with grain size not greater than 43 microns into the mixture of industrial alcohol and phenolic resin in the weight ratio of 100 to 500 to 3, dissolving the phenolic resin powder in alcohol fast and adsorbing the phenolic resin powder onto the surface of the blue tungsten grains, centrifugal deposition, drying to form one layer of phenolic resin film on the surface of each nanometer blue tungsten grain, and test to test the film on H2Gradually decompose at a temperature below 850 deg.C to form carbon film, and the residual carbon film is in H2The gas can be used as a reducing agent to participate in reduction reaction in the process of reducing the blue tungsten.
The phenolic resin film is always coated on the surface of the blue tungsten particles in the process of reducing the blue tungsten particles into the tungsten particles, so that the new tungsten particles are prevented from contacting with each other, and are aggregated and recrystallized to grow into micron-sized large-particle tungsten powder.
5. Separation of nano blue tungsten powder by continuous high-speed centrifugal machine
The nano blue tungsten alcohol slurry separated by a high-speed (5000-6000 rpm) rotary liquid type nano particle classifier after shearing and crushing is generally suspension of nano blue tungsten, the natural settling time is more than 150 hours, a continuous high-speed centrifugal separator is in a state of rotating at a high speed (10000-15000 rpm), the suspension of the nano blue tungsten is uninterruptedly added, nano blue tungsten particles in the liquid are automatically separated from alcohol liquid under the action of the centrifugal separator, clarified alcohol liquid is continuously and automatically discharged and recovered from the centrifugal separator, and the centrifugal separator can form pipeline networking automatic control with a shearing machine, the rotary liquid particle classifier and the continuous high-speed centrifugal separator. The industrial alcohol separated by the continuous centrifuge can be repeatedly used because of containing phenolic resin. And drying the nano blue tungsten slurry centrifugally precipitatedby the high-speed centrifuge to prepare the nano blue tungsten powder coated with the separant.
6. Air exhaust and drainage H2Preparing nano tungsten powder by reduction:
two ends enter H2A stainless steel tube type reduction furnace for exhausting air and draining water in the middle section. Is designed according to the temperature zone of two-stage furnace, and the low-temperature zone is a down-boat through H2The high temperature zone is a reverse boat through H2. Approximately reduced to W in the middle section of the furnace tube2.72——WO2And an air exhaust drain pipe is arranged at the position of the tungsten oxide, namely the position where the tungsten particles grow most easily by the water vapor, so that the water vapor in the reaction product is timely exhausted. The reduction temperature is 700-740 ℃; and preserving the heat for 60-90 minutes. The reaction formula is as follows: ，H2the cross-sectional flow is 30-40 ml/cm2Minute, H2The dew point at the gas inlet was-40 ℃. The cooled nano tungsten powder discharged from the furnace is easy to self-ignite and should be immediately used as power frequency N2Sieving with 15 μm sieve, spraying acetone-oleic acid solution in tungsten powder, packaging, storing or pouring into industrial alcohol for slow passivation. The average particle size of the tungsten powder reduced at low temperature can be ensured to be less than or equal to 80 nm. Nevertheless, this is trueA small amount of tungsten particles can form bridging aggregates, so that before the first product leaves a factory, a high-speed interlaminar shearing machine is still needed for shearing and crushing, and corresponding centrifugal precipitation, drying and power frequency N are needed2Air flow vibrating screen
7. Preparing a nano carbide mixture:
the obtained uncut nano tungsten powder, nano carbon black powder (the average particle diameter is less than or equal to 30nm) and phenolic resin powder (the average particle diameter is less than or equal to 44 mu m) are weighed and proportioned according to the mass ratio of the tungsten powder to the carbon black powder to the phenolic resin powder of 100: 6.73: 3, the materials are preliminarily stirred and mixed to prepare a rough mixed material, then the rough mixed material and industrial alcohol are respectively put into a high-speed interlaminar shearing crusher according to the mass ratio of 1: 5 to be crushed at one side, and meanwhile, the surfaces of tungsten particles are coated with phenolic resin thin films, and the rough mixed material is sheared, crushed and coated according to 40 minutes/kg. The second coating of phenolic resin film is to prevent nanometer tungsten grains from approaching to each other before forming WC grains and to avoid aggregation, re-crystallization and growth, and the sheared mixed material slurry is also centrifugally separated, alcohol recovered and stoved to produce mixed carbide material, which is then transferred to low temperature carbonization
8. Low-temperature carbonization:
the prepared mixture is put into a stainless steel tube furnace H2Carbonizing at 980-1000 ℃ for 60-80 minutes under the protection of gas, wherein the reaction formula is as follows: the nanometer WC powder after being discharged from the furnace is also processed before leaving the factory, namely, the nanometer WC powder is crushed into bridge-connected aggregates by an ultra-high-speed interlaminar shearing machine, the cyclone particles are classified, coarse particles are returned to continue shearing, centrifugal separation and recovery of alcohol are carried out, drying is carried out at 70 ℃ in vacuum, and power frequency N is carried out2Screening by a gas flow vibrating screen, detecting granularity, vacuum packaging and the like. The WC powder with the average grain diameter less than or equal to 90nm can be prepared, and the shape of the grains is nearly spherical.
9. Product ex-factory pretreatment procedure:
adding industrial alcohol into WC powder, crushing the bridging aggregate in a superhigh speed interlaminar shearing crusher, liquid rotating and grading the suspended slurry, continuous centrifugal settling, centrifugal separation of alcohol, stoving, sieving with 15 micron sieve to obtain spherical nanometer tungsten carbide powder with average particle size not greater than 90nm
The invention has the advantages that:
1. as the difficult problems to be solved in the industrial production of the nano-powder are solved in the main process, such as the high-pressure supersonic nozzle, the nano WO can be continuously and efficiently prepared3Pulverizing; the ultrahigh-speed interlaminar shearing machine can solve the problem that micron-sized brittle particles are crushed into nanometer-sized ultrafine particles, and is equipment with highest energy and best crushing effect in micron particle crushers recorded in all documents at present; the high-speed hydrocyclone classifier can separate coarser particles from small particles in the nanoscale powder, and can be connected with a shearing machine and a continuous modeThe centrifuge forms a circulating system, on one hand, large particles are separated out and returned to the shearing machine for continuous crushing, and on the other hand, particles smaller than 80nm can be sent to the continuous centrifuge; air exhaust and drainage H2Reduction furnace, which solves H from equipment for a long time2The water in the reduction furnace is difficult to drain. The six devices form a new generation of nano tungsten powder and a complete set of process equipment for producing nano tungsten carbide powder.
2. The new phenolic resin process can prevent the new tungsten grains from being close to each other or being evaporated and condensed in gas phase at high temperature to form tungsten grain aggregation, re-crystallization and growth. The phenolic resin separant can be used as a reducing agent to participate in the processes of tungsten blue reduction and tungsten powder carbonization, can not bring any foreign impurities into products, is lower in price than the original ammonium dichromate and ammonium metavanadate separants, is easy to add, and has good process operability, and the latter can still bring chromium and vanadium impurities.
3. The nano tungsten powder produced by the method has uniform granularity of tungsten carbide powder, narrow granularity distribution and no bridging granule. The average grain diameter of the tungsten powder is less than or equal to 80m, and the average grain diameter of the tungsten carbide powder is less than or equal to 90 nm. The particles are approximately spherical in shape.
Drawings
The invention is further illustrated with reference to figure 1:
FIG. 1 is a flow chart of the preparation process of the present invention, in which nanoscale WO is prepared3The powder 1 is prepared by firstly preparing nano W0 by high-temperature high-pressure supersonic spray thermal conversion method3And (3) powder. Low temperature H2Reducing to prepare blue tungsten 2, and performing H reaction at 420-500 DEG C2Gas reduction to prepare loose and porous nano WO2.9Blue tungsten powder; ultrahigh-speed interlaminar shear crushing of the blue tungsten particles 3 is ultrahigh-speed interlaminar shear crushing, and the blue tungsten particles are further sheared and crushed to form a suspension of nano blue tungsten and alcohol. Adding a release agent phenolic resin 4, namely adding the release agent phenolic resin, adding the release agent phenolic resin into the thinner nano blue tungsten suspension, and continuously shearing and mixing in a shearing machine to coat a layer of release agent on the surfaces of the nano blue tungsten particles to prevent the release agent from being coated on the surfaces of the nano blue tungsten particlesDuring the reduction process, the new tungsten particles are close to each other and are crystallized and grown. The continuous high-speed centrifugal separation of nano blue tungsten powder 5 is to prepare nano blue tungsten powder coated with a separant by using a continuous high-speed centrifugal separator to centrifugally separate nano blue tungsten suspension slurry containing phenolic resin, recovering alcohol, precipitating and drying. Air exhaust and drainage H2The reduction preparation of the nano tungsten powder 6 is to feed H from two specially-made ends2And a reduction furnace for exhausting air and draining water at the middle section, wherein low-temperature air exhausting and draining H is carried out at 700-750 DEG C2Reducing to prepare tungsten powder with the average grain diameter less than or equal to 80nm, namely a first product. The pre-factory treatment 7 of the first product is a pre-factory treatment process of the first product, and comprises the steps of crushing the bridged granules by using an interlaminar shear crusher, centrifugally separating alcohol, drying, detecting granularity, carrying out vacuum packaging and the like.
And (3) preparing a nano carbide mixture 8, namely preparing the nano carbide mixture, namely mixing nanotungsten powder and nano carbon black powder in an interlayer shearing machine, and simultaneously adding phenolic resin (tungsten powder, carbon black and phenolic resin) to prepare the nano carbide mixture. Low temperature carbonization of 9 in stainless steel tube furnace, H2And (3) carbonizing at the low temperature of 980-1000 ℃ for 60-80 minutes under the protection of gas to prepare nano tungsten carbide powder, namely a second product. The second product nanometer WC powder pre-treatment before delivery 10 is a treatment procedure before delivery of the second product nanometer WC powder, the WC powder after being discharged from the furnace needs to be subjected to ultrahigh-speed interlaminar shearing, crushing, bridging and granulating, hydrocyclone classification, continuous centrifugal settling, centrifugal alcohol separation, drying and power frequency airflow vibration screening through a 15 mu m sieve, and the nanometer tungsten carbide powder with spherical particle shape and average particle size less than or equal to 90nm is prepared.
Detailed Description
Example 1 preparation of 10kg of nano W powder and 10.652kg of nano WC powder was carried out as follows
1. Preparation of Nano WO3Powder of
34.08 liters of high-concentration ammonium tungstate solution is weighed, WO thereof3The content is 370 g/L, and the supersonic spray heat conversion method is adopted, the air injection pressure is 3.5MPa, and the air injection speed is 700 m.s-1The spray angle α of the nozzle is 45 degrees, the focal length F is 13mm, the nano-scale WO 12.61kg is firstly prepared according to 350 ml/min, the liquid flow conveying speed is 320 ml/min, the hot air temperature is 350 ℃, and the drying is carried out by countercurrent hot air3Powder with average particle size less than or equal to 50 nm.
2、H2Reduction preparation of loose porous blue tungsten powder
Using stainless steel tube type reducing furnace at 500 deg.C for 60 min, H2Gas cross section flow rate of 20ml/cm2And then reducing to prepare loose and porous blue tungsten powder with the average grain diameter less than or equal to 40 nm.
3. Ultra-high-speed interlaminar shear crusher for crushing blue tungsten particles
The raw materials are mixed according to the mass ratio of the blue tungsten, the industrial alcohol and the phenolic resin of 100: 500: 3, and then the mixture is put into an ultra-high speed interlaminar shearing crusher to be sheared according to 20000 revolutions per minute and 40 minutes per kg, the slurry is led into a high speed 6000 revolutions per minute hydrocyclone classifier to continuously separate large particles in the shearing process, and the large particles are returned to a shearing machine to be sheared continuously, and the time is not increased according to the originally set 40 minutes per kg of the shearing machine. And transferring the sheared nano blue-tungsten slurry to the next working procedure.
4. Continuous high speed centrifugal separation
Introducing the nano blue tungsten suspension slurry subjected to shearing crushing and hydrocyclone classification into a continuous high-speed (10000 r/m) centrifugal separator from a pipeline, continuously centrifuging, separating nano blue tungsten powder from industrial alcohol, wherein the separated industrial alcohol is clear and transparent but contains phenolic resin and can be repeatedly used, and after the blue tungsten powder is taken out and naturally air-dried, transferring to an air-extracting and water-draining type low-temperature H2And (5) a reduction process.
5. Air-extracting and water-draining type low-temperature H2Preparing nano tungsten powder by reduction:
at both ends by feeding H2In the stainless steel single-tube reducing furnace with the middle section exhausting and draining, the temperature is 740 ℃, the temperature is kept for 60 minutes, and H2The cross-sectional flow rate is 40ml/cm2The thickness of the layer of the tungsten material is less than or equal to 7mm, H2The dew point of the gas inlet is-40 ℃, and the tungsten powder with the average grain diameter less than or equal to 80nm can be prepared.
6. Treatment procedure before delivery
If as the firstWhen the product leaves the factory, the treatment procedure before leaving the factory is carried out, namely, the industrial alcohol is added according to the mass ratio of the nano tungsten powder to the industrial alcohol of 1: 5. The bridging granules are crushed in a high-speed interlaminar shearing machine, and large granules are separated and returned by a high-speed hydrocyclone particle size classifier, and are continuously sheared. Centrifuging the fine-particle nano tungsten powder suspension slurry by a continuous high-speed centrifuge, recovering alcohol, taking out nano tungsten powder blocks, drying, and performing work frequency N2The gas flow vibrating screen is sieved by a 15-micron sieve to obtain 10kg of nano tungsten powder, and a small amount of acetone-oleic acid solution is sprayed into the tungsten powder in time to prevent the tungsten powder from spontaneous combustion.
7. Performance detection
And (4) performing BET particle size, XRD phase composition detection and X-ray small angle particle size analysis. The process can prepare 10kg of nearly spherical nano tungsten powder with the average grain diameter less than or equal to 80 nm.
8. And (7) vacuum packaging. And (5) performing vacuum packaging after the product is qualified.
9. Preparation of nano tungsten carbide mixture
10kg of nano tungsten powder which is reduced out of a furnace in the 5 embodiment and is not subjected to factory pre-treatment and carbon black powder with the average particle size of less than or equal to 30nm, phenolic resin with the maximum particle size of less than or equal to 44 mu m is weighed and mixed according to the mass ratio of the nano tungsten powder to the carbon black powder to the phenolic resin powder of 100: 6.73: 3 to prepare a coarse mixed material through preliminary stirring and mixing, then the coarse mixed material and industrial alcohol are respectively put into a high-speed interlayer shearing crusher according to the mass ratio of 1: 5 to be crushed, and meanwhile, the surfaces of tungsten particles are coated with phenolic resin thin films, and the tungsten particles are sheared, crushed and coated according to 40 min/kg. The secondary coating of the phenolic resin film aims to prevent the nano tungsten particles from being close to each other to generate aggregation recrystallization growth before the WC particles are formed, and the sheared mixture slurry is also subjected to centrifugal separation, alcohol recovery and drying to prepare a carbide mixture, and then the carbide mixture is subjected to low-temperature carbonization.
10. Low-temperature carbonization for preparing nano WC powder
Loading the mixed material of nano tungsten carbide in stainless steel tube furnace, H2Under the protection of gas, preserving heat for 60 minutes at 1000 ℃, and carbonizing, wherein the reaction formula is as follows: preparing nanometer WC powderPowder with average particle size of less than or equal to 90nm
11. Broken bridged aggregate hydrocyclone classification
Crushing the bridging granules by using an ultrahigh-speed interlaminar shearing machine, returning the coarse WC particles to the shearing machine through a high-speed hydrocyclone particle size classifier, repeatedly shearing, centrifugally separating, drying at 70 ℃ in vacuum, recovering alcohol, and drying to prepare 10.65kg of WC powder with the average particle size of less than or equal to 90nm, wherein the particles are nearly spherical.
12. Performance detection
Performing BET particle size analysis, chemical analysis to determine total carbon and free carbon, XRD phase composition detection and X-ray small angle particle size analysis.
13. And (6) packaging.
Packaging qualified products
Example 2: when 1kg of nano W powder and 1.0652kg of nano WC powder are prepared, the method comprises the following steps:
1. 3.6 liters of high-concentration ammonium tungstate solution and WO thereof are weighed3The content is 350 g/l, the air injection pressure is 2.5MPa, and the air injection speed is 650 m.s-1Firstly preparing the nano-scale WO by a supersonic spray heat conversion method under the condition of drying the hot air by the countercurrent hot air at the hot air temperature of 250 DEG C3Powder, spray angle α of nozzle is 45 degree, focal length F is 13mm, and conveying speed of 280 ml/separating flow is adopted to obtain 1.26kg nanometer WO3Powder with average particle size less than or equal to 50 nm.
2、H2Reduction preparation of loose porous blue tungsten powder
Using stainless steel tube type reducing furnace at 420 ℃ and H2Gas cross section flow rate of 20ml/cm2The mixture is divided, the temperature is kept for 80 minutes, and the mixture is reduced to prepare loose and porous blue tungsten powder with the average grain diameter less than or equal to 40 nm.
3. 4, exactly the same as 3 and 4 in example 1
5. Low temperature H for air exhaust and drainage2Preparing nano tungsten powder by reduction:
at both ends by feeding H2In the stainless steel single-tube reducing furnace with middle section exhausting and draining, the temperature is 700 ℃, the temperature is kept for 90 minutes, and H2The cross-sectional flow rate is 30ml/cm2And (8) dividing. H2The dew point at the gas inlet was-40 ℃. 1kg of nano tungsten powder is obtained after reduction, and power frequency N is immediately used2The gas flow vibrating screen is screened by a 15-micron screen, and a small amount of acetone-oleic acid solution is sprayed into the tungsten powder after screening to prevent spontaneous combustion. The average grain diameter of the tungsten powder is less than or equal to 80nm
6.7, 8, the same as 6, 7, 8 in example 1, except that the amount of the reduced tungsten powder in 7 was 1 kg.
9. Preparation of nano tungsten carbide mixture
The same as 9 in example 1 except that 1kg of nano tungsten powder was prepared, the same as 9 in example 1.
10. Low-temperature carbonization for preparing nano WC powder
Substantially the same as 10 in example 1, except that the carbonization was carried out in a stainless steel tube furnace at 980 ℃ for 80 minutes. The WC powder with the average grain diameter less than or equal to 90nm is 1.06kg, and the shape of the grains is nearly spherical.
11. 12 and 13 are identical to 11, 12 and 13 in embodiment 1.
Claims (8)
1. A method for preparing nanometer-level superfine tungsten powder and nanometer-level tungsten carbide powder is characterized by comprising the following steps: firstly preparing the nano-scale WO by adopting a supersonic air spray heat conversion method with the high temperature of 250-350 ℃ and the high pressure of 2.5-3.5 MPa3Oxide powder of H2Reducing the gas into WO at the temperature of 420-500 DEG C2.9Blue tungsten powder using WO3→WO2.9Phase change stress crushing effect, namely adding industrial alcohol after loose and porous nano blue tungsten powder is prepared, further crushing blue tungsten particles by using an ultrahigh-speed interlaminar shear crusher, carrying out particle size classification by using a high-speed hydrocyclone classifier, settling and separating nano blue tungsten particle slurry by using a continuous centrifuge, and returning large blue tungsten powder to the ultrahigh-speed interlaminar shear to continue shearing and crushing; adding phenolic resin separant in the shearing and crushing process of blue tungsten, coating nano blue tungsten particles, and feeding H into two ends2Reducing a first product tungsten powder with the average grain diameter less than or equal to 80nm in a reducing furnace with air exhaust and drainage at the middle section at 700-740 ℃, then mixing the nano tungsten powder with nano carbon black powder, simultaneously adding a phenolic resin isolating agent, mixing in an ultra-high speed interlaminar shearing machine to prepare carbonized slurry, and then separatingAfter core drying, carbonizing at 980-1000 ℃, crushing the bridge-connected aggregatesby a high-speed interlaminar shearing machine after discharging, then carrying out hydrocyclone classification, carrying out continuous centrifugal sedimentation, carrying out centrifugal separation on alcohol, drying, passing through a power frequency airflow vibrating screen, and passing through a 15-micron screen to prepare WC powder with the average particle size of less than or equal to 90nm, wherein the particle shape is nearly spherical.
2. The method of claim 1, wherein: preparation of nano WO by high-temperature high-pressure supersonic spray thermal conversion method3Powder: the atomized solution is directly prepared from high-concentration ammonium tungstate solution and WO thereof3The content of the spray is 350-370 g/L, the circular gap air flow resonant type supersonic atomizing nozzle used for spraying has the short focal length F of 13mm and the spraying angle α of 45 degrees, the pressure of compressed air is 2.5-3.5 MPa, and the spraying speed is 650-700 m.s-1(ii) a The liquid flow conveying speed is 280-320 ml/min, the hot air temperature is 250-350 ℃, and the obtained nano WO3The water content of the powder is reduced to 15 percent, and the WO can be ensured3The average particle size of the powder is less than or equal to 50 nm.
3. The method of claim 1, wherein: by H2Preparing loose and porous blue tungsten powder particles by low-temperature reduction: reducing by adopting a stainless steel tube type reducing furnace at the reduction temperature of 420-500 ℃ and H2Gas cross section flow rate of 20ml/cm2The reduction time is 60 to 80 minutes, and the WO is added3Reduction of the powder to WO2.9。
4. The method of claim 1, wherein: ultra-high-speed interlaminar shear crushing of blue tungsten particles: preparing slurry from loose and porous blue tungsten powder according to the mass ratio of blue tungsten to industrial alcohol of 1: 5, and putting the slurry into a shearing machine for circularly shearing according to 40 min/kg; separating the blue tungsten particles larger than 40nm from the slurry by a high-speed rotary liquid type nano particle classifier, and returning to the shearing machine for continuous shearing; suspending the blue tungsten particles with the particle size less than or equal to 40nm in industrial alcohol; after the blue tungsten is crushed by an ultra-high-speed interlaminar shearing machine, the grain diameters of all blue tungsten grains are ensured to be less than or equal to 40 nm.
5. The method of claim 1, wherein: the phenolic resin isolating agent is used to coat nano blue-tungsten particles, and the phenolic resin powder with grain size less than or equal to 43 microns is added according to the mass ratio of blue-tungsten, industrial alcohol and phenolic resin of 100: 500: 3, and through the processes of ultrahigh-speed interlaminar shearing, centrifugal precipitation of slurry and drying, the surface of every nano blue-tungsten particle is coated with a layer of phenolic resin film, and said film is tested in H2Gradually decompose at a temperature below 850 deg.C to form carbon film, and the residual carbon film is in H2The gas is used as a reducing agent to participate in reduction reaction in the process of reducing the blue tungsten.
6. The method of claim 1, wherein: continuous high-speed centrifugal separation of nano blue tungsten powder: the sheared and crushed nano blue tungsten suspension is separated by 10000-15000 r/min of a continuous high-speed centrifuge, the nano blue tungsten suspension is uninterruptedly added under the state of high-speed rotation, nano blue tungsten particles in the liquid are automatically separated from alcohol liquid under the centrifugal action and are compressed onto the side wall of the centrifuge, and clarified alcohol liquid is continuously and automatically discharged and recovered from the centrifuge.
7. The method of claim 1, wherein: air exhaust and drainage H2Preparing nano tungsten powder by reduction: is fed at both ends with H2Gas, exhausting water from the middle section of the reduction furnace, keeping the temperature at 700-740 ℃ for 60-90 minutes, and H2The flow of the gas cross section is 30-40 ml/cm2Dividing; h2The dew point of the gas inlet is-40 ℃, and low-temperature air extraction and drainage H are carried out2Reducing to obtain the nano tungsten powder with the average grain diameter less than or equal to 80 nm.
8. The method of claim 1, wherein: preparing a nano carbide mixture: the obtained nano tungsten powder is mixed with carbon black powder whose average grain size is less than or equal to 30nm and phenolic resin powder whose grain size is less than or equal to 44 micrometers, according to the mass ratio of tungsten powder, carbon black powder and phenolic resin powder of 100: 6.73: 3 the raw materials are weighed, mixed and stirred to obtain coarse mixed material, then according to the mass ratio of coarse mixed material and industrial alcohol of 1: 5 the coarse mixed material and industrial alcohol are mixed and stirred to obtain the invented productRespectively putting the tungsten particles into a high-speed interlaminar shearing crusher to crush one surface, coating a phenolic resin film on the surfaces of the tungsten particles, and shearing, crushing and coating the tungsten particles according to 40 minutes/kg; the sheared mixture slurry is also subjected to centrifugal separation to recover alcohol, is dried to prepare a carbide mixture, and is then carbonized at low temperature; in a stainless steel tube furnace, H2And (4) carrying out gas protection, keeping the temperature at 980-1000 ℃ for 60-80 minutes, and preparing the nano WC powder.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN100357180C (en) * | 2006-04-07 | 2007-12-26 | 北京科技大学 | Method of microwave synthetizing nano powder of tungsten carbide |
| CN100340481C (en) * | 2006-04-14 | 2007-10-03 | 北京科技大学 | Process for self-propagating high-temperature synthesis of nano tungsten carbide powder |
| CN100395182C (en) * | 2006-04-30 | 2008-06-18 | 北京科技大学 | Method for preparing nanopowder of tungsten carbide |
| CN101983804B (en) * | 2010-12-03 | 2012-07-04 | 中南大学 | Method for preparing nearly-spherical tungsten powder |
| CN102179512B (en) * | 2011-04-25 | 2012-12-05 | 北京科技大学 | Method for preparing cobalt coated nano tungsten carbide hard alloy spraying powder |
| CN103302309B (en) * | 2013-06-17 | 2016-04-20 | 南昌大学 | A kind of preparation method of nanometer tungsten carbide |
| CN105478753B (en) * | 2015-12-15 | 2018-02-06 | 北京矿冶研究总院 | Tungsten carbide and tungsten composite powder and preparation method thereof |
| CN107470646B (en) * | 2017-08-28 | 2020-12-08 | 湖南科技大学 | Preparation method of superfine tungsten powder composite powder |
| RU2667452C1 (en) * | 2017-09-29 | 2018-09-19 | Общество с ограниченной ответственностью "Вириал" | Method for obtaining nano-dimensional powder of tungsten carbide |
| CN107585768B (en) * | 2017-10-24 | 2020-07-28 | 株洲硬质合金集团有限公司 | Method for preparing superfine tungsten carbide powder by oxidation-reduction method |
| CN114078608A (en) * | 2020-08-18 | 2022-02-22 | 成都虹波实业股份有限公司 | Method for producing tungsten powder for high-temperature conductor slurry |
| RU2763814C1 (en) * | 2021-01-29 | 2022-01-11 | Сергей Рудольфович Вишняков | Method for producing nanodispersed powders |
| CN114012100A (en) * | 2021-11-09 | 2022-02-08 | 宁波新睦科技有限公司 | Raw material powder preparation process for powder metallurgy |
| CN117566742B (en) * | 2024-01-17 | 2024-03-15 | 崇义章源钨业股份有限公司 | Recycling method of thermal mosaic tungsten waste |
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