阅读说明：本技术 超细碳化钨粉及其制备方法和硬质合金 (Superfine tungsten carbide powder, preparation method thereof and hard alloy ) 是由 张龙辉 周俊安 钟志强 徐国钻 林丽萍 于 2021-08-02 设计创作，主要内容包括：本发明公开了一种超细碳化钨粉及其制备方法和硬质合金,该方法包括：(1)将紫钨在氢气气氛下进行还原,以便得到超细钨粉；(2)将所述超细钨粉进行钝化处理；(3)将步骤(2)得到的钝化超细钨粉与炭黑和抑制剂混合进行碳化,以便得到碳化钨块；(4)将所述碳化钨块进行破碎,以便得到超细碳化钨粉,其中,所述紫钨的比表面积为3.0～3.8m～(2)/g。由此,该方法可以制备出BET≥3.0m～(2)/g的超细碳化钨粉。(The invention discloses superfine tungsten carbide powder, a preparation method thereof and hard alloy, wherein the method comprises the following steps: (1) reducing the purple tungsten in a hydrogen atmosphere to obtain superfine tungsten powder; (2) passivating the superfine tungsten powder; (3) mixing the passivated superfine tungsten powder obtained in the step (2) with carbon black and an inhibitor for carbonization so as to obtain a tungsten carbide block; (4) crushing the tungsten carbide block to obtain superfine tungsten carbide powder, wherein the specific surface area of the purple tungsten is 3.0-3.8 m 2 (ii) in terms of/g. Therefore, the method can prepare the product with the BET being more than or equal to 3.0m 2 The superfine tungsten carbide powder per gram.)

1. A method for preparing ultrafine tungsten carbide powder is characterized by comprising the following steps:

(1) reducing the purple tungsten in a hydrogen atmosphere to obtain superfine tungsten powder;

(2) passivating the superfine tungsten powder;

(3) mixing the passivated superfine tungsten powder obtained in the step (2) with carbon black and an inhibitor for carbonization so as to obtain a tungsten carbide block;

(4) crushing the tungsten carbide block to obtain superfine tungsten carbide powder,

wherein the specific surface area of the purple tungsten is 3.0-3.8 m²/g。

2. The method according to claim 1, wherein the purple tungsten is prepared by the following method:

calcining tungsten oxide furnace end powder at low temperature in an oxygen-rich atmosphere to obtain tungsten trioxide;

carrying out high-temperature reduction calcination on the tungsten trioxide in a reducing atmosphere to obtain the purple tungsten,

wherein, the tungsten oxide furnace end powder comprises tungsten trioxide, ammonium paratungstate and intermediate tungsten oxide.

3. The method according to claim 1 or 2, wherein in the step (1), the flow rate of hydrogen in the reduction process is 40-60 m³The time is 4-6 h.

4. The method according to claim 3, wherein in the step (1), the feeding speed of the purple tungsten is 25-40 kg/h, and the reduction temperature is 630-940 ℃.

5. The method according to claim 1, wherein in the step (2), the passivation treatment is carried out by rapidly cooling the ultrafine tungsten powder in an inert atmosphere, wherein the flow rate of the inert atmosphere is 5-20L/min.

6. The method according to claim 1, wherein in the step (3), the carbon black and the inhibitor are used in an amount of 100: (6.5-6.84): (0.2-0.8) mixing;

optionally, in step (3), the inhibitor comprises at least one of vanadium carbide, chromium carbide and tantalum carbide.

7. The method according to claim 1 or 6, wherein in the step (3), the carbonization temperature is 1100-1200 ℃ and the carbonization time is 2-4 h.

8. The method according to claim 1, wherein in step (4), the crushing is carried out using a gas crushing apparatus having a grinding gas pressure of 7 to 10mbar and a classifying wheel rotation speed of 3800 to 4500 r/min.

9. An ultrafine tungsten carbide powder, characterized in that the ultrafine tungsten carbide powder is prepared by the method according to any one of claims 1 to 8.

10. A cemented carbide produced using the ultrafine tungsten carbide powder according to claim 9.

Technical Field

The invention belongs to the field of powder metallurgy, and particularly relates to ultrafine tungsten carbide powder, a preparation method thereof and hard alloy.

Background

The nano/ultra-fine grain hard alloy has superior performance which is incomparable with common hard alloy, and the capability of meeting the processing requirement of modern processing industry and special application field on new materials is greatly improved. The nano/superfine structure hard alloy has the characteristics of high wear resistance and high toughness, and is widely applied to manufacturing tools and dies which are suitable for high load, high stress wear, sharpness and good rigidity, such as Printed Circuit Board (PCB) micro-drills, V-CUT cutters, milling cutters and the like.

The main raw material of the nano/ultra-fine grain hard alloy is ultra-fine tungsten carbide powder, and the quality of the tungsten carbide powder is mainly influenced by the quality of the ultra-fine tungsten powder and tungsten oxide. Research shows that the purple tungsten consists of a great amount of irregular needle-shaped or rod-shaped whiskers, the whiskers are mutually staggered to form an arch bridge shape to cause a great number of communicated pores, and the excellent air permeability of the purple tungsten determines that the purple tungsten is the most suitable raw material for producing the superfine tungsten carbide at present. The main process flow is as follows: tungsten trioxide is used as a raw material, purple tungsten and superfine tungsten powder are prepared in a reducing atmosphere, a proper amount of carbon black is added, the mixture is uniformly mixed and carbonized in a molybdenum wire furnace, and the obtained tungsten carbide block is crushed by airflow to prepare the superfine tungsten carbide powder. The conventional tungsten trioxide is generally small in specific surface area, low in porosity, poor in air permeability and not beneficial to reduction reaction, and the morphology of the purple tungsten is difficult to stably control, so that more abnormally-grown particles exist in subsequently-prepared superfine tungsten carbide, and the BET (BET) is difficult to reach 3.0m²More than g.

Disclosure of Invention

The present invention is directed to solving, at least to some extent, one of the technical problems in the related art. Therefore, the invention aims to provide the ultrafine tungsten carbide powder, the preparation method thereof and the hard alloy, wherein the method can prepare the tungsten carbide powder with the BET being more than or equal to 3.0m²The superfine tungsten carbide powder per gram.

In one aspect of the present invention, a method for preparing ultrafine tungsten carbide powder is provided. According to an embodiment of the invention, the method comprises:

(1) reducing the purple tungsten in a hydrogen atmosphere to obtain superfine tungsten powder;

(2) passivating the superfine tungsten powder;

(3) mixing the passivated superfine tungsten powder obtained in the step (2) with carbon black and an inhibitor for carbonization so as to obtain a tungsten carbide block;

(4) crushing the tungsten carbide block to obtain superfine tungsten carbide powder;

wherein the specific surface area of the purple tungsten is 3.0-3.8 m²/g。

According to the method for preparing the ultrafine tungsten carbide powder, the specific surface area is 3.0-3.8 m²The/g of purple tungsten is reduced in hydrogen atmosphere to obtain the superfine tungsten powder. Because the superfine tungsten powder has high activity and is easy to spontaneously combust, the superfine tungsten powder needs to be passivated so as to obtain passivated superfine tungsten powder, thereby improving the safety of subsequent carbonization reaction; then mixing the passivated superfine tungsten powder with carbon black and an inhibitor, wherein the passivated superfine tungsten powder and the carbon black are subjected to carbonization reaction, and the inhibitor can further reduce the activity of the superfine tungsten powder, so that the purpose of inhibiting the growth of tungsten carbide is achieved; and sintering at high temperature to obtain tungsten carbide blocks, and finally crushing the tungsten carbide blocks to obtain the superfine tungsten carbide powder. Thus, BET ≥ 3.0m can be prepared by employing the method of the present application²The superfine tungsten carbide powder per gram.

In addition, the method for preparing ultrafine tungsten carbide powder according to the above embodiment of the present invention may further have the following additional technical features:

in some embodiments of the invention, the purple tungsten is prepared by the following method: calcining tungsten oxide furnace end powder at low temperature in an oxygen-rich atmosphere to obtain tungsten trioxide; and carrying out high-temperature reduction calcination on the tungsten trioxide under a reducing atmosphere so as to obtain the purple tungsten, wherein the tungsten oxide furnace end powder comprises tungsten trioxide, ammonium paratungstate and intermediate tungsten oxide.

In some embodiments of the present invention, in the step (1), the hydrogen flow rate in the reduction process is 40-60 m³The time is 4-6 h.

In some embodiments of the invention, in the step (1), the feeding speed of the purple tungsten is 25-40 kg/h, and the reduction temperature is 630-940 ℃.

In some embodiments of the invention, in the step (2), the passivation treatment is implemented by rapidly cooling the ultrafine tungsten powder in an inert atmosphere, wherein the flow rate of the inert atmosphere is 5-20L/min.

In some embodiments of the present invention, in step (3), the carbon black and the inhibitor are used in an amount such that the mass ratio of the passivated ultrafine tungsten powder to the carbon black to the inhibitor is 100: (6.5-6.84): (0.2-0.8) mixing.

In some embodiments of the invention, in step (3), the inhibitor comprises at least one of vanadium carbide, chromium carbide and tantalum carbide.

In some embodiments of the present invention, in the step (3), the carbonization temperature is 1100-1200 ℃ and the carbonization time is 2-4 h.

In some embodiments of the invention, in the step (4), the crushing is carried out by using a gas crushing device, the grinding gas pressure of the gas crushing device is 7-10 mbar, and the rotating speed of the classifying wheel is 3800-4500 r/min.

In a second aspect of the invention, an ultrafine tungsten carbide powder is provided. According to the embodiment of the invention, the ultrafine tungsten carbide powder is prepared by the method. Thus, the BET of not less than 3.0m can be prepared by the above method²The/g ultrafine tungsten carbide powder can be used for preparing hard alloy with high hardness and high toughness, and further can be used for manufacturing tools and dies which are suitable for high load, high stress abrasion, sharpness and good rigidity.

In a third aspect of the invention, a cemented carbide is presented. According to the embodiment of the invention, the hard alloy is prepared by adopting the ultrafine tungsten carbide powder. Therefore, the hard alloy has higher hardness and toughness, and can be applied to manufacturing tools and dies which are adaptive to high load, high stress abrasion, sharpness and good rigidity.

Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1 is a schematic flow diagram of a method for preparing ultrafine tungsten carbide powder according to one embodiment of the present invention;

FIG. 2 is a schematic process flow diagram of a method for preparing ultrafine tungsten carbide powder according to an embodiment of the present invention;

FIG. 3 is a schematic flow diagram of a method of treating tungsten oxide burner dust according to one embodiment of the present invention;

FIG. 4 is an SEM photograph of an ultrafine tungsten carbide powder prepared according to example 1;

FIG. 5 is an SEM photograph of an ultrafine tungsten carbide powder prepared according to example 2;

FIG. 6 is an SEM photograph of an ultrafine tungsten carbide powder prepared according to example 3;

FIG. 7 is an SEM photograph of an ultrafine tungsten carbide powder prepared according to example 4;

FIG. 8 is an SEM image of an ultrafine tungsten carbide powder prepared according to comparative example 1;

fig. 9 is an SEM image of the ultra-fine tungsten carbide powder prepared according to comparative example 2.

Detailed Description

Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, and the embodiments described below with reference to the accompanying drawings are exemplary and intended to be illustrative of the present invention and should not be construed as limiting the present invention.

In one aspect of the present invention, a method for preparing ultrafine tungsten carbide powder is provided. Referring to fig. 1-2, the method includes, according to an embodiment of the invention:

s100: the purple tungsten is reduced in hydrogen atmosphere

In the step, the specific surface area is 3.0-3.8 m²And reducing the/g of purple tungsten in a hydrogen atmosphere to obtain the superfine tungsten powder.

Further, the feeding speed of the purple tungsten is 25-40 kg/h, and the hydrogen flow is 40-60 m³H is used as the reference value. The inventor finds that the higher the feeding speed of the purple tungsten is, the thicker the purple tungsten layer is, the thicker the tungsten powder prepared by reduction is, and if the feeding speed of the purple tungsten is too high, hydrogen in the furnace is not enough to completely reduce the purple tungsten, so that the product quality is influenced; if the feeding speed of the purple tungsten is too slow, the reduction speed is too fast, and the generated tungsten powder is subjected to solid-phase sintering and grows up, so that the preparation of the superfine tungsten powder is not facilitated. Meanwhile, the larger the hydrogen flow is, the finer the tungsten powder is, and if the hydrogen flow is too large, the refining influence on the tungsten powder is not large, so that hydrogen waste is caused, and the large-flow hydrogen easily carries away more fine powder, so that the furnace end powder is too much; if the hydrogen flow is too small, the reduction reaction is incomplete, thereby affecting the product quality. Therefore, the feeding speed and the hydrogen flow of the purple tungsten can improve the product quality, and avoid the waste of hydrogen and the production of excessive furnace end powder.

Furthermore, in the reduction process, the reduction temperature is 630-940 ℃, and the time is 4-6 hours. The inventor finds that if the reduction temperature is too low, the required reduction time is longer, and incomplete reduction of the powder is easily caused; if the reduction temperature is too high, the reduction reaction speed is accelerated, and the coarser the tungsten powder granularity is, the more adverse is the preparation of the superfine tungsten powder. Meanwhile, if the reduction time is too long, the tungsten powder grows up by sintering, which is not beneficial to the preparation of ultrafine powder; if the reduction time is too short, the reduction is easy to be incomplete, and the oxygen content of the tungsten powder is high. Therefore, the reduction temperature and time are favorable for preparing the superfine tungsten powder.

According to an embodiment of the invention, the reduction process comprises a first reduction, a second reduction and a third reduction, and the temperatures of the first reduction, the second reduction and the third reduction are gradually increased in a gradient manner, wherein the temperature of the first reduction is 630-720 ℃, the temperature of the second reduction is 750-830 ℃, and the temperature of the third reduction is 840-940 ℃.

Further, referring to fig. 3, the purple tungsten is prepared by the following method:

sa: calcining tungsten oxide furnace end powder at low temperature in oxygen-enriched atmosphere

In the step, the tungsten oxide furnace end powder is calcined at low temperature in an oxygen-rich atmosphere so as to obtain the tungsten trioxide. The inventor finds that the tungsten trioxide with a single phase, large specific surface area and good air permeability is prepared by low-temperature calcination pretreatment because the tungsten oxide furnace end powder phase has complex components and the purple tungsten prepared directly by using the tungsten oxide furnace end powder phase as a raw material has the defects of poor appearance, low specific surface area, non-uniform particles and the like.

According to an embodiment of the present invention, the tungsten oxide furnace dust includes tungsten trioxide, ammonium paratungstate and intermediate tungsten oxide. Specifically, the sources of the tungsten oxide furnace end powder are as follows: ammonium paratungstate can produce a large amount of water vapor and ammonia gas in the calcining process, ammonia gas can be decomposed into inert gas nitrogen and strong reducing gas hydrogen at high temperature, and in order to obtain tungsten trioxide with a single phase, an air draft measure opposite to the feeding direction is usually adopted so as to achieve the effect of timely discharging the water vapor, the ammonia gas and the hydrogen gas. During the air draft process, a large amount of fine tungsten oxide and unreacted ammonium paratungstate powder can be drawn out of the furnace tube along with the air, so that tungsten oxide furnace end powder comprising tungsten trioxide, ammonium paratungstate and intermediate tungsten oxide is generated, and the intermediate tungsten oxide generally refers to an intermediate product in the tungsten oxide preparation process by using ammonium paratungstate.

Further, the feeding speed of the tungsten oxide furnace end powder is 200-300 kg/h. The inventors found that if the feeding speed of the tungsten oxide burner powder is too slow, the yield is insufficient, and if the feeding speed of the tungsten oxide burner powder is too fast, the reaction is liable to be incomplete. Thus, with the feed rate of the present application, the reaction can be guaranteed to be complete and the yield can be increased.

Further, the low-temperature calcination is carried out in a rotary furnace, the rotating speed of the rotary furnace is 20-30 r/min, and the temperature of the low-temperature calcination is 420-500 ℃. The inventor finds that if the rotating speed of the rotary furnace is too low, the material calcination time is longer, the cracks of the particles are easily closed, the porosity is reduced, and the air permeability of the particles is poor; if the rotating speed of the rotary furnace is too high, the calcination time of the material is insufficient, incomplete calcination is easily caused, and the phase of the tungsten trioxide is not single. Meanwhile, if the temperature of the low-temperature calcination is too low, incomplete calcination is easily caused, and if the temperature of the low-temperature calcination is too high, particle sintering growth, crack closure and air permeability reduction are easily caused. Therefore, the tungsten trioxide with single phase, large specific surface area and good air permeability can be obtained by adopting the rotating speed of the rotary kiln and the low-temperature calcining temperature.

Furthermore, the low-temperature calcination process is accompanied by air draft, preferably, air draft measures opposite to the feeding direction are adopted, and the frequency of the air draft is 1-4 Hz. The inventor finds that because the content of ammonium paratungstate in the tungsten oxide furnace end powder is low, the amount of water vapor and ammonia generated by calcination is low, the air draft frequency can be relatively low, too high air draft frequency easily causes the materials in the furnace to be taken out along with air in the calcination process, a large amount of tungsten oxide furnace end powder is generated again, and the recovery of the materials is not facilitated. From this, adopt the exhaust frequency of this application, can avoid producing tungsten oxide furnace end powder once more to be favorable to the recovery of material.

Preferably, before the tungsten oxide furnace end powder is calcined at low temperature in an oxygen-rich atmosphere, the tungsten oxide furnace end powder is subjected to ultrasonic sieving pretreatment, so that large-particle impurities and mechanical inclusions are removed, and the purity of the material is ensured.

Sb: carrying out high-temperature reduction calcination on tungsten trioxide in a reducing atmosphere

In this step, the tungsten trioxide is subjected to high-temperature reduction calcination in a reducing atmosphere to obtain a rod-like purple tungsten. Compared with the purple tungsten obtained by only carrying out high-temperature reduction calcination on the tungsten oxide furnace end powder, the rodlike purple tungsten obtained by firstly carrying out low-temperature calcination on the tungsten oxide furnace end powder in an oxygen-enriched atmosphere and then carrying out high-temperature reduction calcination in a reducing atmosphere has higher specific surface area and more excellent performance and is more suitable for the production of superfine tungsten powder and superfine tungsten carbide powder; compared with the prior art that the rodlike purple tungsten with excellent performance is prepared by using tungsten trioxide with high specific surface area and good air permeability, the tungsten oxide furnace end powder is recycled, so that the cost is greatly reduced.

Further, the feeding speed of the tungsten trioxide is 80-120 kg/h. The inventor finds that if the feeding speed of the tungsten trioxide is too high, the material layer in the furnace is too thick, the material layer is easy to reduce and cannot be prepared into single-phase purple tungsten, and meanwhile, the feeding speed is too high, the partial pressure of water vapor in the furnace is large, and rod-shaped purple tungsten with short length and thick diameter is easy to generate; if the feeding speed of the tungsten trioxide is too slow, the production efficiency is low, the material layer in the furnace is thin, the reduced material is few, the concentration of the reducing gas is relatively high, the tungsten trioxide is excessively reduced to generate tungsten dioxide instead of purple tungsten, and meanwhile, excessive sintering is easy to occur to influence the product quality. Thus, by using the feed rate of tungsten trioxide of the present application, it is possible to obtain a single-phase purple tungsten, and avoid excessive reduction, excessive sintering, and the formation of a rod-like purple tungsten having a short length and a large diameter.

Further, the temperature of the high-temperature calcination is 700-800 ℃. The inventors found that if the temperature of the high-temperature calcination is too low, the reaction rate is slow and the reduction degree is insufficient, thereby resulting in a complex phase composition of the purple tungsten; if the high-temperature calcination temperature is too high, the columnar purple tungsten is easy to sinter and grow. Therefore, by adopting the high-temperature calcination temperature, the proper reduction degree can be ensured, and the rod-shaped purple tungsten with single phase component can be obtained.

Further, the flow rate of the reducing atmosphere is 0.5 to 1.2m³And/h, wherein the reducing atmosphere is ammonia gas, a mixed gas containing nitrogen and hydrogen gas or a mixed gas containing ammonia gas and nitrogen gas. The inventor finds that if the flow of the reducing atmosphere is too low, water vapor generated in the reducing process cannot be discharged in time, so that crystal grains grow and materials are agglomerated; if the flow rate of the reducing atmosphere is too high, excessive reduction is easily caused, and tungsten dioxide and even tungsten powder are generated. Therefore, by adopting the reducing atmosphere flow, the excessive reduction of the tungsten trioxide, the growth of crystal grains and the agglomeration of materials can be avoided.

Preferably, the high-temperature calcination is carried out in a rotary furnace, and the rotating speed of the rotary furnace is 10-25 r/min. The inventor finds that if the rotating speed of the rotary furnace is too slow, the production efficiency is influenced, so that the production cost is increased; if the rotating speed of the rotary furnace is too high, the materials are easy to be reduced in place, so that the phase components are complex, and the single-phase purple tungsten cannot be prepared. Therefore, the rotating speed of the rotary furnace can reduce the production cost and obtain the single-phase purple tungsten.

The inventor finds that firstly, tungsten oxide furnace end powder is subjected to low-temperature calcination in an oxygen-rich atmosphere, and because the tungsten oxide furnace end powder has complex phase components, the purple tungsten directly prepared by taking the tungsten oxide furnace end powder as a raw material has the defects of poor appearance, low specific surface area, uneven particles and the like, low-temperature calcination pretreatment is required, so that the tungsten trioxide with a single phase, large specific surface area and good air permeability is prepared; then the tungsten trioxide obtained by low-temperature calcination is subjected to high-temperature reduction calcination in a reducing atmosphere, so that the BET (BET) value more than or equal to 3.0m can be stably prepared²Purple tungsten in the shape of a long and thin rod. Compared with the purple tungsten obtained by only carrying out high-temperature reduction calcination on the tungsten oxide furnace end powder, the rodlike purple tungsten obtained by carrying out low-temperature calcination on the tungsten oxide furnace end powder in an oxygen-enriched atmosphere and then carrying out high-temperature reduction calcination in a reducing atmosphere has the advantages that the specific surface area of the rodlike purple tungsten is higher, the performance is more excellent, and the rodlike purple tungsten is more suitable for production of superfine tungsten powder and superfine tungsten carbide powder; compare simultaneously in prior art and utilize the excellent bar-like purple tungsten of tungsten trioxide preparation performance that high specific surface area and gas permeability are good, this application has realized the recovery processing to tungsten oxide furnace end powder to greatly reduced the cost. In addition, compared with the treatment of tungsten oxide furnace end powder by ammonia dissolving, impurity removing and recrystallization recovery processes, the treatment cost is obviously reduced. Therefore, the method for treating the tungsten oxide furnace end powder can stably prepare the tungsten oxide furnace end powder with the BET of more than or equal to 3.0m²The tungsten oxide furnace end powder has the advantages that the tungsten oxide furnace end powder is thin and long in rod shape, the recovery cost of the existing tungsten oxide furnace end powder is reduced, the production efficiency is improved, and the productivity of the tungsten oxide furnace end powder is greatly improved.

S200: passivating the superfine tungsten powder

In this step, the ultrafine tungsten powder obtained in step S100 is passivated. Because the superfine tungsten powder has high activity and is easy to self-ignite, the superfine tungsten powder needs to be passivated, thereby improving the safety of subsequent carbonization reaction. Specifically, the passivation treatment is realized by rapidly cooling the superfine tungsten powder in an inert atmosphere.

Furthermore, the flow rate of the inert atmosphere is 5-20L/min. The inventor finds that if the flow of the inert atmosphere is too large, the tungsten powder is easy to be taken away, and the material waste is caused; if the flow of the inert atmosphere is too small, the cooling speed is slow, the passivation treatment time is long, and therefore the efficiency is low. From this, adopt the flow of the inert atmosphere of this application, can improve passivation efficiency and avoid the material extravagant.

S300: mixing the passivated superfine tungsten powder obtained in the step S200 with carbon black and an inhibitor for carbonization

In the step, the passivated superfine tungsten powder obtained in the step S200 is mixed with carbon black and an inhibitor for carbonization, wherein the passivated superfine tungsten powder and the carbon black are subjected to carbonization reaction, and the inhibitor can further reduce the activity of the superfine tungsten powder, so that the purpose of inhibiting the growth of tungsten carbide is achieved, and a tungsten carbide block is obtained after high-temperature sintering.

Further, the amount of the carbon black and the inhibitor is determined according to the mass ratio of the passivated superfine tungsten powder to the carbon black to the inhibitor being 100: (6.5-6.84): (0.2-0.8) mixing. The inventors found that if the carbon black content is too high, too high free carbon is easily caused to affect the powder properties; if the content of carbon black is too low, the tungsten powder is not carbonized completely and has a brittle phase W₂C is formed and also affects powder properties. In addition, the inhibitor has a certain inhibiting effect on the growth of crystal grains, and if the content of the inhibitor is too high, the effect of refining cannot be better achieved by continuously increasing the content of the inhibitor; if the content of the inhibitor is too low, the inhibition effect is poor, and the product requirement cannot be met. Therefore, the performance of the superfine tungsten carbide powder can be improved by adopting the proportion of the application.

Further, the carbonization temperature is 1100-1200 ℃, and the time is 2-4 h. The inventor finds that if the carbonization temperature is too high and the carbonization time is too long, the particles are easy to sinter and grow, and the preparation of the superfine tungsten carbide is not facilitated; if the carbonization temperature is too low and the carbonization time is too short, incomplete carbonization is easy to occur, thereby affecting the product quality. Therefore, the carbonization temperature and the carbonization time are adopted, and the superfine tungsten carbide powder is favorably prepared.

It should be noted that the type of the above inhibitor is not particularly limited, and those skilled in the art can select the inhibitor according to actual needs, including at least one of vanadium carbide, chromium carbide and tantalum carbide.

S400: crushing the tungsten carbide block

In this step, the tungsten carbide block obtained in step S300 is crushed to obtain ultrafine tungsten carbide powder.

Preferably, the crushing is carried out by adopting gas crushing equipment, the grinding gas pressure of the gas crushing equipment is 7-10 mbar, and the rotating speed of a classifying wheel is 3800-4500 r/min. The inventor finds that the tungsten carbide powder prepared by the method has finer granularity as the rotating speed of the grading wheel and the pressure of the grinding gas are higher, and if the rotating speed of the grading wheel and the pressure of the grinding gas are too high, the loss of the grading wheel and equipment is increased, the service life of the equipment is shortened, and the production cost is increased. If the rotating speed of the grading wheel and the pressure of the grinding gas are too low, the crushing degree of the tungsten carbide is not enough, the granularity is thick, and the preparation of the superfine tungsten carbide powder is not facilitated. Therefore, the adoption of the rotating speed of the grading wheel and the pressure of the grinding gas is beneficial to preparing and obtaining the superfine tungsten carbide powder, and the production cost is reduced.

The inventor finds that the specific surface area is 3.0-3.8 m²The/g of purple tungsten is reduced in hydrogen atmosphere to obtain the superfine tungsten powder. Because the superfine tungsten powder has high activity and is easy to spontaneously combust, the superfine tungsten powder needs to be passivated so as to obtain passivated superfine tungsten powder, thereby improving the safety of subsequent carbonization reaction; then mixing the passivated superfine tungsten powder with carbon black and an inhibitor, wherein the passivated superfine tungsten powder and the carbon black are subjected to carbonization reaction, and the inhibitor can further reduce the activity of the superfine tungsten powder, so that the purpose of inhibiting the growth of tungsten carbide is achieved; and sintering at high temperature to obtain tungsten carbide blocks, and finally crushing the tungsten carbide blocks to obtain the superfine tungsten carbide powder. Thus, BET ≥ 3.0m can be prepared by employing the method of the present application²The superfine tungsten carbide powder per gram. Further, the tungsten oxide furnace end powder is subjected to low-temperature calcination and high-temperature reduction calcination to obtain the rodlike purple tungsten, and the specific surface area of the rodlike purple tungsten reaches 3.0m²More than g, and more excellent performance, compared with the purple tungsten obtained by reducing the conventional tungsten trioxide, the prepared superfine tungsten carbide powder has higher specific surface area which reaches 3.0m by taking the purple tungsten as the raw material²More than g, can be used for preparing hard alloy with high hardness and high toughness, and further can be applied to manufacturing hard alloy adapting to high load and high stressThe method has the advantages that the tool and the die are worn, sharp and good in rigidity, and tungsten oxide furnace end powder is recycled, so that the production cost is greatly reduced.

In a second aspect of the invention, an ultrafine tungsten carbide powder is provided. According to the embodiment of the invention, the ultrafine tungsten carbide powder is prepared by the method. Thus, the BET of not less than 3.0m can be prepared by the above method²The/g ultrafine tungsten carbide powder can be used for preparing hard alloy with high hardness and high toughness, and further can be used for manufacturing tools and dies which are suitable for high load, high stress abrasion, sharpness and good rigidity. It should be noted that the features and advantages described above for the method for preparing ultrafine tungsten carbide powder are also applicable to the ultrafine tungsten carbide powder, and are not described herein again.

In a third aspect of the invention, a cemented carbide is presented. According to the embodiment of the invention, the hard alloy is prepared by adopting the ultrafine tungsten carbide powder. Therefore, the hard alloy has higher hardness and toughness, and can be applied to manufacturing tools and dies which are suitable for high load, high stress abrasion, sharpness and good rigidity. It should be noted that the features and advantages described above for the ultrafine tungsten carbide powder and the preparation method thereof are also applicable to the cemented carbide, and are not described herein again.

The invention will now be described with reference to specific examples, which are intended to be illustrative only and not to be limiting in any way.

Example 1

1. The tungsten oxide furnace end powder is subjected to ultrasonic sieving pretreatment for removing large-particle impurities and mechanical impurities and ensuring the purity of the material.

2. And (3) feeding the sieved tungsten oxide furnace end powder into a rotary furnace through a spiral feeder to perform low-temperature oxygen-enriched calcination, wherein the calcination process comprises the following steps: the rotating speed of the furnace tube is 20r/min, the temperature is 420 ℃, the air draft frequency is 1Hz, the feeding speed is 200kg/h, and the specific surface area of the obtained tungsten trioxide is 2.8m²Increase in g to 3.2m²/g。

3. The trioxyization after low-temperature oxygen-enriched calcinationAnd (3) conveying the tungsten into another rotary furnace through an automatic feeding and discharging device, and preparing the rod-shaped purple tungsten by adopting a high-temperature reduction calcining process. The specific process comprises the following steps: the rotating speed of the furnace tube is 10r/min, the temperature is 730 ℃, and NH is added₃The flow rate is 0.7m³The feed rate was 80 kg/h. The specific surface area of the prepared purple tungsten is 3.08m²And/g, the microscopic morphology is in the shape of an elongated rod, most of the rods are adhered to one another, and a small part of the rods exist in a single rod shape.

4. Reducing the purple tungsten serving as a raw material in a hydrogen atmosphere to obtain hydrogen with the flow rate of 44m³The reduction time is 4h, the feeding amount is 30kg/h, and the reduction temperature is 650/780/940 ℃.

5. The ultrafine tungsten powder is passivated under inert atmosphere to obtain passivated ultrafine tungsten powder, and the preparation process comprises the following steps: the flow rate of the inert atmosphere was 8L/min.

6. Taking passivated superfine tungsten powder as a main raw material, and adding the passivated superfine tungsten powder, carbon black and TaC in a mass ratio of 100: 6.72: 0.3, after being uniformly mixed, carbonizing to obtain a tungsten carbide block, and crushing by airflow to obtain superfine tungsten carbide powder, wherein the carbonizing and crushing process comprises the following steps: carbonizing at 1200 deg.C for 2.5h in hydrogen atmosphere, and pulverizing the obtained tungsten carbide block with grinding gas pressure of 7mbar and rotation speed of 4200 r/min.

7. The BET of the prepared superfine tungsten carbide powder is 3.05m²The particles are uniform, the dispersibility is good, and no coarse particles and nano-aggregates exist, and an SEM image is shown in figure 4.

Example 2

1. The tungsten oxide furnace end powder is subjected to ultrasonic sieving pretreatment for removing large-particle impurities and mechanical impurities and ensuring the purity of the material.

2. And (3) feeding the sieved tungsten oxide furnace end powder into a rotary furnace through a spiral feeder to perform low-temperature oxygen-enriched rapid calcination, wherein the calcination process comprises the following steps: the rotating speed of the furnace tube is 30r/min, the temperature is 500 ℃, the air draft frequency is 4Hz, the feeding speed is 280kg/h, and the specific surface area of the obtained tungsten trioxide is 2.8m²Increase in g to 3.5m²/g。

3. The tungsten trioxide after low-temperature oxygen-enriched calcination is automatically fed and dischargedThe device is conveyed to another rotary furnace, and the rod-shaped purple tungsten is prepared by adopting a high-temperature reduction calcination process. The specific process comprises the following steps: the rotating speed of the furnace tube is 20r/min, the temperature is 800 ℃, and NH is added₃The flow rate is 0.6m³/h，N₂The flow rate is 0.3m³The feed rate was 110 kg/h. The specific surface area of the prepared purple tungsten is 3.02m²The surface layer of the particles is in a slender rod shape and is mutually bonded, and the inner layer is in a thick rod shape with larger diameter.

4. The superfine tungsten powder is prepared by reducing the purple tungsten serving as a raw material in a hydrogen atmosphere, and the preparation process comprises the following steps: the hydrogen flow rate was 50m³The reduction time is 5h, the feeding amount is 30kg/h, and the reduction temperature is 650/820/920 ℃.

5. The ultrafine tungsten powder is passivated under inert atmosphere to obtain passivated ultrafine tungsten powder, and the preparation process comprises the following steps: the flow rate of the inert atmosphere was 10L/min.

6. The preparation method comprises the following steps of taking passivated superfine tungsten powder as a main raw material, and adding the passivated superfine tungsten powder, carbon black and VC in a mass ratio of 100: 6.72: 0.4, after being uniformly mixed, carbonizing to obtain a tungsten carbide block, and crushing by airflow to obtain superfine tungsten carbide powder, wherein the carbonizing and crushing process comprises the following steps: carbonizing at 1100 deg.C for 3.5h in hydrogen atmosphere, and pulverizing the obtained tungsten carbide block with grinding gas pressure of 7mbar and rotation speed of 4200 r/min.

7. The BET of the prepared superfine tungsten carbide powder is 3.25m²The particles are uniform, the dispersibility is good, no coarse particles exist, a small amount of nano-aggregates exist due to BET, and the SEM image is shown in FIG. 5.

Example 3

1. The tungsten oxide furnace end powder is subjected to ultrasonic sieving pretreatment for removing large-particle impurities and mechanical impurities and ensuring the purity of the material.

2. And (3) feeding the sieved tungsten oxide furnace end powder into a rotary furnace through a spiral feeder to perform low-temperature oxygen-enriched rapid calcination, wherein the calcination process comprises the following steps: the rotating speed of the furnace tube is 27r/min, the temperature is 460 ℃, the air draft frequency is 2Hz, the feeding speed is 260kg/h, and the specific surface area of the obtained tungsten trioxide is 2.8m²Increase in g to 3.8m²/g。

3. Calcining low-temperature oxygen-enriched materialAnd conveying the sintered tungsten trioxide to another rotary furnace through an automatic feeding and discharging device, and preparing the rod-shaped purple tungsten by adopting a high-temperature reduction calcining process. The specific process comprises the following steps: the rotating speed of the furnace tube is 15r/min, the temperature is 760 ℃, and N is₂The flow rate is 0.3m³/h，H₂Flow quantity 0.3m³The feed rate was 100 kg/h. The specific surface area of the prepared purple tungsten is 3.27m²And/g, the microscopic morphology is mostly in the shape of a slender rod, a small part is in the shape of a short rod, most rods are bonded together, and a small part exists in the shape of a single rod.

4. The superfine tungsten powder is prepared by reducing the purple tungsten serving as a raw material in a hydrogen atmosphere, and the preparation process comprises the following steps: the hydrogen flow rate was 56m³The reduction time was 5.5h, the feed rate was 35kg/h and the reduction temperature was 650/820/920 ℃.

5. The ultrafine tungsten powder is passivated under inert atmosphere to obtain passivated ultrafine tungsten powder, and the preparation process comprises the following steps: the flow rate of the inert gas atmosphere was 15L/min.

6. The passivated superfine tungsten powder is used as a main raw material and is mixed with the passivated superfine tungsten powder, carbon black and Cr₃C₂The mass ratio of (A) to (B) is 100: 6.72: 0.4, after being uniformly mixed, carbonizing to obtain a tungsten carbide block, and crushing by airflow to obtain superfine tungsten carbide powder, wherein the carbonizing and crushing process comprises the following steps: carbonizing at 1150 deg.C for 3.0h in hydrogen atmosphere, wherein the gas flow crushing condition of the obtained tungsten carbide block is grinding gas pressure of 9mbar, and the rotation speed of the grading wheel is 4100 r/min.

7. The BET of the prepared superfine tungsten carbide powder is 3.34m²The particles are uniform and have no coarse particles, and more nano-aggregates are present due to large BET, and the SEM image is shown in FIG. 6.

Example 4

1. The tungsten oxide furnace end powder is subjected to ultrasonic sieving pretreatment for removing large-particle impurities and mechanical impurities and ensuring the purity of the material.

2. And (3) feeding the sieved tungsten oxide furnace end powder into a rotary furnace through a spiral feeder to perform low-temperature oxygen-enriched rapid calcination, wherein the calcination process comprises the following steps: the rotating speed of the furnace tube is 27r/min, the temperature is 480 ℃, the air draft frequency is 2Hz, the feeding speed is 260kg/h, and the obtained ratio of the tungsten trioxideThe surface area is 2.8m²Increase in g to 4.0m²/g。

3. And (3) conveying the tungsten trioxide calcined by the low-temperature oxygen enrichment into another rotary furnace through an automatic feeding and discharging device, and preparing the rod-shaped purple tungsten by adopting a high-temperature reduction calcination process. The specific process comprises the following steps: the rotating speed of the furnace tube is 15r/min, the temperature is 780 ℃, and N is₂The flow rate is 0.6m³/h，H₂The flow rate is 0.3m³The feed rate was 100kg/h, and the specific surface area of the produced purple tungsten was 3.58m²The/g is in a slender rod shape in a microscopic shape, the dispersibility is good, and only a small amount of bonding phenomenon exists.

4. The superfine tungsten powder is prepared by reducing the purple tungsten serving as a raw material in a hydrogen atmosphere, and the preparation process comprises the following steps: the hydrogen flow rate was 56m³The reduction time was 5.5h, the feed rate was 35kg/h and the reduction temperature was 650/820/920 ℃.

5. The ultrafine tungsten powder is passivated under inert atmosphere to obtain passivated ultrafine tungsten powder, and the preparation process comprises the following steps: the flow rate of the inert gas atmosphere was 18L/min.

6. The passivated superfine tungsten powder is used as a main raw material and is mixed with the passivated superfine tungsten powder, carbon black and Cr₃C₂And VC in a mass ratio of 100: 6.72: 0.4: 0.35, after being uniformly mixed, the mixture is carbonized to obtain a tungsten carbide block, and superfine tungsten carbide powder is obtained after airflow crushing, wherein the carbonization and crushing process comprises the following steps: carbonizing at 1120 deg.C for 3.5h in hydrogen atmosphere, wherein the gas flow crushing condition of the obtained tungsten carbide block is grinding gas pressure of 9mbar, and the rotation speed of the grading wheel is 4100 r/min.

7. The BET of the prepared superfine tungsten carbide powder is 3.48m²The particles are uniform and have no coarse particles, and a large number of nanoagglomerates are present due to BET, and the SEM image is shown in fig. 7.

Comparative example 1

1. The tungsten oxide furnace end powder is subjected to ultrasonic sieving pretreatment for removing large-particle impurities and mechanical impurities and ensuring the purity of the material.

2. And (2) feeding the sieved tungsten oxide furnace end powder into a rotary furnace through a spiral feeder to perform high-temperature reduction calcination, wherein the specific process comprises the following steps: the rotating speed of the furnace tube is 14r/min, the temperature is 740 ℃, and NH is added₃The flow rate is 0.6m³H, the feed rate is 60kg/h, and the specific surface area of the prepared purple tungsten is 2.86m²The large part of the bar-shaped material is thick bar-shaped with larger diameter, the bonding phenomenon is serious, and a large amount of small broken short bars exist, and only a small amount of long and thin bar-shaped materials exist.

3. The superfine tungsten powder is prepared by reducing the purple tungsten serving as a raw material in a hydrogen atmosphere, and the preparation process comprises the following steps: the hydrogen flow rate was 56m³The reduction time was 5.5h, the feed rate was 35kg/h and the reduction temperature was 650/820/920 ℃.

4. The ultrafine tungsten powder is passivated under inert atmosphere to obtain passivated ultrafine tungsten powder, and the preparation process comprises the following steps: the flow rate of the inert gas atmosphere was 12L/min.

5. The passivated superfine tungsten powder is used as a main raw material and is mixed with the passivated superfine tungsten powder, carbon black and Cr₃C₂The mass ratio of (A) to (B) is 100: 6.72: 0.4, after being uniformly mixed, carbonizing to obtain a tungsten carbide block, and crushing by airflow to obtain superfine tungsten carbide powder, wherein the carbonizing and crushing process comprises the following steps: carbonizing at 1150 deg.C for 3.0h in hydrogen atmosphere, wherein the gas flow crushing condition of the obtained tungsten carbide block is grinding gas pressure of 9mbar, and the rotation speed of the grading wheel is 4100 r/min.

6. BET of ultrafine tungsten carbide powder is 2.9m²In terms of/g, a small amount of coarse particles were present, and the SEM image is shown in FIG. 8.

Comparative example 2

1. The method takes conventional tungsten trioxide as a raw material, and the tungsten trioxide enters a rotary furnace through a spiral feeder to be subjected to high-temperature reduction calcination, and the specific process comprises the following steps: the rotating speed of the furnace tube is 14r/min, the temperature is 740 ℃, and NH is added₃The flow rate is 0.6m³H, the feed rate is 60kg/h, and the specific surface area of the prepared purple tungsten is 2.8m²/g。

2. The superfine tungsten powder is prepared by reducing the purple tungsten serving as a raw material in a hydrogen atmosphere, and the preparation process comprises the following steps: the hydrogen flow rate was 56m³The reduction time was 5.5h, the feed rate was 35kg/h and the reduction temperature was 650/820/920 ℃.

3. The ultrafine tungsten powder is passivated under inert atmosphere to obtain passivated ultrafine tungsten powder, and the preparation process comprises the following steps: the flow rate of the inert gas atmosphere was 12L/min.

4. Will passivate the superThe fine tungsten powder is used as main raw material, and is mixed with passivated superfine tungsten powder, carbon black and Cr₃C₂The mass ratio of (A) to (B) is 100: 6.72: 0.4, after being uniformly mixed, carbonizing to obtain a tungsten carbide block, and crushing by airflow to obtain superfine tungsten carbide powder, wherein the carbonizing and crushing process comprises the following steps: carbonizing at 1150 deg.C for 3.0h in hydrogen atmosphere, wherein the gas flow crushing condition of the obtained tungsten carbide block is grinding gas pressure of 9mbar, and the rotation speed of the grading wheel is 4100 r/min.

5. BET of ultrafine tungsten carbide powder is 2.78m²In terms of/g, a small amount of coarse particles were present, and the SEM image is shown in FIG. 9.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.

Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.