CN115383128A - Method for preparing coarse-particle tungsten powder by tungsten trioxide reduction - Google Patents

Abstract

The invention discloses a method for preparing coarse-particle tungsten powder by tungsten trioxide reduction, which comprises the steps of putting tungsten trioxide and tungsten hexachloride into a ball mill according to a certain mass ratio, uniformly mixing, putting the mixture of the tungsten trioxide and the tungsten hexachloride into a reduction furnace, introducing hydrogen at a relatively low temperature for first-stage reduction, volatilizing the tungsten hexachloride, reducing the tungsten hexachloride into metal tungsten deposited on the surface of the tungsten trioxide, and introducing a mixed gas of hydrogen and water vapor at a high temperature for second-stage enhanced reduction to promote the growth of tungsten powder particles, thereby preparing the coarse-particle tungsten powder. The method has the advantages that the defect that the product purity is reduced due to alkali metal residues in the traditional method for preparing the coarse-grained tungsten powder by doping the alkali metal Na/Li can be avoided, and the coarse-grained tungsten powder with high purity and complete crystallization can be prepared under mild reaction conditions.

Description

A method for preparing coarse tungsten powder by reduction of tungsten trioxide

technical field

The invention relates to the field of tungsten powder metallurgy, in particular to a method for preparing coarse tungsten powder by reduction of tungsten trioxide powder.

Background technique

Coarse-grained tungsten carbide has the advantages of good toughness, high hardness, high thermal conductivity, good red hardness, etc., and is widely used in various fields such as petroleum drilling, mining tools, hard surface materials, and stamping dies. Tungsten powder is the raw material for preparing tungsten carbide cemented carbide. Since the particle size of tungsten powder and tungsten carbide has obvious heredity, the preparation of coarse tungsten powder is the key to the preparation of ultra-coarse tungsten carbide cemented carbide.

Tungsten powder is usually prepared from tungsten oxide powder by reduction process. At present, there are many processes for preparing coarse-grained tungsten powder. According to the principle of the process, there are mainly the following methods: (1) Coarse-grained tungsten powder is prepared by high-temperature hydrogen reduction of tungsten oxide. Yellow tungsten (WO ₃ ) or blue tungsten (WO _2.92 ) is used as raw material, and the coarse particle tungsten powder is prepared by hydrogen reduction at a temperature above 1300°C for a long time. This process has the advantages of uniform tungsten powder particles and less false particles, but due to the high reduction temperature and high requirements for furnace equipment, it has the disadvantages of high energy consumption and high cost. For example, the patent 201810931907.8 "A method for preparing ultra-coarse tungsten powder by reducing tungsten oxide in a high-temperature liquid phase" discloses that tungsten oxide and tungsten powder are used as raw materials, and the average Ultra-coarse tungsten powder with a particle size of 58-70um. (2) Coarse tungsten powder is prepared by hydrogen reduction by doping tungsten oxide powder with alkali metal (Na or Li). This process utilizes the property that tungsten oxide and alkali metal oxides are easy to form low-melting point compounds, and hydrogen reduction is carried out at a higher temperature to prepare coarse-grained tungsten powder. Due to the limited volatility of alkali metals, especially when doped with Li, a certain amount of alkali metals often remain in the tungsten powder prepared by reduction, which has an adverse effect on the performance of tungsten products. In addition, the ultra-coarse tungsten powder prepared by this process has more false particles. For example, patent 202010684540.1 "Method for preparing ultra-coarse tungsten powder with narrow particle size distribution and tungsten powder" discloses that tungsten oxide, sodium tungstate and water are mixed, dried to obtain sodium-doped tungsten oxide powder, and 1000 in a tube furnace Under the condition of ℃, hydrogen reduction is carried out to prepare ultra-coarse tungsten powder with an average particle size of 40um. (3) Using tungsten oxide or a mixture of tungsten oxide powder and tungsten powder as raw materials, water vapor and hydrogen are passed into the reduction furnace for long-term reduction to prepare ultra-coarse tungsten powder. This process has the disadvantages of long reduction time and low production efficiency. For example, patent 200910044492.3 discloses using tungsten oxide powder as a raw material, passing a mixed gas of water vapor and hydrogen into the reduction furnace, and reducing at 1350°C for 50 hours to prepare ultra-coarse tungsten powder with an average particle size of 30um.

Contents of the invention

The main purpose of the present invention is to solve the technical problem of preparing ultra-coarse tungsten powder in the existing process to a certain extent, and to propose a new method for preparing ultra-coarse tungsten powder with uniform particle size under relatively mild conditions. Tungsten carbide provides high-quality raw materials.

In order to achieve the above object, a method for preparing coarse tungsten powder by reduction of tungsten trioxide proposed by the present invention comprises the following steps:

(1) Put tungsten trioxide and tungsten hexachloride into a ball mill according to a certain mass ratio and mix for a certain period of time to obtain a mixture of tungsten trioxide and tungsten hexachloride;

(2) Put the mixture of tungsten trioxide and tungsten hexachloride into a boat, and place it in a reduction furnace to raise it to a certain temperature, then pass in hydrogen for a period of reduction and keep it for a certain period of time, so that hexachloride Tungsten is volatilized and reduced to metal tungsten and precipitated on the surface of tungsten trioxide;

(3) Then further increase the temperature in the reduction furnace, and pass the mixed gas of hydrogen and water vapor into the reduction furnace for two-stage enhanced reduction, and keep it warm for a certain period of time, so as to obtain coarse tungsten powder.

Preferably, the particle size of tungsten trioxide in step (1) is 12-18um, the mass ratio of tungsten hexachloride and tungsten trioxide powder is 10%-30%, and the mixing time is 0.5-1 hour.

Preferably, the particle size of the tungsten trioxide described in step (1) is 18um.

Preferably, the mass ratio of tungsten hexachloride and tungsten trioxide powder in step (1) is 20%.

Preferably, the reaction temperature in step (2) is 350-400° C., the hydrogen flow rate is 200-400 ml/min, and the reaction time is 0.5-2 hours.

Preferably, the reduction temperature in step (3) is 800-1000°C, the flow rate of hydrogen is 300-600ml/min, the flow rate of water vapor is 100-300ml/min, and the holding time is 2-5 hours.

The technical principle that the present invention adopts is as follows:

In the present invention, tungsten trioxide is used as a raw material, and a certain proportion of tungsten hexachloride powder and tungsten oxide powder are mixed evenly, and tungsten chloride has the characteristics of high activity and high volatility. One-stage reduction, so that tungsten chloride is reduced to metal tungsten and deposited on the surface of tungsten trioxide, at the same time, part of tungsten trioxide is pre-reduced, and then the second-stage enhanced reduction is carried out at a higher temperature using a mixture of hydrogen and water vapor. Coarse tungsten powder is thus prepared. Since the boiling point of tungsten hexachloride is 348°C, when the reduction temperature is above 350°C, the highly active tungsten chloride will volatilize and be reduced to metal tungsten deposited on the surface of tungsten trioxide, making the particles of tungsten trioxide increase. At the same time, the tungsten deposited on the surface of tungsten trioxide can act as a seed crystal, which increases the particle size of the tungsten powder during the two-stage enhanced reduction process, thereby preparing coarse tungsten powder. Since tungsten hexachloride has the natural advantages of being volatile and easy to reduce, it has a better effect than relying on "volatility-deposition" to promote the growth of tungsten powder by means of doping alkali metal and introducing wet hydrogen. In addition, the process adopts a two-stage reduction process. In the two-stage enhanced reduction process, the tungsten trioxide powder deposited on the surface of tungsten can be further reduced and grown, which is conducive to the preparation of coarse-grained tungsten powder.

Compared with the prior art, the present invention has the following beneficial effects:

By adjusting the corresponding process parameters, the new method can prepare coarse tungsten powder with uniform particle size, complete shape and average particle size of 22-36um. The process has the advantages of uniform tungsten powder particle size, mild reaction conditions, high product purity, complete tungsten powder crystal form, and easy industrialization.

Description of drawings

Fig. 1 is the SEM figure of the prepared tungsten powder of embodiment 3;

Fig. 2 is the XRD figure of the tungsten powder prepared in embodiment 3;

Fig. 3 is the SEM figure of the prepared tungsten powder of embodiment 4;

Fig. 4 is the XRD figure of the prepared tungsten powder of embodiment 4;

Fig. 5 is the SEM figure of the prepared tungsten powder of embodiment 5;

FIG. 6 is an XRD pattern of the tungsten powder prepared in Example 5.

Detailed ways

The embodiments of the present invention are specifically described below through examples, and the following examples are intended to illustrate the present invention rather than further limit the protection scope of the present invention.

Example 1

Step 1: Take 30 grams of tungsten trioxide powder with an average particle size of 18um and 3.0 grams of tungsten hexachloride powder and mix them in a ball mill for 1 hour to obtain a mixture of tungsten trioxide and tungsten hexachloride.

Step 2: Put the mixed material in Step 1 into a reduction furnace and heat up to 400° C., then pass in hydrogen for reduction, the hydrogen flow rate is 400 ml/min, and react for 2 hours.

Step 3: Raise the temperature in the reduction furnace to 1000°C, and feed the mixed gas of hydrogen and water vapor, the flow rate of hydrogen gas is 600ml/min, the flow rate of water vapor is 300ml/min, react for 5 hours, and then cool with the furnace, Coarse tungsten powder with an average particle size of 30um was prepared. Tungsten powder has uniform particle size, regular shape, and less adhesion between particles.

Example 2

Step 1: Take 30 grams of tungsten trioxide powder with an average particle size of 18um and 6.0 grams of tungsten hexachloride powder and mix them in a ball mill for 1 hour to obtain a mixture of tungsten trioxide and tungsten hexachloride.

Step 2: Put the mixed material in Step 1 into a reduction furnace and heat up to 400° C., then pass in hydrogen for reduction, the hydrogen flow rate is 400 ml/min, and react for 2 hours.

Step 3: Raise the temperature in the reduction furnace to 1000°C, and feed the mixed gas of hydrogen and water vapor, the flow rate of hydrogen gas is 600ml/min, the flow rate of water vapor is 300ml/min, react for 5 hours, and then cool with the furnace, Coarse tungsten powder with an average particle size of 36um was prepared. Tungsten powder has uniform particle size, regular shape and good dispersion.

Example 3

Step 1: Take 30 grams of tungsten trioxide powder with an average particle size of 18um and 9 grams of tungsten hexachloride powder and mix them in a ball mill for 1 hour to obtain a mixture of tungsten trioxide and tungsten hexachloride.

Step 2: Put the mixed material in Step 1 into a reduction furnace and heat up to 400° C., then pass in hydrogen for reduction, the hydrogen flow rate is 400 ml/min, and react for 2 hours.

Step 3: Raise the temperature in the reduction furnace to 1000°C, and feed the mixed gas of hydrogen and water vapor, the flow rate of hydrogen gas is 600ml/min, the flow rate of water vapor is 300ml/min, react for 5 hours, and then cool with the furnace, Coarse-grained tungsten powder with complete shape, part of particle cohesion and average particle size of 32um was prepared. The scanning electron microscope SEM and XRD analysis results of tungsten powder are shown in Figure 1 and Figure 2.

Comparative example 1

Step 1: Take 30 grams of tungsten trioxide powder with an average particle size of 18um and 2.4 grams of tungsten hexachloride powder and mix them in a ball mill for 1 hour to obtain a mixture of tungsten trioxide and tungsten hexachloride.

Step 2: Put the mixed material in Step 1 into a reduction furnace and heat up to 400° C., then pass in hydrogen for reduction, the hydrogen flow rate is 400 ml/min, and react for 2 hours.

Step 3: Raise the temperature in the reduction furnace to 1000°C, and feed the mixed gas of hydrogen and water vapor, the flow rate of hydrogen gas is 600ml/min, the flow rate of water vapor is 300ml/min, react for 5 hours, and then cool with the furnace, Coarse tungsten powder with an average particle size of 27um was prepared. Tungsten powder has uniform particle size, regular shape, and less adhesion between particles.

Comparative example 2

Step 1: Take 30 grams of tungsten trioxide powder with an average particle size of 18um and 10.5 grams of tungsten hexachloride powder and mix them in a ball mill for 1 hour to obtain a mixture of tungsten trioxide and tungsten hexachloride.

Step 2: Put the mixed material in Step 1 into a reduction furnace and heat up to 400° C., then pass in hydrogen for reduction, the hydrogen flow rate is 400 ml/min, and react for 2 hours.

Step 3: Raise the temperature in the reduction furnace to 1000°C, and feed the mixed gas of hydrogen and water vapor, the flow rate of hydrogen gas is 600ml/min, the flow rate of water vapor is 300ml/min, react for 5 hours, and then cool with the furnace, Coarse tungsten powder with an average particle size of 28um was prepared. The morphology of tungsten powder is relatively regular, the particle size uniformity of tungsten powder is deviation, and some particles are stuck together.

It can be seen from the particle size data of the tungsten powder in the above Examples 1-3 and Comparative Example 1-2 that the mass ratio of tungsten trioxide and tungsten hexachloride has a great influence on the particle size of the tungsten powder. When the mass ratio of tungsten hexachloride to tungsten trioxide is 8%, the average particle size of the prepared tungsten powder is 27um, and the tungsten powder has uniform particle size, regular shape and good dispersion. When the mass ratio of tungsten hexachloride to tungsten trioxide is 20%, the average particle size of the prepared tungsten powder is 36um, and the tungsten powder has uniform particle size and good dispersibility. When the mass ratio of tungsten hexachloride to tungsten trioxide increases to 30%, the average particle size of tungsten powder prepared by reduction is 32um, but the uniformity of particle size distribution is deviated. When the mass ratio of tungsten hexachloride to tungsten trioxide is further increased to 35%, the average particle size of the tungsten powder prepared by reduction is 28um, the uniformity of the particle size distribution of the tungsten powder becomes worse, and some tungsten powder sticks more seriously. This may be due to the increase in the mass ratio of tungsten hexachloride, part of the tungsten did not precipitate on the surface of the tungsten trioxide powder during the first-stage reduction process, but formed fine-grained tungsten powder and crystallized separately, so that the tungsten powder in the second-stage enhanced reduction process The phenomenon of poor particle size uniformity. Therefore, in the process of operation, it is necessary to adjust the process parameters to prepare coarse-grained tungsten powder with uniform particle size and complete crystallization.

Example 4

Step 1: Take 30 grams of tungsten trioxide powder with an average particle size of 12um and 6 grams of tungsten hexachloride powder and mix them in a ball mill for 1.0 hour to obtain a mixture of tungsten trioxide and tungsten hexachloride.

Step 2: Put the mixture in Step 1 into a reduction furnace and heat up to 350° C., and then pass in hydrogen for reduction. The hydrogen flow rate is 200 ml/min, and react for 0.5 hours.

Step 3: Raise the temperature in the reduction furnace to 800°C, and feed a mixed gas of hydrogen and water vapor, the flow rate of hydrogen gas is 300ml/min, the flow rate of water vapor is 100ml/min, react for 2 hours, and then cool with the furnace, Granular tungsten powder with relative deviation in particle size uniformity and an average particle size of 22um was prepared. The scanning electron microscope SEM and XRD analysis results of tungsten powder are shown in Figure 3 and Figure 4.

Example 5

Step 1: Take 30 grams of tungsten trioxide powder with an average particle size of 15 μm and 3 grams of tungsten hexachloride powder and mix them in a ball mill for 0.5 hour to obtain a mixture of tungsten trioxide and tungsten hexachloride.

Step 2: Put the mixture in Step 1 into a reduction furnace and heat up to 350° C., and then pass in hydrogen for reduction. The hydrogen flow rate is 200 ml/min, and react for 0.5 hours.

Step 3: Raise the temperature in the reduction furnace to 800°C, and feed a mixed gas of hydrogen and water vapor, the flow rate of hydrogen gas is 300ml/min, the flow rate of water vapor is 100ml/min, react for 2 hours, and then cool with the furnace, Coarse tungsten powder with uniform particle size, complete shape and average particle size of 24um was prepared. The scanning electron microscope SEM and XRD analysis results of tungsten powder are shown in Figure 5 and Figure 6.

Example 6

Step 1: Take 30 grams of tungsten trioxide powder with an average particle size of 18um and 6 grams of tungsten hexachloride powder and mix them in a ball mill for 0.6 hours to obtain a mixture of tungsten trioxide and tungsten hexachloride.

Step 2: put the mixture in step 1 into a reduction furnace and heat up to 370° C., and then pass in hydrogen for reduction. The hydrogen flow rate is 300 ml/min, and react for 1.5 hours.

Step 3: Then raise the temperature in the reduction furnace to 900°C, and feed the mixed gas of hydrogen and water vapor, the flow rate of hydrogen gas is 400ml/min, the flow rate of water vapor is 200ml/min, react for 4 hours, and then cool with the furnace, Coarse tungsten powder with an average particle size of 29um was prepared. Compared with the tungsten powder in Example 5, the tungsten powder in Example 6 has a uniform particle size and a complete and regular shape, and the XRD analysis results show that it is tungsten powder.

Claims (6)

1. A method for preparing coarse tungsten powder by reduction of tungsten trioxide, is characterized in that, comprises the following steps: (1) Put tungsten trioxide and tungsten hexachloride into a ball mill according to a certain mass ratio and mix for a certain period of time to obtain a mixture of tungsten trioxide and tungsten hexachloride; (2) Put the mixture of tungsten trioxide and tungsten hexachloride into a boat, and place it in a reduction furnace to raise it to a certain temperature, then pass in hydrogen for a period of reduction and keep it for a certain period of time, so that hexachloride Tungsten is volatilized and reduced to metal tungsten and precipitated on the surface of tungsten trioxide; (3) Then further increase the temperature in the reduction furnace, and pass the mixed gas of hydrogen and water vapor into the reduction furnace for two-stage enhanced reduction, and keep it warm for a certain period of time, so as to obtain coarse tungsten powder. 2. The method according to claim 1, characterized in that the particle size of tungsten trioxide described in step (1) is 12-18um, and the mass ratio of tungsten hexachloride and tungsten trioxide powder is 10%-30 %, the mixing time is 0.5-1 hour. 3. The method according to claim 2, characterized in that the tungsten trioxide particle size described in step (1) is 18um. 4. The method according to claim 2, characterized in that the mass ratio of tungsten hexachloride and tungsten trioxide powder is 20% in step (1). 5. The method according to claim 1, characterized in that the reaction temperature in step (2) is 350-400°C, the hydrogen flow rate is 200-400ml/min, and the reaction time is 0.5-2 hours. 6. The method according to claim 1, characterized in that, the reduction temperature described in step (3) is 800-1000°C, the flow rate of hydrogen is 300-600ml/min, the flow rate of water vapor is 100-300ml/min, The holding time is 2-5 hours.

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