A method for preparing low-carbon ultrafine tungsten carbide powder assisted by ammonium metatungstate

Abstract

The invention discloses a method for preparing ultrafine tungsten carbide powder assisted by ammonium metatungstate, wherein the preparation method generally includes dissolving tungsten hexachloride and hydroquinone in ethanol and stirring and dissolving them as raw materials at room temperature, and then mixing the two to obtain a clear mixed solution; ammonium metatungstate is added to the above-mentioned mixed solution, and stirred evenly, and then placed in a water bath to react for a period of time; the mixed solution after the reaction is completed is placed in an oven for drying and ground into powder; the powder is then placed in a high-temperature tube furnace, and protective gas is introduced into the tube furnace, and calcined at 1100-1500°C for 60-480min to obtain tungsten carbide powder. The embodiment of the present invention not only has a simple preparation process, an easy-to-control reaction process, a short production cycle, and low cost, but also the prepared tungsten carbide powder has a high purity, a finer particle size, and a low free carbon content, and can be widely used in the hard alloy fields of industrial machinery, cutting tools, abrasives, and other finishing processes.

Description

Technical Field

[0001] The present invention relates to the technical field of tungsten carbide powder preparation, in particular to a method for preparing low-carbon ultrafine tungsten carbide powder with the assistance of ammonium metatungstate. Background Art

[0002] Tungsten carbide, with its extremely high hardness, is known as the "teeth of industry." Tungsten carbide, a classic material in this field, features a high melting point (2600-2850°C), high hardness, excellent corrosion and wear resistance, low friction coefficient, high thermal stability, and low thermal expansion coefficient. Combined with binders (Co, Fe, Ni), it forms a cemented carbide that is widely used in industrial machinery, cutting tools, abrasives, and other finishing applications. It is suitable for metalworking, drilling, and mining industries operating under high pressure, high temperature, and corrosive environments. Therefore, the quality requirements for tungsten carbide powders are very high, such as ultrafine grains, good dispersion, high purity, and low carbon content.

[0003] At present, the preparation methods of tungsten carbide powder mainly include solid phase method, liquid phase method and gas phase method. Among them, the solid phase method is mostly used for industrial production, but this method is cumbersome, inefficient, time-consuming and energy-consuming; in addition, the solid phase method mostly uses mechanical mixing, and the product contains more impurities; the gas phase method mostly uses combustible gas, and the preparation process is very risky and costly; although the liquid phase method can produce high-purity ultrafine tungsten carbide powder, the use of complex organic matter makes the free carbon content uncontrollable. Since the stoichiometric ratio of W:C in the preparation process of tungsten carbide powder is in a relatively small range, accurate calculation and strict material control are required to obtain tungsten carbide powder with a low carbon content. Generally, the more direct way is to use a mechanical mixture of tungsten powder and carbon powder at a ratio of nearly 1:1. And after high-temperature sintering, tungsten carbide powder with low carbon content is obtained, but it is also easier to introduce other element impurities; the use of the liquid phase method can obtain ultrafine tungsten carbide powder with higher purity. In order to obtain a uniform precursor solution, the carbon source used in the liquid phase method is generally an organic carbon source, such as sorbitol, glucose, phenols, etc. Since this type of carbon source has a complex molecular structure, unstable chemical changes are prone to occur during the precursor preparation and sintering stages; when the amount of carbon source is too small, the carbon content is insufficient and the by-product W2C is produced; when the amount of carbon source is too much, the prepared tungsten carbide powder has more free carbon, which ultimately makes the free carbon content of the tungsten carbide powder difficult to control. Summary of the Invention

[0004] To address the above-mentioned shortcomings in the prior art, the present invention provides a method for preparing low-carbon, ultrafine tungsten carbide powder using ammonium metatungstate as an aid. This method uses ammonium metatungstate, an inorganic substance, to consume and regulate excess carbon in an organic liquid precursor, thereby achieving the production of low-carbon tungsten carbide powder using a liquid precursor method and effectively controlling the free carbon content. The method features a simple preparation process, easily controllable reaction processes, a short production cycle, and low costs. Furthermore, the prepared tungsten carbide powder has high purity, a fine particle size, and a low free carbon content, and the free carbon content can also be adjusted.

[0005] To achieve the above object, the present invention adopts the following technical solution: a method for preparing low-carbon ultrafine tungsten carbide powder with the assistance of ammonium metatungstate, comprising the following steps:

[0006] Step A: adding tungsten chloride to ethanol at a concentration of 0.3 mol / L-1.5 mol / L and stirring at a constant temperature until the solution is completely clear to obtain a tungsten source solution; mixing hydroquinone with ethanol and stirring at a constant temperature until the solution is completely clear to obtain a carbon source solution; and uniformly adding the tungsten source solution dropwise to the carbon source solution and stirring uniformly to obtain a liquid precursor mixed solution, wherein the molar ratio of tungsten chloride in the tungsten source solution to hydroquinone in the carbon source solution is 2:(1.5-5);

[0007] Step B: adding ammonium metatungstate to the liquid precursor mixed solution, wherein the molar ratio of ammonium metatungstate to tungsten chloride in step A is 1:(20-90), and then heating and stirring in a water bath to obtain an adjusted tungsten carbide precursor solution;

[0008] Step C: drying the adjusted tungsten carbide precursor solution and grinding it into powder, then placing it into a high-temperature tube furnace, introducing a protective gas and calcining it at high temperature to obtain tungsten carbide powder.

[0009] Further improvement of the method for preparing low-carbon ultrafine tungsten carbide powder assisted by ammonium metatungstate:

[0010] Preferably, in step A, the temperature of the constant temperature stirring is 20-90°C.

[0011] Preferably, in step A, the tungsten source solution and the carbon source solution are prepared by constant temperature magnetic stirring at a stirring speed of 100-800 rpm.

[0012] Preferably, in step A, the tungsten source solution is slowly added dropwise to the carbon source solution at a rate of 0.5-10 mL / min.

[0013] Preferably, in step B, after adding ammonium metatungstate, the temperature of the water bath is heated to 30-80° C. and stirring is continued for 30-120 minutes.

[0014] Preferably, in step C, the adjusted tungsten carbide precursor solution is dried at a temperature of 60-120° C. for a time of 4-24 hours.

[0015] Preferably, in step C, the air flow rate of the protective gas is 0.005-50 liters / minute, the calcination temperature is 1100-1500° C., and the calcination time is 60-480 minutes.

[0016] Preferably, the specific parameters of the high-temperature calcination in step C are as follows: using high-purity argon as the protective gas, the high-temperature tube furnace is heated from room temperature to 1000°C at a rate of 1-5°C / min, then heated to 1100-1500°C at a rate of 0.5-2°C / min, and kept warm for 60-480min, then cooled to 1000°C at a rate of 0.5-2°C / min, then cooled to 200-400°C at a rate of 1-5°C / min, and finally cooled naturally to room temperature.

[0017] Preferably, in step C, the adjusted tungsten carbide precursor solution is dried and then ground into powder for 0.5-4 hours.

[0018] Preferably, the concentration of hydroquinone in the carbon source solution in step A is 1.1-3.7 mol / L.

[0019] The beneficial effects of the present invention compared to the prior art are:

[0020] 1. The present invention uses tungsten chloride, hydroquinone and ethanol to prepare a liquid precursor mixed solution, and after adding ammonium metatungstate, it is constant temperature treated in a water bath to promote the complexation between the raw materials. Then the precursor is dried and ground into powder, and calcined at high temperature to obtain tungsten carbide powder with high purity, fine particle size and good sintering performance. In addition, the process is simple, the production efficiency is high and the energy consumption is low.

[0021] 2. This invention uses a liquid-phase precursor method to prepare tungsten carbide powder. During the precursor preparation stage, hydroquinone complexes with tungsten alkoxide to form a completely uniform long-chain structure of WOC, which is the key to achieving nanoscale and good dispersibility. In addition, during the precursor preparation process, the above-mentioned organic molecular structure can be obtained without the need for high temperature and high pressure experimental conditions, making the experimental process simple and efficient.

[0022] 3. In the present invention, tungsten chloride is used as the main tungsten source to participate in the main synthesis of tungsten carbide, while ammonium metatungstate is used as an auxiliary tungsten source in a relatively small amount. Its main function is to utilize the oxygen element in ammonium metatungstate to react with the carbon element in the liquid phase to generate gaseous carbon monoxide or carbon dioxide during the calcination process to regulate and reduce the excess carbon caused by the use of the liquid phase precursor method. This method effectively solves the problem of being unable to control the carbon content in the organic hybrid liquid phase precursor method to obtain low-carbon tungsten carbide powder due to the use of a complex organic carbon source.

[0023] 4. The auxiliary reagent ammonium metatungstate used in the present invention can control the carbon content of the subsequent tungsten carbide powder preparation at the precursor stage. This is mainly because ammonium metatungstate can evenly complex with tungsten alkoxide in the precursor solution. This mixing method effectively produces high-purity, ultrafine, impurity-free powder. After calcination, there are no other impurity peaks in the XRD spectrum. This avoids the problem of impurity introduction caused by mechanical mixing for precise carbon control, and can be used directly without secondary treatment.

[0024] 5. The present invention improves the yield of tungsten carbide powder preparation to a certain extent. Since ammonium metatungstate also contains tungsten, the tungsten element in it also plays a role in regulating and reducing the carbon content, and forms tungsten carbide products, thereby improving the yield of tungsten carbide powder. It can be seen that the auxiliary use of ammonium metatungstate achieves a two-pronged effect without any other side effects.

[0025] 6. The calcination conditions of the present invention are prepared under inert gas. Its formation process relies solely on its own carbothermal reduction process and carburization process, and does not require reducing gases such as hydrogen and methane, which are high-risk gases. This greatly improves the safety factor of powder preparation. This high-temperature calcination process allows the carbothermal reduction reaction to proceed fully, thereby obtaining high-purity tungsten carbide powder.

[0026] 7. The preparation method of the present invention is more likely to prepare powder materials with small and uniform particle size. The tungsten carbide powder is fine in size, with a particle size of 100nm-300nm, and is spherical in shape and evenly distributed, with good microscopic morphology.

[0027] 8. The method provided by the present invention has a simple preparation process, does not require special instruments and drugs, does not involve any complicated processing steps, is very convenient and suitable for large-scale synthesis of cemented carbide materials in an economical way, and has the potential for commercialization and industrialization. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The X-ray diffraction patterns of the tungsten carbide powders prepared in Examples 1-3 of the present invention and Comparative Examples 1 and 2 are shown.

[0029] Figure 2This is a scanning electron microscope photograph of the tungsten carbide powder prepared in Example 1 of the present invention.

[0030] Figure 3 This is a scanning electron microscope photograph of the tungsten carbide powder prepared in Example 2 of the present invention.

[0031] Figure 4 This is a scanning electron microscope photograph of the tungsten carbide powder prepared in Example 3 of the present invention.

[0032] Figure 5 This is a scanning electron microscope photograph of the tungsten carbide powder prepared in Comparative Example 1.

[0033] Figure 6 This is a scanning electron microscope photograph of the tungsten carbide powder prepared in Comparative Example 2.

[0034] Figure 7 This is a bar chart of the free carbon content of the tungsten carbide powders prepared in Example 1, Example 2, Example 3 and Comparative Example 1. DETAILED DESCRIPTION

[0035] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below in conjunction with the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0036] Example 1

[0037] This embodiment provides a method for preparing low-carbon ultrafine tungsten carbide powder with the assistance of ammonium metatungstate, which specifically includes the following steps:

[0038] Step A: Weigh 5.9 g of tungsten hexachloride and mix it with 20 ml of ethanol, and stir it at a constant temperature until the solution is completely clear, which serves as the tungsten source solution. Weigh 1.3 g of hydroquinone and mix it with 10 ml of ethanol, and stir it at a constant temperature until the solution is completely clear, which serves as the carbon source solution. The concentration of tungsten chloride in the tungsten source solution is 0.75 mol / L, and the molar ratio of tungsten chloride in the tungsten source solution to hydroquinone in the carbon source solution is 2:1.67.

[0039] The tungsten source solution was uniformly added dropwise to the carbon source solution at a rate of 2 mL / min and stirred evenly to obtain a clear liquid precursor mixed solution;

[0040] Step B: Weigh 0.5 g of ammonium metatungstate powder, with a molar ratio of ammonium metatungstate to tungsten chloride in step A of 1:88, and slowly add it to the above liquid precursor mixed solution under continuous stirring. Place it in a 60° C. water bath and stir for 1 hour to obtain an adjusted mixed solution;

[0041] Step C, placing the adjusted mixed solution in a constant temperature drying oven, drying it at 80°C for 12h to make it completely dry, and grinding it into powder, then putting it into a graphite crucible, placing it in a high-temperature tube furnace, using high-purity argon (Ar≥99.999%) as a protective gas, heating it from room temperature to 1000°C at a rate of 5°C / min, then heating it to 1250°C at a rate of 2°C / min, and keeping it warm for 360min, then cooling it to 1000°C at a rate of 2°C / min, then cooling it to 300°C at a rate of 5°C / min, and finally cooling it naturally to room temperature to obtain tungsten carbide powder.

[0042] Example 2

[0043] This embodiment provides a method for preparing low-carbon ultrafine tungsten carbide powder with the assistance of ammonium metatungstate, which specifically includes the following steps:

[0044] Step A: Weigh 5.9 g of tungsten hexachloride and mix it with 20 ml of ethanol, and stir it at a constant temperature until the solution is completely clear, which serves as the tungsten source solution. Weigh 1.3 g of hydroquinone and mix it with 10 ml of ethanol, and stir it at a constant temperature until the solution is completely clear, which serves as the carbon source solution. The concentration of tungsten chloride in the tungsten source solution is 0.75 mol / L, and the molar ratio of tungsten chloride in the tungsten source solution to hydroquinone in the carbon source solution is 2:1.67.

[0045] The tungsten source solution was uniformly added dropwise to the carbon source solution at a rate of 2 mL / min and stirred evenly to obtain a clear liquid precursor mixed solution;

[0046] Step B: Weigh 0.6 g of ammonium metatungstate powder, with a molar ratio of ammonium metatungstate to tungsten chloride in step A of 1:73, and slowly add it to the above liquid precursor mixed solution under continuous stirring. Place it in a 60°C water bath and stir for 1 hour to obtain an adjusted mixed solution;

[0047] Step C, placing the adjusted mixed solution in a constant temperature drying oven, drying it at 80°C for 12h to make it completely dry, and grinding it into powder, then putting it into a graphite crucible, placing it in a high-temperature tube furnace, using high-purity argon (Ar≥99.999%) as a protective gas, heating it from room temperature to 1000°C at a rate of 5°C / min, then heating it to 1250°C at a rate of 2°C / min, and keeping it warm for 360min, then cooling it to 1000°C at a rate of 2°C / min, then cooling it to 300°C at a rate of 5°C / min, and finally cooling it naturally to room temperature to obtain tungsten carbide powder.

[0048] Example 3

[0049] This embodiment provides a method for preparing low-carbon ultrafine tungsten carbide powder with the assistance of ammonium metatungstate, which specifically includes the following steps:

[0050] Step A: Weigh 5.9 g of tungsten hexachloride and mix it with 20 ml of ethanol, and stir it at a constant temperature until the solution is completely clear, which serves as the tungsten source solution. Weigh 1.3 g of hydroquinone and mix it with 10 ml of ethanol, and stir it at a constant temperature until the solution is completely clear, which serves as the carbon source solution. The concentration of tungsten chloride in the tungsten source solution is 0.75 mol / L, and the molar ratio of tungsten chloride in the tungsten source solution to hydroquinone in the carbon source solution is 2:1.67.

[0051] The tungsten source solution was uniformly added dropwise to the carbon source solution at a rate of 2 mL / min and stirred evenly to obtain a clear liquid precursor mixed solution;

[0052] Step B: Weigh 0.7 g of ammonium metatungstate powder, with a molar ratio of ammonium metatungstate to tungsten chloride in step A of 1:63, and slowly add it to the above liquid precursor mixed solution under continuous stirring. Place it in a 60°C water bath and stir for 1 hour to obtain an adjusted mixed solution;

[0053] Step C, placing the adjusted mixed solution in a constant temperature drying oven, drying it at 80°C for 12h to make it completely dry, and grinding it into powder, then putting it into a graphite crucible, placing it in a high-temperature tube furnace, using high-purity argon (Ar≥99.999%) as a protective gas, heating it from room temperature to 1000°C at a rate of 5°C / min, then heating it to 1250°C at a rate of 2°C / min, and keeping it warm for 360min, then cooling it to 1000°C at a rate of 2°C / min, then cooling it to 300°C at a rate of 5°C / min, and finally cooling it naturally to room temperature to obtain tungsten carbide powder.

[0054] Comparative Example 1

[0055] This comparative example provides a method for preparing low-carbon ultrafine tungsten carbide, which specifically includes the following steps:

[0056] Step A: Weigh 5.9 g of tungsten hexachloride and mix it with 20 ml of ethanol, and stir it at a constant temperature until the solution is completely clear, which serves as the tungsten source solution. Weigh 1.3 g of hydroquinone and mix it with 10 ml of ethanol, and stir it at a constant temperature until the solution is completely clear, which serves as the carbon source solution. The concentration of tungsten chloride in the tungsten source solution is 0.75 mol / L, and the molar ratio of tungsten chloride in the tungsten source solution to hydroquinone in the carbon source solution is 2:1.67.

[0057] The tungsten source solution was uniformly added dropwise to the carbon source solution at a rate of 2 mL / min and stirred evenly to obtain a clear liquid precursor mixed solution;

[0058] Step B: Place the above liquid precursor mixed solution in a 60°C water bath and stir for 1 hour;

[0059] Step C, placing the mixed solution after the water bath reaction in a constant temperature drying oven, drying it at 80°C for 12h to make it completely dry, and grinding it into powder, then putting it into a graphite crucible, placing it in a high-temperature tube furnace, using high-purity argon (Ar≥99.999%) as a protective gas, heating it from room temperature to 1000°C at a rate of 5°C / min, then heating it to 1250°C at a rate of 2°C / min, and keeping it warm for 360min, then cooling it to 1000°C at a rate of 2°C / min, and then cooling it to 300°C at a rate of 5°C / min, and finally naturally cooling it to room temperature, thereby obtaining tungsten carbide powder.

[0060] Comparative Example 2

[0061] This comparative example provides a method for preparing low-carbon ultrafine tungsten carbide, which specifically includes the following steps:

[0062] Step A: Weigh 5.9 g of tungsten hexachloride and mix it with 20 ml of ethanol, and stir it at a constant temperature until the solution is completely clear, which serves as the tungsten source solution. Weigh 1.1 g of hydroquinone and mix it with 10 ml of ethanol, and stir it at a constant temperature until the solution is completely clear, which serves as the carbon source solution. The concentration of tungsten chloride in the tungsten source solution is 0.75 mol / L, and the molar ratio of tungsten chloride in the tungsten source solution to hydroquinone in the carbon source solution is 2:1.33.

[0063] The tungsten source solution was uniformly added dropwise to the carbon source solution at a rate of 2 mL / min and stirred evenly to obtain a clear liquid precursor mixed solution;

[0064] Step B: Place the above liquid precursor mixed solution in a 60°C water bath and stir for 1 hour;

[0065] Step C, placing the mixed solution after the water bath reaction in a constant temperature drying oven, drying it at 80°C for 12h to make it completely dry, and grinding it into powder, then putting it into a graphite crucible, placing it in a high-temperature tube furnace, using high-purity argon (Ar≥99.999%) as a protective gas, heating it from room temperature to 1000°C at a rate of 5°C / min, then heating it to 1250°C at a rate of 2°C / min, and keeping it warm for 360min, then cooling it to 1000°C at a rate of 2°C / min, and then cooling it to 300°C at a rate of 5°C / min, and finally naturally cooling it to room temperature, thereby obtaining tungsten carbide powder.

[0066] Purity detection and morphology observation

[0067] (1) X-ray diffraction analyzer was used to perform material detection on the tungsten carbide powders prepared in Example 1, Example 2, Example 3, Comparative Example 1 and Comparative Example 2 of the present invention, thereby obtaining the following: Figure 1 The X-ray diffraction pattern shown. Figure 1It can be seen that Comparative Example 2 of the present invention reduces the carbon source content relative to Comparative Example 1. From the XRD, it can be seen that the phase of Comparative Example 2 contains W2C and W byproducts, which is mainly caused by the lack of carbon source. After increasing the carbon source ratio, as shown in Comparative Example 1, the obtained XRD pattern is a single WC phase, but it is obvious that the XRD peak has a bulge at a smaller diffraction angle. The free carbon content of the prepared WC powder is relatively high, indicating that it is difficult to accurately control the carbon content using this method. In this case, ammonium metatungstate needs to be added as an auxiliary tungsten source to regulate the carbon content. By adding a certain amount of ammonium metatungstate, Examples 1, 2, and 3 can all successfully prepare WC powders with high purity from the XRD patterns. Moreover, compared with Comparative Example 1, the carbon bulge at a smaller XRD diffraction angle is not obvious, proving that the introduction of ammonium metatungstate qualitatively reduces the free carbon content in Comparative Example 1 and does not affect the phase of the WC powder by causing impurities, thereby preparing high-purity, low-carbon WC powder.

[0068] (2) The tungsten carbide powders prepared in Examples 1-3 and Comparative Examples 1-2 were observed using a scanning electron microscope to obtain the following: Figure 2-6 The scanning electron microscope photo shown. Figure 2 、 Figure 3 、 Figure 4 It can be seen that the microstructures of the tungsten carbide powders prepared in Examples 1, 2 and 3 of the present invention are all granular, and the particle size is relatively uniform, about 200 nm. Figure 5 This is a scanning electron microscope photo of the tungsten carbide powder obtained in Comparative Example 1. Figure 5 It can be seen that the microstructure of the tungsten carbide powder prepared in Comparative Example 1 is granular, and the particle size is relatively uniform, about 200nm. The black part in the scanning electron microscope image is the free carbon contained in the tungsten carbide powder. By comparing Example 1, Example 2, and Example 3 with Comparative Example 1, it can be seen that the proportion of black free carbon in the examples is significantly reduced. Figure 6 The scanning electron micrograph of Comparative Example 2 shows that when the carbon source content is reduced, a single WC phase cannot be obtained, and the product contains W2C with relatively strong bonding properties. Excessive carbon source will produce more free carbon. The free carbon content of the final tungsten carbide nanopowder can be effectively adjusted by introducing ammonium metatungstate into the liquid precursor in the present embodiment.

[0069] (3) The free carbon of the tungsten carbide powders prepared in Example 1, Example 2, Example 3 and Comparative Example 1 of the present invention was measured using a carbon-sulfur analyzer, thereby obtaining the following: Figure 7The free carbon content change graph is shown. From the change in free carbon content in the graph, it can be seen that the carbon content of Comparative Example 1 is 9.484%, the free carbon content of Example 1 is 3.976%, the free carbon content of Example 2 is 2.632%, and the free carbon content of Example 3 is 1.447%. The above data further prove that the free carbon content of the embodiment and the comparative example can be effectively adjusted by introducing ammonium metatungstate into the liquid precursor in the embodiment of the present invention, so as to effectively adjust the free carbon content of the tungsten carbide nanopowder finally obtained.

[0070] In summary, it can be seen that the embodiment of the present invention not only has a simple preparation process, easy to control the reaction process, short production cycle and low cost, but also the prepared tungsten carbide powder has high purity, finer particle size and lower free carbon content, which can enhance the mechanical properties and sintering driving force of cemented carbide in the subsequent forming process, and reduce the sintering performance of cemented carbide due to the presence of free carbon.

[0071] Those skilled in the art will appreciate that the foregoing descriptions are merely specific embodiments of the present invention, and not exhaustive. It should be noted that numerous variations and modifications are possible for those skilled in the art, and all such variations and modifications that do not exceed the scope of the claims should be considered within the scope of protection of the present invention.

Claims

1. A method for preparing low-carbon ultrafine tungsten carbide powder with the assistance of ammonium metatungstate, characterized in that: The following steps are involved: Step A: adding tungsten chloride to ethanol at a concentration of 0.3 mol / L-1.5 mol / L, stirring at a constant temperature until the solution is completely clear, to serve as a tungsten source solution; mixing hydroquinone with ethanol and stirring at a constant temperature until the solution is completely clear, to serve as a carbon source solution; The tungsten source solution is uniformly added dropwise to the carbon source solution and stirred to obtain a liquid precursor mixed solution, wherein the molar ratio of tungsten chloride in the tungsten source solution to hydroquinone in the carbon source solution is 2:(1.5-5); Step B: adding ammonium metatungstate to the liquid precursor mixed solution, wherein the molar ratio of ammonium metatungstate to tungsten chloride in step A is 1:(20-90), and then heating and stirring in a water bath to obtain an adjusted tungsten carbide precursor solution; Step C: drying the adjusted tungsten carbide precursor solution and grinding it into powder, then placing it into a high-temperature tube furnace, introducing a protective gas and calcining it at high temperature to obtain tungsten carbide powder.

2. The method for preparing low-carbon ultrafine tungsten carbide powder with the assistance of ammonium metatungstate according to claim 1, characterized in that: In step A, the temperature of the constant temperature stirring is 20-90°C.

3. The method for preparing low-carbon ultrafine tungsten carbide powder with the assistance of ammonium metatungstate according to claim 1, characterized in that: In step A, a tungsten source solution and a carbon source solution are prepared by constant temperature magnetic stirring at a stirring speed of 100-800 rpm.

4. The method for preparing low-carbon ultrafine tungsten carbide powder with the assistance of ammonium metatungstate according to claim 1, characterized in that: In step A, the tungsten source solution is slowly added dropwise to the carbon source solution at a rate of 0.5-10 mL / min.

5. The method for preparing low-carbon ultrafine tungsten carbide powder with the assistance of ammonium metatungstate according to claim 1, characterized in that: In step B, after adding ammonium metatungstate, the temperature of the water bath is heated to 30-80° C. and stirring is continued for 30-120 minutes.

6. The method for preparing low-carbon ultrafine tungsten carbide powder with the assistance of ammonium metatungstate according to claim 1, characterized in that: In step C, the adjusted tungsten carbide precursor solution is dried at a temperature of 60-120° C. for a time of 4-24 hours.

7. The method for preparing low-carbon ultrafine tungsten carbide powder with the assistance of ammonium metatungstate according to claim 1, characterized in that: In step C, the air flow rate of the protective gas is 0.005-50 liters / minute, the calcination temperature is 1100-1500° C., and the calcination time is 60-480 minutes.

8. The method for preparing low-carbon ultrafine tungsten carbide powder with the assistance of ammonium metatungstate according to claim 1 or 7, characterized in that: The specific parameters of the high-temperature calcination in step C are as follows: using high-purity argon as a protective gas, the high-temperature tube furnace is heated from room temperature to 1000°C at a rate of 1-5°C / min, then heated to 1100-1500°C at a rate of 0.5-2°C / min, and kept at this temperature for 60-480 minutes, then cooled to 1000°C at a rate of 0.5-2°C / min, then cooled to 200-400°C at a rate of 1-5°C / min, and finally cooled naturally to room temperature.

9. The method for preparing low-carbon ultrafine tungsten carbide powder with the assistance of ammonium metatungstate according to claim 1 or 7, characterized in that: In step C, the adjusted tungsten carbide precursor solution is dried and then ground into powder for 0.5-4 hours.

10. The method for preparing low-carbon ultrafine tungsten carbide powder with the assistance of ammonium metatungstate according to claim 1, characterized in that: The concentration of hydroquinone in the carbon source solution of step A is 1.1-3.7 mol / L.

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