A method for preparing ultra-coarse tungsten carbide powder based on liquid tungsten oxide carbon thermal reduction

Abstract

The application discloses a kind of based on liquid tungsten oxide carbon thermal reduction ultra-coarse tungsten carbide powder preparation method, belong to powder metallurgy technical field.The method includes: tungsten oxide is mixed with carbon black, and mixed powder is obtained;The mixed powder is placed in inert atmosphere and is treated by three-stage heating, so that the tungsten oxide is dehydrated, pre-reduction is experienced, and is melted into liquid state, and carbon thermal reduction reaction is carried out with the carbon black;After reaction, in-situ weak oxygen decarburization treatment is carried out, and the ultra-coarse tungsten carbide powder is obtained;The three-stage heating is: first stage is heated to 280-320 DEG C and is dehydrated, second stage is heated to 1150-1200 DEG C and is pre-reduced, and third stage is heated to 1250-1600 DEG C, so that tungsten oxide is in liquid melt state, and carbon thermal reduction reaction occurs with carbon black.The method provided by the application has the advantages of simple process, wide raw material adaptability, high product purity, uniform grain and the like.

Description

Technical Field

[0001] This invention relates to the field of powder metallurgy technology, and in particular to a method for preparing ultra-coarse tungsten carbide powder based on the thermal reduction of liquid tungsten oxide. Background Technology

[0002] Tungsten carbide (WC) is widely used in cemented carbide, cutting tools, and mining machinery due to its high hardness, high wear resistance, and excellent high-temperature stability. Among them, ultra-coarse tungsten carbide, with its low brittleness and high toughness, is in high demand in cemented carbide applications requiring heavy loads and impact resistance.

[0003] Existing processes for preparing ultra-coarse tungsten carbide have significant limitations: the traditional two-step method requires first reducing tungsten oxide with hydrogen to prepare metallic tungsten powder, which is then mixed with carbon black for carbonization. This process is cumbersome and prone to introducing impurities in intermediate steps, resulting in low solid-solid mass transfer efficiency and uneven grain growth with a wide size distribution. Existing one-step carbothermal reduction methods are mostly suitable only for single tungsten oxide raw materials, making it difficult to balance reduction rate and grain size control, and easily leading to incomplete reactions and excessive byproducts (W2C, free carbon). Furthermore, current research on one-step carbothermal reduction methods mainly focuses on preparing ultrafine or nanoscale tungsten carbide, with the technical approach being to suppress grain growth by controlling low temperatures and rapid reactions; however, research on using the carbothermal reduction process to promote uniform grain growth for preparing ultra-coarse tungsten carbide has not been reported. Simultaneously, the problem of residual free carbon is prominent in existing carbothermal reduction methods, which usually rely on precise carbon mixing control, and effective post-treatment decarburization methods are still lacking.

[0004] Therefore, how to achieve controllable preparation of ultra-coarse tungsten carbide in a one-step carbothermal reduction method, while simultaneously addressing issues such as low mass transfer efficiency, difficulty in controlling free carbon, and poor raw material compatibility, is a pressing technical challenge in this field. Thus, developing a method for preparing ultra-coarse tungsten carbide powder based on the carbothermal reduction of liquid tungsten oxide is of great significance for promoting the development of ultra-coarse tungsten carbide. Summary of the Invention

[0005] This invention aims to overcome the shortcomings of existing processes, such as complex processes, low mass transfer efficiency, difficulty in grain control, limited raw material compatibility, and numerous by-products. It provides a method for preparing ultra-coarse tungsten carbide powder based on the carbothermic reduction of liquid tungsten oxide. By optimizing the segmented heating system under a high-temperature argon atmosphere, it achieves efficient compatibility with different tungsten oxide raw materials, taking into account both the versatility of raw materials and the excellent properties of ultra-coarse tungsten carbide products, such as high purity and uniform grain size.

[0006] To achieve the above objectives, the technical solution adopted in this invention is as follows: tungsten oxide and carbon black are uniformly mixed in a stoichiometric ratio and placed in a tube furnace under an argon atmosphere. A continuous reaction of "preheating-prereduction-melting carbonization" is achieved through a three-stage heating process. In the second stage, a medium-temperature prereduction gradually transforms the high-valence tungsten oxide into low-valence oxides, preparing for the high-temperature melting reaction in the third stage. In the third stage, the temperature rises to 1250-1600℃, where the tungsten oxide enters a molten state, forming a liquid-phase reaction medium. Carbon black particles are dispersed in the liquid phase, and uniform nucleation and grain growth of tungsten carbide are achieved through mass transfer at the solid-liquid interface, directly preparing ultra-coarse tungsten carbide powder. After the reaction is completed, in-situ weak oxygen decarburization is performed within the tube furnace without the need for material transfer, achieving efficient and high-purity preparation.

[0007] Compared with existing technologies, the core difference of this invention lies in the following: existing one-step carbothermic reduction methods are all carried out under solid-state reaction conditions, with mass transfer relying on solid-solid interface diffusion, limiting the reaction rate, and requiring suppression of grain growth to obtain nanoscale products; while this invention utilizes the melting characteristics of tungsten oxide at high temperatures to construct a liquid-phase reaction environment, promoting uniform grain growth through enhanced mass transfer in the liquid phase, thereby obtaining ultra-coarse tungsten carbide. Simultaneously, this invention directly performs weak oxygen decarburization within the reaction equipment, avoiding the introduction of impurities during the transfer process and achieving precise control of free carbon.

[0008] The technical solution of the present invention is as follows:

[0009] This invention provides a method for preparing ultra-coarse tungsten carbide powder based on the thermal reduction of liquid tungsten oxide, comprising the following steps:

[0010] Tungsten oxide and carbon black are mixed to obtain a mixed powder; the mixed powder is placed in an inert atmosphere and subjected to a three-stage heating process, so that the tungsten oxide undergoes dehydration and pre-reduction and then melts into a liquid state, and undergoes a carbothermic reduction reaction with the carbon black; after the reaction is completed, in-situ weak oxygen decarburization treatment is performed to obtain the ultra-coarse tungsten carbide powder.

[0011] Preferably, the method for preparing ultracoarse tungsten carbide powder based on the carbothermic reduction of liquid tungsten oxide includes the following steps:

[0012] Step 1: Ball mill and mix tungsten oxide and carbon black to obtain a mixed powder;

[0013] Step 2: Spread the mixed powder evenly in a corundum boat, then place the boat in a tube furnace and introduce an inert atmosphere to replace the air in the furnace.

[0014] Step 3: Perform a three-stage heating process on the tubular furnace under an inert atmosphere. The first stage involves heating to 280-320℃ and holding for 25-35 minutes, the second stage involves heating to 1150-1200℃ and holding for 1-2 hours, and the third stage involves heating to 1250-1600℃ and holding for 2-4 hours.

[0015] Step 4: After the heat preservation is completed, the furnace is cooled to 280-320℃, and weak oxygen decarburization is carried out in a mixed atmosphere of inert atmosphere and air. Then, the furnace is cooled to room temperature to obtain the ultra-coarse tungsten carbide.

[0016] Step 5: Take out the ultra-coarse tungsten carbide, grind it lightly in an agate mortar and sieve it to obtain ultra-coarse tungsten carbide powder.

[0017] Preferably, the tungsten oxide and carbon black are mixed in a mass ratio of 1:(0.205-0.265).

[0018] Preferably, the tungsten oxide is selected from WO3, WO4, and WO3. 2.9 WO 2.72 At least one of them.

[0019] More preferably, the tungsten oxide is WO3 or WO4. 2.9 WO 2.72 A mixture in a mass ratio of (1-2):(1-2):(1-2).

[0020] Preferably, in step 1, the ball-to-material ratio of the ball milling mixture is (1-5):1, the rotation speed is 100-150 r / min, and the mixing time is 60-90 min.

[0021] Preferably, in step 2, the inert atmosphere flow rate is 3-5 L / min, and the replacement time is 30-60 min.

[0022] Preferably, in step 3, the heating rate of the heating process is 9-11℃ / min.

[0023] Preferably, in step 4, the weak oxygen decarbonization is carried out in a mixed atmosphere of inert atmosphere and air, wherein the flow rate ratio of the inert atmosphere to air is (3-5):1.

[0024] Preferably, in step 4, the heat preservation time for weak oxygen decarburization is 2-4 hours.

[0025] Preferably, the inert atmosphere is argon.

[0026] Preferably, in step 5, the sample is sieved through a 180-220 mesh sieve.

[0027] Preferably, the ultracoarse tungsten carbide powder has a Fisher's standard particle size (FSSS) of 6.14-8.20 μm and free carbon C. f ≤0.03%.

[0028] Further explanation of the invention, regarding the three-stage heating process: The first stage involves low-temperature dehydration to remove adsorbed water and crystal water from the raw materials, preventing moisture from reacting with carbon black at high temperatures to generate interfering gases such as CO and H2, which would affect the carbothermic reduction reaction pathway; the second stage involves medium-temperature pre-reduction to gradually reduce WO3 to WO. 2.9 WO 2.72 The use of low-valence oxides not only reduces the reduction load in the third stage, but also makes it easier for tungsten oxide to reach a molten state during the heating process in the third stage, ensuring the uniformity of liquid phase formation. In the high-temperature melting reduction-carburization (1250-1600℃) in the third stage, liquid tungsten oxide has significant fluidity and wettability, which can fully encapsulate carbon black particles and form a large solid-liquid interface. The mass transfer coefficient is significantly improved compared to the solid-solid interface, thereby significantly increasing the reaction rate. At the same time, it is beneficial to obtain ultra-coarse tungsten carbide with uniform grain size and narrow size distribution in the subsequent process.

[0029] Further explanation of the invention regarding in-situ weak oxygen decarburization: After the carbonization reaction, trace amounts of free carbon may remain in the product. This invention directly introduces a mixture of argon and air into a tube furnace to perform weak oxygen decarburization at 280-320°C. This temperature ensures a high rate of free carbon oxidation removal while being far below the temperature at which tungsten carbide undergoes significant oxidation in air. Therefore, free carbon can be selectively removed without damaging the tungsten carbide grains.

[0030] The present invention has the following beneficial effects:

[0031] 1. Compared with existing technologies, this invention provides a method for preparing ultra-coarse tungsten carbide powder based on the carbothermic reduction of liquid tungsten oxide, achieving a one-step preparation of highly efficient, high-purity, and high-performance tungsten carbide with a significantly simplified process. This invention abandons the traditional two-step approach of first reducing tungsten oxide to tungsten powder and then carbonizing it, creatively utilizing molten tungsten oxide and carbon black for liquid-solid carbothermic reduction to directly obtain tungsten carbide in one step. The method provided by this invention not only shortens the process and reduces energy consumption and equipment costs, but also greatly enhances mass transport at the molten reaction interface, enabling rapid and uniform growth of tungsten carbide grains, resulting in a product with large grains and a concentrated particle size distribution. Simultaneously, in-situ weak oxygen decarburization after the reaction efficiently removes free carbon without transferring materials, effectively avoiding the introduction of impurities in intermediate steps and ensuring the high purity of the final product. Example data shows that the obtained ultra-coarse tungsten carbide powder has a Fisher's Score (FSSS) of 6.14-8.20 μm and a free carbon content of C2. f With a concentration of ≤0.03%, it exhibits excellent overall performance.

[0032] 2. Compared with existing technologies, the process of this invention has strong versatility and good raw material compatibility. The three-stage programmed temperature rise involved in the method provided by this invention can precisely control the reaction process of tungsten oxides with different properties, thereby stably adapting to WO3 and WO4.2.9 WO 2.72 This invention utilizes a variety of common tungsten oxide raw materials and mixtures thereof. This frees the invention from heavy reliance on specific high-purity, specific-form raw materials, broadens the range of raw material selection, enhances the adaptability and economy of the process, and makes it more suitable for diverse raw material supply scenarios in industry. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0034] Figure 1 This is a SEM image of the ultra-coarse tungsten carbide powder obtained in Example 1 of the present invention;

[0035] Figure 2 This is a SEM image of the ultra-coarse tungsten carbide powder obtained in Example 2 of the present invention;

[0036] Figure 3 This is a SEM image of the ultra-coarse tungsten carbide powder obtained in Example 3 of the present invention;

[0037] Figure 4 This is a SEM image of the ultra-coarse tungsten carbide powder obtained in Example 4 of the present invention;

[0038] Figure 5 This is a SEM image of the tungsten carbide powder obtained in Comparative Example 1 of the present invention.

[0039] Figure 6 This is a SEM image of the tungsten carbide powder obtained in Comparative Example 2 of the present invention.

[0040] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0041] The technical solutions described below in conjunction with the embodiments will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] This invention provides a method for preparing ultra-coarse tungsten carbide powder based on the thermal reduction of liquid tungsten oxide, comprising the following steps:

[0043] Tungsten oxide and carbon black are mixed to obtain a mixed powder; the mixed powder is placed in an inert atmosphere and subjected to a three-stage heating process, so that the tungsten oxide undergoes dehydration and pre-reduction and then melts into a liquid state, and undergoes a carbothermic reduction reaction with the carbon black; after the reaction is completed, in-situ weak oxygen decarburization treatment is performed to obtain the ultra-coarse tungsten carbide powder.

[0044] Preferably, the method for preparing ultracoarse tungsten carbide powder based on the carbothermic reduction of liquid tungsten oxide includes the following steps:

[0045] Step 1: Ball mill and mix tungsten oxide and carbon black to obtain a mixed powder;

[0046] Step 2: Spread the mixed powder evenly in a corundum boat, then place the boat in a tube furnace and introduce an inert atmosphere to replace the air in the furnace.

[0047] Step 3: Perform a three-stage heating process on the tubular furnace under an inert atmosphere. The first stage involves heating to 280-320℃ and holding for 25-35 minutes, the second stage involves heating to 1150-1200℃ and holding for 1-2 hours, and the third stage involves heating to 1250-1600℃ and holding for 2-4 hours.

[0048] Specifically, the temperature of the first stage of heating can be any one of 280℃, 290℃, 300℃, 310℃, 320℃, or a range between two of these; the holding time of the first stage of heating can be any one of 25min, 28min, 30min, 32min, 35min, or a range between two of these; and the temperature of the second stage of heating can be any one of 1150℃, 1160℃, 1170℃, 1180℃, 1190℃, 1200℃, or a range between two of these. The temperature range for the second stage of heating can be any one of 1h, 1.2h, 1.5h, 1.8h, 2h, or a range between two of these; the temperature range for the third stage of heating can be any one of 1250℃, 1300℃, 1350℃, 1400℃, 1450℃, 1500℃, 1550℃, 1600℃, or a range between two of these; the holding time for the third stage of heating can be any one of 2h, 2.5h, 3h, 3.5h, 4h, or a range between two of these.

[0049] Step 4: After the heat preservation is completed, the furnace is cooled to 280-320℃, and weak oxygen decarburization is carried out in a mixed atmosphere of inert atmosphere and air. Then, the furnace is cooled to room temperature to obtain the ultra-coarse tungsten carbide.

[0050] Specifically, the temperature for furnace cooling can be any one of 280°C, 290°C, 300°C, 310°C, and 320°C, or a range between two of them.

[0051] Step 5: Take out the ultra-coarse tungsten carbide, grind it lightly in an agate mortar and sieve it to obtain ultra-coarse tungsten carbide powder.

[0052] Preferably, the tungsten oxide and carbon black are mixed in a mass ratio of 1:(0.205-0.265).

[0053] Specifically, the tungsten oxide and carbon black can be mixed in any one of the following mass ratios or a range between the two: 1:0.205, 1:0.21, 1:0.23, 1:0.235, 1:0.25, and 1:0.265.

[0054] Preferably, the tungsten oxide is selected from WO3, WO4, and WO3. 2.9 WO 2.72 At least one of them.

[0055] More preferably, the tungsten oxide is WO3 or WO4. 2.9 WO 2.72 A mixture in a mass ratio of (1-2):(1-2):(1-2).

[0056] Preferably, in step 1, the ball-to-material ratio of the ball milling mixture is (1-5):1, the rotation speed is 100-150 r / min, and the mixing time is 60-90 min.

[0057] Specifically, the ball-to-material ratio in the ball milling process can be any one of 1:1, 2:1, 3:1, 4:1, 5:1, or a range between two of these; the rotational speed can be any one of 100 r / min, 110 r / min, 120 r / min, 130 r / min, 140 r / min, 150 r / min, or a range between two of these; and the mixing time can be any one of 60 min, 65 min, 70 min, 75 min, 80 min, 85 min, 90 min, or a range between two of these.

[0058] Preferably, in step 2, the inert atmosphere flow rate is 3-5 L / min, and the replacement time is 30-60 min.

[0059] Specifically, the inert atmosphere flow rate can be any one of 3L / min, 3.5L / min, 4L / min, 4.5L / min, 5L / min, or a range between two of them; the replacement time can be any one of 30min, 40min, 50min, 60min, or a range between two of them.

[0060] Preferably, in step 3, the heating rate of the heating process is 9-11℃ / min.

[0061] Specifically, the heating rate of the heating process can be any one of 9℃ / min, 10℃ / min, 11℃ / min, or a range between two of them.

[0062] Preferably, in step 4, the weak oxygen decarbonization is carried out in a mixed atmosphere of inert atmosphere and air, wherein the flow rate ratio of the inert atmosphere to air is (3-5):1.

[0063] Specifically, the flow ratio of the inert atmosphere to air can be any one of 3:1, 4:1, 5:1, or a range between the two.

[0064] Preferably, in step 4, the heat preservation time for weak oxygen decarburization is 2-4 hours.

[0065] Specifically, the holding time for weak oxygen decarbonization is any one of 2h, 2.5h, 3h, 3.5h, 4h, or a range between two of them.

[0066] Preferably, the inert atmosphere is argon.

[0067] Preferably, in step 5, the sample is sieved through a 180-220 mesh sieve.

[0068] Preferably, the ultracoarse tungsten carbide powder has a Fisher's standard particle size (FSSS) of 6.14-8.20 μm and free carbon C. f ≤0.03%.

[0069] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0070] Example 1

[0071] A method for preparing ultracoarse tungsten carbide powder based on the carbothermic reduction of liquid tungsten oxide includes the following steps:

[0072] Step 1: Add WO3 and carbon black to a planetary ball mill at a mass ratio of 1:0.25 and mix them. The ball-to-material ratio is 3:1, the rotation speed is 120 r / min, and the time is 75 min to obtain a mixed powder.

[0073] Step 2: Spread the mixed powder obtained in Step 1 evenly in a corundum boat, then place the boat in a tube furnace and introduce argon gas to replace the air in the furnace. The argon gas flow rate is 4L / min and the replacement time is 45min.

[0074] Step 3: Maintain an argon flow rate of 4 L / min and perform a three-stage heating process on the tube furnace under an argon atmosphere at a heating rate of 10 °C / min. The first stage is to heat to 300 °C and hold for 30 min, the second stage is to heat to 1200 °C and hold for 1.5 h, and the third stage is to heat to 1550 °C and hold for 3 h.

[0075] Step 4: After the heat preservation is completed, the furnace is cooled to 300°C. A weak oxygen decarburization atmosphere is introduced, in which the flow ratio of argon to air is 4:1 and the heat preservation time is 2.5 hours. After the heat preservation is completed, the furnace is cooled to room temperature to obtain ultra-crude tungsten carbide.

[0076] Step 5: Take out the ultra-coarse tungsten carbide obtained in Step 4, lightly grind it in an agate mortar, and sieve it through a 200-mesh sieve to obtain ultra-coarse tungsten carbide powder. Testing showed that the FSSS of this ultra-coarse tungsten carbide powder was 8.20 μm, and C... t It is 6.12%, C f It is 0.01%.

[0077] The SEM image of the ultra-coarse tungsten carbide powder obtained in this embodiment is as follows: Figure 1 As shown, by Figure 1 It can be seen that the ultra-coarse tungsten carbide powder has large grains, regular morphology, clear grain boundaries, uniform particle size distribution, no obvious agglomeration or impurity phases, and significant ultra-coarse crystal characteristics.

[0078] Example 2

[0079] A method for preparing ultracoarse tungsten carbide powder based on the carbothermic reduction of liquid tungsten oxide includes the following steps:

[0080] Step 1, put WO 2.9 The mixture was added to a planetary ball mill at a mass ratio of 1:0.23 with carbon black, and the ball-to-material ratio was 2:1. The mill speed was 130 r / min and the time was 80 min to obtain a mixed powder.

[0081] Step 2: Spread the mixed powder obtained in Step 1 evenly in a corundum boat, then place the boat in a tube furnace and purge the air in the furnace with argon gas at a flow rate of 3.5 L / min for 40 min.

[0082] Step 3: Maintain an argon flow rate of 3.5 L / min and perform a three-stage heating process on the tube furnace under an argon atmosphere at a heating rate of 10 °C / min. The first stage involves heating to 300 °C and holding for 30 min, the second stage involves heating to 1200 °C and holding for 1 h, and the third stage involves heating to 1400 °C and holding for 3.5 h.

[0083] Step 4: After the heat preservation is completed, the furnace is cooled to 300°C. A weak oxygen decarburization atmosphere is introduced, in which the flow ratio of argon to air is 4:1. The heat preservation time is 3.5 hours. After the heat preservation is completed, the furnace is cooled to room temperature to obtain ultra-crude tungsten carbide.

[0084] Step 5: Take out the ultra-coarse tungsten carbide obtained in Step 4, lightly grind it in an agate mortar, and sieve it through a 200-mesh sieve to obtain ultra-coarse tungsten carbide powder. Testing showed that the FSSS of this ultra-coarse tungsten carbide powder was 6.14 μm, and the C...t It is 6.13%, C f It is 0.02%.

[0085] The SEM image of the ultra-coarse tungsten carbide powder obtained in this embodiment is as follows: Figure 2 As shown, by Figure 2 It can be seen that the obtained ultra-coarse tungsten carbide powder has large grains, regular morphology, clear grain boundaries, uniform particle size distribution, no obvious agglomeration and impurity phases, and significant ultra-coarse crystal characteristics.

[0086] Example 3

[0087] A method for preparing ultracoarse tungsten carbide powder based on the carbothermic reduction of liquid tungsten oxide includes the following steps:

[0088] Step 1, put WO 2.72 The mixture was added to a planetary ball mill at a mass ratio of 1:0.21 with carbon black, and the ball-to-material ratio was 4:1. The mill speed was 140 r / min and the time was 65 min to obtain a mixed powder.

[0089] Step 2: Spread the mixed powder obtained in Step 1 evenly in a corundum boat, then place the boat in a tube furnace and purge the air in the furnace with argon gas at a flow rate of 4.5 L / min for 50 min.

[0090] Step 3: Maintain the argon flow rate at 4.5 L / min and perform a three-stage heating process on the tube furnace under an argon atmosphere at a heating rate of 10 °C / min. The first stage is to heat to 300 °C and hold for 30 min, the second stage is to heat to 1200 °C and hold for 2 h, and the third stage is to heat to 1350 °C and hold for 4 h.

[0091] Step 4: After the heat preservation is completed, the furnace is cooled to 300°C. A weak oxygen decarburization atmosphere is introduced, in which the flow ratio of argon to air is 4:1 and the heat preservation time is 2.5 hours. After the heat preservation is completed, the furnace is cooled to room temperature to obtain ultra-crude tungsten carbide.

[0092] Step 5: Take out the ultra-coarse tungsten carbide obtained in Step 4, lightly grind it in an agate mortar, and sieve it through a 200-mesh sieve to obtain ultra-coarse tungsten carbide powder. Testing showed that the FSSS of this ultra-coarse tungsten carbide powder was 7.10 μm, and C... t It is 6.14%, C f It is 0.03%.

[0093] The SEM image of the ultra-coarse tungsten carbide powder obtained in this embodiment is as follows: Figure 3 As shown, by Figure 3 It can be seen that the obtained ultra-coarse tungsten carbide powder has large grains, regular morphology, clear grain boundaries, uniform particle size distribution, no obvious agglomeration and impurity phases, and significant ultra-coarse crystal characteristics.

[0094] Example 4

[0095] A method for preparing ultracoarse tungsten carbide powder based on the carbothermic reduction of liquid tungsten oxide includes the following steps:

[0096] Step 1: Add tungsten oxide and carbon black to a planetary ball mill at a mass ratio of 1:0.235 and mix. The tungsten oxide is WO3 and WO4. 2.9 WO 2.72 A mixed powder was obtained by mixing a material with a mass ratio of 1:1:1, a ball-to-material ratio of 3:1, rotating at a speed of 130 r / min, and for 90 min.

[0097] Step 2: Spread the mixed powder obtained in Step 1 evenly in a corundum boat, then place the boat in a tube furnace and introduce argon gas to replace the air in the furnace. The argon gas flow rate is 4L / min and the replacement time is 50min.

[0098] Step 3: Maintain an argon flow rate of 4 L / min and perform a three-stage heating process on the tube furnace under an argon atmosphere at a heating rate of 10 °C / min. The first stage involves heating to 300 °C and holding for 30 min, the second stage involves heating to 1200 °C and holding for 1.5 h, and the third stage involves heating to 1450 °C and holding for 3.5 h.

[0099] Step 4: After the heat preservation is completed, the furnace is cooled to 300°C. A weak oxygen decarburization atmosphere is introduced, in which the flow ratio of argon to air is 4:1 and the heat preservation time is 2.5 hours. After the heat preservation is completed, the furnace is cooled to room temperature to obtain ultra-crude tungsten carbide.

[0100] Step 5: Take out the ultra-coarse tungsten carbide obtained in Step 4, lightly grind it in an agate mortar, and sieve it through a 200-mesh sieve to obtain ultra-coarse tungsten carbide powder. Testing showed that the FSSS of this ultra-coarse tungsten carbide powder was 6.57 μm, and C... t It is 6.13%, C f It is 0.01%.

[0101] The SEM image of the ultra-coarse tungsten carbide powder obtained in this embodiment is as follows: Figure 4 As shown, by Figure 4 It can be seen that the obtained ultra-coarse tungsten carbide powder has large grains, regular morphology, clear grain boundaries, uniform particle size distribution, no obvious agglomeration and impurity phases, and significant ultra-coarse crystal characteristics.

[0102] Comparative Example 1

[0103] The difference between this comparative example and Example 1 is that this comparative example provides a conventional two-step method for preparing tungsten carbide powder, including the following steps:

[0104] Step 1: Spread WO3 evenly in a corundum boat, and then place the boat in a tube furnace for reduction to obtain tungsten powder. The reduction temperature is 1200℃, the reduction time is 1.5h, the heating rate is 10℃ / min, the hydrogen atmosphere is used, and the hydrogen flow rate is 4L / min.

[0105] Step 2: Add the tungsten powder and carbon black obtained in Step 1 into a planetary ball mill at a mass ratio of 1:0.068 and mix them. The ball-to-material ratio is 3:1, the rotation speed is 120 r / min, and the time is 75 min to obtain a mixed powder.

[0106] Step 3: Spread the mixed powder obtained in Step 2 evenly in a corundum boat, then place the boat in a tube furnace and introduce argon gas to replace the air in the furnace. The argon gas flow rate is 4L / min and the replacement time is 45min.

[0107] Step 4: Maintain an argon flow rate of 4 L / min and perform a two-stage heating process on the tube furnace under an argon atmosphere at a heating rate of 10 °C / min. The first stage temperature is 300 °C and the first stage holding time is 30 min. The second stage temperature is 1550 °C and the second stage holding time is 3 h.

[0108] Step 5: After the heat preservation is completed, the furnace is cooled to 300°C. A weak oxygen decarburization atmosphere is introduced, in which the flow ratio of argon to air is 4:1 and the heat preservation time is 2.5 hours. After the heat preservation is completed, the furnace is cooled to room temperature to obtain tungsten carbide.

[0109] Step 6: Remove the tungsten carbide, lightly grind it in an agate mortar, and sieve it through a 200-mesh sieve to obtain tungsten carbide powder. Testing showed that the FSSS of this tungsten carbide powder was 4.34 μm, and the C... t It is 6.14%, C f It is 0.13%.

[0110] The SEM image of the tungsten carbide powder obtained in this comparative example is shown below. Figure 5 As shown, by Figure 5 It can be seen that the obtained tungsten carbide powder has fine grains and a wide particle size distribution, with obvious fine grains and agglomeration, and does not reach the ultra-coarse level, with poor grain uniformity.

[0111] Comparative Example 2

[0112] The difference between this comparative example and Example 1 is that this comparative example does not use a three-stage heating process, but includes the following steps:

[0113] Step 1: Add WO3 and carbon black to a planetary ball mill at a mass ratio of 1:0.25 and mix them. The ball-to-material ratio is 3:1, the rotation speed is 120 r / min, and the time is 75 min to obtain a mixed powder.

[0114] Step 2: Spread the mixed powder obtained in Step 1 evenly in a corundum boat, then place the boat in a tube furnace and introduce argon gas to replace the air in the furnace. The argon gas flow rate is 4L / min and the replacement time is 45min.

[0115] Step 3: Maintain an argon flow rate of 4 L / min and heat the tube furnace in an argon atmosphere at a heating rate of 10 °C / min, where the temperature is 1550 °C and the holding time is 5 h.

[0116] Step 4: After the heat preservation is completed, the furnace is cooled to 300°C. A weak oxygen decarburization atmosphere is introduced, in which the flow ratio of argon to air is 4:1 and the heat preservation time is 2.5 hours. After the heat preservation is completed, the furnace is cooled to room temperature to obtain tungsten carbide.

[0117] Step 5: Take out the tungsten carbide obtained in Step 4, lightly grind it in an agate mortar, and sieve it through a 200-mesh sieve to obtain tungsten carbide powder. The FSSS of this tungsten carbide powder is tested to be 5.75 μm, and C... t It is 6.12%, C f It is 0.01%.

[0118] The SEM image of the tungsten carbide powder obtained in this comparative example is shown below. Figure 6 As shown, by Figure 6 It can be seen that the obtained tungsten carbide powder has a generally fine grain size and uneven morphology. Some particles have obvious sharp edges and broken features, and are accompanied by a lot of small fragmented particles. The particle size distribution is wide and does not form the typical ultra-coarse and complete grain morphology of the example. The grain growth uniformity is poor and the ultra-coarsening effect is insufficient.

[0119] Comparative Example 3

[0120] The difference between this comparative example and Example 1 is that this comparative example did not undergo decarbonization treatment, and included the following steps:

[0121] Step 1: Add WO3 and carbon black to a planetary ball mill at a mass ratio of 1:0.25 and mix them. The ball-to-material ratio is 3:1, the rotation speed is 120 r / min, and the time is 75 min to obtain a mixed powder.

[0122] Step 2: Spread the mixed powder obtained in Step 1 evenly in a corundum boat, then place the boat in a tube furnace and introduce argon gas to replace the air in the furnace. The argon gas flow rate is 4L / min and the replacement time is 45min.

[0123] Step 3: Maintain an argon flow rate of 4 L / min and perform a three-stage heating process on the tube furnace under an argon atmosphere at a heating rate of 10 °C / min. The first stage temperature is 300 °C and the first stage holding time is 30 min; the second stage temperature is 1200 °C and the second stage holding time is 1.5 h; the third stage temperature is 1550 °C and the third stage holding time is 3 h. After the holding time is completed, the furnace is cooled to room temperature to obtain ultra-crude tungsten carbide.

[0124] Step 4: Take out the ultra-coarse tungsten carbide obtained in Step 3, lightly grind it in an agate mortar, and sieve it through a 200-mesh sieve to obtain ultra-coarse tungsten carbide powder. Testing showed that the FSSS of this ultra-coarse tungsten carbide powder was 7.86 μm, and C... t It is 6.40%, C f It is 0.27%.

[0125] Examples 1-4 above respectively used WO3 and WO 2.9 WO 2.72 Using both the powder and its mixture as tungsten sources, high-performance ultra-coarse tungsten carbide powder was successfully prepared, demonstrating the versatility of the raw materials in this invention. The FSSS of the products in each embodiment was 6.14-8.20 μm, and C... f ≤0.03%, and SEM image ( Figure 1-4 The sample exhibits coarse grains, regular morphology, clear grain boundaries, and uniform grain size distribution, with no obvious agglomerates or impurity phases, demonstrating significant ultra-coarse crystal characteristics. In contrast, the FSSS of the product in Comparative Example 1 is only 4.34 μm, failing to reach the ultra-coarse level, and has a high free carbon content of 0.13%; the FSSS of the product in Comparative Example 2 is 5.75 μm, and the SEM image (…) Figure 6 The results showed that the overall grain size was relatively fine and the morphology was uneven. Some particles had obvious sharp edges and broken features, accompanied by a large number of small fragmented particles. The grain size distribution was wide and did not form the typical ultra-coarse and complete grain morphology of the examples. The grain growth uniformity was poor. Although the product of Comparative Example 3 obtained larger grains with an FSSS of 7.86 μm, the free carbon was as high as 0.27%. The comprehensive performance of the products of Examples 1-4 was better than that of Comparative Examples 1-3, indicating that the technical solution of the present invention, which combines three-stage heating and in-situ weak oxygen decarburization, has significant advantages over the traditional two-step method, isothermal carbonization method and non-decarburization process.

[0126] In summary, this invention provides a method for preparing ultra-coarse tungsten carbide powder based on the carbothermic reduction of liquid tungsten oxide, achieving a one-step preparation of efficient, high-purity, and high-performance tungsten carbide with a significantly simplified process. This invention abandons the traditional two-step approach of first reducing tungsten oxide to tungsten powder and then carbonizing it, creatively utilizing molten tungsten oxide and carbon black for liquid-solid carbothermic reduction to directly obtain tungsten carbide in one step. The method provided by this invention not only shortens the process and reduces energy consumption and equipment costs, but also greatly enhances mass transport at the molten reaction interface, enabling rapid and uniform growth of tungsten carbide grains, resulting in a product with coarse grains and a concentrated particle size distribution. Simultaneously, the in-situ weak oxygen decarburization after the reaction efficiently removes free carbon without transferring materials, effectively avoiding the introduction of impurities in intermediate steps and ensuring the high purity of the final product. Compared to existing technologies, the three-stage programmed temperature rise involved in the method provided by this invention can precisely control the reaction process of tungsten oxides with different properties, thus stably adapting to WO3 and WO4. 2.9 WO 2.72 This invention utilizes a variety of common tungsten oxide raw materials and mixtures thereof. This frees the invention from heavy reliance on specific high-purity, specific forms of raw materials, broadens the range of raw material selection, and enhances the adaptability and economy of the process. The process of this invention has strong universality and good raw material compatibility, making it more suitable for diverse raw material supply scenarios in industry.

[0127] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for preparing ultracoarse tungsten carbide powder based on the thermal reduction of liquid tungsten oxide, characterized in that, Includes the following steps: Tungsten oxide and carbon black are mixed to obtain a mixed powder; the mixed powder is placed in an inert atmosphere and subjected to a three-stage heating process, so that the tungsten oxide undergoes dehydration and pre-reduction and then melts into a liquid state, which then undergoes a carbothermic reduction reaction with the carbon black; after the reaction is completed, in-situ weak oxygen decarburization treatment is performed to obtain the ultra-coarse tungsten carbide powder. Specifically, the following steps are included: Step 1: Ball mill and mix tungsten oxide and carbon black to obtain a mixed powder; Step 2: Spread the mixed powder evenly in a corundum boat, then place the boat in a tube furnace and introduce an inert atmosphere to replace the air in the furnace. Step 3: Perform a three-stage heating process on the tubular furnace under an inert atmosphere. The first stage involves heating to 280-320℃ and holding for 25-35 minutes, the second stage involves heating to 1150-1200℃ and holding for 1-2 hours, and the third stage involves heating to 1250-1600℃ and holding for 2-4 hours. Step 4: After the heat preservation is completed, the furnace is cooled to 280-320℃, and weak oxygen decarburization is carried out in a mixed atmosphere of inert atmosphere and air. Then, the furnace is cooled to room temperature to obtain ultra-crude tungsten carbide. Step 5: Take out the ultra-coarse tungsten carbide, lightly grind it in an agate mortar and grind it, and then sieve it to obtain the ultra-coarse tungsten carbide powder; In step 4, weak oxygen decarbonization is carried out in a mixed atmosphere of inert atmosphere and air, and the flow rate ratio of the inert atmosphere to air is (3-5):

1. The ultracoarse tungsten carbide powder has a Fisher's standard particle size (FSSS) of 6.14-8.20 μm and free carbon C. f ≤0.03%.

2. The method for preparing ultra-coarse tungsten carbide powder based on the thermal reduction of liquid tungsten oxide according to claim 1, characterized in that: The tungsten oxide and carbon black are mixed at a mass ratio of 1:(0.205-0.265); the tungsten oxide is selected from WO3, WO4, and WO3. 2.9 WO 2.72 At least one of them.

3. The method for preparing ultra-coarse tungsten carbide powder based on the thermal reduction of liquid tungsten oxide according to claim 1, characterized in that: In step 1, the ball-to-material ratio of the ball milling mixture is (1-5):1, the rotation speed is 100-150 r / min, and the mixing time is 60-90 min.

4. The method for preparing ultra-coarse tungsten carbide powder based on the thermal reduction of liquid tungsten oxide according to claim 1, characterized in that: In step 2, the inert atmosphere flow rate is 3-5 L / min, and the replacement time is 30-60 min.

5. The method for preparing ultra-coarse tungsten carbide powder based on the thermal reduction of liquid tungsten oxide according to claim 1, characterized in that: In step 3, the heating rate of the heating process is 9-11℃ / min.

6. The method for preparing ultra-coarse tungsten carbide powder based on the thermal reduction of liquid tungsten oxide according to claim 1, characterized in that: In step 4, the heat preservation time for weak oxygen decarburization is 2-4 hours.

7. The method for preparing ultra-coarse tungsten carbide powder based on the thermal reduction of liquid tungsten oxide according to claim 1, characterized in that: The inert atmosphere is argon.

Images