Medium-grained tungsten carbide powder, its preparation method and use

Abstract

The application belongs to the technical field of metallurgy, and particularly relates to medium-granularity tungsten carbide powder and a preparation method and application thereof. The preparation method comprises the following steps: S1, obtaining high-purity ammonium paratungstate, and calcining the high-purity ammonium paratungstate to obtain tungsten oxide, wherein K in the high-purity ammonium paratungstate is less than or equal to 1 ppm, Na in the high-purity ammonium paratungstate is less than or equal to 1 ppm, and the specific surface area of the tungsten oxide is 0.3-1.0 m 2 / g; S2, first hydrogen reduction, second hydrogen reduction and third hydrogen reduction are performed on the tungsten oxide to obtain tungsten powder; S3, the tungsten powder is sieved and carbon is added to obtain a tungsten-carbon mixture, carbonization, crushing and sieving are performed on the tungsten-carbon mixture to obtain medium-granularity tungsten carbide powder. The application selects high-purity ammonium paratungstate with less than 1 ppm of impurity elements such as potassium and sodium as raw material, which can effectively reduce abnormal growth of tungsten powder particles caused by impurity elements in the reduction process, tungsten powder particles are developed completely by adopting three-stage hydrogen reduction, the powder activity is low, and the particle size increase is small in the subsequent carbonization process.

Description

Technical Field

[0001] This application relates to the field of metallurgical technology, specifically to a medium-particle tungsten carbide powder, its preparation method, and its application. Background Technology

[0002] Medium-sized tungsten carbide powder is a core raw material for preparing cemented carbide. With its advantages of balancing hardness and toughness, it is widely used in cutting tools, mining drilling tools, and wear-resistant parts. It compensates for the insufficient hardness of coarse-grained tungsten carbide powder while avoiding the high production cost and molding difficulty of fine-grained tungsten carbide powder. Current research focuses on optimizing the preparation process and improving performance. On the one hand, by improving traditional processes such as carbothermal reduction and spray pyrolysis, combined with modification techniques using alloying elements such as TaC and NbC, precise control of powder particle size uniformity and sphericity can be achieved. On the other hand, green preparation technologies (such as microwave heating and plasma treatment) have become a research hotspot, aiming to reduce production energy consumption and pollution. Simultaneously, advanced characterization methods such as laser particle size analyzers and scanning electron microscopes are used to deepen the research on the correlation between powder microstructure and performance.

[0003] The research and production of medium-particle tungsten carbide powder still faces many unresolved issues, particularly the tendency for particle size to fluctuate during carbonization, making batch consistency difficult to guarantee and directly impacting the performance stability of subsequent cemented carbide products. Fluctuations in the purity of raw material tungsten oxide are also a significant factor affecting mass production quality. Especially when raw materials contain impurities that affect reduction and carbonization reactions, abnormal structures may appear in localized areas, significantly reducing the alloy's bending strength and fracture toughness, severely impacting product consistency. Therefore, developing a medium-particle tungsten carbide powder with high purity, minimal particle size increase during carbonization, and good tungsten carbide grain uniformity during alloy sintering is crucial for meeting the demands of high-end cemented carbide manufacturing, enhancing the competitiveness of the industrial chain, and ensuring product performance stability. To address the current problems of high potassium and sodium content (elements that easily cause powder growth) and high powder activity leading to large and unstable particle size increases during carbonization of medium-particle tungsten powder, and to ensure uniform tungsten carbide grains without abnormal particle growth during subsequent alloy preparation, a medium-particle tungsten carbide powder, its preparation method, and its applications are urgently needed. Summary of the Invention

[0004] To solve the above-mentioned technical problems, this application provides a method for preparing medium-particle tungsten carbide powder, comprising the following steps: S1, obtaining high-purity ammonium paratungstate, calcining the high-purity ammonium paratungstate to obtain tungsten oxide, wherein the K in the high-purity ammonium paratungstate is ≤1 ppm, the Na in the high-purity ammonium paratungstate is ≤1 ppm, and the specific surface area of ​​the tungsten oxide is 0.3-1.0 m². 2 / g; S2, the tungsten oxide is subjected to a first hydrogen reduction, a second hydrogen reduction, and a third hydrogen reduction to obtain tungsten powder; S3, the tungsten powder is sieved and carbonized to obtain a tungsten-carbon mixture, and the tungsten-carbon mixture is carbonized, crushed, and sieved to obtain medium-particle tungsten carbide powder.

[0005] As a preferred embodiment of the method for preparing medium-particle tungsten carbide powder according to this application, in step S1, the calcination temperature is 800-850℃ and the calcination time is 1-2h.

[0006] In a preferred embodiment of the method for preparing medium-particle tungsten carbide powder according to this application, in step S2, the temperature of the first hydrogen reduction is 850-900℃, the temperature of the second hydrogen reduction is 900-950℃, the temperature of the third hydrogen reduction is 950-1000℃, the time of the first hydrogen reduction is 30-90 min, the time of the second hydrogen reduction is 30-90 min, and the time of the third hydrogen reduction is 30-90 min.

[0007] In a preferred embodiment of the method for preparing medium-particle tungsten carbide powder as described in this application, in step S2, the hydrogen flow rate for the first hydrogen reduction is 300-400 L / h, the hydrogen flow rate for the second hydrogen reduction is 300-400 L / h, the hydrogen flow rate for the third hydrogen reduction is 300-400 L / h, the loading amount of the first hydrogen reduction is 80-160 g / boat, the loading amount of the second hydrogen reduction is 80-160 g / boat, and the loading amount of the third hydrogen reduction is 80-160 g / boat.

[0008] In a preferred embodiment of the method for preparing medium-particle tungsten carbide powder as described in this application, in step S3, the total carbon content of the tungsten-carbon mixture is 6.16-6.18 wt%.

[0009] In a preferred embodiment of the method for preparing medium-particle tungsten carbide powder as described in this application, in step S3, the carbonization temperature is 1800-2000℃ and the carbonization time is 1-2h.

[0010] In a preferred embodiment of the method for preparing medium-particle tungsten carbide powder as described in this application, in step S3, the particle size of the medium-particle tungsten carbide powder is 1.05-1.1 times the particle size of the tungsten powder.

[0011] This application also provides a medium-particle tungsten carbide powder, which is prepared using the above-described method for preparing medium-particle tungsten carbide powder.

[0012] As a preferred embodiment of the medium-particle tungsten carbide powder described in this application, the medium-particle tungsten carbide powder has a Fisher particle size of 3.0-3.4µm, a compound carbon content of 6.10-6.11wt%, and a free carbon content of 0.02-0.03wt%.

[0013] This application also provides an application of the above-mentioned medium-particle tungsten carbide powder in cemented carbide.

[0014] The beneficial effects of this application are as follows:

[0015] This application provides a medium-particle tungsten carbide powder, its preparation method, and its application. This application selects high-purity ammonium paratungstate with impurity elements such as potassium and sodium content of less than 1 ppm as raw material, which can effectively reduce the abnormal growth of tungsten powder particles caused by impurity elements during the reduction process, improve the uniformity of tungsten powder, and thus reduce the probability of adverse factors occurring in subsequent carbonization and sintering processes.

[0016] The tungsten oxide produced by high-temperature calcination of ammonium paratungstate has a low specific surface area. After high-temperature reduction with a low loading amount, the powder activity is low, and the particle size increase after carbonization is small (5%-10%), resulting in good uniformity of the cemented carbide. Low calcination temperature results in a large specific surface area of ​​tungsten oxide, which is unfavorable for subsequent reactions; high temperature results in a small change in the specific surface area of ​​tungsten oxide, offering no advantage. A large specific surface area of ​​tungsten oxide leads to a large particle size increase during reduction and carbonization. A small loading amount and a large hydrogen flow rate result in small tungsten powder particles, leading to small tungsten carbide particles prepared from it, resulting in high hardness but reduced toughness and strength in the cemented carbide. Conversely, a large loading amount and a small hydrogen flow rate result in large tungsten powder particles that are prone to incomplete reduction, leading to coarse tungsten carbide particles prepared from it, resulting in low hardness and poor wear resistance in the cemented carbide, failing to meet the requirements for high-performance cemented carbide preparation. High-temperature reduction in all three stages with a long reduction time results in fully developed tungsten powder particles, low powder activity, and a small particle size increase during subsequent carbonization. If the first two stages of low-temperature reduction are short, the tungsten powder particles will be poorly developed and have high powder activity, resulting in a large increase in particle size during the subsequent carbonization process.

[0017] The low-activity tungsten powder prepared by high-temperature reduction exhibits a small increase in particle size during carbonization. Carbonization at 1900-2000℃ promotes the complete development of tungsten carbide, further reducing powder surface activity. This reduces excessive local dissolution and precipitation during alloy sintering, preventing abnormal particle growth and improving the uniformity of tungsten carbide grains in the alloy. Low carbonization temperature and short time lead to incomplete carbonization and underdeveloped, highly active tungsten carbide particles; high carbonization temperature and long time result in severe solid-phase sintering, excessive particle agglomeration, and poor uniformity of the tungsten carbide powder. Airflow breaking effectively breaks up sintering necks and agglomerations caused by high-temperature carbonization, improving powder uniformity.

[0018] The medium-particle tungsten carbide powder prepared in this application has a Fisher particle size of 3.0-3.4 µm, a combined carbon content of 6.10-6.11 wt%, and a free carbon content of 0.02-0.03 wt%. Using the medium-particle tungsten carbide powder prepared in this application as raw material, 6% cobalt powder, alcohol, and paraffin wax are added. After wet milling and pressing, the mixture is sintered at 1430℃ for 1 h to obtain a cemented carbide. The cemented carbide exhibits good uniformity in its metallographic structure, a hardness HV10 of 1490-1510, and a fracture toughness of 13-14 MPa·m. 1 / 2 Flexural strength 3000-3300MPa. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application 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 this application. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0020] Figure 1 This is an electron microscope image of the medium-particle tungsten carbide powder prepared in Example 4;

[0021] Figure 2 The image shows the metallographic structure of the cemented carbide prepared in Example 4.

[0022] Figure 3 The image shows the metallographic structure of the cemented carbide prepared in Comparative Example 1.

[0023] Figure 4 The image shows the metallographic diagram of the cemented carbide prepared in Comparative Example 6.

[0024] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0025] The technical solutions in the embodiments will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0026] This application provides a method for preparing medium-particle tungsten carbide powder, comprising the following steps: S1, obtaining high-purity ammonium paratungstate, calcining the high-purity ammonium paratungstate to obtain tungsten oxide, wherein the K in the high-purity ammonium paratungstate is ≤1 ppm, the Na in the high-purity ammonium paratungstate is ≤1 ppm, and the specific surface area of ​​the tungsten oxide is 0.3-1.0 m². 2 / g;

[0027] The calcination temperature is 800-850℃, and the calcination time is 1-2 hours;

[0028] Specifically, the calcination temperature is any one or any two of 800℃, 810℃, 820℃, 830℃, 840℃, and 850℃; the calcination time is any one or any two of 1h, 1.5h, and 2h.

[0029] S2. The tungsten oxide is subjected to a first hydrogen reduction, a second hydrogen reduction, and a third hydrogen reduction to obtain tungsten powder;

[0030] The temperature for the first hydrogen reduction is 850-900℃, the temperature for the second hydrogen reduction is 900-950℃, and the temperature for the third hydrogen reduction is 950-1000℃. The time for the first hydrogen reduction is 30-90 min, the time for the second hydrogen reduction is 30-90 min, and the time for the third hydrogen reduction is 30-90 min. The hydrogen flow rate for the first hydrogen reduction is 300-400 L / h, the hydrogen flow rate for the second hydrogen reduction is 300-400 L / h, and the hydrogen flow rate for the third hydrogen reduction is 300-400 L / h. The loading amount of the first hydrogen reduction on the boat is 80-160 g / boat, the loading amount of the second hydrogen reduction on the boat is 80-160 g / boat, and the loading amount of the third hydrogen reduction on the boat is 80-160 g / boat.

[0031] Specifically, the temperature for the first hydrogen reduction is within the range of any one or any two of 850℃, 860℃, 870℃, 880℃, 890℃, and 900℃; the temperature for the second hydrogen reduction is within the range of any one or any two of 900℃, 910℃, 920℃, 930℃, 940℃, and 950℃; and the temperature for the third hydrogen reduction is within the range of any one or any two of 950℃, 960℃, 970℃, 980℃, 990℃, and 1000℃.

[0032] S3. The tungsten powder is sieved and carbonized to obtain a tungsten-carbon mixture. The tungsten-carbon mixture is then carbonized, crushed, and sieved to obtain medium-particle tungsten carbide powder.

[0033] The total carbon content of the tungsten-carbon mixture is 6.16-6.18 wt%; the carbonization temperature is 1800-2000℃, and the carbonization time is 1-2 h; the particle size of the medium-particle tungsten carbide powder is 1.05-1.1 times that of the tungsten powder.

[0034] Specifically, the carbonization temperature is any one or any two of 1800℃, 1850℃, 1900℃, 1950℃, and 2000℃; the carbonization time is any one or any two of 1h, 1.5h, and 2h.

[0035] This application also provides a medium-particle tungsten carbide powder, which is prepared by the above-described method for preparing medium-particle tungsten carbide powder. The medium-particle tungsten carbide powder has a Fisher particle size of 3.0-3.4µm, a combined carbon content of 6.10-6.11wt%, and a free carbon content of 0.02-0.03wt%.

[0036] This application also provides an application of the above-mentioned medium-particle tungsten carbide powder in cemented carbide.

[0037] The technical solution of this application will be further described below with reference to specific embodiments.

[0038] Example 1

[0039] A medium-particle tungsten carbide powder, its preparation method, and its applications include:

[0040] S1. Obtain high-purity ammonium paratungstate, and calcine it to obtain tungsten oxide. The high-purity ammonium paratungstate contains 0.6 ppm K and 0.5 ppm Na, and the specific surface area of ​​the tungsten oxide is 1.0 m². 2 / g;

[0041] The calcination temperature was 800℃, and the calcination time was 1 hour.

[0042] S2. Tungsten oxide is subjected to a first hydrogen reduction, a second hydrogen reduction, and a third hydrogen reduction to obtain tungsten powder;

[0043] The temperature for the first hydrogen reduction is 850℃, the temperature for the second hydrogen reduction is 900℃, and the temperature for the third hydrogen reduction is 950℃. The time for the first hydrogen reduction is 30 min, the time for the second hydrogen reduction is 30 min, and the time for the third hydrogen reduction is 30 min. The hydrogen flow rate for the first hydrogen reduction is 300 L / h, the hydrogen flow rate for the second hydrogen reduction is 300 L / h, and the hydrogen flow rate for the third hydrogen reduction is 300 L / h. The loading amount of the first hydrogen reduction is 80 g / boat, the loading amount of the second hydrogen reduction is 80 g / boat, and the loading amount of the third hydrogen reduction is 80 g / boat.

[0044] S3. After sieving and adding carbon to the tungsten powder, a tungsten-carbon mixture is obtained. The tungsten-carbon mixture is then carbonized, crushed, and sieved to obtain medium-particle tungsten carbide powder.

[0045] The total carbon content of the tungsten-carbon mixture is 6.18 wt%; the carbonization temperature is 1900℃ and the carbonization time is 1 h; the particle size of the medium-particle tungsten carbide powder is 1.09 times that of the tungsten powder.

[0046] The medium-sized tungsten carbide powder prepared in Example 1 was tested, and the results showed that the Fisher particle size of the medium-sized tungsten carbide powder was 3.0 µm, the content of compound carbon in the medium-sized tungsten carbide powder was 6.11 wt%, and the content of free carbon in the medium-sized tungsten carbide powder was 0.02 wt%.

[0047] Using the medium-particle tungsten carbide powder prepared in Example 1 as raw material, 6% cobalt powder, alcohol, and paraffin were added. After wet milling and pressing, the mixture was sintered at 1430℃ for 1 hour to obtain cemented carbide. The cemented carbide has a uniform microstructure, a hardness HV10 of 1510, and a fracture toughness of 13 MPa·m. 1 / 2 Its flexural strength is 3000MPa.

[0048] Example 2

[0049] A medium-particle tungsten carbide powder, its preparation method, and its applications include:

[0050] S1. Obtain high-purity ammonium paratungstate, and calcine it to obtain tungsten oxide. The high-purity ammonium paratungstate contains 0.6 ppm K and 0.5 ppm Na, and the specific surface area of ​​the tungsten oxide is 0.6 m². 2 / g;

[0051] The calcination temperature was 830℃, and the calcination time was 1.5 hours.

[0052] S2. Tungsten oxide is subjected to a first hydrogen reduction, a second hydrogen reduction, and a third hydrogen reduction to obtain tungsten powder;

[0053] The temperature for the first hydrogen reduction is 880℃, the temperature for the second hydrogen reduction is 930℃, and the temperature for the third hydrogen reduction is 980℃. The time for the first hydrogen reduction is 60 min, the time for the second hydrogen reduction is 60 min, and the time for the third hydrogen reduction is 60 min. The hydrogen flow rate for the first hydrogen reduction is 350 L / h, the hydrogen flow rate for the second hydrogen reduction is 350 L / h, and the hydrogen flow rate for the third hydrogen reduction is 350 L / h. The loading amount of the first hydrogen reduction is 120 g / boat, the loading amount of the second hydrogen reduction is 120 g / boat, and the loading amount of the third hydrogen reduction is 120 g / boat.

[0054] S3. After sieving and adding carbon to the tungsten powder, a tungsten-carbon mixture is obtained. The tungsten-carbon mixture is then carbonized, crushed, and sieved to obtain medium-particle tungsten carbide powder.

[0055] The total carbon content of the tungsten-carbon mixture is 6.17 wt%; the carbonization temperature is 1800℃ and the carbonization time is 1.5 h; the particle size of the medium-particle tungsten carbide powder is 1.08 times that of the tungsten powder.

[0056] The medium-sized tungsten carbide powder prepared in Example 2 was tested, and the results showed that the Fisher particle size of the medium-sized tungsten carbide powder was 3.2 µm, the content of compound carbon in the medium-sized tungsten carbide powder was 6.10 wt%, and the content of free carbon in the medium-sized tungsten carbide powder was 0.03 wt%.

[0057] Using the medium-particle tungsten carbide powder prepared in Example 2 as raw material, 6% cobalt powder, alcohol, and paraffin were added. After wet milling and pressing, the mixture was sintered at 1430℃ for 1 hour to obtain cemented carbide. The cemented carbide has a uniform microstructure, a hardness HV10 of 1501, and a fracture toughness of 13.3 MPa·m. 1 / 2 Its flexural strength is 3086 MPa.

[0058] Example 3

[0059] A medium-particle tungsten carbide powder, its preparation method, and its applications include:

[0060] S1. Obtain high-purity ammonium paratungstate, and calcine it to obtain tungsten oxide. The high-purity ammonium paratungstate contains 0.6 ppm K and 0.5 ppm Na, and the specific surface area of ​​the tungsten oxide is 0.3 m². 2 / g;

[0061] The calcination temperature was 850℃, and the calcination time was 2 hours.

[0062] S2. Tungsten oxide is subjected to a first hydrogen reduction, a second hydrogen reduction, and a third hydrogen reduction to obtain tungsten powder;

[0063] The temperature for the first hydrogen reduction is 900℃, the temperature for the second hydrogen reduction is 950℃, and the temperature for the third hydrogen reduction is 1000℃. The time for the first hydrogen reduction is 30 min, the time for the second hydrogen reduction is 30 min, and the time for the third hydrogen reduction is 30 min. The hydrogen flow rate for the first hydrogen reduction is 400 L / h, the hydrogen flow rate for the second hydrogen reduction is 400 L / h, and the hydrogen flow rate for the third hydrogen reduction is 400 L / h. The loading amount of the first hydrogen reduction is 160 g / boat, the loading amount of the second hydrogen reduction is 160 g / boat, and the loading amount of the third hydrogen reduction is 160 g / boat.

[0064] S3. After sieving and adding carbon to the tungsten powder, a tungsten-carbon mixture is obtained. The tungsten-carbon mixture is then carbonized, crushed, and sieved to obtain medium-particle tungsten carbide powder.

[0065] The total carbon content of the tungsten-carbon mixture is 6.16 wt%; the carbonization temperature is 2000℃ and the carbonization time is 2 hours; the particle size of the medium-particle tungsten carbide powder is 1.1 times that of the tungsten powder.

[0066] The medium-particle tungsten carbide powder prepared in Example 2 was tested, and the results showed that the Fisher particle size of the medium-particle tungsten carbide powder was 3.4 µm, the content of compound carbon in the medium-particle tungsten carbide powder was 6.11 wt%, and the content of free carbon in the medium-particle tungsten carbide powder was 0.02 wt%.

[0067] Using the medium-particle tungsten carbide powder prepared in Example 3 as raw material, 6% cobalt powder, alcohol, and paraffin were added. After wet milling and pressing, the mixture was sintered at 1430℃ for 1 hour to obtain cemented carbide. The cemented carbide has a uniform microstructure, a hardness HV10 of 1490, and a fracture toughness of 13.4 MPa·m. 1 / 2 Its flexural strength is 3195 MPa.

[0068] Example 4

[0069] A medium-particle tungsten carbide powder, its preparation method, and its applications include:

[0070] S1. Obtain high-purity ammonium paratungstate, and calcine it to obtain tungsten oxide. The high-purity ammonium paratungstate contains 0.6 ppm K and 0.5 ppm Na, and the specific surface area of ​​the tungsten oxide is 0.35 m². 2 / g;

[0071] The calcination temperature was 850℃, and the calcination time was 1 hour.

[0072] S2. Tungsten oxide is subjected to a first hydrogen reduction, a second hydrogen reduction, and a third hydrogen reduction to obtain tungsten powder;

[0073] The temperature for the first hydrogen reduction is 900℃, the temperature for the second hydrogen reduction is 950℃, and the temperature for the third hydrogen reduction is 1000℃. The time for the first hydrogen reduction is 90 min, the time for the second hydrogen reduction is 90 min, and the time for the third hydrogen reduction is 90 min. The hydrogen flow rate for the first hydrogen reduction is 300 L / h, the hydrogen flow rate for the second hydrogen reduction is 300 L / h, and the hydrogen flow rate for the third hydrogen reduction is 300 L / h. The loading amount of the first hydrogen reduction is 120 g / boat, the loading amount of the second hydrogen reduction is 120 g / boat, and the loading amount of the third hydrogen reduction is 120 g / boat.

[0074] S3. After sieving and adding carbon to the tungsten powder, a tungsten-carbon mixture is obtained. The tungsten-carbon mixture is then carbonized, crushed, and sieved to obtain medium-particle tungsten carbide powder.

[0075] The total carbon content of the tungsten-carbon mixture is 6.16 wt%; the carbonization temperature is 1900℃ and the carbonization time is 1 h; the particle size of the medium-particle tungsten carbide powder is 1.05 times that of the tungsten powder.

[0076] Please see Figure 1 , Figure 1 The image shows an electron microscope image of the medium-particle tungsten carbide powder prepared in Example 4. The medium-particle tungsten carbide powder prepared in Example 4 was tested, and the results showed that the Fisher particle size of the medium-particle tungsten carbide powder was 3.3 µm, the content of compound carbon in the medium-particle tungsten carbide powder was 6.11 wt%, and the content of free carbon in the medium-particle tungsten carbide powder was 0.02 wt%.

[0077] Using the medium-particle tungsten carbide powder prepared in Example 4 as raw material, 6% cobalt powder, alcohol, and paraffin were added. After wet milling and pressing, the mixture was sintered at 1430°C for 1 hour to obtain a cemented carbide. Please refer to [link to relevant documentation]. Figure 2 , Figure 2 The image shows the metallographic structure of the cemented carbide prepared in Example 4. The cemented carbide has a uniform microstructure, a hardness HV10 of 1503, and a fracture toughness of 14 MPa·m. 1 / 2 Its flexural strength is 3300MPa.

[0078] Comparative Example 1

[0079] The difference between this comparative example and Example 4 is that ammonium paratungstate is used instead of high-purity ammonium paratungstate in step S1. The K content in the ammonium paratungstate is 5 ppm, and the Na content in the ammonium paratungstate is 5 ppm. All other steps are the same as in Example 4.

[0080] The specific surface area of ​​tungsten oxide is 0.39 m². 2 / g, the particle size of medium-sized tungsten carbide powder is 1.18 times that of tungsten powder.

[0081] The medium-sized tungsten carbide powder prepared in Comparative Example 1 was tested. The results showed that the Fisher particle size of the medium-sized tungsten carbide powder was 3.7 µm, the content of compound carbon in the medium-sized tungsten carbide powder was 6.11 wt%, and the content of free carbon in the medium-sized tungsten carbide powder was 0.02 wt%.

[0082] Using the medium-particle tungsten carbide powder prepared in Comparative Example 1 as raw material, 6% cobalt powder, alcohol, and paraffin were added. After wet milling and pressing, the mixture was sintered at 1430℃ for 1 hour to obtain cemented carbide. Please refer to [link to relevant documentation]. Figure 3 , Figure 3 The image shows the metallographic structure of the cemented carbide prepared in Comparative Example 1. The cemented carbide exhibits poor uniformity in its microstructure, with a hardness (HV10) of 1460 and a fracture toughness of 13.0 MPa·m. 1 / 2 Its flexural strength is 2950 MPa.

[0083] Comparative Example 2

[0084] The difference between this comparative example and Example 4 is that the temperature of the first hydrogen reduction in step S2 is 750°C, the temperature of the second hydrogen reduction is 880°C, and the temperature of the third hydrogen reduction is 930°C. All other steps are the same as in Example 4.

[0085] The particle size of medium-sized tungsten carbide powder is 1.13 times that of tungsten powder.

[0086] The medium-sized tungsten carbide powder prepared in Comparative Example 2 was tested. The results showed that the Fisher particle size of the medium-sized tungsten carbide powder was 3.54 µm, the content of compound carbon in the medium-sized tungsten carbide powder was 6.09 wt%, and the content of free carbon in the medium-sized tungsten carbide powder was 0.04 wt%.

[0087] Using medium-particle tungsten carbide powder prepared in Comparative Example 2 as raw material, 6% cobalt powder, alcohol, and paraffin were added. After wet milling and pressing, cemented carbide was obtained by sintering at 1430℃ for 1 hour. The cemented carbide exhibited poor uniformity in its microstructure, a hardness (HV10) of 1485, and a fracture toughness of 12.5 MPa·m. 1 / 2 Its flexural strength is 2901 MPa.

[0088] Comparative Example 3

[0089] The difference between this comparative example and Example 4 is that in step S1, the calcination temperature is 700°C and the calcination time is 1 hour, while the other steps are the same as in Example 4.

[0090] The specific surface area of ​​tungsten oxide is 2.3 m². 2 / g, the particle size of medium-sized tungsten carbide powder is 1.15 times that of tungsten powder.

[0091] The medium-sized tungsten carbide powder prepared in Comparative Example 3 was tested. The results showed that the Fisher particle size of the medium-sized tungsten carbide powder was 3.6 µm, the content of compound carbon in the medium-sized tungsten carbide powder was 6.08 wt%, and the content of free carbon in the medium-sized tungsten carbide powder was 0.05 wt%.

[0092] Using medium-particle tungsten carbide powder prepared in Comparative Example 3 as raw material, 6% cobalt powder, alcohol, and paraffin were added. After wet milling and pressing, cemented carbide was obtained by sintering at 1430℃ for 1 hour. The cemented carbide exhibited poor uniformity in its microstructure, a hardness (HV10) of 1470, and a fracture toughness of 12.9 MPa·m. 1 / 2 Its flexural strength is 2800MPa.

[0093] Comparative Example 4

[0094] The difference between this comparative example and Example 4 is that the carbonization temperature in step S3 is 1700°C, while the other steps are the same as in Example 4.

[0095] The particle size of medium-sized tungsten carbide powder is 1.05 times that of tungsten powder.

[0096] The medium-sized tungsten carbide powder prepared in Comparative Example 4 was tested. The results showed that the Fisher particle size of the medium-sized tungsten carbide powder was 3.31 µm, the content of compound carbon in the medium-sized tungsten carbide powder was 6.08 wt%, and the content of free carbon in the medium-sized tungsten carbide powder was 0.04 wt%.

[0097] Using medium-particle tungsten carbide powder prepared in Comparative Example 4 as raw material, 6% cobalt powder, alcohol, and paraffin were added. After wet milling and pressing, cemented carbide was obtained by sintering at 1430℃ for 1 hour. The cemented carbide exhibited poor uniformity in its microstructure, a hardness (HV10) of 1478, and a fracture toughness of 12.69 MPa·m. 1 / 2 Its flexural strength is 2930 MPa.

[0098] Comparative Example 5

[0099] The difference between this comparative example and Example 4 is that in step S2, segmented hydrogen reduction is not performed, but a single-stage hydrogen reduction is used. The hydrogen reduction temperature is 950°C and the time is 270 min. All other steps are the same as in Example 4.

[0100] The particle size of medium-sized tungsten carbide powder is 1.14 times that of tungsten powder.

[0101] The medium-sized tungsten carbide powder prepared in Comparative Example 5 was tested. The results showed that the Fisher particle size of the medium-sized tungsten carbide powder was 3.56 µm, the content of compound carbon in the medium-sized tungsten carbide powder was 6.09 wt%, and the content of free carbon in the medium-sized tungsten carbide powder was 0.04 wt%.

[0102] Using medium-particle tungsten carbide powder prepared in Comparative Example 5 as raw material, 6% cobalt powder, alcohol, and paraffin were added. After wet milling and pressing, cemented carbide was obtained by sintering at 1430℃ for 1 hour. The cemented carbide exhibited poor uniformity in its microstructure, a hardness (HV10) of 1469, and a fracture toughness of 12.94 MPa·m. 1 / 2 Its flexural strength is 2740 MPa.

[0103] Comparative Example 6

[0104] The difference between this comparative example and Example 4 is that the temperature of the first hydrogen reduction in step S2 is 930°C, the temperature of the second hydrogen reduction is 980°C, and the temperature of the third hydrogen reduction is 1080°C. All other steps are the same as in Example 4.

[0105] The particle size of medium-sized tungsten carbide powder is 1.09 times that of tungsten powder.

[0106] The medium-sized tungsten carbide powder prepared in Comparative Example 6 was tested. The results showed that the Fisher particle size of the medium-sized tungsten carbide powder was 3.1 µm, the content of compound carbon in the medium-sized tungsten carbide powder was 6.08 wt%, and the content of free carbon in the medium-sized tungsten carbide powder was 0.05 wt%.

[0107] Using the medium-particle tungsten carbide powder prepared in Comparative Example 6 as raw material, 6% cobalt powder, alcohol, and paraffin were added. After wet milling and pressing, the mixture was sintered at 1430℃ for 1 hour to obtain cemented carbide. Please refer to [link to relevant documentation]. Figure 4 , Figure 4 The image shows the metallographic structure of the cemented carbide prepared in Comparative Example 6. The cemented carbide exhibits poor uniformity in its microstructure, containing abnormally large particles. Its hardness (HV10) is 1498, and its fracture toughness is 11.7 MPa·m. 1 / 2 Its flexural strength is 2705 MPa.

[0108] Comparative Example 7

[0109] The difference between this comparative example and Example 4 is that the carbonization temperature in step S3 is 2100°C, while the other steps are the same as in Example 4.

[0110] The particle size of medium-sized tungsten carbide powder is 1.13 times that of tungsten powder.

[0111] The medium-sized tungsten carbide powder prepared in Comparative Example 7 was tested. The results showed that the Fisher particle size of the medium-sized tungsten carbide powder was 3.5 µm, the content of compound carbon in the medium-sized tungsten carbide powder was 6.11 wt%, and the content of free carbon in the medium-sized tungsten carbide powder was 0.02 wt%.

[0112] Using medium-particle tungsten carbide powder prepared in Comparative Example 7 as raw material, 6% cobalt powder, alcohol, and paraffin were added. After wet milling and pressing, cemented carbide was obtained by sintering at 1430℃ for 1 hour. The cemented carbide exhibited poor uniformity in its microstructure, a hardness (HV10) of 1472, and a fracture toughness of 12.7 MPa·m. 1 / 2 Its flexural strength is 2840 MPa.

[0113] As can be seen from the above examples and comparative examples: Example 4, combined with Comparative Example 1, shows that increasing the purity of the raw material ammonium paratungstate can effectively reduce the abnormal growth of tungsten powder particles caused by impurities during the reduction process, improve the uniformity of tungsten powder, reduce the particle size increase during the subsequent carbonization process, thereby improving the metallographic uniformity, fracture toughness, and bending strength of the prepared cemented carbide; Example 4, combined with Comparative Example 2, shows that high-temperature reduction is beneficial for preparing tungsten powder with low surface activity, reducing its particle size increase during the carbonization process, thereby obtaining a cemented carbide with a uniform microstructure and good fracture toughness and bending strength; Example 4, combined with Comparative Example 3, shows that tungsten oxide with a low specific surface area helps to prepare tungsten powder with low activity, reducing its particle size increase during the subsequent carbonization process, thereby obtaining a cemented carbide with a uniform microstructure and good fracture toughness and bending strength; Example 4, combined with Comparative Example 4, shows that... High-temperature carbonization can obtain surface-active tungsten carbide while producing tungsten carbide with high combined carbon and low free carbon, resulting in a uniform alloy microstructure and high fracture toughness and bending strength. Example 4, combined with Comparative Example 5, shows that segmented gradient high-temperature reduction helps to obtain tungsten powder with low surface activity, reducing its particle size increase during the carbonization process, thereby producing a cemented carbide with a uniform microstructure and high fracture toughness and bending strength. Example 4, combined with Comparative Example 6, shows that if the reduction temperature is too high, solid-phase diffusion is severe, producing more sintering necks, ultimately leading to abnormally large particles in the alloy, thereby reducing the overall performance of the alloy, and decreasing fracture toughness and bending strength. Example 4, combined with Comparative Example 7, shows that if the carbonization temperature is too high, the particle size of the tungsten powder is easily increased during the carbonization process, and the solid-phase sintering between tungsten carbide particles is severe, resulting in a poor alloy microstructure and decreased fracture toughness and bending strength. Examples 1-4, combined with Comparative Examples 1-7, show that high-purity ammonium paratungstate, low specific surface area tungsten oxide, high-temperature long-term segmented gradient reduction process, and reasonable carbonization process design all contribute to the preparation of tungsten powder with low surface activity and low particle size increase during carbonization. The resulting cemented carbide has a uniform metallographic structure and high fracture toughness and bending strength.

[0114] The above description is only a preferred embodiment of this application and does not limit the patent scope of this application. All equivalent structural transformations made using the content of this application's specification under the inventive concept of this application, or direct / indirect applications in other related technical fields, are included within the patent protection scope of this application.

Claims

1. An application of medium-particle tungsten carbide powder in cemented carbide, characterized in that, The method for preparing the medium-particle tungsten carbide powder includes the following steps: S1. Obtain high-purity ammonium paratungstate, and calcine the high-purity ammonium paratungstate to obtain tungsten oxide, wherein the K in the high-purity ammonium paratungstate is ≤1 ppm, the Na in the high-purity ammonium paratungstate is ≤1 ppm, and the specific surface area of ​​the tungsten oxide is 0.3-1.0 m². 2 / g; S2. The tungsten oxide is subjected to a first hydrogen reduction, a second hydrogen reduction, and a third hydrogen reduction to obtain tungsten powder, that is, the tungsten oxide is subjected to a segmented gradient high-temperature reduction to obtain tungsten powder. S3. The tungsten powder is sieved and carbonized to obtain a tungsten-carbon mixture. The tungsten-carbon mixture is then carbonized, crushed, and sieved to obtain medium-particle tungsten carbide powder. In step S1, the calcination temperature is 800-850℃ and the calcination time is 1-2 hours. In step S2, the temperature of the first hydrogen reduction is 850-900℃, the temperature of the second hydrogen reduction is 900-950℃, and the temperature of the third hydrogen reduction is 950-1000℃. The time for the first hydrogen reduction is 30-90 min, the time for the second hydrogen reduction is 30-90 min, and the time for the third hydrogen reduction is 30-90 min. The hydrogen flow rate for the first hydrogen reduction is 300-400 L / h, the hydrogen flow rate for the second hydrogen reduction is 300-400 L / h, and the hydrogen flow rate for the third hydrogen reduction is 300-400 L / h. The loading amount of the first hydrogen reduction is 80-160 g / boat, the loading amount of the second hydrogen reduction is 80-160 g / boat, and the loading amount of the third hydrogen reduction is 80-160 g / boat. In step S3, the carbonization temperature is 1850-2000℃, and the carbonization time is 1-1.5h; the particle size of the medium-particle tungsten carbide powder is 1.05-1.1 times that of the tungsten powder, and the total carbon content of the tungsten-carbon mixture is 6.16-6.18wt%. The medium-particle tungsten carbide powder has a Fisher particle size of 3.0-3.4µm, a combined carbon content of 6.10-6.11wt%, and a free carbon content of 0.02-0.03wt%.

Images