阅读说明：本技术 一种超粗晶碳化钨粉末及其制备方法 (Ultra-coarse grain tungsten carbide powder and preparation method thereof ) 是由 孙浩斌 颜练武 司守佶 姚海滨 常江 刘欣 李昌业 李晓艳 邵长昆 付道龙 李伟 于 2020-05-20 设计创作，主要内容包括：本发明涉及一种超粗晶碳化钨粉末及其制备方法。步骤包括：将钨粉与碳黑进行混合,所述碳黑占所述钨粉的重量百分比为1.5-2.0％,在1700±20℃下进行碳化,冷却出料、球磨破碎,得到料I；将料I与碳黑混合,所述碳占所述钨粉的重量百分比为2.0-2.5％,然后在1850±20℃下进行碳化,冷却出料破碎得到料II；将料II经总碳分析分析后,根据碳化钨碳的含量要求为6.13％将碳黑补齐,并将料II和补齐的碳黑混合均匀,然后在2200±50℃下进行碳化,冷却出料破碎破碎过筛,得到超粗晶碳化钨粉末。有益效果：该方法得到40-45微米的超粗晶碳化钨粉末,可有效实现碳化钨晶粒的定向生长。(The invention relates to ultra-coarse grain tungsten carbide powder and a preparation method thereof. The method comprises the following steps: mixing tungsten powder and carbon black, wherein the weight percentage of the carbon black in the tungsten powder is 1.5-2.0%, carbonizing at 1700 +/-20 ℃, cooling, discharging, and performing ball milling and crushing to obtain a material I; mixing the material I with carbon black, wherein the carbon accounts for 2.0-2.5% of the tungsten powder by weight percent, then carbonizing at 1850 +/-20 ℃, cooling, discharging and crushing to obtain a material II; analyzing and analyzing the total carbon of the material II, filling up carbon black according to the content requirement of tungsten carbide carbon of 6.13 percent, uniformly mixing the material II and the filled carbon black, carbonizing at 2200 +/-50 ℃, cooling, discharging, crushing and sieving to obtain ultra-coarse tungsten carbide powder. Has the advantages that: the method can obtain ultra-coarse grain tungsten carbide powder of 40-45 microns, and can effectively realize the directional growth of tungsten carbide grains.)

1. A preparation method of ultra-coarse grain tungsten carbide powder is characterized by comprising the following steps:

(1) mixing tungsten powder and carbon black for the first time, wherein the carbon black in the first mixing accounts for 1.5-2.0 percent of the weight of the tungsten powder, carbonizing at 1700 +/-20 ℃, cooling, discharging, and performing ball milling and crushing to obtain a material I;

(2) carrying out secondary mixing on the material I and carbon black, wherein the carbon black in the secondary mixing accounts for 2.0-2.5% of the weight of the tungsten powder in the step (1), then carbonizing at 1850 +/-20 ℃, cooling, discharging and crushing to obtain a material II;

(3) and (3) analyzing the total carbon of the material II, filling up carbon black according to the requirement of 6.13 percent of the carbon content, uniformly mixing the material II and the filled carbon black, carbonizing at 2200 +/-50 ℃, cooling, discharging, crushing and sieving to obtain the ultra-coarse tungsten carbide powder.

2. The method according to claim 1, wherein the carbonization in steps (1), (2) and (3) is performed in a vertical high temperature intermediate frequency furnace with a hydrogen flow of 3-4m³The loading amount of each furnace is 300-310 kg, and the cooling time is 22-24 hours.

3. The method according to claim 1, wherein the carbonization in the step (1) is carried out while continuously raising the temperature to the desired carbonization temperature for 6 to 6.5 hours, and the holding time after raising the temperature is 4 to 4.5 hours.

4. The method according to claim 1, wherein the carbonization in the step (2) is carried out while continuously raising the temperature to the desired carbonization temperature for 7 to 7.5 hours, and the temperature is maintained for 5.0 to 5.5 hours after raising the temperature.

5. The method according to claim 1, wherein the carbonization in the step (3) is carried out while continuously raising the temperature to the desired carbonization temperature for 10 to 11 hours, and the temperature is maintained for 6.0 to 6.5 hours after raising the temperature.

6. The method according to claim 1, wherein the fisher-tropsch size of the tungsten powder in step (1) is 35 to 40 μm.

7. The ultra-coarse grain tungsten carbide powder is characterized in that the Fisher size of the ultra-coarse grain tungsten carbide powder is 40-45 mu m, the total carbon is 6.13 +/-0.03%, the free carbon is less than or equal to 0.06%, and the combined carbon is more than or equal to 6.09%.

Technical Field

The invention belongs to the field of preparation of new materials for powder metallurgy, and relates to ultra-coarse grain tungsten carbide powder and a preparation method thereof.

Background

The ultra-coarse grain hard alloy has better strength, hardness and wear resistance, good impact toughness, and has the advantages of high reliability, long service life and the like when being applied to industries such as steel, dies, mining, construction and the like. For example, after the super coarse grain alloy is adopted for highway pavement milling, the service life of the super coarse grain alloy is prolonged by more than 1 time compared with the conventional hard alloy.

The research level of China in the aspect of ultra-coarse grain hard alloy is low, and the main performance is as follows: the alloy has fine grain size and poor impact toughness. The main reasons are that the WC powder has finer grains (particularly has fine granularity in a grinding state) and poorer powder uniformity, and the extra-coarse tungsten carbide powder in China also has the obvious defects of more powder lattice defects and incomplete crystallization, so that the powder is easy to break in the wet grinding process.

The essence of the tungsten powder carbonization process is the diffusion process of carbon atoms in tungsten crystal grains, and the diffusion of carbon is preferentially carried out along the surface with the largest atomic distance, namely a close-packed surface, and is firstly converted into W₂C then turns to WC. Since the carbon density is low and the particles are fine during the compounding of the carbon blend, the tungsten particles are surrounded by the carbon. As the carbonization process proceeds, carbon atoms diffuse inward from the periphery of the tungsten crystal grains at the same time, and a plurality of crystal nuclei are generated and grown up, respectively, to form polycrystalline grains. Meanwhile, in the process of converting the W phase into the WC phase, the mass is increased by 6 percent, and the density is increased by 19.3g/cm³The reduction is 15.7g/cm³The diameter of the single tungsten particle is expanded by 10 percent, the volume of the single tungsten particle is expanded by 36 percent, one part of the tungsten particle is brittle by releasing the stress of the particle, and the other part of the tungsten particle is brittleMany microscopic defects are formed inside the divided WC particles. Thus resulting in tungsten carbide particles that are not wear resistant.

Disclosure of Invention

In view of the above-mentioned deficiencies of the prior art, the present invention provides a method for preparing ultra-coarse tungsten carbide powder. The method can obtain ultra-coarse grain tungsten carbide powder of 40-45 microns, and can effectively realize the directional growth of tungsten carbide grains.

A preparation method of ultra-coarse grain tungsten carbide powder comprises the following steps:

(1) mixing tungsten powder and carbon black for the first time, wherein the carbon black in the first mixing accounts for 1.5-2.0 percent of the weight of the tungsten powder, carbonizing at 1700 +/-20 ℃, cooling, discharging, and performing ball milling and crushing to obtain a material I;

(2) carrying out secondary mixing on the material I and carbon black, wherein the carbon black in the secondary mixing accounts for 2.0-2.5% of the weight of the tungsten powder in the step (1), then carbonizing at 1850 +/-20 ℃, cooling, discharging and crushing to obtain a material II;

(3) analyzing and analyzing the total carbon of the material II, filling carbon black according to the requirement of 6.13 percent of the carbon content of the tungsten carbide, uniformly mixing the material II and the filled carbon black, carbonizing at 2200 +/-50 ℃, cooling, discharging, crushing and sieving to obtain the ultra-coarse grain tungsten carbide powder.

Preferably, the carbonization in the steps (1), (2) and (3) adopts a vertical high-temperature intermediate frequency furnace, and the hydrogen flow is 3-4m³The loading amount of each furnace is 300-310 kg, and the cooling time is 22-24 hours.

Preferably, the temperature is continuously increased to the required carbonization temperature during carbonization in the step (1), the temperature increasing time is 6 to 6.5 hours, and the heat preservation time after temperature increase is 4 to 4.5 hours.

Preferably, the temperature is continuously increased to the required carbonization temperature during carbonization in the step (2), the temperature increasing time is 7 to 7.5 hours, and the heat preservation time after temperature increase is 5.0 to 5.5 hours.

Preferably, the temperature is continuously increased to the required carbonization temperature during carbonization in the step (3), the temperature increasing time is 10 to 11 hours, and the heat preservation time after temperature increase is 6.0 to 6.5 hours.

Preferably, the Fisher size of the tungsten powder in the step (1) is 35-40 microns.

The invention also provides ultra-coarse grain tungsten carbide powder, the Fisher size of the ultra-coarse grain tungsten carbide powder is 40-45 mu m, the total carbon is 6.13 +/-0.03%, the free carbon is less than or equal to 0.06%, and the combined carbon is more than or equal to 6.09%.

Has the advantages that: the method can obtain ultra-coarse grain tungsten carbide powder of 40-45 microns, and can effectively realize the directional growth of tungsten carbide grains. In the tungsten powder carbonization process, it is important to realize the directional growth of the tungsten carbide grains after nucleation, so that the tungsten carbide grains can be prevented from being crushed due to expansion in different directions or forming a large number of microscopic defects due to excessive grain boundaries. The invention adopts three-stage carbon preparation to effectively realize the directional growth of tungsten carbide grains.

Detailed Description

The invention provides ultra-coarse grain tungsten carbide powder, the Fisher size of which is 40-45 mu m, and the main component requirements of which are shown in Table 1.

TABLE 1 ultra-coarse tungsten carbide powder principal Components requirements

Analysis item	Total carbon	Free carbon	Combined carbon
				Index (%)	6.13±0.03	≤0.06	≥6.09

A preparation method of ultra-coarse grain tungsten carbide powder comprises the following steps:

(1) firstly, mixing tungsten powder with 1.5-2.0 wt% of metallurgical-grade carbon black, then carbonizing for 4-4.5 hours at 1700 +/-20 ℃ in a vertical high-temperature intermediate frequency furnace, cooling, discharging, and performing ball milling and crushing to obtain a material I;

(2) mixing the material I with 2.0-2.5 wt% of carbon, then carrying out heat preservation carbonization for 5.0-5.5 hours at 1850 +/-20 ℃ in a vertical high-temperature intermediate frequency furnace, cooling, discharging and crushing to obtain a material II;

(3) and (3) analyzing the material II, uniformly mixing the material II with the supplemented carbon according to the stoichiometric ratio, then carrying out heat preservation carbonization for 6.0-6.5 hours at the temperature of 2200 +/-50 ℃, cooling, discharging, crushing, and sieving to obtain ultra-coarse grain tungsten carbide powder of 40-45 microns.

In the present application, it is important to distribute carbon in stages and to carbonize in stages. In the tungsten powder carbonization process, the realization of the directional growth of the tungsten carbide grains after nucleation is important, so that the tungsten carbide grains can be prevented from being crushed due to expansion in different directions or forming a large number of microscopic defects due to excessive grain boundaries. The invention adopts three-stage carbon preparation to effectively realize the directional growth of the tungsten carbide crystal grains.

In order to facilitate continuous production, the invention adopts a vertical high-temperature intermediate frequency furnace. When the medium frequency furnace is adopted for carbonization, the hydrogen flow is 3-4m³The loading amount of each furnace is 300-310 kg, and the cooling time is 22-24 hours.

When the intermediate frequency furnace is adopted for carbonization, the temperature is continuously raised to the required carbonization temperature, and the temperature rise time is respectively as follows: 6-6.5 hours in step (1), 7-7.5 hours in step (2) and 10-11 hours in step (3). The heat preservation time is respectively as follows: 4-4.5 hours in step (1), 5.0-5.5 hours in step (2) and 6.0-6.5 hours in step (3).

The Fisher size of the tungsten powder in the step (1) is 35-40 microns. In order to achieve the aim, the tungsten powder as the raw material has large granularity, the invention adopts undoped ultra-coarse grain tungsten powder produced by the company as the raw material, and the Fisher granularity of the tungsten powder is 35-40 microns.

The present application is illustrated below with reference to specific examples.