A preparation method of fine tungsten carbide powder with increased specific surface area

Abstract

The present invention discloses a preparation method of fine tungsten carbide powder with increased specific surface area. Using blue tungsten as the raw material and selecting a rotary furnace that supplies hydrogen both forward and backward as the equipment, under the furnace environment with a furnace temperature of 700 - 1000 °C, a forward hydrogen flow rate of 400 - 500 m³ / h, and a reverse hydrogen flow rate of 50 - 100 m³ / h, hydrogen reduction is carried out to prepare fine tungsten powder with a specific surface area of 0.8 - 1.4 m² / g and a Fisher particle size of 1.0 - 2.0 μm; then carbon is added according to a carbon addition coefficient of 6.14%, and the tungsten powder and carbon black are uniformly mixed in a carbon addition mixer, and the carbon addition mixing time is 60 - 90 min; then the tungsten-carbon mixed powder is carbonized at 1400 - 1460 °C in a hydrogen-protected molybdenum wire carbonization furnace, and after airflow crushing, fine tungsten carbide powder with a specific surface area increased relative to that of the tungsten powder is finally prepared.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation of fine tungsten carbide powder, and particularly to a method for preparing fine tungsten carbide powder with increased specific surface area. Background Art

[0002] With the continuous development and progress of the domestic and international high-end fine-grained cemented carbide field, the quality requirements for tungsten carbide powder raw materials are becoming increasingly strict, especially higher standards are put forward for the looseness and particle size uniformity of fine tungsten carbide powder. In the traditional batch production process of preparing fine tungsten carbide powder, tungsten powder is carbonized after carbon addition, which is a process of particle size growth. In terms of specific surface area, usually the specific surface area index of tungsten powder is higher than that of the fine tungsten carbide powder produced, and the specific surface area of fine tungsten carbide is less than half of the specific surface area of tungsten powder. For example: when preparing fine tungsten carbide by the traditional method: when the specific surface area of tungsten powder is 6 - 8 m 2 / g, the specific surface area of the prepared fine tungsten carbide is 2.0 - 2.5 m 2 / g; when the specific surface area of tungsten powder is 2.5 - 3.0 m 2 / g, the specific surface area of the prepared fine tungsten carbide is 1.2 - 1.5 m 2 / g. It can be seen that in the traditional method of preparing fine tungsten carbide, after tungsten powder is carbonized and crushed by air flow, the specific surface area of the prepared fine tungsten carbide shows a significant decreasing trend relative to the specific surface area of tungsten powder.

[0003] At the same time, the specific surface area of tungsten powder used in the traditional method of producing fine tungsten carbide is relatively high, and its micro-activity is large. After the carbonization reaction, it is easy to cause abnormal coarsening of fine tungsten carbide particles, which in turn makes the microcrystalline grain uniformity of cemented carbide worse and affects the service performance such as the flexural strength of alloy products. When the specific surface area of tungsten powder is relatively low, the micro-activity of tungsten powder will be significantly reduced.

[0004] Therefore, it is necessary to provide a method for preparing fine tungsten carbide powder with increased specific surface area, so that while the specific surface area of tungsten powder is relatively low, the specific surface area of the fine tungsten carbide powder prepared by it will not decrease but increase relative to tungsten powder, thereby significantly reducing the abnormal particle coarsening of fine tungsten carbide and making it suitable for the production of high-quality fine-grained cemented carbide products. Summary of the Invention

[0005] The object of the present invention is to provide a method for preparing fine tungsten carbide powder with increased specific surface area. This method uses blue tungsten as the raw material and, in an internal and external double furnace tube rotary reduction furnace, through the way of forward and reverse hydrogen, hydrogen reduction is carried out to prepare tungsten powder with a relatively low specific surface area. Then, through the general process in the tungsten industry for producing fine tungsten carbide - carbon mixing, hydrogen - passing molybdenum wire furnace carbonization and air flow crushing, fine tungsten carbide powder with a specific surface area increased compared to that of the tungsten powder is prepared. Its specific surface area not only does not decrease compared to the tungsten powder, but instead increases.

[0006] To achieve the above object, the present invention provides the following technical solution: A method for preparing fine tungsten carbide powder with increased specific surface area, comprising the following steps:

[0007] (a) Preparing raw materials: Using blue tungsten as the raw material, and the blue tungsten is prepared from one of single - crystal ammonium paratungstate or quasi - single - crystal ammonium paratungstate.

[0008] (b) Selecting equipment: Using an internal and external double furnace tube rotary reduction furnace.

[0009] (c) Preparing tungsten powder: Putting the blue tungsten into the internal and external double furnace tube rotary reduction furnace, carrying out forward and reverse hydrogen reduction to prepare tungsten powder with a low specific surface area. The furnace temperature of the internal and external double furnace tube rotary reduction furnace is set at 700 - 1000 °C, the forward hydrogen flow rate is 400 - 500 m 3 / h, and the reverse hydrogen flow rate is 50 - 100 m 3 / h.

[0010] (d) Preparing fine tungsten carbide powder with increased specific surface area: Mixing the tungsten powder and carbon black in a carbon - mixing device according to a carbon - mixing coefficient of 6.14% for 60 - 90 min to obtain a tungsten - carbon mixed powder. Then putting the tungsten - carbon mixed powder into a hydrogen - passing protected molybdenum wire carbonization furnace for carbonization, setting the temperature at 1400 - 1460 °C, and then carrying out air flow crushing to finally prepare fine tungsten carbide powder with increased specific surface area.

[0011] Preferably, the single - crystal ammonium paratungstate is one of continuous crystallization or batch crystallization, the quasi - single - crystal ammonium paratungstate is one of continuous crystallization or batch crystallization, and then the single - crystal ammonium paratungstate or the quasi - single - crystal ammonium paratungstate is calcined to obtain the blue tungsten.

[0012] Preferably, the internal and external double furnace tube rotary reduction furnace is a rotary furnace that simultaneously uses forward and reverse hydrogen supply. The furnace tubes of the rotary furnace that simultaneously uses forward and reverse hydrogen supply are arranged with the front end higher and the rear end lower, and the furnace tubes are divided into a forward hydrogen reduction section and a reverse hydrogen reduction section; wherein the forward hydrogen reduction section includes a front inner furnace tube and a premixing chamber. The front inner furnace tube is axially installed in the furnace tube. A forward hydrogen reduction zone is formed between the front inner furnace tube and the furnace tube. A premixing chamber is formed between the head of the front inner furnace tube and the head of the furnace tube. The head of the furnace tube is provided with a forward hydrogen inlet. The head of the front inner furnace tube is provided with an exhaust pipe passing through the premixing chamber and leading to hydrogen return purification; the reverse hydrogen reduction section includes a discharge pipe and a rear inner furnace tube. The rear inner furnace tube is axially installed in the furnace tube. The front end of the rear inner furnace tube is closed. There is a certain distance between the front end of the rear inner furnace tube and the rear end of the front inner furnace tube. The rear end of the rear inner furnace tube is arranged close to the discharge pipe; the end of the discharge pipe is provided with a reverse hydrogen inlet; the rotary furnace that simultaneously uses forward and reverse hydrogen supply can produce tungsten powder with a low specific surface area.

[0013] Preferably, the specific surface area of the tungsten powder is 0.8 - 1.4 m 2 / g, and the Fisher particle size is 1.0 - 2.0 μm.

[0014] Preferably, the total carbon range of the fine tungsten carbide powder with increased specific surface area is 6.10% - 6.20%, the specific surface area is 1.0 - 1.6 m 2 / g, and the Fisher particle size is 0.7 - 0.9 μm.

[0015] The preparation method of the fine tungsten carbide powder with increased specific surface area provided by the present invention has the following beneficial effects:

[0016] The present invention uses a rotary furnace that simultaneously uses forward and reverse hydrogen supply and the reduction method of forward and reverse hydrogen rotary furnace. It can not only produce tungsten powder with a relatively low specific surface area, but also has low equipment energy consumption and high equipment automation, and is suitable for large-scale production.

[0017] The tungsten powder specially prepared by the present invention has a relatively low specific surface area and a greatly reduced microscopic activity of the tungsten powder. Then, by using the general process for producing fine tungsten carbide in the tungsten industry - carbon mixing, hydrogen passing molybdenum wire furnace carbonization and air flow crushing, the prepared fine tungsten carbide powder will not only not reduce in specific surface area compared with the tungsten powder, but will increase instead, and is suitable for the production of high-quality fine-grained cemented carbide. Description of the Drawings

[0018] Figure 1 It is a scanning electron microscope image of the fine tungsten carbide powder with increased specific surface area provided by Embodiment 1 of the present invention magnified 1000 times;

[0019] Figure 2 It is a scanning electron microscope image of the fine tungsten carbide powder with increased specific surface area provided by Embodiment 1 of the present invention magnified 5000 times. Detailed Description of the Invention

[0020] To make the technical means, creative features, achieved purposes and effects of the present invention easy to understand, the preparation method of the present invention will be further described below in conjunction with specific embodiments. Example

[0021] A preparation method of specific surface area-increased fine tungsten carbide powder is provided, including the following steps:

[0022] (a) Prepare raw materials: Use continuous crystallization type single crystal ammonium paratungstate, and obtain blue tungsten after calcination.

[0023] (b) Select equipment: Select a rotary furnace with both forward and reverse hydrogen supply.

[0024] (c) Prepare tungsten powder: Put blue tungsten into a rotary furnace with both forward and reverse hydrogen supply. The blue tungsten enters the premixing chamber through the feeder. Forward hydrogen enters through the hydrogen inlet at the head of the furnace tube. The forward hydrogen flow rate is 500 m 3 / h. The blue tungsten is pre-mixed with hydrogen and moves forward while reacting with hydrogen to undergo a reduction reaction in the gap between the furnace tube and the front inner furnace tube as the rotary furnace tube rotates. The furnace temperature is set at 700 - 920 °C. The reverse hydrogen flow rate is 100 m 3 / h. The reverse hydrogen enters from the hydrogen inlet at the tail of the furnace and flows reversely to meet the blue tungsten along the gap between the rear inner furnace tube and the furnace tube, cooling the tungsten powder with gas and performing a reduction reaction on the residual oxygen content to obtain the required tungsten powder.

[0025] (d) Prepare specific surface area-increased fine tungsten carbide powder: Charge carbon for the tungsten powder and carbon black, and mix them in a carbon charging mixer according to a coefficient of 6.14%. After mixing for 90 minutes, a tungsten-carbon mixed powder is prepared. Then, the tungsten-carbon mixed powder is put into a hydrogen-protected molybdenum wire carbonization furnace, and carbonization is carried out at a furnace temperature of 1400 - 1440 °C. Finally, after air flow crushing, specific surface area-increased fine tungsten carbide powder is prepared.

[0026] The indexes such as the specific surface area and Fisher particle size of the finally prepared specific surface area-increased fine tungsten carbide powder are shown in Table 1. As Figure 1 and Figure 2 shown, the particle morphology of the prepared specific surface area-increased fine tungsten carbide powder is uniform. Example

[0027] A preparation method of specific surface area-increased fine tungsten carbide powder is provided, including the following steps:

[0028] (a) Prepare raw materials: Use batch crystallization single crystal ammonium paratungstate, and obtain blue tungsten after calcination.

[0029] (b) Select equipment: Select a rotary furnace with both forward and reverse hydrogen supply.

[0030] (c) Preparation of tungsten powder: Blue tungsten is placed into a rotary furnace with both forward and reverse hydrogen supply. The blue tungsten enters the premixing chamber through a feeder. Forward hydrogen enters through the hydrogen inlet at the head of the furnace tube, with a forward hydrogen flow rate of 450 m 3 / h. The blue tungsten is premixed with hydrogen and, as the rotary furnace tube advances in the gap between the furnace tube and the front inner furnace tube, a reduction reaction occurs with hydrogen. The furnace temperature is set at 800 - 960 °C, and the reverse hydrogen flow rate is 80 m 3 / h. The reverse hydrogen enters through the hydrogen inlet at the tail of the furnace and flows reversely to meet the blue tungsten in the gap between the rear inner furnace tube and the furnace tube, for gas cooling of the tungsten powder and reduction reaction of the residual oxygen content, obtaining the required tungsten powder.

[0031] (d) Preparation of fine tungsten carbide powder with increased specific surface area: Tungsten powder and carbon black are carbon-matched, and mixed in a carbon-matching mixer according to a coefficient of 6.14%. After mixing for 70 minutes, a tungsten-carbon mixed powder is prepared. Then, the tungsten-carbon mixed powder is placed into a hydrogen-protected molybdenum wire carbonization furnace, and carbonization is carried out at a furnace temperature of 1400 - 1460 °C. Finally, after airflow crushing, fine tungsten carbide powder with increased specific surface area is prepared.

[0032] The indicators such as the specific surface area and Fisher particle size of the finally prepared fine tungsten carbide powder with increased specific surface area are shown in Table 1. Example

[0033] A method for preparing fine tungsten carbide powder with increased specific surface area is provided, including the following steps:

[0034] (a) Preparation of raw materials: Continuous crystallization type single crystal ammonium paratungstate is used and blue tungsten is obtained through calcination.

[0035] (b) Selection of equipment: A rotary furnace with both forward and reverse hydrogen supply is selected. [[ID=--]]

[0036] (c) Preparation of tungsten powder: Blue tungsten is placed into a rotary furnace with both forward and reverse hydrogen supply. The blue tungsten enters the premixing chamber through a feeder. Forward hydrogen enters through the hydrogen inlet at the head of the furnace tube, with a forward hydrogen flow rate of 400 m 3 / h. The blue tungsten is premixed with hydrogen and, as the rotary furnace tube advances in the gap between the furnace tube and the front inner furnace tube, a reduction reaction occurs with hydrogen. The furnace temperature is set at 850 - 1000 °C, and the reverse hydrogen flow rate is 50 m 3 / h. The reverse hydrogen enters through the hydrogen inlet at the tail of the furnace and flows reversely to meet the blue tungsten in the gap between the rear inner furnace tube and the furnace tube, for gas cooling of the tungsten powder and reduction reaction of the residual oxygen content, obtaining the required tungsten powder.

[0037] (d)Preparation of fine tungsten carbide powder with increased specific surface area: Tungsten powder and carbon black are carbon-matched and mixed in a carbon-mixing blender according to a coefficient of 6.14%. After 60 minutes of mixing, a tungsten-carbon mixed powder is prepared. Then, the tungsten-carbon mixed powder is placed in a hydrogen-protected molybdenum wire carbonization furnace, and the furnace temperature is set at 1400 - 1440 °C for carbonization. Finally, after air-flow crushing, fine tungsten carbide powder with increased specific surface area is prepared.

[0038] The specific surface area, Fisher particle size and other indexes of the finally prepared fine tungsten carbide powder with increased specific surface area are shown in Table 1.

[0039] Table 1 Comparison table of various indexes of tungsten powder and fine tungsten carbide powder with increased specific surface area in Examples 1 - 3

[0040] Serial number <![CDATA[Specific surface area of tungsten powder (m 2 / g)]]> Fischer particle size of tungsten powder (μm) <![CDATA[Specific surface area growth of fine tungsten carbide powder Specific surface area (m 2 / g)]]> Fischer particle size of fine WC powder with increased specific surface area (μm) Total carbon of fine WC powder with increased specific surface area (%) Example 1 1.40 2.00 1.52 0.79 6.11 Example 2 1.23 1.56 1.38 0.85 6.15 Example 3 1.00 1.13 1.17 0.87 6.13

[0041] It can be seen from the data in the above table that the specific surface area of the fine tungsten carbide powder with increased specific surface area prepared in Examples 1 - 3 is higher than that of the tungsten powder used, and the Fisher particle size is also lower than that of the tungsten powder used. Compared with other traditional process methods for preparing tungsten carbide from fine tungsten powder, the effect that the specific surface area of the fine tungsten carbide powder is lower than that of the tungsten powder used is significantly different. It can be seen that through the preparation method provided by the present invention, during the normal production process of the fine tungsten carbide powder with increased specific surface area, not only does the specific surface area of the fine tungsten carbide powder not decrease, but it actually increases.

Claims

1. A preparation method of fine tungsten carbide powder with increased specific surface area, characterized in that: It includes the following steps: (a) Prepare raw materials: Using blue tungsten as the raw material, and the blue tungsten is prepared from single crystal ammonium paratungstate. (b) Select equipment: Adopt an internal and external double furnace tube rotary reduction furnace. The internal and external double furnace tube rotary reduction furnace is a rotary furnace that supplies hydrogen in both forward and reverse directions at the same time. The furnace tubes of the rotary furnace that supplies hydrogen in both forward and reverse directions are set with the front higher and the rear lower, and the furnace tubes are divided into a forward hydrogen reduction part and a reverse hydrogen reduction part; among them, the forward hydrogen reduction part includes a front inner furnace tube and a premixing chamber. The front inner furnace tube is axially installed in the furnace tube, and a forward hydrogen reduction zone is formed between the front inner furnace tube and the furnace tube. A premixing chamber is formed between the head of the front inner furnace tube and the head of the furnace tube. The head of the furnace tube is provided with a forward hydrogen inlet, and the head of the front inner furnace tube is provided with an exhaust pipe passing through the premixing chamber to go to hydrogen purification for recycling; the reverse hydrogen reduction part includes a discharge pipe and a rear inner furnace tube. The rear inner furnace tube is axially installed in the furnace tube. The front end of the rear inner furnace tube is closed. There is a certain distance between the front end of the rear inner furnace tube and the rear end of the front inner furnace tube. The rear end of the rear inner furnace tube is arranged close to the discharge pipe; the end of the discharge pipe is provided with a reverse hydrogen inlet; The rotary furnace that supplies hydrogen in both forward and reverse directions at the same time can prepare tungsten powder with a low specific surface area. (c) Prepare tungsten powder: Put the blue tungsten into the internal and external double furnace tube rotary reduction furnace, and carry out forward and reverse hydrogen reduction to prepare tungsten powder with a low specific surface area. The specific steps are as follows: Put the blue tungsten into the forward and reverse hydrogen supply rotary furnace. The blue tungsten enters the premixing chamber through the feeder. The forward hydrogen enters through the hydrogen inlet at the head of the furnace tube, and the forward hydrogen flow rate is 400 - 500 m 3 / h. The blue tungsten is premixed with hydrogen and undergoes a reduction reaction with hydrogen while advancing between the gaps of the furnace tube and the front inner furnace tube as the rotary furnace tube rotates. The furnace temperature is set at 700 - 1000 °C, and the reverse hydrogen flow rate is 50 - 100 m 3 / h. The reverse hydrogen enters from the hydrogen inlet at the furnace tail, flows reversely to meet the blue tungsten along the gap between the rear inner furnace tube and the furnace tube, cools the tungsten powder with gas, and conducts a reduction reaction on the residual oxygen content to obtain the tungsten powder; The specific surface area of the tungsten powder is 0.8 - 1.4 m 2 / g, and the Fisher particle size is 1.0 - 2.0 μm; (d) Prepare fine tungsten carbide powder with increased specific surface area: Mix the tungsten powder and carbon black in a carbon mixing coefficient of 6.14% in a carbon mixing device for 60 - 90 minutes to obtain a tungsten-carbon mixed powder, and then put the tungsten-carbon mixed powder into a hydrogen-protected molybdenum wire carbonization furnace for carbonization. The set temperature is 1400 - 1460 °C, and then carry out air flow crushing to finally prepare fine tungsten carbide powder with increased specific surface area. The total carbon range of the specific surface area-increased fine tungsten carbide powder is 6.10% - 6.20%, the specific surface area is 1.0 - 1.6 m 2 / g, and the Fisher particle size is 0.7 - 0.9 μm.

2. The preparation method of a specific surface area-increased fine tungsten carbide powder according to claim 1, characterized in that: The single crystal ammonium paratungstate is one of continuous crystallization or batch crystallization, and then the single crystal ammonium paratungstate is calcined to obtain the blue tungsten.

Images