Preparation method of fine tungsten carbide powder with increased specific surface area

Abstract

The invention discloses a preparation method of fine tungsten carbide powder with increased specific surface area, which comprises the following steps: by taking blue tungsten as a raw material and adopting a rotary furnace for supplying hydrogen clockwise and anticlockwise simultaneously as selected equipment, carrying out hydrogen reduction at the furnace temperature of 700-1000 DEG C under the in-furnace environment that the downstream hydrogen flow is 400-500m < 3 > / h and the anticlockwise hydrogen flow is 50-100m < 3 > / h, thereby obtaining the fine tungsten carbide powder with increased specific surface area. The fine-particle tungsten powder with the specific surface area of 0.8-1.4 m < 2 > / g and the Fisher particle size of 1.0-2.0 microns can be prepared; carbon blending is conducted according to the carbon blending coefficient of 6.14%, tungsten powder and carbon black are evenly mixed in a carbon blending mixer, and the carbon blending mixing time ranges from 60 min to 90 min; and carbonizing the tungsten-carbon mixed powder at 1400-1460 DEG C in a molybdenum wire carbonization furnace under the protection of hydrogen, and crushing by airflow to finally prepare the fine tungsten carbide powder of which the specific surface area is increased relative to the specific surface area of the tungsten powder.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation of fine tungsten carbide powder, and particularly relates 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 greatly reduced.

[0004] Therefore, a method for preparing fine tungsten carbide powder with increased specific surface area is needed, so that while the specific surface area of tungsten powder is relatively low, the specific surface area of the fine tungsten carbide powder prepared therefrom will not only not decrease but increase relative to the tungsten powder, thereby greatly reducing the occurrence of 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, in an internal and external double furnace tube rotary reduction furnace, through the way of forward and reverse hydrogen, hydrogen reduction is used 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 the tungsten powder is prepared, and 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: (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.

[0007] (b) Selecting equipment: Using an internal and external double furnace tube rotary reduction furnace.

[0008] (c) Preparing tungsten powder: Putting the blue tungsten into the internal and external double furnace tube rotary reduction furnace, performing 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.

[0009] (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 performing air flow crushing to finally prepare fine tungsten carbide powder with increased specific surface area.

[0010] 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.

[0011] Preferably, the internal and external double furnace tube rotary reduction furnace is a rotary furnace that supplies hydrogen in both forward and reverse directions simultaneously. The furnace tubes of the rotary furnace that supplies hydrogen in both forward and reverse directions are set 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. Among them, the forward hydrogen reduction section includes a front inner furnace tube and a premixing chamber. The front inner furnace tube is axially installed inside 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, 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 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 supplies hydrogen in both forward and reverse directions can produce tungsten powder with a low specific surface area.

[0012] 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.

[0013] Preferably, the total carbon range of the fine tungsten carbide powder with an 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.

[0014] The preparation method of the fine tungsten carbide powder with an increased specific surface area provided by the present invention has the following beneficial effects: The present invention adopts a rotary furnace that supplies hydrogen in both forward and reverse directions simultaneously and uses the reduction method of forward and reverse hydrogen rotary furnaces. 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 degree, and is suitable for large-scale production.

[0015] For the tungsten powder specially prepared by the present invention, the specific surface area of the tungsten powder is relatively low, and the microscopic activity of the tungsten powder is greatly reduced. Then, by using the general process in the tungsten industry for producing fine tungsten carbide, namely 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 instead increase, and is suitable for the production of high-quality fine-grained cemented carbide. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a scanning electron microscope image of the fine tungsten carbide powder with an increased specific surface area provided by Embodiment 1 of the present invention magnified 1000 times; Figure 2 It is a scanning electron microscope image of the fine tungsten carbide powder with an increased specific surface area provided by Embodiment 1 of the present invention magnified 5000 times. DETAILED DESCRIPTION OF THE INVENTION

[0017] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the preparation method of the present invention is further described below in conjunction with specific embodiments. Example

[0018] A method for preparing fine tungsten carbide powder with increased specific surface area is provided, comprising the following steps: (a) Preparation of raw materials: Use continuous crystallization of single crystal ammonium paratungstate and calcination to obtain blue tungsten.

[0019] (b) Equipment selection: Select a rotary furnace that uses both forward and reverse hydrogen supply.

[0020] (c) Preparation of tungsten powder: blue tungsten is placed in a rotary furnace with both forward and reverse hydrogen supply. The blue tungsten enters the premixing chamber through the feeder, and the forward hydrogen enters through the hydrogen port at the head of the furnace tube. The forward hydrogen flow rate is 500m 3 / h, blue tungsten is pre-mixed with hydrogen, and it moves forward with the rotary furnace tube in the gap between the furnace tube and the front inner furnace tube while reacting with hydrogen for reduction. The furnace temperature is set at 700-920℃, and the reverse hydrogen flow rate is 100m 3 / h, reverse hydrogen enters from the hydrogen port at the furnace tail, flows along the gap between the rear inner furnace tubes and meets the blue tungsten in the reverse direction, performs gas cooling on the tungsten powder, and reduces the residual oxygen content to obtain the required tungsten powder.

[0021] (d) Preparation of fine tungsten carbide powder with increased specific surface area: tungsten powder and carbon black are mixed in a carbon mixing mixer at a coefficient of 6.14%. After mixing for 90 minutes, a tungsten-carbon mixed powder is prepared. The tungsten-carbon mixed powder is then placed in a hydrogen-protected molybdenum wire carbonization furnace, and the furnace temperature is set to 1400-1440°C for carbonization. Finally, the fine tungsten carbide powder with increased specific surface area is prepared through air flow crushing.

[0022] The specific surface area, Fisher particle size and other indicators of the fine tungsten carbide powder with increased specific surface area prepared at last are shown in Table 1. Figure 1 and Figure 2 As shown, the prepared tungsten carbide powder has a finer specific surface area and a uniform particle morphology. Example

[0023] A method for preparing fine tungsten carbide powder with increased specific surface area is provided, comprising the following steps: (a) Preparation of raw materials: Intermittent crystallization of single crystal ammonium paratungstate is used, and blue tungsten is obtained by calcination.

[0024] (b) Equipment selection: Select a rotary furnace that uses both forward and reverse hydrogen supply.

[0025] (c) Preparation of tungsten powder: blue tungsten is placed in a rotary furnace with both forward and reverse hydrogen supply. The blue tungsten enters the premixing chamber through the feeder, and the forward hydrogen enters through the hydrogen port at the head of the furnace tube. The forward hydrogen flow rate is 450m3 / h. The blue tungsten is pre-mixed with hydrogen and, as it advances along with the rotary furnace tube in the gap between the furnace tube and the front inner furnace tube, it undergoes a reduction reaction 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 from the hydrogen inlet at the furnace tail, flows countercurrently 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 undergoes a reduction reaction on the residual oxygen content to obtain the required tungsten powder.

[0026] (d) Preparing fine tungsten carbide powder with increased specific surface area: Carbonize the tungsten powder and carbon black. Mix them in a carbon mixing device according to a coefficient of 6.14%. After mixing for 70 minutes, prepare a tungsten-carbon mixed powder. Then, put the tungsten-carbon mixed powder into a hydrogen-protected molybdenum wire carbonization furnace, set the furnace temperature at 1400 - 1460 °C for carbonization, and finally, through air flow crushing, prepare the fine tungsten carbide powder with increased specific surface area.

[0027] 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

[0028] Provide a method for preparing fine tungsten carbide powder with increased specific surface area, including the following steps: (a) Preparing raw materials: Use continuous crystallization type single crystal ammonium paratungstate, and obtain blue tungsten through calcination.

[0029] (b) Selecting equipment: Select a rotary furnace that supplies hydrogen both forward and backward.

[0030] (c) Preparing tungsten powder: Put the blue tungsten into a rotary furnace that supplies hydrogen both forward and backward. The blue tungsten enters the premixing chamber through a feeder. The forward hydrogen enters through the hydrogen inlet at the head of the furnace tube, and the forward hydrogen flow rate is 400 m 3 / h. The blue tungsten is pre-mixed with hydrogen and, as it advances along with the rotary furnace tube in the gap between the furnace tube and the front inner furnace tube, it undergoes a reduction reaction 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 from the hydrogen inlet at the furnace tail, flows countercurrently 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 undergoes a reduction reaction on the residual oxygen content to obtain the required tungsten powder.

[0031] (d) Preparing fine tungsten carbide powder with increased specific surface area: Carbonize the tungsten powder and carbon black. Mix them in a carbon mixing device according to a coefficient of 6.14%. After mixing for 60 minutes, prepare a tungsten-carbon mixed powder. Then, put the tungsten-carbon mixed powder into a hydrogen-protected molybdenum wire carbonization furnace, set the furnace temperature at 1400 - 1440 °C for carbonization, and finally, through air flow crushing, prepare the fine tungsten carbide powder with increased specific surface area.

[0032] 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. Table 1 Comparison table of various indexes of tungsten powder and fine tungsten carbide powder with increased specific surface area in Examples 1-3 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 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 method for preparing fine tungsten carbide powder with increased specific surface area, characterized in that: The steps include: (a) Preparation of raw materials: blue tungsten is used as the raw material, and the blue tungsten is prepared by using one of single crystal ammonium paratungstate or quasi-single crystal ammonium paratungstate; (b) Equipment selection: Use an inner and outer double-tube rotary reduction furnace; (c) Preparation of tungsten powder: The blue tungsten is placed in the inner and outer double-tube rotary reduction furnace for forward and reverse hydrogen reduction to prepare tungsten powder with low specific surface area. The furnace temperature of the inner and outer double-tube rotary reduction furnace is set at 700-1000°C, and the forward hydrogen flow rate is 400-500m 3 / h, reverse hydrogen flow rate is 50-100m 3 / h; (d) Preparation of fine tungsten carbide powder with increased specific surface area: The tungsten powder and carbon black are mixed in a carbon mixing mixer according to a carbon mixing coefficient of 6.14% for a mixing time of 60-90 minutes to obtain a tungsten-carbon mixed powder. The tungsten-carbon mixed powder is then placed in a hydrogen-protected molybdenum wire carbonization furnace for carbonization at a set temperature of 1400-1460°C, and then air flow crushing is performed to finally prepare fine tungsten carbide powder with increased specific surface area.

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

3. The method for preparing fine tungsten carbide powder with increased specific surface area according to claim 1, characterized in that: The inner and outer double-tube rotary reduction furnace is a rotary furnace that simultaneously supplies hydrogen in both the forward and reverse directions.

4. The method for preparing fine tungsten carbide powder with increased specific surface area according to claim 1, characterized in that: The specific surface area of ​​the tungsten powder is 0.8-1.4m 2 / g, and the Fisher particle size is 1.0-2.0μm.

5. The method for preparing fine tungsten carbide powder with increased specific surface area as claimed in claim 4, characterized in that: The specific surface area of ​​the fine tungsten carbide powder is in the range of 6.10%-6.20% total carbon and 1.0-1.6m 2 / g, and the Fisher particle size is 0.7-0.9μm.

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