Preparation method of blue tungsten with low oxygen index, needle-shaped surface and high specific surface area

Abstract

The invention discloses a preparation method of low-oxygen-index surface needle-shaped high-specific-surface blue tungsten, which comprises the following steps: by taking ammonium paratungstate as a raw material, putting the raw material into a mechanically-sealed rotary calcining furnace with the furnace tube inner diameter of 400mm, and calcining at the calcining temperature of 580-620 DEG C in a first zone, 600-660 DEG C in a second zone and 600-640 DEG C in a third zone for 1-3 hours; the feeding frequency is 13-19 Hz, the furnace rotation frequency is 25-35 Hz, the negative pressure in the furnace is-400 + / -200 mm water column, the nitrogen flow is 0-4 M < 3 > / h, the low-oxygen-index surface-needle-shaped high-specific-surface blue tungsten is prepared, the oxygen index is 2.90-2.94, the surface of the low-oxygen-index surface-needle-shaped high-specific-surface blue tungsten is full of fine needle-shaped morphology, the specific surface area reaches 10-14 m < 2 > / g, and the low-oxygen-index surface-needle-shaped high-specific-surface blue tungsten can be used for preparing the high-specific-surface blue tungsten. The method is suitable for producing high-quality fine, superfine and nano-particle tungsten powder, tungsten carbide powder and corresponding hard alloy products.

Description

Technical Field

[0001] The invention relates to the technical field of tungsten oxide preparation, and in particular to a method for preparing low oxygen index surface needle-shaped high specific surface area blue tungsten. Background Art

[0002] With the development and progress of high-end fine, ultrafine and nano cemented carbides at home and abroad, the high-end demand for raw materials is becoming more and more stringent, especially the demand for the micromorphology and microstructure stability of raw materials is becoming stronger and stronger. A special purple tungsten product specially used for the production of ultrafine nano tungsten powder has an oxygen index of about 2.72, and the surface of the microscopic particles is needle-shaped, but the specific surface area of ​​purple tungsten is not high, resulting in insufficient air permeability from the surface to the inside, and the control of mass production of purple tungsten is difficult. Therefore, most manufacturers in the industry use high specific surface area blue tungsten to replace purple tungsten to produce ultrafine nano tungsten powder. However, the oxygen index of fine-grained high-specific-surface-area blue tungsten produced by traditional preparation methods is generally between 2.95-2.98. The higher the oxygen index, the more difficult it is to reduce with hydrogen. At the same time, its microscopic surface morphology is generally a flat plate with a few cracks, and the flat plate without cracks on the microscopic surface of fine-grained high-specific-surface-area blue tungsten is not conducive to the entry of hydrogen and the reaction with the oxygen atoms inside the particles. In addition, the calcination temperature of blue tungsten produced by traditional processes is generally around 700°C, and the maximum temperature can reach around 750°C. The higher the furnace temperature, the higher the heat required, and the higher the power consumption of the equipment production. Therefore, it is difficult for high-specific-surface-area blue tungsten produced by traditional preparation methods to achieve a low oxygen index and a needle-like surface microscopic morphology, and the power consumption required for production is also high.

[0003] Low oxygen index can not only reduce the proportion of oxidation volatilization deposition growth in the blue tungsten reduction process, but also reduce hydrogen consumption and power consumption; the needle-shaped micro-morphology of the surface can not only improve the micro-morphology fineness of fine-grained tungsten powder, promote the hydrogen penetration reduction of fine-grained tungsten powder, but also the needle-shaped morphology is easy to break into many uniform small grains after reduction, reducing the agglomeration of tungsten powder, thereby improving the quality of tungsten powder; high specific surface area blue tungsten is conducive to accelerating the hydrogen permeation rate, improving the hydrogen reduction efficiency, and increasing the water discharge rate, reducing the proportion of water volatilization deposition growth. Therefore, it is necessary to provide a preparation method of blue tungsten with a low oxygen index surface and a high specific surface area, which can be calcined at a low temperature of about 600°C. Compared with the traditional process, the power consumption of the equipment can be greatly reduced. The prepared blue tungsten with a low oxygen index surface and a high specific surface area is suitable for the production of high-quality fine, ultrafine and nano-particle tungsten powder, tungsten carbide powder and corresponding cemented carbide products. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing blue tungsten with a low oxygen index surface and a high specific surface area. Ammonium paratungstate is used as a raw material, and the blue tungsten with a low oxygen index surface and a high specific surface area is prepared by calcining in a mechanically sealed rotary calcining furnace by adjusting process parameters.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for preparing a low oxygen index surface needle-shaped high specific surface area blue tungsten, comprising the following steps: (a) selecting ammonium paratungstate as a preparation raw material; (b) Selecting a mechanical seal rotary calcining furnace as the preparation equipment; (c) After the ammonium paratungstate is placed in the mechanical seal rotary calcining furnace, the process parameters of the mechanical seal rotary calcining furnace are adjusted to perform calcination, the calcination time is 30 minutes, after the calcination is completed, the ammonium paratungstate is taken out of the furnace and cooled by cooling water, and then sieved by a sieve machine, and finally a blue tungsten powder with a low oxygen index surface needle shape and high specific surface area is prepared; The process parameters are as follows: the first zone furnace temperature is 580-620°C, the second zone furnace temperature is 600-660°C, the third zone furnace temperature is 600-640°C, the feeding frequency is 16±3Hz, the furnace rotation frequency is 30±5Hz, the negative pressure in the furnace is -400±200mm water column, and the nitrogen flow rate is 0-4M 3 / h.

[0006] Preferably, the ammonium paratungstate is one of continuously crystallized ammonium paratungstate and intermittently crystallized ammonium paratungstate, the grains of the continuously crystallized ammonium paratungstate are in a quasi-single crystal morphology, and the grains of the intermittently crystallized ammonium paratungstate are in a polycrystalline morphology.

[0007] Preferably, the inner diameter of the furnace tube of the mechanical seal rotary calcining furnace is 400 mm.

[0008] Preferably, the oxygen index of the low oxygen index surface needle-shaped high specific surface area blue tungsten is 2.90-2.94, the microscopic surface is fine needle-shaped, and the specific surface area is 10-14m 2 / g.

[0009] The present invention provides a method for preparing a low oxygen index needle-shaped high specific surface area blue tungsten, and its beneficial effects are as follows: The method provided by the present invention has a low furnace temperature setting, which is beneficial to saving equipment energy consumption. High specific surface area blue tungsten can be prepared without nitrogen, which is beneficial to saving nitrogen gas consumption. By adjusting process parameters, it can be applied to different raw materials and has strong applicability.

[0010] The method provided by the present invention can prepare blue tungsten with a low oxygen index and a high specific surface area and a needle-shaped surface. The blue tungsten has the characteristics of a low oxygen index and a needle-shaped surface microstructure on the basis of a high specific surface area. The low oxygen index reduces the growth ratio of oxidation volatilization deposition in the reduction process of the blue tungsten. The needle-shaped surface microstructure can not only improve the microstructure fineness of fine-grained tungsten powder and promote hydrogen penetration reduction of the fine-grained tungsten powder, but also the needle-shaped morphology can be easily broken into many uniform small grains after reduction, thereby reducing the agglomeration of tungsten powder. The quality of tungsten powder prepared by using the blue tungsten with a low oxygen index and a high specific surface area can be improved, and the blue tungsten is suitable for producing high-quality fine, ultrafine and nano-grained tungsten powder, tungsten carbide powder and corresponding cemented carbide products. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a 1000-fold magnified image of the needle-shaped blue tungsten with a low oxygen index surface and a high specific surface area provided by Example 1 of the present invention; Figure 2 This is a 10,000-fold magnified scanning electron microscope image of the needle-shaped blue tungsten with a low oxygen index surface and a high specific surface area provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0012] 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.

[0013] Example 1

[0014] A method for preparing needle-shaped blue tungsten with a low oxygen index and a high specific surface area is provided, comprising the following steps: (a) Continuously crystallized ammonium paratungstate is used, and the grains of continuously crystallized ammonium paratungstate are of single crystal morphology; (b) A mechanically sealed rotary calcining furnace with a furnace tube inner diameter of 400 mm; (c) After the continuous crystallized ammonium paratungstate is fed into the mechanically sealed rotary calcining furnace through the feed bin, the furnace temperature is set to 620°C for the first zone, 660°C for the second zone, and 640°C for the third zone. The feed frequency is 16 Hz, the furnace rotation frequency is 25 Hz, the negative pressure in the furnace is -400 mm water column, and the nitrogen flow rate is 0 M 3 / h, the calcination time is 30min, and after the calcination, it is taken out of the furnace and cooled by cooling water, and then sieved by a sieve machine, and finally a low oxygen index surface needle-shaped high specific surface area blue tungsten powder is prepared.

[0015] The various indicators of the finally prepared low oxygen index surface needle-shaped high specific surface area blue tungsten powder are shown in Table 1. The surface morphology is as follows Figure 1 and Figure 2 As shown, the prepared low oxygen index needle-shaped high specific surface area blue tungsten powder particles have a needle-shaped surface.

[0016] Example 2

[0017] A method for preparing needle-shaped blue tungsten with a low oxygen index and a high specific surface area is provided, comprising the following steps: (a) Continuously crystallized ammonium paratungstate is used, and the grains of continuously crystallized ammonium paratungstate are of single crystal morphology; (b) A mechanically sealed rotary calcining furnace with a furnace tube inner diameter of 400 mm; (c) After the continuous crystallized ammonium paratungstate is fed into the mechanically sealed rotary calcining furnace through the feed bin, the furnace temperature is set to 580°C for the first zone, 630°C for the second zone, and 600°C for the third zone. The feed frequency is 17 Hz, the furnace rotation frequency is 30 Hz, the negative pressure in the furnace is -200 mm water column, and the nitrogen flow rate is 2 M 3 / h, the calcination time is 30min, and after the calcination, it is taken out of the furnace and cooled by cooling water, and then sieved by a sieve machine, and finally a low oxygen index surface needle-shaped high specific surface area blue tungsten powder is prepared.

[0018] The various indicators of the finally prepared low oxygen index surface needle-shaped high specific surface area blue tungsten powder are shown in Table 1.

[0019] Example 3

[0020] A method for preparing needle-shaped blue tungsten with a low oxygen index and a high specific surface area is provided, comprising the following steps: (a) intermittent crystallization of ammonium paratungstate is adopted, and the grains of intermittent crystallization of ammonium paratungstate are polycrystalline; (b) A mechanically sealed rotary calcining furnace with a furnace tube inner diameter of 400 mm; (c) After the intermittently crystalline ammonium paratungstate is fed into the mechanically sealed rotary calcining furnace through the feed bin, the furnace temperature is set to 580°C for the first zone, 600°C for the second zone, and 600°C for the third zone, the feed frequency is 15Hz, the furnace rotation frequency is 35Hz, the negative pressure in the furnace is -600mm water column, and the nitrogen flow rate is 0M 3 / h, the calcination time is 30min, and after the calcination, it is taken out of the furnace and cooled by cooling water, and then sieved by a sieve machine, and finally a low oxygen index surface needle-shaped high specific surface area blue tungsten powder is prepared.

[0021] The various indicators of the finally prepared low oxygen index surface needle-shaped high specific surface area blue tungsten powder are shown in Table 1.

[0022] Example 4

[0023] A method for preparing needle-shaped blue tungsten with a low oxygen index and a high specific surface area is provided, comprising the following steps: (a) intermittent crystallization of ammonium paratungstate is adopted, and the grains of intermittent crystallization of ammonium paratungstate are polycrystalline; (b) A mechanically sealed rotary calcining furnace with a furnace tube inner diameter of 400 mm; (c) After the intermittent crystallized ammonium paratungstate is fed into the mechanically sealed rotary calcining furnace through the feed bin, the furnace temperature is set to 600°C for the first zone, 640°C for the second zone, and 610°C for the third zone. The feed frequency is 17 Hz, the furnace rotation frequency is 30 Hz, the negative pressure in the furnace is -300 mm water column, and the nitrogen flow rate is 4 M 3 / h, the calcination time is 30min, and after the calcination, it is taken out of the furnace and cooled by cooling water, and then sieved by a sieve machine, and finally a low oxygen index surface needle-shaped high specific surface area blue tungsten powder is prepared.

[0024] The various indicators of the finally prepared low oxygen index surface needle-shaped high specific surface area blue tungsten powder are shown in Table 1.

[0025] Table 1 Various indicators of low oxygen index surface needle-shaped high specific surface area blue tungsten powder of Examples 1-4 serial number Oxygen Index <![CDATA[Specific surface area (m 2 / g)]]> Example 1 2.93 11.54 Example 2 2.92 13.26 Example 3 2.94 10.98 Example 4 2.92 12.37 The oxygen index detection method in Table 1 adopts the titration method commonly used in the industry to detect the oxygen index of tungsten oxide, and the specific surface area detection adopts the nitrogen adsorption specific surface area detection analyzer commonly used in the industry for detection.

[0026] It can be seen from the data in the above table that, in Examples 1-4, when different raw materials and different process parameters are used, the oxygen index and specific surface area of ​​the blue tungsten powder with a low oxygen index surface and a high specific surface area are prepared, which meet the requirements of the present invention. It can be seen that the preparation method provided by the present invention can reduce the oxygen index of the blue tungsten powder with a low oxygen index surface and a high specific surface area, increase the specific surface area of ​​the blue tungsten powder with a low oxygen index surface and a high specific surface area, and make its surface appear needle-shaped by adjusting the process parameters and applying different raw materials.

Claims

1. A method for preparing blue tungsten with low oxygen index and high specific surface area and needle-shaped surface, characterized in that: The following steps are included: (a) selecting ammonium paratungstate as a preparation raw material; (b) Selecting a mechanical seal rotary calcining furnace as the preparation equipment; (c) After the ammonium paratungstate is placed in the mechanical seal rotary calcining furnace, the process parameters of the mechanical seal rotary calcining furnace are adjusted to perform calcination, the calcination time is 30 minutes, after the calcination is completed, the ammonium paratungstate is taken out of the furnace and cooled by cooling water, and then sieved by a sieve machine, and finally a blue tungsten powder with a low oxygen index surface needle shape and high specific surface area is prepared; The process parameters are as follows: the first zone furnace temperature is 580-620°C, the second zone furnace temperature is 600-660°C, the third zone furnace temperature is 600-640°C, the feeding frequency is 16±3Hz, the furnace rotation frequency is 30±5Hz, the negative pressure in the furnace is -400±200mm water column, and the nitrogen flow rate is 0-4M 3 / h.

2. The method for preparing the low oxygen index needle-shaped high specific surface area blue tungsten according to claim 1, characterized in that: The ammonium paratungstate is one of continuously crystallized ammonium paratungstate and intermittently crystallized ammonium paratungstate. The grains of the continuously crystallized ammonium paratungstate are in a quasi-single crystal morphology, and the grains of the intermittently crystallized ammonium paratungstate are in a polycrystalline morphology.

3. The method for preparing the low oxygen index needle-shaped high specific surface area blue tungsten according to claim 1, characterized in that: The inner diameter of the furnace tube of the mechanical seal rotary calcining furnace is 400 mm.

4. The method for preparing the low oxygen index needle-shaped high specific surface area blue tungsten according to any one of claims 1 to 3, characterized in that: The oxygen index of the low oxygen index surface needle-shaped high specific surface area blue tungsten is 2.90-2.94, the microscopic surface is fine needle-shaped, and the specific surface area is 10-14m 2 / g.

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