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

Abstract

The preparation method comprises the following steps: by taking ammonium paratungstate as a raw material, putting the raw material into a mechanically-sealed rotary calcining furnace with a furnace tube inner diameter of 400mm, and calcining at a temperature of 400 DEG C for 2-3 hours, thereby obtaining the low-oxygen-index surface-needle-shaped high-specific-surface blue tungsten powder, namely the low-oxygen-index surface-needle-shaped high-specific-surface blue tungsten powder. Under the calcining temperature that the furnace temperature of a first zone is 580-620 DEG C, the furnace temperature of a second zone is 600-660 DEG C, the furnace temperature of a third zone is 600-640 DEG C, 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, and the blue tungsten with the low oxygen index, the needle-shaped surface and the high specific surface area is prepared, 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 of the blue tungsten reaches 10-14 m < 2 > / g, and the blue tungsten 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] This invention relates to the field of tungsten oxide preparation technology, and particularly to a method for preparing low-oxygen-index needle-like high specific surface area blue tungsten and its products. Background Technology

[0002] With the development and progress of high-end fine, ultrafine, and nano-hard alloys both domestically and internationally, the demand for high-end raw materials is becoming increasingly stringent, especially regarding the stability of their microstructure and morphology. A special type of purple tungsten, specifically designed for producing ultrafine nano-tungsten powder, has an oxygen index of approximately 2.72 and exhibits a needle-like morphology on its microparticle surface—a typical characteristic of purple tungsten. This has been verified by existing technology. The needle-like morphology results in better uniformity of the prepared tungsten powder. However, purple tungsten has a low specific surface area, leading to insufficient surface-to-internal permeability. Furthermore, the large-scale production of purple tungsten is difficult to control. Therefore, most manufacturers in the industry use high-specific-surface-area blue tungsten instead of purple tungsten to produce ultrafine nano-tungsten powder. However, the oxygen index of fine-particle high-specific-surface-area blue tungsten produced by traditional methods is generally between 2.95 and 2.98. The higher the oxygen index, the more difficult it is to reduce with hydrogen. Simultaneously, its microscopic surface morphology is generally a flat plate with a few cracks. The flat plate-like surface of fine-particle high-specific-surface-area blue tungsten without cracks is not conducive to the entry of hydrogen gas to react with the oxygen atoms inside the particles. Furthermore, the calcination temperature of traditional blue tungsten production is generally around 700℃, with a maximum temperature reaching around 750℃. Higher furnace temperatures require more heat, resulting in higher power consumption in the equipment. Therefore, it is difficult to achieve a low oxygen index and a needle-like surface morphology in high-specific-surface-area blue tungsten produced by traditional methods, and the power consumption required for production is also relatively high.

[0003] A low oxygen index not only reduces the proportion of oxidation, volatilization, and deposition growth during the reduction of blue tungsten, but also lowers hydrogen and electricity consumption. The needle-like microstructure on the surface not only improves the fineness of the tungsten powder particles and promotes hydrogen permeation reduction, but also facilitates the breakage of the needle-like particles into many uniform small grains after reduction, reducing tungsten powder agglomeration and thus improving powder quality. High specific surface area blue tungsten accelerates hydrogen permeation, increases hydrogen reduction efficiency, and improves moisture removal speed, reducing the proportion of moisture volatilization and deposition growth. Therefore, a method for preparing low-oxygen-index, needle-like, high-specific-surface-area blue tungsten and its products are needed. Calcination at a low temperature of around 600℃ can significantly reduce equipment power consumption compared to traditional processes. The prepared low-oxygen-index, needle-like, high-specific-surface-area blue tungsten is suitable for producing 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 this invention is to provide a method for preparing low-oxygen-index needle-like high-specific-surface-area blue tungsten and its products. Using ammonium paratungstate as raw material, the low-oxygen-index needle-like high-specific-surface-area blue tungsten is prepared by calcining in a mechanically sealed rotary calcining furnace by adjusting process parameters.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing needle-like high specific surface area blue tungsten with a low oxygen index, comprising the following steps:

[0006] (a) Ammonium paratungstate was selected as the raw material for preparation;

[0007] (b) Select a mechanically sealed rotary calcining furnace as the preparation equipment;

[0008] (c) After the ammonium paratungstate is placed into the mechanically sealed rotary calcining furnace, the process parameters of the mechanically sealed rotary calcining furnace are adjusted for calcination. The calcination time is 30 minutes. After calcination, the ammonium paratungstate is removed from the furnace, cooled by cooling water, and then sieved by a sieve to finally prepare low oxygen index needle-like high specific surface area blue tungsten powder.

[0009] The process parameters are as follows: furnace temperature for the first zone 580-620℃, furnace temperature for the second zone 600-660℃, and furnace temperature for the third zone 600-640℃; feeding frequency 16±3Hz; furnace rotation frequency 30±5Hz; furnace internal negative pressure -400±200mm water column; and nitrogen flow rate 0-4M. 3 / h.

[0010] Preferably, the ammonium paratungstate is one of continuously crystalline ammonium paratungstate or intermittently crystalline ammonium paratungstate, wherein the grains of the continuously crystalline ammonium paratungstate have a near-single crystal morphology, and the grains of the intermittently crystalline ammonium paratungstate have a polycrystalline morphology.

[0011] Preferably, the inner diameter of the furnace tube of the mechanically sealed rotary calcining furnace is 400 mm.

[0012] The present invention also provides a product prepared by the above-described method for preparing low-oxygen-index, needle-like, high-specific-surface-area blue tungsten. The product is a low-oxygen-index, needle-like, high-specific-surface-area blue tungsten with an oxygen index of 2.90-2.94, a microscopic surface consisting of fine needles, and a specific surface area of ​​10⁻¹⁴ m². 2 / g.

[0013] This invention provides a method for preparing low-oxygen-index, needle-like, high-specific-surface-area blue tungsten, and the resulting product, which has the following beneficial effects:

[0014] The method provided by this invention has a low furnace temperature setting, which helps to save equipment energy consumption. It can prepare high specific surface area blue tungsten without nitrogen gas, which helps to save nitrogen gas consumption. By adjusting the process parameters, it can be applied to different raw materials, making it highly adaptable.

[0015] The method provided by this invention produces low-oxygen-index, needle-like, high-specific-surface-area blue tungsten, which, in addition to its high specific surface area, also features a low oxygen index and a needle-like microstructure. The low oxygen index reduces the proportion of oxidation, volatilization, deposition, and growth during the blue tungsten reduction process. The needle-like microstructure not only improves the fineness of the microstructure of fine tungsten powder and promotes hydrogen permeation reduction, but also makes it easier for the needle-like morphology to break into many uniform small grains after reduction, reducing the agglomeration of tungsten powder. The needle-like morphology is a typical characteristic of purple tungsten oxide, as verified by existing technology. Purple tungsten oxide is due to the presence of the needle-like morphology, which makes the prepared tungsten powder more uniform. Therefore, the needle-like microstructure of the product of this invention can improve the quality of tungsten powder prepared using low-oxygen-index, needle-like, high-specific-surface-area blue tungsten, and is suitable for producing high-quality fine, ultrafine, and nano-particle tungsten powder, tungsten carbide powder, and corresponding cemented carbide products. Attached Figure Description

[0016] Figure 1 This is a 1000x magnified scanning electron microscope image of the low-oxygen-index, needle-like, high-specific-surface-area blue tungsten provided in Embodiment 1 of the present invention.

[0017] Figure 2 This is a 10,000x magnified scanning electron microscope image of the low oxygen index, needle-like, high specific surface area blue tungsten provided in Embodiment 1 of the present invention. Detailed Implementation

[0018] To make the technical means, creative features, objectives and effects of this invention easier to understand, the preparation method of this invention is further described below with reference to specific embodiments.

[0019] Example 1

[0020] A method for preparing needle-like high specific surface area blue tungsten with low oxygen index and product is provided, comprising the following steps:

[0021] (a) Continuous crystallization ammonium paratungstate is used, and the grains of continuous crystallization ammonium paratungstate have a near-single crystal morphology;

[0022] (b) A mechanically sealed rotary calcining furnace with an inner diameter of 400 mm is used;

[0023] (c) After continuously crystalline ammonium paratungstate is fed into the mechanically sealed rotary calcining furnace through the feed hopper, the furnace temperature is set to 620℃ for the first zone, 660℃ for the second zone, and 640℃ for the third zone. The feeding frequency is 16Hz, the furnace rotation frequency is 25Hz, the negative pressure inside the furnace is -400mm water column, and the nitrogen flow rate is 0M. 3 The calcination time is 30 minutes, and after calcination, the powder is cooled with cooling water and then sieved through a sieve to finally prepare low oxygen index needle-like high specific surface area blue tungsten powder.

[0024] The various properties of the low-oxygen-index, needle-like, high-specific-surface-area blue tungsten powder prepared are shown in Table 1, and the surface morphology is as follows: Figure 1 and Figure 2 As shown, the prepared low-oxygen-index, needle-like, high-specific-surface-area blue tungsten powder particles exhibit needle-like structures on their surface.

[0025] Example 2

[0026] A method for preparing needle-like high specific surface area blue tungsten with low oxygen index and product is provided, comprising the following steps:

[0027] (a) Continuous crystallization ammonium paratungstate is used, and the grains of continuous crystallization ammonium paratungstate have a near-single crystal morphology;

[0028] (b) A mechanically sealed rotary calcining furnace with an inner diameter of 400 mm is used;

[0029] (c) After continuously crystalline ammonium paratungstate is fed into the mechanically sealed rotary calcining furnace through the feed hopper, the furnace temperature is set to 580℃ for the first zone, 630℃ for the second zone, and 600℃ for the third zone. The feeding frequency is 17Hz, the furnace rotation frequency is 30Hz, the negative pressure inside the furnace is -200mm water column, and the nitrogen flow rate is 2M. 3 The calcination time is 30 minutes, and after calcination, the powder is cooled with cooling water and then sieved through a sieve to finally prepare low oxygen index needle-like high specific surface area blue tungsten powder.

[0030] The various properties of the low oxygen index, needle-like, high specific surface area blue tungsten powder prepared in the end are shown in Table 1.

[0031] Example 3

[0032] A method for preparing needle-like high specific surface area blue tungsten with low oxygen index and product is provided, comprising the following steps:

[0033] (a) Intermittently crystallized ammonium paratungstate is used, and the grains of intermittently crystallized ammonium paratungstate have a polycrystalline morphology;

[0034] (b) A mechanically sealed rotary calcining furnace with an inner diameter of 400 mm is used;

[0035] (c) After intermittently crystallizing ammonium paratungstate is fed into the mechanically sealed rotary calcining furnace through the feed hopper, 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 furnace internal negative pressure is -600mm water column; and the nitrogen flow rate is 0M. 3 The calcination time is 30 minutes, and after calcination, the powder is cooled with cooling water and then sieved through a sieve to finally prepare low oxygen index needle-like high specific surface area blue tungsten powder.

[0036] The various properties of the low oxygen index, needle-like, high specific surface area blue tungsten powder prepared in the end are shown in Table 1.

[0037] Example 4

[0038] A method for preparing low-oxygen-index, needle-like, high-specific-surface-area blue tungsten and its product is provided, comprising the following steps:

[0039] (a) Intermittently crystallized ammonium paratungstate is used, and the grains of intermittently crystallized ammonium paratungstate have a polycrystalline morphology;

[0040] (b) A mechanically sealed rotary calcining furnace with an inner diameter of 400 mm is used;

[0041] (c) After intermittently crystallizing ammonium paratungstate is fed into the mechanically sealed rotary calcining furnace through the feed hopper, the furnace temperature is set to 600℃ for the first zone, 640℃ for the second zone, and 610℃ for the third zone. The feeding frequency is 17Hz, the furnace rotation frequency is 30Hz, the negative pressure inside the furnace is -300mm water column, and the nitrogen flow rate is 4M. 3 The calcination time is 30 minutes, and after calcination, the powder is cooled with cooling water and then sieved through a sieve to finally prepare low oxygen index needle-like high specific surface area blue tungsten powder.

[0042] The various properties of the low oxygen index, needle-like, high specific surface area blue tungsten powder prepared in the end are shown in Table 1.

[0043] Table 1. Display of various indicators for low oxygen index, needle-like high specific surface area blue tungsten powders from Examples 1-4

[0044] 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

[0045] 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 is detected by a nitrogen adsorption specific surface area analyzer commonly used in the industry.

[0046] As can be seen from the data in the table above, under the conditions of using different raw materials and different process parameters in Examples 1-4, the oxygen index and specific surface area of ​​the prepared low oxygen index needle-shaped high specific surface area blue tungsten powder both 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 low oxygen index needle-shaped high specific surface area blue tungsten powder by adjusting the process parameters and applying different raw materials, thereby increasing the specific surface area of ​​the low oxygen index needle-shaped high specific surface area blue tungsten powder and making its surface needle-shaped.

Claims

1. A method for preparing needle-like high specific surface area blue tungsten with low oxygen index, characterized in that: It includes the following steps: (a) Ammonium paratungstate was selected as the raw material for preparation; (b) Select a mechanically sealed rotary calcining furnace as the preparation equipment; (c) After the ammonium paratungstate is placed into the mechanically sealed rotary calcining furnace, the process parameters of the mechanically sealed rotary calcining furnace are adjusted for calcination. The calcination time is 30 minutes. After calcination, the ammonium paratungstate is removed from the furnace, cooled by cooling water, and then sieved by a sieve to finally prepare low oxygen index needle-like high specific surface area blue tungsten powder. The process parameters are as follows: furnace temperature for the first zone 580-620℃, furnace temperature for the second zone 600-660℃, and furnace temperature for the third zone 600-640℃; feeding frequency 16±3Hz; furnace rotation frequency 30±5Hz; furnace internal negative pressure -400±200mm water column; and nitrogen flow rate 0-4M. 3 / h.

2. The method for preparing low-oxygen-index, needle-like, high-specific-surface-area blue tungsten as described in claim 1, characterized in that: The ammonium paratungstate is either continuously crystalline or intermittently crystalline. The continuously crystalline ammonium paratungstate has a near-single-crystal morphology, while the intermittently crystalline ammonium paratungstate has a polycrystalline morphology.

3. The method for preparing low-oxygen-index, needle-like, high-specific-surface-area blue tungsten as described in claim 1, characterized in that: The inner diameter of the furnace tube of the mechanically sealed rotary calcining furnace is 400 mm.

4. The product prepared by the method for preparing low-oxygen-index needle-like high specific surface area blue tungsten as described in any one of claims 1-3, characterized in that: The product is a low-oxygen-index, needle-like, high-specific-surface-area blue tungsten, with an oxygen index of 2.90-2.94, a microscopic surface consisting of fine needles, and a specific surface area of ​​10-14 m². 2 / g.

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