CN108455614B - Method for preparing nano WC powder at low temperature and in short process - Google Patents
Method for preparing nano WC powder at low temperature and in short process Download PDFInfo
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- CN108455614B CN108455614B CN201810126042.8A CN201810126042A CN108455614B CN 108455614 B CN108455614 B CN 108455614B CN 201810126042 A CN201810126042 A CN 201810126042A CN 108455614 B CN108455614 B CN 108455614B
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Abstract
The invention discloses a method for preparing nano WC powder at low temperature and in a short process, which takes water-soluble ammonium metatungstate and glucose as raw materials, adds ammonium dichromate and ammonium metavanadate as inhibitors, adds the raw materials and the inhibitors into pure water, heats and stirs the mixture evenly, and then obtains the target product nano WC powder through the processes of spray drying, calcining, reduction and carbonization. The nanometer WC powder prepared by the method has the advantages of stable performance, single phase, uniform components, narrow particle size distribution, fine crystal grains and easy control of powder components, and has the capacity of industrial and batch production.
Description
Technical Field
The invention belongs to a method for preparing raw material powder for producing nano/superfine hard alloy, and particularly relates to a method for preparing nano tungsten carbide (WC) powder by adopting a water-soluble method, a low temperature and a short process. The nanometer WC powder prepared by the method can be applied to dot matrix printer drill bits, integrated circuit board micro drill bits, high-precision numerical control machining drill bits and milling cutters, medical dental drills, difficult-to-machine material cutters and the like.
Background
With the development of modern processing materials to high-end aluminum alloy, titanium alloy, magnesium alloy, high-performance copper alloy, stainless steel and amorphous materials, the appearance and application of various difficult-to-process materials, and the development of advanced manufacturing systems, high-speed cutting, ultra-precision processing and green manufacturing, the development of cutter materials to high performance is promoted.
The hard alloy is commonly called as an industrial tooth, and has high strength, high hardness, high wear resistance, low thermal expansion coefficient, high elastic modulus and good chemical stability, so that the hard alloy occupies an important position in the aspects of modern tool materials, wear-resistant materials, corrosion-resistant and high-temperature-resistant materials and the like, and is widely applied to wire drawing dies, machining, material cutting, mining drill bits, wear-resistant and corrosion-resistant parts, structural components and the like in various fields of national economy.
The hard alloy cutter material belongs to a cermet material and is a brittle material, and the contradiction (high strength, low hardness, low strength and high hardness) between the strength and the hardness (toughness and wear resistance) of the hard alloy cutter material is always a main factor which troubles the development of the hard alloy cutter material. For a long time, people have been making continuous efforts, such as adjusting alloy components, improving alloy structure, adding trace elements, adopting new process equipment and other measures, trying to harmonize the contradiction between the two and organically combining the two, which is always the direction of people's efforts.
Researches find that on the premise of keeping the cobalt content unchanged, when the WC grain size is reduced to below 1 mu m, the hardness and the strength of the hard alloy are simultaneously improved, and the performance is more excellent along with the further reduction of the WC grain size, so that a new way is found for solving the contradiction between the hardness and the strength of the hard alloy. It follows that a significant improvement in cemented carbide properties can be achieved by reducing the microstructure dimensions while maintaining the chemical composition and microstructure uniformity.
The preparation of nano-structure hard alloy is carried out on the premise that nano WC powder is used. The traditional process for producing WC powder starts from the preparation of Ammonium Paratungstate (APT), and the phase evolution process is as follows: APT → tungsten oxide → tungsten (W) powder → WC powder, i.e.: APT is used as a raw material to produce tungsten oxide by adopting a rotary kiln, the tungsten oxide is reduced into W powder by adopting a reduction furnace, and the W powder is prepared into superfine/nano WC powder by preparing carbon black, ball-milling and mixing materials and reducing a carbonization furnace at the temperature of not less than 1300 ℃. The most key to the production of nano WC powder by the traditional process is the production of tungsten oxide powder, and tungsten oxide produced by APT calcination-reduction has four forms (yellow tungsten WO)3Blue tungsten WO2.9Tungsten, WO2.72Brown tungsten WO2) At present, the nano WC powder can be produced only by adopting the purple tungsten, and the grain size of the powder is less than or equal to 200 nm. Production of WO by APT calcination-reduction2.72Has strict requirements on equipment and environment, is not properly controlled and is easy to generate WO3、WO2.9、WO2.72、WO2Complexes of, and WO2.72The W powder reduced into the powder has fine granularity, is easy to oxidize and spontaneously combust, and is easy to grow up when the reduction control is not proper. Meanwhile, in the carbonization process, W powder and light carbon black are easy to mix unevenly, and the reduction carbonization is easy to cause component segregation.
Disclosure of Invention
Aiming at the defects of the existing nanometer WC powder production process, the invention aims to provide a method for preparing nanometer WC powder at low temperature and in short flow, and the problems to be solved are as follows: avoiding APT calcination-reduction to form various tungsten oxides, WO2.72The W powder reduced by the method is easy to oxidize and spontaneously combust, the W powder crystal grains are easy to grow up due to improper reduction control, and the component segregation is easy to cause when the W powder is mixed with carbon black.
In order to realize the purpose of the invention, the following technical scheme is adopted:
the invention discloses a method for preparing nano WC powder at low temperature and in a short process, which is characterized by comprising the following steps: the method comprises the steps of taking water-soluble ammonium metatungstate and glucose as raw materials, adding ammonium dichromate and ammonium metavanadate as inhibitors, adding the raw materials and the inhibitors into pure water, heating and stirring uniformly, and then carrying out spray drying, calcining and reduction carbonization processes to obtain the target product nano WC powder. The method specifically comprises the following steps:
1) ingredients
Mixing materials according to the mass percentage of 60-70% of water-soluble ammonium metatungstate, 29-38% of glucose, 0.1-1.0% of ammonium metavanadate and 0.1-1.0% of ammonium dichromate;
adding the materials into pure water which accounts for 0.4-1.5 times of the total mass of the materials, and uniformly stirring at 50-100 ℃ to obtain mixed slurry with the pH value of 1-5;
2) spray drying
Centrifugal spray drying is carried out on the mixed slurry obtained in the step 1) to obtain spherical precursor composite powder, wherein the centrifugal spray drying conditions are as follows: the air inlet temperature is 180-260 ℃, the air outlet temperature is 80-150 ℃, the rotation speed of the atomizer is 10000-15000 r/min, and the feeding speed is 2-4 kg/min;
3) calcination of
Introducing nitrogen into the spherical precursor composite powder obtained in the step 2) at the temperature of 450-650 ℃ for calcining for 30-90 min, and crushing a spherical shell by dry ball milling to obtain carbon-coated nano WO3Powder;
4) reduction carbonization
Coating the carbon obtained in the step 3) with nano WO3Feeding H into the powder at 850-1250 DEG C2And CH4According to the volume ratio (90-99): and (1) reducing and carbonizing the mixed gas formed in the step (1) to (10) for 30 to 120min to obtain the target product nano WC powder.
Compared with the prior art, the invention has the beneficial effects that:
1. the invention mixes ammonium metatungstate and glucose to prepare slurry by a solution method, so that tungsten and carbon atoms are uniformly mixed at a molecular level, and high-speed centrifugal spray drying is adopted to provide a premise for preparing nano powder, and the obtained precursor spherical powder has large specific surface area, thereby reducing W atoms and C atoms to form WAnd C, reducing and carbonizing the powder. The precursor composite powder prepared by spray drying ammonium metatungstate and glucose is calcined to form pure WO with single phase3And the problems that various tungsten oxides are easily formed in the APT calcination-reduction process, the tungsten oxides are reduced into tungsten powder to be spontaneously combusted, crystal grains grow up and the like, and the control is difficult are solved. At the same time, WO formed after calcination3The nano WC composite powder is synthesized by in-situ reaction with the activated carbon at low temperature, and component segregation and dirty caused by uneven mixing of W powder and carbon black in the traditional process are avoided.
2. The preparation method has the advantages of short process flow, simple process, less working procedures, low requirements on equipment and environment, and is more favorable for quality control of the nano tungsten carbide powder.
3. The nanometer WC powder prepared by the method has the advantages of stable performance, single phase, uniform components, narrow particle size distribution, fine crystal grains and easy control of powder components, and has the capacity of industrial and batch production.
Drawings
FIG. 1 is a schematic view of the preparation process of the nano WC powder of the invention;
FIG. 2 is an SEM photograph of a precursor composite powder obtained in example 2 of the present invention;
FIG. 3 shows carbon-coated nano-WO obtained in example 2 of the present invention3SEM photograph of the powder;
FIG. 4 shows carbon-coated nano-WO obtained in example 2 of the present invention3XRD photograph of powder
FIG. 5 is an SEM photograph of the nano WC powder obtained in example 2 of the present invention;
fig. 6 is an XRD photograph of the nano WC powder obtained in example 2 of the present invention;
fig. 7 is a SEM elemental surface distribution photograph of the nano WC powder obtained in example 2 of the present invention, in which: (a) WC powder; (b) a W element; (c) and C element.
Detailed Description
The following embodiments of the present invention will be described in detail with reference to the accompanying drawings, which are provided for implementing the technical solution of the present invention, and provide detailed embodiments and specific procedures, but the scope of the present invention is not limited to the following embodiments.
Example 1
This example prepares nano WC powder as follows:
1) ingredients
Dissolving 100Kg of water-soluble ammonium metatungstate, 54Kg of glucose, 0.6Kg of ammonium metavanadate and 0.9Kg of ammonium dichromate in pure water with the mass 1.0 time of the total mass of the solid, and uniformly stirring at 80 ℃ to obtain mixed slurry with the pH value of 4;
2) spray drying
Centrifugal spray drying is carried out on the mixed slurry obtained in the step 1) to obtain spherical precursor composite powder, wherein the centrifugal spray drying conditions are as follows: the air inlet temperature is 260 ℃, the air outlet temperature is 140 ℃, the rotational speed of the atomizer is 15000r/min, and the feeding rate is 3.4 kg/min;
3) calcination of
Introducing nitrogen into the spherical precursor composite powder obtained in the step 2) at the temperature of 600 ℃ for calcining for 60min, and crushing a spherical shell by dry ball milling to obtain carbon-coated nano WO3Powder;
4) reduction carbonization
Coating the carbon obtained in the step 3) with nano WO3Powder at 1200 ℃ in H2:CH4Reduction carbonization was performed for 60min under an atmosphere of (volume ratio) ═ 98.5:1.5, to obtain nano WC powder.
The physical properties and chemical composition of the obtained nano WC powder were measured in this example and the results are shown in table 1.
Example 2
This example prepares nano WC powder as follows:
1) ingredients
Dissolving 100Kg of water-soluble ammonium metatungstate, 49Kg of glucose, 0.4Kg of ammonium metavanadate and 0.8Kg of ammonium dichromate in pure water with the mass being 0.6 times of the total mass of the solid, and uniformly stirring at 60 ℃ to obtain mixed slurry with the pH value of 3.2;
2) spray drying
Carrying out centrifugal spray drying on the mixed slurry obtained in the step 1) to obtain precursor composite powder, wherein the centrifugal spray drying conditions are as follows: the air inlet temperature is 260 ℃, the air outlet temperature is 120 ℃, the rotating speed of the atomizer is 12000r/min, and the feeding rate is 3.0 kg/min;
the scanning electron microscope analysis of the precursor composite powder obtained in this example is performed, and the result is shown in fig. 2, which shows that the obtained precursor composite powder has a spherical structure, high sphericity, less breakage and good fluidity.
3) Calcination of
Introducing nitrogen into the spherical precursor composite powder obtained in the step 2) at 550 ℃ for calcining for 60min, and crushing a spherical shell by dry ball milling to obtain carbon-coated nano WO3Powder;
for the carbon-coated nano WO obtained in this example3The powder was analyzed by scanning electron microscopy, and the results are shown in fig. 3, which shows that the obtained carbon-coated nano tungsten oxide powder is easy to be broken and uniform in ball milling, and the sintered surface can be increased and the porosity can be reduced by ball milling).
For the carbon-coated nano WO obtained in this example3The powder was analyzed by X-ray diffraction, and the results are shown in FIG. 4, which shows that the obtained carbon-coated nano tungsten oxide powder is WO3The phase is pure and single, and no other tungsten oxide phase WO appears in the powder2.9、WO2.72、WO2。
4) Reduction carbonization
Subjecting the carbon-coated nano tungsten oxide powder obtained in the step 3) to H treatment at 1150 DEG C2:CH4Reduction carbonization was performed in an atmosphere of 97.5:2.5 (volume ratio) for 100min to obtain a nano WC powder.
The nano WC powder obtained in the embodiment is analyzed by a scanning electron microscope, and the result is shown in FIG. 5, which shows that the obtained nano WC powder has uniform grain size, small grain size and average grain size of 60 nm. .
The X-ray diffraction analysis of the nano WC powder obtained in this example showed that the nano WC powder obtained in this example was completely carbonized, had pure phase, was a simple WC phase, and did not have a carbon-deficient phase (W) as shown in fig. 62C、W3C、W)。
The element surface distribution of the nano WC powder obtained in this example was analyzed by a field emission scanning electron microscope at 10000 times magnification, and the results are shown in fig. 7, which shows that the obtained nano WC powder W, C has a uniform element distribution.
This example tested the physical properties and chemical composition of the resulting nano WC powder and the results are shown in table 1.
Example 3
This example prepares nano WC powder as follows:
1) ingredients
Dissolving 100Kg of water-soluble ammonium metatungstate, 46Kg of glucose, 0.3Kg of ammonium metavanadate and 0.9Kg of ammonium dichromate in pure water with mass being 0.8 times of the total mass of the solid, and uniformly stirring at 70 ℃ to obtain mixed slurry with pH of 3.4;
2) spray drying
Centrifugal spray drying is carried out on the mixed slurry obtained in the step 1) to obtain spherical precursor composite powder, wherein the centrifugal spray drying conditions are as follows: the air inlet temperature is 260 ℃, the air outlet temperature is 115 ℃, the rotational speed of the atomizer is 10000r/min, and the feeding rate is 2.8 kg/min;
3) calcination of
Introducing nitrogen into the spherical precursor composite powder obtained in the step 2) at 500 ℃ for calcination for 80min, and then crushing the spherical shell by dry ball milling to obtain carbon-coated nano WO3Powder;
4) reduction carbonization
Coating the carbon obtained in the step 3) with nano WO3Powder at 1100 deg.C in H2:CH4The reduction carbonization was performed for 120min under an atmosphere of 94.5:5.5 (volume ratio) to obtain a nano WC powder.
The physical properties and chemical composition of the obtained nano WC powder were measured in this example and the results are shown in table 1.
TABLE 1 physical Properties and chemical compositions of Nano WC powder obtained in examples of the invention
As can be seen from Table 1, the nano WC powder prepared by the method has the advantages of large specific surface area, low apparent density and wide particle size distribution range, and the particle size distribution range is narrow after airflow crushing and grading in the later period; the nano WC powder prepared by the method has low oxygen content and low free carbon content.
The present invention is not limited to the above exemplary embodiments, and any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (1)
1. A method for preparing nanometer WC powder at low temperature and in short flow is characterized in that: taking water-soluble ammonium metatungstate and glucose as raw materials, adding ammonium dichromate and ammonium metavanadate as inhibitors, adding the raw materials and the inhibitors into pure water, heating and stirring uniformly, and then carrying out spray drying, calcining and reduction carbonization processes to obtain a target product, namely nano WC powder; the method specifically comprises the following steps:
1) ingredients
Mixing 60-70% of water-soluble ammonium metatungstate, 29-38% of glucose, 0.1-1.0% of ammonium metavanadate and 0.1-1.0% of ammonium dichromate in percentage by mass;
adding the materials into pure water which accounts for 0.4-1.5 times of the total mass of the materials, and uniformly stirring at 50-100 ℃ to obtain mixed slurry with the pH value of 1-5;
2) spray drying
Centrifugal spray drying is carried out on the mixed slurry obtained in the step 1) to obtain spherical precursor composite powder, wherein the centrifugal spray drying conditions are as follows: the air inlet temperature is 180-260 ℃, the air outlet temperature is 80-150 ℃, the rotation speed of the atomizer is 10000-15000 r/min, and the feeding speed is 2-4 kg/min;
3) calcination of
Introducing nitrogen into the spherical precursor composite powder obtained in the step 2) at the temperature of 450-650 ℃ for calcining for 30-90 min, and crushing a spherical shell by dry ball milling to obtain carbon-coated nano WO3Powder;
4) reduction carbonization
Coating the carbon obtained in the step 3) with nano WO3Feeding H into the powder at 850-1250 DEG C2And CH4According to the volume ratio (90-99): (1E >10) And reducing and carbonizing the formed mixed gas for 30-120 min to obtain the target product nano WC powder.
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| CN109055796A (en) * | 2018-08-30 | 2018-12-21 | 浙江德威硬质合金制造有限公司 | Low temperature synthesis WC is the method that raw material produce hard alloy |
| CN108675299A (en) * | 2018-08-30 | 2018-10-19 | 浙江德威硬质合金制造有限公司 | Low temperature synthesizes the preparation method of WC |
| CN109128141B (en) * | 2018-09-30 | 2020-10-02 | 合肥工业大学 | Preparation method of nano WC-Co composite powder |
| CN110029261B (en) * | 2019-05-10 | 2020-07-14 | 重庆文理学院 | Preparation method of micro-nano hard alloy cutter material |
| CN110817879B (en) * | 2019-12-04 | 2021-06-18 | 北京科技大学 | Method for synthesizing nano WC powder by using carbon thermal reduction combustion precursor |
| CN112408485B (en) * | 2020-11-26 | 2023-02-03 | 江西理工大学 | Method for preparing tungsten oxide with array micro/nano structure |
| CN113184853B (en) * | 2021-05-26 | 2022-12-27 | 崇义章源钨业股份有限公司 | Superfine tungsten carbide powder and preparation method and application thereof |
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| CN103302309B (en) * | 2013-06-17 | 2016-04-20 | 南昌大学 | A kind of preparation method of nanometer tungsten carbide |
| CN103658677B (en) * | 2013-12-30 | 2016-06-08 | 北京科技大学 | The preparation method of a kind of nano powder of tungsten carbide |
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