CN114472913B - Preparation method of high-pressure blank strength tungsten powder - Google Patents
Preparation method of high-pressure blank strength tungsten powder Download PDFInfo
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Abstract
The application relates to a preparation method of high-pressure compact strength tungsten powder, which aims to further improve the dependence of the preparation method of tungsten powder on specific raw materials in the prior art and further improve the compact strength of the tungsten powder. The application improves the specific reduction process in the tungsten powder preparation process, and controls the hydrogen flow and the gas inlet and outlet flow ratio of the first reduction process, the second reduction process and the third reduction process in the hydrogen reduction process, and further controls the reduction temperature and the reduction time, thereby preparing the tungsten powder with higher green compact strength. The preparation method of the high-pressure compact strength tungsten powder can be suitable for a plurality of wide tungsten oxide raw materials such as yellow tungsten, blue tungsten, purple tungsten and the like, can stably prepare the tungsten powder with compact strength not less than 4.7MPa without adopting special tungsten oxide raw materials, and has very wide application market prospect.
Description
Technical Field
The application belongs to the field of powder metallurgy, and particularly relates to a preparation method of high-pressure compact strength tungsten powder.
Background
Tungsten is a nonferrous metal, also an important strategic metal, tungsten ore is called as "heavy stone" in ancient times, the tungsten content in crust is 0.001%, 20 tungsten-containing minerals have been found, and china is the largest tungsten storage country in the world. Tungsten has a high melting point, a low vapor pressure and a low evaporation rate. Tungsten has very stable chemical property, does not react with air and water at normal temperature, and does not react with any concentration of hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid and aqua regia when not heated. Tungsten has the advantages of high density, high melting point and boiling point, good high-temperature mechanical property, low vapor pressure, high hardness, high electric conductivity, low thermal expansion coefficient and the like, and is widely applied to manufacturing guns, nozzles of rocket propellers, armor-piercing bullets, metal-cutting blades, drills, superhard dies, wire-drawing dies and the like, and is also commonly used for optical instruments, chemical instruments and the like.
The tungsten crucible is one of common metal tungsten products, can be used in vacuum inert gas with the temperature of less than 2600 ℃, and is widely applied to industries such as rare earth smelting, quartz glass, crystal growth and the like due to the characteristics of small pollution and long service life. For the preparation of pure tungsten products like tungsten crucibles, it is required that the tungsten powder has a better formability and a higher green strength. The conventional tungsten powder has the advantages of concentrated particle size distribution, regular morphology and the like, but has the defects of poor formability, low green compact strength and the like, and is not beneficial to the preparation of tungsten crucibles. Therefore, the development of tungsten powder with high green strength has strong practical significance.
At present, research on preparing high-pressure blank strength tungsten powder mainly focuses on raw materials, and special raw materials (such as high-phase blue tungsten, transition state purple tungsten and the like) are adopted for batching, and then corresponding high-pressure blank strength tungsten powder is prepared through hydrogen reduction. However, the production of high-phase blue tungsten mainly uses a closed rotary furnace, and utilizes ammonia gas generated in the calcination process to decompose into hydrogen and nitrogen, and the hydrogen is used for deoxidizing tungsten oxide to prepare high-pressure compact strength tungsten powder. Because of closed calcination, water vapor generated by the reaction is difficult to remove, and the materials are agglomerated, so that the product quality is affected. Therefore, the production of the high-phase blue tungsten has the defects of easy agglomeration of materials, furnace blockage, high production cost, unstable component control and the like.
In order to improve the defect of the high-phase blue tungsten material, the patent CN112846210A discloses a method for using transition state purple tungsten as the material, wherein the transition state purple tungsten comprises most of purple tungsten and a small part of WO 2 According to the composition, reducing gas is introduced in the production process, water vapor generated by the reaction can be discharged in time, the oxygen content is reduced, and tungsten powder with higher green strength can be obtained after reduction under the hydrogen atmosphere, but the maximum green strength of the tungsten powder prepared by the method can reach 4.6MPa, the green strength of the tungsten powder needs to be further improved, and the quality of products needs to be further improved. Moreover, the method is still limited by the special choice of raw materials, and has high cost. In addition, patent CN112846211a adopts a method of feeding tungsten oxide into a tube furnace in a hydrogen gasThe tungsten powder with high compact strength is prepared by reduction under the atmosphere, but the embodiment shows that the maximum compact strength of the tungsten powder prepared by the method can reach 4.5MPa, the compact strength of the tungsten powder needs to be further improved, and the quality of the product needs to be further improved. Moreover, the method of arranging the air inlet pipe plug at the position close to the air inlet and the air outlet pipe plug at the position close to the air outlet in the pipe furnace is adopted, so that the production cost is increased, and the production efficiency and the quality of products can be influenced by the existence of the air pipe plug.
Therefore, most of the production processes or researches on high-pressure compact strength tungsten powder are carried out around the selection of raw materials or the addition of other devices, so that higher standards are provided for the preparation process and equipment of the tungsten powder, meanwhile, the production limitation of the tungsten powder is larger, the production efficiency and the production cost are required to be further improved, the compact strength of the tungsten powder is required to be further improved, and the quality of products is required to be further improved. Moreover, from the studies disclosed so far, there is no systematic study on improvements in the reduction process in the process of preparing tungsten powder. Therefore, the existing preparation method of the high-pressure billet strength tungsten powder needs to be further improved.
Disclosure of Invention
In order to further improve the compact strength of the tungsten powder, the application further improves the reduction process in the traditional tungsten powder preparation process, thereby providing an improved preparation method of the tungsten powder with high compact strength. The preparation method of the high-pressure compact strength tungsten powder can be suitable for various wide tungsten oxide raw materials such as yellow tungsten, blue tungsten, purple tungsten and the like, the raw materials with special composition types are not needed, the conventional tungsten oxide raw materials are adopted, and the tungsten powder with compact strength more than or equal to 4.7MPa can be stably prepared by adjusting the specific method and conditions of a hydrogen reduction process.
In one aspect of the application, a method of preparing high green strength tungsten powder is provided. The preparation method of the high-pressure billet strength tungsten powder comprises the following steps:
(1) Spreading a tungsten oxide raw material in a boat;
(2) Performing a first reduction process, wherein the hydrogen flow rate in the first reduction process is controlled to be 500-800L/h, and the air inlet/outlet flow rate ratio is 1:1;
(3) Performing a second reduction process, wherein the hydrogen flow rate in the second reduction process is controlled to be 300-500L/h, and the air inlet/outlet flow rate ratio is 1:0.9-0.8;
(4) Performing a third reduction process, wherein the hydrogen flow rate in the third reduction process is controlled to be 300-400L/h, and the air inlet and outlet flow rate ratio is 1:0.9-0.8;
(5) Sieving the reduced tungsten powder.
In addition, the method for preparing the high-pressure blank strength tungsten powder can also have the following additional technical characteristics:
further, the tungsten oxide raw material in the step (1) is specifically selected from one or more of yellow tungsten, blue tungsten or violet tungsten;
further, in the step (1), the thickness of the material layer horizontally paved in the boat is controlled to be 6-15 mm;
further, in the step (2), the reduction temperature in the first reduction process is 550-590 ℃, and the heat preservation time is 0.5-1.5 h;
further, in the step (3), the reduction temperature in the second reduction process is 790-840 ℃, and the heat preservation time is 1-3 h;
further, in the third reduction process in the step (4), the reduction temperature is 1000-1050 ℃, and the heat preservation time is 1-3 hours;
further, controlling the reduction temperatures of the first reduction process, the second reduction process and the third reduction process to be gradually increased in a gradient manner;
further, controlling the temperature difference between the second reduction process and the temperature in the first reduction process to be larger than the temperature difference between the third reduction process and the temperature in the second reduction process;
further, in the step (5), the reduced tungsten powder is sieved by a 200-mesh sieve, and coarse particles and mechanical inclusions are removed.
The application has the beneficial effects that:
1. by adopting the improved preparation method of the tungsten powder with high green compact strength, the tungsten powder with green compact strength more than or equal to 4.7MPa can be stably prepared, and the green compact strength and the product quality of the tungsten powder are further improved.
2. The application creatively realizes the increase of the hydrogen pressure in the furnace by controlling the gas inlet and outlet flow ratio of the furnace tube, thereby promoting the reduction reaction, increasing the generation of tungsten powder particles, enabling more tungsten powder with irregular morphology to be easily formed under the high pressure condition and effectively improving the compact strength of the tungsten powder.
3. The inventor researches find that the low-temperature reduction in the first reduction process is favorable for the generation of tungsten dioxide, and can effectively improve the particle size distribution of tungsten powder so as to ensure that the tungsten powder has a wider diameter distance. The inventor researches also find that tungsten powder with higher green strength can be better prepared by controlling the temperature difference between the temperature in the second reduction process and the temperature in the first reduction process to be larger than the temperature difference between the temperature in the third reduction process and the temperature in the second reduction process. Because the temperature difference between the second reduction process and the first reduction process is relatively large, the rapid reduction and sintering of tungsten powder can be better realized due to the large temperature difference, and tungsten powder with more irregular morphology and agglomeration morphology can be obtained while the wide particle size distribution is obtained, so that tungsten powder with higher green compact strength is obtained. In addition, because the tungsten powder has obvious edges in the pressing process to increase sliding resistance, the inter-particle bridging phenomenon is generated, the phenomenon becomes a fracture source of the tungsten powder green compact, and finally the green compact strength is reduced. The application can reduce the oxygen content in the powder by controlling the high temperature in the third reduction process and smoothly agglomerate the surface of the particles at the same time, thereby improving the pressing density of tungsten powder. However, if the temperature difference between the temperature in the third reduction process and the temperature in the second reduction process is too large, the prepared tungsten powder green compact is more likely to generate a fracture phenomenon. Therefore, the temperature difference between the third reduction process and the second reduction process is controlled to be relatively smaller, so that the green compact strength of the tungsten powder is further improved.
Detailed Description
The present application will be further described in the following examples for the purpose of more clearly understanding the objects, technical solutions and advantageous effects of the present application, but the scope of the present application is not limited to the following examples, which are given by way of illustration only and are not intended to limit the scope of the present application in any way. The instruments and devices referred to in the following examples are conventional instruments and devices unless otherwise specified; the related raw materials are all commercial conventional industrial raw materials unless specified; the processing and manufacturing methods are conventional methods unless otherwise specified. It should be understood that the description is only illustrative and is not intended to limit the scope of the application. In addition, in the following description, descriptions of well-known structures and techniques are omitted so as not to unnecessarily obscure the present application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated.
In one aspect of the application, a method of preparing high green strength tungsten powder is provided. The preparation method of the high-pressure billet strength tungsten powder comprises the following steps:
(1) Spreading a tungsten oxide raw material in a boat;
(2) Performing a first reduction process, wherein the hydrogen flow rate in the first reduction process is controlled to be 500-800L/h, and the air inlet/outlet flow rate ratio is 1:1;
(3) Performing a second reduction process, wherein the hydrogen flow rate in the second reduction process is controlled to be 300-500L/h, and the air inlet/outlet flow rate ratio is 1:0.9-0.8;
(4) Performing a third reduction process, wherein the hydrogen flow rate in the third reduction process is controlled to be 300-400L/h, and the air inlet and outlet flow rate ratio is 1:0.9-0.8;
(5) Sieving the reduced tungsten powder.
Further, the hydrogen flow rate in the first reduction process is controlled to be 500-800L/h; controlling the hydrogen flow rate in the second reduction process to be 300-500L/h; controlling the hydrogen flow rate in the third reduction process to be 300-400L/h. The inventor finds that the high-pressure blank strength tungsten powder can be prepared more easily by controlling the hydrogen flow rates in the three reduction processes within the above ranges. Because the reduction temperature in the first reduction process is lower, the low-temperature reduction is favorable for the generation of tungsten dioxide, and the particle size distribution of tungsten powder can be effectively improved, so that the tungsten powder has a wider diameter distance, and therefore, the tungsten powder with high green strength can be obtained more easily. Therefore, the hydrogen flow rate in the first reduction process is controlled to be 500-800L/h, and the reaction is quicker and more sufficient by adopting larger hydrogen flow rate. And because the flow rate ratio of the gas inlet and the gas outlet in the first reduction process is 1:1, the gas flows smoothly, the hydrogen with larger flow rate can realize fast inlet and fast outlet, the reaction is more sufficient, and the quality of the product is improved. In addition, the inventor found that if the hydrogen flow rate is too high, the moisture generated by the reaction is discharged quickly, and the tungsten powder has finer granularity; if the hydrogen flow is too low, the water produced by the reaction is slowly discharged, and the tungsten powder has coarser granularity. Therefore, by adopting the medium hydrogen flow range of the application, the optimal reaction rate and yield can be ensured, the cost is reduced, and the tungsten powder with relatively higher green compact strength can be prepared.
Further, the air inlet/outlet flow rate ratio in the first reduction process is controlled to be 1:1; controlling the air inlet and outlet flow ratio in the second reduction process to be 1:0.9-0.8; controlling the air inlet and outlet flow ratio in the third reduction process to be 1:0.9-0.8. The inventor creatively realizes the increase of the gas pressure in the furnace by controlling the gas inlet and outlet flow rate ratio of the furnace tube, because the gas inlet and outlet flow rate ratio in the second reduction process and the third reduction process is larger than 1, the water vapor and volatile substances generated in the reaction process can not be completely and effectively discharged, so the water vapor and volatile substances gradually accumulate in the furnace tube, a certain pressure difference can be formed in the furnace tube, on one hand, the increase of the hydrogen pressure in the furnace tube can promote the reduction reaction to be more rapidly carried out, the generation of tungsten powder particles is increased, and on the other hand, the water vapor and volatile substances generated in the reaction process can not be timely discharged, so that the tungsten powder with more irregular shapes can be promoted to be formed, and the compact strength of the tungsten powder is effectively improved.
Further, the tungsten oxide raw material in the step (1) is specifically selected from one or more of yellow tungsten, blue tungsten or violet tungsten; in the W-O system, there are four stable oxides: yellow oxide (WO) 3 ) Blue oxide (WO 2.90 ) Purple oxide (WO 2.72 ) And tan oxide (WO) 2 ). Blue tungsten oxide refers to a series of non-integer ratio oxides of tungsten. Chemical formula of WO x Representing mainly WO 2.9 . Each tungsten oxide has its unique crystal structure and is therefore physicalThe chemical properties are also different. The method of the application can be widely applied to various common tungsten oxide raw materials such as yellow tungsten, blue tungsten or purple tungsten, and the like due to improvement of the hydrogen reduction process.
Further, in the step (1), the thickness of the material layer flatly paved in the boat is controlled to be 6-15 mm; in order to make the subsequent hydrogen reduction effect better, the thickness of the material layer of the tungsten oxide raw material paved in the boat is preferably controlled to be 6-15 mm. The inventor finds that if the thickness of the material layer is too high, the reaction is incomplete, and the product quality is affected; if the thickness of the material layer is too low, the yield is small and the powder particle size is fine. Specifically, in the hydrogen reduction process, hydrogen enters the interior of particles and reacts with the interior and the surface of the particles, if the thickness of a material layer is too low, water vapor generated by the reaction is discharged in time, and the action of a volatilization-deposition growth mechanism is low, so that the granularity of the prepared tungsten powder is finer, and under the process condition that the reduction is thorough, the thickness of the material layer can be increased to meet the granularity requirement of the powder, and meanwhile, the yield is effectively improved. Therefore, the optimal reaction rate and yield can be ensured by adopting the thickness of the material layer of the application, and the tungsten powder with relatively higher green compact strength can be prepared.
Further, in the step (2), the reduction temperature in the first reduction process is 550-590 ℃, and the heat preservation time is 0.5-1.5 h;
further, in the step (3), the reduction temperature in the second reduction process is 790-840 ℃, and the heat preservation time is 1-3 h;
further, in the third reduction process in the step (4), the reduction temperature is 1000-1050 ℃, and the heat preservation time is 1-3 hours;
further, the temperature of the first reduction process is controlled to be 550-590 ℃, the heat preservation time is controlled to be 0.5-1.5 h, the temperature of the second reduction process is controlled to be 790-840 ℃, the heat preservation time is controlled to be 1-3 h, the temperature of the third reduction process is controlled to be 1000-1050 ℃, and the heat preservation time is controlled to be 1-3 h. The inventor researches and discovers that the high-pressure billet strength tungsten powder is easier to prepare in the reasonable temperature range.
Further, the reduction temperatures of the first reduction process, the second reduction process and the third reduction process are controlled to be gradually increased in a gradient manner. The increasing reaction temperature can lead the reduction process to be orderly carried out, and the granularity and the morphology of the tungsten powder can be effectively controlled. The uniform reduction temperature is difficult to effectively control the granularity and morphology of tungsten powder, the granularity of the powder is coarse when the temperature is too high, the reaction time is long when the temperature is too low, and the phenomenon of incomplete reduction is easy to occur. The increasing reaction temperature does not cause the reduction temperature to suddenly increase or suddenly decrease to cause abnormal internal structure of tungsten powder, and the green compact strength of the tungsten powder is reduced. In addition, because the tungsten powder can increase sliding resistance due to obvious edges in the pressing process, the inter-particle bridging phenomenon is generated, thereby becoming a fracture source of the tungsten powder green compact and finally reducing the compact strength of the tungsten powder green compact. The high temperature range in the third reduction process is controlled to be 1000-1050 ℃, the high temperature reduction can reduce the oxygen content in the powder, and the surface of the agglomerated particles is smooth, so that the pressing density and the green compact strength of the tungsten powder are improved.
Further, the inventors have studied to find that by controlling the reduction times of the first, second and third reduction processes within the above-described ranges, it is possible to more easily produce tungsten powder of high green strength. The longer the heat preservation time is, the sintering growth among tungsten powder particles is carried out to form a sintering neck, which is not beneficial to the improvement of the pressed compact strength, and the production efficiency is reduced, so that the production cost is high; and the heat preservation time is too short, so that the powder reduction reaction is incomplete, and the product quality is further affected. Therefore, the reduction temperature and the heat preservation time in the range can ensure the optimal reaction rate and yield, reduce the cost and prepare the tungsten powder with relatively higher green compact strength.
Further, the inventor researches have found that by controlling the temperature difference between the second reduction process and the first reduction process to be larger than the temperature difference between the third reduction process and the second reduction process, tungsten powder with higher green strength can be better prepared. Because the temperature difference between the second reduction process and the first reduction process is relatively large, the rapid reduction and sintering of tungsten powder can be better realized due to the large temperature difference, and tungsten powder with more irregular morphology and agglomeration morphology can be obtained while the wide particle size distribution is obtained, so that tungsten powder with higher green compact strength is obtained. On the contrary, if the temperature difference between the temperature in the third reduction process and the temperature in the second reduction process is too large, the third reduction temperature is too high, so that the influence on the reduction reaction and the morphology of the tungsten powder is large, and the prepared tungsten powder is easier to generate fracture phenomenon, so that the pressed compact strength of the tungsten powder is influenced. Therefore, the temperature difference between the third reduction process and the second reduction process is controlled to be smaller than the temperature difference between the second reduction process and the first reduction process, so that tungsten powder with wide particle size distribution and more irregular morphology and agglomeration morphology can be better obtained, and the green compact strength of the tungsten powder is further improved.
Further, in the step (5), the reduced tungsten powder is sieved by a 200-mesh sieve, and coarse particles and mechanical inclusions are removed.
The application will now be described with reference to specific examples, which are intended to be illustrative only and not limiting in any way.
Embodiment one:
1. the tungsten yellow is used as raw material, which is spread in a boat, and the thickness of the material layer is controlled at 7mm.
2. The temperature is kept for 1.5h at 550 ℃, the hydrogen flow is 500L/h, and the air inlet and outlet flow ratio is 1:1.
3. Preserving the heat for 1.5h at 800 ℃, wherein the hydrogen flow is 300L/h, and the air inlet and outlet flow ratio is 1:0.9.
4. Preserving the heat for 3h at 1050 ℃, wherein the hydrogen flow is 300L/h, and the gas inlet and outlet flow ratio is 1:0.9.
5. And (3) sieving the reduced tungsten powder with a 200-mesh sieve to remove coarse particles and mechanical inclusions.
6. The strength of the tungsten powder compact is 4.7Mpa.
Embodiment two:
1. the tungsten yellow is used as raw material, which is spread in a boat, and the thickness of the material layer is controlled at 7mm.
2. Preserving the heat for 0.8h at 590 ℃, wherein the hydrogen flow is 800L/h, and the air inlet/outlet flow ratio is 1:1.
3. The temperature is kept for 2.5h at 840 ℃, the hydrogen flow is 500L/h, and the air inlet and outlet flow ratio is 1:0.9.
4. Preserving heat for 2h at 1000 ℃, wherein the hydrogen flow is 400L/h, and the air inlet and outlet flow ratio is 1:0.9.
5. And (3) sieving the reduced tungsten powder with a 200-mesh sieve to remove coarse particles and mechanical inclusions.
6. The strength of the tungsten powder compact is 5.0Mpa.
Embodiment III:
1. the tungsten yellow is used as raw material, which is spread in a boat, and the thickness of the material layer is controlled at 9mm.
2. Preserving heat for 1h at 570 ℃, wherein the hydrogen flow is 600L/h, and the air inlet and outlet flow ratio is 1:1.
3. The temperature is kept for 3 hours at 820 ℃, the hydrogen flow is 4500L/h, and the air inlet/outlet flow ratio is 1:0.9.
4. The temperature is kept for 1.5h at 1020 ℃, the hydrogen flow is 350L/h, and the air inlet and outlet flow ratio is 1:0.9.
5. And (3) sieving the reduced tungsten powder with a 200-mesh sieve to remove coarse particles and mechanical inclusions.
6. The strength of the tungsten powder compact is 5.3Mpa.
Embodiment four:
1. the tungsten yellow is used as raw material, which is spread in a boat, and the thickness of the material layer is controlled at 7mm.
2. Preserving the heat for 0.8h at 590 ℃, wherein the hydrogen flow is 800L/h, and the air inlet/outlet flow ratio is 1:1.
3. Preserving the heat for 2.5h at 840 ℃, wherein the hydrogen flow is 400L/h, and the gas inlet and outlet flow ratio is 1:0.8.
4. The temperature is kept for 2 hours at 1050 ℃, the hydrogen flow is 400L/h, and the gas inlet and outlet flow ratio is 1:0.9.
5. And (3) sieving the reduced tungsten powder with a 200-mesh sieve to remove coarse particles and mechanical inclusions.
6. The strength of the tungsten powder compact is 5.8Mpa.
Fifth embodiment:
1. blue tungsten is used as a raw material, the blue tungsten is flatly paved in a boat, and the thickness of a material layer is controlled to be 7mm.
2. Preserving the heat for 0.8h at 590 ℃, wherein the hydrogen flow is 800L/h, and the air inlet/outlet flow ratio is 1:1.
3. Preserving the heat for 2.5h at 840 ℃, wherein the hydrogen flow is 400L/h, and the gas inlet and outlet flow ratio is 1:0.8.
4. The temperature is kept for 2 hours at 1050 ℃, the hydrogen flow is 400L/h, and the gas inlet and outlet flow ratio is 1:0.9.
5. And (3) sieving the reduced tungsten powder with a 200-mesh sieve to remove coarse particles and mechanical inclusions.
6. The strength of the tungsten powder compact is 6.4Mpa.
Example six:
1. the purple tungsten is used as a raw material, the purple tungsten is flatly paved in a boat, and the thickness of a material layer is controlled to be 13mm.
2. Preserving the heat for 0.8h at 590 ℃, wherein the hydrogen flow is 800L/h, and the air inlet/outlet flow ratio is 1:1.
3. Preserving the heat for 2.5h at 840 ℃, wherein the hydrogen flow is 400L/h, and the gas inlet and outlet flow ratio is 1:0.8.
4. The temperature is kept for 2 hours at 1050 ℃, the hydrogen flow is 400L/h, and the air inlet and outlet flow ratio is 1:0.8.
5. And (3) sieving the reduced tungsten powder with a 200-mesh sieve to remove coarse particles and mechanical inclusions.
6. The strength of the tungsten powder compact is 6.1Mpa.
Comparative example one:
1. the tungsten yellow is used as raw material, which is spread in a boat, and the thickness of the material layer is controlled at 7mm.
2. Preserving the heat for 0.8h at 590 ℃, wherein the hydrogen flow is 800L/h, and the air inlet/outlet flow ratio is 1:1.
3. Preserving the heat for 2.5h at 840 ℃, wherein the hydrogen flow is 400L/h, and the air inlet and outlet flow ratio is 1:1.
4. Preserving heat for 2h at 1050 ℃, wherein the hydrogen flow is 400L/h, and the gas flow ratio of inlet and outlet is 1:1.
5. And (3) sieving the reduced tungsten powder with a 200-mesh sieve to remove coarse particles and mechanical inclusions.
6. The strength of the tungsten powder compact is 3.6Mpa.
Comparative example two:
1. the tungsten yellow is used as raw material, which is spread in a boat, and the thickness of the material layer is controlled at 7mm.
2. The temperature is kept for 1h at 590 ℃, the hydrogen flow is 800L/h, and the air inlet/outlet flow ratio is 1:1.
3. Preserving heat for 1h at 840 ℃, wherein the hydrogen flow is 400L/h, and the air flow ratio of inlet and outlet is 1:1.
4. Preserving the heat for 1h at 1050 ℃, wherein the hydrogen flow is 400L/h, and the gas flow ratio of inlet and outlet is 1:1.
5. And (3) sieving the reduced tungsten powder with a 200-mesh sieve to remove coarse particles and mechanical inclusions.
6. The strength of the tungsten powder compact is 3.0Mpa.
Comparative example three:
1. the method comprises the steps of taking tungsten yellow as a raw material, spreading the tungsten yellow in a boat, controlling the thickness of a material layer to be 6mm, then placing the boat in a tube furnace with a furnace plug, reducing the boat in a hydrogen atmosphere, controlling the flow of hydrogen supplied through an air inlet to be 300L/h, wherein the tube furnace comprises three reduction belts (namely a first reduction belt, a second reduction belt and a third reduction belt in sequence), the temperature of the first reduction belt is controlled to be 700 ℃, the heat preservation time is 1h, the temperature of the second reduction belt is controlled to be 820 ℃, the heat preservation time is 1h, the temperature of the third reduction belt is controlled to be 950 ℃, and the heat preservation time is 1h.
2. And (3) sieving the reduced high-pressure compact strength tungsten powder with a 200-mesh sieve to remove coarse particles and mechanical inclusions.
3. The strength of the tungsten powder compact is 4.5Mpa.
Comparative example four:
1. the tungsten yellow is used as raw material, which is spread in a boat, and the thickness of the material layer is controlled at 7mm.
2. Preserving the heat for 0.8h at 590 ℃, wherein the hydrogen flow is 800L/h, and the air inlet/outlet flow ratio is 1:1.
3. Preserving the heat for 2.5h at 840 ℃, wherein the hydrogen flow is 400L/h, and the air inlet and outlet flow ratio is 1:1.
4. The temperature is kept for 2 hours at 1050 ℃, the hydrogen flow is 400L/h, and the gas inlet and outlet flow ratio is 1:0.9.
5. And (3) sieving the reduced tungsten powder with a 200-mesh sieve to remove coarse particles and mechanical inclusions.
6. The strength of the tungsten powder compact is 4.7Mpa.
Comparative example five:
1. the tungsten yellow is used as raw material, which is spread in a boat, and the thickness of the material layer is controlled at 7mm.
2. Preserving the heat for 0.8h at 590 ℃, wherein the hydrogen flow is 800L/h, and the air inlet/outlet flow ratio is 1:1.
3. Preserving the heat for 2.5h at 840 ℃, wherein the hydrogen flow is 400L/h, and the gas inlet and outlet flow ratio is 1:0.8.
4. Preserving heat for 2h at 1050 ℃, wherein the hydrogen flow is 400L/h, and the gas flow ratio of inlet and outlet is 1:1.
5. And (3) sieving the reduced tungsten powder with a 200-mesh sieve to remove coarse particles and mechanical inclusions.
6. The strength of the tungsten powder compact is 4.9Mpa.
Comparative example six:
1. the tungsten yellow is used as raw material, which is spread in a boat, and the thickness of the material layer is controlled at 7mm.
2. Preserving the heat for 0.8h at 590 ℃, wherein the hydrogen flow is 800L/h, and the air inlet/outlet flow ratio is 1:1.
3. Preserving the heat for 2.5h at 780 ℃, wherein the hydrogen flow is 400L/h, and the air inlet and outlet flow ratio is 1:0.8.
4. The temperature is kept for 2 hours at 1050 ℃, the hydrogen flow is 400L/h, and the gas inlet and outlet flow ratio is 1:0.9.
5. And (3) sieving the reduced tungsten powder with a 200-mesh sieve to remove coarse particles and mechanical inclusions.
6. The strength of the tungsten powder compact is 5.2Mpa.
The high green strength tungsten powder green strength measurements obtained in examples and comparative examples are shown in table 1 below:
TABLE 1
| Numbering device | Green compact strength (MPa) | Numbering device | Green compact strength (MPa) |
| Example 1 | 4.7Mpa | Example 2 | 5.0Mpa |
| Example 3 | 5.3Mpa | Example 4 | 5.8Mpa |
| Example 5 | 6.4Mpa | Example 6 | 6.1Mpa |
| Comparative example 1 | 3.6Mpa | Comparative example 2 | 3.0Mpa |
| Comparative example 3 | 4.5Mpa | Comparative example 4 | 4.7Mpa |
| Comparative example 5 | 4.9Mpa | Comparative example 6 | 5.2Mpa |
Therefore, the tungsten powder prepared by the method has relatively higher green compact strength, and the green compact strength of the prepared tungsten powder is more than or equal to 4.7MPa.
The above embodiments are only illustrative of and explain the present application and should not be construed as limiting the scope of the application. All techniques implemented based on the above description of the application are intended to be included within the scope of the application.
Claims (5)
1. The preparation method of the high-pressure blank strength tungsten powder is characterized by comprising the following steps of:
(1) Spreading a tungsten oxide raw material in a boat;
(2) Performing a first reduction process, wherein the hydrogen flow rate in the first reduction process is controlled to be 600-800L/h, and the air inlet/outlet flow rate ratio is 1:1; the reduction temperature in the first reduction process is 550-590 ℃, and the heat preservation time is 0.5-1.5 h;
(3) Performing a second reduction process, wherein in the second reduction process, the hydrogen flow is controlled to be 300-500L/h, and the air inlet/outlet flow ratio is 1:0.9-0.8; the reduction temperature in the second reduction process is 790-840 ℃, and the heat preservation time is 1-3 h;
(4) Performing a third reduction process, wherein in the third reduction process, the hydrogen flow is controlled to be 300-400L/h, and the air inlet and outlet flow ratio is 1:0.9-0.8; the reduction temperature in the third reduction process is 1000-1050 ℃, and the heat preservation time is 1-3 h;
(5) Sieving the reduced tungsten powder;
controlling the reduction temperatures of the first reduction process, the second reduction process and the third reduction process to gradually increase in a gradient manner; the temperature difference between the temperature in the second reduction process and the temperature in the first reduction process is controlled to be larger than the temperature difference between the temperature in the third reduction process and the temperature in the second reduction process.
2. The method for producing high-pressure green strength tungsten powder according to claim 1, wherein the tungsten oxide raw material in step (1) is specifically selected from one or more of yellow tungsten, blue tungsten and violet tungsten.
3. The method of preparing high-pressure green strength tungsten powder according to any one of claims 1 to 2, wherein the thickness of the layer of material laid in the boat in step (1) is controlled to be 6 to 15mm.
4. The method for producing high-strength tungsten powder according to claim 1, wherein the reduced tungsten powder in step (5) is passed through a 200-mesh sieve to remove coarse particles and mechanical inclusions.
5. A high green strength tungsten powder prepared by the method of any one of claims 1-4.
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