High-performance potassium-doped tungsten rod and preparation method and application thereof

Abstract

The invention discloses a high-performance potassium-doped tungsten rod and a preparation method and application thereof, and belongs to the technical field of powder metallurgy, and the method relates to the steps of material selection, pre-reduction, vacuum spray doping, reduction, batch pickling, mixing, hard film cold isostatic pressing forming, low-temperature impurity removal, vertical melting pre-sintering, medium-frequency sintering and the like. By accurately controlling the rare earth element doping process and optimizing doping agent preparation, uniform distribution of rare earth elements in the tungsten rod is achieved, and compared with the prior art, the grain refinement effect and the mechanical performance of the high-performance potassium-doped tungsten rod are remarkably improved. The prepared potassium-doped tungsten rod has the advantages of small average grain size and high bending resistance, is suitable for the fields of cathode materials of electronic devices, heating elements of high-temperature furnaces, filaments in the lighting industry, high-temperature furnaces in the semiconductor industry and the like, and meets the requirements of the modern industry for high-performance tungsten materials.

Description

Technical Field

[0001] The invention relates to the technical field of powder metallurgy, and in particular to a high-performance potassium-doped tungsten rod and a preparation method and application thereof. Background Art

[0002] In modern industry and technology, tungsten and its alloy materials are widely used in various fields due to their excellent physical and chemical properties, including but not limited to electronic devices, high-temperature furnace heating elements, filaments in the lighting industry, high-temperature furnaces and ion implantation machine parts in the semiconductor industry, wire cutting in the photovoltaic industry, radiotherapy and diagnostic equipment parts for medical equipment, and industrial heating elements, etc. These applications place extremely high demands on the performance of tungsten materials, especially in terms of high-temperature stability, mechanical strength, electron emission performance, and wear resistance.

[0003] The existing tungsten rod preparation technology has been able to produce tungsten rod products with certain performance, but in some high-performance applications, the existing tungsten rod performance still has limitations. For example, traditional tungsten rods may show poor creep resistance at high temperatures, large grain size, resulting in insufficient strength and toughness of the material, as well as insufficient electron emission performance. These problems limit the use of tungsten rods in higher performance applications.

[0004] To solve these problems, researchers have been exploring ways to improve the performance of tungsten materials by doping with rare earth elements. Rare earth element doping can refine the grains, improve the thermal stability and mechanical properties of the material, and thus enhance the overall performance of the tungsten rod. However, the uniform distribution and effective doping of rare earth elements remain a technical challenge. Traditional doping methods may lead to uneven distribution of rare earth elements, affecting the uniformity of material properties.

[0005] In the prior art, Chinese invention patent CN117604307A discloses a rare earth tungsten rod and its preparation method. The rare earth oxide is pretreated in advance. By controlling the moisture content of the rare earth oxide, the strength of the pressed tungsten rod blank can be improved, and it is not easy to be damaged during transportation and sintering, and the molding is good; and the water-containing rare earth oxide and tungsten are divided into equal parts, and the mixing is carried out by adding multiple alternating mixing methods to avoid the rare earth oxide powder in the mixer. Dead corners and uneven mixing can be avoided, and the uniform distribution of rare earth oxide in tungsten powder can be improved. After implementation, the rare earth oxide of the rare earth tungsten rod is uniformly doped; the density of the rare earth tungsten rod prepared by the invention is 17.8-18.8 g / cm 3 , the diameter is 20-22mm, the number of grains in the radial section of the tungsten rod is 3000-3600, the extreme difference of rare earth element content in different regions is less than 0.05%, and the porosity is less than 5%. However, the average grain size of the rare earth tungsten rod obtained by the invention is still large, and the bending resistance is not high. Summary of the invention

[0006] In view of the limitations of the prior art, the present invention aims to provide a high-performance potassium-doped tungsten rod and a preparation method and application thereof. By precisely controlling the doping process and optimizing the preparation of the dopant, the rare earth elements are evenly distributed in the tungsten rod, thereby significantly improving the grain refinement effect and mechanical properties of the tungsten rod to meet the needs of higher performance applications.

[0007] In view of the existing technology, the present invention provides a high-performance potassium-doped tungsten rod and its preparation method and application

[0008] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0009] A method for preparing a high-performance potassium-doped tungsten rod is as follows:

[0010] (1) Material selection

[0011] Monoclinic ammonium paratungstate and spherical ammonium paratungstate are mixed as production raw materials;

[0012] (2) Pre-reduction

[0013] Using a reduction furnace with no less than four temperature zones to pre-reduce the production raw material obtained in step (1) to obtain ammonium tungsten bronze;

[0014] (3) Vacuum spray doping

[0015] In the first stage, the ammonium tungsten bronze obtained in step (2) is placed in a vacuum doping container and evacuated to ≤500Pa;

[0016] In the second stage, potassium hydroxide, silicic acid and aluminum nitrate are dissolved in water, and nitric acid is added and stirred continuously to form a doping solution. Subsequently, the doping solution is heated to 40-50° C. and sprayed through the spray hole of the vacuum doping container, and the spray valve is opened to 1 / 5-1 / 3 to ensure that 1 / 4-1 / 2 of the doping solution is sprayed within 1-2 hours. During this process, the steam valve is opened to 1 / 4-1 / 2 to maintain a steam pressure of 0.1-0.2 MPa, and the power of the vacuum pump is maintained at 20%-40%, while ensuring continuous stirring and heating of the materials in the container to maintain the temperature in the furnace at 55-85° C.;

[0017] In the third stage, the stirring frequency of the container is increased, the temperature in the furnace is maintained at 85-95°C, and the remaining doping solution is sprayed in within 30-50 minutes. At this time, the steam valve is opened to 2 / 5-4 / 5, the steam pressure is maintained at 0.1-0.2MPa, and the vacuum pump power is maintained at 20%-40%;

[0018] In the fourth stage, after the doping agent is sprayed, the steam valve is fully opened, the steam pressure is increased to 0.2-0.3MPa, and the temperature in the furnace is increased to 100-120℃, and the drying is continued for 3-4 hours until the water is completely evaporated. Subsequently, the vacuum pump power is increased to 70-90%. When the vacuum degree in the vacuum doping container reaches 400-500MPa, the steam heating system is turned off, and water cooling is performed until the temperature in the furnace drops to 50-55℃. Finally, the discharge valve is opened and the 20-100 mesh screen is passed to obtain potassium-ammonium-doped tungsten bronze.

[0019] (4) Restore

[0020] Using a five-temperature zone reduction furnace to reduce the potassium-ammonium-doped tungsten bronze obtained in step (3) to obtain potassium-doped tungsten powder;

[0021] (5) Batch pickling

[0022] The potassium-doped tungsten powder obtained in step (4) is washed with 3-5 mol / L dilute hydrochloric acid and 1-3 mL / L dilute hydrofluoric acid to remove ineffective potassium and other impurities, and then washed with 50-70° C. water, dried, and crushed through a 150-170 mesh sieve to obtain acid-washed potassium-doped tungsten powder;

[0023] (6) Mixing

[0024] The acid-washed potassium-doped tungsten powder obtained in step (5) is mixed in a high-speed mixer under nitrogen protection for 60 to 120 minutes, cooled to 40 to 50° C., and then passed through a 150 to 200 mesh sieve to obtain a potassium-doped powder;

[0025] (7) Hard film cold isostatic pressing

[0026] According to the requirement of 3000g-4000g / piece, the potassium-doped powder obtained in step (6) is loaded into a rubber hard mold sleeve with a length of 700mm-900mm, an inner diameter of 25.5mm-27mm, and a wall thickness of 1.8mm-2.2mm, vibrated, sealed and tightened, placed in a cold isostatic press, and pressed at a pressure of 140-170MPa to obtain a potassium-doped tungsten green body;

[0027] (8) Low temperature impurity removal

[0028] The potassium-doped tungsten green body obtained in step (7) is fired in a hydrogen protection furnace at 1000-1100° C. for 40-60 minutes to improve the strength, thereby obtaining a potassium-doped tungsten green body with improved strength;

[0029] (9) Vertical melting pre-sintering

[0030] The potassium-doped tungsten blank obtained in step (8) is pre-sintered in a vertical melting furnace, and more than 95% of impurities are removed under the protection of hydrogen. The appearance is dark gray, and the upper and lower sections are uniformly crystallized without any frame crystals. An incompletely dense potassium-doped tungsten rod is obtained;

[0031] (10) Medium frequency sintering

[0032] The incompletely dense potassium-doped tungsten rod obtained in step (9) is sintered in a medium frequency furnace and placed vertically in a stacking firing manner. The sintering is performed under hydrogen protection by adopting a double hydrogen feeding method at the bottom and top of the furnace. The sintering process is automatically controlled by an infrared temperature measurement + PLC temperature control system; and a high-performance potassium-doped tungsten rod is obtained.

[0033] In the material selection of step (1), monoclinic ammonium paratungstate and spherical ammonium paratungstate are mixed in a weight ratio of 4:1 to 1.5.

[0034] In the step (2), the temperatures of the four temperature zones in the pre-reduction are 300°C to 330°C, 390°C to 410°C, 410°C to 430°C, and 430°C to 450°C, respectively, and the hydrogen flow rate is 0.3m 3 / h~0.4m 3 / h, the pre-reduction boat weight is 720g-800g, passed through a 20-100 mesh sieve, and pushed for 10-20 minutes.

[0035] In the second stage of the vacuum spray doping in step (3), the contents of various substances are 2 to 3 parts by weight of potassium hydroxide, 4.5 to 5.5 parts by weight of silicic acid, and 1.8 to 3 parts by weight of aluminum nitrate solids, which are completely dissolved in 50 to 70 L of water at 50 to 70° C., and then 0.5 to 2 L of 2 to 5 mol / L dilute nitric acid is added.

[0036] The temperatures of the five temperature zones in the reduction step (4) are 660°C to 680°C, 710°C to 740°C, 790°C to 820°C, 820°C to 840°C, and 840°C to 870°C, respectively, and the hydrogen flow rate is 4m 3 / h~7m 3 / h, the boat loading amount is 350g ~ 550g, and the effective reduction time is 6h ~ 8h.

[0037] In the step (9), the pre-sintering is carried out in the following order: heating, heating, heat preservation, and heat preservation;

[0038] The current / time parameters are as follows: heating (0A~2800A) / 5min, heating (2800A~3850A) / 6min, heating (3850A~4820A) / 6min, keeping warm (4820A~4820A) / 21min;

[0039] Hydrogen flow rate is 1.8~2.2m 3 / h.

[0040] In the step (10), the sintering system is sequentially heating, heat preservation, heating, heat preservation, heating, heat preservation, heating, heat preservation, heating, heat preservation, heating, heat preservation, heating, and heat preservation; the temperature / time parameters are sequentially: (0-1250°C) / 430min, heat preservation: 1250°C / 90min, heating (1250-1500°C) / 150min, heat preservation 1500°C / 120min, heating (1500-1500°C) / 120min, heat preservation 1500°C / 120min, heating (1500-1500°C) / 120min, heat preservation 1500°C / 120min, heat preservation 1500°C / 120min, heat preservation 1500°C / 120min, heat preservation 1500°C / 120min, heat preservation 1500°C / 120 1800℃) / 361min, keep warm at 1800℃ / 150min, heat up (1800~1900℃) / 180min, keep warm at 1900℃ / 150min, heat up (1900~2000℃) / 240min, keep warm at 2000℃ / 120min, heat up (2000~2050℃) / 180min, keep warm at 2050℃ / 300min.

[0041] Preferably, the material selection in step (1) is to use additives, monoclinic ammonium paratungstate and spherical ammonium paratungstate mixed in a mass ratio of 0.1-0.3:4:1-1.5 as production raw materials.

[0042] The preparation method of the additive is as follows, in parts by weight:

[0043] Add 2 to 4 parts of lanthanum nitrate, 2 to 4 parts of yttrium nitrate and 80 to 120 parts of ammonium metatungstate to 300 to 500 parts of water, mix well, then add 0.5 to 1 part of Tween 80, stir and mix, then add 70 to 90 parts of citric acid to obtain a mixed solution, place the mixed solution in a water bath, control the temperature at 70 to 90° C., heat for 1 to 3 hours to obtain a pretreated product, dry at 120 to 140° C. to remove moisture, and obtain an additive.

[0044] Preferably, the preparation method of the additive is as follows, in parts by weight:

[0045] 2-4 parts of lanthanum nitrate, 2-4 parts of yttrium nitrate and 80-120 parts of ammonium metatungstate are added to 300-500 parts of water, mixed evenly, then 0.5-1 part of Tween 80 is added, stirred and mixed, and then 70-90 parts of a complexing agent is added, wherein the complexing agent is a mixture of ethylenediaminetetraacetic acid and tartaric acid in a mass ratio of 1-3:2-4 to obtain a mixed solution, the mixed solution is placed in a water bath, the temperature is controlled at 70-90°C, heated for 1-3 hours to obtain a pretreated product, and dried at 120-140°C to remove moisture to obtain an additive.

[0046] The high-performance potassium-doped tungsten rod prepared by the present invention is applied to cathode materials of electronic devices, heating elements of high-temperature furnaces, filaments in the lighting industry, high-temperature furnaces and ion implantation machine parts in the semiconductor industry, wire cutting in the photovoltaic industry, radioactive treatment and diagnostic equipment parts of medical equipment, and industrial heating elements.

[0047] The functions of each substance in the present invention are as follows:

[0048] Monoclinic ammonium paratungstate and spherical ammonium paratungstate are the main production raw materials. These two types of ammonium tungstate provide the basic components of tungsten, ensuring the tungsten content and quality of the final product. Their mixing ratio affects the efficiency of the subsequent reduction and doping processes.

[0049] Potassium hydroxide is one of the doping agents. Potassium hydroxide provides potassium element. Potassium doping helps to improve the high temperature performance and creep resistance of tungsten materials.

[0050] During the doping process, silicate promotes the combination of tungsten powder and potassium and improves the material structure, but it may also affect the thermal stability of the material.

[0051] Aluminum nitrate is another dopant that provides aluminum element. The presence of aluminum helps to improve the mechanical properties and oxidation resistance of the material.

[0052] Dilute nitric acid plays a role in adjusting the pH value and promoting the dissolution of metal ions in the doping solution, ensuring the uniform distribution of the dopant and the reaction efficiency.

[0053] The addition of Tween 80 surfactant improves the fluidity and uniformity of the solution, promotes the dispersion of lanthanum nitrate and yttrium nitrate, and reduces agglomeration.

[0054] The complexing agent helps to form a stable complex with metal ions, enhance the solubility and uniform distribution of rare earth elements, and thus improve the overall performance of potassium-doped tungsten rods.

[0055] During the reduction process, hydrogen acts as a reducing agent and can reduce ammonium tungsten bronze to tungsten powder, ensuring the purity and performance of tungsten.

[0056] The rubber hard mold sleeve is used in the molding process to ensure that the potassium-doped powder maintains its shape and size during cold isostatic pressing, improving the consistency and quality of the finished product.

[0057] Through the synergistic effect of these substances, the present invention can effectively prepare high-performance potassium-doped tungsten rods to meet the needs of specific applications.

[0058] Compared with the prior art, it has the following beneficial effects:

[0059] 1) The present invention achieves effective refinement of the grain size of potassium-doped tungsten rods by using specific additives and a precisely controlled doping process. This refined grain structure helps to improve the mechanical properties of the material, especially during processing such as stretching and bending.

[0060] 2) Due to the reduction of grain size and the uniform distribution of rare earth elements, the potassium-doped tungsten rod prepared in the present invention exhibits higher bending resistance, which means that the tungsten rod has better toughness and fracture resistance in practical applications, such as when it is drawn into tungsten wire.

[0061] 3) The potassium-doped tungsten rod of the present invention is superior to the prior art in terms of microstructure and mechanical properties, which is manifested in higher yield and qualified rate, as well as better performance indicators such as tensile strength and high-temperature recrystallization temperature. These improved properties enable the product of the present invention to have a longer service life and better reliability in practical applications. DETAILED DESCRIPTION

[0062] Monoclinic ammonium paratungstate, content WO 3 : 88.5%, screening particle size: 40 mesh.

[0063] Spherical ammonium paratungstate, content WO 3 : 88.5%, particle size 200nm.

[0064] The remaining raw materials in the examples and comparative examples of the present invention are all commercially available products.

[0065] The design idea of ​​the present invention is to refine the grain size of the potassium-doped tungsten rod and improve its bending resistance by precisely controlling the steps and conditions of doping with rare earth elements and optimizing the preparation method of the dopant. Specifically, the present invention introduces additives containing rare earth elements in the material selection stage, and precisely controls the preparation and injection conditions of the doping solution in the vacuum spray doping stage, and adopts specific parameter settings in the subsequent reduction, pickling, mixing, molding and sintering processes to ensure the uniform distribution of rare earth elements in the tungsten rod and the refinement of grains, thereby preparing a high-performance potassium-doped tungsten rod with excellent performance.

[0066] Example 1

[0067] A method for preparing a high-performance potassium-doped tungsten rod is as follows:

[0068] (1) Material selection

[0069] Monoclinic ammonium paratungstate and spherical ammonium paratungstate are mixed in a mass ratio of 4:1.3 as the production raw materials, and the total weight of the production raw materials is 800kg;

[0070] (2) Pre-reduction

[0071] The production raw material obtained in step (1) was pre-reduced using a four-zone reduction furnace, with the temperatures of the temperature zones being 320°C, 400°C, 420°C and 440°C, respectively, with a pre-reduction boat weight of 760 g and a hydrogen flow rate of 0.3 m 3 / h, push speed for 16 minutes, pass through a 50-mesh sieve to obtain ammonium tungsten bronze;

[0072] (3) Vacuum spray doping

[0073] In the first stage, the ammonium tungsten bronze obtained in step (2) is placed in a vacuum doping container and evacuated to 350 Pa;

[0074] In the second stage, 2.3 kg of potassium hydroxide, 5 kg of silicic acid and 2.2 kg of aluminum nitrate were dissolved in 60 L of deionized water at 60° C., and 1.2 L of 4 mol / L dilute nitric acid was added and stirred continuously to form a doping solution. Subsequently, the doping solution was heated to 45° C. and sprayed through the spray hole of the vacuum doping container, and the spray valve was opened to 1 / 4 to ensure that 1 / 3 of the doping solution was sprayed within 1.5 hours. During this process, the steam valve was opened to 1 / 3 to maintain a steam pressure of 0.15 MPa, and the power of the vacuum pump was maintained at 30%, while ensuring continuous stirring and heating of the materials in the container to maintain the temperature in the furnace at 75° C.;

[0075] In the third stage, the stirring frequency of the container is increased, the temperature in the furnace is maintained at 90°C, and the remaining doping solution is sprayed in within 40 minutes. At this time, the steam valve is opened to 2 / 3, the steam pressure is maintained at 0.15MPa, and the vacuum pump power is maintained at 30%;

[0076] In the fourth stage, after the dopant is sprayed, the steam valve is fully opened, the steam pressure is increased to 0.25MPa, and the temperature in the furnace is increased to 110℃, and the drying is continued for 3.5 hours until the water is completely evaporated. Then, the vacuum pump power is increased to 80%. When the vacuum degree in the vacuum doping container reaches 450MPa, the steam heating system is turned off and water cooling is performed until the temperature in the furnace drops to 53℃. Finally, the discharge valve is opened and passed through a 50-mesh screen to obtain potassium-ammonium-doped tungsten bronze.

[0077] (4) Restore

[0078] The potassium ammonium doped tungsten bronze obtained in step (3) is reduced once using a five-zone reduction furnace, wherein the temperatures of the temperature zones are 670°C, 730°C, 800°C, 830°C, and 855°C, respectively, and the hydrogen flow rate is 6m 3 / h, boat loading 450g, reduction time 7 hours, to obtain potassium-doped tungsten powder;

[0079] (5) Batch pickling

[0080] The potassium-doped tungsten powder obtained in step (4) is washed with 4 mol / L dilute hydrochloric acid and 2 mL / L dilute hydrofluoric acid to remove ineffective potassium and other impurities, then washed with 60°C water, dried and crushed through a 160-mesh sieve to obtain acid-washed potassium-doped tungsten powder;

[0081] (6) Mixing

[0082] The acid-washed potassium-doped tungsten powder obtained in step (5) was mixed in a high-speed mixer under nitrogen protection for 90 minutes, cooled to 45° C. and then passed through a 180-mesh sieve to obtain a potassium-doped mixed powder;

[0083] (7) Hard film cold isostatic pressing

[0084] According to the requirement of 3000 g / piece, the potassium-doped powder obtained in step (6) is loaded into a rubber hard mold sleeve with a length of 800 mm, an inner diameter of 25 mm, and a wall thickness of 2 mm, vibrated, sealed and tightened, placed in a cold isostatic press, and pressed at a pressure of 150 MPa to obtain a potassium-doped tungsten green body;

[0085] (8) Low temperature impurity removal

[0086] The potassium-doped tungsten green body obtained in step (7) is fired in a hydrogen protection furnace at 1050° C. for 50 minutes to improve the strength, thereby obtaining a potassium-doped tungsten green body with improved strength;

[0087] (9) Vertical melting pre-sintering

[0088] The potassium-doped tungsten blank obtained in step (8) is pre-sintered in a vertical melting furnace, and more than 95% of impurities are removed under the protection of hydrogen. The appearance is dark gray, and the upper and lower sections are uniformly crystallized without any frame crystals. An incompletely dense potassium-doped tungsten rod is obtained;

[0089] The pre-sintering process is as follows: heating up, heating up, keeping warm, and keeping warm;

[0090] The current / time parameters are as follows: heating (0A~2800A) / 5min, heating (2800A~3850A) / 6min, heating (3850A~4820A) / 6min, keeping warm (4820A~4820A) / 21min;

[0091] Hydrogen flow rate is 2.0m 3 / h;

[0092] (10) Medium frequency sintering

[0093] The incompletely dense potassium-doped tungsten rod obtained in step (9) is sintered in a medium frequency furnace and placed vertically in a stacking firing mode. The sintering is performed under hydrogen protection by using a double hydrogen feeding mode at the bottom and top of the furnace. The sintering process is automatically controlled by an infrared temperature measurement + PLC temperature control system.

[0094] The sintering system is in the order of heating, heat preservation, heating, heat preservation, heating, heat preservation, heating, heat preservation, heating, heat preservation, heating, heat preservation, heating, heat preservation; the temperature / time parameters are in the order of: (0-1250℃) / 430min, heat preservation: 1250℃ / 90min, heating (1250-1500℃) / 150min, heat preservation 1500℃ / 120min, heating (1500-1800℃) / 36 1min, keep warm at 1800℃ / 150min, heat up (1800~1900℃) / 180min, keep warm at 1900℃ / 150min, heat up (1900~2000℃) / 240min, keep warm at 2000℃ / 120min, heat up (2000~2050℃) / 180min, keep warm at 2050℃ / 300min; high performance potassium-doped tungsten rod is obtained.

[0095] Example 2

[0096] The preparation method of a high-performance potassium-doped tungsten rod is basically the same as that of Example 1, the only difference being that the material selection method in step (1) is different.

[0097] (1) Material selection

[0098] Additives, monoclinic ammonium paratungstate and spherical ammonium paratungstate are mixed in a mass ratio of 0.2:4:1.3 as production raw materials;

[0099] The preparation method of the additive is as follows:

[0100] Add 6 g of cerium nitrate and 100 g of ammonium metatungstate to 400 g of water and mix well, then add 0.8 g of Tween 80, stir and mix, and then add 80 g of citric acid to obtain a mixed solution, place the mixed solution in a water bath, control the temperature at 80°C, heat for 2 hours to obtain a pretreated product, and dry it at 130°C to remove moisture to obtain an additive.

[0101] Example 3

[0102] The preparation method of a high-performance potassium-doped tungsten rod is basically the same as that of Example 1, the only difference being that the material selection method in step (1) is different.

[0103] (1) Material selection

[0104] Additives, monoclinic ammonium paratungstate and spherical ammonium paratungstate are mixed in a mass ratio of 0.2:4:1.3 as production raw materials;

[0105] The preparation method of the additive is as follows:

[0106] Add 6 g of lanthanum nitrate and 100 g of ammonium metatungstate to 400 g of water and mix well, then add 0.8 g of Tween 80, stir and mix, and then add 80 g of citric acid to obtain a mixed solution, place the mixed solution in a water bath, control the temperature at 80°C, heat for 2 hours to obtain a pretreated product, and dry it at 130°C to remove moisture to obtain an additive.

[0107] Example 4

[0108] The preparation method of a high-performance potassium-doped tungsten rod is basically the same as that of Example 1, the only difference being that the material selection method in step (1) is different.

[0109] (1) Material selection

[0110] Additives, monoclinic ammonium paratungstate and spherical ammonium paratungstate are mixed in a mass ratio of 0.2:4:1.3 as production raw materials;

[0111] The preparation method of the additive is as follows:

[0112] 6 g of samarium nitrate and 100 g of ammonium metatungstate were added to 400 g of water and mixed evenly. Then, 0.8 g of Tween 80 was added and stirred to mix. Then, 80 g of citric acid was added to obtain a mixed solution. The mixed solution was placed in a water bath and the temperature was controlled at 80° C. and heated for 2 hours to obtain a pretreated product. The pretreated product was dried at 130° C. to remove moisture and obtain an additive.

[0113] Example 5

[0114] The preparation method of a high-performance potassium-doped tungsten rod is basically the same as that of Example 1, the only difference being that the material selection method in step (1) is different.

[0115] (1) Material selection

[0116] Additives, monoclinic ammonium paratungstate and spherical ammonium paratungstate are mixed in a mass ratio of 0.2:4:1.3 as production raw materials;

[0117] The preparation method of the additive is as follows:

[0118] 6 g of yttrium nitrate and 100 g of ammonium metatungstate were added to 400 g of water and mixed evenly. Then, 0.8 g of Tween 80 was added and stirred to mix. Then, 80 g of citric acid was added to obtain a mixed solution. The mixed solution was placed in a water bath and the temperature was controlled at 80° C. and heated for 2 hours to obtain a pretreated product. The pretreated product was dried at 130° C. to remove moisture and obtain an additive.

[0119] Example 6

[0120] The preparation method of a high-performance potassium-doped tungsten rod is basically the same as that of Example 1, the only difference being that the material selection method in step (1) is different.

[0121] (1) Material selection

[0122] Additives, monoclinic ammonium paratungstate and spherical ammonium paratungstate are mixed in a mass ratio of 0.2:4:1.3 as production raw materials;

[0123] The preparation method of the additive is as follows:

[0124] 6 g of gadolinium nitrate and 100 g of ammonium metatungstate were added to 400 g of water and mixed evenly. Then, 0.8 g of Tween 80 was added and stirred to mix. Then, 80 g of citric acid was added to obtain a mixed solution. The mixed solution was placed in a water bath and the temperature was controlled at 80° C. and heated for 2 hours to obtain a pretreated product. The pretreated product was dried at 130° C. to remove moisture and obtain an additive.

[0125] Example 7

[0126] The preparation method of a high-performance potassium-doped tungsten rod is basically the same as that of Example 1, the only difference being that the material selection method in step (1) is different.

[0127] (1) Material selection

[0128] Additives, monoclinic ammonium paratungstate and spherical ammonium paratungstate are mixed in a mass ratio of 0.2:4:1.3 as production raw materials;

[0129] The preparation method of the additive is as follows:

[0130] Add 6 g of neodymium nitrate and 100 g of ammonium metatungstate to 400 g of water and mix well, then add 0.8 g of Tween 80, stir and mix, and then add 80 g of citric acid to obtain a mixed solution, place the mixed solution in a water bath, control the temperature at 80°C, heat for 2 hours to obtain a pretreated product, and dry it at 130°C to remove moisture to obtain an additive.

[0131] Example 8

[0132] The preparation method of a high-performance potassium-doped tungsten rod is basically the same as that of Example 1, the only difference being that the material selection method in step (1) is different.

[0133] (1) Material selection

[0134] Additives, monoclinic ammonium paratungstate and spherical ammonium paratungstate are mixed in a mass ratio of 0.2:4:1.3 as production raw materials;

[0135] The preparation method of the additive is as follows:

[0136] 3 g of lanthanum nitrate, 3 g of yttrium nitrate and 100 g of ammonium metatungstate were added to 400 g of water and mixed evenly. Then, 0.8 g of Tween 80 was added and stirred to mix. Then, 80 g of citric acid was added to obtain a mixed solution. The mixed solution was placed in a water bath and the temperature was controlled at 80° C. and heated for 2 hours to obtain a pretreated product. The pretreated product was dried at 130° C. to remove moisture and obtain an additive.

[0137] Example 9

[0138] The preparation method of a high-performance potassium-doped tungsten rod is basically the same as that of Example 1, the only difference being that the material selection method in step (1) is different.

[0139] (1) Material selection

[0140] Additives, monoclinic ammonium paratungstate and spherical ammonium paratungstate are mixed in a mass ratio of 0.2:4:1.3 as production raw materials;

[0141] The preparation method of the additive is as follows:

[0142] 3 g of lanthanum nitrate, 3 g of yttrium nitrate and 100 g of ammonium metatungstate were added to 400 g of water and mixed evenly. Then 0.8 g of Tween 80 was added and stirred to mix. Then 80 g of ethylenediaminetetraacetic acid was added to obtain a mixed solution. The mixed solution was placed in a water bath and the temperature was controlled at 80° C. and heated for 2 hours to obtain a pretreated product, which was dried at 130° C. to remove moisture and obtain an additive.

[0143] Example 10

[0144] The preparation method of a high-performance potassium-doped tungsten rod is basically the same as that of Example 1, the only difference being that the material selection method in step (1) is different.

[0145] (1) Material selection

[0146] Additives, monoclinic ammonium paratungstate and spherical ammonium paratungstate are mixed in a mass ratio of 0.2:4:1.3 as production raw materials;

[0147] The preparation method of the additive is as follows:

[0148] 3 g of lanthanum nitrate, 3 g of yttrium nitrate and 100 g of ammonium metatungstate were added to 400 g of water and mixed evenly. Then, 0.8 g of Tween 80 was added and stirred to mix. Then, 80 g of tartaric acid was added to obtain a mixed solution. The mixed solution was placed in a water bath and the temperature was controlled at 80° C. and heated for 2 hours to obtain a pretreated product. The pretreated product was dried at 130° C. to remove moisture and obtain an additive.

[0149] Embodiment 11

[0150] The preparation method of a high-performance potassium-doped tungsten rod is basically the same as that of Example 1, the only difference being that the material selection method in step (1) is different.

[0151] (1) Material selection

[0152] Additives, monoclinic ammonium paratungstate and spherical ammonium paratungstate are mixed in a mass ratio of 0.2:4:1.3 as production raw materials;

[0153] The preparation method of the additive is as follows:

[0154] 3 g of lanthanum nitrate, 3 g of yttrium nitrate and 100 g of ammonium metatungstate are added to 400 g of water and mixed evenly, then 0.8 g of Tween 80 is added, stirred and mixed, and then 80 g of a complexing agent is added, wherein the complexing agent is a mixture of ethylenediaminetetraacetic acid and tartaric acid in a mass ratio of 2:3 to obtain a mixed solution, the mixed solution is placed in a water bath, the temperature is controlled at 80°C, and heated for 2 hours to obtain a pretreated product, which is dried at 130°C to remove moisture to obtain an additive.

[0155] Comparative Example 1

[0156] The preparation method of a high-performance potassium-doped tungsten rod is basically the same as that of Example 1, the only difference being that the material selection method in step (1) is different.

[0157] (1) Material selection

[0158] Additives, monoclinic ammonium paratungstate and spherical ammonium paratungstate are mixed in a mass ratio of 0.2:4:1.3 as production raw materials;

[0159] The additive is a mixture of cerium nitrate and ammonium metatungstate in a ratio of 3:50.

[0160] Test Example 1

[0161] Grain size test

[0162] The high-performance potassium-doped tungsten rods prepared in the embodiments of the present invention and the comparative examples were subjected to the standard method of GB / T6394-2017 “Method for Determination of Average Grain Size of Metals”, and the average grain size of the samples was determined by a Zeiss polarizing microscope.

[0163] The test results are shown in Table 1.

[0164] Table 1

[0165]

[0166]

[0167] Test Example 2

[0168] Toughness test

[0169] The high-performance potassium-doped tungsten rods prepared in the embodiments of the present invention and the comparative examples are drawn into tungsten wires with a diameter of 0.4 mm using conventional processes in the art, and the toughness of the tungsten wires is determined by the number of 90° bending resistances.

[0170] The test results are shown in Table 2.

[0171] Table 2

[0172]

[0173]

[0174] It can be seen from the test data in Tables 1 and 2 that the high-performance potassium-doped tungsten rod prepared in Example 11 of the present invention has the smallest average grain size and the tungsten wire processed into it has the highest bending resistance.

[0175] The additives used in Examples 2 to 11, compared with the case where no additives are used in Example 1, have the effect of refining the grains and improving the toughness of the material as a whole. The addition of rare earth elements and complexing agents in the additives helps to form more evenly distributed rare earth oxides in the tungsten powder. These oxides act as obstacles to grain growth and effectively inhibit the growth of grains, thereby reducing the grain size. At the same time, the surfactant in the additive may improve the fluidity and uniformity of the mixture, further promoting the refinement of the grains. In addition, the complexing agent in the additive may enhance the solid solubility of rare earth elements in the tungsten matrix, improve the thermal stability and mechanical properties of the material, and thus show higher bending resistance during the process of drawing into tungsten wire. These combined effects make the tungsten rod doped with additives have better microstructure and mechanical properties.

[0176] Lanthanum nitrate and yttrium nitrate play an important role as rare earth element dopants in the preparation of high-performance potassium-doped tungsten rods. They work together through multiple mechanisms to refine the grain size and improve the material properties. First, the oxides of lanthanum and yttrium act as grain growth obstacles, which can increase the grain boundary energy and inhibit grain growth. Secondly, the solid solution of these rare earth elements in tungsten enhances the lattice distortion and increases the resistance to dislocation movement, thereby enhancing the strength and hardness of the material and further promoting grain refinement. In addition, due to the synergistic effect of the two rare earth elements, the doping distribution is more uniform, which helps to form a finer and more uniform grain structure and improves the overall uniformity of the material. Rare earth elements also provide additional pinning points on the grain boundaries, reduce the migration rate of the grain boundaries, and further inhibit the growth of grains. Finally, rare earth doping increases the recrystallization temperature of tungsten, allowing the material to maintain a fine grain structure at higher temperatures, which is crucial for enhancing the high-temperature strength and stability of the material. The combined effect of these mechanisms enables the doped tungsten rod to exhibit better mechanical properties and thermal stability, especially in high-temperature applications. The combination of lanthanum nitrate and yttrium nitrate in doped tungsten rods achieves grain refinement and improvement of material mechanical properties through multiple mechanisms such as grain refinement, solid solution strengthening, uniformity of doping distribution, grain boundary pinning and increase in recrystallization temperature.

[0177] In Example 11, by compounding EDTA and tartaric acid as complexing agents, the grain size of the rare earth oxide-doped nano-tungsten powder can be more effectively controlled and its bending resistance can be improved compared to using citric acid, EDTA or tartaric acid alone. This synergistic effect may be due to the fact that EDTA, as a multi-dentate complexing agent, can form stable complexes with a variety of metal ions, while tartaric acid contains multiple carboxyl groups and can also form complexes with metal ions. Under acidic conditions, the presence of these two complexing agents makes the rare earth ions and WO4 2 -The complexation with oxygen-containing ligands is more stable, thus forming a more evenly distributed rare earth doping phase in the sol-gel process. This even distribution helps to form quasi-spherical particles with uniform particle size and no agglomeration during the reduction process, so that the final product has a finer grain size and better mechanical toughness, thereby improving the bending resistance of the material.

[0178] The above embodiments are merely preferred implementations of the present invention. Any simple modification, amendment and substitution of the above embodiments based on the technical essence of the present invention shall fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a high-performance potassium-doped tungsten rod, characterized in that: The steps include: (1) Mixing monoclinic ammonium paratungstate and spherical ammonium paratungstate; (2) Pre-reduction to obtain ammonium tungsten bronze; (3) dissolving potassium hydroxide, silicic acid and aluminum nitrate in water, adding nitric acid, and continuously stirring to form a doping solution, and vacuum spraying the doping solution to obtain potassium-ammonium-doped tungsten bronze; (4) reducing the potassium-ammonium-doped tungsten bronze to obtain potassium-doped tungsten powder; (5) acid washing to obtain acid washed potassium-doped tungsten powder; (6) mixing to obtain potassium-doped powder; (7) pressing and forming to obtain a potassium-doped tungsten green body; (8) firing to obtain a potassium-doped tungsten blank; (9) vertical melting pre-sintering to obtain an incompletely dense potassium-doped tungsten rod; (10) Sintering in a medium frequency furnace to obtain a high-performance potassium-doped tungsten rod.

2. The method for preparing a high-performance potassium-doped tungsten rod according to claim 1, characterized in that: The steps include: (1) Material selection Monoclinic ammonium paratungstate and spherical ammonium paratungstate are mixed as production raw materials; (2) Pre-reduction Using a reduction furnace with no less than four temperature zones to pre-reduce the production raw material obtained in step (1) to obtain ammonium tungsten bronze; (3) Vacuum spray doping In the first stage, the ammonium tungsten bronze obtained in step (2) is placed in a vacuum doping container and evacuated to ≤500Pa; In the second stage, potassium hydroxide, silicic acid and aluminum nitrate are dissolved in water, and nitric acid is added, and stirred continuously to form a doping solution. Subsequently, the doping solution is heated to 40-50° C. and sprayed through the spray hole of the vacuum doping container; In the third stage, the stirring frequency of the container is increased, the temperature in the furnace is maintained at 85-95°C, and the remaining doping solution is sprayed in within 30-50 minutes; In the fourth stage, after the dopant is sprayed, the steam valve is fully opened to increase the steam pressure and the temperature in the furnace, and the drying is continued until the water is completely evaporated. Then, the vacuum pump power is increased, the steam heating system is turned off, and water cooling is performed. Finally, the discharge valve is opened and the material passes through the screen to obtain potassium-ammonium-doped tungsten bronze. (4) Restore Using a five-temperature zone reduction furnace to reduce the potassium-ammonium-doped tungsten bronze obtained in step (3) to obtain potassium-doped tungsten powder; (5) Batch pickling The potassium-doped tungsten powder obtained in step (4) is washed with dilute hydrochloric acid and dilute hydrofluoric acid to remove ineffective potassium and other impurities, then washed with water, dried, crushed and sieved to obtain acid-washed potassium-doped tungsten powder; (6) Mixing The acid-washed potassium-doped tungsten powder obtained in step (5) is mixed in a high-speed mixer under nitrogen protection, and after cooling, is sieved to obtain a potassium-doped mixed powder; (7) Hard film cold isostatic pressing The potassium-doped powder obtained in step (6) is placed in a rubber hard mold sleeve, vibrated, sealed and tightened, and pressed into shape to obtain a potassium-doped tungsten green body; (8) Low temperature impurity removal The potassium-doped tungsten green body obtained in step (7) is fired in a hydrogen protection furnace to obtain a potassium-doped tungsten green body with improved strength; (9) Vertical melting pre-sintering Pre-sintering the potassium-doped tungsten blank obtained in step (8) in a vertical melting furnace to obtain an incompletely dense potassium-doped tungsten rod; (10) Medium frequency sintering The incompletely dense potassium-doped tungsten rod obtained in step (9) is sintered in a medium frequency furnace to obtain a high-performance potassium-doped tungsten rod.

3. The method for preparing a high-performance potassium-doped tungsten rod according to claim 1, characterized in that: In the material selection of step (1), monoclinic ammonium paratungstate and spherical ammonium paratungstate are mixed in a weight ratio of 4:1 to 1.

5.

4. The method for preparing a high-performance potassium-doped tungsten rod according to claim 1, characterized in that: In the step (2), the temperatures of the four temperature zones in the pre-reduction are 300°C to 330°C, 390°C to 410°C, 410°C to 430°C, and 430°C to 450°C, respectively, and the hydrogen flow rate is 0.3m 3 / h~0.4m 3 / h, the pre-reduction boat weight is 720g-800g, passed through a 20-100 mesh sieve, and pushed for 10-20 minutes.

5. The method for preparing a high-performance potassium-doped tungsten rod according to claim 1, characterized in that: In the second stage of the vacuum spray doping in step (3), the contents of various substances are 2 to 3 parts by weight of potassium hydroxide, 4.5 to 5.5 parts by weight of silicic acid, and 1.8 to 3 parts by weight of aluminum nitrate solids, which are completely dissolved in 50 to 70 L of water at 50 to 70° C., and then 0.5 to 2 L of 2 to 5 mol / L dilute nitric acid is added.

6. The method for preparing a high-performance potassium-doped tungsten rod according to claim 1, characterized in that: The temperatures of the five temperature zones in the reduction step (4) are 660°C to 680°C, 710°C to 740°C, 790°C to 820°C, 820°C to 840°C, and 840°C to 870°C, respectively, and the hydrogen flow rate is 4m 3 / h~7m 3 / h, the boat loading amount is 350g ~ 550g, and the effective reduction time is 6h ~ 8h.

7. The method for preparing a high-performance potassium-doped tungsten rod according to claim 1 or 2, characterized in that: The material selection in the step (1) is to use additives, monoclinic ammonium paratungstate and spherical ammonium paratungstate mixed in a mass ratio of 0.1-0.3:4:1-1.5 as production raw materials.

8. The method for preparing a high-performance potassium-doped tungsten rod according to claim 7, characterized in that: The preparation method of the additive is as follows, in parts by weight: Add 2 to 4 parts of lanthanum nitrate, 2 to 4 parts of yttrium nitrate and 80 to 120 parts of ammonium metatungstate to 300 to 500 parts of water, mix well, then add 0.5 to 1 part of Tween 80, stir and mix, then add 70 to 90 parts of citric acid to obtain a mixed solution, place the mixed solution in a water bath, control the temperature at 70 to 90° C., heat for 1 to 3 hours to obtain a pretreated product, dry at 120 to 140° C. to remove moisture, and obtain an additive.

9. A high performance potassium-doped tungsten rod, characterized in that: The method is manufactured by the manufacturing method according to any one of claims 1 to 8.

10. The use of the high performance potassium-doped tungsten rod as claimed in claim 9, characterized in that: The high-performance potassium-doped tungsten rod is used in cathode materials of electronic devices, heating elements of high-temperature furnaces, filaments in the lighting industry, high-temperature furnaces in the semiconductor industry, ion implantation machine parts, wire cutting in the photovoltaic industry, radiotherapy and diagnostic equipment parts for medical equipment, and industrial heating elements.

Images