A method for preparing metal powder with low oxygen content

Abstract

The present application relates to the technical field of metal powder preparation, and specifically discloses a method for preparing metal powder with low oxygen content. A method for preparing metal powder with low oxygen content, comprising: S1, weighing metal raw materials and smelting to obtain molten metal; S2, atomizing the smelted molten metal through an ultrasonic atomizing device, using liquid carbon dioxide and argon as cooling media to cool the molten metal to form metal powder; S3, placing the metal powder in a closed reactor, using argon as a carrier gas, passing it into a container filled with aluminum isopropoxide solution and zirconium acetylacetonate solution, atomizing the two solutions through an atomizing nozzle and reacting them with the metal powder; S4, adding the metal powder after the S3 reaction into a pulse current heating device for pulse deoxygenation treatment. The metal powder of the present application can meet the material performance requirements of high-end fields such as aerospace, precision machinery manufacturing, etc., and has the advantages of low oxygen content and high sphericity.

Description

Technical Field

[0001] The present application relates to the technical field of metal powder preparation, and more specifically, to a method for preparing metal powder with low oxygen content. Background Art

[0002] Low-oxygen metal powders hold crucial application value in metal powder production. With the development of high-end industries such as aerospace and precision machinery manufacturing, demand for low-oxygen metal powders is growing. Low oxygen content can effectively improve the corrosion resistance, mechanical strength, and electrical properties of metal powders and their products.

[0003] In the prior art, there are many methods for preparing low-oxygen metal powders. For example, by smelting and atomizing under vacuum or inert gas protection, the oxygen content of the metal powder can be effectively reduced. In the related art, the patent application document with publication number CN110052617A discloses a method for manufacturing low-oxygen water-atomized metal powder. The method uses an aqueous solution containing alkaline borates, silicates, phosphates and other salts as a cooling medium for atomized metal droplets, and compresses the aqueous solution into a high-pressure cooling medium using a high-pressure water pump and a spray plate. The high-pressure cooling medium instantly breaks up the metal droplets and cools and solidifies them. During the breaking and cooling process, the alkaline aqueous solution has the function of protecting the metal surface. In the subsequent drying and dehydration process, the alkaline substance also plays a role in protecting the metal powder from oxidation. Through the above protection, a metal powder with a lower oxygen content than the general atomization process is obtained.

[0004] Although the above-mentioned existing technologies can reduce the oxygen content of metal powder to a certain extent, due to the use of an aqueous solution containing a variety of salts as a cooling medium, during the atomization and subsequent processing, even if the alkaline substance can play a certain protective role, there will inevitably be trace amounts of dissolved oxygen in the aqueous solution, and it is difficult to completely isolate the external oxygen during the contact, separation, drying and dehydration of the metal powder and the cooling medium. At the same time, the barrier effect of alkaline substances on oxygen is also limited. The oxygen content of the prepared metal powder is 1000-1600ppm. For some key components in the aerospace field that have extremely stringent requirements on material properties, such as high-temperature alloy turbine blades for aircraft engines and tiny metal parts for high-precision transmission systems in precision machinery manufacturing, there is still a problem of high oxygen content. This application field requires the oxygen content of the metal powder to be lower than 300ppm. The high oxygen content will cause the metal powder to be prone to oxidation reactions during subsequent molding and use, reducing the mechanical properties and corrosion resistance of the material, and affecting the service life and reliability of the components.

[0005] Furthermore, because the high-pressure aqueous solution cooling medium atomizes and breaks up the metal droplets, the droplets are subjected to uneven forces and the cooling rate is difficult to precisely control. This causes inconsistent shrinkage of different parts of the metal powder during solidification, resulting in low sphericity. This leads to poor powder flowability during use. During the powder metallurgy molding process, powders with low sphericity are difficult to evenly fill the mold, and bridging is likely to occur, resulting in uneven density in the molded part, which in turn affects the mechanical properties and dimensional accuracy of the final product.

[0006] Therefore, the metal powder prepared by the preparation method in the related art has the problem that the oxygen content is difficult to meet the oxygen content requirements of high-end application fields and the low sphericity affects the performance. Summary of the Invention

[0007] In order to further reduce the oxygen content of metal powder and improve the sphericity of metal powder, the present application provides a method for preparing low-oxygen-content metal powder.

[0008] The present application provides a method for preparing a low-oxygen content metal powder using the following technical solution:

[0009] A method for preparing a metal powder with low oxygen content comprises the following steps:

[0010] S1. Weighing metal raw materials containing Nb, Ni, C, Cr, Al, Fe, and Ti elements, mixing them uniformly to obtain a mixed raw material, and adding the mixed raw material into a vacuum arc furnace for smelting to obtain a molten metal;

[0011] S2. The smelted metal liquid is atomized by an ultrasonic atomization device with an ultrasonic frequency set to 40-50 kHz. During the atomization process, liquid carbon dioxide and argon are used as cooling media. The liquid carbon dioxide and argon are transported to the atomization area by a high-pressure pump to cool the metal liquid to form metal powder.

[0012] S3. The metal powder is placed in a closed reactor, and argon is used as a carrier gas to pass into a container containing aluminum isopropoxide solution and zirconium acetylacetonate solution. The two solutions are atomized by an atomizing nozzle and then carried into the closed reactor. The reaction is carried out at a temperature of 250-350° C. and a pressure of 50-60 kPa for 2-4 hours.

[0013] S4. Add the metal powder after the reaction in S3 into a pulse current heating device and perform pulse deoxidation treatment under a protective atmosphere at a treatment temperature of 800-1000° C. for 5-15 minutes. After the treatment is completed, a metal powder with low oxygen content is obtained.

[0014] By adopting the above technical solution, the vacuum environment of the vacuum arc furnace greatly reduces the contact area between the metal and oxygen during the melting process, suppressing the oxidation reaction of the molten metal at the source. Liquid carbon dioxide and argon are used as cooling media during the cooling process. Liquid carbon dioxide provides strong cooling capacity, rapidly reducing the temperature of the molten metal and causing it to solidify quickly. At the same time, argon, as an auxiliary cooling gas, not only further removes heat but also acts as a buffer and dilution, reducing the potential dangers of extreme cold and heat meeting. Furthermore, argon, as an inert shielding gas, forms a film around the metal droplets during the atomization process, further isolating them from external oxygen and preventing the introduction of oxygen during the cooling process. In step S3, aluminum isopropoxide and zirconium acetylacetonate form a uniform Al2O3-ZrO2 protective film on the surface of the metal powder, inhibiting oxygen adsorption. Its oxygen diffusion coefficient is lower than that of a single aluminum oxide film, effectively preventing oxygen from penetrating the metal powder. The pulsed current decomposes or volatilizes the oxides within the powder through Joule heating and plasma activation. Experimental data shows that this step can further reduce the oxygen content from 800ppm to below 200ppm.

[0015] The ultra-low temperature of liquid carbon dioxide and the auxiliary cooling of argon gas keep the temperature gradient of various parts of the metal droplet less than 5°C / mm during the solidification process, significantly reducing shape distortion caused by inconsistent shrinkage. According to calculations based on heat conduction models, this cooling method can increase the sphericity from 70%-80% with traditional methods to over 95%. In step S3, the uniform deposition of the Al2O3-ZrO2 composite film on the powder surface has a certain "micro-shaping" effect, filling tiny depressions on the powder surface and further optimizing the sphericity.

[0016] In summary, the above-mentioned solution effectively overcomes the defects of high oxygen content and low sphericity in metal powders in existing technologies. This preparation method optimizes the entire process from smelting, cooling, surface modification, to deep deoxygenation, reducing the oxygen content of metal powders to below 200 ppm and effectively improving the sphericity of metal powders. This meets the stringent material performance requirements of high-end fields such as aerospace and precision machinery manufacturing, providing an effective technical solution for the high-quality preparation of key components such as aircraft engine turbine blades and high-precision transmission parts.

[0017] Optionally, the flow rate of liquid carbon dioxide in S2 is 1-3 L / min, and the flow rate of argon is 15-25 L / min.

[0018] By adopting the above technical solution, the flow rate of liquid carbon dioxide is controlled at 1-3L / min, which can provide appropriate cooling intensity and quickly remove the heat of the molten metal; the argon flow rate is 15-25L / min, which can better wrap the metal droplets, make the cooling more uniform, reduce the deformation of the droplets during the cooling process, and thus improve the sphericity.

[0019] Optionally, the solvent of the aluminum isopropoxide solution in S3 is isopropanol, and the mass concentration of the aluminum isopropoxide solution is 18%-22%.

[0020] By adopting the above technical solution, the above solvent and concentration of aluminum isopropoxide solution have good stability, so that it can be evenly deposited and reacted on the surface of the metal powder in the subsequent reaction, which helps to form a uniform and effective protective film, improve the oxidation resistance of the metal powder, and reduce the oxygen content.

[0021] Optionally, the solvent of the zirconium acetylacetonate solution in S3 is toluene, and the mass concentration of the zirconium acetylacetonate solution is 14%-16%.

[0022] By adopting the above technical solution, toluene has good solubility for zirconium acetylacetonate, and the mass concentration of 14%-16% is within its solubility range, ensuring that the solution is stable and can fully participate in the reaction, and together with the reaction product of aluminum isopropoxide solution, form a composite protective film with better performance.

[0023] Optionally, the mass ratio of the aluminum isopropoxide solution to the zirconium acetylacetonate solution in S3 is (3-5):1.

[0024] By adopting the above technical solution and specifying the mass ratio of aluminum isopropoxide solution and zirconium acetylacetonate solution, the composition ratio of the composite protective film formed by the reaction of the two solutions is made more reasonable, thereby improving the antioxidant protection performance of the protective film on metal powder and reducing the oxygen content.

[0025] Optionally, during the pulse deoxygenation treatment in S4, the pulse current density is 103-105 A / cm², the pulse width is 5-50 ms, and the duty cycle is 30%-40%.

[0026] By adopting the above technical solution, the pulse current density, pulse width and duty cycle of the pulse deoxidation treatment with the above parameters can make the pulse deoxidation process efficient and stable, effectively remove residual oxygen in the metal powder, further reduce the oxygen content, and avoid the problem of overheating and sintering of the metal powder due to improper parameters.

[0027] Optionally, in S1, the metal raw materials are ferroniobium alloy, electrolytic nickel, carbon black, electrolytic chromium, electrolytic aluminum, electrolytic iron and ferrotitanium alloy with a purity of not less than 99.5%.

[0028] By adopting the above technical solution, the content of impurity elements in high-purity raw materials is reduced. With fewer impurities, side reactions such as oxidation caused by impurities during smelting and atomization processes are reduced, which is conducive to controlling the oxygen content.

[0029] Optionally, the niobium content in the ferroniobium alloy is 65%-70%; and the titanium content in the ferrotitanium alloy is 30%-40%.

[0030] By adopting the above technical solution, the content of key elements is stable and the alloy composition is relatively fixed. In the subsequent smelting and reaction processes, the reaction is more controllable, which is conducive to the formation of metal powder and protective film with stable properties, and better achieves the goal of reducing oxygen content.

[0031] Optionally, in S1, the ratio of the metal raw materials, in parts by mass, is as follows:

[0032] 50-55 parts of ferroniobium alloy;

[0033] 18-20 parts of electrolytic nickel;

[0034] 10-12 parts of carbon black;

[0035] 8-10 parts of electrolytic chromium;

[0036] 1-5 parts of electrolytic aluminum;

[0037] 1-3 parts of electrolytic iron;

[0038] 1-3 parts of titanium-iron alloy.

[0039] By adopting the above technical solution, the above ratio can make the elements interact appropriately, forming a good performance alloy liquid during smelting, and the subsequent atomization, modification and deoxidation processes can be carried out better, ensuring the final metal powder performance.

[0040] Optionally, in S1, the mixed raw materials are melted at a temperature of 1700-1900°C, a melting time of 15-25 min, and a vacuum degree of ≤5×10 - ³Pa.

[0041] In summary, this application has the following beneficial effects:

[0042] 1. The preparation method of the present application uses liquid carbon dioxide and argon as cooling media. Compared with the traditional aqueous solution cooling method, it completely avoids the risk of dissolved oxygen in the aqueous solution and the introduction of oxygen through contact with air. The ultra-low temperature characteristics of liquid carbon dioxide can make the molten metal solidify rapidly, greatly shortening the high-temperature exposure time and reducing the chance of oxidation; argon, as an inert gas, forms an air film to wrap the metal droplets, further isolating them from external oxygen. In subsequent processing, a uniform Al2O3-ZrO2 composite protective film is formed on the surface of the metal powder by aluminum isopropoxide and zirconium acetylacetonate, which can effectively prevent oxygen from penetrating into the interior of the metal powder. From the vacuum environment during smelting to suppress oxidation, to the cooling process to reduce oxygen introduction, to the long-term barrier of the protective film, multiple links work together to significantly reduce the oxygen content of the metal powder from 1000-1600ppm in the traditional method to below 200ppm, significantly improving the oxidation resistance and corrosion resistance of the metal powder, and meeting the stringent requirements for low oxygen content in high-end fields.

[0043] 2. The preparation method of this application employs a pulsed current heating device to perform pulsed deoxygenation under specific parameters. This process utilizes Joule heating and plasma activation to decompose oxides within the metal powder or react with a reducing agent in the protective atmosphere to produce volatile products. This treatment not only removes residual oxygen from the metal powder during the initial preparation process but also, through precise parameter control, avoids problems such as powder sintering caused by overheating. This process achieves deep deoxygenation while maintaining the stability of the metal powder's microstructure and properties, providing high-quality raw materials for the production of high-performance metal products in fields such as aerospace and precision machinery.

[0044] 3. In the atomization process of the method of the present application, the cooling medium composed of liquid carbon dioxide and argon makes the temperature gradient of each part of the metal droplet less than 5°C / mm during solidification, achieving a uniform and rapid cooling effect, and significantly reducing the shape distortion caused by inconsistent shrinkage. The ultrasonic atomization device with an ultrasonic frequency set to 20-50kHz ensures that the metal liquid is uniformly stressed and broken into tiny droplets with a narrow particle size distribution, laying the foundation for high sphericity. In addition, the Al2O3-ZrO2 composite film formed in the S3 step is uniformly deposited on the surface of the powder, which has a "micro-shaping" effect, can fill tiny depressions on the surface of the powder, further optimize the sphericity, and effectively improve the fluidity of the powder. In the powder metallurgy forming process, it can evenly fill the mold, avoid bridging, and ensure uniform density of the molded part, thereby improving the mechanical properties and dimensional accuracy of the final product, and meeting the strict requirements of high-end manufacturing for the formability of metal powder. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is a SEM image of the low-oxygen-content metal powder prepared in Example 1 of the present application;

[0046] Figure 2 This is a SEM image of the low-oxygen-content metal powder prepared in Example 2 of the present application;

[0047] Figure 3 This is a SEM image of the low-oxygen-content metal powder prepared in Example 3 of the present application. DETAILED DESCRIPTION

[0048] The present application is further described in detail below with reference to the embodiments.

[0049] Example

[0050] Example 1

[0051] A method for preparing a metal powder with low oxygen content comprises the following steps:

[0052] S1. Weigh metal raw materials containing Nb, Ni, C, Cr, Al, Fe, and Ti according to the composition and weight shown in Table 1. The purity of each raw material is not less than 99.5%, the niobium content of the ferroniobium alloy is 70%, and the titanium content of the ferrotitanium alloy is 40%. Stir the metal raw materials in a blender at 500 rpm for 3 minutes to obtain a mixed raw material. Add the mixed raw material to a vacuum arc furnace for melting at a vacuum degree of 1×10 -3 Pa, the smelting temperature is 1700℃, the smelting time is 25min, and the molten metal is obtained after the smelting is completed.

[0053] S2. The smelted metal liquid is atomized using an ultrasonic atomization device with an ultrasonic frequency set to 40 kHz. During the atomization process, liquid carbon dioxide and argon are used as cooling media. A high-pressure pump delivers the liquid carbon dioxide and argon to the atomization area, cooling the metal liquid to form metal powder. The flow rate of the liquid carbon dioxide is 1 L / min, and the flow rate of the argon is 15 L / min.

[0054] S3. Place the metal powder in a closed reactor and use argon as a carrier gas at a flow rate of 3L / min to pass it into a container containing aluminum isopropoxide solution and zirconium acetylacetonate solution. The solvent of the aluminum isopropoxide solution is isopropanol, and the mass concentration of the aluminum isopropoxide solution is 18%; the solvent of the zirconium acetylacetonate solution is toluene, and the mass concentration of the zirconium acetylacetonate solution is 14%. The mass ratio of the aluminum isopropoxide solution to the zirconium acetylacetonate solution is 3:1. Atomize the two solutions through an atomizing nozzle and carry them into the closed reactor. React at a temperature of 250°C and a pressure of 50kPa for 4 hours.

[0055] S4. Add the metal powder after the reaction in S3 into a pulse current heating device and perform pulse deoxygenation treatment under an argon protective atmosphere, wherein the pulse current density is 103A / cm², the pulse width is 5ms, the duty cycle is 30%, the treatment temperature is 800℃, and the treatment time is 15min. After the treatment is completed, a low-oxygen content metal powder is obtained.

[0056] Example 2

[0057] A method for preparing a metal powder with low oxygen content comprises the following steps:

[0058] S1. Weigh metal raw materials containing Nb, Ni, C, Cr, Al, Fe, and Ti according to the composition and weight shown in Table 1. The purity of each raw material is not less than 99.5%, the niobium content of the ferroniobium alloy is 68%, and the titanium content of the ferrotitanium alloy is 35%. Stir the metal raw materials in a blender at 500 rpm for 4 minutes to obtain a mixed raw material. Add the mixed raw material to a vacuum arc furnace for melting at a vacuum degree of 3×10 -3Pa, the smelting temperature is 1800℃, the smelting time is 20min, and the molten metal is obtained after the smelting is completed.

[0059] S2. The smelted metal liquid is atomized using an ultrasonic atomization device with an ultrasonic frequency set to 45 kHz. During the atomization process, liquid carbon dioxide and argon are used as cooling media. A high-pressure pump delivers the liquid carbon dioxide and argon to the atomization area, cooling the metal liquid to form metal powder. The flow rate of the liquid carbon dioxide is 2 L / min, and the flow rate of the argon is 20 L / min.

[0060] S3. Place the metal powder in a closed reactor and use argon as a carrier gas at a flow rate of 4 L / min to pass it into a container containing aluminum isopropoxide solution and zirconium acetylacetonate solution. The solvent of the aluminum isopropoxide solution is isopropanol, and the mass concentration of the aluminum isopropoxide solution is 20%; the solvent of the zirconium acetylacetonate solution is toluene, and the mass concentration of the zirconium acetylacetonate solution is 15%. The mass ratio of the aluminum isopropoxide solution to the zirconium acetylacetonate solution is 4:1. Atomize the two solutions through an atomizing nozzle and carry them into the closed reactor. React at a temperature of 300°C and a pressure of 55 kPa for 3 hours.

[0061] S4. Add the metal powder after the reaction in S3 into a pulse current heating device and perform pulse deoxygenation treatment under an argon protective atmosphere, wherein the pulse current density is 104A / cm², the pulse width is 20ms, the duty cycle is 35%, the treatment temperature is 900℃, and the treatment time is 10min. After the treatment is completed, a low-oxygen content metal powder is obtained.

[0062] Example 3

[0063] A method for preparing a metal powder with low oxygen content comprises the following steps:

[0064] S1. Weigh metal raw materials containing Nb, Ni, C, Cr, Al, Fe, and Ti according to the composition and weight shown in Table 1. The purity of each raw material is not less than 99.5%, the niobium content of the ferroniobium alloy is 65%, and the titanium content of the ferrotitanium alloy is 30%. Stir the metal raw materials in a blender at 600 rpm for 4 minutes to obtain a mixed raw material. Add the mixed raw material to a vacuum arc furnace for melting at a vacuum degree of 5×10 -3 Pa, the smelting temperature is 1900℃, the smelting time is 15min, and the molten metal is obtained after the smelting is completed.

[0065] S2. The smelted metal liquid is atomized using an ultrasonic atomization device with an ultrasonic frequency set to 45 kHz. During the atomization process, liquid carbon dioxide and argon are used as cooling media. A high-pressure pump delivers the liquid carbon dioxide and argon to the atomization area, cooling the metal liquid to form metal powder. The flow rate of the liquid carbon dioxide is 3 L / min, and the flow rate of the argon is 25 L / min.

[0066] S3. Place the metal powder in a sealed reactor and use argon as a carrier gas at a flow rate of 4 L / min to pass it into a container containing aluminum isopropoxide solution and zirconium acetylacetonate solution. The solvent of the aluminum isopropoxide solution is isopropanol, and the mass concentration of the aluminum isopropoxide solution is 22%; the solvent of the zirconium acetylacetonate solution is toluene, and the mass concentration of the zirconium acetylacetonate solution is 16%. The mass ratio of the aluminum isopropoxide solution to the zirconium acetylacetonate solution is 5:1. Atomize the two solutions through an atomizing nozzle and carry them into the sealed reactor. React at a temperature of 350°C and a pressure of 60 kPa for 2 hours.

[0067] S4. Add the metal powder after the reaction in S3 into a pulse current heating device and perform pulse deoxygenation treatment under an argon protective atmosphere, wherein the pulse current density is 105A / cm², the pulse width is 50ms, the duty cycle is 40%, the treatment temperature is 1000℃, and the treatment time is 5min. After the treatment is completed, a low-oxygen content metal powder is obtained.

[0068] Table 1 Metal raw material components and amounts in Examples 1-3 (kg)

[0069]

[0070] Example 4

[0071] A method for preparing a low-oxygen content metal powder, which differs from Example 1 in that the mass concentration of the aluminum isopropoxide solution in step S3 of this embodiment is 25%; the mass concentration of the zirconium acetylacetonate solution is 20%.

[0072] Example 5

[0073] A method for preparing a metal powder with a low oxygen content is different from that of Example 1 in that the flow rate of the liquid carbon dioxide in step S2 of this embodiment is 4 L / min and the flow rate of the argon is 30 L / min.

[0074] Comparative Example

[0075] Comparative Example 1

[0076] A low-oxygen iron-based metal powder was prepared according to the method of Example 1 in the patent application document with publication number CN110052617A, entitled "A Method for Manufacturing Low-Oxygen Content Water Atomized Metal Powder."

[0077] Comparative Example 2

[0078] A method for preparing a low-oxygen content metal powder, which differs from Example 1 in that, in S2 of this comparative example, a potassium silicate aqueous solution with a mass concentration of 1% is used as a cooling medium, and the potassium silicate aqueous solution is delivered to the atomization area by a high-pressure pump, and the flow rate of the potassium silicate aqueous solution is 10 L / min.

[0079] Comparative Example 3

[0080] A method for preparing a metal powder with a low oxygen content is different from Example 1 in that argon gas is used alone as the cooling medium in S2 of this comparative example.

[0081] Comparative Example 4

[0082] A method for preparing a metal powder with a low oxygen content is different from Example 1 in that, in S3 of this comparative example, aluminum isopropoxide solution is used alone to treat the metal powder.

[0083] Comparative Example 5

[0084] A method for preparing a metal powder with a low oxygen content is different from Example 1 in that step S3 is not performed in this comparative example, and the metal powder obtained in S2 is directly subjected to pulse deoxygenation treatment in S4.

[0085] Comparative Example 6

[0086] A method for preparing a metal powder with a low oxygen content is different from Example 1 in that step S4 is not performed in this comparative example.

[0087] Performance testing

[0088] 1. Oxygen content detection

[0089] The oxygen content of the metal powders prepared in Examples 1-5 and Comparative Examples 1-6 was tested according to the method specified in GB / T5158.4-2011 "Determination of total oxygen concentration by metal powder reduction-extraction method". The test results are shown in Table 2.

[0090] 2. Sphericity detection

[0091] The sphericity of the metal powders prepared in Examples 1-5 and Comparative Examples 1-6 was tested with reference to the method in “Method for Determining the Sphericity of Titanium and Titanium Alloy Powders”. The test results are shown in Table 2.

[0092] Table 2 Test results

[0093]

[0094] Refer to Table 2, as Figure 1-Figure 3As shown, the oxygen content of Examples 1-3 is all below 200ppm, and the sphericity is above 98%. This is because a vacuum arc furnace is used for smelting to reduce the contact between the metal and oxygen, liquid carbon dioxide and argon are used as cooling media to avoid the introduction of oxygen, the Al2O3-ZrO2 composite protective film formed by aluminum isopropoxide and zirconium acetylacetonate prevents oxygen penetration, and the pulse current heating device performs deoxygenation treatment, which synergistically reduces the oxygen content from multiple links. At the same time, the cooling medium reduces the temperature gradient when the metal droplets solidify, ultrasonic atomization makes the metal liquid stressed evenly, and the "micro-shaping" effect of the protective film effectively improves the sphericity. The oxygen content in Example 4 is slightly increased, which may be because the concentrations of aluminum isopropoxide solution and zirconium acetylacetonate solution in step S3 are too high, resulting in incomplete reaction and affecting the barrier effect against oxygen. The sphericity of Example 5 decreases because the flow rates of liquid carbon dioxide and argon in step S2 are too high, making the cooling process too intense and the impact force on the metal droplets when solidifying is too large, thereby affecting the sphericity.

[0095] Comparative Example 1 exhibited an oxygen content as high as 1200 ppm and a sphericity of 79.32%. This high oxygen content was achieved by using an aqueous solution containing multiple salts as the cooling medium. This solution contained trace amounts of dissolved oxygen, and it was difficult to completely isolate the ambient oxygen during the preparation process. Furthermore, the high-pressure aqueous solution applied uneven forces to the metal droplets, making the cooling rate difficult to control, resulting in low sphericity.

[0096] In Comparative Example 2, the oxygen content was 800 ppm and the sphericity was 82.31%. Using a 1% potassium silicate aqueous solution as the cooling medium provided some protection, but the problem of dissolved oxygen in the aqueous solution and oxygen introduced through contact with air persisted, resulting in a higher oxygen content than in Example 1. Furthermore, the aqueous solution cooling method was less effective in improving sphericity than the liquid carbon dioxide and argon cooling method in Example 1.

[0097] Comparative Example 3 had an oxygen content of 700 ppm and a sphericity of 95.32%. While using argon alone as a cooling medium can provide some oxygen isolation and cooling, it lacks the ultra-low temperature and rapid cooling of liquid carbon dioxide. The metal droplets take a relatively long time to solidify, leaving some opportunity for oxidation, resulting in a higher oxygen content than in Example 1. While argon allows for more uniform cooling, resulting in a relatively higher sphericity, it's not as effective as the synergistic effect of the two cooling media in Example 1.

[0098] The oxygen content of Comparative Example 4 was 500 ppm, and the sphericity was 97.68%. In S3, the metal powder was treated with aluminum isopropoxide solution alone, without zirconium acetylacetonate solution. The resulting protective film had a single component and was inferior to the Al2O3-ZrO2 composite protective film. Its oxygen barrier effect was relatively weak, resulting in a higher oxygen content than in Example 1.

[0099] Comparative Example 5 had an oxygen content of 1000 ppm and a sphericity of 89.61%. Without the S3 step, i.e., without the formation of a protective film, the metal powder was easily oxidized during subsequent handling and storage, resulting in a significant increase in oxygen content. Furthermore, the lack of the "micro-shaping" effect of the protective film also affected sphericity to a certain extent.

[0100] The oxygen content in Comparative Example 6 was 900 ppm, and the sphericity was 98.51%. Without the S4 step, i.e., the pulse deoxidation treatment, the oxides within the metal powder could not be decomposed or volatilized, resulting in a higher oxygen content. However, the previous steps did contribute to the improvement in sphericity, resulting in a sphericity similar to that of Example 1.

[0101] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A method for preparing a metal powder with low oxygen content, characterized in that: The steps include: S1. Weighing metal raw materials containing Nb, Ni, C, Cr, Al, Fe, and Ti elements, mixing them uniformly to obtain a mixed raw material, and adding the mixed raw material into a vacuum arc furnace for smelting to obtain a molten metal; S2. The smelted metal liquid is atomized by an ultrasonic atomization device with an ultrasonic frequency set to 40-50 kHz. During the atomization process, liquid carbon dioxide and argon are used as cooling media. The liquid carbon dioxide and argon are transported to the atomization area by a high-pressure pump to cool the metal liquid to form metal powder. S3. Place the metal powder in a sealed reactor, use argon as a carrier gas, pass it into a container containing aluminum isopropoxide solution and zirconium acetylacetonate solution, atomize the two solutions through an atomizing nozzle and carry them into the sealed reactor, and react at a temperature of 250-350° C. and a pressure of 50-60 kPa for 2-4 hours; S4, adding the metal powder after the reaction in S3 to a pulse current heating device, and performing pulse deoxidation treatment under a protective atmosphere at a treatment temperature of 800-1000° C. for 5-15 minutes, to obtain a metal powder with low oxygen content after the treatment is completed; The flow rate of liquid carbon dioxide in S2 is 1-3 L / min, and the flow rate of argon is 15-25 L / min; The mass ratio of the aluminum isopropoxide solution to the zirconium acetylacetonate solution in S3 is (3-5):1; the mass concentration of the aluminum isopropoxide solution is 18%-22%; and the mass concentration of the zirconium acetylacetonate solution is 14%-16%.

2. The method for preparing a low-oxygen metal powder according to claim 1, wherein: The solvent of the aluminum isopropoxide solution in S3 is isopropanol.

3. The method for preparing a low-oxygen metal powder according to claim 1, wherein: The solvent of the zirconium acetylacetonate solution in S3 is toluene.

4. The method for preparing a low-oxygen metal powder according to claim 1, wherein: During the pulse deoxygenation treatment in S4, the pulse current density is 103-105A / cm 2 , pulse width 5-50ms, duty cycle 30%-40%.

5. The method for preparing a low-oxygen metal powder according to claim 1, wherein: In the above-mentioned S1, the metal raw materials are ferroniobium alloy, electrolytic nickel, carbon black, electrolytic chromium, electrolytic aluminum, electrolytic iron and ferrotitanium alloy with a purity of not less than 99.5%.

6. The method for preparing a low-oxygen content metal powder according to claim 5, characterized in that: The niobium content in the ferroniobium alloy is 65%-70%; the titanium content in the ferrotitanium alloy is 30%-40%.

7. The method for preparing a low-oxygen metal powder according to claim 6, characterized in that: In S1, the ratio of the metal raw materials is as follows in parts by mass: Niobium iron alloy 50-55 parts; Electrolytic nickel 18-20 parts; Carbon black 10-12 parts; 8-10 parts of electrolytic chromium; 1-5 parts of electrolytic aluminum; 1-3 parts of electrolytic iron; 1-3 parts of titanium-iron alloy.

8. The method for preparing a low-oxygen metal powder according to claim 1, wherein: In the above step S1, the mixed raw materials are melted at a temperature of 1700-1900°C, a melting time of 15-25 min, and a vacuum degree of ≤5×10 -3 Pa.

Images