Preparation method of low-oxygen-content metal powder

Abstract

The invention relates to the technical field of metal powder preparation, and particularly discloses a preparation method of low-oxygen-content metal powder. The invention discloses a preparation method of low-oxygen-content metal powder. The preparation method comprises the steps that S1, metal raw materials are weighed and smelted, and molten metal is obtained; s2, molten metal obtained after smelting is atomized through an ultrasonic atomization device, and liquid carbon dioxide and argon are adopted as cooling media to enable the molten metal to be cooled to form metal powder; s3, the metal powder is placed in a closed reaction kettle, argon serves as carrier gas, the metal powder is introduced into a container containing an aluminum isopropoxide solution and a zirconium acetylacetonate solution, and the two solutions are atomized through an atomization nozzle and then react with the metal powder; and S4, the metal powder obtained after the reaction in the S3 is added into a pulse current heating device to be subjected to pulse oxygen removal treatment. The metal powder can meet the requirements of aerospace, precision machinery manufacturing and other high-end fields for material performance, and has the advantages of being low in oxygen content and high in sphericity degree.

Description

Technical Field

[0001] This application relates to the technical field of metal powder preparation. More specifically, it relates to a method for preparing metal powder with low oxygen content. Background Art

[0002] In the field of metal powder preparation, metal powder with low oxygen content has crucial application value. With the development of high-end industries such as aerospace and precision machinery manufacturing, the demand for metal powder with low oxygen content is increasing day by day. Low oxygen content can effectively improve the corrosion resistance, mechanical strength, electrical properties, etc. of metal powder and its products.

[0003] In the prior art, there are already various methods for preparing low-oxygen metal powder. For example, by melting and atomizing under vacuum or inert gas protection, the oxygen content of metal powder can be effectively reduced. In related technologies, a patent application document with the publication number CN110052617A discloses a method for manufacturing low-oxygen content water atomized metal powder. This method uses an aqueous solution containing salts such as alkaline borate, silicate, and phosphate as the cooling medium for atomizing metal droplets, and compresses this aqueous solution into a high-pressure cooling medium using a high-pressure water pump and a spray disc. This high-pressure cooling medium instantaneously breaks and cools the metal droplets, and the alkaline aqueous solution has a role in protecting the metal surface during the breaking and cooling process. The alkaline substance also plays a role in protecting the metal powder from oxidation during the subsequent drying and dehydration process. Through the above protection, metal powder with a lower oxygen content than that in the general atomization process is obtained.

[0004] Although the above prior art can reduce the oxygen content of metal powder to a certain extent, since an aqueous solution containing various salts is used as the cooling medium, in the atomization and subsequent treatment processes, even though 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 external oxygen during the processes of contact, separation, drying, and dehydration between the metal powder and the cooling medium. At the same time, the oxygen barrier effect of the alkaline substance also has a certain limit. The oxygen content of the prepared metal powder is 1000 - 1600 ppm. For the manufacture of some key components in the aerospace field with extremely strict requirements for material properties, such as the high-temperature alloy turbine blades of aeroengines and the tiny metal parts used in the high-precision transmission system in precision machinery manufacturing, there is still a situation where the oxygen content is too high. This application field requires the oxygen content of the metal powder to be lower than 300 ppm. High oxygen content will cause the metal powder to easily undergo oxidation reactions during subsequent forming and use processes, reducing the mechanical properties and corrosion resistance of the material, and affecting the service life and reliability of the components.

[0005] Moreover, when the high-pressure aqueous solution cooling medium atomizes and breaks the metal droplets, the force on the droplets is uneven and the cooling rate is difficult to precisely control. During the solidification process of the metal powder, the shrinkage of each part is inconsistent, resulting in a low sphericity of the metal powder. When in use, there is a problem of poor powder fluidity. During the powder metallurgy forming process, powders with low sphericity are difficult to uniformly fill the mold, and bridging phenomena are likely to occur, resulting in uneven density of the formed parts, 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 technology has problems that the oxygen content is difficult to meet the oxygen content requirements of high-end application fields and the low sphericity affects the use performance. Summary of the Invention

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

[0008] The preparation method for metal powder with low oxygen content provided by the present application adopts the following technical solution: A preparation method for metal powder with low oxygen content includes the following steps: S1. Weigh metal raw materials containing elements Nb, Ni, C, Cr, Al, Fe, and Ti, mix them evenly to obtain a mixed raw material, and add the mixed raw material into a vacuum arc furnace for melting to obtain a metal liquid; S2. Atomize the melted metal liquid through an ultrasonic atomization device, set the ultrasonic frequency to 40 - 50 kHz. During the atomization process, use liquid carbon dioxide and argon as the cooling medium, and transport liquid carbon dioxide and argon to the atomization area through a high-pressure pump to cool the metal liquid to form metal powder; S3. Place the metal powder in a closed reaction kettle, use argon as the carrier gas, and introduce it into a container filled with aluminum isopropoxide solution and zirconium acetylacetonate solution. After atomizing the two solutions through an atomizing nozzle, carry them into the closed reaction kettle, and react for 2 - 4 h under the conditions of a temperature of 250 - 350 °C and a pressure of 50 - 60 kPa; S4. Add the metal powder after the reaction in S3 into a pulsed current heating device, and perform pulsed deoxidation treatment under a protective atmosphere. The treatment temperature is 800 - 1000 °C, the treatment time is 5 - 15 min, and after the treatment is completed, metal powder with low oxygen content is obtained.

[0009] By adopting the above technical solutions, 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 from the source. During the cooling process, liquid carbon dioxide and argon are used as cooling media. Liquid carbon dioxide can provide strong cooling capacity, rapidly reduce the temperature of the molten metal, and make it solidify quickly. At the same time, argon, as an auxiliary cooling gas, can not only further remove heat, but also play a role in buffering and dilution, reducing the potential danger when extremely cold and extremely hot meet. In addition, argon, as an inert protective gas, forms a gas film to wrap the metal droplets during the atomization process, further isolating the outside oxygen and preventing the introduction of oxygen elements during the cooling process. In step S3, a uniform Al2O3-ZrO2 protective film is formed on the surface of the metal powder by aluminum isopropoxide and zirconium acetylacetonate, inhibiting the adsorption of oxygen. Its oxygen diffusion coefficient is lower than that of a single alumina film, effectively preventing oxygen from penetrating into the interior of the metal powder. The pulsed current, through the Joule heat effect and plasma activation, decomposes or volatilizes the oxides inside the powder. Experimental data shows that this step can further reduce the oxygen content from 800 ppm to below 200 ppm.

[0010] The ultra-low temperature of liquid carbon dioxide and the auxiliary cooling of argon make the temperature gradient of each part of the metal droplets less than 5 °C / mm during the solidification process, significantly reducing the shape distortion caused by inconsistent shrinkage. According to the heat conduction model calculation, this cooling method can increase the sphericity from 70%-80% of the traditional method to more than 95%. In step S3, the uniform deposition process of the Al2O3-ZrO2 composite film on the powder surface has a certain "micro-shaping" effect, which can fill the tiny depressions on the powder surface and further optimize the sphericity.

[0011] In summary, through the above solutions, the defects of high oxygen content and low sphericity of metal powder in the existing technology can be effectively overcome. This preparation method optimizes the whole process from melting, cooling, surface modification to deep deoxidation, can reduce the oxygen content of metal powder to below 200 ppm, and effectively improve the sphericity of metal powder, meeting the strict requirements of material properties in high-end fields such as aerospace and precision machinery manufacturing, and providing an effective technical solution for the high-quality preparation of key components such as aeroengine turbine blades and high-precision transmission parts.

[0012] 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.

[0013] By adopting the above technical solutions, the flow rate of liquid carbon dioxide is controlled at 1-3 L / min, which can provide appropriate cooling intensity and quickly take away the heat of the molten metal; the flow rate of argon is from 15 to 25 L / 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.

[0014] Optionally, the solvent of the aluminum isopropoxide solution in S3 is isopropanol, and the mass concentration of the aluminum isopropoxide solution is 18% - 22%.

[0015] By adopting the above technical solution, the aluminum isopropoxide solution with the above solvent and concentration has good stability, enabling it to be evenly deposited and react on the surface of the metal powder in the subsequent reaction, contributing to the formation of a uniform and effective protective film, improving the antioxidant ability of the metal powder, and reducing the oxygen content.

[0016] Optionally, the solvent of the zirconium acetylacetonate solution in S3 is toluene, and the mass concentration of the zirconium acetylacetonate solution is 14% - 16%. <9000045>By adopting the above technical solution, toluene has good solubility for zirconium acetylacetonate, and a mass concentration of 14% - 16% is within its solubility range, ensuring the stability of the solution and enabling it to fully participate in the reaction, and jointly forming a composite protective film with better performance with the reaction product of the aluminum isopropoxide solution.

[0018] Optionally, the mass ratio of the aluminum isopropoxide solution to the zirconium acetylacetonate solution in S3 is (3 - 5):1.

[0019] By adopting the above technical solution, specifying the mass ratio of the aluminum isopropoxide solution to the zirconium acetylacetonate solution makes the component ratio of the composite protective film formed by the reaction of the two solutions more reasonable, improving the antioxidant protection performance of the protective film for the metal powder and reducing the oxygen content.

[0020] Optionally, during the pulse deoxidation 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%.

[0021] By adopting the above technical solution, the pulse current density, pulse width, and duty cycle of the pulse deoxidation treatment with the above parameters enable the pulse deoxidation process to proceed efficiently and stably, effectively removing the residual oxygen in the metal powder, further reducing the oxygen content, and avoiding the problem of overheating and sintering of the metal powder caused by improper parameters.

[0022] Optionally, in S1, the metal raw materials are ferro-niobium alloy with a purity of not less than 99.5%, electrolytic nickel, carbon black, electrolytic chromium, electrolytic aluminum, electrolytic iron, and ferro-titanium alloy.

[0023] By adopting the above technical solution, high-purity raw materials reduce the content of impurity elements. With fewer impurities, side reactions such as oxidation caused by impurities during melting, atomization, etc. are reduced, which is beneficial to controlling the oxygen content.

[0024] Optionally, the content of niobium in the ferro-niobium alloy is 65% - 70%; the content of titanium in the ferro-titanium alloy is 30% - 40%.

[0025] By adopting the above technical solution, the content of key elements is stable, the alloy composition is relatively fixed, and in subsequent processes such as melting and reaction, the reaction is more controllable, which is conducive to the formation of metal powders and protective films with stable properties, etc., and better achieves the goal of reducing the oxygen content.

[0026] Optionally, in the S1, the ratio of the metal raw materials is as follows by mass: Ferroniobium alloy: 50 - 55 parts; Electrolytic nickel: 18 - 20 parts; Carbon black: 10 - 12 parts; Electrolytic chromium: 8 - 10 parts; Electrolytic aluminum: 1 - 5 parts; Electrolytic iron: 1 - 3 parts; Ferrotitanium alloy: 1 - 3 parts.

[0027] By adopting the above technical solution, the above ratio can make the elements interact properly, form an alloy liquid with good performance during melting, and the subsequent atomization, modification and deoxidation processes can proceed better, ensuring the performance of the final metal powder.

[0028] Optionally, in the S1, when melting the mixed raw materials, the melting temperature is 1700 - 1900 °C, the melting time is 15 - 25 min, and the vacuum degree ≤ 5×10 - ³ Pa.

[0029] In summary, the present application has the following beneficial effects: 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 oxygen introduced by contacting air. The ultra-low temperature characteristics of liquid carbon dioxide can quickly solidify the metal liquid, greatly shortening the high-temperature exposure time and reducing the chance of oxidation; argon, as an inert gas, forms a gas film to wrap the metal droplets, further isolating external oxygen. In subsequent processing, a uniform Al2O3-ZrO2 composite protective film is formed on the surface of the metal powder through aluminum isopropoxide and zirconium acetylacetonate, which can effectively prevent oxygen from penetrating into the metal powder. From suppressing oxidation in the vacuum environment during melting, to reducing oxygen introduction during the cooling process, and then to the long-term barrier of the protective film, multiple links cooperate to greatly reduce the oxygen content of the metal powder from 1000 - 1600 ppm in the traditional method to below 200 ppm, significantly improving the antioxidant performance and corrosion resistance of the metal powder, and meeting the strict requirements for low oxygen content in high-end fields.

[0030] 2. The preparation method of this application uses a pulsed current heating device to perform pulsed deoxidation treatment under specific parameters. Utilizing the Joule heat effect and plasma activation, the oxides inside the metal powder are decomposed or react with reducing agents in the protective atmosphere to form volatile products. This treatment process can not only remove the residual oxygen in the metal powder during the previous preparation process, but also avoid problems such as powder sintering caused by overheating by precisely controlling the parameters. While achieving deep deoxidation, it ensures the stability of the microstructure and properties of the metal powder, providing high-quality raw materials for the production of high-performance metal products in fields such as aerospace and precision machinery manufacturing.

[0031] 3. During the atomization process of the method of this application, a cooling medium composed of liquid carbon dioxide and argon enables the temperature gradient of each part of the metal droplets to be less than 5 °C / mm during solidification, achieving a uniform and rapid cooling effect, significantly reducing shape distortion caused by inconsistent shrinkage. An ultrasonic atomization device with an ultrasonic frequency set at 20 - 50 kHz ensures uniform force on the metal liquid and breaks it into tiny droplets with a narrow particle size distribution, laying the foundation for high sphericity. In addition, the Al2O3-ZrO2 composite film formed in step S3 is uniformly deposited on the powder surface and has a "micro-shaping" effect, which can fill the tiny depressions on the powder surface, further optimizing the sphericity, effectively improving the fluidity of the powder. During the powder metallurgy forming process, it can uniformly fill the mold, avoid bridging phenomena, ensure uniform density of the formed parts, thereby improving the mechanical properties and dimensional accuracy of the final product, and meeting the strict requirements for the formability of metal powder in high-end manufacturing. Brief Description of the Drawings

[0032] Figure 1 SEM image of the low-oxygen-content metal powder prepared in Example 1 of this application; Figure 2 SEM image of the low-oxygen-content metal powder prepared in Example 2 of this application; Figure 3 SEM image of the low-oxygen-content metal powder prepared in Example 3 of this application. Detailed Description of the Embodiments

[0033] The following further elaborates on this application in conjunction with the embodiments.

[0034] Embodiment Embodiment 1 A method for preparing a low-oxygen-content metal powder includes the following steps: S1. Weigh metal raw materials containing elements Nb, Ni, C, Cr, Al, Fe, and Ti according to the components and weights shown in Table 1. Among them, the purity of each raw material is not less than 99.5%. The content of niobium in ferro-niobium alloy is 70%, and the content of titanium in ferro-titanium alloy is 40%. Stir the metal raw materials in a blender at a speed of 500 r / min for 3 min to obtain a mixed raw material. Then add the mixed raw material into a vacuum arc furnace for melting. The vacuum degree is 1×10 -3 Pa, the melting temperature is 1700 °C, and the melting time is 25 min. After melting, a metal liquid is obtained.

[0035] S2. Atomize the melted metal liquid through an ultrasonic atomization device. The ultrasonic frequency is set to 40 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 through a high-pressure pump to cool the metal liquid to form metal powder. Among them, the flow rate of liquid carbon dioxide is 1 L / min, and the flow rate of argon is 15 L / min.

[0036] S3. Place the metal powder in a closed reaction kettle. Use argon with a flow rate of 3 L / min as the carrier gas and introduce it into a container filled with aluminum isopropoxide solution and zirconium acetylacetonate solution. Among them, 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 reaction kettle. React at a temperature of 250 °C and a pressure of 50 kPa for 4 h; S4. Add the metal powder after the reaction in S3 into a pulsed current heating device and perform pulsed deoxidation treatment under an argon protection atmosphere. Among them, the pulsed current density is 103 A / cm², the pulse width is 5 ms, the duty cycle is 30%, the treatment temperature is 800 °C, and the treatment time is 15 min. After the treatment, a metal powder with a low oxygen content is obtained.

[0037] Example 2 A method for preparing a metal powder with a low oxygen content, comprising the following steps: S1. Weigh metal raw materials containing elements Nb, Ni, C, Cr, Al, Fe, and Ti according to the components and weights shown in Table 1. Among them, the purity of each raw material is not less than 99.5%. The content of niobium in ferro-niobium alloy is 68%, and the content of titanium in ferro-titanium alloy is 35%. Stir the metal raw materials in a blender at a speed of 500 r / min for 4 min to obtain a mixed raw material. Then add the mixed raw material into a vacuum arc furnace for melting. The vacuum degree is 3×10 -3 Pa, the melting temperature is 1800 °C, and the melting time is 20 min. After melting, a metal liquid is obtained.

[0038] S2. Atomize the molten metal through an ultrasonic atomization device. Set the ultrasonic frequency to 45 kHz. During the atomization process, use liquid carbon dioxide and argon as cooling media. Deliver liquid carbon dioxide and argon to the atomization area through a high-pressure pump to cool the metal liquid to form metal powder. Among them, the flow rate of liquid carbon dioxide is 2 L / min, and the flow rate of argon is 20 L / min.

[0039] S3. Place the metal powder in a closed reaction kettle. Use argon with a flow rate of 4 L / min as the carrier gas and introduce it into a container filled with aluminum isopropoxide solution and zirconium acetylacetonate solution. Among them, 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 reaction kettle, and react for 3 h under the conditions of a temperature of 300 °C and a pressure of 55 kPa; S4. Add the metal powder after the reaction in S3 to a pulsed current heating device and perform pulsed deoxidation treatment under an argon protection atmosphere. Among them, the pulsed current density is 104 A / cm², the pulse width is 20 ms, the duty cycle is 35%, the treatment temperature is 900 °C, and the treatment time is 10 min. After the treatment, low-oxygen-content metal powder is obtained.

[0040] Example 3 A method for preparing low-oxygen-content metal powder, comprising the following steps: S1. Weigh metal raw materials containing Nb, Ni, C, Cr, Al, Fe, and Ti elements according to the components and weights shown in Table 1. Among them, the purity of each raw material is not less than 99.5%, the content of niobium in the ferro-niobium alloy is 65%, and the content of titanium in the ferro-titanium alloy is 30%. Stir the metal raw materials in a mixer at a speed of 600 r / min for 4 min to obtain a mixed raw material. Add the mixed raw material to a vacuum arc furnace for melting. The vacuum degree is 5×10 -3 Pa, the melting temperature is 1900 °C, and the melting time is 15 min. After melting, metal liquid is obtained.

[0041] S2. Atomize the molten metal through an ultrasonic atomization device. Set the ultrasonic frequency to 45 kHz. During the atomization process, use liquid carbon dioxide and argon as cooling media. Deliver liquid carbon dioxide and argon to the atomization area through a high-pressure pump to cool the metal liquid to form metal powder. Among them, the flow rate of liquid carbon dioxide is 3 L / min, and the flow rate of argon is 25 L / min.

[0042] S3. Place the metal powder in a closed reaction kettle. Use argon with a flow rate of 4 L / min as the carrier gas and introduce it into a container filled with aluminum isopropoxide solution and zirconium acetylacetonate solution. Among them, 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 then carry them into the closed reaction kettle. React for 2 h under the conditions of a temperature of 350 °C and a pressure of 60 kPa; S4. Add the metal powder after the reaction in S3 into a pulsed current heating device and perform pulsed deoxidation treatment under an argon protection atmosphere. Among them, the pulsed current density is 105 A / cm², the pulse width is 50 ms, the duty cycle is 40%, the treatment temperature is 1000 °C, and the treatment time is 5 min. After the treatment, a metal powder with a low oxygen content is obtained.

[0043] Table 1 Metal raw material components and dosages (kg) in Examples 1 - 3

[0044] Example 4 A preparation method of a metal powder with a low oxygen content, which is different from Example 1 in that in step S3 of this example, the mass concentration of the aluminum isopropoxide solution is 25%; the mass concentration of the zirconium acetylacetonate solution is 20%.

[0045] Example 5 A preparation method of a metal powder with a low oxygen content, which is different from Example 1 in that in step S2 of this example, the flow rate of liquid carbon dioxide is 4 L / min, and the flow rate of argon is 30 L / min.

[0046] Comparative Example Comparative Example 1 A low-oxygen iron-based metal powder was prepared according to the method of Example 1 in the patent application document with the publication number CN110052617A and the name of a manufacturing method of a water atomized metal powder with a low oxygen content.

[0047] Comparative Example 2 A preparation method of a metal powder with a low oxygen content, which is different from Example 1 in that in this comparative example, an aqueous potassium silicate solution with a mass concentration of 1% is used as the cooling medium in S2, and the aqueous potassium silicate solution is sent to the atomization area through a high-pressure pump, and the flow rate of the aqueous potassium silicate solution is 10 L / min.

[0048] Comparative Example 3 A preparation method of a metal powder with a low oxygen content, which is different from Example 1 in that in this comparative example, only argon is used as the cooling medium in S2.

[0049] Comparative Example 4 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.

[0050] Comparative Example 5 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.

[0051] Comparative Example 6 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.

[0052] Performance testing 1. Oxygen content detection 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.

[0053] 2. Sphericity detection 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.

[0054] Table 2 Test results

[0055] Refer to Table 2, as Figures 1 - 3 As 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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 a low oxygen content, characterized in that, It includes the following steps: S1. Weigh metal raw materials containing Nb, Ni, C, Cr, Al, Fe, and Ti elements, mix them evenly to obtain a mixed raw material, and add the mixed raw material into a vacuum arc furnace for melting to obtain a metal liquid; S2. Atomize the melted metal liquid through an ultrasonic atomization device. The ultrasonic frequency is set at 40 - 50 kHz. During the atomization process, liquid carbon dioxide and argon are used as cooling media, and they are transported to the atomization area through a high-pressure pump to cool the metal liquid to form metal powder; S3. Place the metal powder in a closed reaction kettle, use argon as a carrier gas, and introduce it into a container filled with an aluminum isopropoxide solution and a zirconium acetylacetonate solution. The two solutions are atomized by an atomizing nozzle and then carried into the closed reaction kettle, and react for 2 - 4 h under the conditions of a temperature of 250 - 350 °C and a pressure of 50 - 60 kPa; S4. Add the metal powder after the reaction in S3 into a pulsed current heating device, and perform pulsed deoxidation treatment under a protective atmosphere. The treatment temperature is 800 - 1000 °C, the treatment time is 5 - 15 min, and low-oxygen-content metal powder is obtained after the treatment is completed.

2. The preparation method of a metal powder with low oxygen content according to claim 1, characterized in that, In S2, the flow rate of liquid carbon dioxide is 1 - 3 L / min, and the flow rate of argon is 15 - 25 L / min.

3. The preparation method of a metal powder with low oxygen content according to claim 1, characterized in that, In S3, the solvent of the aluminum isopropoxide solution is isopropanol, and the mass concentration of the aluminum isopropoxide solution is 18% - 22%.

4. The preparation method of a metal powder with low oxygen content according to claim 3, characterized in that, In S3, the solvent of the zirconium acetylacetonate solution is toluene, and the mass concentration of the zirconium acetylacetonate solution is 14% - 16%.

5. The preparation method of a metal powder with low oxygen content according to claim 4, characterized in that, In S3, the mass ratio of the aluminum isopropoxide solution to the zirconium acetylacetonate solution is (3 - 5):

1.

6. The preparation method of a metal powder with low oxygen content according to claim 1, characterized in that, In S4, during the pulsed deoxidation treatment, the pulsed current density is 103 - 105 A / cm², the pulse width is 5 - 50 ms, and the duty cycle is 30% - 40%.

7. The preparation method of a metal powder with low oxygen content according to claim 1, characterized in that: In S1, the metal raw materials are ferro-niobium alloy with a purity of not less than 99.5%, electrolytic nickel, carbon black, electrolytic chromium, electrolytic aluminum, electrolytic iron, and ferro-titanium alloy.

8. A method for preparing a metal powder with a low oxygen content according to claim 7, characterized in that The content of niobium in the ferro-niobium alloy is 65% - 70%; the content of titanium in the ferro-titanium alloy is 30% - 40%.

9. The preparation method of a metal powder with a low oxygen content according to claim 8, characterized in that, In S1, the ratio of the metal raw materials, by mass parts, is as follows: 50 - 55 parts of ferro-niobium alloy; 18 - 20 parts of electrolytic nickel; 10 - 12 parts of carbon black; 8 - 10 parts of electrolytic chromium; 1 - 5 parts of electrolytic aluminum; 1 - 3 parts of electrolytic iron; 1 - 3 parts of ferro-titanium alloy.

10. The preparation method of a metal powder with low oxygen content according to claim 1, characterized in that, In the step S1, when smelting the mixed raw materials, the smelting temperature is 1700 - 1900 °C, the smelting time is 15 - 25 min, and the vacuum degree ≤ 5×10 - 3 Pa.

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