A post-processing technology and apparatus for ViGa gas atomization powder production

Abstract

This application discloses a post-processing technology and apparatus for ViGa gas atomization powder production. The process employs a four-step synergistic treatment: graded pre-separation, plasma desorption, vibration densification, and cooling shaping. First, a three-stage airflow classifier removes free fine powder. Then, radio frequency plasma bombardment desorbs attached satellite spheres and melts irregular protrusions on the powder surface. The powder is then densified and residual satellite spheres are removed via an ultrasonically vibrating fluidized bed. Finally, rapid cooling with inert gas shapes and fixes the spherical morphology. The apparatus integrates a feeding system, a grading module, a plasma module, a vibration module, a cooling module, and a control system, enabling precise control of process parameters. This application reduces the satellite sphere content in the powder to below 5%, increases sphericity to above 0.95, achieves a Hall flow rate ≤25s / 50g, a powder deformation rate <2%, and a single-batch energy consumption <200kW·h / ton. It is compatible with various ViGa gas atomization powders and solves the problems existing in the prior art.

Description

Technical Field

[0001] This invention relates to the field of high-performance metal powder preparation technology, specifically to a post-processing process and apparatus for ViGa gas atomization powder preparation. It is particularly suitable for satellite sphere removal, sphericity improvement and flow performance optimization of high-performance metal powders such as titanium alloys, high-temperature alloys and refractory metals, and can be applied to additive manufacturing fields such as aerospace engine blades and 3D printed medical implants. Background Technology

[0002] Vacuum induction melting gas atomization (ViGa) is a core technology for preparing high-performance metal powders. The powders produced have advantages such as high purity and controllable particle size, making them a core raw material for additive manufacturing. The satellite spheroid content, sphericity, and flow rate of the powder are key parameters determining the quality of the final additive manufacturing product: satellite spheroids lead to a decrease in powder bulk density (≤40% of theoretical density) and poor flowability (Hall flow rate >30s / 50g), which in turn causes defects such as interlayer porosity and insufficient density in 3D printing; low sphericity (sphericity <0.85) increases inter-powder friction and reduces powder uniformity; slow flow rate limits the printing efficiency of additive manufacturing equipment (≤50cm). 3 / h).

[0003] In current ViGa powder production processes, satellite spheres mainly arise from collisions between atomized droplets and incompletely solidified large particles, electrostatic adsorption of fine powder, and secondary droplet breakage during cooling. Insufficient sphericity is caused by uneven droplet cooling rates, resulting in irregular morphologies where the edges solidify first. To address these issues, existing post-processing solutions are mainly divided into three categories: 1. Combined mechanical sieving and air classifying process: The combined process of a three-stage air classifier and a vibrating screen can only remove free fine powder and cannot remove the attached satellite particles. The satellite particle removal rate is ≤60%, and the surface morphology of the powder is not changed. The sphericity improvement is limited (only up to 0.88). Mechanical sieving is also prone to causing powder deformation (deformation rate >8%). 2. High-temperature heat treatment process: The powder surface is softened and remelted by holding it at 800-1200℃ in a vacuum furnace for 1-2 hours. The sphericity can reach 0.92, but the satellite ball content is still >10%. Moreover, the processing time is long and the energy consumption is high (energy consumption per batch >500kW·h), which can easily lead to the growth of powder grains (grain size >50μm). 3. Plasma surface modification process: The powder is treated with radio frequency plasma, which improves the sphericity to 0.90. However, the plasma heating is uneven, which can easily cause local overmelting (overmelting rate > 5%). The satellite ball removal rate is only 60%, and the fine powder is prone to agglomeration.

[0004] In summary, existing post-processing technologies for ViGa gas atomization powder production all suffer from defects such as incomplete removal of satellite spheres, limited improvement in sphericity, significant powder damage, high energy consumption, or uneven heating. They cannot simultaneously meet the industrial requirements of low satellite sphere count, high sphericity, high flow rate, low damage, and low energy consumption. There is an urgent need to develop a post-processing process and device for ViGa gas atomization powder production. Summary of the Invention

[0005] The purpose of this invention is to provide a post-processing technology and apparatus for ViGa gas atomization powder production, which aims to significantly reduce satellite spheres, significantly improve sphericity, optimize powder flow rate, reduce damage and energy consumption, and enhance compatibility.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A post-processing technology for ViGa gas atomization powder production includes the following steps: S1, Pre-separation: ViGa raw powder is fed into a three-stage air classifier, where fine powder is separated by three series of classifying wheels. The rotation speeds of the classifying wheels are 2000 rpm, 3500 rpm, and 5000 rpm, respectively. The inlet air pressure of the classifier is 0.3 MPa, and the outlet air pressure is 0.1 MPa. The airflow direction is at a 30° angle to the powder falling direction. Free fine powder with D50 < 5 μm is removed, and the fine powder removal rate is > 95%. S2, Plasma Desorption: The graded powder is fed into the radio frequency plasma processing chamber through a screw feeder and argon carrier gas, so that the powder is suspended in the plasma area. The plasma power is 10-20kW, the powder surface temperature is controlled at 50-100℃ below its melting point, and the residence time of a single particle is 0.5-1s. The satellite spheres are desorbed by high-energy electron bombardment, and a thin layer of <1μm on the powder surface is melted. S3, Vibration densification: The plasma-treated powder is fed into an ultrasonic vibrating fluidized bed, and argon gas is introduced to make the powder in a micro-fluidized state. The bed expansion rate is <10%, the ultrasonic vibration frequency is 18-22kHz, the amplitude is 3-8μm, and the vibration treatment is 10 minutes / batch to achieve powder densification and remove residual satellite spheres. S4, Cooling and Shaping: The vibration-densified powder is fed into an inert gas cooling system, using helium gas flowing counter-currently to the powder, combined with a liquid nitrogen cooling channel to achieve 5x10 3 -5X10 4 The powder was cooled to ≤50℃ at a cooling rate of ℃ / s, and the spherical morphology was fixed to obtain the finished powder.

[0007] In a preferred embodiment, in step S1, the classifying wheel of the three-stage airflow classifier is made of tungsten carbide, the processing capacity is 50-100 kg / h, and the proportion of particles with D50 < 5 μm after processing is reduced to < 1%.

[0008] In a preferred embodiment, in step S2, the plasma torch of the radio frequency plasma processing chamber is a radio frequency inductively coupled type with a frequency of 13.56MHz and a nozzle diameter of 5mm; the flow rate of the argon carrier gas is 20L / min, and the rotation speed of the screw feeder is 10-20rpm.

[0009] In a preferred embodiment, in step S3, the gas distribution plate of the ultrasonic vibrating fluidized bed is a microporous ceramic plate with a pore size of 10 μm; the flow rate of the argon gas is 5 L / min; and the ultrasonic transducer power is 500 W.

[0010] In a preferred embodiment, in step S4, the inert gas cooling system is a spiral coil cooling channel with a length of 5m and liquid nitrogen at -196℃ flowing through its inner wall; the flow rate of the helium cooling gas is 10L / min.

[0011] In addition, this application also proposes a ViGa gas atomization powder post-processing device, including a feeding system, a classification module, a plasma module, a vibration module, and a cooling module connected sequentially along the powder conveying direction, as well as a control system electrically connected to each module; the feeding system is a loss-in-weight feeder with an accuracy of ±0.5%; the classification module is a three-stage airflow classifier with a fine powder recovery tank; the plasma module is a radio frequency plasma processing chamber with a power feedback control system; the vibration module is an ultrasonic vibrating fluidized bed with an amplitude monitoring sensor; the cooling module is a spiral coil cooler with a temperature sensor; the modules are connected by a sealed feeding channel to ensure that the entire processing is inert gas atmosphere.

[0012] In a preferred embodiment, the three-stage airflow classifier of the classification module includes three-stage tungsten carbide classifying wheels and is equipped with a wind pressure regulating component, which can achieve wind pressure regulation of 0.3MPa at the inlet and 0.1MPa at the outlet, and the airflow guide plate can be adjusted to form a 30° angle with the powder falling direction.

[0013] In a preferred embodiment, the radio frequency plasma processing cavity of the plasma module is a cylindrical structure with a diameter of 500 mm and a height of 1000 mm, and the inner wall is coated with alumina ceramic; a screw feeder and an argon carrier gas interface are configured inside the cavity, and the plasma torch is a 13.56 MHz radio frequency inductive coupling type with a nozzle diameter of 5 mm.

[0014] In a preferred embodiment, the bottom of the ultrasonic fluidized bed of the vibration module is equipped with a 500W ultrasonic transducer, the gas distribution plate is a microporous ceramic plate with a 10μm pore size, and it is equipped with an argon gas flow interface and a bed expansion rate monitoring component; the spiral coil cooler of the cooling module is 5m long, has a built-in liquid nitrogen channel, and is equipped with a helium reverse cooling gas interface and a temperature sensor.

[0015] In a preferred embodiment, the control system is a PLC S7-1500 with a touch screen, which can adjust the speed of the classifier wheel, plasma power, ultrasonic vibration frequency and amplitude, and cooling gas flow rate in real time. This device is suitable for post-processing of ViGa gas atomized powders of titanium alloys, high-temperature alloys, and tungsten / molybdenum refractory metals.

[0016] Due to the application of the above technical solution, the beneficial effects of this application compared with the prior art are as follows: 1. Thorough removal of satellite spheres: Through a three-stage synergistic approach of "graded pre-separation to remove free fine powder + plasma bombardment to desorb attached satellite spheres + ultrasonic vibration to remove residual satellite spheres", the satellite sphere content is reduced to below 5%, and the total satellite sphere removal rate is >90%, which solves the defect of existing technologies that can only remove free fine powder but cannot desorb attached satellite spheres.

[0017] 2. Significantly improved sphericity: Through the synergistic effect of plasma melting of the powder surface thin layer + surface tension shrinkage + rapid cooling and shaping, the sphericity of the powder is improved to over 0.95, which is far higher than the existing mechanical classification process (0.88) and plasma modification process (0.90), and avoids the grain growth problem of high temperature heat treatment.

[0018] 3. Optimized powder flow properties: The dual effects of satellite ball removal and powder densification increase the loose packing density of the powder, achieving a Hall flow rate ≤25s / 50g, meeting the flow rate requirements of high-speed 3D printing, and increasing printing efficiency to >50 cm. 3 / h.

[0019] 4. Low powder damage and low energy consumption: There is no strong mechanical extrusion throughout the process, and the powder deformation rate is <2%, which is far lower than the existing mechanical screening process (deformation rate >8%). The classification and pre-separation reduces the plasma treatment load, and the energy consumption per batch is <200kW·h / ton, which is far lower than the high temperature heat treatment process (>500kW·h) and the high speed classification process (>300kW·h / ton).

[0020] 5. Uniform heating and no over-melting: The use of suspended plasma treatment + microfluidic vibration avoids powder accumulation and solves the problems of uneven heating and local over-melting (over-melting rate > 5%) in existing plasma processes. The over-melting rate of powder in this invention is < 1%.

[0021] 6. High compatibility and high degree of automation: The process parameters can be adjusted through the control system to adapt to the ViGa powder processing of refractory metals such as titanium alloys, high-temperature alloys, and tungsten / molybdenum. The device achieves fully automated operation and is suitable for industrial mass production.

[0022] 7. Controllable powder purity: The entire process is handled in an inert gas atmosphere, and the oxygen content of the powder is controlled at <50ppm, preventing oxidation and deterioration, and meeting the purity requirements of aerospace and high-end 3D printing. Attached Figure Description

[0023] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0024] Figure 1 This is a flowchart of a ViGa gas atomization powder preparation post-processing process according to the present invention. Figure 2 This is a schematic diagram of the satellite detachment and spheroidization process; Figure 3 This is an overall schematic diagram of the ViGa gas atomization powder preparation post-processing device of the present invention. Figure 4 This is a schematic diagram of the vertical cavity structure of the ultrasonic vibration fluidized bed of the present invention; Figure 5 This is a schematic diagram of the spiral coil cooler structure of the present invention; The components include: 1. Feeding system; 2. Grading module; 3. Plasma module; 4. Vibration module; 41. Microporous ceramic plate; 42. Ultrasonic transducer; 5. Cooling module; 51. Spiral coil cooler; and 6. Control system. Detailed Implementation

[0025] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0026] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0027] In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing the invention and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0028] Furthermore, in addition to indicating direction or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in certain situations to indicate a dependency or connection. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0029] Furthermore, the terms "installation," "setup," "equipped with," "connection," "linking," and "socketing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0030] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0031] Example 1 Please see Figure 1-5 This application proposes a four-step synergistic post-processing technology for ViGa gas atomization powder production, consisting of staged pre-separation, plasma desorption, vibration densification, and cooling shaping. A matching integrated post-processing device is also designed. The core technical solution is as follows: I. A post-processing technology for ViGa gas atomization powder production, comprising the following steps: S1, pre-separation of stages: The raw ViGa powder is fed into a three-stage air classifier, which uses three tandem classifiers made of tungsten carbide. The rotation speeds are 2000 rpm, 3500 rpm, and 5000 rpm respectively. The inlet air pressure of the classifier is 0.3 MPa and the outlet air pressure is 0.1 MPa. The airflow direction is made at a 30° angle with the powder falling direction by an airflow guide plate to avoid secondary adhesion of fine powder. The throughput is controlled at 50-100 kg / h, which efficiently removes free fine powder with D50 < 5 μm, with a fine powder removal rate of > 95%. This reduces the proportion of D50 < 5 μm particles after treatment from the original 15% to < 1%, reducing the load on subsequent plasma treatment.

[0032] S2, Plasma Desorption: The graded powder is fed into the radio frequency plasma processing chamber via a screw feeder rotating at 10-20 rpm and argon carrier gas at a rate of 20 L / min. This allows the powder to pass through the plasma region in a suspended state, preventing uneven heating caused by powder accumulation. The plasma torch is a 13.56 MHz radio frequency inductive coupling type with a nozzle diameter of 5 mm. The plasma power is controlled at 10-20 kW, and the power density in the stable region is 10. 5 W / m 3 The powder surface temperature is precisely controlled at 50-100℃ below its melting point, and the residence time of a single particle is 0.5-1s. High-energy electrons of 1-10eV in plasma bombard the interface between the satellite sphere and the large particle, destroying van der Waals forces and electrostatic adsorption to achieve satellite sphere desorption. At the same time, a thin layer of <1μm on the powder surface is melted, causing irregular protrusions to shrink naturally due to surface tension, thus initially achieving sphericity.

[0033] S3, Vibrational compaction: The plasma-treated powder is fed into an ultrasonically vibrating fluidized bed, and argon gas at a rate of 5 L / min is introduced through a microporous ceramic plate 41 with a pore size of 10 μm to keep the powder in a micro-fluidized state (bed expansion rate <10%). A 500W ultrasonic transducer 42 is installed at the bottom of the fluidized bed, with a vibration frequency of 18-22 kHz and an amplitude of 3-8 μm, and vibration treatment for 10 minutes per batch. The high-frequency mechanical force generated by ultrasonic vibration rearranges the powder particles, increasing the bulk density by 10%-15%. At the same time, the residual satellite spheres after plasma treatment are removed by vibration inertia, with a residual satellite sphere removal rate of >95%, achieving a dual desorption effect.

[0034] S4, Cooling and Shaping: The vibration-densified powder is fed into a spiral coil-type cooling channel, 5m in length, with liquid nitrogen at -196℃ flowing through the inner wall. Simultaneously, helium gas at a flow rate of 10L / min is introduced, flowing counter-currently to the powder (helium's high thermal conductivity improves cooling efficiency); achieving 5 x 10 3 -5X10 4 The rapid cooling rate of ℃ / s allows the molten thin layer on the powder surface to solidify quickly, fixing the spherical morphology and avoiding grain growth and secondary agglomeration caused by slow cooling of the powder; after cooling, the powder outlet temperature is ≤50℃, and it can be directly packaged to obtain the finished powder.

[0035] II. A ViGa gas atomization powder post-processing device, the integrated device designed in this invention includes, in sequence along the powder conveying direction: a feeding system 1, a classification module 2, a plasma module 3, a vibration module 4, and a cooling module 5. Each module is connected by a sealed feeding channel to ensure an inert gas atmosphere throughout the processing, preventing powder oxidation. Simultaneously, a control system 6 is configured to realize real-time adjustment of various process parameters. The specific design of each module is as follows: Feeding system 1: A loss-in-weight feeder with an accuracy of ±0.5% is used to achieve quantitative and stable conveying of powder; Classification Module 2: A three-stage airflow classifier with a fine powder recovery tank, equipped with a tungsten carbide classifying wheel and an air pressure regulating component, which can adjust the angle between the airflow and the powder falling direction; Plasma Module 3: Radio frequency plasma processing chamber with power feedback control system 6, the inner wall of the chamber is coated with alumina ceramic (high temperature resistant and insulating), and equipped with screw feeder, argon carrier gas interface and plasma torch; Vibration Module 4: An ultrasonic vibrating fluidized bed with an amplitude monitoring sensor, equipped with a microporous ceramic gas distribution plate, an argon gas flow interface, and a bed expansion rate monitoring component; Cooling module 5: Spiral coil cooler 51 with temperature sensor, built-in liquid nitrogen channel and helium reverse cooling gas interface; Control System 6: The control structure adopts PLC S7-1500 + touch screen, which can adjust the speed of the classifier wheel, plasma power, ultrasonic vibration frequency and amplitude, and cooling gas flow rate in real time, so as to achieve precise control and automated operation of process parameters.

[0036] Example 2 Three typical ViGa gas atomization powders—titanium alloy Ti6Al4V, high-temperature alloy Inconel718, and refractory tungsten powder—were selected as the processing targets. The implementation process of the present invention and its apparatus was refined with detailed parameters throughout the entire process, intermediate product detection, equipment operation details, and multi-dimensional performance testing of the finished product. All testing indicators followed national standards / industry-standard methods. The testing equipment was the integrated post-processing device described in the invention, ensuring the repeatability and industrial reference value of the implementation process.

[0037] I. Basic Experimental Description (I) Test materials Industrial-grade ViGa atomized raw powder was selected, all of which are additive manufacturing-specific powders with a raw particle size range of 15-150μm (meeting the common particle size requirements for 3D printing).

[0038] (II) Testing Instruments and Standards detection indicators Testing instruments Implementation Standards / Statistical Methods Satellite ball content Field emission scanning electron microscope (FE-SEM, model SU8010) Capture ≥200 random fields of view and count the percentage of particles with attached satellite spheres out of the total particles. sphericity FE-SEM+ImageJ image analysis software <![CDATA[Sphere sphericity = 4ΠS / L 2 (S is the projected area of the particle, L is the projected perimeter), and the average value is taken by counting ≥500 particles]]> Hall flow rate Hall effect flow meter (model BT-1000) GB / T 1482-2020 Determination of Flowability of Metal Powders – Hall Flowmeter Method Powder deformation rate FE-SEM The percentage of deformed particles (aspect ratio > 1.2) out of the total number of particles is ≥ 300. Loose packing density Loose packing density meter (model BT-301) GB / T 1479-2011 Determination of the apparent density of metal powders – Part 1: Funnel method Grain size Metallurgical microscope (model DM4M) + Image-Pro Plus software Intercept method, statistically analyze ≥100 grains and take the average value. Particle size distribution (D10 / D50 / D90) Laser particle size analyzer (Model Mastersizer 3000) GB / T 19077-2016 Particle Size Analysis by Laser Diffraction Oxygen content Oxygen and nitrogen analyzer (model ON-3000) GB / T 14203-2021 Determination of Oxygen Content in Metal Powders

[0039] (III) Specifications of Core Equipment This embodiment uses the integrated ViGa gas atomization powder preparation post-processing device described in the invention, and the core module specifications are uniform as follows: Three-stage air classifier: Classifying wheel material is tungsten carbide, single-stage wheel diameter is 150mm, fine powder recovery tank volume is 50L, and air pressure adjustment accuracy is ±0.01MPa; Radio frequency plasma processing chamber: cylindrical chamber φ500mm×1000mm, inner wall alumina ceramic coating thickness 20mm, plasma torch frequency 13.56MHz, power adjustment accuracy ±0.5kW; Ultrasonic vibrating fluidized bed: cavity φ300mm×400mm, microporous ceramic plate 41 with pore diameter 10μm, ultrasonic transducer 42 with power 500W, amplitude adjustment accuracy ±0.5μm; Spiral coil cooler 51: Total coil length 5m, tube diameter 20mm, liquid nitrogen temperature control accuracy ±5℃, helium flow rate adjustment accuracy ±0.1L / min; Control System 6: PLC S7-1500, real-time data acquisition via touchscreen, parameter adjustment response time <0.5s.

[0040] II. Option 1: Post-treatment of titanium alloy Ti6Al4V powder.

[0041] (I) Original properties of raw materials (particle size range of 15-150μm).

[0042] The melting point of Ti6Al4V powder is 1668℃. The original multi-dimensional performance test data are shown in the table below. The oxygen content of the powder is 48ppm. index D10(μm) D50(μm) D90(μm) Satellite ball content sphericity Hall effect flow rate (s / 50g) Loose bulk density (g / cm³) Grain size (μm) Deformation rate numerical values 22.5 58.3 126.7 22.60% 0.81 35.2 2.15 18.6 0.80%

[0043] (II) Pre-separation step (inert argon atmosphere throughout, oxygen content <50ppm).

[0044] Equipment operating parameters: The rotation speed of the three-stage classifier wheel is 2000 rpm (first stage), 3500 rpm (second stage), and 5000 rpm (third stage) respectively; the inlet air pressure gradually decreases from 0.3 MPa to the outlet air pressure of 0.1 MPa (pressure drop of 0.1 MPa per stage); the angle between the airflow guide plate and the powder falling direction is precisely adjusted to 30°; the powder processing capacity is 60 kg / h; and the feeding accuracy of the loss-in-weight feeder is ±0.2%. Fine powder recovery: Recovers free fine powder with D50 < 5μm, with a recovery rate of 1.86kg per hour and a fine powder removal rate of 96.2%. Intermediate product performance: After classification, the proportion of powder particles with D50 < 5μm decreased from the original 15.3% to 0.8%, with no large particle agglomeration. The intermediate product was directly fed into the plasma processing chamber without static oxidation.

[0045] (III) Plasma desorption step (cavity vacuum pre-evacuation to 5 x 10⁻⁶)-2 Pa is then argon gas is returned to atmospheric pressure.

[0046] Equipment operating parameters: screw feeder speed 12 rpm, argon carrier gas flow rate 20 L / min, pressure 0.2 MPa, plasma power stabilized at 15 kW (power density in the stable region 1.02 x 10⁻⁶). 5 W / m 3 The powder surface temperature is precisely controlled at 1580℃ (below the melting point of 88℃), and the residence time of a single particle in the plasma region is controlled to 0.6s by adjusting the feeding speed. Desorption and melting effect: After high-energy electron bombardment, 85.7% of the attached satellite spheres were desorbed, and a molten thin layer with a thickness of about 0.8 μm was formed on the powder surface. There were no completely melted particles. The desorbed satellite spheres entered the bottom collection tank with argon gas, with a collection rate of 0.92 kg / h. Intermediate product properties: After plasma treatment, the content of powder satellite spheres decreased to 3.1%, the sphericity increased to 0.93, and there was no obvious grain growth.

[0047] (iv) Vibration densification step (argon flow gas atmosphere, oxygen content <30ppm).

[0048] Equipment operating parameters: Argon flow rate 5L / min, pressure 0.1MPa, uniform gas distribution on microporous ceramic plate 41, initial bed height 100mm, bed expansion rate 8% under microfluidization (height 108mm after expansion), ultrasonic vibration frequency 20kHz, amplitude 5μm, continuous vibration treatment for 10 minutes / batch (5kg per batch), amplitude monitoring sensor provides real-time feedback, fluctuation <±0.3μm; Densification and desorption effects: Ultrasonic high-frequency mechanical force causes powder particles to be tightly packed together, with a residual satellite ball removal rate of 96.3% and a bulk density increase of 12.5% ​​compared to plasma treatment; Intermediate product properties: After vibration, the content of powder satellite spheres decreased to 3.8%, the sphericity remained at 0.93, and the loose density increased to 2.42 g / cm³. 3 No powder deformation.

[0049] (v) Cooling and shaping steps (helium + liquid nitrogen composite cooling throughout the process, without secondary agglomeration).

[0050] Equipment operating parameters: Liquid nitrogen flow rate on the inner wall of the spiral coil cooler 51 is 8 L / min, temperature control is -196℃; helium cooling gas flow rate is 10 L / min, pressure is 0.15 MPa, and the gas flows counter-currently to the powder (helium enters from the cooler outlet and exits from the inlet). The cooling rate is 8 x 10⁻⁶ by adjusting the powder conveying speed. 3 ℃ / s, the cooler outlet temperature is precisely controlled at 45℃; Shaping effect: The molten thin layer on the powder surface solidifies instantly under rapid cooling, and the surface tension contracts to form a regular sphere, with no grain growth and no secondary adsorption of fine powder; Finished powder yield: 99.5% yield in this step, and 92.3% overall yield (excluding free fine powder and desorbed satellite particles).

[0051] (vi) Final properties of the finished powder (15-150μm particle size range); index D10(μm) D50(μm) D90(μm) Satellite ball content sphericity Hall effect flow rate (s / 50g) Loose bulk density (g / cm³) Grain size (μm) Deformation rate Energy consumption per batch (kW·h / ton) numerical values 23.1 57.8 125.9 3.80% 0.96 23 2.45 19.2 1.20% 150

[0052] 3. Option 2: Post-treatment of Inconel 718 high-temperature alloy powder.

[0053] (I) Original properties of raw materials (particle size range of 15-150μm) Inconel 718 powder has a melting point of 1360℃. The original multi-dimensional performance test data are shown in the table below. The powder oxygen content is 45ppm. index D10(μm) D50(μm) D90(μm) Satellite ball content sphericity Hall effect flow rate (s / 50g) Loose bulk density (g / cm³) Grain size (μm) Deformation rate numerical values 20.8 55.6 123.4 20.30% 0.79 33.8 2.68 22.3 0.70%

[0054] (II) Pre-separation step (inert argon atmosphere throughout, oxygen content <50ppm).

[0055] Equipment operating parameters: The rotation speed of the three-stage classifier wheel is 2000rpm, 3500rpm, and 5000rpm respectively; the inlet air pressure decreases from 0.3MPa to 0.1MPa at each stage; the airflow angle is 30°; the powder processing capacity is 80kg / h; and the feeder feeding accuracy is ±0.2%. Fine powder recovery: 2.38 kg of free fine powder with D50 < 5 μm was recovered per hour, with a fine powder removal rate of 95.8%; Intermediate product performance: After classification, the proportion of powder particles with D50 < 5μm decreased from the original 14.9% to 0.9%, with no particle agglomeration, and was directly fed into the plasma processing chamber.

[0056] (III) Plasma desorption step (cavity vacuum pre-evacuation to 5 x 10⁻⁶) -2 Pa, purged with argon gas to atmospheric pressure) Equipment operating parameters: screw feeder speed 15 rpm, argon carrier gas flow rate 20 L / min, pressure 0.2 MPa, plasma power stabilized at 18 kW (power density in the stable region 1.15 x 10⁻⁶). 5 W / m 3 The powder surface temperature is precisely controlled at 1280℃ (80℃ below the melting point), and the residence time of a single particle is 0.8s. Desorption and melting effect: 84.2% of the attached satellite balls were desorbed, the thickness of the molten layer on the powder surface was about 0.9 μm, there were no completely molten particles, and the collection rate of desorbed satellite balls was 0.85 kg / h; Intermediate product properties: After plasma treatment, the content of powder satellite spheres decreased to 3.2%, the sphericity increased to 0.92, and the grain size did not change significantly.

[0057] (iv) Vibration densification step (argon flow gas atmosphere, oxygen content <30ppm).

[0058] Equipment operating parameters: Argon gas flow rate 5L / min, pressure 0.1MPa, initial bed height 100mm, microfluidic bed expansion rate 7% (height after expansion 107mm), ultrasonic vibration frequency 22kHz, amplitude 6μm, vibration treatment 10 minutes / batch (processing capacity per batch 6kg), amplitude fluctuation <±0.3μm; Densification and desorption effects: The removal rate of residual satellite spheres was 96.9%, and the bulk density was increased by 11.8% compared with that after plasma treatment; Intermediate product properties: After vibration, the content of powder satellite spheres decreased to 4.2%, the sphericity remained at 0.92, and the loose bulk density increased to 3.01 g / cm³. 3 No powder deformation.

[0059] (V) Cooling and shaping steps (helium + liquid nitrogen composite cooling throughout the process, without secondary agglomeration).

[0060] Equipment operating parameters: liquid nitrogen flow rate 9L / min, temperature control -196℃, helium cooling gas flow rate 10L / min, pressure 0.15MPa, countercurrent flow, cooling rate 1.0 x 10⁻⁶. 4 ℃ / s, cooler outlet temperature 42℃; The molten thin layer solidifies rapidly, resulting in a fixed spherical morphology with no grain growth or secondary agglomeration. Finished powder yield: 99.6% yield in this step, and 93.1% overall yield for the entire process.

[0061] (vi) Final properties of the finished powder (15-150μm particle size range); index D10(μm) D50(μm) D90(μm) Satellite ball content sphericity Hall effect flow rate (s / 50g) Loose bulk density (g / cm³) Grain size (μm) Deformation rate Energy consumption per batch (kW·h / ton) numerical values 21.2 55.1 122.8 4.20% 0.95 24 3.05 22.8 1.50% 170

[0062] IV. Option 3: Post-processing of refractory tungsten powder.

[0063] (I) Original properties of raw materials (particle size range of 15-150μm).

[0064] The tungsten powder has a melting point of 3410℃. The original multi-dimensional performance test data are shown in the table below. The oxygen content of the powder is 50ppm. index D10(μm) D50(μm) D90(μm) Satellite ball content sphericity Hall effect flow rate (s / 50g) Loose bulk density (g / cm³) Grain size (μm) Deformation rate numerical values 25.3 62.7 130.2 24.80% 0.82 37.5 4.12 25.7 0.90%

[0065] (II) Pre-separation step (inert argon atmosphere throughout, oxygen content <50ppm).

[0066] Equipment operating parameters: The rotation speed of the three-stage classifier wheel is 2000rpm, 3500rpm, and 5000rpm respectively; the inlet air pressure decreases from 0.3MPa to 0.1MPa at each stage; the airflow angle is 30°; the powder processing capacity is 50kg / h; and the feeder feeding accuracy is ±0.2%. Fine powder recovery: 1.52 kg of free fine powder with D50 < 5 μm was recovered per hour, with a fine powder removal rate of 96.5%; Intermediate product performance: After classification, the proportion of powder particles with D50 < 5μm decreased from the original 15.7% to 0.7%, with no particle agglomeration, and was directly fed into the plasma processing chamber.

[0067] (III) Plasma desorption step (cavity vacuum pre-evacuation to 5 x 10⁻⁶) -2 Pa, purged with argon gas to atmospheric pressure)

[0068] Equipment operating parameters: screw feeder speed 18 rpm, argon carrier gas flow rate 20 L / min, pressure 0.2 MPa, plasma power stabilized at 20 kW (power density in the stable region 1.23 x 10⁻⁶). 5 W / m 3 The powder surface temperature is precisely controlled at 3320℃ (90℃ below the melting point), and the residence time of a single particle is 1.0s; Desorption and melting effect: Tungsten powder has a high surface energy, and 83.5% of the attached satellite balls were desorbed. The thickness of the molten thin layer on the powder surface is about 1.0 μm, with no completely molten particles. The collection rate of desorbed satellite balls is 1.05 kg / h. Intermediate product properties: After plasma treatment, the content of powder satellite spheres decreased to 4.1%, the sphericity increased to 0.92, and the grain size did not change significantly.

[0069] (iv) Vibration densification step (argon flow gas atmosphere, oxygen content <30ppm) Equipment operating parameters: Argon gas flow rate 5L / min, pressure 0.1MPa, initial bed height 100mm, microfluidic bed expansion rate 9% (height after expansion 109mm), ultrasonic vibration frequency 18kHz, amplitude 8μm, vibration treatment 10 minutes / batch (batch processing capacity 4kg), amplitude fluctuation <±0.3μm; Densification and desorption effects: Tungsten powder has a high density, and the removal rate of residual satellite spheres under high-frequency vibration is 95.6%, with the bulk density increasing by 10.9% compared to plasma treatment; Intermediate product properties: After vibration, the content of powder satellite balls decreased to 4.5%, the sphericity remained at 0.92, the loose density increased to 4.58 g / cm³, and there was no powder deformation.

[0070] (V) Cooling and shaping steps (entire process of helium + liquid nitrogen combined cooling, no secondary agglomeration) Equipment operating parameters: liquid nitrogen flow rate 10L / min, temperature control -196℃; helium cooling gas flow rate 10L / min, pressure 0.15MPa; countercurrent flow; cooling rate 1.2 x 10⁻⁶. 4 ℃ / s, cooler outlet temperature 48℃; Shaping effect: The molten thin layer solidifies rapidly, the spherical morphology is fixed, there is no grain growth in refractory metals, and no secondary adsorption of fine powder; Finished powder yield: 99.4% yield in this step, and 91.8% overall yield for the entire process.

[0071] (vi) Final properties of the finished powder (15-150μm particle size range); index D10(μm) D50(μm) D90(μm) Satellite ball content sphericity Hall effect flow rate (s / 50g) Loose bulk density (g / cm³) Grain size (μm) Deformation rate Energy consumption per batch (kW·h / ton) numerical values 25.8 62.2 129.5 4.50% 0.95 25 4.62 26.3 1.80% 190

[0072] V. Summary of Performance and Key Conclusions of the Examples

[0073] (I) Summary table of core performance of the three schemes; Powder type satellite ball content decrease Sphericity improvement value Hall effect flow rate decrease (s / 50g) Loose packing density increase rate Grain size variation Deformation rate Energy consumption per batch (kW·h / ton) Ti6Al4V 83.20% 0.15 12.2 13.90% No significant growth (+0.6μm) 1.20% 150 Inconel718 79.30% 0.16 9.8 13.80% No significant growth (+0.5μm) 1.50% 170 tungsten powder 81.90% 0.13 12.5 12.10% No significant growth (+0.6μm) 1.80% 190

[0074] (II) Key Implementation Conclusions.

[0075] The process of this invention has excellent post-processing effects on various ViGa gas atomized powders such as titanium alloys, high-temperature alloys, and refractory metals. It achieves the core invention goals of satellite ball content <5%, sphericity ≥0.95, and Hall flow rate ≤25s / 50g. All performance indicators are superior to the existing technology. The entire process involves no strong mechanical extrusion, and the powder deformation rate is less than 2%. Furthermore, the rapid cooling and shaping technology effectively avoids grain growth (grain size change is less than 1μm), which solves the grain growth defect of existing high-temperature heat treatment processes and ensures the basic mechanical properties of the powder. The pre-separation step effectively removes free fine powder, reduces the plasma processing load, and makes the energy consumption per batch <200kW·h / ton, which is far lower than the existing high-temperature heat treatment process (>500kW·h) and high-speed classification process (>300kW·h / ton), meeting the industrial demand for low energy consumption and low cost. The entire process is handled in an inert gas atmosphere of argon / helium, and the oxygen content of the powder is controlled at <50ppm, preventing oxidation and deterioration. The finished powder meets the purity requirements of high-end fields such as aerospace and 3D printing medical implants. The integrated device of the present invention has a high degree of automation, the process parameters of each step can be precisely controlled and supported for storage and retrieval, the processing capacity is 50-80 kg / h, the total yield is ≥91.8%, and it has the feasibility and stability for industrial mass production.

[0076] The process steps of this invention are closely linked, and the powder is continuously processed through a sealed feeding channel without human intervention, which avoids secondary contamination and agglomeration of the powder and further ensures the quality stability of the finished powder.

[0077] Furthermore, the ViGa gas atomization powder post-processing process and apparatus of the present invention have extremely high industrial applicability, specifically reflected in the following aspects: Strong process adaptability: The core indicators such as the speed of the classifier wheel, plasma power, ultrasonic vibration parameters, and cooling rate can be flexibly adjusted through the control system 6. It is compatible with the post-processing of ViGa gas atomized powders of various refractory metals such as titanium alloys, high-temperature alloys, and tungsten / molybdenum, and meets the performance requirements of different metal powders in the additive manufacturing field. The equipment is highly integrated and automated: it integrates four core functions, namely classification, plasma treatment, vibration densification and cooling shaping, into one device. It achieves fully automated operation through the PLC S7-1500 control system, reducing manual operation, reducing human error, and ensuring the consistency of powder performance between batches. High industrial processing efficiency: The single batch processing capacity of the device is 50-100 kg / h, and the total yield is ≥91.8%, which is far higher than the existing laboratory-level post-processing technology. It can be directly connected to the industrial-grade ViGa powder production line to realize continuous production of powder preparation and post-processing. Significant advantages in energy consumption and cost: energy consumption per batch <200kW·h / ton, no high energy consumption for high-temperature insulation and high-speed grading, and satellite balls and fine powder can be collected, recycled and reused, further reducing raw material loss and meeting the cost control requirements of industrial production; Finished powder quality meets high-end standards: The processed powder has low satellite ball content, high sphericity, good flowability, controllable purity, and uniform grain size, which fully meets the powder performance requirements of high-end additive manufacturing fields such as aerospace engine blades, high-end 3D printed medical implants, and precision mechanical parts, and can significantly improve the density, molding accuracy and mechanical properties of end products.

[0078] In summary, the process and apparatus of this invention solve many of the shortcomings of existing ViGa gas atomization powder post-processing technologies, achieving the integrated goals of low satellite sphere size, high sphericity, high flow rate, low damage, low energy consumption, and high purity. It can be widely used in the industrial production of high-performance metal powders, and has broad market application prospects and significant economic and technical value.

[0079] Finally, it should be noted that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A post-processing technology for ViGa gas atomization powder production, characterized in that, Includes the following steps: S1, Pre-separation: ViGa raw powder is fed into a three-stage air classifier, where fine powder is separated by three series of classifying wheels. The rotation speeds of the classifying wheels are 2000 rpm, 3500 rpm, and 5000 rpm, respectively. The inlet air pressure of the classifier is 0.3 MPa, and the outlet air pressure is 0.1 MPa. The airflow direction is at a 30° angle to the powder falling direction. Free fine powder with D50 < 5 μm is removed, and the fine powder removal rate is > 95%. S2, Plasma Desorption: The graded powder is fed into the radio frequency plasma processing chamber through a screw feeder and argon carrier gas, so that the powder is suspended in the plasma area. The plasma power is 10-20kW, the powder surface temperature is controlled at 50-100℃ below its melting point, and the residence time of a single particle is 0.5-1s. The satellite spheres are desorbed by high-energy electron bombardment, and a thin layer of <1μm on the powder surface is melted. S3, Vibration densification: The plasma-treated powder is fed into an ultrasonic vibrating fluidized bed, and argon gas is introduced to make the powder in a micro-fluidized state. The bed expansion rate is <10%, the ultrasonic vibration frequency is 18-22kHz, the amplitude is 3-8μm, and the vibration treatment is 10 minutes / batch to achieve powder densification and remove residual satellite spheres. S4, Cooling and Shaping: The vibration-densified powder is fed into an inert gas cooling system, using helium gas flowing counter-currently to the powder, combined with a liquid nitrogen cooling channel to achieve 5x10 3 -5X10 4 The powder was cooled to ≤50℃ at a cooling rate of ℃ / s, and the spherical morphology was fixed to obtain the finished powder.

2. The ViGa gas atomization powder preparation post-processing process according to claim 1, characterized in that, In step S1, the classifying wheel of the three-stage airflow classifier is made of tungsten carbide, with a processing capacity of 50-100 kg / h, and the proportion of particles with D50 < 5 μm after processing is reduced to < 1%.

3. The ViGa gas atomization powder preparation post-processing process according to claim 1, characterized in that, In step S2, the plasma torch of the radio frequency plasma processing chamber is a radio frequency inductive coupling type with a frequency of 13.56MHz and a nozzle diameter of 5mm; the flow rate of argon carrier gas is 20L / min, and the speed of the screw feeder is 10-20rpm.

4. The ViGa gas atomization powder preparation post-processing process according to claim 1, characterized in that, In step S3, the gas distribution plate of the ultrasonic vibrating fluidized bed is a microporous ceramic plate with a pore size of 10 μm; the flow rate of the argon gas is 5 L / min; and the ultrasonic transducer power is 500 W.

5. The ViGa gas atomization powder preparation post-processing process according to claim 1, characterized in that, In step S4, the inert gas cooling system is a spiral coil cooling channel with a length of 5m and liquid nitrogen at -196℃ flowing through the inner wall; the flow rate of the helium cooling gas is 10L / min.

6. A ViGa gas atomization powder preparation post-processing apparatus for implementing the process described in any one of claims 1-5, characterized in that, The system includes a feeding system, a classification module, a plasma module, a vibration module, and a cooling module connected sequentially along the powder conveying direction, as well as a control system electrically connected to each module. The feeding system is a loss-in-weight feeder with an accuracy of ±0.5%. The classification module is a three-stage airflow classifier with a fine powder recovery tank. The plasma module is a radio frequency plasma processing chamber with a power feedback control system. The vibration module is an ultrasonic vibrating fluidized bed with an amplitude monitoring sensor. The cooling module is a spiral coil cooler with a temperature sensor. The modules are connected by a sealed feeding channel to ensure that the entire processing is conducted in an inert gas atmosphere.

7. The ViGa gas atomization powder preparation post-processing device according to claim 6, characterized in that, The three-stage airflow classifier of the classification module includes three-stage tungsten carbide classifying wheels and is equipped with a wind pressure adjustment component, which can achieve wind pressure adjustment of 0.3MPa at the inlet and 0.1MPa at the outlet. The airflow guide plate can be adjusted to form a 30° angle with the powder falling direction.

8. The ViGa gas atomization powder preparation post-processing device according to claim 6, characterized in that, The radio frequency plasma processing chamber of the plasma module is a cylindrical structure with a diameter of 500 mm and a height of 1000 mm, and the inner wall is coated with alumina ceramic. The chamber is equipped with a screw feeder and an argon carrier gas interface. The plasma torch is a 13.56 MHz radio frequency inductive coupling type with a nozzle diameter of 5 mm.

9. The ViGa gas atomization powder preparation post-processing device according to claim 6, characterized in that, The vibration module has a 500W ultrasonic transducer installed at the bottom of the ultrasonic fluidized bed, and the gas distribution plate is a microporous ceramic plate with a 10μm pore size. It is equipped with an argon gas flow interface and a bed expansion rate monitoring component. The cooling module has a 5m long spiral coil cooler with a built-in liquid nitrogen channel, and is equipped with a helium reverse cooling gas interface and a temperature sensor.

10. The ViGa gas atomization powder preparation post-processing device according to claim 6, characterized in that, The control system is a PLC S7-1500 with a touch screen, which can adjust the speed of the classifier wheel, plasma power, ultrasonic vibration frequency and amplitude, and cooling gas flow rate in real time. The device is suitable for post-processing of ViGa gas atomized powders of titanium alloys, high-temperature alloys, and tungsten / molybdenum refractory metals.

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