Dual-stage gas-liquid synergistic atomization powder production device and method

Abstract

The application discloses a kind of two-stage gas-liquid collaborative atomization powder preparation device and method, device includes vacuum smelting furnace, atomization container, first atomization component, second atomization component and collection component;Vacuum smelting furnace is used to form melt for smelting, atomization container is connected with vacuum smelting furnace to supply melt atomization, first atomization component and second atomization component are respectively arranged in atomization container and along the axial direction of atomization container interval distribution, there is atomization focusing area between first atomization component and second atomization component, first atomization component includes multiple gas mist nozzles, multiple gas mist nozzles are distributed around the axis of atomization container, multiple gas mist nozzles are all towards atomization focusing area;Second atomization component includes multiple liquid mist nozzles, multiple liquid mist nozzles are distributed around the axis of atomization container;Collection component is used to collect atomized droplet and cool to form solid powder particle.The application can realize that powder granularity distribution is uniform, promote fine powder yield and reduce production cost.

Description

Technical Field

[0001] This application relates to the field of atomization technology, and in particular to a two-stage gas-liquid synergistic atomization powder-making device and method. Background Technology

[0002] Atomization powder preparation is a core technology in additive manufacturing (3D printing), powder metallurgy, and other fields. The quality of the metal powder prepared by atomization (including particle size distribution, sphericity, oxygen content, and flowability) directly affects the performance of the end product. Existing atomization powder preparation technologies mainly include gas atomization and liquid atomization. Among them, gas atomization is widely used due to its simple process, low cost, and the high sphericity and low oxygen content of the powder produced. However, in traditional gas atomization technology, the powder particle size distribution is wide, the yield of fine powder is generally less than 30%, and the production cost remains high. Summary of the Invention

[0003] Therefore, it is necessary to provide a two-stage gas-liquid synergistic atomization powder making device that can achieve uniform powder particle size distribution, improve fine powder yield, and reduce production costs.

[0004] One embodiment of this application provides a two-stage gas-liquid synergistic atomization powder-making device.

[0005] A two-stage gas-liquid synergistic atomization powder-making device includes a vacuum melting furnace, an atomizing container, a first atomizing component, a second atomizing component, and a collecting component. The vacuum melting furnace is used to melt raw materials to form a melt. The atomizing container is connected to the vacuum melting furnace to receive the melt and atomize it. The first atomizing component and the second atomizing component are respectively disposed within the atomizing container and spaced apart along the axial direction of the atomizing container. An atomization focusing area is formed between the first atomizing component and the second atomizing component. The first atomizing component includes... The atomizing component includes multiple aerosol nozzles distributed around the axis of the atomizing container, all facing the atomization focusing area. The aerosol nozzles are used to atomize the melt into droplet particles using a first inert gas. The second atomizing component includes multiple liquid atomizing nozzles distributed around the axis of the atomizing container. The liquid atomizing nozzles are used to shear and atomize the droplet particles using a liquid second inert gas flow to form atomized droplets. The collecting component is used to collect the atomized droplets and cool them to form solid powder particles.

[0006] In some embodiments, the atomizing container is provided with a guide tube, one end of which is connected to the vacuum melting furnace and the other end extends to the atomizing focusing area.

[0007] In some embodiments, the two-stage gas-liquid co-atomization powder-making device further includes a heating component connected to the guide tube to heat the guide tube and maintain a preset temperature range.

[0008] In some embodiments, the flow guide pipe is provided with a flow regulating valve.

[0009] In some embodiments, the flow guide extends along the axis of the atomizing container, and each of the aerosol nozzles faces the same position on the axis of the atomizing container.

[0010] In some embodiments, the centerline of the aerosol nozzle forms an angle of 15° to 45° with the axis of the atomizing container.

[0011] In some embodiments, the angle between the centerline of the aerosol nozzle and the axis of the atomizing container is adjustable.

[0012] In some embodiments, the plurality of aerosol nozzles are distributed at equal intervals.

[0013] In some embodiments, the fan-shaped mist surfaces of adjacent aerosol nozzles partially overlap.

[0014] In some embodiments, the two-stage gas-liquid co-atomization powder-making device further includes an inert gas storage tank, the atomizing container having an inert gas interface, the inert gas interface communicating with each of the aerosol nozzles, and the inert gas storage tank communicating with the inert gas interface.

[0015] In some embodiments, an airflow regulating valve is provided on the pipeline between the inert gas storage tank and the inert gas interface.

[0016] In some embodiments, the two-stage gas-liquid co-atomization powder-making device further includes an atomizing liquid storage tank, the atomizing container having an inert atomizing liquid interface, the atomizing liquid interface communicating with each of the liquid mist nozzles, and the atomizing liquid storage tank communicating with the atomizing liquid interface.

[0017] In some embodiments, the two-stage gas-liquid co-atomization powder making device further includes a filter element connected to the vacuum melting furnace, the filter element being used to filter and remove oxide impurities from the raw materials entering the vacuum melting furnace.

[0018] In some embodiments, the two-stage gas-liquid synergistic atomization powder-making device further includes a liquid-pouring trough, which is disposed inside the atomizing container and located between the first atomizing component and the second atomizing component. The liquid-pouring trough is connected to the second atomizing component, and the inner wall of the liquid-pouring trough gradually narrows from the first atomizing component to the second atomizing component.

[0019] In some embodiments, the collecting component includes a cooling chamber that communicates with the atomizing container for collecting the atomized droplets, and the cooling chamber is also provided with a cooling gas interface.

[0020] In some embodiments, the collecting component further includes a cyclone separator communicating with the cooling chamber for collecting the solid powder particles cooled by the cooling chamber.

[0021] In some embodiments, the collecting component further includes a purification component connected to the cyclone separator, the purification component being used to remove impurities from the solid powder particles.

[0022] In some embodiments, the collecting component further includes a filter screen connected to the impurity removal component, the filter screen being used to screen the solid powder particles after impurity removal by particle size.

[0023] One embodiment of this application provides a two-stage gas-liquid synergistic atomization powder production method.

[0024] A two-stage gas-liquid synergistic atomization powder preparation method, employing the two-stage gas-liquid synergistic atomization powder preparation device described in any of the above embodiments, includes the following steps:

[0025] Control the vacuum melting furnace to melt the raw materials into a melt;

[0026] Multiple aerosol nozzles of the first atomizing component are controlled to spray a first inert gas at a first pressure to expel oxygen from the atomizing container;

[0027] The melt in the vacuum melting furnace is controlled to enter the atomizing container and atomize into droplet particles under the action of a first inert gas at the first pressure;

[0028] Multiple liquid mist nozzles of the second atomizing component are controlled to spray a second pressure of liquid inert gas to shear and atomize the droplet particles to form atomized droplets;

[0029] In addition, the collecting component is controlled to collect the atomized droplets and cool them to form solid powder particles.

[0030] In some embodiments, the vacuum level inside the vacuum melting furnace is controlled to be 5 × 10⁻⁶. -4 Pa ~ 6×10 - 4 Pa.

[0031] In some embodiments, the melting temperature in the vacuum melting furnace is controlled at 1700℃~1800℃, and the holding time is 30min~40min.

[0032] In some embodiments, the first inert gas and the second inert gas each independently comprise argon and / or nitrogen.

[0033] In some embodiments, the temperature of the first inert gas is controlled to be between 0°C and 50°C.

[0034] In some embodiments, the first pressure is 1.5 MPa to 2 MPa.

[0035] In some embodiments, the temperature of the liquid second inert gas is controlled to be -196°C to -190°C.

[0036] In some embodiments, the second pressure is 5 MPa to 6 MPa.

[0037] In some embodiments, the droplet particles have a diameter of 50 μm to 200 μm.

[0038] In some embodiments, the atomized droplets have a particle size of 15 μm to 150 μm.

[0039] In some embodiments, the cooling treatment of the atomized droplets satisfies the following condition: the atomized droplets are purged with a protective gas at a controlled temperature below 0°C.

[0040] In some embodiments, the flow rate of the protective gas at a temperature below 0°C is 20 L / min to 100 L / min. In some embodiments, the protective gas includes at least one of nitrogen and argon.

[0041] In some embodiments, the cooling rate of the atomized droplets is controlled to be 3 × 10⁻⁶. 4 ℃ / s ~5×10 4 ℃ / s.

[0042] In some embodiments, the two-stage gas-liquid synergistic atomization powder production method further includes the following step: vacuum drying the solid powder particles.

[0043] In some embodiments, the vacuum drying process satisfies the following conditions: vacuum drying at 100°C to 120°C for 1 hour to 1.5 hours.

[0044] In some embodiments, the two-stage gas-liquid synergistic atomization powder production method further includes the following step: removing impurities from the solid powder particles.

[0045] In some embodiments, the impurity removal process includes magnetic separation for impurity removal;

[0046] In some embodiments, the two-stage gas-liquid synergistic atomization powder production method further includes the following step: the solid powder particles are subjected to particle size screening.

[0047] In some embodiments, the particle size classification includes 15μm~53μm and 53μm~106μm particle size classes.

[0048] The aforementioned two-stage gas-liquid synergistic atomization powder-making device produces solid powder particles with uniform particle size distribution, improves fine powder yield, and reduces production costs. Specifically, the two-stage gas-liquid synergistic atomization powder-making device provided in this application uses a vacuum melting furnace to melt the raw materials to form a melt, and an atomization container connected to the vacuum melting furnace to receive the melt. An atomization focusing area exists between the first atomization component and the second atomization component. The first atomization component includes multiple aerosol nozzles, all facing the atomization focusing area. The supersonic airflow unique to the aerosol nozzles performs primary atomization of the melt to form droplet particles, achieving efficient and uniform breakage of the melt. Subsequently, the second atomization component includes multiple liquid atomization nozzles, which use airflow to perform secondary shearing atomization of the droplet particles to form atomized liquid droplets. Through the synergistic effect of the two-stage atomization, the problems of uneven breakage and wide particle size distribution inherent in single atomization methods are effectively avoided. Finally, a collection component is used to collect the atomized droplets and cool them to form solid powder particles. Through the above-mentioned two-stage gas-liquid synergistic atomization mechanism, this device significantly improves the uniformity of droplet size during atomization. The prepared solid powder particles have the characteristics of narrow particle size distribution and high fine powder yield, while reducing production costs and overcoming the defects of low fine powder yield and severe particle size polarization in the existing technology. Attached Figure Description

[0049] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0050] To gain a more complete understanding of this application and its beneficial effects, the following description will be provided in conjunction with the accompanying drawings. In the following description, the same reference numerals denote the same parts.

[0051] Figure 1 This is a schematic diagram of a two-stage gas-liquid synergistic atomization powder-making device according to an embodiment of this application;

[0052] Figure 2 This is a side view of the two-stage gas-liquid synergistic atomization powder-making device according to an embodiment of this application;

[0053] Figure 3 This is a schematic diagram showing the cooperation between the first atomizing component and the second atomizing component of the two-stage gas-liquid synergistic atomization powder-making device according to an embodiment of this application;

[0054] Figure 4 This is a schematic diagram of the aerosol nozzle of the two-stage gas-liquid synergistic atomization powder-making device according to an embodiment of this application;

[0055] Figure 5 This is a schematic diagram of the liquid mist nozzle of the two-stage gas-liquid synergistic atomization powder-making device according to an embodiment of this application.

[0056] Explanation of reference numerals in the attached figures

[0057] 10. Two-stage gas-liquid synergistic atomization powder making device; 100. Vacuum melting furnace; 200. Atomizing container; 210. Guide pipe; 211. Flow regulating valve; 300. First atomizing component; 310. Gas mist nozzle; 400. Second atomizing component; 410. Liquid mist nozzle; 500. Collection component; 510. Cooling chamber; 520. Cyclone separator; 530. Impurity removal component; 540. Filter screen; 600. Inert gas storage tank; 700. Atomizing liquid storage tank; 800. Liquid pouring tank. Detailed Implementation

[0058] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0059] In this application, unless otherwise expressly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two elements or the interaction between two elements, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances. In this application, unless otherwise expressly specified and limited, "on" or "below" a second feature can mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium.

[0060] In the description of this application, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the number itself, while "above," "below," and "within" are understood to include the number itself. The terms "first" and "second" are used only to distinguish technical features and should not be construed as indicating or implying relative importance, or implicitly specifying the number of technical features indicated, or implicitly specifying the sequential relationship of the technical features indicated.

[0061] In this document, "optionally," "optionally," and "optional" mean that something is optional, meaning that one can choose between two parallel options: "with" or "without." If multiple "options" appear in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "option" is independent. In this application, descriptions such as "optionally contains" and "optionally includes" indicate "contains or does not contain."

[0062] In this application, unless otherwise stated, the sum of the parts of each component in the composition may be 100 parts by weight. Unless otherwise specified, the percentages (including weight percentages) in this application are based on the total weight of the composition, and "wt%" in this document means mass percentage.

[0063] In this document, unless otherwise stated, the reaction steps may be performed in the order described herein or not. For example, other steps may be included between reaction steps, and the order of reaction steps may be appropriately interchanged. This is something that those skilled in the art can determine based on conventional knowledge and experience. Preferably, the reaction methods described herein are performed sequentially.

[0064] In this application, the term "numerical interval" (i.e., numerical range) refers to a range of values. Unless otherwise specified, the distribution of selectable values ​​within this numerical interval is considered continuous, and includes the two endpoints (i.e., the minimum and maximum values) of the interval, as well as every value between these endpoints. Unless otherwise specified, when a numerical interval refers only to integers within that interval, it includes the two endpoints of the range and every integer between them, effectively listing every integer. When multiple numerical ranges are provided to describe features or characteristics, these ranges can be merged. In other words, unless otherwise specified, the numerical ranges disclosed in this application should be understood to include any and all subranges included therein. The "numerical value" in this numerical interval can be any quantitative value, such as a number, percentage, or proportion. The term "numerical interval" can broadly include percentage intervals, proportion intervals, ratio intervals, and other quantitative intervals.

[0065] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0066] This application provides a two-stage gas-liquid synergistic atomization powder making device 10 to solve the problems of wide powder particle size distribution, fine powder yield generally below 30%, and high production costs in conventional gas atomization technology. The two-stage gas-liquid synergistic atomization powder making device 10 will be described below with reference to the accompanying drawings.

[0067] The two-stage gas-liquid synergistic atomization powder-making device 10 provided in one embodiment of this application is exemplary; please refer to [link to example]. Figure 1 As shown, Figure 1 This is a schematic diagram of the structure of a two-stage gas-liquid synergistic atomization powder-making device 10 provided in one embodiment of this application. The two-stage gas-liquid synergistic atomization powder-making device 10 of this application can be used for atomization powder making.

[0068] To more clearly illustrate the structure of the two-stage gas-liquid synergistic atomization powder making device 10, the following will describe the two-stage gas-liquid synergistic atomization powder making device 10 in conjunction with the accompanying drawings.

[0069] For example, please refer to Figure 1 and Figure 2 As shown, Figure 2 This is a side view of a two-stage gas-liquid synergistic atomization powder-making device 10 according to an embodiment of this application. The device 10 includes a vacuum melting furnace 100, an atomizing container 200, a first atomizing component 300, a second atomizing component 400, and a collecting component 500. The vacuum melting furnace 100 is used to melt raw materials to form a melt. The atomizing container 200 is connected to the vacuum melting furnace 100 to receive the melt and atomize it. The first atomizing component 300 and the second atomizing component 400 are respectively disposed within the atomizing container 200 and spaced apart along the axial direction of the atomizing container 200. See also... Figure 3 As shown, Figure 3This is a schematic diagram illustrating the interaction between a first atomizing component 300 and a second atomizing component 400 in a two-stage gas-liquid synergistic atomization powder-making apparatus 10 according to an embodiment of this application. An atomization focusing region is located between the first atomizing component 300 and the second atomizing component 400. The first atomizing component 300 includes a plurality of aerosol nozzles 310. The plurality of aerosol nozzles 310 are distributed around the axis of the atomization container 200. All aerosol nozzles 310 face the atomization focusing region. The aerosol nozzles 310 are used to atomize the melt using a first inert gas to form droplet particles. The second atomizing component 400 includes a plurality of liquid atomizing nozzles 410. The plurality of liquid atomizing nozzles 410 are distributed around the axis of the atomization container 200. The liquid atomizing nozzles 410 are used to shear and atomize the droplet particles using a liquid second inert gas flow to form atomized droplets. A collecting component 500 is used to collect the atomized droplets and cool them to form solid powder particles.

[0070] The aforementioned two-stage gas-liquid synergistic atomization powder making device 10 produces solid powder particles with uniform particle size distribution, improves fine powder yield, and reduces production costs. Specifically, the two-stage gas-liquid synergistic atomization powder making device 10 provided in this application includes a vacuum melting furnace 100 for melting raw materials to form a melt, an atomizing container 200 connected to the vacuum melting furnace 100 to receive the melt, and an atomization focusing area between the first atomizing component 300 and the second atomizing component 400. The first atomizing component 300 includes multiple aerosol nozzles 310, all facing the atomization focusing area. The supersonic airflow from the nozzles 310 primary atomizes the melt into droplets, achieving efficient and uniform breakup of the melt. Subsequently, the second atomizing component 400 includes multiple liquid atomizing nozzles 410. These nozzles utilize airflow to perform secondary shearing atomization on the droplets, forming atomized droplets. This two-stage atomization synergy effectively avoids the problems of uneven breakup and wide particle size distribution inherent in single atomization methods. Finally, a collecting component 500 collects the atomized droplets and cools them to form solid powder particles. Through this two-stage gas-liquid synergistic atomization mechanism, the device significantly improves the uniformity of droplet size during atomization. The resulting solid powder particles exhibit a narrow particle size distribution and high fine powder yield, while simultaneously reducing production costs and overcoming the shortcomings of existing technologies, such as low fine powder yield and severe particle size polarization.

[0071] In some implementations, see Figure 4 As shown, Figure 4 This is a schematic diagram of the aerosol nozzle 310 of a two-stage gas-liquid synergistic atomization powder making device 10 according to an embodiment of this application. The aerosol nozzle 310 includes a Laval nozzle.

[0072] In some embodiments, the atomizing container 200 is provided with a guide tube 210, one end of which is connected to the vacuum melting furnace 100 and the other end extends to the atomization focusing area.

[0073] In some embodiments, the two-stage gas-liquid co-atomization powder-making device 10 further includes a heating component. The heating component is connected to the guide pipe 210 to heat the guide pipe 210 and maintain it within a preset temperature range. The heating component is not shown in the accompanying drawings. During the smelting process, the guide pipe 210 at the outlet of the smelting furnace is kept in a preheated state to prevent the melt from contacting the low-temperature pipe wall and causing solidification and blockage.

[0074] In some embodiments, a flow regulating valve 211 is provided on the guide pipe 210. The flow regulating valve 211 is used to adjust the opening of the guide pipe 210 to control the flow rate of the melt entering the atomizing container 200.

[0075] In some embodiments, the guide tube 210 extends along the axis of the atomizing container 200, and each atomizing nozzle 310 faces the same position on the axis of the atomizing container 200. The axis of the guide tube 210 is precisely aligned with the axis of the atomizing container to ensure that the melt can be stably discharged along a preset path. It should be noted that the "same position" on the axis of the atomizing container 200 where each atomizing nozzle 310 faces is a virtual position, that is, the position where the extension lines of the axes of each atomizing nozzle 310 intersect.

[0076] In some embodiments, the centerline of the aerosol nozzle 310 forms an angle of 15° to 45° with the axis of the atomizing container 200.

[0077] In some embodiments, the angle between the centerline of the aerosol nozzle 310 and the axis of the atomizing container 200 is adjustable. In this application, multiple aerosol nozzles 310 are arranged in a circular array at the same annular position, and the aerosol nozzles 310 can adjust the spray angle to enhance the abrasive effect of the gas jet on the molten metal.

[0078] In some embodiments, the number of aerosol nozzles 310 is eight, which are evenly distributed in a ring. On the ring surface, the included angle between adjacent aerosol nozzles 310 is 45°. Each aerosol nozzle 310 is tilted downwards at an angle of 15° to 45° towards the atomization focusing area. A first inert gas is ejected through the flat slit of the liquid-aerosol nozzle 310, forming a 75° fan-shaped mist surface. The fan-shaped mist surfaces of adjacent aerosol nozzles 310 overlap, achieving full circumferential coverage of the atomization focusing area. The high-pressure first inert gas impacts the melt column formed by the melt at the atomization focusing area, breaking it into fine droplet particles. Simultaneously, the first inert gas provides initial cooling to the droplet particles, inhibiting their growth. It is easy to understand that in other embodiments, the number of aerosol nozzles 310 can also be other numbers.

[0079] In some implementations, see Figure 5 As shown, Figure 5This is a schematic diagram of the liquid mist nozzle 410 of a two-stage gas-liquid synergistic atomization powder making device 10 according to an embodiment of this application. Multiple gas mist nozzles 310 are distributed at equal intervals.

[0080] In some embodiments, the fan-shaped mist surfaces of adjacent aerosol nozzles 310 partially overlap. The effect of the fan-shaped mist surfaces of adjacent aerosol nozzles 310 overlapping can be achieved by adjusting the number of aerosol nozzles 310 and the opening angle of the aerosol nozzles 310 to ensure that the fan-shaped mist surfaces of adjacent aerosol nozzles 310 partially overlap, so as to further achieve spray coverage on a circumference.

[0081] In some embodiments, the liquid mist nozzle 410 faces the first atomizing component 300, and the liquid mist nozzle 410 uses a liquid second inert gas to counteract the droplet particles formed by the first atomizing component 300, thereby achieving precise refinement of the primary droplet particles and obtaining finer atomized droplets.

[0082] In some embodiments, the liquid mist nozzle 410 is detachably connected to the atomizing container 200. This detachable connection facilitates the disassembly, cleaning, and maintenance of the liquid mist nozzle 410, improving operational convenience.

[0083] In some embodiments, the orifice diameter of the liquid mist nozzle 410 is 0.1 mm to 0.5 mm. For example, the orifice diameter of the liquid mist nozzle 410 may include, but is not limited to, 0.1 mm, 0.12 mm, 0.15 mm, 0.18 mm, 0.2 mm, 0.22 mm, 0.25 mm, 0.28 mm, 0.3 mm, 0.32 mm, 0.35 mm, 0.38 mm, 0.4 mm, 0.42 mm, 0.45 mm, 0.48 mm, 0.5 mm, or any range between the foregoing.

[0084] The aerosol nozzle 310 and the liquid aerosol nozzle 410 are arranged coaxially and can work synchronously. A first inert gas, such as high-pressure argon, is accelerated by the aerosol nozzle 310 and ejected as a supersonic gas flow. The aerosol nozzle 310 is pointed at the atomization focusing area at a 30° angle. The supersonic gas flow ejected by the aerosol nozzle 310 forms an inert gas curtain surrounding the atomization focusing area. On the one hand, the inert gas curtain can isolate the air and prevent the high-temperature droplets from oxidizing during the atomization process. On the other hand, the supersonic gas flow can also perform secondary shearing atomization on the initially broken droplets, further refining the particle size, while accelerating the cooling and solidification rate of the droplets and improving the sphericity of the powder.

[0085] In some embodiments, the two-stage gas-liquid co-atomizing powder-making device 10 further includes an inert gas storage tank 600. The atomizing container 200 has an inert gas interface that communicates with each aerosol nozzle 310. The inert gas storage tank 600 is connected to the inert gas interface.

[0086] In some embodiments, an airflow regulating valve is installed on the pipeline between the inert gas storage tank 600 and the inert gas interface.

[0087] In some embodiments, the two-stage gas-liquid co-atomizing powder-making device 10 further includes an atomizing liquid storage tank 700, and the atomizing container 200 has an atomizing liquid interface that communicates with each liquid mist nozzle 410. The atomizing liquid storage tank 700 is connected to the atomizing liquid interface.

[0088] In some embodiments, the two-stage gas-liquid co-atomization powder-making device 10 further includes a filter component connected to the vacuum melting furnace 100. The filter component is used to filter and remove oxide impurities from the raw materials entering the vacuum melting furnace 100. In this application, the raw material pretreatment uses the vacuum melting furnace 100 and the filter component to perform raw material melting and impurity filtration, removing oxide impurities from the raw materials entering the vacuum melting furnace 100 and ensuring the high purity of the molten metal.

[0089] In some embodiments, the two-stage gas-liquid synergistic atomization powder making device 10 further includes a liquid pouring tank, which is disposed inside the atomization container 200 and located between the first atomization component 300 and the second atomization component 400. The liquid pouring tank is connected to the second atomization component 400, and the inner wall of the liquid pouring tank gradually narrows from the first atomization component 300 to the second atomization component 400.

[0090] In some embodiments, the collecting component 500 includes a cooling chamber 510 that communicates with the atomizing container 200 for collecting atomized droplets, and the cooling chamber 510 is also provided with a cooling gas interface.

[0091] In some embodiments, the collecting component 500 further includes a cyclone separator 520, which communicates with the cooling chamber 510 and is used to collect solid powder particles cooled from the cooling chamber 510.

[0092] In some embodiments, the cyclone grading of the cyclone separator 520 is adjustable. Rapid solidification and narrow particle size distribution of solid powder particles are achieved through controllable cooling rate and cyclone grading within the cooling chamber 510.

[0093] In some embodiments, the collecting component 500 further includes a cleaning component 530, which is connected to the cyclone separator 520 and is used to remove impurities from solid powder particles.

[0094] In some embodiments, the impurity removal component 530 includes a magnetic separator.

[0095] In some embodiments, the collecting component 500 further includes a filter screen 540 connected to the impurity removal component 530. The filter screen 540 is used to screen the solid powder particles after impurity removal by particle size classification. This application improves the purity and particle size uniformity of the powder by setting the impurity removal component 530 to remove impurities from the solid powder particles, and by further improving the powder purity and particle size uniformity by magnetic separation and sieving through the filter screen 540.

[0096] One embodiment of this application provides a two-stage gas-liquid synergistic atomization powder production method.

[0097] A two-stage gas-liquid synergistic atomization powder preparation method, employing the two-stage gas-liquid synergistic atomization powder preparation device 10 of any of the above embodiments, includes the following steps:

[0098] S10, control the vacuum melting furnace 100 to melt the raw materials to form a melt.

[0099] S20. The multiple aerosol nozzles 310 of the first atomizing component 300 are controlled to spray a first inert gas at a first pressure to expel oxygen from the atomizing container 200. The first inert gas is used for pre-purging to remove residual air from each pipe and nozzle, preventing subsequent oxidation of the melt upon contact with air.

[0100] S30. Control the melt in the vacuum melting furnace 100 to enter the atomizing container 200 and atomize it into droplet particles under the action of the first inert gas at the first pressure.

[0101] S40, the multiple liquid mist nozzles 410 of the second atomizing component 400 spray a second pressure of liquid second inert gas to shear and atomize the droplet particles to form atomized droplets.

[0102] S50, the control collection unit 500 collects the atomized droplets and cools them to form solid powder particles.

[0103] In some embodiments, the flow rate of the melt entering the atomizing container 200 from the vacuum melting furnace 100 in S30 is typically 0.5 kg / min to 2 kg / min. For example, the values ​​of the flow rate of the melt entering the atomizing container 200 from the vacuum melting furnace 100 include, but are not limited to: 0.5 kg / min, 0.6 kg / min, 0.7 kg / min, 0.8 kg / min, 0.9 kg / min, 1.0 kg / min, 1.1 kg / min, 1.2 kg / min, 1.3 kg / min, 1.4 kg / min, 1.5 kg / min, 1.6 kg / min, 1.7 kg / min, 1.8 kg / min, 1.9 kg / min, 2.0 kg / min, or any range between the foregoing.

[0104] In some embodiments, the vacuum level inside the vacuum melting furnace 100 is controlled to be 5 × 10⁻⁶. -4 Pa ~ 6×10 -4 Pa. For example, the value for controlling the vacuum level within the vacuum melting furnace 100 includes, but is not limited to: 5 × 10 Pa. -4 Pa, 5.2 × 10 -4 Pa, 5.4 × 10 -4 Pa, 5.6 × 10 -4 Pa, 5.8 × 10 -4 Pa, 6.0 × 10 -4 Pa or the range between any two of the aforementioned.

[0105] In some embodiments, the melting temperature within the vacuum melting furnace 100 is controlled to be 1700°C to 1800°C, and the holding time is 30 min to 40 min. For example, the value of the melting temperature within the vacuum melting furnace 100 includes, but is not limited to: 1700°C, 1710°C, 1720°C, 1730°C, 1740°C, 1750°C, 1760°C, 1770°C, 1780°C, 1790°C, 1800°C, or any range between the two aforementioned; for example, the value of the holding time during melting within the vacuum melting furnace 100 includes, but is not limited to: 30 min, 31 min, 32 min, 33 min, 34 min, 35 min, 36 min, 37 min, 38 min, 39 min, 40 min, or any range between the two aforementioned.

[0106] In some embodiments, the first inert gas and the second inert gas independently comprise argon and / or nitrogen, respectively.

[0107] In some embodiments, the temperature of the first inert gas is controlled to be between 0°C and 50°C. For example, the value of the temperature of the first inert gas may include, but is not limited to: 0°C, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, or any range between the foregoing.

[0108] In some embodiments, the first pressure is 1.5 MPa to 2 MPa. For example, the value of the first pressure includes, but is not limited to: 1.5 MPa, 1.55 MPa, 1.6 MPa, 1.65 MPa, 1.7 MPa, 1.75 MPa, 1.8 MPa, 1.85 MPa, 1.9 MPa, 1.95 MPa, 2.0 MPa, or any range between the foregoing.

[0109] In some embodiments, the temperature of the liquid second inert gas is controlled to be between -196°C and -190°C. For example, the value of the temperature of the liquid second inert gas is not limited to: -196°C, -195°C, -194°C, -193°C, -192°C, -191°C, -190°C, or any range between the foregoing.

[0110] In some embodiments, the second pressure is 5 MPa to 6 MPa. For example, the value of the second pressure includes, but is not limited to: 5.0 MPa, 5.1 MPa, 5.2 MPa, 5.3 MPa, 5.4 MPa, 5.5 MPa, 5.6 MPa, 5.7 MPa, 5.8 MPa, 5.9 MPa, 6.0 MPa, or any range between the foregoing.

[0111] In some embodiments, the droplet particles have a diameter of 50 μm to 200 μm.

[0112] In some embodiments, the atomized droplets have a particle size of 15 μm to 150 μm.

[0113] In some embodiments, the cooling treatment of the atomized droplets meets the following condition: the atomized droplets are purged with a protective gas at a controlled temperature below 0°C.

[0114] In some embodiments, the flow rate of the protective gas at a temperature below 0°C is 20 L / min to 100 L / min.

[0115] In some embodiments, the protective gas temperature is -50°C to -25°C. For example, the protective gas temperature may include, but is not limited to, -50°C, -48°C, -45°C, -42°C, -40°C, -38°C, -35°C, -32°C, -30°C, -28°C, -25°C, or any range between the foregoing.

[0116] In some embodiments, the cooling rate of the atomized droplets is controlled to be 3 × 10⁻⁶. 4 ℃ / s ~5×10 4 ℃ / s. It should be noted that the total temperature drop of a molten metal droplet cooling from over a thousand degrees Celsius to a solid state is only one or two thousand degrees Celsius. The actual cooling process lasts only tens to hundreds of microseconds, not a full second. Cooling rate 10 5 At a temperature of ℃ / s, that is, a temperature drop of 1℃ every 10 microseconds, tiny metal droplets solidify instantly, which is why spherical powders with extremely fine grains and little segregation can be obtained.

[0117] In some embodiments, the two-stage gas-liquid synergistic atomization powder production method further includes the following step: vacuum drying the solid powder particles.

[0118] In some embodiments, the vacuum drying process satisfies the following conditions: vacuum drying at a temperature of 100°C to 120°C for 1 hour to 1.5 hours. For example, the vacuum drying temperature includes, but is not limited to, 100°C, 102°C, 105°C, 108°C, 110°C, 112°C, 115°C, 118°C, 120°C, or any range between the two aforementioned; the vacuum drying time includes, but is not limited to, 1.0 hour, 1.1 hour, 1.2 hour, 1.3 hour, 1.4 hour, 1.5 hour, or any range between the two aforementioned.

[0119] In some embodiments, the two-stage gas-liquid synergistic atomization powder production method further includes the following step: removing impurities from the solid powder particles.

[0120] In some embodiments, the impurity removal process includes magnetic separation. Magnetic separation is a physical purification method based on the difference in magnetic properties of materials. It mainly utilizes the fact that when a magnetic field is applied to a mixture of materials, magnetic impurities such as iron, cobalt, nickel and their oxides or iron-containing minerals are magnetically adsorbed, while non-magnetic target components are unaffected. Thus, impurities are effectively separated by magnetic separation equipment such as drum magnetic separators and high-gradient magnetic separators.

[0121] In some embodiments, the two-stage gas-liquid synergistic atomization powder production method further includes the following step: particle size screening of solid powder particles.

[0122] In some embodiments, particle size screening includes 15μm~53μm and 53μm~106μm particle size grades. It should be noted that in this application, 15μm~53μm powder is the mainstream high-end powder in the industry, mostly used for SLM / L-PBF laser selective melting (metal powder-layout printing, the core application), fine laser cladding, and a small amount of high-end plasma spraying. 53μm~106μm coarse powder is mainly used for powder-fed additive printing, such as (EBM electron beam powder-layout 3D printing, DED directional energy deposition, mainstream thermal spraying, traditional powder metallurgy sintering, etc.). A cyclone separator blows the finer powder to a more distant collection chamber, while the coarser powder remains in a closer collection chamber, working in conjunction with the screen to achieve screening of powders of different particle sizes.

[0123] In this application, the process parameters are optimized. By adjusting parameters such as the pressure of the first inert gas, the temperature of the liquid second inert gas, the spray angle of the atomizing nozzle 310, and the cooling rate of the cooling chamber, the particle size of the solid powder particles can be controlled as needed. Argon and / or nitrogen are used for protection throughout the process to prevent the metal droplets from being oxidized. An inert liquid such as liquid nitrogen is selected as the atomizing liquid, which can achieve a finer particle size without introducing new impurities.

[0124] This application employs a two-stage synergistic atomization structure, combining the rapid fragmentation advantages of gas atomization with the precise refinement characteristics of liquid atomization. Simultaneously, through inert gas protection and impurity removal, particle size screening, and other processes, the impurity content in the prepared solid powder particles is reduced, thereby improving the overall performance of the powder. The aforementioned two-stage gas-liquid synergistic atomization powder preparation device 10 can simultaneously meet the four core requirements of solid powder particles: narrow particle size distribution, high sphericity, low impurity content, and high production efficiency, making it suitable for preparing 3D printing metal powders.

[0125] Example 1

[0126] This embodiment provides a two-stage gas-liquid synergistic atomization powder production method.

[0127] In this embodiment, TC4 titanium alloy ingots are used as raw materials.

[0128] This embodiment employs a two-stage gas-liquid synergistic atomization powder production method. Figures 1-5 The two-stage gas-liquid synergistic atomization powder-making device 10 shown includes the following steps:

[0129] S100, Evacuate the vacuum melting furnace 100 to 5×10 -4 Pa, argon gas is introduced for protection, heated to 1700℃, held for 30 minutes, and the TC4 titanium alloy ingot raw material is melted in a vacuum melting furnace 100 to form a melt; oxide impurities in the melt are removed by a ceramic filter assembly.

[0130] S200, adjust the spray angle of multiple aerosol nozzles 310 to 25° downwards, that is, the angle with the axis of the atomizing container 200 is 25°, introduce argon gas into the aerosol nozzles 310 as atomizing gas, control the spray pressure to 1.5MPa, the gas temperature to 50℃, and discharge the oxygen in the atomizing container 200.

[0131] S300: The melt in the vacuum melting furnace 100 is continuously fed into the atomizing container 200 and atomized into droplet particles with a diameter of 50μm~200μm under the action of argon gas at a pressure of 1.5MPa.

[0132] S400, multiple liquid atomizing nozzles 410 of the second atomizing component 400 spray liquid argon gas at a pressure of 5 MPa and a temperature of -196°C to shear and atomize the droplet particles to form atomized droplets with a diameter of 15-150 μm.

[0133] S500: Control the atomized droplets to enter the cooling chamber 510. Argon gas is introduced into the cooling chamber 510 at a flow rate of 10 m / s. The cooling temperature is controlled at 0℃. The secondary droplets rapidly solidify at a cooling rate of 5 × 10⁻⁶ m / s. 4 The temperature is ℃ / s and it is cooled to form solid powder particles.

[0134] S600: Solid powder particles are collected by cyclone separator 520, vacuum dried at 100℃ for 1.5h, and after magnetic separation to remove impurities, TC4 titanium alloy powder with two particle size grades of 15μm~53μm and 53μm~106μm is screened by multi-layer sieve.

[0135] After testing, the obtained TC4 titanium alloy powder has a sphericity of 98.5%, an impurity content of 0.03%, and a flowability of 32s / 50g, which meets the requirements of SLM additive manufacturing process.

[0136] Example 2

[0137] This embodiment provides a two-stage gas-liquid synergistic atomization powder production method.

[0138] In this embodiment, Inconel 718 alloy ingots are used as raw materials.

[0139] The preparation method in this embodiment is basically the same as that in Example 1, except that the gas pressure in S200 and S300 is 1.8 MPa, the nozzle angle of the aerosol nozzle 310 is 30°, the pressure of liquid argon in S400 is 6 MPa, and the cooling rate is 8 × 10⁻⁶. 4 °C / s. Inconel 718 powder was prepared in this example.

[0140] After testing, the obtained Inconel 718 powder has a particle size distribution of 15μm~150μm, sphericity ≥98.2%, impurity content ≤0.04%, and flowability ≥31s / 50g, which meets the requirements of EBM additive manufacturing process for high-temperature alloy powder.

[0141] The above-mentioned two-stage gas-liquid synergistic atomization powder-making device 10 has at least the following beneficial effects:

[0142] (1) Excellent powder performance: The solid powder particles prepared have a narrow particle size distribution that can be adjusted from 15 to 150 μm, sphericity ≥ 98%, impurity content ≤ 0.05%, and flowability ≥ 30 s / 50 g, which meets the requirements of additive manufacturing processes such as SLM and EBM.

[0143] (2) High production efficiency: Breaking through the technical limitations of single gas / liquid atomization, it adopts a series working mode of "gas crushing-liquid refining": the first-stage gas atomization uses supersonic airflow to quickly crush molten metal and form uniform primary droplets; the second-stage liquid atomization uses inert low-temperature liquid to reverse impact to achieve precise droplet refining, while using the rapid heat absorption characteristics of liquid to improve the cooling rate. Compared with traditional single atomization technology, the yield of fine powder is increased by more than 40% and can achieve large-scale production.

[0144] (3) The nozzles of the aerosol nozzle 310 are arranged in a ring array and the spray angle is adjustable from 15° to 45°. They are combined with the liquid inlet groove on the inner wall that gradually narrows from the first atomizing component 300 to the second atomizing component 400 to enhance the rotational kinetic energy of the airflow and improve the uniformity of droplet breakage. The liquid mist nozzle 410 is detachable and has an aperture design of 0.1mm to 0.5mm. It can be flexibly replaced according to the target powder particle size to achieve on-demand control of the particle size range of 15μm to 150μm, and adapt to the needs of different additive manufacturing processes (SLM / EBM).

[0145] (4) Stable and reliable process: From raw material pretreatment to finished product packaging, a four-level purification mechanism of "vacuum melting and filtration + inert gas protection + inert liquid atomization + impurity removal and classification" is constructed. Among them, the vacuum induction melting furnace has built-in impurity filtration components. Argon and / or nitrogen are introduced to isolate air throughout the atomization and cooling process. The atomizing liquid uses an inert medium to avoid secondary pollution. Finally, the impurity content of solid powder particles is ≤0.05%, which solves the problem of poor fluidity caused by metal droplet oxidation and excessive impurities in traditional atomization processes.

[0146] (5) Balancing high quality and large-scale production: The cooling chamber 510 uses a protective gas with a controllable airflow rate of 5m / s to 20m / s and a temperature of -50℃ to -25℃ for cooling, and the cooling rate can reach 3×10 4At ℃ / s, it achieves rapid solidification of solid powder particles, forming highly spherical particles (≥98%); combined with a cyclone separator 520 and a multi-layer filter screen 540, it achieves powder classification and collection and precise particle size screening, improving the fine powder yield by more than 40% compared to single atomization technology, thus balancing high quality and large-scale production.

[0147] (6) Wide applicability: The entire process parameters of the preparation method of this application can be precisely controlled. The equipment used has a simple structure, low maintenance cost, and is easy to promote in industry. It is applicable to the preparation of various metals and alloy powders such as titanium alloy, high temperature alloy, stainless steel, and aluminum alloy.

[0148] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0149] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0150] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims, and the specification and drawings can be used to interpret the content of the claims.

Claims

1. A two-stage gas-liquid synergistic atomization powder-making device, characterized in that, The system includes a vacuum melting furnace, an atomizing container, a first atomizing component, a second atomizing component, and a collecting component. The vacuum melting furnace is used to melt raw materials to form a melt. The atomizing container is connected to the vacuum melting furnace to receive the melt and atomize it. The first and second atomizing components are respectively disposed within the atomizing container and spaced apart along the axial direction of the atomizing container. An atomization focusing area is formed between the first and second atomizing components. The first atomizing component includes multiple aerosol nozzles distributed around the axis of the atomizing container, all facing the atomization focusing area. The aerosol nozzles are used to atomize the melt into droplet particles using a first inert gas. The second atomizing component includes multiple liquid atomizing nozzles distributed around the axis of the atomizing container. The liquid atomizing nozzles are used to atomize the droplet particles into atomized liquid droplets using a liquid second inert gas. The collecting component is used to collect the atomized liquid droplets and cool them to form solid powder particles.

2. The two-stage gas-liquid synergistic atomization powder-making device according to claim 1, characterized in that, The atomizing container is provided with a guide tube, one end of which is connected to the vacuum melting furnace and the other end extends to the atomizing focusing area.

3. The two-stage gas-liquid synergistic atomization powder-making device according to claim 2, characterized in that, It also satisfies at least one of the following conditions: (1) It also includes a heating component, which is connected to the guide tube to heat the guide tube and maintain a preset temperature range; (2) A flow regulating valve is provided on the guide pipe.

4. The two-stage gas-liquid synergistic atomization powder-making device according to claim 2, characterized in that, The guide tube extends along the axis of the atomizing container, and each of the aerosol nozzles faces the same position on the axis of the atomizing container. Optionally, the centerline of the aerosol nozzle has an angle of 15° to 45° with the axis of the atomizing container; further optionally, the angle between the centerline of the aerosol nozzle and the axis of the atomizing container is adjustable. Optionally, the plurality of aerosol nozzles are distributed at equal intervals; Optionally, the fan-shaped mist surfaces of adjacent aerosol nozzles partially overlap.

5. The two-stage gas-liquid synergistic atomization powder-making device according to any one of claims 1 to 4, characterized in that, It also satisfies at least one of the following conditions: (1) It also includes an inert gas storage tank, the atomizing container having an inert gas interface, the inert gas interface being connected to each of the aerosol nozzles, and the inert gas storage tank being connected to the inert gas interface; Optionally, a flow stabilizing valve is installed on the pipeline between the inert gas storage tank and the inert gas interface; (2) It also includes an atomizing liquid storage tank, the atomizing container having an atomizing liquid interface, the atomizing liquid interface being connected to each of the liquid mist nozzles, and the atomizing liquid storage tank being connected to the atomizing liquid interface.

6. The two-stage gas-liquid synergistic atomization powder-making device according to any one of claims 1 to 4, characterized in that, It also includes a filter element connected to the vacuum melting furnace, which is used to filter and remove oxide impurities from the raw materials entering the vacuum melting furnace.

7. The two-stage gas-liquid synergistic atomization powder-making device according to any one of claims 1 to 4, characterized in that, It also includes a liquid pouring tank, which is disposed inside the atomizing container and located between the first atomizing component and the second atomizing component. The liquid pouring tank is connected to the second atomizing component, and the inner wall of the liquid pouring tank gradually narrows from the first atomizing component to the second atomizing component.

8. The two-stage gas-liquid synergistic atomization powder-making device according to any one of claims 1 to 4, characterized in that, The collecting component includes a cooling chamber, which is provided with a cooling gas interface and is connected to the atomizing container for collecting the atomized droplets; Optionally, the collecting component further includes a cyclone separator, which communicates with the cooling chamber and is used to collect the solid powder particles cooled by the cooling chamber. Optionally, the collecting component further includes a purification component connected to the cyclone separator, the purification component being used to remove impurities from the solid powder particles; Optionally, the collecting component further includes a filter screen connected to the impurity removal component, the filter screen being used to screen the solid powder particles after impurity removal by particle size.

9. A two-stage gas-liquid synergistic atomization powder production method, characterized in that, The two-stage gas-liquid synergistic atomization powder-making device according to any one of claims 1 to 8 includes the following steps: Control the vacuum melting furnace to melt the raw materials into a melt; Multiple aerosol nozzles of the first atomizing component are controlled to spray a first inert gas at a first pressure to expel oxygen from the atomizing container; The melt in the vacuum melting furnace is controlled to enter the atomizing container and atomize into droplet particles under the action of a first inert gas at the first pressure; Multiple liquid mist nozzles of the second atomizing component are controlled to spray a second pressure of liquid inert gas to atomize the droplet particles into atomized droplets; Additionally, the control collection component collects the atomized droplets and cools them to form solid powder particles.

10. The two-stage gas-liquid synergistic atomization powder production method according to claim 9, characterized in that, It also satisfies at least one of the following conditions: (1) Control the vacuum degree in the vacuum melting furnace to 5×10 -4 Pa ~ 6×10 -4 Pa; (2) The melting temperature in the vacuum melting furnace is controlled at 1700℃~1800℃ and the holding time is 30min~40min; (3) The first inert gas and the second inert gas each independently comprise argon and / or nitrogen; (4) Control the temperature of the first inert gas from 0℃ to 50℃; (5) Control the first pressure to be 1.5 MPa to 2 MPa; (6) Control the temperature of the liquid second inert gas to -196℃ to -190℃; (7) Control the second pressure to 5 MPa~6 MPa; (8) The droplet particles have a diameter of 50 μm to 200 μm; (9) The particle size of the atomized droplets is 15μm~150μm; (10) The cooling treatment of the atomized droplets meets the following conditions: the atomized droplets are purged with a protective gas at a controlled temperature below 0°C; Optionally, the protective gas includes at least one of nitrogen and argon; Optionally, the flow rate of the protective gas at a temperature below 0°C is 20 L / min to 100 L / min; Optionally, the cooling rate of the atomized droplets is controlled to be 3 × 10⁻⁶. 4 ℃ / s ~5×10 4 ℃ / s; (11) It also includes the following step: vacuum drying the solid powder particles; Optionally, the vacuum drying process meets the following conditions: vacuum drying at 100℃~120℃ for 1h~1.5h; (12) It also includes the following step: removing impurities from the solid powder particles; Optionally, the impurity removal process includes magnetic separation for impurity removal; (13) It also includes the following step: the solid powder particles are subjected to particle size screening; Optionally, the particle size classification includes 15μm~53μm and 53μm~106μm particle size classes.

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