Supersonic atomizer with double Laval structures and use method of supersonic atomizer

Abstract

The invention discloses a supersonic atomizer of a double-Laval structure and a using method of the supersonic atomizer, and belongs to the technical field of metal powder preparation through gas atomization. The supersonic atomizer comprises a gas atomizing nozzle of a cylindrical structure, and a cooling device is arranged on the periphery of the gas atomizing nozzle. A through hole is formed in the center of the gas atomization nozzle, and a liquid guide pipe is arranged in the through hole in a sleeved mode and used for metal melt to flow through. A circle of gas containing cavity is formed in the gas atomizing nozzle around the through hole, the gas containing cavity is connected with a gas inlet pipe, and the end, close to the gas atomizing nozzle, of the gas inlet pipe is of a Laval structure; a plurality of gas flow channels are arranged at the bottom of the gas accommodating cavity around an outlet of the liquid guide pipe; the airflow channel is of a Laval structure. The supersonic atomizer of the double-Laval structure is suitable for atomization of all metal and alloy melts with the melting point below 1600 DEG C, and prepared metal powder has the advantages of being fine in particle size, high in sphericity degree, good in fluidity and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of preparing metal powder by gas atomization, and relates to a supersonic atomizer with a double Laval structure and a use method thereof. Background Art

[0002] Gas atomization technology is one of the main methods for producing high-performance metal powders, and its principle is mainly based on the gas jet principle. In the gas atomization process, compressed gas is used to pass through a fine nozzle to break the liquid metal flow into tiny particles under the impact of high-speed airflow. These particles are suspended in the air and form a mist, which can then be collected and processed to obtain the desired powder. The powder produced by gas atomization has the advantages of good sphericity and controllable particle size distribution. The gas atomization nozzle is the core part of the gas atomization technology, and the structure of the nozzle determines the performance and preparation efficiency of the metal powder. With the application of additive manufacturing technology in aerospace, national defense and military industries, improving the preparation rate of metal powders with fine particle size (particle size less than 53μm) and high sphericity and reducing the cost of powder making have become the development trend of current gas atomization powder making technology. At present, the main technical features of the atomization nozzle are annular hole type and annular gap type. After the gas passes through the gas outlet, it converges at a certain angle and the metal liquid is broken and atomized at the intersection of the gas. In order to obtain a high-speed airflow that breaks up the liquid metal flow, it is necessary to use a contraction-expansion-contraction type Laval nozzle to obtain a supersonic airflow, improve the atomization efficiency, and produce a powder with a finer particle size.

[0003] However, when the existing atomizing nozzle is atomized, the molten metal liquid flow directly passes through the guide channel, resulting in too high an internal ambient temperature of the atomizing nozzle. The excessively high temperature slows down the airflow velocity and has an adverse effect on the rupture atomization result. In addition, the airflow outlets of the traditional atomization powder making technology are all cylindrical holes. After the liquid metal flow flows out of the guide tube, the high-pressure gas first breaks the metal liquid column, so that the surface of the liquid metal flow is broken into fine particles. The particles are broken twice by the high-pressure gas during the falling process, so that the liquid particles are broken into fine powder. The main problems of traditional circular holes in the field of atomization are as follows: 1. The gas ejected from the circular hole is unevenly distributed in space, and the gas velocity decays greatly, which may cause the metal liquid flow to be inconsistently acted upon by the airflow during the crushing process, resulting in uneven particle size distribution of the metal powder obtained after crushing. 2. When the circular hole outlet ejects gas, eddy currents and turbulence may occur, which increases energy consumption and thus reduces the effective utilization rate of energy, and may also affect the crushing effect. 3. The interaction between gas and molten metal flow is not sufficient, which increases the probability of satellite ball formation and reduces the quality of powder. Summary of the invention

[0004] The purpose of the present invention is to solve the technical problems of large gas velocity attenuation, excessively high operating temperature and large energy loss in the atomizing nozzle in the prior art, and to provide a supersonic atomizer with a double Laval structure and a method for using the same.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: In the first aspect, the present invention discloses a supersonic atomizer with a double Laval structure, comprising an atomization nozzle with a cylindrical structure, wherein a cooling device is arranged on the periphery of the atomization nozzle; a through hole is arranged at the center of the atomization nozzle, and a liquid guide tube is arranged in the through hole for molten metal to flow through; a circle of gas containing chamber is arranged around the through hole inside the atomization nozzle, and the gas containing chamber is connected to an air inlet pipe, and one end of the air inlet pipe close to the atomization nozzle is a Laval structure; a plurality of air flow channels are arranged around the outlet of the liquid guide tube at the bottom of the gas containing chamber; and the air flow channels are of a Laval structure.

[0006] Further improvements are: The cooling device is a circulating water cooling device sleeved on the periphery of the aerosol nozzle; the circulating water cooling device is a circular cavity structure; the circulating water cooling device is connected with a water supply pipe and a drainage pipe.

[0007] The circulating water cooling device is provided with an arc-shaped groove for accommodating the air inlet pipe; the water delivery pipe and the drainage pipe are symmetrically arranged with respect to the air inlet pipe.

[0008] The liquid guide tube is a tubular structure and is made of ceramic material; a metal melt containing cavity with an outer diameter larger than the inner diameter of the through hole is arranged on the upper part of the liquid guide tube.

[0009] The interior of the liquid guide tube is a metal melt guide cavity, and the metal melt guide cavity is an expanded spiral hole; the inlet and outlet cross sections of the metal melt guide cavity are both gear-shaped, and the deflection angle between the two cross sections is 18°~36°.

[0010] The bottom of the gas containing chamber is a conical surface structure around the outlet of the liquid guiding tube; the inside of the gas containing chamber is a tapered structure from the liquid inlet end to the liquid outlet end; the side surface of the upper wall of the gas containing chamber is an arc curve design with an arc radius of 10-12 mm; the side surface of the lower wall is an inwardly inclined straight line design with an angle of 4°-8° with the horizontal line.

[0011] The number of the air flow channels is 24 to 48.

[0012] The air flow channel includes a throat with a prismatic structure and an expansion section with a pyramidal structure; the ratio of the throat length to the expansion section length is 1:1-1:2; the ratio of the throat cross-sectional area to the expansion section bottom area is 1:1-1:3.

[0013] The ratio of the axial length of the contraction section of the Laval structure part on the intake pipe to the inlet width of the contraction section is 1:1-3:1, the ratio of the inlet width of the contraction section to the throat width is 1:1-5:1, and the ratio of the outlet width of the expansion section to the throat width is in the range of 1:1-3:1.

[0014] In a second aspect, the present invention discloses a method for using the supersonic atomizer, comprising the following steps: Step 1, inserting the liquid guide tube into the through hole of the aerosol nozzle, and then installing a cooling device on the aerosol nozzle; Step 2: Connect the air inlet pipe to the external gas cylinder; connect the cooling device to the external water tank and start cooling water circulation; Step three, dripping the molten metal into the liquid guide tube, the molten metal flows out along the liquid guide tube, and the outflowing molten metal is impacted and broken into fine molten droplets by the supersonic gas flow field flowing out from the air flow channel at the bottom of the atomization nozzle and gradually solidifies into metal powder.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The invention discloses a supersonic atomizer with a double Laval structure. By adopting an air inlet pipe and an air flow channel of the Laval structure, the atomizer can stably deliver a supersonic airflow into a gas containing chamber. This design not only improves the stability and uniformity of the airflow, but also ensures that the airflow can maintain a low energy loss during high-speed flow, thereby realizing efficient airflow utilization. Since the air flow channel of the Laval structure has excellent fluid mechanics properties, the gas can be quickly accelerated to a supersonic state and the gas can be effectively injected into the gas containing chamber. This design significantly shortens the filling time of the air cavity and improves the response speed and working efficiency of the atomizer. By optimizing the design of the gas channel, the atomizer can more efficiently utilize the airflow energy and reduce the downtime caused by unstable airflow or energy loss. Therefore, the working time of the atomizer is effectively extended, and the reliability and stability of the equipment are improved. The double Laval structure supersonic atomizer is suitable for atomizing all metal and alloy melts with a melting point below 1600°C. This feature makes the atomizer widely applicable in the field of metal powder preparation and can meet the atomization requirements of different metal materials. The metal powder prepared by the atomizer has the advantages of fine particle size, high sphericity and good fluidity. These characteristics make the prepared metal powder have better performance and performance in subsequent processing and application, and improve the quality and added value of the product.

[0016] Furthermore, the air flow channel includes a throat with a prismatic structure and an expansion section with a pyramidal structure, which expands the range of high-speed air flow, and the air flow has a wider area of ​​action on the molten metal. The staggered arrangement of the gas channels effectively improves space utilization and increases the maximum number of apertures.

[0017] Furthermore, the spiral metal melt guide cavity of the guide tube causes the molten metal to flow out in a divergent manner, thereby increasing the contact area with the airflow, and providing a better impact and crushing effect of the airflow on the molten metal, thereby effectively reducing energy loss and improving the fine powder collection rate.

[0018] Furthermore, the setting of the circulating water cooling device effectively reduces the impact of molten metal and high-speed airflow on the atomizer temperature during the atomization process, and the annular liquid holding chamber adjusts the cooling water flow rate according to the working temperature to ensure the stability and safety of the powder making process.

[0019] The invention discloses a method for using a supersonic atomizer with a double Laval structure. The method has clear steps and is easy to operate. By gradually assembling and connecting the equipment, the metal powder can be prepared quickly and efficiently. At the same time, the method utilizes the efficient crushing ability of the supersonic airflow, and can crush the metal melt into fine droplets in a short time, greatly improving the production efficiency. The metal powder prepared by the method has the advantages of fine particle size, high sphericity and good fluidity. These characteristics benefit from the strong impact and uniform dispersion of the supersonic airflow on the metal melt, so that the prepared metal powder has excellent morphology and performance, providing high-quality raw materials for subsequent processing and application. In the method, the atomization nozzle is cooled by installing a cooling device, which effectively prevents the high-temperature metal melt from thermal damage to the equipment and prolongs the service life of the equipment. At the same time, the connection between the cooling device and the external water tank ensures the smooth circulation of the cooling water, further enhancing the stability and reliability of the equipment. The method is suitable for the atomization preparation of a variety of metal and alloy melts, and can adjust the parameters such as the flow rate, pressure and water temperature of the air inlet pipe according to the needs to adapt to the characteristics and requirements of different metal materials. This flexibility and applicability make this method have broad application prospects in the field of metal powder preparation. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0021] Figure 1 A cross-sectional view of a supersonic atomizer with a double Laval structure in the present invention; Figure 2 It is a partial cross-sectional view of an air inlet pipe in a supersonic atomizer with a double Laval structure in the present invention; Figure 3A schematic diagram of the arrangement structure of the air flow channel in a supersonic atomizer with a double Laval structure in the present invention; Figure 4 A schematic diagram of the airflow channel structure in a supersonic atomizer with a double Laval structure in the present invention; Figure 5 It is a schematic diagram of the structure of a liquid guide tube in a supersonic atomizer with a double Laval structure in the present invention; Figure 6 A top view of a supersonic atomizer with a double Laval structure in the present invention; Figure 7 A schematic diagram of a connecting conduit of a supersonic atomizer with a double Laval structure in the present invention; Figure 8 A schematic diagram of gas flow in a supersonic atomizer with a double Laval structure in the present invention; Fig. 9 This is a SEM photo of 316L stainless steel powder in an embodiment of the present invention.

[0022] Among them: 1-atomizing nozzle; 2-gas containing chamber; 3-air flow channel; 4-air inlet pipe; 5-nozzle center hole; 6-circulating water cooling device; 7-liquid containing chamber; 8-water pipe; 9-drain pipe; 10-arc groove; 11-liquid guide pipe; 12-metal melt containing chamber; 13-metal melt guide chamber. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0024] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0026] In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. indicate an orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use, it is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0027] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", which does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0028] In the description of the embodiments of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0029] The present invention is further described in detail below in conjunction with the accompanying drawings: See also Figure 1 and Figure 6 The embodiment of the present invention discloses a supersonic atomizer with a double Laval structure, including an atomizing nozzle 1 with a cylindrical structure, and a cooling device is arranged on the periphery of the atomizing nozzle 1; a through hole is arranged in the center of the atomizing nozzle 1, and a liquid guide tube 11 is arranged in the through hole for the metal melt to flow through; the upper part of the through hole is a cylindrical surface, and the lower part is a conical surface. The diameter of the cylindrical surface is the same as the diameter of the lower part of the liquid guide tube, which is 8~12mm; the diameter of the conical surface gradually increases from the inside to the outside, and the diameter at the inlet is 8~12mm, and the diameter at the outlet is 12~16mm. A circle of gas containing chamber 2 is arranged around the through hole inside the atomizing nozzle 1, and the gas containing chamber 2 is connected to the air inlet pipe 4, and the end of the air inlet pipe 4 close to the atomizing nozzle 1 is a Laval structure; the upper wall side of the gas containing chamber 2 is designed as a circular arc curve, and the arc radius is 10~12mm; the lower wall side is designed as a straight line inclined inward, and the angle with the horizontal line is 4°~8°. A plurality of air flow channels 3 are arranged at the bottom of the gas containing chamber 2 around the outlet of the liquid guiding tube 11; the air flow channels 3 are Laval structures.

[0030] The bottom of the gas containing chamber 2 is a conical surface structure around the outlet of the liquid guiding tube 11; the inside of the gas containing chamber 2 is a tapered structure from the liquid inlet end to the liquid outlet end; the side surface of the upper wall of the gas containing chamber 2 is an arc curve design with an arc radius of 10-12 mm; the side surface of the lower wall is an inwardly inclined straight line design with an angle of 4°-8° with the horizontal line.

[0031] See also Figure 2 The air inlet of the air pipe is a Laval structure. The contraction section is designed using the quintic curve method. The width of the throat is 3~6mm. The expansion section is designed using the Fuerst method. According to the principles of aerodynamics, the air flow velocity at the air inlet can reach supersonic speed. In the Laval structure air pipe, the ratio of the axial length L1 of the contraction section to the inlet width a of the contraction section is 1:1~3:1, and the ratio of the inlet width a of the contraction section to the throat width b is 1:1~5:1. In the Laval structure air pipe, the ratio of the outlet width c of the expansion section to the throat width b is determined by the Mach number Ma designed by the production plan, and the ratio ranges from 1:1 to 3:1.

[0032] See also Figure 3 and Figure 4 , the number of the gas flow channels 3 is 24 to 48. The gas flow channel 3 includes a throat of a prism structure and an expansion section of a pyramid structure; the Laval gas channel is composed of a triangular prism-shaped throat and a triangular prism-shaped expansion section, the ratio of the throat length a to the expansion section length b is 1:1 to 1:2, and the ratio of the throat cross-sectional area S1 to the expansion section bottom area S2 is 1:1 to 1:3. The angle formed by the center line of the gas channel expansion section and the center axis of the nozzle is the atomization spray angle, and the angle range is 32° to 51°. The range of high-speed airflow is expanded, the area of ​​action of the airflow on the molten metal is wider, and the staggered arrangement of the gas channels effectively improves the space utilization and increases the maximum number of apertures.

[0033] See also Figure 5 The liquid guide tube 11 is a tubular structure made of ceramic material; the upper part of the liquid guide tube 11 is provided with a metal melt receiving chamber 12 whose outer diameter is larger than the inner diameter of the through hole. The interior of the liquid guide tube 11 is a metal melt diversion chamber 13, which is an expanded spiral hole; the inlet and outlet sections of the metal melt diversion chamber 13 are both gear-shaped, with 14 to 20 gear teeth, and the deflection angle between the two sections is 18° to 36°. The spiral metal melt diversion chamber of the diversion tube will cause the molten metal to flow out in a divergent manner, increase the contact area with the airflow, and provide a better impact and crushing effect of the airflow on the molten metal, reduce energy loss, and improve the fine powder collection rate.

[0034] See also Figure 7The cooling device is a circulating water cooling device 6 sleeved on the periphery of the atomizing nozzle 1; the circulating water cooling device 6 is a circular cavity structure; the circulating water cooling device 6 is connected to a water delivery pipe 8 and a drainage pipe 9. The circulating water cooling device 6 is provided with an arc groove 10 for accommodating the air inlet pipe 4; the water delivery pipe 8 and the drainage pipe 9 are symmetrically arranged about the air inlet pipe 4.

[0035] The embodiment of the present invention discloses a method for using a supersonic atomizer, comprising the following steps: Step 1: insert the liquid guide tube 11 into the through hole of the aerosol nozzle 1, and then install a cooling device on the aerosol nozzle 1; Step 2: connect the air inlet pipe 4 to the external gas cylinder; connect the cooling device to the external water tank and start cooling water circulation; Step three, dripping the molten metal into the liquid conduit 11, the molten metal flows out along the liquid conduit 11, and the outflowing molten metal is impacted by the supersonic gas flow field flowing out from the gas flow channel 3 at the bottom of the atomizing nozzle 1 and broken into fine molten droplets and gradually solidified into metal powder.

[0036] Insert the lower end cylinder of the liquid guide tube 11 into the through hole of the aerosol nozzle 1, then install the aerosol nozzle 1 into the hollow area of ​​the circulating water cooling device 6, and embed the air inlet pipe 4 into the arc groove 10, so that the aerosol nozzle 1, the circulating water cooling device 6 and the liquid guide tube 11 are combined into an integral supersonic atomizer.

[0037] After the atomizer is installed, connect the air inlet pipe to the external gas cylinder. Figure 8 As shown, the airflow enters the gas containing chamber at supersonic speed through the Laval-type air intake pipe, and is ejected at supersonic speed through the annular airflow channel at the bottom of the gas containing chamber, and multiple airflows converge into a stable gas flow field. The water pipe 8 and the drain pipe 9 are connected to the external water tank, and the water pipe 8 starts to take in water, and the water fills the liquid containing chamber and flows out from the drain pipe 9. The inside of the atomizer is cooled by the water circulation system, and then the metal melt is dripped into the metal melt containing chamber 12, and the metal melt flows out along the metal melt guide chamber 13 in a spiral. The outflowing metal melt is broken into fine droplets by the impact of the supersonic gas flow field at the bottom of the center hole of the atomization nozzle and gradually solidifies into metal powder.

[0038] In summary, the present invention effectively solves the shortcomings of large gas velocity attenuation, excessively high operating temperature, and large energy loss by combining the atomizing nozzle, the guide tube, and the circulating water cooling device, narrows the particle size distribution of the metal powder, improves the fine powder collection rate, and meets the particle size and performance requirements of the additive manufacturing technology for the metal powder particles.

[0039] The working principle of the present invention is as follows: The supersonic atomizer in the present invention is composed of three parts: an atomizing nozzle, a circulating water cooling device and a liquid guide tube. In the atomizing nozzle of the present invention, a center hole is provided at the upper end of the nozzle body for fixing the liquid guide tube. An annular air cavity is provided inside, and a single gas supply pipe is provided on the outer wall of the annular air cavity. The gas supply pipe is connected to an external gas cylinder, and the air inlet where the gas supply pipe is connected to the annular air cavity is a Laval structure. The atomizing nozzle is a ring hole type design, and inside the annular air cavity, the bottom of the annular air cavity is a conical surface, and the conical surface is surrounded by a gas channel, and the gas channel and the upper and lower walls of the annular air cavity form a Laval structure.

[0040] Example 1 In this experimental example, a supersonic atomizer with a double Laval structure in the present invention was used, the injection angle α was 30°, the diameter Φ of the flow guide tube 11 was 10 mm, the ratio of the throat length to the expansion section in the gas channel 3 was 1:2, and the ratio of the throat width to the expansion section was 1:3. The material was 316L stainless steel melt, the melting temperature was 1600°C, the atomizing gas was argon, and the atomizing pressure was 4 MPa. The SEM image of the 316L stainless steel powder prepared by the atomizer is shown in FIG. Fig. 9 After atomization, the prepared powder was screened by standard analysis to determine the powder particle size. The proportion of 316L stainless steel powder with a particle size less than 100 μm was 84%, and the proportion of powder particle size below 53 μm was 64%. The average particle size of the powder was D 50 It is 38μm.

[0041] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A supersonic atomizer with a double Laval structure, characterized in that: The invention comprises an aerosol nozzle (1) of cylindrical structure, wherein a cooling device is arranged at the periphery of the aerosol nozzle (1); a through hole is arranged at the center of the aerosol nozzle (1), wherein a liquid guide tube (11) is sleeved in the through hole for metal melt to flow through; a circle of gas containing chamber (2) is arranged around the through hole inside the aerosol nozzle (1), wherein the gas containing chamber (2) is connected to an air inlet tube (4), wherein one end of the air inlet tube (4) close to the aerosol nozzle (1) is of Laval structure; a plurality of air flow channels (3) are arranged at the bottom of the gas containing chamber (2) around the outlet of the liquid guide tube (11); and the air flow channels (3) are of Laval structure.

2. The supersonic atomizer with a double Laval structure according to claim 1, characterized in that: The cooling device is a circulating water cooling device (6) sleeved on the periphery of the aerosol nozzle (1); the circulating water cooling device (6) is a circular cavity structure; the circulating water cooling device (6) is connected to a water supply pipe (8) and a drainage pipe (9).

3. The supersonic atomizer with a double Laval structure according to claim 2, characterized in that: The circulating water cooling device (6) is provided with an arc-shaped groove (10) for accommodating the air intake pipe (4); the water delivery pipe (8) and the drainage pipe (9) are symmetrically arranged with respect to the air intake pipe (4).

4. The supersonic atomizer with a double Laval structure according to claim 1, characterized in that: The liquid guiding tube (11) is a tubular structure and is made of ceramic material; a molten metal containing cavity (12) having an outer diameter greater than the inner diameter of the through hole is provided on the upper portion of the liquid guiding tube (11).

5. The supersonic atomizer with a double Laval structure according to claim 4, characterized in that: The interior of the liquid guiding tube (11) is a metal melt guiding cavity (13), and the metal melt guiding cavity (13) is an expanded spiral hole; the inlet and outlet cross sections of the metal melt guiding cavity (13) are both gear-shaped, and the deflection angle between the two cross sections is 18° to 36°.

6. The supersonic atomizer with a double Laval structure according to claim 1, characterized in that: The bottom of the gas containing chamber (2) is a conical structure around the outlet of the liquid guiding tube (11); the interior of the gas containing chamber (2) is a tapered structure from the liquid inlet end to the liquid outlet end; the side surface of the upper wall of the gas containing chamber (2) is an arc curve design with an arc radius of 10 to 12 mm; the side surface of the lower wall is an inwardly inclined straight line design with an angle of 4° to 8° with the horizontal line.

7. The supersonic atomizer with a double Laval structure according to claim 1, characterized in that: The number of the air flow channels (3) is 24 to 48.

8. The supersonic atomizer with a double Laval structure according to claim 1, characterized in that: The air flow channel (3) comprises a throat of a prism structure and an expansion section of a pyramid structure; the ratio of the length of the throat to the length of the expansion section is 1:1-1:2; and the ratio of the cross-sectional area of ​​the throat to the bottom area of ​​the expansion section is 1:1-1:

3.

9. The supersonic atomizer with a double Laval structure according to claim 1, characterized in that: The ratio of the axial length of the contraction section of the Laval structure part on the air inlet pipe (4) to the contraction section inlet width is 1:1-3:1, the ratio of the contraction section inlet width to the throat width is 1:1-5:1, and the ratio of the expansion section outlet width to the throat width is in the range of 1:1-3:

1.

10. A method for using the supersonic atomizer according to any one of claims 1 to 9, characterized in that: The following steps are involved: Step 1: insert the liquid guide tube (11) into the through hole of the aerosol nozzle (1), and then install a cooling device on the aerosol nozzle (1); Step 2: connect the air inlet pipe (4) to the external gas cylinder; connect the cooling device to the external water tank and start cooling water circulation; Step three, dripping the molten metal into the liquid guide tube (11), the molten metal flows out along the liquid guide tube (11), and the outflowing molten metal is impacted by the supersonic gas flow field flowing out from the gas flow channel (3) at the bottom of the atomization nozzle (1) and broken into fine molten droplets, which are gradually solidified into metal powder.

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