Method for optimizing nozzle and flow guide pipe tail end coupling structure to prevent gas atomization nozzle from being blocked and nozzle

Abstract

The invention relates to a gas atomization powder preparation technology, and provides a method for optimizing modification of the tail end of a flow guide pipe and preventing a nozzle from being blocked. According to the method, the continuity and stability of the atomization process are ensured by optimizing a geometric structure, material selection and technological parameters. The tail end of the flow guide pipe is of a conical shrinkage structure, the divergence angle ranges from 40 degrees to 45 degrees, the height of a shrinkage section ranges from 2.0 mm to 6.0 mm, the inner diameter ranges from 3.0 mm to 6.0 mm, the width of a small platform is smaller than or equal to 1.0 mm, and metal melt retention is reduced. And the service life is prolonged by adopting a ZrO2 or SiC high-heat-resistant ceramic material. The atomization gas pressure is 3.5-4.5 MPa, the melt temperature is 1500-1650 DEG C, the vacuum degree is less than or equal to 5 * 10 <-3 > Pa, and efficient atomization is ensured. A spraying disc flow channel is of a Laval structure or a gradually-shrinking structure, the coupling distance between an air outlet and the tail end of the flow guide pipe is 5-7 mm, and the gas-liquid interaction is optimized. After optimization, the sphericity degree of powder is improved, satellite powder is reduced, and the service life of the nozzle is prolonged by 30%. The gas consumption is reduced by 20%, and the maintenance cost is reduced by 15-20%. The nozzle is effectively prevented from being blocked, the atomization efficiency and the powder quality are improved, and important industrial application value is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of aerosol powder making, and particularly relates to a method for optimizing the coupling structure between the nozzle and the end of the guide tube to prevent the aerosol nozzle from being blocked. By adjusting the expansion angle and structural design of the end of the guide tube, the residence time of the metal melt in the nozzle area and the probability of collision with the guide tube wall are reduced, the nozzle is prevented from being blocked, and the continuity and powder quality of aerosol powder making are improved. Background Art

[0002] Gas atomization powder making technology is the core process for preparing metal powders and is widely used in additive manufacturing, powder metallurgy, thermal spraying and other fields. As a key component of gas atomization equipment, the tightly coupled nozzle and the coupling structure of the nozzle and the end of the guide tube have an important influence on the stability of the gas atomization process and the performance of the powder. In the prior art, there is often a small platform structure at the end of the guide tube, which makes it easy for the metal melt to contact and stay on the inner wall of the nozzle guide tube during the atomization process, forming a solidification layer, and eventually causing the nozzle to be blocked. In addition, the unreasonable design of the expansion angle of the end structure of the guide tube will aggravate the reflux of the melt and turbulent disturbance, further increasing the risk of blockage. Existing research has mostly focused on the optimization of the inner diameter of the guide tube and the gas injection angle, while there is less systematic research on the optimization of the end structure of the guide tube, resulting in frequent blockage and interruption of the atomization process and high production costs. Summary of the invention

[0003] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a method for optimizing the coupling structure between the nozzle and the end of the guide tube to prevent clogging of the aerosol nozzle. By adjusting the expansion angle of the end structure of the guide tube, shortening the width of the small platform and optimizing the material selection, the residence time of the molten metal in the nozzle area and the probability of collision with the guide tube wall are reduced, the nozzle is prevented from being blocked, and the atomization efficiency and powder quality are improved.

[0004] To achieve the above object, the technical solution of the present invention is as follows:

[0005] A method for optimizing the coupling structure between the nozzle and the end of the guide tube to prevent the aerosol nozzle from clogging. By optimizing the geometric shape of the end of the guide tube, material selection and aerosol process parameters, the probability of nozzle clogging during the aerosol process is reduced to ensure the continuity and stability of the atomization process. The specific technical solution includes the following:

[0006] In the method for optimizing the coupling structure between the nozzle and the end of the guide tube to prevent the aerosol nozzle from being blocked, the expansion angle of the end of the guide tube is designed to be 40°-45°. Through numerical simulation and experimental verification, this angle range can effectively shorten the width of the small platform at the end of the guide tube (≤1.0mm), reduce the contact area between the metal melt and the small platform, and reduce the risk of melt retention and solidification.

[0007] In the method for preventing the aerosol nozzle from being blocked by optimizing the coupling structure between the nozzle and the end of the guide tube, the height of the contraction section at the end of the guide tube is 2.0-6.0 mm, and the inner diameter is 3.0-6.0 mm. The design of the contraction section helps to guide the metal melt to be evenly distributed in the radial direction, avoiding direct contact with the inner wall of the nozzle, while enhancing the gas-liquid interaction and improving the secondary crushing efficiency.

[0008] The method for preventing aerosol nozzle clogging by optimizing the coupling structure between the nozzle and the end of the guide tube controls the width of the small platform at the end of the guide tube to within 1.0 mm by optimizing the expansion angle and the contraction section design, thereby further reducing the retention of molten metal in the nozzle area.

[0009] The method for optimizing the coupling structure between the nozzle and the end of the guide tube to prevent the aerosol nozzle from being blocked is that the guide tube is made of a highly heat-resistant and corrosion-resistant ceramic material, preferably ZrO 2 Or SiC ceramic material, its temperature resistance is ≥2000℃, thermal conductivity is ≤30W / (m·K), which can effectively resist the erosion of high-temperature melt and extend the service life of the guide tube.

[0010] The method for preventing the atomizing nozzle from being blocked by optimizing the coupling structure between the nozzle and the end of the guide tube controls the atomizing gas pressure at 3.5-4.5 MPa, ensures that the gas flow rate reaches supersonic speed, and enhances the crushing effect on the metal melt.

[0011] The method for preventing aerosol nozzle blockage by optimizing the coupling structure between the nozzle and the end of the guide tube controls the temperature of the metal melt at 1500-1650° C., ensuring that the melt has good fluidity while avoiding oxidation or volatilization of the material due to excessive temperature.

[0012] The method for preventing the aerosol nozzle from being blocked by the coupling structure between the optimized nozzle and the end of the guide tube is as follows: the vacuum degree of the atomizing tank is ≤5×10- 1 Pa, reducing the impact of impurities in the gas on the atomization process.

[0013] In the method for preventing atomization nozzle blockage by optimizing the coupling structure between the nozzle and the end of the guide tube, the gas-liquid ratio (GMR) is controlled at 1.5-1.7 to ensure that the interaction strength between the gas and the molten metal is moderate, thereby avoiding uneven atomization or nozzle blockage caused by too high or too low a gas-liquid ratio.

[0014] Advantages and beneficial effects of the present invention:

[0015] (1) Optimize the geometric structure of the end of the guide tube to improve the continuity of atomization

[0016] The invention optimizes the geometric modification of the end of the guide tube, shortens the width of the small platform, effectively reduces the probability of metal melt being retained at the outlet of the guide tube, prevents melt accumulation and solidification layer formation, and thus reduces the risk of nozzle blockage. The improved structure ensures that the metal liquid flow always maintains smooth flow when entering the atomization area, achieves more stable continuous atomization, and improves the stability and production efficiency of the atomization powder making process.

[0017] (2) Optimize the expansion angle to improve the sphericity of the powder and the uniformity of the particle size distribution

[0018] In the present invention, by optimizing the expansion angle to 40°–45°, the shearing effect of the atomizing airflow on the metal melt is enhanced, the powder particles are made more uniform, and the powder sphericity is significantly improved. At the same time, the optimized design reduces the generation of satellite powders, reduces the coarse powder content, and makes the powder particle size distribution more concentrated. The D50 (median particle size) can be controlled within the ideal range of 21–25 μm, improving the fluidity and filling performance of the powder, and providing a guarantee for the preparation of high-performance metal powders.

[0019] (3) High heat-resistant ceramic materials increase nozzle life

[0020] The present invention uses high heat-resistant ceramic material as the main material of the guide tube. Compared with traditional metal materials, ceramic materials have stronger resistance to high temperature and thermal shock. Combined with the optimized geometric modification, the material can effectively reduce the thermal mechanical effect of the metal melt on the guide tube, reduce nozzle wear, improve corrosion resistance, increase the service life of the nozzle by more than 30%, reduce replacement frequency, and reduce production and maintenance costs.

[0021] (4) Reduce gas consumption and maintenance costs, and improve economic benefits

[0022] The present invention reduces gas consumption by about 20% and energy consumption in the production process by finely adjusting process parameters while ensuring high atomization efficiency. At the same time, the optimized design makes the equipment run more stably, reduces the number of unplanned shutdowns caused by nozzle blockage or spray disc burnout, thereby reducing the frequency of equipment maintenance, reducing the overall operating cost by 15%-20%, and significantly improving the economic benefits and market competitiveness of atomized powder making. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 : Schematic diagram of the structure of the optimized guide tube end structure tightly coupled nozzle provided by the present invention (marking the expansion angle and the small platform width).

[0024] Figure 2 : Comparison of atomization process when the expansion angle of the guide tube end is 30° and 45° (numerical simulation cloud map).

[0025] Figure 3: SEM photograph of the nickel-based alloy powder in Example 1 (expansion angle 40°).

[0026] Figure 4 : Industrial site photo of the blockage at the end of the guide pipe in Comparative Example 1.

[0027] Figure 5 : Comparison of powder particle size distribution curves under different expansion angles. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments.

[0029] The present invention relates to the technical field of aerosol powder making, and specifically provides a method for optimizing the shaping of the end of a guide tube to prevent clogging of an aerosol nozzle. The method reduces the probability of nozzle clogging during the aerosolization process by optimizing the geometric shaping, material selection and aerosol process parameters of the end of the guide tube, thereby ensuring the continuity and stability of the atomization process. The end of the guide tube adopts a conical contraction structure with an expansion angle of 40°-45°, a contraction section height of 2.0-6.0mm, an inner diameter of 3.0-6.0mm, and a small platform width controlled within 1.0mm to reduce metal melt retention. The guide tube is made of highly heat-resistant and corrosion-resistant ceramic materials (such as ZrO 2 Or SiC), temperature resistance ≥2000℃, thermal conductivity ≤30W / (m·K), and extended service life. The atomizing gas pressure is 3.5-4.5MPa, the metal melt temperature is 1500-1650℃, the vacuum degree is ≤5×10-3Pa, and the gas-liquid ratio (GMR) is 1.5-1.7, ensuring a stable and efficient atomization process. The spray plate consists of an upper cover and a base. The gas flow channel is designed as a Laval structure or a tapered structure. The coupling distance between the spray plate outlet and the end of the guide tube is 5-7mm, ensuring that the interaction strength between the gas and the metal melt is moderate. By optimizing the geometric modification of the end of the guide tube, shortening the width of the small platform, reducing the probability of metal melt retention, avoiding the formation of a solidification layer, and achieving continuous atomization. When the expansion angle is 40°-45°, the sphericity of the powder is improved, the satellite powder is reduced, and the particle size distribution is more concentrated (D50=21-25μm). High heat-resistant ceramic material combined with geometric modification reduces the thermomechanical effect between the melt and the guide tube, and the service life is increased by more than 30%. Through the optimization of process parameters, gas consumption is reduced (reduced by 20%) and equipment maintenance frequency, and the overall cost is reduced by 15%-20%. The present invention effectively solves the problem of aerosol nozzle blockage by optimizing the modification of the end of the guide tube and combining material and process parameter regulation, significantly improving atomization continuity and powder quality, and has important industrial application value.

[0030] The close-coupled nozzle structure is mainly composed of an atomizing spray disc and a guide tube, wherein the atomizing spray disc is composed of a coaxial spray disc upper cover and a spray disc base seal. A gas resonance chamber is formed inside the spray disc. After the high-pressure gas enters the gas resonance chamber, a stable airflow spray field is formed at the outlet of the spray disc. This resonance chamber design can optimize the gas distribution, so that the high-pressure gas acts evenly on the molten metal, thereby improving the atomization efficiency and ensuring the uniformity of the atomized particles.

[0031] The guide tube runs through the center hole of the spray plate cover and is fixed to the spray plate in a tight coupling manner. The guide tube adopts a cylindrical hole structure inside, so that the molten metal maintains a stable flow when flowing through the guide tube. The molten metal first enters the system through the cylindrical section of the guide tube, where the pressure is relatively uniform, and then flows into the contraction section. The design of the contraction section increases the flow rate of the molten metal before entering the atomization area of ​​the spray plate, which enhances the shear effect during atomization and improves the droplet breakup effect.

[0032] The end of the guide tube is equipped with an expansion section with an expansion angle of 9°. This structure can effectively reduce the turbulence effect of the liquid flow at the outlet, so that the molten metal presents a more stable flow state when entering the gas atomization spray disc. In addition, the existence of the expansion section helps to buffer the rapid changes in the flow rate of the molten metal, optimize the droplet formation process, and improve the atomization quality.

[0033] The contraction section of the guide tube is set with a contraction angle of 30-60°, which is used to increase the exit velocity of the molten metal in the nozzle by reducing the flow cross-sectional area. When the molten metal passes through this area, due to the optimized design of the contraction angle, the liquid will form a slender stream, which will have a strong shearing effect with the high-pressure gas sprayed from the atomization spray disc, and finally achieve efficient atomization. By adjusting the contraction angle, the particle size distribution of the droplets can be further optimized, making the atomized particles more uniform and adapting to different process requirements.

[0034] In summary, the tightly coupled nozzle structure achieves efficient and uniform metal liquid atomization through the resonance effect of the atomizing spray disc, the fluid stability control of the guide tube, the buffering effect of the terminal expansion section, and the flow velocity optimization of the contraction section, thereby improving the quality of metal powder or coating materials and optimizing the stability of the production process.

[0035] See also Figure 1, which is a structural schematic diagram of a tightly coupled nozzle structure provided by the present invention. As shown in the figure, it includes an atomizing spray disc 10 and a guide tube 20 tightly coupled with the atomizing spray disc 10, wherein the atomizing spray disc 10 is composed of a coaxial spray disc upper cover 1 and a spray disc base 2, wherein the spray disc upper cover 1 and the spray disc base 2 are combined and sealed to form a gas resonance chamber 5 and a spray disc gas outlet 6; a center hole penetrating the thickness of the spray disc upper cover is provided at the center position of the spray disc upper cover 1, and the guide tube 20 is inserted into the center hole and forms a tightly coupled assembly structure with the atomizing spray disc 10; an expansion section 8 is provided at the end of the guide tube, and the expansion angle of the expansion section at the end of the guide tube is 9; the inner core 3 of the guide tube 20 is a cylindrical hole, and the outer part is an integrally formed cylindrical section 4 and a contraction section 7, the upper end of the cylindrical section 4 is a molten metal inlet, and the end of the contraction section 7 is a molten metal outlet; the contraction angle of the contraction section 7 of the guide tube is 30-60°.

[0036] The key core technology of the tightly coupled nozzle structure provided by the present invention is to regulate the expansion angle 9 of the expansion section 8 at the end of the guide tube. It is found through experiments that setting the expansion angle to 35-45° can greatly promote the interaction intensity between the atomizing gas and the metal liquid flow, improve the atomization efficiency, and increase the fine powder recovery rate; at the same time, the position of the atomization reflux zone is reasonably controlled, which not only improves the gas / liquid ratio and obtains a higher fine powder recovery rate, but also avoids the upward reflux of the metal liquid flow, thereby reducing the probability of nozzle clogging and spray disc burning, ensuring the continuity and stability of the atomization powder making process, thereby improving the economic benefits.

[0037] The tightly coupled nozzle structure provided by the present invention achieves precise gas-liquid mixing control by tightly coupling the atomizing spray disc 10 with the guide tube 20. The spray disc upper cover 1 and the spray disc base 2 are combined to form a sealed gas resonance chamber 5, which is used to stabilize the high-pressure atomized gas and spray it evenly to the outlet area of ​​the guide tube through the spray disc outlet 6. The center hole of the guide tube 20 passes through the spray disc upper cover 1, so that the guide tube can be firmly inserted into the spray disc and form a tight fit, ensuring that the gas and the metal liquid flow can be efficiently mixed at the best position during the atomization process.

[0038] The metal liquid flow enters from the metal liquid inlet (the upper end of the cylindrical section 4) of the guide tube 20 and flows downward through the cylindrical hole 3. When flowing through the contraction section 7, the liquid flow is further contracted due to the contraction angle (30-60°) to form a high-speed metal jet. At the end expansion section 8 of the guide tube, due to the effect of the expansion angle 9 (35-45°), the metal liquid flow will expand significantly in this area, increasing the interaction area between the atomizing gas and the metal flow, thereby significantly improving the atomization efficiency.

[0039] After being ejected from the nozzle outlet 6, the atomizing gas enters the expansion section 8 at the end of the guide tube. Due to the optimization of the expansion angle, the gas forms a strong turbulent effect here, and violently shears with the high-speed flowing metal liquid flow, causing the metal liquid flow to break into fine particles, achieving efficient atomization. At the same time, the structural design reasonably controls the position of the atomizing reflux zone, prevents gas reflux from interfering with the flow of metal liquid, improves the gas / liquid ratio, and enables the kinetic energy of the atomizing gas to be more efficiently converted into liquid crushing kinetic energy, thereby improving the fine powder recovery rate of the atomized powder.

[0040] The reasonable expansion angle 9 controls the flow field distribution of the atomizing airflow, avoids the phenomenon of upward reflux of the molten metal, and thus reduces the risk of nozzle blockage. In addition, the design effectively reduces the direct impact of the high-temperature molten metal on the nozzle outlet 6, reduces the possibility of burning of the nozzle, and increases the service life of the nozzle. Finally, the tightly coupled nozzle structure improves economic benefits while ensuring continuous and stable atomization and powder making, and reduces maintenance costs and unplanned downtime in the production process.

[0041] Embodiment 1:

[0042] The expansion angle of the end of the guide tube is 40°, the height of the contraction section is 4.0mm, and the inner diameter is 4.0mm. The guide tube is made of ZrO 2 Ceramic, temperature resistance ≥2000℃, thermal conductivity 25W / (m·K). The width of the small platform at the end of the guide tube is controlled at 0.8mm to reduce the retention of molten metal. The spray plate consists of an upper cover and a base. The gas flow channel is designed as a Laval structure. The coupling distance between the spray plate outlet and the end of the guide tube is 6.0mm. The inner wall thickness of the cylindrical hole on the upper cover of the spray plate is 1.5mm to ensure that the interaction strength between the gas and the molten metal is moderate. The atomizing gas pressure is 4.0MPa, the gas is argon, and the flow rate reaches supersonic. The temperature of the molten metal is 1600℃, and the vacuum degree is 3.5×10-3Pa. The gas-liquid ratio (GMR) is 1.6 to ensure a stable atomization process.

[0043] The results of Example 1 show that the atomization process is continuous and there is no nozzle clogging. The prepared nickel-based alloy powder has a particle size of D50 = 23 μm, a sphericity of >95%, and a satellite powder ratio of <5%. The service life of the guide tube is significantly extended, and the continuous atomization time reaches more than 8 hours.

[0044] Embodiment 2:

[0045] The expansion angle at the end of the guide tube is 45°, the height of the contraction section is 5.0mm, and the inner diameter is 5.0mm. The guide tube is made of SiC ceramic, with a temperature resistance of ≥2000℃ and a thermal conductivity of 20W / (m·K). The width of the small platform at the end of the guide tube is controlled at 0.5mm to further reduce the retention of the molten metal. The gas flow channel of the spray plate is designed as a tapered structure, and the coupling distance between the spray plate outlet and the end of the guide tube is 5.5mm. The inner wall thickness of the cylindrical hole on the upper cover of the spray plate is 1.2mm to ensure that the interaction strength between the gas and the molten metal is moderate. The atomizing gas pressure is 3.5MPa, the gas is nitrogen, and the flow rate reaches supersonic. The molten metal temperature is 1550℃ and the vacuum degree is 4.0×10-3Pa. The gas-liquid ratio (GMR) is 1.7 to ensure a stable atomization process.

[0046] The results of Example 2 show that the atomization process is continuous and there is no nozzle clogging. The particle size of the prepared iron-based alloy powder is D50 = 21 μm, the sphericity is > 96%, and the proportion of satellite powder is < 4%. The service life of the guide tube is significantly extended, and the continuous atomization time reaches more than 10 hours.

[0047] Comparative Example 1:

[0048] The expansion angle of the end of the guide tube is 30°, the height of the contraction section is 4.0mm, and the inner diameter is 4.0mm. The guide tube is made of ZrO 2 Ceramic, temperature resistance ≥2000℃, thermal conductivity 25W / (m·K). The width of the small platform at the end of the guide tube is 1.5mm, and the metal melt is easy to be retained. The gas flow channel of the spray plate is designed as a Laval structure, and the coupling distance between the spray plate outlet and the end of the guide tube is 6.0mm. The inner wall thickness of the cylindrical hole on the spray plate cover is 1.5mm. The atomizing gas pressure is 4.0MPa, the gas is argon, and the flow rate reaches supersonic. The metal melt temperature is 1600℃, and the vacuum degree is 3.5×10-3Pa. The gas-liquid ratio (GMR) is 1.6.

[0049] The results of comparative example 1 show that a solidified layer is formed at the small platform at the end of the guide tube during atomization, and the nozzle is completely blocked after 30 minutes. The prepared powder particle size D50 = 35 μm, sphericity <90%, and satellite powder ratio >10%. The service life of the guide tube is significantly shortened, and the continuous atomization time is only 0.5 hours.

[0050] Comparative Example 2:

[0051] The expansion angle at the end of the guide tube is 50°, the height of the contraction section is 5.0mm, and the inner diameter is 5.0mm. The guide tube is made of SiC ceramic, with a temperature resistance of ≥2000℃ and a thermal conductivity of 20W / (m·K). The width of the small platform at the end of the guide tube is 0.3mm, but the air flow disturbance is aggravated. The gas flow channel of the spray plate is designed as a tapered structure, and the coupling distance between the spray plate outlet and the end of the guide tube is 5.5mm. The inner wall thickness of the cylindrical hole on the upper cover of the spray plate is 1.2mm. The atomizing gas pressure is 3.5MPa, the gas is nitrogen, and the flow rate reaches supersonic. The metal melt temperature is 1550℃, and the vacuum degree is 4.0×10-3Pa. The gas-liquid ratio (GMR) is 1.7.

[0052] The results of comparative example 2 show that the air flow disturbance intensifies during atomization, the powder particle size distribution becomes wider (D50=35 μm), and the proportion of satellite powder increases to 15%. The service life of the guide tube is extended, but the powder quality decreases, which does not meet industrial requirements.

[0053] In summary, it can be seen from the comparison between the embodiment and the comparative example that when the expansion angle at the end of the guide tube is 40°-45°, the atomization process is continuous and stable, the powder quality is significantly improved, and the nozzle clogging problem is effectively solved. When the expansion angle is 30° and 50° in the comparative example, the atomization process has problems to varying degrees, which verifies the effectiveness and necessity of the optimized design of the present invention.

[0054] It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for optimizing the shape of the end of a guide tube to prevent clogging of an aerosol nozzle, characterized in that: The end of the guide tube is designed as a contraction structure, with an expansion angle of 40°-45°, a contraction section height of 2.0-6.0mm, an inner diameter of 3.0-6.0mm, and a small platform width of ≤1.0mm.

2. The method according to claim 1, characterized in that The guide tube is made of ZrO2 or SiC ceramics, with a temperature resistance of ≥2000°C and a thermal conductivity of ≤30W / (m·K).

3. The method according to claim 1, characterized in that The atomizing gas pressure is 3.5-4.5MPa, the molten metal temperature is 1500-1650℃, and the gas-liquid ratio (GMR) is 1.5-1.

7.

4. The method according to claim 1, characterized in that: The flow channel of the gas resonance chamber is designed as a Laval structure or a tapered structure.

5. The close-coupled nozzle structure according to claim 1, characterized in that: The guide tube is made of ZrO2 ceramic material or SiC ceramic material.

6. A tightly coupled nozzle structure, characterized in that: It includes an atomizing spray disc and a guide tube tightly coupled with the atomizing spray disc, the atomizing spray disc includes a spray disc upper cover and a spray disc base, the spray disc upper cover and the spray disc base are combined and sealed to form a gas resonance chamber and a spray disc air outlet, a center hole penetrating the thickness of the spray disc upper cover is provided at the center position of the spray disc upper cover, the guide tube is inserted into the center hole and forms a tightly coupled assembly structure with the atomizing spray disc, the guide tube includes a cylindrical section, a contraction section and a terminal expansion section, the upper end of the cylindrical section is a molten metal inlet, the terminal of the contraction section is a molten metal outlet, the contraction section has a contraction angle, and the terminal expansion section has an expansion angle.

7. The close-coupled nozzle structure according to claim 6, characterized in that: The spray plate upper cover and the spray plate base are connected via a sealing structure to prevent gas leakage and limit the volume of the gas resonance chamber.

8. The close-coupled nozzle structure according to claim 6, characterized in that: The inner core of the guide tube is a cylindrical hole, and the outer portion is composed of an integrally formed cylindrical section and a contraction section, wherein the contraction angle of the contraction section is 30°-60°.

9. The close-coupled nozzle structure according to claim 6, characterized in that: The expansion angle of the terminal expansion section of the guide tube is 35°-45°.

10. The close-coupled nozzle structure according to claim 6, characterized in that: The spray plate air outlets are evenly distributed on the periphery of the atomizing spray plate; the spray plate base is provided with a cooling channel to reduce the heat load of the nozzle structure.

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