A double-layer gas atomization nozzle for improving the sphericity of powder

Abstract

The present invention relates to a double-layer gas atomization nozzle for improving the sphericity of powder. The atomization nozzles used in the existing processes cannot effectively ensure the sphericity of metal powder. The double-layer gas atomization nozzle of the present invention is characterized in that it is composed of an upper nozzle and a lower nozzle. The upper nozzle is a convergent nozzle structure, and the lower nozzle is a Laval structure. The lower nozzle is a structure that first converges and then diverges, and forms a convergent surface, a throat structure, and a divergent surface. The present invention uses the upper and lower nozzles for secondary fragmentation and dispersion, making the fragmented metal small droplets more uniform, ensuring more sufficient spheroidization during the atomization and cooling process, thereby ensuring the sphericity of the powder. In addition, the double-layer atomization nozzle can generate a larger negative pressure area, the air flow will be smoother, avoiding atomization blockage and improving the atomization efficiency. At the same time, the nozzle is tightly sealed by threads, has good high-temperature stability, a simple structure, and is easy to assemble.

Description

Technical Field

[0001] The present invention relates to the field of powder preparation devices, and particularly to a double-layer gas atomization nozzle for improving the sphericity of powder. Background Art

[0002] Currently, the methods for powder preparation mainly include atomization method, reduction method, crushing method, mechanical alloying method, etc. Among them, the atomization method is the most important powder-making process. Compared with other methods, the powder prepared by the atomization method has the advantages of high sphericity, uniform and stable composition, good fluidity, etc. Therefore, the powder prepared by the atomization method is mainly applied to high-end industries such as additive manufacturing, vacuum brazing, and soft magnetic materials. Among them, sphericity is one of the most important parameters of atomized powder, which affects performance parameters such as surface morphology, apparent density, tapped density, and fluidity, and thus affects the performance of subsequent powder products.

[0003] Due to the different atomization processes, the sphericity of the prepared metal powder is not the same. The gas atomization process is one of the most important technologies for preparing spherical powder, and its process feature is to use an inert gas medium flowing out of the nozzle to break and cool the molten metal liquid flow into fine metal powder particles. The most crucial factor affecting the sphericity of the powder is whether the broken small metal droplets are fully spheroidized before solidification.

[0004] The double-layer nozzle structure designed in Patent CN105436509A (a double-layer restricted nozzle for metal atomization with electromagnetic field assistance) is mainly for improving atomization efficiency and preventing nozzle blockage, rather than specifically optimizing the nozzle design for improving the sphericity of powder; Patent CN110640155A (a method for improving the sphericity of metal powder prepared by gas atomization method) mainly improves the sphericity of the powder from the temperature of the gas in the gas atomization method and the heating power of the induction coil, and the process is relatively complex. Summary of the Invention

[0005] The purpose of the present invention is to propose a double-layer gas atomization nozzle for improving the sphericity of powder, which has a simple structure and can effectively improve the sphericity of gas atomized powder, aiming at the shortcomings of the existing technology.

[0006] In order to achieve the above purpose, the present invention adopts the following technical scheme: A double-layer gas atomization nozzle for improving the sphericity of powder, characterized in that the double-layer gas atomization nozzle is composed of an upper nozzle and a lower nozzle. The upper nozzle is a convergent nozzle structure, and the lower nozzle is a Laval structure. The lower nozzle is a structure that first converges and then diverges, and forms a convergent surface, a throat structure, and a divergent surface.

[0007] Preferably, the included angle of the air outlet holes of the upper nozzle is 0-10°, the inner diameter is 4-8 mm, and the air outlet of the nozzle is of an annular slit type.

[0008] Preferably, the included angle of the air outlet holes of the lower nozzle is 36 - 45°, the inner diameter is 20 - 32 mm, and the air outlet of the nozzle adopts an annular slit type.

[0009] Preferably, the upper nozzle and the lower nozzle are connected by threaded fastening and sealed connection, and the seal is a high-strength ceramic sealing material such as a high-purity boron nitride ring, which can effectively improve the sealing effect under high-temperature conditions.

[0010] Preferably, the width of the circular ring of the contraction section of the upper nozzle is 0.5 - 0.8 mm.

[0011] Preferably, the contraction surface of the lower nozzle is converged by two smooth curves to form an included angle of 40 - 75°, the throat structure is a smooth arc surface, the expansion surface is diverged by two straight lines to form an included angle of 3 - 5°, and the width of the annular slit at the end of the expansion surface is 0.5 - 1.0 mm.

[0012] Preferably, a method for preparing powder by using a double-layer gas atomization nozzle is characterized in that the atomization nozzle according to any one of claims 1 - 6 is installed in a fixed position of the atomization system, the material is loaded into a corundum crucible, after vacuumizing and filling with argon, medium-frequency heating and refining are started, when the melt reaches superheat, the molten metal is poured into the above double-layer gas atomization nozzle and atomization is immediately started, and the metal liquid flow forms uniform and stable spherical powder after being broken, dispersed and cooled in the atomization nozzle.

[0013] The present invention adopts a double-layer gas atomization nozzle structure, the upper nozzle is a contraction-type nozzle structure, and the lower nozzle is a Laval-type structure, which can perform secondary dispersion and fragmentation on the metal liquid flow, ensure that sufficient surface energy is obtained during the dispersion and fragmentation process, make the broken metal small droplets more uniform, ensure more sufficient spheroidization during the atomization and cooling process, and thus ensure the powder sphericity.

[0014] In addition, the double-layer atomization nozzle can generate a larger negative pressure area, the air flow will be smoother, avoid atomization blockage, and improve the atomization efficiency. At the same time, the nozzle is connected by threaded fastening and sealed connection, has good high-temperature stability, simple structure, and is easy to assemble. It reduces the influence of human factors on the installation accuracy of the atomization nozzle, provides good protection for the atomization nozzle, and is beneficial to preparing gas atomized powder with high sphericity. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a schematic diagram of the atomization nozzle structure;

[0016] Figure 2 is the high-flux soft magnetic alloy powder prepared by using this atomization nozzle.

[0017] Figure 3 is the eutectic high-entropy alloy powder prepared by using this atomization nozzle. DETAILED DESCRIPTION OF THE INVENTION

[0018] Next, in combination with the accompanying drawings in the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0019] As Figure 1 shown, a double-layer gas atomization nozzle for improving the sphericity of powder mainly includes an upper nozzle and a lower nozzle, and is fastened and sealed by threads. In order to improve the fragmentation effect of the metal liquid flow and ensure that the liquid droplets are dispersed into uniformly sized liquid droplets, this double-layer gas atomization nozzle is designed to be composed of an upper nozzle 1 and a lower nozzle 2. The upper nozzle adopts a convergent nozzle structure design, and the width of the convergent section ring is 0.6 mm. The included angle α of the nozzle outlet hole is 3°, the inner diameter is 6 mm, and the outlet of the nozzle adopts an annular slit type. The lower nozzle adopts a Laval type structure design, which is a structure of first contraction and then expansion, and forms a contraction surface 3, a throat structure 4, and an expansion surface 5. The contraction surface is converged by two smooth curves to form an included angle of 55°. The throat structure is a smooth arc surface. The expansion surface is diverged by two straight lines to form an included angle of 3°, and the width of the annular slit at the end of the expansion surface is 0.9 mm. The included angle β of the lower nozzle outlet hole is 38°, the inner diameter is 25 mm, and the outlet of the nozzle adopts an annular slit type.

[0020] During operation, taking the preparation of eutectic high-entropy alloy powder and high magnetic flux soft magnetic alloy powder as examples, the atomization nozzle is installed in the fixed position of the atomization system, the material is loaded into the corundum crucible, and then the vacuum is evacuated and filled with argon, and then medium-frequency heating and refining are started. When the melt reaches the superheat degree, the molten metal is poured into the above double-layer gas atomization nozzle and atomization immediately starts. The metal liquid flow is broken, dispersed, and cooled in the atomization nozzle to form uniform and stable spherical powder, as Figure 2 and Figure 3 shown.

[0021] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. A double-layer gas atomization nozzle for improving the sphericity of powder, characterized in that the double-layer gas atomization nozzle is composed of an upper nozzle and a lower nozzle. The upper nozzle is a convergent nozzle structure, and the lower nozzle is a Laval structure. The lower nozzle is a structure that first converges and then diverges, and forms a contraction surface, a throat structure and a divergence surface; the included angle of the air outlet holes of the upper nozzle is 0 to 10°, the inner diameter is 4-8 mm, and the air outlet of the nozzle adopts an annular slit type; the included angle of the air outlet holes of the lower nozzle is 36 to 45°, the inner diameter is 20-32 mm, and the air outlet of the nozzle adopts an annular slit type; the contraction surface of the lower nozzle is converged by two smooth curves to form an included angle of 40-75°. The throat structure is a smooth arc surface, and the divergence surface is two straight lines diverging to form an included angle of 3-5°. The width of the annular slit at the end of the divergence surface is 0.5-1.0 mm.

2. The double-layer gas atomization nozzle according to claim 1, characterized in that the upper nozzle and the lower nozzle are connected by threaded fastening and sealed connection, and the seal is a high-strength ceramic sealing material.

3. The double-layer gas atomization nozzle according to claim 1, characterized in that the width of the circular ring of the contraction section of the upper nozzle is 0.5-0.8 mm.

4. A method for preparing powder by using a double-layer gas atomization nozzle, characterized in that the atomization nozzle according to any one of claims 1-3 is installed in a fixed position of the atomization system, the material is loaded into a corundum crucible, after vacuum is pumped and argon is filled, medium-frequency heating and refining are started. When the melt reaches superheat, the molten metal is poured into the above double-layer gas atomization nozzle and atomization is immediately started. The metal liquid flow forms uniform and stable spherical powder after being broken, dispersed and cooled in the atomization nozzle.

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