Laval atomizing nozzle and plasma atomizing powder making device for preparing TC4 alloy powder

Abstract

The invention discloses a Laval atomizing nozzle and a plasma atomizing powder preparation device for preparing TC4 alloy powder, and belongs to the field of TC4 alloy powder preparation. The nozzle comprises a nozzle inlet, a nozzle outlet, a conical outer wall and a convergence-expansion type Laval flow channel, wherein the convergence-expansion type Laval flow channel is arranged between the nozzle inlet and the nozzle outlet; the conical outer wall is arranged on the periphery of the convergence-expansion type Laval flow channel, and connecting and fixing structures are arranged at the two ends of the conical outer wall; the plasma atomization powder making device for preparing the TC4 alloy powder comprises a Laval atomization nozzle, a plasma torch, an atomization cavity and a wire feeding mechanism. On the basis of the nozzle with the convergent-expanded Laval runner, the highest airflow speed can reach 617.7 mm / s under the condition that argon is input under the pressure intensity of 0.5 MPa, TC4 wires can be efficiently crushed and atomized, the production efficiency of TC4 powder is improved, the powder sphericity rate is increased, and the fine powder yield is increased.

Description

Technical Field

[0001] The present invention belongs to the field of preparation of TC4 alloy powder, and particularly relates to a Laval atomizing nozzle and a plasma atomizing powder preparation device for preparing TC4 alloy powder. Background Art

[0002] Additive Manufacturing (AM), also known as 3D printing, is an advanced processing and manufacturing technology based on layer-by-layer material deposition of digital models, and is also a revolutionary industrial manufacturing process. Among the raw materials of additive manufacturing processes, TC4 alloy materials have a very wide range of application scenarios. Due to their low density, high specific strength, excellent corrosion resistance, good biocompatibility, high-temperature stability, as well as excellent machining and welding properties, they have become key materials for additive manufacturing and have received extensive attention and applications in the fields of aerospace (such as aircraft engine blades, fuselage structural components, etc.), medical implant devices (such as artificial joints, dental implants, etc.), and the automotive industry (such as lightweight chassis, high-performance racing car components, etc.). For products manufactured using titanium and titanium alloy powders as raw materials, the performance parameters of the key raw material powders will directly affect the quality of the final product, and the manufacturing cost will also directly affect the market competitiveness of the final finished product. The physical and chemical properties of titanium alloy powders will significantly affect the mechanical properties of the materials and are closely related to the mechanical properties of the formed parts.

[0003] Currently, the core principle of the plasma atomization process is to use plasma torches symmetrically installed at the top of the melting chamber to form a high-temperature plasma focus with a temperature even up to 10,000 K. A special wire feeding mechanism feeds the metal wire into the plasma convergence area, where the metal wire material is quickly melted or vaporized at high temperature, and is dispersed and atomized into ultra-fine droplets by the high-speed impact of the plasma, and finally gradually cools and solidifies into spherical metal powder in an inert gas atmosphere.

[0004] In the plasma atomization process, the melting of the metal wire and the atomization of the powder start simultaneously. It not only has a high atomization efficiency but also can avoid the drawback of introducing impurities due to the molten nozzle material mixing into the metal droplets during the traditional atomization process. Therefore, the plasma atomization technology can prepare TC4 alloy powder with high purity, high fine powder yield, good sphericity, good fluidity, no satellite powder, and very few hollow powders. Summary of the Invention

[0005] Objective of the Invention: To solve the problem of low yield of fine powder in TC4 powder in current plasma atomization powder preparation technology, the first objective of the present invention is to provide a Laval atomization nozzle capable of preparing TC4 alloy powder with high purity, high yield of fine powder, good sphericity, good fluidity, no satellite powder and extremely few hollow powders. The second objective of the present invention is to provide a plasma atomization powder preparation device for preparing TC4 alloy powder containing the above Laval atomization nozzle.

[0006] Technical Solution: The Laval atomization nozzle described in the present invention includes a nozzle inlet, a nozzle outlet, a conical outer wall and a convergent-divergent Laval flow channel. Among them, the convergent-divergent Laval flow channel is arranged between the nozzle inlet and the nozzle outlet, and includes a contraction section, a throat section and a divergence section from top to bottom. The throat section is a smooth arc structure; the conical outer wall is arranged around the convergent-divergent Laval flow channel, and connection and fixing structures are provided at both ends of the conical outer wall.

[0007] Further, the total length of the Laval atomization nozzle is 40 - 50 mm. Among them, the diameter of the nozzle inlet is 15 - 16 mm, and the diameter of the nozzle outlet is jointly determined by the diameter of the throat section and the half-cone angle of the divergence section; the inner wall of the contraction section is a conical structure, the length of the contraction section is 30 - 40 mm, and the half-cone angle is 5 - 15°; the throat section is a smooth arc wall surface, the diameter is 3 - 6 mm, and the length is 0 - 5 mm; the length of the divergence section is 10 - 20 mm, and the half-cone angle is 8 - 24°.

[0008] Preferably, the diameter of the nozzle inlet is 15.8 mm, the diameter of the nozzle outlet is 11.67 mm, the length of the contraction section is 36 mm, the half-cone angle is 8°, the diameter of the throat section is 4.4 mm, the length is 0 mm, and the length of the divergence section is 9 mm, and the half-cone angle is 22°.

[0009] Further, the connection and fixing structure is a thread, and the material of the conical outer wall is graphite.

[0010] The plasma atomization powder preparation device for preparing TC4 alloy powder described in the present invention includes the above Laval atomization nozzle, a plasma torch, an atomization chamber and a wire feeding mechanism. The Laval atomization nozzle is installed in the plasma torch through the connection and fixing structures at both ends of the conical outer wall. The nozzle inlet of the Laval atomization nozzle is connected to the anode outlet of the plasma torch, the nozzle outlet of the Laval atomization nozzle is communicated with the atomization chamber, and the wire feeding mechanism is connected to the atomization chamber for feeding TC4 wire into the atomization chamber.

[0011] Further, the conical outer wall is provided with a stepped structure to facilitate the cooperation between the Laval atomization nozzle and the plasma torch. At the same time, the main part of the conical outer wall is connected with the plasma torch by standard thread to facilitate the adjustment of the distance between the Laval atomization nozzle and the position of the TC4 wire at the outlet.

[0012] In the above device, the nozzle inlet of the Laval atomizing nozzle is connected to the anode outlet of the plasma torch for introducing the high-temperature plasma jet generated by the plasma torch; the nozzle outlet communicates with the atomizing chamber for discharging the high-temperature and high-speed plasma jet; the nozzle is fastened and sealed by threads and connected to the plasma torch to ensure that the distance between the nozzle and the TC4 wire can be adjusted according to the actual working conditions; the converging-diverging Laval flow channel ensures that the high-temperature plasma jet flowing through the nozzle is accelerated to the supersonic stage.

[0013] Beneficial effects: Compared with the prior art, the present invention has the following remarkable effects: The present invention realizes efficient and stable production in the process of preparing TC4 powder by plasma through readjusting reasonable structural parameters of the Laval atomizing nozzle, significantly improves the flow velocity of the plasma jet passing through the internal flow channel of the nozzle, ensures the uniformity and size controllability of the atomized droplets during the atomization process, and can effectively improve the production efficiency, powder purity, powder sphericity and fine powder yield of TC4 powder. While ensuring the quality of the produced powder, it reduces the production cost of the powder product and improves the production efficiency. Description of the Drawings

[0014] Figure 1 It is the main sectional view of the Laval atomizing nozzle in Embodiment 1;

[0015] Figure 2 It is the structural schematic diagram of the internal flow channel of the Laval atomizing nozzle in Embodiment 1;

[0016] Figure 3 It is the velocity field cloud diagram of the Laval atomizing nozzle in Embodiment 1 simulated by Fluent. Detailed Embodiment

[0017] The present invention will be further described in detail below in conjunction with the embodiments and the drawings.

[0018] Embodiment 1: The plasma atomization powder preparation device for preparing TC4 alloy powder provided in this embodiment includes a Laval atomizing nozzle, a plasma torch, an atomizing chamber and a wire feeding mechanism.

[0019] As Figure 1 - Figure 2As shown in the figure, the Laval atomizing nozzle includes the Laval atomizing nozzle inlet 1, the thread 2, the conical outer wall 3, the convergent-divergent Laval flow channel 4, and the Laval atomizing nozzle outlet 5. The Laval atomizing nozzle inlet 1 is connected to the anode outlet of the plasma torch and is used to introduce the high-temperature plasma jet generated by the plasma torch. The thread 2 is connected to the plasma torch through threads to ensure that the distance between the nozzle and the wire can be adjusted according to the actual working conditions. The conical outer wall 3 can reduce the adhesion of powder on the outer wall of the nozzle during the actual atomization powder-making process. The convergent-divergent Laval flow channel 4 ensures that the high-temperature plasma jet flowing through the nozzle is accelerated to the supersonic stage. The Laval atomizing nozzle outlet 5 communicates with the atomization chamber and is used to export the high-temperature and high-speed plasma jet.

[0020] In the convergent-divergent Laval flow channel, the inlet diameter d1 is fixed at 15.8 mm, the length of the contraction section l1 is 36 mm, the half-cone angle θ of the contraction section is 8°, the length of the throat section d2 is 0 mm, the diameter of the throat section is 4.4 mm, the throat section is a smooth arc structure, the length of the expansion section l2 is 9 mm, the half-cone angle α of the expansion section is 22°, and the outlet diameter d3 is 11.67 mm.

[0021] Under the pressure of 0.5 MPa, the Laval atomizing nozzle can increase the velocity of the plasma argon jet to 617.7 m / s, as shown in Figure 3 .

[0022] During actual operation, taking the plasma atomization of TC4 alloy powder as an example, the Laval atomizing nozzle is installed at the front end of the plasma torch system through threaded connection. The TC4 wire is fed into the atomization chamber through the wire feeding mechanism. Then, after evacuating and filling with argon, the plasma torch is started. The plasma torch excites the argon gas flow into an argon plasma jet and introduces it into the Laval atomizing nozzle to achieve supersonic flow of the plasma jet. It is exported from the Laval atomizing nozzle outlet to the surface of the TC4 metal wire, starting the wire melting process and the jet atomization and fragmentation process. Finally, the molten metal liquid forms uniform and stable spherical TC4 metal powder after fragmentation, cooling, and solidification.

Claims

1. A Laval atomizing nozzle, characterized in that, It includes a nozzle inlet, a nozzle outlet, a conical outer wall, and a convergent-divergent Laval flow channel. Among them, the convergent-divergent Laval flow channel is arranged between the nozzle inlet and the nozzle outlet, and from top to bottom, it includes a contraction section, a throat section, and an expansion section. The throat section is a smooth arc-shaped structure; the conical outer wall is arranged around the convergent-divergent Laval flow channel, and connection and fixing structures are provided at both ends of the conical outer wall.

2. The Laval atomizing nozzle according to claim 1, wherein The total length of the Laval atomizing nozzle is 40 - 50 mm.

3. The Laval atomizing nozzle according to claim 1, characterized in that, The diameter of the nozzle inlet is 15 - 16 mm; the diameter of the nozzle outlet is jointly determined by the diameter of the throat section and the half-cone angle of the expansion section.

4. The Laval atomizing nozzle according to claim 1, characterized in that, The inner wall of the contraction section is a conical structure, the length of the contraction section is 30 - 40 mm, and the half-cone angle is 5 - 15°.

5. The Laval atomizing nozzle according to claim 1, characterized in that, The throat section is a smooth arc-shaped wall surface, with a diameter of 3 - 6 mm and a length of 0 - 5 mm.

6. The Laval atomizing nozzle according to claim 1, characterized in that, The length of the expansion section is 10 - 20 mm, and the half-cone angle is 8 - 24°.

7. The Laval atomizing nozzle according to claim 1, characterized in that, The diameter of the nozzle inlet is 15.8 mm, the diameter of the nozzle outlet is 11.67 mm, the length of the contraction section is 36 mm, the half-cone angle is 8°, the diameter of the throat section is 4.4 mm, the length is 0 mm, the length of the expansion section is 9 mm, and the half-cone angle is 22°.

8. The Laval atomizing nozzle according to claim 1, characterized in that, The connection and fixing structure is a thread.

9. The Laval atomizing nozzle according to claim 1, characterized in that, The material of the conical outer wall is graphite.

10. A plasma atomization powder making device for preparing TC4 alloy powder, characterized in that, It includes the Laval atomizing nozzle according to any one of claims 1 - 8, a plasma torch, an atomization chamber, and a wire feeding mechanism. The Laval atomizing nozzle is installed in the plasma torch through the connection and fixing structures at both ends of the conical outer wall. The nozzle inlet of the Laval atomizing nozzle is connected to the anode outlet of the plasma torch, the nozzle outlet of the Laval atomizing nozzle is communicated with the atomization chamber, and the wire feeding mechanism is connected to the atomization chamber for feeding TC4 wire into the atomization chamber.

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