Conveying spheroidizing system and method for plasma spheroidizing of superfine titanium alloy powder

Abstract

The invention relates to the technical field of powder spheroidizing, in particular to a conveying spheroidizing system and method for plasma spheroidizing of superfine titanium alloy powder. The invention discloses a conveying and spheroidizing system for plasma spheroidizing of superfine titanium alloy powder. The conveying and spheroidizing system comprises an in-situ activation grading device, a coaxial layered conveying device and a plasma spheroidizing device, the in-situ activation grading device comprises a sealed stock bin, a vertical shaft stirring paddle and a side shaft stirring paddle, wherein the vertical shaft stirring paddle and the side shaft stirring paddle are arranged in the stock bin. According to the conveying and spheroidizing system, low-energy-consumption and high-stability activation and conveying of superfine powder can be achieved, the defect of adhesion of coarse powder and fine powder is overcome, products controllable in particle size distribution and extremely high in sphericity degree can be obtained, adhesion and accumulation of the powder on a nozzle of the radio frequency induction plasma torch are avoided, and the service life of the powder is prolonged. The problems that energy consumption and stability of a traditional powder feeding technology are poor, coarse powder and fine powder are prone to adhesion due to mixed conveying of the coarse powder and fine powder, and powder particles are prone to adhesion and accumulation on the inner wall of a nozzle are solved.

Description

Technical Field

[0001] This invention relates to the field of powder spheroidization processing technology, and in particular to a conveying and spheroidizing system and method for plasma spheroidization of ultrafine titanium alloy powder. Background Technology

[0002] Plasma spheroidization is a key technology for preparing high-performance spherical metal powders. It transforms irregularly shaped metal powders into spherical or near-spherical particles through high-temperature melting and surface tension. Specifically, it involves generating high-temperature plasma using a radio frequency magnetic field, feeding the powder into a radio frequency induction plasma torch for melting, forming spherical droplets under surface tension, and then rapidly cooling and solidifying to form spherical powder. However, existing plasma spheroidization technologies for ultrafine, irregular titanium alloy powders face three major bottlenecks: 1. Technical bottlenecks in powder feeding: The inherent poor flowability and strong cohesion of this type of powder render traditional powder feeding methods ineffective. Mechanical powder feeding (such as using scrapers, vibration, etc.) cannot effectively break up agglomerates and instead causes granulation problems, which can easily lead to blockage or pulsating powder feeding (referring to an unstable and discontinuous powder conveying state). In pneumatic fluidization powder feeding, the carrier gas is used as the main driving force input to overcome the cohesion of the powder and maintain the overall fluidization state. Its gas flow rate needs to meet the minimum fluidization conditions, which is difficult to flexibly reduce according to actual conveying or process requirements. Therefore, the energy consumption is huge, and the subsequent throttling adjustment also increases the complexity and instability of the system.

[0003] 2. Bottleneck in the matching of raw materials and processes: During the spheroidization process, the particle size of the powder directly affects its heating and flight behavior in the plasma flame. Fine powder, due to its large specific surface area, heats up quickly and melts in a short time; while coarse powder is the opposite. In existing technologies, coarse and fine powders are mixed and transported, causing fine powder to easily collide and adhere with the melting coarse powder before it is fully melted, forming "satellite spheres" (i.e., composite structures formed by fine powder colliding, adhering, and solidifying with the melting coarse powder before it is fully melted, adhering to its surface) or severely irregular agglomerates, which damages the particle size distribution and sphericity of the final product.

[0004] 3. Safety bottleneck in equipment operation: Due to the low density of titanium alloy, it is extremely easy to deviate from the preset flight trajectory in the high-speed, strong airflow field at the exit of the radio frequency induction plasma torch. Once powder particles collide with and adhere to the inner wall of the high-temperature ceramic nozzle, they will accumulate rapidly, causing localized overheating in that area, generating huge thermal stress, and ultimately leading to thermal fatigue cracking of the ceramic tube, posing a serious safety hazard and risk of equipment downtime. Summary of the Invention

[0005] In response to the problems raised in the background technology, the purpose of this invention is to provide a conveying and spheroidizing system for plasma spheroidization of ultrafine titanium alloy powder. This system can achieve low-energy consumption and high-stability activation and conveying of ultrafine powder, eliminate the defect of coarse and fine powder adhesion, obtain products with controllable particle size distribution and extremely high sphericity, and avoid powder adhesion and accumulation in the nozzle of the radio frequency induction plasma torch. This solves the problems of energy consumption and stability of traditional powder feeding technology, the problem of coarse and fine powder adhesion caused by mixed conveying of coarse and fine powder in the prior art, and the problem of powder particles easily adhering and accumulating on the inner wall of the nozzle.

[0006] Another objective of this invention is to propose a method using the above-described conveying and spheroidizing system for plasma spheroidizing of ultrafine titanium alloy powder, which can produce dense, highly spherical particles. The integrated in-situ activation and grading device, coaxial layered conveying device, and plasma spheroidizing device enable the conveying and spheroidizing process of ultrafine titanium alloy powder to be completed in the same conveying and spheroidizing system, effectively improving the conveying and spheroidizing efficiency.

[0007] The above-mentioned technical objective of the present invention is achieved through the following technical solution: A conveying and spheroidizing system for plasma spheroidizing of ultrafine titanium alloy powder includes an in-situ activation and classification device, a coaxial layered conveying device, and a plasma spheroidizing device. The in-situ activation and grading device includes a sealed hopper and a vertical shaft agitator and a side shaft agitator disposed within the hopper. The vertical shaft agitator is positioned axially at the bottom of the hopper to axially push the ultrafine titanium alloy powder at the bottom of the hopper to the side edge of the hopper. The side shaft agitator is positioned radially on the side wall of the hopper to radially shear the ultrafine titanium alloy powder to disperse it. The rotational speed of the vertical shaft agitator is lower than that of the side shaft agitator. The upper part of the silo is provided with a primary powder outlet, a secondary powder outlet, and a carrier gas inlet that are connected to the interior of the silo. The primary powder outlet is located below the secondary powder outlet, and the carrier gas inlet is located between the primary powder outlet and the secondary powder outlet. The carrier gas inlet is used to introduce carrier gas and send coarse powder out from the primary powder outlet and fine powder out from the secondary powder outlet. The coaxial layered conveying device includes a central tube, a first interlayer tube, and a second interlayer tube that are isolated from each other and coaxially arranged from the inside to the outside; the central tube is connected to the secondary powder outlet and is used to convey the graded fine powder; the first interlayer tube is connected to the primary powder outlet and is used to convey the graded coarse powder; the second interlayer tube is connected to a constraining air source and is used to form a constraining air curtain around the coarse powder. The plasma spheroidizing device includes a radio frequency induction plasma torch, the nozzle of which is connected to the output end of the coaxial layered conveying device. The radio frequency induction plasma torch is used to receive and melt the powder conveyed by the coaxial layered conveying device.

[0008] To further explain, the in-situ activation and grading device also includes a carrier gas inlet pipe, a primary powder outlet pipe, and a secondary powder outlet pipe. The inlet end of the carrier gas inlet pipe is connected to a carrier gas source, and the outlet end of the carrier gas inlet pipe is connected to the carrier gas inlet. The first interlayer tube is connected to a primary powder inlet tube, one end of the primary powder outlet tube is connected to the primary powder outlet, and the other end of the primary powder outlet tube is connected to the primary powder inlet tube. The central tube is connected to a secondary powder inlet tube, one end of the secondary powder outlet tube is connected to the secondary powder outlet, and the other end of the secondary powder outlet tube is connected to the secondary powder inlet tube; The carrier gas inlet pipe, the primary powder outlet pipe, and the secondary powder outlet pipe are respectively arranged along the radial direction of the silo.

[0009] To further clarify, the flow rate of the carrier gas in the silo is 1-20 L / min.

[0010] To further explain, the silo wall is provided with a hollow interlayer, the silo is provided with a first cooling water inlet and a first cooling water outlet, the first cooling water inlet is connected to the bottom of the hollow interlayer, and the first cooling water outlet is connected to the top of the hollow interlayer.

[0011] Furthermore, the in-situ activation and grading device also includes a vacuum extraction pipe, an argon backfill pipe, and an oxygen content sensor. One end of the vacuum extraction pipe is connected to the interior of the silo, and the other end of the vacuum extraction pipe is connected to a vacuum pump. One end of the argon backfill pipe is connected to an argon gas source, and the other end of the argon backfill pipe is connected to the interior of the silo. The oxygen content sensor is installed inside the silo; The silo is also equipped with a feeding port, which is connected to the interior of the silo.

[0012] To further explain, an annular air cavity is formed between the second interlayer tube and the first interlayer tube, and the second interlayer tube is connected to a constrained air source inlet pipe, which is arranged radially along the second interlayer tube.

[0013] Furthermore, the coaxial layered conveying device also includes a cooling water pipe, which is coaxially arranged with the central pipe, the first interlayer pipe and the second interlayer pipe. The cooling water pipe is sleeved outside the second interlayer pipe, and a cooling water cavity is formed between the cooling water pipe and the second interlayer pipe. The cooling water pipe is provided with a second cooling water inlet and a second cooling water outlet.

[0014] To further explain, the radio frequency induction plasma torch includes a sheath, a radio frequency induction coil, and a ceramic tube. The ceramic tube is disposed on the inner wall of the sheath, the radio frequency induction coil is disposed inside the sheath, and the ceramic tube has a ventilation space inside. The radio frequency induction coil and the ceramic tube together form the nozzle. The bottom of the coaxial layered conveying device is the output end, which is located within the ventilation space and corresponds to the radio frequency induction coil.

[0015] To further clarify, the particle size of the ultrafine titanium alloy powder is 1–25 μm.

[0016] A spheroidizing method for transporting powder, applied to the aforementioned spheroidizing system for plasma spheroidizing ultrafine titanium alloy powder, the spheroidizing method comprising the following steps: Ultrafine titanium alloy powder is added into the hopper, carrier gas is introduced, and the vertical shaft agitator and the side shaft agitator are started. The vertical shaft agitator rotates and axially pushes the ultrafine titanium alloy powder at the bottom of the hopper to the side edge of the hopper. The side shaft agitator rotates and radially shears the ultrafine titanium alloy powder to disperse the powder. Coarse powder is sent out from the primary powder outlet, and fine powder is sent out from the secondary powder outlet. The coarse powder delivered from the primary powder outlet enters the first interlayer tube, and the fine powder delivered from the secondary powder outlet enters the central tube. A confining air source is introduced into the second interlayer tube to form a confining air curtain around the coarse powder. Fine powder, coarse powder, and constrained air curtain enter the nozzle of the radio frequency induction plasma torch from the output end of the coaxial layered conveying device. The radio frequency induction plasma torch receives and melts the powder conveyed by the coaxial layered conveying device.

[0017] Compared with the prior art, the embodiments of the present invention have the following beneficial effects: 1. A composite mixing system is formed by the vertical shaft agitator and the side shaft agitator. The carrier gas does not need to undertake the main functions of powder fluidization and de-agglomeration. The activation, de-agglomeration and classification of powder are mainly achieved by the composite mixing and the partitioning in the hopper. The carrier gas is only used as an auxiliary medium. The gas volume is not constrained by the minimum fluidization condition, which realizes low energy consumption and high stability activation and conveying of ultrafine powder, and solves the energy consumption and stability problems of traditional powder feeding technology.

[0018] 2. By adopting the technical approach of "in-situ classification - coaxial conveying - differentiated spheroidization," the different melting characteristics of coarse and fine powders are matched, fundamentally eliminating the defect of coarse and fine powder adhesion. This results in products with controllable particle size distribution and extremely high sphericity. It solves the technical problem in existing technologies where mixed conveying of coarse and fine powders easily leads to adhesion, affecting the product's particle size distribution and sphericity.

[0019] 3. By using a constrained air curtain to protect the powder flow, contact between the powder and the nozzle (ceramic tube wall) of the RF induction plasma torch is avoided. This prevents powder from adhering and accumulating on the nozzle (ceramic tube wall), ensuring the long-term safe and stable operation of the RF induction plasma torch. This solves the technical problem of existing methods where powder particles easily adhere and accumulate on the inner wall of the nozzle, affecting the safety and service life of the equipment.

[0020] 4. By integrating the in-situ activation and grading device, the coaxial layered conveying device, and the plasma spheroidizing device, a high degree of integration of powder activation and grading, conveying, and spheroidizing processes is achieved, thereby improving powder yield and product quality. Attached Figure Description

[0021] Figure 1 This is a perspective view (dashed lines show the internal structure) of an in-situ activation and classification device for a transport and spheroidization system for plasma spheroidization of ultrafine titanium alloy powder, according to an embodiment of the present invention.

[0022] Figure 2 This is a schematic diagram illustrating in-situ dynamic classification of powder within a silo, according to an embodiment of the present invention.

[0023] Figure 3 This is a perspective view of a coaxial layered conveying device for a plasma spheroidizing system for ultrafine titanium alloy powder, according to an embodiment of the present invention.

[0024] Figure 4 This is a schematic diagram of the assembly structure of the output end of the coaxial layered conveying device and the radio frequency induction plasma torch of the plasma spheroidizing device according to an embodiment of the present invention. Figure 5 This is a partial schematic diagram of the assembly structure of the output end of the coaxial layered conveying device and the radio frequency induction plasma torch of the plasma spheroidizing device according to an embodiment of the present invention.

[0025] Figure 6 This is a scanning electron microscope (SEM) image of the particles obtained after spheroidization in Example 1.

[0026] Figure 7 This is a scanning electron microscope (SEM) image of the particles obtained after spheroidizing Comparative Example 1.

[0027] In the attached diagram: 1-In-situ activation and grading device; 11-Hopper; 111-Primary powder outlet; 112-Secondary powder outlet; 113-Carrier gas inlet; 114-First cooling water inlet; 115-First cooling water outlet; 116-Feeding port; 12-Vertical shaft agitator; 13-Side shaft agitator; 14-Carrier gas inlet pipe; 15-Primary powder outlet pipe; 16-Secondary powder outlet pipe; 17-Hollow jacket; 18-Vacuum extraction pipe; 19-Argon backfill pipe; 2-Coaxial layered conveying device; 21-Central pipe; 211-Secondary powder inlet pipe; 22-First jacket pipe; 221-Primary powder inlet pipe; 2 3-Second interlayer tube, 231-Constraint air source inlet pipe, 24-Annular air chamber, 25-Cooling water pipe, 251-Second cooling water inlet, 252-Second cooling water outlet, 26-Cooling water chamber, 3-Plasma spheroidizing device, 31-Radio frequency induction plasma torch, 311-Sheath, 312-Radio frequency induction coil, 313-Ceramic tube, 314-Ventilation space, 315-Quartz tube, 101-Fine powder, 102-Coarse powder, 103-Constraint air curtain, 104-Plasma flame, 200-Mechanical throwing and feeding area, 300-Buffer separation transition area, 400-Pneumatic precision conveying area. Detailed Implementation

[0028] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0029] In the description of this invention, it should be understood that the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, features defined with "first" and "second" may explicitly or implicitly include one or more of these features, used to distinguish and describe features, without any order or emphasis.

[0030] like Figures 1 to 5 As shown, a conveying and spheroidizing system for plasma spheroidizing of ultrafine titanium alloy powder includes an in-situ activation and classification device 1, a coaxial layered conveying device 2, and a plasma spheroidizing device 3. The in-situ activation and grading device 1 includes a sealed hopper 11 and a vertical shaft agitator 12 and a side shaft agitator 13 disposed within the hopper 11. The vertical shaft agitator 12 is disposed axially at the bottom of the hopper 11 and is used to axially push the ultrafine titanium alloy powder at the bottom of the hopper 11 to the side edge of the hopper 11. The side shaft agitator 13 is disposed radially at the side wall of the hopper 11 and is used to radially shear the ultrafine titanium alloy powder to disperse the powder. The rotational speed of the vertical shaft agitator 12 is lower than that of the side shaft agitator 13. The upper part of the hopper 11 is provided with a primary powder outlet 111, a secondary powder outlet 112 and a carrier gas inlet 113 that are connected to the interior of the hopper 11. The primary powder outlet 111 is located below the secondary powder outlet 112, and the carrier gas inlet 113 is located between the primary powder outlet 111 and the secondary powder outlet 112. The carrier gas inlet 113 is used to introduce carrier gas and send coarse powder 102 out from the primary powder outlet 111 and fine powder 101 out from the secondary powder outlet 112. The coaxial layered conveying device 2 includes a central tube 21, a first interlayer tube 22, and a second interlayer tube 23 that are isolated from each other and coaxially arranged from the inside to the outside. The central tube 21 is connected to the secondary powder outlet 112 and is used to convey the graded fine powder 101. The first interlayer tube 22 is connected to the primary powder outlet 111 and is used to convey the graded coarse powder 102. The second interlayer tube 23 is connected to a constraining air source and is used to form a constraining air curtain 103 around the coarse powder 102. The plasma spheroidizing device 3 includes a radio frequency induction plasma torch 31. The nozzle of the radio frequency induction plasma torch 31 is connected to the output end of the coaxial layered conveying device 2. The radio frequency induction plasma torch 31 is used to receive and melt the powder conveyed by the coaxial layered conveying device 2.

[0031] This invention, by setting up an in-situ activation and grading device 1, a coaxial layered conveying device 2, and a plasma spheroidizing device 3, allows titanium alloy powder to undergo the following treatment in the aforementioned devices: In the hopper 11 of the in-situ activation and grading device 1, the vertical shaft agitator 12, operating at a lower speed, axially pushes the powder at the bottom of the hopper 11 to the side edge of the hopper 11. The side shaft agitator 13, operating at a higher speed, performs high-intensity radial shearing and throwing on the powder, achieving powder dispersal and activation (activation refers to breaking down the soft agglomerate structure of the powder, making the powder unstable, reducing interparticle cohesion, improving its responsiveness to airflow, and making it easier to stably deliver powder). The carrier gas introduced through the carrier gas inlet 113... Under the combined effect of the powder's own gravity, the powder achieves in-situ dynamic classification within the hopper 11: coarse powder 102 is enriched in the lower part of the hopper 11, and fine powder 101 is enriched in the upper part of the hopper 11, thus forming a coarse powder 102 enrichment zone and a fine powder 101 enrichment zone within the hopper 11. The primary powder outlet 111 is correspondingly located in the coarse powder 102 enrichment zone, from which coarse powder 102 is discharged. The second powder outlet is correspondingly located in the fine powder 101 enrichment zone, from which fine powder 101 is discharged.

[0032] Under the transport of carrier gas, the classified fine powder 101 enters the central tube 21 located in the center through the secondary powder outlet 112, while the classified coarse powder 102 enters the first interlayer tube 22 sleeved outside the central tube 21 through the primary powder outlet 111. The outermost second interlayer tube 23 is connected to the confining gas source, forming a protective confining air curtain 103 in the second interlayer tube 23. The confining air curtain 103 is ejected from the gap between the second interlayer tube 23 and the first interlayer tube 22, forming a confining air curtain 103 surrounding the coarse powder 102. 3 plays two core roles: (1) Physical isolation: It isolates the coarse powder 102 ejected from the first interlayer tube 22 from the nozzle (wall of ceramic tube 313) of the radio frequency induction plasma torch 31, preventing the powder from adhering and accumulating on the nozzle (wall of ceramic tube 313) of the radio frequency induction plasma torch 31; (2) Kinetic energy constraint: It applies a centripetal constraint force to the entire powder flow, ensuring that the powder maintains a stable bundle trajectory before entering the strongly turbulent radio frequency induction plasma torch 31, fundamentally eliminating the contact between the powder and the nozzle (wall of ceramic tube 313) of the radio frequency induction plasma torch 31. In particular, due to the protective effect of the outer ring coarse powder 102 flow, it prevents the airflow of the radio frequency induction plasma torch 31 from blowing away the central fine powder 101 and causing it to deviate from the plasma flame.

[0033] The composite gas flow carrying coarse and fine powders enters the core high-temperature zone of the plasma flame 104 generated by the nozzle of the radio frequency induction plasma torch 31. Since the fine powder 101 and the coarse powder 102 enter the plasma flame 104 through different conveying channels in the coaxial layered conveying device 2, and the corresponding carrier gas flow rate, axial conveying gas velocity and aerodynamic response characteristics to the airflow are different, the movement behavior and residence time of the coarse powder 102 and the fine powder 101 in the plasma flame 104 are different.

[0034] Specifically, the fine powder 101 has a small particle size and light weight, and its aerodynamic response to airflow is high. Under the carrying capacity of a high carrier gas flow rate, it can be more easily accelerated by the airflow and maintain a high axial conveying speed. After entering the plasma flame 104, the fine powder 101 moves rapidly with the core high-temperature airflow, heats up quickly and completes melting, thus passing through the core high-temperature zone with a shorter residence time, avoiding vaporization or agglomeration due to overheating.

[0035] In contrast, coarse powder 102 has a larger particle size and higher mass, resulting in relatively lower aerodynamic responsiveness to airflow. Even under the action of a carrier gas, its axial acceleration capability is limited. With a relatively low carrier gas flow rate, coarse powder 102 exhibits a lower axial transport velocity and a relatively longer residence time in the plasma flame 104, thereby enabling it to fully absorb heat and achieve complete melting within the core high-temperature zone.

[0036] Through the spatial separation and time-differentiated spheroidization process formed by the combined effects of differences in carrier gas flow rate and powder aerodynamic response, coarse powder 102 and fine powder 101 can complete the melting process separately and independently in the plasma flame 104 without interfering with each other. This effectively avoids the collision, adhesion, satellite spheres, and irregular agglomeration phenomena caused by asynchronous melting of coarse and fine powders in traditional mixed powder feeding processes. After leaving the plasma flame 104, the molten droplets rapidly enter the cooling zone, shrink and solidify into dense, highly spherical particles under the action of surface tension.

[0037] The aforementioned delivery and spheroidizing system for plasma spheroidization of ultrafine titanium alloy powder has the following significant effects: 1. The vertical shaft agitator 12 and the side shaft agitator 13 form a composite agitation. The carrier gas does not need to undertake the main functions of powder fluidization and de-agglomeration. The activation, de-agglomeration and classification of the powder are mainly achieved by the composite agitation and the partitioning within the hopper 11. The carrier gas is only used as an auxiliary medium. The gas volume is not constrained by the minimum fluidization condition, thus achieving low energy consumption and high stability activation and conveying of ultrafine powder, solving the energy consumption and stability problems of traditional powder feeding technology.

[0038] 2. By adopting the technical approach of "in-situ classification - coaxial conveying - differentiated spheroidization," the different melting characteristics of coarse powder 102 and fine powder 101 are matched, fundamentally eliminating the defect of coarse and fine powder adhesion. This results in products with controllable particle size distribution and extremely high sphericity. It solves the technical problem in existing technologies where mixed conveying of coarse and fine powders easily leads to adhesion, affecting the product's particle size distribution and sphericity.

[0039] 3. By using a constrained air curtain 103 to protect the powder flow, contact between the powder and the nozzle (wall of the ceramic tube 313) of the radio frequency induction plasma torch 31 is prevented. This avoids powder adhesion and accumulation on the nozzle (wall of the ceramic tube 313) of the radio frequency induction plasma torch 31, ensuring the long-term safe and stable operation of the radio frequency induction plasma torch 31. This solves the technical problem of existing equipment where powder particles easily adhere and accumulate on the inner wall of the nozzle, affecting the safety and service life of the equipment.

[0040] 4. By integrating the in-situ activation and grading device 1, the coaxial layered conveying device 2, and the plasma spheroidizing device 3, a high degree of integration of powder activation and grading, conveying, and spheroidizing processes is achieved, thereby improving powder yield and product quality.

[0041] Furthermore, the in-situ activation and grading device 1 also includes a carrier gas inlet pipe 14, a primary powder outlet pipe 15, and a secondary powder outlet pipe 16. The inlet end of the carrier gas inlet pipe 14 is connected to a carrier gas source, and the outlet end of the carrier gas inlet pipe 14 is connected to the carrier gas inlet 113. The first interlayer tube 22 is connected to a primary powder inlet tube 221, one end of the primary powder outlet tube 15 is connected to the primary powder outlet 111, and the other end of the primary powder outlet tube 15 is connected to the primary powder inlet tube 221. The central tube 21 is connected to a secondary powder inlet tube 211, one end of the secondary powder outlet tube 16 is connected to the secondary powder outlet 112, and the other end of the secondary powder outlet tube 16 is connected to the secondary powder inlet tube 211; The carrier gas inlet pipe 14, the primary powder outlet pipe 15, and the secondary powder outlet pipe 16 are respectively arranged along the radial direction of the silo 11, such that the gas injection direction of the carrier gas inlet pipe 14 is basically parallel to the powder outlet direction of the primary powder outlet pipe 15 and the secondary powder outlet pipe 16.

[0042] Specifically, such as Figure 2 As shown, the process of in-situ dynamic classification of powder within silo 11 is as follows: The vertical shaft agitator 12 controls the amount of powder supplied to the throwing area per unit time at a lower rotation speed, while the side shaft agitator 13 adjusts the degree of powder dispersion and the initial motion state obtained under the throwing action at a higher rotation speed, thereby affecting the rising height of the powder after it is thrown.

[0043] The carrier gas inlet 113 is located between the primary powder outlet 111 and the secondary powder outlet 112, and the gas injection direction of the carrier gas inlet pipe 14 is basically parallel to the powder outlet direction of the primary powder outlet pipe 15 and the secondary powder outlet pipe 16, so that no forced conveying airflow is formed within the height range of the primary powder outlet 111, and this area is mainly a buffer separation transition zone 300 with low airflow velocity.

[0044] Within the buffer separation transition zone 300, larger powder particles are difficult to rise continuously with the airflow under the action of gravity and inertia. Their throwing kinetic energy decays rapidly, and they migrate towards the primary powder outlet 111 and are discharged under the action of lateral airflow disturbance. Smaller powder particles continue to move upward under the combined action of throwing and overall rising carrier air, enter the upper pneumatic fine separation and conveying zone 400 and are discharged through the secondary powder outlet 112.

[0045] Furthermore, in the mechanical throwing feeding zone 200 at the bottom of the hopper 11, the mechanical throwing action applied by the side-shaft agitator 13 to the powder imparts initial motion inertia to the powder. Due to the small mass and high aerodynamic responsiveness of the fine powder 101 particles, it is easier for them to obtain an initial upward velocity under the throwing action, and after entering the buffer separation transition zone 300, they cooperate with the rising carrier gas to achieve continuous upward movement. In contrast, although the larger coarse powder 102 particles are also subjected to the throwing action, their initial velocity is limited, and under the influence of gravity and inertial decay, they are difficult to effectively cooperate with the rising carrier gas, thus remaining within the height range of the primary powder outlet 111.

[0046] In summary, from bottom to top, the material bin 11 comprises a mechanical throwing and feeding zone 200, a buffer separation and transition zone 300, and a pneumatic fine separation and conveying zone 400. In the mechanical throwing and feeding zone 200, the powder concentration is high, exhibiting continuous tumbling and localized throwing. In the buffer separation and transition zone 300, the powder exhibits a sparse-dense alternating distribution, with coarse and fine powders coexisting but moving in different directions. The powder's movement in this area is primarily controlled by mechanical throwing inertia and gravity separation, with the carrier gas serving only as a co-conveying medium (at a relatively low volume). In the pneumatic fine separation and conveying zone 400, the powder concentration is low, dominated by fine powder 101 with small particle size and light weight (at a relatively high volume). Through the coordinated control of throwing intensity and carrier gas flow field, powders of different particle sizes can form a stable and controllable classification and conveying path within the same device.

[0047] Preferably, the vertical shaft agitator 12 rotates at 50–500 rpm, and the side shaft agitator 13 rotates at 500–3000 rpm. The low-speed vertical shaft agitator 12 continuously pushes the powder at the bottom of the hopper 11 towards the working area of ​​the high-speed side shaft agitator 13. The high-speed side shaft agitator 13 then strongly shears and throws the powder, effectively breaking up powder agglomeration. Under the combined action of the upward drag force of the carrier gas and gravity, a dynamic fluidized separation field is formed. The heavier coarse powder 102 settles to the lower side of the hopper 11 and is drawn out through the primary powder outlet 111; the lighter fine powder 101 is carried to the upper part by the carrier gas flow and is drawn out through the secondary powder outlet 112. To further explain, the rotational speed of the vertical shaft agitator 12 is used to control the amount of powder supplied to the mechanical throwing zone per unit time, ensuring it is lower than the throwing capacity of the side shaft agitator 13, thereby preventing excessive instantaneous powder accumulation. The rotational speed of the side shaft agitator 13 is used to fully disperse the powder and impart the initial motion speed required for powder throwing. Functionally, the vertical shaft agitator 12 and the side shaft agitator 13 serve the purpose of "limited powder supply and sufficient throwing," achieving the aforementioned grading and conveying effects. The difference in rotational speed between the vertical shaft agitator 12 and the side shaft agitator 13 can be adjusted according to powder characteristics, device size, and process requirements. Specifically, one vertical shaft agitator 12 is provided, and one or more side shaft agitators 13 are provided. The vertical shaft agitator 12 and the side shaft agitator 13 can be driven to rotate by a motor. Providing multiple side shaft agitators 13 on the side wall of the hopper 11 can improve the powder shearing and throwing capacity.

[0048] It should be noted that at the outlet end of the coaxial layered conveying device 2, in the transition area between coarse powder 102 and fine powder 101, no static or low-speed contact interface is formed. Instead, a dynamic separation zone of high-speed shearing is formed under the combined action of the constrained air curtain 103 and the carrier gas. Due to the significant differences in particle size, mass, and aerodynamic response characteristics between coarse powder 102 and fine powder 101, their responses to flow field disturbances in this area differ, resulting in different motion trajectories and avoiding synchronous motion or contact states with relative velocity approaching zero. Therefore, no adhesion between coarse and fine powders occurs in the transition area between coarse powder 102 and fine powder 101. At the same time, the fine powder 101 in the center rapidly enters the core region of the plasma flame under the action of a higher carrier gas volume, and its residence time in the high-temperature zone is short; the outer ring coarse powder 102 enters the plasma region with a lower carrier gas volume, forming a misalignment with the heating process of fine powder 101 in terms of spatial position and time scale, thereby avoiding contact between coarse powder 102 and fine powder 101 in a softened or molten state. Furthermore, the coarse powder 102 in the outer ring region forms a relatively stable powder channel under the action of the constrained air curtain 103, which acts as a pneumatic shield for the fine powder 101 in the center, further weakening the lateral disturbance at the nozzle of the radio frequency induction plasma torch 31 and preventing the fine powder 101 from shifting or adhering to the surface of the coarse powder 102. Through the synergistic effect of the above multiple mechanisms, the adhesion and agglomeration of coarse powder 102 and fine powder 101 at the boundary are fundamentally suppressed.

[0049] To further explain, the flow rate of the carrier gas in the silo 11 is 1 to 20 L / min.

[0050] Specifically, the carrier gas inlet 113 is directly connected to the interior of the hopper 11. The carrier gas source is argon. The main function of the carrier gas is to transport the powder and at the same time protect the titanium alloy powder from oxidation.

[0051] In traditional pneumatic fluidized bed powder feeding, carrier gas serves as the primary driving force to overcome powder cohesion and maintain overall fluidization. During fluidization, the entire powder bed needs to be supported, resulting in a minimum fluidization velocity. When the gas velocity is less than this minimum, the gas merely "seeps" through the powder bed, leaving the powder as a solid mass. When the gas velocity exceeds the minimum fluidization velocity, the particles are lifted, loosened, and suspended by the gas. Therefore, in traditional fluidization processes, the gas flow rate must meet the minimum fluidization condition. In contrast, the carrier gas flow rate of this invention is 1–20 L / min. In the hopper 11, the powder is dispersed and activated through mechanical shearing and throwing by the side-shaft agitator 13. Only a smaller volume of carrier gas is needed to feed the powder into the plasma flame 104 via the coaxial layered conveying device 2. In this invention, a carrier gas is used to participate in the gas-solid coupling and classification process of the powder. The carrier gas is mainly used to build a stable flow field environment, rather than as the main power source to overcome the static accumulation and agglomeration of the powder. The carrier gas does not need to undertake the main function of powder fluidization and deagglomeration. The carrier gas is only used as an auxiliary medium. That is, the activation and throwing of powder are mainly achieved by the vertical shaft agitator 12 and the side shaft agitator 13. Therefore, the gas volume is not constrained by the minimum fluidization condition and can be flexibly adjusted according to the actual conveying or process requirements to achieve stable operation.

[0052] To further explain, before operation, the conveying and spheroidizing system of the present invention introduces an inert gas into the hopper 11 to form a stable protective atmosphere. In this state, the gas within the hopper 11 is essentially in a static or quasi-static equilibrium, serving only for oxidation prevention and environmental isolation; the protective atmosphere does not participate in the powder conveying or grading process. During operation, an additional carrier gas is introduced, creating a gentle and controllable gas flow within the hopper 11. This assists the powder in overcoming local resistance and maintaining continuous powder output. By adjusting the carrier gas flow rate, the hopper 11 can maintain a positive working pressure of approximately 2–20 kPa relative to atmospheric pressure. Under stable operating conditions, the typical carrier gas flow rate adjustment range is 1–20 L / min, and the typical hopper volume is 1–100 L, thus enabling the carrier gas to assist the powder in overcoming local resistance and maintaining continuous powder output.

[0053] To further explain, the wall of the silo 11 is provided with a hollow interlayer 17, the silo 11 is provided with a first cooling water inlet 114 and a first cooling water outlet 115, the first cooling water inlet 114 is connected to the bottom of the hollow interlayer 17, and the first cooling water outlet 115 is connected to the top of the hollow interlayer 17.

[0054] When the vertical shaft agitator 12 and the side shaft agitator 13 rotate continuously, the friction between the vertical shaft agitator 12 and the side shaft agitator 13 and the powder, as well as between the powder particles, inevitably generates heat. If this heat accumulates, it can easily cause the temperature inside the hopper 11 to rise, thereby exacerbating the oxidation tendency of the titanium alloy powder. To address this, a hollow jacket 17 is provided in the wall of the hopper 11. A cooling water channel is formed within the hollow jacket 17. By providing a first cooling water inlet 114 and a first cooling water outlet 115, cooling water is introduced from the bottom of the hollow jacket 17 and flows out from the first cooling water outlet 115 at the top of the hollow jacket 17. This allows the cooling water to circulate within the hollow jacket 17, effectively removing the heat generated during the agitation process, thereby maintaining the temperature inside the hopper 11 within a safe range and reducing the possibility of oxidation of the titanium alloy powder.

[0055] Specifically, the first cooling water inlet 114 and the first cooling water outlet 115 are respectively connected to the corresponding inlet and outlet of the water chiller. The function of the cooling water is to reduce the heat and temperature in the silo 11 and reduce the possibility of oxidation of the titanium alloy powder.

[0056] Furthermore, the in-situ activation and grading device 1 also includes a vacuum extraction pipe 18, an argon backfill pipe 19, and an oxygen content sensor. One end of the vacuum extraction pipe 18 is connected to the interior of the silo 11, and the other end of the vacuum extraction pipe 18 is connected to a vacuum pump. One end of the argon backfill pipe 19 is connected to an argon gas source, and the other end of the argon backfill pipe 19 is connected to the interior of the silo 11. The oxygen content sensor is installed inside the silo 11; The hopper 11 is also provided with a feeding port 116, which is connected to the interior of the hopper 11.

[0057] Specifically, by setting up the vacuum extraction pipe 18 and the argon gas backfill pipe 19, titanium alloy powder is added into the silo 11 through the feeding port 116. Then, the vacuum pump and the vacuum extraction pipe 18 are used to evacuate the inside of the silo 11. Next, the argon gas source is turned on, and argon gas is backfilled into the silo 11 through the argon gas backfill pipe 19, achieving vacuuming and argon gas replacement inside the silo 11, reducing the oxygen content inside the silo 11 to below the safe threshold of 50 ppm. Specifically, the oxygen content sensor is used to monitor the oxygen content inside the silo 11.

[0058] Specifically, the vacuum extraction pipe 18 and the argon backfill pipe 19 are respectively located on the top surface of the silo 11 to facilitate vacuum extraction and argon backfilling. The silo 11 is cylindrical, and the feeding port 116 is located on the top surface at the center of the silo 11. The opening and closing of the feeding port 116 is controlled by a quick-release butterfly valve to facilitate feeding and sealing of the silo 11.

[0059] It should be noted that the vacuum extraction pipe 18, the argon backfill pipe 19, the carrier gas inlet pipe 14, the primary powder outlet pipe 15, and the secondary powder outlet pipe 16 all pass through the hollow interlayer 17 and are connected to the interior of the silo 11. The vertical shaft agitator 12 and the side shaft agitator 13 both pass through the hollow interlayer 17 and enter the interior of the silo 11 to achieve agitation.

[0060] To further explain, an annular air cavity 24 is formed between the second interlayer tube 23 and the first interlayer tube 22. The second interlayer tube 23 is connected to a constraint air source inlet pipe 231, which is arranged radially along the second interlayer tube 23.

[0061] Specifically, the cross-sections of the central tube 21, the first interlayer tube 22, and the second interlayer tube 23 are circular. By setting the constraint air source inlet pipe 231 to be arranged radially along the second interlayer tube 23, the constraint air source enters the annular air cavity 24 radially (instead of axially). The constraint air source will rotate at high speed along the annular air cavity 24 arranged axially to form an annular constraint air curtain 103.

[0062] Specifically, the constraining gas source is the inert gas argon.

[0063] To further explain, the powder forms an axial composite powder flow through the coaxial layered conveying device 2, which includes fine powder 101 conveyed by the central tube 21 and coarse powder 102 conveyed by the first interlayer 22. The fine powder 101 and coarse powder 102 are each carried by their respective carrier gases, and the amount of carrier gas can be set according to the powder particle size characteristics and the requirements of the plasma spheroidization process. In the coaxial layered conveying device 2, the constraining air source is ejected through the annular air chamber 24 to form a high-speed protective constraining air curtain 103 for the powder. The constraining air curtain 103 does not participate in the powder conveying. It is ejected through the annular air chamber 24 between the second interlayer tube 23 and the first interlayer tube 22, forming an axially extending annular constraining air curtain 103 around the composite powder flow. The volumetric flow rate of the constraining air source in the annular air chamber 24 can be set to about 0.5 to 3 times the sum of the flow rates of the carrier air for conveying fine powder 101 and coarse powder 102 (that is, the flow rate of the carrier air in the hopper 11). (It should be noted that the constraining air source introduced into the annular air chamber 24 is an independent air path and does not come from the carrier air diversion in the hopper 11. The flow rate of the constraining air source in the annular air chamber 24 can be controlled by the flow rate regulating device.) Furthermore, the sum of the cross-sectional area of ​​the powder conveying channel of the central tube 21 for conveying fine powder 101 and the cross-sectional area of ​​the powder conveying channel formed between the first interlayer 22 and the central tube 21 for conveying coarse powder 102 is the total cross-sectional area of ​​the powder conveying channel. The equivalent annular gap area at the outlet of the annular air cavity 24 is smaller than the total cross-sectional area of ​​the powder conveying channel, so that the gas velocity of the constraint air curtain 103 at the outlet of the annular air cavity 24 is higher than the axial conveying gas velocity of the composite powder flow. This allows the constraint air curtain 103 to effectively radially cover and constrain the overall composite powder flow, preventing the powder from diffusing during the conveying process and contacting the nozzle (the wall of the ceramic tube 313) of the radio frequency induction plasma torch 31, ensuring that the powder maintains a stable bundle trajectory before entering the strongly turbulent radio frequency induction plasma torch 31.

[0064] Furthermore, the coaxial layered conveying device 2 also includes a cooling water pipe 25, which is coaxially arranged with the central pipe 21, the first interlayer pipe 22 and the second interlayer pipe 23. The cooling water pipe 25 is sleeved outside the second interlayer pipe 23, and a cooling water cavity 26 is formed between the cooling water pipe 25 and the second interlayer pipe 23. The cooling water pipe 25 is provided with a second cooling water inlet 251 and a second cooling water outlet 252.

[0065] Specifically, the second cooling water inlet 251 and the second cooling water outlet 252 are respectively connected to the corresponding inlet and outlet of the water chiller. By introducing cooling water into the cooling water chamber 26, the coaxial layered conveying device 2 can be prevented from being melted by high-temperature plasma thermal erosion in the radio frequency induction plasma torch 31.

[0066] Specifically, the coaxial layered conveying device 2 has a structure consisting of a central tube 21, a first interlayer tube 22, a second interlayer tube 23, and a cooling water pipe 25 nested from the inside out. The interior of the central tube 21, the space between the first interlayer tube 22 and the central tube 21, the space between the first interlayer tube 22 and the second interlayer tube 23, and the space between the second interlayer tube 23 and the cooling water pipe 25 are not interconnected. The secondary powder inlet pipe 211 passes through the cooling water pipe 25, the second interlayer tube 23, and the first interlayer tube 22 and then connects to the central tube 21. The primary powder inlet pipe 221 passes through the cooling water pipe 25 and the second interlayer tube 23 and then connects to the first interlayer tube 22. The confining air source inlet pipe 231 passes through the cooling water pipe 25 and then connects to the second interlayer tube 23.

[0067] Specifically, the second cooling water inlet 251 and the second cooling water outlet 252 are symmetrically arranged on the upper part of the cooling water pipe 25. The bottom end of the cooling water pipe 25 is sealed to the second jacketed pipe 23. Cooling water entering from the second cooling water inlet 251 fills the cooling water cavity 26 from top to bottom under the action of gravity, and then exits from the second cooling water outlet 252 on the other side. The cooling water circulates continuously to ensure the cooling effect. Preferably, a baffle can also be provided inside the cooling water cavity 26. The upper end of the baffle is fixedly connected to the inner top wall of the cooling water pipe 25, and a gap is left between the lower end of the baffle and the inner bottom wall of the cooling water pipe 25. The baffle separates the cooling water cavity 26. Cooling water enters one side of the baffle from top to bottom and then fills the other side of the baffle from bottom to top, extending the circulation path of the cooling water and improving the cooling effect.

[0068] To further explain, the radio frequency induction plasma torch 31 includes a sheath 311, a radio frequency induction coil 312, and a ceramic tube 313. The ceramic tube 313 is disposed on the inner wall of the sheath 311, the radio frequency induction coil 312 is disposed inside the sheath 311, and a ventilation space 314 is provided inside the ceramic tube 313. The radio frequency induction coil 312 and the ceramic tube 313 together form the nozzle. The bottom of the coaxial layered conveying device 2 is the output end, which is located in the ventilation space 314 and is positioned corresponding to the radio frequency induction coil 312.

[0069] By directly placing the output end of the coaxial layered conveying device 2 within the ventilation space 314 inside the ceramic tube 313, and after the ventilation space 314 in the middle is ventilated (a quartz tube 315 is installed in the ventilation space 314; the space between the quartz tube 315 and the coaxial layered conveying device 2 is used for the flow of intermediate gas, and the space between the quartz tube 315 and the ceramic tube 313 is used for the flow of edge gas; the intermediate gas and edge gas can be argon gas, the intermediate gas being the excitation gas of the radio frequency induction plasma torch 31 itself, and the edge gas being the plasma confinement gas of the radio frequency induction plasma torch 31), the intermediate gas and edge gas... The gas path used for powder delivery and confinement gas is independent of each other. The central gas and the edge gas are gases ejected from their respective corresponding gas channels (each with its own independent gas source and flow regulation device). Under the action of the radio frequency induction coil 312, the plasma flame 104 is generated in an excited state. That is, the central powder delivery method allows the powder to directly enter the energy core area of ​​the plasma flame 104, effectively utilizing the energy of the entire plasma flame 104. The energy utilization rate of the plasma flame 104 is high, the powder delivery rate to the energy core area of ​​the plasma flame 104 is high, and the spheroidization rate is high.

[0070] Specifically, the secondary powder inlet pipe 211, the primary powder inlet pipe 221, and the confinement gas source inlet pipe 231 are all located on the upper part of the coaxial layered conveying device 2. The bottom of the central pipe 21 has an opening for fine powder 101 to be output to the radio frequency induction plasma torch 31. The bottom of the first interlayer pipe 22 and the bottom of the central pipe 21 have an opening for coarse powder 102 to be output to the radio frequency induction plasma torch 31. The bottom of the second interlayer pipe 23 and the bottom of the first interlayer pipe 22 have an opening for the confinement gas source to be discharged. Fine powder 101, coarse powder 102, and confinement gas source are all conveyed from top to bottom. The coaxial layered conveying device 2 is located on the internal central axis of the ceramic tube 313, realizing the feeding of powder to the plasma flame 104 from top to bottom.

[0071] To further clarify, the particle size of the ultrafine titanium alloy powder is 1–25 μm.

[0072] After being transported and spheroidized by the aforementioned transport and spheroidization system for plasma spheroidization of ultrafine titanium alloy powder with a particle size of 1–25 μm, dense, highly spherical particles can be obtained.

[0073] Specifically, the coarse powder 102 has a particle size between 8 and 25 μm (inclusive of 8 μm and 25 μm), and the fine powder 101 has a particle size between 1 and 8 μm (inclusive of 1 μm, exclusive of 8 μm).

[0074] A spheroidizing method for transporting powder, applied to the aforementioned spheroidizing system for plasma spheroidizing ultrafine titanium alloy powder, the spheroidizing method comprising the following steps: Ultrafine titanium alloy powder is added into the hopper 11, carrier gas is introduced, and the vertical shaft agitator 12 and the side shaft agitator 13 are started. The vertical shaft agitator 12 rotates and pushes the ultrafine titanium alloy powder at the bottom of the hopper 11 axially to the side edge of the hopper 11. The side shaft agitator 13 rotates and performs radial shearing on the ultrafine titanium alloy powder to disperse the powder. Coarse powder 102 is sent out from the primary powder outlet 111, and fine powder 101 is sent out from the secondary powder outlet 112. The coarse powder 102 delivered from the primary powder outlet 111 enters the first interlayer tube 22, and the fine powder 101 delivered from the secondary powder outlet 112 enters the central tube 21. A confining air source is introduced into the second interlayer tube 23 to form a confining air curtain 103 around the coarse powder 102. Fine powder 101, coarse powder 102, and constrained air curtain 103 enter the nozzle of the radio frequency induction plasma torch 31 from the output end of the coaxial layered conveying device 2. The radio frequency induction plasma torch 31 receives and melts the powder conveyed by the coaxial layered conveying device 2.

[0075] Through the conveying and spheroidizing system for plasma spheroidizing of ultrafine titanium alloy powder, dense, highly spherical particles can be obtained. The integrated in-situ activation and grading device 1, coaxial layered conveying device 2, and plasma spheroidizing device 3 enable the conveying and spheroidizing process of ultrafine titanium alloy powder to be completed in the same conveying and spheroidizing system, effectively improving the conveying and spheroidizing efficiency.

[0076] Example 1 The aforementioned transport and spheroidizing system for plasma spheroidization of ultrafine titanium alloy powder is used to transport and spheroidize ultrafine titanium alloy powder with a particle size of 1–25 μm. The transport and spheroidizing method is as follows: Step S1: Add ultrafine titanium alloy powder into the silo 11 through the feeding port 116. After feeding, close the feeding port 116. Evacuate the inside of the silo 11 using a vacuum pump and vacuum extraction pipe 18. Then, turn on the argon gas source and refill the silo 11 with argon gas through the argon gas backfill pipe 19 to reduce the oxygen content inside the silo 11 to below the safe threshold of 50 ppm. Introduce carrier gas (specifically argon gas) and start the vertical shaft agitator 12 and the side shaft agitator 13 to introduce gas into the hollow interlayer 17. Cooling water is introduced, the flow rate of the carrier gas in the hopper 11 is 10L / min, the rotation speed of the vertical shaft agitator 12 is 300rpm, the rotation speed of the side shaft agitator 13 is 1000rpm, the vertical shaft agitator 12 rotates and axially pushes the ultrafine titanium alloy powder at the bottom of the hopper 11 to the side edge of the hopper 11, the side shaft agitator 13 rotates and radially shears the ultrafine titanium alloy powder to disperse the powder, coarse powder 102 is sent out from the primary powder outlet 111, and fine powder 101 is sent out from the secondary powder outlet 112; Step S2: Coarse powder 102 from the primary powder outlet 111 enters the first jacketed tube 22, and fine powder 101 from the secondary powder outlet 112 enters the central tube 21. Cooling water is introduced into the cooling water pipe 25, and a confinement gas source (specifically argon) is introduced into the second jacketed tube 23 to form a confinement gas curtain 103 around the coarse powder 102. In addition, argon is introduced as the central gas and the edge gas, respectively, with the following specific parameters: The inner diameter of the central tube 21 is 3 mm, and the cross-sectional area of ​​the powder conveying channel of the central tube 21 for conveying fine powder 101 is approximately 7.1 mm². 2 The cross-sectional area of ​​the powder conveying channel 102 formed between the first interlayer 22 and the central tube 21 is 12 mm. 2 Total cross-sectional area of ​​powder conveying channel: ≈ 19 mm 2 The equivalent annular gap area at the outlet of the annular gas cavity 24 is 2 mm. 2 ; Total flow rate of carrier gas in the silo (= fine powder 101 + coarse powder 102): 10 L / min; of which the central fine powder 101 distribution is 6 L / min; the outer ring coarse powder 102 distribution is 4 L / min; the constrained air source flow rate of the annular air chamber 24 is 10 L / min; Based on the flow rate of the central fine powder 101 and the cross-sectional area of ​​the powder conveying channel of the central pipe 21, the gas velocity in the powder feeding channel of the central fine powder 101 is calculated to be 14 m / s; similarly, the gas velocity in the powder feeding channel of the coarse powder 102 is calculated to be 5.5 m / s; and the gas velocity in the constrained air curtain 103 is 83 m / s. That is, the gas velocity of the confining air curtain 103 is higher than the axial transport gas velocity of the composite powder flow. In step S3, fine powder 101, coarse powder 102, and constrained air curtain 103 enter the nozzle of the radio frequency induction plasma torch 31 from the output end of the coaxial layered conveying device 2. The radio frequency induction plasma torch 31 receives and melts the powder conveyed by the coaxial layered conveying device 2. The molten droplets cool after leaving the plasma flame 104 of the radio frequency induction plasma torch 31 and shrink into dense, highly spherical particles under the action of surface tension, such as... Figure 6 As shown, the titanium alloy particles spheroidized using the conveying spheroidizing system for plasma spheroidization of ultrafine titanium alloy powder have a high sphericity, and the large particles formed by coarse powder 102 and the small particles formed by fine powder 101 are independently dispersed (with very few irregular agglomerates).

[0077] Comparative Example 1 Replace the in-situ activation and grading device 1 and the coaxial layered conveying device 2 of the plasma spheroidization system for ultrafine titanium alloy powder in Example 1 with existing vibratory powder feeding equipment. Powder is fed using a vibratory feeding method, with the remaining devices and steps unchanged. The output end of the vibratory powder feeding device is directly connected to the nozzle of the radio frequency induction plasma torch 31. The molten droplets passing through the nozzle of the radio frequency induction plasma torch 31 are cooled after leaving the plasma flame 104. Figure 7 As shown, the titanium alloy particles formed have a low sphericity, most of the particles are irregular in shape, and there are visible "satellite ball" structures with multiple small particles adhering to the surface of large particles, resulting in poor product quality.

[0078] The technical principles of the present invention have been described above with reference to specific embodiments. These descriptions are merely for explaining the principles of the invention and should not be construed as limiting the scope of protection of the invention in any way. Based on this explanation, those skilled in the art can readily conceive of other specific embodiments of the invention without inventive effort, and these embodiments will all fall within the scope of protection of the present invention.

Claims

1. A conveying and spheroidizing system for plasma spheroidization of ultrafine titanium alloy powder, characterized in that, This includes an in-situ activation and grading device, a coaxial layered transport device, and a plasma spheroidization device; The in-situ activation and grading device includes a sealed hopper and a vertical shaft agitator and a side shaft agitator disposed within the hopper. The vertical shaft agitator is positioned axially at the bottom of the hopper to axially push the ultrafine titanium alloy powder at the bottom of the hopper to the side edge of the hopper. The side shaft agitator is positioned radially on the side wall of the hopper to radially shear the ultrafine titanium alloy powder to disperse it. The rotational speed of the vertical shaft agitator is lower than that of the side shaft agitator. The upper part of the silo is provided with a primary powder outlet, a secondary powder outlet, and a carrier gas inlet that are connected to the interior of the silo. The primary powder outlet is located below the secondary powder outlet, and the carrier gas inlet is located between the primary powder outlet and the secondary powder outlet. The carrier gas inlet is used to introduce carrier gas and send coarse powder out from the primary powder outlet and fine powder out from the secondary powder outlet. The coaxial layered conveying device includes a central tube, a first interlayer tube, and a second interlayer tube that are isolated from each other and coaxially arranged from the inside to the outside; the central tube is connected to the secondary powder outlet and is used to convey the graded fine powder; the first interlayer tube is connected to the primary powder outlet and is used to convey the graded coarse powder; the second interlayer tube is connected to a constraining air source and is used to form a constraining air curtain around the coarse powder. The plasma spheroidizing device includes a radio frequency induction plasma torch, the nozzle of which is connected to the output end of the coaxial layered conveying device. The radio frequency induction plasma torch is used to receive and melt the powder conveyed by the coaxial layered conveying device.

2. The conveying and spheroidizing system for plasma spheroidization of ultrafine titanium alloy powder according to claim 1, characterized in that, The in-situ activation and grading device further includes a carrier gas inlet pipe, a primary powder outlet pipe, and a secondary powder outlet pipe. The inlet end of the carrier gas inlet pipe is connected to a carrier gas source, and the outlet end of the carrier gas inlet pipe is connected to the carrier gas inlet. The first interlayer tube is connected to a primary powder inlet tube, one end of the primary powder outlet tube is connected to the primary powder outlet, and the other end of the primary powder outlet tube is connected to the primary powder inlet tube. The central tube is connected to a secondary powder inlet tube, one end of the secondary powder outlet tube is connected to the secondary powder outlet, and the other end of the secondary powder outlet tube is connected to the secondary powder inlet tube; The carrier gas inlet pipe, the primary powder outlet pipe, and the secondary powder outlet pipe are respectively arranged along the radial direction of the silo.

3. The conveying and spheroidizing system for plasma spheroidization of ultrafine titanium alloy powder according to claim 1, characterized in that, The flow rate of the carrier gas in the silo is 1-20 L / min.

4. The conveying and spheroidizing system for plasma spheroidization of ultrafine titanium alloy powder according to claim 1, characterized in that, The silo wall is provided with a hollow interlayer, and the silo is provided with a first cooling water inlet and a first cooling water outlet. The first cooling water inlet is connected to the bottom of the hollow interlayer, and the first cooling water outlet is connected to the top of the hollow interlayer.

5. The conveying and spheroidizing system for plasma spheroidization of ultrafine titanium alloy powder according to claim 1, characterized in that, The in-situ activation and grading device also includes a vacuum extraction pipe, an argon backfill pipe and an oxygen content sensor. One end of the vacuum extraction pipe is connected to the inside of the silo, and the other end of the vacuum extraction pipe is connected to a vacuum pump. One end of the argon backfill pipe is connected to an argon gas source, and the other end of the argon backfill pipe is connected to the inside of the silo. The oxygen content sensor is installed inside the silo; The silo is also equipped with a feeding port, which is connected to the interior of the silo.

6. The conveying and spheroidizing system for plasma spheroidization of ultrafine titanium alloy powder according to claim 1, characterized in that, An annular air cavity is formed between the second interlayer tube and the first interlayer tube. The second interlayer tube is connected to a constrained air source inlet pipe, which is arranged radially along the second interlayer tube.

7. The conveying and spheroidizing system for plasma spheroidization of ultrafine titanium alloy powder according to claim 1, characterized in that, The coaxial layered conveying device further includes a cooling water pipe, which is coaxially arranged with the central pipe, the first interlayer pipe and the second interlayer pipe. The cooling water pipe is sleeved outside the second interlayer pipe, and a cooling water cavity is formed between the cooling water pipe and the second interlayer pipe. The cooling water pipe is provided with a second cooling water inlet and a second cooling water outlet.

8. The conveying and spheroidizing system for plasma spheroidization of ultrafine titanium alloy powder according to claim 1, characterized in that, The radio frequency induction plasma torch includes a sheath, a radio frequency induction coil, and a ceramic tube. The ceramic tube is disposed on the inner wall of the sheath, the radio frequency induction coil is disposed inside the sheath, and the ceramic tube has a ventilation space inside. The radio frequency induction coil and the ceramic tube together form the nozzle. The bottom of the coaxial layered conveying device is the output end, which is located within the ventilation space and corresponds to the radio frequency induction coil.

9. The conveying and spheroidizing system for plasma spheroidization of ultrafine titanium alloy powder according to claim 1, characterized in that, The particle size of the ultrafine titanium alloy powder is 1–25 μm.

10. A method for transporting and sphericalizing materials, characterized in that, The conveying and spheroidizing system for plasma spheroidizing of ultrafine titanium alloy powder, as described in any one of claims 1 to 9, comprises the following steps: Ultrafine titanium alloy powder is added into the hopper, carrier gas is introduced, and the vertical shaft agitator and the side shaft agitator are started. The vertical shaft agitator rotates and axially pushes the ultrafine titanium alloy powder at the bottom of the hopper to the side edge of the hopper. The side shaft agitator rotates and radially shears the ultrafine titanium alloy powder to disperse the powder. Coarse powder is sent out from the primary powder outlet, and fine powder is sent out from the secondary powder outlet. The coarse powder delivered from the primary powder outlet enters the first interlayer tube, and the fine powder delivered from the secondary powder outlet enters the central tube. A confining air source is introduced into the second interlayer tube to form a confining air curtain around the coarse powder. Fine powder, coarse powder, and constrained air curtain enter the nozzle of the radio frequency induction plasma torch from the output end of the coaxial layered conveying device. The radio frequency induction plasma torch receives and melts the powder conveyed by the coaxial layered conveying device.

Images