Multi-stage atomization metal powder preparation system and method based on rotating electrode

Abstract

The invention provides a multi-stage atomization metal powder preparation system and method based on a rotating electrode, and belongs to the technical field of gas atomization powder preparation. Comprising a plasma rotating electrode atomization device which comprises an atomization chamber, a rotating part, a clamping part, a plasma gun and an alloy bar; the alloy bar is clamped and fixed by the clamping component and extends into the atomizing chamber to directly face the plasma gun, and the rotating component is used for driving the alloy bar to rotate at a high speed; and the multi-stage gas atomization device is arranged at the downstream of the plasma rotating electrode atomization device and is formed by connecting a plurality of gas atomization units in series, and each stage of gas atomization unit comprises a gas atomization bin, a collection bin and a plurality of gas atomization nozzles. Multi-stage atomization is carried out on powder prepared by rotating electrode atomization, so that the collected powder has higher particle size uniformity, the particle size of the collected powder is smaller, the collected powder is more concentrated, and the probability that hollow powder and satellite powder appear when a traditional rotating electrode atomization method is used for preparing the hollow powder and the satellite powder is greatly reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of gas atomization powder making, and in particular relates to a metal powder preparation system and method based on multi-stage atomization of rotating electrodes. Background Art

[0002] Additive manufacturing is based on the three-dimensional mathematical model file of parts. Various types of materials (powders, wires, thin plates, etc.) are transformed from two-dimensional graphics into three-dimensional shapes through bonding, melting and other means. Therefore, the industry also calls additive manufacturing 3D printing technology, which includes plasma rotating electrode atomization method.

[0003] The atomization of the plasma rotating electrode atomization method (PREP) is a process in which the surface of the alloy rod is melted by the energy of the heat source to form a molten pool. Under the centrifugal force generated by the high-speed rotation of the alloy rod, the droplets in the molten pool escape from the surface of the liquid film and are thrown into the atomization chamber to cool and solidify into particles. The plasma rotating electrode atomization (PREP) powder has the advantages of high sphericity, good fluidity, and small powder oxygen increment, and is widely used in the field of additive manufacturing. However, due to factors such as the rotation speed limitation of the PREP method, the cost of preparing powder by the PREP method is too high, and the yield of fine powder is low. There are still preparation defects such as flaky powder, satellite powder, and hollow powder in the preparation process.

[0004] Therefore, how to achieve higher uniformity of atomized particles, more stable and significantly refined particle size in the aerosol powder making process to meet the quality requirements of fine particles is one of the problems that technicians in this field need to solve. Summary of the invention

[0005] The present invention aims to solve the above technical problems existing in the prior art. To this end, the present invention proposes a metal powder preparation system and method based on multi-stage atomization of rotating electrodes, which effectively improves the uniformity of atomized particles, greatly refines the particle size, and reduces hollow and satellite powders.

[0006] The technical solution of the present invention is as follows:

[0007] A metal powder preparation system based on multi-stage atomization of a rotating electrode, comprising:

[0008] The plasma rotating electrode atomization device comprises an atomization chamber, a rotating component, a clamping component, a heating component, a plasma gun and an alloy rod; the alloy rod is clamped and fixed by the clamping component and extends into the interior of the atomization chamber, the end face of the alloy rod in the atomization chamber faces the plasma gun, the rotating component is used to drive the alloy rod to rotate at a high speed, and the heating component is used to heat the end face of the alloy rod in the atomization chamber;

[0009] A multi-stage atomization device, which is arranged downstream of the plasma rotating electrode atomization device, is obtained by connecting a plurality of atomization units in series, wherein each stage of the atomization unit comprises an atomization bin, a collection bin and a plurality of atomization nozzles, wherein the top of the atomization bin in each stage of the atomization unit is provided with a first filter hole, the bottom is provided with a second filter hole, and a plurality of atomization nozzles are evenly distributed along the circumference of the atomization bin, with the nozzles facing the inside of the atomization bin; the top of the collection bin is directly connected to the bottom of the atomization bin, and except for the collection bin of the last stage of the atomization unit, the bottoms of the remaining collection bins are provided with a third filter hole;

[0010] The third filter hole is not smaller than the diameter of the second filter hole in the corresponding aerosol unit; the diameter of the second filter hole of the aerosol bin of each level of aerosol unit decreases successively, and the second filter hole of the aerosol bin of each level of aerosol unit is always smaller than the first filter hole.

[0011] As a preferred embodiment of the present invention, the alloy rod is driven by a rotating component to rotate at a high speed and is fed axially, and the axis of the alloy rod coincides with the axis of the plasma gun.

[0012] As a preferred embodiment of the present invention, the diameters of the first filter holes of the aerosol chambers of the aerosol units of each stage are the same.

[0013] As a preferred embodiment of the present invention, the aerosol nozzle is provided with multiple layers of staggered guide plates inside.

[0014] As a preferred embodiment of the present invention, the guide plate is provided with micropores of 0.05mm-0.2mm.

[0015] As a preferred embodiment of the present invention, the diameter of the nozzle of the aerosol nozzle is between 0.5 mm and 2 mm, and an adjustable flow limiting plate is provided at the nozzle.

[0016] As a preferred embodiment of the present invention, the number of series-connected stages of the multi-stage atomization device is 2-4 stages.

[0017] As a preferred embodiment of the present invention, the inner wall of the atomizing chamber is coated with an anti-stick coating.

[0018] As a preferred embodiment of the present invention, it also includes a control system; the control system is connected to the rotating parts and plasma gun of the plasma rotating electrode atomization device, and can dynamically adjust the rotation speed of the alloy rod and the working parameters of the plasma gun; and is connected to the atomization nozzle of the multi-stage atomization device, and can dynamically adjust the injection flow rate and fluid temperature of the atomization nozzle.

[0019] A method for preparing metal powder in a metal powder preparation system based on a multi-stage atomization of a rotating electrode, characterized in that it comprises:

[0020] The end face of the alloy rod in the atomization chamber faces the plasma gun. The plasma gun discharges to melt the area where the end face of the alloy rod contacts the arc. The rotating component then drives the alloy rod to rotate at high speed, and the metal droplets are thrown out under the action of centrifugal force. The cooled metal droplets become metal powder and fall into the multi-stage gas atomization device under the action of gravity.

[0021] In the multi-stage atomization device, the spray flow rate and fluid temperature of the atomization nozzles of each stage of the atomization unit are regulated to atomize the metal powder step by step, and the final metal powder is collected in the collection bin of the last stage of the atomization unit.

[0022] The beneficial effects of the present invention are:

[0023] In the metal powder preparation system described in the present invention, the alloy rod is powdered by the centrifugal force of high-speed rotation after being heated, and is then thrown out and subjected to the action of a plasma gun to enter a multi-stage atomization device. Then, each stage of the atomization device is provided with an atomization bin, a collection bin and a plurality of atomization nozzles, which can perform multi-stage atomization on the powder prepared by rotating electrode atomization, so that the collected powder has a higher particle size uniformity, and the collected powder particle size is smaller and more concentrated, which greatly reduces the probability of hollow powder and satellite powder appearing in the traditional rotating electrode atomization method, realizes the efficient preparation of metal powder, and has significant advantages in the field of metal powder preparation. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the structure of a metal powder preparation system based on multi-stage atomization of rotating electrodes;

[0025] In the figure, 1-atomization chamber, 2-alloy rod, 3-metal powder, 4-plasma gun, 5-atomization nozzle, 6-atomization chamber, 7-collecting chamber, 8-clamping component, 9-rotating component, and 10-heating component. DETAILED DESCRIPTION

[0026] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, but are not intended to limit the present invention in any form. It should be pointed out that a person of ordinary skill in the art can make several changes and improvements without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0027] Combination Figure 1 As shown, the present invention proposes a metal powder preparation system based on multi-stage atomization of a rotating electrode, which includes a rotating electrode atomization part and a gas atomization part, which respectively correspond to a plasma rotating electrode atomization device, a multi-stage gas atomization device and a control system.

[0028] The plasma rotating electrode atomization device comprises an atomization chamber 1, a rotating component 9, a clamping component 8, a heating component 10, a plasma gun 4 and an alloy rod 2; the alloy rod 2 is clamped and fixed by the clamping component 8 and extends into the interior of the atomization chamber 1, and the end face of the alloy rod 2 in the atomization chamber 1 faces the plasma gun 4, the rotating component 9 is used to drive the alloy rod 2 to rotate at a high speed, and the heating component is used to heat the end face of the alloy rod in the atomization chamber;

[0029] In a specific implementation of the present invention, an alloy rod opening is provided in the atomizing chamber 1 and the rotating component 9, so that the alloy rod 2 can pass through the alloy rod opening to reach the atomizing chamber 1. Under the clamping action of the clamping component 8, the rotating component 9 can drive it to rotate at high speed, and the clamping component 8 can also drive the alloy rod 2 to feed axially. The rotating component 9 is the core power of the plasma rotating electrode atomization device. It is realized by a rotating electrode, a motor, and a transmission device. Under the close cooperation of the motor and the transmission device, the rotating electrode can achieve high-speed and extremely stable rotation around its own axis. The transmission device greatly reduces the energy loss during the transmission process with its excellent transmission efficiency of up to 90%-98%, thereby providing a continuous and stable power input for the rotating electrode, ensuring that its rotation speed is stable at a high level, and the maximum speed can reach 32000r / min. The strong centrifugal force generated by this high-speed rotation plays an indispensable role in the subsequent atomization process, and can effectively overcome the surface tension of the liquid to be atomized, so that the liquid is quickly dispersed and initially broken on the surface of the rotating electrode, creating favorable conditions for subsequent fine atomization.

[0030] The atomization chamber 1 is a key place in the entire atomization process. The alloy rod 2 extends into the atomization chamber 1. The alloy rod 2 rotates at high speed and feeds axially under the drive of the rotating component 9. The axis of the alloy rod 2 coincides with the axis of the plasma gun 4. Under the action of the plasma gun 4, the surface of the alloy rod 2 melts to form a molten pool. Under the centrifugal force generated by the high-speed rotation of the alloy rod 2, the droplets in the molten pool escape from the surface of the liquid film and are thrown out, and atomization occurs. After cooling, they are discharged from the bottom mist outlet into the multi-stage gas atomization device. The inner wall of the atomization chamber 1 is also coated with a special anti-stick coating, which is made of polytetrafluoroethylene or its modified material. With its extremely low surface energy and excellent chemical stability, it effectively prevents the atomized liquid from condensing and hanging on the inner wall of the chamber, ensuring the smooth progress of the atomization process and avoiding the decline in powder quality and equipment cleaning problems caused by hanging on the wall.

[0031] The multi-stage atomization device is arranged downstream of the plasma rotating electrode atomization device, and is obtained by connecting a plurality of atomization units in series. Each stage of the atomization unit includes an atomization bin 6, a collection bin 7 and a plurality of atomization nozzles 5. The radius of the atomization bin 6 is 1-3 times the radius of the collection bin 7. The top of the atomization bin 6 in each stage of the atomization unit is provided with a first filter hole, and the bottom is provided with a second filter hole. A plurality of atomization nozzles 5 are evenly distributed along the circumference of the atomization bin 6, and the nozzles face the inside of the atomization bin 6. The number is not less than 3 and not more than 5. The top of the collection bin 7 is directly connected to the bottom of the atomization bin 6. Except for the collection bin 7 of the last stage of the atomization unit, the bottoms of the other collection bins 7 are provided with a third filter hole. The multi-stage atomization device is arranged downstream of the plasma rotating electrode atomization device, and is obtained by connecting a plurality of atomization units in series. It is obtained that each level of aerosolization unit includes an aerosolization bin 6, a collection bin 7 and a plurality of aerosolization nozzles 5, and the top of the aerosolization bin 6 in each level of aerosolization unit is provided with a first filter hole, the bottom is provided with a second filter hole, and a plurality of aerosolization nozzles 5 are evenly distributed along the circumference of the aerosolization bin 6, and the nozzles face the inside of the aerosolization bin 6; the top of the collection bin 7 is directly connected to the bottom of the aerosolization bin 6, and except for the collection bin 7 of the last level of aerosolization unit, the bottom of the remaining collection bins 7 is provided with a third filter hole; the third filter hole is not less than the diameter of the second filter hole in the corresponding aerosolization unit; the diameter of the second filter hole of the aerosol bin 6 of the aerosolization unit of each level decreases successively, and the second filter hole of the aerosol bin 6 of each level of aerosolization unit is always smaller than the first filter hole; the diameter of the first filter hole of the aerosol bin 6 of the aerosolization unit of each level is the same. By designing the filter hole that is not passed, it is preferred that the radius of the powder that can pass through the next level is 0.2 times that of the previous level.

[0032] In a specific implementation of the present invention, the main body of the aerosol nozzle 5 is made of stainless steel or ceramic composite material. The stainless steel material gives the nozzle good mechanical strength and excellent processing performance, so that it can withstand certain pressure and impact, ensuring that the structure is stable and reliable during long-term use; the ceramic composite material provides the nozzle with excellent corrosion resistance and chemical stability, so that it can adapt to various injection fluids with corrosive or special chemical properties, and broadens the application range of the device. The series number of the multi-stage aerosol device is 2-4 levels, and the nozzle is provided with a multi-layer staggered distribution of guide plates with 0.05mm-0.2mm micropores, and an adjustable flow limiting plate is provided at the nozzle; when the fluid (airflow) enters the nozzle, it will be guided by the guide plate, and after multiple diversions and convergences, the fluid is evenly dispersed under the action of the micropores, and the flow rate of the fluid ejected from the nozzle can be kept highly consistent. This uniform and stable flow rate ensures the uniformity of the effect on the powder particles and avoids the problem of inconsistent powder refinement effect caused by flow rate differences. The nozzle of the preferred nozzle is circular in shape with a diameter between 0.5mm and 2mm. The gas flow rate of the nozzle is between 400m / s and 450m / s. By precisely controlling the flow rate and flow rate of the injection fluid, a stable powder refining effect is maintained.

[0033] The control system is connected to the rotating component 9 and the plasma gun 4 of the plasma rotating electrode atomization device, and can dynamically adjust the rotation speed of the alloy rod 2 and the working parameters of the plasma gun 4; and is connected to the atomization nozzle 5 of the multi-stage atomization device, and can dynamically adjust the injection flow rate and fluid temperature of the atomization nozzle 5.

[0034] In this embodiment, the Figure 1 The method for preparing metal powder of the device shown mainly includes two stages:

[0035] Stage 1: The end face of the alloy rod 2 in the atomization chamber 1 faces the plasma gun 4. The plasma gun 4 causes the end face of the alloy rod 2 and the arc contact area to become molten through discharge. The alloy rod 2 is then driven to rotate at high speed by the rotating component 9. The metal droplets are thrown out under the action of centrifugal force. The cooled metal droplets become metal powder 3 and fall into the multi-stage gas atomization device under the action of gravity.

[0036] Stage 2: In the multi-stage atomization device, the injection flow rate and fluid temperature of the atomization nozzle 5 of each stage of the atomization unit are adjusted to atomize the metal powder step by step, and the final metal powder is collected in the collection bin 7 of the last stage of the atomization unit.

[0037] In a specific implementation of the present invention, the manufacturing process of the alloy rod 2 in the above-mentioned stage 1 is as follows:

[0038] According to the mass percentage, the ingredients are prepared according to the proportion of each element in the alloy (the sum of the mass percentage of each group is 100%), and the ingots are obtained by vacuum induction furnace smelting and electroslag remelting process, and rolled into alloy bars, which meet the current corresponding metal standards. The smelted alloy bars are fine-turned into alloy electrode bars, and after removing the iron oxide scale, the metal electrode bars that meet the requirements of the plasma rotating electrode atomization powder making method are obtained. (The density of the metal electrode bar is 99%, and there are no obvious casting defects such as looseness and shrinkage)

[0039] The atomization chamber 1 needs to be pre-vacuumed. When the vacuum degree of the vacuum treatment is less than 3×10 -3 After Pa, the protective gas was introduced, and the protective gas was argon gas, so that the pressure in the chamber reached 0.1×10 -5 Pa. Set the working parameters of the plasma gun 4 and the rotation speed of the alloy rod 2. After reaching the powder making set value, the atomization powder making conditions are met and the atomization function is started. The plasma gun 4 heats the end surface of the high-speed rotating alloy rod 2 to form a molten pool, and evenly melts it and is thrown out at high speed by the centrifugal force generated by the rotation. The liquid is quickly cooled into powder particles in an inert gas environment. The condensed powder particles are subjected to the next step of multi-stage atomization under the protection of the inert gas.

[0040] According to Frenkel electron theory, the surface tension of liquid is calculated as follows:

[0041]

[0042] In formula 1, σ is the surface tension of the liquid, Z is the number of valence electrons, e is the electron charge, and R is the distance between atoms.

[0043] According to the powder particle size calculation formula of atomization powder making, see the following formula 2, it can be seen that as the tension γ on the surface of the molten pool decreases, the obtained powder particle size will decrease accordingly.

[0044]

[0045] In formula 2, ρ represents the density of liquid metal, D represents the diameter of electrode bar, γ represents the surface tension of liquid metal, ω represents the angular velocity of rotation of electrode bar, and η is a dimensionless correction factor.

[0046] In a specific implementation of the present invention, the above-mentioned stage 2 uses a multi-stage atomization chamber 6 (2-4 stages, each stage collects powders with a difference of 0.2 times of the powder radius) and a multi-channel atomization nozzle 5 (3-5 nozzles, flow rate 400-450m / s) to grade the powder, and after the secondary atomization process, the prepared powder particles are smaller.

[0047] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A metal powder preparation system based on multi-stage atomization of rotating electrodes, characterized in that: include: A plasma rotating electrode atomization device comprises an atomization chamber (1), a rotating component (9), a clamping component (8), a heating component (10), a plasma gun (4) and an alloy rod (2); the alloy rod (2) is clamped and fixed by the clamping component (8) and extends into the interior of the atomization chamber (1); the end face of the alloy rod (2) in the atomization chamber (1) faces the plasma gun (4); the rotating component (9) is used to drive the alloy rod (2) to rotate at a high speed; and the heating component (10) is used to heat the end face of the alloy rod (2) in the atomization chamber (1); A multi-stage atomization device is arranged downstream of a plasma rotating electrode atomization device and is obtained by connecting a plurality of atomization units in series. Each stage of the atomization unit comprises an atomization bin (6), a collection bin (7) and a plurality of atomization nozzles (5). The atomization bin (6) in each stage of the atomization unit is provided with a first filter hole at the top and a second filter hole at the bottom. The plurality of atomization nozzles (5) are evenly distributed along the circumference of the atomization bin (6), and the nozzles face the inside of the atomization bin (6). The top of the collection bin (7) is directly connected to the bottom of the atomization bin (6). Except for the collection bin (7) of the last stage of the atomization unit, the bottoms of the remaining collection bins (7) are provided with a third filter hole. The third filter hole is not smaller than the diameter of the second filter hole in the corresponding aerosol unit; the diameter of the second filter hole of the aerosol bin (6) of each level of aerosol unit decreases successively, and the second filter hole of the aerosol bin (6) of each level of aerosol unit is always smaller than the first filter hole.

2. The metal powder preparation system based on multi-stage atomization of rotating electrodes according to claim 1 is characterized in that: The alloy rod (2) is driven by the rotating component (9) to rotate at high speed and feed axially, and the axis of the alloy rod (2) coincides with the axis of the plasma gun (4).

3. The metal powder preparation system based on multi-stage atomization of rotating electrodes according to claim 1, characterized in that: The diameters of the first filter holes of the aerosol chambers (6) of the aerosol units at each stage are the same.

4. The metal powder preparation system based on multi-stage atomization of rotating electrodes according to claim 1, characterized in that: The aerosol nozzle (5) is internally provided with multiple layers of staggered guide plates.

5. The metal powder preparation system based on multi-stage atomization of rotating electrodes according to claim 4 is characterized in that: The guide plate is provided with micropores of 0.05mm-0.2mm.

6. The metal powder preparation system based on multi-stage atomization of rotating electrodes according to claim 1, characterized in that: The diameter of the nozzle of the aerosol nozzle (5) is between 0.5 mm and 2 mm, and an adjustable flow limiting plate is provided at the nozzle.

7. The metal powder preparation system based on multi-stage atomization of rotating electrodes according to claim 1, characterized in that: The number of series-connected stages of the multi-stage gas atomization device is 2-4.

8. The metal powder preparation system based on multi-stage atomization of rotating electrodes according to claim 1, characterized in that: The inner wall of the atomization chamber (1) is coated with an anti-stick coating.

9. The metal powder preparation system based on multi-stage atomization of rotating electrodes according to claim 1, characterized in that: Also includes control systems; The control system is connected to the rotating component (9) and the plasma gun (4) of the plasma rotating electrode atomization device, and can dynamically adjust the rotation speed of the alloy rod (2) and the working parameters of the plasma gun (4); and is connected to the atomization nozzle (5) of the multi-stage atomization device, and can dynamically adjust the injection flow rate and fluid temperature of the atomization nozzle (5).

10. A method for preparing metal powder using a metal powder preparation system based on a rotating electrode multi-stage atomization as claimed in claim 1, characterized in that: include: The end face of the alloy rod (2) in the atomization chamber (1) faces the plasma gun (4). The plasma gun (4) causes the end face of the alloy rod (2) and the arc contact area to become molten through discharge. The alloy rod (2) is then driven to rotate at high speed by the rotating component (9). Metal droplets are thrown out under the action of centrifugal force. The cooled metal droplets become metal powder and fall into the multi-stage gas atomization device under the action of gravity. In the multi-stage atomization device, the spray flow rate and fluid temperature of the atomization nozzles (5) of each stage of the atomization unit are regulated to atomize the metal powder step by step, and the final metal powder is collected in the collection bin (7) of the last stage of the atomization unit.

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