A plasma generator and a plasma spheroidizing device with controllable temperature distribution

Abstract

The present application relates to the technical field of high-temperature material processing, and in particular to a plasma generator and a plasma spheroidization device with controllable temperature distribution. The plasma generator provided in the present application comprises: a cathode module, including a water-cooled cathode; an anode module, including at least three anodes, and the three anodes are arranged around the cathode axis of the water-cooled cathode; an arc-starting module, having a powder feeding channel for generating a starting arc; wherein the powder feeding direction of the powder feeding channel intersects with the cathode axis to form a powder feeding convergence point, and the powder feeding convergence point is located between the cathode head of the water-cooled cathode and the plane where the anode axes of at least three anodes are located, and at the same time, the powder feeding convergence point is also located above the arc generated by the cathode head and the anode head of the anode. Through the above-mentioned arrangement, the present application simplifies the arc energy transfer process and improves energy utilization efficiency.

Description

Technical Field

[0001] The present application relates to the technical field of high-temperature material processing, and in particular to a plasma generator and a plasma spheroidization device with controllable temperature distribution. Background Art

[0002] The widely used plasma spheroidization technology can be divided into radio frequency plasma spheroidization and arc plasma spheroidization. Radio frequency plasma spheroidization technology generates a high-frequency electromagnetic field through an induction coil, thereby quickly heating the inert gas in the cavity and exciting it into plasma. This technology first converts the electrical energy of the high-frequency power supply into electromagnetic energy through an induction coil. Under the action of the electromagnetic field, the electrons in the working gas obtain enough energy to collide with gas atoms or molecules, resulting in ionization. This process produces a large number of free electrons and ions, forming a high-temperature plasma, and the electromagnetic energy is converted into thermal energy. In this process, energy is converted from electrical energy to electromagnetic energy and then to thermal energy. The energy conversion is two times, and the efficiency of both energy conversions is low. Therefore, the energy utilization rate of this technology is low, and the energy consumption per unit mass of powder for spheroidization treatment is high. In addition, the powder to be treated is easy to adhere to the inner wall of the quartz tube of the plasma torch, causing the quartz tube to break, the maintenance cost is high, and the equipment structure is complex, which limits its wide application in industry.

[0003] The arc plasma spheroidization technology uses an arc between electrodes to excite an inert gas to form a plasma. Arc plasma spheroidization has the characteristics of high temperature and rapid melting, and is suitable for the spheroidization of refractory materials. The arc can be regarded as an element that converts electrical energy into other energies. It can convert electrical energy into thermal energy, light energy, magnetic energy and mechanical energy, most of which is converted into thermal energy. Therefore, the arc plasma spheroidization technology has a high energy utilization rate and low energy consumption per unit mass of powder for spheroidization. The arc temperature is very high, reaching more than 10000K, which is higher than the melting point of almost all existing materials. Therefore, this technology can spheroidize high-melting-point materials such as metal tungsten, aluminum oxide, and zirconium oxide. High arc temperature can also provide high superheat. The greater the superheat, the faster the heat is transferred to the powder material, the faster the powder processing speed is, the higher the production efficiency is, and it is suitable for large-scale material processing.

[0004] There are two types of arc plasma spheroidization devices in the prior art, namely Figure 5 and Figure 6 As shown, Figure 5The figure shows an arc plasma spheroidizing device with powder delivery outside the gun. The anode shell 31 is fixedly connected to the anode 32. The insulating sleeve 33 and the insulating ring 35 ensure that the small anode 36 and the plurality of intermediate electrodes 34 are insulated from the anode and each other. The cathode insulation 37 is connected to the anode shell 31 and is connected to the water-cooled cathode 38. A powder delivery channel 39 is arranged outside the outlet of the spheroidizing device. When the device is working, the protective gas is introduced, and an arc is caused between the small anode 36 and the water-cooled cathode 38. Then the arc root on the small anode 36 is transferred to the anode 32. Finally, the arc is maintained between the water-cooled cathode 38 and the anode 32. The arc excites the plasma jet, and the powder to be treated is injected into the plasma jet through the powder delivery channel 39 to complete the powder spheroidization.

[0005] Figure 6 The figure shows an arc plasma spheroidizing device with powder feeding in the gun, wherein the cathode housing 40 is fixedly connected to the cathode 41, and the cathode insulation 42 and the anode insulation 43 are connected to the cathode housing 40, thereby ensuring the insulation between the cathode housing 40 and the anode seat 44 and the anode 45. The anode seat 44 is connected to the anode insulation 43 and is connected to the anode 45. The powder feeding channel runs through the anode seat 44 and the anode 45. When the device is working, a protective gas is introduced, and an arc is caused between the cathode 41 and the anode 45. The arc is elongated and maintained under the influence of the gas force, and the arc excites the plasma jet. The powder to be treated is injected into the plasma jet through the powder feeding channel to complete the powder spheroidization.

[0006] However, the above-mentioned conventional arc plasma spheroidizing device has the following technical problems:

[0007] 1. The high temperature and high energy arc is not fully utilized, and the temperature of spheroidization treatment is low. Traditional technology uses the high temperature of the arc to excite plasma, adopts the powder delivery technology outside the gun, and uses the plasma jet outside the gun to treat the powder. The plasma jet temperature is lower than the arc temperature, and the temperature further decays after the jet is ejected from the gun.

[0008] 2. The distance between the cathode and cathode is fixed, and the length of the arc cannot be adjusted. The temperature distribution of the jet can only be adjusted through limited process parameters. Due to the water-cooling structure, sealing structure, and compact conductive / insulating structure, traditional technology is forced to use anodes and cathodes in fixed positions. This means that the arc length between the cathode and cathode cannot be adjusted, and the energy is transferred to the working gas within a fixed and limited arc length, and the transfer efficiency is limited. It is forced to adjust the temperature distribution of the plasma jet by adjusting the process parameters (mainly adjusting the current value), but the adjustment of the current is limited. On the one hand, the size of the cathode head is fixed. According to the empirical formula, the maximum working current I = 65D (D is the cathode head diameter, in mm, and I is in A), and the working current cannot be increased indefinitely; on the other hand, as the current increases, the arc temperature rises, and the middle pole that constrains the arc cannot withstand excessively high temperatures.

[0009] 3. Due to the mechanical constraints of the intermediate pole cavity, the arc diameter cannot be adjusted. In order to increase the arc length, arc voltage, and improve the arc stability, the traditional arc plasma spheroidization technology adopts a cascade intermediate pole structure. In order to compress the arc, the inner diameter of the intermediate pole cavity of this structure is usually small, with a typical value of 10mm, so the traditional technology cannot adjust the arc diameter.

[0010] 4. Powder is not easily delivered to the high-temperature area of ​​the jet when the powder is delivered through a vertical single hole. The traditional technology uses powder delivery technology outside the gun, with only one powder delivery channel, and the powder delivery speed is perpendicular to the jet speed. If the powder delivery speed is too high, the powder will pass through the high-temperature jet without being spheroidized; if the powder speed is too low, the powder cannot be delivered to the high-temperature area in the center of the jet.

[0011] 5. There is an electrode ablation problem, which affects the stability and working time of the plasma torch. The traditional technology adopts a single cathode and single anode structure. The cathode material is tungsten and the anode material is copper. The copper anode with a lower melting point is more prone to ablation problems. Large and small pits appear at the landing point of the anode arc root. On the one hand, these pits affect the original surface state and structure of the electrode, which may cause the arc root to fail to fall to the expected position, affecting the stability of the torch; on the other hand, as the working time increases, the pits gradually make the anode thinner, and the anode must be stopped and replaced. The ablation problem is more serious under high current working parameters.

[0012] 6. (For the in-gun powder feeding technology) The powder feeding channel is easily blocked. The in-gun powder feeding technology opens a powder feeding hole in the cup-shaped anode. The diameter of the powder feeding hole is small, and the electrode temperature is high, which makes the powder easily melt at the outlet of the powder feeding hole and the powder feeding channel blocked.

[0013] 7. (For the in-gun powder feeding technology) Powder and powder feeding gas affect the stability of the torch, and thus the stability of the spheroidization. Due to the use of traditional arc plasma spheroidization technology, the arc is confined in a very small cavity. The in-gun powder feeding technology delivers the powder directly to the highly compressed arc. The conductivity of the arc becomes unstable due to the influence of the powder, resulting in an unstable plasma jet state, which in turn affects the stability of the spheroidization process. In addition, the aerodynamic force brought by the powder feeding gas will cause the arc to move, and the arc root will deviate from the normal arc root landing point, causing the arc to fluctuate, and also aggravating the instability of the plasma jet state, which in turn affects the stability of the spheroidization process. Summary of the invention

[0014] The present application provides a plasma generator, which reduces the energy transfer process and increases the temperature of spheroidization treatment.

[0015] In a first aspect, an embodiment of the present application provides a plasma generator, comprising:

[0016] A cathode module, including a water-cooled cathode;

[0017] An anode module, comprising at least three anodes, wherein the three anodes are arranged around a cathode axis of a water-cooled cathode;

[0018] An arc striking module having a powder feeding channel for generating a starting arc;

[0019] Among them, the position where the powder feeding direction of the powder feeding channel intersects with the cathode axis forms a powder feeding convergence point, which is located between the cathode head of the water-cooled cathode and the plane where the anode axes of at least three anodes are located. At the same time, the powder feeding convergence point is also located above the arc generated by the cathode head and the anode head of the anode.

[0020] In the plasma generator provided in the embodiment of the present application, the number of anodes is three to twelve, and the cathode axis is perpendicular to the plane where the anode axis is located.

[0021] In the plasma generator provided in the embodiment of the present application, the arc striking module includes a small anode, the powder feeding channel is evenly distributed around the cathode axis, and the angle j between the powder feeding channel and the cathode axis satisfies the following relationship: 20°≤j≤50°;

[0022] The number s of powder feeding channels satisfies the following relationship: s=2y, where y is the number of anodes.

[0023] The plasma generator provided in the embodiment of the present application also includes a water-cooled furnace head, a furnace head insulation, and a cathode insulation. The anode module includes an anode insulation and anode water cooling. The side wall of the water-cooled furnace head is provided with a plurality of openings, and the anode insulation is inserted at the opening. The anode passes through the anode insulation and extends into the water-cooled furnace head. The anode water cooling is connected to the anode insulation and connected to the anode. The arc striking module is arranged at the top of the water-cooled furnace head, and the furnace head insulation is arranged at the connection between the arc striking module and the water-cooled furnace head. The water-cooled cathode is inserted into the arc striking module, and the cathode head is exposed at the bottom surface of the arc striking module. The cathode insulation is arranged between the water-cooled cathode and the arc striking module. A cavity processing chamber is formed inside the water-cooled furnace head. The water-cooled cathode is placed vertically, and the cathode axis coincides with the axis of the inner wall of the water-cooled furnace head. At least three anodes are located on a horizontal plane at the same height. At least three anodes are arranged to form a circular channel, and the center of the circular channel is located on the cathode axis.

[0024] In the plasma generator provided in the embodiment of the present application, a rotating mechanism is provided on the anode for rotating the anode with the anode axis as the axis.

[0025] In the plasma generator provided in the embodiment of the present application, the rotating mechanism includes an insulating coupling and a rotating servo motor, the insulating coupling is connected to the anode located at the outer end of the water-cooled furnace head, and the rotating shaft of the rotating servo motor is connected to the insulating coupling.

[0026] In the plasma generator provided in the embodiment of the present application, a feeding mechanism is provided on the anode for driving the anode to approach or move away from the cathode axis.

[0027] In the plasma generator provided in the embodiment of the present application, the feeding mechanism includes a slide, a screw, and a feeding servo motor. The slide is connected to the anode at the outer end of the water-cooled furnace head, the slide is threadedly connected to the screw, and the feeding servo motor is connected to the screw.

[0028] In the plasma generator provided in the embodiment of the present application, the distance from the convergence point of the cathode axis and the anode axis to the anode head is 10 mm to 50 mm, and the distance from the convergence point of the anode axis to the cathode head is 20 mm to 80 mm.

[0029] In a second aspect, the present application also provides a plasma spheroidization device with controllable temperature distribution, comprising: an upper furnace body, a lower furnace body, a three-way pipe, a fan pipe, a powder collecting tank, a fan, and a plasma generator according to any one of the first aspects, the plasma generator being arranged at the upper furnace body and connected to the upper furnace body, the upper furnace body is fixedly connected to the lower furnace body, the fan pipe is connected to the fan, and the fan pipe and the powder collecting tank are both connected to the lower furnace body through a three-way pipe.

[0030] The beneficial effects of this application are as follows:

[0031] The plasma generator provided by the present application is provided with a water-cooled cathode, at least three anodes and an arc-strike module, wherein the three anodes are arranged around the cathode axis of the water-cooled cathode, and the powder-feeding direction of the powder-feeding channel intersects with the cathode axis to form a powder-feeding convergence point, and the powder-feeding convergence point is located between the cathode head of the water-cooled cathode and the plane where the anode axes of at least three anodes are located, and at the same time, the powder-feeding convergence point is also located above the arc generated by the cathode head and the anode head of the anode. When the plasma generator is working, the arc-strike module first causes the starting arc, and after a short arc-strike time, the starting arc on the arc-strike module will be transferred to the anode, and the arc landing points are distributed on the surfaces of the cathode head and the anode head. The energy of the arc excites the inert gas into a plasma jet in the channel surrounded by at least three anode heads.

[0032] The powder delivery convergence point is located between the cathode head of the water-cooled cathode and the plane where the anode axes of at least three anodes are located. At the same time, the powder delivery convergence point is also located above the arc generated by the cathode head and the anode head of the anode, which allows the powder to be directly delivered to the arc between the cathode and the anode. Compared with the conventional plasma spheroidization technology of the prior art that delivers powder outside the gun, the plasma jet is excited by the arc heating between the cathode and the anode, and the original powder is injected into the plasma jet to spheroidize the powder. The present application uses the arc to directly process the powder material, which increases the temperature of the spheroidization treatment and expands the range of high melting point materials that can be processed. The use of the arc to process the powder provides a higher temperature difference for melting the powder, increases the melting speed of the powder, and improves the rate of processing the powder. In addition, the design provides a shorter energy transfer route, that is, the energy is directly transferred from the heat energy of the arc to the powder to be processed, which reduces the energy loss in the intermediate process and improves the energy utilization efficiency.

[0033] The temperature distribution controllable plasma spheroidization device provided in the present application includes an upper furnace body, a lower furnace body, a three-way pipe, a fan pipe, a powder collecting tank, a fan, and a plasma generator. The arranged plasma generator provides a shorter energy transfer route, that is, the energy is directly transferred from the heat energy of the arc to the powder to be processed, thereby reducing the energy loss in the intermediate process, directly processing the powder material with the arc, increasing the temperature of the spheroidization process, and expanding the range of high melting point materials that can be processed. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0035] Figure 1 It is a schematic diagram of a front cross-sectional structure of a plasma generator provided in an embodiment of the present application;

[0036] Figure 2 is a schematic diagram of a top view of the structure of a plasma generator provided in an embodiment of the present application;

[0037] Figure 3 It is a schematic diagram of an overall structure embodiment of a plasma generator provided in an embodiment of the present application;

[0038] Figure 4 It is a schematic diagram of the structure of a plasma spheroidization device with controllable temperature distribution provided in an embodiment of the present application;

[0039] Figure 5 It is a schematic diagram of the structure of an arc plasma spheroidizing device with powder delivered outside the gun in the prior art;

[0040] Figure 6 It is a schematic diagram of the structure of an arc plasma spheroidizing device with powder feeding in a gun in the prior art;

[0041] Figure 7 This is the arc state diagram taken through the filter in Experiment #1;

[0042] Figure 8 This is the plasma jet state diagram of Experiment #1;

[0043] Fig. 9 This is the arc state diagram taken through the filter in Experiment #5;

[0044] Fig.10 This is a diagram of the plasma jet state of Experiment #5.

[0045] Description of main components and symbols:

[0046] 1. Water-cooled furnace head; 2. Furnace head insulation; 3. Small anode; 4. Cathode insulation; 5. Water-cooled cathode; 6. Cathode head; 7. Powder feeding channel; 8. Powder feeding convergence point; 9. Electric arc; 10. Anode head; 11. Anode insulation; 12. Anode; 13. Convergence point of cathode and anode axis; 14. Plasma jet; 15. Cavity processing chamber; 16. Anode water cooling;

[0047] 17. Plasma generator; 18. Insulation coupling; 19. Rotation servo motor; 20. Slide; 21. Screw; 22. Feed servo motor; 23. Furnace head connecting plate;

[0048] 24. Three-anode furnace head assembly; 25. Upper part of furnace body; 26. Lower part of furnace body; 27. Three-way pipe; 28. Fan pipe; 29. ​​Powder collecting tank; 30. Fan;

[0049] 31. Anode shell; 32. Anode; 33. Insulation sleeve; 34. Intermediate pole; 35. Insulation ring; 36. Small anode; 37. Cathode insulation; 38. Water-cooled cathode; 39. Powder feeding channel;

[0050] 40. cathode housing; 41. cathode; 42. cathode insulation; 43. anode insulation; 44. anode seat; 45. anode. DETAILED DESCRIPTION

[0051] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0052] In conjunction with the accompanying drawings, some embodiments of the present application are described in detail below. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0053] It should be understood that the terms used in this application specification are only for the purpose of describing specific embodiments and are not intended to limit the application. As used in this application specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0054] It should be understood that, in order to facilitate the clear description of the technical solutions of the embodiments of the present application, in the embodiments of the present application, the words "first", "second", etc. are used to distinguish the same items or similar items with substantially the same functions and effects. For example, the first groove and the second groove are only used to distinguish different grooves, and their order is not limited. Those skilled in the art can understand that the words "first", "second", etc. do not limit the quantity and execution order, and the words "first", "second", etc. do not necessarily limit them to be different.

[0055] It should be further understood that the term “and / or” used in the specification and appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0056] Terminology explanation:

[0057] Water-cooled furnace head 1: used to support other structures, enclose the processing chamber, protect the operators, and position the anode 12. Its size can be flexibly designed according to the power of the equipment.

[0058] Furnace head insulation 2: used for insulation between the water-cooled furnace head 1 and the small anode 3.

[0059] Small anode 3: used for arc striking, having a water cooling structure and a powder feeding channel 7.

[0060] Cathode insulating member 4: used to support the cathode, insulate the cathode from the small anode 3, and has a rotary air supply structure.

[0061] Water-cooled cathode 5: one of the working electrodes, the tip of which is made of tungsten and has a water-cooling structure, used to generate a starting arc.

[0062] Cathode head 6: cathode tip, cathode arc 9 arc root landing point, made of tungsten.

[0063] Powder feeding channel 7: the path for powder to be fed into the processing chamber.

[0064] Powder feeding convergence point 8: the theoretical convergence point of the six powder feeding channels 7.

[0065] Arc 9: A conductive mechanism between the cathode and anode, used to generate a plasma jet 14.

[0066] Anode head 10: the tip of anode 12, the landing point of the arc root of anode 12, made of graphite.

[0067] Anode insulation 11: used for insulation between the water-cooled furnace head 1 and the anode 12.

[0068] Anode 12: One of the working electrodes, the tip of which is made of graphite and has a water-cooling structure, and is used to generate an arc 9.

[0069] Convergence point of the yin and yang pole axis 13: The theoretical convergence point of the yin and yang pole axis, used to evaluate the relative position between the yin and yang poles.

[0070] Plasma jet 14: A high-temperature jet generated by the arc 9 between the cathode and anode.

[0071] Cavity processing chamber 15: where the arc 9 is generated and the material is processed.

[0072] Anode water cooling 16 : its function is to cool the anode 12 .

[0073] refer to Figure 1-Figure 10 In order to solve the above technical problems, an embodiment of the present application provides a plasma generator 17, including: a cathode module, including a water-cooled cathode 5; an anode module, including at least three anodes 12, and the three anodes 12 are arranged around the cathode axis of the cathode head 6 of the water-cooled cathode 5; an arc striking module, having a powder feeding channel 7, for generating a starting arc; wherein, a powder feeding convergence point 8 is formed at a position where the powder feeding direction of the powder feeding channel 7 intersects with the cathode axis, and the powder feeding convergence point 8 is located between the water-cooled cathode 5 and the plane where the anode 12 axes of the at least three anodes 12 are located, and at the same time, the powder feeding convergence point 8 is also located above the arc 9 generated by the cathode head 6 and the anode head 10 of the anode 12.

[0074] When the plasma generator 17 is working, the arc starting module first causes the starting arc. After a short arc starting time, the starting arc on the arc starting module will be transferred to the anode 12, and the arc 9 landing points are distributed on the surfaces of the cathode head 6 and the anode head 10. The energy of the arc 9 excites the inert gas into a plasma jet 14 in the channel surrounded by at least three anode heads 10. The powder delivery convergence point 8 is located between the water-cooled cathode 5 and the plane where the anode 12 axis of at least three anodes 12 is located. At the same time, the powder delivery convergence point 8 is also located above the arc 9 generated by the cathode head 6 and the anode head 10 of the anode 12, which allows the powder to be processed to be directly delivered to the arc 9 between the cathode and cathode. Compared with the conventional plasma spheroidization technology of the prior art of powder delivery outside the gun, the arc 9 between the cathode and cathode is used to heat and excite the plasma jet 14, and the original powder is injected into the plasma jet 14 to spheroidize the powder. The present application uses the arc 9 to directly process the powder material, which increases the temperature of the spheroidization treatment and expands the range of high melting point materials that can be processed. The use of the arc 9 to process the powder provides a higher temperature difference for melting the powder, which increases the melting speed of the powder and improves the rate of processing the powder. In addition, the design provides a shorter energy transfer route, that is, the energy is directly transferred from the heat energy of the arc 9 to the powder to be processed, which reduces the energy loss in the intermediate process and improves the energy utilization efficiency.

[0075] In this embodiment, the arc striking module includes a small anode 3 , the plasma generator 17 also includes a water-cooled furnace head 1 , a furnace head insulation 2 , and a cathode insulation 4 , and the anode module includes an anode insulation 11 and an anode water cooling 16 .

[0076] The side wall of the water-cooled furnace head 1 is provided with a plurality of openings, and an anode insulating member 11 is inserted into the opening, and the anode 12 extends into the water-cooled furnace head 1 through the anode insulating member 11, and the anode water cooling 16 is connected to the anode insulating member 11 and connected to the anode 12, and the arc-starting module is arranged at the top of the water-cooled furnace head 1, and the furnace head insulating member 2 is arranged at the connection between the arc-starting module and the water-cooled furnace head 1, and the water-cooled cathode 5 is inserted into the arc-starting module, and the cathode head 6 is exposed at the bottom surface of the arc-starting module. The cathode insulating member 4 is arranged between the water-cooled cathode 5 and the arc-starting module, and a cavity processing chamber 15 is formed inside the water-cooled furnace head 1, and the water-cooled cathode 5 is placed vertically, and the cathode axis coincides with the axis of the inner wall of the water-cooled furnace head 1, and at least three anodes 12 are located on the same height of the horizontal plane, and at least three anodes 12 are arranged to form a circular channel, and the center of the circular channel is located on the cathode axis.

[0077] The volume of the cavity treatment chamber 15 is much larger than that of the treatment chamber of the prior art, and the mechanical constraint of the inner wall of the water-cooled furnace head 1 on the arc 9 is eliminated, so that the arc 9 can fully expand to form a larger high-temperature area. In addition, the large treatment chamber cavity allows the arc 9 to expand under vacuum. The lower end of the treatment chamber is fixedly connected to the upper part 25 of the furnace body and the lower part 26 of the furnace body, and is connected to the fan 30 through the three-way pipe 27 and the fan pipe 28. The fan 30 starts to run, and a negative pressure is formed in the treatment chamber. The lower the air pressure, the greater the expansion of the diameter and length of the arc 9 and the plasma jet 14, the lower the energy density, and the lower the temperature, which is suitable for rapid processing of materials with low melting points, such as metal copper, stainless steel, titanium alloy, etc.; on the contrary, the higher the air pressure, the smaller the arc 9 and the plasma jet 14 are compressed, and the higher the temperature, which is suitable for processing materials with high melting points, such as aluminum oxide, metal tungsten, zirconium oxide, etc. In addition, the arc 9 has no mechanical constraints from the cavity and can expand freely. The expanded arc 9 reduces the influence of the powder on the conductivity of the arc 9 , improves the stability of the arc 9 , and further improves the stability of the plasma jet 14 .

[0078] When the plasma generator 17 is working, a starting arc is first caused between the water-cooled cathode 5 and the small anode 3. After a short arc ignition time, the starting arc on the small anode 3 will be transferred to the anode 12, and the arc 9 landing points are distributed on the cathode head 6 and the three anode heads 10. The energy of the arc 9 excites the inert gas into a plasma jet 14 in the channel surrounded by the three anode heads 10. The small anode 3 has 6 powder feeding channels 7, and the powder feeding convergence point 8 is the physical convergence point of the axis of the powder feeding channel 7. The convergence point 13 of the anode and cathode axes is the intersection of the plane where the cathode axis and the three anode 12 axes are located. The plasma generator 17 composed of the above structure is connected to the insulating coupling 18, the rotary servo motor 19, the slide 20, the screw 21, and the feed servo motor 22 in turn, all of which are located on the furnace head connection plate 23. The plasma generator 17 is fixedly connected to the furnace body upper part 25, the furnace body lower part 26, the three-way pipe 27, the powder collecting tank 29, the fan pipe 28, and the fan 30, together forming a plasma spheroidizing device with controllable temperature distribution.

[0079] In some embodiments, the number of anodes 12 is three to twelve, and the cathode axis is perpendicular to the plane where the axis of the anode 12 is located.

[0080] When the equipment is working, the arc 9 ablates the cathode less than the anode 12. The ablation phenomenon is affected by the current. The larger the current, the more significant the ablation effect. Therefore, the configuration of multiple anodes 12 is conducive to reducing the current of a single anode 12 and alleviating the ablation problem of anode 12. In addition, the more anodes 12 there are, on the one hand, the more uniform the circumferential temperature distribution of the arc 9; on the other hand, the closer the distance between adjacent anode heads 10, the more likely the instability of the arc 9 from the cathode head 6 to one anode head 10 and then to the adjacent anode head 10 will occur, which in turn reduces the uniformity of the circumferential temperature distribution of the arc 9. In addition, due to physical size limitations, the actual optimal number of anodes 12 is configured to be 3 to 12.

[0081] In some embodiments, the arc striking module includes a small anode 3, and the powder feeding channels 7 are evenly distributed around the cathode axis. The angle j between the powder feeding channels 7 and the cathode axis satisfies the following relationship: 20°≤j≤50°; the number s of the powder feeding channels 7 satisfies the following relationship: s=2y, where y is the number of anodes 12.

[0082] On the small anode 3, 6 oblique powder feeding channels 7 are evenly distributed around the cathode axis. When the position of the powder feeding convergence point 8 is determined, the smaller the angle between the powder feeding channel 7 and the cathode axis, the closer the outlet of the powder feeding channel 7 is to the plasma jet 14. On the one hand, the higher the proportion of powder fed into the plasma jet 14, the more conducive to improving the spheroidization rate; on the other hand, the powder is more likely to melt at the outlet of the powder feeding channel 7 and thus block the powder feeding channel 7. The optimal angle between the powder feeding channel 7 and the cathode axis is between 20° and 50°. As for the number of powder feeding channels 7, the more the number, the better the uniformity of the powder. However, due to the physical size of the equipment, the number of powder feeding channels 7 cannot be infinite, and the optimal number should simultaneously meet the following requirements: it is an even number and an integer multiple of the number of anodes 12. When the powders of an even number of powder feeding channels 7 converge to the center of the jet, a vertical downward combined velocity is synthesized. Even if the powder feeding velocity is too large, it will not pass through the high temperature area of ​​the jet. Powder feeding channels 7 that are an integer multiple of the number of anodes 12 can make the powder more evenly distributed to the high temperature area near each anode 12. In addition, the powder delivery airflow that converges obliquely toward the center will not affect the landing point of the cathode arc root, reducing the fluctuation of the arc 9, thereby increasing the stability of the spheroidization process.

[0083] In some embodiments, it also includes a water-cooled furnace head 1, a furnace head insulation 2, and a cathode insulation 4. The anode module includes an anode insulation 11 and an anode water cooling 16. The side wall of the water-cooled furnace head 1 is provided with a plurality of openings, and the anode insulation 11 is inserted at the opening. The anode 12 passes through the anode insulation 11 and extends into the water-cooled furnace head 1. The anode water cooling 16 is connected to the anode insulation 11 and connected to the anode 12. The arc striking module is arranged at the top of the water-cooled furnace head 1, and the furnace head insulation 2 is arranged at the connection between the arc striking module and the water-cooled furnace head 1. The water-cooled cathode 5 is inserted into the arc striking module, and the cathode head 6 is exposed at the bottom surface of the arc striking module. The cathode insulation 4 is arranged between the water-cooled cathode 5 and the arc striking module. A cavity processing chamber 15 is formed inside the water-cooled furnace head 1. The water-cooled cathode 5 is placed vertically, and the cathode axis coincides with the axis of the inner wall of the water-cooled furnace head 1. At least three anodes 12 are located on a horizontal plane at the same height. At least three anodes 12 are arranged to form a circular channel, and the center of the circular channel is located on the cathode axis.

[0084] Furthermore, the outer ends of the three anodes 12 are fixedly connected to the insulating coupling 18 and the output shaft of the rotary servo motor 19 in turn, and the rotary servo motor 19 is fixedly connected to the slide 20, the slide 20 is connected to the screw 21 through a ball screw pair, the screw 21 is fixedly connected to the output shaft of the feed servo motor 22, and the screw 21 itself is fixedly connected to the furnace head connecting plate 23. The distance from the convergence point 13 of the anode and cathode axes to the anode head 10 can be adjusted by the movement of the feed servo motor 22, and this distance can be adjusted when the spheroidizing device is running. The distance from the convergence point 13 of the anode and cathode axes to the cathode head 6 can be adjusted by replacing the furnace head insulating parts 2 of different thicknesses, and this distance can be adjusted when the machine is shut down. As shown in the attached figure Figure 5 , Attachment Figure 6As shown, due to its compact structure, the conventional plasma spheroidization technology is forced to use only fixed-position cathodes and anodes. This means that the length of the arc 9 between the cathode and anode cannot be adjusted, and the energy is transferred to the working gas within a fixed, limited length of the arc 9, and the transfer efficiency is limited. By adjusting the distance from the cathode and anode axis convergence point 13 to the cathode and anode, the diameter of the plasma jet 14 can be adjusted, and then the temperature distribution in the high-temperature area can be adjusted. The larger the distance between the cathode and anode, the larger the diameter of the plasma jet 14, the lower the energy density, and the lower the jet temperature. Conversely, the smaller the diameter of the plasma jet 14, the higher the jet temperature. This can deal with powders with different melting points. For high melting point materials, such as aluminum oxide, metal tungsten, zirconium oxide, etc., higher temperatures are required; for metal copper, stainless steel, titanium alloy, etc., particularly high temperatures are not required, so part of the temperature can be sacrificed to increase the size of the high-temperature area to increase the powder processing speed. After experiments, the optimal distance between the convergence point 13 of the anode and cathode axes and the anode head 10 is 10mm to 50mm. If the distance is too large, it is easy to cause arc breaking, that is, the arc 9 between the anode and cathode is extinguished; if the distance is too small, the anode head 10 will be ablated more, shortening the working time of the anode 12. After experiments, the optimal distance between the convergence point 13 of the anode and cathode axes and the cathode head 6 is 20mm to 80mm. If the distance is too large, it will be difficult to successfully start the arc; if the distance is too small, the powder will be easily delivered to the surface of the anode head 10, reducing the powder spheroidization rate.

[0085] In some embodiments, a rotating mechanism is provided on the anode 12 for rotating the anode 12 around the axis of the anode 12 .

[0086] The rotating mechanism includes an insulating coupling 18 and a rotating servo motor 19 . The insulating coupling 18 is connected to the anode 12 at the outer end of the water-cooled furnace head 1 , and the rotating shaft of the rotating servo motor 19 is connected to the insulating coupling 18 .

[0087] The outer end of the anode 12 is connected to the rotary servo motor 19, and the anode 12 can be controlled to rotate when the spheroidizing equipment is working. As the anode 12 rotates, the arc root of the anode 12 is more evenly distributed on the surface of the anode head 10, the electrode is evenly ablated, the working time of the anode 12 is extended, the equipment downtime is reduced, and the production efficiency of the spheroidizing process is increased.

[0088] In some embodiments, the consumable anode 12 is made of graphite, and the outer end of the anode 12 is connected to the feed servo motor 22. The graphite anode head 10 is hemispherical, and the arc 9 arc root landing point is evenly distributed on the surface of the anode head 10 to avoid the charge gathering at a certain point on the surface of the anode 12 and forming a tip discharge phenomenon. The tip discharge phenomenon causes the temperature of the anode 12 to be higher and the ablation is severe. When the spheroidizing equipment is working, the graphite anode 12 is gradually ablated, consumed, and shortened, which causes the distance between the cathode and cathode to change, thereby changing the stability of the spheroidizing process. By controlling the feed movement of the anode 12 when the equipment is working, the change in the relative position of the cathode and cathode caused by the consumption of the anode 12 can be compensated, thereby improving the stability of the equipment. There is no need to stop the machine to replace the anode 12, which extends the continuous working time of the anode 12, improves the efficiency of material processing, and reduces the cost of production.

[0089] In some embodiments, the powder delivery channel 7 is separated from the cathode and anode 12, so the powder delivery channel 7 can be independently water-cooled and does not share cooling water with the cathode and anode. Independent water cooling ensures that the powder delivery channel 7 maintains a relatively low temperature, suppresses the problem of powder clogging the powder delivery channel 7 due to high temperature melting, and reduces the failure rate of the equipment.

[0090] In some embodiments, a feeding mechanism is provided on the anode 12 for driving the anode 12 to approach or move away from the cathode axis.

[0091] The feeding mechanism includes a slide 20 , a screw 21 , and a feeding servo motor 22 . The slide 20 is connected to the anode 12 at the outer end of the water-cooled furnace head 1 . The slide 20 is threadedly connected to the screw 21 , and the feeding servo motor 22 is connected to the screw 21 .

[0092] The distance from the convergence point 13 of the anode and cathode axes to the anode head 10 can be adjusted by the movement of the feed servo motor 22, and this distance can be adjusted when the spheroidizing device is in operation. By adjusting the distance from the convergence point 13 of the anode and cathode axes to the anode and cathode, the diameter of the plasma jet 14 can be adjusted, and then the temperature distribution in the high-temperature area can be adjusted. The larger the distance between the anode and cathode, the larger the diameter of the plasma jet 14, the lower the energy density, and the lower the jet temperature. Conversely, the smaller the diameter of the plasma jet 14, the higher the jet temperature. This can handle powders with different melting points. For high melting point materials, such as aluminum oxide, metal tungsten, zirconium oxide, etc., higher temperatures are required; for metal copper, stainless steel, titanium alloy, etc., particularly high temperatures are not required, so part of the temperature can be sacrificed to increase the size of the high-temperature area to increase the powder processing speed.

[0093] In some embodiments, the distance from the convergence point 13 of the cathode axis and the anode 12 axis to the anode head 10 is 10 mm to 50 mm, and the distance from the convergence point 13 of the cathode axis to the cathode head 6 is 20 mm to 80 mm. Referring to the following experimental table, a series of changes caused by changes in the distance from the convergence point to the cathode head 6 and the anode head 10 are shown.

[0094] Experimental table

[0095] Experiment No. #1 #2 #3 #4 #5 Distance from the converging point to the cathode head 40mm 30mm 40mm 40mm 40mm Distance from the convergence point to the anode head 20mm 20mm 10mm 20mm 20mm Current 140A 140A 140A 140A 140A Air flow 50SLM 50SLM 50SLM 50SLM 50SLM Air pressure 1atm 1atm 1atm 0.6atm 0.2atm Plasma jet diameter middle middle Small big maximum Plasma jet length middle short middle long longest

[0096] Compared with Experiment #2, Experiment #1 has a smaller distance from the convergence point to the cathode head 6, so the arc 9 of Experiment #1 is longer, which can stimulate more plasma, and the plasma jet 14 is longer. Compared with Experiment #3, Experiment #1 has a larger distance from the convergence point to the anode head 10, and the diameter of the plasma jet 14 increases accordingly. Compared with Experiment #4 and Experiment #5, since the gas pressure in the furnace is smaller, the gas pressure has a smaller compression force on the arc 9, so the arc 9 of Experiment #5 has a larger diameter of about 25mm, the plasma jet 14 has a larger diameter of about 80mm, and the plasma jet 14 is longer, exceeding 450mm; the arc 9 of Experiment #1 has a smaller diameter of about 15mm, the plasma jet 14 has a smaller diameter of about 50mm, and the plasma jet 14 is shorter, about 300mm.

[0097] Figure 7 This is the arc state diagram taken through the filter of experiment #1. The arc diameter is about 15mm at a pressure of 1atm. The cavity of the traditional arc plasma generator for spheroidization is narrow, with a typical value of 10mm, and the diameter of the arc generated must be less than 10mm. Compared with the traditional arc plasma spheroidization technology, the present invention can produce an arc with a larger diameter, and the powder is directly delivered to the high-temperature arc, which improves energy utilization and improves the efficiency of powder processing.

[0098] Figure 8 This is the plasma jet state diagram of experiment #1. At a pressure of 1 atm, the plasma jet diameter is about 50 mm and the plasma jet length is about 300 mm. The conventional arc plasma spheroidization technology uses a narrow cavity to constrain the arc, resulting in a jet approximately equal to the cavity diameter, that is, the generated plasma jet diameter is about 10 mm and the length is about 300 mm. Compared with the conventional arc plasma spheroidization technology, the present invention can produce a plasma jet with a larger diameter, expand the range of powder processing, and improve the efficiency of powder processing.

[0099] Fig. 9This is the arc state diagram taken through the filter of experiment #5. At a pressure of 0.2atm, the arc diameter is about 25mm, which is further increased compared to the arc diameter at a pressure of 1atm, that is, the core high temperature area is relatively large. This shows that the present invention can generate an arc with a larger diameter at low pressure, and the powder is directly delivered to the high temperature arc, which improves energy utilization and further improves the efficiency of powder processing.

[0100] Fig.10 This is the plasma jet state diagram of experiment #5. At a pressure of 0.2 atm, the plasma jet diameter is about 80 mm and the plasma jet length is about 450 mm. The plasma jet diameter produced by the conventional arc plasma spheroidization technology is about 10 mm and the length is about 300 mm. Under low pressure, the present invention can produce a plasma jet with a larger diameter and longer length than the conventional arc plasma spheroidization technology, which expands the range of powder processing and further improves the efficiency of powder processing.

[0101] pass Figure 7-Figure 10 It can be seen that by comparing the arc state and jet state of Experiment #1 and Experiment #5, the influence of gas pressure on the arc and jet state can be seen. The greater the gas pressure, the greater the compression force on the arc and plasma jet, and the smaller and shorter the arc and jet are. At the same time, it also shows that it is feasible to control the arc and plasma jet state by gas pressure to achieve the purpose of adapting to the processing of different materials.

[0102] On the other hand, the present application provides a plasma spheroidization device with controllable temperature distribution, comprising: a furnace upper part 25, a furnace lower part 26, a three-way pipe 27, a fan pipe 28, a powder collecting tank 29, a fan 30, and a plasma generator 17 described in any one of the embodiments of the present application, wherein the plasma generator is arranged in the furnace upper part 25 and is connected to the furnace upper part 25, the furnace upper part 25 is fixedly connected to the furnace lower part 26, the fan pipe 28 is connected to the fan 30, and the fan pipe 28 and the powder collecting tank 29 are both connected to the furnace lower part 26 through the three-way pipe 27.

[0103] In summary, the plasma generator 17 provided in the embodiment of the present application solves the above technical problems in the following ways:

[0104] 1. The powder is directly delivered to the arc 9, and the heat energy of the high temperature arc 9 and the plasma jet 14 is used to treat the powder. The spheroidization treatment temperature is relatively high, so that the technology can process high melting point materials. The higher the superheat, the faster the melting rate of the powder to be treated, and the higher the production efficiency. The energy loss is reduced and the energy utilization efficiency is improved.

[0105] 2. The three anodes 12 are connected to the feed servo motor 22 respectively, and the anode and cathode positions are adjustable. By adjusting the distance between the anode and cathode, the length of the arc 9 can be adjusted, and the size of the high temperature area of ​​the processed powder can be adjusted, and the adjustable range of the temperature distribution in the high temperature area is increased.

[0106] 3. There is no mechanical constraint between the cathode and cathode, and the arc 9 is relatively freely exposed to the working gas. The size of the high-temperature jet is adjusted by adjusting the vacuum degree of the spheroidizing chamber. The lower the air pressure in the spheroidizing chamber, the larger the size of the high-temperature arc 9 and the jet expands, the lower the energy density and the lower the temperature.

[0107] 4. Use multi-hole oblique powder feeding, and the powder feeding channel 7 shoots into the vertical arc 9 at an acute angle. Multi-hole oblique powder feeding, when the powder converges to the center of the jet, it synthesizes a vertical downward combined speed. Even if the powder feeding speed is too high, it will not pass through the high temperature area of ​​the jet. The powder converges to the center from multiple directions around the high temperature area, and the powder is more evenly distributed in the high temperature area. (For the powder feeding technology in the gun) The powder feeding gas converges to the center, which will not affect the arc root landing point, reducing the fluctuation of the arc 9.

[0108] 5. At least three anodes 12 are provided, and the current flowing through each anode 12 is only a part of the total current. This method reduces the current of the anode 3 and alleviates the anode 12 ablation problem.

[0109] 6. The powder delivery channel 7 is separated from the cathode and anode and is independently water-cooled. This ensures a lower temperature in the powder delivery channel 7 and prevents powder blockage.

[0110] 7. The anode 12 is a spherical graphite consumable electrode. The three anodes 12 are connected to the feed servo motor 22 respectively. The anode head 10 is shortened due to the ablation and consumption of the arc 9. The position of the anode head 10 can be adjusted by the servo motor, and there is no need to stop the machine to replace the electrode. The continuous working time of the anode 12 is extended. The ball head design makes the arc root landing point evenly distributed on the surface of the anode head 10, which is not easy to produce tip discharge phenomenon, and increases the working life of the anode 12.

[0111] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed in the present application, and these modifications or replacements should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A plasma generator, characterized in that: include: A cathode module, including a water-cooled cathode; An anode module, comprising at least three anodes, wherein the three anodes are arranged around the cathode axis of the water-cooled cathode; An arc striking module having a powder feeding channel for generating a starting arc; Wherein, a powder feeding convergence point is formed at a position where the powder feeding direction of the powder feeding channel intersects with the cathode axis, and the powder feeding convergence point is located between the cathode head of the water-cooled cathode and the plane where the anode axes of at least three anodes are located, and at the same time, the powder feeding convergence point is also located above the arc generated by the cathode head and the anode head of the anode; It also includes a water-cooled furnace head, a furnace head insulation, and a cathode insulation. The anode module includes an anode insulation and anode water cooling. The side wall of the water-cooled furnace head is provided with a plurality of openings, and the anode insulation is inserted at the opening. The anode passes through the anode insulation and extends into the water-cooled furnace head. The anode water cooling is connected to the anode insulation and connected to the anode. The arc striking module is arranged at the top of the water-cooled furnace head, and the furnace head insulation is arranged at the connection between the arc striking module and the water-cooled furnace head. The water-cooled cathode is inserted into the arc striking module, and the cathode head is exposed at the bottom surface of the arc striking module. The cathode insulation is arranged between the water-cooled cathode and the arc striking module. A cavity processing chamber is formed inside the water-cooled furnace head. The water-cooled cathode is placed vertically, and the cathode axis coincides with the axis of the inner wall of the water-cooled furnace head. At least three of the anodes are located on a horizontal plane at the same height. At least three of the anodes are arranged to form a circular channel, and the center of the circular channel is located on the cathode axis.

2. The plasma generator according to claim 1, characterized in that: The number of the anodes is three to twelve, and the cathode axis is perpendicular to the plane where the anode axis is located.

3. The plasma generator according to claim 1, characterized in that: The arc striking module includes a small anode, the powder feeding channel is evenly distributed around the cathode axis, and the angle j between the powder feeding channel and the cathode axis satisfies the following relationship: 20°≤j≤50°; The number s of the powder delivery channels satisfies the following relationship: s=2y, wherein y is the number of anodes.

4. The plasma generator according to claim 1, characterized in that The anode is provided with a rotating mechanism for rotating the anode with the anode axis as the axis.

5. The plasma generator according to claim 4, characterized in that The rotating mechanism comprises an insulating coupling and a rotating servo motor. The insulating coupling is connected to the anode at the outer end of the water-cooled furnace head, and the rotating shaft of the rotating servo motor is connected to the insulating coupling.

6. The plasma generator according to claim 1, characterized in that The anode is provided with a feeding mechanism for driving the anode to approach or move away from the cathode axis.

7. The plasma generator according to claim 6, characterized in that The feeding mechanism comprises a slide, a screw and a feeding servo motor. The slide is connected to the anode at the outer end of the water-cooled furnace head. The slide is threadedly connected to the screw, and the feeding servo motor is connected to the screw.

8. The plasma generator according to claim 1 or 7, characterized in that: The distance from the convergence point of the cathode axis and the anode axis to the anode head is 10 mm to 50 mm, and the distance from the convergence point of the anode axis to the cathode head is 20 mm to 80 mm.

9. A plasma spheroidization device with controllable temperature distribution, characterized in that: include: A furnace body upper part, a furnace body lower part, a three-way pipe, a fan pipe, a powder collecting tank, a fan, and a plasma generator according to any one of claims 1 to 8, wherein the plasma generator is arranged on the furnace body upper part and communicated with the furnace body upper part, the furnace body upper part is fixedly connected to the furnace body lower part, the fan pipe is connected to the fan, and the fan pipe and the powder collecting tank are both communicated with the furnace body lower part through the three-way pipe.

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