Electron beam melting-ultrasonic atomization pulverizing system and method

Abstract

The invention relates to an electron beam melting-ultrasonic atomization pulverizing system and method, belongs to the technical field of preparation of metal powder materials, and solves the problems that in an existing metal powder preparation technology, high-melting-point metal powder is difficult to prepare, and due to medium introduction, the powder purity is low, the cost is high, the sphericity degree of the powder is low, and the particle size is uncontrollable. The electron beam melting-ultrasonic atomization pulverizing system comprises an electron beam system, a vacuum system, a cooling system, an ultrasonic pulverizing system and a powder collecting system. By means of the system, powder preparation under the high-vacuum condition can be achieved, medium introduction is avoided, impurity removal is promoted, and low-oxygen ultra-pure powder can be obtained easily; the energy density of electron beams is high, and preparation of high-melting-point metal powder can be successfully achieved; by means of ultrasonic atomization, the metal powder is high in sphericity degree, controllable in particle size and few in defect, and the method is particularly suitable for preparing ultrapure powder of refractory metal (such as W, Mo and Ta) and active metal (such as Ti, Nb, Co and V).

Description

Technical Field

[0001] The invention relates to the technical field of preparation of metal powder materials, and in particular to an electron beam melting-ultrasonic atomization powder making system and method. Background Art

[0002] Metal powder is an important raw material for powder near-net forming technologies such as additive manufacturing, powder metallurgy, surface coating, and injection molding. Its own properties have an important influence on the stability of the forming process and the performance of the product. Spherical powder has good fluidity and uniformity, better filling and compaction properties during the forming process, and can produce high-precision, high-performance products. It can also reduce powder waste and agglomeration and improve process efficiency. At present, the commonly used methods for preparing spherical metal powders include vacuum induction atomization powder making, electrode induction atomization powder making, plasma rotating electrode atomization powder making, plasma atomization powder making, water atomization powder making, radio frequency plasma spheroidization powder making, ultrasonic atomization powder making, etc.

[0003] However, in the process of metal melting, vacuum induction atomization powder production requires a crucible to hold the molten metal, which is easy to introduce pollutants; the powder obtained by electrode induction atomization has satellite balls (big balls stick to small balls), and there may be holes inside the powder. In addition, it is difficult to prepare ultra-high melting point metal (W, Mo, Ta, etc.) powder; the powder obtained by plasma atomization has a large particle size, and the raw material for preparation needs to be wire, and the applicable metal is limited, and plasma rotating electrode atomization powder production also has the disadvantage of large powder particle size; the shape of the powder obtained by water atomization is difficult to control, the loose packing ratio is low, the fluidity is poor, and the active metal is easy to react with the atomization medium water at high temperature, reducing the purity of the product; the radio frequency plasma spheroidization method is not suitable for the preparation of low melting point metal powder, and the spheroidization process has limited effect on the removal of impurities. Ultrasonic atomization powder production is a process in which the molten metal is atomized into tiny droplets by high-frequency vibration generated by ultrasonic waves, and solidified into metal powder after cooling. The prepared powder has good sphericity, controllable particle size, and a narrow particle size range. However, existing ultrasonic atomization powder making methods all use induction or arc plasma as a heat source to melt the metal raw materials. The vacuum degree of the powder making process is not high, and the impurity removal effect is limited. It is difficult to prepare powders of high-melting-point refractory metals using induction as a heat source. When arc plasma is used as a heat source, the vacuum degree is low. Due to the use of high-purity argon, the cost of powder preparation is high.

[0004] In view of the deficiencies in the prior art, a new method and system for preparing spherical metal powder is needed to avoid the introduction of argon, plasma or other media (such as high-pressure water) during the powder making process to improve the purity of the metal powder, and to achieve the preparation of refractory metal spherical powders, improve the performance of the metal powder and reduce costs. Summary of the invention

[0005] In view of the above analysis, an embodiment of the present invention aims to provide an electron beam melting-ultrasonic atomization powder making system and method to solve at least one of the problems in the existing metal powder preparation technology, namely, the difficulty in preparing high melting point metal powder, the introduction of medium leading to low powder purity and high cost, low powder sphericity, uncontrollable particle size and many metallurgical defects.

[0006] In a first aspect, an embodiment of the present invention provides an electron beam melting-ultrasonic atomization powder making system, the system comprising:

[0007] Furnace body 2;

[0008] An electron beam system, including an electron gun 12, for generating and emitting an electron beam 13 to melt a metal material 14 to form metal droplets, and to heat a metal atomizing plate 5;

[0009] A vacuum system, including an electron gun vacuum system and a furnace vacuum system, which are used to provide a vacuum environment for the electron beam 13 to be generated and a vacuum environment for the electron beam 13 to be used;

[0010] An ultrasonic powder making system, used to atomize the metal molten droplets to form metal micro droplets 4;

[0011] A cooling system, used for cooling the furnace body 2, the horn 6 and the metal powder 11;

[0012] A powder collecting system for collecting the prepared metal powder 11;

[0013] Among them, the electron beam system is arranged above the furnace body 2; the ultrasonic powder making system is arranged in the furnace body 2; the electron gun vacuum system is connected to the electron beam system, the furnace body vacuum system is arranged on the furnace body 2, the cooling system is arranged on the inner wall of the furnace body 2, around the amplitude transformer 6, and the side wall and bottom of the powder collecting tank 10; the powder collecting system is arranged below the furnace body 2.

[0014] Furthermore, the electron gun vacuum system includes a molecular pump 1 and a first mechanical pump 3 - 1 .

[0015] Furthermore, the furnace vacuum system includes a diffusion pump 16, a secondary Roots pump 17, a primary Roots pump 18 and a second mechanical pump 3-2.

[0016] Furthermore, the ultrasonic powder making system includes a metal atomizing plate 5, an ultrasonic generating device and a feeding mechanism 15, wherein the feeding mechanism 15 is used for feeding materials so that the melting end surface of the metal material 14 is located above the metal atomizing plate 5, and the ultrasonic generating device is provided below the metal atomizing plate 5.

[0017] Furthermore, the metal material 14 does not completely block the emission path of the electron beam, so that the electron beam acts on the metal atomization plate 5 at the same time.

[0018] Furthermore, the metal atomization plate 5 has the same material as the metal material 14 .

[0019] Furthermore, the distance between the electron gun 12 and the metal atomization plate 5 is adjustable within the range of 500-1500 mm.

[0020] Furthermore, the distance between the metal material 14 and the metal atomizing plate 5 is adjustable within the range of 50-500 mm.

[0021] In a second aspect, an embodiment of the present invention provides a method for preparing metal powder, the method comprising:

[0022] (1) Pre-treating the metal material to obtain a clean metal material to be treated;

[0023] (2) Under vacuum conditions, the metal material to be processed is electron beam melted to obtain metal droplets;

[0024] (3) ultrasonically atomizing the metal molten droplets to form atomized metal micro-droplets;

[0025] (4) The atomized metal droplets are cooled and solidified during movement, and then collected to obtain metal powder.

[0026] Furthermore, in step (2), the pressure in the vacuum state is 1×10 -3 -8×10 -3 Pa.

[0027] Furthermore, the method also includes: further cooling the collected metal powder.

[0028] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0029] 1. The system of the present invention melts metal materials through electron beams. The energy density of electron beams is high, and they can melt high-melting-point metals (W, Mo, Ta, etc.), and various metal powders with different melting points can be prepared by adjusting the power of electron beams;

[0030] The molten metal droplets fall on the metal atomization plate to form a micro-molten pool, and then under the action of ultrasound, the liquid metal sputters to form metal mist, which is cooled and solidified to obtain metal powder. Compared with gas atomization, the metal powder prepared by ultrasonic atomization has good sphericity (>0.95), high fine powder acquisition rate (powder below 75μm accounts for more than 60%), and there is no swirling airflow in ultrasonic atomization, which reduces the probability of particle collision and avoids the formation of hollow powder and satellite powder;

[0031] The present invention prepares powder under high vacuum conditions. The high vacuum environment is conducive to the removal of gas impurities (O, N, etc.) in the molten droplet, while avoiding the pollution caused by the introduction of media (such as argon, plasma, high-pressure water, etc.), which is conducive to obtaining low-oxygen ultra-pure powders. It is particularly suitable for the preparation of ultra-pure powders of active metals (such as Ti, Nb, Co, V) and reduces costs.

[0032] 2. The present invention controls the movement of metal materials through a horizontal feeding mechanism to ensure that the molten end surface of the metal material is located within the electron beam bombardment range above the metal atomizing plate, and the metal material does not completely block the transmission path of the electron beam, so that part of the electron beam bombards the metal atomizing plate, thereby achieving the purpose of melting the metal and heating the metal atomizing plate, ensuring the temperature required for atomization and powder making, and facilitating the sputtering of metal molten droplets to form metal micro-droplets, and is particularly suitable for the preparation of high melting point and even refractory metal powders; a single electron beam heat source is used to simplify the structure of the powder making system.

[0033] 3. The metal atomizing plate used in the present invention has the same material as the metal material, does not require a crucible, avoids the introduction of pollutants, and is conducive to obtaining high-purity metal powder.

[0034] 4. The powder making system and method of the present invention can prepare metal powder with a melting point range of 200-3500°C by adjusting the electron beam power (5-500kW), and is suitable for a wide variety of materials. The raw materials used are metal rods and metal bars, which are easy to obtain and conducive to industrial promotion. High-purity argon is not used in the powder making process, and a single heat source system is adopted, which effectively simplifies the system structure and reduces production costs.

[0035] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0037] Figure 1 This is a schematic diagram of the electron beam melting-ultrasonic atomization powder making system of the present invention;

[0038] Figure 2 This is the flow chart of electron beam melting-ultrasonic atomization powder making of the present invention;

[0039] Reference numerals:

[0040] 1-molecular pump; 2-furnace body; 3-1-first mechanical pump; 3-2-second mechanical pump; 4-atomized metal micro-droplets; 5-metal atomizing plate; 6-horn; 7-ultrasonic transducer; 8-1-inlet / outlet of cooling system; 8-2 cooling water of powder collecting system; 8-3 cooling water of horn; 9-ultrasonic generator; 10-powder collecting tank; 11-metal powder; 12-electron gun; 13-electron beam; 14-metal material; 15-feeding mechanism; 16-diffusion pump; 17-secondary Roots pump; 18-primary Roots pump; 19-gate valve. DETAILED DESCRIPTION

[0041] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0042] The commonly used methods for preparing spherical metal powders in the prior art include vacuum induction gas atomization powder making, electrode induction gas atomization powder making, plasma rotating electrode atomization powder making, plasma atomization powder making, water atomization powder making, radio frequency plasma spheroidization powder making, induction / arc ultrasonic atomization powder making, etc. However, these existing methods are prone to one or more of the following problems in the powder preparation process: using a crucible to hold the metal melt, it is easy to introduce pollutants; the obtained powder particle size is large and has many defects (hollow powder, satellite powder); the preparation of ultra-high melting point metal (W, Mo, Ta, etc.) powder is relatively difficult; the obtained powder particle size is large (D50 is greater than 100μm); the preparation raw material needs to be wire, and the applicable metals are limited; the shape of the obtained powder is difficult to control, the loose packing ratio is low, and the fluidity is poor; active metals are easy to react with the atomization medium or impurities at high temperature, reducing the purity of the product; the powder preparation process has limited effect on the removal of impurities; the equipment structure is complex; and the cost is high.

[0043] Therefore, the present invention provides an electron beam melting-ultrasonic atomization powder making system, which is a metal powder making system based on electron beam heating and ultrasonic atomization, such as Figure 1 As shown, including:

[0044] Furnace body 2;

[0045] An electron beam system, including an electron gun 12, for generating and emitting an electron beam 13 to melt a metal material 14 to form metal droplets and heat a metal atomizing plate 5;

[0046] A vacuum system, including an electron gun vacuum system and a furnace vacuum system, which are used to provide a vacuum environment for the electron beam 13 to be generated and a vacuum environment for the electron beam 13 to be used;

[0047] An ultrasonic powder making system, used to atomize the metal molten droplets to form metal micro droplets 4;

[0048] A cooling system, used for cooling the furnace body 2, the horn 6 and the metal powder 11;

[0049] A powder collecting system for collecting the prepared metal powder 11;

[0050] Among them, the electron beam system is arranged above the furnace body 2; the ultrasonic powder making system is arranged in the furnace body 2; the electron gun vacuum system is connected to the electron beam system, the furnace body vacuum system is arranged on the furnace body 2, the cooling system is arranged on the inner wall of the furnace body 2, around the amplitude transformer 6, and the side wall and bottom of the powder collecting tank 10; the powder collecting system is arranged below the furnace body 2.

[0051] According to a preferred embodiment of the present invention, the electron gun vacuum system includes a molecular pump 1 and a first mechanical pump 3-1, which are connected to evacuate the gun body of the electron gun; wherein a valve is provided on the pipe connecting the electron gun 12 and the molecular pump 1; and a valve is provided on the pipe connecting the molecular pump 1 and the first mechanical pump 3-1.

[0052] According to a preferred embodiment of the present invention, the vacuum system includes a diffusion pump 16 , a secondary Roots pump 17 , a primary Roots pump 18 and a second mechanical pump 3 - 2 , which are used to evacuate the furnace body 2 .

[0053] Specifically, one end of the diffusion pump 16 is connected to the furnace body 2, and the other end is connected to the secondary Roots pump 17. One end of the secondary Roots pump 17 is also connected to the furnace body 2 through a gas pipeline, and the other end is connected to the primary Roots pump 18. The other end of the primary Roots pump 18 is connected to the second mechanical pump 3-2. Pneumatic valves are provided on the pipelines between the diffusion pump 16 and the furnace body 2, between the diffusion pump 16 and the secondary Roots pump 17, and between the secondary Roots pump 17 and the furnace body 2. The high vacuum state inside the furnace body 2 is ensured by the joint action of the diffusion pump 16, the secondary Roots pump 17, the primary Roots pump 18 and the second mechanical pump 3-2.

[0054] According to a preferred embodiment of the present invention, a flange is provided on the upper end surface of the furnace body 2, and the electron gun 12 is connected to the furnace body via the flange, and the emitted electron beam is used to melt the metal material 14.

[0055] It should be noted that the system of the present invention adjusts the electron beam to melt metal materials through the electron beam system. The electron beam has a high energy density and can melt refractory metals (W, Mo, Ta, etc.). The electron beam power can be adjusted within the range of 5-500kW to prepare various metal powders with different melting points. According to a preferred embodiment of the present invention, the electron beam power for preparing metal titanium powder is 15-30kW.

[0056] Preferably, a sealing device is provided at the connection between the electron gun 12 and the furnace body 2 to ensure the airtightness of the entire furnace body.

[0057] According to a preferred embodiment of the present invention, the ultrasonic powder making system comprises a metal atomizing plate 5, an ultrasonic generator and a feeding mechanism 15. The feeding mechanism 15 is used to feed materials so that the melting end surface of the metal material 14 is located above the metal atomizing plate 5, and the ultrasonic generator is provided below the metal atomizing plate 5.

[0058] The metal material of the present invention can be a metal rod material or a metal strip material.

[0059] According to a preferred embodiment of the present invention, the ultrasonic generating device includes an ultrasonic generator 9 , an ultrasonic transducer 7 , and a horn 6 .

[0060] According to a preferred embodiment of the present invention, the amplitude transformer 6 is connected to the metal atomization plate 5 via a support rod or a thread, so that the metal atomization plate 5 can be easily replaced.

[0061] According to a preferred embodiment of the present invention, the horn 6 is cooled by a cooling system. During the powder making process, the temperature of the metal atomization plate 5 is high due to the action of the electron beam, and the horn needs to be cooled to prevent heat from being transferred to the ultrasonic transducer through the horn, thereby affecting the normal operation of the ultrasonic transducer; in addition, too high a temperature will also cause the metal atomization plate to melt directly, reducing the atomization efficiency.

[0062] During the use of the electron beam melting-ultrasonic atomization powder making system of the present invention, the metal material 14 moves under the drive of the feeding mechanism 15 so that the melting end face is located within the bombardment range of the electron beam 13, and the melted droplets fall onto the metal atomization plate 5. Under the action of the ultrasonic generating device, the droplets in contact with the metal atomization plate are broken up by the ultrasonic wave and sputtered out to produce atomized micro-droplets 4. The atomized micro-droplets 4 cool down during the falling process and when in contact with the side wall of the furnace body 2, solidify to form metal particles, and fall into the powder collecting tank 10 connected to the furnace body 2 for collection.

[0063] According to a preferred embodiment of the present invention, a cooling system is provided in the side wall surface of the furnace body 2. According to a preferred embodiment of the present invention, a cold water pipe inlet of the cooling system is located on one side of the furnace body 2, and a cold water pipe outlet is located on the other side of the furnace body 2. The cooling system is used to keep the inner wall surface of the furnace body 2 in a cooling state (<40°C) to preliminarily cool the prepared metal powder.

[0064] Preferably, in order to ensure the airtightness of the furnace body 2 , a sealing device is provided at the cold water pipe inlet and the cold water pipe outlet on the furnace body 2 .

[0065] Furthermore, the lower end of the furnace body 2 is connected to the powder collecting system.

[0066] According to a preferred embodiment of the present invention, the lower end surface of the furnace body 2 is configured as a cone structure with a larger upper portion and a smaller lower portion, and the lower portion of the cone is connected to the powder collecting system, which is beneficial to the collection of metal fine powder.

[0067] Specifically, the powder collecting system includes a gate valve 19 and a powder collecting tank 10 . Circulating cooling water is provided on the side wall and the bottom of the powder collecting tank 10 to further cool the collected metal powder 11 .

[0068] Furthermore, after the metal powder 11 is collected, the gate valve 19 provided at the connection between the furnace body 2 and the powder collecting system is inserted to complete the vacuum sealing of the powder tank body, and the powder collecting tank 10 is transferred to the powder screening equipment. The powder is screened to obtain ultra-pure low-oxygen metal powder.

[0069] In the present invention, the metal droplets melted by the electron beam fall on the metal atomization plate, and then under the action of the ultrasonic wave controlled by the ultrasonic powder making system, the liquid droplets are sputtered to form metal atomized micro-droplets, and metal powder is obtained after cooling and solidification. Compared with the gas atomization in the prior art, the metal powder prepared by ultrasonic atomization has good sphericity (>0.95), high fine powder acquisition rate (powder below 75μm accounts for more than 60%), and there is no swirling airflow in the ultrasonic atomization, which reduces the probability of particle collision and avoids the generation of hollow powder and satellite powder.

[0070] The present invention prepares powder under high vacuum conditions, avoids contamination caused by the introduction of media (such as argon, plasma, high-pressure water, etc.), is conducive to obtaining low-oxygen ultra-pure powder, is particularly suitable for the preparation of ultra-pure powder of active metals (such as Ti, Nb, Co, V), and reduces costs.

[0071] According to a preferred embodiment of the present invention, the present invention accurately controls the movement of the metal material 14 through the feeding mechanism 15, which not only ensures that the molten end face of the metal material 14 is located within the electron beam bombardment range above the metal atomization plate 5, but also the metal material 14 does not completely block the emission path of the electron beam, so that part of the electron beam is emitted to the metal atomization plate 5, and the purpose of melting the metal and heating the metal atomization plate is achieved at the same time, ensuring the temperature required for melt atomization and powder making, which is conducive to promoting the sputtering of molten droplets to form metal micro-droplets 4, and is particularly suitable for the preparation of high melting point and even refractory metal powders; at the same time, it simplifies the structure of the electron beam melting-ultrasonic atomization powder making system.

[0072] According to a preferred embodiment of the present invention, the metal atomizing plate 5 is arranged directly below the electron gun 12, and the distance from the electron gun 12 is 500-1500mm. This distance can ensure that the electron beam has a good heating effect on the metal atomizing plate after being focused. If the distance is too large, the electron beam cannot be focused or the focusing radius is too large; if the distance is too small, the space for atomization operation is limited. According to a preferred embodiment of the present invention, the distance between the metal atomizing plate and the electron gun is 700mm.

[0073] According to a preferred embodiment of the present invention, the metal atomization plate 5 is made of the same material as the metal material 14, and does not require a crucible, thereby avoiding the introduction of pollutants and facilitating the acquisition of high-purity metal powder.

[0074] According to a preferred embodiment of the present invention, the metal atomization plate 5 is arranged horizontally.

[0075] It should be noted that the metal atomization plate 5 can be tilted, with its center position set on the central axis of the electron beam. The tilt angle of the metal atomization plate is adjustable in the range of 0°-60° to the left or right of the horizontal, so that the prepared powder can move in one direction, which is convenient for powder collection.

[0076] According to a preferred embodiment of the present invention, the distance between the horizontal metal material and the metal atomizing plate is 50-500 mm. If the distance is too large, the molten droplets will be overcooled and the atomization effect will be poor; if the distance is too small, the metal atomizing plate will be overheated and melted, affecting the yield of the metal powder. According to a preferred embodiment of the present invention, the distance between the horizontal metal material and the metal atomizing plate is 100 mm.

[0077] The present invention also provides a method for preparing metal powder by electron beam melting-ultrasonic atomization, combining Figure 2 The flow chart shown in the figure adopts the aforementioned electron beam melting-ultrasonic atomization powder making system of the present invention, and the method includes:

[0078] (1) Pre-treating the metal material to obtain a clean metal material to be treated;

[0079] (2) Under vacuum conditions, the metal material to be processed is electron beam melted to obtain metal droplets;

[0080] (3) ultrasonically atomizing the metal molten droplets to form atomized metal micro-droplets;

[0081] (4) The atomized metal droplets are cooled and solidified during movement, and then collected to obtain metal powder.

[0082] The preparation method of the present invention melts the metal material by electron beam and heats the metal atomizing plate. Under the action of ultrasonic wave, the molten droplets dripping onto the metal atomizing plate are sputtered to form droplets, and the metal powder is obtained after cooling and solidification. The powder is prepared under high vacuum conditions to avoid the introduction of the medium and promote the removal of impurities, which is conducive to obtaining low-oxygen ultra-pure powder. The energy density of the electron beam is high, and the preparation of high-melting-point metal powder is successfully achieved from two aspects of melting the metal and providing a heat source for heating the atomizing plate, and the equipment structure is simple. Ultrasonic atomization makes the metal powder have high sphericity, controllable particle size and few defects, and is particularly suitable for the preparation of ultra-pure powders of refractory metals (such as W, Mo, Ta) and active metals (such as Ti, Nb, Co, V).

[0083] In some embodiments of the present invention, the pretreatment described in step (1) includes: checking the surface state of the material, cleaning the surface when there are contaminants on the surface, confirming that the surface is clean and free of contamination, and keeping the metal raw material in a dry state.

[0084] In order to ensure that ultra-pure metal powder is obtained later, raw materials with higher purity are selected in step (1) as much as possible; for example, the purity of the selected metal raw material can be 3N to 5N level (excluding gas impurity content).

[0085] In some embodiments of the present invention, step (2) is to electron beam melt the metal material to be processed under vacuum. Specifically, step (2) includes:

[0086] S1: Clean the contaminants in the electron beam melting furnace body and furnace wall to avoid the introduction of foreign impurities during drip melting and ultrasonic atomization;

[0087] S2: Place the metal material 14 to be processed into the feeding mechanism, then close the silo door and the electron beam furnace door; start the cooling system and vacuum system, and after the diffusion pump 16 is preheated, pump the furnace body 2 and the gun body to the target vacuum state (vacuum degree 1×10 -3 ~8×10 -3 Pa), then start the electron gun 12 to preheat the equipment;

[0088] S3: After preheating is completed, the power of the electron gun 12 is slowly increased, and the end of the metal material 14 and the metal atomization plate 5 are preheated by a large beam spot annular scanning method, and then the ultrasonic generator 9 is started to make the metal atomization plate 5 vibrate at a high frequency;

[0089] S4: Adjust the parameters of electron beam melting (beam spot radius and scanning radius, scanning frequency, scanning position, etc.) so that the top of the metal material 14 begins to melt to form molten droplets, which drip onto the surface of the metal atomization plate 5 under the action of gravity.

[0090] In steps S3 and S4, the use of large beam spot annular scanning can improve the uniformity of heating.

[0091] In step S2, the metal material 14 is placed in the feeding mechanism 15, and the end surface of the metal material to be melted is located within the electron beam bombardment range above the metal atomizing plate.

[0092] According to some preferred embodiments of the present invention, in step (3), a suitable frequency of the ultrasonic generator 9 is selected within the range of 5 to 80 kHz (preferably 30-80 kHz), and reasonable electron beam melting parameters are combined so that the molten droplets dripping onto the atomizing plate are broken up and sputtered by high-frequency vibrations to produce atomized metal micro-droplets 4.

[0093] According to some preferred embodiments of the present invention, in step (4), the atomized micro-droplets 4 solidify after cooling to form metal spherical powder, and fall into the powder collection device below under the action of gravity. In order to enable the atomized micro-droplets after sputtering to be quickly cooled, the temperature of the inner wall of the furnace body is maintained below 40°C. If the temperature is too high, the droplet cooling speed will be slow, affecting the powder making efficiency. According to a preferred embodiment of the present invention, the temperature of the water flowing out of the outlet of the cold water pipe is 32°C.

[0094] According to some preferred embodiments of the present invention, the preparation method of the present invention further comprises the following steps:

[0095] (5) starting the feeding mechanism 15 to allow the metal material 14 to move slowly horizontally, and the powder preparation process is continued by regulating the feeding, electron beam melting, and ultrasonic atomization parameters;

[0096] (6) When the horizontal feeding mechanism reaches the maximum stroke, the electron gun power is reduced to 0 kW, the ultrasonic generator 9 is paused, and then the standby feeding mechanism is started;

[0097] (7) Repeat S3 to step (5) in step (2);

[0098] (8) When all the raw materials have been pulverized, the power of the electron gun 12 is reduced to 0 kW, and the ultrasonic generator 9 is paused, and then the electron gun 12 is turned off to allow the metal powder 11 to be fully cooled in the powder collecting tank 10;

[0099] (9) After the metal powder 11 is completely cooled, the gate valve 19 is inserted to complete the vacuum sealing of the powder collecting tank 10. After the electron beam equipment is completely cooled, the electron beam melting equipment is turned off; the powder collecting tank 10 is transferred to the powder screening equipment, and the powder is screened to obtain ultra-pure low-oxygen metal powder.

[0100] Different from the prior art, the raw materials of the present invention are metal rods or strips, which are easy to obtain and conducive to industrial promotion; the preparation of metal powder with a melting point range of 200-3500°C is achieved by adjusting the electron beam power within a certain range, and a wide variety of materials are suitable; and a single heat source system is used to effectively simplify the system structure and reduce production costs. The electron beam power range of the present invention is 5-500kW. According to a preferred embodiment of the present invention, the electron beam power for preparing metal titanium powder is 20kW, and the morphology and flow rate of the metal material droplet are optimized by adjusting the electron beam spot radius, scanning frequency, scanning distance, etc.

[0101] In order to avoid the introduction of impurity gases and to more effectively remove volatile impurities and gas impurities (such as O, N, etc.) in the metal, the vacuum state in the powder making process of the present invention is 1×10 -3 -8×10 -3 Pa, which is conducive to obtaining low-oxygen ultra-pure powder; according to a preferred embodiment of the present invention, the vacuum state during the powder making process is 5×10 -3 Pa.

[0102] Different from the prior art, the entire powder making process of the present invention does not require the introduction of high-purity argon or other media, which is not only conducive to improving the purity of the powder, but also effectively simplifies the system structure and reduces production costs.

[0103] In order to ensure that the molten end surface of the metal material is always within the bombardment range of the electron beam, and according to the actual preparation needs of the metal powder, the metal material does not completely block the emission path of the electron beam, so that part of the electron beam bombards the metal atomization plate, and the purpose of melting the metal and heating the metal atomization plate is achieved at the same time, the speed of the metal material movement described in the present invention is 5-50mm / min, which not only ensures the melting temperature of the metal material, but also ensures the temperature required for molten droplet atomization powder making, which is conducive to promoting the sputtering of molten droplets to form metal micro droplets, and is particularly suitable for the preparation of high melting point and even refractory metal powders; at the same time, the structure of the electron beam melting-ultrasonic atomization powder making system is simplified; and the melting speed of the metal rod and the falling time of the molten droplet are adjusted in combination with the relevant parameters of the electron beam, thereby controlling the particle size and quality of the obtained powder.

[0104] In order to ensure the smelting efficiency of the metal material and simplify the process steps, the diameter of the metal rod is 30-100 mm and the length is 200-2000 mm.

[0105] Example 1

[0106] like Figure 1 As shown, an electron beam melting-ultrasonic atomization powder making system of this embodiment includes a furnace body, an electron beam system, a vacuum system, a cooling system, an ultrasonic powder making system and a powder collecting system.

[0107] The electron beam system emits electron beams to melt metal materials 14 to form metal droplets, and various low-melting-point and high-melting-point metal powders can be prepared by adjusting the power of the electron beam 13. For example, by adjusting the power of the electron beam within the range of 5-500kW, metal bars with a melting point of 200-3500°C can be melted.

[0108] like Figure 1 As shown, the vacuum system includes an electron gun vacuum system and a furnace vacuum system, which are used to provide a vacuum environment (vacuum degree is 1×10 -3 -8×10 -3 Pa), avoid powder contamination caused by the introduction of the medium, and promote the degassing and impurity removal of the melt to obtain low-oxygen ultra-pure powder; wherein the electron gun vacuum system includes a molecular pump 1 and a first mechanical pump 3-1; the furnace body vacuum system includes a diffusion pump 16, a second-stage Roots pump 17, a first-stage Roots pump 18 and a second mechanical pump 3-2.

[0109] like Figure 1 As shown, the ultrasonic powder making system includes a metal atomizing plate 5, an ultrasonic generating device and a feeding mechanism 15, wherein the feeding mechanism 15 is used to provide a metal material 14 so that the molten end surface of the metal material 14 is located within the electron beam bombardment range above the metal atomizing plate 5, and the metal material 14 does not completely block the emission path of the electron beam 13, so that part of the electron beam bombards the metal atomizing plate 5 to ensure that the metal atomizing plate 5 has a higher temperature; the ultrasonic generating device is arranged below the metal atomizing plate 5, including an ultrasonic generator 9, a horn 6 and an ultrasonic transducer 7, which is used to atomize the metal molten droplets to form metal micro-droplets 4; wherein the metal atomizing plate 5 has the same material as the metal material 14 to reduce the introduction of pollutants; the distance between the electron gun 12 and the metal atomizing plate 5 is 700 mm, and the distance between the metal material and the metal atomizing plate is 100 mm.

[0110] The inner wall of the furnace body 2 is provided with a cooling system, and the inner wall of the furnace body is kept at a relatively low temperature (less than 40° C.) through a circulating water cooling system, which is conducive to rapid cooling of the powder; the circulating water cooling system in the prior art can be used.

[0111] The lower end of the furnace body 2 is designed as a cone structure, and the lower part of the cone is connected to the powder collecting system. A gate valve 19 is provided at the connection to vacuum seal the powder collecting tank 10 after the preparation of the metal powder 11 is completed to avoid oxidation of the metal powder 11 and the introduction of impurities.

[0112] The metal material 14 is driven by the feeding mechanism 15 to move so that the melting end face is within the bombardment range of the electron beam, and the melted molten liquid falls onto the metal atomizing plate 5. Under the action of the ultrasonic generator, the dripping metal droplets are crushed by the ultrasonic wave and sputtered out to produce atomized micro-droplets 4. The atomized micro-droplets 4 cool down and solidify to form metal particles during the movement, and further cool down after contacting the side wall of the furnace body 2, and fall into the powder collecting system connected to the lower end face of the furnace body 2 for collection; by adjusting the frequency of ultrasonic atomization, the power of the electron beam, the powder making speed, etc., different working states are used to adjust the sphericity and particle size of the obtained metal powder, and reduce the defects of the metal powder, including hollow powder and satellite powder defects. For example, the frequency of ultrasonic atomization is set to 30-80kHz.

[0113] Example 2

[0114] like Figure 2 As shown in the flow chart, this embodiment is a method for preparing metal Ti powder using an electron beam melting-ultrasonic atomization powder making system, comprising:

[0115] (1) Pretreatment of metal materials: The raw material used in the present invention is metal Ti, which is in the shape of a rod, with a diameter of 50 mm, a length of 1500 mm, and a purity of 4N; the surface state of the rod is checked, the surface is cleaned, and it is confirmed that the surface is clean and free of pollution, and the rod is dried at 30°C;

[0116] Clean the contaminants on the inner wall of the furnace to avoid the introduction of foreign impurities during the powder making process, and then load the prepared metal bars into the feeding mechanism;

[0117] Start the circulating water cooling system and electron beam melting equipment, and use the vacuum system to reduce the pressure inside the furnace to 5×10 -3 Pa, ensure that the temperature of the water flowing out from the cooling water outlet is below 40°C;

[0118] (2) adjusting the position of the metal rod in the feeding mechanism so that the end surface of the metal material to be melted is located within the bombardment range of the electron beam and above the metal atomizing plate;

[0119] (3) Start the electron gun with an electron beam power of 5 kW to preheat the end of the rod and the metal atomization plate so that the end of the rod becomes red hot under the action of the electron beam; start the ultrasonic generator with an ultrasonic frequency of 40 kHz to cause high-frequency vibration of the metal atomization plate;

[0120] (4) Adjust the electron beam power to 20 kW so that the top of the bar begins to melt and form molten droplets, which drip onto the surface of the metal atomization plate under the action of gravity;

[0121] (5) The molten droplets on the surface of the metal atomizing plate are broken up and sputtered by high-frequency vibration, producing atomized metal micro-droplets. The atomized micro-droplets cool and solidify to form metal spherical powders, which fall into the powder collecting system below;

[0122] The feeding mechanism is started to make the metal bar move slowly horizontally at a speed of 20 mm / min, so that the powder preparation process continues;

[0123] (6) When the horizontal feeding mechanism reaches the maximum stroke, reduce the electron gun power to 0 kW and pause the ultrasonic generator; then start the standby feeding mechanism, slowly increase the electron gun power, and use a large beam spot circular scanning method to preheat the end of the rod and the metal atomization plate; start the ultrasonic generator to make the metal atomization plate vibrate at high frequency;

[0124] (7) Repeat steps (4) to (6). When all the raw material rods are pulverized, reduce the electron gun power to 0 kW, pause the ultrasonic generator, and then turn off the electron gun to allow the powder to fully cool in the powder collection tank; insert the gate valve to complete the vacuum sealing of the powder tank, and turn off the electron beam melting equipment after the electron beam equipment has cooled down.

[0125] The obtained powder was passed through a 100-mesh sieve to obtain the target segment powder; after testing, the D50 of the obtained powder was 45-50 μm, the particle size distribution range was narrow, the powder with a particle size of less than 75 μm accounted for more than 60%, the sphericity was greater than 0.95, and the oxygen content was 260 ppm.

[0126] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. An electron beam melting-ultrasonic atomization powder making system, characterized in that: The system comprises: Furnace body (2); An electron beam system comprises an electron gun (12) for generating and emitting an electron beam (13) to melt a metal material (14) to form metal droplets and to heat a metal atomizing plate (5); A vacuum system, comprising an electron gun vacuum system and a furnace vacuum system, which are used to provide a vacuum environment for the electron beam (13) to generate and a vacuum environment for the electron beam (13) to use, respectively; An ultrasonic powder making system, used for atomizing the metal molten droplets to form metal micro droplets (4); A cooling system, used for cooling the furnace body (2), the horn (6) and the metal powder (11); A powder collecting system for collecting the produced metal powder (11); The electron beam system is arranged above the furnace body (2); the ultrasonic powder making system is arranged inside the furnace body (2); the electron gun vacuum system is connected to the electron beam system, the furnace body vacuum system is arranged on the furnace body (2), the cooling system is arranged on the inner wall of the furnace body (2), around the amplitude transformer (6), and the side wall and bottom of the powder collecting tank (10); the powder collecting system is arranged below the furnace body (2).

2. The system according to claim 1, characterized in that The electron gun vacuum system comprises a molecular pump (1) and a first mechanical pump (3-1); The furnace vacuum system comprises a diffusion pump (16), a secondary Roots pump (17), a primary Roots pump (18) and a second mechanical pump (3-2).

3. The system according to claim 1, characterized in that The ultrasonic powder making system comprises a metal atomizing plate (5), an ultrasonic generating device and a feeding mechanism (15). The feeding mechanism (15) is used for feeding materials so that the melting end surface of the metal material (14) is located above the metal atomizing plate (5). The ultrasonic generating device is provided below the metal atomizing plate (5).

4. The system according to claim 3, characterized in that The metal material (14) does not completely block the emission path of the electron beam (13), so that the electron beam (13) acts on the metal atomization plate (5) at the same time.

5. The system according to claim 1, characterized in that The metal atomizing plate (5) has the same material as the metal material (14).

6. The system according to claim 1, characterized in that The distance between the electron gun (12) and the metal atomization plate (5) is adjustable within the range of 500-1500 mm.

7. The system according to claim 1, characterized in that The distance between the metal material (14) and the metal atomizing plate (5) is adjustable within the range of 50-500 mm.

8. A method for preparing metal powder using the electron beam melting-ultrasonic atomization powder making system according to any one of claims 1 to 7, characterized in that: The method comprises: (1) Pre-treating the metal material to obtain a clean metal material to be treated; (2) Under vacuum conditions, the metal material to be processed is electron beam melted to obtain metal droplets; (3) ultrasonically atomizing the metal molten droplets to form atomized metal micro-droplets; (4) The atomized metal droplets are cooled and solidified during movement, and then collected to obtain metal powder.

9. The method according to claim 8, characterized in that In step (2), the pressure of the vacuum state is 1×10 -3 -8×10 -3 Pa.

10. The method according to claim 8, characterized in that The method further comprises cooling the collected metal powder.

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