A method for preparing superfine powder by taking a strip as a pulse discharge electrode and a device thereof

Abstract

The application provides a method for preparing superfine powder by taking a strip as a pulse discharge electrode and a device thereof. The device specifically comprises a pulse power generator, a first electrode, a second electrode, an electrode driving assembly and a discharge medium; the first electrode is a strip-shaped consumable electrode, the second electrode is a consumable electrode or a non-consumable electrode, and the two are driven and connected through the electrode driving assembly to form a powder preparation space. The application takes a metal strip or an alloy strip as a discharge electrode, stably feeds the strip through an assembly, and realizes continuous preparation of powder. Since there is no recast layer of repeated melting and solidification in the process of preparing powder by the strip pulse discharge, all the powder is formed, and thus the energy utilization rate, the powder yield and the production efficiency are greatly improved. Compared with a bulk electrode, the composition of the strip is more uniform, so that the powder with uniform composition can be prepared. The superfine metal powder obtained by the application has high sphericity, uniform shape, smooth surface, no obvious satellite powder, irregular powder and inclusions.

Description

Technical Field

[0001] This invention belongs to the field of metal powder materials technology, specifically relating to a method and apparatus for preparing ultrafine powders using strip as a pulse discharge electrode. Background Technology

[0002] With the continuous development of industrial technology, the demand for metal powder materials is increasing. Currently, the main methods for preparing metal powder materials are mechanical methods, physical methods, and physicochemical methods. However, these methods limit the particle size and make it difficult to prepare powders with arbitrary particle sizes in the range of 1 to 100 micrometers. In particular, it is very difficult to prepare ultrafine spherical powders with a particle size of less than 10 micrometers.

[0003] Pulse discharge machining (PDM) is a processing technique that utilizes electrical energy. During PDM, the tool and workpiece do not contact each other; instead, pulsed sparks are continuously generated between them. The localized, instantaneous high temperatures generated during the discharge gradually erode away the metal material. This method can be used to prepare conductive materials such as aluminum alloys, copper alloys, stainless steel, nickel-based superalloys, iron-based amorphous alloys, and silicon. During PDM, the etched material cools and solidifies in the discharge medium, eventually forming fine powder due to surface tension. The powders prepared by PDM exhibit good sphericity and few or no satellite particles, promoting its widespread application and rapid development in the field of powder material preparation.

[0004] In existing technologies, pulse discharge methods for preparing powder mainly fall into two categories: rod-shaped devices and oscillating drum devices. However, rod-shaped electrodes have low powder preparation efficiency, approximately 1 g / h, which cannot meet the needs of industrial production and is generally used for experimental research. Oscillating drum devices can improve production efficiency by increasing the simultaneous discharge point, but the wide particle size distribution and low proportion of ultrafine powder also make it difficult to meet the requirements. Furthermore, the above-mentioned devices have several problems during powder preparation. For example, when using bulk metal as the pulse discharge electrode, more than 50% of the molten metal repeatedly melts and solidifies to form a recast layer instead of powder, resulting in significant energy loss. Also, the discharge electrode material is bulk, and the grain / grain boundary sizes within the bulk are generally larger than the ultrafine powder particle size, leading to uneven composition of the prepared ultrafine powder.

[0005] Therefore, how to improve the energy utilization rate in the powder making process and achieve the uniformity of composition of ultrafine powder through continuous powder making is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a method for continuously preparing ultrafine metal powder. By setting up a pulse power generator outside a cavity, and a first electrode, a second electrode, an electrode driving assembly, and a discharge medium inside the cavity, ultrafine spherical metal powder can be continuously prepared. This method features simple equipment, safe preparation, and low energy consumption. The ultrafine metal powder prepared by this device has high sphericity, uniform shape, smooth surface, and a particle size range of 0.5-30 μm, with a high powder preparation efficiency of 80 g / h.

[0007] To achieve the above objectives, the present invention provides an apparatus for continuously preparing ultrafine powder using strip material as a pulse discharge electrode, comprising a pulse power generator disposed outside a cavity, and a first electrode, a second electrode, an electrode driving assembly, and a discharge medium disposed inside the cavity; the first electrode is a consumable electrode, and the second electrode is either a consumable electrode or a non-consumable electrode, both of which are connected to the pulse power generator; the electrode driving assembly is driven to the first electrode and / or the second electrode to form a powder-making space between the first electrode and the second electrode; the discharge medium is filled in the powder-making space, and the consumable electrode is subjected to pulsed plasma generated by the pulse power generator to form ultrafine metal powder.

[0008] In a preferred embodiment, the first electrode is a consumable electrode, and the second electrode is either a consumable electrode or a non-consumable electrode. The materials of the two electrodes can be the same or different. When the second electrode is a consumable electrode, in order to ensure the purity of the metal powder, the materials of the first electrode and the second electrode are preferably the same.

[0009] In a preferred embodiment, the first electrode and the second electrode are connected to the pulse power generator. Specifically, the first electrode and the second electrode can be directly connected to the two stages of the pulse power generator, or they can be connected to the pulse power generator via an electrode driving assembly. When connected, the first electrode can be connected to the power anode and the second electrode can be connected to the power cathode, or the first electrode can be connected to the power cathode and the second electrode can be connected to the power anode.

[0010] In a preferred embodiment, the driving mode of the electrode driving assembly includes: feeding, horizontal rotation, vibration, or reciprocating translation; when the driving mode is feeding, the feeding speed of the electrode is 0.01-1 m / min; when the driving mode is vibration, the vibration frequency of the electrode is 50-1000 Hz, and the amplitude is 0.1-3 mm; when the driving mode is horizontal rotation, the rotational speed of the electrode is 1-1000 r / s; when the driving mode is reciprocating translation, the translational speed of the electrode is 0.1-1 m / min.

[0011] In a preferred embodiment, the first electrode is strip-shaped, and the second electrode is rod-shaped or block-shaped.

[0012] In a preferred embodiment, the first electrode is made of strip metal or strip alloy, and the second electrode is made of rod-shaped or block-shaped conductive material.

[0013] During their long-term research on pulsed discharge powder production, the inventors discovered that when rod-shaped or block-shaped electrodes melt, the molten metal pool is surrounded by an unmelted solid alloy. Due to the liquid-solid interface constraint, most of the liquid metal cannot splash out of the molten pool to form powder, but instead forms a remelted area. Based on this technical problem, the inventors, by changing the electrode shape and corresponding driving method, selected a strip electrode—a previously unparalleled consumable electrode—from among many electrode shapes. Compared to other electrode shapes, the molten pool of the strip electrode can cover the entire thickness of the strip material. When the molten metal splashes, it is not constrained by the surrounding liquid-solid interface, and almost all of it splashes out of the molten pool to form spherical powder, thus further increasing powder production efficiency. Moreover, the relatively thin strip electrode can be rolled up first and continuously conveyed from the roll during pulsed discharge powder production. Therefore, there is no specific limitation on the length of the strip electrode, thereby achieving the technical effect of continuous preparation of ultrafine metal powder, further improving production efficiency and capacity.

[0014] In a preferred embodiment, the strip electrode has the following dimensions: width 1-200 mm, thickness 10-100 μm; the rod electrode has the following dimensions: diameter 1-100 mm; and the block electrode has the following dimensions: length 1-100 mm, width 1-50 mm, thickness 1-10 mm.

[0015] More preferably, the strip electrode has the following dimensions: width 1-100mm, thickness 10-50μm; the rod electrode has the following dimensions: diameter 40-60mm; and the block electrode has the following dimensions: length 10-50mm, width 10-50mm, thickness 2-8mm.

[0016] In a preferred embodiment, the movement of the first and second electrodes after being driven by the electrode driving assembly includes: the motor driving assembly driving the first electrode to move in one manner while the second electrode moves in another manner, or the electrode driving assembly driving the first electrode to move in two or more manners simultaneously, while the second electrode remains stationary. For example, in one embodiment, the electrode driving assembly drives the first electrode to rotate horizontally while the second electrode is fed. In another embodiment, the electrode driving assembly drives the first electrode to rotate horizontally while feeding, and the second electrode remains stationary. Verification has shown that the above driving methods can achieve the technical effect of highly efficient powder production.

[0017] In a preferred embodiment, when the electrode driving assembly drives the formation of a powder-making space between the first electrode and the second electrode, the distance between the two electrodes is 0-3 mm.

[0018] In a preferred embodiment, the discharge medium is filled in the powder-making space. Specifically, the discharge medium can be filled from outside the electrode, or the first electrode and / or the second electrode can be made hollow and the discharge medium can be filled from inside the electrode; as long as the gap area between the first electrode and the second electrode is filled with the discharge medium.

[0019] In a preferred embodiment, the discharge medium can be kept flowing or kept stationary. Preferably, the discharge medium flow rate is 0-1 m / s, and more preferably, the discharge medium flow rate is 0.1 m / s.

[0020] In a preferred embodiment, the discharge medium comprises a liquid and / or a gas, wherein the liquid and gas are specifically in the form of a water mist; preferably, the discharge medium is distilled water and / or an inert gas; more preferably, the discharge medium is kerosene.

[0021] Another objective of this invention is to provide a method for mass-producing ultrafine metal powders using the aforementioned apparatus. By adjusting the pulse power supply parameters, ultrafine metal powders with different particle size distributions can be continuously and batch-produced. This method offers advantages such as simple processing, high controllability, and suitability for large-scale industrial production.

[0022] To achieve the above objectives, the present invention provides a method for mass-producing ultrafine metal powder using the above-mentioned device, comprising the following steps: after setting the pulse power supply parameters, the first electrode and / or the second electrode are driven to move using the electrode driving component; the pulsed plasma generated by the pulse power supply generator bombards the surface of the consumable electrode, causing the consumable electrode to melt and form a molten pool; simultaneously, the pulse voltage applied to the electrode breaks down the discharge medium between the electrodes; the physical explosion caused at the discharge point by the sudden increase in inter-electrode pressure and temperature causes the molten metal droplets of the consumable electrode to be ejected from the molten pool; subsequently, the metal droplets cool and solidify in the discharge medium, forming spherical powder under the action of surface tension.

[0023] In a preferred embodiment, the pulse power supply parameters are: frequency: 500-10000000Hz; discharge current: 0.1-1000A; pulse width: 0.1μs-50μs; preferably, the pulse power supply parameters are: frequency: 500Hz, 600Hz, 700Hz, 800Hz, 900Hz, 1000Hz; discharge current: 100A, 150A, 200A, 400A; pulse width: 20μs, 30μs, 40μs. Powders with different particle size distributions can be prepared by adjusting the discharge current. Under the same conditions, as the current increases, the powder particle size also increases. For example, a current of 100A yields powder with an average particle size of 9.6μm, while a current of 200A yields powder with an average particle size of 28μm.

[0024] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0025] 1. In this invention, the movement between the electrodes allows the pulsed plasma generated by the pulsed power supply to bombard the electrodes, melting the metal on the surface of the consumable electrode. Simultaneously, the impact force generated when the discharge medium breaks down causes a physical explosion in the molten area, completely ejecting the molten metal droplets from the strip-shaped consumable electrode from the molten pool without forming a recast layer. Furthermore, the stable powder-making space formed between the two ends of the strip-shaped first electrode and the second electrode, under the action of the tape-feeding assembly, allows the metal droplets to be continuously ejected and broken, continuously producing spherical powder.

[0026] 2. The equipment used in this invention has a simple structure, is safe to use, and requires low energy consumption. Only the pulse power supply parameters need to be adjusted to continuously and in batches prepare ultrafine metal powders with different particle size distributions. It offers strong controllability and is suitable for large-scale industrial production.

[0027] 3. The ultrafine metal powder obtained by the preparation method of the present invention has high sphericity, uniform shape, smooth surface, and particle size range of 0.5-30μm. It also has high powdering efficiency, reaching 80g / h. Attached Figure Description

[0028] These and / or other aspects and advantages of the present invention will become clearer and more readily understood from the following detailed description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:

[0029] Figure 1 This is a schematic diagram of the apparatus for mass production of ultrafine metal powder according to Embodiment 1 of the present invention;

[0030] Figure 2 This is a SEM image of the metal strip after powder preparation in Example 1 of the present invention;

[0031] Figure 3 This is a SEM image of the metal powder prepared in Example 1 of the present invention;

[0032] Figure 4 This is a particle size distribution diagram of the metal powder prepared in Example 1 of the present invention;

[0033] Figure 5 This is a SEM image of the metal strip after powder preparation in Example 2 of the present invention;

[0034] Figure 6 This is a SEM image of the metal powder prepared in Example 2 of the present invention;

[0035] Figure 7 This is a particle size distribution diagram of the metal powder prepared in Example 2 of the present invention.

[0036] Explanation of key figure labels:

[0037] 1-First electrode, 2-Second electrode, 3-Metal particle, 4-Discharge medium, 5-Pulse power generator, 6-Cavity, 7-Electrode drive assembly. Detailed Implementation

[0038] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. However, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0039] This invention provides a method and apparatus for preparing ultrafine powder using strip material as a pulse discharge electrode, which solves the problems of low powder preparation efficiency, high energy loss, and poor powder composition uniformity in the prior art.

[0040] This invention is the first to use metal or alloy strips as discharge electrodes, achieving continuous powder preparation through stable strip feeding via a component. Because the metal or alloy strips do not undergo repeated melting and solidification during pulse discharge powder preparation, but instead form entirely powder, energy utilization, powder yield, and production efficiency are significantly improved. Furthermore, compared to bulk electrodes, the strip material has a more uniform composition, thus enabling the preparation of powders with homogeneous composition. This invention allows for the control of powder particle size range by altering the pulse power supply parameters, enabling the preparation of various ultrafine metal powders without significant satellite powders, irregularly shaped powders, or inclusions.

[0041] Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art, and the raw materials used are all commercially available products.

[0042] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0043] Example 1:

[0044] A strip of FeSi alloy with a thickness of 100 μm and a width of 100 mm is selected as the first electrode (1), which is connected to the negative terminal of the pulse power generator through an electrode driving assembly. A block of FeSi alloy with a length, width, and thickness of 50 mm × 10 mm × 2 mm is selected as the second electrode (2), which is connected to the positive terminal of the pulse power generator through another electrode driving assembly. The gap between the first electrode and the second electrode is filled with kerosene as the discharge medium (4), and the discharge medium flow rate is 0.1 m / s. The first electrode, the second electrode, the discharge medium, and the electrode driving assembly are arranged inside the cavity, and the pulse power generator is arranged outside the cavity.

[0045] Control power supply parameters: Frequency 500Hz, Current 150A, Pulse width 30μs.

[0046] After the power is turned on, the electrode driving assembly (7) drives the second electrode to feed at 1 m / min, while the first electrode moves horizontally and repeatedly at 0.5 m / min, so that the distance between the two electrodes is 1 mm. As the first electrode moves horizontally, a motion is generated between the electrodes. The pulse voltage applied to the electrodes breaks down the discharge medium (4) and generates a spark. At the same time, the pulse plasma generated by the pulse power supply bombards the electrodes, causing the metal on the surface of the two electrodes to melt. When the pressure and temperature between the electrodes increase sharply, the physical explosion at the discharge point throws out the liquid metal particles (3) formed after melting. Subsequently, the metal particles (3) cool and solidify in the discharge medium (4) and form spherical powder under the action of surface tension. The SEM of the prepared spherical metal powder is shown in Figure 1. Figure 3 As shown in the figure, the metal powder has high sphericity, uniform shape, and smooth surface.

[0047] After processing for 1 hour, the first and second electrodes were weighed and found to have decreased in weight by 16.6 g and 15.5 g respectively, indicating a processing efficiency of 32.1 g / h. The resulting spherical metal powder had a particle size range of 0.5-28 μm, and its particle size distribution is shown in the figure. Figure 4 As shown.

[0048] Example 2:

[0049] A 25μm thick, 100mm wide strip of Fe-based amorphous alloy is selected as the first electrode, connected to the negative terminal of the pulse power generator via an electrode driving assembly. A 100mm long, 50mm diameter non-consumable cylindrical graphite electrode is selected as the second electrode, connected to the positive terminal of the pulse power generator via another electrode driving assembly. Distilled water is introduced from outside the electrodes, filling the gap between the first and second electrodes with distilled water as the discharge medium, which remains stationary. The first electrode, second electrode, discharge medium, and electrode driving assembly are arranged inside the cavity, while the pulse power generator is arranged outside the cavity.

[0050] Control power supply parameters: Frequency 100000Hz, Current 15A, Pulse width 4μs.

[0051] After power is turned on, the electrode driving assembly drives the first electrode to feed the strip to the non-consumable graphite electrode at a feed rate of 1 m / min. The distance between the two electrodes is 1 mm. Simultaneously, the electrode driving assembly drives the second electrode to rotate horizontally at 1000 r / s, causing motion between the electrodes. The pulsed voltage applied to the electrodes breaks down the discharge medium, generating sparks. At the same time, the pulsed plasma generated by the pulsed power supply bombards the electrodes, causing the metal on the surface of the two electrodes to melt. The physical explosion caused at the discharge point by the sudden increase in inter-electrode pressure and temperature ejects the molten liquid metal particles. Subsequently, the metal particles cool and solidify in the discharge medium, forming spherical powder under the action of surface tension. The SEM image of the prepared spherical metal powder is shown below.Figure 6 As shown in the figure, the metal powder has high sphericity, uniform shape, and smooth surface.

[0052] After processing for 1 hour, the first and second electrodes were weighed and found to have decreased in weight by 80 g and 0.01 g respectively, indicating a processing efficiency of 80 g / h. The resulting spherical metal powder had a particle size range of 0.5-13 μm, and its particle size distribution is shown in the figure. Figure 7 As shown.

[0053] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A device for continuous preparation of ultrafine powder using a strip pulse discharge electrode, characterized in that, It includes a pulse power generator disposed outside the cavity, and a first electrode, a second electrode, an electrode driving assembly, and a discharge medium disposed inside the cavity; the first electrode is a consumable electrode, and the second electrode is either a consumable electrode or a non-consumable electrode, both of which are connected to the pulse power generator; the electrode driving assembly is driven to the first electrode and / or the second electrode to form a powder-making space between the first electrode and the second electrode. The powder-making space is filled with the discharge medium, and the consumable electrode is subjected to pulsed plasma generated by the pulse power generator to form ultrafine metal powder. The first electrode is made of strip metal or strip alloy, and the second electrode is made of rod-shaped or block-shaped conductive material. The dimensions of the strip-shaped first electrode are: width 1-200mm, thickness 10-100μm; the dimensions of the rod-shaped second electrode are: diameter 1-100mm; the dimensions of the block-shaped second electrode are: length 1-100mm, width 1-50mm, thickness 1-10mm. When the electrode driving assembly drives the first electrode and the second electrode to form a powder-making space, the distance between the two electrodes is 0-3mm. The pulse power supply parameters are: frequency: 500-10,000,000 Hz; discharge current: 0.1-1000 A; pulse width: 0.1 μs-50 μs; The device utilizes the motion between the electrodes to bombard them with pulsed plasma generated by a pulsed power supply. The surface metal of the consumable electrode is melted. At the same time, the impact force generated when the discharge medium breaks down causes a physical explosion in the molten area. The molten metal droplets of the strip consumable electrode are completely ejected from the molten pool without forming a recast layer.

2. The apparatus for continuous preparation of ultrafine powder using a strip pulse discharge electrode as described in claim 1, characterized in that, The driving modes of the electrode driving assembly include: feeding, horizontal rotation, vibration, or reciprocating translation.

3. The apparatus for continuous preparation of ultrafine powder using a strip pulse discharge electrode as described in claim 1, characterized in that, The discharge medium includes liquid and / or gas.

4. A method for continuously preparing ultrafine powder using any one of the apparatuses described in claims 1-3, characterized in that, Includes the following steps: After setting the pulse power supply parameters, the first electrode and / or the second electrode are driven to move using the electrode drive component. The pulsed plasma generated by the pulse power supply generator bombards the surface of the consumable electrode, causing the consumable electrode to melt and form a molten pool. At the same time, the pulse voltage applied to the electrode breaks down the discharge medium between the electrodes. The physical explosion caused at the discharge point when the inter-electrode pressure and temperature of the electrode suddenly increase causes the molten metal droplets of the consumable electrode to be ejected from the molten pool. Subsequently, the metal droplets cool and solidify in the discharge medium and form spherical powder under the action of surface tension.

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