A centrifugal atomization device for ultrafine metal powder

Abstract

The present invention discloses a centrifugal atomization device for ultrafine metal powders, wherein a liquid storage tank is connected to a smelting furnace via a liquid discharge valve, and the smelting furnace and / or liquid storage tank are connected to a hot air system via an air supply pipe, and a liquid outlet pipe of the liquid storage tank penetrates the top surface of a spray tower and a nozzle is fixed at the lower end, and a plurality of nozzles inclined downward are evenly distributed on the nozzle; a circular ring is coaxially fixed to the top surface of an atomizing disk, and a plurality of vertical grooves are evenly distributed on the inner side wall of the circular ring, and the upper part of the groove penetrates the top surface of the circular ring and the lower part extends to the top surface of the atomizing disk; the atomizing disk is coaxially fixed to the motor shaft of an electric motor, and the electric motor is fixed to the inner wall of the spray tower via a motor bracket. The present invention arranges an inclined nozzle on the nozzle, which can reduce the erosion of the center position of the atomizing disk by the molten metal and improve the uniformity of the distribution of the molten metal; and arranges a groove on the circular ring of the atomizing disk, which can make the molten metal fly out in the form of filaments to reduce the particle size of the powder and improve the sphericity of the powder, and has the characteristics of compact structure, stable atomization process, high degree of spheroidization of the powder, and fine and uniform particle size of the powder.

Description

Technical Field

[0001] The invention relates to the technical field of new materials, and in particular to an ultrafine metal powder centrifugal atomization device with compact structure, stable atomization process, high powder spheroidization degree, fine and uniform powder particle size. Background Art

[0002] Ultrafine powders include tiny solid particles of metals, non-metals, organics, inorganics and organisms. There is no clear definition at present. In foreign countries, ultrafine powders are generally considered to be particles with a size less than 3μm, and in China, particles with a size less than 30μm are generally considered to be ultrafine powders, and are further subdivided into micron-level (1~30μm), submicron-level (1~0.1μm) and nanometer-level (0.001~0.1μm). As the particle size of ultrafine powder particles decreases, their surface electronic structure and crystal structure change, resulting in surface effects, small size effects, quantum effects and macroscopic quantum tunneling effects that bulk materials do not have, making their optical, magnetic, acoustic, electrical and mechanical properties very different from normal, so they are widely used in medicine, chemical industry, electronics, energy and building decoration.

[0003] Ultrafine powders are usually prepared by physical crushing (grinding, mechanical crushing, spraying, explosion, etc.) and chemical synthesis. The chemical synthesis method produces powders through chemical reactions or phase transformations, from ions, atoms, and molecules through nucleus formation and crystal growth. However, due to the complex production process, high cost, and low output, it is not widely used. The physical crushing method is to crush the material through the action of mechanical force. Compared with the chemical synthesis method, it has the advantages of low cost, simple process and high output, and has become the main method for preparing ultrafine powders. Centrifugal atomization is a commonly used method in physical powder making technology. Its main component is a disc that rotates at high speed around its own axis. The molten metal falling on the disc is broken into small droplets under the action of centrifugal force, and shrinks into powder particles in a protective atmosphere.

[0004] In the existing centrifugal atomization technology, centrifugal rotating disc atomizers are generally divided into three types in terms of structure: smooth disc, blade disc, and nozzle disc. Smooth discs are rarely used because the molten metal easily slips on the high-speed rotating flat disc surface, so their atomization capacity is average. The blade disc is designed to solve the problem of the smooth disc being easy to slip, and a blade-like grille is set on the flat disc surface; however, since the raised grille is easily worn, the atomization capacity is reduced, which shortens the effective service life of the atomizer disc. The nozzle disk is a flat atomizing disk formed by changing the rectangular outlet of the blade disk into a circular one, lining the nozzle with wear-resistant material, or providing a circular ring on the outer edge of the flat disk surface and circumferentially providing a number of penetrating nozzles on the circular ring; although the effective service life of the nozzle disk has been improved, its flat structure has not changed, and the molten metal flying away from the nozzle is dispersed and thrown down horizontally due to the centrifugal force and gravity. When the molten metal falls on the atomizing disk, it is dispersed into droplets of different sizes and performs centrifugal motion. The droplets move at different speeds and have long movement paths, and the heat dissipation is fast, resulting in the solidification speed of some droplets being much faster than the spheroidization speed. After cooling, the small droplets are entrained by the large droplets to the surface and then cooled to form satellite balls. Therefore, the prepared ultrafine powder is easy to agglomerate, the degree of spheroidization is not high, and there are many satellite balls, which seriously affects the quality of the atomized particles.

[0005] In addition, the existing centrifugal atomization method generally uses a DC nozzle to introduce the molten metal into the atomizing disk, but the center of the atomizing disk is easily eroded by the high-temperature molten metal ejected by the DC nozzle to form a small pit. The formation of the small pit in the atomizing disk not only affects the flow direction of the molten metal during rotation, but also forms tumor spots at the pit, thereby changing the quality of the atomizing disk, which is not conducive to the high-speed and stable operation of the atomizing disk. In addition, the existing atomizing disk is connected to the motor through a support, and the heat conduction of the molten metal on the atomizing disk will cause the support to overheat and deform. If the heat generated by the motor during high-speed rotation is not dissipated in time, the life of the motor will be greatly shortened, thereby reducing the reliability, stability and efficiency of the atomizing device. Summary of the invention

[0006] The object of the present invention is to provide a centrifugal atomization device for ultrafine metal powders which has a compact structure, a stable atomization process, a high degree of powder spheroidization, and fine and uniform powder particle size.

[0007] The present invention is implemented as follows: it includes a smelting furnace, a liquid storage tank, and a spray tower, wherein the upper part of the liquid storage tank is connected to the lower part of the smelting furnace through a drain valve, and the smelting furnace and / or the liquid storage tank are connected to the hot air supply system through an air supply pipe, and the liquid outlet pipe at the lower part of the liquid storage tank penetrates the top surface of the spray tower; a nozzle is fixedly arranged on the liquid outlet pipe extending from the liquid storage tank into the spray tower, and a plurality of nozzles with axes inclined downward are uniformly distributed in the circumferential direction at the lower part of the nozzle; an atomizing disk is arranged below the nozzle, and a circular ring is coaxially fixedly arranged on the top surface of the atomizing disk, and a plurality of inclined grooves are uniformly distributed in the circumferential direction on the inner side wall of the circular ring, and the upper part of the groove penetrates the top surface of the circular ring and the lower part extends to the top surface of the atomizing disk; the atomizing disk is coaxially fixedly connected to the motor shaft of the motor arranged below, and the motor is fixedly connected to the inner wall of the spray tower through a motor bracket;

[0008] The inner side wall of the circular ring is a cylindrical wall perpendicular to the top surface of the atomizing disk or a conical wall inclined outward; the groove includes inclined sections at the upper and middle parts and an arc-shaped transition section at the lower part, the generatrix angle α between the inclined section and the inner side wall of the circular ring is 30-60°, and the upper end of the arc-shaped transition section is tangent to the lower end of the inclined section;

[0009] The nozzle is a cylinder with an inverted cone at the bottom. The upper end of the nozzle is fixedly connected to the liquid outlet pipe of the liquid storage tank. The inverted cone is evenly distributed with multiple layers of nozzles in the circumferential direction.

[0010] The beneficial effects of the present invention are:

[0011] The present invention evenly distributes a number of inclined nozzles around the nozzle. When the molten metal is ejected from the nozzles to the high-speed rotating atomizing disk, the erosion of the center of the atomizing disk by the molten metal ejected from the existing direct current nozzle can be avoided. In addition, the ejected molten metal will automatically adjust the distribution range of the spray on the atomizing disk according to the hot air pressure in the smelting furnace and / or the liquid storage tank, so that the molten metal is sprayed in a ring shape on the disk surface of the atomizing disk to form an ultra-thin liquid film. Compared with the direct current nozzle, the distribution uniformity of the molten metal on the atomizing disk can be improved, thereby avoiding the problem of easy agglomeration of ultrafine powders caused by uneven distribution of the molten metal; the movement path of the molten metal on the atomizing disk can be shortened and the heat loss of the molten metal can be reduced, so as to solve the problem of low spheroidization degree and a large number of satellite spheres of ultrafine powders caused by rapid solidification of the molten metal on the existing atomizing disk, thereby improving the quality of the atomized powder, and the structure and control are also simpler.

[0012] The present invention evenly distributes a number of inclined nozzles around the nozzle. Compared with the existing split structure, the integrated structure can reduce the overall processing difficulty, thereby ensuring the accuracy of the angle, size, etc. of each nozzle, so that the molten metal sprayed by the nozzle on the atomizing disk is more evenly distributed; and since the nozzle of the integrated structure does not have the installation gap in the split structure, there will be no local leakage that causes uneven distribution of molten metal on the atomizing disk and blockage caused by local accumulation in the nozzle.

[0013] The present invention arranges a circular ring with a plurality of inclined grooves on the top surface of the atomizing disk, so that the molten metal enters the grooves under the action of centrifugal force and gravity, and then flies away from the atomizing disk in the form of parabolic filaments to be atomized, which can not only avoid the problem of the molten metal slipping on the surface of the atomizing disk, but also the groove structure can alleviate the problem of reduced atomization ability caused by wear of the molten metal. The groove structure can change the molten metal from the existing flat throwing to the upward throwing flying away from the atomizing disk, which not only can expand the atomization and dispersion effect of the molten metal to reduce the size of the droplets, but also the expanded atomization and dispersion effect of the molten metal can quickly cool the atomized metal droplets, which can avoid the problem of poor sphericity and rough surface caused by slow cooling of the molten metal droplets, thereby ensuring that the particle size of the atomized powder is fine and the sphericity of the atomized powder can be improved. In particular, the groove is divided into an inclined section and an arc-shaped transition section at the bottom. The arc-shaped transition section can ensure that the molten metal on the atomizing disk flows smoothly into the groove, thereby reducing the heat loss in the flow process of the molten metal, thereby avoiding the problem of low degree of spheroidization of ultrafine powder and a large number of satellite balls caused by the rapid solidification of the molten metal on the atomizing disk, further improving the quality of the atomized powder.

[0014] Although the groove on the circular ring on the top surface of the atomizing disk of the present invention extends the movement path of the molten metal compared to a flat atomizing disk, due to the cooperation of a nozzle with a plurality of nozzles arranged circumferentially, the molten metal sprayed on the surface of the atomizing disk forms a ring shape to compensate for the movement path of the molten metal extended by the groove. Thus, while ensuring the fine particle size and high degree of spheroidization of the powder brought by the groove and the uniform distribution of the molten metal brought by the nozzle with an inclined nozzle, it can also avoid the problem that the long movement path of the molten metal on the existing atomizing disk leads to rapid solidification, resulting in low degree of spheroidization of ultrafine powder and a large number of satellite balls.

[0015] The present invention further fixes heat dissipation ribs on the pillar connecting the atomizing disk and the motor shaft of the motor. The heat dissipation ribs can expand the heat dissipation capacity of the pillar, thereby preventing the pillar from overheating and deformation due to heat conduction of the metal liquid on the atomizing disk, and also allowing the heat generated by the high-speed rotation of the motor to be dissipated in time, thereby significantly improving the life of the motor and ensuring the smooth operation of the atomizing disk.

[0016] Therefore, the invention has the characteristics of compact structure, stable atomization process, high degree of powder spheroidization, and fine and uniform powder particle size. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the three-dimensional structure of the present invention;

[0018] Figure 2 It is a schematic diagram of the three-dimensional structure of the nozzle of the present invention;

[0019] Figure 3This is one of the three-dimensional structural schematic diagrams of the atomizing disk of the present invention;

[0020] Figure 4 for Figure 3 Schematic diagram of the axial section structure;

[0021] Figure 5 This is the second schematic diagram of the three-dimensional structure of the atomizer disk of the present invention;

[0022] In the figure: 1-smelting furnace, 2-liquid storage tank, 3-spray tower, 4-drain valve, 5-air supply pipe, 6-nozzle, 601-nozzle, 602-inverted cone, 7-atomizing disk, 701-ring, 702-groove, 7021-inclined section, 7022-arc transition section, 703-step hole, 704-atomizing disk body, 8-motor, 9-motor bracket, 10-heat dissipation ribs, 11-discharging port, 12-silo, 13-discharging valve, 14-powder storage tank, 15-hot blast furnace, 16-air blower, 17-feeding pipe. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0024] like Figures 1 to 5 As shown, the present invention comprises a smelting furnace 1, a liquid storage tank 2, and a spray tower 3. The upper part of the liquid storage tank 2 is connected to the lower part of the smelting furnace 1 through a drain valve 4. The smelting furnace 1 and / or the liquid storage tank 2 are connected to the hot air supply system through an air supply pipe 5. The liquid outlet pipe at the lower part of the liquid storage tank 2 penetrates the top surface of the spray tower 3. It is characterized in that a nozzle 6 is fixedly arranged on the liquid outlet pipe extending from the liquid storage tank 2 to the spray tower 3, and a plurality of spray nozzles with axes tilted downward are evenly distributed in the circumferential direction at the lower part of the nozzle 6. Mouth 601; an atomizing disk 7 is arranged below the nozzle 6, and a circular ring 701 is coaxially fixedly arranged on the top surface of the atomizing disk 7, and a plurality of inclined grooves 702 are evenly distributed on the inner wall of the circular ring 701 in the circumferential direction, and the upper part of the groove 702 passes through the top surface of the circular ring 701 and the lower part extends to the top surface of the atomizing disk 7; the atomizing disk 7 is coaxially fixedly connected to the motor shaft of the motor 8 arranged below, and the motor 8 is fixedly connected to the inner wall of the spray tower 3 through the motor bracket 9.

[0025] like Figure 3 and 5As shown, the inner wall of the ring 701 is a cylindrical wall perpendicular to the top surface of the atomizing disk 7 or a conical wall inclined outward; the groove 702 includes an upper and middle inclined section 7021 and a lower arc-shaped transition section 7022, and the generatrix angle between the inclined section 7021 and the inner wall of the ring 701 is 30 to 60 degrees, and the upper end of the arc-shaped transition section 7022 is tangent to the lower end of the inclined section 7021.

[0026] The pitch of the inclined sections 7021 is 1-2 mm and the groove width is 0.4-0.8 mm. The inclined sections 7021 occupy 1 / 2-2 / 3 of the height of the inner wall of the ring 701 . The radius of the arc-shaped transition section 7022 is 1 mm.

[0027] The groove 702 is an iso-depth groove with the same depth from top to bottom or a deepening groove that gradually becomes shallower from the upper end to the lower end. The groove depth at the top of the groove 702 is 1~2mm; the inclined section 7021 is a rectangular groove, a C-shaped groove, a U-shaped groove or a V-shaped groove, and the arc-shaped transition section 7022 has the same groove width as the inclined section 7021.

[0028] like Figure 5 As shown, a step hole 703 is coaxially arranged at the lower end of the circular ring 701, and the inner diameter of the step hole 703 is not less than the circumscribed circle diameter of the bottom of each groove 702 on the inner wall of the circular ring 701. The atomizer disk 7 also includes a flat atomizer disk body 704. The step hole 703 of the circular ring 701 is tightly fitted on the atomizer disk body 704, and the atomizer disk body 704 is coaxially fixedly connected with the motor shaft of the motor 8 arranged below.

[0029] like Figure 2 As shown, the nozzle 6 is a cylinder with an inverted cone 602 at the bottom. The upper end of the nozzle 6 is fixedly connected to the liquid outlet pipe of the liquid storage tank 2. The inverted cone 602 has multiple layers of nozzles 601 evenly distributed circumferentially.

[0030] The nozzle 601 is a straight hole or a trumpet hole with a larger outer side and a smaller inner side. The diameter of the straight hole is 0.3-0.6 mm, and the diameter of the small end of the trumpet hole is 0.1-0.2 mm. The cone angle of the inverted frustum 602 is 80-120°.

[0031] The axis of each nozzle 601 on the inverted cone 602 is perpendicular to the generatrix of the inverted cone 602, or the angle between the axis of each nozzle 601 and the axis of the inverted cone 602 gradually decreases from top to bottom.

[0032] like Figure 1 As shown, a heat dissipation fin 10 is coaxially fixed on the support to which the atomizing disk 7 is fixedly connected with the motor shaft of the motor 8 .

[0033] The heat dissipation rib 10 is a metal sheet with a diameter of 0.5-0.7 times the diameter of the atomizer disk 7 and a thickness of 2-3 mm. The distance between the heat dissipation rib 10 and the motor 8 is 0.3-0.4 times the distance between the motor 8 and the atomizer disk 7 .

[0034] The nozzle 6 and / or the atomizing disk 7 are made of any one of high temperature and corrosion resistant materials selected from stainless steel, titanium alloy, alumina ceramics, tungsten-molybdenum alloy, tungsten-niobium alloy, and tungsten carbide alloy.

[0035] The outer surface of the nozzle 6 and / or the atomizing disk 7 is sprayed with a thermal barrier coating by a plasma spraying method.

[0036] The bottom layer of the thermal barrier coating is a metal coating and the surface layer is a ceramic coating.

[0037] The hot air supply system delivers high temperature gas into the smelting furnace 1 through the air supply pipe 5 for smelting and / or the liquid storage tank 2 for heat preservation of the molten metal.

[0038] Example 1

[0039] Use Figure 2 The present invention is shown as a nozzle 6 for molten alloy liquid, wherein the nozzle 601 is a straight hole with a diameter of 0.3 mm, and the cone angle of the inverted cone 602 is 90°; Figure 1 , 3 The present invention shown in FIG. 4 is used as the atomizing disk 7 and the heat dissipation fin 10, wherein the generatrix angle between the inclined section 7021 and the inner wall of the ring 701 is 45°, the spacing is 1mm and the groove width is 0.6mm. Figure 1 The equipment shown produces Sn-Pb alloy solder powder. The diameter of the atomizing disk 7 is 60 mm and the rotation speed is 50000~60000 r / min. Nitrogen is used as the atomizing atmosphere. The alloy superheat is 40~50°C. The average particle size D (50) of the prepared ultrafine powder is 33.14 μm.

[0040] Example 2

[0041] Use Figure 2 The present invention is shown as a nozzle 6 for molten alloy liquid, wherein the nozzle 601 is a trumpet hole with a small end diameter of 0.1 mm, and the cone angle of the inverted cone 602 is 120°; Figure 1 , 3 The present invention shown in FIG. 4 is used as the atomizing disk 7 and the heat dissipation fin 10, wherein the generatrix angle between the inclined section 7021 and the inner wall of the ring 701 is 30°, the spacing is 2mm and the groove width is 0.4mm. Figure 1The equipment shown produces Sn-Ag-Cu alloy solder powder. The diameter of the atomizing disk 7 is 60 mm and the rotation speed is 70000~80000 r / min. Nitrogen is used as the atomizing atmosphere. The alloy superheat is 60~70°C. The average particle size D (50) of the prepared ultrafine powder is 13.94 μm.

[0042] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A centrifugal atomization device for ultrafine metal powders, comprising a smelting furnace (1), a liquid storage tank (2), and a spray tower (3), wherein the upper portion of the liquid storage tank (2) is connected to the lower portion of the smelting furnace (1) via a liquid discharge valve (4), the smelting furnace (1) and / or the liquid storage tank (2) is connected to a hot air supply system via an air supply pipe (5), and the liquid outlet pipe at the lower portion of the liquid storage tank (2) penetrates the top surface of the spray tower (3); characterized in that A nozzle (6) is fixedly arranged on a liquid outlet pipe extending from the liquid storage tank (2) to the spray tower (3), and a plurality of nozzles (601) with axes inclined downward are evenly distributed in the circumferential direction on the lower part of the nozzle (6); an atomizing disk (7) is arranged below the nozzle (6), and a circular ring (701) is coaxially fixedly arranged on the top surface of the atomizing disk (7), and a plurality of inclined grooves (702) are evenly distributed in the circumferential direction on the inner side wall of the circular ring (701), and the upper part of the groove (702) passes through the top surface of the circular ring (701) and the lower part extends to the top surface of the atomizing disk (7); the atomizing disk (7) is coaxially fixedly connected to the motor shaft of a motor (8) arranged below, and the motor (8) is fixedly connected to the inner wall of the spray tower (3) via a motor bracket (9); The inner side wall of the circular ring (701) is a cylindrical wall perpendicular to the top surface of the atomizing disk (7) or a conical wall inclined outward; the groove (702) comprises upper and middle inclined sections (7021) and a lower arc-shaped transition section (7022); the generatrix angle α between the inclined section (7021) and the inner side wall of the circular ring (701) is 30 to 60°, and the upper end of the arc-shaped transition section (7022) is tangent to the lower end of the inclined section (7021); The nozzle (6) is a cylinder with an inverted cone (602) provided at the bottom. The upper end of the nozzle (6) is fixedly connected to the liquid outlet pipe of the liquid storage tank (2). The inverted cone (602) has multiple layers of nozzles (601) evenly distributed circumferentially.

2. The ultrafine metal powder centrifugal atomization device according to claim 1, characterized in that The pitch of the inclined sections (7021) is 1-2 mm and the groove width is 0.4-0.8 mm. The inclined sections (7021) occupy 1 / 2-2 / 3 of the height of the inner wall of the circular ring (701). The radius of the arc-shaped transition section (7022) is 1 mm.

3. The ultrafine metal powder centrifugal atomization device according to claim 1, characterized in that The groove (702) is a groove of equal depth with the same depth from top to bottom or a groove of gradually shallower depth from the upper end to the lower end, and the groove depth at the top of the groove (702) is 1-2 mm; the inclined section (7021) is a rectangular groove, a C-shaped groove, a U-shaped groove or a V-shaped groove, and the arc-shaped transition section (7022) has the same groove width as the inclined section (7021).

4. The ultrafine metal powder centrifugal atomization device according to claim 1, characterized in that A step hole (703) is coaxially arranged at the lower end of the circular ring (701); the inner diameter of the step hole (703) is not less than the diameter of the circumscribed circle at the bottom of each groove (702) on the inner wall of the circular ring (701); the atomizer disk (7) further comprises a flat atomizer disk body (704); the step hole (703) of the circular ring (701) is tightly fitted on the atomizer disk body (704); the atomizer disk body (704) is coaxially fixedly connected to the motor shaft of the electric motor (8) arranged below.

5. The ultrafine metal powder centrifugal atomization device according to claim 1, characterized in that The nozzle (601) is a straight hole or a trumpet hole that is larger on the outside and smaller on the inside. The diameter of the straight hole is 0.3-0.6 mm, and the diameter of the small end of the trumpet hole is 0.1-0.2 mm. The cone angle of the inverted cone (602) is 80-120°.

6. The ultrafine metal powder centrifugal atomization device according to claim 1, characterized in that The axis of each nozzle (601) on the inverted cone (602) is perpendicular to the generatrix of the inverted cone (602), or the angle between the axis of each nozzle (601) and the axis of the inverted cone (602) gradually decreases from top to bottom.

7. The ultrafine metal powder centrifugal atomization device according to any one of claims 1 to 4, characterized in that A heat dissipation fin (10) is coaxially fixed on a support to which the atomizing disk (7) is fixedly connected to the motor shaft of the electric motor (8).

8. The ultrafine metal powder centrifugal atomization device according to claim 7, characterized in that The heat dissipation rib (10) is a metal sheet with a diameter of 0.5 to 0.7 times the diameter of the atomizing disk (7) and a thickness of 2 to 3 mm, and the distance between the heat dissipation rib (10) and the motor (8) is 0.3 to 0.4 times the distance between the motor (8) and the atomizing disk (7).

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