WO2020063619A1 - Device and method for preparing superfine low-melting-point spherical metal powder using one-by-one droplet atomization method - Google Patents

Abstract

A device and method for preparing superfine low-melting-point spherical metal powder using a one-by-one droplet atomization method. The device comprises a housing (13), as well as a crucible (7) and a powder collecting area which are arranged in the housing (13). A rotating disc (9) provided in the powder collecting area is an inlaid structure; a material having poor thermal conductivity is selected as a base body part of the rotating disc, and a metal material of which the wetting angle relative to droplets (15) is smaller than 90 degrees is selected and inlaid into a main body part to serve as an atomization plane (24) of the rotating disc (9); and the rotating disc (9) is internally provided with vent holes (25). The preparation method combines a pulse micro-hole injection method and a centrifugal atomization method, a rotating disc structure is matched, and the surface of the rotating disc is subjected to induction heating, so that molten metal replaces a traditional molten metal splitting mode, and a fibrous splitting mode which may be realized only when an atomization medium is a water solution or an organic solution is realized. Great progress is made for the aspect of super refinement, and the prepared low-melting-point superfine metal spherical powder has high sphericity, good fluidity and spreadability, is free of satellite droplets, and meets the requirements for use.

Description

Device and method for preparing ultrafine low melting point spherical metal powder by droplet-by-drop atomization method Technical field

The invention belongs to the technical field of preparing ultrafine spherical microparticles, and in particular, relates to a device and method for preparing ultrafine low melting point spherical metal powder by a droplet-by-drop atomization method.

Background technique

With the technological change, spherical metal powders have a great demand for 3D printing rapid prototyping, semiconductor integrated circuits, and other aspects, and the quality requirements are also increasing. 3D printing metal powder requires high sphericity, uniform particle size, no satellite drops, and good spreadability and uniform flow.

At present, domestic and foreign methods for producing spherical metal powder include atomization, including gas atomization, water atomization, and centrifugal atomization. However, the dispersion degree of the powder prepared by the above atomization method is relatively wide, and it must be sieved multiple times to obtain particles that meet the requirements of use. Moreover, the sphericity is poor. There are a large number of satellite drops on the powder, which cannot meet the requirements for use. low efficiency.

Most of the powders used in China are imported and far from meeting the requirements for use. Therefore, it is of great significance to explore a device and method for preparing ultrafine spherical metal powder with high preparation efficiency and high powder quality.

Summary of the Invention

According to the above-mentioned technical problems in the existing metal powder preparation process, such as poor fluidity and spreadability, low yield, and low efficiency, a device and method for preparing ultra-fine low-melting spherical metal powder by the droplet-by-drop atomization method are provided. . The invention mainly combines the two methods of the pulse micro-hole spray method and the centrifugal atomization method, and simultaneously designs the structure of the turntable and inductively heats the surface of the turntable, so that the metal liquid breaks through the traditional splitting mode of the molten metal and achieves only Compared with the existing centrifugal atomization technology, the fibrous splitting method that can be achieved when the atomizing medium is an aqueous solution or an organic solution, the powder obtained by atomization in this linear splitting mode can make a leap forward in ultra-fineness. At the same time, a low melting point ultrafine metal spherical powder with high sphericity, good fluidity and spreadability, and no satellite drops can be prepared by this mode.

The technical means adopted by the present invention are as follows:

A device for preparing ultrafine low melting point spherical metal powder by a droplet-by-drop atomization method, comprising: a shell, a crucible disposed in the shell, and a powder collection area, wherein the powder collection area is placed in the shell At the bottom, the crucible is placed at the upper part of the powder collection area;

The crucible is an inner and outer nested ring structure with a center line as an axis. The bottom of the inner receiving cavity of the crucible and the bottom of the outer receiving cavity of the crucible are provided with a central hole penetrating therethrough. A space for the circulation of molten metal is provided between the bottom of the cavity and the bottom of the outer receiving cavity; the inner cavity of the crucible is provided with a transmission rod connected to a piezoelectric ceramic provided outside the casing, and The lower end of the transmission rod is provided with a pressing tablet, which is directly above the center hole of the inner cavity;

The shell is provided with a crucible air inlet pipe that extends into the crucible. The shell is also provided with a mechanical pump and a diffusion pump that communicate with the crucible. The shell is also provided with a cavity. Intake pipe and cavity bleed valve;

The powder collection area includes a collection tray provided at the bottom of the housing and a turntable connected to a motor and used to atomize metal powder particles, provided above the collection tray;

The turntable includes a base body, an atomizing plane and a vent hole;

The longitudinal section of the base body composed of the upper receiving part and the lower supporting part is similar to a "T-shaped" main structure, and the upper surface of the receiving part is provided with a circular groove with a certain radius coaxial with the center of the circle; The base body is made of a material having a thermal conductivity of less than 20W / m / k;

The atomizing plane is a disc structure, the disc structure matches the circular groove and interference fits with the circular groove, and the atomizing plane adopts a wetting angle with the atomized droplet. Made of materials less than 90 °;

The vent hole is disposed in the receiving portion and the support portion, the upper end surface of the vent hole is in contact with the lower end surface of the atomizing plane, and the lower end of the vent hole is in communication with the outside;

An induction heating coil is also provided on the periphery of the turntable.

The above crucible form has two inner and outer chambers. That is, the metal material is placed in the outer chamber. During the melting process, the liquid flows and converges to the area of the central hole of the crucible. And the transmission lever above the tablet moves down, so that the liquid droplets are ejected from the central hole at the bottom of the crucible. Of course, the form of the crucible is not limited to the above. As long as there is a closed chamber in the crucible, a back pressure can be generated after being filled with the protective gas, and a structural form that can promote the liquid to flow to the area near the center hole can be used. The volume of the shell should be sufficient for the droplets to fall to the bottom of the collecting tray after centrifugal crushing, to ensure that they will not solidify on the inner wall of the shell, and the area of the collecting tray must be large enough to collect powder. .

Preferably, the height of the base body is 10-20 mm, and the height of the support portion should not be too high, and it should be smaller than the height of the receiving portion. The upper end surface of the atomizing plane protrudes from the upper end surface of the receiving portion, and the protruding range is 0.1-0.5 mm. The protruding height only needs to meet the requirement that the discrete metal droplets do not contact the substrate and fly directly into the chamber and fall into the collection tray. The diameter of the receiving portion ranges from 10 to 100 mm, and the diameter of the circular groove ranges from 5 to 90 mm.

The substrate is made of zirconium dioxide ceramic, silica glass, or stainless steel, and is not limited to the foregoing materials, as long as it meets a material with a thermal conductivity of less than 20 W / m / k. The upper end face of the vent hole is less than or equal to the lower end face of the atomization plane. The purpose of the vent hole is to clean the gas in the turntable when the vacuum is drawn, and it is safer when the turntable is rotating at high speed. The larger the contact area between the upper end surface of the air hole and the lower end surface of the atomizing plane, the better the stability of the atomizing plane when the vacuum is evacuated.

Further, a thermocouple is arranged in the crucible, and a resistance heater is also arranged outside the crucible. Preferably, the wetting angle of the material of the crucible with the molten metal placed therein is greater than 90 °.

Further, the diameter of the central hole of the crucible is between 0.02mm-2.0mm.

Further, the rotation speed of the turntable is 10,000 rpm to 50,000 rpm.

Further, the heating thickness range of the induction heating coil is between 5-20mm, and it is connected to a frequency converter and a regulated power supply provided outside the casing, and the voltage control range of the regulated power supply is between 0-50V. between.

Further, in a top-down direction of the device, the piezoelectric ceramic, the transmission rod, the crucible, the resistance heater, the pressing piece, the turntable, and the induction heating coil Located on the same axis.

The invention also discloses a method for preparing ultrafine low melting point spherical metal powder by using the above-mentioned device drop-by-drop atomization method, which is characterized by including the following steps,

① Loading: Put the metal material to be melted into the outer accommodation cavity of the upper crucible set in the shell and seal it;

② Evacuation: use a mechanical pump and a diffusion pump to evacuate the crucible and the shell, and fill it with a high-purity inert protective gas (usually helium or argon), so that the pressure in the shell reaches a preset value;

③ Resistance heating: Set the heating parameters using resistance heaters according to the melting point of the raw materials to be heated, and monitor the temperature in the crucible in real time through the thermocouple set in the crucible, and keep the temperature after the metal material is completely melted;

④ Induction heating: using a motor to make the turntable rotate at a high speed at a preset speed, and then using an induction heating coil to heat the upper surface of the turntable rotating at a high speed above the melting point temperature of the metal material;

④ Particle preparation: high-purity inert protective gas is passed in through the crucible first air inlet tube and the crucible second air inlet tube provided on the shell and extending into the crucible, and back pressure is generated in the crucible, which promotes Molten metal fills the central hole at the bottom of the crucible; a certain wave-shaped pulse signal is input to the piezoelectric ceramic, and the piezoelectric ceramic generates a downward displacement, and a transmission rod connected to the piezoelectric ceramic and provided on the piezoelectric ceramic The tablet under the transmission rod is transmitted to the molten metal in the area near the center hole, so that the molten metal is ejected from the bottom of the center hole to form a uniform droplet;

Uniform droplets fall freely on a high-speed rotating turntable. In the molten state, the uniform droplets first drop in the center of the turntable. Due to the small centrifugal force at this time, the droplets will not be dispersed immediately, but will be round. Spread on the turntable. When the centrifugal force is sufficiently large in a certain range, the spreading metal will be dispersed on the turntable in the form of fiber lines to the edge of the turntable under the action of the centrifugal force. Finally, it will split into tiny droplets and fly out. During the dropping process, no container solidifies to form metal powder, which is dropped onto the collecting pan, and at the same time, the tablet and the transmission rod are restored to the initial state, and the molten pool in the crucible is supplemented with molten metal liquid to the center hole;

⑤ Particle collection: Use a collection tray provided at the bottom of the shell to collect uniform spherical metal powder.

Further, the loading amount of the metal material into the outer receiving cavity is 50% -70% of the volume of the outer receiving cavity.

Further, the pressure in the casing after evacuating reaches 0.1 MPa, and the heat preservation time is 15-20 minutes after the metal material is completely melted.

Further, an induction heating voltage range of the induction heating coil is 0-50V, and an induction heating time is 5-15min.

Compared with the prior art, the present invention has the following advantages:

The invention discloses a device and method for preparing ultra-fine low melting point spherical metal powder by using a pulsed micro-hole spraying method and a centrifugal atomization method, and a method for preparing ultra-fine low melting point spherical metal powder. The function of the molten metal material in the crucible under pressure and pulse disturbance Then, it is sprayed through the central hole at the bottom of the crucible to form uniform droplets. The uniform droplets land on the rotating disk rotating at high speed and spread on the disk. The spreading metal will be fiber-like on the rotating disk under the action of centrifugal force. Discrete to the edge of the turntable, and finally split into tiny droplets that fly out, and the micro-droplets do not solidify during the dropping process. The traditional pulsed microporous jet method has high sphericity and consistent thermal history, but the powder produced has not yet achieved ultra-fineness. After combining with the centrifugal atomization method, the fiber linear division of the molten metal was achieved. This greatly improves the miniaturization of the metal powder (particle size is less than 50 μm), and can achieve a controllable particle size, which meets the needs of molding technology.

In addition, the turntable disclosed in the present invention is a mosaic structure, which uses a material with poor thermal conductivity, that is, less than 20W / m / k as a substrate, which can effectively reduce the heat transferred from the turntable to the high-speed motor and prevent it from affecting the high-speed motor. Normal operation; using a material with good wettability with the atomized melt material, that is, a wetting angle of less than 90 °, as the atomization plane, which is conducive to the spread of droplets on the atomization plane, so that the metal liquid can be fully atomized; The atomizing plane and the inner wall of the substrate are fixed in an interference fit to ensure that the atomizing plane does not fly out when the turntable is rotating at high speed to ensure its safety. When the atomizing plane is installed on the turntable, the atomizing plane and the substrate There are pores. When a high vacuum is applied to the cavity, a great pressure difference will be generated at both ends of the atomizing plane, which will affect the stability of the atomizing plane. Therefore, an air hole is provided between the receiving part and the supporting part of the turntable base. The lower end surface of the atomizing plane is communicated with the outside world, so that the pressure at both ends of the atomizing plane is consistent, and the stability and safety of the turntable during high-speed centrifugal atomization are further ensured.

The process of the invention has strong controllability, which is manifested in the following points: The crucible temperature can be accurately controlled by the resistance heater; the pressure difference between the crucible and the shell can be controlled by passing an inert gas into the crucible and the shell, and the crucible can be controlled at the same time. The molten metal in the chamber is continuously replenished into the central hole of the crucible; the size of the central hole at the bottom of the crucible can control the size of the droplet; the induction heating coil can control the temperature of the surface of the turntable, and the speed of the turntable can be controlled to control the fibrous shape of the molten metal. The splitting effect can further control the particle size distribution of the metal fine particles; the adjustable and controllable process parameters can obtain ultra-fine spherical metal powder.

The invention can efficiently prepare ultra-fine metal powder that meets the requirements for use, has controllable particle size, narrow distribution interval, high sphericity, consistent thermal history, simple structure, low cost, and high yield, and is suitable for industrial production.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description These are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without paying creative labor.

FIG. 1 is a schematic structural diagram of the present invention.

FIG. 2 is a schematic structural diagram of a turntable of the present invention.

FIG. 3 is a comparison diagram of the powder prepared by the device and method of the present invention and the powder prepared by the unmodified device, wherein (a) is a powder prepared by the present invention, and (b) is a powder prepared by the prior art.

FIG. 4 is a comparison diagram of the surface of the turntable of the present invention after the experiment with that of the original turntable, wherein (a) is the surface of the turntable with fibrous splits, and (b) is the surface of the turntable in the prior art.

FIG. 5 is a liquid flow line diagram on the surface of the turntable of the present invention, wherein (a) is a liquid flow line in the middle portion of the turntable, and (b) is a liquid flow line on the edge of the turntable.

In the picture: 1. Piezoelectric ceramics; 2. Crucible first intake pipe; 3. Transmission rod; 4. Resistance heater 5. Pressing sheet; 6. Right molten pool; 7. Crucible; 8. Cavity; 9. Turntable; 10; Electric motor; 11, Metal powder; 12, Collection tray; 13, Housing; 14, Induction heating coil; 15, Droplet; 16, Cavity intake pipe; 17, Mechanical pump; 18, Diffusion pump; 19 Cavity vent valve; 20, left molten pool; 21, second crucible gas inlet tube; 22, receiving portion; 23, support portion; 24, atomizing plane; 25, vent hole.

detailed description

It should be noted that, in the case of no conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the drawings and embodiments.

In order to make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments It is only a part of the embodiments of the present invention, but not all the embodiments. The following description of at least one exemplary embodiment is actually merely illustrative and is in no way intended to limit the invention and its application or uses. Based on the embodiments of the present invention, all other embodiments obtained by a person of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

It should be noted that the terminology used herein is only for describing specific embodiments and is not intended to limit the exemplary embodiments according to the present invention. As used herein, the singular forms are intended to include the plural forms as well, unless the context clearly indicates otherwise, and it should also be understood that when the terms "including" and / or "including" are used in this specification, they indicate There are features, steps, operations, devices, components, and / or combinations thereof.

Unless specifically stated otherwise, the relative arrangement of the components and steps, numerical expressions, and numerical values set forth in these embodiments do not limit the scope of the present invention. At the same time, it should be clear that, for the convenience of description, the dimensions of the various parts shown in the drawings are not drawn according to the actual proportional relationship. Techniques, methods, and equipment known to those of ordinary skill in the relevant field may not be discussed in detail, but where appropriate, the techniques, methods, and equipment should be considered as part of the authorization specification. In all examples shown and discussed herein, any specific value should be construed as exemplary only and not as a limitation. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that similar reference numerals and letters indicate similar items in the following drawings, so once an item is defined in one drawing, it need not be discussed further in subsequent drawings.

In the description of the present invention, it needs to be understood that the orientation words such as "front, back, up, down, left, right", "horizontal, vertical, vertical, horizontal", "top, bottom" and the like indicate the orientation Or the positional relationship is usually based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplified description. Unless stated to the contrary, these positional words do not indicate and imply the device or element referred to. It must have a specific orientation or be constructed and operated in a specific orientation, so it cannot be understood as a limitation on the scope of protection of the present invention: the orientation words "inside and outside" refer to the inside and outside relative to the outline of each component itself.

For the convenience of description, spatially relative terms such as "above", "above", "above", "above", etc. can be used here to describe as shown in the figure Shows the spatial position relationship between one device or feature and other devices or features. It should be understood that spatially relative terms are intended to encompass different orientations in use or operation in addition to the orientation of the device as described in the figures. For example, if a device in the figure is turned over, devices described as "above" or "above" other devices or constructions will be positioned "below the other devices or constructions" or "below" Under its device or structure. " Thus, the exemplary term "above" may include both directions "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or at other orientations), and the relative description of space used here is explained accordingly.

In addition, it should be noted that the use of words such as "first" and "second" to limit parts is only for the convenience of distinguishing the corresponding parts. Unless otherwise stated, the above terms have no special meaning and cannot be understood. To limit the scope of protection of the present invention.

As shown in FIG. 1, the present invention provides a device for preparing ultrafine low melting point spherical metal powder by a droplet-by-drop atomization method, which includes a shell 13, a crucible 7 disposed in the shell 13, and a powder collection area. Wherein the powder collection area is placed at the bottom of the housing 13 and the crucible 7 is placed at the upper part of the powder collection area;

The crucible 7 is an inner and outer nested ring structure with a center line as an axis. From the figure, the crucible 7 can be divided into two left and right chambers, namely a left molten pool 20 and a right molten pool 6, Essentially, the two molten pools are in the same annular chamber (inside the outer accommodating chamber). In actual use, metal materials can be injected into the molten pool on one side according to the amount of powder prepared, which can be partially or completely poured; The bottom of the inner receiving cavity of the crucible 7 and the bottom of the outer receiving cavity of the crucible 7 are provided with a central hole penetrating therebetween. A molten metal is provided between the bottom of the inner receiving cavity and the bottom of the outer receiving cavity. Circulation space; the inner cavity of the crucible 7 is provided with a transmission rod 3 connected to a piezoelectric ceramic 1 provided outside the housing 13, and a pressing plate 5 is provided at the lower end of the transmission rod 3. 5 directly above the central hole of the content receiving cavity;

The shell 13 is also provided with a crucible air inlet pipe that extends into the crucible 7 at positions corresponding to the left molten pool 20 and the right molten pool 6 in the figure, which are crucibles corresponding to the left molten pool 20 respectively. The second intake pipe 21 and the crucible first intake pipe 2 corresponding to the right molten pool 6, the casing 13 is further provided with a mechanical pump 17, a diffusion pump 18, and a casing 13 which are in communication with the crucible 7. There is also a cavity air inlet pipe 16 and a cavity air release valve 19;

The powder collection area includes a collection disk 12 provided at the bottom of the housing and a turntable 9 for atomizing metal powder particles connected to the motor 10 and disposed above the collection disk 12;

As shown in FIG. 2, the turntable 9 includes a base body, an atomizing plane 24 and a vent hole 25;

The longitudinal section of the base body composed of the upper receiving part 22 and the lower supporting part 23 is similar to a "T-shaped" main structure. The upper surface of the receiving part 22 is provided with a circular recess with a certain radius coaxial with the center of the circle. A groove; wherein the base body is made of a material having a thermal conductivity less than 20W / m / k;

The atomizing plane 24 is a disc structure. The disc structure matches the circular groove and interference fits with the circular groove. The atomizing plane 24 adopts 15 Made of materials with a wetting angle of less than 90 °;

The ventilation hole 25 is penetratingly provided in the receiving portion 22 and the support portion 23. An upper end surface of the ventilation hole 25 is in contact with a lower end surface of the atomizing plane 24, and a lower end of the ventilation hole 25 is outside. Connected

An induction heating coil 14 is also provided on the periphery of the turntable 9. The heating thickness range of the induction heating coil 14 is between 5-20mm, and it is connected to a frequency converter and a regulated power supply provided outside the casing 13, and the voltage control range of the regulated power supply is between 0-50V. between. Using a motor to make the turntable rotate at a high speed at a preset speed, and then using an induction heating coil 14 to heat the upper surface of the turntable 9 rotating at a high speed to a temperature above the melting point of the metal material;

The diameter of the central hole of the crucible 7 ranges from 0.02 mm to 2.0 mm.

The rotation speed of the turntable is 10,000 rpm to 50,000 rpm.

In the top-down direction of the device, the piezoelectric ceramics 1, the transmission rod 3, the crucible 7, the resistance heater 4, the pressing plate 5, the turntable 9, and the The induction heating coil 14 is located on the same axis.

During operation, the crucible 7 and the casing 13 are evacuated by using a mechanical pump 17 and a diffusion pump 18, and the material to be prepared in the crucible 7 is resisted by the resistance heater 4 under the condition that a back pressure is generated by passing in an inert gas. The heating is performed, and a certain waveform pulse signal is input to the piezoelectric ceramic 1. The piezoelectric ceramic 1 generates a downward displacement and is transmitted to the molten metal in the vicinity of the central hole of the crucible 7 by the transmission rod 3 and the pressing plate 5 so that the molten metal is removed from the crucible The lower central hole sprays out to form a uniform liquid droplet 15, which drops freely on the rotating disc 9 which rotates at a high speed. In the molten state, the uniform liquid droplet 15 drops to the center of the rotating disc 9 first. The centrifugal force is small, and the droplets 15 will not be dispersed immediately, but will be spread on the rotating disk 9 in a circular shape. When the centrifugal force is spread to a certain range is large enough, the spreading metal will rotate under the effect of centrifugal force. The disc 9 is dispersed in a fiber line shape to the edge of the rotating disc 9 and finally splits into tiny droplets that fly out. The micro-droplets solidify without a container during the falling process to form metal powder 11 and land on the collecting disc 12.

The invention also discloses a method for preparing ultrafine low melting point spherical metal powder by using the above-mentioned device droplet-by-drop atomization method, including the following steps,

① Loading: The metal material to be melted is placed in the crucible 7 provided in the upper part of the casing 13 and sealed; the amount of the metal material loaded into the outer receiving cavity is the volume of the outer receiving cavity 50% -70%.

② Evacuation: use the mechanical pump 17 and the diffusion pump 18 to evacuate the crucible 7 and the casing 13 and fill it with a high-purity inert protective gas to make the pressure in the casing 13 reach a preset value; the casing The pressure after evacuating in 13 reaches 0.1 MPa, and the heat preservation time is 15-20 minutes after the metal material is completely melted.

③ Resistance heating: Set the heating parameters using the resistance heater 4 according to the melting point of the raw material to be heated, and monitor the temperature in the crucible 7 in real time through the thermocouple set in the crucible 7, and keep the temperature after the metal material is completely melted;

④ Induction heating: Use the motor 10 to rotate the turntable 9 at a high speed at a preset speed, and then use the induction heating coil 14 to heat the upper surface of the high-speed rotating turntable 9 above the melting point of the metal material; The induction heating voltage range is 0-50V, and the induction heating time is 5-15min.

④ Particle preparation: a high-purity inert protective gas is passed through the crucible first inlet pipe 2 and the crucible second inlet pipe 21 provided on the shell 13 and extending into the crucible 7, and the crucible 7 A back pressure is generated to cause the molten metal to fill the central hole at the bottom of the crucible 7; a pulse signal of a certain wave shape is input to the piezoelectric ceramic 1, the piezoelectric ceramic 1 generates a downward displacement, and is connected with the piezoelectric ceramic 1 The connected transmission rod 3 and the pressing plate 5 disposed below the transmission rod 3 are transmitted to the molten metal in the vicinity of the center hole, so that the molten metal is ejected from the bottom of the center hole to form a uniform droplet 15;

The uniform droplet 15 freely falls on the rotating disc 9 that rotates at a high speed. The uniform droplet 15 in the molten state first drops in the center of the disc 9. Due to the small centrifugal force at this time, the droplet 15 will not be dispersed immediately, and It will spread on the turntable 9 in a circular shape. When the centrifugal force is sufficiently large in a certain range, the spreading metal will be dispersed in a fiber line on the turntable 9 to the edge of the turntable 9 under the action of the centrifugal force, and finally split into tiny ones. The liquid droplets fly out, and the micro-droplets solidify without a container during the falling process to form metal powder 11 and land on the collecting tray 12 while restoring the tablet 5 and the transmission rod 3 to the initial state. The molten pool in the crucible 7 The center hole is supplemented with molten metal liquid;

⑤ Particle collection: Use a collection pan 12 provided at the bottom of the casing to collect uniform spherical metal powder.

Example 1

The specific embodiment of batch preparing Sn63Pb37 alloy spherical powder by using the device shown in FIG. 1:

Cut the Sn63Pb37 welding wire into small pieces of about 5mm, and then put them into the crucible 7's molten pool after ultrasonic vibration cleaning. Choose the size of the central hole of the crucible according to your needs. The diameter of the central hole ranges from 0.02mm to 2.0mm. For particles, select a central hole of 0.02mm-1.0mm. For example, if preparing 50μm-100μm particles, select a central hole of 1.0mm-2.0mm. The amount of Sn63Pb37 raw material should be 50% -70% of the volume of the molten pool.

Use the mechanical pump 17 and the diffusion pump 18 to evacuate the crucible 7 and the shell 13 to 0.001pa; use the crucible first inlet tube 2 and the crucible second inlet tube 20, and the cavity inlet tube 16 is inert. Gas argon makes the pressure in the shell 13 and crucible 7 reach 0.1 MPa;

Install the resistance heater 4 on the crucible 7 and insert a thermocouple at the bottom of the crucible 7; choose a copper-inlaid stainless steel turntable 9 for experiment to install on the motor 10, install an induction heating coil 14 around the turntable 9, and seal the housing 13;

The resistance heater 4 is used to heat the crucible 7, the heating temperature is 260 ° C, the heating speed is 15 ° C / min, and the heat is maintained for 10 minutes, so that all the metal materials in the crucible 7 are melted;

The motor 10 is used to make the speed of the turntable 9 24000r / min, and then the induction heating voltage of the induction heating coil 14 is set to 21V, the induction heating current is 8A, and the induction heating time is 10min. The surface of the high speed rotating turntable 9 is heated to a metal material. The melting temperature is above 183 ℃;

The piezoelectric ceramic 1 is input with a trapezoidal wave pulse signal and the frequency is set to 100 Hz. The piezoelectric ceramic 1 generates a downward displacement and is transmitted to the molten metal in the vicinity of the central hole of the crucible 7 by the transmission rod 3 and the pressing plate 5 so that the molten metal The uniform droplet 15 is sprayed out from the central hole in the lower part of the crucible, and the uniform droplet 15 drops freely on the rotating disc 9 that rotates at a high speed. The uniform droplet 15 in the molten state first drops on the center of the disc 9, because the centrifugal force is relatively low Small, the droplets 15 will not be scattered immediately, but will be spread on the turntable 9 in a circular shape. When the centrifugal force is spread to a certain range, the spread metal will become fibers on the turntable 9 under the action of centrifugal force. The lines are dispersed to the edge of the turntable 9 and finally split into tiny liquid droplets that fly out. The microdroplets solidify without a container during the falling process to form a metal powder 11 and land on the collection tray 12.

After the preparation is finished, stop applying trapezoidal wave pulse signal to the piezoelectric ceramic 1 to stop the droplet ejection; stop the high-speed motor 10 so that the turntable 9 stops rotating; turn off the resistance heater 4 and the induction heating coil 14 until the temperature drops to room temperature ， Remove the metal powder 11 in the collection pan 12; Finally, close the cavity air inlet pipe 16 and the crucible into the first air pipe 2 and the crucible second air pipe 20, and use the mechanical pump 10 to draw the crucible 7 and the housing 13 to a low vacuum of 5Pa To keep the device in a vacuum when it is deactivated.

As shown in FIG. 3, it can be seen from (b) that the particle diameter of the powder prepared in the prior art is relatively coarse and hemispherical is generated, and (a) is a powder prepared by the method of the present invention, and the particle diameter of the powder is obtained Obviously miniaturization, the particle size meets the requirements for use, and the sphericity becomes higher, and the surface morphology of the powder becomes better, and no hemisphere is generated.

As shown in FIG. 4, (b) is an atomizing disc obtained after atomization in the prior art, because the wettability of the atomizing disc material and the prepared metal powder material is too small, and the temperature of the turntable is too low during the atomization process. , Resulting in a liquid-like split of the liquid, and a thicker solidified liquid film will appear on the atomized surface. The liquid film surface is very rough, which is not conducive to the further atomization of the subsequent metal droplets, which will seriously affect the atomization effect and atomization efficiency . (a) For the atomized surface obtained by the method of the present invention, it can be seen that the atomization mode is changed into an obvious fibrous splitting mode, and the linear splitting mode greatly improves the miniaturization and production efficiency of the metal powder.

As shown in Figure 5, (a) is the fluid flow line in the middle part of the turntable. From the figure, the width of the fluid flow lines is less than 50 μm, which can explain that the reason for the fineness of the powder produced by this method is due to the fine fibers. Formed like a liquid stream. (b) is the liquid flow line at the edge of the turntable, and the traces left by the small liquid droplets can be seen, so that it can be explained that the metal liquid is dispersed at the edge by complete centrifugal atomization.

In summary, the present invention makes the metal liquid break through the splitting mode of the traditional molten metal, and realizes the fibrous splitting mode that can be achieved only when the atomizing medium is an aqueous or organic solution. Compared with the existing centrifugal atomizing technology, The powder obtained by atomization under this linear splitting mode can make great progress in ultra-fineness. At the same time, this mode can be used to prepare high-sphericity, good fluidity and spreadability, and no satellite drops that meet the requirements for use. Low melting point ultrafine metal spherical powder.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention, but not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: The technical solutions described in the foregoing embodiments can still be modified, or some or all of the technical features can be equivalently replaced; and these modifications or replacements do not depart from the essence of the corresponding technical solutions of the technical solutions of the embodiments of the present invention. range.

Claims (9)

A device for preparing ultrafine low melting point spherical metal powder by a droplet-by-drop atomization method, comprising: a shell (13), a crucible (7) arranged in the shell (13), and a powder collection area, wherein The powder collection area is placed at the bottom of the casing (13), and the crucible (7) is placed at the upper part of the powder collection area; The crucible (7) is an inner and outer nested ring structure with a center line as an axis. The bottom of the inner cavity of the crucible (7) and the bottom of the outer accommodation cavity of the crucible (7) are provided with a phase. A penetrating central hole is provided with a space for molten metal circulation between the bottom of the inner receiving cavity and the bottom of the outer receiving cavity; the inner receiving cavity of the crucible (7) is provided and disposed in the casing (13) A transmission rod (3) connected to an external piezoelectric ceramic (1), a lower end of the transmission rod (3) is provided with a pressing plate (5), and the pressing plate (5) is directly facing the inner cavity. Above the center hole The shell (13) is provided with a crucible air inlet pipe that extends into the crucible (7), and the shell (13) is further provided with a mechanical pump (17) communicating with the crucible (7) ), A diffusion pump (18), the casing (13) is further provided with a cavity intake pipe (16) and a cavity exhaust valve (19); The powder collection area includes a collection plate (12) provided at the bottom of the casing and a turntable (9) for atomizing metal particles connected to the motor (10) provided above the collection plate (12); It is characterized by: The turntable (9) includes a base body, an atomizing plane (24), and a vent hole (25); The base is a "T-shaped" main structure with a vertical section formed by an upper receiving portion (22) and a lower supporting portion (23). The upper surface of the receiving portion (22) is provided coaxially with the center of the circle. A circular groove with a certain radius; wherein the base body is made of a material having a thermal conductivity less than 20W / m / k; The atomizing plane (24) is a disc structure, the disc structure matches the circular groove of the receiving portion and interference fits with the circular groove, and the atomizing plane (24) Made of a material with a wetting angle of less than 90 ° with the atomized droplets (15); The vent hole (25) is provided through the receiving portion (22) and the support portion (23), and an upper end surface of the vent hole (25) is in contact with a lower end surface of the atomizing plane (24). The lower end of the vent hole (25) is in communication with the outside world; An induction heating coil (14) is also provided on the periphery of the turntable (9). The device for preparing ultrafine low melting point spherical metal powder according to the drop-by-drop atomization method according to claim 1, wherein the diameter of the central hole of the crucible (7) is between 0.02 mm and 2.0 mm. The device for preparing ultrafine low melting point spherical metal powder according to the droplet-by-drop atomization method according to claim 1, wherein the rotation speed of the turntable (9) is 10,000 rpm-50,000 rpm. The device for preparing ultrafine low melting point spherical metal powder according to the droplet-by-drop atomization method according to claim 1, wherein the heating thickness range of the induction heating coil (14) is between 5-20mm, and The frequency converter outside the casing (13) is connected to a regulated power supply, and the voltage control range of the regulated power supply is between 0-50V. The device for preparing ultrafine low melting point spherical metal powder according to the droplet-by-drop atomization method according to claim 1, characterized in that, in a direction from the top of the device, the piezoelectric ceramic (1), The transmission rod (3), the crucible (7), the pressing piece (5), the turntable (9), and the induction heating coil (14) are located on the same axis. A method for preparing ultrafine low melting point spherical metal powder by using the device droplet-by-drop atomization method according to any one of claims 1-5, comprising the following steps, ① Loading: The metal material to be melted is placed in the outer accommodation cavity of the upper crucible (7) provided inside the casing (13) and sealed; ② Evacuation: use a mechanical pump (17) and a diffusion pump (18) to evacuate the crucible (7) and the casing (13), and fill it with a high-purity inert protective gas to make the inside of the casing (13) Pressure reaches a preset value; ③ Resistance heating: Set the heating parameters using the resistance heater (4) according to the melting point of the raw material to be heated, and monitor the temperature in the crucible (7) in real time through the thermocouple set in the crucible (7). Insulation after the material is completely melted; ④ Induction heating: the motor (10) is used to make the turntable (9) rotate at a high speed at a preset speed, and then the induction heating coil (14) is used to heat the upper surface of the high-speed rotating turntable (9) above the melting point of the metal material ; ④ Particle preparation: the crucible first inlet pipe (2) and the crucible second inlet pipe (21) are arranged on the shell (13) and protrude into the crucible (7), and a high-purity inert protective gas is provided. When it is passed in, back pressure is generated in the crucible (7), and the molten metal is caused to fill the central hole at the bottom of the crucible (7); a pulse signal of a certain waveform is input to the piezoelectric ceramic (1), and the piezoelectric ceramic (1) A downward displacement is generated, which is transmitted by the transmission rod (3) connected to the piezoelectric ceramic (1) and the pressing piece (5) disposed below the transmission rod (3) to the melting of the area near the center hole. Metal, so that molten metal is ejected from the bottom of the central hole to form a uniform droplet (15); The uniform droplet (15) freely falls on the high-speed rotating disc (9). The uniform droplet (15) in the molten state first drops on the center of the disc (9). Due to the small centrifugal force at this time, the droplet ( 15) It will not be scattered immediately, but will be spread on the turntable (9) in a circular shape. When the centrifugal force is spread to a certain range, the spread metal will be presented on the turntable (9) under the action of centrifugal force. The fibers are linearly dispersed to the edge of the turntable (9), and finally split into tiny droplets that fly out. The microdroplets solidify without a container during the falling process, forming a metal powder (11), and landing on the collection tray (12). The tablet (5) and the transmission rod (3) return to the initial state, and the molten metal liquid in the crucible (7) is replenished to the center hole; ⑤ Particle collection: Use a collection tray (12) provided at the bottom of the casing to collect uniform spherical metal powder. The method for preparing ultrafine low melting point spherical metal powder according to the droplet-by-drop atomization method according to claim 6, wherein the loading amount of the metal material into the outer receiving cavity is the outer receiving 50% -70% of the cavity volume. The method for preparing ultrafine low melting point spherical metal powder according to the drop-by-drop atomization method according to claim 6, characterized in that the pressure after the vacuum in the casing (13) reaches 0.1 MPa, and the metal material is completely melted The holding time is 15-20 minutes. The method according to claim 6, wherein the induction heating coil (14) has an induction heating voltage range of 0-50V and an induction heating time of 5-15min.

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