CN108031649B

CN108031649B - Method for grading metal powder

Info

Publication number: CN108031649B
Application number: CN201810071866.XA
Authority: CN
Inventors: 龚强
Original assignee: SUZHOU SIMEITE SURFACE MATERIAL TECHNOLOGY Co Ltd
Current assignee: SUZHOU SIMEITE SURFACE MATERIAL TECHNOLOGY Co Ltd
Priority date: 2018-01-25
Filing date: 2018-01-25
Publication date: 2020-02-07
Anticipated expiration: 2038-01-25
Also published as: CN108031649A

Abstract

The invention claims a method for classifying spherical and spheroidal micron-sized metal powder by air flow so as to achieve the effects of high dispersion of particles, high consistency of particle size distribution and no secondary pollution. The method mainly comprises the following main steps: 1. accelerating the material by using a selective high-pressure gas source, and 2, classifying and collecting the gas flow. The crushing and dispersing method can greatly improve the dispersibility and the particle size consistency of different metal particle products, effectively remove ultra-fine (the average particle size is less than 0.1um) and ultra-large irregular metal particles (the average particle size is more than 10um), particularly utilize a high-pressure air source as material conveying power, and effectively avoid secondary pollution of an equipment body and the environment to the products in the treatment process by using the backflow air flow in a grading system, so that the obtained metal powder products completely meet the requirements of producing high-end conductive paste and 3D printing materials.

Description

Method for grading metal powder

Technical Field

The invention belongs to the technical field of metal powder grading treatment, and particularly relates to a method for grading, collecting and treating spherical and spheroidal metal powder products according to different particle sizes.

Background

The metal powder with high crystallinity, high dispersion, high particle size consistency and high spherical morphology is widely applied to the industries of solar energy, 3D printing, electronic component manufacturing in the electronic industry, batteries, chemical catalysis, jewelry and the like. With the development of high refinement of solar energy and 3D printing materials and the development of electronic components towards miniaturization and high performance, the requirement for the particle size uniformity (the width of the PSD) of metal powder is higher and higher.

The traditional grading treatment of metal powder with different particle sizes adopts mechanical screening and airflow centrifugal grading: mechanical screening is limited by the aperture of a screen mesh, so that micron-sized metal powder cannot be effectively separated in screening, particularly small-particle-size particles; the airflow centrifugal classification adopts different blades to classify particles with different particle sizes at different rotating speeds, the small particles are not well classified by the method, and particularly, the falling of metal on the surface of the blade is caused when the classified metal particles collide with the blades rotating at high speed, so that the product is polluted. The present invention is directed to solving the above problems.

Disclosure of Invention

The invention aims to solve the technical problem of metal particle grading in the prior art, provides a spherical and spheroidal micron-sized metal powder treatment step, optimizes combination, particularly coats the surface of metal particles, and utilizes airflow as power to convey and grade, thereby achieving high dispersion of materials, high uniformity of particle size distribution and no secondary pollution.

In order to solve the technical problem, the invention provides a method for grading metal powder, which comprises the following steps:

(1) adding metal powder to be subjected to grading treatment to a feeding hole, and conveying the material to a grading disc of a grading and collecting device by using high-pressure airflow;

(2) at least more than two grading collecting channels are constructed by the stop blocks in the grading discs, the grading collecting channels are respectively connected with respective cyclone traps in the grading collecting device, and after high-pressure gas carrying metal powder materials enters the grading disc grading collecting channels, the high-pressure gas flows along the curved surfaces of the stop blocks according to the weight of the metal particles under the action of backflow airflow from the induced draft fan and enters different channels, so that the metal particles with different particle size intervals can be collected by the cyclone traps.

In the preferable technical scheme of the invention, the metal powder in the step (1) is added to an automatic feeder connected with a feeding hole of the grading and collecting device, and the automatic feeder adopts a vector screw feeder for feeding. The feeding amount is different from 0.1 kg to 300 kg per hour. The feed inlet is the venturi feed inlet.

The high-pressure gas in the step (1) adopts compressed air or high-pressure nitrogen or high-pressure argon, and the pressure is 0.01-15 MPa.

In the preferable technical scheme of the invention, in the step (2), the lighter metal particles flow along the curved surface of the alloy block stopper along with the airflow due to small inertia; the heavy metal particles fly to the far grading collection channel due to large inertia after entering the cyclone catcher of the near grading collection channel; the heaviest metal particles fly to the farthest grading collection channel due to large inertia after entering the cyclone collector of the farther grading collection channel; a cyclone trap entering the furthest graded collection channel; therefore, metal particles with different mass and particle sizes respectively enter the cyclone catcher from different channels constructed by different stop blocks according to different masses.

In the step (2), the stop blocks are wear-resistant alloy stop blocks, and two or three grading collection channels are constructed in the grading disc by the stop blocks.

In the preferred technical scheme, the invention also comprises a step (3), two ends of the induced draft fan are respectively connected with the outlet of the cyclone catcher and the backflow gas inlet of the grading disc through backflow air pipes, and a (pneumatic or electric) butterfly valve arranged on the backflow air pipe entering the grading disc and a variable frequency motor of the induced draft fan are respectively controlled through differential pressure transmitters respectively arranged at the inlet and the outlet of the induced draft fan, so that the backflow flow and the backflow pressure of the induced draft fan in the grading disc and the cyclone catcher are ensured by controlling the opening degree of the butterfly valve and the rotating speed of the induced draft fan, and the backflow pressure balance in the whole system is controlled. Therefore, the flying distance and direction of the metal particles and the collecting effect of the cyclone catcher are effectively and stably controlled, and metal particle products with different particle size intervals are stably obtained.

In a preferred technical scheme of the present invention, the metal powder is selected from silver metal particles, titanium alloy metal particles, nickel-cobalt metal particles, silver-coated copper metal particles, or silver-coated nickel metal particles.

The metal powders or particles of the present invention are generally referred to as spherical and spheroidal metal powders or particles.

The invention has the advantages and beneficial effects that:

(1) the method of the invention utilizes the vector feeder to stabilize the feeding amount and utilizes the automatic control system to control the air flow pressure balance in the grading system, thereby greatly improving the particle size distribution and the dispersion of the metal particles, achieving the requirements of high dispersion and high uniformity of the particle size distribution, and effectively grading and dispersing the metal spherical and spheroidal powder raw materials with the average particle size of 0.2-50 microns and the maximum particle size of not more than 100 microns according to different particle size intervals.

(2) The method can stably obtain the high-dispersion products with different grain size intervals and yield by a regulating the feeding speed of the automatic feeder, b regulating the pressure and flow of high-pressure gas, c regulating the position of the alloy stopper, d regulating the reflux air volume and air pressure of the induced draft fan and e regulating the opening of the butterfly valve.

(3) The method of the invention can process sensitive metal powder products by selecting different high-pressure gas sources, such as explosion-proof and anti-oxidation requirements and the like. The obtained metal powder product completely meets the requirements of high-end conductive paste (solar positive silver paste) and 3D printing material on high dispersibility, high particle size consistency and high purity.

(4) The method can completely avoid the secondary pollution to the product in the process of crushing, grading and collecting the equipment body.

(5) The method has the advantages of large treatment capacity, good dispersion, small loss, high automation degree, high grading precision and stable yield.

Drawings

FIG. 1 is a graph of the primary particle size distribution of an SMT001 series silver powder feedstock.

FIG. 2 is a particle size distribution diagram of fine powder after the SMT001 series silver powder classification treatment.

FIG. 3 is a particle size distribution diagram of the medium powder after the SMT001 series silver powder classification treatment.

FIG. 4 is a graph showing a particle size distribution of the coarse powder after the SMT001 series silver powder classification treatment.

FIG. 5 is an SEM (1.5K) of a raw SMT001 series silver powder.

FIG. 6 is an SEM (1.5K) of the SMT001 series silver powder fine powder after treatment.

FIG. 7 is a SEM (1.5K) of processed SMT001 series silver powder.

FIG. 8 is an SEM (1.5K) of the treated SMT001 series silver powder coarse powder.

FIG. 9 is a graph showing a distribution of primary particle diameters of S6 series silver powder raw materials.

FIG. 10 is a particle size distribution diagram of the fine powder after the classification treatment of the S6 series silver powder.

Fig. 11 is a distribution diagram of the particle size of the medium powder after the classification treatment of the S6 series silver powder.

Fig. 12 is a particle size distribution diagram of coarse powder after the classification treatment of the S6 series silver powder.

FIG. 13 is an SEM (1.5K) of S6 series silver powder raw material.

FIG. 14 is an SEM (1.5K) of the treated S6 series silver powder fine powder.

FIG. 15 is a SEM (1.5K) of powder particles in S6 series silver powder after treatment.

FIG. 16 is an SEM (1.5K) of the treated S6 series silver powder coarse powder.

Fig. 17 is an electron micrograph SEM of the titanium alloy raw material powder.

FIG. 18 is a SEM image of a medium powder obtained by classifying a titanium alloy powder.

FIG. 19 is a flow chart of a method of homogenizing metal powder in accordance with one embodiment of the present invention.

Detailed Description

The above-described scheme is further illustrated below with reference to specific examples. It should be understood that these examples are for illustrative purposes and are not intended to limit the scope of the present invention. The conditions used in the examples may be further adjusted according to the conditions of the particular manufacturer, and the conditions not specified are generally the conditions in routine experiments.

Introduction and summary

The present invention is illustrated by way of example and not by way of limitation. It should be noted that references to "an" or "one" embodiment in this disclosure are not necessarily to the same embodiment, but to at least one.

Various aspects of the invention are described below. It will be apparent, however, to one skilled in the art that the present invention may be practiced according to only some or all aspects of the present invention. For purposes of explanation, specific numbers, materials and configurations are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without specific details. In other instances, well-known features are omitted or simplified in order not to obscure the present invention.

Various operations will be described as multiple discrete steps in turn, and in a manner that is most helpful in understanding the present invention; however, the description in order should not be construed as to imply that these operations are necessarily order dependent.

Various embodiments will be described in terms of typical classes of reactants. It will be apparent to those skilled in the art that the present invention may be practiced using any number of different types of reactants, not just those provided herein for purposes of illustration. Furthermore, it will also be apparent that the invention is not limited to any particular hybrid example.

The grading and collecting device used in the invention has the following types: SMT-BD-30H (manufactured by Simulter surface materials science and technology, Suzhou). The grading and collecting device comprises an automatic feeder, a grading disc, a plurality of cyclone traps and an induced draft fan, the automatic feeder is connected to the grading disc through a Venturi tube,

at least more than two grading collecting channels are constructed in the grading disc by a baffle block, the grading collecting channels are respectively connected with respective cyclone collectors,

one end of the induced draft fan is connected with a reflux air inlet of the grading disc through a reflux air pipe, the other end is respectively connected with outlets of the cyclone catcher (a plurality of) through a main pipe,

and the inlet and the outlet of the induced draft fan are respectively provided with a differential pressure transmitter to respectively control the pneumatic or electric butterfly valve arranged on the backflow air pipe entering the grading disc and the variable frequency motor of the induced draft fan, control the opening size of the butterfly valve and the rotating speed of the induced draft fan, effectively ensure the backflow flow and pressure of the induced draft fan in the grading disc, and simultaneously ensure the stable airflow pressure in the cyclone catcher, thereby controlling the backflow pressure balance in the whole system.

Example 1

20 kg of crushed and well dispersed spherical SMT001 silver powder is added into a grading and collecting device through an automatic feeder, compressed air is used as a high-pressure air source, the pressure is 3 kg, the feeding speed is 10 kg/h, and the backflow air amount of an induced draft fan is 70%; taking fine powder, medium powder and coarse powder to verify the effect: PSD data and particle size distribution diagram (FIGS. 1-4); b, electron micrograph: SMT001 series silver powder raw materials, SMT 001-fine powder, SMT 001-medium powder and SMT 001-coarse powder (figures 5-8); by electron microscope photos and PSD analysis, the particle size distribution consistency of the processed spherical silver powder is obviously good, and the dispersibility is improved.

Table 1: PSD data statistics and distribution before and after S3 series silver powder treatment in example 1:

categories	D10	D50	D90	D100
					SMT001 series silver powder raw material	0.93	1.61	2.72	5.11
Fine powder of SMT001 series silver powder after treatment	0.55	0.99	1.75	3.22
					Processed SMT001 series silver powder	0.92	1.54	2.58	4.54
Treated SMT001 series silver powder coarse powder	1.54	3.15	5.79	9.9

Example 2

100 kg of dispersed and crushed S6 series spherical silver powder is added into a grading and collecting device through an automatic feeder, compressed air is used as a high-pressure air source, the pressure is 6 kg, the feeding speed is 50 kg/h, and the backflow air quantity of an induced draft fan is 80%; after grading and collection are finished, taking the fine powder, the medium powder and the coarse powder to verify the effect: PSD data and particle size distribution diagram (FIGS. 9-12); b, electron micrograph: raw materials of S6 series silver powder, S6-fine powder, S6-medium powder and S6-coarse powder (figures 13-16); by electron microscope photos and PSD analysis, the particle size distribution consistency of the processed spherical silver powder is obviously good, and the dispersibility is improved.

Table 2 statistics and distribution of PSD data before and after treatment of the S6 series silver powder of example 2:

categories	D10	D50	D90	D100
					S6 series silver powder raw material	0.71	1.19	1.96	3.12
Processed S6 series silver powder fine powder	0.43	0.79	1.45	2.74
					Processed S6 series silver powder medium powder	0.78	1.29	2.12	3.94
Treated S6 series silver powder coarse powder	1.17	1.68	2.4	4.01

Example 3

Taking 5 kilograms of well dispersed titanium alloy spherical powder, adding the powder into a grading and collecting device through an automatic feeder, adopting nitrogen as a high-pressure air source, wherein the pressure is 4 kilograms, the feeding speed is 5 kilograms per hour, and 90 percent of backflow air of an induced draft fan is taken as medium powder to take the following electron microscope photos: SEM 3-electron micrograph of titanium alloy raw powder (fig. 17), SEM 3-medium powder obtained after classification and collection (fig. 18); the electron microscope photo shows that the treated material has good particle size distribution consistency and the dispersibility of the material is greatly improved.

The above-described specific embodiments are merely preferred embodiments of the present invention, and it should be noted that, for those skilled in the art, various modifications or substitutions can be made without departing from the principle of the present invention, and these modifications or substitutions should also be regarded as the protection scope of the present invention.

Claims

1. A method of classifying metal powder, comprising the steps of:

(2) at least more than three grading collecting channels are constructed in the grading disc by the stop blocks, the grading collecting channels are respectively connected with respective cyclone traps, after the high-pressure gas carries the metal powder material to enter the grading collecting channels of the grading disc, under the action of backflow airflow from the induced draft fan, the metal powder material flows along the curved surfaces of the stop blocks according to the light weight of the metal particles and enters different channels, and the light metal particles enter the cyclone traps of the adjacent grading collecting channels; heavier metal particles fly to the far grading collection channel and enter the cyclone catcher of the far grading collection channel; the heaviest metal particles fly towards the farthest grading collection channel and enter the cyclone catcher of the farthest grading collection channel; metal particles with different mass and particle sizes respectively enter the cyclone catcher from different channels constructed by different stop blocks according to different masses, and the metal particles in different particle size intervals are collected by the cyclone catcher;

(3) the draught fan both ends are connected respectively by the backward flow tuber pipe whirlwind trap export and the import of hierarchical dish backward flow air current, and through the pressure difference changer who installs respectively at draught fan entry and export, come the butterfly valve of difference control installation on the backward flow tuber pipe that gets into the hierarchical dish and the inverter motor of draught fan to through control butterfly valve aperture size and draught fan rotational speed, guarantee then that the interior fan backward flow of hierarchical dish and whirlwind trap flows and pressure, control the backward flow pressure balance in the entire system.

2. The method of classification processing according to claim 1, wherein the metal powder of step (1) is fed to an automatic feeder connected to a feed port of the classification collecting means, and the automatic feeder feeds by a vector screw feeder.

3. A method of staged treatment according to claim 1, wherein in step (1), the feed inlet is a venturi feed inlet.

4. The method of classification processing according to claim 1, wherein in the step (2), the stopper is a wear-resistant alloy stopper.

5. A method of classification as claimed in claim 1, characterized in that the metal powder is selected from silver metal particles or titanium alloy metal particles or nickel cobalt metal particles or silver-clad copper metal particles or silver-clad nickel metal particles.