CN114974874B - Method for preparing regenerated magnet by using waste sintered NdFeB magnet - Google Patents
Method for preparing regenerated magnet by using waste sintered NdFeB magnet Download PDFInfo
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- H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
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- H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
- H01F1/0571—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes
- H01F1/0573—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes obtained by reduction or by hydrogen decrepitation or embrittlement
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- H01F1/053—Alloys characterised by their composition containing rare earth metals
- H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
- H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
- H01F1/0571—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes
- H01F1/0575—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together
- H01F1/0577—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together sintered
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- H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
- H01F41/0253—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets
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Abstract
The invention discloses a method for preparing a regenerated magnet by using waste sintered NdFeB magnets, which comprises the following steps: the method comprises the steps of sequentially carrying out surface pretreatment, hydrogen crushing, high-pressure air flow grinding to prepare powder, two-stage cyclone separation treatment on the waste sintered NdFeB magnet, then carrying out surface treatment on the obtained powder, carrying out orientation compression molding, high-temperature sintering and heat treatment on the obtained powder, and finally obtaining the regenerated magnet. The method can effectively obtain the regenerated powder with fine granularity and uniform distribution, so that the regenerated magnet has the advantages of high magnetic property, low oxygen content and good demagnetization curve squareness, and the waste sintered neodymium-iron-boron magnet can be effectively recycled.
Description
Technical Field
The invention belongs to the technical field of permanent magnet material recovery, and particularly relates to a method for preparing a regenerated magnet by using a waste sintered NdFeB magnet.
Background
Rare earth is an important non-renewable resource and is an important constituent element of rare earth permanent magnet materials. As the rare earth permanent magnet material with the highest performance and the widest application, the sintered neodymium iron boron permanent magnet material is greatly developed, the annual output is continuously increased, and a large amount of rare earth resources are consumed. On the other hand, in the production and processing process of sintered NdFeB products, from initial raw materials to final finished products, waste materials are inevitably generated in each process, and a large number of finished products such as NdFeB motors are scrapped, so that the number of waste sintered NdFeB magnets available each year is huge. The regenerated sintered NdFeB magnet is prepared by using the waste sintered NdFeB permanent magnet, so that the secondary rare earth resource can be developed and utilized, the primary rare earth resource is saved, and the pollution of the waste magnet is reduced.
The recovery treatment process of the waste sintered NdFeB magnet at present mainly comprises the steps of cleaning, crushing and pulverizing the waste sintered NdFeB magnet, adding a certain amount of rare earth metal or alloy powder, and then performing compression molding, sintering and heat treatment to finally obtain the regenerated sintered NdFeB magnet, as described in the publication No. CN107363263A, CN111613402A, CN109192495A and the like.
However, the waste sintered NdFeB magnet is mainly composed of RE 2 Fe 14 B magnetic main phase and located at RE 2 Fe 14 B grain boundary rare earth-rich phase composition between main phase grains, wherein RE 2 Fe 14 The main phase B is the main source of the magnetic performance of the magnet, the grain boundary rare earth-rich phase plays a role in helping sintering and densification of the magnet in the preparation process of the magnet, plays a role in magnetic isolation in the final magnet, and blocks two adjacent RE 2 Fe 14 Direct contact between grains of main phase B to prevent RE 2 Fe 14 The grain growth of the main phase B is critical to the improvement of the coercive force of the magnet. The rare earth-rich phase at the grain boundary mainly comprises rare earth elements with high chemical activity, and in the production and manufacturing process of the magnet, the rare earth-rich phase is extremely easy to react with oxygen in the environment to generate rare earth oxide, so that the oxygen content of the whole magnet is increased; the sharp corners of the main phase grains also lead to an increase in oxygen content due to contact with rare earth rich phases. The general oxygen content of the sintered NdFeB magnet is 500-2500ppm, and oxygen elements mainly exist in the grain boundary rare earth-rich phase and the main phase grain sharp angle, but in the process of preparing the regenerated magnet by directly crushing the waste sintered NdFeB magnet, the rare earth-rich phase and the grain sharp angle further react with oxygen in the environment, and the grain sharp angle and the grain boundary rare earth-rich phase with high oxygen content are not beneficial to the liquid phase sintering densification of the magnet; in order to obtain densified recycled magnets, it is necessary to regenerateThe magnetic powder is added with a large amount of rare earth powder or rare earth-rich alloy powder, and the rare earth-rich alloy are both non-magnetic phases, so that the high performance of the regenerated magnet is not facilitated by adding a large amount of rare earth and the rare earth-rich alloy.
In addition, the main phase grain size of the waste sintered NdFeB magnet is larger, the conventional crushing and pulverizing process is difficult to obtain regenerated powder with fine granularity and uniform distribution, the regenerated powder with coarse granularity is not beneficial to the improvement of the coercive force of the regenerated magnet, and the regenerated powder with wide distribution is not beneficial to the uniformity of the magnetic performance of the magnet, so that the square degree of a demagnetization curve is poor; the regenerated powder with more edges and corners is not beneficial to powder orientation during compression molding, and the residual magnetism of the regenerated magnet is directly influenced.
Disclosure of Invention
In view of the above, the present invention is needed to provide a method for preparing a regenerated magnet by using waste sintered neodymium-iron-boron magnets, and the regenerated magnet prepared by the method has the characteristics of low oxygen content and high magnetic performance.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
the invention provides a method for preparing a regenerated magnet by using waste sintered NdFeB magnets, which comprises the following steps:
obtaining a waste sintered NdFeB magnet M0, preprocessing the waste sintered NdFeB magnet M0, and removing a coating and/or a plating layer and/or an oxidation corrosion layer and/or pollutants on the surface of the magnet M0 to obtain a magnet M1;
carrying out hydrogen crushing on the magnet M1 to obtain coarse powder P1 with the hydrogen content of 1500-2500 ppm;
carrying out high-pressure air flow grinding on the coarse powder P1 to obtain air flow grinding powder P2;
carrying out two-stage cyclone separation treatment on the airflow milled powder P2 to obtain regenerated powder P3;
forming a rare earth-rich layer on the surface of the regenerated powder P3 to obtain modified powder P4;
and carrying out orientation compression molding, high-temperature sintering and heat treatment on the modified powder P4 in sequence to obtain the regenerated magnet.
Further, the waste sintered neodymiumThe main phase component of the iron-boron magnet M0 is RE x Fe y M y1 B z Wherein RE is at least one of rare earth metals; m is at least one of Co, cu, al, ga, zr, nb; x, y1 and z are mass fractions of corresponding elements respectively, and x is more than or equal to 29 and less than or equal to 33, y1 is more than or equal to 0 and less than or equal to 3,0.95 and z is more than or equal to 1.05, and y=100-x-y 1-z.
Further, the pretreatment mode comprises at least one of mechanical polishing, chemical dissolution and ultrasonic water washing.
Further, the hydrogen crushing step comprises vacuumizing, charging hydrogen, absorbing hydrogen, dehydrogenating and cooling.
Further, the high-pressure air flow grinding powder is carried out under the condition of nitrogen or rare gas, and the grinding gas pressure is more than or equal to 0.8MPa.
Further, the two-stage cyclone separation treatment process specifically comprises the following steps: separating large particles in the powder through first-stage cyclone separation; the superfine powder in the powder is separated by a second cyclone separation.
Further, the particle size distribution of the regenerated powder P3 satisfies D 10 ≥1.5μm，3.5μm≤D 50 ≤4.5μm，4≤D 90 /D 10 ≤4.5。
Further, the rare earth-rich layer at least contains one rare earth metal layer or rare earth alloy layer, and the formation mode of the rare earth-rich layer is selected from one of vacuum evaporation and sputtering coating;
preferably, the total mass of the rare earth rich layer is 4% -7% of the modified powder P4.
Further, the rare earth-rich layer is a rare earth metal layer or a metal composite layer comprising a rare earth metal layer, and the rare earth metal layer is a metal Pr layer, a metal Nd layer or a metal PrNd layer;
the metal composite layer also comprises at least one metal Cu layer or metal Al layer, wherein the mass of the rare earth element accounts for more than 80% of the total mass of the metal composite layer.
Further, the rare earth-rich layer is a rare earth alloy layer, and the rare earth alloy layer comprises PrCu, prAl, ndCu, ndAl, prCuAl or NdCuAl, wherein the mass of rare earth elements is more than 80% of the total mass of the rare earth alloy layer.
Compared with the prior art, the invention has the following beneficial effects:
the method mainly comprises the steps of surface pretreatment of the waste magnet, crushing and pulverizing the waste magnet, surface modification of the regenerated powder and preparation of the regenerated magnet.
In the hydrogen crushing process, the hydrogen content in the neodymium iron boron coarse powder is controlled to be 1500-2500ppm, and the characteristics of high brittleness and high hydrogen reducibility of rare earth-rich phase hydrides and neodymium iron boron alloy hydrides are utilized to improve the brittleness and oxidation resistance of the neodymium iron boron coarse powder, so that the coarse powder is easy to crush and refine, the high-oxygen rare earth-rich phase on the powder surface is easy to collide and fall off, and the edges and corners on the powder surface are easy to collide and fall off.
In the air flow grinding process, high-pressure air flow grinding is utilized to increase collision force of mutual collision of coarse powder, reduce powder granularity, and simultaneously grind out protruding edges and corners on the surface of regenerated magnetic powder and adhered rare earth-rich phases with high oxygen content, so as to obtain regenerated neodymium-iron-boron alloy powder with fewer edges and corners.
Carrying out two-stage cyclone separation on the powder subjected to the air flow grinding, and separating larger particles in the powder through one-stage cyclone separation; and separating superfine powder in the powder by utilizing second-stage cyclone separation, and finally obtaining regenerated powder with uniform particle size distribution. The main phase grain edges and corners and the high-oxygen rare earth-rich phase which fall off in the high-pressure air flow grinding process can be separated from the regenerated powder in the two-stage cyclone separation process due to finer granularity, so that the finally obtained regenerated powder also has the characteristics of high main phase occupation ratio and low oxygen content.
Rare earth loss in the step of crushing and pulverizing the waste magnets is supplemented by forming a rare earth-rich layer on the surface of the regenerated NdFeB powder P3.
In general, the invention removes the high-oxygen rare-earth-rich phase and the sharp angle of the regenerated magnetic powder in the waste magnet by controlling the hydrogen content in hydrogen crushing and simultaneously utilizing a high-pressure air flow mill and a secondary cyclone separation, fully utilizes the magnetic main phase in the waste magnet, and finally realizes the high performance of the regenerated magnet.
Detailed Description
The following detailed description of embodiments of the invention is exemplary and is provided merely to illustrate the invention and is not to be construed as limiting the invention.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
The embodiment of the invention discloses a method for preparing a regenerated magnet by using a waste sintered neodymium-iron-boron magnet, which mainly comprises the steps of surface pretreatment, crushing and pulverizing, surface modification, regenerated magnet preparation and the like of the waste sintered neodymium-iron-boron magnet. Crushing and pulverizing, and removing sharp edges and corners and high-oxygen rare-earth-rich phases on the surface of the regenerated powder by utilizing high-pressure air flow mill and multi-cyclone separation treatment to obtain regenerated powder with high magnetic main phase ratio, low oxygen content and few edges and corners; in the powder surface modification step, a rare earth-rich modified metal or alloy layer is formed on the surface of the powder, and the rare earth loss in the crushing and pulverizing step is supplemented, so that the regenerated magnet has the characteristics of low oxygen content and high magnetic property.
In a specific embodiment of the invention, the method mainly comprises the following process steps:
pretreatment of waste NdFeB magnet M0
The waste neodymium-iron-boron magnet M0 is not particularly limited, and is mainly waste materials generated in the production and processing process of sintered neodymium-iron-boron products or waste magnets with severely reduced magnetic properties after long-time use. In some specific embodiments of the invention, the main phase component of the waste sintered NdFeB magnet M0 is RE x Fe y M y1 B z Wherein RE is at least one of rare earth metals; m is at least one of Co, cu, al, ga, zr, nb; x, y1 and z are mass fractions of corresponding elements, and x is more than or equal to 29 and less than or equal to 33, y1 is more than or equal to 0 and less than or equal to 3,0.95 and z is more than or equal to 1.05, and y=100-x-y 1-z. The M0 magnetic property of the waste NdFeB magnetThe main source of energy is RE 2 Fe 14 And B magnetic phase.
Since the surface of the spent neodymium-iron-boron magnet M0 is typically formed with a coating and/or plating and/or oxidation corrosion layer and/or some other contaminants, the pretreatment described herein primarily treats the surface of the spent neodymium-iron-boron magnet M0 to remove the coating and/or plating and/or oxidation corrosion layer and/or contaminants from the surface. It is understood that the pretreatment mode is not particularly limited, and may be adjusted according to the actual situation of the surface of the waste neodymium-iron-boron magnet M0, and according to the embodiment of the present invention, the pretreatment mode includes, but is not limited to, mechanical polishing, chemical dissolution (such as acid-base treatment), ultrasonic water washing, and the like. The magnet M1 is obtained by a pretreatment to such an extent that no macroscopic coating and/or plating and/or oxidation tarnishing and/or other contaminants remain on the surface of the magnet M1.
Crushing and pulverizing the magnet M1
The process of crushing and pulverizing described herein mainly includes hydrogen crushing, high-pressure air-flow pulverizing and two-stage cyclone separation to obtain regenerated magnetic powder.
Specifically, the magnet M1 is crushed by hydrogen to obtain coarse powder P1, the hydrogen crushing adopts a conventional mode in the field, the main steps comprise vacuumizing, charging hydrogen, absorbing hydrogen, dehydrogenating, cooling and the like, and the hydrogen content of the coarse powder P1 is controlled to be 1500-2500ppm by adjusting the dehydrogenation temperature and the dehydrogenation time. By utilizing the characteristics of high brittleness and high hydrogen reducibility of rare earth-rich phase hydrides and neodymium iron boron alloy hydrides, the hydrogen content of coarse powder P1 is controlled, the brittleness and oxidation resistance of neodymium iron boron coarse powder are improved, the coarse powder P1 is easy to crush and refine subsequently, the high-oxygen rare earth-rich phase on the powder surface is easy to collide and fall off, and the edges and corners on the powder surface are easy to collide and fall off.
Further, the coarse powder P1 is subjected to high-pressure air-jet milling to obtain air-jet milled powder P2. Coarse powder P due to high pressure jet mill 1 The powder is mutually collided and crushed under the drive of high-pressure nitrogen gas flow, and sharp edges and corners on the surface of the powder collide with high-oxygen rare earth-rich phases to fall off to form superfine powder when coarse powder collides and is crushed; in other words, the high pressure air stream mill increases the coarse powderThe collision force of the collision between the two components reduces the granularity of the powder, and can grind out the protruding edges and corners on the surface of the magnetic powder and the adhered high-oxygen-content rare earth-rich phase, thereby obtaining the airflow milled powder P2 with fewer edges and corners. According to the embodiment of the invention, the high-pressure air flow grinding powder is carried out under the condition of nitrogen, and the pressure of the nitrogen is more than or equal to 0.8MPa.
Further, the air-flow milled powder P2 is subjected to two-stage cyclone separation treatment to obtain regenerated powder P3. Specifically, larger particles in the powder are separated by primary cyclone separation; and separating superfine powder in the powder through second-stage cyclone separation, and finally obtaining the regenerated magnetic powder with uniform particle size distribution. The main phase grain edges and corners and the high-oxygen rare earth-rich phase which fall off in the high-pressure air flow grinding process can be separated from the regenerated powder in the secondary cyclone separation process due to finer granularity, so that the finally obtained regenerated powder also has the characteristics of high main phase occupation ratio and low oxygen content. It will be appreciated that the specific cyclone parameters may be adjusted according to the actual circumstances and are therefore not specifically limited herein. The particle size distribution of the obtained regenerated powder P3 satisfies D 10 ≥1.5μm，3.5μm≤D 50 ≤4.5μm，4≤D 90 /D 10 ≤4.5。
Surface modification of reclaimed powder P3
Because the loss of rare earth is caused in the process of crushing and pulverizing the waste magnet, a rare earth-rich layer is formed on the surface of the regenerated powder P3 to obtain modified powder P4 so as to supplement the loss of rare earth in the process of crushing and pulverizing the waste magnet. The rare earth-rich layer is a coating layer including at least one rare earth metal or rare earth alloy, and the manner of formation thereof is not particularly limited, and may be any conventional manner in the art. Preferably, a thin soil layer is formed on the surface of the regenerated powder P3 by physical vapor deposition, such as vacuum evaporation, sputtering, etc., wherein the total mass of the thin soil layer is 4% -7% of the modified powder P4.
In some specific embodiments of the present invention, the rare earth-rich layer is a rare earth metal layer or a metal composite layer including a rare earth metal layer, the rare earth metal layer is a metal Pr layer, a metal Nd layer, or a metal PrNd layer; the metal composite layer further comprises at least one metal Cu layer or metal Al layer (the sequence of the metal Cu layer and the rare earth metal layer is not particularly limited), wherein the mass of the rare earth element accounts for more than 80% of the total mass of the metal composite layer.
In other specific embodiments of the present invention, the rare earth-rich layer is a rare earth alloy layer, and the rare earth alloy layer is composed of PrCu, prAl, ndCu, ndAl, prCuAl or NdCuAl, wherein the mass of the rare earth element is 80% or more of the total mass of the rare earth alloy layer.
More preferably, in some specific embodiments of the present invention, during the deposition to form the rare earth layer, the modified powder P4 is kept in a moving state, and the deposition position is continuously changed, for example, by using an external magnetic field, mechanical vibration, etc., so that the surface of the modified powder P4 is uniformly covered with the rare earth layer, and the modified powder is easy to sinter and densify. The rare earth elements are uniformly distributed, so that the growth of crystal grains in the subsequent sintering densification process is restrained, and the magnet performance is improved.
Preparation of regenerated magnet
Specifically, the modified powder P4 is subjected to the steps of orientation press molding, high-temperature sintering and heat treatment to obtain a regenerated magnet. It will be appreciated that the process steps for preparing the recycled magnet are all conventional means in the art and are not particularly limited. According to the embodiment of the invention, the orientation press molding is performed in a magnetic field with the strength of more than 1.8T; the high-temperature sintering process is that sintering is carried out for 2-5 hours at 1030-1080 ℃, and the specific sintering temperature and sintering time can be freely adjusted according to the granularity and the components of the powder so as to realize the aim of sintering densification of the magnet; the heat treatment process is that heat treatment is carried out for 2-5 hours at 850-920 ℃, after cooling to room temperature, heat treatment is carried out for 2-5 hours at 450-600 ℃, and specific heat treatment temperature and heat treatment time can be freely adjusted according to the magnet components so as to improve the coercive force of the magnet.
The invention can prepare the high-performance regenerated magnet through a series of treatments, which is mainly beneficial to the better performance consistency of the regenerated magnetic powder with uniform granularity distribution, and the square degree of the demagnetization curve can be obviously improved; the regenerated magnetic powder particles with fewer edges and corners can be well oriented along the direction of an external magnetic field in the compression molding stage, and the grain orientation consistency of the magnet is high and the magnetic performance is higher; the main phase is a magnetic phase, and the magnetic performance of the magnet with high main phase ratio is also higher; the oxygen content directly influences the coercive force of the magnet, and the lower oxygen content can reduce the consumption of rare earth elements, thereby improving the coercive force of the magnet. The regenerative magnet of the present invention has high performance.
The present invention will be illustrated by the following examples, which are given for illustrative purposes only and are not intended to limit the scope of the present invention in any way, and unless otherwise specified, the conditions or procedures not specifically described are conventional and the reagents and materials employed are commercially available.
Example 1
Collecting the component Pr 6.8 Nd 23.8 Fe 66.1 B 1 Co 0.6 Al 0.3 Cu 0.2 Zr 0.2 The method comprises the following steps of (wt%) producing a waste permanent magnet M10 in the production process of the sintered NdFeB magnet, and preparing a regenerated magnet:
pretreatment of the surface of the waste magnet: and removing the coating/plating layer, the oxide layer and other pollutants on the surface of the magnet M10 by using a mechanical polishing and ultrasonic washing mode to obtain the waste magnet M11, wherein the surface of the waste magnet M11 has no macroscopic coating/plating layer and/or oxide rust layer and/or other pollutant residues.
Crushing and pulverizing the waste magnet: carrying out hydrogen crushing treatment on the waste magnet M11 to obtain regenerated neodymium iron boron coarse powder P11 with hydrogen content of 1500 ppm; carrying out high-pressure nitrogen air flow grinding (the pressure of nitrogen is 0.85 MPa) on the coarse powder P11 to obtain air flow grinding powder P12; performing secondary cyclone separation treatment on the airflow milled powder P12 to obtain regenerated powder P13, wherein the particle size distribution of the regenerated powder P13 is D 10 ＝1.55μm，D 50 ＝3.67μm，D 90 /D 10 ＝4.2。
Surface modification of regenerated powder: and depositing a rare earth metal Nd coating on the surface of the regenerated powder P13 by utilizing a magnetron sputtering mode, and supplementing rare earth loss in the step of crushing and pulverizing the waste magnet to obtain modified powder P14, wherein the total weight of the rare earth metal Nd coating is 4% of the total weight of the modified powder P14.
Preparation of a regenerated magnet: and (3) compression molding the modified powder P14 into a pressed compact in a 2T magnetic field, and performing high-temperature sintering and heat treatment on the pressed compact to prepare the high-performance regenerated sintered NdFeB permanent magnet, wherein the sintering process is that sintering is performed for 5 hours at 1050 ℃, the heat treatment process is that heat treatment is performed for 3 hours at 900 ℃, and the heat treatment is performed for 3 hours at 500 ℃ after cooling.
Comparative examples 1 to 1
The present comparative example uses the same embodiment as in example 1, except that:
(1) Carrying out hydrogen crushing and full dehydrogenation treatment on the waste magnet M11, wherein the hydrogen content of the obtained regenerated NdFeB coarse powder is 800ppm;
(2) Particle diameter D of the obtained regenerated powder P13 10 ＝1.65μm，D 50 ＝3.94μm，D 90 /D 10 ＝4.4。
It can be seen that the powder of comparative example 1-1 had a larger particle size than that of example 1 under the same air-flow grinding process conditions, because of the low hydrogen content and poor brittleness of the hydrogen dust, and the difficulty in crushing the powder.
Comparative examples 1 to 2
The present comparative example uses the same embodiment as in example 1, except that:
the coarse powder P11 is subjected to conventional pressure nitrogen jet milling treatment, the nitrogen pressure is 0.5MPa, and the particle size distribution of the prepared regenerated powder P13' is D 10 ＝1.57μm，D 50 ＝3.75μm，D 90 /D 10 ＝4.3。
It can be seen that the regenerated powder P13 "produced in this comparative example had an overall particle size larger than that of example 1, since the normal pressure air-stream mill was difficult to grind.
Comparative examples 1 to 3
The present comparative example uses the same embodiment as in example 1, except that:
carrying out primary cyclone separation treatment on the airflow milled powder P12 to separate ultrafine powder in the powderThe particle size distribution of the regenerated powder 13' "obtained was D 10 ＝1.63μm，D 50 ＝3.88μm，D 90 /D 10 ＝4.5。
It can be seen that since the conventional primary cyclone separation treatment is mainly for separating the ultrafine powder from the powder, the larger particles in the powder are not separated, and thus the final powder coarse powder particles in this comparative example are more, and the overall particle size is larger than that of example 1.
Comparative examples 1 to 4
The present comparative example uses the same embodiment as in example 1, except that:
the regenerated powder P13 in example 1 was not subjected to surface modification, and the same amount of modified substance powder (rare earth rich layer composition) was mixed into the regenerated powder P13 in a powder mixing manner.
The magnetic properties of the regenerated magnets in example 1 and comparative examples 1-1, 1-2, 1-3, 1-4 were tested at room temperature using a permanent magnet material measurement system according to the method specified in GB/T3217-2013; the oxygen content of the regenerated magnets in example 1 and comparative examples 1-1, 1-2, 1-3, 1-4 was tested using an oxygen content tester; the rare earth content of the regenerated magnets in example 1 and comparative examples 1-1, 1-2, 1-3, 1-4 was tested using an inductively coupled plasma emission spectrometer. The results are shown in Table 1.
TABLE 1 magnetic Properties, oxygen content and rare earth content of example 1 and corresponding comparative examples
As can be seen from Table 1, the regenerated magnet obtained in example 1 has the characteristics of high magnetic properties, low oxygen content, and good degree of square of demagnetization curve.
Example 2
Collecting the component Pr 6.5 Nd 23 Dy 1.5 Fe 66.3 B 1 Co 1 Al 0.3 Cu 0.2 Nb 0.2 (wt%) waste permanent magnet M20 produced in the production process of sintered NdFeB magnet and preparation step of regenerated magnetThe method comprises the following steps:
pretreatment of the surface of the waste magnet: and (3) removing the coating/plating layer, the oxide layer and other pollutants on the surface of the magnet M20 by utilizing a dilute hydrochloric acid dissolution and ultrasonic water washing mode to obtain the waste magnet M21, so that the surface of the waste magnet M21 has no macroscopic coating/plating layer, oxide rust layer and other pollutants residues.
Crushing and pulverizing the waste magnet: carrying out hydrogen crushing treatment on the waste magnet M21 to obtain regenerated neodymium iron boron coarse powder P21 with the hydrogen content of 1800 ppm; carrying out high-pressure nitrogen gas jet milling (the pressure of nitrogen is 0.9 MPa) on the coarse powder P21 to obtain jet milled powder P22; carrying out secondary cyclone separation treatment on the airflow milled powder P22 to obtain regenerated powder P23, wherein the particle size of the regenerated powder P23 is D 10 ＝1.52μm，D 50 ＝3.55μm，D 90 /D 10 ＝4.3。
Surface modification of regenerated powder: and depositing a rare earth metal Pr coating on the surface of the regenerated powder P23 by utilizing a vacuum evaporation mode, and supplementing rare earth loss in the step of crushing and pulverizing the waste magnet to obtain modified powder P24, wherein the total weight of the rare earth metal Pr coating is 5% of the total weight of the modified powder.
Preparation of a regenerated magnet: and (3) compression molding the modified powder P24 into a pressed compact in a magnetic field of 1.8T, and performing high-temperature sintering and heat treatment on the pressed compact to prepare the high-performance regenerated sintered NdFeB permanent magnet, wherein the sintering process is sintering for 3 hours at 1060 ℃, the heat treatment process is heat treatment for 3 hours at 900 ℃, and the heat treatment for 3 hours at 480 ℃ after cooling.
Comparative example 2-1
The present comparative example uses the same embodiment as in example 2, except that:
(1) Carrying out hydrogen crushing and full dehydrogenation treatment on the waste magnet M21, wherein the hydrogen content of the obtained regenerated NdFeB coarse powder is 1000ppm;
(2) Particle diameter D of the obtained regenerated powder P23 10 ＝1.63μm，D 50 ＝3.85μm，D 90 /D 10 ＝4.5。
It can be seen that the powder of comparative example 2-1 had a larger particle size than that of example 2 under the same air-flow grinding process conditions, because of the low hydrogen content and poor brittleness of the hydrogen dust, and the difficulty in crushing the powder.
Comparative examples 2 to 2
The present comparative example uses the same embodiment as in example 2, except that:
carrying out conventional pressure nitrogen jet milling treatment on coarse powder P21, wherein the nitrogen pressure is 0.5MPa, and the particle size D of the obtained regenerated powder P23' is obtained 10 ＝1.56μm，D 50 ＝3.78μm，D 90 /D 10 ＝4.4。
It can be seen that the normal pressure air flow mill powder was difficult to grind, and the overall particle size in this comparative example was larger than that in example 2.
Comparative examples 2 to 3
The present comparative example uses the same embodiment as in example 2, except that:
carrying out primary cyclone separation treatment on the airflow milled powder P22 to separate ultrafine powder in the powder, wherein the particle size of the obtained regenerated powder P23' "is D 10 ＝1.61μm，D 50 ＝3.89μm，D 90 /D 10 ＝4.6。
It can be seen that the conventional primary cyclone separation treatment is mainly used for separating ultrafine powder from powder, and larger particles in the powder are not separated, so that coarse powder particles in the final powder are more, and the overall particle size is larger than that of example 2.
Comparative examples 2 to 4
The present comparative example uses the same embodiment as in example 2, except that:
the regenerated powder P23 in example 2 was not subjected to the surface modification step, and the same amount of modified substance powder (rare earth rich layer composition) was mixed into the regenerated powder P23 in a powder mixing manner.
The magnetic properties of the regenerated magnets in example 2 and comparative examples 2-1, 2-2, 2-3, 2-4 were tested at room temperature using a permanent magnet material measurement system according to the method specified in GB/T3217-2013; the oxygen content of the regenerated magnets in example 2 and comparative examples 2-1, 2-2, 2-3, 2-4 was measured using an oxygen content tester; the rare earth content of the regenerated magnets in example 2 and comparative examples 2-1, 2-2, 2-3, 2-4 were tested using an inductively coupled plasma emission spectrometer. The test results are shown in Table 2.
TABLE 2 magnetic Properties, oxygen content and rare earth content of example 2 and corresponding comparative examples
As can be seen from Table 2, the regenerated magnet produced in example 2 has the characteristics of high magnetic properties, low oxygen content, and good square shape of the demagnetization curve.
Example 3
Collecting Nd as the component 28 Dy 1.5 Ho 1 Fe 67.7 B 1 Al 0.3 Cu 0.1 Ga 0.2 Nb 0.2 The method comprises the following steps of (wt%) producing waste permanent magnets M30 in the production process of sintered NdFeB magnets, and preparing regenerated magnets:
pretreatment of the surface of the waste magnet: and removing the coating/plating layer, the oxide layer and other pollutants on the surface of the magnet M30 by using a sand paper polishing and ultrasonic water washing mode to obtain the waste magnet M31, so that the surface of the waste magnet M31 has no macroscopic coating/plating layer, oxide rust layer and other pollutant residues.
Crushing and pulverizing the waste magnet: carrying out hydrogen crushing treatment on the waste magnet M31 to obtain regenerated neodymium iron boron coarse powder P31 with the hydrogen content of 2000 ppm; carrying out high-pressure nitrogen gas jet milling (the pressure of nitrogen is 1 MPa) on the coarse powder P31 to obtain jet milled powder P32; performing secondary cyclone separation treatment on the airflow milled powder P32 to obtain regenerated powder P33, wherein the particle size of the regenerated powder P33 meets D 10 ＝1.55μm，D 50 ＝3.76μm，D 90 /D 10 ＝4.2。
Surface modification of regenerated powder: and depositing a layer of rare earth metal Pr+a layer of metal Al coating on the powder surface of the regenerated powder P33 by utilizing a magnetron sputtering coating method, and supplementing rare earth loss in the step of crushing and pulverizing the waste magnet to obtain modified powder P34, wherein the mass of the rare earth metal Pr coating accounts for 80% of the total mass of the whole coating, and the total weight of the coating is 5% of the total weight of the modified powder.
Preparation of a regenerated magnet: and (3) compression molding the modified powder P34 into a pressed compact in a magnetic field of 1.8T, and performing high-temperature sintering and heat treatment on the pressed compact to prepare the high-performance regenerated sintered NdFeB permanent magnet, wherein the sintering process is sintering for 5 hours at 1070 ℃, the heat treatment process is heat treatment for 3 hours at 900 ℃, and the heat treatment is performed for 3 hours at 480 ℃ after cooling.
Example 4
Collecting Nd as the component 28 Ho 3 Fe 67.3 B 1 Al 0.3 Ga 0.2 Zr 0.2 The method comprises the following steps of (wt%) producing a waste permanent magnet M40 in the production process of the sintered NdFeB magnet, and preparing a regenerated magnet:
pretreatment of the surface of the waste magnet: and removing the coating/plating layer, the oxide layer and other pollutants on the surface of the magnet M40 by using a mechanical sand blasting and ultrasonic water washing mode to obtain the waste magnet M41, so that the surface of the magnet M41 has no macroscopic coating/plating layer, oxide rust layer and other pollutants residues.
Crushing and pulverizing the waste magnet: carrying out hydrogen crushing treatment on the waste magnet M41 to obtain regenerated neodymium iron boron coarse powder P41 with the hydrogen content of 2100 ppm; carrying out high-pressure nitrogen gas jet milling (the pressure of nitrogen is 0.9 MPa) on the coarse powder P41 to obtain jet milled powder P42; performing secondary cyclone separation treatment on the airflow milled powder P42 to obtain regenerated powder P43, wherein the particle size of the regenerated powder P43 meets D 10 ＝1.63μm，D 50 ＝3.84μm，D 90 /D 10 ＝4.1。
Surface modification of regenerated powder: pr is deposited on the powder surface of the regenerated powder P43 by utilizing a magnetron sputtering coating mode 80 Cu 20 (wt.%) alloy coating layer, supplementing rare earth loss in the step of crushing and pulverizing waste magnet to obtain modified powder P44, pr 80 Cu 20 (wt.%) the total weight of the alloy overlay was 6% of the total weight of the modified powder.
Preparation of a regenerated magnet: and (3) compression molding the modified powder P44 into a pressed compact in a 2.0T magnetic field, and performing high-temperature sintering and heat treatment on the pressed compact to prepare the high-performance regenerated sintered NdFeB permanent magnet, wherein the sintering process is sintering for 5 hours at 1065 ℃, the heat treatment process is heat treatment for 3 hours at 900 ℃, and the heat treatment for 3 hours at 480 ℃ after cooling.
Example 5
Collecting the component Pr 10 Nd 17.5 Gd 4 Fe 66.32 B 0.98 Co 0.5 Al 0.3 Ga 0.2 Co 0.2 The method comprises the following specific steps of (wt%) producing waste permanent magnets M50 in the production process of sintered NdFeB magnets, and preparing regenerated magnets:
pretreatment of the surface of the waste magnet: and (3) removing the coating/plating layer, the oxide layer and other pollutants on the surface of the magnet M50 by utilizing a dilute hydrochloric acid dissolution and ultrasonic water washing mode to obtain the waste magnet M51, so that the surface of the magnet M51 has no macroscopic coating/plating layer, oxide rust layer and other pollutants residues.
Crushing and pulverizing the waste magnet: carrying out hydrogen crushing treatment on the waste magnet M51 to obtain regenerated neodymium iron boron coarse powder P51 with the hydrogen content of 2300 ppm; carrying out high-pressure nitrogen gas jet milling (the pressure of nitrogen is 0.8 MPa) on the coarse powder P51 to obtain jet milled powder P52; performing secondary cyclone separation treatment on the airflow milled powder P52 to obtain regenerated powder P53, wherein the particle size of the regenerated powder P53 meets D 10 ＝1.78μm，D 50 ＝4.4μm，D 90 /D 10 ＝4.0。
Surface modification of regenerated powder: nd is deposited on the surface of the regenerated powder P53 by utilizing a magnetron sputtering coating mode 80 Cu 10 Al 10 And (wt%) alloy coating layer to supplement rare earth loss in the step of crushing and pulverizing waste magnet to obtain modified powder P54. Wherein Nd 80 Cu 10 Al 10 The total weight of the alloy coating layer (wt%) was 7% of the total weight of the modified powder.
Preparation of a regenerated magnet: and (3) compression molding the modified powder P54 into a pressed compact in a magnetic field of 1.9T, and performing high-temperature sintering and heat treatment on the pressed compact to prepare the high-performance regenerated sintered NdFeB permanent magnet, wherein the sintering process is sintering for 5 hours at 1065 ℃, the heat treatment process is heat treatment for 5 hours at 900 ℃, and the heat treatment is performed for 5 hours at 480 ℃ after cooling.
Example 6
Collecting Nd as the component 25 Ho 4 Gd 3 Fe 66 B 1 Al 0.4 Ga 0.2 Cu 0.2 Zr 0.2 The method comprises the following specific steps of (wt%) producing waste permanent magnets M60 in the production process of sintered NdFeB magnets, and preparing regenerated magnets:
pretreatment of the surface of the waste magnet: and removing the coating/plating layer, the oxide layer and other pollutants on the surface of the magnet M60 by using a mechanical shot blasting and ultrasonic water washing mode to obtain the waste magnet M61, so that the surface of the magnet M61 has no macroscopic coating/plating layer, oxide rust layer and other pollutants residues.
Crushing and pulverizing the waste magnet: carrying out hydrogen crushing treatment on the waste magnet M61 to obtain regenerated neodymium iron boron coarse powder P61 with the hydrogen content of 2500 ppm; carrying out high-pressure nitrogen gas (the pressure of nitrogen is 0.9 MPa) jet milling treatment on the coarse powder P61 to obtain jet milled powder P62; performing secondary cyclone separation treatment on the airflow milled powder P62 to obtain regenerated powder P63, wherein the particle size of the regenerated powder P63 meets D 10 ＝1.53μm，D 50 ＝3.77μm，D 90 /D 10 ＝4.3。
Surface modification of regenerated powder: and depositing a layer of rare earth metal Pr+a layer of metal Al+a layer of metal Cu coating on the powder surface of the regenerated powder P63 by utilizing a magnetron sputtering coating method, and supplementing rare earth loss in the step of crushing and pulverizing the waste magnet to obtain modified powder P64, wherein the mass of the rare earth metal Pr coating accounts for 90% of the total mass of the whole coating, and the total weight of the coating is 5.5% of the total weight of the modified powder.
Preparation of a regenerated magnet: and (3) compression molding the modified powder P64 into a pressed compact in a 2T magnetic field, and performing high-temperature sintering and heat treatment on the pressed compact to prepare the high-performance regenerated sintered NdFeB permanent magnet, wherein the sintering process is sintering for 5 hours at 1070 ℃, the heat treatment process is heat treatment for 3 hours at 880 ℃, and the heat treatment for 3 hours at 480 ℃ after cooling.
The magnetic properties of the regenerated magnets of examples 3-6 were tested at room temperature using a permanent magnet material measurement system according to the method specified in GB/T3217-2013; the oxygen content of the regenerated magnet in examples 3 to 6 was measured using an oxygen content tester; the rare earth content of the regenerated magnets in examples 3-6 were tested using an inductively coupled plasma emission spectrometer. The test results are shown in Table 3.
TABLE 3 magnetic Properties, oxygen content and rare earth content of examples 3-6
As can be seen from Table 3, the regenerated magnets produced in examples 3 to 6 have the characteristics of high magnetic properties, low oxygen content, and good square shape of the demagnetization curve.
The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The above examples illustrate only a few embodiments of the invention, which are described in detail and are not to be construed as limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of protection of the present invention is to be determined by the appended claims.
Claims (9)
1. The method for preparing the regenerated magnet by using the waste sintered NdFeB magnet is characterized by comprising the following steps of:
obtaining a waste sintered NdFeB magnet M0, preprocessing the waste sintered NdFeB magnet M0, and removing a coating and/or a plating layer and/or an oxidation corrosion layer and/or pollutants on the surface of the magnet M0 to obtain a magnet M1;
carrying out hydrogen crushing on the magnet M1 to obtain coarse powder P1 with the hydrogen content of 1500-2500 ppm;
carrying out high-pressure air flow grinding on the coarse powder P1 under the condition of nitrogen or rare gas, wherein the grinding gas pressure is more than or equal to 0.8MPa, and obtaining air flow grinding powder P2; through the high-pressure air flow mill, the collision force of collision between coarse powder P1 is increased, the powder granularity is reduced, and the protruding edges and corners on the surface of the magnetic powder and the adhered high-oxygen-content rare earth-rich phase can be removed, so that the air flow mill powder P2 with fewer edges and corners is obtained;
carrying out two-stage cyclone separation treatment on the airflow milled powder P2 to obtain regenerated powder P3; the two-stage cyclone separation treatment process specifically comprises the following steps: separating large particles in the powder through first-stage cyclone separation; separating superfine powder from the powder by a second cyclone separation;
forming a rare earth-rich layer on the surface of the regenerated powder P3 to obtain modified powder P4;
and carrying out orientation compression molding, high-temperature sintering and heat treatment on the modified powder P4 in sequence to obtain the regenerated magnet.
2. The method for preparing a regenerated magnet using a waste sintered NdFeB magnet according to claim 1, wherein the main phase component of the waste sintered NdFeB magnet M0 is RE x Fe y M y1 B z Wherein RE is at least one of rare earth metals; m is at least one of Co, cu, al, ga, zr, nb; x, y1 and z are mass fractions of corresponding elements respectively, and x is more than or equal to 29 and less than or equal to 33, y1 is more than or equal to 0 and less than or equal to 3,0.95 and z is more than or equal to 1.05, and y=100-x-y 1-z.
3. The method for preparing a regenerated magnet from waste sintered neodymium-iron-boron magnet according to claim 1, wherein the pretreatment mode comprises at least one of mechanical polishing, chemical dissolution and ultrasonic water washing.
4. The method for producing a regenerated magnet using a spent sintered neodymium-iron-boron magnet according to claim 1, wherein the hydrogen crushing step comprises vacuumizing, charging hydrogen, absorbing hydrogen, dehydrogenating, and cooling.
5. The method for preparing a regenerated magnet using waste sintered NdFeB magnet according to claim 1, wherein the particle size distribution of the regenerated powder P3 satisfies D 10 ≥1.5μm，3.5μm≤D 50 ≤4.5μm，4≤D 90 /D 10 ≤4.5。
6. The method for preparing a regenerated magnet by using a waste sintered neodymium-iron-boron magnet according to claim 1, wherein the rare earth-rich layer at least contains one rare earth metal layer or rare earth alloy layer, and the rare earth-rich layer is formed by one of vacuum evaporation and sputtering coating.
7. The method for producing a regenerated magnet using a waste sintered neodymium-iron-boron magnet according to claim 6, wherein the total mass of the rare earth rich layer is 4% -7% of the modified powder P4.
8. The method for preparing a regenerated magnet by using a waste sintered neodymium-iron-boron magnet according to claim 6 or 7, wherein the rare earth-rich layer is a rare earth metal layer or a metal composite layer comprising a rare earth metal layer, and the rare earth metal layer is a metal Pr layer, a metal Nd layer or a metal PrNd layer;
the metal composite layer also comprises at least one metal Cu layer or metal Al layer, wherein the mass of the rare earth element accounts for more than 80% of the total mass of the metal composite layer.
9. The method for preparing a regenerated magnet by using a waste sintered neodymium-iron-boron magnet according to claim 6 or 7, wherein the rare earth-rich layer is a rare earth alloy layer, and the rare earth alloy layer is PrCu, prAl, ndCu, ndAl, prCuAl or NdCuAl, wherein the mass of the rare earth element is 80% or more of the total mass of the rare earth alloy layer.
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