CN112908665B - Infiltration method for improving coercivity of sintered neodymium-iron-boron - Google Patents
Infiltration method for improving coercivity of sintered neodymium-iron-boron Download PDFInfo
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- SCRZPWWVSXWCMC-UHFFFAOYSA-N terbium(iii) oxide Chemical compound [O-2].[O-2].[O-2].[Tb+3].[Tb+3] SCRZPWWVSXWCMC-UHFFFAOYSA-N 0.000 claims description 3
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- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 2
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F41/00—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
- 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
- H01F41/0266—Moulding; Pressing
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F41/00—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
- 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
- H01F41/0293—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 diffusion of rare earth elements, e.g. Tb, Dy or Ho, into permanent magnets
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Manufacturing Cores, Coils, And Magnets (AREA)
- Hard Magnetic Materials (AREA)
Abstract
The invention discloses a penetration method for improving the coercivity of sintered neodymium iron boron, which comprises the following steps: uniformly mixing neodymium iron boron powder and heavy rare earth powder, and preparing the mixed powder into a neodymium iron boron blank magnet; step two, processing the obtained neodymium iron boron blank magnet into a magnet base material with a preset size; step three, coating flux dispersion liquid on the surface of the magnet base material obtained in the step two; and step four, carrying out secondary tempering treatment on the magnet base material coated with the flux dispersion liquid in a vacuum sintering furnace. The method can improve the permeability of the heavy rare earth, thereby improving the coercive force of the magnet, and having little influence on remanence.
Description
Technical Field
The present invention belongs to the field of permanent magnetic RE material technology. More specifically, the invention relates to a penetration method for improving the coercivity of sintered neodymium iron boron.
Background
The sintered Nd-Fe-B magnet has high remanence and coercive force, so that the sintered Nd-Fe-B magnet is widely applied to the fields of consumer electronics, medical instruments, aerospace, information and the like, and the high magnetic energy product of the sintered Nd-Fe-B magnet enables the application of some small and highly integrated high-tech products to be possible. With the development of clean energy technology, especially in the fields of new energy automobiles and permanent magnet motors, the demand of neodymium iron boron is rapidly increased. However, in these fields, the ndfeb magnet needs to work at a higher temperature, but the ndfeb magnet has poor thermal stability, which puts higher requirements on the coercivity of the magnet.
The method for improving the coercive force of the neodymium iron boron magnet mainly comprises the following two steps: the coercive force of the magnet can be obviously improved by adding the heavy rare earth Dy or Tb by an alloying method, but the method can cause excessive decline of remanence, and the heavy rare earth resource is limited, so that the waste of the heavy rare earth resource is caused in large-scale production, the manufacturing cost is increased, and the method is not beneficial to long-term development. The other method is to improve the coercive force of the magnet by a grain boundary diffusion method. The method needs to attach heavy rare earth or heavy rare earth compounds on the surface of the magnet, and the attachment method comprises surface coating, dip coating, magnetron sputtering and the like. However, the utilization rate of heavy rare earth attached to the surface is low, and great waste exists. And the penetration distance is limited, the consistency of the magnet is poor, and the magnet with larger size is difficult to penetrate.
Disclosure of Invention
An object of the present invention is to solve at least the above problems and/or disadvantages and to provide at least the advantages described hereinafter.
Still another object of the present invention is to provide a percolation method for increasing the coercivity of sintered nd-fe-b, which can increase the percolation capability of heavy rare earth, thereby increasing the coercivity of the magnet with very little effect on remanence.
To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, there is provided an infiltration method for improving coercivity of sintered nd-fe-b, comprising:
uniformly mixing neodymium iron boron powder and heavy rare earth powder, and preparing the mixed powder into a neodymium iron boron blank magnet;
step two, processing the obtained neodymium iron boron blank magnet into a magnet base material with a preset size;
step three, coating flux dispersion liquid on the surface of the magnet base material obtained in the step two;
and step four, carrying out secondary tempering treatment on the magnet base material coated with the flux dispersion liquid in a vacuum sintering furnace.
Preferably, the infiltration method for improving the coercivity of the sintered neodymium iron boron further includes the following steps before the third step: preparing a fluxing agent dispersion liquid; the preparation process of the fluxing agent dispersion liquid comprises the following steps:
mixing fluxing agent powder, adhesive and dispersing agent in a weight ratio of 10-100 to obtain fluxing agent dispersion liquid, wherein the density of the fluxing agent dispersion liquid is 0.1-3g/cm 3 The flux powder is one or a combination of potassium sulfate, sodium nitrate, boron oxide, sodium sulfate, magnesium sulfate, lithium carbonate and lead oxide, the adhesive is one or a combination of polyvinyl pyrrolidone (PVP), polyethylene glycol, polypropylene glycol, polyisobutylene or polyacrylic acid, methyl cellulose and ethyl cellulose, and the dispersant is one or a combination of methanol, ethanol, ethylene glycol, propanol, benzene, toluene, ethylene glycol, ethyl acetate and propyl acetate.
Preferably, in the infiltration method for improving coercivity of sintered neodymium iron boron, in the first step, the heavy rare earth is a combination of one or more of a heavy rare earth simple substance, a heavy rare earth alloy, a heavy rare earth fluoride and a heavy rare earth oxide, an average size range of the heavy rare earth powder is 0.1 to 2 micrometers, an average size range of the neodymium iron boron powder is 2 to 8 micrometers, and a proportion range of the heavy rare earth powder to the neodymium iron boron powder is 0.01wt% to 0.5wt% when mixing.
Preferably, in the infiltration method for improving the coercivity of the sintered neodymium iron boron, in the fourth step, the secondary tempering treatment specifically includes: firstly, heating the mixture in vacuum for 3 to 8 hours at the temperature of 850 to 950 ℃, and then heating the mixture in vacuum for 1 to 4 hours at the temperature of 480 to 600 ℃.
Preferably, the infiltration method for improving the coercivity of the sintered neodymium iron boron further includes, before the step one:
the neodymium iron boron flail sheet is prepared by smelting and flail sheet processes,
neodymium iron boron powder was prepared by hydrogen crushing, medium crushing and coarse powder mixing processes.
Preferably, the infiltration method for improving the coercivity of the sintered neodymium iron boron specifically includes the following steps of coating a flux dispersion liquid on the surface of the magnet base material obtained in the second step:
removing oil and acid washing of the magnet base material to remove surface impurities;
the flux dispersion liquid is coated on the surface of the magnet base material in a dip-coating, brush-coating or spraying way, and the coating amount of the flux dispersion liquid is 0.05-1 g/cm 2 ；
And drying the surface of the coated magnet base material at the temperature of 50-120 ℃.
Preferably, the infiltration method for improving the coercivity of the sintered neodymium iron boron specifically comprises the following steps of:
the mixed powder is pressed and molded under the anaerobic condition, and the density of the magnet of the neodymium iron boron blank after pressing is 3.75 to 4.2g/cm 3 ；
And (3) carrying out vacuum sintering on the pressed neodymium iron boron blank magnet for 3-8 h at the temperature of 980-1100 ℃.
Preferably, in the infiltration method for improving the coercivity of the sintered neodymium iron boron, in the second step, the thickness of the magnet base material is less than 2 cm.
Preferably, in the infiltration method for improving the coercivity of the sintered neodymium iron boron, the heavy rare earth is one or more of terbium fluoride, dysprosium fluoride, terbium oxide and dysprosium oxide.
The invention at least comprises the following beneficial effects: according to the invention, the neodymium iron boron powder and the heavy rare earth powder are uniformly mixed, so that the heavy rare earth elements can be uniformly dispersed at a crystal boundary, and the problem of poor performance consistency of the sintered magnet can be solved. And preparing the mixed powder into a neodymium iron boron blank magnet, processing the neodymium iron boron blank magnet into a magnet base material with a preset size, coating the fluxing agent dispersion liquid on the surface of the magnet base material, and finally performing secondary tempering treatment on the magnet base material coated with the fluxing agent dispersion liquid in a vacuum sintering furnace. The advantages of this are that the flux can obviously reduce the melting point of the grain boundary phase, increase the fluidity of the grain boundary phase during tempering, and enable the heavy rare earth elements to be fully diffused in the grain boundary phase, thereby forming a continuous region with high rare earth content at the boundary of the main phase. Meanwhile, after the grain boundary is permeated by the heavy rare earth, the grain boundary rare earth-rich phase is more continuous and clearer, the isolation exchange coupling effect is more effective, and the coercive force of the magnet is increased. In addition, the invention can also reduce the use amount of heavy rare earth, thereby greatly saving the production cost.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention.
Drawings
Fig. 1 is a schematic flow chart of a permeation method for improving the coercivity of sintered neodymium iron boron according to an embodiment of the present invention.
Detailed Description
The present invention is described in further detail below with reference to the attached drawings so that those skilled in the art can implement the invention by referring to the description text.
It will be understood that terms such as "having," "including," and "comprising," as used herein, do not preclude the presence or addition of one or more other elements or groups thereof.
As shown in fig. 1, the infiltration method for improving the coercivity of the sintered neodymium iron boron provided by the embodiment of the present invention includes:
s10, preparing the neodymium iron boron flail sheet through smelting and flail sheet processes.
S20, preparing neodymium iron boron powder through hydrogen crushing, medium crushing and coarse powder mixing.
S30, uniformly mixing neodymium iron boron powder and heavy rare earth powder, and preparing the mixed powder into a neodymium iron boron blank magnet;
wherein, make neodymium iron boron blank magnet with the powder after the mixture specifically include:
s31, pressing and forming the mixed powder under the oxygen-free condition, wherein the density of the magnet of the pressed neodymium iron boron blank is 3.75-4.2g/cm 3 ；
S32, vacuum sintering the pressed neodymium iron boron blank magnet for 3-8 hours at the temperature of 980-1100 ℃.
Wherein, the heavy rare earth is one or the combination of more of a heavy rare earth simple substance, a heavy rare earth alloy, a heavy rare earth fluoride and a heavy rare earth oxide, the average size range of the heavy rare earth powder is 0.1-2 microns, the average size range of the neodymium iron boron powder is 2-8 microns, and the proportion range of the heavy rare earth powder and the neodymium iron boron powder is 0.01-0.5 wt% when the heavy rare earth powder and the neodymium iron boron powder are mixed. The heavy rare earth is one or a combination of more of terbium fluoride, dysprosium fluoride, terbium oxide and dysprosium oxide.
And S40, processing the obtained neodymium iron boron blank magnet into a magnet base material with a preset size, wherein the thickness of the magnet base material is preferably less than 2 cm.
S50, preparing flux dispersion liquid; the preparation process of the fluxing agent dispersion liquid comprises the following steps:
mixing fluxing agent powder, adhesive and dispersing agent in a weight ratio of 10-100 to obtain fluxing agent dispersion liquid, wherein the density of the fluxing agent dispersion liquid is 0.1-3g/cm 3 Wherein the fluxing agent powder is potassium sulfate, sodium nitrate, boron oxide, sodium sulfate, magnesium sulfate, lithium carbonate,The adhesive is one or more of polyvinylpyrrolidone (PVP), polyethylene glycol, polypropylene glycol, polyisobutylene or polyacrylic acid, methylcellulose and ethyl cellulose, and the dispersing agent is one or more of methanol, ethanol, ethylene glycol, propanol, benzene, toluene, ethylene glycol, ethyl acetate and propyl acetate.
And S60, coating the flux dispersion liquid on the surface of the magnet base material.
The specific process comprises the following steps:
s61, removing oil and acid washing of the magnet base material to take out surface impurities;
s62, coating the flux dispersion liquid on the surface of the magnet base material in a dip-coating, brush-coating or spraying manner, wherein the coating amount of the flux dispersion liquid is 0.05-1 g/cm 2 ；
S63, drying the surface of the coated magnet base material at the temperature of 50-120 ℃.
And S70, performing secondary tempering treatment on the magnet base material coated with the flux dispersion liquid in a vacuum sintering furnace.
Wherein, the secondary tempering treatment specifically comprises the following steps: firstly, heating in vacuum for 3-8 h at 850-950 ℃, and then heating in vacuum for 1-4 h at 480-600 ℃.
The sintered Nd-Fe-B magnet consists of a main phase, a grain boundary phase and a boron-rich phase, wherein the main phase plays a determining role in the residual magnetism of the magnet. The boron-rich phase belongs to the impurity phase, and the smaller the volume fraction, the better. Besides the coercive force of the magnet is influenced by the components of the magnet, the structural organization of grain boundary phases and the components of the grain boundary phases have great influence on the coercive force of the magnet. The grain boundary phase is mainly composed of rare earth elements having a lower melting point than the main phase. Therefore, the neodymium-iron-boron powder and the heavy rare earth powder are uniformly mixed, so that the heavy rare earth elements can be uniformly dispersed at the grain boundary, and the problem of poor performance consistency of the sintered magnet can be solved. And preparing the mixed powder into a neodymium iron boron blank magnet, processing the neodymium iron boron blank magnet into a magnet base material with a preset size, coating the fluxing agent dispersion liquid on the surface of the magnet base material, and finally performing secondary tempering treatment on the magnet base material coated with the fluxing agent dispersion liquid in a vacuum sintering furnace. The advantages of this are that the flux can obviously reduce the melting point of the grain boundary phase, increase the fluidity of the grain boundary phase during tempering, and enable the heavy rare earth elements to be fully diffused in the grain boundary phase, thereby forming a continuous region with high rare earth content at the boundary of the main phase. Meanwhile, after the grain boundary is permeated by the heavy rare earth, the grain boundary rare earth-rich phase is more continuous and clearer, the isolation exchange coupling effect is more effective, and the coercive force of the magnet is increased. In addition, the invention can also reduce the use amount of heavy rare earth, thereby greatly saving the production cost.
The following description will be given with reference to specific examples.
Example 1:
step 1, selecting neodymium iron boron with the mark number of 42H as a base material, and pouring and throwing raw materials;
step 2, preparing neodymium-iron-boron powder by hydrogen crushing, medium crushing and jet milling of the throwing sheet in the step 1, wherein the average particle size of the powder is 3.2-33 mu m, and then adding terbium fluoride powder with the average particle size of 0.5 mu m to ensure that the mass ratio of the terbium fluoride powder: neodymium iron boron powder in an amount of 0.5wt% was mixed for 4 hours using a V-type mixer;
step 3, the mixed powder is subjected to orientation compression in a 1.5T magnetic field, and the density of a pressed compact is 3.8g/cm 3 Sintering the pressed blank for 5 hours at 1030 ℃ under a vacuum condition to obtain a neodymium iron boron blank;
step 4, ultrasonically dispersing 100g of boron oxide powder and 1g of polyvinylpyrrolidone into ethanol, wherein the size of the boron oxide powder is 1.2 mu m;
step 5, processing the neodymium iron boron blank into a magnet base material with the thickness of 50 x 30 x 4mm, removing oil and acid cleaning to remove surface impurities, dip-coating the base material in the boron oxide dispersion liquid prepared in the step 4 for 2 times, and drying for 30min at the temperature of 100 ℃, wherein the measured density of the attached boron oxide is 0.2g/cm 3 ；
And (3) carrying out secondary tempering treatment on the coated magnet substrate, wherein the primary tempering temperature is 900 ℃, the heat preservation time is 5 hours, the secondary tempering temperature is 520 ℃, and the tempering time is 3 hours.
The magnetic properties of the samples of example 1 are shown in table 1.
TABLE 1
Example 2:
step 1, selecting neodymium iron boron with the grade of 42H as a base material, and pouring and throwing raw materials;
and 2, preparing neodymium-iron-boron powder by hydrogen crushing, medium crushing and airflow milling of the throwing pieces in the step 1, wherein the average particle size of the powder is 3.2-33 mu m, and then adding dysprosium fluoride powder with the average particle size of 0.5 mu m to ensure that the dysprosium fluoride powder: neodymium iron boron powder with weight ratio of 0.5wt% was mixed for 4 hours using a V-type blender;
step 3, the mixed powder is subjected to orientation compression in a 1.5T magnetic field, and the density of a pressed compact is 3.8g/cm 3 Sintering the pressed blank for 5 hours at 1030 ℃ under a vacuum condition to obtain a neodymium iron boron blank;
step 4, ultrasonically dispersing 100g of boron oxide powder and 1g of polyvinylpyrrolidone into propanol, wherein the size of the boron oxide powder is 2 microns;
step 5, processing the neodymium iron boron blank into a magnet base material with the thickness of 50 x 30 x 4mm, removing oil and acid cleaning to remove surface impurities, dip-coating the base material in the lithium fluoride dispersion prepared in the step 4 for 2 times, and drying for 30min at the temperature of 100 ℃, wherein the measured density of the attached boron oxide is 0.2g/cm 3 ；
And 6, carrying out secondary tempering treatment on the coated magnet substrate, wherein the primary tempering temperature is 900 ℃, the heat preservation time is 5 hours, the secondary tempering temperature is 520 ℃, and the tempering time is 3 hours.
The magnetic properties of the sample of example 2 are shown in Table 2.
TABLE 2
Example 3:
step 1, selecting neodymium iron boron with the grade of 52H as a base material, and pouring and throwing raw materials;
and 2, preparing neodymium-iron-boron powder by hydrogen crushing, medium crushing and airflow milling of the throwing pieces in the step 1, wherein the average particle size of the powder is 3.2-33 mu m, and then adding terbium fluoride powder with the average particle size of 0.5 mu m to ensure that the terbium fluoride powder: neodymium iron boron powder in an amount of 0.5wt% was mixed for 4 hours using a V-type mixer;
step 3, the mixed powder is subjected to orientation compression in a 1.5T magnetic field, and the density of a pressed compact is 3.8g/cm 3 Sintering the pressed blank for 5 hours at 1070 ℃ under a vacuum condition to obtain a neodymium iron boron blank;
step 4, ultrasonically dispersing 100g of lithium carbonate powder and 1g of polyvinylpyrrolidone in ethanol, wherein the size of the lithium carbonate powder is 1.2 mu m;
step 5, processing the neodymium iron boron blank into a magnet base material with the thickness of 50 x 30 x 4mm, removing oil and acid cleaning to remove surface impurities, dip-coating the base material in the lithium carbonate dispersion liquid prepared in the step 4 for 2 times, and drying for 30min at the temperature of 100 ℃, wherein the measured density of the attached lithium carbonate is 0.2g/cm 3 ；
And 6, carrying out secondary tempering treatment on the coated magnet substrate, wherein the primary tempering temperature is 860 ℃, the heat preservation time is 4 hours, the secondary tempering temperature is 490 ℃, and the tempering time is 2 hours.
The magnetic properties of the samples of example 3 are shown in table 3.
TABLE 3
Example 4:
step 1, selecting neodymium iron boron with the grade of 42H as a base material, and pouring and throwing raw materials;
and 2, preparing neodymium-iron-boron powder by hydrogen crushing, medium crushing and airflow milling of the throwing piece in the step 1, wherein the average particle size of the powder is 3.2-33 mu m, and then adding terbium fluoride powder with the average particle size of 1 mu m to ensure that the terbium fluoride powder: neodymium iron boron powder in an amount of 0.5wt% was mixed for 4 hours using a V-type mixer;
step 3, the mixed powder is directionally pressed in a magnetic field of 1.5T, and the density of a pressed compact is 3.8g/cm 3 Sintering the pressed blank for 5 hours at 1030 ℃ under a vacuum condition to obtain a neodymium iron boron blank;
step 4, ultrasonically dispersing 100g of lead oxide powder and 3g of polyvinylpyrrolidone into ethanol, wherein the size of the lead oxide powder is 1.2 mu m;
step 5, processing the neodymium iron boron blank into a magnet base material with the thickness of 50 x 30 x 8mm, removing oil and acid cleaning to remove surface impurities, dip-coating the base material in the lead oxide dispersion liquid prepared in the step 4 for 2 times, and drying at the temperature of 100 ℃ for 30min, wherein the measured density of the attached lead oxide is 0.2g/cm 3 ；
And 6, carrying out secondary tempering treatment on the coated magnet base material, wherein the primary tempering temperature is 900 ℃, the heat preservation time is 5 hours, the secondary tempering temperature is 520 ℃, and the tempering time is 3 hours.
The magnetic properties of the samples of example 4 are shown in Table 4.
TABLE 4
As described above, the method of the present embodiment can improve the permeability of the heavy rare earth, thereby improving the coercive force of the magnet, and has very little influence on remanence.
While embodiments of the invention have been disclosed above, it is not intended to be limited to the uses set forth in the specification and examples. It can be applied to all kinds of fields suitable for the present invention. Additional modifications will readily occur to those skilled in the art. It is therefore intended that the invention not be limited to the exact details and illustrations described and illustrated herein, but fall within the scope of the appended claims and equivalents thereof.
Claims (7)
1. A penetration method for improving the coercivity of sintered neodymium iron boron is characterized by comprising the following steps:
step one, uniformly mixing neodymium iron boron powder and heavy rare earth powder, and preparing the mixed powder into a neodymium iron boron blank magnet, wherein in the step one, the heavy rare earth is one or a combination of multiple of a heavy rare earth simple substance, a heavy rare earth alloy, a heavy rare earth fluoride and a heavy rare earth oxide, the average size range of the heavy rare earth powder is 0.1-2 micrometers, the average size range of the neodymium iron boron powder is 2-8 micrometers, and the proportion range of the heavy rare earth powder and the neodymium iron boron powder is 0.01-0.5 wt% during mixing;
step two, processing the obtained neodymium iron boron blank magnet into a magnet base material with a preset size;
step three, coating flux dispersion liquid on the surface of the magnet base material obtained in the step two, wherein the step three is preceded by the following steps: preparing a fluxing agent dispersion liquid; the preparation process of the fluxing agent dispersion liquid comprises the following steps:
mixing fluxing agent powder, adhesive and dispersing agent in a weight ratio of 10-100 to obtain fluxing agent dispersion liquid, wherein the density of the fluxing agent dispersion liquid is 0.1-3g/cm 3 The flux powder is one or a combination of more of potassium sulfate, sodium nitrate, boron oxide, sodium sulfate, magnesium sulfate, lithium carbonate and lead oxide, the adhesive is one or a combination of more of polyvinylpyrrolidone (PVP), polyethylene glycol, polypropylene glycol, polyisobutylene or polyacrylic acid, methylcellulose and ethylcellulose, and the dispersant is one or a combination of more of methanol, ethanol, glycol, propanol, benzene, toluene, glycol, ethyl acetate and propyl acetate;
and step four, carrying out secondary tempering treatment on the magnet base material coated with the flux dispersion liquid in a vacuum sintering furnace.
2. The infiltration method for improving the coercivity of sintered neodymium-iron-boron according to claim 1, wherein in the fourth step, the secondary tempering treatment specifically comprises: firstly, heating the mixture in vacuum for 3 to 8 hours at the temperature of 850 to 950 ℃, and then heating the mixture in vacuum for 1 to 4 hours at the temperature of 480 to 600 ℃.
3. The infiltration method for improving the coercivity of sintered NdFeB as claimed in claim 1, further comprising, before the step one:
the neodymium iron boron flail sheet is prepared by smelting and flail sheet processes,
neodymium iron boron powder was prepared by hydrogen crushing, medium crushing and coarse powder mixing processes.
4. The infiltration method for improving coercivity of sintered neodymium iron boron according to claim 1, wherein the step of coating the flux dispersion liquid on the surface of the magnet base material obtained in the step two specifically comprises:
removing oil and acid washing from the magnet base material to remove surface impurities;
the flux dispersion liquid is coated on the surface of the magnet base material in a dip-coating, brush-coating or spraying way, and the coating amount of the flux dispersion liquid is 0.05-1 g/cm 2 ；
And drying the surface of the coated magnet base material at the temperature of 50-120 ℃.
5. The infiltration method for improving the coercivity of sintered NdFeB as claimed in claim 1, wherein the step of making the mixed powder into a NdFeB blank magnet specifically comprises:
pressing the mixed powder under the anaerobic condition to form, wherein the density of the magnet of the pressed neodymium iron boron blank is 3.75-4.2g/cm 3 ；
And (3) carrying out vacuum sintering on the pressed neodymium iron boron blank magnet for 3-8 h at the temperature of 980-1100 ℃.
6. The infiltration method for improving the coercivity of sintered NdFeB as claimed in claim 1, wherein in step two, the thickness of the magnet substrate is less than 2 cm.
7. The infiltration method for improving coercivity of sintered NdFeB in claim 1, wherein the heavy rare earth is one or more of terbium fluoride, dysprosium fluoride, terbium oxide, dysprosium oxide, terbium hydride and dysprosium hydride.
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| CN103456451A (en) * | 2013-09-12 | 2013-12-18 | 南京理工大学 | Method for preparing room temperature high magnetic energy product anti-corrosion sintered NdFeB |
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