CN113838622A - High-coercivity sintered neodymium-iron-boron magnet and preparation method thereof - Google Patents
High-coercivity sintered neodymium-iron-boron magnet and preparation method thereof Download PDFInfo
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
- H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
- H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
- H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
- H01F1/047—Alloys characterised by their composition
- 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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- 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
Abstract
A high-coercivity sintered Nd-Fe-B magnet and a preparation method thereof belong to the field of rare earth permanent magnet materials, can solve the problems of high cost, reduction of the remanence and the magnetic energy product of magnets and incapability of large-scale production in the existing method for improving the coercivity of an Nd-Fe-B magnet, prepare jet milling powder of three sintered Nd-Fe-B magnets, mix the three jet milling powder, perform die pressing and cold isostatic pressing after uniform mixing to prepare green bodies, and perform sintering heat preservation treatment and heat treatment on the green bodies to obtain the sintered Nd-Fe-B magnet with high coercivity. The method of the invention can make the heavy rare earth alloy powder and the light alloy powder attach to the surface of the Nd-Fe-B magnetic powder, broaden the crystal boundary diffusion channel, fully disperse the heavy rare earth around the crystal grains, magnetically harden the surface of the crystal grains and obtain a good crystal boundary structure. The coercive force is further improved, the magnetic dilution of the magnet is reduced, the manufacturing process and equipment are simple, the operation is convenient, and the method is suitable for large-scale industrial production.
Description
Technical Field
The invention belongs to the technical field of rare earth permanent magnet materials, and particularly relates to a high-coercivity sintered neodymium-iron-boron magnet and a preparation method thereof.
Background
Since the sintered Nd-Fe-B magnet is a magnetic material with the strongest comprehensive magnetic performance, the sintered Nd-Fe-B magnet is widely applied to various environment-friendly fields, such as hybrid electric vehicle motors, medical instruments, wind driven generators, communication equipment, aerospace and advanced science and technology fields, due to the excellent magnetic performance and high cost performance of the sintered Nd-Fe-B magnet since the discovery in 1984. At present, the maximum remanence of sintered neodymium iron boron can be 1.55T, which is 96% of a theoretical value, but the coercive force is only 1/6-1/3% of the theoretical value. Therefore, increasing the coercivity of a magnet is currently the most important task.
At present, the improvement of the coercive force of the neodymium iron boron magnet is mainly realized by improving the magnetocrystalline anisotropy field of main phase crystal grains and improving a crystal boundary structure. In the actual production process, two process modes are generally adopted: one is to add heavy rare earth elements in the stage of smelting, namely add a large amount of heavy rare earth elements such as Dy, Tb, etc. while smelting, this direct addition mode has greatly raised the cost, not merely cause the strategic resource of heavy rare earth to consume seriously, and because of the anti-ferromagnetic coupling effect between Dy/Tb and Fe atom, have reduced remanence and magnetic energy product of the magnet; the other is grain boundary diffusion, namely, the heavy rare earth element permeates to the surface of the magnet by surface treatment methods such as sputtering, surface coating and the like to play a role in surface magnetic hardening, and meanwhile, the heavy rare earth element cannot enter the main phase alloy too much to cause obvious magnetic dilution. However, the diffusion depth is limited, and only small magnets can be prepared, which cannot be mass-produced.
In order to reduce the amount of heavy rare earth, the coercivity is greatly increased and mass production is achieved. Intergranular doping with heavy rare earth compounds is an effective method. The heavy rare earth alloy is designed to reduce the melting point of heavy rare earth elements, and liquid diffusion occurs at a certain sintering temperature higher than the melting point of the heavy rare earth elements, so that the magnetocrystalline anisotropy field of the main phase grains is improved. However, in the conventional double-alloy technology, the main phase crystal grains cannot be completely divided by the grain boundary phase, so that the coercivity of the neodymium iron boron magnet is not greatly increased.
Disclosure of Invention
The invention aims at the problems of high cost, reduction of remanence and magnetic energy product of the magnet and incapability of large-scale production in the existing method for improving the coercive force of the neodymium iron boron magnet, improves a high coercive force sintered neodymium iron boron magnet and a preparation method thereof, and is suitable for mass production.
The invention adopts the following technical scheme:
the high-coercivity sintered neodymium-iron-boron magnet comprises mixed metal powder consisting of main alloy powder and auxiliary alloy powder, wherein the auxiliary alloy powder comprises heavy rare earth alloy powder with a melting point lower than 1000 ℃ and light metal nano powder with a melting point lower than 800 ℃, the heavy rare earth alloy powder accounts for 0-4% of the mass ratio of the mixed metal powder, and the light metal nano powder accounts for 0-0.6% of the mass ratio of the mixed metal powder.
Further, the main alloy powder has a composition of [ (Pr)2Nd8)]a Fe100-a-b-c Bb McThe average grain size is 2.6 mu M, wherein M is one or more of Cu, Co, Zr, Ga and Al, a is more than or equal to 29.1 and less than or equal to 40, b is more than or equal to 0.9 and less than or equal to 1.1, and c is more than or equal to 0.5 and less than or equal to 2.5.
Further, the component of the heavy rare earth alloy powder is HRexMe100-xThe grain diameter is 2-6 mu m, wherein HRe comprises one or more of heavy rare earth elements Dy, Tb and Ho, and Me comprises one or more of Fe, Al, Cu, Mg, Ga, Co and Mn.
Further, the light metal nano powder comprises any one of Al, Mg and Ga, the granularity is less than 100nm, and the composition of the light metal nano powder and the heavy rare earth alloy powder is HRexMe100-xMe in (a) is not repeated.
A preparation method of a high-coercivity sintered neodymium-iron-boron magnet comprises the following steps:
firstly, preparing a neodymium iron boron main alloy raw material according to component design, smelting the prepared raw material, quickly solidifying and throwing to prepare a neodymium iron boron alloy cast sheet, placing the neodymium iron boron alloy cast sheet in a hydrogen treatment furnace, performing hydrogen absorption treatment and high-temperature dehydrogenation treatment, and then preparing neodymium iron boron main alloy fine powder through air flow grinding;
secondly, preparing heavy rare earth alloy powder according to component design, obtaining an alloy melt-spun sheet by adopting a rapid hardening and melt-spun sheet technology, and preparing the auxiliary heavy rare earth alloy powder by hydrogen crushing and air flow milling; preparing light metal nano powder;
thirdly, mixing the main alloy powder and the two auxiliary alloy powders;
fourthly, after mixing, carrying out orientation forming and pressing to obtain a green body; sintering and heat-treating the green body to obtain a sintered neodymium-iron-boron magnet blank;
and fifthly, performing heat treatment on the sintered neodymium iron boron magnet blank to obtain a high-coercivity sintered neodymium iron boron magnet.
Further, the mixing in the third step was mixed in a three-dimensional blender for 5 hours.
Further, the orientation forming and pressing in the fourth step is to perform orientation forming and isostatic pressing on the mixed powder in a 2T magnetic field to obtain a green compact; the sintering and heat treatment are that the pressed compact is sintered for 5 hours in vacuum at 1000-1100 ℃, and then is tempered for 3 hours at 900 ℃.
Further, the heat treatment in the fifth step is a second-stage tempering treatment at 480-560 ℃ for 4 h.
The invention utilizes a mixed doping method to improve the coercive force and utilizes the synergistic effect of two types of alloy powder. The melting point of the light metal is lower, about 650 ℃, and the light metal can be fully melted during high-temperature sintering, so that a grain boundary diffusion channel is dredged, and the fluidity of a grain boundary phase is improved. After the heavy rare earth compound is melted, the heavy rare earth compound is fully distributed around the main phase grains along a grain boundary diffusion channel, so that a hard magnetic layer can be formed on the surfaces of the grains to improve the coercivity. The combination of the two is beneficial to improving the utilization rate of the heavy rare earth elements, reducing the quantity of the agglomerate-shaped heavy rare earth intergranular phases and enabling the heavy rare earth elements to be uniformly distributed in the magnet. The synergistic effect of the two is more effective in improving the coercivity.
The invention has the following beneficial effects:
according to the method, two auxiliary alloy powders with different properties are added into the main alloy powder, the metals such as low-melting-point nano metals Al, Cu and Mg are firstly melted in the sintering process, a diffusion channel is opened, the fluidity of a grain boundary phase is improved, the heavy rare earth alloy can be uniformly distributed around a main phase grain after being subsequently melted, the utilization rate of the heavy rare earth is improved, a uniform hard magnetic layer is formed, and the coercivity can be obviously improved while the residual magnetism is ensured not to be greatly reduced.
Detailed Description
The following examples are further illustrative of the present invention as to the technical content of the present invention, but the essence of the present invention is not limited to the following examples, and those skilled in the art can and should understand that any simple changes or substitutions based on the spirit of the present invention should fall within the protection scope of the present invention.
For the following examples of the present application, the neodymium iron boron main alloy powder is prepared from the same raw material by the same process, so that the performance comparison is facilitated, and each example only has different proportions and types of the auxiliary alloy powder added between the grains.
Example 1
The neodymium iron boron preparation method in the embodiment comprises the following steps:
step 1, preparing a main alloy, and smelting a neodymium iron boron main alloy quick-setting sheet, wherein the nominal components are as follows: (Pr)2Nd8)31Fe66.62B0.98(CoCuZr)1.4And refining the main alloy sheet by using a vacuum induction rapid hardening casting sheet technology.
Step 2, preparing an auxiliary alloy A, and smelting a neodymium iron boron auxiliary alloy quick-setting sheet, wherein the weight percentage of the auxiliary alloy quick-setting sheet is as follows: tb80Fe20. The fine powder is obtained by hydrogen crushing and airflow milling. The auxiliary alloy B is common nano Al powder in the market.
And 3, mixing the main alloy powder with the auxiliary alloy A and the auxiliary alloy B according to the weight ratio of 98.8:1: 0.2.
And 4, placing the mixed powder in a three-dimensional mixer to mix the powder for 5 hours.
And 5, placing the powder in a magnetic field for vertical orientation, and pressing the powder into a green body, wherein the magnetic field intensity of the orientation is 2.0T.
Step 6, sintering the pressed green body in vacuum at 1050 ℃ for 5 hours; and then tempering and heat preservation are carried out for 3h at 900 ℃, and after tempering and heat preservation are carried out for 4h at 500 ℃, the furnace is cooled to room temperature, and the sintered neodymium-iron-boron magnet is obtained.
The magnet prepared in the example 1 is different from the magnet prepared in the comparative example 1 in that two auxiliary alloy powders are added, the rest process steps and parameters are unchanged, the performance of the magnet is obtained after detection, the remanence is 13.541kGs, and the coercive force reaches 19.080 kOe.
Example 2
The neodymium iron boron preparation method in the embodiment comprises the following steps:
step 1, preparing a main alloy, and smelting a neodymium iron boron main alloy quick-setting sheet, wherein the nominal components are as follows: (Pr)2Nd8)31Fe66.62B0.98(CoCuZr)1.4And refining the main alloy sheet by using a vacuum induction rapid hardening casting sheet technology.
Step 2, preparing an auxiliary alloy A, and smelting a neodymium iron boron auxiliary alloy quick-setting sheet, wherein the weight percentage of the auxiliary alloy quick-setting sheet is as follows: tb80Fe20. The fine powder is obtained by hydrogen crushing and airflow milling. The auxiliary alloy B is common nano Al powder in the market.
And 3, mixing the main alloy powder with the auxiliary alloy A and the auxiliary alloy B according to the weight ratio of 98.6:1: 0.4.
And 4, placing the mixed powder in a three-dimensional mixer to mix the powder for 5 hours.
And 5, placing the uniformly mixed powder in a magnetic field for vertical orientation, and pressing into a green body, wherein the magnetic field intensity of the orientation is 2.0T.
Step 6, sintering the pressed green body in vacuum at 1050 ℃ for 5 hours; and then tempering and heat preservation are carried out for 3h at 900 ℃, and after tempering and heat preservation are carried out for 4h at 500 ℃, the furnace is cooled to room temperature, and the sintered neodymium-iron-boron magnet is obtained.
The magnet prepared in the example 2 is different from the magnet prepared in the example 1 in that the percentage of the light alloy is increased to 0.4%, the rest process steps and parameters are unchanged, the performance of the magnet is obtained after detection, the remanence is 13.250kGs, and the coercive force reaches 20.330 kOe.
Example 3
The neodymium iron boron preparation method in the embodiment comprises the following steps:
step 1, preparing a main alloy, and smelting a neodymium iron boron main alloy quick-setting sheet, wherein the nominal components are as follows: (Pr)2Nd8)31Fe66.62B0.98(CoCuZr)1.4Rapid hardening casting technique by vacuum inductionAnd (4) refining the main alloy sheet.
Step 2, preparing an auxiliary alloy A, and smelting a neodymium iron boron auxiliary alloy quick-setting sheet, wherein the weight percentage of the auxiliary alloy quick-setting sheet is as follows: tb80Fe20And refining the auxiliary alloy sheet by using a sheet technology. The fine powder is obtained by hydrogen crushing and airflow milling. The auxiliary alloy B is common nano Al powder in the market.
And 3, mixing the main alloy powder with the auxiliary alloy A and the auxiliary alloy B according to the weight ratio of 98.4:1: 0.6.
And 4, placing the mixed powder in a three-dimensional mixer to mix the powder for 5 hours.
And 5, placing the powder in a magnetic field for vertical orientation, and pressing the powder into a green body, wherein the magnetic field intensity of the orientation is 2.0T.
Step 6, sintering the pressed green body in vacuum at 1050 ℃ for 5 hours; and then tempering and heat preservation are carried out for 3h at 900 ℃, and after tempering and heat preservation are carried out for 4h at 500 ℃, the furnace is cooled to room temperature, and the sintered neodymium-iron-boron magnet is obtained.
The magnet prepared in the example 3 is different from the magnet prepared in the example 2 in that the percentage of the light alloy is increased to 0.6%, the rest process steps and parameters are unchanged, the performance of the magnet is obtained after detection, the remanence is 13.003kGs, and the coercive force reaches 21.590 kOe.
Comparative example 1
The preparation method of neodymium iron boron in the comparative example comprises the following steps:
step 1, preparing a main alloy, and smelting a neodymium iron boron main alloy quick-setting sheet, wherein the nominal components are as follows: (Pr)2Nd8)31Fe66.62B0.98(CoCuZr)1.4，Pr2Nd8The master alloy sheet is made of common praseodymium-neodymium alloy in the market by utilizing a vacuum induction rapid hardening casting sheet technology.
Step 2, preparing an auxiliary alloy A, and smelting an auxiliary alloy rapid hardening sheet, wherein the auxiliary alloy rapid hardening sheet comprises the following components in percentage by weight: tb80Fe20Pulverizing with hydrogen and mechanically pulverizing to obtain fine powder.
Step 3, mixing the main alloy powder and the auxiliary alloy powder according to the ratio of 99: 1 and mixing.
And 4, mixing the powder for 5 hours, then vertically orienting in a magnetic field, and pressing into a green body, wherein the intensity of the oriented magnetic field is 2.0T.
And 5, sintering the pressed green body in vacuum at 1050 ℃ for 5 hours, then tempering and preserving heat at 900 ℃ for 3 hours, and tempering and preserving heat at 500 ℃ for 4 hours, and cooling the furnace to room temperature to obtain the sintered neodymium-iron-boron magnet.
The magnet prepared in comparative example 1 was not added with light alloy powder, and the magnet performance was obtained after the examination, the remanence was 13.70kGs, and the coercive force reached 18.17 kOe.
Comparative example 2
The neodymium iron boron preparation method in the embodiment comprises the following steps:
step 1, preparing a main alloy, and smelting a neodymium iron boron main alloy quick-setting sheet, wherein the nominal components are as follows: (Pr)2Nd8)31Fe66.62B0.98(CoCuZr)1.4And refining the main alloy sheet by using a vacuum induction rapid hardening casting sheet technology.
And 2, the auxiliary alloy B is common nano Al powder in the market.
Step 3, mixing the main alloy powder and the auxiliary alloy powder according to a weight ratio of 99.8: mixing at a ratio of 0.2.
And 4, placing the mixed powder in a three-dimensional mixer to mix the powder for 5 hours.
And 5, placing the powder in a magnetic field for vertical orientation, and pressing the powder into a green body, wherein the magnetic field intensity of the orientation is 2.0T.
Step 6, sintering the pressed green body in vacuum at 1050 ℃ for 5 hours; and then tempering and heat preservation are carried out for 3h at 900 ℃, and tempering and heat preservation are carried out for 4h at 500 ℃ and furnace cooling is carried out to room temperature, so as to obtain the sintered neodymium-iron-boron magnet.
The magnet prepared in the comparative example 2 is not added with heavy rare earth alloy powder, the place different from the comparative example 1 is that the light alloy powder is added, the rest process steps and parameters are unchanged, the performance of the magnet is obtained after detection, the remanence is 13.736kGs, and the coercive force reaches 15.910 kOe.
Comparative example 3
The neodymium iron boron preparation method in the embodiment comprises the following steps:
step 1, preparing a main alloy, and refining a neodymium iron boron main alloyThe alloy rapid hardening piece comprises the following nominal components: (Pr)2Nd8)31Fe66.62B0.98(CoCuZr)1.4And refining the main alloy sheet by using a vacuum induction rapid hardening casting sheet technology.
And 2, the auxiliary alloy B is common nano Al powder in the market.
Step 3, mixing the main alloy powder and the auxiliary alloy powder according to a weight ratio of 99.6: mixing at a ratio of 0.4.
And 4, putting the powder into a three-dimensional mixer to mix for 5 hours.
And 5, placing the powder in a magnetic field for vertical orientation, and pressing the powder into a green body, wherein the magnetic field intensity of the orientation is 2.0T.
Step 6, sintering the pressed green body in vacuum at 1050 ℃ for 5 hours; and then tempering and heat preservation are carried out for 3h at 900 ℃, and after tempering and heat preservation are carried out for 4h at 500 ℃, the furnace is cooled to room temperature, and the sintered neodymium-iron-boron magnet is obtained.
The magnet prepared in the comparative example 3 is not added with the heavy rare earth alloy powder, the difference from the comparative example 2 is that the proportion of the added light alloy powder is increased to 0.4%, the rest process steps and parameters are unchanged, the performance of the magnet is obtained after detection, the remanence is 13.596kGs, and the coercive force reaches 16.520 kOe.
Comparative example 4
The neodymium iron boron preparation method in the embodiment comprises the following steps:
step 1, preparing a main alloy, and smelting a neodymium iron boron main alloy quick-setting sheet, wherein the nominal components are as follows: (Pr)2Nd8)31Fe66.62B0.98(CoCuZr)1.4And refining the main alloy sheet by using a vacuum induction rapid hardening casting sheet technology.
And 2, the auxiliary alloy B is common nano Al powder in the market.
Step 3, mixing the main alloy powder and the auxiliary alloy powder according to a weight ratio of 99.4: mixing at a ratio of 0.6.
And 4, putting the powder into a three-dimensional mixer to mix for 5 hours.
And 5, placing the powder in a magnetic field for vertical orientation, and pressing the powder into a green body, wherein the magnetic field intensity of the orientation is 2.0T.
Step 6, sintering the pressed green body in vacuum at 1050 ℃ for 5 hours; and then tempering and heat preservation are carried out for 3h at 900 ℃, and after tempering and heat preservation are carried out for 4h at 500 ℃, the furnace is cooled to room temperature, and the sintered neodymium-iron-boron magnet is obtained.
The magnet prepared in the comparative example 4 is not added with the heavy rare earth alloy powder, the difference from the comparative example 3 is that the proportion of the added light alloy powder is increased to 0.6%, the rest process steps and parameters are unchanged, the performance of the magnet is obtained after detection, the remanence is 13.485kGs, and the coercive force reaches 16.913 kOe.
Comparative example 5
The preparation method of neodymium iron boron in the comparative example comprises the following steps:
step 1, preparing a main alloy, and smelting a neodymium iron boron main alloy quick-setting sheet, wherein the nominal components are as follows: (Pr)2Nd8)31Fe66.62B0.98(CoCuZr)1.4，Pr2Nd8The master alloy sheet is made of common praseodymium-neodymium alloy in the market by utilizing a vacuum induction rapid hardening casting sheet technology. The fine powder is obtained by hydrogen crushing and airflow milling.
And 4, mixing the fine powder for 5 hours, then vertically orienting the fine powder in a magnetic field, and pressing the fine powder into a green body, wherein the intensity of the oriented magnetic field is 2.0T.
And 5, sintering the pressed green body in vacuum at 1050 ℃ for 5 hours, then tempering and preserving heat at 900 ℃ for 3 hours, and tempering and preserving heat at 500 ℃ for 4 hours, and cooling the furnace to room temperature to obtain the sintered neodymium-iron-boron magnet.
The magnet prepared in the comparative example is not added with auxiliary alloy powder, and the performance of the magnet is obtained after detection, the remanence is 13.911kGs, and the coercive force reaches 14.330 kOe.
The magnet properties obtained in different ways are exhibited using table 1 for the above examples 1 to 7 and comparative example 1.
By magnet performance analysis, e.g. example 1 to example 3, relativeIn comparative example 1, the auxiliary alloy Tb was used80Fe20And the magnet prepared by the nano Al adding mode can improve the coercive force. In comparative example 1 and comparative example 2, heavy rare earth Tb was added80Fe20The auxiliary alloy and the nano Al auxiliary alloy show that the coercive force of the comparative example 1 is increased by a larger extent than that of the comparative example 2. Comparative examples 2 to 4 are the increase of the addition amount of the nano Al auxiliary alloy, and it can be seen that the increase of the coercive force of the magnet obtained in comparative examples 2 to 4 is reduced; examples 1 to 3, relative to comparative examples 1, 2, 3, 4, by doping the secondary alloy Tb80Fe20And the coercivity of the magnet can be greatly improved by the aid of the nano Al, the improvement range of the coercivity exceeds the sum of the increment of the coercivity of the single-doped auxiliary alloy, and particularly, when the content of the nano Al is improved, the larger the improvement range of the coercivity of the mixed-doped magnet is, the higher the increment of the coercivity of the mixed-doped auxiliary alloy is, the higher the increment of the mixed-doped magnet is, and the higher the increment of the mixed-doped magnet is, the higher the increment of the single-doped auxiliary alloy is, and the higher the increment of the coercivity of the mixed-doped auxiliary alloy is, the higher the increment of the mixed-doped auxiliary alloy is, and is 1.507 kOe.
In addition, in the preparation method, the neodymium iron boron magnet is prepared by selecting the auxiliary alloy according to the value ranges of the respective components of the two auxiliary alloys with different properties, taking values in the end values and the interval range, and adding the heavy rare earth alloy powder in an amount of 1-4 wt%, so that the effects of the embodiments 1-3 can be achieved, and the coercive force of the neodymium iron boron is improved.
According to the preparation method for improving the performance of the neodymium iron boron by adding the heavy rare earth with low amount, the secondary alloy powder is mixed and doped to optimize the grain boundary phase, the nano Al powder with low melting point is fully melted in the sintering process, the grain boundary diffusion channel is widened, the subsequent heavy rare earth alloy powder is fully dispersed around grains after being melted, and gradually diffused into the main phase to form a hard magnetic shell layer on the periphery of the grains; the coercive force can be obviously improved while ensuring a small reduction of the remanence.
Claims (8)
1. The utility model provides a high coercivity sintered neodymium iron boron magnet which characterized in that: the alloy powder comprises mixed metal powder consisting of main alloy powder and auxiliary alloy powder, wherein the auxiliary alloy powder comprises heavy rare earth alloy powder with the melting point lower than 1000 ℃ and light metal nano powder with the melting point lower than 800 ℃, the heavy rare earth alloy powder accounts for 0-4% of the mass of the mixed metal powder, and the light metal nano powder accounts for 0-0.6% of the mass of the mixed metal powder.
2. The high coercivity sintered neodymium iron boron magnet according to claim 1, characterized in that: the main alloy powder comprises [ (Pr)2Nd8)]a Fe100-a-b-c Bb McThe average grain size is 2.6 mu M, wherein M is one or more of Cu, Co, Zr, Ga and Al, a is more than or equal to 29.1 and less than or equal to 40, b is more than or equal to 0.9 and less than or equal to 1.1, and c is more than or equal to 0.5 and less than or equal to 2.5.
3. The high coercivity sintered neodymium iron boron magnet according to claim 1, characterized in that: the component of the heavy rare earth alloy powder is HRexMe100-xThe grain diameter is 2-6 mu m, wherein HRe comprises one or more of heavy rare earth elements Dy, Tb and Ho, and Me comprises one or more of Fe, Al, Cu, Mg, Ga, Co and Mn.
4. The high coercivity sintered neodymium iron boron magnet according to claim 1, characterized in that: the light metal nano powder comprises any one of Al, Mg and Ga, the granularity is less than 100nm, and the light metal nano powder and the heavy rare earth alloy powder are HRexMe100-xMe in (a) is not repeated.
5. A method of manufacturing a high coercivity sintered nd fe-b magnet according to any one of claims 1 to 4, characterized by: the method comprises the following steps:
firstly, preparing a neodymium iron boron main alloy raw material according to component design, smelting the prepared raw material, quickly solidifying and throwing to prepare a neodymium iron boron alloy cast sheet, placing the neodymium iron boron alloy cast sheet in a hydrogen treatment furnace, performing hydrogen absorption treatment and high-temperature dehydrogenation treatment, and then preparing neodymium iron boron main alloy fine powder through air flow grinding;
secondly, preparing heavy rare earth alloy powder according to component design, obtaining an alloy melt-spun sheet by adopting a rapid hardening and melt-spun sheet technology, and preparing the auxiliary heavy rare earth alloy powder by hydrogen crushing and air flow milling; preparing light metal nano powder;
thirdly, mixing the main alloy powder and the two auxiliary alloy powders;
fourthly, after mixing, carrying out orientation forming and pressing to obtain a green body; sintering and heat-treating the green body to obtain a sintered neodymium-iron-boron magnet blank;
and fifthly, performing heat treatment on the sintered neodymium iron boron magnet blank to obtain a high-coercivity sintered neodymium iron boron magnet.
6. The method for preparing the high-coercivity sintered neodymium-iron-boron magnet according to claim 5, wherein the method comprises the following steps: in the third step, the mixture is mixed in a three-dimensional mixer for 5 hours.
7. The method for preparing the high-coercivity sintered neodymium-iron-boron magnet according to claim 5, wherein the method comprises the following steps: the fourth step of the orientation forming and pressing into green compact is to carry out orientation forming and isostatic pressing on the mixed powder in a 2T magnetic field to obtain a green compact; the sintering and heat treatment are that the pressed compact is sintered for 5 hours in vacuum at 1000-1100 ℃, and then is tempered for 3 hours at 900 ℃.
8. The method for preparing the high-coercivity sintered neodymium-iron-boron magnet according to claim 5, wherein the method comprises the following steps: in the fifth step, the heat treatment is a second-stage tempering treatment at 480-560 ℃ for 4 h.
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