CN113517125B - High-stability sintered NdFeB magnet and preparation method thereof - Google Patents
High-stability sintered NdFeB magnet and preparation method thereof Download PDFInfo
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- CN113517125B CN113517125B CN202110785379.1A CN202110785379A CN113517125B CN 113517125 B CN113517125 B CN 113517125B CN 202110785379 A CN202110785379 A CN 202110785379A CN 113517125 B CN113517125 B CN 113517125B
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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
- 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
Abstract
The invention discloses a high-stability sintered NdFeB magnet and a preparation method thereof. First, the components of the molten alloy are (Dy) a Nd 1‑a ) x (Co b Fe 1‑b ) 100‑x‑y B y Alloy I and composition of (Dy) a Nd 1‑a ) x Tb 55‑x Fe 30 (Cu c Al d Ga 1‑c‑d ) 15 Tb is then controlled in the grain boundary rare earth rich phase and RE in the final magnet by blending Tb-rich alloy II in Tb-free alloy I 2 Fe 14 In the surface layer of the B phase crystal grain, tb element plays a role in enriching rare earth phase and RE in the grain boundary 2 Fe 14 The strengthening effect of the surface layer of the B phase crystal grain improves the coercive force of the magnet and the coercive force temperature coefficient of the magnet, and the obtained product has the characteristics of high magnetic field stability and high coercive force thermal stability.
Description
Technical Field
The invention belongs to the field of rare earth permanent magnet materials, and particularly relates to a high-stability sintered NdFeB magnet and a preparation method thereof.
Background
The sintered NdFeB permanent magnetic material is a permanent magnetic functional material with highest comprehensive magnetic performance and the widest application, is named as contemporary 'magnetic king', and is a key supporting material for promoting the development of related fields such as energy, information and the like. Since the advent of the 80 s of the 20 th century, sintered neodymium-iron-boron magnets are widely applied to various fields such as automobile industry, medical equipment, electronic information, aerospace and the like by virtue of excellent magnetic performance and extremely high cost performance, and become a key support for the development of the related fields to intelligence, miniaturization and light weight. In recent years, with the continuous improvement of the performance of sintered NdFeB magnets, the application fields of the sintered NdFeB magnets are also continuously expanded.
However, the sintered neodymium-iron-boron permanent magnet material has poor magnetic field stability (low coercive force) and the heavy rare earth content of the high coercive force magnet is high. Because the heavy rare earth resources are less in reserves and high in price, a large amount of heavy rare earth resources are used, sustainable exploitation and use of the heavy rare earth resources are not facilitated, and the production and manufacturing cost of the magnet is also obviously increased. In addition, the addition of heavy rare earth metal can reduce the residual magnetism of the magnet, thereby reducing the magnetic field intensity provided by the magnet in space, and being unfavorable for the light weight and miniaturization of related devices.
Meanwhile, the sintered NdFeB permanent magnet material has poor thermal stability, and has higher temperature coefficient of remanence and temperature coefficient of coercive force, and the remanence and coercive force are obviously reduced along with the rise of temperature. The higher remanence temperature coefficient directly influences the stability of a magnetic field provided by the magnet in the surrounding space, so that the stability of related devices is influenced; the higher coercivity temperature coefficient makes the magnet prone to reverse magnetization at high temperatures, resulting in reduced or even failure of the magnet performance. The sintered NdFeB magnet with higher temperature coefficient can not meet the application requirements in the fields of frequent temperature change, high-temperature permanent magnet motor and the like, and further development of the NdFeB permanent magnet industry is limited. The samarium cobalt permanent magnet with better temperature resistance or a cooling system with complex design can only be applied in the fields for cooling the magnet, cobalt belongs to precious strategic metal due to rare samarium reserves, the use of the samarium cobalt permanent magnet also improves the production and manufacturing cost of a combined device or equipment to a certain extent, the design of the cooling system also increases the difficulty of device design, manufacture, maintenance and repair, and popularization and application of the device or equipment are limited.
Furthermore, the sintered NdFeB permanent magnet material has poor corrosion resistance and is extremely easy to generate corrosion failure in the use environment, although various surface protection coatings are researched and developed in recent years for the surface protection of the NdFeB permanent magnet, and the application requirements are basically met. However, the research shows that the corrosion resistance of the NdFeB permanent magnet can directly influence the adhesive force and the protective capability of the protective coating, and the research on improving the corrosion resistance of the NdFeB permanent magnet is a key for further improving the overall corrosion resistance of the magnet.
Through research and development for many years, various methods for improving the magnetic field stability, the thermal stability and the corrosion resistance of the sintered NdFeB permanent magnet material have been disclosed. However, these methods are mainly aimed at one or two of the three or have limited improvement effect on the performance of sintered NdFeB permanent magnet materials. In order to meet the application requirements in the fields of strong corrosion, high temperature and strong demagnetizing field, new process technology must be developed, and meanwhile, the magnetic field stability, thermal stability and corrosion resistance of the sintered neodymium-iron-boron magnet are remarkably improved.
Disclosure of Invention
In view of the above, the invention provides a high-stability sintered neodymium-iron-boron magnet and a preparation method thereof, and the magnetic field stability, the thermal stability and the corrosion resistance of the magnet are improved by controlling the distribution of Co element, tb element and O element, and the prepared sintered neodymium-iron-boron magnet has the characteristic of high stability.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
the preparation method of the sintered NdFeB magnet comprises the following steps:
alloy smelting: the smelting component is Dy a Nd 1-a ) x (Co b Fe 1-b ) 100-x-y B y Alloy I and composition of (Dy) a Nd 1-a ) x Tb 55-x Fe 30 (Cu c Al d Ga 1-c-d ) 15 Alloy II of (a); wherein a, x, b, y, c, d is the mass percent of the corresponding elements respectively, and the values are respectively as follows: a is more than or equal to 0.20 and less than or equal to 0.25, x is more than or equal to 29 and less than or equal to 30, b is more than or equal to 0.1 and less than or equal to 0.2,0.98, y is more than or equal to 1.00,0.3 and less than or equal to c is more than or equal to 0.4,0.3 and less than or equal to d is more than or equal to 0.4;
and (3) crystallization treatment: preparing the alloy I into a micro-crystal thin belt I, and preparing the alloy II into a nano-crystal thin belt II;
crushing and pulverizing: crushing the micro-crystal thin strip I into powder by utilizing a hydrogen crushing and airflow grinding process to obtain powder I with the average granularity of 2-2.5 mu m, and crushing the nano-crystal thin strip II into powder to obtain powder II with the average granularity of 1-1.5 mu m;
powder modification: adding 0.5-1% of antioxidant into the powder I, and uniformly mixing to obtain modified powder I; according to the proportion of 1kg of powder II corresponding to 0.1-0.2 mol of oxygen, introducing high-purity oxygen into a charging bucket for storing the powder II, and continuously stirring to obtain modified powder II; the antioxidant is one of Butyl Hydroxy Anisole (BHA), dibutyl hydroxy toluene (BHT) and Tertiary Butyl Hydroquinone (TBHQ).
Powder mixing: uniformly mixing modified powder I and modified powder II according to the proportion of modified powder II= (94-95) to (5-6) to obtain mixed powder; preferably, the powder mixing step can be further mixed with a lubricant with a mass fraction of 1-2%o, wherein the lubricant is zinc stearate and has a molecular formula of: zn (C) 17 H 35 COO) 2 。
Preparing a magnet: and (3) placing the mixed powder in a magnetic field of not less than 2T for compression molding to prepare a pressed compact, and sequentially carrying out high-temperature vacuum sintering and heat treatment on the pressed compact to obtain the sintered NdFeB magnet. Preferably, the green compact is subjected to cold isostatic pressing of 150 to 250MPa for 30 to 60 seconds before being subjected to high-temperature vacuum sintering. Further preferably, the high temperature vacuum sintering has a vacuum degree of more than 1×10 -2 Pa, the high-temperature vacuum sintering temperature is 1050-1100 ℃, and the sintering time is 3-5 hours. The heat treatment is two-stage heat treatment, namely primary heat treatment and secondary heat treatment in sequence; wherein: the temperature of the primary heat treatment is 880-920 ℃ and the time is 3-6 h; the temperature of the secondary heat treatment is 480-520 ℃ and the time is 3-6 h.
In the steps, high-purity argon is used for protecting materials in the steps of alloy smelting, crystallization treatment, hydrogen crushing for crushing and pulverizing, vacuum sintering for preparing a magnet and heat treatment; the air flow grinding step of crushing and pulverizing, the modification step of powder I, the powder mixing step and the compression molding step of magnet preparation utilize high-purity nitrogen to protect materials and prevent the materials from contacting oxygen or water vapor.
The invention also provides a sintered NdFeB magnet prepared by the preparation method, which is prepared from RE 2 Fe 14 The main phase crystal grain and the crystal boundary rare earth-rich phase positioned around the main phase crystal grain are composed, and the oxygen content is 1000 ppm-2000 ppm; the RE 2 Fe 14 RE in B is Nd, dy and Tb, and RE is 2 Fe 14 The mass fraction of Tb in the main phase crystal grain of B is less than or equal to 1%, and the mass fraction of Co in the crystal boundary rare earth-rich phase is less than or equal to 5%. Further, the coercive force of the sintered NdFeB magnet is more than 30kOe, the absolute value of the residual magnetic temperature coefficient at 20-120 ℃ is less than 0.08%/K, and the absolute value of the coercive force temperature coefficient at 20-200 ℃ is less than 0.40%/K; corrosion weight loss after 500 hours PCT test < 2mg/cm 2 The test conditions were 120℃at 100% RH, 2atm.
Compared with the prior art, the invention has the beneficial effects that:
(1) Controlling Tb element in grain boundary rare earth rich phase and RE in final magnet by blending Tb element-rich alloy II powder in Tb-free alloy I powder 2 Fe 14 In the surface layer of the B phase crystal grain, the Tb element fully plays the rare earth-rich phase and RE of the grain boundary 2 Fe 14 The strengthening effect of the surface layer of the B-phase crystal grain improves the coercive force of the magnet and the coercive force temperature coefficient of the magnet. The prepared sintered NdFeB magnet has the characteristics of high magnetic field stability and high coercivity and thermal stability.
(2) Co content in the grain boundary phase is controlled by controlling the rare earth-rich phase content in alloy I so that Co element is mainly present in RE 2 Fe 14 Phase B; by adding RE-free 2 Fe 14 Alloy II of B phase makes Co element exist in each main phase grain of final magnet, and fully exerts Co element on RE 2 Fe 14 The residual magnetism temperature coefficient of the phase B is improved. The prepared sintered NdFeB magnet has the characteristic of high residual magnetism and heat stability.
(3) Because the oxidation resistance of the nanocrystalline powder is stronger, the reaction between the powder and oxygen is milder and more uniform in the modification process of the powder II by controlling the grain size of the alloy II (nanocrystalline), and the oxygen content distribution in the final magnet is more uniform. The prepared sintered NdFeB magnet has the characteristic of excellent corrosion resistance.
Detailed Description
In order that the invention may be readily understood, a more particular description of the invention will be rendered by reference to specific embodiments that are illustrated in the appended drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
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.
Example 1
The smelting component is Dy 0.2 Nd 0.8 ) 29 (Co 0.2 Fe 0.8 ) 70.02 B 0.98 And (Dy) 0.2 Nd 0.8 ) 29 Tb 26 Fe 30 (Cu 0.32 Al 0.38 Ga 0.3 ) 15 (the subscripts corresponding to the above elements indicate mass fractions thereof, hereinafter the same) of alloy I 1 And alloy II 1 The method comprises the steps of carrying out a first treatment on the surface of the Alloy I is respectively quenched by melt rapid quenching equipment 1 And II 1 To produce the micro-crystal thin belt I 1 And nanocrystalline ribbon II 1 The method comprises the steps of carrying out a first treatment on the surface of the Respectively grinding the thin belt I by using hydrogen crushing and air flow grinding process 1 And II 1 Crushing into powder I with average particle size of 2 μm 1 And powder II having an average particle size of 1 μm 1 The method comprises the steps of carrying out a first treatment on the surface of the In powder I 1 Adding 0.5%o (mass fraction) of Butyl Hydroxy Anisole (BHA) as antioxidant, mixing uniformly to obtain modified powder I 1 The method comprises the steps of carrying out a first treatment on the surface of the According to 1kg of powder II 1 High-purity oxygen is introduced into the storage powder II according to the proportion of 0.1mol of oxygen 1 Continuously stirring to obtain modified powder II 1 The method comprises the steps of carrying out a first treatment on the surface of the Modified powder I was prepared at a mass ratio of 94:6 1 And modified powder II 1 Uniformly mixing to obtain mixed powder; compression molding the mixed powder in a 2T magnetic field to obtain a powder having a density of 4.0g/cm 3 And then vacuum sintering and heat treatment are carried out to obtain the sintered NdFeB magnet with high stability. Wherein: the vacuum degree in the sintering process is more than 1 multiplied by 10 -2 Pa, the vacuum sintering temperature is 1050 ℃, and the sintering time is 5 hours; the heat treatment comprises a primary heat treatment process and a secondary heat treatment process, wherein the primary heat treatment temperature is 880 ℃, and the heat treatment time is 3 hours; the secondary heat treatment temperature is 500 ℃, and the heat treatment time is 3 hours.
Removing powder II 1 And in the modification step, except high-purity oxygen is introduced, and in other steps, high-purity argon or high-purity nitrogen is used for protecting the material, so that the material is prevented from being contacted with oxygen or water vapor. Wherein: the alloy smelting step, the crystallization treatment step, the hydrogen crushing step of crushing and pulverizing, the vacuum sintering step and the heat treatment step of magnet preparation all utilize high-purity argon to protect materials; air flow grinding step of crushing and pulverizing, and powder I 1 The modification step, the powder mixing step and the compression molding step of the magnet preparation utilize high-purity nitrogen to protect materials.
Comparative example 1
According to modified powder I 1 And II 1 Mixed component Dy 5.8 Nd 23.2 Tb 1.56 Fe 54.46 Co 13.16 Cu 0.29 Al 0.34 Ga 0.2 7 B 0.92 Smelting alloy III 1 The method comprises the steps of carrying out a first treatment on the surface of the Alloy III using melt rapid quenching apparatus 1 To produce micro-crystal thin belt III 1 The method comprises the steps of carrying out a first treatment on the surface of the Thin strip III is prepared by hydrogen crushing and air flow grinding to prepare powder 1 Crushing into powder III with average particle size of 2 μm 1 The method comprises the steps of carrying out a first treatment on the surface of the In powder III 1 Adding 0.5%o (mass fraction) of Butyl Hydroxy Anisole (BHA) as antioxidant, mixing uniformly to obtain modified powder III 1 The method comprises the steps of carrying out a first treatment on the surface of the Modified powder in 2T magnetic fieldIII 1 Compression molding to obtain a density of 4.0g/cm 3 Is then sintered in vacuo and heat treated. The protection requirements for the vacuum sintering and heat treatment process parameters and the sample preparation process are the same as in example 1.
Example 2
The smelting component is Dy 0.21 Nd 0.79 ) 29.2 (Co 0.16 Fe 0.84 ) 69.82 B 0.98 And (Dy) 0.21 Nd 0.79 ) 29.2 Tb 25.8 Fe 30 (Cu 0.36 Al 0.34 Ga 0.3 ) 15 Alloy I of (2) 2 And alloy II 2 The method comprises the steps of carrying out a first treatment on the surface of the Alloy I is respectively quenched by melt rapid quenching equipment 2 And II 2 To produce the micro-crystal thin belt I 2 And nanocrystalline ribbon II 2 The method comprises the steps of carrying out a first treatment on the surface of the Respectively grinding the thin belt I by using hydrogen crushing and air flow grinding process 2 And II 2 Crushing into powder I with average particle size of 2.1 μm 2 Powder II having an average particle size of 1.5. Mu.m 2 The method comprises the steps of carrying out a first treatment on the surface of the In powder I 2 Adding 0.6 per mill (mass fraction) of dibutyl hydroxy toluene (BHT) as antioxidant, and mixing to obtain modified powder I 2 The method comprises the steps of carrying out a first treatment on the surface of the According to 1kg of powder II 2 High-purity oxygen is introduced into the storage powder II according to the proportion of 0.14mol of oxygen 2 Continuously stirring to obtain modified powder II 2 The method comprises the steps of carrying out a first treatment on the surface of the Modified powder I was prepared at a mass ratio of 94:6 2 And modified powder II 2 Uniformly mixing, and simultaneously mixing 1 per mill (mass fraction) of zinc stearate as a lubricant to obtain mixed powder; compression molding the mixed powder in a 2.2T magnetic field to obtain a powder having a density of 3.6g/cm 3 Isostatic pressing treatment is carried out for 1 minute under the condition of 250MPa, and then vacuum sintering and heat treatment are carried out, thus obtaining the sintered NdFeB magnet with high stability. Wherein: the vacuum degree in the sintering process is more than 8 multiplied by 10 -3 Pa, the vacuum sintering temperature is 1060 ℃, and the sintering time is 5 hours; the heat treatment comprises a primary heat treatment process and a secondary heat treatment process, wherein the primary heat treatment temperature is 900 ℃, and the heat treatment time is 3 hours; the secondary heat treatment temperature was 520 ℃ and the heat treatment time was 3 hours).
Removing powder II 2 In the modification step, besides high-purity oxygen is introduced,in other steps, high-purity argon or high-purity nitrogen is used for protecting the material, so that the material is prevented from being contacted with oxygen or water vapor. Wherein: the alloy smelting step, the crystallization treatment step, the hydrogen crushing step of crushing and pulverizing, the vacuum sintering step and the heat treatment step of magnet preparation all utilize high-purity argon to protect materials; air flow grinding step of crushing and pulverizing, and powder I 2 The modification step, the powder mixing step and the compression molding step of the magnet preparation utilize high-purity nitrogen to protect materials.
Comparative example 2
According to modified powder I 2 And II 2 Mixed component Dy 6.13 Nd 23.07 Tb 1.55 Fe 56.93 Co 10.50 Cu 0.32 Al 0.31 Ga 0.27 B 0.92 Smelting alloy III 2 The method comprises the steps of carrying out a first treatment on the surface of the Alloy III using melt rapid quenching apparatus 2 To produce micro-crystal thin belt III 2 The method comprises the steps of carrying out a first treatment on the surface of the Thin strip III is prepared by hydrogen crushing and air flow grinding to prepare powder 2 Crushing into powder III with average particle size of 2 μm 2 The method comprises the steps of carrying out a first treatment on the surface of the In powder III 1 Adding 0.6 per mill (mass fraction) of dibutyl hydroxy toluene (BHT) as antioxidant and 1 per mill (mass fraction) of zinc stearate as lubricant, and mixing to obtain modified powder III 2 The method comprises the steps of carrying out a first treatment on the surface of the Modified powder III in a magnetic field of 2.2T 2 Compression molding to obtain a density of 3.6g/cm 3 Is isostatically pressed for 1 minute under the condition of 250MPa, and then is vacuum sintered and heat-treated. The protection requirements for the vacuum sintering and heat treatment process parameters and the sample preparation process are the same as in example 2.
Example 3
The smelting component is Dy 0.22 Nd 0.78 ) 29.4 (Co 0.14 Fe 0.86 ) 69.6 Alloy I of B 3 The sum component is (Dy) 0.22 Nd 0.78 ) 29.4 Tb 25.6 Fe 30 (Cu 0.38 Al 0.32 Ga 0.3 ) 15 Alloy II of (2) 3 The method comprises the steps of carrying out a first treatment on the surface of the Alloy I is respectively quenched by melt rapid quenching equipment 3 And II 3 To produce the micro-crystal thin belt I 3 And nanocrystalline ribbon II 3 The method comprises the steps of carrying out a first treatment on the surface of the Pulverizing by hydrogen crushing and air flow grindingThe process respectively carries out the process on the thin belt I 3 And II 3 Crushing into powder I with average particle size of 2.2 μm 3 Powder II having an average particle size of 1.3. Mu.m 3 The method comprises the steps of carrying out a first treatment on the surface of the In powder I 3 Adding 0.8%o (mass fraction) of Tertiary Butyl Hydroquinone (TBHQ) as antioxidant, and mixing uniformly to obtain modified powder I 3 The method comprises the steps of carrying out a first treatment on the surface of the According to 1kg of powder II 3 High-purity oxygen is introduced into the storage powder II according to the proportion of 0.12mol of oxygen 3 Continuously stirring to obtain modified powder II 3 The method comprises the steps of carrying out a first treatment on the surface of the Modified powder I was prepared at a mass ratio of 95:5 3 And modified powder II 3 Uniformly mixing, and simultaneously mixing zinc stearate with the mass fraction of 2 per mill as a lubricant to obtain mixed powder; compression molding the mixed powder in a 2T magnetic field to obtain a powder having a density of 3.7g/cm 3 And (3) carrying out isostatic pressing treatment for 30 seconds under the condition of 220MPa, and then carrying out vacuum sintering and heat treatment to obtain the high-stability sintered NdFeB magnet. Wherein: the vacuum degree in the sintering process is more than 6 multiplied by 10 -3 Pa, the vacuum sintering temperature is 1070 ℃, and the sintering time is 4 hours; the heat treatment comprises a primary heat treatment process and a secondary heat treatment process, wherein the primary heat treatment temperature is 900 ℃, and the heat treatment time is 4 hours; the secondary heat treatment temperature was 500℃and the heat treatment time was 3 hours).
Removing powder II 3 And in the modification step, except high-purity oxygen is introduced, and in other steps, high-purity argon or high-purity nitrogen is used for protecting the material, so that the material is prevented from being contacted with oxygen or water vapor. Wherein: the alloy smelting step, the crystallization treatment step, the hydrogen crushing step of crushing and pulverizing, the vacuum sintering step and the heat treatment step of magnet preparation all utilize high-purity argon to protect materials; air flow grinding step of crushing and pulverizing, and powder I 3 The modification step, the powder mixing step and the compression molding step of the magnet preparation utilize high-purity nitrogen to protect materials.
Comparative example 3
According to modified powder I 3 And II 3 Mixed component Dy 6.47 Nd 22.93 Tb 1.28 Fe 58.36 Co 9.26 Cu 0.285 Al 0.24 Ga 0.225 B 0.95 Smelting alloy III 3 The method comprises the steps of carrying out a first treatment on the surface of the By means ofMelt rapid quenching apparatus for alloy III 3 To produce micro-crystal thin belt III 3 The method comprises the steps of carrying out a first treatment on the surface of the Thin strip III is prepared by hydrogen crushing and air flow grinding to prepare powder 3 Crushing into powder III with average particle size of 2 μm 3 The method comprises the steps of carrying out a first treatment on the surface of the In powder III 3 Adding 0.5%o (mass fraction) of Tertiary Butyl Hydroquinone (TBHQ) as antioxidant and 1%o (mass fraction) of zinc stearate as lubricant, and mixing uniformly to obtain modified powder III 3 The method comprises the steps of carrying out a first treatment on the surface of the Modified powder III in a 2T magnetic field 3 Compression molding to obtain a density of 3.7g/cm 3 Is isostatically pressed for 30 seconds under 220MPa, and then vacuum sintered and heat-treated. The protection requirements for the vacuum sintering and heat treatment process parameters and the sample preparation process are the same as in example 3.
Example 4
The smelting component is Dy 0.23 Nd 0.77 ) 29.6 (Co 0.18 Fe 0.82 ) 69.41 B 0.99 Alloy I of (2) 4 The sum component is (Dy) 0.23 Nd 0.77 ) 29.6 Tb 25.4 Fe 30 (Cu 0.4 Al 0.3 Ga 0.3 ) 15 Alloy II of (2) 4 The method comprises the steps of carrying out a first treatment on the surface of the Alloy I is respectively quenched by melt rapid quenching equipment 4 And II 4 To produce the micro-crystal thin belt I 4 And nanocrystalline ribbon II 4 The method comprises the steps of carrying out a first treatment on the surface of the Respectively grinding the thin belt I by using hydrogen crushing and air flow grinding process 4 And II 4 Crushing into powder I with average particle size of 2.3 μm 4 Powder II having an average particle size of 1.4. Mu.m 4 The method comprises the steps of carrying out a first treatment on the surface of the In powder I 4 Adding 0.7 per mill (mass fraction) of Butyl Hydroxy Anisole (BHA) as antioxidant, and mixing to obtain modified powder I 4 The method comprises the steps of carrying out a first treatment on the surface of the According to 1kg of powder II 4 High-purity oxygen is introduced into the storage powder II according to the proportion of 0.16mol of oxygen 4 Continuously stirring to obtain modified powder II 4 The method comprises the steps of carrying out a first treatment on the surface of the Modified powder I was prepared at a mass ratio of 94:6 4 And modified powder II 4 Uniformly mixing, and simultaneously mixing 1.3 per mill (mass fraction) of zinc stearate as a lubricant to obtain mixed powder; compression molding the mixed powder in a 2.1T magnetic field to obtain a powder having a density of 3.7g/cm 3 Is isostatically pressed for 40 seconds under 200MPaAnd performing vacuum sintering and heat treatment to obtain the high-stability sintered NdFeB magnet. Wherein: the vacuum degree in the sintering process is more than 8 multiplied by 10 -3 Pa, the vacuum sintering temperature is 1080 ℃, and the sintering time is 4 hours; the heat treatment comprises a primary heat treatment process and a secondary heat treatment process, wherein the primary heat treatment temperature is 920 ℃, and the heat treatment time is 5 hours; the secondary heat treatment temperature was 520 ℃ and the heat treatment time was 5 hours).
Removing powder II 4 And in the modification step, except high-purity oxygen is introduced, and in other steps, high-purity argon or high-purity nitrogen is used for protecting the material, so that the material is prevented from being contacted with oxygen or water vapor. Wherein: the alloy smelting step, the crystallization treatment step, the hydrogen crushing step of crushing and pulverizing, the vacuum sintering step and the heat treatment step of magnet preparation all utilize high-purity argon to protect materials; air flow grinding step of crushing and pulverizing, and powder I 4 The modification step, the powder mixing step and the compression molding step of the magnet preparation utilize high-purity nitrogen to protect materials.
Comparative example 4
According to modified powder I 4 And II 4 Mixed component Dy 6.81 Nd 22.79 Tb 1.52 Fe 55.31 Co 11.74 Cu 0.36 Al 0.27 Ga 0.27 B 0.93 Smelting alloy III 4 The method comprises the steps of carrying out a first treatment on the surface of the Alloy III using melt rapid quenching apparatus 4 To produce micro-crystal thin belt III 4 The method comprises the steps of carrying out a first treatment on the surface of the Thin strip III is prepared by hydrogen crushing and air flow grinding to prepare powder 4 Crushing into powder III with average particle size of 2.3 μm 4 The method comprises the steps of carrying out a first treatment on the surface of the In powder III 4 Adding 0.7 per mill (mass fraction) of Butyl Hydroxy Anisole (BHA) as antioxidant and 1.3 per mill (mass fraction) of zinc stearate as lubricant, and mixing to obtain modified powder III 4 The method comprises the steps of carrying out a first treatment on the surface of the Modified powder III in a magnetic field of 2.1T 4 Compression molding to obtain a density of 3.7g/cm 3 Is isostatically pressed for 40 seconds under 200MPa, and then vacuum sintered and heat-treated. The protection requirements for the vacuum sintering and heat treatment process parameters and the sample preparation process are the same as in example 4.
Example 5
The smelting components are respectively as followsDy 0.24 Nd 0.76 ) 29.8 (Co 0.1 Fe 0.9 ) 69.2 Alloy I of B 5 The sum component is (Dy) 0.24 Nd 0.76 ) 29.8 Tb 25.2 Fe 30 (Cu 0.34 Al 0.36 Ga 0.3 ) 15 Alloy II of (2) 5 The method comprises the steps of carrying out a first treatment on the surface of the Alloy I is respectively quenched by melt rapid quenching equipment 5 And II 5 To produce the micro-crystal thin belt I 5 And nanocrystalline ribbon II 5 The method comprises the steps of carrying out a first treatment on the surface of the Respectively grinding the thin belt I by using hydrogen crushing and air flow grinding process 5 And II 5 Crushing into powder I with average particle size of 2.4 μm 5 Powder II having an average particle size of 1.1. Mu.m 5 The method comprises the steps of carrying out a first treatment on the surface of the In powder I 5 Adding 0.9%o (mass fraction) of Tertiary Butyl Hydroquinone (TBHQ) as antioxidant, and mixing uniformly to obtain modified powder I 5 The method comprises the steps of carrying out a first treatment on the surface of the According to 1kg of powder II 5 High-purity oxygen is introduced into the storage powder II according to the proportion of 0.2mol of oxygen 5 Continuously stirring to obtain modified powder II 5 The method comprises the steps of carrying out a first treatment on the surface of the Modified powder I was prepared at a mass ratio of 95:5 5 And modified powder II 5 Uniformly mixing, and simultaneously mixing 1.6 per mill (mass fraction) of zinc stearate as a lubricant to obtain mixed powder; compression molding the mixed powder in a 2.2T magnetic field to obtain a powder having a density of 3.8g/cm 3 And (3) carrying out isostatic pressing treatment for 50 seconds under the condition of 220MPa, and then carrying out vacuum sintering and heat treatment to obtain the high-stability sintered NdFeB magnet. Wherein: the vacuum degree in the sintering process is more than 6 multiplied by 10 -3 Pa, the vacuum sintering temperature is 1100 ℃, and the sintering time is 3 hours; the heat treatment comprises a primary heat treatment process and a secondary heat treatment process, wherein the primary heat treatment temperature is 900 ℃, and the heat treatment time is 3 hours; the secondary heat treatment temperature was 480℃and the heat treatment time was 4 hours).
Removing powder II 5 And in the modification step, except high-purity oxygen is introduced, and in other steps, high-purity argon or high-purity nitrogen is used for protecting the material, so that the material is prevented from being contacted with oxygen or water vapor. Wherein: the alloy smelting step, the crystallization treatment step, the hydrogen crushing step of crushing and pulverizing, the vacuum sintering step and the heat treatment step of magnet preparation all utilize high-purity argon to protect materials; air flow mill for crushing and pulverizingStep, powder I 5 The modification step, the powder mixing step and the compression molding step of the magnet preparation utilize high-purity nitrogen to protect materials.
Comparative example 5
According to modified powder I 5 And II 5 Mixed component Dy 7.15 Nd 22.65 Tb 1.26 Fe 60.67 Co 6.57 Cu 0.255 Al 0.27 Ga 0.225 B 0.95 Smelting alloy III 5 The method comprises the steps of carrying out a first treatment on the surface of the Alloy III using melt rapid quenching apparatus 5 To produce micro-crystal thin belt III 5 The method comprises the steps of carrying out a first treatment on the surface of the Thin strip III is prepared by hydrogen crushing and air flow grinding to prepare powder 5 Crushing into powder III with average particle size of 2.4 μm 5 The method comprises the steps of carrying out a first treatment on the surface of the In powder III 5 Adding 0.9 per mill (mass fraction) of tert-butylhydroquinone (TBHQ) as antioxidant and 1.6 per mill (mass fraction) of zinc stearate as lubricant, and mixing to obtain modified powder III 5 The method comprises the steps of carrying out a first treatment on the surface of the Modified powder III in a magnetic field of 2.2T 5 Compression molding to obtain a density of 3.8g/cm 5 Is isostatically pressed for 50 seconds under 220MPa, and then vacuum sintered and heat-treated. The protection requirements for the vacuum sintering and heat treatment process parameters and the sample preparation process are the same as in example 5.
Example 6
The smelting component is Dy 0.25 Nd 0.75 ) 30 (Co 0.12 Fe 0.88 ) 69.01 B 0.99 Alloy I of (2) 6 The sum component is (Dy) 0.25 Nd 0.75 ) 30 Tb 25 Fe 30 (Cu 0.3 Al 0.4 Ga 0.3 ) 15 Alloy II of (2) 6 The method comprises the steps of carrying out a first treatment on the surface of the Alloy I is respectively quenched by melt rapid quenching equipment 6 And II 6 To produce the micro-crystal thin belt I 6 And nanocrystalline ribbon II 6 The method comprises the steps of carrying out a first treatment on the surface of the Respectively grinding the thin belt I by using hydrogen crushing and air flow grinding process 6 And II 6 Crushing into powder I with average particle size of 2.5 μm 6 Powder II having an average particle size of 1.2. Mu.m 6 The method comprises the steps of carrying out a first treatment on the surface of the In powder I 6 Adding 1%of dibutyl hydroxy toluene (BHT) as antioxidant, mixing to obtain modified powder I 6 The method comprises the steps of carrying out a first treatment on the surface of the According to1kg of powder II 6 High-purity oxygen is introduced into the storage powder II according to the proportion of 0.18mol of oxygen 6 Continuously stirring to obtain modified powder II 6 The method comprises the steps of carrying out a first treatment on the surface of the Modified powder I was prepared at a mass ratio of 95:5 6 And modified powder II 6 Uniformly mixing, and simultaneously mixing 1.8 per mill (mass fraction) of zinc stearate as a lubricant to obtain mixed powder; compression molding the mixed powder in a 2.2T magnetic field to obtain a powder having a density of 3.9g/cm 3 And (3) carrying out isostatic pressing treatment for 50 seconds under the condition of 150MPa, and then carrying out vacuum sintering and heat treatment to obtain the high-stability sintered NdFeB magnet. Wherein: the vacuum degree in the sintering process is more than 8 multiplied by 10 -3 Pa, the vacuum sintering temperature is 1090 ℃, and the sintering time is 3 hours; the heat treatment comprises a primary heat treatment process and a secondary heat treatment process, wherein the primary heat treatment temperature is 900 ℃, the heat treatment time is 4 hours, the secondary heat treatment temperature is 480 ℃, and the heat treatment time is 5 hours.
Removing powder II 6 And in the modification step, except high-purity oxygen is introduced, and in other steps, high-purity argon or high-purity nitrogen is used for protecting the material, so that the material is prevented from being contacted with oxygen or water vapor. Wherein: the alloy smelting step, the crystallization treatment step, the hydrogen crushing step of crushing and pulverizing, the vacuum sintering step and the heat treatment step of magnet preparation all utilize high-purity argon to protect materials; air flow grinding step of crushing and pulverizing, and powder I 6 The modification step, the powder mixing step and the compression molding step of the magnet preparation utilize high-purity nitrogen to protect materials.
Comparative example 6
According to modified powder I 6 And II 6 Mixed component Dy 7.5 Nd 22.5 Tb 1.25 Fe 59.19 Co 7.87 Cu 0.225 Al 0.3 Ga 0.22 5 B 0.94 Smelting alloy III 6 The method comprises the steps of carrying out a first treatment on the surface of the Alloy III using melt rapid quenching apparatus 6 To produce micro-crystal thin belt III 6 The method comprises the steps of carrying out a first treatment on the surface of the Thin strip III is prepared by hydrogen crushing and air flow grinding to prepare powder 6 Crushing into powder III with average particle size of 2.5 μm 6 The method comprises the steps of carrying out a first treatment on the surface of the In powder III 6 Adding 1%of dibutylhydroxytoluene (BHT) as an anti-theft agentThe oxidant and 1.8 per mill (mass fraction) of zinc stearate are used as lubricant, and the modified powder III is obtained after uniform mixing 6 The method comprises the steps of carrying out a first treatment on the surface of the Modified powder III in a magnetic field of 2.2T 6 Compression molding to obtain a density of 3.9g/cm 3 Is isostatically pressed for 50 seconds under 150MPa, and then vacuum sintered and heat-treated. The protection requirements for the vacuum sintering and heat treatment process parameters and the sample preparation process are the same as in example 6.
The Tb element distribution, co element distribution, oxygen content, coercive force, residual magnetic temperature coefficient, coercive force temperature coefficient, and corrosion weight loss of examples 1 to 6 and comparative examples 1 to 6 were comparatively tested, and the results are shown in table 1. From the comparison of the data in table 1, it can be found that the Tb element distribution, co element distribution and O element content in the magnet can be controlled by the technique of the present invention: the Tb content in the main phase of the examples is significantly lower than that of the comparative examples, the Co content in the grain boundary phase of the examples is significantly lower than that of the comparative examples, and the oxygen content of the examples is higher than that of the comparative examples. With the same composition, the coercivity of the examples is significantly higher than that of the comparative examples, the temperature coefficient of the examples is better than that of the comparative examples, and the corrosion weight loss of the examples is lower than that of the comparative examples.
Table 1 relevant properties of the magnets produced in examples 1 to 6 and comparative examples 1 to 6
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 (10)
1. A preparation method of a sintered NdFeB magnet is characterized by comprising the following steps: the method comprises the following steps:
alloy smelting: the smelting component is Dy a Nd 1-a ) x (Co b Fe 1-b ) 100-x-y B y Alloy I and composition of (Dy) a Nd 1-a ) x Tb 55-x Fe 30 (Cu c Al d Ga 1-c-d ) 15 Alloy II of (a); wherein a, x, b, y, c, d is the mass percent of the corresponding elements respectively, and the values are respectively as follows: a is more than or equal to 0.20 and less than or equal to 0.25, x is more than or equal to 29 and less than or equal to 30, b is more than or equal to 0.1 and less than or equal to 0.2,0.98, y is more than or equal to 1.00,0.3 and less than or equal to c is more than or equal to 0.4,0.3 and less than or equal to d is more than or equal to 0.4;
and (3) crystallization treatment: preparing the alloy I into a micro-crystal thin belt I, and preparing the alloy II into a nano-crystal thin belt II;
crushing and pulverizing: crushing the micro-crystal thin strip I into powder to obtain powder I, and crushing the nano-crystal thin strip II into powder to obtain powder II;
powder modification: adding an antioxidant into the powder I, and uniformly mixing to obtain modified powder I; introducing oxygen into the powder II while continuously stirring to obtain modified powder II;
powder mixing: uniformly mixing the modified powder I and the modified powder II to obtain mixed powder;
preparing a magnet: and (3) placing the mixed powder in a magnetic field of not less than 2T for compression molding to prepare a pressed compact, and sequentially carrying out high-temperature vacuum sintering and heat treatment on the pressed compact to obtain the sintered NdFeB magnet.
2. The method for preparing the sintered neodymium-iron-boron magnet according to claim 1, wherein the method comprises the following steps: in the step of crushing and pulverizing, the average granularity of the powder I is 2-2.5 mu m; the average particle size of the powder II is 1 μm to 1.5. Mu.m.
3. The method for preparing the sintered neodymium-iron-boron magnet according to claim 1, wherein the method comprises the following steps: in the step of powder modification, the antioxidant is one of butyl hydroxy anisole, dibutyl hydroxy toluene and tertiary butyl hydroquinone; the addition amount of the antioxidant is 0.5-1 per mill of the mass of the powder I; the amount of oxygen introduced into the powder II is 0.1 to 0.2mol of oxygen per 1kg of powder II.
4. The method for preparing the sintered neodymium-iron-boron magnet according to claim 1, wherein the method comprises the following steps: in the powder mixing step, the mass ratio of the modified powder I to the modified powder II is (94-95) to (5-6).
5. The method for preparing a sintered neodymium-iron-boron magnet according to claim 4, wherein: in the step of powder mixing, adding a lubricant into the modified powder I and the modified powder II when mixing; the lubricant is zinc stearate, and the molecular formula is as follows: zn (C) 17 H 35 COO) 2 The method comprises the steps of carrying out a first treatment on the surface of the The addition amount of the lubricant is 1-2 per mill of the mass of the finally obtained mixed powder.
6. The method for preparing the sintered neodymium-iron-boron magnet according to claim 1, wherein the method comprises the following steps: in the preparation of the step magnet, the density of the pressed compact was 3.6g/cm 3 ～4.0g/cm 3 。
7. The method for preparing a sintered neodymium-iron-boron magnet according to claim 6, wherein the method comprises the following steps: the pressed compact is subjected to cold isostatic pressing treatment of 150-250 MPa for 30-60 seconds before high-temperature vacuum sintering.
8. The method for preparing the sintered neodymium-iron-boron magnet according to claim 1, wherein the method comprises the following steps: in the preparation of the step magnet, the vacuum degree of the high-temperature vacuum sintering is more than 1 multiplied by 10 -2 Pa; the high-temperature vacuum sintering temperature is 1050-1100 ℃, and the sintering time is 3-5 hours.
9. The method for preparing the sintered neodymium-iron-boron magnet according to claim 1, wherein the method comprises the following steps: in the preparation of the magnet, the heat treatment is two-stage heat treatment, namely primary heat treatment and secondary heat treatment in sequence; wherein: the temperature of the primary heat treatment is 880-920 ℃ and the time is 3-6 h; the temperature of the secondary heat treatment is 480-520 ℃ and the time is 3-6 h.
10. A sintered neodymium-iron-boron magnet, characterized in that it is prepared by a method for preparing a sintered neodymium-iron-boron magnet according to any one of claims 1-9; the sintered NdFeB magnet is made of RE 2 Fe 14 The main phase crystal grain and the crystal boundary rare earth-rich phase positioned around the main phase crystal grain are composed, and the oxygen content is 1000 ppm-2000 ppm; the RE 2 Fe 14 RE in B is Nd, dy and Tb, and RE is 2 Fe 14 The mass fraction of Tb in the main phase crystal grains is less than or equal to 1%, and the mass fraction of Co in the grain boundary rare earth-rich phase is less than or equal to 5%; the coercive force of the sintered NdFeB magnet is more than 30kOe, the absolute value of the residual magnetic temperature coefficient is less than 0.08 percent/K at 20-120 ℃, and the absolute value of the coercive force temperature coefficient is less than 0.40 percent/K at 20-200 ℃; corrosion weight loss after 500 hours PCT test < 2mg/cm 2 The test conditions were 120℃at 100% RH, 2atm.
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