CN108806910B - Method for improving coercive force of neodymium iron boron magnetic material - Google Patents
Method for improving coercive force of neodymium iron boron magnetic material Download PDFInfo
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- CN108806910B CN108806910B CN201710310266.XA CN201710310266A CN108806910B CN 108806910 B CN108806910 B CN 108806910B CN 201710310266 A CN201710310266 A CN 201710310266A CN 108806910 B CN108806910 B CN 108806910B
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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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- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/14—Treatment of metallic powder
- B22F1/145—Chemical treatment, e.g. passivation or decarburisation
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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
Abstract
The invention discloses a method for improving the coercive force of a neodymium iron boron magnetic material, which comprises the following steps: providing sintered neodymium iron boron magnetic powder as a main phase material; providing a heavy rare earth-iron alloy ingot, and carrying out HDDR treatment on the heavy rare earth-iron alloy ingot to obtain heavy rare earth nanocrystalline powder serving as an auxiliary phase material; and uniformly mixing the sintered neodymium-iron-boron magnetic powder with the heavy rare earth nanocrystalline powder, and then sintering and annealing to obtain the neodymium-iron-boron magnetic material with high coercivity. According to the invention, the heavy rare earth nanocrystalline powder treated by HDDR is used as a structure modified alloy, the distribution of heavy rare earth elements is regulated while the grain boundary components and structure are improved, and the grain growth in the liquid phase sintering process is utilized to form a shell structure of heavy rare earth on the surface layer of the grain, so that the coercive force of the magnet can be greatly improved on the premise of ensuring high remanence, and the utilization rate of the heavy rare earth elements is improved.
Description
Technical Field
the invention particularly relates to a method for improving the coercive force of a neodymium iron boron magnetic material, and belongs to the technical field of magnetic materials.
background
The neodymium iron boron magnetic material is a magnetic material with the best magnetic property, which can realize industrial production at present and is widely applied to various fields in production and life. However, due to its low Curie temperature (310 ℃ to 510 ℃), in some high temperature environments the magnetic properties deteriorate drastically and no longer meet the service requirements. And the coercive force of the neodymium iron boron magnetic material is improved, and the loss of the magnetic performance of the neodymium iron boron magnetic material at higher temperature can be eliminated or reduced.
At present, the method for improving the coercive force of the neodymium iron boron sintered magnet mainly comprises the steps of directly adding heavy rare earth elements into a smelting alloy, refining crystal grains, diffusing and the like.
although the coercive force can be improved by directly adding the heavy rare earth element, the heavy rare earth element forms antiferromagnetic coupling with Fe in the Nd2Fe14B (2: 14:1 for short) main phase, so that the remanence of the heavy rare earth element is obviously reduced. On the other hand, the efficiency of improving the coercive force by adding heavy rare earth elements in smelting is not high, and the coercive force is improved by about 2kOe by adding every 1% of the heavy rare earth elements in mass ratio by taking Dy as an example.
Diffusion is another important method for improving the coercivity of the sintered neodymium iron boron, and the principle of the diffusion is mainly to realize the change of the atomic concentration at different positions through the migration motion of atoms at high temperature. By adopting a diffusion method, a shell structure wrapped by the phase of rich rare earth 2:14:1 can be formed on the surface layer of the crystal grains, and the reverse magnetization nucleation of the crystal grain boundary is reduced, so that the coercive force is greatly improved on the premise of having little influence on remanence. However, limited by the depth of diffusion, diffusion is generally only used for processing thin slice magnet samples, and has no obvious effect on the improvement of the coercive force of a large block magnet.
Disclosure of Invention
the invention mainly aims to provide a method for improving the coercive force of a neodymium iron boron magnetic material, so as to overcome the defects in the prior art.
in order to achieve the purpose, the technical scheme adopted by the invention comprises the following steps:
The embodiment of the invention provides a method for improving the coercive force of a neodymium iron boron magnetic material, which comprises the following steps:
Providing sintered neodymium iron boron magnetic powder as a main phase material;
Providing a heavy rare earth-iron alloy ingot, and carrying out HDDR treatment on the heavy rare earth-iron alloy ingot to obtain heavy rare earth nanocrystalline powder, wherein the HDDR treatment comprises hydrogenation, disproportionation, dehydrogenation and recombination treatment in sequence;
And uniformly mixing the sintered neodymium-iron-boron magnetic powder with the heavy rare earth nanocrystalline powder, and then sintering and annealing to obtain the neodymium-iron-boron magnetic material with high coercivity.
in some preferred embodiments, the method comprises: according to the atomic ratio of the heavy rare earth element to the iron element of 1: 2-1: 3, smelting the heavy rare earth metal simple substance and the iron simple substance under the protection of inert gas, and cooling to obtain the heavy rare earth-iron alloy ingot.
Further, the heavy rare earth element comprises dysprosium and/or terbium.
Compared with the prior art, the invention has the advantages that:
1. Compared with other preparation processes of rare earth-containing nanocrystalline particles, the method for improving the coercive force of the neodymium iron boron magnetic material adopts HDDR reaction to process the rare earth-iron compound to obtain heavy rare earth nanocrystalline powder, and the process equipment is simple, the conditions are easy to meet, and large-scale preparation can be realized;
2. The method for improving the coercive force of the neodymium iron boron magnetic material provided by the invention utilizes the heavy rare earth nanocrystalline treated by HDDR as a structure modified alloy, improves the components and the structure of a crystal boundary, and can regulate and control the distribution of heavy rare earth elements. The dispersibility of the magnetic powder particles is enhanced by utilizing the characteristic of fine nanocrystalline particles, so that the heavy rare earth atoms are uniformly diffused to a main phase shallow surface layer in the liquid phase sintering process to form a shell structure of a heavy rare earth element enriched surface layer, the coercive force of the magnet is improved on the premise of ensuring high remanence, and the utilization rate of the heavy rare earth elements is further improved;
3. The method for improving the coercive force of the neodymium iron boron magnetic material adopts an HDDR process, and the product has a nanocrystalline structure and is easy to separate. In practical application, common industrial production modes such as jet milling, ball milling and the like can be adopted, and even the manual grinding and separation under protective gas can be carried out;
4. The method for improving the coercive force of the neodymium iron boron magnetic material has an obvious improvement effect on the coercive force, and taking dysprosium as an example, the addition of 1% of dysprosium by mass fraction can improve 3.59 kOe.
Drawings
FIG. 1 is a graph showing a magnetic property test of a magnet after addition of Dy-Fe nano-crystalline powders having different Dy contents and an original magnet in example 1 of the present invention;
FIG. 2 is a graph showing a magnetic property test of the original magnet and the magnet after Dy-Fe nano-crystalline powders having different Dy contents were added in example 2 of the present invention;
FIG. 3 is a graph showing the magnetic property test curves of the original magnet and the magnet after Tb-Fe nano-crystal powder with different Tb contents is added in example 3 of the present invention;
fig. 4 and 5 are SEM images of the heavy rare earth nanocrystalline particles obtained by HDDR treatment in example 1 of the present invention.
Detailed Description
In recent years, there are many reports on the improvement of coercivity by modifying grain boundaries with intercrystalline addition of a low-melting-point nonmagnetic auxiliary phase. The action mechanism can be simply summarized as that the non-ferromagnetic auxiliary phase with the melting point lower than the sintering temperature forms a liquid phase in the sintering process, and a good magnetic isolation effect is formed among crystal grains while the crystal grains are lubricated and the surface defects and edges and corners of the crystal grains are eliminated, so that the effect of improving the coercive force is achieved. Therefore, the proper intergranular additives can play a good role in modifying the microstructure of the magnet in the sintering process.
In view of the defects of the prior art, the inventor of the present invention has made extensive research and practice to propose the technical solution of the present invention, and further explains the technical solution, the implementation process and the principle, etc. as follows. It is to be understood, however, that within the scope of the present invention, each of the above-described features of the present invention and each of the features described in detail below (examples) may be combined with each other to form new or preferred embodiments. Not to be reiterated herein, but to the extent of space.
The method for improving the coercive force of the neodymium iron boron magnetic material provided by the embodiment of the invention comprises the following steps:
Providing sintered neodymium iron boron magnetic powder as a main phase material;
Providing a heavy rare earth-iron alloy ingot, and carrying out HDDR treatment on the heavy rare earth-iron alloy ingot to obtain heavy rare earth nanocrystalline powder, wherein the HDDR treatment comprises hydrogenation, disproportionation, dehydrogenation and recombination treatment in sequence;
And uniformly mixing the sintered neodymium-iron-boron magnetic powder with the heavy rare earth nanocrystalline powder, and then sintering and annealing to obtain the neodymium-iron-boron magnetic material with high coercivity.
further, the HDDR process includes four stages of hydrogen absorption-disproportionation-dehydrogenation-recombination (HDDR), and the main mechanism is that rare earth atoms and hydrogen react at high temperature to generate fine hydride and other phase small particles, and nanocrystals with uniform size are generated in the dehydrogenation-recombination process in a nucleation and growth manner.
As one of the preferable schemes, the method comprises the following steps: according to the atomic ratio of the heavy rare earth element to the iron element of 1: 2-1: 3, smelting the heavy rare earth metal simple substance and the iron simple substance under the protection of inert gas, and cooling to obtain the heavy rare earth-iron alloy ingot.
Preferably, the smelting temperature is higher than the single-phase liquidus line of the rare earth metal simple substance and the iron simple substance by more than 50 ℃.
Preferably, the heavy rare earth element may be dysprosium, terbium, or the like.
Wherein the heavy rare earth-iron alloy ingot melted under the protection of inert gas should be cooled as fast as possible or eliminated from segregation in the subsequent annealing heat treatment.
Preferably, the smelting and cooling process comprises near-rapid solidification of cast pieces or cooling of an induction smelting copper mold.
Wherein, during the hydrogenation process of the heavy rare earth-iron alloy cast ingot by using the hydrogen heat treatment furnace, at least the hydrogen pressure is ensured to be above 50kPa so as to ensure sufficient hydrogen absorption.
In some preferred embodiments, during the HDDR process, the heavy rare earth-iron alloy ingot may be subjected to a hydrogen saturation treatment in a hydrogen atmosphere at a pressure of 50kPa or more to complete the hydrogenation treatment, thereby obtaining a heavy rare earth-iron alloy powder.
More specifically, the heavy rare earth-iron alloy ingot provided by the invention can be completely crushed to form powder with the particle size of about 10-100 μm through saturated hydrogen absorption in the HDDR reaction process, so that the ingot does not need to be subjected to any previous coarse crushing.
in some preferred embodiments, the heavy rare earth-iron alloy powder after the hydrogenation treatment may be treated in a hydrogen atmosphere at a pressure of 50 to 150kPa at 700 to 900 ℃ for more than 2 hours during the HDDR treatment to complete the disproportionation treatment. Preferably, the time of the disproportionation treatment is 2-3 h.
Further, taking dysprosium and terbium as examples, the preferable hydrogen pressure is 100kPa, the furnace body temperature is 780-840 ℃, and the disproportionation reaction time is 3 h.
In some preferred embodiments, in the HDDR process, the disproportionated heavy rare earth-iron alloy powder may be subjected to a dehydrogenation process, i.e., a low-vacuum dehydrogenation (slow dehydrogenation) process, in a vacuum environment with a pressure of 50 to 100Pa at a temperature of 700 to 900 ℃.
Preferably, the dehydrogenation treatment temperature is 780-840 ℃, the pressure is 50-100 Pa, and the time is 1-1.5 h.
In some preferred embodiments, in the HDDR treatment process, the heavy rare earth-iron alloy powder after the low vacuum treatment may be treated in an environment with a hydrogen pressure of 10 "1 or less at a temperature of 700 ℃ to 900 ℃ for more than 30min to complete the recombination treatment, so as to obtain the heavy rare earth nanocrystalline powder.
Preferably, the hydrogen pressure is 10 < -2 > to 10 < -1 > Pa, and the treatment time is 30 to 45 min.
Further, taking dysprosium and terbium as examples, the preferred hydrogen pressure is 10-2Pa and the heat treatment time is 45 min.
in some embodiments, after the HDDR process is complete, the high vacuum system of the hydrogen heat treatment furnace may be turned on, the residual hydrogen is pumped out, and the furnace tube is cooled by air cooling.
In the invention, through the HDDR treatment process, the heavy rare earth nanocrystalline powder with the grain size of 100 nm-1 μm and the average particle Size (SMD) of about 10-100 μm (before separation) can be finally obtained.
in some preferred embodiments, after the HDDR process is completed, the heavy rare earth nanocrystalline powder can be separated by physical grinding, using the characteristic of weak bonding force between the obtained heavy rare earth nanocrystalline particles, so as to obtain an auxiliary phase heavy rare earth nanocrystalline powder with an average particle size SMD of 0.5-1.5 μm, wherein the size of the crystal particles contained in the auxiliary phase heavy rare earth nanocrystalline powder is 100 nm-1 μm.
Preferably, the physical grinding mode comprises high-energy ball milling, hydrogen breaking-air flow milling and other processes.
In some preferred embodiments, the method further comprises: uniformly mixing the sintered neodymium-iron-boron magnetic powder with the heavy rare earth nanocrystalline powder, sintering for 2-4 hours at 980-1100 ℃, and annealing for 2-3 hours at 850-900 ℃ and 450-500 ℃ respectively to obtain the neodymium-iron-boron magnetic material with high coercivity.
In some more specific embodiments, the HDDR process may specifically include:
Placing the heavy rare earth-iron alloy cast ingot in a hydrogen heat treatment furnace, and saturating the heavy rare earth-iron alloy cast ingot in hydrogen atmosphere to absorb hydrogen to complete hydrogen absorption treatment;
Heating the furnace chamber of the hydrogen heat treatment furnace to 700-900 ℃ at the heating rate of 5-10 ℃/min, keeping the hydrogen pressure in the furnace chamber at 50-150 kPa, and preserving heat and pressure for 2-3 h to complete disproportionation treatment;
vacuumizing the furnace chamber of the hydrogen heat treatment furnace until the pressure of hydrogen in the furnace chamber is 50-100 Pa, preserving heat at 700-900 ℃ for 1h, then adjusting the pressure of the hydrogen in the furnace chamber of the hydrogen heat treatment furnace to be below 10-1, preserving heat at 700-900 ℃ for 45min, and finishing high-vacuum desorption and recovery treatment;
Removing hydrogen in a furnace cavity of a hydrogen heat treatment furnace, and cooling to obtain heavy rare earth nanocrystalline powder with the grain size of 100 nm-1 mu m and the average grain size of 10-100 mu m;
Separating the heavy rare earth nanocrystalline powder in a physical grinding mode, wherein the average grain diameter of the separated heavy rare earth nanocrystalline powder is 0.5-1.5 mu m, and the size of crystal grains contained in the heavy rare earth nanocrystalline powder is 100 nm-1 mu m.
Further, the sintered neodymium-iron-boron magnetic powder comprises a neodymium-iron-boron magnetic material taking an Nd2Fe14B phase (2: 14:1 phase for short) as a main phase.
The sintered neodymium iron boron magnetic powder can comprise magnetic powder which is obtained through processes such as near rapid solidification and ingot casting and is suitable for preparation of sintered neodymium iron boron.
Preferably, the mass of the heavy rare earth nanocrystalline powder is 1% -4% of the mass of the sintered neodymium iron boron magnetic powder.
In conclusion, the invention utilizes the heavy rare earth nanocrystalline powder treated by HDDR as the structure modified alloy, regulates and controls the distribution of heavy rare earth elements while improving the components and the structure of a crystal boundary, utilizes the uniform diffusion of the crystal grain growth in the liquid phase sintering process on the surface layer of the crystal grain to form a shell structure of heavy rare earth, and achieves the purposes of improving the coercive force of a magnet on the premise of ensuring high remanence and further improving the utilization rate of the heavy rare earth elements.
the technical solution of the present invention is further described in detail by the following examples. However, the examples are chosen only for the purpose of illustrating the invention and are not to be construed as limiting the scope of the invention.
example 1
1) Polishing and brightening a raw material metal Dy, weighing 1.5kg of pure metal Dy and Fe respectively according to the atomic ratio of 1:2 of Dy to Fe, putting the pure metal Dy and Fe into a medium-frequency induction smelting furnace, flushing 0.5MPa argon gas for smelting after gas washing, and casting the pure metal Dy and Fe in a copper mold to obtain a Dy-Fe alloy ingot.
2) And (3) putting the Dy-Fe alloy ingot into a hydrogen heat treatment furnace, washing the gas, filling 50kPa hydrogen into the furnace, and waiting for the Dy-Fe alloy ingot to absorb hydrogen, wherein the hydrogen needs to be supplemented in time. After the hydrogen pressure is not changed, a heating program is set, the temperature is increased to 840 ℃ according to the temperature of 10 ℃ per minute, the temperature is kept for 2 hours, and the hydrogen pressure is maintained at 50 kPa. In the low vacuum stage, the hydrogen pressure is maintained at 100Pa, the temperature is maintained at 840 ℃, and the residence time is 30 min. In the high vacuum stage, the diffusion pump is turned on to dehydrogenate, the temperature is maintained at 840 ℃, and the residence time is 30 min. And closing the heating system, filling argon, and cooling the furnace body by using a fan. Under the protection of nitrogen, Dy-Fe nanocrystalline powder was taken out by using a transition glove box, and SEM images thereof are shown in FIGS. 4 and 5. The Dy-Fe nanocrystalline powder was further crushed using a jet mill to obtain Dy-Fe nanocrystalline powder having an average particle diameter (SMD) of 1.58 μm.
3) 2.5kg of a mixture is prepared according to the mass ratio (Pr0.2Nd0.8) of 30Fe67.3B0.95Al0.75Co0.9Cu0.1, and a casting sheet is smelted by a rapid hardening furnace; hydrogen crushing furnace is used to prepare hydrogen crushing powder, and the hydrogen crushing powder is milled by airflow to obtain the magnetic powder without heavy rare earth with the average grain diameter (SMD) of 2.3 mu m.
4) respectively mixing the magnetic powder without the heavy rare earth and Dy-Fe nanocrystalline powder according to the total content of Dy of 0%, 1% and 2% to obtain magnetic powder; under the protection of nitrogen, completing the orientation and pre-pressing of the magnetic powder in a pressing glove box; the blank was pressed with a cold isostatic press at 200MPa for 13 s.
5) Putting the pressed blank into a vacuum furnace under the protection of nitrogen, and setting the sintering temperature to be 1030 ℃ for 2 hours; and after sintering, filling argon, air cooling, and respectively carrying out tempering processes of 900 ℃ and 500 ℃ for 2 hours.
6) And preparing a sample of the prepared magnet according to the relevant test standard, and completing the test of the demagnetization curve on an NIM-500C magnetic property test system. The results are shown in Table 1, and the magnetic property curves are shown in FIG. 1.
TABLE 1 additive magnetic Properties for different Dy contents in example 1
| Dy content | Remanence (kGs) | coercive force (kOe) | maximum magnetic energy product (MGOe) | Squareness degree |
| 0％Dy | 13.45 | 15.07 | 42.59 | 0.92 |
| 1％Dy | 13.59 | 18.63 | 43.99 | 0.91 |
| 2％Dy | 13.34 | 21.34 | 42.28 | 0.85 |
Example 2
1) 2.5kg of materials are mixed according to the mass ratio of Nd29Fe69.93Cu0.1B0.97, and sequins are smelted by a rapid hardening furnace; hydrogen crushing is carried out by using a hydrogen crushing furnace, and magnetic powder with the average particle Size (SMD) of 3 mu m is obtained by airflow milling.
2) Respectively mixing the magnetic powder without heavy rare earth and Dy-Fe nanocrystalline powder prepared in the embodiment 1 according to the total content of Dy of 0% and 2% to obtain magnetic powder; under the protection of nitrogen, finishing the orientation and the prepressing of the magnetic powder in a profiling glove box; the blank was pressed with a cold isostatic press at 200MPa for 13 s.
3) under the protection of nitrogen, putting the pressed blank into a vacuum furnace, and setting the sintering temperature to be 1080 ℃ for 2 hours; and after sintering, filling argon, air cooling, and respectively carrying out tempering processes of 900 ℃ and 500 ℃ for 2 hours.
4) And preparing a sample of the prepared magnet according to the relevant test standard, and completing the test of the demagnetization curve on an NIM-500C magnetic property test system. The results are shown in Table 2, and the magnetic property curves are shown in FIG. 2.
TABLE 2 additive magnetic Properties for different Dy contents in example 2
| Dy content | Remanence (kGs) | Coercive force (kOe) | maximum magnetic energy product (MGOe) | Squareness degree |
| 0％Dy | 14.4 | 11.23 | 50.03 | 0.92 |
| 2％Dy | 13.79 | 18.4 | 46.15 | 0.93 |
example 3
1) polishing and brightening a raw material metal Tb, weighing 1kg of pure metals Tb and Fe respectively according to the atomic ratio of Tb to Fe of 1:2, putting the pure metals Tb and Fe into a medium-frequency induction rapid hardening furnace for gas washing for 2 times to be below 10-2Pa, then filling 0.5MPa argon, opening a heating system to slowly increase the power until the liquid phase temperature reaches 1260 ℃, and keeping the temperature for 5min at the temperature. Adjusting the speed of a copper rod, opening a cooling system, and pouring the liquid phase at a certain speed to obtain the rapid hardening tablet with the thickness of between 150 and 200 mu m.
2) And (3) putting the Tb-Fe rapid hardening sheet into a hydrogen heat treatment furnace, filling 50kPa hydrogen after gas washing, and waiting for hydrogen absorption of the Tb-Fe alloy cast ingot, wherein the hydrogen needs to be supplemented in time. After the hydrogen pressure is not changed, a heating program is set, the temperature is increased to 860 ℃ according to the temperature of 10 ℃ per minute, the temperature is kept for 2 hours, and the hydrogen pressure is maintained at 50 kPa. In the low vacuum stage, the hydrogen pressure is maintained at 100Pa, the temperature is kept at 860 ℃, and the reaction lasts for 30 min. In the high vacuum stage, the diffusion pump is turned on to dehydrogenate, the temperature is maintained at 860 ℃, and the reaction lasts for 30 min. And closing the heating system, filling argon, and cooling the furnace body by using a fan. Taking Tb-Fe nanocrystalline powder out by using a transition glove box under the protection of nitrogen. And further crushing the Tb-Fe nanocrystalline powder by using an air flow mill to obtain nanocrystalline powder.
3) 2.5kg of materials are mixed according to the mass ratio of Nd30Fe66.B1Al0.75Co0.9Cu0.1, and a casting sheet is smelted by a rapid hardening furnace; hydrogen crushing furnace is used to prepare hydrogen crushing powder, and the hydrogen crushing powder is milled by airflow to obtain the magnetic powder without heavy rare earth with the average particle Size (SMD) of 2.5 mu m.
4) Respectively mixing the magnetic powder without the heavy rare earth and Tb-Fe nanocrystalline powder according to the total content of Tb of 0% and 2%; under the protection of nitrogen, completing the orientation and pre-pressing of the magnetic powder in a pressing glove box; the blank was pressed at 200MPa in a cold isostatic press, maintaining the pressure for 13 s.
5) Under the protection of nitrogen, putting the pressed blank into a vacuum furnace, and setting the sintering temperature to 1050 ℃ for 2 hours; and after sintering, filling argon, air cooling, and respectively carrying out tempering processes of 900 ℃ and 500 ℃ for 2 hours.
6) And preparing a sample of the prepared magnet according to the relevant test standard, and completing the test of the demagnetization curve on an NIM-500C magnetic property test system. The results are shown in Table 3, and the magnetic property curves are shown in FIG. 3.
TABLE 3 additive magnetic Properties for different Tb contents in example 2
| Tb content | Remanence (kGs) | coercive force (kOe) | Maximum magnetic energy product (MGOe) | Squareness degree |
| 0％Tb | 13.57 | 15.25 | 44.36 | 0.95 |
| 2％Tb | 13.29 | 24.05 | 43.08 | 0.94 |
Through the embodiments 1-3, it can be found that, by using the heavy rare earth nanocrystalline powder treated by HDDR as the structural modification alloy, the grain boundary composition and structure are improved, the distribution of heavy rare earth elements is regulated and controlled, the grain growth in the liquid phase sintering process is uniformly diffused on the surface layer of the grain to form a shell structure of heavy rare earth, the coercive force of the magnet is improved on the premise of ensuring high remanence, and the utilization rate of the heavy rare earth elements is further improved.
in addition, the inventors of the present invention also conducted experiments with other raw materials and conditions, etc. listed in the present specification, in the manner of examples 1 to 3, and also produced a neodymium iron boron magnetic material having a higher coercive force.
It should be understood that the above-mentioned embodiments are merely illustrative of the technical concepts and features of the present invention, and are intended to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.
Claims (16)
1. A method for improving the coercive force of a neodymium iron boron magnetic material is characterized by comprising the following steps:
Providing sintered neodymium iron boron magnetic powder as a main phase material;
Providing a heavy rare earth-iron alloy ingot, and carrying out HDDR treatment on the heavy rare earth-iron alloy ingot to obtain heavy rare earth nanocrystalline powder, wherein the HDDR treatment comprises the following steps: placing the heavy rare earth-iron alloy cast ingot in a hydrogen atmosphere with the pressure of more than 50kPa for saturation hydrogen absorption to complete hydrogenation treatment, and obtaining heavy rare earth-iron alloy powder;
Treating the heavy rare earth-iron alloy powder subjected to hydrogenation treatment at 700-900 ℃ for more than 2h in a hydrogen atmosphere with the pressure of 50-150 kPa to complete disproportionation treatment;
Carrying out dehydrogenation treatment on the heavy rare earth-iron alloy powder subjected to disproportionation treatment in a vacuum environment with the pressure of 50-100 Pa at the temperature of 700-900 ℃;
Processing the heavy rare earth-iron alloy powder subjected to dehydrogenation treatment for more than 30min at the temperature of 700-900 ℃ in the environment with the hydrogen pressure of less than 10-1Pa, and finishing recombination treatment to obtain the heavy rare earth nanocrystalline powder;
And uniformly mixing the sintered neodymium-iron-boron magnetic powder with the heavy rare earth nanocrystalline powder, and then sintering and annealing to obtain the neodymium-iron-boron magnetic material with high coercivity.
2. The method for improving the coercivity of a neodymium-iron-boron magnetic material as claimed in claim 1, wherein: the average grain diameter of the heavy rare earth nanocrystalline powder is 0.5-1.5 mu m, and the size of crystal grains contained in the heavy rare earth nanocrystalline powder is 100 nm-1 mu m.
3. The method for improving the coercivity of a neodymium-iron-boron magnetic material as claimed in claim 1, wherein: the sintered neodymium iron boron magnetic powder comprises sintered neodymium iron boron magnetic powder taking Nd2Fe14B phase as a main phase.
4. The method for improving the coercivity of a neodymium-iron-boron magnetic material as claimed in claim 1, wherein: the mass ratio of the heavy rare earth nanocrystalline powder to the sintered neodymium iron boron magnetic powder is 1-4: 100.
5. The method for improving the coercivity of a neodymium-iron-boron magnetic material according to claim 1, characterized by comprising the following steps of: according to the atomic ratio of the heavy rare earth element to the iron element of 1: 2-1: 3, smelting the heavy rare earth metal simple substance and the iron simple substance under the protection of inert gas, and cooling to obtain the heavy rare earth-iron alloy ingot.
6. the method for improving the coercivity of a neodymium-iron-boron magnetic material as claimed in claim 5, wherein: the smelting temperature is higher than the single-phase liquidus of the rare earth metal simple substance and the iron simple substance by more than 50 ℃.
7. The method for improving the coercivity of a neodymium-iron-boron magnetic material as claimed in claim 5, wherein: the heavy rare earth elements include dysprosium and/or terbium.
8. The method for improving the coercivity of a neodymium-iron-boron magnetic material as claimed in claim 5, wherein: the smelting and cooling process comprises near-rapid solidification of cast pieces or induction smelting of copper mold cooling.
9. The method for improving the coercivity of a neodymium-iron-boron magnetic material as claimed in claim 1, wherein: the average particle size of the heavy rare earth-iron alloy powder is 10-100 mu m.
10. The method for improving the coercivity of a neodymium-iron-boron magnetic material as claimed in claim 1, wherein: the disproportionation treatment time is 2-3 h, and the temperature is 780-840 ℃.
11. The method for improving the coercivity of a neodymium-iron-boron magnetic material as claimed in claim 1, wherein: the temperature of the dehydrogenation treatment is 780-840 ℃, the pressure is 50-100 Pa, and the time is 1-1.5 h.
12. The method for improving the coercivity of a neodymium-iron-boron magnetic material as claimed in claim 1, wherein: the hydrogen pressure is 10 < -2 > to 10 < -1 > Pa, and the treatment time is 30 to 45 min.
13. the method for improving the coercivity of a neodymium iron boron magnetic material according to claim 1, characterized by further comprising: separating the heavy rare earth nanocrystalline powder in a physical grinding mode.
14. The method for improving the coercivity of a neodymium iron boron magnetic material according to claim 13, wherein: the physical grinding mode comprises high-energy ball milling and/or jet milling.
15. the method for improving the coercivity of a neodymium iron boron magnetic material according to claim 1, characterized by further comprising: uniformly mixing the sintered neodymium-iron-boron magnetic powder with the heavy rare earth nanocrystalline powder, sintering for 2-4 hours at 980-1100 ℃, and annealing for 2-3 hours at 850-900 ℃ and 450-500 ℃ respectively to obtain the neodymium-iron-boron magnetic material with high coercivity.
16. The method for improving the coercivity of the neodymium-iron-boron magnetic material according to claim 1 is characterized by specifically comprising the following steps of:
Placing the heavy rare earth-iron alloy cast ingot in a hydrogen heat treatment furnace, and saturating the heavy rare earth-iron alloy cast ingot in hydrogen atmosphere to absorb hydrogen to complete hydrogenation treatment;
Heating the furnace chamber of the hydrogen heat treatment furnace to 700-900 ℃ at the heating rate of 5-10 ℃/min, keeping the hydrogen pressure in the furnace chamber at 50-150 kPa, and preserving heat and pressure for 2-3 h to complete disproportionation treatment;
vacuumizing the furnace chamber of the hydrogen heat treatment furnace until the pressure of hydrogen in the furnace chamber is 50-100 Pa, preserving the heat at 700-900 ℃ for 1h to finish dehydrogenation treatment, then adjusting the pressure of the hydrogen in the furnace chamber of the hydrogen heat treatment furnace to be below 10-1Pa, preserving the heat at 700-900 ℃ for more than 30min, and finishing recombination treatment;
Cooling the furnace body to obtain heavy rare earth nanocrystalline powder, wherein the particle size range of the heavy rare earth nanocrystalline powder is 10-100 mu m;
Separating the heavy rare earth nanocrystalline powder in a physical grinding mode, wherein the average grain diameter of the separated heavy rare earth nanocrystalline powder is 0.5-1.5 mu m, and the size of crystal grains contained in the heavy rare earth nanocrystalline powder is 100 nm-1 mu m.
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| WO2022006912A1 (en) * | 2020-07-10 | 2022-01-13 | 瑞声声学科技(深圳)有限公司 | Auxiliary alloy powder for permanent magnet material and preparation method therefor, and permanent magnet material |
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