阅读说明：本技术 一种低含氧量、高磁性能各向异性钕铁硼磁粉的制备方法 (Preparation method of anisotropic neodymium iron boron magnetic powder with low oxygen content and high magnetic performance ) 是由 赖陶颖 于 2021-10-29 设计创作，主要内容包括：本发明公开了一种各向异性钕铁硼磁粉的制备方法,包括：步骤S1：准备合金铸锭；步骤S2：对合金铸锭进行均质化热处理、吸氢粉碎；步骤S3：进行HDDR处理；其中,在步骤S1、步骤S2或步骤S3中添加钙还原剂。本发明的方法在不改变原有HDDR工艺的基础上,少量引入金属钙,即可显著降低磁粉的氧化程度,大幅提高磁粉的各项技术指标,而且引入的钙不需要额外追加去除工序,具有成本低、操作简便、有益效果显著的特点。(The invention discloses a preparation method of anisotropic neodymium iron boron magnetic powder, which comprises the following steps: step S1: preparing an alloy ingot; step S2: carrying out homogenization heat treatment and hydrogen absorption crushing on the alloy cast ingot; step S3: performing HDDR treatment; wherein a calcium reducing agent is added in step S1, step S2, or step S3. According to the method, on the basis of not changing the original HDDR process, a small amount of metal calcium is introduced, so that the oxidation degree of the magnetic powder can be obviously reduced, various technical indexes of the magnetic powder are greatly improved, and the introduced calcium does not need to additionally add a removal process, so that the method has the characteristics of low cost, simplicity and convenience in operation and obvious beneficial effect.)

1. A method for preparing anisotropic neodymium iron boron magnetic powder comprises the following steps:

step S1: preparing an alloy ingot;

step S2: carrying out homogenization heat treatment and hydrogen absorption crushing on the alloy cast ingot;

step S3: performing HDDR treatment;

characterized in that a calcium reducing agent is added in step S1, step S2, or step S3.

2. The method for preparing anisotropic neodymium iron boron magnetic powder according to claim 1, wherein the amount of the calcium reducing agent is 0.01-0.5% by weight of the total weight of the alloy ingot.

3. The method for preparing anisotropic neodymium iron boron magnetic powder according to claim 2, wherein the amount of the calcium reducing agent is 0.1-0.5% by weight of the total weight of the alloy ingot.

4. The method for preparing anisotropic neodymium iron boron magnetic powder according to claim 1, wherein the calcium reducing agent is any one or more of metallic calcium, calcium hydride and intermetallic compound of calcium.

5. The method for preparing anisotropic neodymium iron boron magnetic powder according to claim 4, wherein the intermetallic compound of calcium is any one or more of calcium copper alloy, calcium aluminum alloy and calcium silicon alloy.

6. The method for preparing anisotropic NdFeB magnetic powder according to any of claims 1 to 5, wherein metallic calcium is added to the alloy ingot in step S1.

7. The method for preparing anisotropic NdFeB magnet powder according to any of claims 1 to 5, wherein in step S2, a calcium reducing agent is added after homogenizing heat treatment of the alloy ingot, and then hydrogen absorption pulverization is performed.

8. The method for preparing anisotropic NdFeB magnet powder according to any of claims 1 to 5, wherein in step S3, a calcium reducing agent is added during HDDR process.

9. The method for preparing anisotropic neodymium-iron-boron magnetic powder according to claim 8, wherein in step S3, a calcium reducing agent is added in the hydrogen absorption disproportionation stage of HDDR treatment.

Technical Field

The invention relates to the technical field of permanent magnet material preparation, in particular to a preparation method of anisotropic neodymium iron boron magnetic powder with low oxygen content and high magnetic performance.

Background

The preparation of anisotropic bonded neodymium iron boron magnetic powder by the HDDR process is well known in the permanent magnet material industry. Through years of development, the HDDR process is mature and controllable, but even if the HDDR process is adopted to produce the anisotropic bonded neodymium iron boron magnetic powder, the magnetic performance still fluctuates greatly, even unqualified products appear, and the main reason is that the magnetic powder is oxidized in different degrees. Specifically, the magnetic powder is oxidized to have low magnetic performance due to factors such as high oxygen content in the master alloy raw material, high oxygen content in hydrogen and argon (i.e., insufficient gas purity), and insufficient sealing performance of a vacuum system and an air supply and exhaust system of the HDDR furnace (i.e., gas leakage during production). In order to further improve the magnetic properties of the HDDR method anisotropic bonded ndfeb powder and the consistency between batches, it is necessary to try to greatly reduce the oxidation of the powder.

The strong reducibility under heating conditions is an inherent property of calcium, and a method of utilizing the reducibility of calcium in the production process of a permanent magnet material has also been reported. For example, chinese patent application publication No. CN87105177A discloses a method for producing an alloy of neodymium iron boron permanent magnet. In the method, metallic calcium, calcium hydride or a mixture thereof is added as a reducing agent, and a raw material neodymium fluoride is reduced into neodymium under a high-temperature condition, so that the neodymium-iron-boron master alloy is prepared. However, this method requires the addition of a large amount of a reducing agent to effect the reduction of neodymium fluoride, for example, an amount of the reducing agent that is 1.0 to 4.0 times the stoichiometric amount (by weight) required to complete the reduction. In addition, the method is a method for preparing the neodymium-iron-boron master alloy, the reducing agent is added for reducing neodymium fluoride, and the method has no reference value for avoiding magnetic powder oxidation in the process of preparing the anisotropic bonded neodymium-iron-boron magnetic powder.

At present, no effective method for reducing the oxidation of the magnetic powder exists in the production process of preparing the anisotropic bonded neodymium iron boron magnetic powder by utilizing the HDDR process.

Disclosure of Invention

In view of the above technical problems, the present invention provides a method for preparing anisotropic neodymium iron boron magnetic powder with low oxygen content and high magnetic performance.

Specifically, the invention is realized by the following technical scheme:

a method for preparing anisotropic neodymium iron boron magnetic powder comprises the following steps:

step S1: preparing an alloy ingot;

step S2: carrying out homogenization heat treatment and hydrogen absorption crushing on the alloy cast ingot;

step S3: performing HDDR treatment;

wherein a calcium reducing agent is added in step S1, step S2, or step S3.

Optionally, the addition amount of the calcium reducing agent is 0.01-0.5% by total weight of the alloy ingot.

Optionally, the addition amount of the calcium reducing agent is 0.1-0.5% based on the total weight of the alloy ingot.

Optionally, the calcium reducing agent is any one or more of metallic calcium, calcium hydride and an intermetallic compound of calcium.

Optionally, the intermetallic compound of calcium is any one or more of a calcium copper alloy, a calcium aluminum alloy and a calcium silicon alloy.

Optionally, in step S1, metallic calcium is added to the alloy ingot.

Alternatively, in step S2, the alloy ingot is subjected to the homogenization heat treatment, then the calcium reducing agent is added, and then the hydrogen absorption pulverization is performed.

Optionally, in step S3, a calcium reducing agent is added during the HDDR process.

Alternatively, in step S3, a calcium reducing agent is added in the hydrogen absorption disproportionation stage of the HDDR process.

Compared with the prior art, the preparation method of the anisotropic neodymium iron boron magnetic powder with low oxygen content and high magnetic performance, provided by the invention, at least has the following beneficial effects:

according to the preparation method of the anisotropic neodymium iron boron magnetic powder with low oxygen content and high magnetic performance, on the basis of not changing the original HDDR process, a small amount of metal calcium is introduced, so that the oxidation degree of the magnetic powder can be remarkably reduced, various technical indexes of the magnetic powder are greatly improved, and the introduced calcium does not need to additionally add a removal process, so that the preparation method has the characteristics of low cost, simplicity and convenience in operation and remarkable beneficial effect.

Detailed Description

The present invention will be described in detail with reference to the following embodiments in order to fully understand the objects, features and effects of the invention. The process of the present invention employs conventional methods or apparatus in the art, except as described below. The following noun terms have meanings commonly understood by those skilled in the art unless otherwise specified.

The HDDR process is an effective method for preparing anisotropic bonded neodymium iron boron (NdFeB) magnetic powder, and includes the steps of Hydrogenation, Disproportionation, dehydrogenation and Recombination. The basic process of HDDR can be described as heat preservation of Nd-Fe-B alloy in hydrogen atmosphere at certain temperature and pressure for certain time to make the original ingot castingHydrogen absorption and disproportionation decomposition of Nd-Fe-B mother phase into disproportionation product Fe₂B. alpha-Fe and NdH₂Then reducing the hydrogen pressure at a certain temperature to ensure that the disproportionation product is dehydrogenated and recombined to generate a neodymium iron boron phase.

In the HDDR process, the magnetic powder is oxidized to different degrees, so that the magnetic performance of the finally obtained anisotropic bonded neodymium iron boron magnetic powder has large fluctuation. In view of the above problem, the inventors of the present invention conducted intensive studies and proposed that calcium is introduced during the process, and by utilizing the strong reducibility of calcium in the red hot state, on one hand, trace oxygen in the furnace atmosphere is absorbed to purify the gas, and on the other hand, the rare earth oxide impurity phase formed by oxidation is reduced to convert it into the rare earth simple substance again, thereby forming a beneficial rare earth alloy phase. Based on the above, the invention provides a preparation method of the anisotropic neodymium iron boron magnetic powder, and the anisotropic neodymium iron boron magnetic powder with low oxygen content and high magnetic performance can be obtained by adopting the preparation method.

The preparation method of the anisotropic neodymium iron boron magnetic powder comprises the following steps:

step S1: and preparing an alloy ingot.

The main components of the alloy ingot are Nd, Fe and B, and in order to obtain anisotropic neodymium iron boron magnetic powder with different performances, alloy elements such as Co, Cu, Nb, Al, Ga, Zr and V can be added according to needs. It is to be understood that the composition of the alloy ingot is a matter of routine choice in the art, and can be set as appropriate by one skilled in the art, as desired. In the following examples, the chemical composition of the alloy ingot was Nd_28.5Fe_69.9B_1.0Ga_0.3Nb_0.3(mass percent), however, it should be understood that this is exemplary only. Other alloy ingot components meeting the preparation requirements of the neodymium iron boron magnetic powder are also suitable for the preparation method of the invention.

The alloy ingot can be prepared by a conventional method, and a person skilled in the art can make reasonable selections according to needs in the actual production process. For example, metals such as Nd, Fe, B, etc. are proportioned according to the chemical composition ratio of the alloy ingot, mixed uniformly, placed in a vacuum induction furnace, melted under the protection of argon, and cast to obtain the alloy ingot. Of course, other common alloy ingot preparation methods are also applicable to the preparation method of the invention.

The alloy cast ingot can also be purchased in the market, as long as the chemical components of the alloy cast ingot meet the preparation requirements of the neodymium iron boron magnetic powder.

Step S2: homogenizing, heat treating, absorbing hydrogen, and pulverizing.

And carrying out homogenization heat treatment on the alloy ingot. The process of the homogenizing heat treatment is a thermal activation process, and the structure and the performance of the interior of the alloy ingot are changed by the homogenizing heat treatment, so that the internal structure is improved, the casting stress is eliminated, and the segregation is reduced. The specific process of the homogenization heat treatment is, for example: heating the mother alloy cast ingot to 1050-1250 ℃ in a high-purity argon environment of 90-110 kPa, preserving the heat for 18-22 hours, and quickly cooling to room temperature after the heat preservation is finished.

After the homogenization heat treatment, the alloy ingot is subjected to hydrogen absorption pulverization. The alloy ingot is coarsely crushed by hydrogen absorption and crushing, thereby being beneficial to the implementation of the subsequent HDDR process. The specific process of hydrogen absorption pulverization is, for example: and sealing the alloy ingot subjected to the homogenization heat treatment in a rotary hydrogen crushing furnace, heating to 190-210 ℃ under the vacuum condition with the vacuum degree superior to 1.0Pa, introducing high-purity hydrogen with the pressure of 90-110 kPa, and maintaining for 0.8-1.2 hours, so that the alloy ingot absorbs hydrogen and is crushed.

Step S3: HDDR process.

The HDDR process specifically comprises the following 3 stages:

(1) in the "hydrogen absorption-disproportionation" step, an alloy ingot after hydrogen absorption and pulverization is charged into a reaction furnace, heated to 800 ℃ or higher (e.g., 820 ℃) under a vacuum condition of a degree of vacuum of more than 1Pa, and a high-purity hydrogen gas (e.g., a high-purity hydrogen gas of 30 kPa) is introduced and maintained for a certain period of time (e.g., 3 hours). The hydrogen absorption-disproportionation reaction is an exothermic reaction, and the alloy ingot in the furnace naturally heats up due to hydrogen absorption.

(2) And in the stage of slow dehydrogenation-recombination, heating is continued, the furnace temperature is kept at 800-840 ℃, and the hydrogen pressure is reduced (for example, the hydrogen pressure is reduced to 3kPa) and maintained for a period of time (for example, 0.5 hour). The slow dehydrogenation-recombination is an endothermic reaction, and the alloy ingot in the furnace is naturally cooled due to the dehydrogenation and has larger cooling amplitude.

(3) And in the stage of complete dehydrogenation, the furnace temperature is kept at 800-840 ℃, and a vacuum unit is used for vacuumizing the reaction furnace to enable the vacuum degree to be better than 1.0 Pa. The reaction mixture is maintained at this temperature and pressure for a certain period of time (e.g., 1 hour), and then highly pure argon (e.g., 100 kPa) is introduced into the reaction furnace and rapidly cooled to room temperature. The complete dehydrogenation is also an endothermic reaction, and the alloy ingot in the furnace is naturally cooled due to the dehydrogenation, but the cooling amplitude is much smaller than that in the previous stage.

The preparation method of the present invention further comprises adding a calcium reducing agent in any one of the above 3 steps, the amount of the added calcium reducing agent being 0.01 wt.% to 0.5 wt.%, for example, 0.01 wt.%, 0.1 wt.%, 0.2 wt.%, 0.3 wt.%, 0.4 wt.%, 0.5 wt.%, etc., based on the weight of the alloy ingot. Preferably, the calcium reducing agent is added in an amount of 0.1 wt.% to 0.5 wt.%, e.g., 0.1 wt.%, 0.15 wt.%, 0.2 wt.%, 0.25 wt.%, 0.3 wt.%, 0.35 wt.%, 0.4 wt.%, 0.45 wt.%, 0.5 wt.%, etc., based on the weight of the alloy ingot.

The source of the calcium reducing agent may be metallic calcium, calcium hydride, various intermetallic compounds of calcium or a mixture of any two or three of them. The calcium intermetallic compound may be any one or more of calcium-containing intermetallic compounds such as calcium copper alloy, calcium aluminum alloy, calcium silicon alloy, etc., and the proportion of each element in the calcium intermetallic compound may be in a conventional proportion. The form of the calcium reducing agent may be any of the common forms, for example, various forms such as powder, granule, needle, chip, block, and the like.

The inventors of the present invention found through research that:

the HDDR process is implemented at 820-850 ℃ and 0-30 kPa negative pressure, under the condition, the metal calcium is in a molten state (the melting point of calcium under normal pressure is about 839 ℃, the melting point of calcium under negative pressure is lower than 839 ℃), calcium vapor is continuously released to the surrounding space, and both gaseous calcium and liquid calcium have strong reducibility, so that on one hand, the HDDR process can be implemented at 820-850 ℃ and 0-30 kPa negative pressureTo absorb trace O in the furnace atmosphere₂Purifying the atmosphere to reduce the oxidation degree of the magnetic powder; on the other hand, harmful rare earth oxide (generated before the HDDR process) is reduced to be converted into a simple substance phase again, and then the harmful rare earth oxide enters a crystal boundary of the surface layer of the magnetic powder particles through crystal boundary diffusion to form a beneficial rare earth-rich crystal boundary phase, so that the demagnetizing coupling effect on main phase crystal grains is achieved, and the coercive force of the magnetic powder is improved. In the process of functioning, two chemical reactions mainly occur: (1)2Ca + O₂→2CaO；(2)3Ca+M₂O₃→ 3CaO +2M, wherein M is mainly a chemically active rare earth element such as Nd, Pr, Dy, Tb, etc.

The introduction time of the calcium reducing agent can be any time before the HDDR process is finished, for example, calcium can be added into the original formula, namely the alloy ingot; or the calcium is not added in the formula of the alloy ingot, and the calcium is added at a certain moment in the execution process of the HDDR process, and the introduction of the calcium does not influence the execution of the HDDR process. The addition amount of the calcium reducing agent is 0.01 wt.% to 0.5 wt.%, less than 0.01 wt.% causes insignificant effects due to too low content, and more than 0.5 wt.% causes degradation of magnetic powder due to too much non-magnetic phase introduced. The added calcium can be mixed in the magnetic powder in the forms of calcium oxide (generated after reduction), simple substance calcium (not participating in chemical reaction) and the like or condensed on the inner wall of the pipeline of the vacuum system. Because the whole addition amount of calcium is very small (generally less than 0.5 wt%), calcium oxide and elementary calcium remained in the magnetic powder are not removed, and calcium condensed on the inner wall of the vacuum system pipeline is cleaned regularly.

On the whole, the more the amount of calcium added, the more calcium and its compounds (non-magnetic impurity phases) remain in the magnetic powder. When the amount of calcium added is less than or equal to 0.5 wt%, the calcium is totally evaporated and reacts with O due to the small amount₂And M₂O₃The chemical reaction is completely converted into CaO, the magnetic powder does not contain simple substance calcium but contains a small amount of calcium oxide, and O is increased along with the increase of the addition amount of calcium₂And M₂O₃The oxygen element in the alloy is increasingly deprived by calcium, more calcium oxide is generated and remained, and more rare earth-rich grain boundary is generatedPhase formation, whereby the oxygen content and remanence B of the magnetic powder_rAll show a descending trend and have coercive force H_cjThe trend is ascending; when calcium is added>At 0.5 wt%, a portion of the calcium evaporates and reacts with O due to the relatively large amount₂And M₂O₃The calcium is not involved in the chemical reaction and remains in the magnetic powder in the form of liquid simple substance calcium, the magnetic powder contains calcium oxide and simple substance calcium, and O is added with the increase of the calcium₂And M₂O₃The oxygen element in the magnetic powder is almost completely removed by calcium, the generation and the residue of calcium oxide and the formation of a rare earth-rich grain boundary phase are increased slowly and gradually saturate, and meanwhile, the liquid elemental calcium in the magnetic powder is increased continuously to cause the magnetic powder particles to be adhered to each other (the orientation degree of the magnetic powder particles is reduced, and the remanence B is further reduced)_r) And caking (which can cause incomplete dehydrogenation of the magnetic powder particles and thus lower coercivity H_cj) After the elemental calcium remained in the magnetic powder is discharged from the furnace, it can produce chemical reaction with oxygen in the air to produce calcium oxide to increase oxygen content of magnetic powder, so that the oxygen content of magnetic powder is slowly raised and its residual magnetism B is_rAnd coercive force H_cjThey all showed a rapid downward trend. Maximum magnetic energy product (BH)_maxIs the maximum value of the product of the magnetic induction intensity B and the magnetic field intensity H on the B-H demagnetization curve, and is generally equal to the remanence B_rAnd intrinsic coercivity H_cjAre all in positive correlation with remanence B_rIs more relevant, therefore (BH)_maxThe amount of calcium added corresponding to the maximum was 0.3 mass%.

In a preferred embodiment, calcium is added to the alloy ingot in the preparation of the alloy ingot in step S1, for example, the chemical component is Nd_28.5Fe_69.6B_1.0Ca_0.3Ga_0.3Nb_0.3(mass%) of the alloy ingot, however, this is merely exemplary, and alloy ingots in which calcium is present in an amount of 0.01 to 0.5% by mass of the alloy ingot may be used in the present invention.

In another preferred embodiment, a reducing agent is added in the step of the homogenization heat treatment, hydrogen absorption pulverization of step S2. For example, after the alloy ingot is subjected to the homogenization heat treatment, the alloy ingot is sealed in a rotary hydrogen furnace together with a calcium reducing agent in an amount of 0.01 to 0.5% by weight based on the total weight of the alloy ingot, and hydrogen-absorbing pulverization is performed under vacuum, heating and passing high-purity hydrogen gas.

In another preferred embodiment, the reducing agent is added in the step of HDDR of step S3, and specifically, the reducing agent may be added during either of the "hydrogen absorption disproportionation" reaction or the "dehydrogenation recombination" reaction of HDDR. Preferably, the reducing agent is added during the "hydrogen uptake disproportionation" reaction of the HDDR process. For example, in the "hydrogen absorption disproportionation" reaction, a calcium reducing agent is added in an amount of 0.01 to 0.5% by weight based on the total weight of the alloy ingot, and the mixture is maintained at 800 ℃ or higher (e.g., 820 ℃) for a certain period of time (e.g., 3 hours) under a high-purity hydrogen atmosphere of a certain pressure (e.g., 30 kPa).

The manner of adding the reducing agent in step S2 or step S3 is simpler than the addition of calcium to the alloy ingot in the process of preparing the alloy ingot in step S1, and the types of the reducing agent that can be selected are more various and are not limited to metallic calcium, but may be calcium hydride or an intermetallic compound of calcium.

Examples

The invention is further illustrated by the following examples, which are not intended to limit the scope of the invention. The experimental methods without specifying specific conditions in the following examples were selected according to the conventional methods and conditions, or according to the commercial instructions.

Example 1:

first, calcium was added to a master alloy to prepare a master alloy having an average thickness of 10mm and a chemical composition of Nd_28.5Fe_69.6B_1.0Ca_0.3Ga_0.3Nb_0.3(mass%) of a master alloy ingot; then, carrying out homogenization heat treatment on the mother alloy ingot, wherein the specific process of the homogenization heat treatment comprises the following steps: heating to 1150 deg.C under 100kPa of high purity argon, maintaining for 20hr, and rapidly cooling to room temperature; then, the alloy cast ingot after the homogenization heat treatment is sealed in a rotary hydrogen crushing furnace and is heated to 200 ℃ under the vacuum condition that the vacuum degree is better than 1.0PaIntroducing high-purity hydrogen gas at 100kPa for 1hr to make alloy ingot absorb hydrogen and crush; finally, implementing the HDDR process: heating to 820 deg.C under vacuum condition with vacuum degree of 1kPa for 3hr → maintaining high purity hydrogen gas at 30kPa for 3hr → continuing heating to 840 deg.C, reducing hydrogen pressure to 3kPa for 0.5hr → vacuumizing at 840 deg.C for 1hr to make vacuum degree of 1.0Pa → introducing high purity argon gas at 100kPa, and rapidly cooling to room temperature.

Example 2:

first, Nd having an average thickness of 10mm and a chemical composition was prepared_28.5Fe_69.9B_1.0Ga_0.3Nb_0.3(mass%) of a master alloy ingot; then, carrying out homogenization heat treatment on the mother alloy ingot, wherein the specific process of the homogenization heat treatment comprises the following steps: heating to 1150 deg.C under 100kPa of high purity argon, maintaining for 20hr, and rapidly cooling to room temperature; then, the alloy ingot after the homogenization heat treatment and granular calcium metal with the integral mass of 0.5 percent of the alloy ingot are sealed in a rotary hydrogen crushing furnace, heated to 200 ℃ under the vacuum condition with the vacuum degree better than 1.0Pa, and introduced with high-purity hydrogen with the pressure of 100kPa and maintained for 1hr, thereby enabling the alloy ingot to absorb hydrogen and be crushed; finally, implementing the HDDR process: heating to 820 deg.C under vacuum condition with vacuum degree of 1kPa for 3hr → maintaining high purity hydrogen gas at 30kPa for 3hr → continuing heating to 840 deg.C, reducing hydrogen pressure to 3kPa for 0.5hr → vacuumizing at 840 deg.C for 1hr to make vacuum degree of 1.0Pa → introducing high purity argon gas at 100kPa, and rapidly cooling to room temperature.

Example 3:

first, Nd having an average thickness of 10mm and a chemical composition was prepared_28.5Fe_69.9B_1.0Ga_0.3Nb_0.3(mass%) of a master alloy ingot; then, carrying out homogenization heat treatment on the mother alloy ingot, wherein the specific process of the homogenization heat treatment comprises the following steps: heating to 1150 deg.C under 100kPa of high purity argon, maintaining for 20hr, and rapidly cooling to room temperature; then, the alloy ingot after the homogenization heat treatment is sealed in a rotary hydrogen crushing furnace, heated to 200 ℃ under the vacuum condition that the vacuum degree is better than 1.0Pa, and high-purity hydrogen with the pressure of 100kPa is introduced and maintained for 1hr, thereby enabling the alloy ingot to absorb hydrogen powderCrushing; finally, implementing the HDDR process: heating to 820 deg.C under vacuum condition with degree of vacuum better than 1kPa, introducing high-purity hydrogen gas of 30kPa for 3hr → continuing heating to 840 deg.C, introducing powdery calcium hydride with the mass of 0.1% of the whole mass of the alloy ingot, reducing the hydrogen pressure to 3kPa for 0.5hr → vacuumizing at 840 deg.C for 1hr to make degree of vacuum better than 1.0Pa → introducing high-purity argon gas of 100kPa, and rapidly cooling to room temperature.

Example 4:

first, Nd having an average thickness of 10mm and a chemical composition was prepared_28.5Fe_69.9B_1.0Ga_0.3Nb_0.3(mass%) of a master alloy ingot; then, carrying out homogenization heat treatment on the mother alloy ingot, wherein the specific process of the homogenization heat treatment comprises the following steps: heating to 1150 deg.C under 100kPa of high purity argon, maintaining for 20hr, and rapidly cooling to room temperature; then, the alloy ingot after the homogenization heat treatment and granular calcium-copper alloy (calcium content is 50 wt.%, copper content is 50 wt.%) with the integral mass of the alloy ingot being 0.2% are sealed in a rotary hydrogen crushing furnace, and the alloy ingot is heated to 200 ℃ under the vacuum condition that the vacuum degree is better than 1.0Pa, high-purity hydrogen gas with 100kPa is introduced and maintained for 1hr, so that the alloy ingot absorbs the hydrogen and is crushed; finally, implementing the HDDR process: heating to 820 deg.C under vacuum condition with vacuum degree of 1kPa for 3hr → maintaining high purity hydrogen gas at 30kPa for 3hr → continuing heating to 840 deg.C, reducing hydrogen pressure to 3kPa for 0.5hr → vacuumizing at 840 deg.C for 1hr to make vacuum degree of 1.0Pa → introducing high purity argon gas at 100kPa, and rapidly cooling to room temperature.

Comparative example 1:

first, Nd having an average thickness of 10mm and a chemical composition was prepared_28.5Fe_69.9B_1.0Ga_0.3Nb_0.3(mass%) of a master alloy ingot; then, carrying out homogenization heat treatment on the mother alloy ingot, wherein the specific process of the homogenization heat treatment comprises the following steps: heating to 1150 deg.C under 100kPa of high purity argon, maintaining for 20hr, and rapidly cooling to room temperature; then, the alloy ingot after the homogenization heat treatment is sealed in a rotary hydrogen crushing furnace, heated to 200 ℃ under the vacuum condition that the vacuum degree is better than 1.0Pa, and high-purity hydrogen with the pressure of 100kPa is introduced and maintained1hr, absorbing hydrogen from the alloy ingot, and pulverizing; finally, implementing the HDDR process: heating to 820 deg.C under vacuum condition with vacuum degree of 1kPa for 3hr → maintaining high purity hydrogen gas at 30kPa for 3hr → continuing heating to 840 deg.C, reducing hydrogen pressure to 3kPa for 0.5hr → vacuumizing at 840 deg.C for 1hr to make vacuum degree of 1.0Pa → introducing high purity argon gas at 100kPa, and rapidly cooling to room temperature.

Comparative example 2:

first, calcium was added to a master alloy to prepare a master alloy having an average thickness of 10mm and a chemical composition of Nd_27.5Fe_67.6B_1.0Ca_0.6Ga_0.3Nb_0.3(mass%) of a master alloy ingot; then, carrying out homogenization heat treatment on the mother alloy ingot, wherein the specific process of the homogenization heat treatment comprises the following steps: heating to 1150 deg.C under 100kPa of high purity argon, maintaining for 20hr, and rapidly cooling to room temperature; then, sealing the alloy ingot subjected to the homogenization heat treatment in a rotary hydrogen crushing furnace, heating to 200 ℃ under the vacuum condition that the vacuum degree is better than 1.0Pa, introducing high-purity hydrogen with the pressure of 100kPa, and maintaining for 1hr, thereby absorbing and crushing the hydrogen of the alloy ingot; finally, implementing the HDDR process: heating to 820 deg.C under vacuum condition with vacuum degree of 1kPa for 3hr → maintaining high purity hydrogen gas at 30kPa for 3hr → continuing heating to 840 deg.C, reducing hydrogen pressure to 3kPa for 0.5hr → vacuumizing at 840 deg.C for 1hr to make vacuum degree of 1.0Pa → introducing high purity argon gas at 100kPa, and rapidly cooling to room temperature.

Comparative example 3:

first, Nd having an average thickness of 10mm and a chemical composition was prepared_28.5Fe_69.9B_1.0Ga_0.3Nb_0.3(mass%) of a master alloy ingot; then, carrying out homogenization heat treatment on the mother alloy ingot, wherein the specific process of the homogenization heat treatment comprises the following steps: heating to 1150 deg.C under 100kPa of high purity argon, maintaining for 20hr, and rapidly cooling to room temperature; then, the alloy ingot after the homogenization heat treatment and granular calcium metal with the mass of 0.75 percent of the whole mass of the alloy ingot are sealed in a rotary hydrogen crushing furnace, and the alloy ingot is heated to 200 ℃ under the vacuum condition with the vacuum degree of more than 1.0Pa, high-purity hydrogen with the pressure of 100kPa is introduced and maintained for 1hr, thereby leading the alloy ingot to beAbsorbing hydrogen and crushing; finally, implementing the HDDR process: heating to 820 deg.C under vacuum condition with vacuum degree of 1kPa for 3hr → maintaining high purity hydrogen gas at 30kPa for 3hr → continuing heating to 840 deg.C, reducing hydrogen pressure to 3kPa for 0.5hr → vacuumizing at 840 deg.C for 1hr to make vacuum degree of 1.0Pa → introducing high purity argon gas at 100kPa, and rapidly cooling to room temperature.

Comparative example 4:

first, Nd having an average thickness of 10mm and a chemical composition was prepared_28.5Fe_69.9B_1.0Ga_0.3Nb_0.3(mass%) of a master alloy ingot; then, carrying out homogenization heat treatment on the mother alloy ingot, wherein the specific process of the homogenization heat treatment comprises the following steps: heating to 1150 deg.C under 100kPa of high purity argon, maintaining for 20hr, and rapidly cooling to room temperature; then, sealing the alloy ingot subjected to the homogenization heat treatment in a rotary hydrogen crushing furnace, heating to 200 ℃ under the vacuum condition that the vacuum degree is better than 1.0Pa, introducing high-purity hydrogen with the pressure of 100kPa, and maintaining for 1hr, thereby absorbing and crushing the hydrogen of the alloy ingot; finally, implementing the HDDR process: heating to 820 ℃ under vacuum condition with vacuum degree better than 1kPa, introducing high-purity hydrogen with 30kPa for 3hr → continuing to heat to 840 ℃, introducing powdery calcium hydride with 1.0% of the whole mass of the alloy ingot, then reducing the hydrogen pressure to 3kPa for 0.5hr → vacuumizing at 840 ℃ for 1hr to make the vacuum degree better than 1.0Pa → introducing high-purity argon with 100kPa, and rapidly cooling to room temperature.

The main differences between examples 1 to 4 of the present invention and comparative examples 1 to 4, as well as the magnetic properties of the obtained magnetic powder samples, are compared to the oxygen content, see table 1.

TABLE 1 comparison of the main differences between the examples and the comparative examples and the magnetic properties, oxygen content of the magnetic powder samples obtained

As can be seen from the data in table 1, the magnetic properties of the neodymium iron boron magnetic powder can be greatly improved and the oxygen content of the magnetic powder can be reduced by adding a specific amount of calcium reducing agent in the preparation process.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other substitutions, modifications, combinations, changes, simplifications, etc., which are made without departing from the spirit and principle of the present invention, should be construed as equivalents and included in the protection scope of the present invention.