阅读说明：本技术 一种钕铁硼材料及其制备方法 (Neodymium iron boron material and preparation method thereof ) 是由 王金磊 黄清芳 黎国妃 兰秋连 李可 于 2020-12-25 设计创作，主要内容包括：本发明公开了一种钕铁硼材料及其制备方法。该钕铁硼材料包含Re-2Fe-(14)B主相晶粒及其壳层、邻接Re-2Fe-(14)B主相晶粒的富Nd相和晶界三角区；Re-2Fe-(14)B主相晶粒中的Re包含Ho和/或Dy；壳层包含(Nd/Ho)-2Fe-(14)B、(Nd/Dy)-2Fe-(14)B和(Nd/Tb)-2Fe-(14)B中的一种或多种；壳层的厚度为0.1～1μm；晶界三角区包含Ho-2O-3、Ho-2S-3、Dy-2O-3和Dy-2O-3中的一种或多种；晶界三角区中的氧化物和/或硫化物占钕铁硼材料的质量百分含量为1～7％。本发明通过改善烧结钕铁硼磁体的晶界微观结构,使得后续晶界扩散后的钕铁硼材料的矫顽力大幅度提升,且能够有效增加扩散深度。(The invention discloses a neodymium iron boron material and a preparation method thereof. The Nd-Fe-B material contains Re 2 Fe 14 B main phase crystal grain, shell thereof, and adjacent Re 2 Fe 14 The Nd-rich phase and the grain boundary triangular region of the B main phase crystal grains; re 2 Fe 14 Re in the B main phase crystal grains contains Ho and/or Dy; the shell layer comprises (Nd/Ho) 2 Fe 14 B、(Nd/Dy) 2 Fe 14 Band (Nd/Tb) 2 Fe 14 One or more of B; the thickness of the shell layer is 0.1-1 μm; the triangular region of grain boundary contains Ho 2 O 3 、Ho 2 S 3 、Dy 2 O 3 And Dy 2 O 3 One or more of; the mass percentage of the oxides and/or sulfides in the crystal boundary triangular region in the neodymium iron boron material is 1-7%. The invention improves the sintered Nd-Fe-B magnetThe grain boundary microstructure of the body greatly improves the coercive force of the neodymium iron boron material after subsequent grain boundary diffusion, and can effectively increase the diffusion depth.)

1. A neodymium iron boron material is characterized by comprising Re₂Fe₁₄B main phase crystal grain, shell thereof, and Re adjacent thereto₂Fe₁₄The Nd-rich phase and the grain boundary triangular region of the B main phase crystal grains;

the Re₂Fe₁₄Re in the B main phase crystal grains contains Ho and/or Dy;

the shell layer comprises (Nd/Ho)₂Fe₁₄B、(Nd/Dy)₂Fe₁₄Band (Nd/Tb)₂Fe₁₄One or more of B;

the thickness of the shell layer is 0.1-1 mu m;

the grain boundary trigone comprises Ho₂O₃、Ho₂S₃、Dy₂O₃And Dy₂O₃One or more of;

and the mass percentage of the oxides and/or sulfides in the crystal boundary triangular region in the neodymium iron boron material is 1-7%.

2. The neodymium-iron-boron material as claimed in claim 1, characterized in that the shell layer has a thickness of 0.45-1 μm, such as 0.45 μm, 0.48 μm, 0.5 μm, 0.56 μm, 0.58 μm or 0.65 μm;

and/or the mass percentage of the oxide and/or sulfide in the grain boundary triangular region in the neodymium iron boron material is 1-3%, such as 1.8%, 1.9%, 2.0%, 2.1% or 2.3%;

and/or, the Re₂Fe₁₄The mass percentage of the B main phase grains in the neodymium iron boron material is 90% to 100%, and is not 100%, preferably 94% to 97%, for example 94.2%, 94.5%, 95.3%, 95.5%, 96%.0% or 96.2%;

and/or the mass percentage of the shell layer in the neodymium iron boron material is less than 1%, and is not 0, preferably less than 0.8%, more preferably 0.3-0.8%, for example, 0.33%, 0.35%, 0.45%, 0.46%, 0.51%, or 0.61%.

3. The neodymium-iron-boron material of claim 1, wherein Re further comprises Nd and/or Pr;

and/or, the shell layer comprises (Nd/Ho)₂Fe₁₄B、(Nd/Dy)₂Fe₁₄Band (Nd/Tb)₂Fe₁₄At least two of B;

and/or the grain boundary triangular region also comprises Nd₂O₃。

4. A preparation method of a neodymium iron boron material is characterized by comprising the following steps: smelting, casting, heat preservation, hydrogen breaking, jet milling, molding, sintering, grain boundary diffusion and aging;

wherein, one or more of Ho, Dy and S are added in the smelting stage;

the temperature of the heat preservation is 500-800 ℃;

and introducing oxygen content at the stage of the jet mill, wherein the oxygen content is 0-20 ppm.

5. The method for preparing the neodymium-iron-boron material according to claim 4, wherein the heat preservation is performed by preserving the cast alloy sheet obtained by casting at a temperature of 500-700 ℃, for example, at 620 ℃;

and/or the heat preservation time is 1-5 h, preferably 3 h;

and/or the heat preservation is carried out in a heat treatment furnace under a vacuum atmosphere or an inert atmosphere; preferably, the vacuum degree of the vacuum atmosphere is less than 0.1Pa, and more preferably less than 0.01 Pa; preferably, the inert atmosphere is argon; preferably, the pressure of the inert atmosphere is 0.01MPa to 0.1MPa, more preferably 0.01MPa to 0.08 MPa;

and/or, when S is added in the smelting, the oxygen content is 0-10 ppm; when the smelting is not added with S, the oxygen content is 10-20 ppm;

and/or the rotating speed of the sorting wheel in the jet mill is 3500-4300 rpm/min, preferably 3900-4100 rpm/min, such as 4000 rpm/min;

and/or the grinding pressure of the jet mill is 0.3-0.75 MPa, preferably 0.6 MPa;

and/or the median particle diameter D50 of the alloy fine powder obtained by the jet milling is 3-5.5 μm, preferably 4 μm;

and/or the grain boundary diffusion is coating diffusion or coating diffusion;

and/or the diffusion source of the grain boundary diffusion is Dy and/or Tb; preferably, when the diffusion source is Dy, the Dy accounts for 0.2-1.2% of the neodymium iron boron material by mass; preferably, when the diffusion source is Tb, Tb accounts for 0.2-1.2% by mass of the neodymium iron boron material, for example, 0.65%;

and/or the heat treatment temperature of the grain boundary diffusion is 800-1000 ℃, preferably 955 ℃;

and/or the heat treatment time of the grain boundary diffusion is 5-20 h, preferably 16 h.

6. The method for preparing neodymium iron boron materials according to claim 4, wherein the smelting is carried out in a high-frequency vacuum smelting furnace;

and/or the vacuum degree of the vacuum smelting furnace is less than 0.1Pa, preferably less than 0.02 Pa;

and/or the smelting temperature is 1450-1550 ℃, preferably 1500-1550 ℃;

and/or the casting is carried out by casting and cooling through a water-cooled copper roller under the protection of inert atmosphere; preferably at 5.5X 10⁴Pa in Ar atmosphere at 10 deg.C²DEG C/sec-10⁴Cooling at a speed of DEG C/second;

and/or the hydrogen absorption temperature of the hydrogen breaker is 20-300 ℃, preferably 100 ℃;

and/or the hydrogen absorption pressure of the hydrogen breaker is 0.12-0.19 MPa, preferably 0.19 MPa;

and/or the dehydrogenation time of the hydrogen cracker is 0.5-5 h, preferably 2 h;

and/or the dehydrogenation temperature of the hydrogen cracker is 450-600 ℃, preferably 550 ℃;

and/or the molding is carried out under the protection of a magnetic field strength of more than 1.6T, for example 1.8T and a nitrogen atmosphere;

and/or, the sintering is vacuum sintering or atmosphere sintering, preferably atmosphere sintering, more preferably argon sintering;

and/or the sintering temperature is 900-1200 ℃, preferably 1050-1080 ℃, for example 1065 ℃;

and/or the sintering time is 3-10 h, preferably 6 h;

and/or the temperature of the aging is 430-560 ℃, preferably 450-490 ℃, such as 450 ℃, 455 ℃, 460 ℃, 470 ℃, 480 ℃ or 490 ℃;

the time of the aging treatment is 2-5 h, for example 3 h.

7. The method for preparing neodymium iron boron materials according to claim 4, characterized in that in the stage of smelting, the Ho is added in the form of Ho-Fe alloy;

and/or, in the stage of the smelting, the Dy is added in the form of a Dy-Fe alloy;

and/or, in the stage of the smelting, the S is added in the form of an S-containing Ho-Fe alloy or an S-containing Dy-Fe alloy;

and/or, when Ho is added in the smelting stage, the Ho accounts for 0.1-8.5%, preferably 0.5-7.5%, for example 1.2% of the neodymium iron boron material;

and/or, when Dy is added in the smelting stage, the Dy accounts for 0-6% of the neodymium iron boron material, such as 0.5%;

and/or when S is added in the smelting stage, the S accounts for 0-0.1%, for example 0.05%, of the neodymium iron boron material;

and/or, the raw materials of the neodymium iron boron material preferably further comprise: one or more of Nd, Dy, Pr, Ho, Tb, Al, S, Cu, Co, Ga, Ti, B, Fe, Zr, Nb, Hf and Mn.

8. The method for preparing the neodymium-iron-boron material according to claim 7, wherein the raw material of the neodymium-iron-boron material contains Nd, and the content of the Nd is 23.5-30.5%, preferably 23.5-28.5%, such as 28.1%;

and/or the raw material of the neodymium iron boron material comprises Al, wherein the content of the Al is 0-0.2%, for example, 0.04%;

and/or the raw material of the neodymium iron boron material contains Cu, and the content of the Cu is 0.05-0.3%, such as 0.1%;

and/or the raw material of the neodymium iron boron material comprises Co, and the content of Co is 0-5%, for example 2.8%;

and/or the raw material of the neodymium iron boron material contains Ga, and the content of the Ga is 0.05-0.5%, such as 0.2%;

and/or the raw material of the neodymium iron boron material contains Ti, and the content of Ti is 0.05-0.4%, for example 0.25%;

and/or the raw material of the neodymium iron boron material comprises B, wherein the content of the B is 0.9-1.02%, such as 0.96%;

and/or the raw material of the neodymium iron boron material contains Fe, and the content of the Fe accounts for the balance of 100% by mass.

9. A neodymium iron boron material is characterized by being prepared by the preparation method of the neodymium iron boron material as claimed in any one of claims 4 to 8.

10. A sintered NdFeB magnet, comprising Re₂Fe₁₄B main phase crystal grain adjacent to Re₂Fe₁₄The Nd-rich phase and the grain boundary triangular region of the B main phase crystal grains;

the Re₂Fe₁₄Re in the B main phase crystal grains contains Ho and/or Dy;

the grain boundary trigone comprises Ho₂O₃、Ho₂S₃、Dy₂O₃And Dy₂O₃One or more of;

the mass percentage of the oxides and/or sulfides in the crystal boundary triangular region in the neodymium iron boron material is 1-7%;

preferably, the preparation method of the sintered nd-fe-b magnet comprises the following steps: smelting, casting, heat preservation, hydrogen breaking, airflow grinding, molding and sintering.

Technical Field

The invention relates to a neodymium iron boron material and a preparation method thereof.

Background

In recent years, with the increasing of green travel, energy conservation and environmental protection, the demand of electric vehicles, variable frequency air conditioner compressors and wind power generation on high coercivity sintered NdFeB magnetic steel is increasing. At present, the preparation of the high-coercivity sintered NdFeB magnetic steel is mainly realized by replacing light rare earth elements by heavy rare earth elements Dy and/or Tb, so that the raw material cost of the sintered NdFeB is increased, the residual magnetism of the magnet is reduced by adding the heavy rare earth elements, and part of the magnetic energy product of the magnet is sacrificed.

In the prior art, heavy rare earth Dy and/or Tb is added into a neodymium iron boron magnet by a Grain Boundary Diffusion technology (GBD for short), so that the coercive force of the magnet is improved, and the remanence of the magnet can be maintained. The principle of the grain boundary diffusion technology is as follows: by heat treatment, the heavy rare earth element Dy and/or Tb is distributed along the Nd-rich phase to the grain boundaries, and a (Nd, Dy or Tb) having a high magnetocrystalline anisotropy field is formed around the main phase₂Fe₁₄The existence of the shell layer of the B phase and the shell layer of the high magnetocrystalline anisotropy field improves the nucleation field of the magnetization reversal domain of the magnet, and in addition, Nd replaced by heavy rare earth Dy and/or Tb in the main phase is discharged into a grain boundary, so that the magnetic isolation effect can be simultaneously realized on the main phase, and the coercive force of the magnet is improved. However, the grain boundary diffusion method is greatly influenced by the thickness of the material, and particularly for products with the thickness of more than 10mm, the grain boundary diffusion method has poor effect, and how to increase the coercive force and diffusion depth of the diffused magnet puts higher requirements on a diffusion matrix.

Patent document CN108511179A discloses a method for preparing high-magnetic sintered neodymium iron boron by hot isostatic pressing low-temperature sintering, which discloses that heavy rare earth suspension (heavy rare earth sulfide or oxide) is coated on the surface of semi-compact sintered neodymium iron boron, and hot isostatic pressing sintering is performed after vacuum tube sealing.

Patent document CN105234386A discloses a method for preparing sintered neodymium iron boron by diffusing heavy rare earth in grain boundary, which comprises mixing heavy rare earth (heavy rare earth oxide or fluoride) with organic solvent to prepare suspension, dispersing the suspension into neodymium iron boron alloy powder to obtain neodymium iron boron powder, heating, cooling, sieving, press-forming, sintering and aging.

In both of the above two prior arts, the oxide/sulfide of heavy rare earth is decomposed into heavy rare earth elements during the heating process when the coated heavy rare earth compound is subjected to grain boundary diffusion. Then the heavy rare earth element is diffused along the grain boundary, the oxygen element is enriched in the neodymium-rich phase of the base material in the diffusion process, and the heavy rare earth element is easy to combine with the oxygen element, so that the diffused heavy rare earth element is agglomerated around the neodymium-rich phase, and the heavy rare earth oxide is formed in the Nd-rich phase. This leads to limited diffusion depth of heavy rare earth elements, resulting in waste of heavy rare earth elements, and failing to form a Dy or Tb-rich shell around the main phase; and Dy and/or Tb is excessively diffused into the main phase after diffusion easily, and the residual magnetism of the product is greatly influenced.

Therefore, a new process needs to be found, the shell layer of the heavy rare earth element can be effectively formed around the main phase, and the coercive force and the diffusion depth of the diffused magnet can be effectively increased.

Disclosure of Invention

The invention provides a neodymium iron boron material and a preparation method thereof, aiming at solving the problems that the prior grain boundary diffusion method is insufficient in heavy rare earth element diffusion depth and cannot effectively improve the coercive force of a magnet. According to the invention, the grain boundary microstructure of the sintered neodymium-iron-boron magnet is improved, so that the coercive force of the neodymium-iron-boron material subjected to subsequent grain boundary diffusion is greatly improved, and the diffusion depth can be effectively increased.

The invention solves the technical problems through the following technical scheme.

One of the technical schemes provided by the invention is as follows: a neodymium-iron-boron material containing Re₂Fe₁₄B main phase crystal grain, shell thereof, and Re adjacent thereto₂Fe₁₄The Nd-rich phase and the grain boundary triangular region of the B main phase crystal grains;

the Re₂Fe₁₄Re in the B main phase crystal grains contains Ho and/or Dy;

the shell layer comprises (Nd/Ho)₂Fe₁₄B、(Nd/Dy)₂Fe₁₄Band (Nd/Tb)₂Fe₁₄One or more of B;

the thickness of the shell layer is 0.1-1 mu m;

the grain boundary trigone comprises Ho₂O₃、Ho₂S₃、Dy₂O₃And Dy₂O₃One or more of;

and the mass percentage of the oxides and/or sulfides in the crystal boundary triangular region in the neodymium iron boron material is 1-7%.

In the present invention, the Nd-rich phase is distributed adjacent Re₂Fe₁₄B, main phase crystal grains; three or more Re in the triangular region of crystal boundary₂Fe₁₄B main phase crystal grains.

In the present invention, for the Re₂Fe₁₄The B primary phase crystal grain, as known to those skilled in the art from the above technical solutions, is still Nd as the main body of the primary phase is Nd because the material itself is an ndfeb material₂Fe₁₄B crystal grains. Re preferably also comprises Nd and/or Pr.

In the present invention, preferably, the shell layer comprises (Nd/Ho)₂Fe₁₄B、(Nd/Dy)₂Fe₁₄Band (Nd/Tb)₂Fe₁₄At least two of B.

In the present invention, the thickness of the shell layer is preferably 0.45 to 1 μm, such as 0.45 μm, 0.48 μm, 0.5 μm, 0.56 μm, 0.58 μm or 0.65 μm.

In the invention, the content of the oxide and/or sulfide in the grain boundary triangular region is preferably 1 to 3% by mass, for example, 1.8%, 1.9%, 2.0%, 2.1% or 2.3% by mass of the neodymium iron boron material.

In the present invention, the grain boundary triangular region preferably further includes Nd₂O₃。

In the present invention, the Re₂Fe₁₄The percentage of the B main phase grains in the neodymium iron boron material is preferably 90% to 100%, and not 100%, and more preferably 94% to 97%, for example 94.2%, 94.5%, 95.3%, 95.5%, 96.0%, or 96.2%.

In the invention, the mass percentage of the shell layer in the neodymium iron boron material is preferably less than 1%, and is not 0, more preferably less than 0.8%, and further more preferably 0.3-0.8%, for example, 0.33%, 0.35%, 0.45%, 0.46%, 0.51%, or 0.61%.

The second technical scheme provided by the invention is as follows: a preparation method of a neodymium iron boron material comprises the following steps: smelting, casting, heat preservation, hydrogen breaking, jet milling, molding, sintering, grain boundary diffusion and aging;

wherein, one or more of Ho, Dy and S are added in the smelting stage;

the temperature of the heat preservation is 500-800 ℃;

and introducing oxygen content at the stage of the jet mill, wherein the oxygen content is 0-20 ppm.

The inventors have found that introducing one or more of Ho, Dy and S during the smelt stage forms the main phase Ho during the smelt stage₂Fe₁₄B and/or Dy₂Fe₁₄And B, then, in the heat preservation process, Ho and/or Dy elements in the Nd-rich phase are enriched towards the edge of the main phase. The oxygen content introduced during the jet milling stage is such that Ho is formed in the grain boundary triangle₂O₃And/or Dy₂O₃(Ho will also be formed if S is introduced in the melting stage₂S₃And/or Dy₂S₃). When Tb is used as diffusion source to make grain boundary diffusion, Ho is used₂Fe₁₄B or Dy₂Fe₁₄B formation energy is greater than Tb₂Fe₁₄Formation energy of B, Tb diffused into the base material cannot be replacedMiddle Ho of main phase₂Fe₁₄B or Dy₂Fe₁₄B, and the phase in the grain boundary trigones makes Tb difficult to concentrate in the grain boundary trigones, and is distributed around the main phase along the Nd-rich phase. Since the Nd-rich phase is liquid and the main phase is solid in the diffusion stage, the diffusion speed of the Tb element diffused into the liquid phase is far higher than that of the solid phase, and finally (NdTb) is formed₂Fe₁₄And B, shell layer. Not only can the coercive force of the product be effectively improved, but also most of Tb diffused into the product is distributed around the main phase (the thickness of the Tb is about 0.1-1 mu m). Not only effectively increases the diffusion depth, but also saves the consumption of Tb. In the case of grain boundary diffusion using Dy as a diffusion source, Dy cannot substitute for Ho in the main phase in principle as described above₂Fe₁₄B or Dy₂Fe₁₄B, and also difficult to enrich in the grain boundary trigones.

In the invention, the smelting is preferably carried out in a high-frequency vacuum smelting furnace to obtain an alloy sheet; the vacuum degree of the vacuum smelting furnace is preferably less than 0.1Pa, and more preferably less than 0.02 Pa; the melting temperature is preferably 1450-1550 ℃, more preferably 1500-1550 ℃.

In the present invention, the casting operation and conditions may be conventional in the art, and the alloy cast sheet is obtained by casting and cooling through a water-cooled copper roller under the protection of inert atmosphere. For example: in an Ar atmosphere (e.g. 5.5X 10)⁴Pa in Ar atmosphere) at 10 deg.f²DEG C/sec-10⁴Cooling at a rate of DEG C/sec.

In the present invention, the heat preservation means that the alloy cast piece obtained by casting is subjected to heat preservation at a temperature of 500 to 700 ℃, for example, 620 ℃. The time for heat preservation is preferably 1-5 h, for example 3 h. The heat-retaining is preferably performed in a heat-treating furnace under a vacuum atmosphere or an inert atmosphere. The degree of vacuum of the vacuum atmosphere is preferably less than 0.1Pa, more preferably less than 0.01 Pa. The inert atmosphere is preferably argon, and the pressure of the inert atmosphere is preferably 0.01 to 0.1MPa, more preferably 0.01 to 0.08 MPa.

In the invention, the operation and conditions of hydrogen breaking can be conventional in the field, generally comprise a hydrogen adsorption process and a dehydrogenation process, and the alloy cast sheet can be subjected to hydrogen breaking treatment to obtain alloy powder. Wherein, the hydrogen absorption temperature of the hydrogen breaking is preferably 20 to 300 ℃, for example 100 ℃; the hydrogen absorption pressure of the hydrogen breaker is preferably 0.12 to 0.19MPa, for example 0.19 MPa; the dehydrogenation time of the hydrogen destruction is preferably 0.5 to 5 hours, such as 2 hours; the dehydrogenation temperature of the hydrogen cracker is preferably 450 to 600 ℃, for example 550 ℃.

In the invention, the jet mill is used for sending the alloy powder into the jet mill to carry out jet mill continuous crushing to obtain alloy fine powder.

Wherein, preferably, when S is added in the smelting, the oxygen content is 0-10 ppm; when the smelting is not added with S, the oxygen content is 10-20 ppm.

Wherein, the rotation speed of the sorting wheel in the jet mill is preferably 3500-4300 rpm/min, more preferably 3900-4100 rpm/min, such as 4000 rpm/min; the grinding pressure of the jet mill is preferably 0.3-0.75 MPa, for example 0.6 MPa; the median diameter D50 of the alloy fine powder is preferably 3 to 5.5 μm, for example 4 μm.

In the present invention, the operation and conditions of the molding may be conventional in the art, and are generally performed under a magnetic field strength of 1.6T or more, for example, 1.8T, and under a nitrogen atmosphere.

In the present invention, the sintering operation and conditions may be conventional in the art, and are generally vacuum sintering or atmosphere sintering, preferably atmosphere sintering, and more preferably argon sintering.

Wherein the sintering temperature is preferably 900-1200 deg.C, more preferably 1050-1080 deg.C, such as 1065 deg.C; the sintering time is preferably 3 to 10 hours, for example 6 hours.

In the invention, the grain boundary diffusion is generally coating diffusion or coating diffusion; the diffusion source of the grain boundary diffusion is preferably Dy and/or Tb; the heat treatment temperature of the grain boundary diffusion is preferably 800-1000 ℃, for example 955 ℃; the heat treatment time for the grain boundary diffusion is preferably 5 to 20 hours, for example, 16 hours.

When the diffusion source is Dy, the Dy accounts for 0.2-1.2% of the neodymium iron boron material by mass.

When the diffusion source is Tb, Tb accounts for 0.2-1.2% of the neodymium iron boron material by mass, for example, 0.65%.

In the present invention, the operation and conditions of the aging may be conventional in the art.

Preferably, the aging temperature is 430-560 ℃, more preferably 450-490 ℃, such as 450 ℃, 455 ℃, 460 ℃, 470 ℃, 480 ℃ or 490 ℃.

Preferably, the time of the aging treatment is 2 to 5 hours, for example, 3 hours.

In the present invention, in the stage of the smelting, the Ho is preferably added in the form of a Ho — Fe alloy; the Dy is preferably added in the form of a Dy-Fe alloy; the S is preferably added in the form of an S-containing Ho-Fe alloy or an S-containing Dy-Fe alloy.

Preferably, when Ho is added in the smelting stage, Ho accounts for 0.1 to 8.5%, more preferably 0.5 to 7.5%, for example, 1.2% of the neodymium iron boron material.

When Dy is added in the smelting stage, the Dy accounts for 0-6% of the neodymium iron boron material, for example, 0.5%.

When S is added in the smelting stage, the S accounts for 0-0.1% of the neodymium iron boron material, for example, 0.05%.

In the present invention, in the smelting stage, the raw materials of the neodymium iron boron material preferably further include: one or more of Nd, Dy, Pr, Ho, Tb, Al, S, Cu, Co, Ga, Ti, B, Fe, Zr, Nb, Hf and Mn.

Preferably, the raw material of the neodymium iron boron material comprises Nd, and the content of the Nd is 23.5-30.5%, and more preferably 23.5-28.5%; for example, 28.1%.

Preferably, the raw material of the neodymium iron boron material includes Al, and the content of Al is 0-0.2%, for example, 0.04%.

Preferably, the raw material of the neodymium iron boron material includes Cu, and the content of Cu is 0.05-0.3%, for example, 0.1%.

Preferably, the raw material of the neodymium iron boron material comprises Co, and the content of Co is 0-5%, for example, 2.8%.

Preferably, the raw material of the neodymium iron boron material includes Ga, and the content of Ga is 0.05-0.5%, for example, 0.2%.

Preferably, the raw material of the neodymium iron boron material includes Ti, and the content of Ti is 0.05-0.4%, for example, 0.25%.

Preferably, the raw material of the neodymium iron boron material comprises B, and the content of B is 0.9-1.02%, for example, 0.96%.

Preferably, the raw material of the neodymium iron boron material contains Fe, and the content of Fe is the balance accounting for 100% by mass.

The third technical scheme provided by the invention is as follows: a neodymium iron boron material is prepared by the preparation method.

The fourth technical scheme provided by the invention is as follows: a sintered NdFeB magnet comprising Re₂Fe₁₄B main phase crystal grain adjacent to Re₂Fe₁₄The Nd-rich phase and the grain boundary triangular region of the B main phase crystal grains;

the Re₂Fe₁₄Re in the B main phase crystal grains contains Ho and/or Dy;

the grain boundary trigone comprises Ho₂O₃、Ho₂S₃、Dy₂O₃And Dy₂O₃One or more of;

and the mass percentage of the oxides and/or sulfides in the crystal boundary triangular region in the neodymium iron boron material is 1-7%.

Wherein the Re, the grain boundary trigones, the Re₂Fe₁₄Preferred embodiments of the B primary phase grains may be as described above.

Preferably, the preparation method of the sintered nd-fe-b magnet comprises the following steps: smelting, casting, heat preservation, hydrogen breaking, airflow grinding, molding and sintering.

Wherein the operations and conditions of the melting, the casting, the holding, the hydrogen fracturing, the jet milling, the forming and the sintering may be as previously described.

On the basis of the common knowledge in the field, the above preferred conditions can be combined randomly to obtain the preferred embodiments of the invention.

The reagents and starting materials used in the present invention are commercially available.

The positive progress effects of the invention are as follows:

re of sintered Nd-Fe-B magnet in the invention₂Fe₁₄B main phase crystal grain (especially Re)₂Fe₁₄Outer edge of B main phase grain) has Ho formed therein₂Fe₁₄B and/or Dy₂Fe₁₄B, and Ho is formed in the triangular region of the grain boundary₂O₃、Ho₂S₃、Dy₂O₃And Dy₂O₃One or more of (a). During grain boundary diffusion treatment, the diffused rare earth elements are mainly distributed around the grains of the main phase along the Nd-rich phase and are difficult to be enriched in the triangular region of the grain boundary, and the diffused rare earth elements continue to be diffused along the edges of the Nd-rich phase and the main phase, so that the diffused rare earth elements are diffused in Re₂Fe₁₄And forming a shell structure outside the B main phase grains. Not only increases the diffusion depth of the diffused rare earth elements, but also saves the consumption of the diffused rare earth elements.

Drawings

Fig. 1 is a diagram of the surface EPMA of the neodymium iron boron magnet of example 5.

Fig. 2 is a diagram of the surface EPMA of the neodymium iron boron magnet of comparative example 5.

Fig. 3 is an EPMA plot of the neodymium iron boron magnet of example 5 at 3mm from the surface.

Fig. 4 is an EPMA plot of the neodymium iron boron magnet of comparative example 5 at 3mm from the surface.

Detailed Description

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

The raw materials used for preparing the ndfeb magnet in this example are shown in table 1, and the preparation process is as follows:

(1) smelting: according to a formula shown in table 1 (in table 1, smelting refers to raw materials added in a smelting stage, and diffusion refers to raw materials added in a diffusion stage), smelting the prepared raw materials in a high-frequency vacuum smelting furnace to obtain an alloy sheet; the vacuum degree of the vacuum smelting furnace is less than 0.02 Pa; the melting temperature is 1500 ℃.

(2) Casting: at 5.5X 10⁴The alloy sheet was cast and cooled by passing through a water-cooled copper roll under Ar atmosphere of Pa to 10 deg.f²DEG C/sec-10⁴Cooling at the speed of DEG C/second to obtain the alloy cast sheet.

(3) And (3) heat preservation: the heat preservation is carried out at the temperature of 620 ℃ for 3 h. The heat preservation is carried out in a heat treatment furnace under the vacuum atmosphere, and the vacuum degree of the vacuum atmosphere is less than 0.01 Pa.

(4) Hydrogen breaking: and (4) carrying out hydrogen breaking on the alloy cast sheet obtained in the step (3), and dividing the hydrogen breaking into a hydrogen adsorption process and a dehydrogenation process. The hydrogen absorption temperature in the hydrogen absorption process is 100 ℃; the hydrogen absorption pressure was 0.19 MPa. The dehydrogenation time of hydrogen destruction is 2 h. The dehydrogenation temperature is 550 ℃, and alloy powder is obtained.

(3) And (3) jet milling: and sending the alloy powder into an airflow mill for airflow milling and continuously crushing to obtain alloy fine powder. The milling chamber of the jet mill in the jet mill contained 20ppm of oxygen.

The rotating speed of a sorting wheel in the jet mill is 4000 rpm/min. The grinding pressure of the jet mill is 0.6 MPa. The resulting alloy fine powder had a median particle diameter D50 of 4 μm.

(4) Molding: the fine powder is oriented and formed under a certain magnetic field intensity to obtain a pressed compact. The molding was carried out under a magnetic field strength of 1.8T and a nitrogen atmosphere.

(5) And (3) sintering: the sintering temperature is 1065 ℃, and the sintering time is 6 h.

(6) Grain boundary diffusion

The diffusion source of grain boundary diffusion is Tb, and coating diffusion is carried out. The heating temperature of the grain boundary diffusion treatment is 955 ℃; the heating time for the grain boundary diffusion treatment was 16 h.

The amount of diffused Tb added was according to the formulation shown in table 1.

(6) Aging

The ageing temperature was 460 ℃. The aging treatment time is 3 h.

Examples 2, 4 and 6

The raw materials were prepared according to the formulation shown in table 1, and the neodymium-iron-boron magnet was obtained under the same process conditions as in example 1 except that the oxygen content in the milling chamber of the jet mill in the jet mill was 10 ppm.

Examples 3 and 5

The raw materials were prepared according to the formulation shown in table 1, and the other process conditions were the same as in example 1, to obtain a neodymium-iron-boron magnet.

Comparative examples 1 and 5

The raw materials were prepared according to the formulation shown in table 1, and the other process conditions were the same as in example 1, to obtain a neodymium-iron-boron magnet.

Comparative examples 2, 4 and 7

The raw materials were prepared according to the formulation shown in table 1, and the neodymium iron boron magnet was prepared under the same process conditions as in example 1 except that the heat preservation in step (3) was not performed.

Comparative example 3

The raw materials were prepared according to the formulation shown in table 1, and the nd-fe-b magnet was obtained under the same process conditions as in example 1 except that the heat preservation in step (3) was not performed and the oxygen content in the milling chamber of the jet mill in the jet mill was 10 ppm.

Comparative example 6

The raw materials were prepared according to the formulation shown in table 1, and the neodymium-iron-boron magnet was obtained under the same process conditions as in example 1 except that the oxygen content in the milling chamber of the jet mill in the jet mill was 60 ppm.

The comparison of structural characteristics and magnetic properties of the crystal phases of the respective examples and comparative examples are shown in tables 2 and 3.

Wherein, Re₂Fe₁₄The mass percentage of the B main phase crystal grains to the neodymium iron boron material, the thickness of the shell layer, the mass ratio of the shell layer to the neodymium iron boron magnet, and the mass percentage of the oxides and/or sulfides in the grain boundary triangular region to the neodymium iron boron material are all related to the size range of the region selected by measurement. When the grain sizes are similar, the thickness of the shell layer is generally in direct proportion to the mass ratio of the shell layer to the neodymium iron boron magnet; when the grain sizes are greatly different, the shell layer occupies the neodymium-iron-boron magnetWill be slightly different.

TABLE 1 weight percentages of raw materials in each example and comparative example

TABLE 2 comparison of structural features of crystal phases in examples and comparative examples

TABLE 3 comparison of magnet Properties in examples and comparative examples

Numbering	Remanence (kGs)	Coercive force (kOe)	High temperature magnetic loss
				Example 1	14	27.5	Magnetic loss at 160 ℃ is 0.5 percent
Example 2	13.9	28.1	Magnetic loss at 160 ℃ is 0.4 percent
				Example 3	14.3	28.2	Magnetic loss at 160 ℃ is 0.35 percent
Example 4	14.25	28.7	Magnetic loss at 160 ℃ is 0.25 percent
				Example 5	12.7	33.5	Magnetic loss at 200 ℃ is 0.10 percent
Example 6	12.62	34.1	Magnetic loss at 200 ℃ is 0.08 percent
				Comparative example 1	14.2	24.5	Magnetic loss at 160 ℃ of 5.2 percent
Comparative example 2	13.7	25.5	Magnetic loss at 160 ℃ of 4.8 percent
				Comparative example 3	14.35	26.5	Magnetic loss at 160 ℃ of 2.5 percent
Comparative example 4	14.1	26.3	Magnetic loss at 160 ℃ is 2.9 percent
				Comparative example 5	14	25.1	Magnetic loss at 200 ℃ of 34.9 percent
Comparative example 6	12.65	29.1	Magnetic loss at 200 ℃ of 9.8 percent
				Comparative example 7	12.7	31.0	Magnetic loss at 200 ℃ is 3.2%

As shown in fig. 1, the EPMA chart at the edge of the surface layer of example 5 shows the distribution of Tb element, and after Tb diffusion, the shell structure containing Tb around the main phase does not enter the main phase.

As shown in fig. 2, the EPMA diagram at the edge of the surface layer of comparative example 5 shows the distribution of Tb element, and after Tb diffusion, the diffused Tb element enters the main phase, and no Tb-containing shell structure is formed.

As shown in FIG. 3, the EPMA graph of example 5 at 3mm from the surface shows the distribution of Tb element, and after Tb diffusion, Tb element is distributed around the grain boundary triangle without entering the interior of the grain boundary triangle.

As shown in fig. 4, the EPMA diagram of comparative example 5 at 3mm from the surface shows the distribution of Tb element, which diffused into the inside of the grain boundary trigones after Tb diffusion and distributed less along and around the grain boundary trigones.

In fig. 1 to 4, the content of Tb element can be determined according to the brightness in the left image, the area with high content of Tb element is gray, and the area without Tb element is black.