CN112008075B

CN112008075B - Rare earth permanent magnet and preparation method thereof

Info

Publication number: CN112008075B
Application number: CN201910450450.3A
Authority: CN
Inventors: 邓小霞; 陈波; 郭强
Original assignee: BYD Co Ltd
Current assignee: BYD Co Ltd
Priority date: 2019-05-28
Filing date: 2019-05-28
Publication date: 2022-02-08
Anticipated expiration: 2039-05-28
Also published as: CN112008075A

Abstract

The invention relates to a rare earth permanent magnet and a preparation method thereof. The rare earth permanent magnet comprises a main phase and a grain boundary phase, wherein the grain boundary phase is isolated and/or coated with the main phase, and the main phase has a core-shell structure; the main phase comprises the following components: r1_xR2_yFe_{100‑x‑y‑z‑u}Co_zB_u(ii) a The grain boundary phase comprises the following components: r3_aR4_bFe_{100‑a‑b‑c‑d‑v}Co_cB_dM_v. The rare earth permanent magnet obtained by the invention reduces the content of dysprosium and/or terbium, reduces the production cost of the rare earth permanent magnet, and improves the coercive force and the heat resistance of the rare earth permanent magnet.

Description

Rare earth permanent magnet and preparation method thereof

Technical Field

The invention relates to a rare earth permanent magnet and a preparation method thereof.

Background

The rare earth permanent magnet is a high and new technical field which is emphatically encouraged and supported by the country, and is widely applied to the fields of wind power generation, energy-saving elevators, variable frequency air conditioners, new energy automobiles, automobile EPS, energy conservation, environmental protection, intelligent robots and the like, and traditional VCM, mobile phones and other consumer electronic products. The use of rare earth permanent magnets in motors represents an industry trend, and is paid more attention because of the advantages of small volume, light weight, high energy conversion efficiency, obvious energy-saving effect and the like. With the development of new energy automobile industry, the demand of high-performance low-cost neodymium-iron-boron magnet is further increased. The new energy automobile motor magnet is generally used in a high-temperature environment, so that the magnet is required to have high coercive force and excellent heat resistance.

At present, the method for improving the coercive force by adopting the traditional process mainly adds a certain amount of heavy rare earth elements, but inevitably causes the reduction of remanence and magnetic energy product and the increase of cost. Great limitations are encountered in developing magnets with double high magnets or combined indices (BHm + Hcj) greater than 75. The improvement and regulation of the organization structure of the neodymium iron boron permanent magnet material, and the development of new technology and technology to improve the magnetic performance are still the directions of people's continuous efforts.

Disclosure of Invention

In order to improve the heat resistance of the rare earth permanent magnet for the new energy automobile motor, reduce the magnetic loss caused by the heat effect as much as possible, and solve the problem of cost increase caused by adding a certain amount of heavy rare earth, the invention provides the rare earth permanent magnet with low cost, high coercive force and good heat resistance and the preparation method thereof.

The first aspect of the invention provides a rare earth permanent magnet, which comprises a main phase and a grain boundary phase, wherein the grain boundary phase is isolated and/or coated with the main phase, and the main phase has a core-shell structure;

the main phase comprises the following components: r1_xR2_yFe_100-x-y-z-uCo_zB_uR1 is selected from Pr and/or Nd, R2 is selected from Dy and/or Tb, wherein x, y, z and u are mass percent, x + y is more than or equal to 26% and less than or equal to 32%, y is more than or equal to 0% and less than or equal to 2%, z is more than or equal to 0% and less than or equal to 3%, and u is more than or equal to 0.8% and less than or equal to 1.2%;

the grain boundary phase comprises the following components: r3_aR4_bFe_{100-a-b-c-d-v}Co_cB_dM_vR3 is selected from Pr and/or Nd, R4 is selected from Dy and/or Tb, M is selected from one or more of Zr, Ga, Cu, Sn, Al, Zn, Bi, Ta, In, Pb, Cd, Tl and Sb, wherein a, b, c, d and v are mass percent, and a + b is more than or equal to 35% and less than or equal to 60%, b is more than or equal to 0% and less than or equal to 3%, c is more than or equal to 0% and less than or equal to 5%, d is more than or equal to 0% and less than or equal to 1.2%, v is more than or equal to 20% and less than or equal to 50%.

The second aspect of the present invention provides a method for producing a rare earth permanent magnet, comprising the steps of:

s1, mixing the main phase alloy raw material and the grain boundary phase alloy raw material, and performing magnetic field orientation compression molding, sintering and first tempering treatment to obtain a rare earth permanent magnet blank;

s2, coating the grain boundary diffusion material on the surface of the rare earth permanent magnet blank, and obtaining the rare earth permanent magnet provided by the first aspect through diffusion process treatment.

The rare earth permanent magnet provided by the invention comprises a main phase and a grain boundary phase, wherein the grain boundary phase separates and/or coats the main phase, namely the grain boundary phase separates adjacent main phases, so that the coercive force reduction caused by the magnetic exchange coupling effect between the adjacent main phases is avoided; and the main phase has a core-shell structure, so that the magnetic isolation effect is further enhanced, the anisotropy of the joint of the main phase and the grain boundary phase is enhanced, and the generation of a reverse magnetization domain is inhibited, thereby improving the coercive force and the heat resistance of the magnet.

Additional features and advantages of the invention will be set forth in the detailed description which follows.

Detailed Description

The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.

The invention provides a rare earth permanent magnet, which comprises a main phase and a grain boundary phase, wherein the grain boundary phase is isolated and/or coated with the main phase, and the main phase has a core-shell structure;

the composition of the main phase is R1_xR2_yFe_100-x-y-z-uCo_zB_uR1 is selected from Pr and/or Nd, R2 is selected from Dy and/or Tb, wherein x, y, z and u are mass percent, x + y is more than or equal to 26% and less than or equal to 32%, y is more than or equal to 0% and less than or equal to 2%, z is more than or equal to 0% and less than or equal to 3%, and u is more than or equal to 0.8% and less than or equal to 1.2%;

In the invention, the rare earth permanent magnet comprises a main phase and a grain boundary phase, wherein the grain boundary phase separates and/or coats the main phase, namely the grain boundary phase separates adjacent main phases, thereby avoiding the coercive force reduction caused by the magnetic exchange coupling effect between the adjacent main phases; and the main phase has a core-shell structure, so that the magnetic isolation effect is further enhanced, the anisotropy of the joint of the main phase and the grain boundary phase is enhanced, and the generation of a reverse magnetization domain is inhibited, thereby improving the coercive force and the heat resistance of the magnet. It should be noted that, in the existing product, a structural defect is easily present at the joint of the main phase and the grain boundary phase, the region of the structural defect is the nucleation center of the anti-magnetization domain, and the anti-magnetization domain can reduce the coercive force of the magnet.

In the present invention, preferably, the core-shell structure includes a core layer and a shell layer containing Dy₂Fe₁₄B phase and/or Tb₂Fe₁₄The phase B can improve the magnetocrystalline anisotropy constant of the surface of the main phase, inhibit the generation of a reverse magnetization domain, reduce or eliminate the defect that the impurity phase at the crystal boundary of the magnet is easy to demagnetize, and effectively improve the coercive force and the heat resistance of the whole magnet. It should be noted that, in the process of preparing the rare earth permanent magnet, impurities such as oxides, carbides, nitrides, etc. are easily introduced to form a grain boundary impurity phase. More preferably, the content of R2 per unit volume in the shell layer is higher than that of R2 per unit volume in the core layer, and R2 is liable to react with other elements of the main phase to form a Dy2Fe14B phase and/or a Tb2Fe14B phase, further improving the coercive force and heat resistance of the magnet.

In the present invention, in order to more favorably obtain a rare earth permanent magnet having high coercive force and heat resistance with little decrease in remanence, the composition of the main phase is such that x, y, z, and u are, in mass percent: x + y is more than or equal to 27 percent and less than or equal to 31 percent, y is more than or equal to 0.5 percent and less than or equal to 1.5 percent, z is more than or equal to 0.5 percent and less than or equal to 2.5 percent, and u is more than or equal to 0.9 percent and less than or equal to 1.1 percent. In the composition of the grain boundary phase, the mass percentages of a, b, c, d and v are as follows: a + b is more than or equal to 40% and less than or equal to 50%, b is more than or equal to 0.5% and less than or equal to 2.5%, c is more than or equal to 0.5% and less than or equal to 4.5%, d is more than or equal to 0.1% and less than or equal to 1%, v is more than or equal to 25% and less than or equal to 40%. The mass content of the grain boundary phase is 3-20% based on the total mass of the main phase and the grain boundary phase, and more preferably, the mass content of the grain boundary phase is 5-15%.

In the invention, the grain boundary phase contains more than one low-melting-point metal element, namely M, and the combination of the element M and other elements in the grain boundary phase is beneficial to reducing the melting point of the grain boundary phase, so that the grain boundary phase is melted to form a diffusion channel of Dy and/or Tb when the grain boundary phase is subjected to the subsequent diffusion process treatment.

In the present invention, preferably, the thickness of the rare earth permanent magnet is 1 to 10 mm; further preferably, the thickness of the rare earth permanent magnet is 2-7 mm.

In the present invention, preferably, the oxygen content of the rare earth permanent magnet is 3000ppm or less; further preferably, the oxygen content of the rare earth permanent magnet is 2000ppm or less.

In the invention, the rare earth permanent magnet also comprises a grain boundary diffusion layer positioned on the surface of the rare earth permanent magnet, and the thickness of the grain boundary diffusion layer is 5-20 μm. If the thickness of the grain boundary diffusion layer is too thick, the magnet cost increases, and the magnet performance decreases.

In the invention, the material of the grain boundary diffusion layer is selected from one or more of an oxide of R5, a fluoride of R5 and a diffusion alloy of R5, and R5 is selected from Dy and/or Tb. Preferably, the mass content of the diffusion alloy is 0-65% by taking the total weight of the materials of the grain boundary diffusion layer as a reference; further preferably, the diffusion alloy has a mass content of 15 to 55%.

In the present invention, preferably, the composition of the diffusion alloy of R5 is: r6_mR7_nFe_100-m-n-p-wCo_pN_wR6 is selected from Pr and/or Nd, R7 is selected from Dy and/or Tb, N is selected from one or more of Ga, Cu, Sn, Al, Zn, Bi, Ta, In, Pb, Cd, Tl and Sb, wherein m, N, p and w are mass percent, m + N is more than or equal to 30% and less than or equal to 70%, N is more than or equal to 20% and less than or equal to 50%, p is more than or equal to 0% and less than or equal to 3%, and w is more than or equal to 25% and less than or equal to 60%. The addition of Co element in the diffusion alloy provided by the invention can improve the corrosion resistance, Curie temperature and heat resistance. More preferably, in the composition of the diffusion alloy, the mass percentages of m, n, p and w are as follows: m + n is more than or equal to 35% and less than or equal to 60%, n is more than or equal to 25% and less than or equal to 45%, p is more than or equal to 0.5% and less than or equal to 2.5%, and w is more than or equal to 35% and less than or equal to 55%. When within the above range, a rare earth permanent magnet having high coercive force and good heat resistance can be further obtained at low cost.

The invention also provides a preparation method of the rare earth permanent magnet, which comprises the following steps:

s1, mixing the main phase alloy raw material and the grain boundary phase alloy raw material, performing magnetic field orientation compression molding, sintering and first tempering treatment to obtain a rare earth permanent magnet blank;

and S2, covering the grain boundary diffusion material on the surface of the rare earth permanent magnet blank, and performing diffusion process treatment to obtain the rare earth permanent magnet.

In the invention, the rare earth permanent magnet blank comprises a main phase and a grain boundary phase, and the grain boundary phase separates and/or coats the main phase. The grain boundary phase contains more than one low-melting-point metal element, namely M, and the combination of the element M and other elements in the grain boundary phase is beneficial to reducing the melting point of the grain boundary phase, so that the grain boundary phase is fused to become a diffusion channel of Dy and/or Tb in the grain boundary diffusion material during the diffusion process treatment.

In the above preparation method step S3, the grain boundary diffusion material includes one or more of an oxide of R5, a fluoride of R5, and a diffusion alloy of R5, and R5 is selected from Dy and/or Tb. The total mass of the grain boundary diffusion material is taken as a reference, and the mass content of the diffusion alloy is 0-65%; the preferred mass content is 15-55%. Preferably, the composition of the diffusion alloy of R5 is: r6_mR7_nFe_100-m-n-p-wCo_pN_wR6 is selected from Pr and/or Nd, R7 is selected from Dy and/or Tb, N is selected from one or more of Ga, Cu, Sn, Al, Zn, Bi, Ta, In, Pb, Cd, Tl and Sb, wherein m, N, p and w are mass percent, m + N is more than or equal to 30% and less than or equal to 70%, N is more than or equal to 20% and less than or equal to 50%, p is more than or equal to 0% and less than or equal to 3%, and w is more than or equal to 25% and less than or equal to 60%.

According to one embodiment of the preparation method of the invention, Dy and/or Tb in the grain boundary diffusion material is higher than Dy and/or Tb in the rare earth permanent magnet blank, rare earth Dy and/or Tb diffuses from the grain boundary diffusion material with high concentration to the rare earth permanent magnet blank with low concentration to enter a grain boundary phase, and Dy and/or Tb in the grain boundary diffusion material can replace Pr and/or Nd on the surface of a main phase to generate Dy on the surface of the main phase₂Fe₁₄B and/or Tb₂Fe₁₄B (i.e. produced with a core-Shell)The main phase of the structure) can improve the magnetocrystalline anisotropy constant of the surface of the main phase, inhibit the generation of a reverse magnetization domain, reduce or eliminate the defect that an impurity phase at the grain boundary of the magnet is easy to demagnetize, and effectively improve the coercive force and the heat resistance of the whole magnet.

The diffusion alloy provided by the invention is low-melting-point alloy, and the melting point of the diffusion alloy is controlled within the range of 600-850 ℃ by adding selected alloy elements to adjust the components of the diffusion alloy. Under the same diffusion temperature, the low-melting-point diffusion alloy is in a molten state, has higher superheat degree and larger diffusion potential energy, and achieves larger diffusion depth. In addition, the low-melting-point diffusion alloy is in a molten state, so that the surface bonding force between the diffusion alloy and the rare earth permanent magnet blank can be enhanced, the addition of an organic binder is omitted, the vacuumizing and glue discharging time is shortened, and the performance reduction caused by part of carbon residue is prevented. Preferably, in the composition of the diffusion alloy, the mass percentages of m, n, p and w are as follows: m + n is more than or equal to 35% and less than or equal to 60%, n is more than or equal to 25% and less than or equal to 45%, p is more than or equal to 0.5% and less than or equal to 2.5%, and w is more than or equal to 35% and less than or equal to 55%.

In the invention, the grain boundary diffusion material can be a single oxide of R5 or a fluoride of R5 or a diffusion alloy containing R5, or can be a mixture of two or three. The method of mixing the mixture is not limited in the present invention, and for example, mechanical stirring, ball milling or the like can be used.

In the present invention, the diffusion alloy may be prepared by a conventional method for preparing an alloy material in the art, and preferably, the preparation method of the diffusion alloy comprises: after the diffusion alloy according to the present invention is compounded, the resulting raw material mixture is melted, and an ingot or a rapidly solidified sheet is obtained. In the preparation of the diffusion alloy, the smelting conditions preferably include: the melting temperature is 600-1000 ℃, and the melting time is 30-70 min.

In the present invention, it is preferable that the grain boundary diffusion material is in a powder form. The average particle diameter of the powdery grain boundary diffusion material is 2 to 20 μm, preferably 5 to 15 μm. If the average grain size is too large, the fusion adhesion bonding (bonding) effect of the powder and the rare earth permanent magnet blank is not good during diffusion; if the average particle diameter is too small, the production cost is high from the practical viewpoint, and it is difficult to control the degree of oxidation.

In the present invention, the method of making the grain boundary diffusion material into powder is not limited, and for example, the grain boundary diffusion material may be made into powder by means of ball milling.

In the present invention, the form of the coating of the grain boundary diffusion material on the surface of the rare earth permanent magnet blank is not limited, and may be selected from coating, spraying, coating, dipping, suspension adhesion, barrel plating electrophoresis, and the like. Preferably, the grain boundary diffusion material powder can be directly coated on the upper and lower surfaces of the rare earth permanent magnet blank, the form is simple, and the cost can be reduced.

In the present invention, preferably, the conditions of the diffusion process treatment include: the temperature is 600-1000 ℃, the time is 2-12h, and the absolute pressure is 10^-5-10^-2Pa。

In the present invention, preferably, the method further includes performing a second tempering treatment on the magnet after the diffusion process treatment, where conditions of the second tempering treatment include: the heating temperature is 400-^-5-10^-2Pa。

According to the invention, in order to facilitate Dy and/or Tb in the grain boundary diffusion material to diffuse to the grain boundary of the rare earth permanent magnet blank, the rare earth permanent magnet blank is preferably of a sheet structure, and the thickness of the rare earth permanent magnet blank is 1-10mm, and more preferably 2-7 mm.

In the present invention, the oxygen content of the rare earth permanent magnet blank is preferably 3000ppm or less, more preferably 2000ppm or less. If the oxygen content is higher than the aforementioned preferable range, the effect of grain boundary diffusion is seriously lowered without forming a grain boundary diffusion layer having high bonding strength with the rare earth permanent magnet blank.

According to the present invention, before the diffusion process treatment, the above-mentioned rare earth permanent magnet blank body is preferably subjected to a surface treatment, which may be, for example, pickling with a 0.3 wt% nitric acid aqueous solution or mechanical polishing.

In the step S1, the main phase alloy raw material and the grain boundary phase alloy raw material are mixed, and the main phase alloy raw material and the grain boundary phase alloy raw material may be respectively melted to obtain an ingot or a rapidly solidified sheet of the main phase alloy raw material and an ingot or a rapidly solidified sheet of the grain boundary phase alloy raw material, and the ingot or the rapidly solidified sheet of the main phase alloy raw material and the ingot or the rapidly solidified sheet of the grain boundary phase alloy raw material are mixed. Further preferably, after the ingot or the quick-setting flake is mixed, the ingot or the quick-setting flake is crushed and pulverized; then the prepared superfine powder of the main phase alloy raw material and the grain boundary phase alloy raw material is subjected to magnetic field orientation compression molding, sintering and tempering to obtain the rare earth permanent magnet blank.

In the preparation of the rare earth permanent magnet blank, the smelting method is a conventional smelting method in the field, and the obtained alloy is an ingot or a rapid hardening sheet. The smelting conditions comprise: the smelting temperature is 800-.

According to the preparation method of the present invention, the crushing method can adopt a crushing method which is conventional in the art as long as the obtained ingot or melt-spun strip can be sufficiently crushed, and preferably, the crushing method adopts hydrogen crushing. Preferably, the hydrogen fragmentation conditions include: absorbing hydrogen at normal temperature (20 +/-5 ℃) for 0.5 to 3 hours under the hydrogen pressure of 0.05 to 1.5MPa, and dehydrogenating for 4 to 10 hours at the temperature of 450 ℃ and 650 ℃.

According to the preparation method of the present invention, the pulverization method may be any conventional pulverization method in the art as long as hydrogen pulverized powder can be made into fine powder of a target particle size, and preferably a jet milling method is employed, and an antioxidant is added before the jet milling is performed. The antioxidant can be any special antioxidant for neodymium iron boron, for example, the special antioxidant for neodymium iron boron with the brand number of KM-01, which is purchased from Beijing Jun Zzefeng scientific and technological development Limited company. In the present invention, it is preferable that the antioxidant is added in an amount of 0.03 to 0.16 wt% based on the total weight of the hydrogen pulverized powder of the main body of the permanent magnetic material obtained in the above-described process. Further, it is preferable to pulverize hydrogen into fine powder having an average particle diameter of 2.5 to 4.5 μm by jet milling.

According to the production method of the present invention, it is preferable that a lubricant is added to the obtained fine powder after pulverization, and the lubricant is not particularly limited in the present invention, and for example, the lubricant may be at least one of gasoline, oleic acid, stearic acid, polyethylene glycol, sorbitan, and glyceryl stearate. Further, it is preferable that the lubricant is added in an amount of 0.02 to 0.17% by weight based on the total weight of the fine powders of the rare earth permanent magnet main body.

According to the preparation method of the present invention, the magnetic field orientation compression molding method may adopt a magnetic field orientation compression molding method of a permanent magnetic material, which is conventional in the art, and preferably, the magnetic field orientation compression molding method includes: performing orientation compression molding in a constant magnetic field or a pulse magnetic field of 2-3.5T, and keeping the orientation compression molding for 60-120s under the isostatic pressure of 170-220 MPa.

According to the preparation method of the present invention, the sintering and first tempering methods may be sintering and tempering methods conventional in the art, and preferably, the sintering conditions include: the sintering temperature is 1035-1090 ℃, and the sintering time is 4-6 h. Preferably, the conditions of the first tempering treatment include: first tempering is carried out at 880-950 ℃ and kept for 2-5h, and then second tempering is carried out at 480-550 ℃ and kept for 3-8 h. And machining the obtained sintered and tempered block into a block with a required shape.

The present invention will be described in detail below by way of examples.

Example 1

Carrying out melt-spinning treatment on a raw material with a formula of Nd27Dy1Fe69.5Co1.5B1 at a surface linear velocity of a copper roller of 1.5m/s, absorbing hydrogen for 1.3h at 23 ℃ under 0.11Mpa hydrogen pressure by using a melt-spun sheet, and then dehydrogenating for 5.3h at 564 ℃ to obtain hydrogen crushed powder. Then, 100 parts by weight of the hydrogen pulverized powder was uniformly mixed with 0.05 part by weight of a neodymium iron boron specific antioxidant (available from beijing jun zefeng scientific and technological development limited company, No. KM-01), followed by grinding by an air mill to prepare a fine powder having an average particle size of 3.2 μm, and then 100 parts by weight of the obtained fine powder was uniformly mixed with 0.025 part by weight of gasoline (available from hao-tian chemical company, No. YS-06) to obtain a main phase alloy powder of a rare earth permanent magnet blank.

A raw material having a formulation of Nd44.2Dy0.8Fe15.7Co3.5B0.8Ga7Sn8Zn5Cu7Al8 was subjected to strip throwing treatment at a copper roll surface linear velocity of 1.4m/s to prepare a grain boundary phase alloy. The obtained melt-spun piece absorbs hydrogen at 23 ℃ for 1.2h under 0.12Mpa hydrogen pressure, and then dehydrogenates at 563 ℃ for 5.2h to prepare hydrogen crushed powder. Then, 100 parts by weight of the hydrogen pulverized powder was uniformly mixed with 0.06 part by weight of a neodymium iron boron specific antioxidant (available from beijing jun zefeng scientific and technological development limited company, No. KM-01), followed by grinding by an air mill to prepare a fine powder having an average particle size of 3.0 μm, and then 100 parts by weight of the obtained fine powder was uniformly mixed with 0.03 part by weight of gasoline (available from hao-tian chemical company, No. YS-06) to obtain a grain boundary phase alloy powder of a rare earth permanent magnet blank.

And uniformly mixing the main phase alloy powder and the grain boundary phase alloy powder, wherein the using amount of the grain boundary phase alloy powder is 10 parts by weight relative to 100 parts by weight of the total using amount of the main phase alloy powder and the grain boundary phase alloy powder.

Forming the alloy powder of the rare earth permanent magnet blank in a constant magnetic field of 2.4T, and keeping for 60s under isostatic pressing of 205 MPa; then sintering for 4.5h at 1075 ℃; performing primary tempering at 910 ℃ for 2.2 h; then, secondary tempering is carried out at 505 ℃, the secondary tempering is kept for 3.2 hours, the oxygen content of the obtained rare earth permanent magnet sintered blank is 1000ppm, and the blank block body is machined into the rare earth permanent magnet blank with the size of 18mm, 15mm in width and 5mm in thickness.

Smelting a raw material with a formula of Nd20Dy30Fe4Co1Ga12Sn10Cu15Al8 at 700 ℃ for 35min to prepare an ingot, then grinding the ingot by ball milling to prepare fine powder with the average particle size of 10 mu m, and uniformly mixing the fine powder with TbF3 powder with the average particle size of 10 mu m, wherein the mass content of the diffusion alloy powder is 35% based on the mixed diffusion powder.

Performing sand blasting on the rare earth permanent magnet blank, uniformly coating diffusion powder on the upper and lower surfaces of a base material, arranging the base material in a heat treatment device, and performing heat treatment under the absolute pressure of 5 × 10^-3And carrying out grain boundary diffusion for 8.5h at Pa and the diffusion temperature of 820 ℃. Then tempering treatment is carried out, the tempering partThe conditions of the treatment include: heating at 520 deg.C for 3.5h under absolute pressure of 2 × 10^-2Pa to obtain the rare earth permanent magnet a1 of the present invention.

Example 2

A rare earth permanent magnet a2 was produced by the method for producing a rare earth permanent magnet of example 1, except that the oxygen content of the obtained sintered compact of the rare earth permanent magnet was 2500 ppm.

Example 3

A rare earth permanent magnet a3 was produced by the method for producing a rare earth permanent magnet of example 1, except that the obtained sintered green block was machined into a rare earth permanent magnet blank having a size of 18mm in length by 15mm in width by 10mm in thickness.

Example 4

A rare earth permanent magnet a4 was produced by the method for producing a rare earth permanent magnet of example 1, except that the diffusion alloy powder of Nd20Dy30Fe4Co1Ga12Sn10Cu15Al8 was coated on the upper and lower surfaces of the rare earth permanent magnet blank separately, and then diffusion heat treatment was performed.

Example 5

A rare earth permanent magnet a5 was produced by the method for producing a rare earth permanent magnet of example 1, except that the diffusion powder was coated on the upper and lower surfaces of a rare earth permanent magnet blank separately with Dy2O3 powder having an average particle diameter of 18 μm, and then subjected to diffusion heat treatment.

Example 6

Carrying out melt-spinning treatment on a raw material with a formula of Pr30.5Tb0.5Fe65.6Co2.5B0.9 at the surface linear velocity of a copper roller of 1.6m/s, absorbing hydrogen for 1.5h at 23 ℃ under the hydrogen pressure of 0.12Mpa, and then dehydrogenating for 5.6h at 562 ℃ to obtain hydrogen crushed powder. Then, 100 parts by weight of the hydrogen pulverized powder was uniformly mixed with 0.055 part by weight of a neodymium iron boron specific antioxidant (available from beijing jun zefeng scientific and technological development limited company, No. KM-01), followed by grinding by an air flow mill to prepare a fine powder having an average particle size of 3.1 μm, and then 100 parts by weight of the obtained fine powder was uniformly mixed with 0.03 part by weight of oleic acid (available from YH-06 brand of hao day chemical company) to obtain a main phase alloy powder of a rare earth permanent magnet blank.

A raw material having a formulation Pr39.5Tb0.5Fe29.5Co4.5B1Zr6Sb7Pb12 was subjected to a strip casting treatment at a surface linear velocity of a copper roll of 1.3m/s to prepare a grain boundary phase alloy. The obtained melt-spun piece was subjected to hydrogen absorption at 23 ℃ for 1.4 hours under a hydrogen pressure of 0.1MPa, and then to dehydrogenation at 560 ℃ for 5.5 hours, to thereby prepare a hydrogen pulverized powder. Then, 100 parts by weight of the hydrogen pulverized powder was uniformly mixed with 0.04 part by weight of a neodymium iron boron specific antioxidant (available from beijing jun zefeng scientific and technological development limited company, No. KM-01), followed by grinding by an air flow mill to prepare a fine powder having an average particle size of 3.3 μm, and then 100 parts by weight of the obtained fine powder was uniformly mixed with 0.035 part by weight of oleic acid (available from hao-06 brand of hao-tian chemical company) to obtain a grain boundary phase alloy powder of a rare earth permanent magnet blank.

And uniformly mixing the main phase alloy powder and the grain boundary phase alloy powder, wherein the using amount of the grain boundary phase alloy powder is 15 parts by weight relative to 100 parts by weight of the total using amount of the main phase alloy powder and the grain boundary phase alloy powder.

Forming the alloy powder of the rare earth permanent magnet blank in a constant magnetic field of 2.2T, and keeping the alloy powder for 70s under the isostatic pressure of 195 Mpa; then sintering for 4.8h at 1073 ℃; performing primary tempering at 900 ℃, and keeping for 2.3 h; then, secondary tempering is carried out at 503 ℃, the secondary tempering is kept for 3.5 hours, the oxygen content of the obtained rare earth permanent magnet sintered blank is 2000ppm, and the blank block body is machined into the rare earth permanent magnet blank with the size of 22mm, 13mm in width and 2mm in thickness.

The raw material with the formula of Pr10Tb25Fe7.5Co2.5Ta20Sb15Pb20 is smelted for 40min at 720 ℃ to prepare an ingot, then the ingot is ground by ball milling to prepare fine powder with the average grain diameter of 5 mu m, and the fine powder is uniformly mixed with Dy2O3 powder with the average grain diameter of 5 mu m, wherein the mass content of the diffusion alloy powder is 55% on the basis of the mixed diffusion powder.

Pickling the permanent magnet blank with 0.3 wt% concentration nitric acid solution, coating the diffusion powder onto the upper and lower surfaces of the permanent magnet blank, setting in heat treating apparatus, and maintaining the absolute pressure at 4X 10^-3And carrying out grain boundary diffusion for 8.3h at the Pa and the diffusion temperature of 825 ℃. Then carrying out tempering treatment, wherein the tempering treatment conditions comprise: heating at 515 deg.C for 3.8h under 1.5 × 10 absolute pressure^-2Pa to obtain the rare earth permanent magnet a6 of the present invention.

Example 7

A rare earth permanent magnet a7 was produced by the production method for a rare earth permanent magnet of example 6, except that the above-described main phase alloy powder and grain boundary phase alloy powder were uniformly mixed, and the amount of the grain boundary phase alloy powder was 17 parts by weight relative to 100 parts by weight of the total amount of the main phase alloy powder and the grain boundary phase alloy powder.

Example 8

Carrying out melt-spinning treatment on a raw material with a formula of Nd25.5Dy1.5Fe71.4Co0.5B1.1 at a surface linear velocity of a copper roller of 1.2m/s, absorbing hydrogen for 1.6h at 23 ℃ under 0.13MPa of hydrogen pressure by using a melt-spun sheet, and then dehydrogenating for 5.8h at 565 ℃ to obtain hydrogen crushed powder. Then, 100 parts by weight of the hydrogen pulverized powder was uniformly mixed with 0.045 part by weight of a neodymium iron boron specific antioxidant (available from beijing jun zefeng scientific and technological development limited, trademark KM-01), followed by grinding by an air flow mill to prepare a fine powder having an average particle size of 2.9 μm, and then 100 parts by weight of the obtained fine powder was uniformly mixed with 0.04 part by weight of oleic acid (available from YH-06 trademark of hao sky chemical) to obtain a main phase alloy powder of a rare earth permanent magnet blank.

A raw material having a formulation of Nd47.5Dy2.5Fe9.4Co0.5B0.1Bi8Ta9Cu6Sn8Tl9 was subjected to strip throwing treatment at a surface linear velocity of a copper roll of 1.4m/s to prepare a grain boundary phase alloy. The obtained melt-spun piece was subjected to hydrogen absorption at 23 ℃ for 1.5 hours under a hydrogen pressure of 0.11MPa, and then to dehydrogenation at 558 ℃ for 5.4 hours to obtain hydrogen pulverized powder. Then, 100 parts by weight of the hydrogen pulverized powder was uniformly mixed with 0.03 part by weight of a neodymium iron boron specific antioxidant (available from beijing jun zefeng scientific and technological development ltd., No. KM-01), followed by grinding by an air flow mill to prepare a fine powder having an average particle size of 3.4 μm, and then 100 parts by weight of the obtained fine powder was uniformly mixed with 0.045 part by weight of stearic acid (available from hao-tian chemical corporation, YSH-06 brand) to obtain a grain boundary phase alloy powder of a rare earth permanent magnet blank.

And uniformly mixing the main phase alloy powder and the grain boundary phase alloy powder, wherein the using amount of the grain boundary phase alloy powder is 5 parts by weight relative to 100 parts by weight of the total using amount of the main phase alloy powder and the grain boundary phase alloy powder.

Forming the alloy powder of the rare earth permanent magnet blank in a constant magnetic field of 2.5T, and keeping for 75s under 190MPa of isostatic pressure; then sintering for 5h at 1072 ℃; performing primary tempering at 905 ℃ for 2.5 hours; and then performing secondary tempering at 500 ℃, keeping for 3.8 hours, obtaining a rare earth permanent magnet sintered blank with the oxygen content of 1200ppm, and mechanically processing a blank block into a rare earth permanent magnet blank with the size of 25mm, 15mm in width and 7mm in thickness.

A raw material having a formulation of Nd15Dy45Fe4.5Co0.5Bi15T10Cd10 was melted at 730 ℃ for 45min, and a strip-casting treatment was performed at a surface linear velocity of a copper roll of 1.7m/s to obtain a diffusion alloy. Grinding the obtained melt-spun piece by ball milling to prepare fine powder with the average particle size of 15 mu m, and uniformly mixing the fine powder with DyF3 powder with the average particle size of 15 mu m, wherein the mass content of the diffusion alloy powder is 15% by taking the mixed diffusion powder as a reference.

Pickling the permanent magnet blank with 0.3 wt% nitric acid solution, coating the diffusion powder on the upper and lower surfaces of the permanent magnet blank, setting in a heat treatment device, and performing grain boundary diffusion at absolute pressure of 4.4 × 10-3Pa and diffusion temperature of 810 deg.C for 8.8 h. Then carrying out tempering treatment, wherein the tempering treatment conditions comprise: heating at 505 deg.c for 4 hr and under 1.0X 10-2Pa absolute pressure to obtain RE permanent magnet A8.

Example 9

A raw material with a formula of Nd21Dy2.1Fe76.1Co0B0.8 is subjected to strip throwing treatment at the surface linear velocity of a copper roller of 1.7m/s, and an obtained strip throwing sheet absorbs hydrogen for 2 hours at the temperature of 23 ℃ under the hydrogen pressure of 0.14MPa, and then is dehydrogenated for 5 hours at the temperature of 559 ℃ to obtain hydrogen crushed powder. Then, 100 parts by weight of the hydrogen pulverized powder was uniformly mixed with 0.035 part by weight of a neodymium iron boron specific antioxidant (available from beijing jun zefeng scientific and technological development ltd., No. KM-01), followed by grinding by an air flow mill to prepare a fine powder having an average particle diameter of 3.5 μm, and then 100 parts by weight of the obtained fine powder was uniformly mixed with 0.05 part by weight of glyceryl stearate (available from hao tian chemical company, YSH-06 brand) to obtain a main phase alloy powder of a rare earth permanent magnet blank.

A raw material formulated into Pr35Dy0Fe43.8Co0B1.2Cd8Tl7Zr5 was subjected to a strip throwing treatment at a copper roll surface linear velocity of 1.5m/s to obtain a grain boundary phase alloy. The obtained melt-spun piece absorbs hydrogen at 23 ℃ for 1.8h under the hydrogen pressure of 0.15Mpa, and then dehydrogenates at 557 ℃ for 6h to prepare hydrogen crushed powder. Then, 100 parts by weight of the hydrogen pulverized powder was uniformly mixed with 0.065 part by weight of a neodymium iron boron specific antioxidant (available from beijing jun zefeng scientific and technological development limited company, brand number KM-01), followed by grinding by an air flow mill to prepare a fine powder having an average particle size of 2.8 μm, and then 100 parts by weight of the obtained fine powder was uniformly mixed with 0.025 part by weight of glyceryl stearate (available from hao-tian chemical company, trade name YSH-06) to obtain a grain boundary phase alloy powder of a rare earth permanent magnet blank.

And uniformly mixing the main phase alloy powder and the grain boundary phase alloy powder, wherein the using amount of the grain boundary phase alloy powder is 4.5 parts by weight relative to 100 parts by weight of the total using amount of the main phase alloy powder and the grain boundary phase alloy powder.

Forming the alloy powder of the rare earth permanent magnet blank in a constant magnetic field of 2.3T, and keeping for 65s under isostatic pressing of 200 MPa; then sintering for 5.8h at 1068 ℃; performing primary tempering at 902 ℃ and keeping for 3 hours; then, secondary tempering is carried out at 495 ℃, the secondary tempering is kept for 4 hours, the oxygen content of the obtained rare earth permanent magnet sintered blank is 2700ppm, and the blank block body is machined into the rare earth permanent magnet blank with the size of 21mm, 18mm in width and 8mm in thickness.

Smelting a raw material with a formula of Pr50Dy20Fe5Co0Zn5In10Sb10 at 715 ℃ for 50min to prepare an ingot, then grinding the ingot by ball milling to prepare fine powder with the average particle size of 4 mu m, and uniformly mixing the fine powder with TbF3 powder with the average particle size of 4 mu m, wherein the mass content of the diffusion alloy powder is 57% based on the mixed diffusion powder.

Pickling the permanent magnet blank with 0.3 wt% nitric acid solution, coating the diffusion powder on the upper and lower surfaces of the permanent magnet blank, setting in a heat treatment device, and performing grain boundary diffusion at absolute pressure of 4.2 × 10-3Pa and diffusion temperature of 815 deg.C for 9 h. Then carrying out tempering treatment, wherein the tempering treatment conditions comprise: heating at 500 deg.c for 4.5 hr and under absolute pressure of 9.5X 10-3Pa to obtain the RE permanent magnet A9.

Example 10

A rare earth permanent magnet a10 was produced by the production method of a rare earth permanent magnet of example 9, except that the diffusion powder was coated on the upper and lower surfaces of the base material separately with TbF3 powder having an average particle diameter of 4 μm, and then subjected to diffusion heat treatment.

Comparative example 1

The rare earth permanent magnet blank prepared according to the method of example 1 was used as the rare earth permanent magnet CA1 of comparative example 1.

Comparative example 2

The process as described in example 1, except that the rare earth permanent magnet blank was prepared using a single alloy process and had a composition of nd28.72dy0.98fe64.12co1.7b0.98ga0.7sn0.8zn0.5cu0.7al0.8, to give rare earth permanent magnet CA 2.

Comparative example 3

According to the method described in example 1, except that the raw material having a formulation of Pr9.6Nd29.3Dy10Fe15.5Co16.5B0.96Al5.5Cu3.2Zr2.4Ga7 was subjected to a strip casting treatment at a surface linear velocity of a copper roll of 1.4m/s to obtain a rare earth permanent magnet CA3 as a grain boundary phase alloy.

Performance testing

According to GB/T3217-1992 test standard, the residual magnetism (Br) and coercive force (Hcj) of rare earth permanent magnet A1-A10 and CA1-CA3 are tested at 22 ℃ by adopting NIM-10000H of China's scientific measurement institute, the temperature is kept for 10H at 180 ℃, the temperature is kept to 22 ℃ after the temperature is kept, and the irreversible loss H of magnetic flux is tested by adopting a fluxmeter_irrThe results obtained are shown in table 1:

TABLE 1

	Br(kGs)	Hcj(kOe)	h_irr（180℃，10h）
				A1	12.71	28.55	2.8
CA1	12.88	20.75	11.7
				CA2	12.79	26.08	6.9
CA3	12.62	24.38	10.1
				A2	12.74	27.64	3.7
A3	12.72	28.01	4.0
				A4	12.77	27.56	3.8
A5	12.69	27.77	4.2
				A6	12.75	29.65	3.2
A7	12.72	28.41	4.1
				A8	12.78	30.14	3.0
A9	12.80	27.36	3.9
				A10	12.83	26.94	4.5

According to the test results in table 1, it can be seen by comparing a1-a10 and CA1-CA3 that the rare earth permanent magnet obtained after grain boundary diffusion by the method of the present invention can obtain higher coercive force and better heat resistance. In addition, although examples 1 to 10 provided rare earth permanent magnets whose remanence was decreased by 1.48% at the maximum as compared with the rare earth permanent magnet provided in comparative example 1 without grain boundary diffusion treatment, the coercive force was increased by 45.25% at the maximum and the magnetic flux irreversible loss was improved by 76.07% at the maximum.

In addition, compared with the rare earth permanent magnet provided by the single alloy method (comparative example 2), the rare earth permanent magnet provided by the invention (example 1) has the advantages that the coercive force of the rare earth permanent magnet prepared by the grain boundary diffusion process is improved by 9.47%, and the irreversible loss of magnetic flux is improved by 59.42%.

Compared with the permanent magnet material obtained by CN105529123A, the rare earth permanent magnet of the invention has similar performance (including coercive force and irreversible loss) to that obtained by CN102024544A under the same condition, but the content of dysprosium and/or terbium of the rare earth permanent magnet is lower than that of the rare earth permanent magnet prepared by a single alloy method of CN 105529123A. In particular, compared with the rare earth permanent magnet with similar performance provided in example 1 of CN105529123A, the rare earth permanent magnet provided in example 1 of the present invention has the content of heavy rare earth metal elements reduced to effective dysprosium content, which is reduced by 60.8 wt%. Therefore, the rare earth permanent magnet provided by the invention has higher coercive force and lower irreversible loss while ensuring higher remanence, and also obviously reduces the content of heavy rare earth metal elements dysprosium and/or terbium and reduces the production cost of the rare earth permanent magnet.

Further, in the case of the method using grain boundary diffusion, the rare earth permanent magnet obtained by the present invention has characteristics including: the remanence is preferably 12.71-12.78kGs, the coercive force is preferably 28.55-30.14kOe, and the irreversible loss of the magnetic flux after 10 hours of heat preservation at 180 ℃ is preferably 2.8-3.2%.

The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.

It should be noted that the various technical features described in the above embodiments can be combined in any suitable manner without contradiction, and the invention is not described in any way for the possible combinations in order to avoid unnecessary repetition.

In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.

Claims

1. The rare earth permanent magnet is characterized by comprising a main phase and a grain boundary phase, wherein the grain boundary phase is isolated and/or coated with the main phase, and the main phase has a core-shell structure;

the main phase comprises the following components: r1_xR2_yFe_100-x-y-z-uCo_zB_uR1 is selected from Pr and/or Nd, R2 is selected from Dy and/or Tb, wherein x, y, z and u are mass percent, and x + y is more than or equal to 27% and less than or equal to 31%, y is more than or equal to 0.5% and less than or equal to 1.5%, z is more than or equal to 0.5% and less than or equal to 2.5%, and u is more than or equal to 0.9% and less than or equal to 1.1%;

the grain boundary phase comprises the following components: r3_aR4_bFe_{100-a-b-c-d-v}Co_cB_dM_vR3 is selected from Pr and/or Nd, R4 is selected from Dy and/or Tb, M is selected from one or more of Zr, Ga, Cu, Sn, Al, Zn, Bi, Ta, In, Pb, Cd, Tl and Sb, wherein a, b, c, d and v are mass percent, and a + b is more than or equal to 40% and less than or equal to 50%, b is more than or equal to 0.5% and less than or equal to 2.5%, c is more than or equal to 0.5% and less than or equal to 4.5%, d is more than or equal to 0.1% and less than or equal to 1%, v is more than or equal to 25% and less than or equal to 40%.

2. The rare earth permanent magnet according to claim 1, wherein the core-shell structure includes a core layer and a shell layer, and the shell layer contains Dy₂Fe₁₄B phase and/or Tb₂Fe₁₄And (B) phase.

3. The rare earth permanent magnet according to claim 2, wherein a content of R2 per unit volume in the shell layer is higher than a content of R2 per unit volume in the core layer.

4. The rare earth permanent magnet according to claim 1, wherein the grain boundary phase is contained in an amount of 3 to 20% by mass based on the total mass of the main phase and the grain boundary phase.

5. The rare earth permanent magnet according to claim 4, wherein the grain boundary phase is contained in an amount of 5 to 15% by mass.

6. The rare earth permanent magnet according to claim 1, wherein the thickness of the rare earth permanent magnet is 1 to 10 mm.

7. The rare earth permanent magnet according to claim 6, wherein the thickness of the rare earth permanent magnet is 2-7 mm.

8. The rare earth permanent magnet according to claim 1, wherein the oxygen content of the rare earth permanent magnet is 3000ppm or less.

9. The rare earth permanent magnet according to claim 8, wherein the oxygen content of the rare earth permanent magnet is 2000ppm or less.

10. The rare earth permanent magnet of claim 1 further comprising a grain boundary diffusion layer on the surface of the rare earth permanent magnet.

11. The rare earth permanent magnet according to claim 10, wherein the thickness of the grain boundary diffusion layer is 5 to 20 μm.

12. The rare earth permanent magnet according to claim 10, wherein the material of the grain boundary diffusion layer is selected from one or more of an oxide of R5, a fluoride of R5, and a diffusion alloy of R5, and R5 is selected from Dy and/or Tb.

13. The rare earth permanent magnet of claim 12 wherein the composition of the diffusion alloy of R5 is: r6_mR7_nFe_100-m-n-p-wCo_pN_wR6 is selected fromR7 is selected from Dy and/or Tb, N is selected from one or more of Ga, Cu, Sn, Al, Zn, Bi, Ta, In, Pb, Cd, Tl and Sb, wherein m, N, p and w are mass percent, m + N is more than or equal to 30% and less than or equal to 70%, N is more than or equal to 20% and less than or equal to 50%, p is more than or equal to 0% and less than or equal to 3%, and w is more than or equal to 25% and less than or equal to 60%.

14. The rare earth permanent magnet according to claim 13, wherein in the composition of the diffusion alloy of R5, the mass percentages of m, n, p, and w are: m + n is more than or equal to 35% and less than or equal to 60%, n is more than or equal to 25% and less than or equal to 45%, p is more than or equal to 0.5% and less than or equal to 2.5%, and w is more than or equal to 35% and less than or equal to 55%.

15. The rare earth permanent magnet according to claim 12, wherein the diffusion alloy of R5 is contained in an amount of 0 to 65% by mass based on the total weight of the material of the grain boundary diffusion layer.

16. A method for preparing a rare earth permanent magnet is characterized by comprising the following steps: s1, mixing the main phase alloy raw material and the grain boundary phase alloy raw material, and performing magnetic field orientation compression molding, sintering and first tempering treatment to obtain a rare earth permanent magnet blank;

s2, coating the grain boundary diffusion material on the surface of the rare earth permanent magnet blank, and obtaining the rare earth permanent magnet according to any one of claims 1-15 after diffusion process treatment.

17. The method of claim 16 wherein the rare earth permanent magnet blank has a thickness of 1-10 mm.

18. The method of claim 17 wherein the rare earth permanent magnet blank has a thickness of 2-7 mm.

19. The method of claim 16 wherein the rare earth permanent magnet blank has an oxygen content of 3000ppm or less.

20. The method of claim 19 wherein the rare earth permanent magnet blank has an oxygen content of 2000ppm or less.

21. The method of claim 16, wherein the grain boundary diffusion material has an average particle size of 2 to 20 μm.

22. The method of claim 21, wherein the grain boundary diffusion material has an average grain size of 5-15 μm.

23. The method of claim 16, wherein the conditions of the diffusion process treatment comprise: the temperature is 600-1000 ℃, the time is 2-12h, and the absolute pressure is 10^-5-10^-2Pa。

24. The method of claim 16, further comprising subjecting the rare earth permanent magnet to a second tempering treatment, wherein conditions of the second tempering treatment include: the heating temperature is 400-^-5-10^-2Pa。