WO2021223436A1

WO2021223436A1 - High-performance neodymium iron boron permanent magnet material and preparation method therefor

Info

Publication number: WO2021223436A1
Application number: PCT/CN2020/134901
Authority: WO
Inventors: 舒泽腾; 郑波; 郭帅; 陈仁杰; 丁广飞; 闫阿儒
Original assignee: 中国科学院宁波材料技术与工程研究所
Priority date: 2020-05-08
Filing date: 2020-12-09
Publication date: 2021-11-11
Also published as: CN111446055A

Abstract

A neodymium iron boron permanent magnet material and a preparation method therefor. The neodymium iron boron permanent magnet material is prepared by an anisotropic magnet as shown in formula (Nd, Pr)_x <sb />Fe_(100-x-y-z)B_yM_z and heavy rare earth as shown in formula Tb_aFe_bAl_100-a-b, and the mass ratio of the heavy rare earth to the total amount of the anisotropic magnet and the heavy rare earth is 0.1-5 wt%. On the basis of reducing the use amount of heavy rare earth elements, the neodymium iron boron permanent magnet material can ensure that the coercive force of a neodymium iron boron magnet is obviously improved while the residual magnetism of the neodymium iron boron magnet is not reduced or slightly reduced, thus greatly reducing production costs.

Description

High-performance neodymium iron boron permanent magnet material and preparation method thereof

This application claims the priority of a Chinese patent application filed with the Chinese Patent Office on May 8, 2020, the application number is 202010382427.8, and the invention title is "a high-performance neodymium iron boron permanent magnet material and its preparation method", and its entire content Incorporated in this application by reference.

Technical field

The invention relates to the technical field of magnetic materials, in particular to a neodymium iron boron permanent magnet material and a preparation method thereof.

Background technique

Sintered NdFeB permanent magnet material is currently the magnetic material with the highest comprehensive magnetic performance among permanent magnet materials. Because neodymium iron boron magnets have high remanence Br and maximum magnetic energy product (BH) _max , they can reduce the volume and cost of magnetic devices. Therefore, this material is widely used in electronic information, medical equipment, and new energy vehicles. In the field of other magnetic devices, it has a wide range of application prospects.

With the rapid development of industrialization, the demand for miniaturization of magnetic devices puts forward higher requirements on neodymium iron boron magnets, not only to greatly increase the remanence Br, but also to increase the coercive force Hcj. At present, the addition of heavy rare earth Tb, Dy and other elements is widely used in industry to increase the anisotropy field, so as to achieve the purpose of increasing the coercive force Hcj of the magnet. The anti-ferromagnetic interaction between the irons leads to a significant reduction in the remanence of the magnet; some researchers use the method of grain boundary diffusion to ensure that the remanence of the magnet does not drop or drop slightly, that is, a large amount of metal elements Tb and Dy are passed Coating or magnetron sputtering, coating on the surface of the magnet, and finally through heat treatment to prepare a neodymium iron boron magnet. Although this method can ensure that the remanence Br of the magnet does not drop or drop slightly, it has strict requirements on the size of the neodymium iron boron magnet. The thickness direction of the magnet orientation generally does not exceed 6mm. Therefore, the research on reducing the amount of heavy rare earths while maintaining high coercivity and high remanence has attracted wide attention.

Summary of the invention

The technical problem solved by the present invention is to provide a neodymium iron boron permanent magnet material. The neodymium iron boron permanent magnet material provided in this application can reduce the use of heavy rare earth elements and ensure that the remanence of the neodymium iron boron magnet does not drop or slightly drops. , The coercivity has been significantly improved.

In view of this, the present application provides a neodymium iron boron permanent magnet material, which is prepared from an anisotropic magnet as shown in formula (I) and heavy rare earth as shown in formula (II). The mass ratio of the anisotropic magnet to the total amount of the heavy rare earth is 0.1-5wt%;

(Nd,Pr) _x Fe _(100-xyz) B _y M _z (Ⅰ);

Tb _a Fe _b Al _100-ab (Ⅱ);

Among them, 28.6wt%≤x≤29.5wt%, 0.85wt%≤y≤0.9wt%, 0＜z≤2.5wt%, M is selected from one of Co, Al, Cu, Zr, Ti, Ni and Ga Or multiple

60wt%≤a≤92wt%, 6wt%≤b≤38wt%, a+b=100wt%.

Preferably, the weight ratio of the heavy rare earth in the total amount of the anisotropic magnet and the heavy rare earth is 1 wt% to 2 wt%.

Preferably, the M is selected from Co, Al, Cu, Zr and Ga.

Preferably, the neodymium iron boron permanent magnet material includes a main phase structure and a shell structure around the main phase structure, the main phase structure is (Nd, Pr) ₂ Fe ₁₄ B, and the shell structure is (Tb ,Nd) ₂ Fe ₁₄ B.

The application also provides a method for preparing the neodymium iron boron permanent magnet material, which includes the following steps:

A) Mixing the anisotropic magnet powder as shown in formula (I) and the heavy rare earth powder as shown in formula (II) to obtain mixed magnetic powder. The mass ratio of the heavy rare earth powder in the mixed magnetic powder is 0.1～ 5wt%;

B) The mixed magnetic powder is oriented, pressed, sintered and tempered in sequence to obtain a neodymium iron boron permanent magnet material;

(Nd,Pr) _x Fe _(100-xyz) B _y M _z (Ⅰ);

Tb _a Fe _b Al _100-ab (Ⅱ);

60wt%≤a≤92wt%, 6wt%≤b≤38wt%, a+b=100wt%.

Preferably, the anisotropic magnet powder is prepared by a hydrogen breaking-jet milling process, and the particle size of the anisotropic magnet powder is 1.5-3.0 μm.

Preferably, the preparation method of the anisotropic magnet powder is specifically:

According to formula (I), the proportion of each element in the anisotropic magnet powder;

Mix the prepared raw materials in an inert atmosphere for smelting to obtain a master alloy;

Rapid solidification of the master alloy into alloy flakes;

The alloy flakes are crushed by hydrogen cracking and jet mill to obtain anisotropic magnet powder.

Preferably, the method for preparing the heavy rare earth powder is specifically:

Ingredients according to the proportion of each element in formula (II);

Mix the prepared raw materials and smelt in an inert atmosphere to obtain a heavy rare earth master alloy;

The master alloy is pulverized through a hydrogen breaking-jet milling process or a ball milling process to obtain heavy rare earth powder; the particle size of the heavy rare earth powder is 0.1 μm-2 μm.

Preferably, the orientation pressing type is specifically:

The mixed magnetic powder is press-formed at 2.3-2.5T, and then statically pressed at 150-200 MPa to obtain a blank magnet.

Preferably, the sintering temperature is 1060°C to 1075°C, the sintering time is 2 to 4 hours, and the tempering treatment includes one-stage tempering and two-stage tempering in a vacuum environment or a protective atmosphere. The temperature of the first-stage tempering is 850-900°C, the time of the first-stage tempering is 1h-3h, the temperature of the second-stage tempering is 480-550°C, and the time of the second-stage tempering It is 1h～3h.

This application provides a neodymium iron boron permanent magnet material, which is prepared from an anisotropic magnet (Nd, Pr) _x Fe _(100-xyz) B _y M _z and heavy rare earth Tb _a Fe _b Al _100-ab ; The Tb and Al elements in the heavy rare earth in the NdFeB permanent magnet material can increase the coercivity, and the Tb element can form the Tb2Fe4B phase with high anisotropy field, which can greatly increase the coercivity Hcj. Al is in the rich NdPr grain boundary. In this case, it can lubricate the grain boundary and increase the coercive force Hcj. The Fe element itself has a higher saturation magnetic polarization and maintains a high remanence Br; therefore, the neodymium iron boron permanent magnet material provided in this application is added with heavy rare earth The components and the amount of addition are controlled, so that the coercivity of the neodymium iron boron permanent magnet material can be significantly improved without the remanence of the neodymium iron boron permanent magnet material being reduced or slightly reduced.

Description of the drawings

Figure 1 is a scanning electron micrograph of an anisotropic neodymium iron boron permanent magnet material [(NdPr) _29.5 Cu _0.2 Al _0.1 Zr _0.2 Co _0.5 Ga _0.1 Fe _bal. B _{0.9 ];}

Figure 2 is a scanning electron micrograph of the neodymium iron boron permanent magnet material obtained in Example 1;

Figure 3 is a scanning electron micrograph of the neodymium iron boron permanent magnet material obtained in Example 2;

4 is a scanning electron micrograph of the neodymium iron boron permanent magnet material obtained in Example 3;

FIG. 5 is a scanning electron microscope photograph of the neodymium iron boron permanent magnet material obtained in Comparative Example 1. FIG.

Detailed ways

In order to further understand the present invention, the preferred embodiments of the present invention are described below in conjunction with examples, but it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

In view of the imbalance of coercivity and remanence of neodymium iron boron magnets in the prior art, this application provides a neodymium iron boron permanent magnet material, which on the basis of reducing the amount of heavy rare earth used, does not reduce the remanence. Or in the case of a slight drop, the coercivity of the neodymium iron boron permanent magnet material can be significantly improved. Specifically, the embodiment of the present invention discloses a neodymium iron boron permanent magnet material, which is prepared from an anisotropic magnet as shown in formula (I) and a heavy rare earth as shown in formula (II). The mass ratio of the anisotropic magnet and the total amount of the heavy rare earth is ≥0.1wt% and ≤5.0wt%;

(Nd,Pr) _x Fe _(100-xyz) B _y M _z (Ⅰ);

Tb _a Fe _b Al _100-ab (Ⅱ);

60wt%≤a≤92wt%, 6wt%≤b≤38wt%, a+b=100wt%.

Among the neodymium iron boron permanent magnet materials described in this application, the anisotropic magnet (Nd, Pr) _x Fe _(100-xyz) B _y M _z has a lower (Nd, Pr) content and a lower B content, so It can maintain high remanence Br, and at the same time there is an abundant NdPr grain boundary phase at the grain boundary of the magnet. The M is selected from one or more of Co, Al, Cu, Zr, Ti, Ni, and Ga. In a specific embodiment, the M is selected from Co, Al, Cu, Zr and Ga, and the M is selected In the case of multiple alloying elements, the content of each element can be adjusted, as long as the total range is 0 to 2.5 (≠0). (Nd, Pr) in this application means one or two of Nd and Pr, and its content can be 28.6wt%, 28.7wt%, 28.8wt%, 28.9wt%, 29.0wt%, 29.1wt%, 29.2 wt%, 29.3 wt%, 29.4 wt%, 29.5 wt%, 29.6% wt, or 29.7% wt. The content of B is 0.86wt%, 0.87wt%, 0.88wt%, 0.89wt% or 0.90wt%. The content of M is 0.2 to 2.3 wt%, and in a specific embodiment, the content of M is 1.0 to 1.8 wt%.

Tb and Al are added to the heavy rare earth component Tb _a Fe _b Al _100-ab to increase the coercivity. The Tb element can form a phase of Tb2Fe4B with a high anisotropy field, which can greatly increase the coercivity Hcj. In the case of abundant NdPr grain boundaries, it can lubricate the grain boundaries and increase the coercivity Hcj. The Fe element itself has a higher saturation magnetic polarization and maintains a high remanence Br.

In the neodymium iron boron permanent magnet material, the heavy rare earth accounts for 0.1 to 5 wt% of the total amount of the anisotropic magnet and the heavy rare earth; in a specific embodiment, the heavy rare earth accounts for the various directions 1 to 2 wt% of the total amount of the heterogeneous magnet and the heavy rare earth; less than 0.1 wt%, the coercive force increasing effect is not obvious, and more than 5 wt%, the remanence Br decreases too much.

The application also provides a preparation method of the above-mentioned neodymium iron boron permanent magnet material, which includes the following steps:

A) Mix the anisotropic magnet powder as shown in formula (I) and the heavy rare earth powder as shown in formula (II) to obtain mixed magnetic powder, and the mass ratio of the heavy rare earth powder in the mixed magnetic powder is ≥0.1wt % And ≤5.0wt%;

(Nd,Pr) _x Fe _(100-xyz) B _y M _z (Ⅰ);

Tb _a Fe _b Al _100-ab (Ⅱ)

60wt%≤a≤92wt%, 6wt%≤b≤38wt%, a+b=100wt%.

In the above preparation process, the present application first mixes the anisotropic magnet powder and the heavy rare earth powder to obtain the mixed powder; the mixing time is 1 to 3 hours. Before the two are mixed, the anisotropic magnet powder and the heavy rare earth powder are prepared separately; the preparation method of the anisotropic magnet powder is specifically as follows:

Rapid solidification of the master alloy into alloy flakes;

The above-mentioned smelting, rapid solidification, hydrogen breaking and jet milling are technical means well known to those skilled in the art, and this application is not particularly limited.

The preparation method of the heavy rare earth powder is specifically as follows:

Ingredients according to the proportion of each element in formula (II);

The master alloy is pulverized through a hydrogen breaking-jet milling process or a ball milling process to obtain heavy rare earth powder.

Likewise, the above-mentioned smelting, hydrogen breaking and jet milling processes are technical means well known to those skilled in the art, and there is no particular limitation on this application.

The anisotropic magnet powder has a particle size of 1.5 to 3.0 m, and the heavy rare earth powder has a particle size of 0.1 to 2.0 m.

After the raw materials are mixed, the mixed magnetic powder obtained above is sequentially subjected to orientation pressing, sintering and tempering, thereby obtaining a neodymium iron boron permanent magnet material; in the above process, the orientation pressing, sintering and tempering are based Technical and technological means well known to those skilled in the art, this application does not impose special restrictions on their technological operations. The orientation molding is specifically to press and mold the mixed magnetic powder at 2.3-2.5T, and then statically press at 150-200 MPa to obtain a blank magnet. The sintering temperature is 1060-1075°C, and the time is 2-4h. The first-stage tempering and the second-stage tempering are sequentially performed in the vacuum environment or protective atmosphere of the tempering treatment, the temperature of the first-stage tempering is 850-900°C, and the time of the first-stage tempering is 1h-3h The temperature of the secondary tempering is 480°C to 550°C, and the time of the secondary tempering is 1h-3h.

The neodymium iron boron permanent magnet material provided by the present application includes a main phase structure and a shell structure uniformly distributed around the main phase structure. The composition of the shell structure is (Tb, Nd) ₂ Fe ₁₄ B. The main phase structure It is (Nd, Pr) ₂ Fe ₁₄ B.

The preparation method of the high-performance neodymium iron boron permanent magnet material provided by the present invention can significantly increase the coercivity of the neodymium iron boron permanent magnet material while not affecting the neodymium iron boron permanent magnet under the condition that the remanence is not reduced or slightly reduced. The magnetic properties of the material are suitable for mass production of large-size blanks; the preparation method of the high-performance neodymium iron boron permanent magnet material provided by the present invention can effectively reduce the amount of heavy rare earth used. The preparation method of the high-performance neodymium iron boron permanent magnet material provided by the invention is simple and easy to implement and can be industrialized.

In order to further understand the present invention, the preparation method of the neodymium iron boron magnetic material provided by the present invention will be described in detail below in conjunction with examples, and the protection scope of the present invention is not limited by the following examples.

Example 1

The chemical formula of anisotropic magnetic powder is (NdPr) _29.5 Cu _0.2 Al _0.1 Zr _0.2 Co _0.5 Ga _0.1 Fe _bal. B _0.9 , the chemical formula of heavy rare earth powder is Tb ₆₀ Fe ₃₈ Al ₂ , and the doping amount of heavy rare earth powder is mixed magnetic powder 1%;

1) The raw materials with a purity of more than 99% are proportioned according to the nominal component mass percentage of (NdPr) _29.5 Cu _0.2 Al _0.1 Zr _0.2 Co _0.5 Ga _0.1 Fe _bal. B _0.9 , and an alloy with a thickness of about 0.4 mm is prepared by the rapid solidification process Flakes, the alloy flakes are prepared by hydrogen breaking and jet milling processes to prepare powders with an average particle size of 2 μm to 3 μm;

2) After mixing the heavy rare earth alloy according to the nominal component mass percentage Tb ₆₀ Fe ₃₈ Al ₂ through smelting, hydrogen breaking and jet milling processes, the powder with an average particle size of 1 μm-2 μm is obtained;

3) Mix the heavy rare earth powder (Tb ₆₀ Fe ₃₈ Al ₂ ) and the anisotropic magnetic powder in a ratio of 1:98 and mix them in the mixer for 2h～3h, and place the uniformly mixed powder in the orientation field of 2T. After pressing down and forming, perform cold isostatic pressing in 200MPa hydraulic oil to obtain a blank magnet;

4) Put the blank magnets in a vacuum sintering furnace at 1070°C for 2h, and cool to room temperature by gas quenching and air cooling, then perform one-stage tempering at 900°C for 2h, and then cool to room temperature by gas quenching and air cooling. After tempering at 500°C for 2h, after the completion of gas quenching and air cooling, after cooling to room temperature, it is out of the furnace, and the neodymium iron boron permanent magnet material can be obtained.

The prepared NdFeB permanent magnet material was tested, and the results are shown in Table 1. From Table 1, the coercivity Hcj of the NdFeB permanent magnet material is higher than that of the permanent magnet material without heavy rare earth magnetic powder. After 3.18kOe, there is almost no change in the remanence Br.

Example 2

This preparation method is basically the same as the preparation method of Example 1, except that the doping amount of the heavy rare earth powder is 2% of the mixed magnetic powder.

The prepared NdFeB permanent magnet material was tested, and the results are shown in Table 1. From Table 1, the coercivity Hcj of the NdFeB permanent magnet material is higher than that of the permanent magnet material without heavy rare earth magnetic powder. When the output is 6.54kOe, the remanence Br is reduced by 0.19kGs.

Example 3

This preparation method is basically the same as the preparation method of Example 1, except that the doping amount of the heavy rare earth powder is 4% of the mixed magnetic powder.

The prepared NdFeB permanent magnet material was tested, and the results are shown in Table 1. From Table 1, the coercivity Hcj of the NdFeB permanent magnet material is higher than that of the permanent magnet material without heavy rare earth magnetic powder. Out of 10.03kOe, the remanence Br is reduced by 1.18kGs.

Table 1 Data Table of Magnetic Properties of NdFeB Magnets Prepared in Each Example

Comparing Figure 1 and Figure 2, it can be seen that the grain boundary phase in Figure 2 is continuous and there is no obvious core-shell structure in the main phase grains. Therefore, the Hcj of the magnet doped with 1% heavy rare earth powder has been significantly improved, but the remaining The magnetic Br did not change significantly.

Comparing Figure 1, Figure 2 and Figure 3, it can be seen that the main phase grains in Figure 3 have an obvious core-shell structure, which improves the magnetocrystalline anisotropy field of the main phase grains, but the heavy rare earth elements exist between the iron. The anti-ferromagnetic effect of the magnet leads to a reduction in the remanence of the magnet. Therefore, the Hcj of the magnet doped with 2% heavy rare earth powder is further improved, but the remanence is slightly reduced.

Comparing Figure 1, Figure 2, Figure 3 and Figure 4, it can be seen that the core-shell structure of the main phase grains in Figure 4 is smaller than that in Figure 3, which indicates that more heavy rare earth elements have entered the main phase. Phase grains further enhance the magnetocrystalline anisotropy field of the main phase grains. Therefore, the magnet Hcj doped with 4% heavy rare earth powder has a further improvement compared with the magnet doped with 2% heavy rare earth powder, but the remanence decreases more obviously.

Comparative example 1

This preparation method is basically the same as the preparation method of Example 1, except that the doping amount of the heavy rare earth powder is 6% of the mixed magnetic powder.

The prepared neodymium iron boron permanent magnet material was tested, and the Br of the magnet prepared in this comparative example was 12.42 KGs, and the Hcj was 28.56 KOe. It can be seen from Fig. 5 that the core of the core-shell structure in the main phase grains is further reduced, which indicates that the heavy rare earth elements are doped too much, which makes the remanence decrease too much.

The description of the above embodiments is only used to help understand the method and the core idea of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown in this document, but should conform to the widest scope consistent with the principles and novel features disclosed in this document.

Claims

A neodymium iron boron permanent magnet material, prepared from an anisotropic magnet as shown in formula (I) and a heavy rare earth as shown in formula (II), where the heavy rare earth accounts for the anisotropic magnet and the The mass ratio of the total amount of heavy rare earths is 0.1-5wt%;

(Nd,Pr) x Fe (100-xyz) B y M z (Ⅰ);

Tb a Fe b Al 100-ab (Ⅱ);

Among them, 28.6wt%≤x≤29.5wt%, 0.85wt%≤y≤0.9wt%, 0＜z≤2.5wt%, M is selected from one of Co, Al, Cu, Zr, Ti, Ni and Ga Or multiple

60wt%≤a≤92wt%, 6wt%≤b≤38wt%, a+b=100wt%.
The neodymium iron boron permanent magnet material according to claim 1, wherein the mass ratio of the heavy rare earth to the total amount of the anisotropic magnet and the heavy rare earth is 1 wt% to 2 wt%.
The neodymium iron boron permanent magnet material according to claim 1, wherein the M is selected from Co, Al, Cu, Zr and Ga.
The neodymium iron boron permanent magnetic material according to any one of claims 1 to 3, wherein the neodymium iron boron permanent magnetic material comprises a main phase structure and a shell structure located around the main phase structure, and the main phase The structure is (Nd, Pr) 2 Fe 14 B, and the shell structure is (Tb, Nd) 2 Fe 14 B.
The preparation method of the neodymium iron boron permanent magnet material of claim 1, comprising the following steps:

A) Mixing the anisotropic magnet powder as shown in formula (I) and the heavy rare earth powder as shown in formula (II) to obtain mixed magnetic powder. The mass ratio of the heavy rare earth powder in the mixed magnetic powder is 0.1～ 5wt%;

B) The mixed magnetic powder is oriented, pressed, sintered and tempered in sequence to obtain a neodymium iron boron permanent magnet material;

(Nd,Pr) x Fe (100-xyz) B y M z (Ⅰ);

Tb a Fe b Al 100-ab (Ⅱ);

Among them, 28.6wt%≤x≤29.5wt%, 0.85wt%≤y≤0.9wt%, 0＜z≤2.5wt%, M is selected from one of Co, Al, Cu, Zr, Ti, Ni and Ga Or multiple

60wt%≤a≤92wt%, 6wt%≤b≤38wt%, a+b=100wt%.
The preparation method according to claim 5, wherein the anisotropic magnet powder is prepared by a hydrogen breaking-jet milling process, and the particle size of the anisotropic magnet powder is 1.5-3.0 m.
The preparation method according to claim 5 or 6, wherein the preparation method of the anisotropic magnet powder is specifically:

According to formula (I), the proportion of each element in the anisotropic magnet powder;

Mix the prepared raw materials in an inert atmosphere for smelting to obtain a master alloy;

Rapid solidification of the master alloy into alloy flakes;

The alloy flakes are crushed by hydrogen cracking and jet mill to obtain anisotropic magnet powder.
The preparation method according to claim 5, wherein the preparation method of the heavy rare earth powder is specifically:

Ingredients according to the proportion of each element in formula (II);

Mix the prepared raw materials and smelt in an inert atmosphere to obtain a heavy rare earth master alloy;

The master alloy is pulverized through a hydrogen breaking-jet milling process or a ball milling process to obtain heavy rare earth powder; the particle size of the heavy rare earth powder is 0.1 μm-2 μm.
The preparation method according to claim 5, characterized in that the orientation pressing is specifically:

The mixed magnetic powder is press-formed at 2.3-2.5T, and then statically pressed at 150-200 MPa to obtain a blank magnet.
The preparation method according to claim 5, wherein the sintering temperature is 1060° C. to 1075° C., the sintering time is 2 to 4 hours, and the tempering treatment includes successively performing in a vacuum environment or a protective atmosphere. The first-stage tempering and the second-stage tempering, the temperature of the first-stage tempering is 850～900℃, the time of the first-stage tempering is 1h～3h, and the temperature of the second-stage tempering is 480℃～ At 550°C, the time for the secondary tempering is 1h-3h.