Neodymium-iron-boron magnet and method for producing the same

Abstract

The application provides a neodymium-iron-boron magnet and a preparation method thereof, and belongs to the technical field of magnetic materials. The neodymium-iron-boron magnet comprises rare earth elements R, transition metal elements T, metal elements M, and B elements, R comprises Pr and Nd, the mass percentage of R is 29wt%-32wt%, R comprises heavy rare earth elements Tb and Dy with a mass percentage of 0-0.1wt%, M at least comprises Ti and Zr, the sum of the mass percentages of Ti and Zr is 0.1wt%-0.6wt%, T comprises Fe or Fe and Co, the mass percentage of B is 0.84wt%-0.94wt%, the neodymium-iron-boron magnet has a main phase and a grain boundary phase comprising a rich rare earth phase, the proportion of the rich rare earth phase in the grain boundary phase is 0.15-0.35, and the atomic proportion of Pr in R in the rich rare earth phase is 0.4-0.5. The neodymium-iron-boron magnet has excellent magnetic performance without heavy rare earth elements or with low heavy rare earth elements.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of magnetic materials, and particularly relates to a neodymium-iron-boron magnet and a preparation method thereof. BACKGROUND

[0002] Sintered neodymium-iron-boron magnets are widely used in many fields such as power machinery, medical devices, automobile industry, wind power generation, and electronics due to their excellent magnetic properties and high cost performance. With the development of downstream products towards miniaturization, micro-miniaturization and light weight, higher requirements are put forward for the magnetic properties of the magnets, especially the coercivity. At present, in order to improve the coercivity of the neodymium-iron-boron magnet and improve the temperature stability, heavy rare earth elements dysprosium (Dy) and terbium (Tb) are often added to form a 、 phase with a higher magnetic crystal anisotropy field. However, the heavy rare earth elements Dy and Tb are antiferromagnetically coupled with Fe, and the addition of them will reduce the remanence and magnetic energy product of the magnet. Moreover, the reserves of heavy rare earth resources are extremely scarce, and the price is high, which undoubtedly greatly increases the production cost of the magnet. At the same time, the heavy rare earth is easily affected by the supply market and other factors, and there is a risk of price instability and large fluctuations, which seriously restricts the sustainable development of the sintered neodymium-iron-boron magnet industry. SUMMARY

[0003] Therefore, in order to at least partially solve the above-mentioned technical problems, the present application provides a neodymium-iron-boron magnet with high coercivity and remanence without heavy rare earth or with low heavy rare earth content and a preparation method thereof.

[0004] According to an embodiment of one aspect of the present application, a neodymium-iron-boron magnet is provided, comprising: rare earth elements R, transition metal elements T, metal elements M, and B elements; the rare earth elements R include Pr and Nd, the mass percentage of the rare earth elements R is 29wt%-32wt%, and the rare earth elements R include 0-0.1wt% of heavy rare earth elements Tb and Dy in terms of mass percentage; the metal elements M at least include Ti and Zr, and the sum of the mass percentages of Ti and Zr is 0.1wt%-0.6wt%; the transition metal elements T include Fe or Fe and Co; the mass percentage of the B elements is 0.84wt%-0.94wt%; and wherein the neodymium-iron-boron magnet has a main phase and a grain boundary phase including a rare earth-rich phase, the proportion of the rare earth-rich phase in the grain boundary phase is 0.15-0.35, and the atomic proportion of Pr in the rare earth elements R in the rare earth-rich phase is 0.4-0.5.

[0005] According to the embodiment of the application, the method for preparing the Nd-Fe-B magnet comprises the following steps: preparing a first alloy powder, the first alloy powder comprising rare earth elements R, B elements, transition metal elements T and metal elements M, the metal elements M comprising Zr, the mass percentage of the rare earth elements R being 29wt%-32wt%, the mass percentage of the B elements being 0.84wt%-0.94wt%, the mass percentage of the Zr elements being 0.1wt%-0.4wt%, the rare earth elements R comprising Pr, Nd, or Pr, Nd and at least one of Dy, Tb, Gd, Ho, Y, La and Ce, wherein the mass percentage of Pr is greater than 8.5wt%, the mass percentage of heavy rare earth elements being 0-0.1wt%; the transition metal elements T comprising Fe, or Fe and Co; preparing a second alloy powder, the second alloy powder comprising rare earth elements R, B elements, transition metal elements T and metal elements M, the metal elements M comprising Ti, the mass percentage of the rare earth elements R being 28.5wt%-31.5wt%, the mass percentage of the B elements being 0.84wt%-0.94wt%, the mass percentage of the Ti elements being 0.1wt%-0.4wt%, the rare earth elements R comprising Pr, Nd, or Pr, Nd and at least one of Dy, Tb, Gd, Ho, Y, La and Ce, the mass percentage of heavy rare earth elements being 0-0.1wt%; the transition metal elements T comprising Fe, or Fe and Co; and mixing the first alloy powder and the second alloy powder at a mass ratio of 1:0.5-1:5 to obtain a mixed alloy powder, the mixed alloy powder being subjected to a forming treatment, a sintering treatment and a tempering treatment to obtain the Nd-Fe-B magnet, wherein the mass percentage of the heavy rare earth elements in the mixed alloy powder is 0-0.1wt%, and the tempering treatment comprises a two-stage tempering process or a three-stage tempering process.

[0006] According to the Nd-Fe-B magnet provided by the above embodiment of the application, the proportion of the rare earth-rich phase in the Nd-Fe-B magnet is 0.15-0.35, and the proportion of Pr in the rare earth elements R in the rare earth-rich phase is 0.4-0.5, so that the Nd-Fe-B magnet has better remanence and coercivity.

[0007] According to the Nd-Fe-B magnet provided by the above embodiment of the application, the proportion of the rare earth-rich phase in the Nd-Fe-B magnet is 0.15-0.35, and the proportion of Pr in the rare earth elements R in the rare earth-rich phase is 0.4-0.5, so that the Nd-Fe-B magnet has better remanence and coercivity. 13 The atomic number ratio of the Zr elements to the Ti elements in the M1 phase is 15-30, the Zr and Ti elements are reduced in local enrichment and precipitation, and the Nd-Fe-B magnet with better performance can be obtained.

[0008] According to the preparation method of the Nd-Fe-B magnet provided by the above-mentioned embodiment of the present application, the Nd-Fe-B magnet is prepared by using a double-alloy method, and the first alloy powder and the second alloy powder are both low-B-content raw materials. The Pr element is used to replace part of the Nd element in the first alloy powder, the content of the Pr element in the first alloy powder is higher than 8.5wt%, and the Zr element is added in an amount of 0.1-0.4wt%, and the Ti element is added in an amount of 0.1-0.4wt% in the second alloy. The above-mentioned first alloy powder and the second alloy powder are mixed to prepare the magnet, which can promote the uniform generation of the rare earth-rich phase in the grain boundary phase, increase the proportion of the rare earth-rich phase, effectively improve the distribution of the Zr element, make the Zr and Ti elements not locally enriched and precipitated, effectively control the B element in the magnet, optimize the structure of the magnet, and obtain better magnetic properties. BRIEF DESCRIPTION OF DRAWINGS

[0009] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings of the embodiments will be briefly introduced below. Obviously, the drawings described in the following description only relate to some embodiments of the present application, and are not a limitation on the present application.

[0010] Figure 1 The SEM image of the Nd-Fe-B magnet provided by the embodiment 2 of the present application.

[0011] Figure 2 The SEM image of the Nd-Fe-B magnet provided by the comparative example 1. DETAILED DESCRIPTION

[0012] In order to make the purpose, technical solutions and advantages of the present application more clear, the present application will be further described in detail below by combining with specific embodiments and referring to the drawings. However, the present application can be implemented in different forms, and should not be interpreted as being limited to the embodiments presented here. On the contrary, the presentation of these embodiments will make the present application complete and fully, and will fully convey the scope of the present application to the person skilled in the art. In the drawings, the sizes and relative sizes of the layers and regions may be exaggerated for clarity, and the same reference signs represent the same elements throughout.

[0013] The terms used herein are only used for describing specific embodiments, and are not intended to limit the present application. The terms "include", "contain" and the like used herein indicate the existence of the described features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0014] In the related art, in order to improve the coercivity of the magnet, a lower B element content formula system is often used. The magnet with lower B content is more sensitive to temperature. In the batch production process, a small change in the content of B element may cause problems in the consistency of the magnet. The instability in the preparation method can be eliminated by adding a certain content of high melting point metal (Ti, Zr, Nb, etc.) to form ZrB2, TiB2 and other compounds at the grain boundary of the triangle region. The present application aims to further improve the coercivity of the magnet under the above low B element content formula system. The technical improvement idea is to appropriately increase the content of Pr element and replace part of Nd element with Pr element, so as to further improve the coercivity. Related research discloses that the content of Pr is increased and Ti, Zr or Nb metal is added to solve the problem of deterioration of temperature coefficient caused by high Pr magnet.

[0015] However, in the further research process, it is found that for the low B element content formula system, when only one of the high melting point elements (Ti, Zr or Nb) is added after replacing part of the Nd element with the Pr element, the coercivity of the magnet cannot be improved by a high amplitude. When two or more high melting point elements are added at the same time, the problem of common precipitation of the two high melting point elements is easy to occur. The precipitation makes the local B element content of the magnet decrease obviously, and forms too much R6T 13 M1 phase, which reduces the remanence of the magnet and makes the local grain boundary phase ferromagnetic, finally leading to the decrease of the coercivity of the magnet, and the high coercivity magnet cannot be obtained.

[0016] Therefore, the present application provides a neodymium-iron-boron magnet and a preparation method thereof, so as to realize a neodymium-iron-boron magnet without heavy rare earth or with low heavy rare earth content, and the neodymium-iron-boron magnet has high remanence and coercivity.

[0017] According to an exemplary embodiment of the present application, the present application provides a neodymium-iron-boron magnet, comprising: rare earth elements R, transition metal elements T, metal elements M, B elements; the rare earth elements R include Pr and Nd, the mass percentage of the rare earth elements R is 29wt%-32wt%, the rare earth elements R include 0-0.1wt% of heavy rare earth elements Tb and Dy in terms of mass percentage; the metal elements M at least include Ti and Zr, and the sum of the mass percentages of Ti and Zr is 0.1wt%-0.6wt%; the transition metal elements T include Fe or Fe and Co; the mass percentage of the B elements is 0.84wt%-0.94wt%; wherein, the neodymium-iron-boron magnet has a main phase and a grain boundary phase including a rare earth-rich phase, the proportion of the rare earth-rich phase in the grain boundary phase is 0.15-0.35, and the atomic proportion of Pr in the rare earth elements R in the rare earth-rich phase is 0.4-0.5.

[0018] In some embodiments, the metal element M includes Ti, Zr, and at least one of Al, Cu, Ga, and Sn; the heavy rare earth element includes terbium (Tb) and dysprosium (Dy), and the mass percentage of the heavy rare earth element in the Nd-Fe-B magnet is preferably 0-0.05wt%.

[0019] According to an embodiment of the present application, the proportion of the rare earth-rich phase in the Nd-Fe-B magnet to the grain boundary phase is 0.15-0.35, and the atomic proportion of Pr in the rare earth-rich phase to the rare earth element R is 0.4-0.5, so that the Nd-Fe-B magnet has better remanence and coercivity.

[0020] In an embodiment of the present application, the atomic percentage of the rare earth element R in the rare earth-rich phase is 35at%-90at%, the atomic percentage of the transition metal element T is 0-55at%, the atomic percentage of the metal element M is 0-20at%, the proportion of the rare earth-rich phase to the grain boundary phase is 0.15-0.35, and the atomic proportion of Pr in the rare earth-rich phase to the rare earth element R is 0.4-0.5, so that the Nd-Fe-B magnet has better remanence and coercivity.

[0021] In an embodiment of the present application, the grain boundary phase further includes R6T 13 M1 phase, R6T 13 The atomic percentage of the rare earth element R in the M1 phase is 20at%-36at%, the atomic percentage of the transition metal element T is 45at%-75at%, and the atomic proportion of the metal element M is 3at%-10at%, R6T 13 The atomic percentage of the transition metal element T in the M1 phase is 45at%-75at%, the atomic proportion of the metal element M is 3at%-10at%, and R6T 13 The atomic ratio of the Zr element to the Ti element in the M1 phase is 15-30.

[0022] In some embodiments, R6T 13 The atomic percentage of the rare earth element R in the M1 phase is, for example, 20at%, 25at%, 30at%, 35at%, or 36at%, but is not limited to the values given. The atomic percentage of the transition metal element T is, for example, 45at%, 50at%, 60at%, 70at%, or 75at%, but is not limited to the values given. The atomic proportion of the metal element M is, for example, 3at%, 5at%, 7at%, 8at%, or 10at%, but is not limited to the values given. R6T 13 The atomic number ratio of the Zr element to the Ti element in the M1 phase is, for example, 15, 20, 25, or 30, but is not limited to the values given.

[0023] According to an embodiment of the present application, the proportion of the rare earth-rich phase in the Nd-Fe-B magnet to the grain boundary phase is 0.15-0.35, and the atomic proportion of Pr in the rare earth-rich phase to the rare earth element R is 0.4-0.5, while the Nd-Fe-B magnet has R6T 13The atomic ratio of the Zr element to the Ti element in the M1 phase is 15-30, which reduces the local enrichment and precipitation of the Zr and Ti elements, and a neodymium-iron-boron magnet with better performance can be obtained. It should be noted that the greater the atomic ratio of the Zr element to the Ti element, the lower the enrichment degree of the Zr and Ti elements.

[0024] In an embodiment of the present application, the mass percentage of the B element is 0.84wt%-0.94wt%, for example, 0.84wt%, 0.86wt%, 0.88wt%, 0.90wt%, 0.94wt%, but is not limited to the values given.

[0025] In some embodiments, the mass percentage of the B element is less than 0.9wt%.

[0026] In an embodiment of the present application, the mass percentage of the Co element is 0.5wt%-2.0wt%, for example, 0.5wt%, 0.55wt%, 0.6wt%, 0.75wt%, 1wt%, 1.5wt%, 2.0wt%, but is not limited to the values given.

[0027] In an embodiment of the present application, the metal element M further includes a Cu element, an Al element, and a Ga element, the mass percentage of the Cu element is 0.1wt%-0.5wt%, the mass percentage of the Al element is 0-0.5wt%, and the mass percentage of the Ga element is 0.1wt%-0.5wt%.

[0028] According to an exemplary embodiment of the present application, the present application provides a preparation method of a neodymium-iron-boron magnet, comprising: operations S1-S3.

[0029] In operation S1, a first alloy powder is prepared, the first alloy powder including a rare earth element R, a B element, a transition metal element T, and a metal element M, the metal element M including Zr, the mass percentage of the rare earth element R being 29wt%-32wt%, the mass percentage of the B element being 0.84wt%-0.94wt%, the mass percentage of the Zr element being 0.1wt%-0.4wt%, the rare earth element R including Pr and Nd, or Pr, Nd, and at least one of Dy, Tb, Gd, Ho, Y, La, and Ce, wherein the mass percentage of Pr is greater than 8.5wt%, the mass percentage of heavy rare earth elements being 0-0.1wt%, and the transition metal element T including Fe, or Fe and Co.

[0030] In embodiments of the present application, the mass percentage of the rare earth element R is, for example, 29 wt%, 29.5 wt%, 30 wt%, 31 wt%, 32 wt%, but is not limited to the values given. The mass percentage of the element B is, for example, 0.84 wt%, 0.86 wt%, 0.90 wt%, 0.92 wt%, 0.94 wt%, but is not limited to the values given. The mass percentage of the element Zr is 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, but is not limited to the values given.

[0031] In embodiments of the present application, the raw materials prepared according to the preset proportions are sequentially subjected to melting, casting, and ribbon drawing to form a ribbon sheet; the ribbon sheet is subjected to hydrogen breaking and air-jet milling to form a first alloy powder having a particle size of 2.7-4.0 μm.

[0032] In embodiments of the present application, the raw materials prepared according to the preset proportions are placed in a vacuum induction furnace for melting, casting, and ribbon drawing to form a ribbon sheet; wherein the vacuum degree of the vacuum induction furnace is 10 -2 Pa~10 2 Pa, the melting temperature is 1300-1500 °C, the casting temperature is 1400-1500 °C, and the thickness of the ribbon sheet is 0.2-0.5 mm.

[0033] In embodiments of the present application, the ribbon sheet is added to a hydrogen breaking furnace, and hydrogen absorption is carried out under the conditions of a hydrogen pressure of 0.15-0.4 MPa and a dehydrogenation temperature of 560-600 °C. Subsequently, air-jet milling is performed to obtain a first alloy powder having a powder particle size of 2.7-4.0 μm, and the pressure in the grinding chamber of the air-jet mill is 0.5-0.7 MPa, for example, 0.68 MPa.

[0034] In some embodiments, the mass percentage of the transition metal element T in the first alloy powder is 64-69 wt%, for example, 64 wt%, 65 wt%, 66 wt%, 68 wt%, 69 wt%, but is not limited to the values given.

[0035] In some embodiments, the mass percentage of the Co element in the first alloy powder is 0.5-2.0 wt%.

[0036] In embodiments of the present application, the metal element M for preparing the first alloy powder further comprises a Cu element, an Al element, and a Ga element; wherein the mass percentage of the Cu element is 0.1-0.5 wt%, the mass percentage of the Al element is 0-0.5 wt%, and the mass percentage of the Ga element is 0.1-0.5 wt%.

[0037] In operation S2, a second alloy powder is prepared, the second alloy powder comprising a rare earth element R, a B element, a transition metal element T, and a metal element M, the metal element M comprising Ti, the mass percentage of the rare earth element R being 28.5 wt% to 31.5 wt%, the mass percentage of the B element being 0.84 wt% to 0.94 wt%, the mass percentage of the Ti element being 0.1 wt% to 0.3 wt%, the rare earth element R comprising Pr and Nd, or Pr, Nd, and at least one of Dy, Tb, Gd, Ho, Y, La, and Ce, the mass percentage of the heavy rare earth element being 0 to 0.1 wt%, and the transition metal element T comprising Fe, or Fe and Co.

[0038] In the embodiment of the present application, the raw materials prepared according to the predetermined proportions are sequentially subjected to melting, casting, and ribbon drawing to form a ribbon sheet; the ribbon sheet is subjected to hydrogen breaking and air-jet milling to form a second alloy powder with a particle size of 2.7 μm to 4.0 μm.

[0039] In the embodiment of the present application, the raw materials prepared according to the predetermined proportions are placed in a vacuum induction furnace for melting, casting, and ribbon drawing, the vacuum degree of the vacuum induction furnace being 10 -2 Pa to 10 2 Pa, the melting temperature being 1300℃ to 1500℃, the casting temperature being 1400℃ to 1500℃, and the thickness of the ribbon sheet being 0.2 mm to 0.5 mm.

[0040] According to the embodiment of the present application, the ribbon sheet is added to a hydrogen breaking furnace, and hydrogen absorption is performed under a hydrogen pressure of 0.3 MPa. Then, air-jet milling is performed to obtain a second alloy powder with a powder particle size of 2.7 μm to 4.0 μm, and the grinding chamber pressure of the air-jet mill is 0.68 MPa.

[0041] In some embodiments, the mass percentage of the transition metal element T in the second alloy powder is 64 wt% to 69 wt%, for example, 64 wt%, 65 wt%, 66 wt%, 68 wt%, or 69 wt%, but is not limited to the values listed.

[0042] In some embodiments, the mass percentage of the Co element in the second alloy powder is 0.5 wt% to 2.0 wt%.

[0043] In the embodiment of the present application, the metal element M of the second alloy powder further comprises a Cu element, an Al element, and a Ga element; wherein the mass percentage of the Cu element is 0.1 wt% to 0.5 wt%, the mass percentage of the Al element is 0 to 0.5 wt%, and the mass percentage of the Ga element is 0.1 wt% to 0.5 wt%.

[0044] In the embodiment of the present application, the mass percentage of Pr in the second alloy powder is greater than 7.5 wt%.

[0045] In operation S3, the first alloy powder and the second alloy powder are mixed in a mass ratio of 1:0.5-1:5 to obtain a mixed alloy powder, and the mixed alloy powder is subjected to a forming treatment, a sintering treatment, and a tempering treatment to obtain the Nd-Fe-B magnet, wherein the mass percentage of the heavy rare earth element in the mixed alloy powder is 0-0.1wt%, and the tempering treatment comprises a two-stage tempering process or a three-stage tempering process.

[0046] In the embodiments of the present application, the mass ratio of the first alloy powder to the second alloy powder may be, for example, 1:0.5, 1:1, 1:2, 1:3, 1:4, 1:5, but is not limited to the values listed.

[0047] In the embodiments of the present application, the mass percentage of the heavy rare earth element in the mixed alloy powder is preferably 0-0.05wt%.

[0048] In the embodiments of the present application, the forming treatment is an orientation forming treatment, and the orientation forming treatment is performed under the condition that the orientation magnetic induction intensity is 1.8T-3.2T.

[0049] In the embodiments of the present application, the sintering treatment comprises sintering in a vacuum induction furnace, and the vacuum degree of the vacuum induction furnace is 10 -2 Pa-10 2 Pa. The sintering temperature is 1050℃-1085℃, which may be, for example, 1050℃, 1060℃, 1070℃, 1080℃, 1085℃, but is not limited to the values listed; and the sintering time is 6h-8h, which may be, for example, 6h, 7h, 8h, but is not limited to the values listed.

[0050] In some embodiments, the tempering process is a two-stage tempering process, and the two-stage tempering process comprises a first-stage tempering heat treatment and a second-stage tempering heat treatment; the temperature of the first-stage tempering heat treatment is 800℃-950℃, which may be, for example, 800℃, 850℃, 880℃, 900℃, 950℃, but is not limited to the values listed; the tempering time is 0.5h-4h, which may be, for example, 0.5h, 1h, 2h, 3h, 4h, but is not limited to the values listed; the temperature of the second-stage tempering heat treatment is 450℃-550℃, which may be, for example, 450℃, 480℃, 500℃, 520℃, 550℃, but is not limited to the values listed; and the tempering time is 2h-10h, which may be, for example, 2h, 4h, 6h, 8h, 10h, but is not limited to the values listed.

[0051] In some embodiments, the tempering process is a three-stage tempering process, and the three-stage tempering process comprises a first-stage tempering heat treatment, a second-stage tempering heat treatment, and a third-stage tempering heat treatment.

[0052] In the embodiment of the present application, the temperature of the first-stage tempering heat treatment is 800-950℃, for example, it can be 800℃, 850℃, 900℃, 920℃, 950℃, but is not limited to the values mentioned; the tempering time is 0.5-4h, for example, it can be 0.5h, 1h, 2h, 3h, 4h, but is not limited to the values mentioned.

[0053] In the embodiment of the present application, the temperature of the second-stage tempering heat treatment is 450-550℃, for example, it can be 450℃, 480℃, 500℃, 520℃, 550℃, but is not limited to the values mentioned; the tempering time is 2-10h, for example, it can be 2h, 5h, 8h, 10h, but is not limited to the values mentioned.

[0054] In the embodiment of the present application, the temperature of the third-stage tempering heat treatment is 600-700℃, for example, it can be 600℃, 620℃, 650℃, 680℃, 700℃, but is not limited to the values mentioned; the tempering time is 2-10h, for example, it can be 2h, 5h, 8h, 10h, but is not limited to the values mentioned.

[0055] The designed neodymium-iron-boron magnet and the preparation method thereof are schematically explained below. It should be noted that the example is only a specific embodiment of the present application, and cannot limit the protection scope of the present application.

[0056] Embodiment 1

[0057] The neodymium-iron-boron magnet is prepared by a double-alloy method. The first alloy powder is prepared. Specifically, referring to Table 1, the raw materials prepared according to the preset proportions are sequentially subjected to melting, casting, and ribbon casting to form a ribbon casting sheet; the melting temperature is 1430℃, the casting temperature is 1400℃, and the average thickness of the ribbon casting sheet is 0.25mm. The ribbon casting sheet is subjected to hydrogen crushing and airflow milling to form a first alloy powder with an average particle size D50 of 3.6μm, wherein the hydrogen crushing has a hydrogen absorption pressure of 0.3MPa and a dehydrogenation temperature of 560℃. When the airflow milling is performed, the grinding chamber pressure of the airflow mill is 0.68MPa, and the grading wheel rotating speed of the airflow mill is 3200r / min.

[0058] The second alloy powder is prepared. Specifically, referring to Table 1, the raw materials prepared according to the preset proportions are sequentially subjected to melting, casting, and ribbon casting to form a ribbon casting sheet; the melting temperature is 1430℃, the casting temperature is 1400℃, and the thickness of the ribbon casting sheet is 0.25mm. The ribbon casting sheet is subjected to hydrogen crushing and airflow milling to form a second alloy powder with an average particle size D50 of 3.6μm, wherein the hydrogen crushing has a hydrogen absorption pressure of 0.3MPa and a dehydrogenation temperature of 560℃. When the airflow milling is performed, the grinding chamber pressure of the airflow mill is 0.68MPa, and the grading wheel rotating speed of the airflow mill is 3200r / min.

[0059] The first alloy powder and the second alloy powder are mixed at a mass ratio of 1:1 to form a mixed alloy powder, and the mixed alloy powder is subjected to a forming treatment, a sintering treatment and a tempering treatment to obtain a neodymium-iron-boron magnet. The sintering temperature is 1060℃, the sintering time is 6h, the tempering treatment includes a first-stage tempering heat treatment and a second-stage tempering heat treatment, the temperature of the first-stage tempering heat treatment is 900℃, the tempering time is 6h, the temperature of the second-stage tempering heat treatment is 500℃, and the tempering time is 6h.

[0060] Example 2

[0061] The neodymium-iron-boron magnet is prepared by using the same preparation method as in Example 1, except that the mass percentage of Zr element in the first alloy powder is 0.4 wt%.

[0062] Example 3

[0063] The neodymium-iron-boron magnet is prepared by using the same preparation method as in Example 1, except that the mass ratio of the first alloy powder to the second alloy powder is 1:2.

[0064] Example 4

[0065] The neodymium-iron-boron magnet is prepared by using the same preparation method as in Example 1, except that the mass ratio of the first alloy powder to the second alloy powder is 1:3.

[0066] Example 5

[0067] The neodymium-iron-boron magnet is prepared by using the same preparation method as in Example 1, except that the tempering treatment includes a first-stage tempering heat treatment, a second-stage tempering heat treatment and a third-stage tempering heat treatment, the temperature of the first-stage tempering heat treatment is 900℃, the tempering time is 4h, the temperature of the second-stage tempering heat treatment is 480℃, the tempering time is 6h, and the temperature of the third-stage tempering heat treatment is 620℃, the tempering time is 6h.

[0068] Comparative Example 1

[0069] The neodymium-iron-boron magnet is prepared by using the same raw material ratio, melting, casting, strip casting, forming, sintering and tempering process as in Example 1, except that a single alloy method is used, as shown in Table 1.

[0070] The ICP component analyzer is used to test the components and contents of the raw materials, alloy powders and neodymium-iron-boron magnets of the examples and Comparative Example 1.

[0071] The permanent magnet material precision measurement system NIM-62000TB is used to test the residual magnetism, coercive force and squareness of the neodymium-iron-boron magnets prepared in the examples and Comparative Example 1, and the test results are shown in Table 2.

[0072] Figure 1 SEM image of the Nd-Fe-B magnet provided for Example 2 of the present application.

[0073] Figure 2 SEM image of the Nd-Fe-B magnet provided for Comparative Example 1.

[0074] The element content of the grain boundary phase of the Nd-Fe-B magnets prepared in Example 2 and Comparative Example 1 was tested, respectively. Specifically, after the Nd-Fe-B magnet was sampled, a scanning electron microscope test was performed on any cross section of the magnet perpendicular to the orientation direction, and all of the main phase and the grain boundary phase in each microstructure cross section were counted. The size of the observation area was, for example, 40 μm x 40 μm and 75 μm x 75 μm, the magnification was 2000-5000 times, and the image analysis software was used for statistical analysis. According to the image contrast, the R6T 13 The M1 phase was shown as a gray grain boundary phase, and the rare earth-rich phase was shown as a white grain boundary phase. The percentage of the area of all rare earth-rich phases in the microstructure observation surface to the total area of the microstructure observation surface could be obtained.

[0075] The atomic percentage of each element in the main phase and the grain boundary phase was analyzed by EDS energy spectrum, and the composition of the grain boundary phase was obtained. 13 The calculation method of the M1 phase [Zr] / [Ti] was to take at least 10 R6T 13 The M1 phase and the ratio of Zr element to Ti element, i.e. [Zr] / [Ti], were calculated, and the average value of all ratios was obtained to obtain the value of [Zr] / [Ti] of the example. [Zr] / [Ti] represents the atomic number ratio of Zr element to Ti element. The test results are shown in Table 3. Figure 1 、 Figure 2 The grain boundary phase marked with o is the R6T 13 M1 phase, the grain boundary phase marked with Δ is the rare earth-rich phase, and the black shadow in the area indicated by → represents the Zr element enrichment area.

[0076] Table 1

[0077]

[0078] Table 2

[0079]

[0080] Table 3

[0081]

[0082] According to the above examples and comparative examples of the present application, by adjusting the preparation process and the raw material ratio, a Nd-Fe-B magnet with more excellent residual magnetism, coercivity and squareness can be obtained. It should be noted that the closer the squareness value is to 1, the more stable the performance of the magnet is.

[0083] According to the embodiment 2 and the comparative example 1, the embodiment 2 and the comparative example 1 use the same raw material ratio to prepare the Nd-Fe-B magnet. Compared with the single alloy process used in the comparative example 1 to prepare the Nd-Fe-B magnet, the embodiment 2 uses the double alloy process to prepare the Nd-Fe-B magnet, and the coercivity is improved. This is because the double alloy process used to prepare the Nd-Fe-B magnet can promote the uniform generation of the rare earth-rich phase in the grain boundary phase, increase the proportion of the rare earth-rich phase, and effectively improve the problem of local enrichment and precipitation of Zr and Ti elements, effectively improve the remanence and coercivity of the magnet.

[0084] According to the embodiment 1 and the embodiment 2, by adjusting the content of Zr element in the first alloy powder, the R6T 13 The atomic ratio of Zr element to Ti element ([Zr] / [Ti]) in the M1 phase of the Nd-Fe-B magnet of the embodiment 1 is less than 18.48, and the remanence, coercivity and squareness of the Nd-Fe-B magnet are improved. 13 The [Zr] / [Ti] in the M1 phase is 18.48, so that the remanence, coercivity and squareness of the Nd-Fe-B magnet are improved. This is because the larger the [Zr] / [Ti], the lower the degree of local enrichment of Zr and Ti elements, which is more conducive to obtaining excellent magnetic properties.

[0085] It is worth mentioning that through the comparison of the embodiment 1 to the embodiment 5, the Nd-Fe-B magnet obtained by the embodiment 3 has more excellent remanence, the Nd-Fe-B magnet obtained by the embodiment 2 has more excellent coercivity, the Nd-Fe-B magnet obtained by the embodiment 4 has more excellent squareness, and the Nd-Fe-B magnet obtained by the embodiment 4 has more excellent comprehensive performance of remanence, coercivity and squareness.

[0086] The ordinal numbers used in the specification and claims, such as "first", "second", "third", etc., are used to modify the corresponding elements, and do not mean that the elements have any ordinal number, nor represent the order of one element and another element, or the order of the manufacturing method. The use of these ordinal numbers is only to distinguish one element with a certain name from another element with the same name.

[0087] The above specific embodiments further illustrate the purpose, technical solutions and advantages of the present application. It should be understood that the above description is only a specific embodiment of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A neodymium-iron-boron magnet, characterized in that The neodymium-iron-boron magnet comprises: a rare earth element R, a transition metal element T, a metal element M, and a B element; the rare earth element R comprises Pr and Nd, the mass percentage of the rare earth element R is 29wt%-32wt%, the rare earth element R comprises 0-0.1wt% of heavy rare earth elements Tb and Dy; the metal element M at least comprises Ti and Zr, wherein the sum of the mass percentages of Ti and Zr is 0.1wt%-0.6wt%; the transition metal element T comprises Fe or Fe and Co; the mass percentage of the B element is 0.84wt%-0.94wt%; wherein the neodymium-iron-boron magnet has a main phase and a grain boundary phase comprising a rare earth-rich phase, the proportion of the rare earth-rich phase in the grain boundary phase is 0.15-0.35, and the atomic proportion of Pr in the rare earth element R in the rare earth-rich phase is 0.4-0.5; The grain boundary phase also includes R6T 13 M1 phase, R6T 13 The atomic ratio of Zr element to Ti element in the M1 phase is 15 to 30.

2. The neodymium-iron-boron magnet according to claim 1, characterized in that the mass percentage of the B element is less than 0.9wt%.

3. The neodymium-iron-boron magnet according to claim 1, characterized in that the mass percentage of the Co element is 0.5wt%-2.0wt%; the metal element M further comprises Cu element, Al element and Ga element, the mass percentage of the Cu element is 0.1wt%-0.5wt%, the mass percentage of the Al element is 0-0.5wt%, and the mass percentage of the Ga element is 0.1wt%-0.5wt%.

4. The method of producing a neodymium-iron-boron magnet according to any one of claims 1 to 3, characterized in that, comprises: preparing a first alloy powder comprising a rare earth element R, a B element, a transition metal element T and a metal element M, the metal element M comprising Zr, the mass percentage of the rare earth element R being 29wt%-32wt%, the mass percentage of the B element being 0.84wt%-0.94wt%, the mass percentage of the Zr element being 0.1wt%-0.4wt%, the rare earth element R comprising Pr and Nd, or Pr, Nd and at least one of Dy, Tb, Gd, Ho, Y, La and Ce, wherein the mass percentage of Pr is greater than 8.5wt%, and the mass percentage of the heavy rare earth element being 0-0.1wt%; the transition metal element T comprising Fe or Fe and Co; preparing a second alloy powder comprising a rare earth element R, a B element, a transition metal element T and a metal element M, the metal element M comprising Ti, the mass percentage of the rare earth element R being 28.5wt%-31.5wt%, the mass percentage of the B element being 0.84wt%-0.94wt%, the mass percentage of the Ti element being 0.1wt%-0.4wt%, the rare earth element R comprising Pr and Nd, or Pr, Nd and at least one of Dy, Tb, Gd, Ho, Y, La and Ce, the mass percentage of the heavy rare earth element being 0-0.1wt%; the transition metal element T comprising Fe or Fe and Co; and mixing the first alloy powder and the second alloy powder in a mass ratio of 1:0.5-1:5 to obtain a mixed alloy powder, wherein the mass percentage of the heavy rare earth element in the mixed alloy powder is 0-0.1wt%, and the mixed alloy powder is subjected to a forming treatment, a sintering treatment and a tempering treatment to obtain the neodymium-iron-boron magnet, wherein the tempering treatment comprises a two-stage tempering process or a three-stage tempering process.

5. The preparation method according to claim 4, characterized in that, The mass percentage of Pr in the second alloy powder is greater than 7.5 wt%.

6. The preparation method according to claim 4, characterized in that, The preparation of the first alloy powder comprises: The raw materials prepared according to the preset proportion are sequentially subjected to melting, casting and ribbon drawing to form a ribbon sheet; The ribbon sheet is subjected to hydrogen crushing and air-jet milling to form the first alloy powder with a particle size of 2.7 μm to 4.0 μm; The melting temperature is 1300℃ to 1500℃, the casting temperature is 1400℃ to 1500℃, and the thickness of the ribbon sheet is 0.2mm to 0.5mm.

7. The preparation method according to claim 4, characterized in that, The mass percentage of the transition metal element T in the preparation of the first alloy powder is 64 wt% to 69 wt%, and the mass percentage of the Co element is 0.5 wt% to 2.0 wt%; The metal element M in the preparation of the first alloy powder further comprises a Cu element, an Al element and a Ga element; The mass percentage of the Cu element is 0.1 wt% to 0.5 wt%, the mass percentage of the Al element is 0 to 0.5 wt%, and the mass percentage of the Ga element is 0.1 wt% to 0.5 wt%.

8. The preparation method according to claim 4, characterized in that, The preparation of the second alloy powder comprises: The raw materials prepared according to the preset proportion are sequentially subjected to melting, casting and ribbon drawing to form a ribbon sheet; The ribbon sheet is subjected to hydrogen crushing and air-jet milling to form the second alloy powder with a particle size of 2.7 μm to 4.0 μm; The melting temperature is 1300℃ to 1500℃, the casting temperature is 1400℃ to 1500℃, and the thickness of the ribbon sheet is 0.2mm to 0.5mm.

9. The preparation method according to claim 4, characterized in that, The mass percentage of the transition metal element T in the preparation of the second alloy powder is 64 wt% to 69 wt%, and the mass percentage of the Co element is 0.5 wt% to 2.0 wt%; The metal element M in the preparation of the second alloy powder further comprises a Cu element, an Al element and a Ga element; The mass percentage of the Cu element is 0.1 wt% to 0.5 wt%, the mass percentage of the Al element is 0 to 0.5 wt%, and the mass percentage of the Ga element is 0.1 wt% to 0.5 wt%.

10. The method of claim 4, wherein, The two-stage tempering process comprises a first-stage tempering heat treatment and a second-stage tempering heat treatment; The temperature of the first-stage tempering heat treatment is 800℃ to 950℃, and the tempering time is 0.5h to 4h; The temperature of the second-stage tempering heat treatment is 450℃ to 550℃, and the tempering time is 2h to 10h.

11. The preparation method according to claim 4, characterized in that, The three-stage tempering process comprises a first-stage tempering heat treatment, a second-stage tempering heat treatment and a third-stage tempering heat treatment; The temperature of the first-stage tempering heat treatment is 800℃ to 950℃, and the tempering time is 0.5h to 4h; The temperature of the second-stage tempering heat treatment is 450℃ to 550℃, and the tempering time is 2h to 10h; The temperature of the third-stage tempering heat treatment is 600℃ to 700℃, and the tempering time is 2h to 10h.

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