SINTERED Nd-Fe-B MAGNET AND MANUFACTURING METHOD THEREOF

Abstract

To provide a sintered Nd-Fe-B magnet having a high performance and a high temperature stably and a manufacturing method thereof.SOLUTION: A sintered Nd-Fe-B magnet includes a main phase Re2Fe14B, a crystal grain boundary phase containing Re and a rare earth-rich phase, where the crystal grain boundary phase includes a first crystal grain boundary phase and a second crystal grain boundary phase. The Re is one or a plurality of rare-earth elements containing at least one of Pr and Nd. The first crystal grain boundary phase is a Ga+Cu-rich amorphous phase at a crystal grain boundary triangle region, and the second crystal grain boundary phase is a Ga+Cu-rich amorphous grain boundary phase formed among adjacent main phase grains. The rare-earth rich phase is Re-O and Re-N, and a total ratio X of a mass of the Re2Fe14B main phase, the first grain boundary phase and the second grain boundary phase to the sintered Nd-Fe-B magnet is 97%≤X<100%.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention belongs to the technical field of manufacturing Nd-Fe-B based magnetic materials, and particularly relates to an Nd-Fe-B based sintered magnetic material having high performance and high temperature stability and a manufacturing method thereof.

Background Art

[0002] Nd-Fe-B based sintered magnetic materials are important functional materials and are used in a wide range of fields such as new energy vehicles, information technology, and medical devices. With the development of technology, the requirements for the comprehensive magnetic properties of Nd-Fe-B based magnetic materials, particularly those related to high temperature stability performance, are increasing.

[0003] In the prior art, in order to meet the requirements of high temperature stability performance, it has generally been common to improve its coercive force by adding or diffusing heavy rare earth elements.

[0004] "Influence of Dy addition on Nd-Fe-B based magnetic materials on high temperature stability and magnetic domains" (Master's thesis of Inner Mongolia University of Science and Technology, China, written by Ju Xiangming, published on June 7, 2013. Non-Patent Document 1) discloses research content on the improvement of the high temperature stability of magnetic materials by adding Dy. Dy mainly enters the main phase, and Dy2Fe 14 B is formed inside the grain boundaries, and the anisotropy magnetic fields of the magnetic material are significantly improved, and the coercive force of the magnetic material is improved. At the same time, Nd is replaced by Dy, and Nd is diffused into the grain boundaries to improve the microstructure and magnetic properties, and to improve the high temperature stability of the magnetic material. Also, "Influence of the addition of Dy 80 Fe 13 Ga7 to the grain boundaries on the high temperature stability and corrosion resistance of Nd-Fe-B based sintered magnetic materials" (published by Zeng Liangliang et al. in "Rare Metals", China, in July 2019. Non-Patent Document 2) shows that Dy 80 Fe 13Adding a Ga7 alloy to increase the coercivity of the magnet, promoting an increase in the number of rare-earth-rich grain boundary phases, and strengthening the demagnetization and exchange coupling effects between the main-phase crystal particles, thereby significantly improving the coercivity and further improving the temperature coefficient of the magnet are disclosed. This method involves adding heavy rare-earth elements or heavy rare-earth compounds to improve the coercivity of the magnet and enhance the high-temperature performance of the magnet, which improves the high-temperature stability of the magnet but results in a soaring cost.

[0005] In the Chinese Patent CN106158203B publication, as a manufacturing method for enhancing the high-temperature stability of Nd-Fe-B-based magnets, a method for manufacturing magnets through a process of Nd-Fe-B and Sm-Fe-N magnetic powders via a high-performance ball mill, powder mixing, magnetic field orientation pre-pressing forming, and plasma discharge sintering is disclosed. This technology utilizes the high inherent properties (Curie temperature 470°C) of Sm-Fe-N magnetic powders to improve the high-temperature stability of Nd-Fe-B-based magnets. However, what is produced in this process is nanocrystalline powder, which is different from the manufacturing process of ordinary Nd-Fe-B-based magnets and is inferior in the magnetic properties of the magnet.

[0006] The microstructure of the magnet has an important influence on the magnetic properties of the magnet. In previous studies, both high-Ga magnets and high-Cu magnets can form Nd-Fe-M-based compounds. However, since the formation energy of Nd-Fe-Ga (-0.046 eV / atom) is lower than that of Nd-Fe-Cu (0.005 eV / atom), it has been found that the Nd-Fe-Ga system is formed first, suppressing the formation of the Nd-Fe-Cu system and causing the grain boundary phases in the magnet to separate. That is, a part becomes a Ga-rich region with an Nd-Fe-Ga structure, and the other part becomes a Cu-rich region containing Cu. Due to such variations in the microstructure of the triangular regions of the grain boundaries, the grain boundary phases between the two particles become non-uniform. Some have a good grain boundary phase between the two particles, while some have no grain boundary phase. Such variations in the grain boundaries reduce the magnetic properties of the magnet and deteriorate its stability.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Non-Patent Document

[0008]

Non-Patent Document 1

Non-Patent Document 2

Disclosure of the Invention

Problems to be Solved by the Invention

[0009] The present invention is made in view of the problems of the above-described prior art, and an object thereof is to provide an Nd-Fe-B-based magnet that improves the high-temperature stability of the magnet and satisfies the requirements for high-temperature performance, and a method for manufacturing the same.

Means for Solving the Problems

[0010] To achieve the above object, the first invention of the present application is an Nd-Fe-B-based sintered magnet, comprising a Re2Fe 14 B main phase, a grain boundary phase containing Re, and a rare earth-rich phase, the grain boundary phase includes a first grain boundary phase and a second grain boundary phase, the Re is one or more rare earth elements including at least one of Pr and Nd, the first grain boundary phase is a Ga+Cu-rich amorphous phase in a triangular region of the grain boundary, the second grain boundary phase is a Ga+Cu-rich amorphous phase formed between adjacent main phase crystal particles, the rare earth-rich phase is Re-O, Re-N, With respect to the total mass of the Nd-Fe-B sintered magnetic material, the total mass ratio X of the 14 Re2FeB main phase, the mass of the first grain boundary phase, and the mass of the second grain boundary phase is 97% ≦ X < 100%, which is characterized by this.

[0011] Also, in one embodiment, the percentage of the area occupied by the first grain boundary phase in any cross-section of the Nd-Fe-B magnetic material is 6 to 15%, the width of the second grain boundary phase is 2 to 20 nm, the total mass of Ga and Cu in the first grain boundary phase is 20 to 40% of the total mass of the first grain boundary phase, the mass percentage of Fe in the first grain boundary phase is 0 to 10%, the total mass of Ga and Cu in the second grain boundary phase is 40 to 70% of the total mass of the second grain boundary phase, and the mass percentage of Fe in the second grain boundary phase is 0 to 10%, which is characterized by this.

[0012] Also, in one embodiment, each element and its mass percentage in the Nd-Fe-B magnetic material are Re is 29.5 to 33.0%, B is 0.85 to 0.98%, M is 0.50 to 5.00%, and Fe is 61.0 to 69.0%, M includes Cu and Ga and at least one of Co, Ti, Zr, V, Mo, and Nb, the mass percentage of Cu is more than 0.45%, the mass percentage of Ga is less than 0.25%, and the mass content ratio Y of Cu and Ga is 1.8 < Y ≦ 10, which is characterized by this.

[0013] Furthermore, in order to achieve the above object, the second invention of the present application is a method for manufacturing an Nd-Fe-B sintered magnetic material composed of the above elements, (Step 1) According to the compounding ratio of the elements used as raw materials, an alloy sheet is manufactured using the strip casting method, and the smelting process in the strip casting method is performed in an argon gas atmosphere, (Step 2) Hydrogen treatment and jet mill pulverization treatment are performed on the alloy sheet to create alloy powder, (Step 3) Form the alloy powder under a uniform magnetic field, and perform cold isostatic pressing to create a magnetic substrate. (Step 4) Sinter the magnetic substrate in a vacuum sintering furnace, and then perform aging treatment. The aging treatment is a two-step annealing process, and both the heat preservation process and the cooling process in the two-step annealing process are carried out in an inert gas atmosphere. This is the feature.

[0014] Also in one embodiment, the temperature of the melting process in Step 1 is 1400 - 1500 °C. This is the feature.

[0015] Also in one embodiment, the particle size of the alloy powder created by the jet mill pulverization treatment in Step 2 is 2.5 - 5.0 μm. This is the feature.

[0016] Also in one embodiment, the magnetic field strength in Step 3 is 1.5 - 2.0 T. This is the feature.

[0017] Also in one embodiment, the sintering temperature of the sintering process in Step 4 is 1030 - 1080 °C, and the treatment time is 6 - 10 hours. This is the feature.

[0018] Also in one embodiment, the temperature of the first annealing treatment in Step 4 is 800 - 900 °C, the heat preservation time is 3 - 5 hours, the temperature of the second annealing treatment is 460 - 520 °C, and the heat preservation time is 1 - 6 hours. This is the feature.

[0019] Also in one embodiment, the inert gas atmosphere in Step 4 is argon gas, the pressure of the inert gas atmosphere in the heat preservation stage is 0.02 - 0.05 MPa, and the pressure of the inert gas atmosphere in the cooling stage is 0.06 - 0.08 MPa. This is the feature.

Advantages of the Invention

[0020] According to the Nd-Fe-B sintered magnet and its manufacturing method according to the present invention, by reasonably adjusting the components of the alloy to reduce the formation of Nd-Fe-Ga and utilizing Nd-Cu characterized by a low melting point, the liquid-phase fluidity of the grain boundary phase and the lubricity between the main phase and the rare-earth rich phase are enhanced. Furthermore, by performing a rapid cooling process, the enrichment of only Cu is suppressed, Ga and Cu are simultaneously enriched, the element distribution is made more uniform, and the uniformity of the magnet structure is enhanced, so that a magnet having a good and continuous grain boundary phase can be formed, and the magnetic properties of the magnet are improved.

[0021] Also, in the two-step aging treatment, heat preservation, and cooling processes, by injecting an inert gas up to a predetermined pressure, the flow of the grain boundary phase in the aging treatment and heat preservation processes is promoted, an excellent grain boundary phase is formed, the cooling rate in the cooling process is increased, and by utilizing the property of the Cu-rich compound that is easy to form an amorphous substance, the grain boundary phase is transformed from a crystal structure to an amorphous structure, thereby improving the high-temperature stability of the magnet.

Brief Description of the Drawings

[0022]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0023] Hereinafter, the principle and features of the present invention will be described in detail with reference to FIGS. 1 to 5. The following examples are only used for the interpretation of the present invention and do not limit the configuration according to the present invention.

[0024] Examples 1 to 6 below were created by varying the components, their contents, and the conditions of each manufacturing process.

[0025] Example 1 (Step 1) The raw materials shown in Table 1 were blended, and the raw materials were melted in a vacuum induction melting furnace, and alloy pieces were created using the strip casting method. The melting temperature was 1450 °C, and the thickness of the alloy pieces was 0.25 to 0.35 mm.

[0026] (Step 2) The alloy pieces were hydrogen pulverized in a hydrogen treatment furnace to form hydrogen pulverized powder, and the hydrogen pulverized powder was further pulverized with a jet mill under a nitrogen gas atmosphere, and the particle size of the powder was set to X50 = 4.0 μm.

[0027] (Step 3) The Nd-Fe-B based magnetic powder obtained in Step 2 was orientation pressed in a magnetic field of 2.0 T under a nitrogen gas atmosphere to create a magnetic substrate.

[0028] (Step 4) The pressed magnetic substrate was sintered in a vacuum sintering furnace at a temperature of 1060 °C, held for 6 hours, and then rapidly cooled. The sintered magnetic body was subjected to aging treatment in two steps. First, in the first aging treatment, it was held at 850 °C for 3 hours and then rapidly cooled. Subsequently, in the second aging treatment, the temperature was raised to 490 °C and held for 3 hours. In the second aging treatment and holding stage, argon gas was injected until the atmospheric pressure reached 0.03 MPa, and then it was rapidly cooled. In the second aging and cooling stage, argon gas was injected until the atmospheric pressure reached 0.06 MPa, and the final Nd-Fe-B based sintered magnetic body was created.

[0029] Examples 2 to 6 were formed, which were basically the same as each manufacturing process of Example 1, with the contents of each component as shown in Table 1 and the parameters of each manufacturing process as shown in Table 2.

[0030] Table 1: Each element component and its content in Examples 1 to 6 JPEG2025105489000002.jpg44170

[0031] Table 2: Parameters of Each Manufacturing Process in Examples 1 to 6 JPEG2025105489000003.jpg60170

[0032] The Nd-Fe-B sintered magnet obtained in the above example is Re2Fe 14 It includes a B main phase, a grain boundary phase containing Re (a Ga+Cu-rich amorphous phase in the triangular region of the grain boundary and a Ga+Cu-rich amorphous phase formed between adjacent main phase crystal particles), and a rare earth-rich phase.

[0033] Figure 1 is a diagram showing the microstructure of the magnet according to Example 1, and it can be seen that the triangular region is a Ga+Cu-rich phase. Figure 2 is a diffraction pattern diagram in the triangular region of the grain boundary of the magnet according to Example 1, and it can be seen that this grain boundary phase has an amorphous structure. Figure 3 is an energy spectrum analysis diagram in the triangular region of the grain boundary of the magnet according to Example 1, and it can be seen that this grain boundary phase is Ga+Cu-rich and has a low Fe content. Figure 4 is an energy spectrum analysis diagram of the grain boundary energy between two crystal particles of the magnet according to Example 1, and it can be seen that this grain boundary phase is Ga+Cu-rich and has a low Fe content.

[0034] The area percentage of the first grain boundary phase was calculated using an image processing method. The processed photos were taken with a scanning electron microscope (ZEISS EVO MA10) at a magnification of 500 times. Five photos were taken for each sample, and the average value was calculated. The area percentage of the first grain boundary phase and the width of the second grain boundary phase of each example are shown in Table 3.

[0035] Table 3: Structure of Nd-Fe-B Sintered Magnets According to Examples 1 to 6 JPEG2025105489000004.jpg62127

[0036] To verify the effects of the examples, the following Comparative Examples 1 to 6 were created. The specific creation process is as follows.

[0037] Comparative Example 1 (Step 1) The raw materials shown in Table 1 were blended, and alloy pieces were produced by the melting alloy die-casting method. The melting temperature was 1450°C, and the thickness of the alloy pieces was 0.25 - 0.35 mm.

[0038] (Step 2) The alloy pieces were hydrogen pulverized in a hydrogen treatment furnace to obtain hydrogen pulverized powder, and the hydrogen pulverized powder was further pulverized by a jet mill under a nitrogen gas atmosphere to make the particle size of the powder X50 = 4.0 μm.

[0039] (Step 3) The above Nd-Fe-B based magnetic powder was orientation pressed in a 2.0 T magnetic field under a nitrogen gas atmosphere to produce a magnetic substrate.

[0040] (Step 4) The magnetic substrate after pressing was sintered in a vacuum sintering furnace at a temperature of 1060°C, held for 6 hours, and then argon gas was injected for rapid cooling. The above sintered magnet was subjected to aging treatment in two steps. First, in the primary aging treatment, it was held at 850°C for 3 hours and then rapidly cooled. Subsequently, in the secondary aging treatment, the temperature was raised to 490°C and held for 3 hours. In the secondary aging and holding stage, it was rapidly cooled without injecting argon gas. In the secondary aging and cooling stage, argon gas was injected until the atmospheric pressure reached 0.05 MPa to produce the final Nd-Fe-B based sintered magnet.

[0041] Comparative Examples 2 - 6 were prepared, which were basically the same as each manufacturing process of Comparative Example 1, with the content of each component as shown in Table 4 and the parameters of each manufacturing process as shown in Table 5.

[0042] Table 4: Each element component and its content in Comparative Examples 1 - 6 JPEG2025105489000005.jpg44170

[0043] Table 5: Parameters of each manufacturing process in Comparative Examples 1 - 6 JPEG2025105489000006.jpg57170

[0044] Figure 5 shows an electron diffraction pattern diagram in the triangular region of the grain boundaries of the magnetic material according to Comparative Example 1. The grain boundary phase here had a crystal structure. Similarly, the area percentage of the first grain boundary phase was calculated using an image processing method. The processed photograph was taken with a scanning electron microscope (ZEISS EVO MA10) at a magnification of 500 times. Five photographs were taken for each sample, and the average value was calculated. Table 6 shows the area percentage of the first grain boundary phase and the width of the second grain boundary phase for each comparative example.

[0045] Table 6: Structure of Nd-Fe-B sintered magnets in Comparative Examples 1 to 6 JPEG2025105489000007.jpg62127

[0046] To verify the excellent magnetic properties of the Nd-Fe-B sintered magnets of the examples, the Nd-Fe-B sintered magnets prepared as each example and each comparative example were measured using a NIM2000 magnetic property measuring device. The results are shown in Table 7.

[0047] Table 7: Magnetic properties of Nd-Fe-B sintered magnets according to Examples 1 to 6 and Comparative Examples 1 to 6 JPEG2025105489000008.jpg85144

[0048] As shown in Table 7, the magnets of Examples 1 to 6 have higher values of Br and Hcj than the magnets of Comparative Examples 1 to 6, and the temperature coefficient β of Hcj at 20 to 70 °C is smaller for Examples 1 and 2 than for Comparative Examples 1 and 2, and the temperature coefficient β of Hcj at 20 to 140 °C is smaller for Examples 3 to 6 than for Comparative Examples 3 to 6.

[0049] From the above data, the Nd-Fe-B sintered magnet according to the present invention has excellent temperature coefficients along with high magnetic properties.

[0050] Each of the above embodiments is merely a preferred embodiment of the present invention and does not limit the present invention. Modifications, improvements, etc. made within the scope of the technical idea of the present invention all fall within the protection scope of the present invention.

Claims

1. An Nd-Fe-B sintered magnet comprising Re ２ Fe １４ a main phase of B, a grain boundary phase containing Re, and a rare earth-rich phase The grain boundary phase includes a first grain boundary phase and a second grain boundary phase, wherein Re is one or more rare earth elements including at least one of Pr and Nd, the first grain boundary phase is a Ga+Cu-rich amorphous phase in the triangular region of the grain boundary, the second grain boundary phase is a Ga+Cu-rich amorphous phase formed between adjacent primary phase crystal particles, the rare earth-rich phase is Re-O, Re-N, The ratio X of the total mass of the Re ２ Fe １４ B main phase, the mass of the first grain boundary phase and the mass of the second grain boundary phase is 97% ≤ X < 100%. and the Nd-Fe-B sintered magnet is characterized by this.

2. The percentage of the area occupied by the first grain boundary phase in any cross-section of the Nd-Fe-B magnetic body is 6 to 15%, and the width of the second grain boundary phase is 2 to 20 nm. The total mass of Ga and Cu in the first grain boundary phase is 20 to 40% of the total mass of the first grain boundary phase, the mass% of Fe in the first grain boundary phase is 0 to 10%, the total mass of Ga and Cu in the second grain boundary phase is 40 to 70% of the total mass of the second grain boundary phase, and the mass% of Fe in the second grain boundary phase is 0 to 10%. The Nd-Fe-B sintered magnet according to claim 1, characterized by this.

3. For each element and its mass% in the Nd-Fe-B magnetic body, Re is 29.5 to 33.0%, B is 0.85 to 0.98%, M is 0.50 to 5.00%, and Fe is 61.0 to 69.0%. M includes Cu and Ga and at least one of Co, Ti, Zr, V, Mo, and Nb. The mass% of Cu is more than 0.45%, and the mass% of Ga is less than 0.25%. The mass content ratio Y of Cu and Ga is 1.8 < Y ≤ 10. The Nd-Fe-B sintered magnet according to claim 1 or 2, characterized by this.

4. A method for manufacturing the Nd-Fe-B sintered magnet according to claim 3, (Step 1) According to the blending ratio of the elements as raw materials, an alloy piece is manufactured using the strip casting method, and the smelting process in the strip casting method is carried out in an argon gas atmosphere. (Step 2) Hydrogen treatment and jet mill pulverization treatment are performed on the alloy piece to create alloy powder. (Step 3) The alloy powder is formed under a uniform magnetic field and cold isostatically pressed to create a magnetic body substrate. (Step 4) The magnetic body substrate is sintered in a vacuum sintering furnace and then aging treatment is performed. The aging treatment is a two-step annealing treatment, and both the heat preservation process and the cooling process in the two-step annealing treatment are carried out in an inert gas atmosphere. A method for manufacturing an Nd-Fe-B sintered magnet, characterized by the following.

5. The temperature of the smelting process in Step 1 is 1400 - 1500 °C. The method for manufacturing an Nd-Fe-B sintered magnet according to Claim 4, characterized by the above.

6. The particle size of the alloy powder produced by the jet mill pulverization treatment in Step 2 is 2.5 - 5.0 μm. The method for manufacturing an Nd-Fe-B sintered magnet according to Claim 4, characterized by the above.

7. The magnetic field strength in Step 3 is 1.5 - 2.0 T. The method for manufacturing an Nd-Fe-B sintered magnet according to Claim 4, characterized by the above.

8. The sintering temperature of the sintering process in Step 4 is 1030 - 1080 °C, and the processing time is 6 - 10 hours. The method for manufacturing an Nd-Fe-B sintered magnet according to Claim 4, characterized by the above.

9. The temperature of the first tempering treatment in Step 4 is 800 - 900 °C, the heat preservation time is 3 - 5 hours, the temperature of the second tempering treatment is 460 - 520 °C, and the heat preservation time is 1 - 6 hours. The method for manufacturing an Nd-Fe-B sintered magnet according to Claim 4, characterized by the above.

10. The inert gas atmosphere in Step 4 is argon gas, the pressure of the inert gas atmosphere in the heat preservation stage is 0.02 - 0.05 MPa, and the pressure of the inert gas atmosphere in the cooling stage is 0.06 - 0.08 MPa. The method for manufacturing an Nd-Fe-B sintered magnet according to Claim 4, characterized by the above.

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