Nd-Fe-B sintered magnetic material and its manufacturing method

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 relates to the technical field of manufacturing Nd-Fe-B based magnetic materials, and more particularly to a Nd-Fe-B based sintered magnetic material having high performance and high temperature stability, and a method for manufacturing the same. [Background technology]

[0002] Nd-Fe-B sintered magnetic materials are important functional materials and are used in a wide range of fields, including new energy vehicles, information technology, and medical devices. With technological developments, there are increasing demands for the comprehensive magnetic properties of Nd-Fe-B magnetic materials, especially for their high-temperature stability.

[0003] In the prior art, in order to satisfy the requirement for high temperature stability, it has been common to improve the coercivity by adding or diffusing heavy rare earth elements.

[0004] "The effect of adding Dy to Nd-Fe-B magnetic materials on high-temperature stability and magnetic domains" (Master's thesis by Maruki Ming, Inner Mongolia University of Science and Technology, China, published on June 7, 2013. Non-patent document 1) discloses research on how the addition of Dy improves the high-temperature stability of magnetic materials. Dy mainly penetrates into the main phase and forms Dy2Fe 14 The formation of B significantly improves the anisotropy field of the magnetic material, improving the coercive force of the magnetic material. At the same time, Nd is substituted for Dy, diffusing Nd into the grain boundaries, improving the microstructure, improving the magnetic properties, and improving the high-temperature stability of the magnetic material. Also, "Dysprosium adsorbed to grain boundaries" 80 Fe 13 "The effect of Ga7 addition on the high temperature stability and corrosion resistance of Nd-Fe-B sintered magnetic materials" (Chinese "Rare Metals" by Zeng Liangliang et al., July 2019, Non-Patent Document 2) states that Dy 80 Fe 13Research has been disclosed that adds a Ga7 alloy to increase the coercivity of a magnetic material, promotes an increase in the number of rare-earth-rich grain boundary phases, and strengthens the demagnetization and exchange coupling between main phase crystal grains, thereby significantly improving the coercivity and further improving the temperature coefficient of the magnetic material. This method adds a heavy rare-earth element or heavy rare-earth compound to increase the coercivity of the magnetic material and enhance its high-temperature performance, improving the high-temperature stability of the magnetic material but at the expense of increased costs.

[0005] Chinese Patent Publication CN106158203B discloses a manufacturing method for improving the high-temperature stability of Nd-Fe-B magnetic materials, which involves manufacturing Nd-Fe-B and Sm-Fe-N magnetic powders through a high-performance ball mill, powder mixing, magnetically oriented pre-pressing, and plasma discharge sintering processes. This technology utilizes the high inherent properties of Sm-Fe-N magnetic powder (Curie temperature 470°C) to improve the high-temperature stability of Nd-Fe-B magnetic materials, but the nanocrystalline powder produced by this process is inferior to the conventional manufacturing process for Nd-Fe-B magnetic materials, resulting in magnetic materials with inferior magnetic properties.

[0006] The microstructure of a magnetic material has a significant impact on its magnetic properties. Previous research has shown that both high-Ga and high-Cu magnetic materials can form Nd-Fe-M compounds. However, because the formation energy of Nd-Fe-Ga (-0.046 eV / atom) is lower than that of Nd-Fe-Cu (0.005 eV / atom), the Nd-Fe-Ga system forms first, suppressing the formation of the Nd-Fe-Cu system, resulting in the separation of the grain boundary phase within the magnetic material. That is, some parts become Ga-rich regions with an Nd-Fe-Ga structure, while the other parts become Cu-rich regions containing Cu. Such variations in the microstructure of the triangular regions of the grain boundaries result in uneven grain boundary phases between two grains. Some grains have good grain boundary phases, while others lack them. This variation in the grain boundaries reduces the magnetic properties and stability of the magnetic material. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Chinese patent CN106158203B publication [Non-patent literature]

[0008] [Non-Patent Document 1] "The effect of Dy addition on high-temperature stability and magnetic domains in Nd-Fe-B magnetic materials" (Master's thesis by Zhu Xiangming, Inner Mongolia University of Science and Technology, China, published June 7, 2013) [Non-patent document 2] "Effect of Dy80Fe13Ga7 addition to grain boundaries on the high-temperature stability and corrosion resistance of Nd-Fe-B sintered magnetic materials" (Zeng Liangliang et al., China's "Rare Metals," July 2019) DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0009] The present invention has been made in consideration of the above-mentioned problems of the conventional art, and has as its object to provide an Nd—Fe—B based magnetic material that improves the high-temperature stability of magnetic materials and satisfies the requirements for high-temperature performance, and a method for producing the same. [Means for solving the problem]

[0010] In order to achieve the above object, the first invention of the present application is a Nd-Fe-B based sintered magnetic material, comprising Re2Fe 14 It includes a 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 grains, The rare earth rich phase is Re—O, Re—N, The total mass ratio X of the masses of the Re2Fe 14 B main phase, the first grain boundary phase, and the second grain boundary phase to the total mass of the Nd-Fe-B sintered magnet 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 magnet 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 percentage of Fe in the first grain boundary phase is 0 to 10%, and 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 magnet 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%, and the mass percentage of Ga is less than 0.25%. The mass content ratio Y of Cu and Ga is 1.8 < Y ≦ 10, which is characterized by this.

[0013] Furthermore, to achieve the above object, the second invention of the present application is a method for manufacturing an Nd-Fe-B sintered magnet composed of the above elements, (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 performed in an argon gas atmosphere. (Step 2) The alloy piece is subjected to hydrogen treatment and jet mill pulverization treatment to create alloy powder. (Step 3) The alloy powder is molded under a uniform magnetic field and cold isostatically pressed to form a magnetic base material; (Step 4) The magnetic base material is sintered in a vacuum sintering furnace and then subjected to an aging treatment, the aging treatment being a two-stage tempering treatment, and both the heat retention step and the cooling step in the two-stage tempering treatment being performed in an inert gas atmosphere.

[0014] In one embodiment, the temperature of the smelting process in step 1 is 1400 to 1500°C.

[0015] In one embodiment, the particle size of the alloy powder produced by the jet mill pulverization treatment in step 2 is 2.5 to 5.0 μm.

[0016] In one embodiment, the magnetic field strength in step 3 is 1.5 to 2.0T.

[0017] In one embodiment, the sintering temperature in the sintering process in step 4 is 1030 to 1080° C., and the treatment time is 6 to 10 hours.

[0018] In one embodiment, the temperature of the first tempering treatment in step 4 is 800 to 900°C, and the temperature retention time is 3 to 5 hours, and the temperature of the second tempering treatment is 460 to 520°C, and the temperature retention time is 1 to 6 hours.

[0019] In one embodiment, the inert gas atmosphere in step 4 is argon gas, the pressure of the inert gas atmosphere in the heat retention stage is 0.02 to 0.05 MPa, and the pressure of the inert gas atmosphere in the cooling stage is 0.06 to 0.08 MPa. [Effects of the Invention]

[0020] According to the Nd-Fe-B based sintered magnetic material and its manufacturing method of the present invention, the alloy components are rationally adjusted to reduce the formation of Nd-Fe-Ga, and Nd-Cu, which is characterized by its low melting point, is used to improve the liquid phase fluidity of the grain boundary phase and the lubricity of the main phase and rare earth-rich phase. Furthermore, by performing a rapid cooling process, enrichment of only Cu is suppressed, and Ga and Cu are enriched simultaneously, making the element distribution more uniform and increasing the uniformity of the magnetic material structure, so that a magnetic material with a good, continuous grain boundary phase can be formed, and the magnetic properties of the magnetic material can be improved.

[0021] Furthermore, by injecting an inert gas up to a predetermined pressure during the two-stage aging treatment, heat retention, and cooling processes, the flow of the grain boundary phase during the aging treatment and heat retention processes is promoted, an excellent grain boundary phase is formed, the cooling rate during the cooling process is increased, and by utilizing the properties of Cu-rich compounds that easily form amorphous structures, the grain boundary phase is converted from a crystalline structure to an amorphous structure, thereby improving the high-temperature stability of the magnetic material. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a microstructure diagram of a magnetic body according to Example 1. FIG. [Figure 2] 3 is an amorphous diffraction pattern diagram in a triangular region of a crystal grain boundary of the magnetic material according to Example 1. FIG. [Figure 3] 4 is an energy spectrum analysis diagram of a triangular region of a crystal grain boundary of the magnetic material according to Example 1. FIG. [Figure 4] 3 is a diagram illustrating an energy spectrum analysis of a grain boundary between two crystal grains of the magnetic material according to Example 1. FIG. [Figure 5] 1 is a diagram showing a crystalline diffraction pattern in a triangular region of a crystal grain boundary of a magnetic material according to Comparative Example 1. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0023] The principles and features of the present invention will be described in detail below with reference to Figures 1 to 5. The following examples are used only to interpret the present invention and are not intended to limit the configuration of the present invention.

[0024] The following Examples 1 to 6 were prepared by varying the components, their contents, and the conditions of the manufacturing process.

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

[0026] (Step 2) The alloy flakes were subjected to hydrogen pulverization in a hydrogen treatment furnace to produce hydrogen pulverized powder, which was then further pulverized in a jet mill under a nitrogen gas atmosphere to a particle size of X50=4.0 μm.

[0027] (Step 3) The Nd-Fe-B magnetic powder obtained in step 2 was pressed to orient it in a nitrogen gas atmosphere and a magnetic field of 2.0 T to produce a magnetic base material.

[0028] (Step 4) The pressed magnetic body was sintered at 1060°C in a vacuum sintering furnace, held at that temperature for six hours, and then rapidly cooled. The sintered magnetic body was then subjected to a two-stage aging treatment. In the first aging treatment, the body was held at 850°C for three hours and then rapidly cooled. In the second aging treatment, the body was heated to 490°C and held at that temperature for three hours. In the second aging treatment and holding stage, argon gas was introduced until the atmospheric pressure reached 0.03 MPa, after which the body was rapidly cooled. In the second aging and cooling stage, argon gas was introduced until the atmospheric pressure reached 0.06 MPa, producing the final Nd-Fe-B sintered magnetic body.

[0029] Examples 2 to 6 were prepared using the same manufacturing steps as in Example 1, with the contents of each component as shown in Table 1 and the parameters of each manufacturing step as shown in Table 2.

[0030] Table 1: Elemental components and their contents in Examples 1 to 6 JPEG0007788784000001.jpg44170

[0031] Table 2: Parameters of each manufacturing process in Examples 1 to 6 JPEG0007788784000002.jpg60170

[0032] The Nd-Fe-B sintered magnetic material obtained in the above example was Re2Fe 14 It contains 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 grains), and a rare earth rich phase.

[0033] FIG. 1 is a diagram showing the microstructure of the magnetic material according to Example 1, showing that the triangular region is a Ga+Cu-rich phase. FIG. 2 is a diffraction pattern diagram of the triangular region of the grain boundary of the magnetic material according to Example 1, showing that this grain boundary phase has an amorphous structure. FIG. 3 is an energy spectrum analysis diagram of the triangular region of the grain boundary of the magnetic material according to Example 1, showing that this grain boundary phase is Ga+Cu-rich and has a low Fe content. FIG. 4 is a grain boundary energy spectrum analysis diagram between two crystal grains of the magnetic material according to Example 1, showing 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 photographs were taken with a scanning electron microscope (ZEISS EVO MA10) at a magnification of 500x. Five photographs 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 for each example are shown in Table 3.

[0035] Table 3: Structures of Nd—Fe—B sintered magnetic materials according to Examples 1 to 6 JPEG0007788784000003.jpg62127

[0036] In order to verify the effects of the examples, the following comparative examples 1 to 6 were prepared. The specific preparation process is as follows.

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

[0038] (Step 2) The alloy flakes were subjected to hydrogen pulverization in a hydrogen treatment furnace to produce hydrogen pulverized powder, which was then further pulverized in a jet mill under a nitrogen gas atmosphere to a particle size of X50=4.0 μm.

[0039] (Step 3) The Nd-Fe-B magnetic powder was orientated and pressed in a nitrogen gas atmosphere and a magnetic field of 2.0 T to prepare a magnetic base material.

[0040] (Step 4) The pressed magnetic body was sintered in a vacuum sintering furnace at 1060°C, held at that temperature for six hours, and then rapidly cooled by injecting argon gas. The sintered magnetic body was then subjected to a two-stage aging treatment. In the first aging treatment, the body was held at 850°C for three hours and then rapidly cooled. In the second aging treatment, the body was heated to 490°C and held at that temperature for three hours. In the second aging and holding stage, the body was rapidly cooled without injecting argon gas. In the second aging and cooling stage, argon gas was injected until the atmospheric pressure reached 0.05 MPa, producing the final Nd-Fe-B sintered magnetic body.

[0041] Comparative Examples 2 to 6 were prepared using basically the same manufacturing steps as Comparative Example 1, with the contents of each component as shown in Table 4 and the parameters of each manufacturing step as shown in Table 5.

[0042] Table 4: Elemental components and their contents in Comparative Examples 1 to 6 JPEG0007788784000004.jpg44170

[0043] Table 5: Parameters of each manufacturing process in Comparative Examples 1 to 6 JPEG0007788784000005.jpg57170

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

[0045] Table 6: Structures of Nd-Fe-B sintered magnetic materials in Comparative Examples 1 to 6 JPEG0007788784000006.jpg62127

[0046] In order to verify the excellent magnetic properties of the Nd-Fe-B based sintered magnetic materials of the examples, the Nd-Fe-B based sintered magnetic materials prepared as the examples and comparative examples 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 magnetic bodies according to Examples 1 to 6 and Comparative Examples 1 to 6 JPEG0007788784000007.jpg85144

[0048] As shown in Table 7, the magnetic materials of Examples 1 to 6 have higher Br and Hcj values ​​than the magnetic materials 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, it is clear that the Nd-Fe-B based sintered magnetic material according to the present invention has high magnetic properties as well as an excellent temperature coefficient.

[0050] The above-described embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention. All modifications and improvements made within the scope of the technical concept of the present invention fall within the scope of protection of the present invention.

Claims

1. A Nd—Fe—B based sintered magnetic material, comprising: Re ２ Fe １４ the alloy includes a B main phase, a grain boundary phase containing Re, and a rare earth rich phase, the grain boundary phase including 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 grains, the rare earth rich phase is Re—O, Re—N, The Re relative to the total mass of the Nd—Fe—B based sintered magnetic material ２ Fe １４ a total mass ratio X of the B main phase, the first grain boundary phase, and the second grain boundary phase is 97%≦X<100%, the percentage of the area occupied by the first grain boundary phase in any cross section of the Nd—Fe—B based magnetic body is 6 to 15%, and the width of the second grain boundary phase is 2 to 20 nm; the sum of the masses of Ga and Cu in the first crystal grain boundary phase is 20 to 40% of the total mass of the first crystal grain boundary phase, the mass% of Fe in the first crystal grain boundary phase is 0 to 10%, the sum of the masses of Ga and Cu in the second crystal grain boundary phase is 40 to 70% of the total mass of the second crystal grain boundary phase, and the mass% of Fe in the second crystal grain boundary phase is 0 to 10%, The elements and their mass percentages in the Nd—Fe—B magnetic material are as follows: 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, Ga, and at least one of Co, Ti, Zr, V, Mo, and Nb; the percent by weight of Cu is greater than 0.45% and the percent by weight of Ga is less than 0.25%; The mass ratio Y of Cu and Ga is 1.8<Y≦10; The Nd-Fe-B based sintered magnetic material is characterized by the above.

2. A method for producing the Nd-Fe-B based sintered magnetic material according to claim 1, comprising: (Step 1) producing alloy flakes using a strip casting method according to the blending ratio of raw material elements, and the smelting step in the strip casting method is carried out in an argon gas atmosphere; (Step 2) subjecting the alloy flakes to hydrogen treatment and jet mill pulverization to produce alloy powder; (Step 3) The alloy powder is molded under a uniform magnetic field and cold isostatically pressed to form a magnetic body; (Step 4) Sintering the magnetic base material in a vacuum sintering furnace at a sintering temperature of 1030 to 1080°C for a treatment time of 6 to 10 hours, followed by aging treatment, the aging treatment being a two-stage tempering treatment, with a first tempering temperature of 800 to 900°C and a temperature-holding time of 3 to 5 hours, and a second tempering temperature of 460 to 520°C and a temperature-holding time of 1 to 6 hours; The heat-retaining step and the cooling step in the two-stage tempering treatment are both performed in an argon gas atmosphere, and the pressure of the argon gas atmosphere in the heat-retaining step is 0.02 to 0.05 MPa, and the pressure of the argon gas atmosphere in the cooling step is 0.06 to 0.08 MPa. A method for producing an Nd-Fe-B based sintered magnetic material.

3. The temperature of the smelting process in step 1 is 1400 to 1500 ° C.

3. The method for producing an Nd-Fe-B based sintered magnetic material according to claim 2.

4. The particle size of the alloy powder produced by the jet mill pulverization process in step 2 is 2.5 to 5.0 μm.

3. The method for producing an Nd-Fe-B based sintered magnetic material according to claim 2.

5. The magnetic field strength in step 3 is 1.5 to 2.0 T.

3. The method for producing an Nd-Fe-B based sintered magnetic material according to claim 2.

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