Sintered R-Fe-B permanent magnet and preparation method and application thereof

Abstract

The invention discloses a sintered R-Fe-B permanent magnet and a preparation method and application thereof, the component of the permanent magnet is ReaT1-a-b-cMbBc, a, b and c are mass fractions: Re is selected from at least one of Sm, La, Ce, Y, Nd, Pr, Ho, Gd, Dy and Tb; m is selected from at least one of Co, Ga, Cu, Al, Nb, Zr and Ti; 28 wt% < = a < = 35 wt%; 0.5 wt% < = b < = 5 wt%; 0.8 wt% < = c < = 1.2 wt%; and the balance of T and inevitable impurity elements. The Re-Fe-M-O phase is located at the triangular grain boundary and plays a pinning role, so that abnormal growth of grains in the heat treatment process is avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of rare earth permanent magnet material preparation, and in particular relates to a sintered Re-Fe-B permanent magnet and a preparation method and application thereof. Background Art

[0002] Permanent magnetic materials, also known as hard magnetic materials, are characterized by high anisotropy field, high coercive force, large hysteresis loop area, large magnetizing field required for magnetization to saturation, and can maintain strong magnetism for a long time after removing the external magnetic field. Among permanent magnetic materials, NdFeB sintered permanent magnets have more outstanding magnetic performance advantages than other permanent magnetic materials. For example, NdFeB sintered permanent magnets have higher magnetic energy product, coercive force and energy density, and have good mechanical properties and are easy to process. These excellent properties have made sintered NdFeB permanent magnets widely used in modern industry and electronic technology, and the more common ones are motors, speakers, magnetic separators, computer disk drives, magnetic resonance imaging equipment, etc.

[0003] The grain size in the magnet becomes smaller and more uniform, which is conducive to the formation of a homogeneous main phase and a continuous grain boundary phase. On this basis, a magnet with high coercive force and high remanence can be obtained through diffusion;

[0004] However, the preparation of magnets in the prior art has problems such as high equipment requirements, long process cycle, and low production efficiency. Therefore, how to effectively improve the coercive force of rare earth magnets, shorten the process cycle and improve production efficiency under conventional production processes is still a problem to be solved urgently. Summary of the invention

[0005] In order to improve the above technical problems, the present invention provides a sintered Re-TB permanent magnet, the composition of the permanent magnet is Re a T 1-a-b-c M b B c , where a, b, c are mass fractions:

[0006] Re is selected from at least one of Sm, La, Ce, Y, Nd, Pr, Ho, Gd, Dy, and Tb;

[0007] M is selected from at least one of Co, Ga, Cu, Al, Nb, Zr and Ti;

[0008] 28wt%≤a≤35wt%;

[0009] 0.5wt%≤b≤5wt%;

[0010] 0.8wt%≤c≤1.2wt%;

[0011] Wherein T is Fe and unavoidable impurity elements.

[0012] According to an embodiment of the present invention, in the permanent magnet, 29wt%≤a≤33wt%, for example, a is 29%, 29.5%, 30%, 30.5%, 31.0%, 31.5%, 32.0%, or 32.5%.

[0013] According to an embodiment of the present invention, in the permanent magnet, 1wt%≤b≤4wt%, for example, b is 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5% or 4.0%.

[0014] According to an embodiment of the present invention, in the permanent magnet, 0.9wt%≤c≤1.05%, preferably, 0.92wt%<c<1.05%; for example, c is 0.9%, 0.95%, 0.98%, 1.00% or 1.05%.

[0015] According to an embodiment of the present invention, the permanent magnet includes a main phase and a grain boundary phase; in the permanent magnet, the grain boundary phase composed of three or more main phase grain gaps is called a triangular grain boundary phase, and the triangular grain boundary phase includes a Re-Fe-MO phase; in the triangular grain boundary phase, the Re-Fe-MO phase accounts for 3-10wt%, and more preferably, the Re-Fe-MO phase accounts for 6%-10%.

[0016] According to an embodiment of the present invention, the main phase is Re x T 1-x-y-z M y B z , where x, y, and z correspond to the mass percentage content;

[0017] 28wt%≤x≤35wt%;

[0018] 0.5wt%≤y≤5wt%;

[0019] 0.8wt%≤z≤1.2wt%;

[0020] Wherein T is Fe and unavoidable impurity elements.

[0021] According to an embodiment of the present invention, in the main phase, 29wt%≤x≤33wt%, for example, x is 29%, 29.5%, 30%, 30.5%, 31.0%, 31.5%, 32.0%, or 32.5%.

[0022] According to an embodiment of the present invention, in the main phase, 1wt%≤y≤4wt%, for example, y is 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5% or 4.0%.

[0023] According to an embodiment of the present invention, in the main phase, 0.9wt%≤z≤1.05%, preferably, 0.92wt%<z<1.05%; for example, z is 0.9%, 0.95%, 0.98%, 1.00% or 1.05%.

[0024] According to an embodiment of the present invention, the grain boundary phase is Re m T 1-m-n M n , where m and n correspond to the mass percentage:

[0025] 30wt%≤m≤60wt%;

[0026] 0.55wt%≤n≤35wt%;

[0027] Wherein T is Fe and unavoidable impurity elements.

[0028] According to an embodiment of the present invention, in the grain boundary phase, 35wt%≤m≤55wt%, for example, m is 35wt%, 40wt%, 45wt%, 50wt% or 55wt%.

[0029] According to an embodiment of the present invention, in the grain boundary phase, 10 wt % ≤ n ≤ 33 wt %; for example, n is 10 wt %, 15 wt %, 20 wt %, 25 wt %, 30 wt % or 33 wt %.

[0030] The present invention also provides a method for preparing the sintered Re-Fe-B permanent magnet, the method comprising the following steps:

[0031] (1) Preparation of quick-setting thin sheets;

[0032] (2) Hydrogen embrittlement treatment: The quick-solidified thin slice in step (1) is subjected to hydrogen absorption and dehydrogenation treatment to obtain alloy hydrogen embrittlement powder;

[0033] (3) Primary coarse grinding: under the protection of inert gas, the alloy hydrogen embrittled powder is added to the air flow mill for the first coarse grinding to prepare the alloy coarse powder;

[0034] (4) Coarse powder stirring and oxygenation: In an inert gas environment, the alloy coarse powder is sheared and stirred, and oxygen-containing gas is added during the stirring process;

[0035] (5) Secondary grinding: under the protection of inert gas, the powder in step (4) is added to a jet mill for secondary grinding to obtain jet mill powder;

[0036] (6) subjecting the jet milled powder in step (5) to shear stirring again under the protection of an inert gas;

[0037] (7) The powder in step (6) is molded into a molded body, and the molded body is heat treated to obtain the permanent magnet.

[0038] Specifically, the preparation method comprises the following steps:

[0039] (1a) Preparation of quick-setting thin sheets: According to Re a T 1-a-b-c M b B c The mass percentage of each element is used to prepare the alloy rapid solidification sheet; Re a T 1-a-b-c M b B c In the equation, a, b, and c are mass fractions:

[0040] 28wt%≤a≤35wt%; 0.5wt%≤b≤5wt%; 0.8wt%≤c≤1.2wt%;

[0041] (2a) Hydrogen embrittlement treatment: The alloy quick-solidified thin sheet in step (1a) is subjected to hydrogen absorption and dehydrogenation treatment to obtain alloy hydrogen embrittlement powder;

[0042] (3a) Primary coarse grinding: under the protection of inert gas, the alloy hydrogen embrittled powder is added into the air flow mill for the first coarse grinding to prepare the alloy coarse powder;

[0043] (4a) Coarse powder stirring and oxygenation: In an inert gas environment, the alloy coarse powder is sheared and stirred, and oxygen-containing gas is added during the stirring process;

[0044] (5) Secondary grinding: under the protection of inert gas, the powder in step (4a) is added to a jet mill for secondary grinding to obtain jet mill powder;

[0045] (6) subjecting the jet milled powder in step (5) to shear stirring again under the protection of an inert gas;

[0046] (7) forming the powder in step (6) into a formed body, and then heat treating the formed body to obtain the permanent magnet;

[0047] Or adopt the preparation method of double alloy, the method is:

[0048] (1b) Preparation of quick-setting thin sheets: According to Re 1 x T 1-x-y-z M y B z The mass percentage of each element in the main alloy is used to prepare the main alloy quick-solidification sheet;

[0049] and according to Re 2 m T 1-m-n Mn The mass percentage of each element in the auxiliary alloy is used to prepare the quick-solidified thin sheet;

[0050] Re 1 x T 1-x-y-z M y B z In 1 At least one or more selected from Sm, La, Ce, Y, Nd, Pr, 28wt%≤x≤35wt%; 0.5wt%≤y≤5wt%; 0.8wt%≤z≤1.2wt%;

[0051] Re 2 m T 1-m-n M n In the equation, m and n correspond to the mass percentages:

[0052] Re 2 At least one or more selected from Dy, Tb, Ho, Gd, 30wt%≤m≤60wt%;

[0053] 0.5wt%≤n≤35wt%;

[0054] (2b) Hydrogen embrittlement treatment: subjecting the main alloy quick-solidified sheet and the auxiliary alloy quick-solidified sheet in step (1b) to hydrogen absorption and dehydrogenation treatment, respectively, to obtain main alloy hydrogen embrittled powder and auxiliary alloy hydrogen embrittled powder;

[0055] (3b) Primary coarse grinding: under the protection of inert gas, the main alloy hydrogen embrittled powder and the auxiliary alloy hydrogen embrittled powder are respectively added into the air flow mill for the first coarse grinding to prepare the main alloy coarse powder and the auxiliary alloy coarse powder;

[0056] (4b) Coarse powder stirring and oxygenation: In an inert gas environment, the main alloy coarse powder and the auxiliary alloy coarse powder are mixed in proportion and sheared and stirred, and oxygen-containing gas is added during the stirring process;

[0057] (5) Secondary grinding: under the protection of inert gas, the powder mixed in step (4b) is added to a jet mill for secondary grinding to obtain jet mill powder;

[0058] (6) subjecting the jet milled powder in step (5) to shear stirring again under the protection of an inert gas;

[0059] (7) forming a molded body by jet milling the powder in step (6), and then heat treating the molded body to obtain the permanent magnet.

[0060] According to an embodiment of the present invention, step (1a) may also be:

[0061] According to Re a T1-a-b-c M b B c The raw materials 1 and 2 are prepared according to the mass percentage of each element, and the raw materials 1 and 2 are respectively prepared into alloy quick-setting thin sheets 1 and alloy quick-setting thin sheets 2; the content of each element in the raw materials 1 and the raw materials 2 can be the same or different.

[0062] Preferably, the addition ratio of raw material 1 to raw material 2 is 90-99%:10-1%.

[0063] For example, raw material 1 is 22.27% Nd, 6.78% Pr, 0.46% Dy, 0.22% Cu, 0.40% Ga, 2.17% Co, 0.33% Al, 0.17% Ti and 1.11% B;

[0064] Raw material 2 is 24.4% Nd, 6.1% Pr, 0.2% Dy, 0.52% Cu, 0.17% Ga, 1.3% Co, 0.07% Al, 0.12% Ti and 1% B.

[0065] According to the embodiment of the present invention, in step (1a), the method for preparing the alloy rapid solidification sheet can be prepared by the alloy rapid solidification sheet process known in the art.

[0066] According to the embodiment of the present invention, in step (1b), the preparation methods of the main alloy rapid solidification sheet and the auxiliary alloy rapid solidification sheet can be prepared by alloy rapid solidification sheet processes known in the art.

[0067] Preferably, the alloy quick-setting sheet process may include the steps of melting, molten metal, heat preservation and pouring, cooling, etc. Preferably, the alloy quick-setting sheet process is carried out in a vacuum melting furnace. Preferably, the heat preservation temperature is 1350-1500°C and the heat preservation time is 8-20min.

[0068] Also preferably, in step (1b), according to Re 1 x T 1-x-y-z M y B z Weigh each raw material according to the mass percentage of each element, and grind each raw material to remove surface oxide scale and oil stain;

[0069] According to Re 2 m T 1-m-n M n Weigh each raw material according to the mass percentage of each element and grind it to remove surface oxide scale and oil stains.

[0070] According to an embodiment of the present invention, in step (1a), the thickness of the alloy rapid solidification sheet is 0.15-0.45 mm.

[0071] According to an embodiment of the present invention, in step (1b), the thickness of the main alloy quick-solidified sheet is 0.15-0.45 mm;

[0072] The thickness of the auxiliary alloy quick-solidified sheet is 0.15-0.45mm.

[0073] According to an embodiment of the present invention, in step (2a) or step (2b), hydrogen absorption and dehydrogenation are carried out in a rotary hydrogen embrittlement furnace.

[0074] According to an embodiment of the present invention, in step (2a) or step (2b), the dehydrogenation temperature is 450-650°C.

[0075] According to an embodiment of the present invention, in step (2a), the maximum size of the alloy hydrogen embrittlement powder is 1-3 mm.

[0076] According to an embodiment of the present invention, in step (2b), the maximum size of the main alloy hydrogen embrittlement powder is 1-3 mm;

[0077] The maximum size of auxiliary alloy hydrogen embrittlement powder is 1-3mm.

[0078] According to an embodiment of the present invention, in step (3a), the average particle size of the alloy coarse powder is 100-300 μm.

[0079] According to an embodiment of the present invention, in step (3b), the average particle size of the main alloy coarse powder is 100-300 μm; the average particle size of the auxiliary alloy coarse powder is 30-50 μm, for example, 30 μm, 35 μm, 40 μm, 45 μm or 50 μm.

[0080] According to an embodiment of the present invention, in step (4b), the mass ratio of the main alloy coarse powder to the auxiliary alloy coarse powder is (96-99):(4-1).

[0081] According to an embodiment of the present invention, in step (4a) and step (4b), the shear stirring is performed in a stirring device containing a stirring pear, and the stirring time is 10-20 hours. In the present invention, the structure and shape of the stirring device are not particularly limited, as long as the friction between the main alloy coarse powder and the auxiliary alloy coarse powder and the friction between the coarse powder and the stirring pear or the silo wall of the stirring device can be achieved.

[0082] According to an embodiment of the present invention, in step (4a) and step (4b), the stirring speed of the shear stirring is 10 rpm-360 rpm.

[0083] According to an embodiment of the present invention, in step (4a) and step (4b), the pressure of the added oxygen-containing gas is 0.2-0.5 MPa, for example, 0.2 MPa, 0.3 MPa, 0.4 MPa or 0.5 MPa. Preferably, the oxygen-containing gas is, for example, oxygen or compressed air.

[0084] Preferably, during the stirring process, oxygen-containing gas is charged into the stirring device, and the oxygen-containing gas is fed in an intermittent manner. For example, each charging process lasts for 2-3 seconds, and the charging interval is 8-10 seconds.

[0085] According to an embodiment of the present invention, in step (4a) and step (4b), the oxygen content during stirring is 10-100 ppm; for example, 10 ppm, 20 ppm, 30 ppm, 40 ppm, 50 ppm, 60 ppm, 70 ppm, 80 ppm, 90 ppm or 100 ppm.

[0086] According to an embodiment of the present invention, in step (4a) and step (4b), a lubricant may be added during the coarse grinding and stirring process. Preferably, the content of the lubricant in the mixture is 0.1-0.5wt%, and the stirring and mixing time after adding the lubricant is 3-10h. Preferably, the lubricant is selected from known reagents in the prior art to achieve sufficient mixing of the powder and easy molding.

[0087] According to an embodiment of the present invention, in step (5), the particle size of the jet milled powder is 2-5 μm; for example, 2 μm, 3 μm, 4 μm or 5 μm.

[0088] According to an embodiment of the present invention, in step (6), the stirring speed of the shear stirring is 10 rpm-360 rpm.

[0089] According to an embodiment of the present invention, in step (7), the shaping step can be performed using methods known in the art.

[0090] According to an embodiment of the present invention, in step (7), in the molding step, the mixture can be dry molded: for example, the mixture is filled into a mold configured in a magnetic field and pressurized to mold the mixture to obtain a molded body. At this time, by molding while applying a magnetic field, the mixture can be molded in a state where the crystal axis is oriented in a specific direction. The applied magnetic field can be a static magnetic field and / or a pulsed magnetic field, and the magnetic field strength is 1.5-2.5T. Alternatively, wet molding can also be used: the mixture is dispersed in a slurry in a solvent such as oil for molding.

[0091] According to an embodiment of the present invention, step (7) is performed under the protection of an inert gas. Preferably, after the molding is completed, the mold is demolded and cold isostatic pressing is performed at a pressure of 150-200 MPa to obtain a green body.

[0092] According to an embodiment of the present invention, in step (7), the heat treatment temperature is 950-1350°C, preferably 1000-1150°C; the heat treatment time is 200-500min, preferably 300-500min. Preferably, after the heat treatment is completed, the blank can be cooled by argon cooling or air cooling to obtain a permanent magnet.

[0093] The present invention also provides the application of the above-mentioned sintered Re-Fe-B permanent magnet in the fields of motors, speakers, magnetic separators, computer disk drives, magnetic resonance imaging equipment, etc., preferably as motor rotor magnetic steel in motors.

[0094] Beneficial effects of the present invention:

[0095] (1) In the process of preparing permanent magnets, the present invention uses a high-speed shear stirring method with a stirring pear to make the alloy coarse powder be subjected to its own impact force during the stirring process, and also to strong shear force, pressure, and friction between the stirring pear blade and the inner wall of the mixer, thereby reducing the sharp areas on the powder surface and spheroidizing the powder, so that the magnet grains become more round. At the same time, during the shear stirring process, pulsed (or intermittent) oxygenation is added to controllably oxidize the alloy coarse powder to form a Re-Fe-MO phase, and after secondary grinding and shear stirring again, the Re-Fe-MO phase is peeled off from the surface of the powder and distributed at the triangular grain boundaries; at the same time, the Re-Fe-MO phase plays a pinning role at the triangular grain boundaries, so that abnormal grain growth is avoided during the heat treatment process.

[0096] (2) The present invention obtains a sintered Re-Fe-B permanent magnet with a rich grain boundary phase in its microstructure by controlling the different ratios of the main alloy and the auxiliary alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0097] Figure 1 It is a diagram of the stirring device of embodiments 1, 2, 3, 4 and 5.

[0098] Figure 2 This is a diagram of the stirring device of Example 6.

[0099] Figure 3 It is the stirring device diagram of comparative examples 1, 2 and 3.

[0100] Figure 4 It is a schematic diagram of Re-Fe-MO phase exfoliation and distribution.

[0101] Figure 5 This is a TEM image of the magnet of Example 1. DETAILED DESCRIPTION

[0102] The technical scheme of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only exemplary descriptions and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are included in the scope that the present invention is intended to protect.

[0103] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0104] Example 1

[0105] A method for preparing a sintered Re-Fe-B permanent magnet, comprising the following steps:

[0106] (1) The materials are prepared according to the composition ratio of the main alloy 1 and the auxiliary alloy 1 in Table 1, and the prepared materials are respectively induction heated to 1500° C. in a vacuum melting furnace and kept warm for 10 min, and then fully electromagnetically stirred, and then poured on the surface of a quenching roller, and after cooling, the main alloy quick-solidified thin sheet and the auxiliary alloy quick-solidified thin sheet are recovered;

[0107] (2) taking the two quick-solidified thin sheets of step (1) and subjecting them to hydrogen absorption-dehydrogenation treatment respectively, and subjecting them to dehydrogenation treatment at 630° C., respectively, to obtain alloy coarse powders; then subjecting them to air jet milling for one coarse grinding, to obtain a main alloy coarse powder of 300 μm and an auxiliary alloy coarse powder of 30 μm;

[0108] (3) Take the two-phase alloy coarse powder of step (2), place it in a mixer in a mass ratio of main alloy coarse powder to auxiliary alloy coarse powder of 99:1, and perform uninterrupted shear stirring with the help of a stirring plow (stirring plow (or stirring device) such as Figure 1 ), the speed of shear stirring is 250rpm, the duration is 10-20h, during which pulse aeration (compressed air) is carried out through the pipeline, the pulse gas pressure is 0.3MPa, the aeration process lasts for 2s, the aeration interval is 10s, and the oxygen content in the silo is controlled at 80ppm;

[0109] (4) grinding the jet mill powder obtained in step (3) by jet milling for a second time to control the particle size to 4 μm;

[0110] (5) subjecting the powder obtained in step (4) to shear stirring again at a stirring speed of 250 rpm;

[0111] (6) filling the magnetic powder of step (5) into a vacuum press mold, pressing and molding the magnetic powder under a magnetic field strength of 2T, and obtaining a green compact after cold isostatic pressing at a pressure of 150 MPa;

[0112] (7) Placing the pressed green sheet in a vacuum sintering furnace for vacuum heat treatment, wherein the high temperature sintering temperature is 1040° C. and the sintering time is 450 min. After the high temperature sintering is completed, the green sheet can be cooled by argon cooling or air cooling to obtain a permanent magnet.

[0113] Table 1: Alloy composition and addition ratio

[0114]

[0115]

[0116] Table 2: Alloy preparation process

[0117]

[0118]

[0119] In Table 2, the particle size refers to the particle size of the coarse powder after the first coarse grinding in step (2).

[0120] "Pears stirred with paddles" means using Figure 1 The stirring device shown;

[0121] "Pears stirred without a paddle" means stirring the pears with a paddle. Figure 2 The stirring device shown.

[0122] In Table 2, “triangular grain boundary distribution” means that the R-Fe-MO phase is distributed in the triangular grain boundary region; “along grain boundary distribution” means that the R-Fe-MO phase is distributed in the grain boundary region other than the triangular grain boundary, such as the two-grain grain boundary.

[0123] Example 2

[0124] (1a) Preparation of rapid solidification thin sheets: single alloy rapid solidification thin sheets were prepared according to the mass percentage of each element in Table 1;

[0125] (2a) Hydrogen embrittlement treatment: subjecting the single alloy quick-solidified thin slice in step (1a) to hydrogen absorption and dehydrogenation treatment to obtain alloy hydrogen embrittled powder;

[0126] (3a) Primary coarse grinding: under the protection of inert gas, the alloy hydrogen embrittled powder is added into the air flow mill for the first coarse grinding to prepare the alloy coarse powder;

[0127] (4a) Coarse powder stirring and oxygenation: In an inert gas environment, the alloy coarse powder is continuously sheared and stirred by means of a stirring plow (or stirring device) such as Figure 1 ), the speed of shear stirring is 250rpm, the duration is 10-20h, during which pulse aeration (compressed air) is carried out through the pipeline, the pulse gas pressure is 0.3MPa, the aeration process lasts for 2s, the aeration interval is 10s, and the oxygen content in the silo is controlled at 80ppm;

[0128] (5) Secondary grinding: Same as Example 1

[0129] (6) subjecting the jet milled powder in step (5) to shear stirring again under the protection of an inert gas;

[0130] (7) Heat treatment: The permanent magnet is obtained in the same manner as in Example 1.

[0131] Example 3

[0132] The raw materials are weighed and mixed according to the ratio of alloy phase 1 and alloy phase 2 in Example 3 in Table 1, and the preparation process is the same as that in Example 1, except that alloy phase 1 and alloy phase 2 are different from those in Example 1;

[0133] Example 4

[0134] The difference between Example 4 and Example 1 is that: in step (2), the particle size of the coarse powder of the main alloy 1 is 300 μm, and the particle size of the coarse powder of the auxiliary alloy 2 is 40 μm;

[0135] Example 5

[0136] The difference between Example 5 and Example 1 is that in step (2), the particle size of the main alloy 1 powder is 300 μm, and the particle size of the auxiliary alloy 3 powder is 50 μm;

[0137] Example 6

[0138] The difference between Example 6 and Example 1 is that in step (3), a stirring pear without a blade is used to shear and stir the mixture. The schematic diagram of the stirring pear is shown in the attached figure. Figure 2 shown.

[0139] Comparative Example 1

[0140] The difference between Comparative Example 1 and Example 1 is that:

[0141] Step (3) uses Figure 3 The three-dimensional mixer shown is used for mixing, and in step (4), air flow milling and oxygenation are performed, the pulse gas pressure is 0.3 MPa, the aeration process lasts for 2 seconds, the aeration interval is 10 seconds, and the oxygen content in the silo is controlled at 80 ppm;

[0142] Comparative Example 2

[0143] The difference between Comparative Example 2 and Example 2 is:

[0144] Step (3) uses Figure 3 The three-dimensional mixer shown is used for mixing, and in step (4), air flow milling and oxygenation are performed, the pulse gas pressure is 0.3 MPa, the aeration process lasts for 2 seconds, the aeration interval is 10 seconds, and the oxygen content in the silo is controlled at 80 ppm;

[0145] Comparative Example 3

[0146] The difference between Comparative Example 3 and Example 3 is that:

[0147] Step (3) uses Figure 3 The three-dimensional mixer shown is used for mixing, and in step (4), air flow milling and oxygenation are performed, the pulse gas pressure is 0.3 MPa, the aeration process lasts for 2 seconds, the aeration interval is 10 seconds, and the oxygen content in the silo is controlled at 80 ppm;

[0148] Figure 5 The magnet TEM image of Example 1 is shown in FIG. Figure 5 It can be seen that the Re-Fe-MO phase is mainly distributed in the triangular grain boundary phase and is evenly distributed.

[0149] The test performances of Examples 1-6 and Comparative Examples 1-3 are shown in Table 3:

[0150] Table 3: Test performance of R-Fe-B permanent magnet

[0151] Br / kGs HkDJ (BH)max / MGO Hk / Hcj Example 1 13.84 19.66 46.5 0.983 Example 2 14.01 18.21 47.2 0.981 Example 3 13.33 17.92 43.1 0.98 Example 4 13.9 18.88 46.9 0.97 Example 5 14.11 17.95 48.3 0.975 Example 6 14.03 18.62 47.8 0.981 Comparative Example 1 13.97 18.53 47.4 0.98 Comparative Example 2 14.05 17.96 47.9 0.98 Comparative Example 3 13.93 17.32 47.1 0.97

[0152] From Table 3 above, we can see that:

[0153] The overall performance of the magnet prepared by the shear stirring and stirring process oxygenation process of the present invention is higher than that of the magnet prepared by the prior art device. The performance is preferably the best when the main alloy and the auxiliary alloy are mixed and then shear stirring and oxygenation are performed.

[0154] The above is an exemplary description of the embodiments of the present invention. However, the protection scope of the present invention is not limited to the above embodiments. Any modification, equivalent substitution, improvement, etc. made by those skilled in the art within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A sintered Re-Fe-B permanent magnet, characterized in that: The composition of the permanent magnet is Re a T 1-a-b-c M b B c , where a, b, c are mass fractions: Re is selected from at least one of Sm, La, Ce, Y, Nd, Pr, Ho, Gd, Dy, and Tb; M is selected from at least one of Co, Ga, Cu, Al, Nb, Zr and Ti; 28wt%≤a≤35wt%; 0.5wt%≤b≤5wt%; 0.8wt%≤c≤1.2wt%; Wherein T is Fe and inevitable impurity elements.

2. The permanent magnet according to claim 1, characterized in that The permanent magnet includes a main phase and a grain boundary phase; in the permanent magnet, the grain boundary phase composed of three or more main phase grain gaps is called a triangular grain boundary phase, and the triangular grain boundary phase includes a Re-Fe-MO phase; in the triangular grain boundary phase, the Re-Fe-MO phase accounts for 3-10wt%.

3. The permanent magnet according to claim 1, characterized in that The main phase is Re x T 1-x-y-z M y B z , where x, y, and z correspond to the mass percentage content; 28wt%≤x≤35wt%; 0.5wt%≤y≤5wt%; 0.8wt%≤z≤1.2wt%; Wherein T is Fe and unavoidable impurity elements.

4. The permanent magnet according to claim 1, characterized in that The grain boundary phase is Re m T 1-m-n M n , where m and n correspond to the mass percentage: 30wt%≤m≤60wt%; 0.5wt%≤n≤35wt%; Wherein T is Fe and unavoidable impurity elements.

5. The method for preparing a permanent magnet according to any one of claims 1 to 4, characterized in that: The preparation method comprises the following steps: (1) Preparation of quick-setting thin sheets; (2) Hydrogen embrittlement treatment: The quick-solidified thin slice in step (1) is subjected to hydrogen absorption and dehydrogenation treatment to obtain alloy hydrogen embrittlement powder; (3) Primary coarse grinding: under the protection of inert gas, the alloy hydrogen embrittled powder is added to the air flow mill for the first coarse grinding to prepare the alloy coarse powder; (4) Coarse powder stirring and oxygenation: In an inert gas environment, the alloy coarse powder is sheared and stirred, and oxygen-containing gas is added during the stirring process; (5) secondary grinding: under the protection of inert gas, adding the powder in step (4) to a jet mill for secondary grinding to obtain jet mill powder; (6) subjecting the jet milled powder in step (5) to shear stirring again under the protection of an inert gas; (7) The powder in step (6) is molded into a molded body, and the molded body is heat treated to obtain the permanent magnet.

6. The method according to claim 5, wherein the preparation method comprises the following steps: (1a) Preparation of quick-setting thin sheets: According to Re a T 1-a-b-c M b B c The mass percentage of each element is used to prepare the alloy rapid solidification sheet; Re a T 1-a-b-c M b B c In the equation, a, b, and c are mass fractions: 28wt%≤a≤35wt%; 0.5wt%≤b≤5wt%; 0.8wt%≤c≤1.2wt%; (2a) Hydrogen embrittlement treatment: The alloy quick-solidified thin sheet in step (1a) is subjected to hydrogen absorption and dehydrogenation treatment to obtain alloy hydrogen embrittlement powder; (3a) Primary coarse grinding: under the protection of inert gas, the alloy hydrogen embrittled powder is added into the air flow mill for the first coarse grinding to prepare the alloy coarse powder; (4a) Coarse powder stirring and oxygenation: In an inert gas environment, the alloy coarse powder is sheared and stirred, and oxygen-containing gas is added during the stirring process; (5) Secondary grinding: under the protection of inert gas, the powder in step (4a) is added to a jet mill for secondary grinding to obtain jet mill powder; (6) subjecting the jet milled powder in step (5) to shear stirring again under the protection of an inert gas; (7) forming the powder in step (6) into a formed body, and then heat treating the formed body to obtain the permanent magnet; Or adopt the preparation method of double alloy, the method is: (1b) Preparation of quick-setting thin sheets: According to Re 1 x T 1-x-y-z M y B z The mass percentage of each element in the main alloy is used to prepare the main alloy quick-solidification sheet; and according to Re 2 m T 1-m-n M n The mass percentage of each element in the auxiliary alloy is used to prepare the quick-solidified thin sheet; Re 1 x T 1-x-y-z M y B z wherein Re1 is selected from at least one or more of Sm, La, Ce, Y, Nd, Pr, 28wt%≤x≤35wt%; 0.5wt%≤y≤5wt%; 0.8wt%≤z≤1.2wt%; Re 2 m T 1-m-n M n In the equation, m and n correspond to the mass percentages: Re 2 At least one or more selected from Dy, Tb, Ho, Gd, 30wt%≤m≤60wt%; 0.5wt%≤n≤35wt%; (2b) Hydrogen embrittlement treatment: subjecting the main alloy quick-solidified sheet and the auxiliary alloy quick-solidified sheet in step (1b) to hydrogen absorption and dehydrogenation treatment, respectively, to obtain main alloy hydrogen embrittled powder and auxiliary alloy hydrogen embrittled powder; (3b) Primary coarse grinding: under the protection of inert gas, the main alloy hydrogen embrittled powder and the auxiliary alloy hydrogen embrittled powder are respectively added into the air flow mill for the first coarse grinding to prepare the main alloy coarse powder and the auxiliary alloy coarse powder; (4b) Coarse powder stirring and oxygenation: In an inert gas environment, the main alloy coarse powder and the auxiliary alloy coarse powder are mixed in proportion and sheared and stirred, and oxygen-containing gas is added during the stirring process; (5) Secondary grinding: under the protection of inert gas, the powder mixed in step (4b) is added to a jet mill for secondary grinding to obtain jet mill powder; (6) subjecting the jet milled powder in step (5) to shear stirring again under the protection of an inert gas; (7) forming a molded body by jet milling the powder in step (6), and then heat treating the molded body to obtain the permanent magnet.

7. The method according to claim 6, wherein in step (3a), the average particle size of the alloy coarse powder is 100-300 μm. Preferably, in step (3b), the average particle size of the main alloy coarse powder is 100-300 μm; and the average particle size of the auxiliary alloy coarse powder is 30-50 μm.

8. The method according to claim 6, wherein in step (4b), the mass ratio of the main alloy coarse powder to the auxiliary alloy coarse powder is (96-99):(4-1). Preferably, in step (4a) and step (4b), the shear stirring is carried out in a stirring device containing a stirring pear, and the stirring time is 10-20 hours. Preferably, in step (4a) or step (4b), the pressure of the added oxygen-containing gas is 0.2-0.5 MPa. Preferably, the oxygen-containing gas is oxygen or compressed air. Preferably, in step (4a) and step (4b), the oxygen content during stirring is 10-100 ppm.

9. The method according to claim 6, wherein in step (5), the particle size of the jet milled powder is 2-5 μm; Preferably, in step (6), the stirring speed of the shear stirring is 10 rpm-360 rpm. Preferably, in step (7), the heat treatment temperature is 950-1350° C., and the heat treatment time is 200-500 min.

10. Application of the permanent magnet according to any one of claims 1 to 4 in the fields of motors, loudspeakers, magnetic separators, computer disk drives, magnetic resonance imaging equipment, etc.

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