Preparation method of rare earth permanent magnet with low magnetic declination

Abstract

The invention discloses a preparation method of a low-magnetic-declination rare earth permanent magnet. The preparation method comprises the following steps: S1, blank preparation: preparing a Re-Fe-B rare earth magnet square blank through processes such as rapid hardening, powder preparation, orientation molding, vacuum sintering and the like; s2, a polished blank is prepared, specifically, six faces of the square blank are ground to be flat, and a magnet polished blank is prepared; s3, magnetizing: magnetizing the magnet polished blank along the orientation direction; s4, marking a basic surface: measuring a magnetic declination angle, and marking efgh as the basic surface which is perpendicular to the magnetic moment M; s5, tempering is conducted; s6, preparing a black wafer, namely preparing the black wafer through machining by taking the marked efgh basic surface as a benchmark; and S7, paillette preparation: carrying out surface treatment on the black piece finished product to obtain a paillette finished product. According to the preparation method of the rare earth permanent magnet with the low magnetic declination angle, the basic surface is marked on the magnetized magnet polished blank, the basic surface efgh is perpendicular to the magnetic moment M, after the magnet polished blank is tempered, follow-up machining is carried out with the marked basic surface as the reference, and the problem that the magnetic declination angle is enlarged due to the fact that no reference surface exists for follow-up machining is solved.

Description

Technical Field

[0001] This invention relates to a method for preparing a rare-earth permanent magnet with low magnetic declination. Background Technology

[0002] Re-Fe-B rare earth permanent magnets are the strongest permanent magnet materials with the strongest comprehensive magnetic properties discovered to date. They are widely used in fields such as 3C electronics, new energy vehicles, wind power generation, industrial motors, drones, humanoid robots, and aerospace, playing an irreplaceable role in information technology and intelligent manufacturing.

[0003] Magnetic declination is the angle between the magnetic moment and the magnetizing field, directly affecting the performance and application of magnetic products. The presence of magnetic declination causes stray fields to be generated in the unmagnetized direction of the magnet, affecting the precision of the sensor. A large magnetic declination will increase the vibration and noise of the permanent magnet motor, leading to a decrease in motor efficiency and accuracy.

[0004] High-performance Re-Fe-B rare earth permanent magnet materials are generally prepared using a vacuum sintering process. The specific steps are: 1. Preparing powder using a rapid solidification-hydrogen-airflow milling process; 2. Pressing the powder into a compact with a uniform orientation using an orientation molding technique; 3. Obtaining anisotropic magnet blanks through vacuum sintering and tempering heat treatment; 4. Machining and surface protection treatment of the blanks to obtain the shape and size required for the application; 5. Assembling and using the magnets after saturation magnetization. During manufacturing, the non-uniformity of the orientation magnetic field and the dimensional shrinkage of the magnets during sintering cause magnetic declination. Since an accurate reference surface cannot be found, improper machining may further amplify the magnetic declination. With industrial development and technological progress, magnetic devices are developing towards higher precision, miniaturization, and intelligence, placing higher demands on the consistency of the output magnetic field of NdFeB rare earth materials. Therefore, developing low magnetic declination magnets and their preparation technology has broad practical significance. Summary of the Invention

[0005] This invention provides a method for preparing a rare-earth permanent magnet with low magnetic declination.

[0006] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0007] A method for preparing a low magnetic declination rare-earth permanent magnet includes the following steps:

[0008] S1. Blank preparation: Re-Fe-B rare earth magnet square blanks are prepared by processes such as rapid solidification, powder making, orientation molding, and vacuum sintering.

[0009] S2. Blank preparation: Grind the six sides of the square blank flat to make a magnet blank;

[0010] S3. Magnetization: Magnetize the magnet blank along the orientation direction;

[0011] S4. Mark the fundamental plane: Measure the magnetic declination and mark efgh as the fundamental plane, which is perpendicular to the magnetic moment M;

[0012] S5, Tempering;

[0013] S6. Black film preparation: Based on the marked efgh fundamental plane, a black film is prepared by machining.

[0014] S7. Glitter preparation: Surface treatment is performed on the black sheet product to obtain the glitter product.

[0015] Preferably, in step S1, Re is at least one element selected from La, Ce, Pr, Nd, Gd, Tb, Dy, Ho, and Y.

[0016] Preferably, in step S1, the orientation forming magnetic field strength is greater than or equal to 2.0T.

[0017] Preferably, in step S1, the compression density is 3.5~4.0 g / cm³. 3 .

[0018] Preferably, in step S1, the vacuum sintering temperature is 1020~1100℃ and the time is 2~10 hours.

[0019] Preferably, in step S3, the magnetization state can be either saturated magnetization or unsaturated magnetization.

[0020] Preferably, in step S4, the magnetic declination is measured using a Vihermholz coil.

[0021] Preferably, in step S5, a two-stage tempering process is used.

[0022] Preferably, in step S5, a three-stage tempering process is used; the temperature of the third-stage tempering is higher than that of the second-stage tempering.

[0023] Preferably, in step S6, using the marked efgh fundamental plane as a reference, the orientation direction a 1 b 1 c 1 d 1 upper end face and a 2 b 2 c 2 d 2 The lower end face is cut into a plane parallel to the basic plane of efgh, and then further machined.

[0024] Compared with existing technologies, the method for preparing low magnetic declination rare earth permanent magnets of the present invention marks a basic surface on the magnet blank after magnetization. The basic surface efgh is perpendicular to the magnetic moment M. After the magnet blank is tempered, the marked basic surface is used as a reference for subsequent processing, which prevents the problem of amplified magnetic declination due to the lack of a reference surface in subsequent processing. Experimental data show that the low magnetic declination Re-Fe-B rare earth magnets prepared by the present invention have a magnetic declination that is significantly lower than that of magnets prepared by traditional processes, and all are within 1°. They can be better applied in high-precision, miniaturized and intelligent fields. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the reference plane for the preparation method of the low magnetic declination rare-earth permanent magnet of the present invention. Reference numerals: M represents the magnetic moment, plane efgh represents the fundamental plane, and plane a... 1 b 1 c 1 d 1 Let plane a be the upper end face along the direction of the magnetic moment. 2 b 2 c 2 d 2 This refers to the lower end face along the direction of the magnetic moment. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0027] A method for preparing a low magnetic declination rare-earth permanent magnet, the specific steps of which are as follows:

[0028] S1. Blank preparation: Re-Fe-B rare earth magnet square blanks are prepared by processes such as rapid solidification, powder making, orientation molding, and vacuum sintering.

[0029] Wherein, Re is at least one element selected from La, Ce, Pr, Nd, Gd, Tb, Dy, Ho, and Y; the orientation molding magnetic field strength is greater than or equal to 2.0T, and the pressing density is 3.5~4.0 g / cm³. 3 The vacuum sintering temperature is 1020~1100℃, and the time is 2~10 hours.

[0030] S2. Blank preparation: Grind the six sides of the square blank flat to make a magnet blank;

[0031] S3. Magnetization: Magnetize the magnet blank along the orientation direction;

[0032] The magnetization state can be either saturated magnetization or unsaturated magnetization.

[0033] S4, such as Figure 1 As shown, the fundamental plane is marked by measuring the magnetic declination and marking the efgh fundamental plane by laser scribing or manual scribing. This fundamental plane is perpendicular to the magnetic moment M.

[0034] Magnetic declination is measured using a Wienheimer Holz coil.

[0035] S5. Tempering: Two-stage or three-stage tempering treatment is adopted;

[0036] The temperature of the third-stage tempering is higher than that of the second-stage tempering.

[0037] S6. Black film preparation: Based on the marked efgh fundamental plane, first, the a-axis of the orientation direction... 1 b 1 c 1 d 1 upper end face and a 2 b 2 c 2 d 2 The lower end face is cut into a plane parallel to the basic plane of efgh, and then further processed into a black sheet through cutting, grinding, chamfering and other machining processes;

[0038] S7. Glitter preparation: The black sheet product is surface treated to obtain the glitter product, namely, a low magnetic declination rare earth permanent magnet.

[0039] Example 1:

[0040] A method for preparing a low magnetic declination rare-earth permanent magnet, the specific process is as follows:

[0041] S1. Blank Preparation: Square blanks for PrNd-Fe-B rare earth magnets were prepared through processes such as rapid solidification, powder preparation, orientation molding, and vacuum sintering; the orientation molding magnetic field strength was 2.0T, and the pressing density was 3.6g / cm³. 3 The vacuum sintering temperature was 1075℃, and the time was 5 hours.

[0042] S2. Blank preparation: Grind the six sides of the square blank flat to make a magnet blank;

[0043] S3. Magnetization: Saturate magnetization of the magnet blank along the orientation direction;

[0044] S4. Marking the fundamental plane: Measure the magnetic declination and mark the efgh fundamental plane by laser scribing. This fundamental plane is perpendicular to the magnetic moment M.

[0045] S5. Tempering: Two-stage tempering process is adopted;

[0046] S6. Black film preparation: Based on the marked efgh fundamental plane, first, the a-axis of the orientation direction... 1 b 1 c 1 d 1 upper end face and a 2 b 2 c 2 d2 The lower end face is cut into a plane parallel to the basic plane of efgh, and then further processed into a black sheet through cutting, grinding, chamfering and other machining processes.

[0047] S7. Glitter preparation: The black sheet product is surface treated to obtain the glitter product, namely, a low magnetic declination rare earth permanent magnet.

[0048] The prepared low magnetic declination rare earth permanent magnet has a size of 25*10*5, where 5 is the magnetization direction; its magnetic declination was measured using a three-dimensional Helmholtz coil, and the measurement data are shown in Table 1.

[0049] Comparative Example 1:

[0050] PrNd-Fe-B rare earth magnets of the same composition were prepared using traditional processes as a comparative example and processed into magnets with dimensions of 25*10*5, where 5 represents the magnetization direction. The magnetic declination was measured using a three-dimensional Helmholtz coil, and the measurement data are shown in Table 1.

[0051] Table 1. Magnetic declination measurement data of rare earth permanent magnets prepared in Example 1 and Comparative Example 1

[0052] Example 1 Magnetic declination (°) Comparative Example 1 Magnetic declination (°) 1 0.213 1 2.122 2 0.256 2 3.521 3 0.425 3 2.126 4 0.317 4 2.527 5 0.562 5 1.566 6 0.428 6 4.298 7 0.519 7 3.121 8 0.289 8 2.108 9 0.382 9 1.124 10 0.511 10 2.265 average value 0.3902 average value 2.4778

[0053] Note: Example 1 and Comparative Example 1 each had 10 parallel samples.

[0054] Example 2:

[0055] A method for preparing a low magnetic declination rare-earth permanent magnet, the specific process is as follows:

[0056] S1. Blank Preparation: Square blanks for PrNdDy-Fe-B rare earth magnets were prepared through processes such as rapid solidification, powder preparation, orientation molding, and vacuum sintering; the orientation molding magnetic field strength was 2.2T, and the pressing density was 3.6 g / cm³. 3 The vacuum sintering temperature was 1080℃, and the time was 5 hours.

[0057] S2. Blank preparation: Grind the six sides of the square blank flat to make a magnet blank;

[0058] S3. Magnetization: Saturate magnetization of the magnet blank along the orientation direction;

[0059] S4. Marking the fundamental plane: Measure the magnetic declination and mark the efgh fundamental plane by laser scribing. This fundamental plane is perpendicular to the magnetic moment M.

[0060] S5. Tempering: Three-stage tempering treatment is adopted, wherein the second-stage tempering temperature is 490℃ and the third-stage tempering temperature is 550℃.

[0061] S6. Black film preparation: Based on the marked efgh fundamental plane, first, the a-axis of the orientation direction...1 b 1 c 1 d 1 upper end face and a 2 b 2 c 2 d 2 The lower end face is cut into a plane parallel to the basic plane of efgh, and then further processed into a black sheet through cutting, grinding, chamfering and other machining processes;

[0062] S7. Glitter preparation: The black sheet product is surface treated to obtain the glitter product, namely, a low magnetic declination rare earth permanent magnet.

[0063] The prepared low magnetic declination rare earth permanent magnet has a size of 15*8*2, where 2 is the magnetization direction; its magnetic declination was measured using a three-dimensional Helmholtz coil, and the measurement data are shown in Table 2.

[0064] Comparative Example 2:

[0065] PrNdDy-Fe-B rare earth magnets of the same composition were prepared using traditional processes as a comparative example and processed into magnets with dimensions of 15*8*2, where 2 represents the magnetization direction. The magnetic declination was measured using a three-dimensional Helmholtz coil, and the measurement data are shown in Table 2.

[0066] Table 2. Magnetic declination measurement data of rare earth permanent magnets prepared in Example 2 and Comparative Example 2

[0067] Example 2 Magnetic declination (°) Comparative Example 2 Magnetic declination (°) 1 0.528 1 1.358 2 0.316 2 4.521 3 0.685 3 3.198 4 0.329 4 2.247 5 0.356 5 2.629 6 0.518 6 3.168 7 0.269 7 2.952 8 0.421 8 1.697 9 0.458 9 2.785 10 0.496 10 3.126 average value 0.4376 average value 2.7681

[0068] Note: Example 2 and Comparative Example 2 each had 10 parallel samples.

[0069] Example 3:

[0070] A method for preparing a low magnetic declination rare-earth permanent magnet, the specific process is as follows:

[0071] S1. Blank Preparation: Square blanks for PrNdCe-Fe-B rare earth magnets were prepared through processes such as rapid solidification, powder preparation, orientation molding, and vacuum sintering; the orientation molding magnetic field strength was 2.0T, and the pressing density was 3.8g / cm³. 3 The vacuum sintering temperature was 1050℃, and the time was 5 hours.

[0072] S2. Blank preparation: Grind the six sides of the square blank flat to make a magnet blank;

[0073] S3. Magnetization: Saturate magnetization of the magnet blank along the orientation direction;

[0074] S4. Marking the fundamental plane: Measure the magnetic declination and mark the efgh fundamental plane by laser scribing. This fundamental plane is perpendicular to the magnetic moment M.

[0075] S5. Tempering: Three-stage tempering treatment is adopted, wherein the second-stage tempering temperature is 460℃ and the third-stage tempering temperature is 640℃.

[0076] S6. Black film preparation: Based on the marked efgh fundamental plane, first, the a-axis of the orientation direction... 1 b 1 c 1 d 1 upper end face and a 2 b 2 c 2 d 2 The lower end face is cut into a plane parallel to the basic plane of efgh, and then further processed into a black sheet through cutting, grinding, chamfering and other machining processes;

[0077] S7. Glitter preparation: The black sheet product is surface treated to obtain the glitter product, namely, a low magnetic declination rare earth permanent magnet.

[0078] The prepared low magnetic declination rare earth permanent magnet has a size of 10*6*1.5, where 1.5 is the magnetization direction; its magnetic declination was measured using a three-dimensional Helmholtz coil, and the measurement data are shown in Table 3.

[0079] Comparative Example 3:

[0080] PrNdCe-Fe-B rare earth magnets of the same composition were prepared using traditional processes as a comparative example and processed into magnets with dimensions of 10*6*1.5, where 1.5 represents the magnetization direction. Magnetic declination was measured using a three-dimensional Helmholtz coil, and the measurement data are shown in Table 3.

[0081] Table 3. Magnetic declination measurement data of rare earth permanent magnets prepared in Example 3 and Comparative Example 3.

[0082] Example 3 Magnetic declination (°) Comparative Example 3 Magnetic declination (°) 1 0.485 1 2.521 2 0.267 2 4.556 3 0.629 3 2.199 4 0.752 4 3.257 5 0.448 5 2.167 6 0.698 6 5.282 7 0.527 7 1.654 8 0.461 8 3.412 9 0.858 9 2.587 10 0.655 10 3.144 average value 0.578 average value 3.0779

[0083] Note: Example 3 and Comparative Example 3 each had 10 parallel samples.

[0084] As shown in Table 1, the average magnetic declination of the PrNd-Fe-B magnet prepared by this invention is 0.3902°, significantly lower than the average magnetic declination of 2.4778° in the comparative example. Table 2 shows that the average magnetic declination of the PrNdDy-Fe-B magnet prepared by this invention is 0.4376°, significantly lower than the average magnetic declination of 2.7681° in the comparative example. Table 3 shows that the average magnetic declination of the PrNdCe-Fe-B magnet prepared by this invention is 0.578°, significantly lower than the average magnetic declination of 3.0779° in the comparative example. Comparing the magnetic declination data in Tables 1-3, it can be seen that the low magnetic declination Re-Fe-B rare earth magnet prepared by this invention has a significantly lower magnetic declination than magnets prepared by traditional processes, and all are within 1°.

[0085] The method for preparing low magnetic declination rare-earth permanent magnets of the present invention marks a basic surface on the magnet blank after magnetization. The basic surface efgh is perpendicular to the magnetic moment M. After the magnet blank is tempered, the marked basic surface is used as a reference for subsequent processing to prevent the problem of amplified magnetic declination due to the lack of a reference surface in subsequent processing. Experimental data show that the low magnetic declination Re-Fe-B rare-earth magnet prepared by the present invention has a magnetic declination that is significantly lower than that of magnets prepared by traditional processes, and is within 1°. It can be better applied in high-precision, miniaturized and intelligent fields.

[0086] Finally, it should be noted that the above embodiments are only illustrative of the technical solutions of the present invention, and not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a low magnetic declination rare-earth permanent magnet, characterized in that, Includes the following steps: S1. Blank preparation: Prepare Re-Fe-B rare earth magnet square blanks; S2. Blank preparation: Grind the six sides of the square blank flat to make a magnet blank; S3. Magnetization: Magnetize the magnet blank along the orientation direction; S4. Mark the fundamental plane: Measure the magnetic declination and mark efgh as the fundamental plane, which is perpendicular to the magnetic moment M; S5, Tempering; S6. Black film preparation: Based on the marked efgh fundamental plane, a black film is prepared by machining. S7. Glitter preparation: Surface treatment is performed on the black sheet product to obtain the glitter product.

2. The method for preparing a low magnetic declination rare-earth permanent magnet according to claim 1, characterized in that, In step S1, Re is at least one element selected from La, Ce, Pr, Nd, Gd, Tb, Dy, Ho, and Y.

3. The method for preparing a low magnetic declination rare-earth permanent magnet according to claim 1, characterized in that, In step S1, the orientation forming magnetic field strength is greater than or equal to 2.0T.

4. The method for preparing a low magnetic declination rare-earth permanent magnet according to claim 1, characterized in that, In step S1, the compression density is 3.5~4.0 g / cm³. 3 .

5. The method for preparing a low magnetic declination rare-earth permanent magnet according to claim 1, characterized in that, In step S1, the vacuum sintering temperature is 1020~1100℃ and the time is 2~10 hours.

6. The method for preparing a low magnetic declination rare-earth permanent magnet according to claim 1, characterized in that, In step S3, the magnetization state can be either saturated magnetization or unsaturated magnetization.

7. The method for preparing a low magnetic declination rare-earth permanent magnet according to claim 1, characterized in that, In step S4, the magnetic declination is measured using a Vihermholz coil.

8. The method for preparing a low magnetic declination rare-earth permanent magnet according to claim 1, characterized in that, In step S5, a two-stage tempering process is employed.

9. The method for preparing a low magnetic declination rare-earth permanent magnet according to claim 1, characterized in that, In step S5, a three-stage tempering process is used; the temperature of the third-stage tempering is higher than that of the second-stage tempering.

10. The method for preparing a low magnetic declination rare-earth permanent magnet according to claim 1, characterized in that, In step S6, using the marked efgh fundamental plane as a reference, the orientation direction a 1 b 1 c 1 d 1 upper end face and a 2 b 2 c 2 d 2 The lower end face is cut into a plane parallel to the basic plane of efgh, and then further machined.

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