A mold for preparing low magnetic declination permanent magnet ferrite magnets and its application

Abstract

This invention relates to the field of permanent magnet material design and preparation technology, specifically to a mold for preparing low magnetic declination permanent magnet ferrite magnets and its application. The invention provides a mold for preparing low magnetic declination permanent magnet ferrite magnets, the mold comprising an upper mold, a lower mold, and a concave mold; the upper mold includes an upper mold body and an upper mold forming part, the upper mold body surrounding the upper mold forming part; the lower mold includes a lower mold body and a lower mold forming part disposed opposite to each other; the concave mold has a square through hole; the magnetic permeability of the material of the concave mold is less than 1.3 × 10⁻⁶. ‑6 H / m; the magnetic permeability of the upper mold body material is less than 1.3×10⁻⁶. ‑6 H / m; the magnetic permeability of the upper mold forming part is greater than 8000 H / m; the magnetic permeability of the lower mold body material is greater than 400 H / m; the magnetic permeability of the lower mold forming part is less than 1.3 × 10⁻⁶ H / m. ‑6 H / m. The permanent magnet ferrite magnet prepared using the mold provided in this invention has a small magnetic declination.

Description

Technical Field

[0001] This invention relates to the field of permanent magnet material design and preparation technology, specifically to a mold for preparing low magnetic declination permanent magnet ferrite magnets and its application. Background Technology

[0002] The presence of magnetic declination causes a magnetic field to be generated in the unmagnetized direction of a magnet, forming a stray magnetic field. With the increasing application of permanent magnets, magnetic declination has become a crucial factor affecting the performance of precision magnetic devices. Square magnets with large magnetic declinations can also cause quality problems in permanent magnet sensors, leading to a series of safety hazards. The magnitude of magnetic declination directly affects the performance of permanent magnet motors. Factors influencing magnetic declination include the motor's load, operating state, and current magnitude. When the current is constant, the smaller the magnetic declination, the greater the torque of the permanent magnet motor. Changes in magnetic declination affect the efficiency of permanent magnet motors. Smaller magnetic declination results in higher efficiency. Increased magnetic declination leads to decreased efficiency because it causes instability in the magnetic field, thus affecting motor efficiency. Using magnets with large magnetic declinations in permanent magnet motors can cause motor vibration, noise, and reduced motor precision, not only preventing the full utilization of the permanent magnet's magnetic properties but also degrading motor performance.

[0003] However, in related technologies, the permanent magnet ferrite magnets prepared by mold fabrication have a large magnetic declination. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the problem of large magnetic declination of permanent magnet ferrite magnets obtained by mold preparation of permanent magnet ferrite magnets in related technologies, thereby providing a mold for preparing permanent magnet ferrite magnets with low magnetic declination and its application.

[0005] This invention provides a mold for preparing low magnetic declination permanent magnet ferrite magnets, the mold comprising an upper mold, a lower mold, and a concave mold;

[0006] The upper mold includes an upper mold body and an upper mold forming part, wherein the upper mold body surrounds the upper mold forming part;

[0007] The lower mold includes a lower mold body and a lower mold forming part that are disposed opposite to each other;

[0008] The upper mold body and the lower mold are adjacent to each other; the lower mold has a square through hole; the lower mold forming part is movably placed in the square through hole of the lower mold; the upper mold forming part and the lower mold forming part are arranged opposite to each other and form a closed cavity with the side wall of the square through hole;

[0009] The magnetic permeability of the die material is less than 1.3 × 10⁻⁶. -6 H / m;

[0010] The magnetic permeability of the upper mold body material is less than 1.3 × 10⁻⁶. -6 H / m;

[0011] The magnetic permeability of the upper mold forming part is greater than 8000 H / m;

[0012] The magnetic permeability of the lower mold body material is greater than 400 H / m;

[0013] The magnetic permeability of the material in the lower mold forming part is less than 1.3 × 10⁻⁶. -6 H / m.

[0014] Preferably, the lower mold forming part includes a first surface of the lower mold forming part and a second surface of the lower mold forming part disposed opposite to each other;

[0015] The upper mold forming part includes an upper mold forming surface and an upper mold forming top surface that are arranged opposite to each other; the lower mold forming part, the first surface of the lower mold forming part, the upper mold forming surface, and the square through hole sidewall form a closed cavity.

[0016] Preferably, the enclosed cavity is square or tile-shaped.

[0017] Preferably, the upper mold forming surface and the upper mold forming top surface are arranged in parallel; the contact surface between the lower mold body and the lower mold forming part is the second surface of the lower mold forming part, and the second surface of the lower mold forming part is arc-shaped.

[0018] Preferably, the distance between the upper mold forming surface and the upper mold forming top surface is 30-80mm; and / or,

[0019] The arc has an arc radius of 10-300°; and / or,

[0020] The diameter of the circle corresponding to the arc is 10-100mm; and / or,

[0021] The minimum distance between the first surface of the lower mold forming part and the second surface of the lower mold forming part is 1-5mm; and / or,

[0022] The maximum distance between the first surface of the lower mold forming part and the second surface of the lower mold forming part is 2-10mm.

[0023] Preferably, the contact surface between the lower mold body and the lower mold forming part is the second surface of the lower mold forming part, and the upper mold forming surface and the second surface of the lower mold forming part are horizontally arranged;

[0024] The upper mold forming surface is an arc.

[0025] The middle of the first surface of the lower mold forming part is a raised arc shape;

[0026] The line connecting the center of the arc corresponding to the upper mold forming surface and the center of the arc corresponding to the protruding part of the lower mold forming section is parallel to the side wall of the square through hole of the concave mold.

[0027] Preferably, the minimum distance between the upper mold forming surface and the upper mold forming top surface is 30-80 mm; and / or,

[0028] The arc corresponding to the forming surface of the upper mold has a radius of 10-300°; and / or,

[0029] The diameter of the circle corresponding to the arc of the upper mold forming surface is 10-100mm; and / or,

[0030] The arc of the raised section of the lower mold forming part is less than or equal to the arc of the corresponding arc of the upper mold forming surface; and / or,

[0031] The diameter of the circle corresponding to the raised arc on the first surface of the lower mold forming part is the same as the diameter of the circle corresponding to the arc on the upper mold forming surface; and / or,

[0032] The maximum distance between the first surface of the lower mold forming part and the second surface of the lower mold forming part is 1-10mm.

[0033] Preferably, the material of the die is selected from non-magnetic hard alloy;

[0034] The upper mold body is made of 304 stainless steel;

[0035] The upper mold forming part is made of pure iron;

[0036] The lower mold body is made of 45# steel;

[0037] The material of the lower mold forming part is selected from non-magnetic hard alloy.

[0038] The present invention also provides a low magnetic declination permanent magnet ferrite magnet, which is prepared using the mold described above for preparing the low magnetic declination permanent magnet ferrite magnet.

[0039] The technical solution of this invention has the following advantages:

[0040] This invention provides a mold for preparing low magnetic declination permanent magnet ferrite magnets. The mold includes an upper mold, a lower mold, and a concave mold. The upper mold includes an upper mold body and an upper mold forming part, with the upper mold body surrounding the upper mold forming part. The lower mold includes a lower mold body and a lower mold forming part disposed opposite to each other. The upper mold body and the concave mold are adjacent to each other. The concave mold has a square through hole. The lower mold forming part is movably disposed in the square through hole of the concave mold. The upper mold forming part and the lower mold forming part are disposed opposite to each other and form a closed cavity with the sidewall of the square through hole. The magnetic permeability of the material of the concave mold is less than 1.3 × 10⁻⁶. -6 H / m; the magnetic permeability of the upper mold body material is less than 1.3×10⁻⁶. -6 H / m; the magnetic permeability of the upper mold forming part is greater than 8000 H / m; the magnetic permeability of the lower mold body material is greater than 400 H / m; the magnetic permeability of the lower mold forming part is less than 1.3 × 10⁻⁶ H / m. -6 H / m.

[0041] In this invention, by optimizing the structure of the mold for the low magnetic declination permanent magnet ferrite and limiting the selection of materials for each component, the microstructure of the permanent magnet ferrite raw material changes in the direction of decreasing magnetic declination under the action of the magnetizing magnetic field during the molding process of the permanent magnet ferrite, thereby resulting in a permanent magnet ferrite with a smaller magnetic declination. Attached Figure Description

[0042] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0043] Figure 1 This is a longitudinal cross-sectional view of a mold used in Embodiment 1 of the present invention for preparing a low magnetic declination permanent magnet ferrite magnet;

[0044] Figure 2 This is a longitudinal cross-sectional view of the mold used in Embodiment 1 of the present invention for preparing a low magnetic declination permanent magnet ferrite magnet;

[0045] Figure 3 This is a longitudinal cross-sectional view of the mold for the permanent magnet ferrite magnet used in Comparative Example 2 of the present invention;

[0046] Figure 4 The magnetic field lines arrangement of the permanent magnet ferrite prepared using the mold provided in Example 2 of this invention;

[0047] Figure 5 The magnetic field lines arrangement of the permanent magnet ferrite prepared using the mold provided in Comparative Example 1 are shown below.

[0048] Figure 6 The magnetic field lines arrangement of the permanent magnet ferrite prepared using the mold provided in Example 3 of this invention;

[0049] Figure 7 The magnetic field lines arrangement of the permanent magnet ferrite prepared using the mold provided in Comparative Example 2 are shown in the present invention.

[0050] Reference numerals: 100, upper mold; 101, upper mold body; 102, upper mold forming part; 103, upper mold forming surface; 104, upper mold forming top surface; 200, cavity mold; 300, lower mold; 301, lower mold forming part; 302, lower mold body; 303, first surface of lower mold forming part; 304, second surface of lower mold forming part; 400, closed cavity. Detailed Implementation

[0051] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0052] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0053] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0054] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0055] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0056] Example 1

[0057] This embodiment provides a mold for preparing a low magnetic declination permanent magnet ferrite magnet, the mold including an upper mold 100, a lower mold 300, and a concave mold 200; as shown... Figure 1 As shown, the upper mold 100 includes an upper mold body 101 and an upper mold forming part 102, with the upper mold body 101 surrounding the upper mold forming part 102.

[0058] The lower mold 300 includes a lower mold body 302 and a lower mold forming part 301 disposed opposite to each other;

[0059] The upper mold body 101 and the lower mold 200 are adjacent to each other; the lower mold 200 has a square through hole; the lower mold forming part 301 is movably placed in the square through hole of the lower mold 200; the upper mold forming part 102 and the lower mold forming part 301 are arranged opposite to each other, and form a closed cavity 400 with the side wall of the square through hole.

[0060] The magnetic permeability of the material of die 200 is less than 1.3 × 10⁻⁶. -6 H / m;

[0061] The magnetic permeability of the upper mold body material 101 is less than 1.3 × 10⁻⁶. -6 H / m;

[0062] The magnetic permeability of the upper mold forming part 102 is greater than 8000 H / m;

[0063] The magnetic permeability of the 302 material used in the lower mold body is greater than 400 H / m;

[0064] The magnetic permeability of the lower mold forming part 301 is less than 1.3 × 10⁻⁶. -6 H / m.

[0065] In one embodiment, the lower mold forming part 301 includes a lower mold forming part first surface 303 and a lower mold forming part second surface 304 disposed opposite to each other;

[0066] The upper mold forming part 102 includes an upper mold forming surface 103 and an upper mold forming top surface 104 that are disposed opposite to each other;

[0067] The lower mold forming part first surface 303, the upper mold forming surface 103, and the square through hole sidewall form a closed cavity 400.

[0068] In one specific embodiment, see Figure 1 The enclosed cavity 400 is square.

[0069] In a more specific embodiment, the upper mold forming surface 103 and the upper mold forming top surface 104 are arranged in parallel.

[0070] The contact surface between the lower mold body 302 and the lower mold forming part 301 is the second surface 304 of the lower mold forming part, which is arc-shaped.

[0071] In a more specific embodiment, the distance between the upper mold forming surface 103 and the upper mold forming top surface 104 is 30-80mm;

[0072] In a more specific embodiment, the arc has an arc radius of 10-300°;

[0073] In a more specific embodiment, the diameter of the circle corresponding to the arc shape is 10-100mm;

[0074] In a more specific embodiment, the minimum distance between the first surface 303 of the lower mold forming part and the second surface 304 of the lower mold forming part is 1-5mm;

[0075] In a more specific embodiment, the maximum distance between the first surface 303 and the second surface 304 of the lower mold forming part is 2-10 mm.

[0076] In another specific embodiment, see Figure 2 The closed cavity 400 is tile-shaped.

[0077] In a more specific embodiment, the contact surface between the lower mold body 302 and the lower mold forming part 301 is the second surface 304 of the lower mold forming part, and the upper mold forming surface 103 and the second surface 304 of the lower mold forming part are horizontally arranged;

[0078] In a more specific embodiment, the upper mold forming surface 103 is arc-shaped;

[0079] In a more specific embodiment, the middle of the first surface 303 of the lower mold forming part is a raised arc shape;

[0080] In a more specific embodiment, the line connecting the center of the arc-shaped corresponding circle of the upper mold forming surface 103 and the center of the protruding arc-shaped corresponding circle of the first surface 303 of the lower mold forming part is parallel to the side wall of the square through hole of the cavity mold 200.

[0081] In a more specific embodiment, the minimum distance between the upper mold forming surface 103 and the upper mold forming top surface 104 is 30-80 mm;

[0082] In a more specific embodiment, the arc corresponding to the upper mold forming surface 103 has an arc of 10-300°;

[0083] In a more specific embodiment, the diameter of the circle corresponding to the arc of the upper mold forming surface 103 is 10-100mm;

[0084] In a more specific embodiment, the arc of the protruding arc of the lower mold forming part 301 is less than or equal to the arc of the arc corresponding to the upper mold forming surface 103;

[0085] In a more specific embodiment, the diameter of the circle corresponding to the raised arc shape on the first surface 303 of the lower mold forming part is the same as the diameter of the circle corresponding to the arc formed by the upper mold 100.

[0086] In a more specific embodiment, the maximum distance between the first surface 303 and the second surface 304 of the lower mold forming part is 1-10 mm.

[0087] In one specific embodiment, the material of the die 200 is selected from non-magnetic cemented carbide (the magnetic permeability of non-magnetic cemented carbide is 1.05 × 10⁻⁶). -6 H / m);

[0088] In one specific embodiment, the upper mold body 101 is made of 304 stainless steel (304 stainless steel has a magnetic permeability of 1.10 × 10⁻⁶). -6 H / m);

[0089] In one specific embodiment, the material of the upper mold forming part 102 is selected from pure iron (the magnetic permeability of pure iron is 8500H / m).

[0090] In one specific embodiment, the material of the lower mold body 302 is selected from 45# steel (the magnetic permeability of 45# steel is 4000H / m).

[0091] In one specific embodiment, the material of the lower mold forming part 301 is selected from non-magnetic cemented carbide (the magnetic permeability of non-magnetic cemented carbide is 1.15 × 10⁻⁶). -6 H / m).

[0092] This embodiment also provides a low magnetic declination permanent magnet ferrite magnet, (1) wet ball milling and mixing of permanent magnet ferrite magnet raw materials to obtain slurry; (2) taking out the lower mold 300; (3) pouring the slurry into the square through hole of the concave mold 200; (4) placing the lower mold 300 in the square through hole of the concave mold 200, so that the lower mold 300 moves relative to the upper mold 100 to press and form, and applying a forming magnetic field in the moving direction of the lower mold 300; to obtain a shaped body; (5) sintering the shaped body to obtain the low magnetic declination permanent magnet ferrite magnet.

[0093] The magnetic permeability of the materials used in the following embodiments and comparative examples is as follows:

[0094] The magnetic permeability of the non-magnetic cemented carbide is 1.05 × 10⁻⁶. -6 H / m;

[0095] The magnetic permeability of 304 stainless steel is 1.10 × 10⁻⁶. -6 H / m;

[0096] The magnetic permeability of pure iron is 8500 H / m;

[0097] The magnetic permeability of 45# steel is 4000 H / m;

[0098] The permeability of the non-magnetic cemented carbide is 1.15 × 10⁻⁶. -6 H / m.

[0099] Example 2

[0100] This embodiment provides a mold for preparing a low magnetic declination permanent magnet ferrite magnet, the mold including an upper mold 100, a lower mold 300, and a concave mold 200; as shown... Figure 1 As shown, the upper mold 100 includes an upper mold body 101 and an upper mold forming part 102, with the upper mold body 101 surrounding the upper mold forming part 102.

[0101] The lower mold 300 includes a lower mold body 302 and a lower mold forming part 301 disposed opposite to each other;

[0102] The upper mold body 101 and the lower mold 200 are adjacent to each other; the lower mold 200 has a square through hole; the lower mold forming part 301 is movably placed in the square through hole of the lower mold 200; the upper mold forming part 102 and the lower mold forming part 301 are arranged opposite to each other, and form a closed cavity 400 with the side wall of the square through hole; the closed cavity 400 is square.

[0103] The die 200 is made of non-magnetic hard alloy; the upper die body 101 is made of 304 stainless steel; the upper die forming part 102 is made of pure iron; the lower die body 302 is made of 45# steel; and the lower die forming part 301 is made of non-magnetic hard alloy.

[0104] The lower mold forming part 301 includes a lower mold forming part first surface 303 and a lower mold forming part second surface 304 disposed opposite to each other;

[0105] The upper mold forming part 102 includes an upper mold forming surface 103 and an upper mold forming top surface 104 that are disposed opposite to each other;

[0106] The lower mold forming part first surface 303, the upper mold forming surface 103, and the square through hole sidewall form a closed cavity 400.

[0107] The upper mold forming surface 103 and the upper mold forming top surface 104 are arranged in parallel.

[0108] The contact surface between the lower mold body 302 and the lower mold forming part 301 is the second surface 304 of the lower mold forming part, which is arc-shaped.

[0109] The distance between the upper mold forming surface 103 and the upper mold forming top surface 104 is 40mm;

[0110] The arc has an arc angle of 30°;

[0111] The diameter of the circle corresponding to the arc is 100mm;

[0112] The minimum distance between the first surface 303 and the second surface 304 of the lower mold forming part is 8mm.

[0113] Example 3

[0114] This embodiment provides a mold for preparing a low magnetic declination permanent magnet ferrite magnet, the mold including an upper mold 100, a lower mold 300, and a concave mold 200; as shown... Figure 2 As shown, the upper mold 100 includes an upper mold body 101 and an upper mold forming part 102, with the upper mold body 101 surrounding the upper mold forming part 102;

[0115] The lower mold 300 includes a lower mold body 302 and a lower mold forming part 301 disposed opposite to each other;

[0116] The upper mold body 101 and the lower mold 200 are adjacent to each other; the lower mold 200 has a square through hole; the lower mold forming part 301 is movably placed in the square through hole of the lower mold 200; the upper mold forming part 102 and the lower mold forming part 301 are arranged opposite to each other, and form a closed cavity 400 with the side wall of the square through hole; the closed cavity 400 is tile-shaped.

[0117] The die 200 is made of non-magnetic hard alloy; the upper die body 101 is made of 304 stainless steel; the upper die forming part 102 is made of pure iron; the lower die body 302 is made of 45# steel; and the lower die forming part 301 is made of non-magnetic hard alloy.

[0118] The contact surface between the lower mold body 302 and the lower mold forming part 301 is the second surface 304 of the lower mold forming part, and the upper mold forming surface 103 and the second surface 304 of the lower mold forming part are horizontally arranged;

[0119] The upper mold forming surface 103 is an arc;

[0120] The middle of the first surface 303 of the lower mold forming part is a raised arc shape;

[0121] The line connecting the center of the arc corresponding to the upper mold forming surface 103 and the center of the protruding arc corresponding to the lower mold forming part first surface 303 is parallel to the side wall of the square through hole of the cavity mold 200.

[0122] The minimum distance between the upper mold forming surface 103 and the upper mold forming top surface 104 is 40mm;

[0123] The arc corresponding to the upper mold forming surface 103 has a radius of 30°.

[0124] The diameter of the circle corresponding to the arc of the upper mold forming surface 103 is 100mm;

[0125] The arc of the raised arc shape on the first surface 303 of the lower mold forming part is 28°; except for the raised arc shape, the other parts of the first surface 303 of the lower mold forming part are perpendicular to the side wall of the square through hole.

[0126] The diameter of the circle corresponding to the raised arc on the first surface 303 of the lower mold forming part is the same as the diameter of the circle corresponding to the arc on the upper mold forming surface 103.

[0127] The maximum distance between the first surface 303 and the second surface 304 of the lower mold forming part is 8mm.

[0128] Comparative Example 1

[0129] This comparative example provides a mold for preparing permanent magnet ferrite magnets.

[0130] The structure is the same as in Example 2, except that the material of the concave mold 200 is selected from non-magnetic hard alloy; the material of the upper mold body 101 is selected from pure iron; the material of the upper mold forming part 102 is selected from pure iron; the material of the lower mold body 302 is selected from 45# steel; and the material of the lower mold forming part 301 is selected from non-magnetic hard alloy.

[0131] Comparative Example 2

[0132] This comparative example provides a mold for preparing permanent magnet ferrite magnets, the mold comprising an upper mold 100, a lower mold 300, and a concave mold 200; as shown... Figure 3 As shown, the upper mold 100 includes an upper mold body 101 and an upper mold forming part 102, with the upper mold body 101 surrounding the upper mold forming part 102;

[0133] The lower mold 300 includes a lower mold body 302 and a lower mold forming part 301 disposed opposite to each other;

[0134] The upper mold body 101 and the lower mold 200 are adjacent to each other; the lower mold 200 has a square through hole; the lower mold forming part 301 is movably placed in the square through hole of the lower mold 200; the upper mold forming part 102 and the lower mold forming part 301 are arranged opposite to each other, and form a closed cavity 400 with the side wall of the square through hole; the closed cavity 400 is tile-shaped.

[0135] The die 200 is made of non-magnetic hard alloy; the upper die body 101 is made of pure iron; the upper die forming part 102 is made of pure iron; the lower die body 302 is made of 45# steel; and the lower die forming part 301 is made of non-magnetic hard alloy.

[0136] The contact surface between the lower mold body 302 and the lower mold forming part 301 is the second surface 304 of the lower mold forming part;

[0137] The upper mold forming surface 103 is an arc;

[0138] The middle of the first surface 303 and the middle of the second surface 304 of the lower mold forming part are raised arc shapes.

[0139] The line connecting the center of the arc corresponding to the upper mold forming surface 103 and the center of the protruding arc corresponding to the lower mold forming part first surface 303 is parallel to the side wall of the square through hole of the cavity mold 200.

[0140] The minimum distance between the upper mold forming surface 103 and the upper mold forming top surface 104 is 40mm;

[0141] The arc corresponding to the upper mold forming surface 103 has a radius of 30°.

[0142] The diameter of the circle corresponding to the arc of the upper mold forming surface 103 is 100mm;

[0143] The arc of the raised arc shape on the first surface 303 of the lower mold forming part is 28°; except for the raised arc shape, the other parts of the first surface 303 of the lower mold forming part are perpendicular to the side wall of the square through hole.

[0144] The arc of the raised arc on the second surface 304 of the lower mold forming part is 28°; except for the raised arc part, the other parts of the second surface 304 of the lower mold forming part are tangent to the raised arc.

[0145] The diameter of the circle corresponding to the raised arc shape on the first surface 303 of the lower mold forming part is the same as the diameter of the circle corresponding to the arc shape of the upper mold 100 forming 303.

[0146] The minimum distance between the first surface 303 and the second surface 304 of the lower mold forming part is 8mm.

[0147] Test case

[0148] Sample preparation:

[0149] S1. Weigh 450g of SrM pre-calcined material, add 0.25wt% SiO2 powder, 0.625wt% CaCO3 powder, 0.5wt% La2O3 powder, and 0.4wt% CoO powder, then add 680mL of deionized water. Use 7.5kg cast steel balls as the ball milling media and perform wet pulverization in a high-efficiency ball mill for 16h to obtain a slurry with a grain size of 0.9μm.

[0150] S2. Using Examples 2 and 3, the molds prepared in Comparative Examples 1 and 2 were molded as follows: The water content in the slurry was adjusted by allowing the slurry to stand and filter for two days until the solid content of the slurry was adjusted to 70wt%. Then, the lower mold 300 was taken out, and the slurry was poured into the square through hole of the concave mold 200. The lower mold 300 was placed in the square through hole of the concave mold 200, and the lower mold 300 was moved relative to the upper mold 100 to press and form with a pressure of 2MPa. An addition forming magnetic field of 15000Oe was applied in the moving direction of the lower mold 300 to obtain the molded body.

[0151] S3. Sintering: The molded body is heat-treated by heating from room temperature to 120°C at a heating rate of 2°C / min and holding for 1 hour to remove moisture. Then, the temperature is increased to 300°C at a heating rate of 3°C / min and held for 1 hour to remove organic impurities. Then, sintering is carried out in an oxygen-rich atmosphere (oxygen content 23%, v / v) at a heating rate of 150°C / h, a sintering temperature of 1215°C, and a holding time of 1 hour to obtain sintered permanent magnet ferrite.

[0152] Ten square permanent magnet ferrites of the same size were prepared using the molds obtained in Example 2 and Comparative Example 1, respectively.

[0153] The magnetic field lines of the permanent magnet ferrite prepared in Example 2 are arranged as follows: Figure 4 Indication;

[0154] The magnetic field lines of the permanent magnet ferrite prepared in Comparative Example 1 are arranged as follows: Figure 5 Indication;

[0155] Ten square permanent magnet ferrites of the same size were prepared using the molds obtained in Example 3 and Comparative Example 2, respectively.

[0156] The magnetic field lines of the permanent magnet ferrite prepared in Example 3 are arranged as follows: Figure 6 Indication;

[0157] The magnetic field lines of the permanent magnet ferrite prepared in Comparative Example 2 are arranged as follows: Figure 7 Indication;

[0158] The magnetic declination of the permanent magnet ferrite prepared above was measured using a magnetic declination tester, and the results are shown in Tables 1 and 2.

[0159] Table 1. Magnetic declination of the square permanent magnet ferrites prepared in Example 2 and Comparative Example 1

[0160]

[0161] Table 2. Magnetic declination of the square permanent magnet ferrites prepared in Example 3 and Comparative Example 2.

[0162]

[0163] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A mold for producing a low magnetic bias angle permanent ferrite magnet, characterized by, The mold comprises an upper die, a lower die, and a female die; The upper die comprises an upper die body and an upper die forming part, and the upper die body surrounds the upper die forming part; The lower die comprises oppositely arranged lower die body and lower die forming part; The upper die body and the female die are adjacent; the female die has a square through hole; the lower die forming part is movably arranged in the square through hole of the female die; the upper die forming part and the lower die forming part are oppositely arranged and form a closed cavity with the side wall of the square through hole; The magnetic permeability of the material of the female mold is less than 1.3 x 10 -6 H / m; The magnetic permeability of the upper die body material is less than 1.3 x 10 -6 H / m; The magnetic permeability of the upper die forming part is greater than 8000 H / m; The magnetic permeability of the material of the lower die body is greater than 400 H / m; The magnetic permeability of the lower mold forming portion is less than 1.3 x 10 -6 H / m.

2. The mold of claim 1, wherein The lower die forming part comprises oppositely arranged lower die forming part first face and lower die forming part second face; The upper die forming part comprises oppositely arranged upper die forming face and upper die forming top face; The lower die forming part first face, the upper die forming face, and the side wall of the square through hole form a closed cavity.

3. The mold of claim 2, wherein, The closed cavity is square.

4. The mold of claim 3, wherein The upper die forming face and the upper die forming top face are arranged in parallel; The contact surface of the lower die body and the lower die forming part is the lower die forming part second face, which is in the form of a circular arc.

5. The mold of claim 4, wherein, The distance between the upper die forming face and the upper die forming top face is 30-80 mm; and / or The radian of the circular arc is 10-300°; and / or The diameter of the corresponding circle of the circular arc is 10-100 mm; and / or The minimum distance between the lower die forming part first face and the lower die forming part second face is 1-5 mm; and / or The maximum distance between the lower die forming part first face and the lower die forming part second face is 2-10 mm.

6. The mold of claim 2, wherein The closed cavity is in the form of a tile.

7. The mold of claim 6, wherein, The contact surface of the lower die body and the lower die forming part is the lower die forming part second face, which is arranged horizontally with the upper die forming face; The upper die forming face is in the form of a circular arc; The middle of the lower die forming part first face is in the form of a convex circular arc; The line connecting the centers of the corresponding circles of the circular arc of the upper die forming face and the convex circular arc of the lower die forming part first face is parallel to the side wall of the square through hole of the female die.

8. The mold of claim 7, wherein, The minimum distance between the upper die forming face and the upper die forming top face is 30-80 mm; and / or The radian of the corresponding circular arc of the upper die forming face is 10-300°; and / or The diameter of the corresponding circle of the circular arc of the upper die forming face is 10-100 mm; and / or The radian of the convex circular arc of the lower die forming part is less than or equal to the radian of the corresponding circular arc of the upper die forming face; and / or The diameter of the corresponding circle of the convex circular arc of the lower die forming part first face is the same as the diameter of the corresponding circle of the circular arc of the upper die forming face; and / or The maximum distance between the lower die forming part first face and the lower die forming part second face is 1-10 mm.

9. The mold according to any one of claims 1 to 8, characterized in that, The material of the female die is selected from non-magnetic hard alloy; The material of the upper die body is selected from 304 stainless steel; The material of the upper die forming part is selected from pure iron; The material of the lower die body is selected from 45# steel; The material of the lower die forming part is selected from non-magnetic hard alloy.

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