Preparation process of rectangular magnetic steel and motor with rectangular magnetic steel

Abstract

The invention discloses a preparation process of rectangular magnetic steel and a motor with the rectangular magnetic steel, and belongs to the technical field of motors. A press coil structure and a mold magnetic circuit are optimized, the press adopts the coil structure with the same number of turns, a punch is arranged on a forming mold and used for pressing the mold, the punch is provided with an inwards-sunken step surface, and the mold is provided with an outwards-sunken step surface matched with the punch. The obtained rectangular magnetic steel has larger surface magnetism and uniform weight, and the problem of motor shaking is effectively solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of motors, and more specifically, relates to a preparation process of a rectangular magnetic steel and a motor having the rectangular magnetic steel. Background Art

[0002] Motors containing rectangular magnets are used in home appliances such as air-conditioning fans and air-conditioning compressors. During use, motor jitter is a common problem. Studies have shown that motor jitter may be caused by the performance of rectangular magnets.

[0003] Patent CN101393792A discloses a permanent magnet with symmetrical magnetic field strengths of left and right arcs. The permanent magnet is in the shape of a tile, and the cross section of the left and right arcs of the tile-shaped permanent magnet is a circular arc. The magnetic field strengths of the left and right arcs of the tile-shaped permanent magnet are the same at the same height. In the orientation field forming, the magnetic tile blank mold has such a position in the orientation field coil: the left and right arc straight lines of the permanent magnet magnetic tile are perpendicular to the circular arc line of the magnetizing coil at the closest position to the magnetic tile blank mold. The permanent magnet with symmetrical magnetic field strengths of the left and right arcs obtained has a difference of less than 3% in magnetic strength of the left and right arcs, which improves the efficiency of the motor and does not cause noise and life problems. The invention improves the surface magnetic uniformity of the permanent magnet by arranging the mold and the magnetic tile in the orientation field forming. It mainly solves the surface magnetic difference between magnetic steel sheets and sheets by making the orientation magnetic circuit of each injection cavity consistent, but still cannot solve the problem of surface magnetic difference between the front and back sides of a single magnetic steel sheet.

[0004] Patent CN112600318A discloses a ferrite product and a forming mold thereof that can reduce the cogging torque of a permanent magnet motor. The permanent magnet ferrite product is tile-shaped, and the crystal arrangement of different parts of the product is magnetized in an n-pole forming orientation according to the designed magnetic deflection angle β; the inner and outer arcs of the product are provided with cogging at the junction of each pole. The forming mold of the invention includes an upper mold water-absorbing plate and a punch, and is characterized in that: the upper mold water-absorbing plate is composed of a first magnetic conductive layer substrate and a first non-magnetic conductive layer embedded therein, the bottom surface of the first non-magnetic conductive layer of the upper mold water-absorbing plate is in contact with the mold cavity, and the punch is composed of a second magnetic conductive layer substrate and a second non-magnetic conductive layer, and the upper end surface of the second magnetic conductive layer substrate is provided with an arc-shaped boss, and the center line of each boss corresponds to the center line of the designed number of poles of the product, but the crystal arrangement of different parts of the product is carried out according to the designed magnetic declination angle β for n-pole forming orientation magnetization, and the orientation effect is difficult to evaluate, and it is impossible to actually verify whether the n-pole forming orientation magnetization is carried out completely according to the designed magnetic declination angle β, and the processing difficulty of the tooth groove is relatively large, the magnetic shoe is easy to break at the tooth groove, and the magnetic pole orientation curve is difficult to concentrate.

[0005] The rectangular magnets produced by the above methods all have the problem of uneven surface magnetism causing motor vibration. Summary of the invention

[0006] 1. Problem to be solved

[0007] In view of the problem that the motor jitters due to the uneven surface magnetism of the rectangular magnetic steel in the existing motor, the first object of the present invention is to provide a preparation process of the rectangular magnetic steel, and the surface magnetism of the rectangular magnetic steel prepared by the process is more uniform;

[0008] The second object of the present invention is to provide a motor, in which a rectangular magnetic steel is provided, so that the rectangular magnetic steel motor does not vibrate.

[0009] 2. Technical solution

[0010] In order to solve the above problems, the technical solution adopted by the present invention is as follows:

[0011] A motor includes a rectangular magnetic steel, which is spaced apart from a magnetic pole piece and circumferentially wound around a motor drive shaft hole, wherein a preparation process of the rectangular magnetic steel specifically includes the following steps:

[0012] S1. Mixing: Mixing the pre-burned material and auxiliary materials in proportion to obtain a mixed material;

[0013] S2. Molding: Use a magnetic material wet molding hydraulic press, assemble a molding die on the press, and press and mold under a certain molding pressure;

[0014] S3, sintering: the blank obtained by forming is sintered to obtain a sintered product;

[0015] S4. Grinding.

[0016] Furthermore, in step S1, the mixture and water are added into a ball mill in a weight ratio of 1: (1.2-1.5) for wet grinding for 10-12 hours to obtain a slurry with a particle size of 0.75-0.85 μm. The moisture content of the slurry is controlled at 30%-35% by a dehydrator for standby use.

[0017] The mixed material includes pre-burned material and auxiliary materials, and its specific formula is an existing mature batch formula, which does not need special adjustment. The pre-burned material is Benxi iron red, and its Fe2O3 content is greater than 99.99%. The auxiliary materials include CaCO3 0.8wt%, La2O3 0.6wt%, Co3O4 0.5wt%, SiO2 0.2wt%, and HBO3 0.1wt% according to the mass percentage of the pre-burned material.

[0018] Furthermore, in step S2, the slurry is pumped into the molding mold through a hydraulic press, the injection pressure is 5-6MPa, the injection time is 1-3s, the holding pressure is 15-20MPa, and the holding time is 30-40s. During the entire molding process, the magnetization state is maintained, the magnetization current is 50-70A, and the orientation magnetic field strength is greater than 600mT. After the molding is completed, the current is reversed for 1s to form an instantaneous reverse magnetic field. The blank can be demagnetized and then demolded. By changing the orientation magnetic circuit of each injection cavity of the mold, the surface magnetic consistency between the front and back surfaces of the single-piece magnetic steel is improved, thereby improving the motor jitter problem.

[0019] Furthermore, during the die-casting process, the press adopts a coil structure with the same number of upper and lower turns. Preferably, the upper coil of the press is 60,000 ampere-turns, and the lower coil of the press is 60,000 ampere-turns.

[0020] Furthermore, the molding mold includes a main runner and a secondary runner, the main runner includes a first main runner and a second main runner connected to the first main runner, the second main runner is connected to the secondary runner, and the injection cavities are connected at equal intervals on both sides of the secondary runner so that the injection paths of all cavities are the same.

[0021] Furthermore, the punch has an inwardly concave step surface, and the die has an outwardly concave step surface matching the punch.

[0022] Furthermore, in step S3, the blank is passed through a roller kiln and sintered at a high temperature of 1175-1235° C. for 2 hours.

[0023] Furthermore, the sintered product is diamond ground to the required size in the drawing in the grinding equipment. The grinding is carried out in the order of shaft height → chord length → thickness → chamfer. During the grinding process, the opposite surfaces are ground synchronously to ensure that the grinding amount of the two opposite surfaces is the same and the chamfer size is consistent. The weight of the product is controlled by controlling the thickness of the product. The thicker the thickness, the heavier the weight.

[0024] The second object of the present invention is to provide a motor, which includes a rectangular magnetic steel, which is spaced apart from the pole pieces and circumferentially wound on the motor drive shaft hole, and the rectangular magnetic steel is manufactured using the above-mentioned preparation process.

[0025] Rectangular magnetic steel is made through slurry grinding, pressing, sintering, grinding, testing and packaging. Its magnetic properties and dynamic balance are the main factors that cause motor jitter. Among them, the main influencing factor of magnetic properties is surface magnetism, which is determined by the press magnetic field and the mold magnetic circuit design; the main influencing factor of dynamic balance is the weight of the rectangular magnetic steel, which is determined by the green density and grinding control process, and the green density is determined by the mold runner design. Therefore, this application effectively solves the problem of rectangular magnetic steel motor jitter by controlling the magnetic properties and dynamic balance factors in the preparation process of rectangular magnetic steel, including the press coil structure and the mold magnetic circuit, and optimizing them.

[0026] 3. Beneficial effects

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) The present invention optimizes the press coil structure and the mold magnetic circuit during the rectangular magnetic steel forming process by controlling the press coil structure and the mold magnetic circuit, so that the surface magnetic properties of the obtained rectangular magnetic steel are more uniform;

[0029] (2) The present invention optimizes the mold flow channel design, controls the green density and the grinding control process, and the obtained rectangular magnetic steel has a more uniform weight;

[0030] (3) The present application controls the factors that affect the magnetic properties and dynamic balance of the motor jitter, optimizes the press coil structure and the mold magnetic circuit, and obtains a rectangular magnetic steel with greater surface magnetism and uniform weight, effectively solving the problem of motor jitter. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The technical solution of the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments, but it should be understood that these drawings are designed only for explanation purposes and are not intended to limit the scope of the present invention. In addition, unless otherwise specified, these drawings are intended only to conceptually illustrate the structural configurations described herein and are not necessarily drawn to scale.

[0032] Figure 1 This is a schematic diagram of the point location of Example 1;

[0033] Figure 2 The simulation result diagram of adjusting the press wire package structure of Example 1 and Comparative Examples 1-5;

[0034] Figure 3 The mold flow channel of comparative example 6 is:

[0035] Figure 4 The mold runner of Example 2;

[0036] Figure 5 Schematic diagram of the numbering of each cavity in the molding mold of Example 2 and Comparative Example 6;

[0037] Figure 6 The punch embedding method and simulation results of comparative example 7;

[0038] Figure 7 The punch embedding method and simulation results of Comparative Example 8;

[0039] Figure 8 The punch embedding method and simulation results of Example 3;

[0040] Fig. 9 The punch embedding method and simulation results of Comparative Example 9;

[0041] Fig.10 It is a schematic diagram of the motor structure of the present invention. DETAILED DESCRIPTION

[0042] The following detailed description of exemplary embodiments of the present invention refers to the accompanying drawings, which form a part of the description, and in which exemplary embodiments of the present invention that can be implemented are shown as examples. Although these exemplary embodiments are described in sufficient detail to enable those skilled in the art to implement the present invention, it should be understood that other embodiments can be implemented and various changes can be made to the present invention without departing from the spirit and scope of the present invention. The following more detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but is only for the purpose of illustrating and not limiting the description of the characteristics and features of the present invention, so as to propose the best mode for performing the present invention and to enable those skilled in the art to implement the present invention. Therefore, the scope of the present invention is limited only by the appended claims.

[0043] It should be understood that the following text is only used to describe one or several specific embodiments of the present invention, and does not strictly limit the scope of protection of the specific claims of the present invention. As used herein, the terms "parallel" and "perpendicular" are not limited to their strict geometric definitions, but include tolerances for reasonable and inconsistent machining or human errors.

[0044] Example 1

[0045] A motor includes a rectangular magnetic steel, which is spaced apart from a magnetic pole piece and circumferentially wound around a motor drive shaft hole, wherein a preparation process of the rectangular magnetic steel specifically includes the following steps:

[0046] S1. Batching: pre-burned material and auxiliary material are mixed in proportion to obtain a mixture, and the mixture and water are added into a ball mill in a weight ratio of 1: (1.2-1.5) for wet grinding for 10-12 hours to obtain a slurry with a particle size of 0.75-0.85 μm. The moisture content of the slurry is controlled at 30%-35% by a dehydrator for standby use;

[0047] Among them, in step S1, the ingredients include pre-burned materials and auxiliary materials, and the specific formula is an existing mature batch formula, which does not require special adjustment. The pre-burned material is Benxi iron red, and its Fe2O3 content is greater than 99.99%. The auxiliary materials include CaCO3 0.8wt%, La2O3 0.6wt%, Co3O4 0.5wt%, SiO2 0.2wt%, and HBO3 0.1wt% according to the mass percentage of the pre-burned material.

[0048] S2. Molding: Use a magnetic material wet molding hydraulic press, assemble the molding die on the press, and press and mold under a certain molding pressure;

[0049] Specifically, the slurry is pumped into the molding mold through a hydraulic press, the injection pressure is 5 MPa, the injection time is 3 s, the holding pressure is 20 MPa, the holding time is 40 s, and the magnetized state is maintained during the entire molding process.

[0050] Specifically, the molding die is arranged on a magnetic material wet molding hydraulic press, and the molding die comprises an upper die and a lower die, wherein a cavity is arranged in the lower die, and the slurry is pumped into the cavity of the lower die through a hydraulic press, and the punch is located in a slot of the lower die, and is used to press the lower die upward, so that the lower die and the upper die are tightly pressed to realize compression molding;

[0051] The magnetizing wire of the press is surrounded by the forming mold, which includes an upper wire package and a lower wire package. The wire package surrounded by the upper mold is the upper wire package, and the wire package surrounded by the lower mold is the lower wire package. The structure of the upper wire package and the lower wire package affects the upper and lower surface magnetic distribution of the rectangular magnetic steel.

[0052] In Example 1, the magnetizing coil structure of the press is that the upper coil is 60,000 ampere-turns, the lower coil is 60,000 ampere-turns, the magnetizing current is 70A, and the orientation magnetic field strength is 650mT. After the molding is completed, the current is reversed for 1s to form a momentary reverse magnetic field, and the blank can be demagnetized and then demolded.

[0053] The simulation results are as follows Figure 2 As shown in Table 1, 9 points are evenly selected on the surface of the product to simulate its surface magnetic results, and the average value is selected. The point positions are as follows Figure 1 As shown, they are located at the center, edge and vertex of the product respectively.

[0054] S3, sintering: the formed blank is sintered in a roller kiln at a high temperature of 1175-1235°C for 2 hours to obtain a sintered product;

[0055] S4. Grinding: The sintered product is diamond ground to the required size in the drawing in the grinding equipment. The grinding is carried out in the order of shaft height → chord length → thickness → chamfer. During the grinding process, the opposite surfaces are ground synchronously to ensure that the grinding amount of the two opposite surfaces is the same and the chamfer size is consistent.

[0056] The surface magnetism in the embodiment is simulated by multi-physics field simulation software, and any software on the market that can meet this requirement can be used. Ferrite is selected as the material, the magnetic field strength is 600mT to 900mT, and the point control is 10000.

[0057] Comparative Example 1

[0058] Comparative Example 1 simulates that the ampere-turns of the upper and lower coils of the press are different, and measures whether the coil structure of the press is an important factor affecting the surface magnetism of the product. The difference between it and Example 1 is that the upper and lower coils of the press have different structures, and the upper coil is 60,000 ampere-turns and the lower coil is 0 turns. The surface magnetism results obtained are shown in Tables 1 and Figure 2 shown.

[0059] Comparative Example 2

[0060] The difference between Comparative Example 2 and Example 1 is that the upper and lower coils of the press have different structures, with the upper coil being 60,000 ampere-turns and the lower coil being 10,000 ampere-turns. Figure 2 shown.

[0061] Comparative Example 3

[0062] The difference between Comparative Example 3 and Example 1 is that the upper and lower coils of the press have different structures, with the upper coil being 60,000 ampere-turns and the lower coil being 20,000 ampere-turns. Figure 2 shown.

[0063] Comparative Example 4

[0064] The difference between Comparative Example 4 and Example 1 is that the upper and lower coils of the press have different structures, with the upper coil being 60,000 ampere-turns and the lower coil being 30,000 ampere-turns. Figure 2 shown.

[0065] Comparative Example 5

[0066] The difference between Comparative Example 5 and Example 1 is that the upper and lower coils of the press have different structures, with the upper coil being 30,000 ampere-turns and the lower coil being 60,000 ampere-turns. Figure 2 shown.

[0067] Table 1 The coil structure of the medium-pressure machine in Example 1 of the present invention and Comparative Examples 1-5

[0068]

[0069]

[0070] Note: The coil has a rated current of 60A and a current of 10,000 ampere-turns. It is usually 60,000 ampere-turns. The magnetizing current is 50-70A. The orientation magnetic field strength is greater than 600mT. If it is less than 60,000 ampere-turns, the orientation magnetic field strength is less than 600mT and cannot be fully oriented.

[0071] It can be seen from Table 1 that through software simulation, the press coil structure is different and the product surface magnetic distribution is different. Among them, the smaller the difference between the upper and lower coil structures, the greater the surface magnetism. This is because the closer the upper and lower coil structures are, the closer the magnetic field strength and direction provided by the upper and lower coils are. At the same time, the more coil turns the upper coil has, the greater the orientation magnetic field strength at the position of the magnetic steel, and the more vertical the orientation direction.

[0072] This shows that the press wire package structure is an important factor affecting the surface magnetism of the product.

[0073] Example 2

[0074] Example 2 adjusts the flow channel of the molding die to measure whether the flow channel factor of the molding die is an important factor affecting the surface magnetism of the product.

[0075] The mold runner of Example 2 is specially designed so that the injection paths of all cavities are the same.

[0076] Specifically, Figure 4 As shown, it includes a main runner and a secondary runner. The main runner includes a first main runner and a second main runner connected to the first main runner. The second main runner is connected to the secondary runner. The injection cavities are connected at equal intervals on both sides of the secondary runner so that the injection paths of all cavities are the same.

[0077] The green density obtained is shown in Table 2. The number of each cavity in the mold is as follows Figure 5 shown.

[0078] Comparative Example 6

[0079] The difference between Comparative Example 6 and Example 2 is that the mold flow path is different, and the middle cavity injection path is long and the two side cavities injection path is short. Figure 3 As shown, it includes a plurality of parallel flow channels, and both sides of the flow channels are connected to the injection cavities at equal intervals.

[0080] The green density obtained is shown in Table 2. The number of each cavity in the mold is as follows Figure 5 shown.

[0081] Table 2 Green density difference of each cavity in Example 2 of the present invention and Comparative Example 6

[0082] <![CDATA[Unit: g / cm 3 > Comparative Example 6 Example 2 1-1 3.053 3.052 1-4 3.088 3.091 1-7 3.049 3.057 4-1 3.138 3.142 4-4 3.432 3.435 4-7 3.143 3.140 7-1 3.051 3.048 7-4 3.092 3.089 7-7 3.056 3.053

[0083] Judging from the difference in green density of each cavity, there is no obvious difference between the ordinary design and the special design, so the mold flow channel method is not an important factor affecting the surface magnetism of the product.

[0084] Example 3

[0085] Example 3 adjusts the mold magnetic circuit to measure whether the mold magnetic circuit factor is an important factor affecting the surface magnetism of the product. In this example, the magnetic circuit condition is adjusted by adjusting the punch inlay method.

[0086] Experimental method: Setting parameters of the press machine: injection pressure 5MPa, injection time 3s, holding pressure 20MPa, holding time 40s, magnetization current 70A, orientation magnetic field strength 650mT. Only the punch structure is replaced in the mold. By adjusting the mold magnetic circuit, measure whether the mold magnetic circuit factor is an important factor affecting the surface magnetism of the product.

[0087] The punch embedding method and magnetic field simulation of Example 3 are as follows Figure 8 As shown, the punch has an inwardly concave step surface, and the die has an outwardly concave step surface matching the punch.

[0088] Comparative Example 7

[0089] The difference between Comparative Example 7 and Example 3 is that the punch embedding method is different. The punch embedding method and the magnetic field simulation are as follows: Figure 6 As shown, the punch is parallel to the die.

[0090] Comparative Example 8

[0091] The difference between Comparative Example 8 and Example 3 is that the punch embedding method is different. The punch embedding method and the magnetic field simulation are as follows: Figure 7 As shown, the punch has an inwardly concave arc surface, and the die has an outwardly concave arc surface matching the punch.

[0092] Comparative Example 9

[0093] The difference between Comparative Example 9 and Example 3 is that the punch embedding method is different. The punch embedding method and the magnetic field simulation are as follows: Fig. 9 As shown, the punch has an outwardly convex arc surface, and the die has an inwardly concave arc surface matching the punch.

[0094] Through magnetic field simulation, it can be seen that the orientation of the magnetic lines of force in the product in Example 3 is the straightest. Since the magnetic lines of force at each position are more concentrated, parallel and vertical, the orientation effect is better. The mold magnetic circuit design is an important factor affecting the surface magnetism of the product. The more uniform and straighter the magnetic lines of force are, the better the orientation of the magnetic tiles is, and the product is more stable when working in the motor.

[0095] Example 4

[0096] In embodiment 4, a motor comprises a rectangular magnetic steel, wherein the rectangular magnetic steel is spaced apart from the magnetic pole piece and circumferentially wound on the motor drive shaft hole, wherein in the molding process of the rectangular magnetic steel, a magnetic material wet molding hydraulic press is used, a molding mold is installed on the press, and the molding is performed under a certain molding pressure;

[0097] The press coil package adopts the upper and lower double coil packages, both of which are 60,000 ampere-turns, and the mold runner is a special design in Example 2, such as Figure 4 As shown; the mold magnetic circuit design adopts Example 3 respectively; the slurry is pumped into the molding mold through a hydraulic press, the injection pressure is 5MPa, the injection time is 3s, the holding pressure is 20MPa, the holding time is 40s, and the magnetization state is maintained during the entire molding process. The magnetization coil is 60,000 ampere-turns, the magnetization current is 70A, and the orientation magnetic field strength is 650mT. After the molding is completed, the current is reversed for 1s to form a momentary reverse magnetic field greater than 600mT, and the blank can be demagnetized and then demolded.

[0098] The final product weight is controlled within 0.3g.

[0099] Select the appropriate product according to the magnetic field difference and weight difference shown in Table 3, and verify it at the client. The product parameters are shown in Table 3.

[0100] Table 3 Example 4 Product Parameters

[0101] product Magnetic variation Product weight difference Product 1 Within 5% Within 0.3g Product 2 Within 5% Within 0.8g Product 3 Within 10% Within 0.3g Product 4 Within 10% Within 0.8g

[0102] Among them, 100 pieces of each product that met the product parameters 1-4 were taken to the client for installation verification. The corresponding motors of these four products showed no jitter during operation. Therefore, by controlling the press coil structure and the mold magnetic circuit and then controlling the surface magnetic difference of the rectangular magnetic steel and controlling the weight difference between products through the thickness size, it is beneficial to improve the problem of motor jitter.

[0103] The results show that product 1 solves the problem of motor jitter for customers, while the other three products still have the problem of motor jitter. This proves that surface magnetism and weight are key factors affecting the problem of motor jitter. The present invention effectively solves the problem of motor jitter by adjusting the factors affecting surface magnetism and weight.

[0104] In summary, this patent mainly addresses the jitter problem of rectangular magnetic steel motors. It improves the surface magnetic difference of the magnetic steel without changing the shape of the magnetic steel, and will not increase the difficulty of producing the magnetic steel.

[0105] The above description is only a preferred embodiment of the present application and an explanation of the technical principles used. Those skilled in the art should understand that the scope involved in the present application is not limited to the technical solution formed by a specific combination of the above-mentioned technical features, but should also cover other technical solutions formed by any combination of the above-mentioned technical features or their equivalent features without departing from the inventive concept, such as a technical solution formed by replacing the above-mentioned features with (but not limited to) technical features with similar functions disclosed in this application.

[0106] Except for the technical features described in the specification, the remaining technical features are known technologies to those skilled in the art. In order to highlight the innovative features of the present invention, the remaining technical features will not be described here in detail.

Claims

1. A process for preparing a rectangular magnetic steel, characterized in that: Includes steps: S1. Mixing: Mixing the pre-burned material and auxiliary materials in proportion to obtain a mixed material; S2. Molding: Use a magnetic material wet molding hydraulic press, assemble a molding die on the press, and press and mold under a certain molding pressure; S3, sintering: the formed blank is sintered to obtain a sintered product; S4, grinding; The characteristic is that the press adopts a coil package structure with the same number of upper and lower turns. The forming die is provided with a punch for pressing the forming die. The punch has an inwardly concave step surface, and the die has an outwardly concave step surface matching the punch.

2. The preparation process according to claim 1, characterized in that: In step S2, the magnetization state is maintained, the magnetization current is 50-70A, and the orientation magnetic field strength is greater than 600mT. After the molding is completed, a reverse current is applied for 1s for demagnetization and demolding.

3. The preparation process according to claim 2, characterized in that: The upper coil of the press is 60,000 ampere-turns, and the lower coil of the press is 60,000 ampere-turns.

4. The preparation process according to claim 1, characterized in that: During the pressing process, the holding pressure is 15-20MPa and the holding time is 30-40s.

5. The preparation process according to claim 1, characterized in that: Pump the slurry into the molding mold with an injection pressure of 5-6MPa and an injection time of 1-3s.

6. The preparation process according to claim 1, characterized in that: The molding mold includes a main runner and a secondary runner, the main runner includes a first main runner and a second main runner connected to the first main runner, the second main runner is connected to the secondary runner, and the injection cavities are connected at equal intervals on both sides of the secondary runner so that the injection paths of all cavities are the same.

7. The preparation process according to claim 1, characterized in that: In step S1, the mixture and water are added into a ball mill in a weight ratio of 1: (1.2-1.5) for wet grinding for 10-12 hours to obtain a slurry with a particle size of 0.75-0.85 μm. The moisture content of the slurry is controlled at 30%-35% by a dehydrator.

8. The preparation process according to claim 7, characterized in that: The mixed material includes pre-burned material and auxiliary materials. The pre-burned material is iron red, and its Fe2O3 content is greater than 99.99%; the auxiliary materials include CaCO3 0.8wt%, La2O3 0.6wt%, Co3O4 0.5wt%, SiO2 0.2wt%, and HBO3 0.1wt% according to the mass percentage of the pre-burned material.

9. The preparation process according to claim 8, characterized in that: In step S3, the blank is sintered at a high temperature of 1175-1235° C. in a roller kiln for 2 hours.

10. A motor, characterized in that: It comprises a rectangular magnetic steel obtained by a preparation process according to any one of claims 1 to 9, wherein the rectangular magnetic steel is spaced apart from the magnetic pole piece and circumferentially wound around the motor drive shaft hole.

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