Die for sintering neodymium-iron-boron magnet

Abstract

The utility model discloses a mould for sintering neodymium-iron-boron magnet, which comprises two first side plates made of non-magnetic materials and two second side plates made of magnetic materials, the two first side plates are oppositely arranged, the two second side plates are oppositely arranged between the two first side plates, and the two second side plates are oppositely arranged between the two first side plates. The two ends of each second side plate abut against the opposite side faces of the two first side plates correspondingly, and a mold cavity is defined by the first side plates and the second side plates. According to the die disclosed by the utility model, the size in the die width direction of the magnetic conductive second side plate is set to be consistent with the die width size of the die cavity, so that a magnetic field can be ensured to be fully saturated and uniform in the die cavity, and the optimal magnetic field orientation is ensured to be obtained in the pressing process of neodymium iron boron powder; therefore, the magnetic performance of the magnetic material and the size uniformity of the magnetic steel can be improved.

Description

Technical Field

[0001] This utility model relates to a mold for sintering NdFeB magnets. Background Technology

[0002] Sintered NdFeB magnets are widely used in electronics, power machinery, medical devices, new energy vehicles, hardware machinery, aerospace, and other fields. In the production process of sintered NdFeB magnets, the molding die structure is a crucial factor affecting product performance. Traditional die structures (such as...) Figure 1 Due to the relatively long length of the magnetic conductive plate in the mold width direction, problems such as poor magnetic focusing effect, low magnetic field, and uneven magnetic field within the mold cavity arise. These problems directly affect the product's performance and appearance, specifically manifested as follows:

[0003] 1. Poor magnetic focusing effect: Due to the long length of the magnetic plate in the width direction, the magnetic field is easy to disperse during propagation and is difficult to effectively concentrate in the mold cavity, resulting in unsaturated magnetic field strength.

[0004] 2. Low magnetic field: Poor magnetic focusing effect directly leads to the magnetic field strength in the mold cavity being lower than the ideal value, which will affect the magnetic field orientation of the magnetic material and thus affect the magnetic properties of the product.

[0005] 3. Uneven magnetic field in the mold cavity: The magnetic field is unevenly distributed in the mold cavity. The magnetic field at the four corners of the mold cavity is higher than that at the center, which causes the NdFeB powder in the mold cavity to be subjected to inconsistent magnetic field effects, thus affecting the uniformity and appearance quality of the product. Utility Model Content

[0006] The technical problem to be solved by this utility model is to overcome the defects of poor magnetic focusing effect and uneven magnetic field in the mold cavity of the existing mold used to produce sintered NdFeB magnets. The present invention provides a mold for sintered NdFeB magnets, which can improve the performance and dimensional consistency of sintered NdFeB magnets and solve the problems of magnetic field unsaturation and uneven magnetic field in conventional molds.

[0007] The present invention solves the above-mentioned technical problems through the following technical solution:

[0008] This invention provides a mold for sintering NdFeB magnets, comprising two first side plates made of non-magnetic material and two second side plates made of magnetic material. The two first side plates are arranged opposite each other, and the two second side plates are arranged opposite each other between the two first side plates. Each second side plate has its two ends abutting against the opposite sides of the two first side plates. The first and second side plates together form a mold cavity. The first side plates are made of non-magnetic mold steel, such as 70Mn or NW-80, while the second side plates are made of magnetic alloy steel, such as Cr12 or low-carbon alloy steel. During use, the second side plates contact the forming press head.

[0009] In this scheme, the width dimension of the second magnetic side plate is set to be consistent with the width dimension of the mold cavity, which can ensure that the magnetic field is fully saturated and uniform in the mold cavity, thereby ensuring that the NdFeB powder obtains the best magnetic field orientation during the pressing process, and thus improving the magnetic properties of the magnetic material and the uniformity of the magnet size.

[0010] Preferably, the second side plate includes a main body and two protrusions located at both ends of the main body. The protrusions are located at the middle of the end faces of the second side plate that abut against the first side plate, and the first side plate has grooves that match the protrusions.

[0011] In this solution, by adopting the above structure, the first side plate and the second side plate maintain a stable structure after installation, avoiding the second side plate from being contacted and squeezed by the forming press head during the use of the mold, which would cause positional displacement and affect the uniformity of the product size.

[0012] Preferably, the protrusion is provided with a limiting hole, and the first side plate is provided with a connecting hole corresponding to the limiting hole; preferably, the limiting hole is a threaded hole.

[0013] In this design, limiting holes are provided to limit the first and second side plates, preventing relative movement between the first and second side plates during mold use.

[0014] Preferably, the two first side plates are arranged in parallel, and the two second side plates are arranged in parallel.

[0015] In this scheme, the above structure can obtain a relatively regular mold cavity, which further ensures that the neodymium iron boron powder inside obtains the best magnetic field orientation during the pressing process, thereby improving the magnetic properties of the magnetic material and the uniformity of the magnet size.

[0016] Preferably, the interior of the first side plate located between the two second side plates is provided with a first insert made of magnetically conductive material, the first insert extending from one end of the first side plate along a direction parallel to the second side plate to the other end. Preferably, the first inserts in the two first side plates are symmetrically arranged in the middle region of the corresponding first side plates.

[0017] In this scheme, by setting a first insert in the non-magnetic first side plate, the distribution of the magnetic field can be guided and changed to a certain extent, thereby guiding the magnetic field lines to be distributed along a more uniform path, which helps to reduce the local concentration and non-uniformity of the magnetic field in the mold cavity, making the magnetic field strength in the entire mold cavity more consistent.

[0018] Preferably, there are multiple first inserts, and a second insert made of a non-magnetic material is provided between two adjacent first inserts.

[0019] In this scheme, this method makes the distribution of magnetic field lines in the mold cavity more dense and orderly, which helps to improve the overall strength of the magnetic field in the mold cavity and makes it easier for the magnetic field in the mold cavity to reach saturation.

[0020] Preferably, the second insert includes a first surface and a second surface that abut against two adjacent first inserts, the first surface and the second surface having the same shape and size.

[0021] Preferably, the cross-section of the second insert is an isosceles triangle, and the cross-section of the first insert is triangular;

[0022] And / or, there are two first inserts within each of the first side panels;

[0023] And / or, the second inserts located within the two first side plates are respectively disposed in the middle of the corresponding first side plates;

[0024] And / or, the insert assemblies consisting of the first insert and the second insert within the two first side plates are symmetrically arranged.

[0025] This invention provides a method for preparing sintered NdFeB magnets, wherein the preparation method uses the mold for sintering NdFeB magnets as described above.

[0026] Preferably, the preparation method includes the following steps:

[0027] S1. Vacuum melt and cast the raw materials for preparing sintered NdFeB magnets into sheet-like structures with a thickness of 0.25-0.35 mm at a casting temperature of 1435-1440℃.

[0028] S2. The obtained sheet-like material is coarsely crushed using a hydrogen crushing process and then dehydrogenated at 570-580℃.

[0029] S3. The product from step S2 is prepared into powder with a particle size of 3.0-3.3 μm using an air jet mill;

[0030] S4. Place the powder obtained in step S3 into a mold for sintering NdFeB magnets, press the blank using a cold isostatic pressing machine, and perform cold isostatic pressing at 180-200MPa.

[0031] S5. The blank after cold isostatic pressing is vacuum sintered at a temperature of 1070-1075℃ and held for 6-8 hours to obtain neodymium iron boron magnets.

[0032] The positive and progressive effects of this invention are as follows: By setting the width dimension of the magnetically conductive second side plate to match the width dimension of the mold cavity, this invention ensures that the magnetic field is fully saturated and uniform within the mold cavity. This ensures that the NdFeB powder achieves optimal magnetic field orientation during pressing, thereby improving the magnetic properties of the magnetic material and the dimensional uniformity of the magnets. Furthermore, by adding inserts within the non-magnetically conductive first side plate, the distribution of the magnetic field can be guided and altered to a certain extent, guiding the magnetic field lines along a more uniform path. This helps reduce local concentration and non-uniformity of the magnetic field within the mold cavity, resulting in a more consistent magnetic field strength throughout the entire mold cavity. Attached Figure Description

[0033] Figure 1 This diagram shows the conventional mold structure for sintering NdFeB magnets and the distribution of magnetic field lines during use.

[0034] Figure 2 This is a schematic diagram of the mold structure used for sintering NdFeB magnets in Embodiment 1 of this utility model.

[0035] Figure 3 for Figure 2 Front view of the mold used for sintering NdFeB magnets.

[0036] Figure 4 This is a diagram showing the magnetic field distribution of the mold used for sintering NdFeB magnets in Embodiment 1 of this utility model during use.

[0037] Figure 5 This is a schematic diagram of the mold structure used for sintering NdFeB magnets in Embodiment 2 of this utility model.

[0038] Figure 6 for Figure 5 Front view of the mold used for sintering NdFeB magnets.

[0039] Figure 7 This is a diagram showing the magnetic field distribution of the mold used for sintering NdFeB magnets in Embodiment 2 of this utility model during use.

[0040] Figure 8 This is a schematic diagram of the mold structure used for sintering NdFeB magnets in Embodiment 3 of this utility model.

[0041] Figure 9 for Figure 8 Front view of the mold used for sintering NdFeB magnets.

[0042] Figure 10 This is a diagram showing the magnetic field distribution of the mold used for sintering NdFeB magnets in Embodiment 3 of this utility model during use.

[0043] Figure 11 This is a schematic diagram of the mold structure used for sintering NdFeB magnets in Embodiment 4 of this utility model.

[0044] Figure 12 for Figure 11 Front view of the mold used for sintering NdFeB magnets.

[0045] Figure 13 This is a diagram showing the magnetic field distribution of the mold used for sintering NdFeB magnets in Embodiment 4 of this utility model during use.

[0046] Figure 14 This is a schematic diagram of the mold structure used for sintering NdFeB magnets in Embodiment 5 of this utility model.

[0047] Figure 15 for Figure 14 Front view of the mold used for sintering NdFeB magnets.

[0048] Figure 16 This is a diagram showing the magnetic field distribution of the mold used for sintering NdFeB magnets in Embodiment 5 of this utility model during use.

[0049] Figure 17 This is a schematic diagram of the mold structure used for sintering NdFeB magnets in Embodiment 6 of this utility model.

[0050] Figure 18 for Figure 17 Front view of the mold used for sintering NdFeB magnets.

[0051] Figure 19 This is a diagram showing the magnetic field distribution of the mold used for sintering NdFeB magnets in Embodiment 6 of this utility model during use.

[0052] Explanation of reference numerals in the attached figures:

[0053] First side plate 100, second side plate 200, main body 210, protrusion 220, mold cavity 300, screw 400, insert assembly 500, first insert 501, second insert 502. Detailed Implementation

[0054] The present invention will be further illustrated by way of embodiments below, but the present invention is not limited to the scope of the embodiments described herein.

[0055] Example 1

[0056] like Figure 2 and Figure 3 As shown, this embodiment provides a mold for sintering NdFeB magnets, including two first side plates 100 made of non-magnetic material and two second side plates 200 made of magnetic material. The two first side plates 100 are arranged opposite each other, and the two second side plates 200 are arranged opposite each other between the two first side plates 100. The two ends of each second side plate 200 abut against the opposite sides of the two first side plates 100, respectively. The first side plates 100 and the second side plates 200 enclose a mold cavity 300. The two first side plates 100 and the two second side plates 200 are arranged in parallel. In this embodiment, the material of the first side plates 100 is NW-80, and the material of the second side plates 200 is Cr12.

[0057] The second side plate 200 includes a main body 210 and two protrusions 220 located at both ends of the main body 210. The protrusions 220 are located at the middle of the two end faces of the second side plate 200 that abut against the first side plate 100. The first side plate 100 is provided with grooves that match the protrusions 220.

[0058] The protrusion 220 is provided with a limiting hole, and the first side plate 100 is provided with a connecting hole corresponding to the limiting hole. The limiting hole does not extend into the main body 210, which can avoid affecting the distribution of the magnetic field in the mold cavity 300, thereby ensuring that the NdFeB powder obtains the best magnetic field orientation during the pressing process. The limiting hole is a threaded hole, and the first side plate 100 and the second side plate 200 are fixed by screws 400 after installation.

[0059] This embodiment also provides a method for preparing a neodymium iron boron magnet, which uses the mold described above for sintering neodymium iron boron magnets. Specifically, it includes the following steps:

[0060] S1. The raw materials for preparing NdFeB magnets are vacuum melted and cast into sheet-like structures with a thickness of 0.25-0.35 mm at a casting temperature of approximately 1440℃. In this embodiment, the raw material for the NdFeB magnets is grade N52 with a composition of (PrNd). 30.5 (GaAlCuCoTiZr) 1.3 Fe 67.245 B 0.955 .

[0061] S2. The obtained sheet-like material is coarsely crushed using hydrogen crushing technology and then dehydrogenated at 570℃.

[0062] S3. The product from step S2 is prepared into powder with a particle size of 3.0 μm using an air jet mill;

[0063] S4. The powder obtained in step S3 is placed into a mold for sintering NdFeB magnets and pressed into a blank of 63.5mm*31mm*42.1mm using a cold isostatic pressing machine (i.e., mold width of 63.5mm, pressing dimension of 31mm, and orientation dimension of 42.1mm), and then subjected to cold isostatic pressing at 200MPa. The mold width refers to the distance between the two first side plates 100, the pressing dimension refers to the distance between the two second side plates 200, and the orientation dimension refers to the dimension of the second side plate 200 perpendicular to the long side of the first side plate 100. The mold is installed on a vertical pressing and horizontal orientation forming press.

[0064] S5. The blank after cold isostatic pressing is vacuum sintered at 1070℃ and held for 6 hours to obtain neodymium iron boron magnet.

[0065] Example 2

[0066] like Figure 5 and Figure 6 As shown, the difference between this embodiment and embodiment 1 is that in the mold for sintering NdFeB magnets in this embodiment, a first insert 501 made of magnetic material is provided in the middle region between the two second side plates 200 in the two first side plates 100. The first insert 501 extends from the end face of one end of the first side plate 100 along a direction parallel to the second side plate 200 to the end face of the other end.

[0067] The first insert 501 is made of Cr12 and has an isosceles triangle cross-section. The base angle of the isosceles triangle is preferably 30°-60° and the base of the isosceles triangle is 30° away from the mold cavity.

[0068] The height of the first insert 501 does not exceed the thickness of the first side plate 100, preferably 8-10 mm, and the width does not exceed the width of the mold cavity 300.

[0069] In this embodiment, the neodymium iron boron magnet was prepared using the same raw materials and methods as in Example 1. The dimensions of the mold cavity 300 were the same as in Example 1.

[0070] Example 3

[0071] like Figure 8 and Figure 9As shown, the difference between this embodiment and Embodiment 2 is that in this embodiment, the cross-sectional shape of the first insert 501 is an isosceles trapezoid, the base angle of the isosceles trapezoid is preferably 30°-60°, and the base edge of the isosceles trapezoid is far away from the mold cavity 300. The height of the first insert 501 does not exceed the thickness of the first side plate 100, preferably 8-10mm, and the width does not exceed the width of the mold cavity 300.

[0072] In this embodiment, the neodymium iron boron magnet was prepared using the same raw materials and methods as in Example 1. The dimensions of the mold cavity 300 were the same as in Example 1.

[0073] Example 4

[0074] like Figure 11 and Figure 12 As shown, the difference between this embodiment and Embodiment 2 is that in this embodiment, the cross-sectional shape of the first insert 501 is rectangular. The height of the first insert 501 does not exceed the thickness of the first side plate 100, preferably 8-10 mm, and the width does not exceed the width of the mold cavity 300.

[0075] In this embodiment, the neodymium iron boron magnet was prepared using the same raw materials and methods as in Example 1. The dimensions of the mold cavity 300 were the same as in Example 1.

[0076] Example 5

[0077] like Figure 14 and Figure 15 As shown, the difference between this embodiment and Embodiment 2 is that in this embodiment, the cross-sectional shape of the first insert 501 is semi-elliptical. The height of the first insert 501 does not exceed the thickness of the first side plate 100, preferably 8-10 mm, and the width does not exceed the width of the mold cavity 300.

[0078] In this embodiment, the neodymium iron boron magnet was prepared using the same raw materials and methods as in Example 1. The dimensions of the mold cavity 300 were the same as in Example 1.

[0079] Example 6

[0080] like Figure 17 and Figure 18 As shown, the difference between this embodiment and Embodiment 2 is that:

[0081] In this embodiment, each first side plate 100 contains two first inserts 501, and a second insert 502 made of non-magnetic material is provided between the two first inserts 501. The first inserts 501 are made of Cr12 and have a completely symmetrical shape; the second insert 502 is made of 304 stainless steel and has an isosceles triangle cross-section. When the second insert 502 is installed, the base of the isosceles triangle is close to the mold cavity 300. The cross-section of the first insert 501 is also an isosceles triangle, and the base angle of the isosceles triangle is preferably 30°-60°. The two first inserts 501 and the second insert 502 form a structure with an isosceles trapezoidal cross-section.

[0082] Each of the two first side plates 100 is provided with an insert assembly 500 consisting of a first insert 501 and a second insert 502, and the insert assembly 500 is located in the middle of the first side plate 100. The height of the insert assembly 500 does not exceed the thickness of the first side plate 100, preferably 8-10 mm, and the width does not exceed the width of the mold cavity 300.

[0083] In this embodiment, the neodymium iron boron magnet was prepared using the same raw materials and methods as in Example 1. The dimensions of the mold cavity 300 were the same as in Example 1.

[0084] Comparative Example

[0085] In this comparative example, the mold for preparing the NdFeB magnet is as follows: Figure 1 As shown, two non-magnetic plates are sandwiched between two magnetic plates, with the ends of the magnetic plates extending beyond the upper and lower end faces of the two non-magnetic plates. In this comparative example, the neodymium iron boron magnet was prepared using the same raw materials and methods as in Example 1, and the mold cavity dimensions were the same as in Example 1.

[0086] Magnetic circuit simulation analysis was performed on the molds of the comparative example and Examples 1-6, respectively. The analysis results are as follows: Figure 1 , Figure 4 , Figure 7 , Figure 10 , Figure 13 , Figure 16 and Figure 19 As shown in the figure. In the figure, Max refers to the maximum value of magnetic flux density B, Min refers to the minimum value of magnetic flux density B, and "tesla" is the unit of magnetic flux density B, "Tesla"; the gray lines in the figure are a schematic diagram of the magnetic field lines distribution within the mold; the colored background in the figure has no special meaning. The comparison of magnetic field strength in the comparative examples and embodiments 1-6 is shown in Table 1 below:

[0087] Table 1. Magnetic field strength data for comparative examples and Examples 1-6.

[0088]

[0089] (1) Magnetic field lines and magnetic induction intensity

[0090] By comparison Figure 1 and Figure 4 As can be seen from the magnetic field lines, the magnetic field lines of Example 1 are more concentrated than those of the comparative example, which can effectively reduce magnetic field diffusion (magnetic leakage) and has a better magnetic concentration effect. The maximum value (1.833T) and minimum value (1.704T) of the magnetic induction intensity B in the mold cavity of Example 1 are both higher than those of the comparative example (1.792T and 1.513T), indicating that the magnetic field of Example 1 is stronger and more concentrated overall.

[0091] By comparison Figure 1 and Figure 7 , Figure 10 , Figure 13 , Figure 16 and Figure 19 The magnetic field lines show that the distribution of magnetic field lines in Examples 2-6 is more concentrated and smoother than that in the comparative example, which can effectively reduce magnetic field diffusion (magnetic leakage) and has a better magnetic concentration effect. The maximum and minimum values ​​of the magnetic induction intensity B in the mold cavity of Examples 2-6 are higher than those in the comparative example (1.792 T and 1.513 T), indicating that the magnetic field of Examples 2-6 is stronger and more concentrated overall.

[0092] (2) Magnetic field homogeneity and saturation characteristics

[0093] By comparison Figure 1 and Figure 4 The magnetic induction intensity B value in the mold cavity of Example 1 fluctuates within a smaller range (the difference between the maximum and minimum magnetic induction intensity B value in Example 1 is 0.129T, while that in the comparative example is 0.279T), indicating a more uniform magnetic field distribution.

[0094] By comparison Figure 1 and Figure 7 , Figure 10 , Figure 13 , Figure 16 and Figure 19 The magnetic induction intensity B value fluctuation range in the mold cavity of Examples 2-6 is smaller (the difference between the maximum and minimum magnetic induction intensity B values ​​in Examples 2-6 is smaller than that in the comparative examples), indicating a more uniform magnetic field distribution.

[0095] Regions with dense and uniform magnetic field lines typically correspond to more stable magnetic field characteristics.

[0096] Therefore, Example 1, by optimizing the magnetic plate, achieved a stronger magnetic focusing effect, higher magnetic induction intensity, and more uniform magnetic field characteristics. Examples 2-6, by optimizing the magnetic plate structure and adding magnetic inserts within the non-magnetic plate, achieved an even stronger magnetic focusing effect, higher magnetic induction intensity, and more uniform magnetic field.

[0097] The following analysis examines the consistency of product dimensions and performance between conventional molds and the molds used in embodiments 1-6 of this utility model:

[0098] (1) Consistency of product dimensions produced by mold

[0099] The same molding press was used to install both conventional molds and the molds described in Examples 1-6 of this utility model to produce product grade N52. The comparative data represents the dimensional consistency data of products produced using conventional molds, while the data from Examples 1-6 represents the dimensional consistency data of products produced using the molds of this utility model. Specific dimensional data are shown in Table 2 below:

[0100] Table 2. Dimensional consistency data of products manufactured using molds in comparative examples and Examples 1-6.

[0101]

[0102] The above data shows that the mold produced by this invention has a smaller dimensional variation and better consistency than conventional molds.

[0103] (2) Consistency of product performance in mold production

[0104] The magnetic properties of the products produced above were tested. The comparative data represents the performance consistency data of products produced using conventional molds, while the data from Examples 1-6 represent the performance consistency data of products produced using the molds of this utility model. Specific performance data are shown in Table 3 below:

[0105] Table 3. Performance consistency data of products manufactured using molds in comparative examples and Examples 1-6.

[0106]

[0107] In Table 3 above, Br stands for Residual Induction, which refers to the magnetic induction intensity retained inside a magnetic material (such as neodymium iron boron or ferrite) after it has been magnetized to saturation by an external magnetic field in a closed environment and the external magnetic field has been removed.

[0108] The Hcj parameter of a magnet refers to its coercivity, also known as intrinsic coercivity (Hcj). Coercivity is the magnetic field strength required to reduce the magnetization of a material to zero under the influence of a magnetic field.

[0109] Data shows that the products produced by the mold of this utility model have good consistency in performance, which is better than that of conventional molds.

[0110] While specific embodiments of this utility model have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of this utility model is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of this utility model, but all such changes and modifications fall within the scope of protection of this utility model.

Claims

1. A mold for sintering NdFeB magnets, comprising two first side plates made of non-magnetic material and two second side plates made of magnetic material, the two first side plates being disposed opposite to each other, characterized in that, Two second side plates are disposed opposite each other between two first side plates, and the two ends of each second side plate abut against the opposite sides of the two first side plates respectively. The first side plates and the second side plates enclose each other to form a mold cavity.

2. The mold for sintering NdFeB magnets as described in claim 1, characterized in that, The second side plate includes a main body and two protrusions located at both ends of the main body. The protrusions are located at the middle of the end faces of the two ends of the second side plate that abut against the first side plate. The first side plate is provided with grooves that match the protrusions.

3. The mold for sintering NdFeB magnets as described in claim 2, characterized in that, The protrusion is provided with a limiting hole, and the first side plate is provided with a connecting hole corresponding to the limiting hole.

4. The mold for sintering NdFeB magnets as described in claim 1, characterized in that, The two first side plates are arranged in parallel, and the two second side plates are arranged in parallel.

5. The mold for sintering NdFeB magnets as described in claim 1, characterized in that, The first side plate located between the two second side plates has a first insert made of magnetic material inside, which extends from one end of the first side plate to the other end in a direction parallel to the second side plate.

6. The mold for sintering NdFeB magnets as described in claim 5, characterized in that, There are multiple first inserts, and a second insert made of non-magnetic material is provided between two adjacent first inserts.

7. The mold for sintering NdFeB magnets as described in claim 6, characterized in that, The second insert includes a first surface and a second surface that fit against two adjacent first inserts, the first surface and the second surface having the same shape and size.

8. The mold for sintering NdFeB magnets as described in claim 7, characterized in that, The cross-section of the second insert is an isosceles triangle, and the cross-section of the first insert is a triangle; And / or, there are two first inserts within each of the first side panels.

9. The mold for sintering NdFeB magnets as described in claim 7, characterized in that, The second inserts located within the two first side plates are respectively disposed in the middle of the corresponding first side plates.

10. The mold for sintering NdFeB magnets as described in claim 7, characterized in that, The insert assemblies, consisting of the first insert and the second insert within the two first side plates, are arranged symmetrically.

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