Grain boundary diffusion anti-deformation method for special-shaped sintered neodymium-iron-boron magnet with large length-diameter ratio

Abstract

The invention relates to a grain boundary diffusion anti-deformation method for a special-shaped sintered neodymium-iron-boron magnet with a large length-diameter ratio, which comprises the following steps of: 1, preparing a concave die and a convex die which are matched with the neodymium-iron-boron magnet, and matching the shape structure of a cavity with the magnet after the concave die and the convex die are assembled; 2, during grain boundary diffusion heating of the neodymium-iron-boron magnet, the neodymium-iron-boron magnet is placed in a cavity formed after the female die and the male die are assembled in the step 1; thirdly, preset pressure is applied to the top after the female die and the male die are assembled; and 4, demolding after the neodymium-iron-boron magnet is cooled. The method has the beneficial effects that deformation of the neodymium-iron-boron magnet during grain boundary diffusion heating is prevented, grinding after diffusion is reduced, and performance reduction caused by excessive grinding is avoided.

Description

Technical Field

[0001] The invention relates to the technical field of NdFeB permanent magnet materials, and in particular to a method for preventing deformation of a large aspect ratio special-shaped sintered NdFeB magnet by grain boundary diffusion. Background Art

[0002] Sintered NdFeB is the magnetic material with the best comprehensive magnetic properties today, and is widely used in new energy vehicles, wind power generation, industrial energy-saving motors, etc. Since the temperature of sintered NdFeB is low, in traditional processes, the heat resistance of the magnet is improved mainly by adding a large amount of heavy rare earth elements. However, since heavy rare earth elements are expensive and adding heavy rare earth elements will damage the saturation magnetization intensity of the magnet, its application in high-temperature fields is limited.

[0003] The grain boundary diffusion technology developed in recent years diffuses the heavy rare earth elements attached to the surface of the magnet into the interior of the magnet along the grain boundaries through high-temperature heat treatment. Since the heavy rare earth elements are mainly distributed in the grain boundaries of the main phase grains and the epitaxial layer, the performance of the magnet can be greatly improved by using a small amount of heavy rare earth elements.

[0004] However, the grain boundary diffusion technology is limited by the diffusion depth and often needs to be cut into small pieces of magnets. During the high-temperature heat treatment process, the magnets are easily thermally deformed, especially those with anisotropic appearance and large aspect ratio. In order to cope with the deformation, not only the size of the product needs to be increased and the amount of material grinding needs to be increased, but also the heavy rare earth-rich area that penetrates the surface cannot be retained, resulting in a decrease in performance and an increase in cost. Summary of the invention

[0005] In summary, in order to overcome the deficiencies of the prior art, the technical problem to be solved by the present invention is to provide a method for preventing deformation of large aspect ratio grain boundary diffusion sintered NdFeB.

[0006] The technical solution of the present invention to solve the above technical problem is as follows: A method for preventing deformation of large aspect ratio grain boundary diffusion sintered NdFeB, comprising the following steps:

[0007] Step 1, preparing a concave mold and a convex mold matching the NdFeB magnet, wherein the shape structure of the cavity after the concave mold and the convex mold are molded together is adapted to the NdFeB magnet;

[0008] Step 2: When the NdFeB magnet is heated by grain boundary diffusion, the NdFeB magnet is placed in the cavity formed by the die and the punch in step 1;

[0009] Step 3, applying a preset pressure to the top of the concave mold and the convex mold after the mold is closed;

[0010] Step 4: De-mould the NdFeB magnet after it cools down.

[0011] The beneficial effects of the present invention are: to prevent the deformation of the NdFeB magnet during the grain boundary diffusion heating, and to ensure the quality of the product.

[0012] On the basis of the above technical solution, the present invention can also be improved as follows:

[0013] Further, the surfaces of the female die and the male die in step one are sandblasted.

[0014] The beneficial effect of adopting the above further solution is: to prevent the adhesion between the die and the magnet during the diffusion process of the die.

[0015] Further, the female die and the male die in step one are made of alloy steel material.

[0016] The beneficial effect of adopting the above further solution is: high temperature resistance and strong anti-deformation ability.

[0017] Further, in step two, multiple NdFeB magnets are placed into the cavity formed after the female die and the male die are closed in a side-by-side and / or stacked manner.

[0018] The beneficial effect of adopting the above further solution is: a pair of female die and male die are used for multiple NdFeB magnets, which improves the production efficiency.

[0019] Further, when multiple NdFeB magnets are stacked, high-temperature resistant particles are sprinkled between the magnets for isolation.

[0020] The beneficial effect of adopting the above further solution is: to prevent the high-temperature adhesion of adjacent magnets.

[0021] Further, after the female die and the male die of different magnets are closed, they are stacked and placed in multiple layers up and down, and the cavity of the lower female die is arranged at the top of the upper male die, and high-temperature resistant heavy objects are placed on the female die and the male die of the top layer.

[0022] The beneficial effect of adopting the above further solution is: to achieve the purpose of large-scale production. Description of the Drawings

[0023] Figure 1 It is a schematic diagram for preventing deformation by using a pair of female die and male die;

[0024] Figure 2 It is a schematic diagram for preventing deformation by using a row of female die and male die;

[0025] Figure 3 It is a schematic diagram for preventing deformation by using multiple rows and multiple layers of female die and male die; Figure 4 It is a schematic diagram for placing multiple NdFeB magnets in a side-by-side manner into a pair of female die and male die to prevent deformation.

[0026] In the drawings, the list of components represented by each reference numeral is as follows:

[0027] 1. Neodymium iron boron magnet, 2. Female die, 3. Male die, 4. Heavy object. Specific implementation mode

[0028] The principles and features of the present invention will be described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0029] Example 1

[0030] A method for preventing deformation of a large aspect ratio grain boundary diffusion sintered neodymium iron boron magnet includes the following steps:

[0031] Step 1: Prepare a female die 2 and a male die 3 that match the neodymium iron boron magnet 1. After the female die 2 and the male die 3 are closed, the shape and structure of the cavity are adapted to the neodymium iron boron magnet 1. The surfaces of the female die 2 and the male die 3 are sandblasted to prevent adhesion to the magnet during the diffusion process of the mold.

[0032] Step 2: When the neodymium iron boron magnet 1 is heated for grain boundary diffusion, place the neodymium iron boron magnet 1 into the cavity formed after the female die 2 and the male die 3 in Step 1 are closed. The female die 2 and the male die 3 are made of alloy steel material, with high temperature resistance and strong anti-deformation ability. 在 Under the restriction of the female die 2 and the male die 3, the purpose of preventing the magnet from deforming is achieved.

[0033] Step 3: Apply a preset pressure to the top of the closed female die 2 and male die 3, such as Figure 1 shown. The method of applying pressure can be by placing a heavy object 4, where the heavy object 4 can be a high-temperature resistant iron block or stone. To achieve large-scale production, the following method can be used to apply a preset pressure to the top of the closed female die 2 and male die 3:

[0034] As Figure 2 and 3 shown, the closed female die 2 and male die 3 of different magnets are stacked vertically, and a high-temperature resistant heavy object 4 is placed on the top layer of the female die 2 and male die 3. Also, the cavity of the lower layer female die 2 is set on the top of the upper layer male die 3. That is, the lower layer female die 2 and male die 3 can utilize the upper layer female die 2 and male die 3 to provide pressure, and the top layer female die 2 and male die 3 provide pressure through the high-temperature resistant heavy object 4. Stacking vertically not only increases the corresponding pressure but also reduces the floor area.

[0035] Example 2

[0036] This example makes the following adjustment to Step 2, and the rest of the operations are the same as in Example 1. Step 2 is specifically as follows:

[0037] As Figure 4As shown, when the NdFeB magnet 1 is heated by grain boundary diffusion, multiple NdFeB magnets 1 are placed in the cavity formed after the female mold 2 and the male mold 3 are closed in step one in a side-by-side or stacked manner. When multiple NdFeB magnets 1 are stacked, high-temperature resistant particles are sprinkled between the magnets for isolation.

[0038] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preventing deformation of large aspect ratio special-shaped sintered NdFeB magnets by grain boundary diffusion, characterized in that: The steps include: Step 1, preparing a concave mold (2) and a convex mold (3) that match the neodymium iron boron magnet (1), wherein the shape structure of the cavity after the concave mold (2) and the convex mold (3) are molded together is adapted to the neodymium iron boron magnet (1); Step 2, when the NdFeB magnet (1) is heated by grain boundary diffusion, the NdFeB magnet (1) is placed in the mold cavity formed by the combination of the concave mold (2) and the convex mold (3) in step 1; Step 3, applying a preset pressure to the top of the female mold (2) and the male mold (3) after they are molded together; Step 4: After the NdFeB magnet (1) is cooled, it can be demoulded.

2. The method for preventing grain boundary diffusion deformation of a large aspect ratio special-shaped sintered NdFeB magnet according to claim 1, characterized in that: The surfaces of the concave mold (2) and the convex mold (3) in step one are sandblasted.

3. The method for preventing grain boundary diffusion deformation of a sintered NdFeB magnet with a large aspect ratio according to claim 1, characterized in that: The concave die (2) and the convex die (3) in step one are made of high temperature resistant alloy steel material.

4. The method for preventing grain boundary diffusion deformation of a sintered NdFeB magnet with a large aspect ratio according to claim 1, characterized in that: In step 2, multiple NdFeB magnets (1) are placed side by side and / or in layers into the mold cavity formed by combining the concave mold (2) and the convex mold (3) in step 1.

5. The method for preventing deformation of a sintered NdFeB magnet with a large aspect ratio by grain boundary diffusion according to claim 4, characterized in that: When multiple NdFeB magnets are stacked, high temperature resistant particles are sprinkled between the magnets for isolation.

6. A method for preventing grain boundary diffusion deformation of a sintered NdFeB magnet with a large aspect ratio according to any one of claims 1 to 5, characterized in that: After the concave dies (2) and the convex dies (3) of different magnets are molded together, they are stacked up and placed in multiple layers, and the cavity of the lower layer of the concave dies (2) is arranged on the top of the upper layer of the convex dies (3), and the convex dies (3) are placed on the topmost layer of the concave dies (2) and the convex dies (3).

Images