A method for treating grain boundary diffusion of NdFeB magnets

Abstract

The present invention provides a grain boundary diffusion treatment method suitable for multi-component alloy diffusers, and relates to an attachment device for multi-component alloy diffusers, and an optimized and matched attachment and diffusion treatment process. The method does not require the multi-component alloy to be crushed, and only requires the multi-component alloy to be prepared into a block material to achieve the attachment of the diffuser, thereby avoiding the oxidation and other problems caused by the multi-component alloy crushing and powdering process, maintaining the excellent characteristics of each component of the multi-component alloy, and ensuring the heavy rare earth diffusion effect; the attachment device for the multi-component alloy diffuser of the present invention is combined with the attachment heat treatment process to flexibly control the thickness of the attachment layer in the pre-treated magnet, and improve the consistency and stability of the diffused magnet. The present invention has a simple process, strong controllability, good repeatability and stability, and is more suitable for the promotion and application of large-scale production.

Description

Technical Field

[0001] The invention belongs to the technical field of magnet diffusion processing, and relates to a diffusion processing method of a NdFeB magnet, and in particular to a processing method for grain boundary diffusion of a NdFeB magnet. Background Art

[0002] Sintered NdFeB magnets have become core functional materials in the fields of electricity, telecommunications, rail transit, new energy vehicles, biomedicine, and household appliances due to their excellent permanent magnetic properties. The working environment of electromechanical equipment in the field of high-tech is complex, and the pursuit of miniaturization, lightweight and high precision of devices has put forward more stringent requirements on the temperature resistance of permanent magnetic materials. The coercive force characterizes the ability of magnets to resist external reverse magnetic fields or other demagnetization effects. It is an important parameter that affects the working temperature of magnets and fundamentally determines the practical application of NdFeB magnets. However, the actual value of the coercive force of ternary NdFeB magnets is less than 30% of the theoretical value, and the temperature tolerance is low. Therefore, there is an urgent need for NdFeB magnets with higher coercive force to meet their applications in high temperature and high precision fields.

[0003] Traditional means of improving the coercive force of NdFeB magnets mainly rely on the addition of large amounts of heavy rare earth elements such as dysprosium and terbium during alloy smelting and dual alloy processes. Although these methods can partially replace light rare earths in the main phase with heavy rare earths to form grains with higher magnetocrystalline anisotropy, excessive amounts of heavy rare earths will enter the interior of the magnet grains, causing serious magnetic dilution, resulting in a significant reduction in the remanence and magnetic energy product of the magnet. In addition, the utilization rate of heavy rare earth elements is low, resulting in a waste of scarce heavy rare earth resources and a high cost of magnet raw materials. The grain boundary diffusion technology of heavy rare earth can significantly improve the coercive force of magnets without reducing the remanence of magnets, and greatly reduce the use of heavy rare earth. It has been widely studied in recent years. Its principle is to deposit the diffuser containing heavy rare earth elements on the surface of NdFeB magnets, and by optimizing the heat treatment process, the heavy rare earth elements diffuse from the surface of the magnet along the grain boundary to the inside of the magnet, and are mainly distributed on the grain boundary and the surface of the grain without entering too much into the grain. A shell with a high magnetocrystalline anisotropy field is formed on the surface of the main phase grains, which plays a role in magnetic hardening and inhibits the nucleation of reverse magnetization domains. At present, the diffusers of grain boundary diffusion mainly include pure metals, oxides, fluorides, hydrides, and alloys. Among them, alloy diffusers can further significantly reduce the content ratio of heavy rare earth compared with other diffusers, and cooperate with other non-rare earth metal elements to improve the efficiency of heavy rare earth elements, expand the depth of diffusion, and promote the high-quality utilization of heavy rare earth elements. Due to the promotion effect of different types of elements on the diffusion effect of heavy rare earths, alloy diffusion materials have developed from binary to ternary, quaternary, and even quinary and above.

[0004] At present, the laboratory research and development of multi-component alloy diffusion products adopts the method of sheet attachment diffusion, that is, the designed multi-component alloy is finely processed into thin sheets and spread on the upper and lower ends of the magnet and diffused heat treatment is performed. This treatment method can ensure the characteristics of the multi-component alloy, thereby achieving a better performance improvement effect of the magnet, but the preparation efficiency of the diffusion magnet is extremely low, which is not conducive to the industrialization of multi-component alloy diffusion, and is limited by the consistency of the quality of the alloy thin sheets, and the performance of batch magnets fluctuates greatly. Conventional diffusion material attachment methods, such as sputtering, vapor deposition, and electrophoretic deposition, cannot meet the uniformity and stability attachment requirements of multi-component diffusion materials, and it is difficult to maintain the established multi-component alloy characteristics of the diffusion material during the attachment process, which greatly reduces the diffusion effect; and the powder coating method (impregnation method) that is usually suitable for industrialization is in the process of crushing the multi-component alloy ingot into powder or preparing the coating slurry. The process flow is cumbersome and complicated, and the consistency of the batch diffusion products is poor. In addition, due to the finer particle size requirements of the rare earth alloy powder, it is easier to cause the oxidation of the alloy components, destroying the low melting point and high wettability characteristics of the multi-component alloy diffusion material, wasting rare earth elements and deteriorating the diffusion effect.

[0005] Therefore, how to find a grain boundary diffusion treatment method suitable for multi-element alloy diffusers to ensure the diffusion effect of heavy rare earths and improve the diffusion efficiency of magnets is of great significance to the development of sintered NdFeB permanent magnet materials and their industries, and is also one of the problems that many forward-looking researchers in the industry need to solve urgently. Summary of the invention

[0006] In view of this, the technical problem to be solved by the present invention is to provide a processing method for grain boundary diffusion of NdFeB magnets. The processing method provided by the present invention involves an attachment device for multi-component alloy diffusers, and an optimized and matched attachment and diffusion treatment process. Under the premise of ensuring the excellent diffusion effect of the multi-component alloy, the diffusion material attachment process flow is simplified. The process is simple, and efficient preparation of diffused magnets can be achieved, and the magnetic properties of the magnets have good consistency and stability.

[0007] The present invention provides a diffusion treatment method for NdFeB magnets, comprising the following steps:

[0008] 1) The multi-component alloy diffusion block and the NdFeB magnet to be treated are bonded and fixed on a multi-component alloy diffusion attachment device, and after attachment heat treatment, a pre-treated magnet is obtained;

[0009] 2) The pre-treated magnet obtained in the above steps is subjected to diffusion heat treatment to obtain a diffusion-treated NdFeB magnet.

[0010] Preferably, the thickness of the multi-element alloy diffusion block is 2 to 5 mm;

[0011] The NdFeB magnet to be processed comprises a plurality of NdFeB magnets to be processed;

[0012] The area of ​​the surface of the multi-element alloy diffusion block material that is bonded to the NdFeB magnet to be processed is greater than the area of ​​the surface of the NdFeB magnet to be processed that is bonded to the NdFeB magnet to be processed;

[0013] The diffusion process includes a grain boundary diffusion process.

[0014] Preferably, the area of ​​the surface of the multi-element alloy diffusion block that is bonded to the NdFeB magnet to be treated is 1.5 to 3 times the area of ​​the surface of the NdFeB magnet to be treated;

[0015] The multi-component alloy diffusion material attachment device tightly fits and fixes the multi-component alloy diffusion material block and the NdFeB magnet to be processed;

[0016] The multi-element alloy diffusion block can be used multiple times in the diffusion treatment process of NdFeB magnets;

[0017] The thickness of the NdFeB magnet to be processed in the diffusion direction is 1 to 8 mm.

[0018] Preferably, the multi-component alloy diffuser attachment device comprises a supporting structure, a multi-component alloy diffuser slot structure, a spring structure and a positioning locking structure;

[0019] The multi-element alloy diffuser slot structure is connected to the support structure via a spring structure;

[0020] A positioning and locking structure is arranged around the support structure;

[0021] The support structure includes an upper substrate and a lower substrate;

[0022] The alloy diffuser slot structure comprises a tray with slots arranged around its periphery;

[0023] The area of ​​the tray is adapted to the area of ​​the surface of the multi-element alloy diffusion block that is in contact with the NdFeB magnet to be processed.

[0024] Preferably, one end of the spring structure is fixed to the support structure, and the other end is fixed to the multi-element alloy diffuser slot structure;

[0025] The number of the alloy diffuser slot structures is greater than or equal to 2;

[0026] The spring structure includes at least 2 sets of spring brackets;

[0027] The number of spring brackets in a group is greater than or equal to 2;

[0028] One of the alloy diffuser slot structures is disposed on the upper substrate via a spring bracket, and the other is disposed on a corresponding position of the lower substrate via a spring bracket;

[0029] When the upper substrate and the lower substrate are fixed, the two alloy diffusion slot structures have upper and lower corresponding positions;

[0030] The positioning and locking structure includes a through hole for bolt fixing and / or a buckle structure for locking.

[0031] Preferably, the step 1) is specifically as follows:

[0032] a) processing and surface treating the NdFeB magnet to obtain a magnet to be processed;

[0033] Processing the multi-element alloy diffusion block into a size that fits the tray of the diffusion slot in the multi-element alloy diffusion attachment device, and then cleaning the surface to obtain the multi-element alloy diffusion block, and fixing it in the diffusion slot;

[0034] b) placing the magnet to be processed obtained in the above steps in a multinary alloy diffuser attachment device, between the diffuser clamping slot on the upper substrate with the multinary alloy diffuser block and the diffuser clamping slot on the lower substrate with the multinary alloy diffuser block, and fitting with the surfaces of the upper and lower multinary alloy diffuser blocks, and then fixing and clamping the substrates by a positioning and locking structure;

[0035] c) The multi-component alloy diffusion material attachment device with the magnet to be treated obtained in the above step is moved as a whole to a vacuum heat treatment furnace, and after the attachment heat treatment, a pre-treated magnet with the diffusion material attached is obtained.

[0036] Preferably, the vacuum degree of the attachment heat treatment is less than or equal to 10 -3 Pa;

[0037] The temperature of the attachment heat treatment is 520-750°C;

[0038] The time of the attachment heat treatment is 0.5 to 2 hours;

[0039] The cooling method after the attachment heat treatment includes rapid cooling;

[0040] The rapid cooling rate is 20-35°C / min.

[0041] Preferably, the degree of vacuum in the diffusion heat treatment is less than or equal to 10 -3 Pa;

[0042] The temperature of the diffusion heat treatment is 850-950°C;

[0043] The diffusion heat treatment time is 4 to 8 hours;

[0044] The cooling method after the diffusion heat treatment includes rapid cooling;

[0045] The rapid cooling rate is 15-25°C / min.

[0046] Preferably, the diffusion heat treatment further includes a tempering heat treatment step;

[0047] The vacuum degree of the tempering heat treatment is less than or equal to 10 -3 Pa;

[0048] The temperature of the tempering heat treatment is 480-520°C;

[0049] The tempering heat treatment time is 4 to 10 hours;

[0050] The cooling method after the tempering heat treatment includes rapid cooling;

[0051] The rapid cooling rate is 15-25°C / min.

[0052] Preferably, the multi-component alloy diffuser has the following general formula:

[0053] H 100-x-y R x M y ;

[0054] wherein H includes one or more of Tb, Dy and Ho;

[0055] R includes one or more of Pr, Nd, Y, Ce and La;

[0056] M includes one or more of Fe, Cu, Al, Ga, Zn, Mg and Mn;

[0057] x is 0 to 70, y is 0 to 30, and x and y are not 0 at the same time.

[0058] The present invention provides a diffusion treatment method for NdFeB magnets, comprising the following steps: firstly, a multi-component alloy diffuser block and a NdFeB magnet to be treated are bonded and fixed on a multi-component alloy diffuser attachment device, and a pre-treated magnet is obtained after attachment heat treatment; then, the pre-treated magnet obtained in the above steps is subjected to diffusion heat treatment to obtain a diffusion-treated NdFeB magnet. Compared with the prior art, the present invention creatively designs a grain boundary diffusion treatment method suitable for multi-component alloy diffusers, which involves an attachment device for multi-component alloy diffusers, and an optimized and matched attachment and diffusion treatment process. The method does not require the multi-component alloy to be crushed, but only requires the multi-component alloy to be prepared into a block to achieve the attachment of the diffuser, thereby avoiding the oxidation and other problems caused by the crushing and powdering process of the multi-component alloy, maintaining the excellent properties of each component of the multi-component alloy, and ensuring the diffusion effect of heavy rare earths; the multi-component alloy diffuser attachment device provided by the present invention adopts a zoned spring structure, which can effectively avoid the problem of insufficient contact between the diffuser and the magnet due to the size error of the magnet to be treated during batch diffusion, thereby improving the quality and efficiency of the diffusion attachment treatment; the multi-component alloy diffuser block in the present invention can be repeatedly used for multiple times. Before each attachment treatment, it is only necessary to perform simple surface treatment on the multi-component alloy diffusion block, thereby improving the utilization rate of the diffusion and reducing the production cost. Moreover, based on the design of the attachment device, the diffusion block is easy to replace and has a high degree of freedom in operation. The attachment device of the multi-component alloy diffusion of the present invention can flexibly control the thickness of the attachment layer in the pre-treated magnet (the magnet after the diffusion is attached) in combination with the attachment heat treatment process, thereby improving the consistency and stability of the diffusion magnet. The relatively low temperature attachment heat treatment adopted by the present invention facilitates the separation of the diffusion and the magnet after the attachment treatment, and the multi-component alloy is not easily deformed at a relatively low temperature due to its relatively high viscosity. The present invention is suitable for batch preparation of multi-component alloy diffusion diffusion-treated magnets, and has a simple process, strong controllability, good repeatability and stability, and is more suitable for the promotion and application of large-scale production.

[0059] Experimental results show that the NdFeB grain boundary diffusion treatment method designed by the present invention is more suitable for the grain boundary diffusion treatment of multi-component alloy diffusions. The method designed by the present invention ensures the excellent properties of the multi-component alloy, greatly improves the performance of the magnet after diffusion, and has good consistency and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 A simplified assembly diagram of the multi-element alloy diffusion attachment device provided by the present invention;

[0061] Figure 2 A schematic diagram of a fabric sample for the attachment process of the multi-element alloy diffusion attachment device provided by the present invention;

[0062] Figure 3 This is a backscattering image of the surface cross section of the pre-treated magnet that has completed the attachment treatment process in Example 1 of the present invention. DETAILED DESCRIPTION

[0063] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples, but it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention rather than limiting the patent claims of the present invention.

[0064] All raw materials of the present invention have no particular limitation on their sources, and can be purchased from the market or prepared according to conventional methods known to those skilled in the art.

[0065] There is no particular limitation on the purity of all raw materials in the present invention. The present invention preferably uses analytically pure materials or materials with conventional purity in the field of NdFeB magnet diffusion treatment.

[0066] The sources and abbreviations of all raw materials in the present invention are conventional sources and abbreviations in the field, and are clear and definite in the field of their relevant uses. Those skilled in the art can purchase them from commercial sources or prepare them by conventional methods based on the abbreviations and corresponding uses.

[0067] The present invention provides a diffusion treatment method for NdFeB magnets, comprising the following steps:

[0068] 1) The multi-component alloy diffusion block and the NdFeB magnet to be treated are bonded and fixed on a multi-component alloy diffusion attachment device, and after attachment heat treatment, a pre-treated magnet is obtained;

[0069] 2) The pre-treated magnet obtained in the above steps is subjected to diffusion heat treatment to obtain a diffusion-treated NdFeB magnet.

[0070] The present invention firstly adheres and fixes a multi-component alloy diffusion block and a NdFeB magnet to be treated on a multi-component alloy diffusion attachment device, and performs attachment heat treatment to obtain a pre-treated magnet.

[0071] In the present invention, the thickness of the multi-element alloy diffusion material block is preferably 2 to 5 mm, more preferably 2.5 to 4.5 mm, and even more preferably 3 to 4 mm.

[0072] In the present invention, the NdFeB magnet to be processed preferably includes a plurality of NdFeB magnets to be processed.

[0073] In the present invention, the surface area of ​​the multi-element alloy diffusion block that is bonded to the NdFeB magnet to be processed is preferably larger than the surface area of ​​the NdFeB magnet to be processed that is bonded to the NdFeB magnet to be processed.

[0074] In the present invention, the pre-treated magnet obtained in the above steps is subjected to diffusion heat treatment to obtain a diffusion-treated NdFeB magnet.

[0075] In the present invention, the diffusion treatment preferably includes a grain boundary diffusion treatment.

[0076] In the present invention, the surface area of ​​the multi-alloy diffusion block bonded to the NdFeB magnet to be treated is preferably 1.5 to 3 times the surface area of ​​the NdFeB magnet to be treated, more preferably 1.8 to 2.7 times, more preferably 2.1 to 2.4 times.

[0077] In the present invention, the multi-component alloy diffusion material attachment device preferably tightly fits and fixes the multi-component alloy diffusion material block and the NdFeB magnet to be processed.

[0078] In the present invention, the multi-component alloy diffusion material block can preferably be used multiple times in the diffusion process of NdFeB magnets, that is, the multi-component alloy diffusion material block of the present invention includes a multi-component alloy diffusion material block with a reusable property.

[0079] In the present invention, the thickness of the NdFeB magnet to be processed in the diffusion direction is preferably 1 to 8 mm, more preferably 2 to 7 mm, more preferably 3 to 6 mm, and more preferably 4 to 5 mm.

[0080] In the present invention, the multi-component alloy diffuser attachment device preferably includes a supporting structure, a multi-component alloy diffuser slot structure, a spring structure and a positioning locking structure.

[0081] In the present invention, the multi-component alloy diffuser slot structure is preferably connected to the support structure via a spring structure.

[0082] In the present invention, a positioning and locking structure is preferably provided around the periphery of the supporting structure.

[0083] In the present invention, the support structure preferably includes an upper substrate and a lower substrate.

[0084] In the present invention, the alloy diffuser slot structure preferably comprises a tray with slots arranged around its periphery.

[0085] In the present invention, the area of ​​the tray is preferably adapted to the area of ​​the surface of the multi-element alloy diffusion block in contact with the NdFeB magnet to be processed.

[0086] In the present invention, one end of the spring structure is preferably fixed to the support structure, and the other end is fixed to the multi-element alloy diffuser slot structure.

[0087] In the present invention, the number of the alloy diffuser slot structures is preferably greater than or equal to 2, more preferably greater than or equal to 3, and more preferably greater than or equal to 4.

[0088] In the present invention, the spring structure preferably includes at least 2 groups of spring brackets, more preferably 3 groups or more of spring brackets, and more preferably 4 groups or more of spring brackets.

[0089] In the present invention, the number of spring brackets in one group is preferably greater than or equal to 2, more preferably greater than or equal to 3, and more preferably greater than or equal to 4.

[0090] In the present invention, one of the alloy diffuser slot structures is preferably disposed on the upper substrate via a spring bracket, and the other is disposed on a corresponding position of the lower substrate via a spring bracket.

[0091] In the present invention, when the upper substrate and the lower substrate are fixed, the two alloy diffuser slot structures preferably have corresponding upper and lower positions.

[0092] In the present invention, the positioning and locking structure preferably includes a through hole for bolt fixing and / or a buckle structure for locking, and more preferably a through hole for bolt fixing or a buckle structure for locking.

[0093] In the present invention, the step 1) is preferably:

[0094] a) processing and surface treating the NdFeB magnet to obtain a magnet to be processed;

[0095] Processing the multi-element alloy diffusion block into a size that fits the tray of the diffusion slot in the multi-element alloy diffusion attachment device, and then cleaning the surface to obtain the multi-element alloy diffusion block, and fixing it in the diffusion slot;

[0096] b) placing the magnet to be processed obtained in the above steps in a multinary alloy diffuser attachment device, between the diffuser clamping slot on the upper substrate with the multinary alloy diffuser block and the diffuser clamping slot on the lower substrate with the multinary alloy diffuser block, and fitting with the surfaces of the upper and lower multinary alloy diffuser blocks, and then fixing and clamping the substrates by a positioning and locking structure;

[0097] c) The multi-component alloy diffusion material attachment device with the magnet to be treated obtained in the above step is moved as a whole to a vacuum heat treatment furnace, and after the attachment heat treatment, a pre-treated magnet with the diffusion material attached is obtained.

[0098] The present invention firstly processes and surface-treats a neodymium iron boron magnet to obtain a magnet to be treated;

[0099] The multi-element alloy diffuser block is processed into a tray size adapted to the diffuser slot in the multi-element alloy diffuser attachment device, and then the surface is cleaned to obtain the multi-element alloy diffuser block, which is fixed in the diffuser slot.

[0100] The present invention then places the magnet to be processed obtained in the above steps in a multi-component alloy diffuser attachment device, located between a diffuser slot on the upper substrate equipped with a multi-component alloy diffuser block and a diffuser slot on the lower substrate equipped with a multi-component alloy diffuser block, and fits with the surfaces of the upper and lower multi-component alloy diffuser blocks, and then fixes and clamps the substrates through a positioning and locking structure.

[0101] Finally, the multi-component alloy diffusion material attachment device with the magnet to be processed obtained in the above steps is moved as a whole to a vacuum heat treatment furnace, and after the attachment heat treatment, a pre-treated magnet with diffusion material attached is obtained.

[0102] In the present invention, the vacuum degree of the attachment heat treatment is preferably less than or equal to 10 -3 Pa, preferably less than or equal to 10 - 4 Pa, preferably less than or equal to 10 -5 Pa.

[0103] In the present invention, the temperature of the adhesion heat treatment is preferably 520 to 750°C, more preferably 570 to 700°C, and even more preferably 620 to 650°C.

[0104] In the present invention, the adhesion heat treatment time is preferably 0.5 to 2 hours, more preferably 0.8 to 1.7 hours, and more preferably 1.1 to 1.4 hours.

[0105] In the present invention, the cooling method after the attachment heat treatment preferably includes rapid cooling.

[0106] In the present invention, the rapid cooling rate is preferably 20 to 35° C. / min, more preferably 23 to 32° C. / min, and more preferably 26 to 29° C. / min.

[0107] In the present invention, the degree of vacuum in the diffusion heat treatment is preferably less than or equal to 10 -3 Pa, preferably less than or equal to 10 - 4 Pa, preferably less than or equal to 10 -5 Pa.

[0108] In the present invention, the temperature of the diffusion heat treatment is preferably 850 to 950°C, more preferably 870 to 930°C, and even more preferably 890 to 910°C.

[0109] In the present invention, the time of the diffusion heat treatment is preferably 4 to 8 hours, more preferably 4.5 to 7.5 hours, more preferably 5 to 7 hours, and more preferably 5.5 to 6.5 hours.

[0110] In the present invention, the cooling method after the diffusion heat treatment preferably includes rapid cooling.

[0111] In the present invention, the rapid cooling rate is preferably 15 to 25° C. / min, more preferably 17 to 23° C. / min, and more preferably 19 to 21° C. / min.

[0112] In the present invention, the diffusion heat treatment preferably includes a tempering heat treatment step after the diffusion heat treatment.

[0113] In the present invention, the vacuum degree of the tempering heat treatment is preferably less than or equal to 10 -3 Pa, preferably less than or equal to 10 - 4 Pa, preferably less than or equal to 10 -5 Pa.

[0114] In the present invention, the temperature of the tempering heat treatment is preferably 480-520°C, more preferably 485-515°C, more preferably 490-510°C, and more preferably 495-505°C.

[0115] In the present invention, the tempering heat treatment time is preferably 4 to 10 hours, more preferably 5 to 9 hours, and more preferably 6 to 8 hours.

[0116] In the present invention, the cooling method after the tempering heat treatment preferably includes rapid cooling.

[0117] In the present invention, the rapid cooling rate is preferably 15 to 25° C. / min, more preferably 17 to 23° C. / min, and more preferably 19 to 21° C. / min.

[0118] In the present invention, the multi-component alloy diffuser preferably has the following general formula:

[0119] H 100-x-y R x M y .

[0120] In the present invention, H preferably includes one or more of Tb, Dy and Ho, and more preferably Tb, Dy or Ho.

[0121] In the present invention, R preferably includes one or more of Pr, Nd, Y, Ce and La, and more preferably includes Pr, Nd, Y, Ce or La.

[0122] In the present invention, M preferably includes one or more of Fe, Cu, Al, Ga, Zn, Mg and Mn, and more preferably is Fe, Cu, Al, Ga, Zn, Mg or Mn.

[0123] In the present invention, x is preferably 0 to 70, more preferably 10 to 60, more preferably 20 to 50, more preferably 30 to 40, and y is preferably 0 to 30, more preferably 10 to 20. Furthermore, x and y are preferably not 0 at the same time.

[0124] In order to complete and refine the overall diffusion process and better ensure the diffusion effect and repeated stability, the diffusion treatment method of the NdFeB magnet preferably includes the following steps:

[0125] The invention discloses a method for treating grain boundary diffusion of NdFeB magnets, comprising: a multi-component alloy diffusion material attachment device and a matching attachment and diffusion treatment process.

[0126] Specifically, the multi-component alloy diffuser attachment device comprises a support structure, an alloy diffuser slot structure, a spring structure and a positioning and locking structure. Preferably, all components are made of high temperature resistant alloy.

[0127] Specifically, the support structure includes a square upper substrate and a lower substrate, and through holes are opened at the four corners of the substrate. Preferably, the support structure has a length of 20 to 300 mm, a width of 20 to 300 mm, and a substrate thickness of 1 to 10 mm.

[0128] Specifically, the alloy diffuser slot structure is composed of a plurality of square trays, and the bottom ends of the two walls of the trays are attached with barbs to fix the diffuser block. Preferably, the inner cavity of the diffuser slot (tray) is 20 to 100 mm long, 20 to 100 mm wide, and 0 to 20 mm high, and the barbs on the edge of the slot are 0.5 to 10 mm thick and 2 mm wide.

[0129] Specifically, the spring structure is a plurality of spring brackets, one end of which is welded to the support structure and the other end is fixed to the bottom of the diffusion tray. Preferably, the spring length is 5 to 40 mm, the spring diameter is 5 to 30 mm, and the spring coefficient is 2 to 20 N / m.

[0130] Specifically, the positioning and locking structure is composed of four groups of bolts inserted into the upper and lower basic through holes and fixed and locked by nuts.

[0131] Specifically, in the multi-element alloy diffuser attachment device, multiple groups of spring brackets in different regions are welded on the upper and lower substrates respectively, and the other end of the bracket can be fixedly connected to the diffuser tray, and a small distance is maintained between the fixed diffuser trays; the multi-element alloy is melted and processed into blocks that meet the size requirements and can be fixed in the diffuser tray; after the upper and lower diffuser trays fix the multi-element alloy diffuser blocks, magnets can be placed and fixed and clamped by a positioning and locking structure; after the device substrate is locked, it can be moved as a whole to a vacuum heat treatment furnace for diffuser attachment heat treatment.

[0132] See also Figure 1 , Figure 1A simplified assembly diagram of the multi-element alloy diffusion attachment device provided by the present invention.

[0133] See also Figure 2 , Figure 2 A schematic diagram of the attachment processing pattern of the multi-element alloy diffusion material attachment device provided by the present invention.

[0134] Figure 1 and Figure 2 In the figure, 1-spring; 2-support substrate; 3-fastening sleeve; 4-slot structure; 5-fastening screw; 6-fastening nut; 7-diffusion source; 8-diffusion matrix.

[0135] Furthermore, the matching attachment and diffusion treatment process includes the following steps:

[0136] Step 1: Preparation of a multi-component alloy diffusion block, wherein the multi-component alloy diffusion has the following chemical formula H 100-x-y R x M y Specifically, H is one or more of Tb, Dy, and Ho, R is one or more of Pr, Nd, Y, Ce, and La, M is one or more of Fe, Cu, Al, Ga, Zn, Mg, and Mn, and x and y are the atomic percentages of the components in the alloy diffusion, x=0-70, y=0-30, and x and y are not both 0;

[0137] Step 2, processing the NdFeB magnet into a specified shape and size, and then pickling, cleaning and drying to obtain a magnet to be processed;

[0138] Step 3, processing the multi-element alloy diffusion material block into a shape and size that meets the requirements of the diffusion material slot (tray) in the multi-element alloy diffusion material attachment device, and then cleaning and drying the surface to obtain the multi-element alloy diffusion material block;

[0139] Step 4, fixing a plurality of sets of multi-element alloy diffusion material blocks in diffusion material slots (trays) in the multi-element alloy diffusion material attachment device respectively;

[0140] Step 5, placing the magnet to be processed in a multi-element alloy diffusion material attachment device, and fixing and clamping the substrate by a positioning and locking structure;

[0141] Step 6, moving the multi-component alloy diffusion material attachment device with the magnet to be processed to a vacuum heat treatment furnace as a whole to perform an attachment heat treatment process;

[0142] Step 7, taking the magnet out of the device to obtain a pre-treated magnet with the diffused matter attached;

[0143] Step eight, placing the pretreated magnet in a vacuum heat treatment furnace for diffusion heat treatment and tempering heat treatment to obtain a final high coercive force NdFeB magnet.

[0144] Specifically, in step 1, as a preferred embodiment, the multi-element alloy diffusion material H 100-x- y R x M y In the equation ( ), x=50~70 and y=10~30.

[0145] Specifically, as a preferred embodiment, the multi-component alloy diffusion block is prepared by the following method: weighing corresponding raw materials according to the atomic percentage of each component of the multi-component alloy diffusion, and sequentially smelting, casting, forging, hot rolling, and cold rolling to obtain;

[0146] Specifically, in the step 2, there are no strict requirements on the size and surface quality of the magnet to be processed. As a preferred embodiment, the thickness of the magnet to be processed in the diffusion direction is controlled to be 1 to 8 mm, and the surface is smooth and free of foreign matter;

[0147] Specifically, in step 3, the surface of the multi-element alloy diffusion block is cleaned by sandpaper polishing, alcohol cleaning and ultrasonic treatment;

[0148] Specifically, as a preferred embodiment, in the step 5, the magnet to be processed is sandwiched between the upper and lower multi-element alloy diffusion blocks, and the surface area of ​​each multi-element alloy diffusion block is 1.5 to 3 times the surface area of ​​each magnet to be processed;

[0149] Specifically, in step 6, the adhesion heat treatment process conditions are: temperature of 520-750°C, time of 0.5-2h, heating with the furnace and keeping warm, then cooling rapidly to room temperature, during which the vacuum degree is not greater than 10 -3 Pa;

[0150] Specifically, in step eight, the diffusion heat treatment process conditions are: temperature of 850-950°C, time of 4-8h, heating with the furnace and keeping warm, then cooling rapidly to room temperature, during which the vacuum degree is not greater than 10 -3 Pa; the tempering heat treatment process conditions are: temperature 480 ~ 520 ℃, time 4 ~ 10h, with the furnace heating and insulation after rapid cooling to room temperature, the vacuum degree is not greater than 10 -3 Pa.

[0151] The above content of the present invention discloses a method for grain boundary diffusion treatment of NdFeB magnets, which relates to an attachment device for multi-component alloy diffusers, and an optimized and matched attachment and diffusion treatment process. The present invention processes the smelted multi-component alloy ingots into blocks, directly assembles them in the attachment device for the multi-component alloy diffusers, then performs an attachment heat treatment process on the NdFeB magnet to be treated and obtains a pre-treated magnet, and then performs diffusion heat treatment on the pre-treated magnet that has completed the attachment to obtain a high-performance NdFeB magnet. The present invention does not need to crush the multi-component alloy into powder. On the premise of ensuring the excellent diffusion effect of the multi-component alloy, the process flow of the diffuser attachment is simplified, and the efficient preparation of the diffused magnet is achieved. The magnet magnetic properties have good consistency and stability, and are suitable for the industrialization of multi-component alloy diffused magnets.

[0152] The above steps of the present invention provide a method for processing grain boundary diffusion of NdFeB magnets, which involves an attachment device for multi-component alloy diffusers, and an optimized and matched attachment and diffusion treatment process. The method does not require the multi-component alloy to be crushed, and only requires the multi-component alloy to be prepared into a block material to achieve the attachment of the diffuser, thereby avoiding the problems such as oxidation caused by the multi-component alloy crushing and powdering process, maintaining the excellent properties of each component of the multi-component alloy, and ensuring the heavy rare earth diffusion effect; the attachment device for the multi-component alloy diffuser provided by the present invention adopts a regional spring structure, which can effectively avoid the problem of insufficient contact between the diffuser and the magnet due to the size error of the magnet to be processed during the batch diffusion process, thereby improving the quality and efficiency of the diffusion attachment treatment; the multi-component alloy diffuser block material in the present invention can be reused many times, and each attachment treatment Before processing, it is only necessary to perform simple surface treatment on the multi-component alloy diffusion block, which improves the utilization rate of the diffusion and reduces the production cost. Based on the design of the attachment device, the diffusion block is easy to replace and has a high degree of freedom in operation. The attachment device of the multi-component alloy diffusion of the present invention can flexibly control the thickness of the attachment layer in the pre-treated magnet (the magnet after the diffusion is attached) in combination with the attachment heat treatment process, thereby improving the consistency and stability of the diffusion magnet. The relatively low temperature attachment heat treatment adopted by the present invention facilitates the separation of the diffusion and the magnet after the attachment treatment, and the multi-component alloy is not easy to deform at a relatively low temperature due to its relatively large viscosity. The present invention is suitable for batch preparation of multi-component alloy diffusion diffusion-treated magnets, and has a simple process, strong controllability, good repeatability and stability, and is more suitable for the promotion and application of large-scale production.

[0153] Experimental results show that the NdFeB grain boundary diffusion treatment method designed by the present invention is more suitable for the grain boundary diffusion treatment of multi-component alloy diffusions. The method designed by the present invention ensures the excellent properties of the multi-component alloy, greatly improves the performance of the magnet after diffusion, and has good consistency and stability.

[0154] In order to further illustrate the present invention, a diffusion treatment method for NdFeB magnets provided by the present invention is described in detail below in combination with the embodiments. However, it should be understood that these embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operating processes are given only to further illustrate the features and advantages of the present invention, rather than to limit the claims of the present invention. The protection scope of the present invention is not limited to the following embodiments.

[0155] Example 1

[0156] 1) Prepare the diffuser attachment device: Assemble and debug the diffuser attachment device including the support structure, the alloy diffuser slot structure, the spring structure and the positioning locking structure. The brief assembly diagram is as follows: Figure 1 The above-mentioned diffuser attachment device adopts the following configuration: the inner cavity size of the diffuser slot (tray) is 60mm×60mm×3mm, the thickness of the barb on the edge of the slot is 1mm, and the width is 2mm; the bottom surface size of the upper and lower supporting substrates is 200mm×200mm, and the substrate thickness is 5mm; the spring length is 20mm, the spring diameter is 20mm, and the spring stiffness coefficient is 4.4N / mm.

[0157] 2) Preparation of diffusion material Tb 25 Pr 60 Cu 10 Al5 (the subscript is the atomic percentage of the corresponding element) multi-element alloy block: according to the chemical formula of the above alloy, the raw materials Tb single substance, Pr single substance, metal Cu and Al (purity of each reaching 99.95%) are weighed, and they are placed in a vacuum induction melting furnace for smelting at a temperature of 1150°C for 15 minutes. Thereafter, the molten alloy liquid is cast into billets, and then forged, hot rolled, cold rolled and machined into 9 square blocks with a thickness of 3 mm and a length and width of 59 mm. The surface oxide scale is removed, the surface is kept flat and rinsed and dried with alcohol.

[0158] 3) 36 sintered NdFeB magnets with a size of 25 mm×25 mm×4 mm were subjected to surface degreasing, pickling, cleaning and air-drying to obtain NdFeB magnets to be processed.

[0159] 4) Placing the diffuser block prepared in step 2) in the diffuser attachment device described in step 1): adjusting or pressing the spring, the diffuser block can be inserted into the diffuser slot (tray).

[0160] 5) Place the NdFeB magnets to be processed prepared in step 3) between the upper and lower diffuser blocks described in step 4). According to the preferred size, place 4 magnets to be processed in each upper and lower tray combination, then insert and adjust the device fastening bolts to make the upper and lower surfaces of the magnets to be processed fit tightly with the diffuser blocks. Figure 2 shown.

[0161] 6) The device described in step 5) together with the built-in magnet is moved into a vacuum heat treatment furnace for attachment heat treatment at a vacuum degree of 7.0×10 -3 Pa, temperature was kept at 700℃ for 1h, and then the pre-treated magnet was obtained after rapid cooling. The backscattering diagram of the surface cross section is shown in Figure 3 shown.

[0162] Figure 3 This is a backscattering image of the surface cross section of the pre-treated magnet that has completed the attachment treatment process in Example 1 of the present invention.

[0163] 7) The pre-treated magnet in step 6) is taken out from the diffusion material attachment device and placed in a vacuum heat treatment furnace for diffusion heat treatment: -3 Pa, keep warm at 900℃ for 4h; after cooling to room temperature, perform tempering heat treatment: maintain vacuum, re-heat to 900℃ and keep warm for 4h, and quickly cool to room temperature to obtain the final high-performance magnet.

[0164] In this embodiment, in order to compare the diffusion effect of the powder coating method on the multi-element alloy diffusion, the nominal composition of Tb is set and melted. 25 Pr 60 Cu 10 Al5 (the subscript is the atomic percentage of the corresponding element) alloy, after rapid solidification casting, hydrogen crushing, air flow milling to obtain a powder with an average particle size of 5μm, the powder is slurried using the best viscosity ratio and solvents such as alcohol and adhesives to obtain powder slurry, and the slurry is further sprayed in batches on the upper and lower surfaces of magnets of the same brand, size and quantity in this embodiment. After drying, the magnets with the diffusion material attached are placed in a vacuum heat treatment furnace and the same diffusion and tempering heat treatment process as step 7) of this embodiment is used to obtain a comparative diffusion magnet. Magnetic properties of 5 magnet samples randomly selected from the magnets obtained in step 7) of this embodiment and the comparative diffusion magnets obtained in the comparative example are measured, and the measurement results are shown in Table 1.

[0165] Table 1. Test results of magnet performance prepared by different processes

[0166]

[0167]

[0168] It can be seen from Table 1 that, compared with the powder coating method, the NdFeB grain boundary diffusion treatment method designed in the present invention is more suitable for the grain boundary diffusion treatment of multi-component alloy diffusions. The method designed in the present invention ensures the excellent properties of the multi-component alloy, greatly improves the performance of the magnet after diffusion, and has good consistency and stability.

[0169] Example 2

[0170] 1) Prepare the diffuser attachment device: Assemble and debug the diffuser attachment device including the support structure, the alloy diffuser slot structure, the spring structure and the positioning locking structure. The brief assembly diagram is as follows: Figure 1 The above-mentioned diffuser attachment device adopts the following configuration: the inner cavity size of the diffuser slot (tray) is 90mm×90mm×4mm, the thickness of the barb on the edge of the slot is 1.5mm, and the width is 2.5mm; the bottom surface size of the upper and lower supporting substrates is 300mm×300mm, and the substrate thickness is 4mm; the spring length is 30mm, the spring diameter is 22mm, and the spring stiffness coefficient is 8.1N / mm.

[0171] 2) Preparation of diffusion material Tb 20 Pr 45 La 15 Cu 10 Al 10 (The subscripts are the atomic percentages of the corresponding elements) Multi-element alloy blocks: According to the chemical formula of the above alloy, the raw materials Tb, Pr, La, metal Cu and Al (with a purity of 99.95%) are weighed and smelted in a vacuum induction melting furnace at a temperature of 1150°C for 15 minutes. The molten alloy is then cast into billets, which are then forged, hot-rolled, cold-rolled and machined into 9 square blocks with a thickness of 4 mm and a length and width of 89 mm. The surface oxide scale is removed, the surface is kept smooth and rinsed and dried with alcohol.

[0172] 3) 36 sintered NdFeB magnets with a size of 35 mm×35 mm×5 mm were subjected to surface degreasing, pickling, cleaning and air-drying to obtain NdFeB magnets to be processed.

[0173] 4) Placing the diffuser block prepared in step 2) in the diffuser attachment device described in step 1): adjusting or pressing the spring, the diffuser block can be inserted into the diffuser slot (tray).

[0174] 5) Place the NdFeB magnets to be processed prepared in step 3) between the upper and lower diffuser blocks described in step 4). According to the preferred size, place 4 magnets to be processed in each upper and lower tray combination, then insert and adjust the device fastening bolts to make the upper and lower surfaces of the magnets to be processed fit tightly with the diffuser blocks. Figure 2 shown.

[0175] 6) The device described in step 5) together with the built-in magnet is moved into a vacuum heat treatment furnace for attachment heat treatment at a vacuum degree of 5.0×10 -3 The pretreated magnet was obtained by keeping the temperature at 650°C for 1.5 h and cooling rapidly.

[0176] 7) The pre-treated magnet in step 6) is taken out from the diffusion material attachment device and placed in a vacuum heat treatment furnace for diffusion heat treatment: at a vacuum degree of 5.0×10 -3 Pa, keep the temperature at 910℃ for 5h; after cooling to room temperature, perform tempering heat treatment: maintain vacuum, re-heat to 910℃ and keep it for 5h, and quickly cool to room temperature to obtain the final high-performance magnet.

[0177] In this embodiment, in order to compare the diffusion effect of the powder coating method on the multi-element alloy diffusion, the nominal composition of Tb is set and melted. 20 Pr 45 La 15 Cu 10 Al 10 (the subscripts are the atomic percentages of the corresponding elements) alloy, after rapid solidification casting, hydrogen crushing, and air flow grinding, a powder with an average particle size of 5 μm is obtained, and the powder is slurried using solvents such as alcohol and adhesives using the optimal viscosity ratio to obtain a powder slurry, and the slurry is further sprayed in batches on the upper and lower surfaces of magnets of the same brand, size and quantity in this embodiment, and after drying, the magnets with the diffusion material attached are placed in a vacuum heat treatment furnace and the same diffusion and tempering heat treatment process as step 7) of this embodiment is used to obtain a comparative diffusion magnet. Five magnet samples are randomly selected from the magnets obtained in step 7) of this embodiment and the comparative diffusion magnets obtained in the comparative example for magnetic property measurement, and the measurement results are shown in Table 2.

[0178] Table 2. Performance test results of magnets prepared by different processes

[0179]

[0180] It can be seen from Table 2 that, compared with the powder coating method, the NdFeB grain boundary diffusion treatment method designed in the present invention is more suitable for the grain boundary diffusion treatment of multi-component alloy diffusions. The method designed in the present invention ensures the excellent properties of the multi-component alloy, greatly improves the performance of the magnet after diffusion, and has good consistency and stability.

[0181] The above is a detailed introduction to a method for treating grain boundary diffusion of a neodymium iron boron magnet provided by the present invention. The principle and implementation method of the present invention are described in detail using specific examples. The description of the above embodiments is only used to help understand the method and its core idea of ​​the present invention, including the best mode, and also enables any technician in the field to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the present invention, the present invention can also be improved and modified in a number of ways, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. The scope of patent protection of the present invention is defined by the claims and may include other embodiments that can be thought of by those skilled in the art. If these other embodiments have structural elements that are not different from the textual expression of the claims, or if they include equivalent structural elements that are not substantially different from the textual expression of the claims, then these other embodiments should also be included in the scope of the claims.

Claims

1. A diffusion treatment method for NdFeB magnets, characterized in that: The following steps are involved: 1) The multi-component alloy diffusion block and the NdFeB magnet to be treated are bonded and fixed on a multi-component alloy diffusion attachment device, and after attachment heat treatment, a pre-treated magnet is obtained; The thickness of the multi-element alloy diffusion block is 2 to 5 mm; The multi-element alloy diffuser attachment device comprises a supporting structure, a multi-element alloy diffuser slot structure, a spring structure and a positioning locking structure; The multi-element alloy diffuser slot structure is connected to the support structure via a spring structure; A positioning and locking structure is arranged around the support structure; The support structure includes an upper substrate and a lower substrate; The alloy diffuser slot structure comprises a tray with slots arranged around its periphery; The area of ​​the tray is adapted to the area of ​​the surface of the multi-element alloy diffusion block and the NdFeB magnet to be processed; The temperature of the attachment heat treatment is 520-750°C; The time of the attachment heat treatment is 0.5 to 2 hours; The attachment heat treatment specifically includes moving the multi-component alloy diffusion material attachment device with the magnet to be treated as a whole to a vacuum heat treatment furnace for attachment heat treatment; 2) subjecting the pretreated magnet obtained in the above step to diffusion heat treatment to obtain a diffusion-treated NdFeB magnet; The temperature of the diffusion heat treatment is 850-950°C; The diffusion heat treatment time is 4 to 8 hours.

2. The diffusion treatment method according to claim 1, characterized in that: The NdFeB magnet to be processed comprises a plurality of NdFeB magnets to be processed; The area of ​​the surface of the multi-element alloy diffusion block material that is bonded to the NdFeB magnet to be processed is greater than the area of ​​the surface of the NdFeB magnet to be processed that is bonded to the NdFeB magnet to be processed; The diffusion process includes a grain boundary diffusion process.

3. The diffusion treatment method according to claim 1, characterized in that: The area of ​​the surface of the multi-element alloy diffusion block material bonded to the NdFeB magnet to be processed is 1.5 to 3 times the area of ​​the surface of the NdFeB magnet to be processed; The multi-component alloy diffusion material attachment device tightly fits and fixes the multi-component alloy diffusion material block and the NdFeB magnet to be processed; The multi-element alloy diffusion block can be used multiple times in the diffusion treatment process of NdFeB magnets; The thickness of the NdFeB magnet to be processed in the diffusion direction is 1 to 8 mm.

4. The diffusion treatment method according to claim 1, characterized in that: One end of the spring structure is fixed on the supporting structure, and the other end is fixed on the multi-element alloy diffuser slot structure; The number of the alloy diffuser slot structures is greater than or equal to 2; The spring structure includes at least 2 sets of spring brackets; The number of spring brackets in one group is greater than or equal to 2.

5. The diffusion treatment method according to claim 1, characterized in that: One of the alloy diffuser slot structures is disposed on the upper substrate via a spring bracket, and the other is disposed on a corresponding position of the lower substrate via a spring bracket; When the upper substrate and the lower substrate are fixed, the two alloy diffusion slot structures have upper and lower corresponding positions; The positioning and locking structure includes a through hole for bolt fixing and / or a buckle structure for locking.

6. The diffusion treatment method according to claim 5, characterized in that: The step 1) is specifically as follows: a) processing and surface treating the NdFeB magnet to obtain a magnet to be processed; Processing the multi-element alloy diffusion block into a size that fits the tray of the diffusion slot in the multi-element alloy diffusion attachment device, and then cleaning the surface to obtain the multi-element alloy diffusion block, and fixing it in the diffusion slot; b) placing the magnet to be processed obtained in the above steps in a multinary alloy diffuser attachment device, between the diffuser clamping slot on the upper substrate with the multinary alloy diffuser block and the diffuser clamping slot on the lower substrate with the multinary alloy diffuser block, and fitting with the surfaces of the upper and lower multinary alloy diffuser blocks, and then fixing and clamping the substrates by a positioning and locking structure; c) The multi-component alloy diffusion material attachment device with the magnet to be treated obtained in the above step is moved as a whole to a vacuum heat treatment furnace, and after the attachment heat treatment, a pre-treated magnet with the diffusion material attached is obtained.

7. The diffusion treatment method according to claim 6, characterized in that: The vacuum degree of the attachment heat treatment is less than or equal to 10 -3 Pa; The cooling method after the attachment heat treatment includes rapid cooling; The rapid cooling rate is 20-35°C / min.

8. The diffusion treatment method according to claim 1, characterized in that: The degree of vacuum in the diffusion heat treatment is less than or equal to 10 -3 Pa; The cooling method after the diffusion heat treatment includes rapid cooling; The rapid cooling rate is 15-25°C / min.

9. The diffusion treatment method according to claim 1, characterized in that: The diffusion heat treatment also includes a tempering heat treatment step; The vacuum degree of the tempering heat treatment is less than or equal to 10 -3 Pa; The temperature of the tempering heat treatment is 480-520°C; The tempering heat treatment time is 4 to 10 hours; The cooling method after the tempering heat treatment includes rapid cooling; The rapid cooling rate is 15-25°C / min.

10. The diffusion treatment method according to claim 1, characterized in that: The multi-element alloy diffuser has the following general formula: H 100-x-y R x M y ; wherein H includes one or more of Tb, Dy and Ho; R includes one or more of Pr, Nd, Y, Ce and La; M includes one or more of Fe, Cu, Al, Ga, Zn, Mg and Mn; x is 0 to 70, y is 0 to 30, and x and y are not 0 at the same time.

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