A high thermal stability magnetic steel and its dysprosium infiltration process

Abstract

The present invention relates to the field of dysprosium infiltration technology, in order to solve the problem of RE6Fe in magnetic steel. 13 In order to solve the problem that the maximum operating temperature is low in the M phase, a high thermal stability magnetic steel and a dysprosium infiltration process thereof are provided, comprising the following steps: S100, vacuum impregnating a NdFeB magnet in a dysprosium infiltration slurry, and performing laser induction during the impregnation process to obtain a pre-modified magnetic steel; S200, subjecting the pre-modified magnetic steel to a heat treatment process to obtain a high thermal stability magnetic steel; the NdFeB magnet comprises: 30wt%-35wt%RE, 0.85wt%-0.9wt%B, 0.6wt%-1.5wt%M, 0.8wt%-1.2wt%N and the balance Fe; RE comprises: Pr and Nd; the NdFeB magnet contains RE6Fe 13 M phase. The present invention improves the dysprosium diffusion process, so that the diffusion of dysprosium is mainly along the grain boundary, and tends to penetrate deep into RE6Fe 13 The M phase changes the aforementioned crystal phase structure by replacing RE with dysprosium. At the same time, dysprosium does not enter or enters less of the Nd₂Fe₁₄B‌ phase, thereby increasing the maximum operating temperature of the magnet.

Description

Technical Field

[0001] The present invention relates to the field of dysprosium infiltration technology, and in particular to a high thermal stability magnetic steel and a dysprosium infiltration technology thereof. Background Art

[0002] Magnets are a type of permanent magnet material with high magnetic properties, widely used in various applications requiring a stable magnetic field. Neodymium iron boron magnets are currently one of the most commonly used magnets. For example, coreless motors generally use sintered neodymium iron boron permanent magnets, which have high remanence, high coercivity, and high magnetic energy product.

[0003] The publication number is CN119786179A, and the patent name is a patent for a sintered NdFeB and its preparation method, which adds RE6Fe to the magnet. 13 M phase, by regulating RE6Fe 13 The volume fraction of M phase and the heat treatment temperature and time are adjusted within the grain boundary phase transformation temperature range to promote RE6Fe 13 The generation or disappearance of the M phase increases or decreases the remanence and coercive force of the magnet, but the maximum operating temperature may be reduced. Summary of the Invention

[0004] The purpose of the present invention is to provide a high thermal stability magnetic steel and its dysprosium infiltration process, so as to solve the problem of RE6Fe in the magnetic steel. 13 The maximum operating temperature is low in M ​​phase.

[0005] The embodiments of the present invention are achieved through the following technical solutions:

[0006] A dysprosium infiltration process for high thermal stability magnetic steel comprises the following steps:

[0007] S100 and NdFeB magnets were vacuum impregnated in dysprosium slurry, and laser induction was performed during the impregnation process to obtain pre-modified magnetic steel; the impregnation pressure was 0.06MPa-0.2MPa, the impregnation time was 20min-35min; the laser power was 500W-600W, and the impact frequency was 7Hz-15Hz;

[0008] S200, pre-modified magnetic steel is subjected to heat treatment process to obtain high thermal stability magnetic steel;

[0009] The NdFeB magnet comprises: 30 wt %-35 wt %RE, 0.85 wt %-0.9 wt %B, 0.6 wt %-1.5 wt %M, 0.8 wt %-1.2 wt %N and the balance Fe;

[0010] RE includes: Pr and Nd; N includes: one or more of Mo, Co and Ni; M includes one or more of Al, Cu and Ga;

[0011] The NdFeB magnet contains RE6Fe 13 M phase.

[0012] On December 31, 2024, the applicant applied for a patent with publication number CN119786179A, which is titled as a sintered NdFeB and its preparation method. 13 M phase, by regulating RE6Fe 13 The volume fraction of M phase and the heat treatment temperature and time are adjusted within the grain boundary phase transformation temperature range to promote RE6Fe 13 The generation or disappearance of M phase increases or decreases the remanence and coercive force of the magnet. The grain boundary phase transition temperature range is 400-750℃. In the process of further research and development, the applicant found that for high-temperature usage scenarios, some magnets made according to the technical solutions provided in the aforementioned application may have a maximum operating temperature that is significantly lower than that of other products, and it is difficult to effectively improve it according to the conventional dysprosium infiltration process. The applicant speculates that one of the reasons is that the RE6Fe in the aforementioned NdFeB magnet product 13 The phase transition of M phase will lead to changes in the properties of magnetic steel such as remanence and coercivity. The operating temperature of magnetic steel is usually lower than the Curie temperature. If RE6Fe 13 The phase transition temperature of the M phase is also lower than the Curie temperature, which may eventually lead to a further decrease in the maximum operating temperature of the magnetic steel. Therefore, the applicant hopes to add RE6Fe 13 M phase, so that its performance can be regulated by the preparation method, and the RE6Fe 13 The influence of the phase transformation of M phase on the performance of magnetic steel, especially the reduction of coercive force and remanence.

[0013] To solve the RE6Fe 13 Products with a low M-phase phase transition temperature, especially those with a phase transition temperature lower than the Curie temperature, have a low maximum operating temperature. The applicant hopes to improve the thermal stability of the magnet by improving the dysprosium infiltration process. Dysprosium is a rare earth element with a very high anisotropy field. Penetrating dysprosium atoms into the surface of the magnet to a certain depth changes the composition and structure of the surface layer of the magnet, thereby enhancing the stability of the magnet in a high-temperature environment and enabling it to maintain high magnetic properties. Conventional dysprosium infiltration processes generally control the process so that the penetration path of dysprosium is mainly diffusion at the grain boundary, reducing the entry of dysprosium into the crystal. The reason is that the diffusion of dysprosium at the grain boundary can greatly improve the high-temperature stability of the magnet. Grain boundary diffusion can reduce the amount of dysprosium used, and after dysprosium enters the crystal, the remanence will decrease, and it may also change the internal magnetic domain structure, which is not conducive to the stability of the magnetic properties.

[0014] In addition to the conventional crystal phase, the magnet in this case also contains additional RE6Fe13 M phase, the applicant improved the conventional dysprosium infiltration process, so that dysprosium partially entered RE6Fe 13 M phase, replacing RE6Fe 13 RE in the M phase to increase RE6Fe 13 The anisotropy of the M phase increases its phase transition temperature, thereby increasing the maximum operating temperature of the magnetic steel. However, in the process of achieving the above-mentioned goals, it is necessary to consider how to improve the process so that dysprosium can enter RE6Fe 13 The M phase replaces RE without or with reduced Nd2Fe 14 Phase B.

[0015] The present invention selects a NdFeB magnet with a specific structure and composition, wherein RE6Fe 13 The phase transition temperature of the M phase is relatively low, which will affect the maximum operating temperature of the magnet. Therefore, the present invention improves the dysprosium infiltration process of the specific NdFeB magnet, and at the same time, in order to allow dysprosium to diffuse along the grain boundaries and to 13 The M phase penetrates into the crystal and does not enter the Nd2Fe 14 The B‌ phase is located within the crystal, which limits the impregnation parameters and laser induction parameters.

[0016] Preferably, M is Al and Ga in a molar ratio of 1:(2-5).

[0017] During the experiment, the applicant found that when M is a different composition, the effect of changes in impregnation parameters and laser induction parameters on the temperature resistance of the product is quite different. The applicant speculates that one of the reasons is that the elements in the alloy phase composition will affect the diffusion path and diffusion rate of dysprosium. Through experiments, it was found that when M is Al and Ga with a molar ratio of 1: (2-5), it is easier to promote dysprosium to RE6Fe when the parameters are adjusted. 13 The intracrystalline diffusion of the M‌ phase can increase the selectivity of the dysprosium diffusion path, thereby reducing the dysprosium to Nd2Fe 14 The intragranular diffusion of B phase allows the remanence to be higher while the magnetic steel achieves the same high temperature resistance.

[0018] Preferably, the temperature of the heat treatment process is 300° C.-600° C., and the time is 3 h-8 h.

[0019] Heat treatment can further promote the diffusion of dysprosium. Heat treatment can be performed under an inert atmosphere, such as argon. During the heat treatment process, the pre-modified magnetic steel can be coated with iron sheet.

[0020] Preferably, the heat treatment process includes: pre-modified magnetic steel is first kept at 300°C-400°C for 2h-5h, then kept at 550°C-600°C for 1h-3h, and finally high thermal stability magnetic steel is obtained.

[0021] During the experiment, the applicant found that when the temperature of the heat treatment process is low, the thermal stability of the final product is relatively poor, while when the temperature of the heat treatment process is too high, the remanence of the product will drop significantly. The applicant speculates that the reason is at least that when a lower heat treatment process temperature is used, it will not only affect the diffusion of dysprosium at the grain boundary, but also affect the diffusion of dysprosium into the grain, thereby reducing the thermal stability. When a higher heat treatment process temperature is used, dysprosium is more likely to enter the Nd2Fe 14 Phase B, the remanence of the product magnetic steel will be reduced. When using a single-stage heat treatment process, it is difficult to meet both thermal stability and remanence at the same time.

[0022] The applicant considered whether it is possible to improve the heat treatment process to increase the selectivity of the diffusion path of dysprosium and improve the performance of the product magnetic steel. Therefore, through the design of temperature control experiments, it was found that the segmented heat treatment process of the present invention can further improve the performance of the magnetic steel. The applicant speculates that the reason is that when dysprosium diffuses along the grain boundary, the different crystal phases are affected by dysprosium to different degrees according to the degree of diffusion. Under the infiltration system of the present invention, the diffusion of dysprosium at the grain boundary increases the Nd2Fe 14 Phase B and RE6Fe 13 The difference between the M phases and the thermal stability of each phase are increased. Therefore, the present invention further promotes the diffusion of dysprosium at the grain boundary through a heat treatment to increase the Nd2Fe 14 Phase B and RE6Fe 13 After the difference between the M phases, the second stage heat treatment at a higher temperature allows dysprosium to further penetrate into RE6Fe 13 M phase, and due to Nd2Fe 14 The stability of the B phase increases, and dysprosium is difficult to penetrate into Nd2Fe 14 Phase B.

[0023] Preferably, after the pre-modified magnetic steel undergoes a heat treatment process, it is cooled to room temperature at a rate of 20°C / min-130°C / min to obtain a magnetic steel with high thermal stability.

[0024] Because the phase structure of the magnetic steel in the present invention is more diverse than that of conventional magnetic steel, excessively fast cooling of the magnetic steel during the cooling process is more likely to cause greater internal stress, which in turn can damage the magnetic properties after microcracks appear. Therefore, the cooling rate in the present invention is reduced to a certain extent. During the slow cooling process, the diffusion of dysprosium from high-concentration areas to low-concentration areas can increase the uniformity of material properties. For example, the hollow cup magnetic steel used in hollow cup motors is usually annular, and the surface of the ring may have annular grooves. The performance difference between its edge and center area is large. For this type of magnetic steel, the regulation of the cooling process is particularly important.

[0025] Preferably, after the pre-modified magnetic steel undergoes a heat treatment process, it is cooled to 250°C-350°C at a rate of 20°C / min-50°C / min, and then cooled to room temperature at a rate of 100°C / min-130°C / min, and finally a magnetic steel with high thermal stability is obtained.

[0026] Reasonable control of the cooling process can increase the coercivity of the product magnet and increase the remanence. The applicant speculates that the reason is that the initial low cooling rate provides the possibility for the dysprosium atoms to migrate again, thereby some dysprosium may migrate out of certain crystal phases, such as in this case, some dysprosium penetrates into RE6Fe 13 During the M phase, it is inevitable that dysprosium will penetrate into Nd2Fe 14 B‌ phase, and during slow cooling, it penetrates into Nd2Fe 14 Dysprosium in the B‌ phase may have migrated out, significantly increasing the remanence. Rapid cooling can better preserve the crystalline structure obtained during the heat treatment, ensuring the performance of the magnetic steel.

[0027] Preferably, the preparation method of the dysprosium infiltration slurry comprises:

[0028] A100, after adding dysprosium oxide to the ethanol solution, add butyl orthosilicate, adjust the pH value of the solution to 5-6, and react at 80°C-100°C for 30min-60min to obtain a primary slurry;

[0029] A200. Adjust the pH value of the initial slurry to 7, then add a coupling agent, and react under an ultrasonic environment at 40°C-50°C for 1h-3h to obtain a dysprosium-infiltrated slurry; the ultrasonic frequency is 30kHz-40kHz.

[0030] During the dysprosium infiltration process, the diffusion path and speed of dysprosium are related to the dysprosium infiltration slurry. Conventional dysprosium infiltration slurry mainly contains dysprosium source, ethanol and silica sol. Among them, silica sol can form a protective film on the surface of NdFeB magnets to prevent the loss of dysprosium and reduce the amount of dysprosium used. In the process of regulating the diffusion path of dysprosium in the present invention, temperature is the core control parameter, and the temperature depends to a certain extent on the Nd2Fe 14 Phase B and RE6Fe 13The difference in thermal stability between the M phases is used to achieve rapid diffusion of dysprosium within the optimal temperature range guided by the diffusion path. The present invention adds an excess of butyl orthosilicate in step A100. Compared to adding butyl orthosilicate in steps, this can improve the uniformity of silica dispersion in the system, reduce the problem of dysprosium diffusing into the film rather than the magnet due to the uniformity of the silica sol protective film, and also reduce the mixing operation of subsequent reactions to a certain extent. In A200, by further adjusting the reaction conditions, the reaction direction of butyl orthosilicate is inclined to react with the coupling agent. At different temperatures, the viscosity of the silica sol varies, and the dispersibility of silica will also vary. When using a conventional dysprosium infiltration slurry, if the temperature is too high, the dispersibility of silica will decrease, and agglomeration may occur. In order to increase the uniformity of the silica sol at the optimal temperature for diffusion path regulation, the present invention modifies the dysprosium infiltration slurry with butyl orthosilicate and a coupling agent. In addition, the improved dysprosium diffusion layer has increased bonding strength with the substrate, inhibiting high-temperature demagnetization.

[0031] The coupling agent can be silane coupling agent A151, KH550 or GPTMS.

[0032] Preferably, the raw materials of the dysprosium infiltration slurry include, in parts by weight: 18-25 parts of dysprosium oxide, 30-50 parts of ethanol, 3-8 parts of butyl orthosilicate and 0.6-1.8 parts of coupling agent.

[0033] The purity of ethanol is greater than 98%.

[0034] Preferably, the high thermal stability magnetic steel is a hollow cup motor magnetic steel, the immersion pressure is 0.15MPa-0.2MPa, and the impact frequency is 10Hz-15Hz.

[0035] For special-structure hollow cup motor magnets, such as long cylinders with through holes rather than low rings, whose end edges may also be notched to change their smooth end walls, such magnets are prone to local performance fluctuations during the dysprosium infiltration process. Dysprosium resource consumption is high and utilization is low, making process adaptability and cost control a challenge. The applicant needs to solve the problem of uniform infiltration of asymmetric curved surfaces and thin-walled areas. Therefore, based on improving the dysprosium infiltration slurry, the process parameters have been further improved. Since temperature is the main factor affecting the diffusion path of the dysprosium infiltration slurry, the further parameter control of the present invention focuses on the impregnation pressure and impact frequency.

[0036] A magnetic steel with high thermal stability produced by the dysprosium infiltration process.

[0037] The present invention has at least the following beneficial effects:

[0038] The present invention improves the dysprosium diffusion process to guide the dysprosium diffusion path, so that the dysprosium diffusion is mainly along the grain boundary, and to a certain extent tends to penetrate into the RE6Fe13 In the M phase, the dysprosium replaces RE, which changes the aforementioned crystal structure to a certain extent. At the same time, dysprosium does not enter or enters less into Nd2Fe 14 B‌ phase, thereby increasing the maximum operating temperature of the magnet and increasing the remanence.

[0039] The present invention provides a NdFeB magnet with a specific structure and composition, which improves the sensitivity of its performance to changes in impregnation parameters and laser-induced parameters and increases the selectivity of dysprosium diffusion paths.

[0040] The present invention uses a two-stage heat treatment process to first increase Nd2Fe 14 Phase B and RE6Fe 13 The difference between the M phase and the RE6Fe phase is so that the dysprosium can be further penetrated into the RE6Fe phase through the second stage heat treatment at a higher temperature. 13 M phase, but it is difficult to penetrate into Nd2Fe 14 Phase B further increases the maximum operating temperature and the remanence of the magnetic steel. DETAILED DESCRIPTION

[0041] In order to make the purpose, method scheme and advantages of the embodiments of the present invention clearer, the method scheme in the embodiments of the present invention is clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0042] Example 1: A dysprosium infiltration process for high thermal stability magnetic steel, comprising the following steps:

[0043] S100 and NdFeB magnets were vacuum impregnated in dysprosium slurry, and laser induction was performed during the impregnation process to obtain pre-modified magnetic steel. The impregnation pressure was 0.06 MPa, the impregnation time was 20 min, the laser power was 500 W, and the impact frequency was 7 Hz.

[0044] S200, pre-modified magnetic steel is subjected to heat treatment process to obtain high thermal stability magnetic steel;

[0045] The NdFeB magnet comprises: 30 wt % RE, 0.85 wt % B, 0.6 wt % Al, 0.8 wt % Mo and the balance Fe;

[0046] RE includes: Pr and Nd in a molar ratio of 1:1;

[0047] The NdFeB magnet contains RE6Fe 13 M phase.

[0048] The temperature of the heat treatment process is 300° C. and the time is 3 hours.

[0049] After the pre-modified magnetic steel undergoes a heat treatment process, it is cooled to room temperature at a rate of 20°C / min to obtain a magnetic steel with high thermal stability.

[0050] In parts by weight, the preparation method of the dysprosium infiltration slurry comprises: dispersing 18 parts of dysprosium oxide in 30 parts of ethanol to obtain the dysprosium infiltration slurry.

[0051] Example 2: A dysprosium infiltration process for high thermal stability magnetic steel, comprising the following steps:

[0052] S100 and NdFeB magnets were vacuum impregnated in dysprosium slurry, and laser induction was performed during the impregnation process to obtain pre-modified magnetic steel. The impregnation pressure was 0.2 MPa, the impregnation time was 35 min, the laser power was 600 W, and the impact frequency was 15 Hz.

[0053] S200, pre-modified magnetic steel is subjected to heat treatment process to obtain high thermal stability magnetic steel;

[0054] The NdFeB magnet comprises: 35 wt % RE, 0.9 wt % B, 1.5 wt % Cu, 1.2 wt % Co and the balance Fe;

[0055] RE includes: Pr and Nd in a molar ratio of 1:1;

[0056] The NdFeB magnet contains RE6Fe 13 M phase.

[0057] The temperature of the heat treatment process is 600° C. and the time is 8 hours.

[0058] After the pre-modified magnetic steel undergoes a heat treatment process, it is cooled to room temperature at a rate of 130° C. / min to obtain a magnetic steel with high thermal stability.

[0059] In parts by weight, the preparation method of the dysprosium infiltration slurry comprises: dispersing 25 parts of dysprosium oxide in 50 parts of ethanol to obtain the dysprosium infiltration slurry.

[0060] Example 3: A dysprosium infiltration process for high thermal stability magnetic steel, comprising the following steps:

[0061] S100 and NdFeB magnets were vacuum impregnated in dysprosium slurry, and laser induction was performed during the impregnation process to obtain pre-modified magnetic steel. The impregnation pressure was 0.16 MPa, the impregnation time was 28 minutes, the laser power was 550 W, and the impact frequency was 12 Hz.

[0062] S200, pre-modified magnetic steel is subjected to heat treatment process to obtain high thermal stability magnetic steel;

[0063] The NdFeB magnet comprises: 32 wt % RE, 0.86 wt % B, 1.2 wt % Ga, 1 wt % Ni and the balance Fe;

[0064] RE includes: Pr and Nd in a molar ratio of 1:1;

[0065] The NdFeB magnet contains RE6Fe 13 M phase.

[0066] The temperature of the heat treatment process is 480° C. and the time is 6 hours.

[0067] After the pre-modified magnetic steel undergoes a heat treatment process, it is cooled to room temperature at a rate of 70°C / min to obtain a magnetic steel with high thermal stability.

[0068] In parts by weight, the preparation method of the dysprosium infiltration slurry comprises: dispersing 22 parts of dysprosium oxide in 40 parts of ethanol to obtain the dysprosium infiltration slurry.

[0069] Example 4: A dysprosium infiltration process for high thermal stability magnetic steel, comprising the following steps:

[0070] S100 and NdFeB magnets were vacuum impregnated in dysprosium slurry, and laser induction was performed during the impregnation process to obtain pre-modified magnetic steel. The impregnation pressure was 0.16 MPa, the impregnation time was 28 minutes, the laser power was 550 W, and the impact frequency was 12 Hz.

[0071] S200, pre-modified magnetic steel is subjected to heat treatment process to obtain high thermal stability magnetic steel;

[0072] The NdFeB magnet comprises: 32 wt % RE, 0.86 wt % B, 1.2 wt % M, 0.2 wt % Ni, 0.8 wt % Co and the balance Fe;

[0073] RE includes: Pr and Nd in a molar ratio of 1:1;

[0074] M is Al and Ga in a molar ratio of 1:2.

[0075] The NdFeB magnet contains RE6Fe 13 M phase.

[0076] The temperature of the heat treatment process is 480° C. and the time is 6 hours.

[0077] After the pre-modified magnetic steel undergoes a heat treatment process, it is cooled to room temperature at a rate of 70°C / min to obtain a magnetic steel with high thermal stability.

[0078] In parts by weight, the preparation method of the dysprosium infiltration slurry comprises: dispersing 22 parts of dysprosium oxide in 40 parts of ethanol to obtain the dysprosium infiltration slurry.

[0079] Example 5: A dysprosium infiltration process for high thermal stability magnetic steel, comprising the following steps:

[0080] S100 and NdFeB magnets were vacuum impregnated in dysprosium slurry, and laser induction was performed during the impregnation process to obtain pre-modified magnetic steel. The impregnation pressure was 0.16 MPa, the impregnation time was 28 minutes, the laser power was 550 W, and the impact frequency was 12 Hz.

[0081] S200, pre-modified magnetic steel is subjected to heat treatment process to obtain high thermal stability magnetic steel;

[0082] The NdFeB magnet comprises: 32 wt % RE, 0.86 wt % B, 1.2 wt % M, 0.2 wt % Ni, 0.8 wt % Co and the balance Fe;

[0083] RE includes: Pr and Nd in a molar ratio of 1:1;

[0084] M is Al and Ga in a molar ratio of 1:5.

[0085] The NdFeB magnet contains RE6Fe 13 M phase.

[0086] The temperature of the heat treatment process is 480° C. and the time is 6 hours.

[0087] In parts by weight, the preparation method of the dysprosium infiltration slurry comprises: dispersing 22 parts of dysprosium oxide in 40 parts of ethanol to obtain the dysprosium infiltration slurry.

[0088] Example 6: A dysprosium infiltration process for high thermal stability magnetic steel, comprising the following steps:

[0089] S100 and NdFeB magnets were vacuum impregnated in dysprosium slurry, and laser induction was performed during the impregnation process to obtain pre-modified magnetic steel. The impregnation pressure was 0.16 MPa, the impregnation time was 28 minutes, the laser power was 550 W, and the impact frequency was 12 Hz.

[0090] S200, pre-modified magnetic steel is subjected to heat treatment process to obtain high thermal stability magnetic steel;

[0091] The NdFeB magnet comprises: 32 wt % RE, 0.86 wt % B, 1.2 wt % M, 0.2 wt % Ni, 0.8 wt % Co and the balance Fe;

[0092] RE includes: Pr and Nd in a molar ratio of 1:1;

[0093] M is Al and Ga in a molar ratio of 1:3.

[0094] The NdFeB magnet contains RE6Fe 13 M phase.

[0095] The temperature of the heat treatment process is 480° C. and the time is 6 hours.

[0096] After the pre-modified magnetic steel undergoes a heat treatment process, it is cooled to room temperature at a rate of 70°C / min to obtain a magnetic steel with high thermal stability.

[0097] In parts by weight, the preparation method of the dysprosium infiltration slurry comprises: dispersing 22 parts of dysprosium oxide in 40 parts of ethanol to obtain the dysprosium infiltration slurry.

[0098] Example 7: A dysprosium infiltration process for high thermal stability magnetic steel, comprising the following steps:

[0099] S100 and NdFeB magnets were vacuum impregnated in dysprosium slurry, and laser induction was performed during the impregnation process to obtain pre-modified magnetic steel. The impregnation pressure was 0.16 MPa, the impregnation time was 28 minutes, the laser power was 550 W, and the impact frequency was 12 Hz.

[0100] S200, pre-modified magnetic steel is subjected to heat treatment process to obtain high thermal stability magnetic steel;

[0101] The NdFeB magnet comprises: 32 wt % RE, 0.86 wt % B, 1.2 wt % M, 0.2 wt % Ni, 0.8 wt % Co and the balance Fe;

[0102] RE includes: Pr and Nd in a molar ratio of 1:1;

[0103] M is Al and Ga in a molar ratio of 1:3.

[0104] The NdFeB magnet contains RE6Fe 13 M phase.

[0105] The temperature of the heat treatment process is 480° C. and the time is 6 hours.

[0106] The heat treatment process includes: pre-modified magnetic steel is first kept at 300° C. for 2 hours, then kept at 550° C. for 1 hour, and finally a magnetic steel with high thermal stability is obtained.

[0107] After the pre-modified magnetic steel undergoes a heat treatment process, it is cooled to room temperature at a rate of 70°C / min to obtain a magnetic steel with high thermal stability.

[0108] In parts by weight, the preparation method of the dysprosium infiltration slurry comprises: dispersing 22 parts of dysprosium oxide in 40 parts of ethanol to obtain the dysprosium infiltration slurry.

[0109] Example 8: A dysprosium infiltration process for high thermal stability magnetic steel, comprising the following steps:

[0110] S100 and NdFeB magnets were vacuum impregnated in dysprosium slurry, and laser induction was performed during the impregnation process to obtain pre-modified magnetic steel. The impregnation pressure was 0.16 MPa, the impregnation time was 28 minutes, the laser power was 550 W, and the impact frequency was 12 Hz.

[0111] S200, pre-modified magnetic steel is subjected to heat treatment process to obtain high thermal stability magnetic steel;

[0112] The NdFeB magnet comprises: 32 wt % RE, 0.86 wt % B, 1.2 wt % M, 0.2 wt % Ni, 0.8 wt % Co and the balance Fe;

[0113] RE includes: Pr and Nd in a molar ratio of 1:1;

[0114] M is Al and Ga in a molar ratio of 1:3.

[0115] The NdFeB magnet contains RE6Fe 13 M phase.

[0116] The temperature of the heat treatment process is 480° C. and the time is 6 hours.

[0117] The heat treatment process includes: pre-modified magnetic steel is first kept at 400° C. for 5 hours, then kept at 600° C. for 1 hour to 3 hours, and finally a magnetic steel with high thermal stability is obtained.

[0118] After the pre-modified magnetic steel undergoes a heat treatment process, it is cooled to room temperature at a rate of 70°C / min to obtain a magnetic steel with high thermal stability.

[0119] In parts by weight, the preparation method of the dysprosium infiltration slurry comprises: dispersing 22 parts of dysprosium oxide in 40 parts of ethanol to obtain the dysprosium infiltration slurry.

[0120] Example 9: A dysprosium infiltration process for high thermal stability magnetic steel, comprising the following steps:

[0121] S100 and NdFeB magnets were vacuum impregnated in dysprosium slurry, and laser induction was performed during the impregnation process to obtain pre-modified magnetic steel. The impregnation pressure was 0.16 MPa, the impregnation time was 28 minutes, the laser power was 550 W, and the impact frequency was 12 Hz.

[0122] S200, pre-modified magnetic steel is subjected to heat treatment process to obtain high thermal stability magnetic steel;

[0123] The NdFeB magnet comprises: 32 wt % RE, 0.86 wt % B, 1.2 wt % M, 0.2 wt % Ni, 0.8 wt % Co and the balance Fe;

[0124] RE includes: Pr and Nd in a molar ratio of 1:1;

[0125] M is Al and Ga in a molar ratio of 1:3.

[0126] The NdFeB magnet contains RE6Fe 13 M phase.

[0127] The temperature of the heat treatment process is 480° C. and the time is 6 hours.

[0128] The heat treatment process includes: pre-modified magnetic steel is first kept at 360° C. for 3.5 hours, and then kept at 570° C. for 2 hours, and finally a magnetic steel with high thermal stability is obtained.

[0129] After the pre-modified magnetic steel undergoes a heat treatment process, it is cooled to room temperature at a rate of 70°C / min to obtain a magnetic steel with high thermal stability.

[0130] In parts by weight, the preparation method of the dysprosium infiltration slurry comprises: dispersing 22 parts of dysprosium oxide in 40 parts of ethanol to obtain the dysprosium infiltration slurry.

[0131] Example 10: A dysprosium infiltration process for high thermal stability magnetic steel, comprising the following steps:

[0132] S100 and NdFeB magnets were vacuum impregnated in dysprosium slurry, and laser induction was performed during the impregnation process to obtain pre-modified magnetic steel. The impregnation pressure was 0.16 MPa, the impregnation time was 28 minutes, the laser power was 550 W, and the impact frequency was 12 Hz.

[0133] S200, pre-modified magnetic steel is subjected to heat treatment process to obtain high thermal stability magnetic steel;

[0134] The NdFeB magnet comprises: 32 wt % RE, 0.86 wt % B, 1.2 wt % M, 0.2 wt % Ni, 0.8 wt % Co and the balance Fe;

[0135] RE includes: Pr and Nd in a molar ratio of 1:1;

[0136] M is Al and Ga in a molar ratio of 1:3.

[0137] The NdFeB magnet contains RE6Fe 13 M phase.

[0138] The heat treatment process includes: pre-modified magnetic steel is first kept at 360° C. for 3.5 hours, and then kept at 570° C. for 2 hours, and finally a magnetic steel with high thermal stability is obtained.

[0139] After the pre-modified magnetic steel undergoes a heat treatment process, it is cooled to 250°C at a rate of 20°C / min, and then cooled to room temperature at a rate of 100°C / min, and finally a magnetic steel with high thermal stability is obtained.

[0140] In parts by weight, the preparation method of the dysprosium infiltration slurry comprises: dispersing 22 parts of dysprosium oxide in 40 parts of ethanol to obtain the dysprosium infiltration slurry.

[0141] Example 11: A dysprosium infiltration process for high thermal stability magnetic steel, comprising the following steps:

[0142] S100 and NdFeB magnets were vacuum impregnated in dysprosium slurry, and laser induction was performed during the impregnation process to obtain pre-modified magnetic steel. The impregnation pressure was 0.16 MPa, the impregnation time was 28 minutes, the laser power was 550 W, and the impact frequency was 12 Hz.

[0143] S200, pre-modified magnetic steel is subjected to heat treatment process to obtain high thermal stability magnetic steel;

[0144] The NdFeB magnet comprises: 32 wt % RE, 0.86 wt % B, 1.2 wt % M, 0.2 wt % Ni, 0.8 wt % Co and the balance Fe;

[0145] RE includes: Pr and Nd in a molar ratio of 1:1;

[0146] M is Al and Ga in a molar ratio of 1:3.

[0147] The NdFeB magnet contains RE6Fe 13 M phase.

[0148] The heat treatment process includes: pre-modified magnetic steel is first kept at 360° C. for 3.5 hours, and then kept at 570° C. for 2 hours, and finally a magnetic steel with high thermal stability is obtained.

[0149] After the pre-modified magnetic steel undergoes a heat treatment process, it is cooled to 350°C at a rate of 50°C / min, and then cooled to room temperature at a rate of 130°C / min, and finally a magnetic steel with high thermal stability is obtained.

[0150] In parts by weight, the preparation method of the dysprosium infiltration slurry comprises: dispersing 22 parts of dysprosium oxide in 40 parts of ethanol to obtain the dysprosium infiltration slurry.

[0151] Example 12: A dysprosium infiltration process for high thermal stability magnetic steel, comprising the following steps:

[0152] S100 and NdFeB magnets were vacuum impregnated in dysprosium slurry, and laser induction was performed during the impregnation process to obtain pre-modified magnetic steel. The impregnation pressure was 0.16 MPa, the impregnation time was 28 minutes, the laser power was 550 W, and the impact frequency was 12 Hz.

[0153] S200, pre-modified magnetic steel is subjected to heat treatment process to obtain high thermal stability magnetic steel;

[0154] The NdFeB magnet comprises: 32 wt % RE, 0.86 wt % B, 1.2 wt % M, 0.2 wt % Ni, 0.8 wt % Co and the balance Fe;

[0155] RE includes: Pr and Nd in a molar ratio of 1:1;

[0156] M is Al and Ga in a molar ratio of 1:3.

[0157] The NdFeB magnet contains RE6Fe 13 M phase.

[0158] The heat treatment process includes: pre-modified magnetic steel is first kept at 360° C. for 3.5 hours, and then kept at 570° C. for 2 hours, and finally a magnetic steel with high thermal stability is obtained.

[0159] After the pre-modified magnetic steel undergoes a heat treatment process, it is cooled to 300°C at a rate of 35°C / min, and then cooled to room temperature at a rate of 115°C / min, and finally a magnetic steel with high thermal stability is obtained.

[0160] In parts by weight, the preparation method of the dysprosium infiltration slurry comprises: dispersing 22 parts of dysprosium oxide in 40 parts of ethanol to obtain the dysprosium infiltration slurry.

[0161] Example 13: A dysprosium infiltration process for high thermal stability magnetic steel, comprising the following steps:

[0162] S100 and NdFeB magnets were vacuum impregnated in dysprosium slurry, and laser induction was performed during the impregnation process to obtain pre-modified magnetic steel. The impregnation pressure was 0.16 MPa, the impregnation time was 28 minutes, the laser power was 550 W, and the impact frequency was 12 Hz.

[0163] S200, pre-modified magnetic steel is subjected to heat treatment process to obtain high thermal stability magnetic steel;

[0164] The NdFeB magnet comprises: 32 wt % RE, 0.86 wt % B, 1.2 wt % M, 0.2 wt % Ni, 0.8 wt % Co and the balance Fe;

[0165] RE includes: Pr and Nd in a molar ratio of 1:1;

[0166] M is Al and Ga in a molar ratio of 1:3.

[0167] The NdFeB magnet contains RE6Fe 13 M phase.

[0168] The heat treatment process includes: pre-modified magnetic steel is first kept at 360° C. for 3.5 hours, and then kept at 570° C. for 2 hours, and finally a magnetic steel with high thermal stability is obtained.

[0169] After the pre-modified magnetic steel undergoes a heat treatment process, it is cooled to 300°C at a rate of 35°C / min, and then cooled to room temperature at a rate of 115°C / min, and finally a magnetic steel with high thermal stability is obtained.

[0170] The preparation method of the dysprosium infiltration slurry comprises:

[0171] A100, in parts by weight, 18 parts of dysprosium oxide were added to 30 parts of ethanol solution, and then 3 parts of butyl orthosilicate were added. The pH value of the solution was adjusted to 5, and the mixture was reacted at 80° C. for 30 minutes to obtain a preliminary slurry.

[0172] A200, adjust the pH value of the initial slurry to 7, then add 0.6 parts of coupling agent KH550, and react under an ultrasonic environment at 40°C for 1h-3h to obtain a dysprosium-infiltrated slurry; the ultrasonic frequency is 30kHz.

[0173] Example 14: A dysprosium infiltration process for high thermal stability magnetic steel, comprising the following steps:

[0174] S100 and NdFeB magnets were vacuum impregnated in dysprosium slurry, and laser induction was performed during the impregnation process to obtain pre-modified magnetic steel. The impregnation pressure was 0.16 MPa, the impregnation time was 28 minutes, the laser power was 550 W, and the impact frequency was 12 Hz.

[0175] S200, pre-modified magnetic steel is subjected to heat treatment process to obtain high thermal stability magnetic steel;

[0176] The NdFeB magnet comprises: 32 wt % RE, 0.86 wt % B, 1.2 wt % M, 0.2 wt % Ni, 0.8 wt % Co and the balance Fe;

[0177] RE includes: Pr and Nd in a molar ratio of 1:1;

[0178] M is Al and Ga in a molar ratio of 1:3.

[0179] The NdFeB magnet contains RE6Fe 13 M phase.

[0180] The heat treatment process includes: pre-modified magnetic steel is first kept at 360° C. for 3.5 hours, and then kept at 570° C. for 2 hours, and finally a magnetic steel with high thermal stability is obtained.

[0181] After the pre-modified magnetic steel undergoes a heat treatment process, it is cooled to 300°C at a rate of 35°C / min, and then cooled to room temperature at a rate of 115°C / min, and finally a magnetic steel with high thermal stability is obtained.

[0182] The preparation method of the dysprosium infiltration slurry comprises:

[0183] A100, in parts by weight, 25 parts of dysprosium oxide were added to 50 parts of ethanol solution, and then 8 parts of butyl orthosilicate were added to adjust the pH value of the solution to 6. The mixture was reacted at 100° C. for 60 minutes to obtain a preliminary slurry;

[0184] A200, adjust the pH value of the initial slurry to 7, then add 1.8 parts of coupling agent KH550, and react under an ultrasonic environment at 50°C for 3 hours to obtain a dysprosium infiltrated slurry; the ultrasonic frequency is 40 kHz.

[0185] Example 15: A dysprosium infiltration process for high thermal stability magnetic steel, comprising the following steps:

[0186] S100 and NdFeB magnets were vacuum impregnated in dysprosium slurry, and laser induction was performed during the impregnation process to obtain pre-modified magnetic steel. The impregnation pressure was 0.16 MPa, the impregnation time was 28 minutes, the laser power was 550 W, and the impact frequency was 12 Hz.

[0187] S200, pre-modified magnetic steel is subjected to heat treatment process to obtain high thermal stability magnetic steel;

[0188] The NdFeB magnet comprises: 32 wt % RE, 0.86 wt % B, 1.2 wt % M, 0.2 wt % Ni, 0.8 wt % Co and the balance Fe;

[0189] RE includes: Pr and Nd in a molar ratio of 1:1;

[0190] M is Al and Ga in a molar ratio of 1:3.

[0191] The NdFeB magnet contains RE6Fe 13 M phase.

[0192] The heat treatment process includes: pre-modified magnetic steel is first kept at 360° C. for 3.5 hours, and then kept at 570° C. for 2 hours, and finally a magnetic steel with high thermal stability is obtained.

[0193] After the pre-modified magnetic steel undergoes a heat treatment process, it is cooled to 300°C at a rate of 35°C / min, and then cooled to room temperature at a rate of 115°C / min, and finally a magnetic steel with high thermal stability is obtained.

[0194] The preparation method of the dysprosium infiltration slurry comprises:

[0195] A100, in parts by weight, 22 parts of dysprosium oxide were added to 40 parts of ethanol solution, and then 6 parts of butyl orthosilicate were added. The pH value of the solution was adjusted to 5.5, and the mixture was reacted at 90° C. for 45 minutes to obtain a preliminary slurry.

[0196] A200, adjust the pH value of the initial slurry to 7, then add 1.2 parts of coupling agent KH550, and react under an ultrasonic environment at 45°C for 2 hours to obtain a dysprosium infiltrated slurry; the ultrasonic frequency is 35 kHz.

[0197] Example 16: A dysprosium infiltration process for high thermal stability magnetic steel, comprising the following steps:

[0198] S100 and NdFeB magnets were vacuum impregnated in dysprosium slurry, and laser induction was performed during the impregnation process to obtain pre-modified magnetic steel. The impregnation pressure was 0.15 MPa, the impregnation time was 28 min, the laser power was 550 W, and the impact frequency was 10 Hz.

[0199] S200, the pre-modified magnetic steel is subjected to a heat treatment process to obtain a high thermal stability magnetic steel; the high thermal stability magnetic steel is a hollow cup motor magnetic steel;

[0200] The NdFeB magnet comprises: 32 wt % RE, 0.86 wt % B, 1.2 wt % M, 0.2 wt % Ni, 0.8 wt % Co and the balance Fe;

[0201] RE includes: Pr and Nd in a molar ratio of 1:1;

[0202] M is Al and Ga in a molar ratio of 1:3.

[0203] The NdFeB magnet contains RE6Fe 13 M phase.

[0204] The heat treatment process includes: pre-modified magnetic steel is first kept at 360° C. for 3.5 hours, and then kept at 570° C. for 2 hours, and finally a magnetic steel with high thermal stability is obtained.

[0205] After the pre-modified magnetic steel undergoes a heat treatment process, it is cooled to 300°C at a rate of 35°C / min, and then cooled to room temperature at a rate of 115°C / min, and finally a magnetic steel with high thermal stability is obtained.

[0206] The preparation method of the dysprosium infiltration slurry comprises:

[0207] A100, in parts by weight, 22 parts of dysprosium oxide were added to 40 parts of ethanol solution, and then 6 parts of butyl orthosilicate were added. The pH value of the solution was adjusted to 5.5, and the mixture was reacted at 90° C. for 45 minutes to obtain a preliminary slurry.

[0208] A200, adjust the pH value of the initial slurry to 7, then add 1.2 parts of coupling agent KH550, and react under an ultrasonic environment at 45°C for 2 hours to obtain a dysprosium infiltrated slurry; the ultrasonic frequency is 35 kHz.

[0209] Example 17: A dysprosium infiltration process for high thermal stability magnetic steel, comprising the following steps:

[0210] S100 and NdFeB magnets were vacuum impregnated in dysprosium slurry, and laser induction was performed during the impregnation process to obtain pre-modified magnetic steel. The impregnation pressure was 0.2 MPa, the impregnation time was 28 min, the laser power was 550 W, and the impact frequency was 15 Hz.

[0211] S200, the pre-modified magnetic steel is subjected to a heat treatment process to obtain a high thermal stability magnetic steel; the high thermal stability magnetic steel is a hollow cup motor magnetic steel;

[0212] The NdFeB magnet comprises: 32 wt % RE, 0.86 wt % B, 1.2 wt % M, 0.2 wt % Ni, 0.8 wt % Co and the balance Fe;

[0213] RE includes: Pr and Nd in a molar ratio of 1:1;

[0214] M is Al and Ga in a molar ratio of 1:3.

[0215] The NdFeB magnet contains RE6Fe 13 M phase.

[0216] The heat treatment process includes: pre-modified magnetic steel is first kept at 300-400°C for 2-5 hours, and then kept at 550-600°C for 1-3 hours, and finally high thermal stability magnetic steel is obtained.

[0217] After the pre-modified magnetic steel undergoes a heat treatment process, it is cooled to 300°C at a rate of 35°C / min, and then cooled to room temperature at a rate of 115°C / min, and finally a magnetic steel with high thermal stability is obtained.

[0218] The preparation method of the dysprosium infiltration slurry comprises:

[0219] A100, in parts by weight, 22 parts of dysprosium oxide were added to 40 parts of ethanol solution, and then 6 parts of butyl orthosilicate were added. The pH value of the solution was adjusted to 5.5, and the mixture was reacted at 90° C. for 45 minutes to obtain a preliminary slurry.

[0220] A200, adjust the pH value of the initial slurry to 7, then add 1.2 parts of coupling agent KH550, and react under an ultrasonic environment at 45°C for 2 hours to obtain a dysprosium infiltrated slurry; the ultrasonic frequency is 35 kHz.

[0221] Example 18: A dysprosium infiltration process for high thermal stability magnetic steel, comprising the following steps:

[0222] S100 and NdFeB magnets were vacuum impregnated in dysprosium slurry, and laser induction was performed during the impregnation process to obtain pre-modified magnetic steel. The impregnation pressure was 0.18 MPa, the impregnation time was 28 minutes, the laser power was 550 W, and the impact frequency was 13 Hz.

[0223] S200, the pre-modified magnetic steel is subjected to a heat treatment process to obtain a high thermal stability magnetic steel; the high thermal stability magnetic steel is a hollow cup motor magnetic steel;

[0224] The NdFeB magnet comprises: 32 wt % RE, 0.86 wt % B, 1.2 wt % M, 0.2 wt % Ni, 0.8 wt % Co and the balance Fe;

[0225] RE includes: Pr and Nd in a molar ratio of 1:1;

[0226] M is Al and Ga in a molar ratio of 1:3.

[0227] The NdFeB magnet contains RE6Fe 13 M phase.

[0228] The heat treatment process includes: pre-modified magnetic steel is first kept at 300-400°C for 2-5 hours, and then kept at 550-600°C for 1-3 hours, and finally high thermal stability magnetic steel is obtained.

[0229] After the pre-modified magnetic steel undergoes a heat treatment process, it is cooled to 300°C at a rate of 35°C / min, and then cooled to room temperature at a rate of 115°C / min, and finally a magnetic steel with high thermal stability is obtained.

[0230] The preparation method of the dysprosium infiltration slurry comprises:

[0231] A100, in parts by weight, 22 parts of dysprosium oxide were added to 40 parts of ethanol solution, and then 6 parts of butyl orthosilicate were added. The pH value of the solution was adjusted to 5.5, and the mixture was reacted at 90° C. for 45 minutes to obtain a preliminary slurry.

[0232] A200, adjust the pH value of the initial slurry to 7, then add 1.2 parts of coupling agent KH550, and react under an ultrasonic environment at 45°C for 2 hours to obtain a dysprosium infiltrated slurry; the ultrasonic frequency is 35 kHz.

[0233] Comparative Example 1: The difference from Example 15 is that N is Zr.

[0234] Comparative Example 2: The difference from Example 15 is that N is Ta.

[0235] Comparative Example 3: The difference from Example 15 is that the pH value of A200 is 5.5.

[0236] Comparative Example 4: The difference from Example 15 is that there is no ultrasonic environment in A200.

[0237] Comparative Example 5: The difference from Example 15 is that 360°C in the heat treatment process is changed to 460°C.

[0238] Comparative Example 6: The difference from Example 18 is that the immersion pressure is 0.08 MPa.

[0239] Comparative Example 7: The difference from Example 18 is that the impact frequency is 7 Hz.

[0240] Comparative Example 8: The difference from Example 18 is that the impregnation pressure is 0.16 MPa, the impact frequency is 12 Hz; and the vacuum impregnation temperature is 80°C.

[0241] Test 1: According to GB / T3217-2013 "Magnetic Test Methods for Permanent Magnet (Hard Magnetic) Materials", the high thermal stability magnetic steel (ring) produced by the dysprosium infiltration process provided in Examples 1-15 and Comparative Examples 1-5 was subjected to performance tests. The test environment temperature was 20±2°C. The test results are shown in Table 1.

[0242] Table 1 Performance test results of annular high thermal stability magnetic steel

[0243]

[0244] The unit of coercive force is kOe; the unit of remanence is kGs; the unit of magnetic energy product is MGOe.

[0245] From the test results of Examples 1-6 in Table 1, it can be seen that the magnetic steel produced by the dysprosium infiltration process provided by the present invention has good magnetic properties. From the comparison of Example 3 and Example 4, it can be seen that the composition of M affects the magnetic properties of the product.

[0246] From the comparison of the test results of Example 7 and Example 6 in Table 1, it can be seen that the staged heat treatment process can significantly improve the magnetic properties of the product. From the test results of Examples 7-9, it can be seen that the test results after the heat treatment process parameters shown in Example 9 are the best.

[0247] From the comparison of the test results of Example 10 and Example 9 in Table 1, it can be seen that the segmented cooling treatment can improve the magnetic properties of the product to a certain extent. From the test results of Examples 10-12, it can be seen that the test results after the cooling treatment parameters are the same as those of Example 12 are the best.

[0248] A comparison of the test results of Example 13 and Example 12 in Table 1 shows that the improvement of the dysprosium-infiltrated slurry can improve the magnetic properties of the product to a certain extent. The test results of Examples 13-15 show that the product test results after using the dysprosium-infiltrated slurry preparation method provided in Example 15 are the best.

[0249] From the comparison of the test results of Comparative Examples 1-2 and Example 15, it can be seen that the composition of N affects the magnetic properties of the product.

[0250] From the comparison of the test results of Comparative Examples 3-4 and Example 15, it can be seen that in the preparation method of the dysprosium infiltration slurry, the pH value of the reaction system in step A200 and the ultrasonic environment both affect the diffusion effect of the dysprosium infiltration slurry.

[0251] From the comparison of the test results of Comparative Example 5 and Example 15, it can be seen that if the temperature in one section of the heat treatment process is too high, the magnetic properties of the product will be affected to a certain extent.

[0252] Test 2: According to GB / T3217-2013 "Magnetic Test Methods for Permanent Magnet (Hard Magnetic) Materials", the high thermal stability magnetic steels produced by the dysprosium infiltration process provided in Examples 16-18 and Comparative Examples 6-7 were subjected to performance tests. The test environment temperature was 20±2°C. The test results are shown in Table 2.

[0253] Table 2 Performance test results of cylindrical high thermal stability magnetic steel

[0254]

[0255] The unit of coercive force is kOe; the unit of remanence is kGs; the unit of magnetic energy product is MGOe.

[0256] From the test results of Examples 16-18 and Comparative Examples 6-7, it can be seen that for cylindrical hollow cup motor magnets, increasing the immersion pressure and impact frequency to a certain extent can improve the magnetic properties of the product to a certain extent.

[0257] From the comparison of the test results of Example 15, Example 18 and Comparative Example 8, it can be seen that promoting the diffusion of dysprosium by increasing the temperature instead of improving the diffusion of dysprosium by the immersion pressure and impact frequency will affect the magnetic properties of the cylindrical hollow cup motor magnet.

[0258] Test 3: According to GB / T 13560-2017 "Sintered NdFeB Permanent Magnet Materials", the high thermal stability magnetic steel (ring) produced by the dysprosium infiltration process provided in Examples 1-15 and Comparative Examples 1-5 was tested for the maximum operating temperature. The test results are shown in Table 3.

[0259] Table 3 Maximum operating temperature test results of annular high thermal stability magnetic steel

[0260]

[0261] The test results of Examples 1-6 in Table 1 show that the magnetic steel produced by the dysprosium infiltration process provided by the present invention has good thermal stability. A comparison of Example 3 and Example 4 shows that the composition of M affects the thermal stability of the product.

[0262] From the comparison of the test results of Example 7 and Example 6 in Table 1, it can be seen that the staged heat treatment process can significantly improve the thermal stability of the product. From the test results of Examples 7-9, it can be seen that the test results after the heat treatment process parameters are the best as shown in Example 9.

[0263] From the comparison of the test results of Example 10 and Example 9 in Table 1, it can be seen that the staged cooling process can improve the thermal stability of the product to a certain extent. From the test results of Examples 10-12, it can be seen that the test results after the cooling process parameters are the same as those of Example 12 are the best.

[0264] A comparison of the test results of Example 13 and Example 12 in Table 1 shows that the improvement of the dysprosium-infiltrating slurry can improve the thermal stability of the product to a certain extent. The test results of Examples 13-15 show that the product test results after using the dysprosium-infiltrating slurry preparation method provided in Example 15 are the best.

[0265] From the comparison of the test results of Comparative Examples 1-2 and Example 15, it can be seen that the composition of N seriously affects the thermal stability of the product.

[0266] From the comparison of the test results of Comparative Examples 3-4 and Example 15, it can be seen that in the preparation method of the dysprosium infiltration slurry, the pH value of the reaction system in step A200 and the ultrasonic environment both affect the diffusion effect of the dysprosium infiltration slurry, and ultimately affect the thermal stability of the product.

[0267] From the comparison of the test results of Comparative Example 5 and Example 15, it can be seen that the temperature in one section of the heat treatment process is too high, which seriously affects the thermal stability of the product.

[0268] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations are readily apparent to those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A dysprosium infiltration process for high thermal stability magnetic steel, characterized in that: The following steps are involved: S100 and NdFeB magnets were vacuum impregnated in dysprosium slurry, and laser induction was performed during the impregnation process to obtain pre-modified magnetic steel; the impregnation pressure was 0.06MPa-0.2MPa, the impregnation time was 20min-35min; the laser power was 500W-600W, and the impact frequency was 7Hz-15Hz; S200, pre-modified magnetic steel is subjected to heat treatment process to obtain high thermal stability magnetic steel; The NdFeB magnet comprises: 30 wt %-35 wt %RE, 0.85 wt %-0.9 wt %B, 0.6 wt %-1.5 wt %M, 0.8 wt %-1.2 wt %N and the balance Fe; RE includes: Pr and Nd; M includes: one or more of Al, Cu and Ga; N includes: one or more of Mo, Co and Ni; The NdFeB magnet contains RE6Fe 13 M phase.

2. The dysprosium infiltration process according to claim 1, characterized in that: M is Al and Ga in a molar ratio of 1:(2-5).

3. The dysprosium infiltration process according to claim 1, characterized in that: The temperature of the heat treatment process is 300° C.-600° C., and the time is 3 h-8 h.

4. The dysprosium infiltration process according to claim 3, characterized in that: The heat treatment process includes: pre-modified magnetic steel is first kept at 300-400°C for 2-5 hours, and then kept at 550-600°C for 1-3 hours, and finally high thermal stability magnetic steel is obtained.

5. The dysprosium infiltration process according to claim 4, characterized in that: After the pre-modified magnetic steel undergoes a heat treatment process, it is cooled to room temperature at a rate of 20°C / min-130°C / min to obtain a magnetic steel with high thermal stability.

6. The dysprosium infiltration process according to claim 5, characterized in that: After the pre-modified magnetic steel undergoes a heat treatment process, it is cooled to 250°C-350°C at a rate of 20°C / min-50°C / min, and then cooled to room temperature at a rate of 100°C / min-130°C / min, and finally a magnetic steel with high thermal stability is obtained.

7. The dysprosium infiltration process according to any one of claims 1 to 6, characterized in that: The preparation method of the dysprosium infiltration slurry comprises: A100, after adding dysprosium oxide to the ethanol solution, add butyl orthosilicate, adjust the pH value of the solution to 5-6, and react at 80°C-100°C for 30min-60min to obtain a primary slurry; A200. Adjust the pH value of the initial slurry to 7, then add a coupling agent, and react under an ultrasonic environment at 40°C-50°C for 1h-3h to obtain a dysprosium-infiltrated slurry; the ultrasonic frequency is 30kHz-40kHz.

8. The dysprosium infiltration process according to claim 7, characterized in that: Calculated by weight, the raw materials of the dysprosium infiltration slurry include: 18-25 parts of dysprosium oxide, 30-50 parts of ethanol, 3-8 parts of butyl orthosilicate and 0.6-1.8 parts of coupling agent.

9. The dysprosium infiltration process according to claim 7, characterized in that: The high thermal stability magnetic steel is a hollow cup motor magnetic steel, the impregnation pressure is 0.15MPa-0.2MPa, and the impact frequency is 10Hz-15Hz.

10. A magnetic steel with high thermal stability produced by the dysprosium infiltration process according to any one of claims 1 to 9.

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