Diffusion method of high-Ga low-B magnet and neodymium-iron-boron magnet

Abstract

The invention provides a diffusion method of a high-Ga low-B magnet and a neodymium-iron-boron magnet. The preparation method comprises the following steps: adhering a diffusant containing heavy rare earth elements to the outer surface of the high-Ga low-B magnet, and performing diffusion treatment on the high-Ga low-B magnet for 20-30 hours under the vacuum degree condition of 1 * 10 <-3 >-1 * 10 <-2 > pa and the temperature condition of 920-960 DEG C; the magnet with high Ga and low B comprises the following components in percentage by weight: 0.3 to 0.5 percent of Ga, 0.25 to 0.5 percent of Cu, 0.9 to 0.95 percent of B, 0.15 to 0.2 percent of Ti, 0.3 to 0.5 percent of Zr, 0 to 1 percent of Co, 29 to 32 percent of Re and the balance of Fe. Re is a rare earth element. On the basis, the problems of low diffusion efficiency, reduced residual magnetism and the like of a high-Ga low-B magnet during diffusion treatment in the prior art are effectively solved.

Description

Technical Field

[0001] The invention relates to the technical field of neodymium iron boron, and in particular to a diffusion method for a high-Ga and low-B magnet and a neodymium iron boron magnet. Background Art

[0002] Sintered NdFeB magnets are widely used in wind power generation, new energy vehicles, consumer electronics and other fields due to their excellent magnetic properties, playing an important role in economic and social development. With the development of new application fields and more stringent application conditions, the demand for products with high coercivity is increasing.

[0003] The main methods for improving coercivity in the industry are high-Ga low-B grain boundary optimization and grain boundary diffusion. The high-Ga low-B grain boundary optimization method uses a unique formula design and corresponding process matching. During the heat treatment process, there is enough Ga and Cu in the magnet to react with Fe in the grain boundary to generate antiferromagnetic Re6Fe in the grain boundary triangle area. 13 B1 phase, which reduces the proportion of Fe in the rare earth-rich phase in the grain boundary, and then transforms the rare earth-rich phase into a non-ferromagnetic phase, which plays a better magnetic isolation role, so as to achieve the purpose of improving coercivity. The grain boundary diffusion method uses magnetron sputtering, evaporation, spraying, printing, electrodeposition and other methods to attach heavy rare earth elements, heavy rare earth alloys (Re-Cu, Re-Al, etc.), and heavy rare earth compounds (Re-F, Re-O) to the surface of the magnet, and diffuses the heavy rare earth to the epitaxial layer of the main phase grains through heat treatment to form a core-shell structure. The heavy rare earth shell is not easy to reverse magnetization, protecting the core main phase, so as to achieve the purpose of improving coercivity.

[0004] However, the effect of organically combining the high-Ga low-B grain boundary optimization method and the grain boundary diffusion method to jointly improve the coercive force is not ideal. It is manifested in that under the same Tb / Dy weight gain and diffusion process conditions, the coercive force improvement is smaller, usually 10-20% smaller than the conventional formula. The reason is that since the B content in the high-Ga low-B NdFeB magnet is less than that in the conventional formula, a large amount of Fe will be surplus in the grain boundary. A large amount of Fe-containing compounds have a high melting point and poor grain boundary fluidity. Under the existing diffusion heat treatment process (800-900℃ / 15-30h), a large amount of Fe in the grain boundary will hinder the diffusion of heavy rare earth Tb / Dy into the interior of the magnet. The small increase in coercive force in the diffusion stage will offset the coercive force advantage accumulated by the high-Ga low-B magnet in the substrate stage.

[0005] For example, in the prior art, in patent CN110428947, 0.3-0.5wt% Cu, 0.05-0.2wt% Ti, and 0.92-0.98wt% B are added to the substrate to prepare a magnet, and grain boundary diffusion is performed. The diffusion temperature is selected to be 800-900°C. After diffusion, the coercive force fluctuates in the range of 24-26kOe, but the diffusion improvement of this formula is limited. One of the reasons is that the diffusion temperature is low and cannot provide enough energy to diffuse the heavy rare earth into the interior of the magnet. In patent CN111599565, 0.35-0.60wt% Cu, 0-0.42wt% Ga, 0.9-1.05wt% B, and 0.01-0.3wt% Zr are added to the substrate to prepare a magnet, and grain boundary diffusion is performed. The diffusion temperature is selected to be 900°C, but the coercive force improvement is limited.

[0006] It can be seen from this that it is necessary to provide a new high-Ga, low-B formula and corresponding diffusion process for grain boundary diffusion, which can not only improve the diffusion efficiency of high-Ga, low-B magnets, but also significantly reduce the defect of reduced remanence caused by high-temperature diffusion. Summary of the invention

[0007] The main purpose of the present invention is to provide a diffusion method and application of high-Ga low-B magnets to solve the problems of low diffusion efficiency and reduced remanence in the diffusion process of high-Ga low-B magnets in the prior art.

[0008] In order to achieve the above object, according to one aspect of the present invention, a diffusion method of a high-Ga low-B magnet is provided, which comprises: attaching a diffusing agent containing a heavy rare earth element to the outer surface of the high-Ga low-B magnet, -3 ~1×10 -2 The high-Ga low-B magnet is diffused for 20 to 30 hours under a vacuum condition of 1.5 wt% pa and a temperature condition of 920 to 960°C; wherein the high-Ga low-B magnet comprises: 0.3 to 0.5 wt% Ga, 0.25 to 0.5 wt% Cu, 0.9 to 0.95 wt% B, 0.15 to 0.2 wt% Ti, 0.3 to 0.5 wt% Zr, 0 to 1 wt% Co, 29 to 32 wt% Re and the remainder Fe; Re is a rare earth element.

[0009] Further, the high Ga low B magnet is diffused at a temperature of 940-960°C for 20-30h; preferably, Re is selected from Nd and one or more of the following optional elements: Pr, Tb, Dy, Ce, La, Gd; preferably, the composition of the high Ga low B magnet includes: 0.3-0.5wt% Ga, 0.25-0.5wt% Cu, 0.9-0.95wt% B, 0.15-0.2wt% Ti, 0.3-0.5wt% Zr, 0.9-1wt% Co, 29-30wt% Re and the remainder Fe; Re is selected from Nd and one or more of the following elements: Pr, Tb, Ce, La and Gd.

[0010] Furthermore, the diffusing agent is selected from one or more of a heavy rare earth element, a heavy rare earth alloy or a heavy rare earth compound; preferably, the heavy rare earth element is selected from terbium or dysprosium; the heavy rare earth alloy is selected from terbium copper alloy, terbium aluminum alloy, dysprosium copper alloy or dysprosium aluminum alloy; the heavy rare earth compound is selected from terbium fluoride, dysprosium fluoride, terbium oxide or dysprosium oxide; preferably, the diffusing agent is attached to the outer surface of the high Ga low B magnet by magnetron sputtering, evaporation, spraying, printing or electrodeposition; preferably, the amount of the diffusing agent used is 3 to 20 g per kilogram of the mass of the high Ga low B magnet.

[0011] Furthermore, the high-Ga, low-B magnet is prepared by the following steps: alloy raw materials are mixed according to a stoichiometric ratio, and then refined and cast in sequence to obtain fling sheets; the fling sheets are subjected to hydrogen crushing, air flow grinding, molding, and sintering in sequence to obtain the high-Ga, low-B magnet.

[0012] Furthermore, the refining treatment temperature is 1500-1550°C; preferably, the pouring treatment temperature is 1400-1450°C.

[0013] Furthermore, the dehydrogenation temperature during the hydrogen crushing process is 510-580°C.

[0014] Furthermore, the powder of the material obtained by the jet milling treatment has an average specific surface diameter of 3.1 to 3.2 μm and a median powder particle size of less than 4.5 μm.

[0015] Furthermore, the molding density of the material obtained by molding is 3.9-4.1 g / cm 3 ; Preferably, the molding includes orientation molding and cold isostatic pressing performed sequentially; further preferably, the orientation magnetic field of the orientation molding is greater than 1.7 T; further preferably, the isostatic pressure of the cold isostatic pressing is 210-250 MPa; further preferably, during the cold isostatic pressing process, the oxygen content is less than 100 ppm.

[0016] Furthermore, the sintering treatment temperature is 1030-1110° C., and the treatment time is 5-10 hours.

[0017] In order to achieve the above object, according to one aspect of the present invention, there is provided a NdFeB magnet obtained by the above-mentioned diffusion method of high-Ga and low-B magnet.

[0018] On the one hand, the present invention optimizes the formula design of high-Ga low-B class magnets. More than 0.3wt% Zr is added to the formula design. Zr plays a pinning role in the grain boundary and can prevent heavy rare earth elements (such as Tb) in the diffusion agent from entering the main phase during high-temperature diffusion. At the same time, 0.3-0.5wt% Ga, 0.25-0.5wt% Cu, 0.9-0.95wt% B and 0.15-0.2wt% Ti are also added to the formula design. The addition and dosage of Ga, Cu, B and Ti can make the comprehensive magnetic properties of the magnet better. On the other hand, the present invention optimizes the diffusion process of high-Ga low-B class magnets, and the vacuum degree in the furnace reaches 1×10 -3 ~1×10 -2 When the diffusion heat treatment is carried out at 940-960°C, the diffusion time is maintained at 20-30h. The magnet of the above-mentioned specific formula is matched with a suitable diffusion temperature to make the grain boundary phase fluidity in the magnet better and increase the diffusion efficiency. If the diffusion temperature is lower than 940°C, the diffusion power is insufficient, and a large amount of Fe in the grain boundary will hinder the heavy rare earth elements (such as Tb and Dy) in the diffusant from diffusing along the grain boundary. If the diffusion temperature is higher than 960°C, the diffusion power is too large, and the heavy rare earth elements (such as Tb and Dy) in the diffusant will diffuse into the interior of the grains, reducing the remanence of the magnet. The invention is based on the above optimization, which can not only improve the diffusion efficiency of high-Ga low-B type magnets, but also significantly reduce the defect of reduced remanence caused by high-temperature diffusion. DETAILED DESCRIPTION

[0019] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0020] As described in the background section of this application, in the prior art, high-Ga low-B magnets have problems such as low diffusion efficiency and reduced remanence during diffusion processing. In order to solve this problem, this application provides a diffusion method for high-Ga low-B magnets, which comprises: attaching a diffusing agent containing heavy rare earth elements to the surface of the high-Ga low-B magnet, -3 ~1×10 -2The high-Ga low-B magnet is diffused for 20 to 30 hours under a vacuum condition of 1.547 W / m and a temperature condition of 940 to 960 °C; the components of the high-Ga low-B magnet include: 0.3 to 0.5 wt% Ga, 0.25 to 0.5 wt% Cu, 0.9 to 0.95 wt% B, 0.15 to 0.2 wt% Ti, 0.3 to 0.5 wt% Zr, 0 to 1 wt% Co, 29 to 32 wt% Re and the remainder Fe; Re is a rare earth element.

[0021] On the one hand, the present invention optimizes the formula design of high-Ga low-B class magnets. More than 0.3wt% Zr is added to the formula design. Zr plays a pinning role in the grain boundary and can prevent heavy rare earth elements (such as Tb) in the diffusion agent from entering the main phase during high-temperature diffusion. At the same time, 0.3-0.5wt% Ga, 0.25-0.5wt% Cu, 0.9-0.95wt% B and 0.15-0.2wt% Ti are also added to the formula design. The addition and dosage of Ga, Cu, B and Ti can make the comprehensive magnetic properties of the magnet better. On the other hand, the present invention optimizes the diffusion process of high-Ga low-B class magnets, and the vacuum degree in the furnace reaches 1×10 -3 ~1×10 -2 When the diffusion heat treatment is carried out at 940-960°C, the diffusion time is maintained at 20-30h. The magnet of the above-mentioned specific formula is matched with a suitable diffusion temperature to make the grain boundary phase fluidity in the magnet better and increase the diffusion efficiency. If the diffusion temperature is lower than 940°C, the diffusion power is insufficient, and a large amount of Fe in the grain boundary will hinder the heavy rare earth elements (such as Tb and Dy) in the diffusant from diffusing along the grain boundary. If the diffusion temperature is higher than 960°C, the diffusion power is too large, and the heavy rare earth elements (such as Tb and Dy) in the diffusant will diffuse into the interior of the grains, reducing the remanence of the magnet. The invention is based on the above optimization, which can not only improve the diffusion efficiency of high-Ga low-B type magnets, but also significantly reduce the defect of reduced remanence caused by high-temperature diffusion.

[0022] It is further supplemented that the ratio of Ga, Cu, B, Ti and Re can be optimized according to the target magnetic properties of the magnet. If the coercive force of the magnet is required to be higher, it is necessary to increase the ratio of Ga, Cu and Ti and reduce the ratio of B and Re to make the antiferromagnetic Re6Fe 13 B1 increases. Diffusion temperature and time are adjusted according to the thickness of the magnet.

[0023] In order to further improve the comprehensive magnetic properties of the product, in a preferred embodiment, Re is selected from Nd and one or more of the following optional elements: Pr, Tb, Dy, Ce, La, Gd. In a preferred embodiment, the high-Ga low-B magnet composition includes: 0.3-0.5wt% Ga, 0.25-0.5wt% Cu, 0.9-0.95wt% B, 0.15-0.2wt% Ti, 0.3-0.5wt% Zr, 0.9-1wt% Co, 29-30wt% Re and the balance Fe; Re is selected from Nd and one or more of the following elements: Pr, Tb, Ce, La and Gd. Based on this, the present application can further improve the diffusion efficiency of high-Ga low-B magnets, and can also significantly reduce the defect of reduced residual magnetism caused by high-temperature diffusion, and the residual magnetic properties of the product are also better. In a preferred embodiment, when Re is Nd, Pr and Tb, the weight ratio of Nd to Pr is 22-28:72-78, and the weight ratio of the total weight of Nd and Pr to Tb is 28-30:1.

[0024] In order to further improve the efficiency of the diffusion treatment, in a preferred embodiment, the diffusing agent is selected from one or more of a heavy rare earth element, a heavy rare earth alloy or a heavy rare earth compound. For example, the heavy rare earth element is selected from Tb or Dy; the heavy rare earth alloy is selected from Tb-Cu, Dy-Al, Dy-Cu or Tb-Al; the heavy rare earth compound is selected from Tb-F, Dy-F, Tb-O or Dy-O. Those skilled in the art can attach the diffusing agent to the outer surface of the high-Ga low-B magnet by magnetron sputtering, evaporation, spraying, printing or electrodeposition. In order to further improve the uniformity of diffusion and improve the performance uniformity of the product, in a preferred embodiment, the amount of the diffusing agent used is 3 to 20 g per kilogram of the mass of the high-Ga low-B magnet.

[0025] In order to further obtain products with better uniformity of magnetic properties, in a preferred embodiment, a high-Ga, low-B magnet is prepared by the following steps: the alloy raw materials are mixed according to a stoichiometric ratio, and then refined and cast in sequence to obtain fling sheets; the fling sheets are subjected to hydrogen crushing, air flow grinding, molding, and sintering in sequence to obtain a high-Ga, low-B magnet.

[0026] The present application does not impose any special restrictions on the refining and casting of the high-Ga low-B magnets, and those skilled in the art can determine the relevant process parameters according to conventional requirements. For example, the refining treatment temperature is 1500-1550°C; the casting treatment temperature is 1400-1450°C.

[0027] In order to further obtain a product with better uniformity of magnetic properties, after pouring, the slugs are crushed into coarse crushed magnetic powder by hydrogen crushing, and the dehydrogenation temperature during the hydrogen crushing process is 510-580°C, so that the coarse crushed magnetic powder obtained has a more suitable particle size and is more conducive to subsequent jet milling. In a preferred embodiment, the powder of the material obtained by jet milling has a specific surface average diameter (SMD) of 3.1-3.2 μm, and the median particle size (X50) of the powder is less than 4.5 μm.

[0028] In a preferred embodiment, the molding density of the material obtained by molding is 3.9-4.1 g / cm 3 In order to further improve the efficiency of product molding, the molding includes orientation molding and cold isostatic pressing in sequence. Preferably, the orientation field of the orientation molding is greater than 1.7T; the isostatic pressure of the cold isostatic pressing is 210-250MPa; and during the cold isostatic pressing process, the oxygen content is less than 100ppm.

[0029] In order to further obtain a product with better magnetic uniformity, the preferred sintering treatment temperature is 1030-1110°C and the treatment time is 5-10h. In a preferred embodiment, before sintering, the preparation method also includes the step of heat treating the material: using step-by-step heating to heat treat the material, first heating to 440-460°C and keeping warm for 0.8-1.2 hours to remove the lubricant and antioxidant in the pressed green sheet, then heating to 580-620°C and keeping warm for 0.8-1.2 hours, and then heating to 780-820°C and keeping warm for 0.8-1.2 hours to remove residual hydrogen and impurities. In a preferred embodiment, after sintering, the preparation method also includes the step of heat treating the sintered material: cooling the sintered material to room temperature, then heating to 880-820°C and keeping warm for 3.8-4.2 hours, cooling to room temperature, and then heating to 450-470°C and keeping warm for 3.8-4.2 hours.

[0030] The present application also provides a NdFeB magnet obtained by the above-mentioned diffusion method of high-Ga low-B magnets. Based on the above reasons, the present application can improve the diffusion efficiency of high-Ga low-B magnets and significantly reduce the reduction of remanence caused by high-temperature diffusion.

[0031] The present application is further described in detail below in conjunction with specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in the present application.

[0032] Example 1

[0033] 1. According to the nominal composition of the main phase alloy (Pr 25 Nd 75 ) 29 Tb1Co1Ga 0.35 Cu 0.25 Ti0.2 Zr 0.35 B 0.945 Fe bal (wt%) was used to prepare the spun sheets (refining temperature 1520°C, casting temperature 1430°C).

[0034] 2. The obtained flings are hydrogen crushed to obtain coarsely crushed magnetic powder (dehydrogenation temperature 550°C).

[0035] 3. The coarsely crushed magnetic powder is obtained and subjected to jet milling (SMD: 3.1-3.2 μm; X50: 4.5 μm).

[0036] 4. The obtained air flow milled powder is oriented and molded to obtain a green body, which is vacuum packaged and cold isostatically pressed to a molding density of 4.0 g / cm 3 , isostatic pressure 220MPa, process oxygen content less than 100ppm, orientation field greater than 1.7T.

[0037] 5. The obtained pressed green body is sintered and heat treated by step-by-step heating, firstly, the temperature is raised to 450°C and kept for 1 hour to remove the lubricant and antioxidant in the pressed green body, then the temperature is raised to 600°C and kept for 1 hour, then the temperature is raised to 800°C and kept for 1 hour to remove the residual hydrogen and impurities, then the temperature is raised to 1090°C and kept for 4 hours to sinter, then the temperature is lowered to 900°C and kept for 3 hours, then the temperature is raised to 1095°C and kept for 4 hours to sinter densely, then cooled to room temperature, then the temperature is raised to 900°C and kept for 4 hours, after cooling to room temperature, the temperature is raised to 460°C and kept for 4 hours.

[0038] 6. A NdFeB magnet A is made into a block.

[0039] 7. Take a slice of NdFeB magnet A: 30×30×3 (orientation direction, unit: mm).

[0040] 8. Print Tb (the dosage is 0.7wt% of the weight of NdFeB magnet square piece A) and perform grain boundary diffusion heat treatment on the NdFeB magnet A slice: heat it to 940℃ under a vacuum of 0.005pa for diffusion treatment, keep it warm for 28 hours until the heavy rare earth is basically completely diffused into the grain boundary, cool it to room temperature, and then heat it to 500℃ and keep it warm for 4 hours.

[0041] Example 2

[0042] The only difference from Example 1 is that during the grain boundary diffusion heat treatment process: the temperature is raised to 920°C under a vacuum condition of 0.005 Pa for diffusion treatment, kept warm for 28 hours until the heavy rare earth is basically completely diffused into the grain boundary, cooled to room temperature, and then raised to 500°C and kept warm for 4 hours.

[0043] Example 3

[0044] The only difference from Example 1 is that the temperature is raised to 960°C for diffusion treatment under a vacuum condition of 0.005 Pa, kept at this temperature for 28 hours until the heavy rare earth is basically completely diffused into the grain boundary, cooled to room temperature, and then raised to 500°C and kept at this temperature for 4 hours.

[0045] Example 4

[0046] The only difference from Example 1 is that according to the nominal composition of the main phase alloy (Pr 25 Nd 75 ) 28 Tb1Co1Ga 0.5 Cu 0.5 Ti 0.15 Zr 0.5 B 0.945 Fe bal (wt. %) was used to prepare the spun sheets (refining temperature 1520°C, pouring temperature 1430°C).

[0047] Comparative Example 1

[0048] 1. According to the nominal composition of the main phase alloy (Pr 25 Nd 75 ) 29 Tb1Co1Ga 0.35 Cu 0.25 Ti 0.2 Zr 0.05 B 0.945 Fe bal (wt%) was used to prepare the spun sheets (refining temperature 1520°C, casting temperature 1420°C).

[0049] 2. The obtained flings are hydrogen crushed to obtain coarsely crushed magnetic powder (dehydrogenation temperature 550°C).

[0050] 3. The coarsely crushed magnetic powder is obtained and subjected to jet milling (SMD: 3.1-3.2 μm; X50: 4.5 μm).

[0051] 4. The obtained air flow milled powder is oriented and molded to obtain a green body, which is vacuum packaged and cold isostatically pressed to a molding density of 4.0 g / cm 3 , isostatic pressure 220MPa, process oxygen content less than 100ppm, orientation field greater than 1.7T.

[0052] 5. The obtained pressed green body is sintered and heat treated: the temperature is raised to 1090°C and kept for 4 hours for sintering, then the temperature is lowered to 900°C and kept for 3 hours, then the temperature is raised to 1092°C and kept for 4 hours for sintering to be dense, then cooled to room temperature, then the temperature is raised to 900°C and kept for 4 hours, after cooling to room temperature, the temperature is raised to 460°C and kept for 4 hours.

[0053] 6. Make a block of NdFeB magnet B.

[0054] 7. Take slice B of NdFeB magnet: 30×30×3 (orientation direction).

[0055] 8. Print Tb (the dosage is 0.7wt% of the weight of NdFeB magnet square piece A) and perform grain boundary diffusion heat treatment on NdFeB magnet B slices: heat to 940℃ for diffusion treatment under a vacuum of 0.005pa, keep warm for 28 hours until the heavy rare earth is basically completely diffused into the grain boundary, cool to room temperature, and then heat to 500℃ and keep warm for 4 hours.

[0056] Comparative Example 2

[0057] The only difference from Comparative Example 1 is that during the grain boundary diffusion heat treatment: the temperature is raised to 920°C under a vacuum condition of 0.005 Pa for diffusion treatment, kept warm for 28 hours until the heavy rare earth is basically completely diffused into the grain boundary, cooled to room temperature, and then heated to 500°C and kept warm for 4 hours.

[0058] Comparative Example 3

[0059] 1. According to the nominal composition of the main phase alloy (Pr 25 Nd 75 ) 29 Tb1Co1Ga 0.2 Cu 0.2 Ti 0.1 Zr 0.08 B 0.96 Fe bal (wt%) was used to prepare the fluff sheets (refining temperature 1520°C, pouring temperature 1410°C).

[0060] 2. The obtained flings are hydrogen crushed to obtain coarsely crushed magnetic powder (dehydrogenation temperature 550°C).

[0061] 3. The coarsely crushed magnetic powder is obtained and subjected to jet milling (SMD: 3.1-3.2 μm; X50: 4.5 μm).

[0062] 4. The obtained air flow milled powder is oriented and molded to obtain a green body, which is vacuum packaged and cold isostatically pressed to a molding density of 4.0 g / cm 3 , isostatic pressure 220MPa, process oxygen content less than 100ppm, orientation field greater than 1.7T.

[0063] 5. The obtained pressed green body is sintered and heat treated: the temperature is raised to 1085°C and kept for 4 hours for sintering, the temperature is then raised to 1090°C and kept for 4 hours for sintering to be dense, and then cooled to room temperature, the temperature is then raised to 900°C and kept for 4 hours, after cooling to room temperature, the temperature is then raised to 460°C and kept for 4 hours.

[0064] 6. Make a block of NdFeB magnet C.

[0065] 7. Take slice C of NdFeB magnet: 30×30×3 (orientation direction).

[0066] 8. Take NdFeB magnet slice C for printing Tb (the dosage is 0.9wt% of the weight of NdFeB magnet square slice A) and grain boundary diffusion heat treatment: heat it to 940℃ under a vacuum of 0.005pa for diffusion treatment, keep it warm for 28 hours until the heavy rare earth is basically completely diffused into the grain boundary, cool it to room temperature, and then heat it to 500℃ and keep it warm for 4 hours.

[0067] Comparative Example 4

[0068] The only difference from Comparative Example 3 is that during the grain boundary diffusion heat treatment: the temperature is raised to 920°C for diffusion treatment under a vacuum condition of 0.005 Pa, kept warm for 28 hours until the heavy rare earth is basically completely diffused into the grain boundary, cooled to room temperature, and then heated to 500°C and kept warm for 4 hours.

[0069] Performance characterization:

[0070] The samples obtained by diffusion heat treatment in the embodiment and the comparative example were subjected to magnetic property testing, and the results were shown in Table 1 below:

[0071] Table 1

[0072]

[0073] Through Example 1, it can be concluded that high-temperature diffusion (940°C) can improve the diffusion effect of high-Ga low-B magnets. By comparing the example and comparative example 1, it can be concluded that the residual magnetism decrease ratio of the blank after high-temperature diffusion after adding Zr is low, indicating that Zr can play a pinning role, preventing a large amount of Tb from entering the main phase to replace Nd and reduce the residual magnetism. By comparing the example and comparative example 3, it can be concluded that under the premise of obtaining similar performance, the cost required for high-temperature diffusion of high-Ga low-B formula is lower than that of conventional diffusion of conventional formula.

[0074] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A diffusion method for high-Ga and low-B magnets, characterized in that: include: The diffuser containing heavy rare earth elements is attached to the outer surface of the high-Ga low-B magnet. -3 ~1×10 -2 Diffusion treatment is performed on the high-Ga and low-B magnets for 20 to 30 hours under vacuum conditions of 1.5 pa and a temperature of 920 to 960° C.; Among them, the high-Ga, low-B magnet components include: 0.3-0.5wt% Ga, 0.25-0.5wt% Cu, 0.9-0.95wt% B, 0.15-0.2wt% Ti, 0.3-0.5wt% Zr, 0-1wt% Co, 29-32wt% Re and the remainder Fe; the Re is a rare earth element.

2. The diffusion method of high-Ga low-B magnet according to claim 1, characterized in that: Performing the diffusion treatment on the high-Ga, low-B magnet at a temperature of 940 to 960° C. for 20 to 30 hours; Preferably, the Re is selected from Nd and one or more of the following optional elements: Pr, Tb, Dy, Ce, La, Gd; Preferably, the composition of the high-Ga, low-B magnet includes: 0.3-0.5wt% Ga, 0.25-0.5wt% Cu, 0.9-0.95wt% B, 0.15-0.2wt% Ti, 0.3-0.5wt% Zr, 0.9-1wt% Co, 29-30wt% Re and the remainder Fe; the Re is selected from Nd and one or more of the following elements: Pr, Tb, Ce, La and Gd.

3. The diffusion method of high-Ga low-B magnet according to claim 1 or 2, characterized in that: The diffusing agent is selected from one or more of a heavy rare earth element, a heavy rare earth alloy or a heavy rare earth compound; Preferably, the heavy rare earth element is selected from terbium or dysprosium; the heavy rare earth alloy is selected from terbium copper alloy, terbium aluminum alloy, dysprosium copper alloy or dysprosium aluminum alloy; the heavy rare earth compound is selected from terbium fluoride, dysprosium fluoride, terbium oxide or dysprosium oxide; Preferably, the diffusant is attached to the outer surface of the high-Ga, low-B magnet by magnetron sputtering, evaporation, spraying, printing or electrodeposition; Preferably, the amount of the diffusing agent used is 3 to 20 g per kilogram of the mass of the high-Ga, low-B magnet.

4. The diffusion method of high-Ga low-B magnet according to any one of claims 1 to 3, characterized in that: The high-Ga and low-B magnets are prepared by the following steps: The alloy raw materials are mixed according to the stoichiometric ratio, and then refined and cast in sequence to obtain a spun sheet; The fling sheets are subjected to hydrogen crushing, air flow grinding, molding and sintering in sequence to obtain the high-Ga and low-B magnets.

5. The diffusion method of high-Ga low-B magnet according to claim 4, characterized in that: The refining treatment temperature is 1500-1550°C; Preferably, the pouring treatment temperature is 1400-1450°C.

6. The diffusion method of high-Ga low-B magnet according to claim 4, characterized in that: The dehydrogenation temperature during the hydrogen crushing process is 510-580°C.

7. The diffusion method of high-Ga low-B magnet according to claim 4, characterized in that: The material obtained by the air flow mill treatment has a powder specific surface average diameter of 3.1-3.2 μm and a powder particle median diameter of less than 4.5 μm.

8. The diffusion method of high-Ga and low-B magnets according to claim 4, characterized in that: The molding density of the material obtained by the molding process is 3.9-4.1 g / cm 3 ; Preferably, the forming comprises orientation forming and cold isostatic pressing performed sequentially; Further preferably, the orientation magnetic field of the orientation molding is greater than 1.7T; Further preferably, the isostatic pressing pressure of the cold isostatic pressing is 210-250 MPa; Further preferably, during the cold isostatic pressing process, the oxygen content is less than 100 ppm.

9. The diffusion method of high-Ga low-B magnet according to claim 4, characterized in that: The sintering treatment temperature is 1030-1110° C., and the treatment time is 5-10 hours.

10. A NdFeB magnet obtained by the diffusion method of a high-Ga, low-B magnet according to any one of claims 1 to 9.

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