Neodymium-iron-boron magnet material and preparation method and application thereof

Abstract

The invention provides a neodymium-iron-boron magnet material and a preparation method and application thereof. The preparation method of the neodymium-iron-boron magnet material comprises the following steps: sequentially performing smelting, casting, powdering, pressing, sintering and grain boundary diffusion on a raw material composition, wherein the raw material composition comprises the following components: 25.0-30.0 mass.% of R, the R is a rare earth element, and the R comprises PrNd and Nd; the contents of the PrNd and the Nd meet the condition that PrNd / (PrNd + Nd) is more than or equal to 0.03 and less than or equal to 0.84; % of M, the content of M is not 0, and M comprises Al, Cu, Ga and X; the contents of Al, Cu and Ga meet the following conditions: Al + Cu + Ga is greater than 0 mass.% and less than or equal to 0.46 mass.%, and Cu is greater than Al and less than or equal to Ga; x comprises one or more of Ti, Zr, Nb, W and Mo; % of B: 0.87 to 1.02 mass.%; and the balance of Fe and unavoidable impurities. The neodymium-iron-boron magnet material disclosed by the invention has excellent magnetic performance and can have ultrahigh residual magnetism and high coercive force at the same time.

Description

Technical Field

[0001] The present invention relates to a neodymium iron boron magnet material, a preparation method thereof and an application thereof. Background Art

[0002] Sintered neodymium iron boron permanent magnets are widely used due to their ultra-high energy density and are known as the "magnetic king". They not only have a very high magnetic energy density and good temperature-resistant service characteristics, but also have good cost performance, so they are widely used in China's pillar industries and emerging industries, such as rail transit, military equipment, wind power generation, low-altitude flight, artificial intelligence, aerospace, medical devices, precision manufacturing and other industries. With the development characteristics of miniaturization, light weight, high efficiency, and intelligence of devices in various fields, higher and higher requirements are also put forward for the performance of rare earth permanent magnets. The development of ultra-high performance magnets has also become the focus of the industry's development, and the development of double-high magnets with ultra-high remanence and high coercivity has become an increasingly popular topic. However, there are few double-high magnets in the prior art that have been certified by authoritative institutions and publicly reported. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the defect that the magnet material in the prior art cannot have both ultra-high remanence and high coercivity, and provides a neodymium iron boron magnet material, a preparation method thereof and an application thereof. The neodymium iron boron magnet material described in the present invention has excellent magnetic properties and can have both ultra-high remanence and high coercivity.

[0004] To achieve the above object, the present invention adopts the following technical solutions.

[0005] In a first aspect, the present invention provides a preparation method of a neodymium iron boron magnet material, which includes the following steps: successively subjecting a raw material composition to melting, casting, powder making, pressing, sintering and grain boundary diffusion; wherein, the raw material composition includes the following components in the following contents:

[0006] R: 25.0 - 30.0 mass.%, wherein R is a rare earth element, and R includes PrNd and Nd; the contents of PrNd and Nd satisfy: 0.03 ≤ PrNd / (PrNd + Nd) ≤ 0.84;

[0007] M: 0 - 3.0 mass.%, wherein the content of M is not 0, and M includes Al, Cu, Ga and X; the contents of Al, Cu and Ga satisfy: 0 mass.% < Al + Cu + Ga ≤ 0.46 mass.%, and Al < Cu ≤ Ga; X includes one or more of Ti, Zr, Nb, W and Mo;

[0008] B: 0.87 - 1.02 mass.%;

[0009] and the balance of Fe and inevitable impurities;

[0010] The mass.% represents the mass percentage based on the total mass of the raw material composition.

[0011] In the present invention, the PrNd may be a conventional PrNd alloy in the art. The mass ratio of Pr element to Nd element in the PrNd may be (10 - 25):(75 - 90), such as 10:90, 20:80 or 25:75.

[0012] In the present invention, "PrNd / (PrNd + Nd)" represents the ratio of the content of PrNd to the sum of the contents of "PrNd and Nd".

[0013] In some embodiments of the present invention, in the raw material composition, the contents of PrNd and Nd satisfy: 0.05 ≤ PrNd / (PrNd + Nd) ≤ 0.20.

[0014] In some specific embodiments of the present invention, in the raw material composition, the contents of PrNd and Nd satisfy: PrNd / (PrNd + Nd) = 0.05, or PrNd / (PrNd + Nd) = 0.08.

[0015] In some embodiments of the present invention, in the raw material composition, the content of Nd is 24.0 - 27.0 mass.%.

[0016] In some embodiments of the present invention, in the raw material composition, the content of PrNd is 2.0 - 5.0 mass.%, such as 2.4 mass.% or 4.3 mass.%.

[0017] In the present invention, the content of R refers to the total rare earth content in the raw material composition.

[0018] In some embodiments of the present invention, the content of R is 28.0 - 29.5 mass.%, such as 28.3 mass.% or 29.4 mass.%.

[0019] In some embodiments of the present invention, the R further includes one or more of Dy, Tb, Pr, Y and Ho.

[0020] In some embodiments of the present invention, the content of M is 1.0 - 2.0 mass.%, such as 1.24 mass.% or 1.42 mass.%.

[0021] In the present invention, "Al + Cu + Ga" refers to the sum of the contents of Al, Cu and Ga.

[0022] In the present invention, "Al < Cu ≤ Ga" represents the magnitude relationship among the contents of Al, Cu, and Ga.

[0023] In some embodiments of the present invention, the contents of Al, Cu, and Ga satisfy: 0.35 mass.% ≤ Al + Cu + Ga ≤ 0.40 mass.%, for example, 0.37 mass.% or 0.38 mass.%.

[0024] In some embodiments of the present invention, the content of Al is 0 - 0.05 mass.%, preferably 0.01 - 0.03 mass.%, for example, 0.01 mass.% or 0.03 mass.%.

[0025] In some embodiments of the present invention, the content of Cu is 0.1 - 0.2 mass.%, for example, 0.15 mass.% or 0.16 mass.%.

[0026] In some embodiments of the present invention, the content of Ga is 0.1 - 0.2 mass.%, for example, 0.2 mass.%.

[0027] In some embodiments of the present invention, the content of X is 0.1 - 0.3 mass.%, for example, 0.25 mass.% or 0.26 mass.%.

[0028] In some embodiments of the present invention, X includes Ti and / or Zr.

[0029] In some embodiments of the present invention, X includes Ti; wherein the content of Ti is preferably 0.05 - 0.1 mass.%, for example, 0.06 mass.% or 0.09 mass.%.

[0030] In some embodiments of the present invention, X includes Zr; wherein the content of Zr is preferably 0.15 - 0.2 mass.%, for example, 0.17 mass.% or 0.19 mass.%.

[0031] In some specific embodiments of the present invention, X includes Ti and Zr; wherein the content of Ti is 0.09 mass.%; the content of Zr is 0.17 mass.%.

[0032] In some specific embodiments of the present invention, X includes Ti and Zr; wherein the content of Ti is 0.06 mass.%; the content of Zr is 0.19 mass.%.

[0033] In some embodiments of the present invention, M further comprises Co; the content of Co is preferably 0.1-0.8 mass.%, more preferably 0.5-0.9 mass.%, such as 0.6 mass.% or 0.8 mass.%.

[0034] In some preferred embodiments of the present invention, the raw material composition comprises components with the following contents:

[0035] PrNd: 2.0-4.5 mass.%;

[0036] Nd: 20.5-28.0 mass.%;

[0037] Al: 0.01-0.03 mass.%;

[0038] Cu: 0.1-0.2 mass.%;

[0039] Ga: 0.1-0.2 mass.%;

[0040] Co: 0.5-1.0 mass.%;

[0041] Ti: 0.05-0.1 mass.%;

[0042] Zr: 0.15-0.2 mass.%;

[0043] B: 0.96-1.0 mass.%;

[0044] Fe: 68.0-70.0 mass.%.

[0045] In some specific embodiments of the present invention, the raw material composition comprises components with the following contents:

[0046] PrNd: 4.3 mass.%;

[0047] Nd: 24.0 mass.%;

[0048] Al: 0.03 mass.%;

[0049] Cu: 0.15 mass.%;

[0050] Ga: 0.20 mass.%;

[0051] Co: 0.6 mass.%;

[0052] Ti: 0.09 mass.%;

[0053] Zr: 0.17 mass.%;

[0054] B: 0.98 mass.%;

[0055] Fe: 69.48 mass.%.

[0056] In some specific embodiments of the present invention, the raw material composition comprises components with the following contents:

[0057] PrNd: 2.4 mass.%;

[0058] Nd: 27.0 mass.%;

[0059] Al: 0.01 mass.%;

[0060] Cu: 0.15 mass.%;

[0061] Ga: 0.18 mass.%;

[0062] Co: 0.8 mass.%;

[0063] Ti: 0.06 mass.%;

[0064] Zr: 0.19 mass.%;

[0065] B: 0.98 mass.%;

[0066] Fe: 68.23 mass.%.

[0067] In the present invention, the melting and the casting can be carried out in a conventional manner in the art. The melting and the casting can be carried out in a continuous furnace.

[0068] In some embodiments of the present invention, the temperature of the melting is 1400 - 1500 °C, such as 1445 °C or 1451 °C.

[0069] In some embodiments of the present invention, the process parameters of the casting include: the rotational speed of the copper roller is 20 - 30 r / min, the degree of supercooling is 160 - 180 °C, and the casting flow rate is 140 - 145 cm 3 / s.

[0070] In some specific embodiments of the present invention, the process parameters of the casting include: the rotational speed of the copper roller is 28 r / min, the degree of supercooling is 170 °C, and the casting flow rate is 140.3 cm 3 / s.

[0071] In some specific embodiments of the present invention, after the casting, it is taken out of the furnace at 40 - 60 °C during cooling, such as 45 °C.

[0072] In some embodiments of the present invention, the thickness of the rapidly solidified sheet obtained by casting is 0.20 - 0.30 mm, such as 0.26 mm or 0.27 mm.

[0073] In some embodiments of the present invention, the columnar crystal width of the rapidly solidified sheet obtained by casting is 2.0 - 3.0 μm, such as 2.7 μm or 2.8 μm.

[0074] In some embodiments of the present invention, the preparation method further includes: subjecting the rapidly solidified sheet obtained by casting to gas atomization treatment with PrNd. Through gas atomization treatment, the rare earth at the grain boundaries of the rapidly solidified sheet can be filled and repaired to a certain extent, so that the rapidly solidified sheet not only obtains a matrix with a super-high matrix volume fraction, but also obtains a relatively continuous grain boundary phase structure, which can greatly reduce the oxidation risk of the powder during the subsequent powder preparation process and prevent the subsequent sintering from being unable to be densified.

[0075] Among them, preferably, the operation of the gas atomization treatment includes: performing physical vapor deposition on the rapidly solidified sheet with PrNd; the temperature of the physical vapor deposition is preferably 600 - 800 °C, and the time of the physical vapor deposition is preferably 4 - 20 h.

[0076] Among them, preferably, after the gas atomization treatment, the PrNd weight gain of the rapidly solidified sheet is 0.5% - 1.0%, such as 0.75%. Among them, the PrNd weight gain refers to the percentage of the mass increase of PrNd in the rapidly solidified sheet after gas atomization treatment to the mass of the rapidly solidified sheet before gas atomization treatment.

[0077] In the present invention, the powder preparation can be carried out in a conventional manner in the art.

[0078] In some embodiments of the present invention, the powder preparation includes hydrogen decrepitation and jet milling performed in sequence.

[0079] In the present invention, the hydrogen decrepitation can be carried out using a continuous hydrogen decrepitation furnace.

[0080] In some embodiments of the present invention, the reaction pressure of the hydrogen decrepitation is 0.08 - 0.1 MPa, such as 0.098 MPa.

[0081] In some embodiments of the present invention, during the hydrogen decrepitation process, the temperature of the dehydrogenation treatment is 500 - 600 °C, such as 570 °C.

[0082] In some embodiments of the present invention, a powder additive is added to the coarse powder obtained by hydrogen decrepitation.

[0083] Among them, preferably, the addition ratio of the powder additive is 1.7 g of the powder additive added per kg of the coarse powder.

[0084] In the present invention, the jet mill can be a multi-nozzle opposed-flow fluidized bed jet mill.

[0085] In some specific embodiments of the present invention, the parameter settings of the jet mill include: the cleaning pressure of the sorting wheel gap maintenance disk is 70 Kpa, the rotation speed of the sorting wheel is 3490 r / min, the mass of the grinding chamber is 58 kg, the grinding pressure is 0.57 MPa, and the side jet pressure is 25 Kpa.

[0086] In some specific embodiments of the present invention, the average particle size SMD of the fine powder obtained by the jet mill is 2.0 - 2.5 μm, such as 2.2 μm.

[0087] In some embodiments of the present invention, a powder additive is added to the fine powder obtained by the jet mill.

[0088] Among them, preferably, the addition ratio of the powder additive is 0.8 g of the powder additive added per kg of the coarse powder.

[0089] In some embodiments of the present invention, the powder additive is added through an on-line additive system.

[0090] In the present invention, adding a powder additive during the jet milling process is a conventional operation in the art, which can prevent particle agglomeration, control the particle size distribution, improve the grinding efficiency, reduce equipment wear, protect the crushing cavity, prevent oxidation or hydrolysis, improve product stability, and improve the adaptability of downstream processes, etc.

[0091] In the present invention, the pressing can be carried out in a conventional manner in the art.

[0092] In some embodiments of the present invention, the pressing is carried out using a fully electric floating press and a combined die.

[0093] In some embodiments of the present invention, the pressing includes orientation pressing.

[0094] Among them, preferably, the process parameters of the orientation pressing include: the size of the pressing orientation direction is 55 mm, the weight of the pressed blank is 780 g, the minimum orientation field at the die forming position is > 1.95 T, and the oxygen content during the whole pressing process is < 50 ppm.

[0095] In some embodiments of the present invention, pre-pressing is also included before the orientation pressing.

[0096] Among them, preferably, the pre-pressing is two-stage pre-pressing, including:

[0097] The first stage: the pre-pressing density is 2.2 g / cm 3 , and the pressing current is 20 A;

[0098] The second stage: the pre-pressing density is 3.0 g / cm 3, the pressing current is 100 A.

[0099] Among them, preferably, the orientation pressing satisfies: the pressing density is 4.0 g / cm 3 , the pressing current is 210 A.

[0100] Among them, preferably, the holding and orientation time of the orientation pressing is 1 - 3 s, such as 2 s.

[0101] In some embodiments of the present invention, the pressing further includes isostatic pressing.

[0102] Among them, preferably, the pressure of the isostatic pressing is 200 MPa.

[0103] In the present invention, the sintering can be carried out in a conventional manner in the art.

[0104] In some embodiments of the present invention, the sintering uses one or more of a high-density graphite box, a molybdenum box, a tungsten box, and a carbon-ceramic box; preferably, the sintering uses a combined box body of a high-density graphite box and a molybdenum box.

[0105] In some embodiments of the present invention, the sintering is carried out in a manner of gradient heating.

[0106] In some embodiments of the present invention, the process of the sintering includes: holding the temperature at 100 - 300 °C, 350 - 450 °C, 550 - 600 °C, 620 - 680 °C, 700 - 780 °C, 810 - 980 °C, and 1000 - 1200 °C respectively.

[0107] Among them, preferably, the holding time at 1000 - 1200 °C is 4 - 15 h.

[0108] In some specific embodiments of the present invention, the process of the sintering includes: holding the temperature at 250 °C, 420 °C, 580 °C, 640 °C, 760 °C, 830 °C, and 1085 °C respectively, and the holding times are 1.5 h, 2.5 h, 1.5 h, 2.5 h, 2 h, 3 h, and 9 h respectively.

[0109] In some embodiments of the present invention, the heating rate during the sintering process is 1 - 3 °C / min, such as 1.5 °C / min.

[0110] In some embodiments of the present invention, aging treatment is further included after the sintering. Among them, preferably, the aging treatment is two-stage aging treatment.

[0111] In some embodiments of the present invention, the two-stage aging treatment includes: holding the temperature at 880 - 930 °C for 3 - 10 h, and then holding the temperature at 450 - 550 °C for 3 - 10 h.

[0112] In some specific embodiments of the present invention, the two-stage aging treatment includes: holding at 905 °C for 3 h and then holding at 505 °C for 5 h.

[0113] In the present invention, the grain boundary diffusion can be carried out in a conventional manner in the art.

[0114] In some embodiments of the present invention, the operation of the grain boundary diffusion includes: applying a diffusion source on the surface of the sintered Nd-Fe-B matrix and performing heat treatment. It should be noted that if aging treatment is performed after sintering, the Nd-Fe-B matrix refers to the magnet obtained after the aging treatment.

[0115] In some embodiments of the present invention, the application method is screen printing, spraying or magnetron sputtering.

[0116] In some embodiments of the present invention, the grain boundary diffusion is carried out by a segmented heat treatment process.

[0117] In some embodiments of the present invention, the segmented heat treatment process of the grain boundary diffusion includes:

[0118] The first stage: the holding temperature is 880 - 950 °C and the time is 5 - 36 h;

[0119] The second stage: the holding temperature is 450 - 550 °C and the time is 3 - 10 h.

[0120] In some specific embodiments of the present invention, the segmented heat treatment process of the grain boundary diffusion includes:

[0121] The first stage: successively hold at 900 °C, 908 °C, 916 °C, 905 °C for 4 h, 4 h, 3 h, 5 h respectively; after the holding ends, cool with argon wind to below 70 °C;

[0122] The second stage: heat up to 505 °C and hold for 5 h.

[0123] In some embodiments of the present invention, the vacuum degree is controlled to be 10 -1 -10 -4 Pa during the grain boundary diffusion process.

[0124] In some embodiments of the present invention, the diffusion source of the grain boundary diffusion includes a heavy rare earth element RH, and the RH includes Dy and / or Tb.

[0125] In some embodiments of the present invention, the mass percentage of the heavy rare earth element RH in the diffusion source accounts for 0.1 - 0.8 mass.% of the mass of the Nd-Fe-B matrix, such as 0.5 mass.%.

[0126] In some embodiments of the present invention, the diffusion source is one or more of the elemental substance, fluoride, hydride, and alloy of RH.

[0127] In some specific embodiments of the present invention, the diffusion source is (Tb-Co-Fe-Cu-PrNd)H alloy.

[0128] In a second aspect, the present invention provides a neodymium iron boron magnet material, which is prepared by using the preparation method of the neodymium iron boron magnet material as described above.

[0129] In the present invention, the volume fraction of the main phase grains in the neodymium iron boron magnet material can be greater than 95.5%, such as 96.24% or 97.53%.

[0130] In some embodiments of the present invention, the carbon content in the neodymium iron boron magnet material is ≤600 ppm, the oxygen content is ≤400 ppm, and the nitrogen content is ≤200 ppm.

[0131] In a third aspect, the present invention provides an application of the neodymium iron boron magnet material as described above as a magnetic device.

[0132] In the present invention, the neodymium iron boron magnet material is applied as a magnetic device in many fields such as rail transit, military equipment, wind power generation, low-altitude flight, artificial intelligence, aerospace, medical devices, precision manufacturing, etc.

[0133] In the present invention, each element symbol has its conventional meaning in the art. Specifically: "Pr" is praseodymium, "Nd" is neodymium, "Dy" is dysprosium, "Tb" is terbium, "Y" is yttrium, "Ho" is holmium, "Al" is aluminum, "Cu" is copper, "Ga" is gallium, "Co" is cobalt, "Ti" is titanium, "Zr" is zirconium, "Nb" is niobium, "W" is tungsten, "Mo" is molybdenum, "Fe" is iron, and "B" is boron.

[0134] In the present invention, unless otherwise specified, the element appearing alone refers to the elemental substance of that element.

[0135] On the basis of conforming to the common knowledge in the art, the above preferred conditions can be combined arbitrarily to obtain various preferred examples of the present invention.

[0136] The reagents and raw materials used in the present invention are all commercially available.

[0137] The positive and progressive effects of the present invention are as follows:

[0138] Through special formulation design, in terms of rare earth elements, PrNd alloy and Nd metal are compounded in a specific ratio, and the dosages of elements such as Al, Cu, and Ga are controlled, achieving further breakthroughs in the performance of NdFeB magnet materials. In this NdFeB magnet material, the volume fraction of the main phase grains is more than 95.5%, and the contents of impurity elements carbon, oxygen, and nitrogen are significantly reduced (carbon content ≤ 600 ppm, oxygen content ≤ 400 ppm, nitrogen content ≤ 200 ppm). It has excellent magnetic properties and can have both ultra-high remanence and high coercivity. Specifically: the remanence can reach more than 14.9 kGs, the coercivity can reach more than 20 kOe, and Hk / Hcj can reach more than 96%. Detailed implementation mode

[0139] The present invention will be further described below by way of examples, but the present invention is not limited to the scope of the described examples. For the experimental methods without specific conditions in the following examples, they are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0140] Example 1

[0141] (1) Melting and casting:

[0142] Weigh each raw material component according to Table 1 and mix them. Then melt them in a continuous furnace at 1451 °C and cast them on a copper roller (the rotation speed of the copper roller is 28 r / min, the undercooling degree is 170 °C, and the casting flow rate is 140.3 cm 3 / s), and take them out of the furnace after cooling to 45 °C to obtain a rapidly solidified sheet. The thickness and columnar crystal width of the rapidly solidified sheet are shown in Table 2. Put the rapidly solidified sheet in a sealed stainless steel barrel, and after fully exhausting oxygen with argon, seal it for standby.

[0143] Perform gas atomization treatment on the rapidly solidified sheet obtained in the above steps. The operation of gas atomization treatment is to perform physical vapor deposition on the rapidly solidified sheet at 690 °C for 8 h using PrNd alloy (where the two elements Pr:Nd = 20:80). The weight gain of PrNd is 0.75%. Here, the weight gain of PrNd refers to the percentage of the mass increase of PrNd in the rapidly solidified sheet after gas atomization treatment to the mass of the rapidly solidified sheet before gas atomization treatment. Through gas atomization treatment, the grain boundaries of the rapidly solidified sheet can be filled and repaired to a certain extent.

[0144] (2) Powder making:

[0145] Perform hydrogen breaking treatment on the rapidly solidified sheet obtained in step (1) using a continuous hydrogen breaking furnace. The reaction pressure is 0.098 MPa, dehydrogenation treatment is carried out at 570 °C, and it is taken out of the furnace in a fully sealed state after cooling to below 40 °C to obtain coarse powder; put the coarse powder into a coarse powder tank that has been fully exhausted of oxygen to below 50 pm in advance, and fill it with argon for pressure maintaining treatment.

[0146] Add a powder additive to the obtained coarse powder. The powder additive consists of Tianjin agent Yuesheng agent (purchased from Tianjin Yuesheng New Materials Research Institute, model YSH-01), Dongyang agent (purchased from Dongyang Antai Magnetic Materials Co., Ltd., YKJ-10), and 120# gasoline with a mass ratio of 1:1:1.8. The addition ratio is 1.7 g of powder additive per kg of coarse powder, and mix and stir for 120 min.

[0147] Use a multi-nozzle impinging fluidized bed jet mill for grinding the powder. First, thoroughly blow out the bottom material in the jet mill without introducing any impurities. Use argon to fully purge oxygen in the jet mill to below 2 ppm, and then load the coarse powder. Start the jet mill. The main parameters of the jet mill are set as follows: the clearance of the sorting wheel gap maintenance disc cleaning pressure is 70 Kpa, the sorting wheel speed is 3490 r / min, the grinding chamber mass is 58 kg, the grinding pressure is 0.57 MPa, and the side spray pressure is 25 Kpa. Prepare fine powder with a high sphericity and an average particle size SMD of about 2.2 μm. The main phase surface of the fine powder prepared by this process has a high rare earth-rich phase coating.

[0148] During the grinding process, use an on-line additive system to add the powder additive (with the same composition as the aforementioned powder additive) to the fine powder receiving tank. The addition ratio is 0.8 g of powder additive per kg of fine powder, and mix and stir for 120 min.

[0149] Sieve the fine powder after the jet mill. The oxygen content throughout the sieving process is less than 50 ppm.

[0150] (3) Pressing: Use a fully electric floating press and a combined die to perform orientation pressing on the fine powder. The size of the pressing orientation direction is 55 mm, the weight of the pressed blank is 780 g, the minimum orientation field at the die forming position is >1.95 T, and the oxygen content throughout the pressing process is <50 ppm. The pressing process adopts a two-stage pre-pressing and pre-orientation process design. First, the pre-pressing density is 2.2 g / cm 3 , the pressing current is 20 A, then the pre-pressing density is 3.0 g / cm 3 , the pressing current is 100 A; then start pressing, the pressing density is 4.0 g / cm 3 , the pressing current is 210 A, and appropriately extend the holding pressure and orientation time (the holding pressure and orientation time is 2 s) to obtain a higher orientation degree.

[0151] Perform isostatic pressing on the obtained pressed green body at a pressure of 200 MPa.

[0152] (4)Sintering: Sintering is carried out using a combined box body of a high-density graphite box and a molybdenum box. Before use, it needs to be baked or dried at a temperature above 250 °C. Place the material obtained in step (3) in the box body and evacuate. Start heating up at a heating rate of about 1.5 °C / min, and perform heat preservation treatments at 250 °C, 420 °C, 580 °C, 640 °C, 760 °C, 830 °C, and 1085 °C respectively. The heat preservation times are 1.5 h, 2.5 h, 1.5 h, 2.5 h, 2 h, 3 h, and 9 h respectively; after sintering, two-stage aging treatments are carried out under vacuum conditions (905 °C, heat preservation for 3 h, 505 °C, heat preservation for 5 h); to obtain the NdFeB matrix.

[0153] (5)Grain boundary diffusion:

[0154] Process the NdFeB matrix into a sample of 30*12*3.5 mm, and perform surface activation treatment by degreasing and ultrasonic cleaning; adopt the screen printing process to attach a diffusion film layer on the surface of the NdFeB matrix. Among them, the composition of the diffusion film layer is (Tb-Co-Fe-Cu-PrNd)H (where the mass ratio of Tb, Co, Fe, Cu, and PrNd is 76:4:4:8:8), and among them, the mass percentage of Tb in the NdFeB matrix is 0.5 mass.%.

[0155] Adopt a segmented heat treatment process for diffusion. Specifically:

[0156] The first stage: successively at 900 °C, 908 °C, 916 °C, 905 °C, and keep warm for 4 h, 4 h, 3 h, and 5 h respectively; after the heat preservation ends, cool with argon air to below 70 °C;

[0157] The second stage: heat up to 505 °C, keep warm for 5 h, cool with nitrogen to below 60 °C and then take out of the furnace to obtain the NdFeB magnetic material. The content of each component in the obtained NdFeB magnetic material is shown in Table 3.

[0158] Example 2

[0159] Weigh each raw material component according to Table 1 and mix them, melt them in a continuous furnace at 1445 °C, and the remaining steps are the same as those in Example 1.

[0160] Comparative Example 1

[0161] (1)Melting and casting:

[0162] Weigh each raw material component according to Table 1 and mix them, melt them in a continuous furnace at 1440 °C, and cast them on a copper roller (copper roller rotation speed 28 r / min, undercooling 170 °C, casting flow rate 140.3 cm 3 / s), cool to 45 °C and then take out of the furnace to obtain a rapidly solidified sheet. The thickness and columnar crystal width of the rapidly solidified sheet are shown in Table 2. Place the rapidly solidified sheet in a sealed stainless steel barrel, and use argon to fully remove oxygen and then seal it for standby.

[0163] The rapidly solidified sheet obtained in the above steps is subjected to gas atomization treatment. The operation of gas atomization treatment is to carry out physical vapor deposition on the rapidly solidified sheet with PrNd at 690 °C for 8 h, and the weight gain of PrNd is 0.75%. Here, the weight gain of PrNd refers to the percentage of the mass increase of PrNd in the rapidly solidified sheet after gas atomization treatment to the mass of the rapidly solidified sheet before gas atomization treatment. Through gas atomization treatment, the grain boundaries of the rapidly solidified sheet can be filled and repaired to a certain extent.

[0164] (2)Powder making:

[0165] The rapidly solidified sheet obtained in step (1) is subjected to hydrogen breaking treatment using a continuous hydrogen breaking furnace. The reaction pressure is 0.098 MPa, dehydrogenation treatment is carried out at 570 °C, and it is cooled to below 40 °C and then taken out of the furnace in a fully sealed manner to obtain coarse powder; the coarse powder is loaded into a coarse powder tank that has been fully deoxygenated to below 50 ppm in advance, and argon is filled for pressure maintaining treatment.

[0166] Conventional powder additives (Tianjin Jiyue Shengji YSH-01) are added to the obtained coarse powder, and the addition ratio is 1.5 g of powder additives per kg of coarse powder, and the powder is mixed and stirred for 120 min.

[0167] A multi-nozzle opposed fluidized bed air classifier mill is used for grinding the powder. First, the bottom material in the air classifier mill is completely blown out without bringing in any impurities. The air classifier mill is fully deoxygenated with nitrogen to below 2 ppm, and then the coarse powder is loaded; the air classifier mill is started, and the main parameters of the air classifier mill are set as follows: the clearance of the sorting wheel gap maintaining disc cleaning pressure is 70 Kpa, the sorting wheel speed is 3490 r / min, the mass of the grinding chamber is 58 kg, the grinding pressure is 0.57 MPa, and the side spray pressure is 25 Kpa. Fine powder with a high sphericity and an average particle size SMD of about 3.0 μm is prepared.

[0168] During the grinding process, an on-line additive system is used to add powder additives (with the same composition as the aforementioned powder additives) to the fine powder receiving tank, and the addition ratio is 0.5 g of powder additives per kg of fine powder. After the air classifier mill, the fine powder is stirred for 120 min.

[0169] (3)Pressing: Semi-automatic pressing is adopted, the minimum orientation field at the die forming position is >1.6 T, and the oxygen content throughout the pressing process is <300 ppm;

[0170] The obtained green compact is then isostatically pressed at a pressure of 200 MPa.

[0171] (4) Sintering: Sintering is carried out using a graphite box, and it needs to be baked or dried at a temperature above 250 °C before use. Place the compacted material body in the box and evacuate. Start heating up, with a heating rate of about 1.5 °C / min, hold at 1095 °C for heat preservation, and the heat preservation time is 6 h; after sintering, two-stage aging treatments are carried out under vacuum conditions (900 °C, hold for 3 h, 500 °C, hold for 5 h); obtain the NdFeB matrix.

[0172] (5) Grain boundary diffusion:

[0173] Process the NdFeB matrix into a sample of 30*12*3.5 mm, and carry out surface activation treatment through degreasing and ultrasonic cleaning; adopt the screen printing process to attach the diffusion film layer TbH on the surface of the magnet. Among them, the mass percentage of Tb in the NdFeB matrix is 0.5%.

[0174] Adopt a segmented heat treatment process for diffusion, specifically:

[0175] The first stage: At 905 °C, hold for 16 h; after the heat preservation ends, cool with argon wind to below 70 °C;

[0176] The second stage: Heat up to 505 °C, hold for 5 h, cool with nitrogen to below 60 °C and then take out of the furnace to obtain the NdFeB magnet material.

[0177] Comparative example 2

[0178] Weigh each raw material component according to Table 1 and mix them, melt at 1450 °C in a continuous furnace, and the remaining steps are the same as those in Comparative example 1.

[0179] Table 1 Content of each component in the NdFeB matrix raw material composition (unit mass.%)

[0180]

[0181] Note: 1 The mass ratio of Pr element to Nd element in PrNd is 20:80.

[0182] Table 2

[0183]

[0184] The test method for the width of the columnar crystals of the spray-formed sheet is as follows: After embedding, polishing and preparing the sample of the spray-formed sheet, take microscopic photos with an SEM electron microscope, and use the line drawing method of ImageJ software to analyze and calculate the width of the columnar crystals. As can be seen from Table 2, the thickness of the spray-formed sheet in the examples of the present invention is smaller, and the width of the columnar crystals is smaller.

[0185] Effect example 1: Material composition determination

[0186] (1)Components of NdFeB magnet materials (after diffusion) and NdFeB matrix (before diffusion)

[0187] Using conventional methods in the art, a high-frequency inductively coupled plasma optical emission spectrometer (ICP-OES) was used to measure the components of the NdFeB matrix (before diffusion) and the NdFeB magnet materials (after diffusion) in the examples and comparative examples. The measurement results are shown in Tables 3 and 4 respectively.

[0188] Table 3 Component contents of NdFeB matrix (unit: mass.%)

[0189]

[0190] Table 4 Component contents of NdFeB magnet materials (unit: mass.%)

[0191]

[0192] (2)Measurement of impurity element contents

[0193] The NdFeB magnet materials (after diffusion) prepared in the examples and comparative examples were broken into small particles, and a carbon-sulfur analyzer CS-3000 (Beijing National Research Institute of Metrology & Metallurgy) and an oxygen-nitrogen-hydrogen analyzer ONH836 (Shanghai Yuzhong Industry Co., Ltd.) were used to conduct carbon and oxygen-nitrogen test analyses respectively. The test data are shown in Table 5 below;

[0194] Table 5

[0195]

[0196] As can be seen from Table 5, the contents of impurity elements carbon, oxygen, and nitrogen in the NdFeB magnet materials prepared in the examples of the present invention are significantly reduced, which is also one of the important factors for the significant improvement of the magnetic properties Br and Hcj.

[0197] (3)Measurement of main phase grain volume fraction

[0198] The main phase grain volume fractions of the NdFeB matrix (before diffusion) and the NdFeB magnet materials (after diffusion) in the examples and comparative examples were measured. After grinding the samples into samples, X-ray spectroscopy analysis was performed to obtain diffraction peak data; image J was used to compare the main phase grains, and the main phase grain volume fraction in the samples was analyzed and processed. The test results are shown in Table 6.

[0199] Table 6

[0200]

[0201] As can be seen from Table 6, the main phase grain volume fraction in the NdFeB magnet materials prepared in the examples of the present invention is higher. In addition, the change in the main phase grain volume fraction of the materials before and after diffusion is not significant.

[0202] Effect Example 2

[0203] The NdFeB substrates (before diffusion) and NdFeB magnet materials (after diffusion) prepared in Examples 1-2 and Comparative Examples 1-2 were respectively processed into standard sample columns of ø10*10 mm, and magnetic properties were tested using NIM62000 in an environment with a constant temperature of 20°C. The test data are shown in Table 7.

[0204] Table 7

[0205]

[0206] In Table 7, "Br" represents the remanence; Hcj represents the intrinsic coercivity; in "Hk / Hcj", Hk represents the knee-point coercivity, Hcj represents the intrinsic coercivity, and Hk / Hcj is a quantization index of squareness, reflecting the rectangularity of the demagnetization curve. The closer its value is to 100%, the stronger the irreversibility of magnetization reversal of the magnet under the action of a reverse magnetic field, the more stable the magnetic domains are before the knee point (Hk), and the better the demagnetization resistance. As can be seen from Table 7, the remanence Br of the NdFeB magnet material prepared in the examples of the present invention can reach more than 14.9 kGs, the intrinsic coercivity Hcj can reach more than 20 kOe, and Hk / Hcj can reach more than 96%. However, the NdFeB magnet materials prepared in the comparative examples cannot achieve the above effects simultaneously.

[0207] Although the specific embodiments of the present invention have been described above, those skilled in the art should understand that this is only for illustration. The protection scope of the present invention is defined by the appended claims. Without departing from the principles and essence of the present invention, those skilled in the art can make various changes or modifications to these embodiments, but these changes and modifications all fall within the protection scope of the present invention.

Claims

1. A preparation method of a neodymium iron boron magnet material, characterized in that, It includes the following steps: Successively subject the raw material composition to smelting, casting, powder making, pressing, sintering, and grain boundary diffusion; wherein, the raw material composition includes components with the following contents: R: 25.0 - 30.0 mass.%, wherein R is a rare earth element, and R includes PrNd and Nd; the contents of PrNd and Nd satisfy: 0.03 ≤ PrNd / (PrNd + Nd) ≤ 0.84; M: 0 - 3.0 mass.%, wherein the content of M is not 0, and M includes Al, Cu, Ga, and X; the contents of Al, Cu, and Ga satisfy: 0 mass.% < Al + Cu + Ga ≤ 0.46 mass.%, and Al < Cu ≤ Ga; X includes one or more of Ti, Zr, Nb, W, and Mo; B: 0.87 - 1.02 mass.%; and the balance of Fe and inevitable impurities; mass.% represents the mass percentage of the total mass of the raw material composition.

2. The preparation method of the neodymium iron boron magnet material according to claim 1, characterized in that, The raw material composition satisfies one or more of the following conditions (1) - (6): (1) The contents of PrNd and Nd satisfy: 0.05 ≤ PrNd / (PrNd + Nd) ≤ 0.20; (2) The mass ratio of Pr to Nd in PrNd is (10 - 25):(75 - 90); (3) The content of R is 28.0 - 29.5 mass.%; (4) The content of Nd is 24.0 - 27.0 mass.%; (5) The content of PrNd is 2.0 - 5.0 mass.%; (6) R further includes one or more of Dy, Tb, Pr, Y, and Ho.

3. The preparation method of the neodymium iron boron magnet material according to claim 1, characterized in that, The raw material composition satisfies one or more of the following conditions (1) - (8): (1) The content of M is 1.0 - 2.0 mass.%; (2) M further includes Co, and the content of Co is 0.1 - 0.8 mass.%; (3) The contents of Al, Cu, and Ga satisfy: 0.35 mass.% ≤ Al + Cu + Ga ≤ 0.40 mass.%; (4) The content of Al is 0 - 0.05 mass.%; (5) The content of Cu is 0.1 - 0.2 mass.%; (6) The content of Ga is 0.1 - 0.2 mass.%; (7) The content of X is 0.1 - 0.3 mass.%; (8) X includes Ti and Zr; wherein the content of Ti is 0.05 - 0.1 mass.%; the content of Zr is 0.15 - 0.2 mass.%.

4. The preparation method of the neodymium-iron-boron magnet material according to claim 1, characterized in that, The raw material composition includes components with the following contents: PrNd: 2.0 - 4.5 mass.%; Nd: 20.5 - 28.0 mass.%; Al: 0.01 - 0.03 mass.%; Cu: 0.1 - 0.2 mass.%; Ga: 0.1 - 0.2 mass.%; Co: 0.5 - 1.0 mass.%; Ti: 0.05 - 0.1 mass.%; Zr: 0.15 - 0.2 mass.%; B: 0.96 - 1.0 mass.%; Fe: 68.0 - 70.0 mass.%.

5. The preparation method of the neodymium iron boron magnet material according to claim 1, characterized in that, The preparation method further includes: subjecting the as-cast rapid solidification sheet to gas atomization treatment with PrNd; wherein the operation of the gas atomization treatment includes: performing physical vapor deposition on the rapid solidification sheet with PrNd; the temperature of the physical vapor deposition is 600 - 800 °C, and the time of the physical vapor deposition is 4 - 20 h; wherein after the gas atomization treatment, the weight gain of PrNd on the rapid solidification sheet is 0.5% - 1.0%.

6. The preparation method of the neodymium iron boron magnet material according to claim 1, characterized in that, The powder making includes hydrogen decrepitation and jet milling performed in sequence; and / or, the sintering uses a combined box body of a high-density graphite box and a molybdenum box; and / or, two-stage aging treatment is further included after the sintering.

7. The preparation method of the neodymium iron boron magnet material according to claim 1, characterized in that, The grain boundary diffusion is carried out by a segmented heat treatment process, including: The first stage: the holding temperature is 880 - 950 °C, and the time is 5 - 36 h; The second stage: the holding temperature is 450 - 550 °C, and the time is 3 - 10 h; And / or, during the grain boundary diffusion process, the vacuum degree is controlled to be 10 -1 -10 -4 Pa; and / or, the diffusion source of the grain boundary diffusion includes heavy rare earth element RH, and the RH includes Dy and / or Tb.

8. A neodymium iron boron magnet material, characterized in that, It is prepared by using the preparation method of the neodymium iron boron magnet material according to any one of claims 1 - 7.

9. The neodymium iron boron magnet material according to claim 8, characterized in that, The volume fraction of the main phase grains in the neodymium iron boron magnet material is more than 95.5%; and / or, the carbon content in the neodymium iron boron magnet material is ≤600 ppm, the oxygen content is ≤400 ppm, and the nitrogen content is ≤200 ppm.

10. Application of a neodymium iron boron magnet material according to claim 8 or 9 as a magnetic device.

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