Neodymium iron boron magnet material and its preparation method and application

Abstract

The present invention provides a neodymium iron boron magnet material, a preparation method thereof, and an application thereof. The preparation method of the neodymium iron boron magnet material comprises the following steps: sequentially subjecting a raw material composition to smelting, casting, pulverizing, pressing, sintering, and grain boundary diffusion; wherein the raw material composition comprises the following components: R: 25.0-30.0 mass%, wherein R is a rare earth element and includes PrNd and Nd; the PrNd and Nd contents satisfy the following conditions: 0.03 ≤ PrNd / (PrNd + Nd) ≤ 0.84; M: 0-3.0 mass%, wherein the M content is not 0 and includes Al, Cu, Ga, and X; the Al, Cu, and Ga contents satisfy the following conditions: 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 remainder is Fe and unavoidable impurities. The NdFeB magnet material of the present invention has excellent magnetic properties and can have both ultra-high remanence and high coercive force.

Description

Technical Field

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

[0002] Sintered NdFeB permanent magnets are widely used due to their ultra-high energy density, earning them the nickname "King of Magnets." Their high magnetic energy density, excellent temperature resistance, and excellent cost-effectiveness have led to their widespread application in my country's pillar industries and emerging sectors, such as rail transit, military equipment, wind power generation, low-altitude flight, artificial intelligence, aerospace, medical devices, and precision manufacturing. With the trend toward miniaturization, lightweighting, efficiency, and intelligent devices across various fields, the performance requirements of rare earth permanent magnets are increasing. The development of ultra-high-performance magnets has become a key focus of industry development, and the development of dual-high remanence and high coercivity magnets has become an increasingly popular topic. However, few dual-high magnets have been certified by authoritative organizations and publicly reported. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the defect of existing magnetic materials that cannot achieve both ultra-high remanence and high coercivity, and to provide a neodymium iron boron magnet material, its preparation method, and application. The neodymium iron boron magnet material described in the present invention has excellent magnetic properties and can achieve both ultra-high remanence and high coercivity.

[0004] In order to achieve the above objectives, the present invention adopts the following technical solutions.

[0005] In a first aspect, the present invention provides a method for preparing a NdFeB magnet material, comprising the following steps: subjecting a raw material composition to sequential melting, casting, pulverizing, pressing, sintering, and grain boundary diffusion; wherein the raw material composition comprises the following components:

[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 the following: 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 the following conditions: 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: 0.87-1.02mass.%;

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

[0010] Mass.% represents the mass percentage of 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 the Pr element to the Nd element in the PrNd may be (10-25):(75-90), for example, 10:90, 20:80, or 25:75.

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

[0013] In some embodiments of the present invention, in the raw material composition, the contents of PrNd and Nd satisfy the following relationship: 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, the content of Nd in the raw material composition is 24.0-27.0 mass%.

[0016] In some embodiments of the present invention, the content of PrNd in the raw material composition is 2.0-5.0 mass%., for example, 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%., for example, 28.3 mass%. or 29.4 mass%.

[0019] In some embodiments of the present invention, the R further comprises 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%., for example, 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 Al content, the Cu content, and the Ga content.

[0023] In some embodiments of the present invention, the contents of Al, Cu and Ga satisfy the following: 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 Al content 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 Cu content is 0.1-0.2 mass%. For example, 0.15 mass%. or 0.16 mass%.

[0026] In some embodiments of the present invention, the Ga content 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 comprises Ti and / or Zr.

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

[0030] In some embodiments of the present invention, X comprises Zr; wherein the content of Zr is preferably 0.15-0.2 mass%., such as 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.%; and 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.%; and the content of Zr is 0.19 mass.%.

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

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

[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 includes the following components:

[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 includes the following components:

[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 smelting and the casting can be performed in a conventional manner in the art and can be performed in a continuous furnace.

[0068] In some embodiments of the present invention, the smelting temperature is 1400-1500°C, for example 1445°C or 1451°C.

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

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

[0071] In some specific embodiments of the present invention, after the casting is completed, the temperature is cooled to 40-60°C, for example, 45°C.

[0072] In some embodiments of the present invention, the thickness of the quick-setting sheet obtained by casting is 0.20-0.30 mm, for example, 0.26 mm or 0.27 mm.

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

[0074] In some embodiments of the present invention, the preparation method further includes atomizing the casted rapid-setting sheet using PrNd. The atomization treatment can fill and repair the rare earth elements at the grain boundaries of the rapid-setting sheet to a certain extent, resulting in a main phase with an ultra-high main phase volume fraction and a relatively continuous grain boundary phase structure in the rapid-setting sheet. This significantly reduces the risk of powder oxidation during subsequent pulverization and prevents subsequent densification failures during sintering.

[0075] Preferably, the atomization treatment operation includes: performing physical vapor deposition on the quick-setting sheet using 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] Preferably, after the atomization treatment, the PrNd weight gain of the quick-setting sheet is 0.5%-1.0%, for example 0.75%. The PrNd weight gain refers to the percentage of the mass increase of PrNd in the quick-setting sheet after the atomization treatment to the mass of the quick-setting sheet before the atomization treatment.

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

[0078] In some embodiments of the present invention, the pulverizing comprises hydrogen crushing and jet milling performed sequentially.

[0079] In the present invention, the hydrogen cracking can be performed using a continuous hydrogen cracking furnace.

[0080] In some embodiments of the present invention, the reaction pressure of the hydrogen cracking is 0.08-0.1 MPa, for example, 0.098 MPa.

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

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

[0083] Preferably, the powder additive is added in an amount of 1.7 g per kg of coarse powder.

[0084] In the present invention, the air flow mill can be carried out using a multi-nozzle collision fluidized bed air flow mill.

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

[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, for example, 2.2 μm.

[0087] In some embodiments of the present invention, powder additives are added to the fine powder obtained by jet milling.

[0088] Preferably, the powder additive is added in an amount of 0.8 g per kg of coarse powder.

[0089] In some embodiments of the present invention, the powder additive is added via an online dosing system.

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

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

[0092] In some embodiments of the present invention, the pressing is performed using an all-electric floating press and a combined mold.

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

[0094] Among them, preferably, the process parameters of the orientation pressing include: pressing orientation direction dimension 55mm, pressing blank gram weight 780g, mold forming position minimum orientation field >1.95T, and the oxygen content throughout the pressing process is less than 50ppm.

[0095] In some embodiments of the present invention, the orientation pressing further includes pre-pressing.

[0096] Preferably, the pre-pressing is a two-stage pre-pressing, including:

[0097] The first section: pre-pressed density is 2.2g / cm 3 , suppressing current 20A;

[0098] Second stage: pre-pressed density 3.0 g / cm 3, suppressing current 100A.

[0099] Preferably, the orientation pressing satisfies: pressing density 4.0 g / cm 3 , suppressing current 210A.

[0100] Preferably, the holding time of the orientation pressing is 1-3s, for example, 2s.

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

[0102] Preferably, the isostatic pressing pressure is 200 MPa.

[0103] In the present invention, the sintering can be performed using conventional methods 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 combination box of a high-density graphite box and a molybdenum box.

[0105] In some embodiments of the present invention, the sintering is performed in a gradient temperature increase manner.

[0106] In some embodiments of the present invention, the sintering process includes: keeping warm 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] Preferably, the holding time at 1000-1200°C is 4-15h.

[0108] In some specific embodiments of the present invention, the sintering process includes: keeping warm at 250℃, 420℃, 580℃, 640℃, 760℃, 830℃ and 1085℃, with the keeping time being 1.5h, 2.5h, 1.5h, 2.5h, 2h, 3h and 9h respectively.

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

[0110] In some embodiments of the present invention, the sintering step further includes an aging treatment, wherein preferably, the aging treatment is a two-stage aging treatment.

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

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

[0113] In the present invention, the grain boundary diffusion can be performed using conventional methods in the art.

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

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

[0116] In some embodiments of the present invention, the grain boundary diffusion is performed using a staged heat treatment process.

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

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

[0119] The second stage: the insulation temperature is 450-550℃ and the time is 3-10h.

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

[0121] The first stage: keep the temperature at 900℃, 908℃, 916℃ and 905℃ for 4h, 4h, 3h and 5h respectively; after the temperature is kept at 900℃, 908℃, 916℃ and 905℃ respectively; cool the temperature to below 70℃ with argon air;

[0122] The second stage: heat to 505℃ and keep warm for 5h.

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

[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 of the heavy rare earth element RH in the diffusion source accounts for 0.1-0.8 mass %, for example, 0.5 mass %, of the NdFeB matrix.

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

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

[0128] In a second aspect, the present invention provides a NdFeB magnet material, which is prepared using the method for preparing the NdFeB magnet material as described above.

[0129] In the present invention, the volume fraction of the main phase grains in the NdFeB magnet material may be greater than 95.5%, for example, 96.24% or 97.53%.

[0130] In some embodiments of the present invention, the carbon content in the NdFeB 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 a use of the aforementioned NdFeB magnet material as a magnetic device.

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

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

[0134] In the present invention, unless otherwise specified, an element appearing alone means a simple substance of the element.

[0135] On the basis of conforming to the common sense in this field, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

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

[0137] The positive progress effect of the present invention is:

[0138] This invention achieves a breakthrough in the performance of NdFeB magnet materials through a unique formula design. This rare earth element (RE) blend includes a PrNd alloy and Nd in specific ratios, along with controlled amounts of elements such as Al, Cu, and Ga. This NdFeB magnet material boasts a primary phase grain volume fraction exceeding 95.5%, significantly reduced levels of carbon, oxygen, and nitrogen as impurities (carbon ≤ 600 ppm, oxygen ≤ 400 ppm, and nitrogen ≤ 200 ppm). The material exhibits excellent magnetic properties, combining ultra-high remanence with high coercivity. Specifically, the remanence can reach over 14.9 kGs, the coercivity over 20 kOe, and an Hk / Hcj ratio exceeding 96%. DETAILED DESCRIPTION

[0139] The present invention is further illustrated by way of examples below, but the present invention is not limited to the scope of the examples. Experimental methods in the following examples where specific conditions are not specified were performed according to conventional methods and conditions, or selected according to the product specifications.

[0140] Example 1

[0141] (1) Melting and casting:

[0142] According to Table 1, the raw materials were weighed and mixed, smelted in a continuous furnace at 1451°C, and cast on a copper roller (copper roller speed 28 r / min, supercooling 170°C, casting flow 140.3 cm 3 / s), cooled to 45℃ and removed from the furnace to obtain a quick-setting sheet. The thickness and columnar crystal width of the quick-setting sheet are shown in Table 2. The quick-setting sheet was placed in a sealed stainless steel barrel, fully deoxygenated with argon gas, and then sealed for later use.

[0143] The quick-setting sheet produced in the above steps was subjected to a gas atomization treatment. The gas atomization treatment involved physical vapor deposition of a PrNd alloy (Pr:Nd in a ratio of 20:80) at 690°C for 8 hours, resulting in a PrNd weight gain of 0.75%. The PrNd weight gain refers to the percentage of PrNd mass increase in the quick-setting sheet after gas atomization treatment compared to the mass of the quick-setting sheet before gas atomization treatment. Gas atomization can fill and repair the grain boundaries of the quick-setting sheet to a certain extent.

[0144] (2) Flour making:

[0145] The quick-setting sheet obtained in step (1) is subjected to hydrogen cracking treatment in a continuous hydrogen cracking furnace, with a reaction pressure of 0.098 MPa and a dehydrogenation treatment at 570°C. The sheet is cooled to below 40°C and then taken out of the furnace in a fully sealed manner to obtain a coarse powder. The coarse powder is loaded into a coarse powder tank that has been fully deoxygenated to below 50 pm in advance, and is filled with argon to maintain the pressure.

[0146] Powder additives were added to the obtained coarse powder. The powder additives consisted 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 in a mass ratio of 1:1:1.8. The addition ratio was 1.7 g of powder additive per kg of coarse powder, and the mixed powder was stirred for 120 minutes.

[0147] A multi-nozzle, opposed-type fluidized bed jet mill was used for grinding. First, the bottom material in the mill was completely blown out to prevent any impurities from entering. Argon was then used to fully deoxygenate the mill to below 2 ppm before the coarse powder was loaded. The mill was then started, with key parameters set to maintain a cleaning pressure of 70 kPa for the separation wheel gap, a separation wheel speed of 3490 r / min, a mill chamber mass of 58 kg, a grinding pressure of 0.57 MPa, and a side spray pressure of 25 kPa. A highly spherical fine powder with an average particle size (SMD) of approximately 2.2 μm was produced. The main phase of the fine powder produced by this process exhibited a high degree of rare earth-rich coating.

[0148] During the grinding process, an online dosing system is used to add powder additives (with the same composition as the aforementioned powder additives) to the fine powder receiving tank at a ratio of 0.8 g of powder additive per kg of fine powder, and the powders are mixed and stirred for 120 minutes.

[0149] The fine powder after air jet milling is screened, and the oxygen content during the whole screening process is less than 50ppm.

[0150] (3) Pressing: A fully electric floating press and a combined mold are used to orient the fine powder. The pressing orientation dimension is 55mm, the pressed blank weight is 780g, the minimum orientation field of the mold forming position is greater than 1.95T, and the oxygen content during the entire pressing process is less than 50ppm. The pressing process adopts a two-stage pre-pressing and pre-orientation process design, with the pre-pressing density of 2.2g / cm 3 , pressing current 20A, and pre-pressing density 3.0 g / cm 3 , pressing current 100A; then start pressing, pressing density 4.0 g / cm 3 , pressing current 210A, and appropriately extending the holding pressure orientation time (holding pressure orientation time is 2s) to obtain a higher orientation degree.

[0151] The obtained compact was isostatically pressed at a pressure of 200 MPa.

[0152] (4) Sintering: Use a high-density graphite box and a molybdenum box to combine the box body for sintering. 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 at a heating rate of about 1.5°C / min, and heat-treat at 250°C, 420°C, 580°C, 640°C, 760°C, 830°C and 1085°C, respectively. The heat-treating time is 1.5h, 2.5h, 1.5h, 2.5h, 2h, 3h, and 9h, respectively. After sintering, perform two-stage aging treatment in a vacuum state (905°C, heat-treating for 3h, 505°C, heat-treating for 5h) to obtain the NdFeB matrix.

[0153] (5) Grain boundary diffusion:

[0154] The NdFeB substrate was processed into a 30*12*3.5mm sample and surface activated by degreasing and ultrasonic cleaning. A diffusion film was then attached to the NdFeB substrate using screen printing. The diffusion film had a composition of (Tb-Co-Fe-Cu-PrNd)H (where the mass ratio of Tb, Co, Fe, Cu, and PrNd was 76:4:4:8:8), with Tb accounting for 0.5 mass% of the NdFeB substrate.

[0155] Diffusion is carried out using a staged heat treatment process, specifically:

[0156] The first stage: keep the temperature at 900℃, 908℃, 916℃ and 905℃ for 4h, 4h, 3h and 5h respectively; after the temperature is kept at 900℃, 908℃, 916℃ and 905℃ respectively; cool the temperature to below 70℃ with argon air;

[0157] The second stage: the temperature was raised to 505°C, kept at this temperature for 5 hours, and cooled to below 60°C using nitrogen gas before being taken out of the furnace to obtain the NdFeB magnet material. The contents of the components in the obtained NdFeB magnet material are shown in Table 3.

[0158] Example 2

[0159] The raw material components were weighed and mixed according to Table 1, and smelted in a continuous furnace at 1445° C. The remaining steps were the same as in Example 1.

[0160] Comparative Example 1

[0161] (1) Melting and casting:

[0162] According to Table 1, the raw materials were weighed and mixed, smelted in a continuous furnace at 1440°C, and cast on a copper roller (copper roller speed 28r / min, supercooling 170°C, casting flow 140.3cm 3 / s), cooled to 45℃ and removed from the furnace to obtain a quick-setting sheet. The thickness and columnar crystal width of the quick-setting sheet are shown in Table 2. The quick-setting sheet was placed in a sealed stainless steel barrel, fully deoxygenated with argon gas, and then sealed for later use.

[0163] The quick-setting sheet produced in the above steps was subjected to a gas atomization treatment. The gas atomization treatment involved physical vapor deposition of PrNd at 690°C for 8 hours, resulting in a PrNd weight gain of 0.75%. The PrNd weight gain refers to the percentage of PrNd mass increase in the quick-setting sheet after atomization treatment compared to the mass of the quick-setting sheet before atomization treatment. The gas atomization treatment can fill and repair the grain boundaries of the quick-setting sheet to a certain extent.

[0164] (2) Flour making:

[0165] The quick-setting sheet obtained in step (1) is subjected to hydrogen cracking treatment in a continuous hydrogen cracking furnace, with a reaction pressure of 0.098 MPa and a dehydrogenation treatment at 570°C. The sheet is cooled to below 40°C and then taken out of the furnace in a fully sealed manner to obtain a coarse powder. The coarse powder is loaded into a coarse powder tank that has been fully deoxygenated to below 50 pm in advance, and is filled with argon to maintain the pressure.

[0166] A conventional powder additive (Tianjin Ji Yuesheng Ji YSH-01) was added to the obtained coarse powder at a ratio of 1.5 g of powder additive per kg of coarse powder, and the powder was mixed and stirred for 120 minutes.

[0167] A multi-nozzle, opposed-type fluidized bed jet mill was used for grinding. First, the bottom material in the mill was completely blown out to prevent any impurities from entering. Nitrogen was then used to fully deoxygenate the mill to below 2 ppm before the coarse powder was added. The mill was started, with the main parameters set to a separation wheel clearance maintenance disc cleaning pressure of 70 kPa, a separation wheel speed of 3490 r / min, a mill chamber mass of 58 kg, a grinding pressure of 0.57 MPa, and a side spray pressure of 25 kPa. A highly spherical fine powder with an average particle size (SMD) of approximately 3.0 μm was produced.

[0168] During the grinding process, an online dosing system is used to add powder additives (with the same composition as the aforementioned powder additives) to the fine powder receiving tank at a ratio of 0.5 g of powder additive per kg of fine powder. After jet milling, the fine powder is stirred for 120 min.

[0169] (3) Pressing: semi-automatic pressing is adopted, the minimum orientation field of the mold forming position is greater than 1.6T, and the oxygen content during the entire pressing process is less than 300ppm;

[0170] The obtained compact was isostatically pressed at a pressure of 200 MPa.

[0171] (4) Sintering: Graphite box sintering is used. Before use, it needs to be baked or dried at a temperature above 250°C. The pressed material is placed in a box and vacuumed. The temperature is raised at a rate of about 1.5°C / min and maintained at 1095°C for 6 hours. After sintering, two-stage aging treatment is performed in a vacuum state (900°C for 3 hours and 500°C for 5 hours). The NdFeB matrix is obtained.

[0172] (5) Grain boundary diffusion:

[0173] The NdFeB substrate was processed into a 30*12*3.5mm sample, and the surface was activated by degreasing and ultrasonic cleaning. A diffusion film layer of TbH was attached to the magnet surface using a screen printing process. The mass of Tb accounted for 0.5% of the mass of the NdFeB substrate.

[0174] Diffusion is carried out using a staged heat treatment process, specifically:

[0175] The first stage: keep at 905℃ for 16h; after the end of the heat preservation, cool to below 70℃ with argon air;

[0176] The second stage: heating to 505°C, keeping the temperature for 5 hours, cooling to below 60°C with nitrogen, and taking out of the furnace to obtain NdFeB magnet material.

[0177] Comparative Example 2

[0178] The raw material components were weighed and mixed according to Table 1, and smelted in a continuous furnace at 1450° C. The remaining steps were the same as those in Comparative Example 1.

[0179] Table 1 Content of each component in the raw material composition of NdFeB matrix (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 columnar crystal width of the rapid-setting sheet was tested as follows: After the rapid-setting sheet was mounted and polished, microscopic images were taken using a scanning electron microscope (SEM). The columnar crystal width was analyzed and calculated using the streak method using ImageJ software. As shown in Table 2, the rapid-setting sheet in the embodiment of the present invention had a smaller thickness and smaller columnar crystal width.

[0185] Effect Example 1: Material Composition Determination

[0186] (1) Compositions of NdFeB magnet material (after diffusion) and NdFeB matrix (before diffusion)

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

[0188] Table 3 Content of each component in NdFeB matrix (unit: mass%)

[0189]

[0190] Table 4 Content of each component of NdFeB magnet material (unit: mass%)

[0191]

[0192] (2) Impurity element content test

[0193] The NdFeB magnet materials (after diffusion) prepared in the Examples and Comparative Examples were crushed into small particles, and carbon and oxygen and nitrogen were tested and analyzed using a carbon-sulfur analyzer CS-3000 (Steel Research Institute Nanotechnology) and an oxygen-nitrogen-hydrogen analyzer ONH836 (Shanghai Yuzhong Industrial Co., Ltd.). 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 material prepared in the embodiment 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) Main phase grain volume fraction test

[0198] The volume fraction of the primary phase grains in the NdFeB matrix (before diffusion) and NdFeB magnet materials (after diffusion) used in the Examples and Comparative Examples was measured. The samples were ground and prepared, and X-ray spectroscopy was performed to obtain diffraction peak data. Image J was used to compare the primary phase grains and analyze the volume fraction of the primary phase grains in the samples. The test results are shown in Table 6.

[0199] Table 6

[0200]

[0201] As can be seen from Table 6, the volume fraction of the main phase grains in the NdFeB magnet material prepared in the embodiment of the present invention is higher. In addition, the volume fraction of the main phase grains in the material before and after diffusion does not change much.

[0202] Effect Example 2

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

[0204] Table 7

[0205]

[0206] In Table 7, "Br" represents remanence; Hcj represents intrinsic coercivity; and "Hk / Hcj" represents knee coercivity, Hcj represents intrinsic coercivity, and Hk / Hcj is a quantitative indicator of squareness, reflecting the rectangularity of the demagnetization curve. The closer the value is to 100%, the stronger the irreversibility of magnetization reversal under a reverse magnetic field, the more stable the magnetic domains remain before the knee point (Hk), and the better the demagnetization resistance. As shown in Table 7, the NdFeB magnet material produced in the embodiment of the present invention can achieve a remanence Br of over 14.9 kGs, an intrinsic coercivity Hcj of over 20 kOe, and an Hk / Hcj ratio of over 96%. However, the NdFeB magnet material produced in the comparative example cannot achieve these results simultaneously.

[0207] Although specific embodiments of the present invention have been described above, those skilled in the art will appreciate that these are merely illustrative and that the scope of the present invention is defined by the appended claims. Those skilled in the art may make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, and such changes and modifications are intended to fall within the scope of the present invention.

Claims

1. A method for preparing a neodymium iron boron magnet material, characterized in that: It includes the following steps: The raw material composition is sequentially subjected to smelting, casting, powdering, pressing, sintering and grain boundary diffusion; wherein the raw material composition includes the following components: 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 the following: 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 the following conditions: 0 mass%.<Al+Cu+Ga≤0.46 mass%., and Al<Cu≤Ga; X includes one or more of Ti, Zr, Nb, W, and Mo; And the balance of Fe and inevitable impurities; PrNd: 2.0-4.5 mass%. Nd: 20.5-28.0mass.%; 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: 0.96-1.0mass.%; Fe: 68.0-70.0 mass.%; Mass.% represents the mass percentage of the total mass of the raw material composition.

2. The method for preparing a NdFeB magnet material according to claim 1, wherein: The raw material composition satisfies one or more of the following conditions (1)-(6): (1) The contents of PrNd and Nd satisfy the following conditions: 0.05≤PrNd / (PrNd+Nd)≤0.20; (2) The mass ratio of Pr to Nd in the PrNd is (10-25):(75-90); (3) The content of R is 28.0-29.5 mass%. (4) The Nd content is 24.0-27.0 mass%. (5) The PrNd content is 2.0-4.3 mass%. (6) The R further comprises one or more of Dy, Tb, Pr, Y and Ho.

3. The method for preparing a NdFeB magnet material according to claim 1, wherein: The raw material composition satisfies one or more of the following conditions (1)-(5): (1) The content of M is 1.0-2.0 mass%. (2) The M further comprises Co, wherein the content of the Co is 0.5-0.8 mass%. (3) The contents of Al, Cu and Ga satisfy the following: 0.35 mass% ≤ Al + Cu + Ga ≤ 0.40 mass%. (4) The Cu content is 0.1-0.16 mass%. (5) The content of X is 0.1-0.3 mass%.

4. The method for preparing a NdFeB magnet material according to claim 1, wherein: The preparation method further comprises: performing aerosol treatment on the quick-setting sheet obtained by casting using PrNd; The atomization treatment includes: performing physical vapor deposition on the quick-setting sheet using PrNd; the physical vapor deposition temperature is 600-800° C., and the physical vapor deposition time is 4-20 hours; Wherein, after the aerosolization treatment, the PrNd weight increase of the quick-setting sheet is 0.5%-1.0%.

5. The method for preparing a NdFeB magnet material according to claim 1, wherein: The powder making comprises hydrogen crushing and air flow milling carried out in sequence; And / or, the sintering adopts a high-density graphite box and a molybdenum box combination box; And / or, the sintering further includes a two-stage aging treatment.

6. The method for preparing a NdFeB magnet material according to claim 1, wherein: The grain boundary diffusion is carried out by a staged heat treatment process, including: The first stage: the holding temperature is 880-950℃, and the holding time is 5-36h; The second stage: the holding temperature is 450-550℃, and the holding time is 3-10h; And / or, the vacuum degree during the grain boundary diffusion process is controlled to be 10 -1 -10 -4 Pa; And / or, the diffusion source of the grain boundary diffusion includes a heavy rare earth element RH, and the RH includes Dy and / or Tb.

7. A neodymium iron boron magnet material, characterized in that: The NdFeB magnet is prepared by the method for preparing the NdFeB magnet material according to any one of claims 1 to 6.

8. The NdFeB magnet material according to claim 7, characterized in that: The volume fraction of the main phase grains in the NdFeB magnet material is greater than 95.5%; And / or, the carbon content in the NdFeB magnet material is ≤600ppm, the oxygen content is ≤400ppm, and the nitrogen content is ≤200ppm.

9. Use of the NdFeB magnet material according to claim 7 or 8 as a magnetic device.

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