Neodymium-iron-boron magnetic powder additive, application thereof and preparation method of neodymium-iron-boron magnet

Abstract

The invention discloses a neodymium-iron-boron magnetic powder auxiliary agent and application thereof and a preparation method of a neodymium-iron-boron magnet. The neodymium iron boron magnetic powder additive comprises a component A and a component B, the component A comprises the following components in parts by weight: 40-85 parts of ethylene bis-erucamide, 20-50 parts of saturated fatty acid containing 8-26 carbon atoms and 0.05-0.5 part of molybdenum disulfide; the component B comprises fatty acid ester and boric acid ester, and the volume ratio of the fatty acid ester to the boric acid ester is 1: (0.5-3). The neodymium-iron-boron magnetic powder additive can effectively improve the magnetic performance of a neodymium-iron-boron magnet.

Description

Technical Field

[0001] The invention relates to a NdFeB magnetic powder additive and application thereof and a method for preparing a NdFeB magnet. Background Art

[0002] NdFeB magnets can be used as core materials for new energy vehicle drive motors and robot servo systems, which places higher demands on the performance of NdFeB magnets. The particle size, distribution and fluidity of NdFeB powders directly determine the performance of the magnets. Traditional commercial modifiers are difficult to meet the needs of anti-oxidation treatment and fluidity improvement of ultrafine magnetic powders and high-abundance magnetic powders, and they have defects such as volatility, strong odor, and poor coating effect, which limits the further improvement of magnet performance. The residual carbon formed by high-temperature carbonization of the modifier interacts with the neodymium-rich phase at the grain boundary, which may deteriorate the performance of the magnet.

[0003] CN118538496A discloses a method for preparing a sintered NdFeB-containing cerium magnet. The raw materials are stacked in sequence in a vacuum belt-spinning furnace, smelted, cast, and cooled in an argon atmosphere to obtain spinning sheets; the spinning sheets are subjected to hydrogen absorption and dehydrogenation in sequence to obtain coarse powder; antioxidants and lubricants are added to the coarse powder, and the powder is mixed and ground using an airflow mill to obtain fine powder; antioxidants, lubricants, and compression molding aids are added to the fine powder, and the mixture is uniformly mixed to obtain magnetic powder. The magnetic powder is vertically pressed, and the pressed magnetic blank is sintered in a vacuum sintering furnace. The antioxidant is at least one of 1-hexadecanol, triphenylmethanol, and calcium stearate. The lubricant is at least one of polyethylene glycol and 120# gasoline. The compression molding aid is at least one of glycerol and ethylene glycol.

[0004] CN11724962A discloses a processing process for NdFeB magnets, wherein NdFeB material is treated in a hydrogen crushing treatment furnace to obtain NdFeB particles; NdFeB coarse powder and a first antioxidant are added to a planetary ball mill, and then anhydrous ethanol is added for ball milling, and then dried after the ball milling to obtain NdFeB coarse powder; the first antioxidant is added to the NdFeB coarse powder, and after mixing, the powder is placed in a gas flow mill for treatment, and after the crushing, the powder is dried to obtain NdFeB fine powder; the second antioxidant is added to acetone and mixed evenly as a spray solvent, and the NdFeB fine powder is placed in a spray evaporator for treatment to obtain NdFeB post-processed product. The NdFeB post-processed product is pressed according to the prefabricated shape to obtain a NdFeB magnet blank. The NdFeB magnet blank is heat treated to obtain a NdFeB magnet. The first antioxidant is a black ester of iron oxide. The second antioxidant is prepared by loading kaempferol derivatives on tantalum pentoxide microspheres.

[0005] The additives added in the above preparation method have limited effect on improving the magnetic properties of NdFeB magnets. Summary of the invention

[0006] One object of the present invention is to provide a NdFeB magnetic powder additive, which can effectively improve the magnetic properties of NdFeB magnets. Another object of the present invention is to provide a use of the NdFeB magnetic powder additive. Another object of the present invention is to provide a method for preparing NdFeB magnets, which can improve the magnetic properties of NdFeB magnets.

[0007] The above object is achieved through the following scheme.

[0008] In one aspect, the present invention provides a NdFeB magnetic powder additive, comprising component A and component B;

[0009] The component A comprises 40 to 85 parts by weight of ethylenebiserucamide, 20 to 50 parts by weight of a saturated fatty acid containing 8 to 26 carbon atoms and 0.05 to 0.5 parts by weight of molybdenum disulfide;

[0010] The component B comprises a fatty acid ester and a boric acid ester represented by formula (I), wherein the volume ratio of the fatty acid ester to the boric acid ester is 1:(0.5-3);

[0011]

[0012] Among them, R 1 ~R 3 Each independently selected from a C1 to C6 alkyl group;

[0013] The fatty acid ester is obtained by polycondensation of an aliphatic monobasic acid containing 8 to 20 carbon atoms and an aliphatic monohydric alcohol containing 1 to 10 carbon atoms.

[0014] According to the NdFeB magnetic powder additive of the present invention, preferably, the saturated fatty acid is selected from one or more of caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid and eicosanoic acid.

[0015] According to the NdFeB magnetic powder additive of the present invention, preferably, the fatty acid ester is obtained by polycondensation of an aliphatic monobasic acid containing 12 to 18 carbon atoms and an aliphatic saturated monohydric alcohol containing 1 to 8 carbon atoms;

[0016] In formula (I), R 1 ~R 3 Each is independently selected from a C2 to C4 alkyl group.

[0017] According to the NdFeB magnetic powder additive of the present invention, preferably, the fatty acid ester is selected from one or more of ethyl oleate, isooctyl oleate, methyl palmitate, methyl laurate, methyl myristate, and methyl stearate;

[0018] The borate ester is selected from one or more of triisopropyl borate, tributyl borate and triethyl borate.

[0019] On the other hand, the present invention provides a use of a NdFeB magnetic powder additive in improving the magnetic properties of NdFeB magnets.

[0020] In another aspect, the present invention provides a method for preparing a neodymium iron boron magnet, comprising the following steps:

[0021] (1) mixing the NdFeB coarse powder and the component A in the NdFeB magnetic powder additive and then jet milling the mixture to obtain NdFeB fine powder;

[0022] (2) mixing the NdFeB fine powder with the component B in the NdFeB magnetic powder additive to obtain modified NdFeB magnetic powder;

[0023] (3) orienting the modified NdFeB fine powder in a magnetic field to obtain a NdFeB blank;

[0024] (4) Sintering and aging the NdFeB blank to obtain a NdFeB magnet.

[0025] According to the preparation method of the present invention, preferably, in step (1), the amount of component A is 0.2 to 0.8‰ of the mass of the NdFeB coarse powder;

[0026] In step (2), the amount of component B is 0.2 to 0.95‰ of the mass of the NdFeB fine powder.

[0027] According to the preparation method of the present invention, preferably, the particle size of the NdFeB coarse powder is in the range of 30 to 400 μm, and the average specific surface diameter of the NdFeB fine powder is in the range of 1.5 to 5 μm;

[0028] The NdFeB blank is first-stage sintered at 340-390°C for 40-70 min, second-stage sintered at 430-550°C for 50-80 min, and third-stage sintered at 1000-1200°C for 3-7 h;

[0029] The aging treatment includes primary aging treatment and secondary aging treatment. The primary aging treatment temperature is 750-1000°C, the primary aging treatment time is 0.2-5h, the secondary aging treatment temperature is 400-650°C, and the secondary aging treatment time is 1-7h.

[0030] The nitrogen content in the NdFeB magnet is 225-742 ppm.

[0031] According to the preparation method of the present invention, preferably, the following steps are further included: smelting the raw materials to form alloy sheets; and hydrogen crushing the alloy sheets to obtain NdFeB coarse powder.

[0032] According to the preparation method of the present invention, preferably, the element composition of the NdFeB coarse powder is as follows:

[0033]

[0034]

[0035] The NdFeB magnetic powder additive of the present invention can improve the fluidity of the magnetic powder, facilitate the molding of the magnetic powder, and obtain a high-density compact with a high degree of orientation. The NdFeB magnetic powder additive of the present invention can omit the isostatic pressing process and perform one-step molding, thereby simplifying the preparation process of the NdFeB magnet. The NdFeB magnetic powder additive of the present invention can significantly improve the magnetic properties of the NdFeB magnet. DETAILED DESCRIPTION

[0036] The present invention is further described below in conjunction with specific implementation modes, but the protection scope of the present invention is not limited thereto.

[0037] <NdFeB magnetic powder additives>

[0038] The NdFeB magnetic powder additive of the present invention comprises component A and component B. In certain embodiments, the NdFeB magnetic powder additive consists of component A and component B. Component A and component B are introduced below.

[0039] Component A

[0040] Component A of the present invention comprises ethylenebiserucamide (EBE), a saturated fatty acid containing 8 to 26 carbon atoms and molybdenum disulfide. Preferably, component A consists of ethylenebiserucamide, a saturated fatty acid containing 8 to 26 carbon atoms and molybdenum disulfide.

[0041] The content of ethylenebiserucamide is 40 to 85 parts by weight, preferably 50 to 75 parts by weight, and more preferably 60 to 70 parts by weight.

[0042] Saturated fatty acids contain 8 to 26 carbon atoms; preferably, saturated fatty acids contain 10 to 22 carbon atoms; more preferably, saturated fatty acids contain 12 to 20 carbon atoms. Saturated fatty acids can be straight-chain saturated fatty acids or branched-chain saturated fatty acids. Preferably, saturated fatty acids are straight-chain saturated fatty acids.

[0043] The saturated fatty acid can be selected from one or more of caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and eicosanoic acid. Preferably, the saturated fatty acid is selected from one or more of lauric acid, palmitic acid, myristic acid, palmitic acid, stearic acid, and eicosanoic acid. More preferably, the saturated fatty acid is selected from one or more of lauric acid, palmitic acid, stearic acid, and eicosanoic acid.

[0044] The content of saturated fatty acid is 20 to 50 parts by weight, preferably 25 to 45 parts by weight, and more preferably 30 to 40 parts by weight.

[0045] The content of molybdenum disulfide is 0.05 to 0.5 parts by weight, preferably 0.1 to 0.4 parts by weight, and more preferably 0.2 to 0.3 parts by weight.

[0046] The component A of the present invention is jet-milled together with the NdFeB coarse powder. The component A of the present invention can effectively improve the fluidity and oxidation resistance of the NdFeB powder and improve the particle size distribution of the NdFeB powder.

[0047] Component B

[0048] Component B of the present invention includes fatty acid esters and boric acid esters. In certain embodiments, component B consists of fatty acid esters and boric acid esters.

[0049] Fatty acid esters are obtained by condensation of aliphatic monobasic acids containing 8 to 20 carbon atoms and aliphatic monohydric alcohols containing 1 to 10 carbon atoms.

[0050] The aliphatic monoacid may be a saturated aliphatic monoacid or an unsaturated aliphatic monoacid. The unsaturated aliphatic monoacid may be an olefinic acid. The aliphatic monoacid may be a straight-chain aliphatic monoacid or a branched-chain aliphatic monoacid. Preferably, the straight-chain aliphatic monoacid is used.

[0051] The aliphatic monobasic acid contains 8 to 20 carbon atoms; preferably, contains 10 to 18 carbon atoms; more preferably, contains 12 to 18 carbon atoms.

[0052] Examples of aliphatic monobasic acids include, but are not limited to, lauric acid, myristic acid, palmitic acid, stearic acid, eicosanoic acid, and oleic acid.

[0053] The aliphatic monohydric alcohol may be a saturated aliphatic monohydric alcohol, a straight-chain aliphatic monohydric alcohol, or a straight-chain aliphatic monohydric alcohol.

[0054] The aliphatic monohydric alcohol contains 1 to 10 carbon atoms, preferably 1 to 8 carbon atoms. In certain embodiments, the aliphatic monohydric alcohol contains 1 to 3 carbon atoms.

[0055] Examples of aliphatic monohydric alcohols include, but are not limited to, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, pentanol, isopentanol, neopentyl alcohol, hexanol, 2-methylpentanol, 3-methylpentanol, 2,3-dimethylbutanol, 2,2-dimethylbutanol, octanol, and isooctyl alcohol.

[0056] Preferably, the fatty acid ester is selected from one or more of ethyl oleate, isooctyl oleate, methyl palmitate, methyl laurate, methyl myristate, and methyl stearate. More preferably, the fatty acid ester is selected from one or more of ethyl oleate, isooctyl oleate, methyl palmitate, and methyl laurate.

[0057] The borate ester is shown in formula (I):

[0058]

[0059] In formula (I), R 1 ~R 3 are independently selected from C1 to C6 alkyl groups; preferably, R 1 ~R 3 are independently selected from C1 to C5 alkyl groups; more preferably, R 1 ~R 3 are independently selected from C2 to C4 alkyl groups. 1 ~R 3 are the same group.

[0060] Examples of alkyl groups include, but are not limited to, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, pentyl, isopentyl, neopentyl, hexyl, 2-methylpentyl, 3-methylpentyl, 2,3-dimethylbutyl, 2,2-dimethylbutyl.

[0061] Examples of borate esters include, but are not limited to, tributyl borate, triisopropyl borate, triethyl borate.

[0062] The volume ratio of the fatty acid ester to the boric acid ester may be 1:(0.5-3); preferably 1:(0.8-2); more preferably 1:(1-1.5).

[0063] The component B of the present invention is mixed with the NdFeB fine powder to improve the lubricity and oxidation resistance of the magnetic powder.

[0064] The component A and the component B of the present invention are used in combination to effectively improve the magnetic properties of the NdFeB magnet.

[0065] <Application of NdFeB Magnetic Powder Additives>

[0066] The NdFeB magnetic powder additive of the present invention can effectively improve the magnetic properties of NdFeB magnets. Therefore, the present invention provides the use of the NdFeB magnetic powder additive in improving the magnetic properties of NdFeB magnets. The magnetic properties are preferably one or more of remanence, coercive force, maximum magnetic energy product, and squareness.

[0067] <Method for preparing NdFeB magnet>

[0068] The method for preparing the NdFeB magnet of the present invention comprises the following steps: (1) preparing NdFeB fine powder; (2) preparing modified NdFeB magnetic powder; (3) preparing NdFeB blank; and (4) obtaining the NdFeB magnet. The details are described below.

[0069] Steps for preparing NdFeB fine powder

[0070] The invention mixes the NdFeB coarse powder and the component A in the NdFeB magnetic powder additive and then performs jet milling to obtain the NdFeB fine powder.

[0071] The amount of component A is 0.2-0.8‰ of the mass of the NdFeB coarse powder, preferably 0.3-0.7‰, and more preferably 0.4-0.6‰. The composition of component A in the NdFeB magnetic powder additive is as described above and will not be repeated here.

[0072] The average diameter of the specific surface area of ​​the NdFeB fine powder may be 1.5 to 5 μm, preferably 2 to 4 μm, and more preferably 2.5 to 3.5 μm.

[0073] NdFeB fine powder D 90 / D 10 It may be 3 to 6; preferably 3.5 to 5.5; and more preferably 4 to 6.

[0074] The repose angle of the NdFeB fine powder is ≤50°; preferably, the repose angle is ≤45°.

[0075] The bulk density of NdFeB fine powder can be 1-3g / cm 3 ; preferably 1.5 to 2.5 g / cm 3 More preferably, 1.7 to 2 g / cm 3 .

[0076] The tap density of NdFeB fine powder can be 2-6g / cm 3 ; preferably 3 to 5 g / cm 3 More preferably, 3.5 to 4 g / cm 3 .

[0077] The particle size of the NdFeB coarse powder may range from 30 to 400 μm, preferably from 45 to 325 μm.

[0078] The NdFeB coarse powder is composed of the following elements: PrNd, Cu, Co, Al, Ga, Zr, B and Fe. Of course, the NdFeB coarse powder may contain inevitable impurities.

[0079] The content of PrNd is 25-35wt%, preferably 27-33wt%, more preferably 30-31wt%. The mass ratio of Pr to Nd can be 1:(1-5), preferably 1:(2-4).

[0080] The content of Cu is 0.03-0.5 wt %, preferably 0.05-0.3 wt %, and more preferably 0.1-0.2 wt %.

[0081] The content of Co is 0.05 to 0.8 wt %, preferably 0.1 to 0.6 wt %, and more preferably 0.3 to 0.5 wt %.

[0082] The content of Al is 0.1 to 0.9 wt %, preferably 0.3 to 0.7 wt %, and more preferably 0.5 to 0.6 wt %.

[0083] The content of Ga is 0.05 to 0.5 wt %, preferably 0.1 to 0.4 wt %, and more preferably 0.2 to 0.3 wt %.

[0084] The content of Zr is 0.05 to 0.5 wt %, preferably 0.1 to 0.4 wt %, and more preferably 0.2 to 0.3 wt %.

[0085] The content of B is 0.8 to 1.0 wt %, preferably 0.9 to 0.95 wt %.

[0086] The jet milling can be carried out in the presence of an inert gas and oxygen. The inert gas can be selected from one or more of nitrogen, helium, neon, and argon. According to one embodiment of the present invention, the inert gas is nitrogen. The gas pressure of the inert gas is 0.3 to 0.6 MPa, preferably 0.4 to 0.5 MPa. The oxygen content can be 5 to 25 ppm, preferably 10 to 20 ppm.

[0087] During the airflow milling process, the rotation speed of the classifying wheel can be 3500-6000 rpm, preferably 4000-5500 rpm, and more preferably 4500-5000 rpm.

[0088] The raw materials can be smelted to obtain alloy flakes, and the alloy flakes can be hydrogen crushed to obtain NdFeB coarse powder.

[0089] In the smelting step, in order to prevent the magnet raw material and the master alloy made therefrom from being oxidized, the smelting is preferably carried out in a vacuum or inert atmosphere. The smelting can be carried out in a vacuum high-frequency induction furnace.

[0090] The master alloy obtained by smelting can be made into alloy sheets by using a rapid solidification strip spinning process.

[0091] Steps for preparing modified NdFeB magnetic powder

[0092] The NdFeB fine powder is mixed with the component B in the NdFeB magnetic powder additive to obtain modified NdFeB magnetic powder.

[0093] The amount of component B is 0.2-0.95‰ of the mass of the NdFeB fine powder; preferably 0.3-0.8‰; more preferably 0.4-0.7‰. The composition of component B is as described above and will not be repeated here.

[0094] The mixing is carried out under the condition that the oxygen content is ≤100 ppm; preferably ≤80 ppm; more preferably ≤50 ppm.

[0095] Mixing can be done by premixing at a low speed and then mixing at a high speed.

[0096] The low-speed mixing can be carried out at a rotation speed of 100 to 300 rpm, preferably at a rotation speed of 150 to 250 rpm. The low-speed mixing time can be 5 to 20 minutes, preferably 10 to 15 minutes.

[0097] The high-speed mixing can be carried out at a rotation speed of 400 to 800 rpm, preferably at a rotation speed of 500 to 700 rpm. The high-speed mixing time can be 10 to 30 minutes, preferably 15 to 25 minutes.

[0098] Steps to obtain NdFeB blank

[0099] The modified NdFeB fine powder is oriented and formed in a magnetic field to obtain a NdFeB blank. The NdFeB blank is obtained without isostatic pressing after the magnetic field orientation forming.

[0100] The magnetic field strength may be 1 to 2.5 Tesla, preferably 1.5 to 2 Tesla. The holding time may be 0.5 to 5 seconds, preferably 1 to 3 seconds.

[0101] The pressing pressure may be 8 to 20 MPa, preferably 10 to 15 MPa.

[0102] The density of NdFeB blank can be 2.0~15g / cm 3 ; preferably 3 to 10 g / cm 3 More preferably, 3.5 to 6 g / cm 3 .

[0103] Steps to obtain NdFeB magnets

[0104] The NdFeB blank is sintered and subjected to aging treatment to obtain a NdFeB magnet.

[0105] Sintering can be performed at different temperatures. The sintering performed at each temperature can be referred to as primary sintering. Preferably, the present invention performs three-stage sintering of the NdFeB blank at three different temperatures.

[0106] The primary sintering temperature may be 340-390° C. In some embodiments, the primary sintering temperature is 360-385° C. The primary sintering time may be 40-70 min. In some embodiments, the primary sintering time is 45-50 min.

[0107] The secondary sintering temperature may be 430-550° C. In some embodiments, the secondary sintering temperature is 480-520° C. The secondary sintering time may be 50-80 min. In some embodiments, the secondary sintering time is 50-65 min.

[0108] The temperature of the third stage sintering may be 1000-1200° C., preferably 1000-1100° C. The time of the third stage sintering may be 3-7 hours, preferably 4-6 hours.

[0109] Sintering can be carried out under vacuum conditions, where vacuum means pressure ≤ 10 -2 Pa; preferably, the pressure ≤ 10 -3 Pa.

[0110] The aging treatment includes primary aging treatment and secondary aging treatment. The primary aging treatment temperature can be 750-1000°C; preferably 800-950°C; more preferably 850-950°C. The primary aging treatment time can be 0.2-5h; preferably 0.5-3h; more preferably 0.5-1h. The secondary aging treatment temperature can be 400-650°C; preferably 450-550°C. The secondary aging treatment time can be 1-7h; preferably 3-6h. This can further improve the magnetic properties of the magnet.

[0111] The above conditions can control the nitrogen content in the NdFeB magnet to be 225-742 ppm. In certain embodiments, the nitrogen content is controlled to be 500-700 ppm.

[0112] The testing method of the present invention is described below:

[0113] Magnetic properties: The test was conducted using a NIM-10000HC permanent magnet tester. The NdFeB magnet was processed into a cylinder with a diameter of 10 mm and a height of 10 mm by wire cutting. The test temperature was 20°C. The test standard was GB / T 3217:2013.

[0114] Embodiments 1 to 4

[0115] Component A consists of 65.8 parts by weight of ethylenebiserucamide, 34 parts by weight of saturated fatty acid and 0.2 parts by weight of molybdenum disulfide.

[0116] Component B is composed of fatty acid ester and boric acid ester in a volume ratio of 1:1.

[0117] Saturated fatty acids, fatty acid esters and boric acid esters are shown in Table 1.

[0118] Table 1

[0119] Saturated fatty acids Fatty acid esters Boric acid esters Example 1 Lauric acid Ethyl oleate Tributyl borate Example 2 Palmitic acid 2-Ethylhexyl Oleate Triisopropyl borate Example 3 Stearic acid Methyl palmitate Tributyl borate Example 4 Eicosanoic acid Methyl laurate Triethyl borate

[0120] Embodiments 5 to 8

[0121] (1) The raw materials are vacuum smelted to obtain alloy flakes. The alloy flakes are hydrogen crushed to obtain NdFeB coarse powder with a particle size range of 45 to 325 μm. The elemental composition of the NdFeB coarse powder is as follows:

[0122] PrNd 30.4wt%, Cu 0.10wt%, Co 0.4wt%, Al 0.5wt%, Ga 0.2wt%, Zr 0.2wt%, B 0.92wt% and the balance is iron. The mass ratio of Pr to Nd is 25:75.

[0123] Component A in the NdFeB magnetic powder additive and NdFeB coarse powder are mixed and then subjected to air flow milling to obtain NdFeB fine powder. The process conditions of air flow milling are as follows: air flow milling is carried out under the conditions of nitrogen and oxygen, wherein the nitrogen pressure is 0.46MPa and the oxygen content is 15ppm; the speed of the classifying wheel is 4800 rpm. The selection and dosage of component A are shown in Table 2, and the parameters of NdFeB fine powder are shown in Table 2.

[0124] Table 2

[0125]

[0126] (2) NdFeB fine powder and component B in the NdFeB magnetic powder additive were mixed in a high-speed shear mixer at a speed of 200 rpm for 10 min and then at a speed of 600 rpm for 20 min under the condition that the oxygen content was less than 50 ppm to obtain modified NdFeB magnetic powder. The selection and amount of component B are shown in Table 3.

[0127] Table 3

[0128]

[0129] (3) After the modified NdFeB magnetic powder is oriented in the magnetic field, the NdFeB blank is obtained without isostatic pressing. The magnetic field strength is 1.8 Tesla, the holding time is 2 seconds, and the pressing pressure is 13 MPa. The density of the NdFeB blank is shown in Table 4.

[0130] Table 4

[0131] Example 5 Example 6 Example 7 Example 8 <![CDATA[Density of neodymium iron boron green body (g / cm 3 )]]> 4.25 4.3 4.2 4.3

[0132] (4) Place the NdFeB blank under a pressure of ≤10 -3 Pa, and then blast cooled to room temperature to obtain a sintered body. The sintered body was subjected to primary aging treatment and secondary aging treatment in sequence, and then argon gas with a temperature of 25°C and a purity of 99.99% was blown into it and cooled to ambient temperature to obtain a NdFeB magnet. The conditions for sintering, primary aging treatment and secondary aging treatment are shown in Table 5. The magnetic properties and density of the obtained NdFeB magnet are shown in Table 6.

[0133] Table 5

[0134]

[0135] Comparative Example 1

[0136] Component A in NdFeB magnetic powder additives is composed of zinc stearate. Component B in NdFeB magnetic powder additives is composed of n-octane. The details are as follows:

[0137] (1) The raw materials are vacuum smelted to obtain alloy flakes. The alloy flakes are hydrogen crushed to obtain NdFeB coarse powder with a particle size range of 45 to 325 μm. The elemental composition of the NdFeB coarse powder is as follows:

[0138] PrNd 30.4wt%, Cu 0.10wt%, Co 0.4wt%, Al 0.5wt%, Ga 0.2wt%, Zr 0.2wt%, B 0.92wt% and the balance is iron. The mass ratio of Pr to Nd is 25:75.

[0139] Component A in the NdFeB magnetic powder additive and NdFeB coarse powder are mixed and then jet milled to obtain NdFeB fine powder. The amount of component A is 0.46‰ of the mass of the NdFeB coarse powder.

[0140] (2) NdFeB fine powder, component B in the NdFeB magnetic powder additive and antioxidant are mixed in a high-speed shear mixer at a speed of 200 rpm for 10 minutes under the condition that the oxygen content is less than 50 ppm, and then mixed at a speed of 600 rpm for 20 minutes to obtain modified NdFeB magnetic powder. The amount of component B accounts for 0.68‰ of the mass of the NdFeB fine powder, and the amount of antioxidant accounts for 0.86‰ of the mass of the NdFeB fine powder.

[0141] (3) After the modified NdFeB magnetic powder is oriented in a magnetic field and formed, the NdFeB blank is obtained without isostatic pressing. The magnetic field intensity is 1.8 Tesla, the holding time is 2 seconds, and the pressing pressure is 13 MPa.

[0142] (4) Place the NdFeB blank under a pressure of ≤10 -3 Pa, the primary sintering was carried out at 360℃ for 45min, the secondary sintering was carried out at 480℃ for 60min, and then the tertiary sintering was carried out at 1050℃ for 6h, and then the sintering was carried out by blast cooling to ambient temperature to obtain a sintered body. The sintered body was subjected to primary aging treatment at 920℃ for 0.5h, secondary aging treatment at 540℃ for 4h, and then argon gas with a temperature of 25℃ and a purity of 99.99% was blown into the body to be cooled to ambient temperature to obtain a NdFeB magnet. The magnetic properties and density of the NdFeB magnet are shown in Table 6.

[0143] Table 6

[0144]

[0145] The present invention is not limited to the above-mentioned embodiments. Without departing from the essential content of the present invention, any deformation, improvement and substitution that can be conceived by those skilled in the art shall fall within the scope of the present invention.

Claims

1. A neodymium iron boron magnetic powder additive, characterized in that: The NdFeB magnetic powder additive comprises component A and component B; The component A comprises 40 to 85 parts by weight of ethylenebiserucamide, 20 to 50 parts by weight of a saturated fatty acid containing 8 to 26 carbon atoms and 0.05 to 0.5 parts by weight of molybdenum disulfide; The component B comprises a fatty acid ester and a boric acid ester represented by formula (I), wherein the volume ratio of the fatty acid ester to the boric acid ester is 1:(0.5-3); Wherein, R1 to R3 are independently selected from C1 to C6 alkyl groups; The fatty acid ester is obtained by polycondensation of an aliphatic monobasic acid containing 8 to 20 carbon atoms and an aliphatic monohydric alcohol containing 1 to 10 carbon atoms.

2. The NdFeB magnetic powder additive according to claim 1, characterized in that: The saturated fatty acid is selected from one or more of caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and eicosanoic acid.

3. The NdFeB magnetic powder additive according to claim 1, characterized in that: The fatty acid ester is obtained by polycondensation of an aliphatic monobasic acid containing 12 to 18 carbon atoms and an aliphatic saturated monohydric alcohol containing 1 to 8 carbon atoms; In formula (I), R1 to R3 are each independently selected from C2 to C4 alkyl groups.

4. The NdFeB magnetic powder additive according to claim 1, characterized in that: The fatty acid ester is selected from one or more of ethyl oleate, isooctyl oleate, methyl palmitate, methyl laurate, methyl myristate, and methyl stearate; The borate ester is selected from one or more of triisopropyl borate, tributyl borate and triethyl borate.

5. Use of the NdFeB magnetic powder additive according to any one of claims 1 to 4 in improving the magnetic properties of NdFeB magnets.

6. A method for preparing a neodymium iron boron magnet, characterized in that: The steps include: (1) mixing NdFeB coarse powder and component A in the NdFeB magnetic powder additive according to any one of claims 1 to 4, and then jet milling to obtain NdFeB fine powder; (2) mixing NdFeB fine powder with component B in the NdFeB magnetic powder additive according to any one of claims 1 to 4 to obtain modified NdFeB magnetic powder; (3) orienting the modified NdFeB fine powder in a magnetic field to obtain a NdFeB blank; (4) Sintering and aging the NdFeB blank to obtain a NdFeB magnet.

7. The preparation method according to claim 6, characterized in that: In step (1), the amount of component A is 0.2-0.8‰ of the mass of the NdFeB coarse powder; In step (2), the amount of component B is 0.2 to 0.95‰ of the mass of the NdFeB fine powder.

8. The preparation method according to claim 6, characterized in that: The particle size of the NdFeB coarse powder is in the range of 30 to 400 μm, and the average specific surface diameter of the NdFeB fine powder is in the range of 1.5 to 5 μm; The NdFeB blank is first-stage sintered at 340-390°C for 40-70 min, second-stage sintered at 430-550°C for 50-80 min, and third-stage sintered at 1000-1200°C for 3-7 h; The aging treatment includes primary aging treatment and secondary aging treatment. The primary aging treatment temperature is 750-1000°C, the primary aging treatment time is 0.2-5h, the secondary aging treatment temperature is 400-650°C, and the secondary aging treatment time is 1-7h. The nitrogen content in the NdFeB magnet is 225-742 ppm.

9. The preparation method according to claim 6, characterized in that: The following steps are also included: The raw materials are smelted to form alloy sheets; the alloy sheets are hydrogen crushed to obtain NdFeB coarse powder.

10. The preparation method according to any one of claims 6 to 9, characterized in that: The elemental composition of the NdFeB coarse powder is as follows:

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