Nd-Fe-B magnetic powder auxiliary agent and application thereof and preparation method of Nd-Fe-B magnet

Abstract

The invention discloses an Nd-Fe-B magnetic powder auxiliary agent, application of the Nd-Fe-B magnetic powder auxiliary agent and a preparation method of an Nd-Fe-B magnet. The Nd-Fe-B magnetic powder auxiliary agent comprises a solid auxiliary agent and a liquid auxiliary agent, the solid additive comprises 45-80 parts by weight of an ethylene amide compound, 22-45 parts by weight of saturated fatty alcohol and 0.03-0.8 part by weight of molybdenum disulfide; the liquid auxiliary agent is prepared from 0.5 to 1.5 volume parts of carboxylic ester compound and 0.5 to 3 volume parts of boric acid ester compound; the carboxylic ester compound is selected from isooctyl oleate, ethyl oleate, methyl palmitate, polyethylene glycol dioleate, methyl myristate, methyl stearate and methyl laurate; the borate compound is selected from triisopropyl borate, triethanolamine borate, tributyl borate, triethyl borate, trimethyl borate, tripropyl borate and triisobutyl borate. The Nd-Fe-B magnetic powder auxiliary agent can effectively improve the magnetic performance of a neodymium-iron-boron magnet.

Description

Technical Field

[0001] The invention relates to a Nd-Fe-B magnetic powder auxiliary agent and application thereof and a method for preparing a Nd-Fe-B magnet. Background Art

[0002] NdFeB magnet is a permanent magnetic material with high magnetic energy product and high coercivity. It occupies an important position in magnetic materials and is widely used in motors, generators, sensors and other fields, which puts higher requirements on the performance of NdFeB magnets. The regulation of grain boundary phase plays an important role in improving the coercivity of NdFeB magnets. Discontinuous grain boundary Nd-rich phase will lead to poor magnetic isolation between adjacent grains, and cause rapid expansion of reverse magnetization domains during demagnetization. Powder engineering is an effective method to regulate the composition and distribution of Nd-rich phase, and high-quality magnetic powder is the cornerstone of preparing high-performance magnets. The preparation and service characteristics of high-performance sintered NdFeB magnets are inseparable from the grain boundary Nd-rich phase, and powder coating modification technology is an effective method to directly regulate the composition and distribution of Nd-rich phase.

[0003] CN104107908A discloses an antioxidant for NdFeB alloy powder making, comprising thymol, calcium stearate, polyethylene glycol octane, aviation kerosene and Stadis 450. The effect of the antioxidant on improving the magnetic properties of NdFeB alloy needs to be improved.

[0004] CN104449740A discloses an antioxidant for sintered NdFeB jet mill, which consists of an antioxidant and an antioxidant aid. The antioxidant consists of one or more of 1-hexadecanol, triphenylmethanol or zinc stearate and ethanol. The antioxidant aid is a mixture of aviation gasoline and petroleum ether. The antioxidant has a modification effect on magnetic powder that needs to be strengthened. Summary of the invention

[0005] One object of the present invention is to provide a Nd-Fe-B magnetic powder additive, which can improve the magnetic properties of sintered Nd-Fe-B magnets. Another object of the present invention is to provide a use of the Nd-Fe-B magnetic powder additive. Another object of the present invention is to provide a method for preparing Nd-Fe-B magnets, and the Nd-Fe-B magnets obtained by the method have higher magnetic properties.

[0006] In one aspect, the present invention provides a Nd-Fe-B magnetic powder additive, comprising a solid additive and a liquid additive;

[0007] The solid additive comprises 45 to 80 parts by weight of an ethyleneamide compound represented by formula (I), 22 to 45 parts by weight of a saturated fatty alcohol and 0.03 to 0.8 parts by weight of molybdenum disulfide; the saturated fatty alcohol contains 10 to 25 carbon atoms;

[0008]

[0009] Wherein, R1 and R2 are independently selected from C10-C25 alkyl groups having at least one hydroxyl substituent;

[0010] The liquid auxiliary agent includes 0.5 to 1.5 parts by volume of a carboxylate compound and 0.5 to 3 parts by volume of a borate compound;

[0011] The carboxylic acid ester compound is selected from one or more of isooctyl oleate, ethyl oleate, methyl palmitate, polyethylene glycol dioleate, methyl myristate, methyl stearate, and methyl laurate;

[0012] The borate ester compound is selected from one or more of triisopropyl borate, triethanolamine borate, tributyl borate, triethyl borate, trimethyl borate, tripropyl borate, and triisobutyl borate.

[0013] According to the Nd-Fe-B magnetic powder additive of the present invention, preferably, R1 and R2 are independently selected from C10-C25 alkyl groups having 1-3 hydroxyl substituents.

[0014] According to the Nd-Fe-B magnetic powder additive of the present invention, preferably, R1 and R2 are independently selected from C13-C20 alkyl groups having 1-3 hydroxyl substituents.

[0015] On the other hand, the present invention provides a use of the above-mentioned Nd-Fe-B magnetic powder additive in improving at least one of the following properties of Nd-Fe-B magnets: (A) remanence; (B) coercive force; (C) maximum magnetic energy product; (D) squareness.

[0016] According to the use of the present invention, preferably, the Nd—Fe—B magnet is a sintered NdFeB magnet.

[0017] In another aspect, the present invention provides a method for preparing a Nd-Fe-B magnet, comprising the following steps:

[0018] (1) mixing the coarse Nd-Fe-B alloy powder and the solid additive in the Nd-Fe-B magnetic powder additive and jet milling the mixture to obtain fine Nd-Fe-B alloy powder;

[0019] (2) mixing fine Nd-Fe-B alloy powder and the liquid additive in the above-mentioned Nd-Fe-B magnetic powder additive to obtain modified magnetic powder;

[0020] (3) The modified magnetic powder is formed and then heat treated to obtain a Nd-Fe-B magnet.

[0021] According to the preparation method of the present invention, preferably, the dosage of the solid additive is 0.1 to 0.75‰ of the mass of the coarse Nd-Fe-B alloy powder, and the dosage of the liquid additive is 0.1 to 0.8‰ of the mass of the fine Nd-Fe-B alloy powder.

[0022] According to the preparation method of the present invention, preferably, after the modified magnetic powder is magnetically oriented and formed, it is not subjected to isostatic pressing treatment to obtain a Nd-Fe-B green body; wherein, the magnetic field strength is 1 to 2.5 T, the molding pressure is 2 to 16 MPa, and the pressure holding time is 0.5 to 10 s.

[0023] According to the preparation method of the present invention, preferably, the heat treatment includes sintering and aging treatment.

[0024] According to the preparation method of the present invention, preferably, the sintering includes three-stage sintering; wherein, the first-stage sintering temperature is 320 to 400 °C, and the first-stage sintering time is 35 to 75 min; the second-stage sintering temperature is 410 to 570 °C, and the second-stage sintering time is 45 to 85 min; the third-stage sintering temperature is 950 to 1250 °C, and the third-stage sintering time is 2.5 to 7.5 h;

[0025] The aging treatment includes two-stage aging treatment; wherein, the first-stage aging treatment temperature is 700 to 1050 °C, and the first-stage aging treatment time is 0.5 to 6 h, the second-stage aging treatment temperature is 380 to 650 °C, and the second-stage aging treatment time is 1 to 7 h;

[0026] The content of nitrogen element in the Nd-Fe-B magnet is 285 to 760 ppm.

[0027] The Nd-Fe-B magnetic powder additive of the present invention can improve the fluidity of the neodymium iron boron magnetic powder, facilitate the molding of the magnetic powder, and obtain a high-density green compact with a high degree of orientation. The neodymium iron boron magnetic powder additive of the present invention can omit the isostatic pressing process for one-time molding and simplify the preparation process of the Nd-Fe-B magnet. The Nd-Fe-B magnetic powder additive of the present invention can significantly improve the magnetic properties of the Nd-Fe-B magnet. Detailed Embodiments

[0028] The following further illustrates the present invention in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0029] <Nd-Fe-B Magnetic Powder Additive>

[0030] The Nd-Fe-B magnetic powder additive of the present invention includes a solid additive and a liquid additive. In some embodiments, the Nd-Fe-B magnetic powder additive consists of a solid additive and a liquid additive. The solid additive and the liquid additive are two separate components and do not mix with each other.

[0031] Solid additives

[0032] The solid additive of the present invention comprises an ethyleneamide compound, a saturated fatty alcohol and molybdenum disulfide. Preferably, the solid additive consists of an ethyleneamide compound, a saturated fatty alcohol and molybdenum disulfide.

[0033] The ethyleneamide compound of the present invention is shown in formula (I):

[0034]

[0035] In formula (I), R1 and R2 are each independently selected from a C10-C25 alkyl group having at least one hydroxyl substituent.

[0036] R1 and R2 are alkyl groups having hydroxyl substituents. The number of hydroxyl substituents is at least one; preferably, the number of hydroxyl substituents is 1 to 3; more preferably, the number of hydroxyl substituents is 1 to 2; most preferably, the number of hydroxyl substituents is 1. The alkyl group may be a straight chain alkyl group or a branched chain alkyl group. The number of carbon atoms in the alkyl group may be 10 to 25; preferably, 13 to 20; more preferably, 15 to 17.

[0037] According to one embodiment of the present invention, the ethyleneamide compound is ethylenebis-12-hydroxystearamide (EBH).

[0038] The content of the ethyleneamide compound is 45 to 80 parts by weight, preferably 55 to 75 parts by weight, and more preferably 65 to 70 parts by weight.

[0039] The saturated fatty alcohol may be a branched saturated fatty alcohol or a straight-chain saturated fatty alcohol. Preferably, the saturated fatty alcohol is a straight-chain saturated fatty alcohol. The saturated fatty alcohol contains 10 to 25 carbon atoms; preferably, the saturated fatty alcohol contains 12 to 22 carbon atoms; more preferably, the saturated fatty alcohol contains 14 to 20 carbon atoms. The saturated fatty alcohol may be selected from one or more of n-dodecyl alcohol, n-tetradecyl alcohol, n-hexadecanol, n-octadecanol, n-eicosanol, and n-docosanol. Preferably, the saturated fatty alcohol is selected from one or more of n-tetradecyl alcohol, n-hexadecanol, n-octadecanol, and n-docosanol.

[0040] The content of the saturated fatty alcohol is 22 to 45 parts by weight, preferably 25 to 40 parts by weight, and more preferably 30 to 35 parts by weight.

[0041] The content of molybdenum disulfide is 0.03 to 0.8 parts by weight, preferably 0.08 to 0.5 parts by weight, and more preferably 0.1 to 0.2 parts by weight.

[0042] The solid additive interacts with the coarse Nd-Fe-B alloy powder during the jet milling process, improves the fluidity and antioxidant properties of the alloy powder, improves the performance of the magnetic powder, and enhances the magnetic properties of the Nd-Fe-B magnet.

[0043] Liquid additives

[0044] The liquid additive of the present invention includes carboxylic acid ester compounds and borate compounds. In certain embodiments, the liquid additive consists of carboxylic acid ester compounds and borate compounds.

[0045] The carboxylic acid ester compounds of the present invention are selected from one or more of isooctyl oleate, ethyl oleate, methyl palmitate, polyethylene glycol dioleate, methyl myristate, methyl stearate, and methyl laurate. Preferably, the carboxylic acid ester compounds are selected from one or more of ethyl oleate, isooctyl oleate, methyl palmitate, and methyl laurate. In certain embodiments, the carboxylic acid ester compound is ethyl oleate. In other embodiments, the carboxylic acid ester compound is methyl palmitate.

[0046] The content of the carboxylic acid ester compounds can be 0.5 to 1.5 parts by volume; preferably 0.8 to 1.5 parts by volume; more preferably 1 to 1.2 parts by volume.

[0047] The borate compounds of the present invention are selected from one or more of triisopropyl borate, triethanolamine borate, tributyl borate, triethyl borate, trimethyl borate, tripropyl borate, and triisobutyl borate; preferably, the borate compounds are selected from one or more of tributyl borate, triisopropyl borate, and triethyl borate. In certain embodiments, the borate compound is tributyl borate. In other embodiments, the borate compound is triisopropyl borate.

[0048] The content of the borate compounds can be 0.5 to 3 parts by volume; preferably 0.8 to 2 parts by volume; more preferably 1 to 1.5 parts by volume.

[0049] The liquid additive of the present invention is mixed with fine Nd-Fe-B alloy powder to improve the lubricity and oxidation resistance of the magnetic powder. The liquid additive of the present invention is used in combination with a solid additive, which can effectively improve the magnetic properties of Nd-Fe-B magnets.

[0050] <Use of Nd-Fe-B Magnetic Powder Additive>

[0051] The Nd-Fe-B magnetic powder additive of the present invention can effectively improve the magnetic properties of Nd-Fe-B magnets. The magnetic properties include remanence, coercivity, maximum magnetic energy product, and squareness. Therefore, the present invention provides the use of the above Nd-Fe-B magnetic powder additive in improving at least one of the following properties of Nd-Fe-B magnets: (A) remanence; (B) coercivity; (C) maximum magnetic energy product; (D) squareness. The Nd-Fe-B magnet can be a sintered neodymium iron boron magnet.

[0052] <Preparation Method of Nd-Fe-B Magnet>

[0053] The method for preparing the NdFeB magnet of the present invention comprises the following steps: (1) a step of modifying coarse powder; (2) a step of modifying fine powder; and (3) a step of molding and heat treatment. In certain embodiments, it further comprises a step of smelting and hydrogen crushing.

[0054] Steps of Smelting and Hydrogen Breaking

[0055] The raw materials are smelted to obtain a master alloy. The master alloy is subjected to a rapid solidification belt spinning process to obtain alloy flakes. The alloy flakes are hydrogen crushed to obtain a coarse Nd-Fe-B alloy powder.

[0056] Preferably, the raw materials are smelted in a vacuum or inert atmosphere to obtain a master alloy, which can prevent the master alloy from being oxidized. The smelting can be carried out in a vacuum induction melting furnace.

[0057] The particle size of the coarse Nd—Fe—B alloy powder may range from 30 to 400 μm, preferably from 45 to 325 μm.

[0058] The coarse Nd-Fe-B alloy powder may be composed of the following elements: PrNd, Cu, Co, Al, Ga, Zr, B and Fe. Of course, the coarse Nd-Fe-B alloy powder may contain inevitable impurities, such as C, O, etc.

[0059] The content of PrNd may be 20-40wt%, preferably 25-35wt%, more preferably 30-31wt%. The mass ratio of Pr to Nd may be 25:(50-90), preferably 25:(60-80), more preferably 25:(65-75).

[0060] The content of Cu is 0.01 to 0.55 wt %, preferably 0.03 to 0.4 wt %, and more preferably 0.05 to 0.2 wt %.

[0061] The content of Co is 0.1 to 0.8 wt %, preferably 0.2 to 0.7 wt %, and more preferably 0.3 to 0.5 wt %.

[0062] The content of Al is 0.2 to 0.9 wt %, preferably 0.3 to 0.8 wt %, and more preferably 0.5 to 0.6 wt %.

[0063] The content of Ga is 0.03 to 0.6 wt %, preferably 0.1 to 0.5 wt %, and more preferably 0.2 to 0.3 wt %.

[0064] The content of Zr is 0.03-0.6 wt %, preferably 0.1-0.5 wt %, and more preferably 0.2-0.3 wt %.

[0065] The content of B is 0.8 to 1.0 wt %, preferably 0.9 to 0.95 wt %.

[0066] Steps for coarse powder modification

[0067] The coarse Nd-Fe-B alloy powder and the solid additive in the Nd-Fe-B magnetic powder additive are mixed and then jet milled to obtain fine Nd-Fe-B alloy powder. The solid additive is as described above and will not be described again here.

[0068] The dosage of the solid additive is 0.1-0.75‰ of the mass of the coarse Nd-Fe-B alloy powder; preferably 0.2-0.6‰; more preferably 0.3-0.55‰.

[0069] The jet milling can be carried out in the presence of an inert gas and O2. The inert gas can be selected from one or more of N2, He, Ne, and Ar. According to one embodiment of the present invention, the inert gas is N2.

[0070] The pressure of the inert gas is 0.2 to 0.7 MPa, preferably 0.3 to 0.6 MPa, and more preferably 0.4 to 0.6 MPa.

[0071] The O2 content can be 5 to 25 ppm; preferably 10 to 20 ppm.

[0072] During the jet milling process, the rotation speed of the classifying wheel may be 3500-6000 rpm, preferably 4000-5500 rpm, and more preferably 4500-5000 rpm.

[0073] The specific surface average diameter of the fine Nd-Fe-B alloy powder may be 1 to 5.5 μm, preferably 1.5 to 4 μm, and more preferably 2 to 3 μm.

[0074] D of fine Nd-Fe-B alloy powder 90 / D 10 It may be 2.5 to 6; preferably 3.5 to 5.5; more preferably 4 to 5.

[0075] The repose angle of the fine Nd—Fe—B alloy powder is ≤50°; preferably, the repose angle is ≤45°.

[0076] The bulk density of fine Nd-Fe-B alloy powder can be 0.8-3.5 g / cm 3 ; preferably 1 to 3 g / cm 3 More preferably, 1.5 to 2 g / cm 3 .

[0077] The tap density of fine Nd-Fe-B alloy powder can be 2-5 g / cm 3 ; preferably 3 to 4.5 g / cm 3More preferably, 3.5 to 4 g / cm 3 .

[0078] Steps for fine powder modification

[0079] The fine Nd-Fe-B alloy powder is mixed with the liquid additive in the above-mentioned Nd-Fe-B magnetic powder additive to obtain modified magnetic powder. The liquid additive is as described above and will not be described again here.

[0080] The amount of the liquid auxiliary agent used is 0.1-0.8‰ of the mass of the fine Nd-Fe-B alloy powder; preferably 0.2-0.7‰; more preferably 0.3-0.6‰.

[0081] The mixing is carried out under the condition that the oxygen content is ≤100 ppm; preferably ≤80 ppm; more preferably ≤50 ppm.

[0082] Mixing can be done by premixing at a low speed and then mixing at a high speed.

[0083] The rotation speed of the low-speed mixing may be 100 to 300 rpm, preferably 150 to 250 rpm. The time of the low-speed mixing may be 5 to 20 minutes, preferably 10 to 15 minutes.

[0084] The speed of high-speed mixing can be 400 to 800 rpm, preferably 500 to 700 rpm. The time of high-speed mixing can be 10 to 30 minutes, preferably 15 to 25 minutes.

[0085] Forming and heat treatment steps

[0086] The modified magnetic powder is formed and then heat treated to obtain a Nd-Fe-B magnet.

[0087] The modified magnetic powder can be oriented in a magnetic field to obtain a Nd-Fe-B blank. After the modified fine powder of the present invention is oriented in a magnetic field, a Nd-Fe-B blank can be obtained without isostatic pressing.

[0088] The magnetic field strength may be 1 to 2.5 T, preferably 1.5 to 2 T.

[0089] The pressing pressure may be 2 to 16 MPa. In some embodiments, the pressing pressure is 10 to 15 MPa. The holding time may be 0.5 to 5 s, preferably 1 to 3 s.

[0090] The density of the Nd-Fe-B body can be 2.0 to 6.0 g / cm 3 ; preferably 3.5 to 5.5 g / cm 3 More preferably, 3.8 to 4.5 g / cm 3 .

[0091] Heat treatment may include sintering and aging.

[0092] Sintering can include three-stage sintering. Sintering can be carried out under vacuum conditions, where vacuum means pressure ≤ 10 -2 Pa; preferably, pressure ≤10 -3 Pa.

[0093] The primary sintering temperature may be 320-400° C. In some embodiments, the primary sintering temperature is 370-390° C. The primary sintering time may be 35-75 min. In some embodiments, the primary sintering time is 40-60 min.

[0094] The secondary sintering temperature may be 410-570° C. In some embodiments, the secondary sintering temperature is 440-500° C. The secondary sintering time may be 45-85 min. In some embodiments, the secondary sintering time is 50-80 min.

[0095] The temperature of the third stage sintering may be 950-1250° C., preferably 1000-1100° C. The time of the third stage sintering may be 2.5-7.5 hours, preferably 3-6 hours.

[0096] The aging treatment may include a secondary aging treatment. The primary aging treatment temperature may be 700 to 1050°C; preferably 800 to 950°C; more preferably 850 to 950°C. The primary aging treatment time may be 0.5 to 6 hours; preferably 0.5 to 3 hours; more preferably 0.5 to 1 hour. The secondary aging treatment temperature may be 380 to 650°C; preferably 450 to 550°C. The secondary aging treatment time may be 1 to 7 hours; preferably 3 to 6 hours.

[0097] The nitrogen content in the Nd-Fe-B magnet of the present invention is 225-742 ppm, preferably 300-700 ppm.

[0098] The testing method of the present invention is described below:

[0099] 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.

[0100] Example 1

[0101] The Nd—Fe—B magnetic powder additive of this embodiment consists of a solid additive and a liquid additive.

[0102] The solid auxiliary agent consists of 68.8 parts by weight of ethylene bis-12-hydroxystearamide, 31.05 parts by weight of n-tetradecanol and 0.15 parts by weight of molybdenum disulfide.

[0103] The liquid additive consists of 1 part by volume of ethyl oleate and 1 part by volume of tributyl borate.

[0104] Example 2

[0105] The Nd—Fe—B magnetic powder additive of this embodiment consists of a solid additive and a liquid additive.

[0106] The solid auxiliary agent consists of 68.8 parts by weight of ethylene bis-12-hydroxystearamide, 31.05 parts by weight of n-hexadecanol and 0.15 parts by weight of molybdenum disulfide.

[0107] The liquid auxiliary agent is composed of 1 part by volume of isooctyl oleate and 1 part by volume of triisopropyl borate.

[0108] Example 3

[0109] The Nd—Fe—B magnetic powder additive of this embodiment consists of a solid additive and a liquid additive.

[0110] The solid auxiliary agent consists of 68.8 parts by weight of ethylene bis-12-hydroxystearamide, 31.05 parts by weight of n-octadecyl alcohol and 0.15 parts by weight of molybdenum disulfide.

[0111] The liquid adjuvant consists of 1 part by volume of methyl palmitate and 1 part by volume of tributyl borate.

[0112] Example 4

[0113] The Nd—Fe—B magnetic powder additive of this embodiment consists of a solid additive and a liquid additive.

[0114] The solid auxiliary agent consists of 68.8 parts by weight of ethylene bis-12-hydroxystearamide, 31.05 parts by weight of n-behenyl alcohol and 0.15 parts by weight of molybdenum disulfide.

[0115] The liquid auxiliary agent consists of 1 part by volume of methyl laurate and 1 part by volume of triethyl borate.

[0116] Embodiments 5 to 8

[0117] The raw materials are vacuum smelted to obtain a master alloy. The master alloy is used to obtain alloy sheets by a rapid solidification belt spinning process. The alloy sheets are hydrogen crushed to obtain a coarse Nd-Fe-B alloy powder. The particle size of the coarse Nd-Fe-B alloy powder ranges from 45 to 325 μm. The elemental composition of the coarse Nd-Fe-B alloy powder is shown in Table 1.

[0118] Table 1

[0119] Example 5 Example 6 Example 7 Example 8 PrNd (wt%) 30.3 30.4 30.4 30.4 Cu(wt%) 0.10 0.10 0.10 0.10 Co(wt%) 0.4 0.4 0.4 0.4 Al(wt%) 0.5 0.5 0.5 0.5 Ga(wt%) 0.2 0.2 0.2 0.2 Zr (wt%) 0.2 0.2 0.2 0.2 B (wt%) 0.92 0.92 0.92 0.92 Fe margin margin margin margin

[0120] Note: The mass ratio of Pr to Nd in PrNd is 25:75.

[0121] The solid additive in the Nd-Fe-B magnetic powder additive and the coarse Nd-Fe-B alloy powder are mixed and then jet milled in an atmosphere of N2 and O2 to obtain fine Nd-Fe-B alloy powder. The N2 pressure is 0.46MPa, the O2 content is 15ppm, and the rotation speed of the classifier wheel is 4800rpm.

[0122] Fine Nd-Fe-B alloy powder and liquid additive in Nd-Fe-B magnetic powder additive were mixed in a mixer at an O2 content of less than 50 ppm and a rotation speed of 200 rpm for 10 minutes, and then mixed at an O2 content of less than 50 ppm and a rotation speed of 600 rpm for 20 minutes to obtain modified magnetic powder.

[0123] After the modified magnetic powder is oriented in the magnetic field and formed without isostatic pressing, a Nd-Fe-B blank is obtained. The magnetic field intensity is 1.8T, the pressing pressure is 13MPa, and the holding time is 2s.

[0124] The Nd-Fe-B blank is heated to a pressure of ≤10 -3 Pa, and then blast-cooled to room temperature to obtain a sintered body. The sintered body is subjected to secondary aging treatment, and then argon is blown in to cool to ambient temperature to obtain a Nd-Fe-B magnet. The temperature of the argon gas is 25°C and the purity is 99.99%.

[0125] The raw materials, process parameters, parameters of fine Nd-Fe-B alloy powder, density of Nd-Fe-B blank, density, nitrogen content and magnetic properties of Nd-Fe-B magnet are shown in Table 2.

[0126] Table 2

[0127]

[0128]

[0129] Comparative Example 1

[0130] Except that the solid additive is zinc stearate, the addition amount is 0.42‰; the liquid additive is methyl oleate, the addition amount is 0.56‰, the rest is the same as Example 1. The parameters of the fine Nd-Fe-B alloy powder, the density of the Nd-Fe-B blank, the density, nitrogen content and magnetic properties of the Nd-Fe-B magnet are shown in Table 3.

[0131] Table 3

[0132]

[0133]

[0134] 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 Nd-Fe-B magnetic powder additive, characterized in that: The Nd-Fe-B magnetic powder additive includes a solid additive and a liquid additive; The solid additive comprises 45 to 80 parts by weight of an ethyleneamide compound represented by formula (I), 22 to 45 parts by weight of a saturated fatty alcohol and 0.03 to 0.8 parts by weight of molybdenum disulfide; the saturated fatty alcohol contains 10 to 25 carbon atoms; Wherein, R1 and R2 are independently selected from C10-C25 alkyl groups having at least one hydroxyl substituent; The liquid auxiliary agent includes 0.5 to 1.5 parts by volume of a carboxylate compound and 0.5 to 3 parts by volume of a borate compound; The carboxylic acid ester compound is selected from one or more of isooctyl oleate, ethyl oleate, methyl palmitate, polyethylene glycol dioleate, methyl myristate, methyl stearate, and methyl laurate; The borate ester compound is selected from one or more of triisopropyl borate, triethanolamine borate, tributyl borate, triethyl borate, trimethyl borate, tripropyl borate, and triisobutyl borate.

2. The Nd-Fe-B magnetic powder additive according to claim 1, characterized in that: R1 and R2 are each independently selected from a C10-C25 alkyl group having 1 to 3 hydroxyl substituents.

3. The Nd-Fe-B magnetic powder additive according to claim 2, characterized in that: R1 and R2 are each independently selected from a C13-C20 alkyl group having 1 to 3 hydroxyl substituents.

4. Use of the Nd-Fe-B magnetic powder additive according to any one of claims 1 to 3 in improving at least one of the following properties of Nd-Fe-B magnets: (A) Remanence; (B) Coercive force; (C) Maximum magnetic energy product; (D) Squareness.

5. The use according to claim 4, characterized in that The Nd—Fe—B magnet is a sintered neodymium iron boron magnet.

6. A method for preparing a Nd-Fe-B magnet, characterized in that: The steps include: (1) mixing a coarse Nd-Fe-B alloy powder and a solid additive in the Nd-Fe-B magnetic powder additive according to any one of claims 1 to 3, and then jet milling the mixture to obtain a fine Nd-Fe-B alloy powder; (2) mixing fine Nd-Fe-B alloy powder and the liquid additive in the Nd-Fe-B magnetic powder additive according to any one of claims 1 to 3 to obtain modified magnetic powder; (3) The modified magnetic powder is formed and then heat treated to obtain a Nd-Fe-B magnet.

7. The preparation method according to claim 6, characterized in that: The amount of solid additive used is 0.1-0.75‰ of the mass of coarse Nd-Fe-B alloy powder, and the amount of liquid additive used is 0.1-0.8‰ of the mass of fine Nd-Fe-B alloy powder.

8. The preparation method according to claim 6, characterized in that: After the modified magnetic powder is oriented in a magnetic field and formed, a Nd-Fe-B blank is obtained without isostatic pressing. The magnetic field intensity is 1 to 2.5 T, the pressing pressure is 2 to 16 MPa, and the holding time is 0.5 to 10 seconds.

9. The preparation method according to claim 6, characterized in that: The heat treatment includes sintering and aging treatment.

10. The preparation method according to claim 9, characterized in that: The sintering includes three stages of sintering; wherein the primary sintering temperature is 320-400°C, and the primary sintering time is 35-75 minutes; the secondary sintering temperature is 410-570°C, and the secondary sintering time is 45-85 minutes; the tertiary sintering temperature is 950-1250°C, and the tertiary sintering time is 2.5-7.5 hours; The aging treatment includes a secondary aging treatment; wherein the primary aging treatment temperature is 700-1050°C, the primary aging treatment time is 0.5-6h, the secondary aging treatment temperature is 380-650°C, and the secondary aging treatment time is 1-7h; The content of nitrogen in the Nd-Fe-B magnet is 285-760 ppm.

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