Preparation method of neodymium-iron-boron magnet

Abstract

The invention discloses a preparation method of a neodymium-iron-boron magnet. The preparation method comprises the following steps that first fine powder with the average particle size being 3-5 microns and second fine powder with the average particle size being 1.5-2.5 microns are mixed, and mixed alloy powder is obtained; the first fine powder contains main alloy fine powder, and the second fine powder contains auxiliary alloy fine powder; wherein the main alloy fine powder has the composition as shown in the formula (I): RE Fe < 100-a-b-c-d-e-f-g > Al Cu < c > Ga < d > Z < d > Co < f > B < g >; wherein the composition of the auxiliary alloy fine powder is shown as a formula (II): RemMnFe (100-m-n-h-j-k-p-q-iAlhCujGakZrpCoqBi (II), and the composition of the auxiliary alloy fine powder is shown as a formula (II). According to the preparation method, the coercive force of the neodymium-iron-boron magnet can be improved.

Description

Technical Field

[0001] The invention relates to a method for preparing a neodymium iron boron magnet. Background Art

[0002] Neodymium iron boron magnets, due to their excellent magnetic properties, are widely used in a variety of fields, including new energy vehicles, wind power generation, and consumer electronics. Currently, the coercivity of neodymium iron boron magnets is relatively low, limiting their application in high-temperature applications. Adding heavy rare earth elements (Dy and Tb) can effectively increase the coercivity of the magnets, but the antimagnetic coupling between the heavy rare earth elements (Dy, Tb) and Fe affects the remanent magnetization. Furthermore, heavy rare earth elements are scarce in the Earth's crust and are expensive. Reducing the use of heavy rare earth elements and producing magnets with both high coercivity and high magnetic energy product is crucial.

[0003] CN108364739A discloses a method for preparing a NdFeB magnet, which comprises preparing a first NdFeB alloy and a second NdFeB alloy. The mass percentages of the first NdFeB alloy and the second NdFeB alloy are as follows: (Nd, RE) a B b M c Fe 100-a-b-c , wherein 26≤a≤33, 0.88≤b≤1.1, 0≤c≤10, RE is one or more of the rare earth elements La, Ce, Pr, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and M is one or more of the rare earth elements Co, Al, Cu, Ga, Nb, Mo, Ti, Zr, and V. The first NdFeB alloy and the second NdFeB alloy are smelted at 1450°C to obtain first and second strip-spinning sheets, respectively; then, they are hydrogen-crushed at 500±10°C, and the hydrogen-crushed alloy powders are dehydrogenated for 5h±20min. Finally, they are subjected to intermediate crushing and jet milling to obtain first and second alloy powders with a particle size of 3-5μm. The first alloy powder is pressed once to form an NdFeB intermediate blank. The NdFeB intermediate blank is then placed in a mold, and the second alloy powder is evenly spread around the NdFeB intermediate blank. After a second pressing, a composite body is obtained. This body is sintered at high temperature and then subjected to either a single-stage or double-stage tempering treatment as needed to produce an NdFeB magnet. The NdFeB intermediate blank obtained by the first pressing is theoretically smaller in all dimensions than the composite body obtained by the second pressing. This method requires two pressing steps and consumes a large amount of heavy rare earths, resulting in low utilization efficiency.

[0004] CN117912784A discloses a method for preparing high-performance sintered NdFeB magnets. The method involves mixing a main phase alloy powder, a supplementary phase alloy powder, and a nano-pure metal powder in specific proportions using a three-dimensional mixer to produce a mixed alloy powder. The mixed alloy powder is then subjected to magnetic field orientation molding in an oxygen-free or low-oxygen environment and a magnetic field strength of 1.5 to 3 Tesla to produce a compact. The compact is vacuum sintered, tempered, and cooled to produce a high-performance sintered NdFeB magnet. This method uses a relatively high amount of heavy rare earth, resulting in limited improvement in the coercivity of the magnet. Summary of the Invention

[0005] In view of this, the present invention aims to provide a method for preparing NdFeB magnets, which can improve the coercivity of NdFeB magnets. Furthermore, this method uses relatively low levels of heavy rare earth elements. Furthermore, this method has minimal impact on the remanence of the magnets and improves the maximum magnetic energy product.

[0006] The present invention provides a method for preparing a neodymium iron boron magnet, comprising the following steps:

[0007] (1) mixing a first fine powder having an average particle size of 3 to 5 μm and a second fine powder having an average particle size of 1.5 to 2.5 μm to obtain a mixed alloy powder; the first fine powder contains a main alloy fine powder, and the second fine powder contains a supplementary alloy fine powder; the weight ratio of the main alloy fine powder to the supplementary alloy fine powder is 1:(0.2 to 0.6);

[0008] The main alloy fine powder has a composition as shown in formula (I):

[0009] RE a Fe 100-a-b-c-d-e-f-g Al b Cu c Ga d Zr e Co f B g (I);

[0010] In formula (I), RE represents Pr and Nd; 28.5≤a≤33, 0.05≤b≤0.3, 0.1≤c≤0.4, 0.05≤d≤0.3, 0.05≤e≤0.4, 0.05≤f≤0.3, 0.84≤g≤0.94; a, b, c, d, e, f and g represent the weight percentage of each element respectively;

[0011] The auxiliary alloy fine powder has a composition as shown in formula (II):

[0012] Re m M n Fe 100-m-n-h-j-k-p-q-i Al h Cu jGa k Zr p Co q B i (II);

[0013] In formula (II), Re is Pr and Nd, M is selected from one or more of Dy and Tb; 1≤n≤8, 28.5≤m+n≤35, 0.05≤h≤0.3, 0.1≤j≤0.4, 0.05≤k≤0.3, 0.05≤p≤0.4, 0.05≤q≤0.3, 0.84≤i≤0.94; m, n, h, j, k, p, q and i respectively represent the weight percentage of each element;

[0014] (2) forming the mixed alloy powder into a compact;

[0015] (3) Sintering the compact to obtain a sintered body; and subjecting the sintered body to aging treatment to obtain a NdFeB magnet.

[0016] According to the preparation method of the present invention, preferably, the sintering temperature is 1050-1080° C., and the sintering time is 3-8 hours.

[0017] According to the preparation method of the present invention, preferably, the sintered body is subjected to primary aging treatment at 850-950° C. for 1-3 hours, and then subjected to secondary aging treatment at 450-550° C. for 1-5 hours.

[0018] According to the preparation method of the present invention, preferably, the average particle size of the first fine powder is 3.5-4.5 μm, and the average particle size of the second fine powder is 1.8-2.2 μm.

[0019] According to the preparation method of the present invention, preferably, the usage ratio of the main alloy fine powder to the auxiliary alloy fine powder is 1:(0.3-0.55).

[0020] According to the preparation method of the present invention, preferably, the mass ratio of Pr to Nd is 1:(2-6).

[0021] According to the preparation method of the present invention, preferably, 29.5≤a≤32, 0.08≤b≤0.2, 0.15≤c≤0.3, 0.08≤d≤0.2, 0.1≤e≤0.3, 0.08≤f≤0.2, 0.88≤g≤0.92;

[0022] 3≤n≤6, 29.5≤m+n≤33, 0.08≤h≤0.2, 0.15≤j≤0.3, 0.08≤k≤0.2, 0.1≤p≤0.3, 0.08≤q≤0.2, 0.88≤i≤0.92.

[0023] According to the preparation method of the present invention, preferably, the main alloy fine powder has the following composition:

[0024] (Pr 0.2 Nd 0.8 ) 30.5 Fe 67.9 Al 0.1 Cu 0.2 Ga 0.1 Zr 0.2 Co 0.1 B 0.9 ;

[0025] The auxiliary alloy fine powder is selected from the following composition:

[0026] (Pr 0.2 Nd 0.8 ) 26.5 Tb4Fe 67.9 Al 0.1 Cu 0.2 Ga 0.1 Zr 0.2 Co 0.1 B 0.9 ;

[0027] (Pr 0.2 Nd 0.8 ) 26.5 6DJ 65.9 Al 0.1 Cu 0.2 Ga 0.1 Zr 0.2 Co 0.1 B 0.9 .

[0028] The preparation method according to the present invention preferably further comprises the following steps:

[0029] Jet milling the raw materials including the main alloy coarse powder to obtain a first fine powder;

[0030] The raw materials including the auxiliary alloy coarse powder are subjected to air flow milling to obtain a second fine powder.

[0031] According to the preparation method of the present invention, preferably, the coercive force of the NdFeB magnet is ≥17 kOe, and the maximum magnetic energy product is ≥45 MGOe.

[0032] The preparation method of the present invention can use less heavy rare earth elements, effectively improve the coercive force of the neodymium iron boron magnet, have little effect on the remanence of the magnet, and improve the maximum magnetic energy product. DETAILED DESCRIPTION

[0033] The present invention will be further described below with reference to specific embodiments, but the protection scope of the present invention is not limited thereto.

[0034] The method for preparing a neodymium iron boron magnet of the present invention comprises the following steps: (1) mixing a first fine powder and a second fine powder; (2) forming the powder; and (3) sintering and aging the powder. In certain embodiments, the method may further comprise one or more of the steps of melting and preparing alloy sheets; hydrogen crushing; and jet milling.

[0035] Step of mixing the first fine powder and the second fine powder

[0036] In the present invention, a first fine powder and a second fine powder are mixed to obtain a mixed alloy powder. The mixing can be performed in a three-dimensional mixer. The mixing time can be 1 to 6 hours, preferably 2 to 5 hours, and more preferably 3 to 4 hours.

[0037] The first fine powder contains main alloy fine powder. In certain embodiments, the first fine powder further contains a first lubricant and a first antioxidant.

[0038] The main alloy fine powder has the composition shown in formula (I):

[0039] RE a Fe 100-a-b-c-d-e-f-g Al b Cu c Ga d Zr e Co f B g (I).

[0040] RE is Pr and Nd. a represents the weight percentage of RE. 28.5≤a≤33; preferably, 29.5≤a≤32; more preferably, 30.5≤a≤31.

[0041] The weight ratio of Pr to Nd may be 1:(2-6); preferably 1:(3-5); and more preferably 1:(4-4.5).

[0042] Al represents aluminum. b represents the weight percentage of Al. 0.05≤b≤0.3; preferably, 0.08≤b≤0.2; more preferably, 0.1≤b≤0.15.

[0043] Cu represents copper. c represents the weight percentage of Cu. 0.1≤c≤0.4; preferably, 0.15≤c≤0.3; more preferably, 0.2≤c≤0.25.

[0044] Ga represents gallium. d represents the weight fraction of Ga. 0.05≤d≤0.3; preferably, 0.08≤d≤0.2; more preferably, 0.1≤d≤0.15.

[0045] Zr represents zirconium. e represents the weight percentage of Zr. 0.05≤e≤0.4; preferably, 0.1≤e≤0.3; more preferably, 0.2≤e≤0.25.

[0046] Co represents cobalt. f represents the weight fraction of Co. 0.05≤f≤0.3; preferably, 0.08≤f≤0.2; more preferably, 0.1≤f≤0.15.

[0047] B represents boron. g represents the weight percentage of B. 0.84 ≤ g ≤ 0.94; preferably, 0.88 ≤ g ≤ 0.92; more preferably, 0.9 ≤ g ≤ 0.91.

[0048] Fe represents the element iron. 100-abcdefg represents the weight fraction of Fe. The weight fraction of Fe is determined by the values ​​of a to g. In certain embodiments, 64 ≤ 100-abcdefg ≤ 70; preferably, 66 ≤ 100-abcdefg ≤ 69; and more preferably, 67 ≤ 100-abcdefg ≤ 67.9.

[0049] In certain embodiments, the master alloy fine powder has the following composition:

[0050] (Pr 0.2 Nd 0.8 ) 30.5 Fe 67.9 Al 0.1 Cu 0.2 Ga 0.1 Zr 0.2 Co 0.1 B 0.9 .

[0051] The first lubricant can be selected from one or more of zinc stearate, sodium stearate, and polyethylene glycol. Preferably, the first lubricant is zinc stearate.

[0052] The first antioxidant can be selected from one or more of calcium stearate, triphenylmethanol, and polyethylene glycol octane. Preferably, the first antioxidant is calcium stearate.

[0053] The content of the main alloy fine powder may be 0.3 to 2.5 parts by weight, preferably 0.8 to 2 parts by weight, and more preferably 1 to 1.5 parts by weight.

[0054] The content of the first lubricant may be 0.01% to 0.1% by mass of the main alloy fine powder; preferably 0.02% to 0.08%; more preferably 0.03% to 0.06%.

[0055] The content of the first antioxidant may be 0.01% to 0.1% by mass of the main alloy fine powder; preferably 0.02% to 0.08%; more preferably 0.03% to 0.06%.

[0056] The average particle size of the first fine powder is 3 to 5 μm, preferably 3.5 to 4.5 μm, and more preferably 3.6 to 3.8 μm.

[0057] The second fine powder contains auxiliary alloy fine powder. In certain embodiments, the second fine powder further contains a second lubricant and a second antioxidant.

[0058] The auxiliary alloy fine powder has a composition as shown in formula (II):

[0059] Re m M n Fe 100-m-n-h-j-k-p-q-i Al h Cu j Ga k Zr p Co q B i (II).

[0060] Re is Pr and Nd. m represents the weight percentage of Re. 24≤m≤29; preferably, 25≤m≤28; more preferably, 26.5≤m≤27.

[0061] The weight ratio of Pr to Nd may be 1:(2-6); preferably 1:(3-5); and more preferably 1:(4-4.5).

[0062] M is selected from one or more of Dy and Tb. In certain embodiments, M is Dy. In other embodiments, M is Tb. n represents the weight percentage of M. 1 ≤ n ≤ 8; preferably, 3 ≤ n ≤ 6; more preferably, 4 ≤ n ≤ 5.

[0063] 29.5≤m+n≤33; preferably, 30≤m+n≤32.5; more preferably, 30.5≤m+n≤31.5.

[0064] Al represents aluminum. h represents the weight percentage of aluminum. 0.05≤h≤0.3; preferably, 0.08≤h≤0.2; more preferably, 0.1≤h≤0.15.

[0065] Cu represents copper. j represents the weight percentage of Cu. 0.1≤j≤0.4; preferably, 0.15≤j≤0.3; more preferably, 0.2≤j≤0.25.

[0066] Ga represents gallium. k represents the weight percentage of Ga. 0.05≤k≤0.3; preferably, 0.08≤k≤0.2; more preferably, 0.1≤k≤0.15.

[0067] Zr represents zirconium. p represents the weight percentage of Zr. 0.05≤p≤0.4; preferably, 0.1≤p≤0.3; more preferably, 0.2≤p≤0.25.

[0068] Co represents cobalt. q represents the weight fraction of Co. 0.05≤q≤0.3; preferably, 0.08≤q≤0.2; more preferably, 0.1≤q≤0.15.

[0069] B represents boron. i represents the weight percentage of B. 0.84≤i≤0.94; preferably, 0.88≤i≤0.92; more preferably, 0.9≤i≤0.91.

[0070] Fe represents the element iron. 100-mnhjkpqi represents the weight fraction of Fe. The weight fraction of Fe is determined by the values ​​of m, n, h, j, k, p, q, and i. In certain embodiments, 64 ≤ 100-mnhjkpqi ≤ 70; preferably, 66 ≤ 100-abcdefg ≤ 69; and more preferably, 67 ≤ 100-abcdefg ≤ 67.9.

[0071] In certain embodiments, the auxiliary alloy fine powder is selected from one of the following compositions:

[0072] (Pr 0.2 Nd 0.8 ) 26.5 Tb4Fe 67.9 Al 0.1 Cu 0.2 Ga 0.1 Zr 0.2 Co 0.1 B 0.9 ;

[0073] (Pr 0.2 Nd 0.8 ) 26.5 6DJ 65.9 Al 0.1 Cu 0.2 Ga 0.1 Zr 0.2 Co 0.1 B 0.9 .

[0074] The second lubricant can be selected from one or more of zinc stearate, sodium stearate, and polyethylene glycol. Preferably, the second lubricant is zinc stearate.

[0075] The second antioxidant can be selected from one or more of calcium stearate, triphenylmethanol, and polyethylene glycol octane. Preferably, the second antioxidant is calcium stearate.

[0076] The content of the auxiliary alloy fine powder may be 0.2 to 1.5 parts by weight, preferably 0.4 to 1 part by weight, and more preferably 0.5 to 0.7 part by weight.

[0077] The content of the second lubricant may be 0.01% to 0.1% of the mass of the auxiliary alloy fine powder; preferably 0.02% to 0.08%; more preferably 0.03% to 0.06%.

[0078] The content of the second antioxidant may be 0.01% to 0.1% of the mass of the auxiliary alloy fine powder; preferably 0.02% to 0.08%; more preferably 0.03% to 0.06%.

[0079] The average particle size of the second fine powder is 1.5 to 2.5 μm, preferably 1.8 to 2.2 μm, and more preferably 1.9 to 2.0 μm.

[0080] The usage ratio of the main alloy fine powder to the auxiliary alloy fine powder is 1:(0.2-0.6); preferably 1:(0.3-0.55); more preferably 1:(0.4-0.54).

[0081] Molding steps

[0082] The present invention shapes the mixed alloy powder to obtain a compact. The mixed alloy powder can be oriented and shaped in a magnetic field, and then isostatically pressed to obtain the compact.

[0083] The magnetic field strength may be 1.0 to 2.5 T, preferably 1.5 to 2.2 T, and more preferably 1.8 to 2.0 T.

[0084] Sintering and aging steps

[0085] The invention sintered the compact to obtain a sintered body; and subjected the sintered body to aging treatment to obtain a NdFeB magnet.

[0086] The sintering temperature may be 1050-1080°C, preferably 1060-1070°C, and more preferably 1065-1070°C.

[0087] The sintering time may be 3 to 8 hours, preferably 4 to 7 hours, and more preferably 5 to 6 hours.

[0088] Aging treatment can include primary aging treatment and secondary aging treatment.

[0089] The primary aging treatment temperature may be 850-950°C, preferably 900-930°C, and more preferably 920-930°C.

[0090] The primary aging treatment time may be 1 to 3 hours, preferably 2 to 3 hours, and more preferably 2 to 2.5 hours.

[0091] The secondary aging treatment temperature may be 450-550°C, preferably 470-500°C, and more preferably 480-490°C.

[0092] The secondary aging treatment time may be 1 to 5 hours, preferably 2 to 4 hours, and more preferably 2 to 3 hours.

[0093] Steps for preparing alloy sheets

[0094] The invention melts the main alloy sheet raw material and then adopts the rapid solidification strip spinning process to prepare the main alloy sheet.

[0095] The melting temperature may be 1400-1500°C, preferably 1420-1460°C, and more preferably 1430-1450°C.

[0096] Melting can be carried out in a vacuum induction melting furnace.

[0097] The thickness of the main alloy sheet may be 0.1 to 0.8 mm, preferably 0.2 to 0.6 mm, and more preferably 0.25 to 0.4 mm.

[0098] The invention melts auxiliary alloy sheet raw materials and then adopts a rapid solidification strip throwing process to prepare the auxiliary alloy sheet.

[0099] The melting temperature may be 1400-1500°C, preferably 1420-1460°C, and more preferably 1430-1450°C.

[0100] Melting can be carried out in a vacuum induction melting furnace.

[0101] The thickness of the auxiliary alloy sheet may be 0.1 to 0.8 mm, preferably 0.2 to 0.6 mm, and more preferably 0.25 to 0.4 mm.

[0102] Steps of hydrogen crushing

[0103] The present invention places the main alloy sheet in a hydrogen crushing furnace for hydrogen crushing treatment, and then dehydrogenates to obtain main alloy coarse powder.

[0104] The average particle size of the main alloy coarse powder may be 10 to 60 μm, preferably 20 to 50 μm, and more preferably 30 to 40 μm.

[0105] The invention places auxiliary alloy flakes in a hydrogen crushing furnace for hydrogen crushing treatment, and then dehydrogenates to obtain auxiliary alloy coarse powder.

[0106] The average particle size of the auxiliary alloy coarse powder may be 10 to 60 μm, preferably 20 to 50 μm, and more preferably 30 to 40 μm.

[0107] Steps of air jet grinding

[0108] The present invention jet mills the raw material comprising the main alloy coarse powder to obtain the first fine powder. In certain embodiments, the raw material further comprises a first lubricant and a first antioxidant.

[0109] The rotation speed of the separator may be 2000-4500 rpm, preferably 3000-4000 rpm, and more preferably 3500-3800 rpm.

[0110] The present invention jet mills the raw material including the auxiliary alloy coarse powder to obtain the second fine powder. In certain embodiments, the raw material further includes a second lubricant and a second antioxidant.

[0111] The rotation speed of the separator may be 4000 to 6500 rpm, preferably 4500 to 6000 rpm, and more preferably 5000 to 5500 rpm.

[0112] The following describes the test method:

[0113] Magnetic properties: Use the NIM-10000H testing system to test the magnetic properties of NdFeB magnets.

[0114] Average particle size: Use a laser particle size analyzer to test the powder particle size.

[0115] Here are the raw materials:

[0116] The first lubricant and the second lubricant are the same, both are zinc stearate.

[0117] The first antioxidant and the second antioxidant are the same, both of which are calcium stearate.

[0118] Example 1

[0119] According to the composition of the main alloy sheet and the auxiliary alloy sheet, the main alloy sheet raw material and the auxiliary alloy sheet raw material are provided. The main alloy sheet raw material and the auxiliary alloy sheet raw material are melted in a vacuum induction melting furnace at 1440°C, and then a rapid solidification strip spinning process is used to prepare a composition of (Pr 0.2 Nd 0.8 ) 30.5 Fe 67.9 Al 0.1 Cu 0.2 Ga 0.1 Zr 0.2 Co 0.1 B 0.9 The main alloy sheet and composition are (Pr 0.2 Nd0.8 ) 26.5 Tb4Fe 67.9 Al 0.1 Cu 0.2 Ga 0.1 Zr 0.2 Co 0.1 B 0.9 The thickness of the auxiliary alloy sheet is 0.28mm. The thickness of the auxiliary alloy sheet is 0.26mm.

[0120] The main alloy sheet and the auxiliary alloy sheet were placed in a hydrogen crushing furnace for hydrogen crushing treatment, and then dehydrogenated to obtain main alloy coarse powder with an average particle size of 35 μm and auxiliary alloy coarse powder with an average particle size of 33 μm.

[0121] A raw material consisting of 1 part by weight of primary alloy coarse powder, a first lubricant, and a first antioxidant was charged into the feed bin of a jet mill. The separator speed was set to 3500 rpm, yielding a first fine powder with an average particle size of 3.8 μm. The first lubricant was used in an amount of 0.05% by weight of the primary alloy coarse powder, and the first antioxidant was used in an amount of 0.05% by weight of the primary alloy coarse powder. A raw material consisting of 0.54 parts by weight of the secondary alloy coarse powder, a second lubricant, and a second antioxidant was charged into the feed bin of a jet mill. The separator speed was set to 5200 rpm, yielding a second fine powder with an average particle size of 2.0 μm. The second lubricant was used in an amount of 0.05% by weight of the secondary alloy coarse powder, and the second antioxidant was used in an amount of 0.05% by weight of the secondary alloy coarse powder.

[0122] The first fine powder and the second fine powder were placed in a three-dimensional mixer and mixed for 3 hours to obtain a mixed alloy powder.

[0123] The mixed alloy powder is oriented and formed in a magnetic field with a magnetic field strength of 2T, and then isostatically pressed to obtain a compact.

[0124] The compact was sintered at 1070°C for 5 hours to obtain a sintered body, which was then subjected to primary aging at 920°C for 2 hours and then to secondary aging at 490°C for 3 hours to obtain a NdFeB magnet.

[0125] The magnetic properties of the obtained NdFeB magnets are shown in Table 1.

[0126] Comparative Example 1

[0127] According to the composition of the main alloy sheet and the auxiliary alloy sheet, the main alloy sheet raw material and the auxiliary alloy sheet raw material are provided. The main alloy sheet raw material and the auxiliary alloy sheet raw material are melted in a vacuum induction melting furnace at 1440°C, and then the rapid solidification strip spinning process is used to prepare the composition of (Pr 0.2 Nd 0.8 ) 30.5 Fe 67.9 Al0.1 Cu 0.2 Ga 0.1 Zr 0.2 Co 0.1 B 0.9 The main alloy sheet and composition are (Pr 0.2 Nd 0.8 ) 26.5 Tb4Fe 67.9 Al 0.1 Cu 0.2 Ga 0.1 Zr 0.2 Co 0.1 B 0.9 The thickness of the auxiliary alloy sheet is 0.28mm. The thickness of the auxiliary alloy sheet is 0.26mm.

[0128] The main alloy sheet and the auxiliary alloy sheet were placed in a hydrogen crushing furnace for hydrogen crushing treatment, and then dehydrogenated to obtain main alloy coarse powder with an average particle size of 35 μm and auxiliary alloy coarse powder with an average particle size of 33 μm.

[0129] A raw material consisting of 1 part by weight of a main alloy coarse powder, 0.54 parts by weight of a supplementary alloy coarse powder, a first lubricant, and a first antioxidant was charged into the feed bin of a jet mill. The separator speed was set at 4400 rpm to produce a fine alloy powder with an average particle size of 3.0 μm. The first lubricant was used in an amount of 0.05% by weight of the total mass of the main and supplementary alloy coarse powders, and the first antioxidant was used in an amount of 0.05% by weight of the total mass of the main and supplementary alloy coarse powders.

[0130] The alloy fine powder was placed in a three-dimensional mixer and mixed for 1 hour to obtain mixed alloy powder.

[0131] The mixed alloy powder is oriented and formed in a magnetic field with a magnetic field strength of 2T, and then isostatically pressed to obtain a compact.

[0132] The green compact was sintered at 1090°C for 3 hours to obtain a sintered body, which was then subjected to primary aging at 920°C for 2 hours and then to secondary aging at 490°C for 3 hours to obtain a NdFeB magnet.

[0133] The magnetic properties of the obtained NdFeB magnets are shown in Table 1.

[0134] Example 2

[0135] According to the composition of the main alloy sheet and the auxiliary alloy sheet, the main alloy sheet raw material and the auxiliary alloy sheet raw material are provided. The main alloy sheet raw material and the auxiliary alloy sheet raw material are melted in a vacuum induction melting furnace at 1435℃, and then the rapid solidification strip spinning process is used to prepare the composition of (Pr 0.2 Nd 0.8 ) 30.5 Fe 67.9Al 0.1 Cu 0.2 Ga 0.1 Zr 0.2 Co 0.1 B 0.9 The main alloy sheet and composition are (Pr 0.2 Nd 0.8 ) 26.5 6DJ 65.9 Al 0.1 Cu 0.2 Ga 0.1 Zr 0.2 Co 0.1 B 0.9 The thickness of the main alloy sheet is 0.3mm. The thickness of the auxiliary alloy sheet is 0.27mm.

[0136] The main alloy sheet and the auxiliary alloy sheet were placed in a hydrogen crushing furnace for hydrogen crushing treatment, and then dehydrogenated to obtain main alloy coarse powder with an average particle size of 38 μm and auxiliary alloy coarse powder with an average particle size of 34 μm.

[0137] A raw material consisting of 1 part by weight of primary alloy coarse powder, a first lubricant, and a first antioxidant was charged into the feed bin of a jet mill. The separator speed was set to 3600 rpm, yielding a first fine powder with an average particle size of 3.6 μm. The first lubricant was used in an amount of 0.05% by weight of the primary alloy coarse powder, and the first antioxidant was used in an amount of 0.05% by weight of the primary alloy coarse powder. A raw material consisting of 0.43 parts by weight of the secondary alloy coarse powder, a second lubricant, and a second antioxidant was charged into the feed bin of a jet mill. The separator speed was set to 5400 rpm, yielding a second fine powder with an average particle size of 1.9 μm. The second lubricant was used in an amount of 0.05% by weight of the secondary alloy coarse powder, and the second antioxidant was used in an amount of 0.05% by weight of the secondary alloy coarse powder.

[0138] The first fine powder and the second fine powder were placed in a three-dimensional mixer and mixed for 3 hours to obtain a mixed alloy powder.

[0139] The mixed alloy powder is oriented and formed in a magnetic field with a magnetic field strength of 2T, and then isostatically pressed to obtain a compact.

[0140] The compact was sintered at 1060°C for 5 hours to obtain a sintered body, which was then aged at 900°C for 2 hours and then aged at 500°C for 3 hours to obtain a NdFeB magnet.

[0141] The magnetic properties of the obtained NdFeB magnets are shown in Table 1.

[0142] Comparative Example 2

[0143] According to the composition of the main alloy sheet and the auxiliary alloy sheet, the main alloy sheet raw material and the auxiliary alloy sheet raw material are provided. The main alloy sheet raw material and the auxiliary alloy sheet raw material are melted in a vacuum induction melting furnace at 1435℃, and then the rapid solidification strip spinning process is used to prepare the composition of (Pr 0.2 Nd 0.8 ) 30.5 Fe 67.9 Al 0.1 Cu 0.2 Ga 0.1 Zr 0.2 Co 0.1 B 0.9 The main alloy sheet and composition are (Pr 0.2 Nd 0.8 ) 26.5 6DJ 65.9 Al 0.1 Cu 0.2 Ga 0.1 Zr 0.2 Co 0.1 B 0.9 The thickness of the main alloy sheet is 0.3mm. The thickness of the auxiliary alloy sheet is 0.27mm.

[0144] The main alloy sheet and the auxiliary alloy sheet were placed in a hydrogen crushing furnace for hydrogen crushing treatment, and then dehydrogenated to obtain main alloy coarse powder with an average particle size of 38 μm and auxiliary alloy coarse powder with an average particle size of 34 μm.

[0145] A raw material consisting of 1 part by weight of a main alloy coarse powder, 0.43 parts by weight of a supplementary alloy coarse powder, a first lubricant, and a first antioxidant was charged into the feed bin of a jet mill. The separator speed was set at 4300 rpm to produce a fine alloy powder with an average particle size of 3.1 μm. The first lubricant was used in an amount of 0.05% by weight of the total mass of the main and supplementary alloy coarse powders, and the first antioxidant was used in an amount of 0.05% by weight of the total mass of the main and supplementary alloy coarse powders.

[0146] The alloy fine powder was placed in a three-dimensional mixer and mixed for 1 hour to obtain mixed alloy powder.

[0147] The mixed alloy powder is oriented and formed in a magnetic field with a magnetic field strength of 2T, and then isostatically pressed to obtain a compact.

[0148] The compact was sintered at 1080°C for 3 hours to obtain a sintered body, which was then aged at 900°C for 2 hours and then aged at 500°C for 3 hours to obtain a NdFeB magnet.

[0149] The magnetic properties of the obtained NdFeB magnets are shown in Table 1.

[0150] Table 1

[0151] Br(kGs) Hcj(kOe) (BH)max(MGOe) Hk / Hcj(%) Example 1 14.25 21.5 50.1 92.5 Comparative Example 1 14.27 19.85 50.02 93.6 Example 2 13.64 18.5 45.3 91.6 Comparative Example 2 13.66 15.8 44.86 90.7

[0152] Comparing Example 1 with Comparative Example 1 shows that, while the Tb content is comparable, the remanence and magnetic energy product do not change significantly, and the coercivity is significantly improved. Comparing Example 2 with Comparative Example 2 shows that, while the Dy content is comparable, the remanence does not change significantly, the magnetic energy product is improved, and the coercivity is significantly improved. Comparing Example 1 with Example 2 shows that Tb has a greater effect on improving the coercivity of the magnet than Dy.

[0153] The present invention is not limited to the above-mentioned embodiments. Any modification, improvement, or substitution that can be conceived by those skilled in the art without departing from the essential content of the present invention shall fall within the scope of the present invention.

Claims

1. A method for preparing a neodymium iron boron magnet, characterized in that: The steps include: (1) mixing a first fine powder having an average particle size of 3 to 5 μm and a second fine powder having an average particle size of 1.5 to 2.5 μm to obtain a mixed alloy powder; the first fine powder contains a main alloy fine powder, and the second fine powder contains a supplementary alloy fine powder; the weight ratio of the main alloy fine powder to the supplementary alloy fine powder is 1:(0.2 to 0.6); The main alloy fine powder has a composition as shown in formula (I): RE a Feb 100-a-b-c-d-e-f-g Al b Cu c Ga d Zr e Co f B g (I); In formula (I), RE represents Pr and Nd; 28.5≤a≤33, 0.05≤b≤0.3, 0.1≤c≤0.4, 0.05≤d≤0.3, 0.05≤e≤0.4, 0.05≤f≤0.3, 0.84≤g≤0.94; a, b, c, d, e, f and g represent the weight percentage of each element respectively; The auxiliary alloy fine powder has a composition as shown in formula (II): King m M n Faith 100-m-n-h-j-k-p-q-i Al h Cu j Ga k Zr p Co q B i (II)? In formula (II), Re is Pr and Nd, M is selected from one or more of Dy and Tb; 1≤n≤8, 28.5≤m+n≤35, 0.05≤h≤0.3, 0.1≤j≤0.4, 0.05≤k≤0.3, 0.05≤p≤0.4, 0.05≤q≤0.3, 0.84≤i≤0.94; m, n, h, j, k, p, q and i respectively represent the weight percentage of each element; (2) forming the mixed alloy powder into a compact; (3) Sintering the compact to obtain a sintered body; and subjecting the sintered body to aging treatment to obtain a NdFeB magnet.

2. The preparation method according to claim 1, characterized in that The sintering temperature is 1050-1080°C, and the sintering time is 3-8 hours.

3. The preparation method according to claim 1, characterized in that The sintered body is subjected to primary aging treatment at 850-950° C. for 1-3 hours, and then to secondary aging treatment at 450-550° C. for 1-5 hours.

4. The preparation method according to claim 1, characterized in that The average particle size of the first fine powder is 3.5 to 4.5 μm, and the average particle size of the second fine powder is 1.8 to 2.2 μm.

5. The preparation method according to claim 1, characterized in that The usage ratio of main alloy fine powder to auxiliary alloy fine powder is 1:(0.3~0.55).

6. The preparation method according to claim 1, characterized in that The mass ratio of Pr to Nd is 1:(2~6).

7. The preparation method according to claim 1, characterized in that 29.5≤a≤32, 0.08≤b≤0.2, 0.15≤c≤0.3, 0.08≤d≤0.2, 0.1≤e≤0.3, 0.08≤f≤0.2, 0.88≤g≤0.92; 3≤n≤6, 29.5≤m+n≤33, 0.08≤h≤0.2, 0.15≤j≤0.3, 0.08≤k≤0.2, 0.1≤p≤0.3, 0.08≤q≤0.2, 0.88≤i≤0.

92.

8. The preparation method according to claim 1, characterized in that The main alloy fine powder has the following composition: (Pr 0.2 Nd 0.8 ) 30.5 Fe 67.9 Al 0.1 The 0.2 Won't 0.1 Zr 0.2 Co 0.1 B 0.9 ; The auxiliary alloy fine powder is selected from the following composition: (Pr 0.2 when 0.8 ) 26.5 Tb4Fe 67.9 the 0.1 With 0.2 Ga 0.1 Zr 0.2 Co. 0.1 B 0.9 ; (Pr 0.2 when 0.8 ) 26.5 Dy6Fe 65.9 the 0.1 With 0.2 Ga 0.1 Zr 0.2 Co. 0.1 B 0.9 。 9. The preparation method according to claim 1, characterized in that The following steps are also included: Jet milling the raw materials including the main alloy coarse powder to obtain a first fine powder; The raw materials including the auxiliary alloy coarse powder are subjected to air flow milling to obtain a second fine powder.

10. The preparation method according to any one of claims 1 to 9, characterized in that: The coercive force of the NdFeB magnet is ≥17 kOe, and the maximum magnetic energy product is ≥45 MGOe.