Preparation method of regenerated sintered neodymium-iron-boron permanent magnet

Abstract

The invention provides a preparation method of a neodymium iron boron permanent magnet, and belongs to the field of permanent magnets. The invention provides a preparation method of a regenerated sintered neodymium-iron-boron permanent magnet, which comprises the following steps of: mixing Ce33Fe67 alloy and neodymium-iron-boron alloy, and performing hydrogen decrepitation to obtain magnetic powder; carrying out orientation molding on the magnetic powder to obtain a green body; and sintering and tempering the green body to obtain the regenerated sintered neodymium-iron-boron permanent magnet, the neodymium-iron-boron alloy comprises waste materials. The waste materials generated in the traditional neodymium iron boron sintering process can be directly utilized from hydrogen decrepitation, and the method does not need to obtain rare earth metal through separation and purification and then manufacture the sintered neodymium iron boron, so that the timeliness of recycling is shortened, the efficiency of recycling is improved, and the cost of recycling is reduced; as the cost of waste materials is relatively low, the production and manufacturing cost of the neodymium-iron-boron magnetic steel can be obviously reduced by adding the waste materials according to a certain proportion.

Description

Technical Field

[0001] This invention relates to the field of permanent magnets, and more specifically to a method for preparing a regenerated sintered NdFeB permanent magnet. Background Technology

[0002] Neodymium iron boron (NdFeB) permanent magnets are mainly composed of rare earth metals, iron, and boron. Due to their extremely high magnetic energy product, coercivity, and remanence, they have rapidly become an indispensable key functional material in modern high-tech industries. They are widely used in new energy vehicle drive motors, wind power generation, precision instruments, consumer electronics, and industrial automation. As their application in various industries increases, their competitiveness also increases dramatically. Therefore, the NdFeB permanent magnet manufacturing industry needs the advantage of stable magnet performance. Summary of the Invention

[0003] This invention provides a method for preparing neodymium iron boron permanent magnets, and the neodymium iron boron permanent magnets prepared by this invention have stable magnetic properties.

[0004] This invention provides a method for preparing regenerated sintered NdFeB permanent magnets, comprising the following steps: Ce 33 Fe 67 The alloy was mixed with neodymium iron boron alloy and then subjected to hydrogen crushing to obtain magnetic powder; The magnetic powder is oriented and shaped to obtain a green body; The green blank is sintered and tempered to obtain the regenerated sintered NdFeB permanent magnet. The neodymium iron boron alloy includes scrap.

[0005] Preferably, the Ce, in terms of mass fraction, 33 Fe 67 The alloy comprises the following elements: Pr 2.5~5.5%, Nd 7.5~16.5%, Ce 10~25%, Co 0.1~0.8%, Ga 0.1~0.5%, Al 0.1~0.5%, Cu 0.2~0.5%, B 0.8~1.2%, Zr 0.1~0.5%, Ti 0.1~0.5%, and the balance Fe.

[0006] Preferably, the neodymium iron boron alloy comprises, by mass fraction, the following elements: Pr 3.75~7.5%, Nd 11.25~22.5%, Ce 0~15%, Gd 0~2%, Ho 0~2%, Co 0.1~0.4%, Ga 0~0.5%, Al 0~1.5%, Cu 0.1~0.4%, B 0.8~1.2%, Zr 0.1~0.3%, Ti 0.1~0.3%, niobium 0~5%, yttrium 0~5%, and the balance Fe.

[0007] Preferably, the Ce33 Fe 67 The mass ratio of the alloy to the NdFeB alloy is 1:1~2.

[0008] Preferably, the hydrogen crushing includes sequentially performing hydrogen absorption and dehydrogenation; The hydrogen pressure during absorption is 0.1~0.2 MPa, and the absorption time is 45~110 min. The dehydrogenation temperature is 450~550℃, the vacuum degree is ≤50pa, and the holding time is ≥10h.

[0009] Preferably, after hydrogen crushing, the process further includes: grinding the powder obtained from hydrogen crushing into powder using an air jet mill to obtain the magnetic powder; The grinding pressure during airflow milling is 5~5.5MPa, the sorting wheel speed is 2000~5000rpm, and the powder output speed is 200~300kg / h; The magnetic powder has an average surface area diameter of 2.4~3.2μm and a particle size distribution D90 / D10 of 4.2~4.5.

[0010] Preferably, the magnetic induction intensity during the orientation molding is ≥1.8T, and the molding pressure is 4~8MPa; The density of the green body is 4.0~4.5 g / cm³. 3 .

[0011] Preferably, the sintering temperature is 1000~1050℃, and the holding time is 2~5h; The vacuum degree of the sintering is 5×10⁻⁶. -2 Below Pa.

[0012] Preferably, the process after sintering and before tempering further includes cooling the sintered blank with a protective gas.

[0013] Preferably, the tempering includes sequentially performing a first-stage tempering process, cooling, and a second-stage tempering process; The vacuum degree of the first-stage tempering process is below 1 Pa, the temperature is 890~920℃, and the time is 1.5~2.5h. The gas used for cooling includes an inert gas; The vacuum degree of the secondary tempering process is below 1 Pa, the temperature is 400~550℃, and the time is 4~6h.

[0014] Ce 33 Fe 67 The combination of alloys with NdFeB alloys can optimize grain boundary distribution, and NdFeB alloys can compensate for the side effects of remanence, resulting in an overall improvement in the stability of magnetic properties.

[0015] The waste generated in the traditional sintering process of NdFeB can be directly utilized from hydrogen crushing. This invention eliminates the need for separation and purification to obtain rare earth metals before sintering NdFeB, shortening the time required for recycling and improving the efficiency and cost of recycling. Since the waste cost is relatively low, adding it in a certain proportion can significantly reduce the production cost of NdFeB magnets.

[0016] Furthermore, this invention modulates Ce 33 Fe 67 High-performance materials can be obtained by combining alloys with waste materials of suitable composition. Detailed Implementation

[0017] This invention provides a method for preparing regenerated sintered NdFeB permanent magnets, comprising the following steps: Ce 33 Fe 67 The alloy was mixed with neodymium iron boron alloy and then subjected to hydrogen crushing to obtain magnetic powder; The magnetic powder is oriented and shaped to obtain a green body; The green blank is sintered and tempered to obtain the regenerated sintered NdFeB permanent magnet. The neodymium iron boron alloy includes scrap.

[0018] This invention will Ce 33 Fe 67 The alloy was mixed with neodymium iron boron alloy and then hydrogen-crushed to obtain magnetic powder.

[0019] In this invention, the Ce 33 Fe 67 The preferred mass ratio of the alloy to the NdFeB alloy is 1:1 to 2. In specific embodiments of the present invention, it can be 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8 or 1:1.9.

[0020] In terms of mass fraction, the Ce 33 Fe 67 The alloy preferably contains 2.5% to 5.5% Pr. In specific embodiments of the present invention, the mass fraction of Pr can be 3%, 3.5%, 4%, 4.5%, or 5%. In terms of mass fraction, the Ce 33 Fe 67 The alloy preferably contains 7.5% to 16.5% Nd. In specific embodiments of the present invention, the mass fraction of the Nd element can be 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or 16%.

[0021] In terms of mass fraction, the present invention Ce 33 Fe67 The alloy preferably contains 10-25% Ce. In specific embodiments of the present invention, the mass fraction of Ce can be 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21% or 22%.

[0022] In terms of mass fraction, the present invention Ce 33 Fe 67 The alloy preferably contains 0.1-0.8% Co. In specific embodiments of the present invention, the mass fraction of Co can be 0.2%, 0.3%, 0.4%, 0.5%, 0.6% or 0.7%.

[0023] In terms of mass fraction, the present invention Ce 33 Fe 67 The alloy preferably contains 0.1-0.5% Ga. In specific embodiments of the present invention, the mass fraction of Ga can be 0.2%, 0.3% or 0.4%.

[0024] In terms of mass fraction, the present invention Ce 33 Fe 67 The alloy preferably contains 0.1-0.5% Al. In specific embodiments of the present invention, the mass fraction of the Al element can be 0.2%, 0.3% or 0.4%.

[0025] In terms of mass fraction, the present invention Ce 33 Fe 67 The alloy preferably contains 0.2% to 0.5% Cu. In specific embodiments of the present invention, the mass fraction of Cu can be 0.3% or 0.4%. In terms of mass fraction, the present invention Ce 33 Fe 67 The alloy preferably contains 0.8-1.2% B. In specific embodiments of the present invention, the mass fraction of B can be 0.9%, 1% or 1.1%.

[0026] In terms of mass fraction, the present invention Ce 33 Fe 67 The alloy preferably contains 0.1% to 0.5% Zr. In specific embodiments of the present invention, the mass fraction of Zr can be 0.2%, 0.3%, or 0.4%.

[0027] In terms of mass fraction, the present invention Ce 33 Fe 67 The alloy preferably contains 0.1-0.5% Ti. In specific embodiments of the present invention, the mass fraction of the Ti element can be 0.2%, 0.3% or 0.4%.

[0028] In terms of mass fraction, the present invention Ce 33 Fe 67 The alloy preferably includes the balance Fe.

[0029] In this invention, the Ce 33 Fe 67 The preferred method for preparing the alloy elements includes the following steps: Ce 33 Fe 67 The raw materials of the alloy are refined and cast to obtain the Ce. 33 Fe 67 alloy.

[0030] In this invention, the refining temperature is preferably 1230±5℃, and the refining time is preferably 6~12min.

[0031] In this invention, the casting temperature is preferably 1110±5℃, and the copper roller rotation speed is preferably 75±5rpm.

[0032] In this invention, the cooling method is preferably argon-filled air cooling, and the cooling rate is preferably 10±2℃ / min.

[0033] In this invention, the Ce 33 Fe 67 The thickness of the alloy is preferably 0.2~0.4 mm.

[0034] The neodymium iron boron alloy includes scrap, which includes neodymium iron boron alloy with substandard appearance, slag generated during the production process, or magnets from disassembled electronic equipment.

[0035] The NdFeB alloy of the present invention preferably contains 3.75% to 7.5% Pr by mass fraction. In specific embodiments of the present invention, the mass fraction of Pr can be 4%, 5%, or 6%. The NdFeB alloy of the present invention preferably includes 11.25-22.5% Nd. In specific embodiments of the present invention, the mass fraction of the Nd element can be 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21% or 22%.

[0036] The neodymium iron boron alloy of the present invention preferably includes 0-15% Ce by mass fraction. In specific embodiments of the present invention, the mass fraction of Ce can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13% or 14%.

[0037] The NdFeB alloy of the present invention preferably includes 0-2% Gd by mass fraction. In specific embodiments of the present invention, the mass fraction of the Gd element can be 0.5%, 0.8%, 1%, 1.2%, 1.5% or 1.8%.

[0038] The elements of the neodymium iron boron alloy of the present invention preferably include 0-2% Ho by mass fraction. In specific embodiments of the present invention, the mass fraction of the Ho element can be 0.5%, 0.8%, 1%, 1.2%, 1.5% or 1.8%.

[0039] The NdFeB alloy of the present invention preferably contains 0.1-0.4% Co by mass fraction. In specific embodiments of the present invention, the mass fraction of Co can be 0.2% or 0.3%.

[0040] The elements of the neodymium iron boron alloy of the present invention preferably include 0 to 0.5% Ga by mass fraction. In specific embodiments of the present invention, the mass fraction of the Ga element can be 0.1%, 0.2%, 0.3% or 0.4%.

[0041] The neodymium iron boron alloy of the present invention preferably contains 0 to 1.5% Al by mass fraction. In specific embodiments of the present invention, the mass fraction of Al can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, or 1.5%.

[0042] The NdFeB alloy of the present invention preferably contains 0.1-0.4% Cu by mass fraction. In specific embodiments of the present invention, the mass fraction of Cu can be 0.2% or 0.3%.

[0043] The NdFeB alloy of the present invention preferably contains 0.8-1.2% B by mass fraction. In specific embodiments of the present invention, the mass fraction of the B element can be 0.9%, 1% or 1.1%.

[0044] The NdFeB alloy of the present invention preferably contains 0.1-0.3% Zr by mass fraction. In a specific embodiment of the present invention, the mass fraction of Zr can be 0.2%.

[0045] The neodymium iron boron alloy of the present invention preferably includes 0.1-0.3% Ti by mass fraction. In a specific embodiment of the present invention, the mass fraction of the Ti element can be 0.2%.

[0046] The neodymium iron boron alloy of the present invention preferably includes 0-5% niobium by mass fraction. In specific embodiments of the present invention, the mass fraction of niobium can be 1%, 2%, 3% or 4%.

[0047] The neodymium iron boron alloy of the present invention preferably includes 0-5% yttrium by mass fraction. In specific embodiments of the present invention, the mass fraction of yttrium may be 1%, 2%, 3% or 4%.

[0048] The neodymium iron boron alloy of the present invention preferably includes the balance Fe by mass fraction.

[0049] In this invention, the hydrogen crushing preferably includes sequential hydrogen absorption and dehydrogenation.

[0050] In this invention, the hydrogen pressure during hydrogen absorption is preferably 0.1~0.2 MPa, and the hydrogen absorption time is preferably 45~110 min. In specific embodiments of this invention, it can be 50 min, 55 min, 60 min, 65 min, 70 min, 75 min, 80 min, 85 min, 90 min, 95 min, 100 min, or 105 min.

[0051] In this invention, the dehydrogenation temperature is preferably 450~550℃, the vacuum degree is ≤50Pa, and the holding time is ≥10h. In specific embodiments of this invention, the dehydrogenation temperature can be 460℃, 470℃, 480℃, 490℃, 500℃, 510℃, 520℃, 530℃ or 540℃, the vacuum degree can be 10Pa, 20Pa, 30Pa or 40Pa, and the holding time can be 20h, 30h, 40h, 50h or 60h.

[0052] After hydrogen crushing, the present invention preferably further includes: subjecting the powder obtained from hydrogen crushing to air jet milling to obtain the magnetic powder.

[0053] In this invention, the grinding pressure during air jet milling is preferably 5~5.5MPa, the sorting wheel speed is preferably 2000~5000rpm, and the powder output speed is preferably 200~300kg / h. In specific embodiments of this invention, the grinding pressure can be 5.1MPa, 5.2MPa, 5.3MPa, or 5.4MPa, the sorting wheel speed can be 2500rpm, 3500rpm, 4000rpm, or 4500rpm, and the powder output speed can be 220kg / h, 250kg / h, or 280kg / h.

[0054] In this invention, the magnetic powder has an average surface area diameter of 2.4~3.2μm and a particle size distribution D90 / D10 of 4.2~4.5. The significance of D90 / D10: distribution width (span), quantitatively describing the uniformity of particle size distribution.

[0055] After obtaining the magnetic powder, the present invention orients and shapes the magnetic powder to obtain a green body.

[0056] In this invention, the magnetic induction intensity during orientation molding is preferably ≥1.8T, and the molding pressure is preferably 4~8MPa. In specific embodiments of this invention, the magnetic induction intensity can be 2T, and the molding pressure can be 5MPa, 6MPa, or 7MPa.

[0057] In this invention, the density of the green body is preferably 4.0~4.5 g / cm³. 3 .

[0058] After obtaining the green blank, the present invention sinters and tempers the green blank to obtain the neodymium iron boron permanent magnet.

[0059] In this invention, the sintering temperature is preferably 1000~1050℃, the holding time is preferably 2~5h, and the vacuum degree is preferably less than 5×10⁻⁶. -2 Pa, in a specific embodiment of the present invention, the sintering temperature can be 1010℃, 1020℃, 1030℃ or 1040℃.

[0060] In this invention, the process after sintering and before tempering further includes cooling the sintered green body with a protective gas.

[0061] In this invention, the tempering preferably includes a first-stage tempering process, cooling, and a second-stage tempering process performed sequentially.

[0062] In this invention, the vacuum degree of the first-stage tempering treatment is preferably below 1 Pa, the temperature is preferably 890~920℃, and the time is preferably 1.5~2.5h; In this invention, the gas used for cooling preferably includes an inert gas.

[0063] In this invention, the vacuum degree of the secondary tempering process is preferably below 1 Pa, the temperature is preferably 400~550℃, and the time is preferably 4~6h.

[0064] After the tempering is completed, the product is preferably cooled.

[0065] The following detailed description of the preparation method of the neodymium iron boron permanent magnet provided by the present invention, in conjunction with the embodiments, should not be construed as limiting the scope of protection of the present invention.

[0066] Example 1 Preparation of Ce 33 Fe 67 Alloy sheet, providing Ce 33 Fe 67 The alloy sheet raw material, by mass fraction, comprises Pr 2.5%, Nd 7.5%, Ce 23%, Co 0.3%, Ga 0.1%, Al 0.3%, Cu 0.4%, B 0.9%, Zr 0.2%, Ti 0.3%, with the balance being Fe.

[0067] We provide sintered NdFeB alloy scrap with the following composition: Pr 5.03%, Nd 15.1%, Ce 10.3%, Gd 1.02%, Co 0.24%, Ga 0.08%, Al 0.36%, Cu 0.17%, B 0.895%, Zr 0.24%, Ti 0.12%, Nb 0.11%, Y 1.65%, and the balance Fe.

[0068] The alloy sheet raw material (PrNd alloy (Pr mass fraction of 25%), and other elemental metals or alloys) is refined and cast to obtain a rapidly solidified cast sheet. The refining conditions are: refining temperature of 1230±5℃ and refining time of 10 min; the casting conditions are: casting temperature of 1110±5℃ and copper roller speed of 75 rpm; the cooling method is argon-filled air cooling, and the cooling rate is 10±2℃ / min. The resulting rapidly solidified cast sheet has a thickness of 0.2~0.4 mm (with good thickness uniformity), a silvery-white appearance with a metallic luster, and a bright surface. The microstructure consists of fine, uniform, equiaxed main phase grains and Nd-rich phases uniformly distributed at the grain boundaries.

[0069] The alloy castings and the sintered NdFeB alloy are mixed at a weight ratio of 1:1 and hydrogen-crushed to obtain coarse hydrogen-crushed powder. The coarse hydrogen-crushed powder is obtained by hydrogen absorption and dehydrogenation in a hydrogen crushing furnace. The rapidly solidified castings obtained by the rapid solidification and spinning process are loaded into the reactor of the hydrogen crushing furnace, ensuring that the reactor is well sealed to prepare for the subsequent creation of a controllable hydrogen environment. High-purity hydrogen at a certain pressure is introduced into the reactor, reacting with the hydrogen to generate hydrides, which generate huge stress inside the alloy, causing the alloy to fracture along grains and across grains. Key control parameters are required: hydrogen pressure 0.15 MPa, hydrogen absorption time 100 min, ensuring complete hydrogen saturation. After hydrogen absorption, dehydrogenation is required. This process decomposes the hydrides and releases hydrogen, but the fractured structure of the alloy is preserved. Key control parameters are required: dehydrogenation temperature 480℃, vacuum degree at the end of dehydrogenation 50 Pa, and holding time 10 h.

[0070] The hydrogen-crushed coarse powder is milled by air jet milling to obtain micron-sized magnetic powder. The milling pressure of air jet milling is 5 MPa and the powder output speed is 220 kg / h. The SMD (magnetic powder area average diameter) of the fine powder obtained after air jet milling is 2.45~2.55 μm and the particle size distribution D90 / D10 is 4.35~4.4.

[0071] The micron-sized magnetic powder was oriented and shaped into a green body using a magnetic field forming press. The pressing was performed under conditions of a magnetic induction intensity of 1.9 T and a forming pressure of 5 MPa. The density of the green body obtained after orientation forming was 4.32 g / cm³. 3 .

[0072] The green blank is sintered and tempered in a vacuum sintering furnace to obtain a sintered body, wherein the vacuum degree of sintering is 5×10⁻⁶. -2 The process involves applying a vacuum of 1 Pa to a temperature of 1010℃ for 3 hours, followed by argon cooling and tempering. The tempering process is divided into a first-stage tempering process and a second-stage tempering process. The first-stage tempering process has a vacuum of 1 Pa, a temperature of 900℃, and a tempering time of 2 hours, followed by nitrogen cooling after the holding period. The second-stage tempering process has a vacuum of 1 Pa, a temperature of 425℃, and a tempering time of 5 hours, followed by nitrogen cooling after the holding period, resulting in a regenerated NdFeB permanent magnet with N35 performance.

[0073] Table 1 Performance parameters of the sample obtained in Example 1

[0074] Example 2 Preparation of Ce 33 Fe 67 Alloy sheet, providing Ce 33 Fe 67 The alloy sheet raw material, by mass percentage, comprises Pr 3.75%, Nd 11.25%, Ce 18%, Co 0.2%, Ga 0.15%, Al 0.2%, Cu 0.3%, B 0.93%, Zr 0.3%, Ti 0.2%, with the balance being Fe.

[0075] We provide sintered NdFeB alloy scrap with the following composition: Pr 6.3%, Nd 18.8%, Ce 4.9%, Gd 0.85%, Co 0.31%, Ga 0.08%, Al 1.1%, Cu 0.23%, B 0.88%, Zr 0.1%, and Ti 0.14%.

[0076] The alloy sheet raw material (PrNd alloy (Pr mass fraction of 25%), and other elemental metals or alloys) is refined and cast to obtain a rapidly solidified cast sheet. The refining conditions are: refining temperature of 1250±5℃ and refining time of 10min. The casting conditions are: melting the auxiliary alloy raw material to obtain an auxiliary alloy cast sheet; casting temperature of 1160±5℃ and copper roller speed of 75rpm; cooling method is argon-filled air cooling, and the cooling rate is 10±2℃ / min. The resulting rapidly solidified cast sheet is required to have a uniform and stable thickness between 0.2 and 0.4mm, a silvery-white appearance with a metallic luster and a bright surface, and a microstructure consisting of fine, uniform, equiaxed main phase grains and Nd-rich phases uniformly distributed at the grain boundaries.

[0077] The alloy castings and sintered NdFeB alloy waste are mixed at a weight ratio of 1:1 and hydrogen-crushed to obtain coarse hydrogen-crushed powder. The coarse hydrogen-crushed powder is obtained by hydrogen absorption and dehydrogenation in a hydrogen crushing furnace. The rapidly solidified castings obtained by the rapid solidification and spinning process are loaded into the reactor of the hydrogen crushing furnace, ensuring that the reactor is well sealed to prepare for the subsequent creation of a controllable hydrogen environment. High-purity hydrogen at a certain pressure is introduced into the reactor, reacting with the hydrogen to generate hydrides, which generate huge stress inside the alloy, causing the alloy to fracture along grains and across grains. The key control parameters are: hydrogen pressure 0.15 MPa, hydrogen absorption time 110 min, to ensure complete hydrogen saturation. After hydrogen absorption, dehydrogenation is required. This process decomposes the hydrides and releases hydrogen, but the fractured structure of the alloy is preserved. The key control parameters are: dehydrogenation temperature 530℃, vacuum degree at the end of dehydrogenation 50 Pa, and holding time 10 h.

[0078] The hydrogen-crushed coarse powder was milled by air jet milling to obtain micron-sized magnetic powder. The air jet milling was carried out in the presence of an oxidant, with a milling pressure of 5.2 MPa and a powder output rate of 205 kg / h. The fine powder obtained after air jet milling had an SMD (magnetic powder area average diameter) of 2.4~2.45 μm and a particle size distribution D90 / D10 of 4.25~4.3.

[0079] The micron-sized magnetic powder is oriented and shaped into a green body using a magnetic field forming press. The pressing is performed under conditions where the magnetic induction intensity is 1.9T and the forming pressure is 4.5MPa. The density of the green body obtained after orientation forming is 4.15 g / cm³. 3 .

[0080] The green blank is sintered and tempered in a vacuum sintering furnace to obtain a sintered body, wherein the vacuum degree of sintering is 5×10⁻⁶. -2The process involves applying a vacuum of 1 Pa to a temperature of 1025℃ for 5 hours, followed by argon cooling and tempering. The tempering process consists of a first-stage tempering and a second-stage tempering. The first-stage tempering is performed at a vacuum of 1 Pa, a temperature of 910℃, and a tempering time of 2 hours, followed by nitrogen cooling after the holding period. The second-stage tempering is performed at a vacuum of 1 Pa, a temperature of 435℃, and a tempering time of 5 hours, followed by nitrogen cooling after the holding period. This process yields a regenerated NdFeB permanent magnet with N45 performance.

[0081] Table 2 Performance parameters of the samples obtained in Example 2

[0082] Example 3 Preparation of Ce 33 Fe 67 Alloy sheet, providing Ce 33 Fe 67 The alloy sheet raw material, by mass percentage, comprises Pr 5.4%, Nd 16.1%, Ce 11.5%, Co 0.3%, Ga 0.1%, Al 0.3%, Cu 0.4%, B 0.9%, Zr 0.2%, Ti 0.3%, with the balance being Fe.

[0083] We provide sintered NdFeB alloy scrap with the following composition: Pr 6.4%, Nd 19.05%, Ce 8.7%, Co 0.28%, Ga 0.11%, Al 0.06%, Cu 0.264%, B 0.902%, Zr 0.185%, Ti 0.124%, and the balance Fe.

[0084] The alloy raw material (PrNd alloy (Pr mass fraction of 25%) and other elemental metals or alloys) is refined and cast to obtain a rapidly solidified cast sheet. The refining conditions are: refining temperature of 1270±5℃ and refining time of 10min. The casting conditions are: melting the alloy raw material to obtain an alloy cast sheet; casting temperature of 1165±℃ and copper roller speed of 75rpm; cooling method is argon-filled air cooling, and the cooling rate is 10±2℃ / min. The resulting rapidly solidified cast sheet is required to have a uniform thickness between 0.2 and 0.4mm (good thickness consistency), a silvery-white appearance with a metallic luster and a bright surface, and a microstructure consisting of fine, uniform, equiaxed main phase grains and Nd-rich phases uniformly distributed at the grain boundaries.

[0085] The alloy castings and sintered NdFeB alloy waste are mixed at a weight ratio of 1:2 and hydrogen-crushed to obtain coarse hydrogen-crushed powder. The coarse hydrogen-crushed powder is obtained by hydrogen absorption and dehydrogenation in a hydrogen crushing furnace. The rapidly solidified castings obtained by the rapid solidification and spinning process are loaded into the reactor of the hydrogen crushing furnace. The reactor is sealed well to prepare for the subsequent creation of a controllable hydrogen environment. High-purity hydrogen at a certain pressure is introduced into the reactor to react with the hydrogen and generate hydrides, which generate huge stress inside the alloy, causing the alloy to fracture along grains and across grains. The key control parameters are: hydrogen pressure 0.15 MPa, hydrogen absorption time of 105 min to ensure hydrogen saturation, and ensuring complete hydrogen absorption. After hydrogen absorption, dehydrogenation is required. This process will decompose the hydrides and release hydrogen, but the fractured structure of the alloy is preserved. The key control parameters are: dehydrogenation temperature 515℃, vacuum degree at the end of dehydrogenation 50 Pa, and holding time 10 h.

[0086] The hydrogen-crushed coarse powder was milled by air jet milling to obtain micron-sized magnetic powder. The air jet milling was carried out in the presence of an oxidant, with a milling pressure of 5.3 MPa and a powder output rate of 206 kg / h. The fine powder obtained after air jet milling had an SMD (magnetic powder area average diameter) of 2.5~2.55 μm and a particle size distribution D90 / D10 of 4.26~4.29.

[0087] The micron-sized magnetic powder was oriented and shaped into a green body using a magnetic field forming press. The pressing was performed under conditions of a magnetic induction intensity of 1.9 T and a forming pressure of 4.3 MPa. The density of the green body obtained after orientation forming was 4.14 g / cm³. 3 .

[0088] The green blank is sintered and tempered in a vacuum sintering furnace to obtain a sintered body. The sintering conditions are a vacuum degree of 5 × 10⁻⁶. -2 The magnet is heated to 1040℃ for 3.5 hours, cooled by argon, and then tempered. The tempering process consists of a first-stage tempering process and a second-stage tempering process. The first-stage tempering process has a vacuum of 1 Pa, a temperature of 910℃, and a tempering time of 2 hours, and is cooled by nitrogen after holding. The second-stage tempering process has a vacuum of 1 Pa, a temperature of 455℃, and a tempering time of 5 hours, and is cooled by nitrogen after holding. This process yields a regenerated NdFeB permanent magnet with N48 performance.

[0089] Table 3 Performance parameters of the samples obtained in Example 3

[0090] Comparative Example 1 Compared with Implementation Example 1, an alloy sheet is prepared according to the composition of the raw materials after mixing the alloy sheet and the scrap. The raw materials of the alloy sheet are: Pr 3.76%, Nd 11.30%, Ce 16.65%, Gd 0.51%, Co 0.27%, Ga 0.09%, Al 0.33%, Cu 0.285%, B 0.8975%, Zr 0.22%, Ti 0.21%, Nb 0.055%, Y 0.825%, and the balance Fe.

[0091] The alloy sheet raw material (PrNd alloy (Pr mass fraction of 25%), elemental metal or alloy) is refined and cast to obtain a rapidly solidified cast sheet. The refining conditions are: refining temperature of 1230±5℃, refining time of 10min; the casting conditions are: casting temperature of 1110±5℃, copper roller speed of 75rpm; the cooling method is argon-filled air cooling, and the cooling rate is 10±2℃ / min. The resulting rapidly solidified cast sheet has a thickness of 0.2~0.4mm (good thickness uniformity), a silvery-white appearance with a metallic luster, and a bright surface. The microstructure consists of fine, uniform, equiaxed main phase grains and Nd-rich phases uniformly distributed at the grain boundaries.

[0092] The alloy castings are hydrogen-crushed to obtain coarse hydrogen-crushed powder. This coarse powder is obtained by hydrogen absorption and dehydrogenation in a hydrogen crushing furnace. The rapidly solidified castings obtained by the rapid solidification and spinning process are loaded into the reactor of the hydrogen crushing furnace. The reactor is sealed well to prepare for creating a controllable hydrogen environment. High-purity hydrogen at a certain pressure is introduced into the reactor. The hydrogen reacts with the hydrogen to generate hydrides, which generate huge stress inside the alloy, causing intergranular and transgranular fractures. Key control parameters are: hydrogen pressure 0.15 MPa, hydrogen absorption time 100 min, and ensuring complete hydrogen saturation. After hydrogen absorption, dehydrogenation is required. This process decomposes the hydrides and releases hydrogen, but the fractured structure of the alloy is preserved. Key control parameters are: dehydrogenation temperature 480℃, vacuum degree at the end of dehydrogenation 50 Pa, and holding time 10 h.

[0093] The hydrogen-crushed coarse powder was milled by air jet milling to obtain micron-sized magnetic powder. The milling pressure of the air jet milling was 5 MPa and the powder output speed was 206 kg / h. The SMD (spot diameter of magnetic powder area) of the fine powder obtained after air jet milling was 2.45~2.55 μm and the particle size distribution D90 / D10 was 4.39.

[0094] The micron-sized magnetic powder was oriented and shaped into a green body using a magnetic field forming press. The pressing was performed under conditions of a magnetic induction intensity of 1.9 T and a forming pressure of 5 MPa. The density of the green body obtained after orientation forming was 4.32 g / cm³. 3 .

[0095] The green blank is sintered and tempered in a vacuum sintering furnace to obtain a sintered body, wherein the vacuum degree of sintering is 5×10⁻⁶. -2 The process involves applying a vacuum of 1 Pa to a temperature of 1010℃ for 3 hours, followed by argon cooling and tempering. The tempering process is divided into a first-stage tempering process and a second-stage tempering process. The first-stage tempering process has a vacuum of 1 Pa, a temperature of 900℃, and a tempering time of 2 hours, followed by nitrogen cooling after the holding period. The second-stage tempering process has a vacuum of 1 Pa, a temperature of 425℃, and a tempering time of 5 hours, followed by nitrogen cooling after the holding period, resulting in a regenerated NdFeB permanent magnet with N35 performance.

[0096] Table 4 Performance parameters of the samples obtained in Comparative Example 1

[0097] Compared with samples 10-11, this invention can significantly improve the performance data compared with the traditional process, with an increase of 1.82% in Br and 4.55% in Hcj.

[0098] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a regenerated sintered NdFeB permanent magnet, characterized in that, Includes the following steps: Ce 33 Fe 67 The alloy was mixed with neodymium iron boron alloy and then subjected to hydrogen crushing to obtain magnetic powder; The magnetic powder is oriented and shaped to obtain a green body; The green blank is sintered and tempered to obtain the regenerated sintered NdFeB permanent magnet. The neodymium iron boron alloy includes scrap.

2. The preparation method according to claim 1, characterized in that, In terms of mass fraction, the Ce 33 Fe 67 Alloys include the following elements: Pr 2.5~5.5%, Nd 7.5~16.5%, Ce 10~25%, Co 0.1~0.8%, Ga 0.1~0.5%, Al 0.1~0.5%, Cu 0.2~0.5%, B 0.8~1.2%, Zr 0.1~0.5%, Ti 0.1~0.5%, balance Fe.

3. The preparation method according to claim 1, characterized in that, The neodymium iron boron alloy comprises the following elements by mass fraction: Pr 3.75~7.5%, Nd 11.25~22.5%, Ce 0~15%, Gd 0~2%, Ho 0~2%, Co 0.1~0.4%, Ga 0~0.5%, Al 0~1.5%, Cu 0.1~0.4%, B 0.8~1.2%, Zr 0.1~0.3%, Ti 0.1~0.3%, niobium 0~5%, yttrium 0~5%, balance Fe.

4. The preparation method according to claim 1, characterized in that, The Ce 33 Fe 67 The mass ratio of the alloy to the NdFeB alloy is 1:1~2.

5. The preparation method according to claim 1, characterized in that, The hydrogen crushing process includes sequential hydrogen absorption and dehydrogenation. The hydrogen pressure during absorption is 0.1~0.2 MPa, and the absorption time is 45~110 min. The dehydrogenation temperature is 450~550℃, the vacuum degree is ≤50pa, and the holding time is ≥10h.

6. The preparation method according to claim 1, characterized in that, The process after hydrogen crushing also includes: grinding the powder obtained from hydrogen crushing into powder using air jet milling to obtain the magnetic powder; The grinding pressure during airflow milling is 5~5.5MPa, the sorting wheel speed is 2000~5000rpm, and the powder output speed is 200~300kg / h; The magnetic powder has an average surface area diameter of 2.4~3.2μm and a particle size distribution D90 / D10 of 4.2~4.

5.

7. The preparation method according to claim 1, characterized in that, The magnetic induction intensity during the orientation molding process is ≥1.8T, and the molding pressure is 4~8MPa; The density of the green body is 4.0~4.5 g / cm³. 3 .

8. The preparation method according to claim 1, characterized in that, The sintering temperature is 1000~1050℃, and the holding time is 2~5h; The vacuum degree of the sintering is 5×10⁻⁶. -2 Below Pa.

9. The preparation method according to claim 1, characterized in that, The process after sintering and before tempering also includes cooling the sintered green body with a protective gas.

10. The preparation method according to claim 1, characterized in that, The tempering process includes sequentially performing a first-stage tempering process, cooling, and a second-stage tempering process. The vacuum degree of the first-stage tempering process is below 1 Pa, the temperature is 890~920℃, and the time is 1.5~2.5h. The gas used for cooling includes an inert gas; The vacuum degree of the secondary tempering process is below 1 Pa, the temperature is 400~550℃, and the time is 4~6h.

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