WO2017133609A1

WO2017133609A1 - Manufacturing method for neodymium-iron-boron magnet

Info

Publication number: WO2017133609A1
Application number: PCT/CN2017/072550
Authority: WO
Inventors: 李忠
Original assignee: 李忠
Priority date: 2016-02-04
Filing date: 2017-01-25
Publication date: 2017-08-10
Also published as: CN105741994A; CN105741994B

Abstract

Disclosed is a manufacturing method for a neodymium-iron-boron magnet, comprising the following steps: step S1, preparing a neodymium-iron-boron preparation powder; step S2, pressing the neodymium-iron-boron preparation powder in an aligning magnetic field to obtain an initial rough body; then demagnetizing, and pressing the initial rough body at a pressure of 100-1500 MPa to obtain a green body; then machining the green body to obtain a shape of a final product of the neodymium-iron-boron magnet; and step S3, sintering the machined green body to obtain a neodymium-iron-boron magnet final product. The manufacturing method for the neodymium-iron-boron magnet of the invention realizes the preparation process of the neodymium-iron-boron magnet with almost no loss, greatly improves the magnetic performance and corrosion resistance of the neodymium-iron-boron magnet, and is very practical.

Description

Title: A method for producing a neodymium iron boron magnet

[0001] The present invention relates to the field of preparation of powder compacts, including metal powder metallurgy, ceramics, ferrites, etc.

In particular, it relates to a method for fabricating a neodymium iron boron magnet.

Background technique

[0002] NdFeB magnets are called "Magnetic King" and have the highest remanence and magnetic energy products of various types of permanent magnet materials. They also have high coercivity, with the performance of commercial NdFeB magnets. Raise, NdFeB devices are moving toward small, ultra-thin, and special-shaped; NdFeB products with a weight of less than 5 grams account for more than 80% of all products, such as NdFeB magnets in some smartphones, their magnets The thickness is only 0.5mm.

[0003] The conventional production process of NdFeB magnets includes the following steps: batching, alloy smelting, casting, pressing, pressing, vacuum sintering, cutting, grinding, and surface treatment. The NdFeB magnet prepared by the conventional production method has the following characteristics:

[0004] 1. The composition of the NdFeB is relatively hard and brittle, and the pressure of the die is too large to be easily delaminated and cracked. Therefore, for the pressed billet before sintering in the prior art, the density is 3-5.5 g/cm 3 , which is only 40-70% of the density of the product after sintering (the density of the NdFeB magnet obtained by sintering is 7.2-7.65 g/cm ³ ) ; plus the NdFeB sintering process is liquid phase sintering, if the product shrinks too much during the sintering process, it is more easily deformed. At the same time, the excessive shrinkage caused by the prior art also affects the orientation degree and the intrinsic coercive force of the NdFeB magnet.

[0005] 2, NdFeB configuration powder particle size is only 2-5μηι, poor fluidity, low mold packing density, that is, using granulation method to improve; the "granules" made, is a fine powder agglomerate, not dense The metal particles, the packing density is only increased to 2 g/cm 3 , and the pressing improvement effect is not obvious. It is very difficult and inefficient to suppress small precision devices.

[0006] 3. When the neodymium iron boron magnet is press-formed, a magnetic field of 1 T or more is required to orient the powder, and the mold is complicated, so that the pressing of the small device is very difficult.

[0007] 4. The production of NdFeB magnets with a high magnetic energy product above N45 needs to control the oxygen content of the finished product to within 3000 PPM, while the NdFeB powder is highly oxidizable and even self-igniting in the air. Therefore, it is a common practice to seal the entire press forming process, which further complicates the forming process. [0008] Based on the above reasons, the current small NdFeB magnets are cut and ground by the sintered bulk material; the surface of the NdFeB magnet with a larger ratio of surface area to volume is mechanically processed. The comprehensive magnetic properties of the crystal structure damage are more obvious. According to the specific surface area of the NdFeB magnets, the comprehensive magnetic properties are reduced by 5-40%. In response to this problem, techniques for recovering the properties of NdFeB magnets by sputtering, plating, heating, and reduction diffusion into the ruthenium, osmium, and ruthenium metal repair crystal structures have been developed to restore the performance of NdFeB magnets. The technically prepared NdFeB products are costly and have poor consistency. In addition, NdFeB magnets are prone to rust, and complex and expensive processes such as electroless plating, epoxy plating, and sputtering aluminum plating have been developed. The corrosion of NdFeB magnets is also closely related to the surface it is machined to damage.

[0009] In addition, the cutting wear loss rate of small NdFeB magnets is 20-60<3⁄4; waste sludge produced by cutting and grinding (mixture of cutting oil and NdFeB in cutting and grinding) is recovered after long-distance transportation. (Because of serious pollution, recycling waste sludge is often carried out in remote places away from NdFeB plants, it is difficult to regulate), oxidative burning, concentrated acid dissolution, sedimentation separation, large amount of water and washing, rare earth element extraction separation, reprecipitation washing, burning The chemical process of burning rare earth oxides, and re-electrolytic smelting into rare earth metals and other complicated steps, the whole process causes 20% of the rare earth materials can not be recovered, and produces a large amount of extremely difficult to treat waste oil wastewater, one ton of ferroniobium The boron waste sludge recovery process produces about 1000 tons of waste acid wastewater. At present, China's NdFeB magnets produce about 110,000 tons, waste mud reaches 50,000 tons, waste acid wastewater exceeds 50 million tons, and the amount of pollutants produced is huge.

technical problem

Problem solution

Technical solution

[0010] The present invention is directed to the problem that in the preparation process of the existing NdFeB magnet, the mechanical processing step causes damage to the surface of the NdFeB magnet, and the same amount of waste is brought about by the same, and a NdFeB magnet is proposed. Production method.

[0011] The present invention provides a method for fabricating a neodymium iron boron magnet, comprising the following steps:

[0012] Step S1, preparing a NdFeB configuration powder;

[0013] Step S2, pressing the NdFeB configuration powder into the initial blank under the magnetic field orientation condition; then demagnetizing, and pressing the initial blank into a green body under a pressure of 100 MPa to 1500 MPa; and then machining the green body The shape of the final product of the bismuth iron-boron magnet; [0014] Step S3, sintering the machined green body into a final product of a neodymium iron boron magnet.

[0015] In the above method for fabricating the neodymium iron boron magnet of the present invention, the step S1 includes:

[0016] weigh 29-35wt% R, 0-4 wt% M. 0.9-1.1 wt% B and 59.9-70.1 wt <3⁄4Fe, and mix; here, R is La, Ce, Pr, Nd, Gd, One or more of Ho, Tb, and Dy; M is Co, Al,

One or more of Cu, Zr, Ga, Nb; the mixed NdFeB material is vacuum smelted, ingot or sputum, and the NdFeB configuration powder is obtained by hydrogen explosion or direct milling.

[0017] In the above method for fabricating the neodymium iron boron magnet of the present invention, in step S2, the machining process includes cutting

One or more steps in grinding, cylindrical grinding, drilling and boring.

[0018] In the above method for producing a neodymium iron boron magnet according to the present invention, the mechanical processing is carried out in an inert atmosphere or a protective oil.

[0019] In the above method for manufacturing a neodymium iron boron magnet according to the present invention, the dust generated during the mechanical processing is filtered and mixed into the NdFeB configuration powder; the edge material produced during the mechanical processing is crushed. , mixed into the NdFeB configuration powder.

[0020] In the above method for manufacturing a neodymium iron boron magnet according to the present invention, in step S3, the machined green body is clamped on a jig, placed in a cartridge, and then sintered together in a vacuum sintering furnace. ; or

[0021] The machined green body is buried with a powder that does not react with the green body, and is sintered together in a vacuum sintering furnace.

[0022] In the above method for manufacturing a neodymium iron boron magnet according to the present invention, a plurality of mechanically processed green layers are laminated tightly

, and the green sheets are padded between the green sheets, and then placed in a vacuum sintering furnace for sintering.

[0023] In the method for fabricating the above-described neodymium iron boron magnet of the present invention, step S3 further includes:

[0024] Fixing the sintered neodymium iron boron magnet with a clamp, and applying external force to press, and holding together at 300 ° C - 12 00 ° C for more than 20 min; then holding at 300 ° C - 700 ° C for 20 min In the above, the shape of the neodymium iron boron magnet is matched with the shape of the jig, and finally the neodymium iron boron magnet is cooled to room temperature to obtain the final product of the neodymium iron boron magnet.

[0025] In the above method for fabricating a neodymium iron boron magnet according to the present invention, the jig is a flat bottom structure, a concave-convex curved surface structure or a hollow support rod structure.

[0026] In the above method for producing a neodymium iron boron magnet according to the present invention, in step S3, a reducing agent is placed in a vacuum sintering furnace together with the machined green body; the reducing agent includes metal calcium, magnesium metal Metal sodium, One or more of calcium hydride, magnesium hydride, and sodium hydride.

Advantageous effects of the invention

Beneficial effect

[0027] The method for preparing a neodymium iron boron magnet of the present invention uses a pressure of 100 MPa to 1500 MPa to press a raw material of niobium, iron, boron and the like into a high-density green body by dosing, vacuum melting and powdering of the NdFeB powder. Then, the green body is machined to form the shape of the final product, and then sintered into a final product, which realizes almost no loss in the preparation process of the NdFeB magnet, and the magnetic properties and resistance of the NdFeB magnet are greatly improved. Corrosion performance, practicality.

Invention embodiment

Embodiments of the invention

[0028] The technical problem to be solved by the present invention is: In the preparation process of the existing NdFeB magnet, the mechanical processing step causes damage to the surface of the NdFeB magnet, and the same amount of waste is brought. With regard to this technical problem, the technical idea proposed by the present invention is: using a pressure of 100 MPa to 1500 MPa to press a raw material of niobium, iron, boron and the like into a high-density raw material by subjecting, vacuum melting and powdering of the NdFeB powder. The blank is then machined to form the shape of the final product and then sintered into the final product.

[0029] Specifically, the method for fabricating the neodymium iron boron magnet of the present invention comprises the following steps:

[0030] Step S1, preparing a NdFeB configuration powder;

[0031] This step S1 comprises batching, vacuum melting, ingot or ribbon, and a milling step. Specifically, the compounding process is: weigh 29-35 wt% R, 0-4 wt<3⁄4M, 0.9-1.1 wt% B, and 59.9-70.1 wt% Fe, and mix; here, R is La, Ce, Pr One or more of Nd, Gd, Ho, Tb, and Dy; M is one or more of Co, Al, Cu, Zr, Ga, and Nb. The prepared NdFeB material is subjected to vacuum melting, ingot casting or boring, and the NdFeB configuration powder is obtained by hydrogen explosion or direct milling; here, the particle size of the NdFeB configuration powder is generally 2-5 μm.

[0032] Step S2, pressing the NdFeB configuration powder into the initial blank under the magnetic field orientation condition (where the magnetic field strength is 1.2T-3.0T); then demagnetizing, and the initial blank is under the pressure of 100MPa-1500MPa Pressing into a green body; then machining the green body into a shape of a final product of a neodymium iron boron magnet;

[0033] In this step, the green body is hydroformed by a hard molding or a rubber molding using a hard molding or a rubber molding under a magnetic field orientation condition. The green body prepared under high pressure has high density and high strength, which can be followed. Machining. After testing, the pressure pressure and the green density have the following correspondence:

[] [Table 1]

[0034] In contrast to the present invention, the pressure pressure used in the conventional pressing process is generally less than 300 MPa, and the resulting green density is generally 3-4.9 g/cm, which results in a large porosity of the green body obtained by the conventional pressing process. The contact area with air is also large, and it is easily oxidized during subsequent processing, handling, and furnace loading. These conditions cause excessive deformation of the sintering shrinkage rate. At the same time, the green body obtained by the conventional pressing process has low strength and cannot be machined.

[0035] Further, in this step, the green body obtained by pressing at a pressure of 100 MPa to 1500 MPa can be cut, ground, externally ground, and drilled after being clamped or bonded to the corresponding fixture. , boring and other mechanical processing. Here, the machining process needs to be carried out under an inert atmosphere (nitrogen, argon or carbon dioxide atmosphere) or in a special protective oil. The waste generated by machining can be filtered and/or pulverized and reused without re-pulping. Specifically, the dust generated during the mechanical processing may be mixed into the NdFeB configuration powder after being filtered; the edge material generated during the mechanical processing may be mixed into the NdFeB configuration powder after being pulverized.

[0036] Step S3, sintering the machined green body into a final product of a neodymium iron boron magnet.

[0037] In this step, the green body obtained in the step S2 has a high density and a small porosity, and the oxidation rate is greatly reduced when it is exposed to the air. At the same time, due to the high density and small shrinkage, the deformation of the product is greatly reduced. When the green body is installed, it can be placed in the material box together with the jig, or it can be buried and supported by the conventional powder metallurgy burying technology (adding the powder which does not react with the green body). For ultra-thin, ultra-fine and other easily deformable blanks, The furnace is reshaped during the aging heat treatment after sintering. Here, the powder to be buried in the green body is alumina, graphite, calcium oxide, zirconium oxide, magnesium oxide or rare earth oxide. In addition, a plurality of machined green layers may be laminated tightly, and the green sheets are padded between them, and then placed together in a vacuum sintering furnace for sintering. Here, the spacer may be a metal foil, a paper, a ceramic sheet, graphite or the like.

[0038] In this step, after the sintering of the neodymium-iron-boron magnet is completed, the neodymium-iron-boron magnet is fixed by a clamp, and external force is applied, and the same is maintained at 300 ° C - 1200 ° C for 20 min or more. Secondary heat treatment; then tempered at 300 ° C - 700 ° C for more than 20 min, a second aging heat treatment, the shape of the NdFeB magnet is consistent with the shape of the fixture, and finally the NdFeB magnet is cooled to room temperature, The final product of the NdFeB magnet is obtained. Here, the heat-treated heat treatment process also softens the NdFeB magnet through high temperature to make it fit with the fixture, which serves the purpose of shaping the NdFeB magnet. Here, the jig may be a flat bottom structure, a concave-convex curved structure or a hollow support rod structure. Here, the aging treatment can also use the conventional method to directly cool the neodymium iron boron magnet at the sintering temperature to 300 ° C - 1200 ° C for more than 20 min to complete the first aging heat treatment; then cool to 300 ° C - The second aging heat treatment is completed by holding at 700 ° C for more than 20 min. This traditional aging treatment is suitable for products that require less precision.

[0039] Preferably, in this step, the reducing agent may also be placed into the vacuum sintering furnace together with the machined green body; the reducing agent includes metal calcium, magnesium metal, sodium metal, calcium hydride, hydrogenation One or more of magnesium and sodium hydride. The reducing agent can improve the sintering atmosphere and prevent the billet from oxidizing during sintering.

[0040] The present invention will be further described in detail below in conjunction with the specific embodiments in order to facilitate the understanding of the invention.

First Embodiment

[0042] Weigh the NdFeB material with 29 wt% Pr-Nd alloy, 2 wt% Gd, 0.5 wt% Co, 1.0 wt% Al, 0.2 wt<3⁄4 Cu, 0.9 wt% BU, and 66.4 wt% Fe, and under vacuum The smelting is carried out in a vacuum melting furnace of 0.3-0.8 Pa to prepare a bismuth iron-boron argon crucible having a melting temperature of 1500 ° C. The cerium-iron-boron argon is then subjected to hydrogen pulverization to obtain a cerium-iron-boron configuration coarse powder. Here, during the hydrogen pulverization process, the dehydrogenation temperature is 540 ° C, and the dehydrogenation time is 4.5 h. Then, the NdFeB configuration coarse powder was subjected to multiple air jet milling to obtain a NdFeB configuration powder having a particle size of 3 μm.

[0043] Under the magnetic field orientation condition, the NdFeB configuration powder is preliminarily pressed and formed by a hard mold, and then demagnetized, where the pressure of the preliminary pressing is 20 MPa; and the pressure is further pressurized to 700 MPa for isostatic pressing to prepare a green body. [0044] The green body is taken, and the two faces are ground by an automatic grinder under an inert atmosphere, and fixed on the material plate. At this time, the size of the green body is 100 mm×100 mm×25.6 mm _; then, the green body is placed on the cutting machine. It is processed into a sheet material having a size of 25.7 mm x 14.1 mm x 1.8 mm. After chamfer polishing, it is placed in a sintered box, buried with ceramic powder, and placed together in a vacuum sintering furnace; the vacuum in the vacuum sintering furnace is pumped to less than 0.2 Pa, and then heated in a vacuum sintering furnace After heating to 500 ° C for 2 h _; then, the temperature was raised to 1100 ° C in a vacuum sintering furnace, kept for 4 h, and then cooled to room temperature to complete the sintering step.

[0045] Next, the NdFeB magnet that completes the sintering step is taken out, and the NdFeB magnet is fixed by a clamp, and is pressed by an external force, and then placed in a vacuum sintering furnace to evacuate the vacuum in the vacuum sintering furnace. To less than 0.2Pa, then heat up to 900 ° C, and keep warm for 2h, complete the first aging treatment; After that, the vacuum sintering furnace is again filled with argon gas, the vacuum sintering furnace is rapidly cooled to 300 ° C, stop cooling The vacuum in the vacuum sintering furnace is pumped to less than 0.2 Pa, then the temperature is raised to 550 ° C, and the temperature is maintained for 2 h to complete the second treatment. Finally, the vacuum sintering furnace was filled with argon gas, and the inside of the vacuum sintering furnace was cooled to room temperature to obtain a final product of a neodymium iron boron magnet having a size of 25 mm x 14 mm x 1.5 mm.

[0046] Another green body of 100 mm×100 rmnx 25.6 mm size is placed in a sintering box and charged into a vacuum sintering furnace; the green body in the vacuum sintering furnace is sintered in the same manner as the final product of the NdFeB magnet of the present embodiment. The process and the aging treatment process were processed, and then cut into 25 mm x 14 mm x 1.5 mm flakes and 25 mm x 14 mm x 10 mm flakes by an inner circular slicer to obtain a final product of the control group.

[0047] Take the three final products of this example, and the final product of the 25mmxl4mmxl.5mm specification control group and the 25mmxl4mmx 10mm specification control group, and use the Chinese Metrology Institute NIM2000 magnetic tester for magnetic performance test. The results are as follows:

[0048]

[0049] It can be seen from the test results that the coercive force and the magnetic energy product of the final product of the NdFeB magnet of the present embodiment are significantly higher than those of the prior art, and it can also be seen that the prior art is produced. The thickness of the product is larger, and the coercive force and magnetic energy product loss are smaller.

[0050] In addition, the raw material loss of the final product of the NdFeB magnet of the present embodiment accounts for only 1.2% of the final product quality of the NdFeB magnet, because the green body of the final product is in the process of machining, powder. Adhered to the pipe and each station. For the final product of the control group, the loss of processing 1.5mm process accounted for 22% of the product quality, the loss of processing 14mm process accounted for 53⁄4> of the product quality, and the loss of processing 25mm process accounted for 6% of the product quality.

[0051] Meanwhile, the final product of the NdFeB magnet of the present embodiment which was not machined and the final product of the machined NdFeB magnet of the present example were subjected to a corrosion resistance test using a salt spray test.

[0052] Specifically, three final products of the neodymium iron boron magnet of the present embodiment are respectively polished and plated with a zinc layer of 8 μm, and at the same time, three final products of the neodymium iron boron magnet of the present embodiment are taken. Each surface was ground to 0.2 mm, then polished, and plated with a zinc layer of 8 μm.

[0053] Then, according to GB/T 10125-1997, three zinc-plated undieseled NdFeB magnets of the present embodiment and three zinc-plated layers are machined separately. The final product of the neodymium iron boron magnet of the present embodiment is subjected to a neutral salt spray test, and the corrosion resistance test results are as follows:

[0054]

[0055] From the above corrosion resistance test results, it can be seen that the corrosion resistance of the NdFeB magnet whose surface has not been subjected to mechanical processing is greatly improved as compared with the NdFeB magnet whose surface has been mechanically destroyed.

Second Embodiment

[0057] The product to be fabricated in this embodiment is a brushless DC motor magnetic tile of 39 _mm x 26 _m x 3.5 mm. The outer arc radius is 62 mm and the inner arc radius is 58.5 mm. The specific test process is as follows:

[0058] Weighing ferroniobium with 30wt<3⁄4Pr-Nd alloy, 2wt% Gd, 0.5wt<3⁄4Co, l.lwt<3⁄4B and 66.4wt% Fe The boron raw material is smelted in a vacuum melting furnace with a vacuum degree of 0.3-0.8 Pa to prepare a bismuth iron-boron argon crucible, and the smelting temperature is 1500 ° C; The NdFeB configuration coarse powder is obtained. Here, during the hydrogen pulverization process, the dehydrogenation temperature is 540 ° C, and the dehydrogenation time is 4.5 h. Then, the NdFeB configuration coarse powder was subjected to multiple air jet milling to obtain 2.5 (xm-diameter NdFeB configuration powder).

[0059] Under the magnetic field orientation condition, the NdFeB configuration powder is preliminarily pressed and formed by a rubber mold, and then demagnetized, where the pressure of the preliminary pressing is 20 MPa; and the pressure is further pressurized to 600 MPa for isostatic pressing to prepare a green body.

[0060] taking the green body, grinding the two faces by an automatic grinder under an inert atmosphere, and fixing on the material plate, at this time, the size of the green body is 100 mm×50 mm×28 mm; then, the green body is processed on a cutting machine. Arc blanks measuring 41.9 mm x 28 mm x 4.2 mm x R62 mm. After chamfer polishing, put it into the sinter box, use the graphite plate or other ceramic plate with the corresponding curvature on the surface as the padding, and put it into the vacuum sintering furnace together; pump the vacuum degree in the vacuum sintering furnace to less than 0.2Pa Then, the temperature of the vacuum sintering furnace was raised to 500 ° C and kept for 2 hours; then, the temperature was raised to 1080 ° C in the vacuum sintering furnace, kept for 4 hours, and then cooled to room temperature to complete the sintering step.

[0061] Next, the neodymium iron boron magnet that completes the sintering step is taken out, the neodymium iron boron magnet is fixed by a clamp, and an external force is pressed, and then placed in a vacuum sintering furnace, and the vacuum degree in the vacuum sintering furnace is pumped. To less than 0.2P a, then heat up to 900 ° C, and keep warm for 2h, complete the first effect treatment; after that, the vacuum sintering furnace is again filled with argon gas, and the vacuum sintering furnace is rapidly cooled to 310 ° C, The cooling was stopped, and the vacuum in the vacuum sintering furnace was pumped to less than 0.2 Pa, then the temperature was raised to 550 ° C, and the temperature was kept for 2 hours to complete the second treatment. Finally, the vacuum sintering furnace was filled with argon gas, and the inside of the vacuum sintering furnace was cooled to room temperature to obtain an arc shape of (39 mm soil 0.08 mm) x (26 mm ± 0.05 mm) x (3.5 mm ± 0.035 mm) x R62 mm. The body is then polished, and nickel-copper-nickel of ΙΟμπι is electroplated to obtain the final product of the neodymium-iron-boron magnet of the present embodiment.

[0062] Another 100 mm x 50 mm x 28 mm green body is placed in a sintered box, buried with ceramic powder, and placed together in a vacuum sintering furnace; the green body in the vacuum sintering furnace is the same as the neodymium iron boron magnet of the present embodiment. The final product is processed in the same sintering process and aging treatment process, and then cut into a 39mmx26mmx3.5mmxR62mm arc product by an inner circular slicer and a wire electric discharge machine, chamfered and polished, and electroplated with ΙΟμηη nickel-copper-nickel to obtain a control group. The final product.

[0063] In the entire manufacturing process, the raw material loss of the final product of the neodymium iron boron magnet of this embodiment only accounts for NdFeB magnetic The final product quality of the body is 3<3⁄4, because the final product is in the direction of 39mm, the dimension in the direction of 39mm exceeds the delivery standard ^mmiO.OSmm), and it needs to be processed by double-side grinding. The green body of the final product is adhered to the pipe and the various stations during the machining process. For the final product of the control group, the loss of the final product in the control group accounted for 35<3⁄4 of the product quality.

At the same time, the corrosion resistance test of the final product of the NdFeB magnet of the present example and the final product of the control group was also carried out by a salt spray test.

[0065] Specifically, the final products of the NdFeB magnets of the present embodiment and the final products of the control group were subjected to a neutral salt spray test according to the provisions of GB/T 10125-1997, and the corrosion resistance test results are as follows: :

[0066] [Number]

[0067] From the above corrosion resistance test results, it can be seen that the corrosion resistance of the NdFeB magnet whose surface has not been subjected to mechanical processing is greatly improved compared with the NdFeB magnet whose surface has been mechanically destroyed.

Third Embodiment

[0069] The NdFeB material was weighed with 29 wt<3⁄4 Pr-Nd alloy, 1.5 wt% Dy, 0.5 wt Co. 1.0 wt% Al, 0.2 wt% Cu, 0.9 wt B, and 66.9 wt% Fe, and the degree of vacuum was The smelting in a vacuum melting furnace of 0.3-O.SPa is carried out to prepare a bismuth iron-boron argon crucible, where the smelting temperature is 1500 ° C; and the yttrium-boron arranging material is crushed to obtain a neodymium iron boron configuration. The coarse powder, here, during the hydrogen pulverization process, the dehydrogenation temperature is 540 ° C, and the dehydrogenation time is 4.5 h. Then, the NdFeB configuration coarse powder was subjected to multiple air jet milling to obtain a NdFeB configuration powder having a particle size of 3 μm.

[0070] Under the magnetic field orientation condition, the NdFeB configuration powder is preliminarily pressed by a hard mold, where the pressure of the preliminary pressing is 20 MPa; then demagnetization, and then pressurized to 200 MPa for isostatic pressing, and made into a <J >12mmx40m m green body.

[0071] The green body is taken, and the green body is placed on a cutting machine under protective oil to form a circular sheet-like material having a size of U mm×1 mm. After chamfer polishing, put it into the sintering box, put it on the graphite or ceramic pad, and put it into the vacuum sintering furnace together; pump the vacuum in the vacuum sintering furnace to less than 0.2Pa, and then give it to the vacuum sintering furnace. Furnace The temperature was raised to 500 ° C and kept for 2 h. Then, the temperature was raised to 1070 ° C in a vacuum sintering furnace, and the temperature was kept for 4 h, and then cooled to 100 ° (:, the sintering step was completed.

[0072] Next, the sintered body is again placed in a vacuum sintering furnace, a flat pad is added to each layer of the blank, and a pressure is applied to the 10-layer pad by adding a stainless steel plate. The vacuum degree in the vacuum sintering furnace is pumped to less than 0.2 Pa, and then the temperature is raised to 900 ° C, and the temperature is kept for 2 hours to complete the first treatment and shaping; after that, the vacuum sintering furnace is again filled with argon gas to make the vacuum The furnace was rapidly cooled to 300 ° C, the cooling was stopped, and the vacuum in the vacuum sintering furnace was pumped to less than 0.2 Pa, then the temperature was raised to 550 ° C, and the temperature was kept for 2 hours to complete the second treatment. Finally, argon gas was charged into the vacuum sintering furnace, and the inside of the vacuum sintering furnace was cooled to room temperature to obtain a final product of NdFeB magnets having a size of OUmmxlmm.

[0073] Another green body having a size of Φ12 mm×40 mm is placed in a sintered box and placed together in a vacuum sintering furnace; the green body in the vacuum sintering furnace adopts the final product of the NdFeB magnet of the present embodiment. The same sintering process and aging treatment process, then the outer circle was ground to 12 mm with a centerless grinder, and cut into 2 mm x 1 mm pieces with an inner circular slicer to obtain a final product of the control group.

[0074] The raw material loss of the final product of the neodymium iron boron magnet of the present embodiment accounts for only 3% of the final product quality of the neodymium iron boron magnet. For the final product of the control group, the loss of the final product in the control process accounted for 37% of the product quality, of which the external wear loss accounted for 10% of the product quality, while the loss of the cutting process accounted for the product. The quality is 27<3⁄4. In addition, the pressure used in the pressing of the green body in the present embodiment is only 200 MPa, so that after the green body of the embodiment is processed, the damage rate is large, which affects the production efficiency of the product; therefore, the applicant The technical solution of the present embodiment is not recommended. In this embodiment, the method for producing the NdFeB of the present invention can also be realized only by demonstrating that the pressure of the pressed green body is 200 MPa.

[0075] The present invention is equally applicable to other products including powder compaction and sintering, such as ferrite, complex shape ceramics, cemented carbide, and the like. Depending on the product, the specific steps can be adjusted accordingly, but the core process of the present invention: Ultrahigh pressure and precision machining of the product prior to sintering is generally applicable.

[0076] It is to be understood that those skilled in the art can devise modifications or variations in the above description, and all such modifications and changes are intended to be included within the scope of the appended claims.

Claims

A method for fabricating a neodymium iron boron magnet, comprising the steps of: step S1, preparing a neodymium iron boron configuration powder;

Step S2: pressing the neodymium iron boron powder into an initial blank under magnetic field orientation; then demagnetizing, and pressing the initial blank into a green body under a pressure of 100 MPa to 1500 MPa; and then machining the green body into ferroniobium The shape of the final product of the boron magnet;

Step S3. Sintering the machined green body into a final product of a neodymium iron boron magnet.

The method of fabricating a neodymium iron boron magnet according to claim 1, wherein the step S1 comprises:

Weigh 29-35 wt% R, 0-4 wt<3⁄4M, 0.9-1.1 wt% B, and 59.9-70.1 wt% Fe, and mix the hook; where R is La, Ce, Pr, Nd, Gd, Ho, Tb And one or more of Dy; M is one or more of Co, Al, Cu, Zr, Ga, Nb; the mixed NdFeB material is subjected to vacuum melting, ingot casting or crucible Hydrogen explosion or direct milling to obtain a NdFeB configuration powder.

The method of manufacturing a neodymium iron boron magnet according to claim 1, wherein in step S2, the machining process comprises one or more steps of cutting, grinding, cylindrical grinding, drilling, and boring. .

The method of producing a neodymium iron boron magnet according to any one of claims 1 to 3, characterized in that the mechanical processing is carried out in an inert atmosphere or a protective oil.

The method for fabricating a neodymium iron boron magnet according to claim 4, wherein the powder generated during the mechanical processing is filtered and mixed into the powder of the NdFeB configuration; the edge material generated during the machining process After pulverization, it is mixed into the NdFeB configuration powder.

A method of fabricating a neodymium iron boron magnet according to claim 1, wherein in step S

In the third, the machined green body is clamped on the jig and placed in a cartridge, and then placed together in a vacuum sintering furnace for sintering; or

The machined green body is buried with a powder that does not react with the green body, and is sintered together in a vacuum sintering furnace.

A method of fabricating a neodymium iron boron magnet according to claim 1, wherein a plurality of blocks are used The machined green layer is laminated tightly, and the green sheets are padded between the green sheets, and then placed in a vacuum sintering furnace for sintering.

[Claim 8] The method of manufacturing the neodymium iron boron magnet according to claim 1, wherein the step S3 further comprises:

固定 Fix the sintered NdFeB magnet with a clamp and apply external force to press it together and keep it at 300°C-1200°C for more than 20min; then keep it at 300°C-700°C for more than 20min.

The shape of the NdFeB magnet is matched with the shape of the jig, and finally the NdFeB magnet is cooled to room temperature to obtain the final product of the NdFeB magnet.

[Claim 9] The method of manufacturing the neodymium iron boron magnet according to claim 8, wherein the jig is a flat bottom structure, a concave-convex curved surface structure, or a hollow support rod structure.

[Claim 10] The method of manufacturing the neodymium iron boron magnet according to claim 1, wherein in step S

In the third embodiment, the reducing agent is placed in the vacuum sintering furnace together with the machined green body; the reducing agent comprises one or more of metal calcium, metallic magnesium, metallic sodium, calcium hydride, magnesium hydride and sodium hydride. Kind.