A low-boron R-Fe-B permanent magnetic material and its preparation method

Abstract

The present invention provides a low-boron R-Fe-B permanent magnet material and a preparation method thereof, and belongs to the technical field of rare earth permanent magnet materials. The present invention crushes and dehydrogenates R-Fe-B-M alloy and grain boundary phase R-Ga-M alloy in sequence respectively, obtains coarse material and mixes with antioxidant, lubricant and dispersant, and then carries out press forming, cold isostatic pressing, vacuum degassing, vacuum low-temperature sintering and aging treatment. In the present invention, the content of R in the R-Fe-B-M alloy is 29wt%~36wt%, and the content of B element is 0.8wt%~0.96wt%, which belongs to an alloy with excessive rare earth elements and low B element content, which is conducive to producing more rare earth-rich grain boundary phases, and the R-Ga-M alloy has a low melting point, which is conducive to liquid phase sintering. In combination with vacuum degassing first, a pressure-assisted diffusion air pressure three-stage heating delay sintering process is used to obtain a low-boron R-Fe-B permanent magnet material.

Description

Technical Field

[0001] The present invention relates to the technical field of rare earth permanent magnet materials, and in particular to a low-boron R-Fe-B permanent magnet material and a preparation method thereof. Background Art

[0002] Nd-Fe-B rare earth permanent magnets are third-generation rare earth permanent magnets with excellent comprehensive magnetic properties, making them core functional materials. The rapid development of new energy vehicles, industrial servo motors, wind power generation, rail transit, and other sectors has fueled growing market demand for high-performance sintered NdFeB magnets.

[0003] The technical route for preparing NdFeB sintered magnets in related processes adopts a grain boundary diffusion process that can greatly improve the utilization efficiency of heavy rare earth resources. That is, the diffusion substrate is treated with grain boundary diffusion in the form of surface impregnation, electrophoretic deposition, evaporation and magnetron sputtering by a diffusion source containing heavy rare earth elements. After the grain boundary diffusion process, it is subjected to high-temperature sintering treatment and heat treatment to obtain permanent magnetic materials. However, there is a problem of high temperature sintering treatment, which is 1060~1085℃. Summary of the Invention

[0004] In view of this, the object of the present invention is to provide a low-boron R-Fe-B permanent magnet material and a preparation method thereof. The present invention can obtain the low-boron R-Fe-B permanent magnet material by vacuum low-temperature sintering.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing a low-boron R-Fe-B permanent magnetic material, comprising the following steps:

[0007] The R-Fe-BM alloy is subjected to a first crushing and a first dehydrogenation in sequence to obtain a coarse R-Fe-BM alloy; in the R-Fe-BM alloy, R is a rare earth element including one or more of Nd, Pr, La, Ce, Y and Sm, and M includes one or more of Cu, Al, Co, Ga, Ni, Ti, Nb, Zr, Ge, Zn, Sn, Ag, V, Cr, Mn, W, Mo and Si; the content of R in the R-Fe-BM alloy is 29wt%-36wt%, and the content of B element is 0.8wt%-0.96wt%;

[0008] The grain boundary phase R-Ga-M alloy is subjected to a second crushing and a second dehydrogenation in sequence to obtain a grain boundary phase R-Ga-M alloy coarse material; in the grain boundary phase R-Ga-M alloy, R is a rare earth element including one or more of Nd, Pr, La, Ce and Sm, and M includes one or more of Dy, Tb, Gd, Y and Ho, and the content of R in the grain boundary phase R-Ga-M alloy is 60wt%-90wt%, the content of Ga is 10wt%-20wt%, and the content of M is 0wt%-30wt% and is not 0wt%;

[0009] The R-Fe-BM alloy coarse material, the grain boundary phase R-Ga-M alloy coarse material, an antioxidant, a lubricant, and a dispersant are mixed, and then pressed under a magnetic field to obtain a blank;

[0010] The blank is subjected to cold isostatic pressing to obtain a compact;

[0011] The compact is sequentially subjected to vacuum degassing, vacuum low-temperature sintering and aging treatment to obtain the low-boron R-Fe-B permanent magnet material, the vacuum low-temperature sintering pressure is 0.05~1MPa, and the vacuum low-temperature sintering includes a first vacuum low-temperature sintering, a second vacuum low-temperature sintering and a third vacuum low-temperature sintering performed sequentially, the temperature of the first vacuum low-temperature sintering is 470~580℃, the holding time of the first vacuum low-temperature sintering is 4~12h, the temperature of the second vacuum low-temperature sintering is 650~730℃, the holding time of the second vacuum low-temperature sintering is 4~12h, the temperature of the third vacuum low-temperature sintering is 900~1000℃, and the holding time of the third vacuum low-temperature sintering is 4~30h.

[0012] Preferably, the mass W1 of the R-Fe-BM alloy coarse material and the mass W2 of the grain boundary phase R-Ga-M alloy coarse material during mixing satisfy the relationship:

[0013] W2=(0.1%~2%)×W1.

[0014] Preferably, the content of the M element in the R-Fe-BM alloy is 1wt%~2wt%, and the balance is Fe element and inevitable impurities; when the M in the R-Fe-BM alloy includes one or more of Ga, Ge, Zn, Sn, Ag and Si, the content of Ga, Ge, Zn, Sn, Ag and Si in the R-Fe-BM alloy is independently 0wt%~0.20wt% and not 0wt%.

[0015] Preferably, the temperature of the first dehydrogenation is 320-580°C.

[0016] Preferably, the temperature of the second dehydrogenation is 400-500°C.

[0017] Preferably, the vacuum degree of the vacuum degassing is lower than 9×10 -3 Pa, the vacuum degassing includes a first vacuum degassing, a second vacuum degassing and a third vacuum degassing performed in sequence, the temperature of the first vacuum degassing is 330~360℃, the insulation time of the first vacuum degassing is 1~4h, the temperature of the second vacuum degassing is 550~580℃, the insulation time of the second vacuum degassing is 1~4h, the temperature of the third vacuum degassing is 850~880℃, and the insulation time of the third vacuum degassing is 1~4h.

[0018] Preferably, the vacuum degree of the aging treatment is lower than 9×10 -3 Pa, the aging treatment includes a first aging treatment and a second aging treatment performed sequentially, the temperature of the first aging treatment is 880-910°C, the holding time of the first aging treatment is 2-4 hours, the temperature of the second aging treatment is 440-520°C, and the holding time of the second aging treatment is 2-4 hours.

[0019] Preferably, the pressure of the cold isostatic pressing treatment is 180-220 MPa.

[0020] Preferably, the intensity of the magnetic field is 1.5~2.5T.

[0021] The present invention also provides a low-boron R-Fe-B permanent magnetic material prepared by the preparation method described in the above technical solution.

[0022] The present invention provides a preparation method of a low-boron R-Fe-B permanent magnet material, comprising the following steps: sequentially performing a first crushing and a first dehydrogenation on a R-Fe-BM alloy to obtain a coarse R-Fe-BM alloy material; wherein R in the R-Fe-BM alloy is a rare earth element, including one or more of Nd, Pr, La, Ce, Y and Sm, and M includes one or more of Cu, Al, Co, Ga, Ni, Ti, Nb, Zr, Ge, Zn, Sn, Ag, V, Cr, Mn, W, Mo and Si; and wherein the R-Fe -BM alloy has an R content of 29wt%~36wt%, and a B content of 0.8wt%~0.96wt%; the grain boundary phase R-Ga-M alloy is subjected to a second crushing and a second dehydrogenation in sequence to obtain a grain boundary phase R-Ga-M alloy coarse material; in the grain boundary phase R-Ga-M alloy, R is a rare earth element including one or more of Nd, Pr, La, Ce and Sm, and M includes one or more of Dy, Tb, Gd, Y and Ho, and the R content in the grain boundary phase R-Ga-M alloy is 60wt%~90wt% , the Ga content is 10wt% to 20wt%, and the M content is 0wt% to 30wt% and not 0wt%; the R-Fe-BM alloy coarse material, the grain boundary phase R-Ga-M alloy coarse material, an antioxidant, a lubricant, and a dispersant are mixed, and then pressed under a magnetic field to obtain a blank; the blank is subjected to cold isostatic pressing to obtain a compact; the compact is sequentially subjected to vacuum degassing, vacuum low-temperature sintering, and aging treatment to obtain the low-boron R-Fe-B permanent magnet material, wherein the vacuum low-temperature sintering pressure is 0. 05~1MPa, the vacuum low-temperature sintering includes a first vacuum low-temperature sintering, a second vacuum low-temperature sintering and a third vacuum low-temperature sintering performed in sequence, the temperature of the first vacuum low-temperature sintering is 470~580℃, the holding time of the first vacuum low-temperature sintering is 4~12h, the temperature of the second vacuum low-temperature sintering is 650~730℃, the holding time of the second vacuum low-temperature sintering is 4~12h, the temperature of the third vacuum low-temperature sintering is 900~1000℃, and the holding time of the third vacuum low-temperature sintering is 4~30h.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] In the present invention, the R-Fe-BM alloy contains 29wt% to 36wt% R and 0.8wt% to 0.96wt% B, making it an alloy with an excess of rare earth elements and a low B content, which is conducive to the production of a large number of rare earth-rich grain boundary phases. The R-Ga-M alloy is a low-melting-point alloy composed primarily of light rare earth elements and supplemented by heavy rare earth elements, which is conducive to liquid phase sintering. Combined with vacuum degassing and a pressure-assisted diffusion gas pressure three-stage temperature increase and delayed sintering process, the raw materials can be melted into a liquid phase during vacuum low-temperature sintering, promoting magnet densification and simultaneously performing grain boundary diffusion sintering. Low-boron R-Fe-B permanent magnet materials can be obtained through vacuum low-temperature sintering. In addition, the present invention adds the R-Ga-M alloy, eliminating the need for an additional grain boundary diffusion process and not limiting the thickness of the magnet. This differs from the related art, which requires the magnets produced through sintering and aging treatment to be machined into a specific shape of diffusion substrate (thickness less than 8mm). At the same time, the present invention reduces the use of gallium (Ga content is less than 0.4wt%), which can reduce production costs and does not require the addition of dedicated grain boundary diffusion equipment. The entire preparation process is short and easy to operate, suitable for large-scale industrial production, further reducing production costs.

[0025] The data of the examples show that the low-boron R-Fe-B permanent magnet material prepared in the present invention has a remanence Br≥14.00 kGs and an intrinsic coercive force Hcj≥20 kOe.

[0026] The present invention also provides a low-boron R-Fe-B permanent magnet material prepared by the preparation method described in the above technical solution. The low-boron R-Fe-B permanent magnet material of the present invention can be applied to new energy vehicles, wind power new energy, automotive energy-saving electrical equipment, energy-saving home appliances, energy-saving elevators, robots and other intelligent equipment as well as smart consumer electronics such as mobile phones. DETAILED DESCRIPTION

[0027] The present invention provides a method for preparing a low-boron R-Fe-B permanent magnetic material, comprising the following steps:

[0028] The R-Fe-BM alloy is subjected to a first crushing and a first dehydrogenation in sequence to obtain a coarse R-Fe-BM alloy; in the R-Fe-BM alloy, R is a rare earth element including one or more of Nd, Pr, La, Ce, Y and Sm, and M includes one or more of Cu, Al, Co, Ga, Ni, Ti, Nb, Zr, Ge, Zn, Sn, Ag, V, Cr, Mn, W, Mo and Si; the content of R in the R-Fe-BM alloy is 29wt%-36wt%, and the content of B element is 0.8wt%-0.96wt%;

[0029] The grain boundary phase R-Ga-M alloy is subjected to a second crushing and a second dehydrogenation in sequence to obtain a grain boundary phase R-Ga-M alloy coarse material; in the grain boundary phase R-Ga-M alloy, R is a rare earth element including one or more of Nd, Pr, La, Ce and Sm, and M includes one or more of Dy, Tb, Gd, Y and Ho, and the content of R in the grain boundary phase R-Ga-M alloy is 60wt%-90wt%, the content of Ga is 10wt%-20wt%, and the content of M is 0wt%-30wt% and is not 0wt%;

[0030] The R-Fe-BM alloy coarse material, the grain boundary phase R-Ga-M alloy coarse material, an antioxidant, a lubricant, and a dispersant are mixed, and then pressed under a magnetic field to obtain a blank;

[0031] The blank is subjected to cold isostatic pressing to obtain a compact;

[0032] The compact is sequentially subjected to vacuum degassing, vacuum low-temperature sintering and aging treatment to obtain the low-boron R-Fe-B permanent magnet material, the vacuum low-temperature sintering pressure is 0.05~1MPa, and the vacuum low-temperature sintering includes a first vacuum low-temperature sintering, a second vacuum low-temperature sintering and a third vacuum low-temperature sintering performed sequentially, the temperature of the first vacuum low-temperature sintering is 470~580℃, the holding time of the first vacuum low-temperature sintering is 4~12h, the temperature of the second vacuum low-temperature sintering is 650~730℃, the holding time of the second vacuum low-temperature sintering is 4~12h, the temperature of the third vacuum low-temperature sintering is 900~1000℃, and the holding time of the third vacuum low-temperature sintering is 4~30h.

[0033] In the present invention, unless otherwise specified, the raw materials used are all commercially available products in the art or raw materials prepared by conventional preparation methods in the art.

[0034] The present invention sequentially performs a first crushing and a first dehydrogenation on an R-Fe-BM alloy to obtain an R-Fe-BM alloy coarse material; in the R-Fe-BM alloy, R is a rare earth element including one or more of Nd, Pr, La, Ce, Y and Sm, and M includes one or more of Cu, Al, Co, Ga, Ni, Ti, Nb, Zr, Ge, Zn, Sn, Ag, V, Cr, Mn, W, Mo and Si; the content of R in the R-Fe-BM alloy is 29wt%-36wt%, and the content of the B element is 0.8wt%-0.96wt%.

[0035] In the present invention, the content of R in the R-Fe-BM alloy can be specifically 29wt%, 29.5wt%, 30wt%, 31wt%, 32wt%, 33wt%, 34wt%, 35wt% or 36wt%, and the content of the B element can be specifically 0.8wt%, 0.85wt%, 0.9wt%, 0.95wt% or 0.96wt%; the R-Fe-BM alloy is an alloy with excess rare earth elements and low B element content, which is conducive to the production of more rare earth-rich grain boundary phases.

[0036] In the present invention, the content of the M element in the R-Fe-BM alloy is preferably 1wt%~2wt%, specifically 1wt%, 1.2wt%, 1.4wt%, 1.55wt%, 1.7wt% or 2wt%, and the balance is Fe element and inevitable impurities; when the M in the R-Fe-BM alloy preferably includes one or more of Ga, Ge, Zn, Sn, Ag and Si, the content of Ga, Ge, Zn, Sn, Ag and Si in the R-Fe-BM alloy is independently 0wt%~0.20wt% and not 0wt%, specifically 0.05wt%, 0.1wt%, 0.15wt% or 0.20wt%; the present invention controls the content of each element in the R-Fe-BM alloy within the above range to form an alloy rich in rare earth content but low in gallium.

[0037] In a specific embodiment of the present invention, the R-Fe-BM alloy is preferably (Pr0.2Nd0.8)30FebalCu0.4Co0.5Ga0.15Zr0.2Ti0.3B0.9 (wt%), (Pr0.2Nd0.8)32FebalCu0.2Co0.5Ga0.1Ti0.15Nb0.25B0.85 (wt%), (Pr0.25Nd0.75)33FebalCu0.3Co0.5Ga0.15Ti0.2Nb0.25B0.85 (wt%) or (Pr0.25Nd0.75)29.5Ce1.5FebalCu0.4Co0.8Ga0.15Zr0.15Nb0.2B0.9 (wt%).

[0038] In the present invention, the R-Fe-BM alloy is preferably used in the form of an alloy casting sheet. The thickness of the alloy casting sheet is preferably 0.1~0.6 mm, specifically 0.1, 0.2, 0.24, 0.26, 0.3, 0.4, 0.5 or 0.6 mm. The present invention has no special limitation on the source of the alloy casting sheet. It is preferred that the alloy casting sheet be prepared by a vacuum thin sheet rapid solidification furnace. The present invention has no special limitation on the specific parameters of the vacuum thin sheet rapid solidification furnace for preparing the alloy casting sheet.

[0039] In the present invention, the temperature of the first dehydrogenation is preferably 320-580°C, specifically 320, 360, 400, 440, 480, 500, 520, 540, 560 or 580°C.

[0040] In the present invention, the first crushing is preferably hydrogen crushing. The present invention has no special limitation on the parameters of the first crushing and the time of the first dehydrogenation, as long as saturated dehydrogenation can be achieved.

[0041] The present invention sequentially performs a second crushing and a second dehydrogenation on a grain boundary phase R-Ga-M alloy to obtain a grain boundary phase R-Ga-M alloy coarse material; in the grain boundary phase R-Ga-M alloy, R is a rare earth element including one or more of Nd, Pr, La, Ce and Sm, and M includes one or more of Dy, Tb, Gd, Y and Ho; the content of R in the grain boundary phase R-Ga-M alloy is 60wt%-90wt%, the content of Ga is 10wt%-20wt%, and the content of M is 0wt%-30wt% and is not 0wt%.

[0042] In the present invention, the content of R in the grain boundary phase R-Ga-M alloy is specifically 60wt%, 70wt%, 80wt% or 90wt%; the content of Ga element can be specifically 10wt%, 15wt% or 20wt%; the content of M element can be specifically 5wt%, 10wt%, 15wt%, 20wt%, 25wt% or 30wt%.

[0043] In the present invention, the melting point of gallium is 29.76°C. By adding gallium to lower the melting point of the alloy, the present invention controls the content of each element in the grain boundary phase R-Ga-M alloy within the above-mentioned range to form a low-melting-point alloy mainly composed of light rare earth elements and supplemented by heavy rare earth elements. During vacuum sintering, it will melt into a liquid phase, which is beneficial to liquid phase sintering and thus reduces the temperature of vacuum low-temperature sintering.

[0044] In a specific embodiment of the present invention, the grain boundary phase R-Ga-M alloy is preferably Pr60Ga20Dy20 (wt%), (Pr0.25Nd0.75)70Ga10Dy10Tb10 or (Pr0.2Nd0.8)60Ga20Dy10Tb10.

[0045] In the present invention, the grain boundary phase R-Ga-M alloy is preferably used in the form of an alloy casting sheet. The thickness of the alloy casting sheet is preferably 0.1~0.6 mm, specifically 0.1, 0.2, 0.24, 0.26, 0.3, 0.4, 0.5 or 0.6 mm. The present invention has no special limitation on the source of the alloy casting sheet. It is preferred that the alloy casting sheet be prepared by a kilogram-grade vacuum rapid quenching furnace or a vacuum thin-sheet rapid solidification furnace. The present invention has no special limitation on the specific parameters of the kilogram-grade vacuum rapid quenching furnace or the vacuum thin-sheet rapid solidification furnace for preparing the alloy casting sheet.

[0046] In the present invention, the temperature of the second dehydrogenation is preferably 400-500°C, specifically 420, 440, 450, 460, 480 or 500°C.

[0047] In the present invention, the second crushing is preferably ball milling or hydrogen crushing. The present invention has no particular limitation on the parameters of the second crushing and the time of the second dehydrogenation, as long as saturated dehydrogenation can be achieved.

[0048] After obtaining the R-Fe-BM alloy coarse material and the grain boundary phase R-Ga-M alloy coarse material, the present invention mixes the R-Fe-BM alloy coarse material, the grain boundary phase R-Ga-M alloy coarse material, an antioxidant, a lubricant and a dispersant, and then performs press molding under a magnetic field to obtain a blank.

[0049] In the present invention, the mass W1 of the R-Fe-BM alloy coarse material and the mass W2 of the grain boundary phase R-Ga-M alloy coarse material during mixing preferably satisfy the relationship:

[0050] W2=(0.1%~2%)×W1, where W2 can specifically be 0.1%×W1, 0.5%×W1, 1%×W1, 1.2%×W1, 1.8%×W1 or 2%×W1.

[0051] The present invention controls the relationship between W1 and W2 within the above range to obtain a low-boron R-Fe-B permanent magnet material with a low gallium content, thereby reducing the amount of gallium used and further reducing production costs.

[0052] In the present invention, the sum of the contents of the antioxidant and the lubricant in the low-boron R-Fe-B permanent magnet material is preferably 0.1-0.13wt%, specifically 0.11wt% or 0.13wt%. In a specific embodiment of the present invention, the content of the antioxidant in the low-boron R-Fe-B permanent magnet material is 0.06wt%, and the content of the lubricant is 0.05wt%.

[0053] In the present invention, the content of the dispersant in the low-boron R-Fe-B permanent magnet material is preferably 0.1 wt %.

[0054] The present invention has no particular limitation on the types of the antioxidant, lubricant and dispersant, and any type and amount known to those skilled in the art may be used.

[0055] The present invention preferably mixes the R-Fe-BM alloy coarse material and the grain boundary phase R-Ga-M alloy coarse material, then adds an antioxidant and a lubricant, and after uniform mixing, performs air flow grinding to pulverize the material, controls the oxygen content to 0-10ppm, and then mixes the obtained powder with a dispersant to obtain a mixture.

[0056] In the present invention, the average particle size of the powder is preferably 2.3-3.5 μm, specifically 2.3, 2.45, 2.5, 2.6, 3 or 3.5 μm.

[0057] In the present invention, the intensity of the magnetic field is preferably 1.5-2.5T, specifically 1.5, 2 or 2.5T.

[0058] In the present invention, the mixed material is preferably placed in an oriented magnetic field that is filled with nitrogen and deoxygenated and has an oxygen content of 100 to 500 ppm (specifically, 100, 200, 300, 400 or 500 ppm) for compression molding to obtain the blank.

[0059] After obtaining the blank, the present invention performs cold isostatic pressing on the blank to obtain a pressed blank.

[0060] In the present invention, the pressure of the cold isostatic pressing treatment is preferably 180-220 MPa, specifically 180, 200 or 220 MPa, and the time is preferably 180 s.

[0061] After obtaining the compact, the present invention sequentially performs vacuum degassing, vacuum low-temperature sintering and aging treatment on the compact to obtain the low-boron R-Fe-B permanent magnet material. The pressure of the vacuum low-temperature sintering is 0.05~1MPa, and the vacuum low-temperature sintering includes a first vacuum low-temperature sintering, a second vacuum low-temperature sintering and a third vacuum low-temperature sintering performed sequentially. The temperature of the first vacuum low-temperature sintering is 470~580°C, and the holding time of the first vacuum low-temperature sintering is 4~12h. The temperature of the second vacuum low-temperature sintering is 650~730°C, and the holding time of the second vacuum low-temperature sintering is 4~12h. The temperature of the third vacuum low-temperature sintering is 900~1000°C, and the holding time of the third vacuum low-temperature sintering is 4~30h.

[0062] In the present invention, the vacuum degree of the vacuum degassing is preferably lower than 9×10 -3Pa, the vacuum degassing preferably includes a first vacuum degassing, a second vacuum degassing and a third vacuum degassing performed in sequence, the temperature of the first vacuum degassing is preferably 330-360°C, specifically 330, 340, 350 or 360°C, the holding time of the first vacuum degassing is preferably 1-4h, specifically 1, 2, 3 or 4h, the temperature of the second vacuum degassing is preferably 550-580°C, specifically 550, 560, 570 or 580°C, the holding time of the second vacuum degassing is preferably 1-4h, specifically 1, 2, 3 or 4h, the temperature of the third vacuum degassing is preferably 850-880°C, specifically 850, 860, 870 or 880°C, the holding time of the third vacuum degassing is preferably 1-4h, specifically 1, 2, 3 or 4h, the present invention preferably waits until the vacuum degree under the previous temperature gradient is restored to below 9×10 -3 Pa, and then the next temperature gradient is carried out. After the three temperature gradients are degassing, the vacuum degree is lower than 9×10 -3 Pa, argon is filled for air cooling, the temperature in the vacuum sintering furnace is lower than 100° C., and then the vacuum low-temperature sintering is performed.

[0063] In the present invention, the vacuum degassing is preferably performed in a vacuum sintering furnace.

[0064] In the present invention, the pressure of the vacuum low-temperature sintering can specifically be 0.05, 0.1, 0.2, 0.4, 0.6, 0.8 or 1 MPa.

[0065] In the present invention, the atmosphere of the vacuum low-temperature sintering is preferably a protective gas, and the protective gas is preferably argon.

[0066] In the present invention, the temperature of the first vacuum low-temperature sintering can be specifically 470, 490, 500, 520, 540, 560 or 580°C, and the holding time of the first vacuum low-temperature sintering can be specifically 4, 6, 8, 10 or 12 hours. The temperature of the second vacuum low-temperature sintering can be specifically 650, 670, 690, 700, 710, 720 or 730°C, and the holding time of the second vacuum low-temperature sintering can be specifically 4, 6, 8, 10 or 12 hours. The temperature of the third vacuum low-temperature sintering can be specifically 900, 950, 980 or 1000°C, and the holding time of the third vacuum low-temperature sintering can be specifically 4, 5, 8, 10, 15, 20, 25 or 30 hours.

[0067] After the vacuum low-temperature sintering is completed, the present invention preferably stops heating and cools the sintered product by air or argon filling until the temperature in the vacuum sintering furnace is below 100° C.

[0068] In the present invention, the vacuum degree of the aging treatment is preferably less than 9×10-3 Pa, the aging treatment preferably includes a first aging treatment and a second aging treatment performed sequentially. The temperature of the first aging treatment is preferably 880-910° C., specifically 880, 890, 900 or 910° C., and the holding time of the first aging treatment is preferably 2-4 hours, specifically 2, 3 or 4 hours. The temperature of the second aging treatment is preferably 440-520° C., specifically 440, 450, 480, 500 or 520° C., and the holding time of the second aging treatment is preferably 2-4 hours, specifically 2, 3 or 4 hours.

[0069] After the first aging treatment is completed, the present invention preferably stops heating, cools the steel sheet by air or argon filling to a temperature below 100° C., and then performs the second aging treatment.

[0070] After the aging treatment is completed, the present invention preferably stops heating and cools the material to a temperature below 80° C. in a vacuum sintering furnace by air cooling or argon filling to obtain the low-boron R—Fe—B permanent magnet material.

[0071] The present invention also provides a low-boron R-Fe-B permanent magnetic material prepared by the preparation method described in the above technical solution.

[0072] In the present invention, the density of the low-boron R-Fe-B permanent magnet material is preferably greater than 7.5 g / cm 3 .

[0073] The low-boron R-Fe-B permanent magnet material of the present invention can be applied to new energy vehicles, wind power new energy, automotive energy-saving electrical equipment, energy-saving home appliances, energy-saving elevators, robots and other intelligent equipment as well as smart consumer electronics such as mobile phones.

[0074] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0075] In the present invention, bal means "balance".

[0076] Example 1

[0077] A method for preparing a low-boron R-Fe-B permanent magnetic material comprises the following steps:

[0078] 1. The composition of the R-Fe-BM alloy sheet is (Pr0.2Nd0.8)30FebalCu0.4Co0.5Ga0.15Zr0.2Ti0.3B0.9 (wt%). The above raw materials are melted in a vacuum sheet rapid solidification furnace to prepare alloy sheets with an average thickness of 0.24 mm.

[0079] 2. The composition of the grain boundary phase R-Ga-M alloy sheet is Pr60Ga20Dy20 (wt%). The above raw materials are vacuum melted to prepare alloy sheets with an average thickness of 0.26 mm.

[0080] 3. The R-Fe-BM alloy flakes were crushed by hydrogen crushing process with dehydrogenation temperature of 500℃ to obtain R-Fe-BM alloy coarse material.

[0081] 4. The grain boundary phase R-Ga-M alloy flakes are crushed by hydrogen crushing process with dehydrogenation temperature at 400°C to obtain grain boundary phase R-Ga-M alloy coarse material.

[0082] 5. The R-Fe-BM alloy coarse material obtained is weighed to a weight of W1, and the grain boundary phase R-Ga-M alloy coarse material is weighed to a weight of W2, where W1 and W2 satisfy the following relationship: W2 = 1.2% × W1.

[0083] 6. The weighed R-Fe-BM alloy coarse material and grain boundary phase RM alloy coarse material are mixed, and antioxidant (the content of antioxidant in low-boron R-Fe-B permanent magnet material is 0.06wt%) and lubricant (the content of lubricant in low-boron R-Fe-B permanent magnet material is 0.05wt%) are added. After the mixture is evenly mixed, it is pulverized by air flow grinding, and the oxygen content is controlled at 10ppm. The average particle size of the obtained powder is 2.8μm. Then, a dispersant (the content of dispersant in low-boron R-Fe-B permanent magnet material is 0.1wt%) is added to mix the powder evenly.

[0084] 7. Weigh the powder obtained by air flow grinding and place it in a 2.0T oriented magnetic field filled with nitrogen and oxygen-exhausted with an oxygen content of 500 ppm for pressing to obtain a blank. The pressed blank is then subjected to cold isostatic pressing (180 MPa, 180 s) to obtain a compact.

[0085] 8. Place the compact into a vacuum sintering furnace for degassing. Wait until the vacuum degree is lower than 9×10 -3 Pa, heating was started, and degassing was carried out at three temperature gradients of 350℃, 580℃, and 850℃ for 1 h, and the vacuum degree at the previous temperature gradient was restored to less than 9×10 -3 Pa, and then the next temperature gradient is carried out. After the three temperature gradients are degassing, the vacuum degree is lower than 9×10 -3Pa, argon is filled and air-cooled, and the temperature in the vacuum sintering furnace is lower than 100℃.

[0086] 9. Vacuum degree is lower than 9×10 -3 After filling with ultrapure argon gas at 0.1MPa at Pa, vacuum low-temperature sintering treatment was carried out, and heating was started. After keeping warm at 580℃ for 10h, the temperature was continued to rise. After keeping warm at 700℃ for 10h, the temperature was continued to rise. After keeping warm at 900℃ for 10h, heating was stopped and air-cooled until the temperature in the vacuum sintering furnace was lower than 100℃.

[0087] 10. Aging treatment, vacuum degree is less than 9×10 -3 Start heating, keep it at 890℃ for 2h, stop heating, charge with argon and cool it to below 100℃, then continue heating to 450℃ and keep it for 4h, stop heating, charge with argon and cool it to below 80℃, then open the furnace door to discharge the material.

[0088] 11. The magnetic properties of the low-boron R-Fe-B permanent magnet material were measured at room temperature. The remanence Br: 14.25kGs, the intrinsic coercivity Hcj: 20.80kOe, and the magnetic energy product (BH) max: 50.19MGOe. The density of the low-boron R-Fe-B permanent magnet material was 7.57g / cm 3 .

[0089] Example 2

[0090] A method for preparing a low-boron R-Fe-B permanent magnetic material comprises the following steps:

[0091] 1. The composition of the R-Fe-BM alloy sheet is (Pr0.2Nd0.8)32FebalCu0.2Co0.5Ga0.1Ti0.15Nb0.25B0.85 (wt%). The above raw materials are melted in a vacuum sheet rapid solidification furnace to prepare alloy sheets with an average thickness of 0.26 mm.

[0092] 2. The composition of the grain boundary phase R-Ga-M alloy sheet is (Pr0.2Nd0.8)60Ga20Dy10Tb10. The above raw materials are vacuum melted to prepare alloy sheets with an average thickness of 0.26 mm.

[0093] 3. The R-Fe-BM alloy flakes were crushed by hydrogen crushing process with dehydrogenation temperature of 560℃ to obtain R-Fe-BM alloy coarse material.

[0094] 4. The grain boundary phase R-Ga-M alloy ingot is crushed by hydrogen crushing process with dehydrogenation temperature at 440℃ to obtain grain boundary phase R-Ga-M alloy coarse material.

[0095] 5. The R-Fe-BM alloy coarse material is weighed to a weight of W1, and the grain boundary phase R-Ga-M alloy coarse material is weighed to a weight of W2, where W1 and W2 satisfy the following relationship: W2 = 2% × W1.

[0096] 6. The weighed R-Fe-BM alloy coarse material and grain boundary phase RM alloy coarse material are mixed, and antioxidant (the content of antioxidant in low-boron R-Fe-B permanent magnet material is 0.06wt%) and lubricant (the content of lubricant in low-boron R-Fe-B permanent magnet material is 0.05wt%) are added. After the mixture is evenly mixed, it is pulverized by air flow grinding, and the oxygen content is controlled at 10ppm. The average particle size of the obtained powder is 2.8μm. Then, a dispersant (the content of dispersant in low-boron R-Fe-B permanent magnet material is 0.1wt%) is added to mix the powder evenly.

[0097] 7. Weigh the powder obtained by air flow milling and place it in a 2.0T oriented magnetic field filled with nitrogen and oxygen-exhausted with an oxygen content of 100 ppm for pressing to obtain a blank. The pressed blank is then subjected to cold isostatic pressing (180 MPa, 180 s) to obtain a compact.

[0098] 8. Place the compact into a vacuum sintering furnace for degassing. Wait until the vacuum degree is lower than 9×10 -3 Pa, heating was started, and degassing was carried out at three temperature gradients of 330 °C, 580 °C, and 860 °C for 1 h. The vacuum degree at the previous temperature gradient was restored to below 9 × 10 -3 Pa, and then the next temperature gradient is carried out. After the three temperature gradients are degassing, the vacuum degree is lower than 9×10 -3 Pa, argon is filled and air-cooled, and the temperature in the vacuum sintering furnace is lower than 100℃.

[0099] 9. Vacuum degree is lower than 9×10 -3 After filling with ultrapure argon gas at 0.2MPa at Pa, vacuum low-temperature sintering treatment is carried out, heating is started, and after keeping warm at 580℃ for 10h, the temperature is continued to rise, and after keeping warm at 720℃ for 10h, the temperature is continued to rise, and after keeping warm at 980℃ for 10h, heating is stopped and air-cooled until the temperature in the vacuum sintering furnace is lower than 100℃.

[0100] 10. Aging treatment, vacuum degree is less than 9×10 -3 Start heating, keep it at 880℃ for 2h, stop heating, charge with argon and cool it to below 100℃, then continue heating to 440℃ and keep it for 4h, stop heating, charge with argon and cool it to below 80℃, then open the furnace door to discharge the material.

[0101] 11. The magnetic properties of the low-boron R-Fe-B permanent magnet material were measured at room temperature. The remanence Br: 14.20 kGs, the intrinsic coercivity Hcj: 25.32 kOe, and the magnetic energy product (BH) max: 50.08 MGOe. The density of the low-boron R-Fe-B permanent magnet material was 7.55 g / cm 3 .

[0102] Example 3

[0103] A method for preparing a low-boron R-Fe-B permanent magnetic material comprises the following steps:

[0104] 1. The composition of the R-Fe-BM alloy sheet is (Pr0.25Nd0.75)33FebalCu0.3Co0.5Ga0.15Ti0.2Nb0.25B0.85 (wt%). The above raw materials are melted in a vacuum sheet rapid solidification furnace to prepare alloy sheets with an average thickness of 0.22 mm.

[0105] 2. The composition of the grain boundary phase R-Ga-M alloy sheet is (Pr0.25Nd0.75)70Ga10Dy10Tb10. The above raw materials are vacuum melted to prepare alloy sheets with an average thickness of 0.24 mm.

[0106] 3. The R-Fe-BM alloy flakes were crushed by hydrogen crushing process with dehydrogenation temperature of 580℃ to obtain R-Fe-BM alloy coarse material.

[0107] 4. The grain boundary phase R-Ga-M alloy flakes are crushed by hydrogen crushing process with dehydrogenation temperature at 450°C to obtain grain boundary phase R-Ga-M alloy coarse material.

[0108] 5. The R-Fe-BM alloy coarse material is weighed to a weight of W1, and the grain boundary phase R-Ga-M alloy coarse material is weighed to a weight of W2, where W1 and W2 satisfy the following relationship: W2 = 2% × W1.

[0109] 6. The weighed R-Fe-BM alloy coarse material and grain boundary phase RM alloy coarse material are mixed, and antioxidant (the content of antioxidant in low-boron R-Fe-B permanent magnet material is 0.06wt%) and lubricant (the content of lubricant in low-boron R-Fe-B permanent magnet material is 0.05wt%) are added. After the mixture is evenly mixed, it is pulverized by air flow grinding, and the oxygen content is controlled at 10ppm. The average particle size of the obtained powder is 2.8μm. Then, a dispersant (the content of dispersant in low-boron R-Fe-B permanent magnet material is 0.1wt%) is added to mix the powder evenly.

[0110] 7. Weigh the powder obtained by air flow milling and place it in a 2.0T oriented magnetic field filled with nitrogen and oxygen-exhausted with an oxygen content of 100 ppm for pressing to obtain a blank. The pressed blank is then subjected to cold isostatic pressing (180 MPa, 180 s) to obtain a compact.

[0111] 8. Place the compact into a vacuum sintering furnace for degassing. Wait until the vacuum degree is lower than 9×10 -3 Pa, heating was started, and degassing was carried out at three temperature gradients of 330 °C, 560 °C, and 850 °C for 1 h. The vacuum degree at the previous temperature gradient was restored to less than 9 × 10 -3 Pa, and then the next temperature gradient is carried out. After the three temperature gradients are degassing, the vacuum degree is lower than 9×10 -3 Pa, argon is filled and air-cooled, and the temperature in the vacuum sintering furnace is lower than 100℃.

[0112] 9. Vacuum degree is lower than 9×10 -3 After filling with ultrapure argon gas at 0.2MPa at Pa, vacuum low-temperature sintering treatment was carried out, heating was started, and after keeping warm at 580℃ for 8h, the temperature was continued to rise, and after keeping warm at 700℃ for 8h, the temperature was continued to rise, and after keeping warm at 980℃ for 8h, heating was stopped and air-cooled until the temperature in the vacuum sintering furnace was lower than 100℃.

[0113] 10. Aging treatment, vacuum degree is less than 9×10 -3 Start heating, keep it at 850℃ for 2h, stop heating, charge with argon and cool it to below 100℃, then continue heating to 460℃ and keep it for 4h, stop heating, charge with argon and cool it to below 80℃, then open the furnace door to discharge the material.

[0114] 11. The magnetic properties of the low-boron R-Fe-B permanent magnet material were measured at room temperature. The remanence Br: 14.15 kGs, the intrinsic coercivity Hcj: 25.20 kOe, and the magnetic energy product (BH) max: 50.10 MGOe. The density of the low-boron R-Fe-B permanent magnet material was 7.60 g / cm 3 .

[0115] Example 4

[0116] A method for preparing a low-boron R-Fe-B permanent magnetic material comprises the following steps:

[0117] 1. The composition of the R-Fe-BM alloy flakes is (Pr0.25Nd0.75)29.5Ce1.5FebalCu0.4Co0.8Ga0.15Zr0.15Nb0.2B0.9 (wt%). The above raw materials are melted in a vacuum sheet rapid solidification furnace to prepare alloy flakes with an average thickness of 0.24 mm.

[0118] 2. The composition of the grain boundary phase R-Ga-M alloy sheet is Pr60Ga20Dy20 (wt%). The above raw materials are vacuum melted to prepare alloy sheets with an average thickness of 0.24 mm.

[0119] 3. The R-Fe-BM alloy flakes were crushed by hydrogen crushing process with dehydrogenation temperature of 560℃ to obtain R-Fe-BM alloy coarse material.

[0120] 4. The grain boundary phase R-Ga-M alloy flakes are crushed by hydrogen crushing process with dehydrogenation temperature at 480°C to obtain grain boundary phase R-Ga-M alloy coarse material.

[0121] 5. The R-Fe-BM alloy coarse material is weighed to a weight of W1, and the grain boundary phase R-Ga-M alloy coarse material is weighed to a weight of W2, where W1 and W2 satisfy the following relationship: W2 = 1.8% × W1.

[0122] 6. The weighed R-Fe-BM alloy coarse material and grain boundary phase RM alloy coarse material are mixed, and antioxidant (the content of antioxidant in low-boron R-Fe-B permanent magnet material is 0.06wt%) and lubricant (the content of lubricant in low-boron R-Fe-B permanent magnet material is 0.05wt%) are added. After the mixture is evenly mixed, it is pulverized by air flow grinding, and the oxygen content is controlled at 10ppm. The average particle size of the obtained powder is 2.8μm. Then, a dispersant (the content of dispersant in low-boron R-Fe-B permanent magnet material is 0.1wt%) is added to mix the powder evenly.

[0123] 7. Weigh the powder obtained by air flow milling and place it in a 2.0T oriented magnetic field filled with nitrogen and oxygen-exhausted with an oxygen content of 100 ppm for pressing to obtain a blank. The pressed blank is then subjected to cold isostatic pressing (180 MPa, 180 s) to obtain a compact.

[0124] 8. Place the compact into a vacuum sintering furnace for degassing. Wait until the vacuum degree is lower than 9×10 -3 Pa, heating was started, and degassing was performed at three temperature gradients of 350 °C, 560 °C, and 850 °C for 1 h. The vacuum degree at the previous temperature gradient was restored to below 9 × 10 -3 Pa, and then the next temperature gradient is carried out. After the three temperature gradients are degassing, the vacuum degree is lower than 9×10 -3 Pa, argon is filled and air-cooled, and the temperature in the vacuum sintering furnace is lower than 100℃.

[0125] 9. Vacuum degree is lower than 9×10 -3After filling with ultrapure argon gas at 0.2MPa at Pa, vacuum low-temperature sintering treatment was carried out, heating was started, and after keeping warm at 560℃ for 8h, the temperature was continued to rise, and after keeping warm at 720℃ for 8h, the temperature was continued to rise, and after keeping warm at 950℃ for 8h, heating was stopped and air-cooled until the temperature in the vacuum sintering furnace was lower than 100℃.

[0126] 10. Aging treatment, vacuum degree is less than 9×10 -3 Start heating, keep warm at 890℃ for 2h, stop heating, charge with argon and cool with air, cool to the temperature below 100℃, continue heating to 480℃ and keep warm for 4h, stop heating, charge with argon and cool with air, until the temperature in the vacuum sintering furnace is below 80℃, open the furnace door and discharge the material.

[0127] 11. The magnetic properties of the low-boron R-Fe-B permanent magnet material were measured at room temperature. The remanence Br: 14.10 kGs, the intrinsic coercivity Hcj: 20.12 kOe, and the magnetic energy product (BH) max: 50.15 MGOe. The density of the low-boron R-Fe-B permanent magnet material was 7.58 g / cm 3 .

[0128] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation thereto. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications shall also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a low-boron R-Fe-B permanent magnetic material, characterized in that: The specific steps are as follows: The R-Fe-BM alloy is subjected to a first crushing and a first dehydrogenation in sequence to obtain a coarse R-Fe-BM alloy; in the R-Fe-BM alloy, R is a rare earth element including one or more of Nd, Pr, La, Ce, Y and Sm, and M includes one or more of Cu, Al, Co, Ga, Ni, Ti, Nb, Zr, Ge, Zn, Sn, Ag, V, Cr, Mn, W, Mo and Si; the content of R in the R-Fe-BM alloy is 29wt%-36wt%, and the content of B element is 0.8wt%-0.96wt%; The grain boundary phase R-Ga-M alloy is subjected to a second crushing and a second dehydrogenation in sequence to obtain a grain boundary phase R-Ga-M alloy coarse material; in the grain boundary phase R-Ga-M alloy, R is a rare earth element including one or more of Nd, Pr, La, Ce and Sm, and M includes one or more of Dy, Tb, Gd, Y and Ho, and the content of R in the grain boundary phase R-Ga-M alloy is 60wt%-90wt%, the content of Ga is 10wt%-20wt%, and the content of M is 0wt%-30wt% and is not 0wt%; The R-Fe-BM alloy coarse material, the grain boundary phase R-Ga-M alloy coarse material, an antioxidant, a lubricant, and a dispersant are mixed, and then pressed under a magnetic field to obtain a blank; The blank is subjected to cold isostatic pressing to obtain a compact; The compact is sequentially subjected to vacuum degassing, vacuum low-temperature sintering and aging treatment to obtain the low-boron R-Fe-B permanent magnet material, wherein the pressure of the vacuum low-temperature sintering is 0.05-1 MPa, and the vacuum low-temperature sintering includes a first vacuum low-temperature sintering, a second vacuum low-temperature sintering and a third vacuum low-temperature sintering performed sequentially, the temperature of the first vacuum low-temperature sintering is 470-580° C., the holding time of the first vacuum low-temperature sintering is 4-12 hours, the temperature of the second vacuum low-temperature sintering is 650-730° C., the holding time of the second vacuum low-temperature sintering is 4-12 hours, the temperature of the third vacuum low-temperature sintering is 900-1000° C., and the holding time of the third vacuum low-temperature sintering is 4-30 hours; During the mixing, the mass W1 of the R-Fe-BM alloy coarse material and the mass W2 of the grain boundary phase R-Ga-M alloy coarse material satisfy the relationship: W2=(0.1%~2%)×W1.

2. The preparation method according to claim 1, characterized in that The content of the M element in the R-Fe-BM alloy is 1wt%~2wt%, and the balance is Fe element and inevitable impurities; when the M in the R-Fe-BM alloy includes one or more of Ga, Ge, Zn, Sn, Ag and Si, the content of Ga, Ge, Zn, Sn, Ag and Si in the R-Fe-BM alloy is independently 0wt%~0.20wt% and is not 0wt%.

3. The preparation method according to claim 1, characterized in that The temperature of the first dehydrogenation is 320-580°C.

4. The preparation method according to claim 1, characterized in that The temperature of the second dehydrogenation is 400-500°C.

5. The preparation method according to claim 1, characterized in that The vacuum degree of the vacuum degassing is lower than 9×10 - 3 Pa, the vacuum degassing includes a first vacuum degassing, a second vacuum degassing and a third vacuum degassing performed in sequence, the temperature of the first vacuum degassing is 330~360℃, the insulation time of the first vacuum degassing is 1~4h, the temperature of the second vacuum degassing is 550~580℃, the insulation time of the second vacuum degassing is 1~4h, the temperature of the third vacuum degassing is 850~880℃, and the insulation time of the third vacuum degassing is 1~4h.

6. The preparation method according to claim 1, characterized in that The vacuum degree of the aging treatment is less than 9×10 - 3 Pa, the aging treatment includes a first aging treatment and a second aging treatment performed sequentially, the temperature of the first aging treatment is 880-910°C, the holding time of the first aging treatment is 2-4 hours, the temperature of the second aging treatment is 440-520°C, and the holding time of the second aging treatment is 2-4 hours.

7. The preparation method according to claim 1, characterized in that The pressure of the cold isostatic pressing treatment is 180-220 MPa.

8. The preparation method according to claim 1, characterized in that The intensity of the magnetic field is 1.5~2.5T.

9. The low-boron R-Fe-B permanent magnet material prepared by the preparation method according to any one of claims 1 to 8.