Sintered neodymium-iron-boron magnet and preparation method thereof

Abstract

The invention relates to a preparation method of a sintered neodymium-iron-boron magnet, the sintered neodymium-iron-boron magnet is prepared from the following raw materials in percentage by mass: less than 1% of aluminum-titanium-boron alloy powder, less than 0.3% of a lubricant and more than 98.7% of neodymium-iron-boron alloy powder, the composition of the aluminum-titanium-boron alloy powder is AlaTibBcMd, M is selected from at least one of Co, Cu, Fe, V, Nb, Ta, Zr or Mg, a, b, c and d are all mass fractions, a is greater than or equal to 92.3% and less than or equal to 94.7%, c is greater than or equal to 94.7%, and d is greater than or equal to 92.3% and less than or equal to 94.7%. 4.5% < = b < = 5.5%, 0.8% < = c < = 1.2%, and 0% < = d < = 1%. The invention further relates to the sintered neodymium-iron-boron magnet. According to the preparation method of the sintered neodymium-iron-boron magnet, the grain boundary microstructure can be improved by reconstructing and optimizing the grain boundary of the neodymium-iron-boron magnet, heavy rare earth elements are not used or a small amount of heavy rare earth elements are used, the intrinsic coercive force of the sintered neodymium-iron-boron magnet is effectively improved under the condition that high remanence is guaranteed, and the magnetic performance of the sintered neodymium-iron-boron magnet is improved. And the sintered neodymium-iron-boron magnet which can meet high-temperature application, has high cost performance and is not limited in thickness is manufactured, and mass production is facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic materials, and particularly to a sintered neodymium iron boron magnet and a preparation method thereof. Background Art

[0002] Remanence and intrinsic coercivity are two important technical indicators for measuring the performance of sintered neodymium iron boron. At present, the remanence of sintered neodymium iron boron magnets produced in batches has reached over 1.47 T, more than 90% of the theoretical value of 1.61 T for neodymium iron boron magnets, and the room for improvement is limited. However, the intrinsic coercivity, which directly affects its actual application temperature, is still only 1 / 10 - 1 / 3 of the theoretical value, and there is still a large room for improvement.

[0003] Currently, the method of adding a certain amount of heavy rare earth elements such as Dy and Tb is usually used to improve the intrinsic coercivity of sintered neodymium iron boron magnets. However, the addition of heavy rare earth elements such as Dy and Tb will significantly reduce the remanence of sintered neodymium iron boron magnets, and the reserves of heavy rare earths are very limited and the price is expensive, and their addition will greatly increase the material cost. Although the grain boundary diffusion process can be used to improve the intrinsic coercivity of sintered neodymium iron boron magnets under the condition of low heavy rare earths, this method has certain limitations on the thickness of neodymium iron boron magnets. Generally, it can only be used to produce products with a thickness of less than several millimeters. For thicker large-sized products, the improvement of its intrinsic coercivity is limited.

[0004] Therefore, how to effectively improve the intrinsic coercivity of sintered neodymium iron boron magnets while ensuring high remanence, and manufacture sintered neodymium iron boron magnets that can meet high-temperature applications and have high cost performance has always been a problem that needs to be urgently solved. Summary of the Invention

[0005] Based on this, in view of the above problems, it is necessary to provide a sintered neodymium iron boron magnet and a preparation method thereof. The preparation method can prepare a sintered neodymium iron boron magnet with high remanence, high intrinsic coercivity and unlimited thickness, and can not use or use a small amount of heavy rare earth elements, with low production cost and convenient for mass production.

[0006] A preparation method of a sintered neodymium iron boron magnet, in terms of mass fraction, the preparation raw materials include: aluminum-titanium-boron alloy powder below 1%, lubricant below 0.3%, and neodymium iron boron alloy powder above 98.7%. Among them, the composition of the aluminum-titanium-boron alloy powder is Al a Ti b B c M d , M is selected from at least one of Co, Cu, Fe, V, Nb, Ta, Zr or Mg, a, b, c, d are all mass fractions, and 92.3% ≤ a ≤ 94.7%, 4.5% ≤ b ≤ 5.5%, 0.8% ≤ c ≤ 1.2%, 0% ≤ d ≤ 1%.

[0007] In one embodiment, the mass fraction of the aluminum-titanium-boron alloy powder is 0.7% or less.

[0008] In one embodiment, based on mass fraction, the preparation raw materials include: 0.2%-0.5% of aluminum-titanium-boron alloy powder, 0.05%-0.15% of lubricant, and 99.35%-99.75% of neodymium-iron-boron alloy powder.

[0009] In one embodiment, the particle size of the aluminum-titanium-boron alloy powder is 2 μm - 20 μm.

[0010] In one embodiment, the composition of the neodymium-iron-boron alloy powder is Nd x Re y Fe 100-x-y-m-n M m B n , where Re is selected from at least one of La, Ce, Y, Pr, Sm, Eu, Gd, Ho, Dy or Tb, M is selected from at least one of V, Ti, Cr, Ni, Mn, Zr, Cu, Ga, Co, Al, In, Nb, Ta, Ag, Sn, Pb, W, Mo, Bi, Mg or Pd, x, y, m, n are all mass fractions, and 14 ≤ x ≤ 32, 0 ≤ y ≤ 15, 0 ≤ m ≤ 5, 0.8 ≤ n ≤ 1.2.

[0011] In one embodiment, the Re is selected from at least one of Pr, La, Ce, Y or Gd;

[0012] and / or, 21 ≤ x ≤ 26, 6 ≤ y ≤ 8, 0.6 ≤ m ≤ 3.2, 0.9 ≤ n ≤ 0.98.

[0013] In one embodiment, the particle size of the neodymium-iron-boron alloy powder is 2.6 μm - 3.4 μm.

[0014] In one embodiment, in the sintering treatment step, the sintering temperature is 1050 °C - 1120 °C, the sintering time is 2 h - 8 h, and the vacuum degree is lower than 5×10 -2 Pa.

[0015] In one embodiment, after the sintering treatment step, a primary tempering treatment and a secondary tempering treatment are carried out. The primary tempering temperature is 850 °C - 950 °C, the time is 1 h - 3 h, the secondary tempering temperature is 430 °C - 550 °C, and the time is 3 h - 6 h.

[0016] A sintered neodymium-iron-boron magnet obtained by the preparation method of the sintered neodymium-iron-boron magnet as described above.

[0017] The present invention prepares a sintered NdFeB magnet by compounding a specific Al-Ti-B alloy powder in NdFeB alloy powder. Thus, during the high-temperature sintering process, due to the low melting point of the Al-Ti-B alloy powder, it can be transformed into a liquid phase with better fluidity, uniformly distributed around the main-phase grains, forming a continuous and uniform thin-layer grain boundary phase, isolating the main-phase grains, and playing a role in inhibiting grain growth and isolating the magnetic coupling of the main-phase grains.

[0018] Therefore, the preparation method of the sintered NdFeB magnet of the present invention can reconstruct and optimize the grain boundaries of the NdFeB magnet, improve the microstructure of the grain boundaries, and can effectively improve the intrinsic coercivity of the sintered NdFeB magnet without using or using a small amount of heavy rare earth elements while ensuring high remanence, manufacturing a sintered NdFeB magnet that can meet high-temperature applications, has high cost performance, is not limited by thickness, and is convenient for mass production. Detailed implementation mode

[0019] To facilitate the understanding of the present invention, the present invention will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. On the contrary, the purpose of providing these embodiments or examples is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments or examples and are not intended to limit the present invention. The optional range of the term "and / or" used herein includes any one of two or more related listed items, and also includes any and all combinations of the related listed items. The any and all combinations include any two related listed items, any more related listed items, or all related listed items.

[0021] The present invention provides a preparation method of a sintered NdFeB magnet. In terms of mass fraction, the preparation raw materials include: less than 1% of Al-Ti-B alloy powder, less than 0.3% of lubricant, and more than 98.7% of NdFeB alloy powder. Among them, the composition of the Al-Ti-B alloy powder is Al a Ti b B c M d , M is selected from at least one of Co, Cu, Fe, V, Nb, Ta, Zr or Mg, a, b, c, d are all mass fractions, and 92.3% ≤ a ≤ 94.7%, 4.5% ≤ b ≤ 5.5%, 0.8% ≤ c ≤ 1.2%, 0% ≤ d ≤ 1%.

[0022] The present invention prepares a sintered NdFeB magnet by compounding a specific Al-Ti-B alloy powder in NdFeB alloy powder. Thus, during the high-temperature sintering process, due to the low melting point of the Al-Ti-B alloy powder, it can be transformed into a liquid phase with better fluidity, uniformly distributed around the main-phase grains, forming a continuous and uniform thin-layer grain boundary phase, isolating the main-phase grains, and playing a role in inhibiting grain growth and isolating the magnetic coupling of the main-phase grains.

[0023] Therefore, the preparation method of the sintered NdFeB magnet of the present invention can reconstruct and optimize the grain boundaries of the NdFeB magnet, improve the microstructure of the grain boundaries, and can effectively improve the intrinsic coercivity of the sintered NdFeB magnet without using or using a small amount of heavy rare earth elements while ensuring high remanence, manufacturing a sintered NdFeB magnet that can meet high-temperature applications, has high cost performance, is not limited in thickness, and is convenient for mass production.

[0024] Among them, the particle size of the Al-Ti-B alloy powder is preferably 2μm - 20μm, and this particle size is beneficial to improving the mixing uniformity of the Al-Ti-B alloy powder and the NdFeB alloy powder. Thus, when high-temperature sintering is carried out subsequently, the liquid phase transformed from the Al-Ti-B alloy powder can be more uniformly distributed around the main-phase grains, further improving the intrinsic coercivity of the sintered NdFeB magnet.

[0025] Specifically, the NdFeB magnet can be either a NdFeB magnet containing light rare earth elements or a NdFeB magnet containing heavy rare earth elements. For example, the composition of the NdFeB alloy powder is Nd x Re y Fe 100-x-y-m-n M m B n , where Re can be selected as light rare earth elements and / or heavy rare earth elements. Thus, by selecting Re, a sintered NdFeB magnet without heavy rare earths or a sintered NdFeB magnet with low heavy rare earths can be prepared.

[0026] Among them, Re is preferably at least one of La, Ce, Y, Pr, Sm, Eu, Gd, Ho, Dy or Tb, M is preferably at least one of V, Ti, Cr, Ni, Mn, Zr, Cu, Ga, Co, Al, In, Nb, Ta, Ag, Sn, Pb, W, Mo, Bi, Mg or Pd, x, y, m, n are all mass fractions, and 14 ≤ x ≤ 32, 0 ≤ y ≤ 15, 0 ≤ m ≤ 5, 0.8 ≤ n ≤ 1.2.

[0027] Preferably, Re is selected from at least one of Pr, La, Ce, Y or Gd.

[0028] Preferably, 21 ≤ x ≤ 26, 6 ≤ y ≤ 8, 0.6 ≤ m ≤ 3.2, 0.9 ≤ n ≤ 0.98.

[0029] Among the above-mentioned neodymium iron boron alloy powders, the particle size is preferably 2.6 μm - 3.4 μm, which is beneficial to the uniform mixing with the aluminum titanium boron alloy powder and further improves the intrinsic coercivity of the sintered neodymium iron boron magnet.

[0030] The neodymium iron boron alloy powder of the present invention can directly crush the existing neodymium iron boron alloy into powder for use, or can prepare the neodymium iron boron alloy and then crush it into powder for use.

[0031] Preferably, when preparing the neodymium iron boron alloy powder, the raw materials are placed in a vacuum melting furnace according to the composition and ratio for melting and spinning to obtain alloy cast sheets, and then after hydrogen crushing the alloy cast sheets, an antioxidant is added for sufficient mixing to obtain coarse powder, and the coarse powder is ground into neodymium iron boron alloy powder by a jet mill. Among them, the mass ratio of the added antioxidant is preferably 0.05% - 0.1%.

[0032] Optionally, the lubricant can improve the mechanical force between the aluminum titanium boron alloy powder and the neodymium iron boron alloy powder, making the powder easy to form and maintaining the high remanence of the sintered neodymium iron boron magnet. The lubricant is preferably Ningbo Haotian HT-3 lubricant and / or Tianjin Yuesheng YSH-06 lubricant.

[0033] In the method for preparing a sintered neodymium iron boron magnet of the present invention, after mixing the aluminum titanium boron alloy powder, the lubricant and the neodymium iron boron alloy powder to obtain a mixture, the mixture is subjected to orientation, pressing, isostatic pressing, sintering and tempering treatments in sequence to obtain a sintered neodymium iron boron magnet.

[0034] Specifically, first place the obtained mixture in a glove box with an oxygen content lower than 0.02% for orientation treatment to obtain a neodymium iron boron magnet green compact, where the magnetic field strength is preferably ≥1.4 T.

[0035] Then, the neodymium iron boron magnet green compact is subjected to pressing treatment to obtain a magnet green compact, and the magnet green compact is then subjected to isostatic pressing to obtain a neodymium iron boron magnet green body.

[0036] Then, place the neodymium iron boron magnet green body in a graphite box, then load it into a sintering furnace for high-temperature vacuum sintering, primary tempering treatment and secondary tempering treatment to obtain a sintered neodymium iron boron magnet. Among them, the sintering temperature is preferably 1050 °C - 1120 °C, the sintering time is preferably 2 h - 8 h, the vacuum degree is preferably lower than 5×10 -2 Pa, the primary tempering temperature is preferably 850 °C - 950 °C, the time is preferably 1 h - 3 h, the secondary tempering temperature is preferably 430 °C - 550 °C, and the time is preferably 3 h - 6 h.

[0037] The present invention also provides a sintered Nd-Fe-B magnet prepared by using the preparation method of the sintered Nd-Fe-B magnet described above. The sintered Nd-Fe-B magnet has high intrinsic coercivity, high remanence, high cost performance, and the thickness is not limited.

[0038] Hereinafter, the sintered Nd-Fe-B magnet and its preparation method will be further described through the following specific examples.

[0039] Example 1

[0040] Nd-Fe-B alloy powder (Pr 0.25 Nd 0.75 ) 29.6 Fe 68.21 Co 0.5 Cu 0.3 Ga 0.3 Zr 0.15 B 0.94 was prepared, with a particle size of 3.1 μm. 0.2% by mass of Al-Ti-B alloy powder Al 94 Ti5B1 and 0.1% of Tianjin Yuesheng YSH-06 lubricant were added to the Nd-Fe-B alloy powder and mixed evenly to obtain a mixture. Among them, the particle size of the Al-Ti-B alloy powder was 20 μm. The mixture was oriented and formed in a magnetic field with an oxygen content of 0.01% and a magnetic field strength of 1.7 T, and then pressed into a green body. The green body was placed in a vacuum sintering furnace, and the vacuum degree was pumped to 2×10 -2 Pa, sintered at 1090 °C for 6 h, and tempered once at 900 °C for 2 h, and then tempered twice at 470 °C for 4 h to obtain a sintered Nd-Fe-B magnet.

[0041] The room temperature performance of the sintered Nd-Fe-B magnet of this example was tested by using a permanent magnet material testing B-H instrument, and the test results are shown in Table 1.

[0042] Example 2

[0043] The difference between Example 2 and Example 1 is that the mass ratio of the added Al-Ti-B alloy powder is 0.3%.

[0044] The room temperature performance of the sintered Nd-Fe-B magnet of this example was tested by using a permanent magnet material testing B-H instrument, and the test results are shown in Table 1.

[0045] Example 3

[0046] The difference between Example 3 and Example 1 is that the mass ratio of the added Al-Ti-B alloy powder is 0.4%.

[0047] The room temperature performance of the sintered Nd-Fe-B magnet of this example was tested by using a permanent magnet material testing B-H instrument, and the test results are shown in Table 1.

[0048] Example 4

[0049] Example 4 is different from Example 1 in that the mass ratio of the added Al-Ti-B alloy powder is 0.5%.

[0050] The room temperature performance of the sintered Nd-Fe-B magnet of this example was tested using a B-H tester for permanent magnetic materials, and the test results are shown in Table 1.

[0051] Example 5

[0052] Example 5 is different from Example 1 in that the mass ratio of the added Al-Ti-B alloy powder is 0.7%.

[0053] The room temperature performance of the sintered Nd-Fe-B magnet of this example was tested using a B-H tester for permanent magnetic materials, and the test results are shown in Table 1.

[0054] Example 6

[0055] The Nd-Fe-B alloy powder (Pr 0.25 Nd 0.75 ) 31 Fe 65.58 Co 1.5 Cu 0.4 Ga 0.4 Zr 0.2 B 0.92 , with a particle size of 3 μm, was prepared. An Al-Ti-B alloy powder Al 94.7 Ti 4.5 B 0.8 with a mass ratio of 0.2% and 0.1% of Tianjin Yuesheng YSH-06 lubricant were added to the Nd-Fe-B alloy powder and mixed evenly to obtain a mixture. Among them, the particle size of the Al-Ti-B alloy powder was 10 μm. The mixture was oriented and formed in a magnetic field with an oxygen content of 0.01% and a magnetic field strength of 1.7 T, and then pressed into a green body. The green body was placed in a vacuum sintering furnace, and the vacuum degree was pumped to 3×10 -2 Pa, sintered at 1085 °C for 6 h, tempered at 900 °C for 2 h for the first time, and then tempered at 490 °C for 4 h for the second time to obtain a sintered Nd-Fe-B magnet.

[0056] The room temperature performance of the sintered Nd-Fe-B magnet of this example was tested using a B-H tester for permanent magnetic materials, and the test results are shown in Table 1.

[0057] Example 7

[0058] Example 7 is different from Example 6 in that the mass ratio of the added Al-Ti-B alloy powder is 0.3%.

[0059] The room temperature performance of the sintered Nd-Fe-B magnet of this example was tested using a B-H tester for permanent magnetic materials, and the test results are shown in Table 1.

[0060] Example 8

[0061] The difference between Example 8 and Example 6 is that the mass ratio of the added Al-Ti-B alloy powder is 0.4%.

[0062] The room temperature properties of the sintered Nd-Fe-B magnet of this example were tested using a B-H tester for permanent magnetic materials, and the test results are shown in Table 1.

[0063] Example 9

[0064] The difference between Example 9 and Example 6 is that the mass ratio of the added Al-Ti-B alloy powder is 0.5%.

[0065] The room temperature properties of the sintered Nd-Fe-B magnet of this example were tested using a B-H tester for permanent magnetic materials, and the test results are shown in Table 1.

[0066] Example 10

[0067] The difference between Example 10 and Example 6 is that the mass ratio of the added Al-Ti-B alloy powder is 0.7%.

[0068] The room temperature properties of the sintered Nd-Fe-B magnet of this example were tested using a B-H tester for permanent magnetic materials, and the test results are shown in Table 1.

[0069] Example 11

[0070] Nd-Fe-B alloy powder (Pr 0.25 Nd 0.75 ) 30 Dy 0.8 Fe 66.65 Co1Cu 0.2 Ga 0.3 Zr 0.13 B 0.92 was prepared, with a particle size of 3 μm. An Al-Ti-B alloy powder Al 92.3 Ti 5.5 B 1.2 Co1 with a mass ratio of 0.2% and 0.1% of Tianjin Yuesheng YSH-06 lubricant were added to the Nd-Fe-B alloy powder, and the mixture was uniformly mixed to obtain a mixture. Among them, the particle size of the Al-Ti-B alloy powder was 5 μm. The mixture was oriented and formed in a magnetic field with an oxygen content of 0.01% and a magnetic field strength of 1.7 T, and then pressed into a green compact. The green compact was placed in a vacuum sintering furnace, and the vacuum degree was pumped to 3×10 -2 Pa, sintered at 1088 °C for 6 h, tempered at 900 °C for 2 h for the first time, and then tempered at 490 °C for 4 h for the second time to obtain a sintered Nd-Fe-B magnet.

[0071] The sintered Nd-Fe-B magnet of this embodiment was tested for room temperature performance using a B-H tester for permanent magnetic materials, and the test results are shown in Table 1.

[0072] Example 12

[0073] The difference between Example 12 and Example 11 is that the mass ratio of the added Al-Ti-B alloy powder is 0.3%.

[0074] The sintered Nd-Fe-B magnet of this embodiment was tested for room temperature performance using a B-H tester for permanent magnetic materials, and the test results are shown in Table 1.

[0075] Example 13

[0076] The difference between Example 13 and Example 11 is that the mass ratio of the added Al-Ti-B alloy powder is 0.4%.

[0077] The sintered Nd-Fe-B magnet of this embodiment was tested for room temperature performance using a B-H tester for permanent magnetic materials, and the test results are shown in Table 1.

[0078] Example 14

[0079] The difference between Example 14 and Example 11 is that the mass ratio of the added Al-Ti-B alloy powder is 0.5%.

[0080] The sintered Nd-Fe-B magnet of this embodiment was tested for room temperature performance using a B-H tester for permanent magnetic materials, and the test results are shown in Table 1.

[0081] Example 15

[0082] The difference between Example 15 and Example 11 is that the mass ratio of the added Al-Ti-B alloy powder is 0.7%.

[0083] The sintered Nd-Fe-B magnet of this embodiment was tested for room temperature performance using a B-H tester for permanent magnetic materials, and the test results are shown in Table 1.

[0084] Comparative Example 1

[0085] The prepared Nd-Fe-B alloy powder (Pr 0.25 Nd 0.75 ) 29.6 Fe 68.21 Co 0.5 Cu 0.3 Ga 0.3 Zr 0.15 B 0.94, with a particle size of 3.1 μm, 0.1% by mass of Tianjin Yuesheng YSH-06 lubricant was added to the neodymium-iron-boron alloy powder, and the mixture was uniformly mixed to obtain a mixture. The mixture was oriented and formed in a magnetic field with an oxygen content of 0.01% and a magnetic field strength of 1.7 T, and then pressed into a green compact. The green compact was placed in a vacuum sintering furnace, and the vacuum degree was pumped to 2×10 -2 Pa, sintered at 1090 °C for 6 h, tempered at 900 °C for 2 h for the first time, and then tempered at 470 °C for 4 h for the second time to obtain a sintered neodymium-iron-boron magnet.

[0086] The room-temperature properties of the sintered neodymium-iron-boron magnet of this comparative example were tested using a permanent magnet material testing B-H instrument, and the test results are shown in Table 1.

[0087] Comparative Example 2

[0088] The neodymium-iron-boron alloy powder (Pr 0.25 Nd 0.75 ) 31 Fe 66.13 Co 1.5 Cu 0.4 Ga 0.4 Zr 0.2 B 0.92 , with a particle size of 3 μm, 0.1% by mass of Tianjin Yuesheng YSH-06 lubricant was added to the neodymium-iron-boron alloy powder, and the mixture was uniformly mixed to obtain a mixture. The mixture was oriented and formed in a magnetic field with an oxygen content of 0.01% and a magnetic field strength of 1.7 T, and then pressed into a green compact. The green compact was placed in a vacuum sintering furnace, and the vacuum degree was pumped to 3×10 -2 Pa, sintered at 1085 °C for 6 h, tempered at 900 °C for 2 h for the first time, and then tempered at 490 °C for 4 h for the second time to obtain a sintered neodymium-iron-boron magnet.

[0089] The room-temperature properties of the sintered neodymium-iron-boron magnet of this comparative example were tested using a permanent magnet material testing B-H instrument, and the test results are shown in Table 1.

[0090] Comparative Example 3

[0091] The neodymium-iron-boron alloy powder (Pr 0.25 Nd 0.75 ) 30 Dy 0.8 Fe 66.65 Co1Cu 0.2 Ga 0.3 Zr 0.13 B 0.92, with a particle size of 3 μm, 0.1% by mass of Tianjin Yuesheng YSH-06 lubricant was added to the neodymium iron boron alloy powder, and the mixture was uniformly mixed to obtain a mixture. The mixture was oriented and formed in a magnetic field with an oxygen content of 0.01% and a magnetic field strength of 1.7 T, and then pressed into a green compact. The green compact was placed in a vacuum sintering furnace, and the vacuum degree was pumped to 3×10 -2 Pa, sintered at 1088 °C for 6 h, annealed at 900 °C for 2 h for the first time, and then annealed at 490 °C for 4 h for the second time to obtain a sintered neodymium iron boron magnet.

[0092] The room temperature performance of the sintered neodymium iron boron magnet of this comparative example was tested using a permanent magnet material testing B-H instrument, and the test results are shown in Table 1.

[0093] Comparative Example 4

[0094] The difference between Comparative Example 4 and Example 1 is that the mass ratio of the added aluminum titanium boron alloy powder is 1.1%.

[0095] The room temperature performance of the sintered neodymium iron boron magnet of this comparative example was tested using a permanent magnet material testing B-H instrument, and the test results are shown in Table 1.

[0096] Comparative Example 5

[0097] The difference between Comparative Example 5 and Example 1 is that the aluminum titanium boron alloy powder with a mass ratio of 0.2% is replaced with aluminum powder with a mass ratio of 0.2%.

[0098] The room temperature performance of the sintered neodymium iron boron magnet of this comparative example was tested using a permanent magnet material testing B-H instrument, and the test results are shown in Table 1.

[0099] Comparative Example 6

[0100] The difference between Comparative Example 6 and Example 1 is that 0.19% by mass of aluminum powder, 0.008% by mass of titanium powder, and 0.002% by mass of boron powder are independently added to the neodymium iron boron alloy powder, and the total mass ratio of the aluminum powder, titanium powder, and boron powder is 0.2%.

[0101] The room temperature performance of the sintered neodymium iron boron magnet of this comparative example was tested using a permanent magnet material testing B-H instrument, and the test results are shown in Table 1.

[0102] Table 1

[0103]

[0104]

[0105] From the comparison of the properties of the sintered Nd-Fe-B magnets obtained in Examples 1-15 and Comparative Examples 1-3 in Table 1, it can be seen that compared with the sintered Nd-Fe-B magnets without adding the Al-Ti-B alloy powder, the intrinsic coercivity of the sintered Nd-Fe-B magnets obtained by adding the Al-Ti-B alloy powder is significantly improved, and the decrease in remanence is small. This indicates that after adding the Al-Ti-B alloy powder to the Nd-Fe-B alloy powder, during high-temperature sintering, the low-melting-point Al-Ti-B will be uniformly distributed around the main-phase grains of Nd-Fe-B in a flowing liquid phase, forming a continuous non-magnetic grain boundary phase, which better isolates the main-phase grains and plays a role in inhibiting grain growth and hindering the magnetic coupling of the main-phase grains. Therefore, the intrinsic coercivity of the sintered Nd-Fe-B magnets is greatly improved.

[0106] In Comparative Example 4, as the addition amount of the Al-Ti-B alloy powder increases, the decrease in remanence increases significantly, but the increase in intrinsic coercivity is small. This indicates that when the addition amount of the Al-Ti-B alloy powder is too large, on the one hand, the proportion of the grain boundary phase increases and the remanence decreases; on the other hand, after introducing more aluminum elements, the excessive aluminum elements may enter the main-phase lattice, which not only does not contribute to the improvement of the intrinsic coercivity, but also causes the remanence to decrease. Therefore, it is necessary to select an appropriate addition ratio to optimize the performance.

[0107] In Comparative Examples 5-6, when adding the same content of other powders, such as aluminum powder, or separate aluminum powder, titanium powder, and boron powder, to the Nd-Fe-B alloy powder, the increase in the coercivity of the obtained sintered Nd-Fe-B magnets is very small, indicating that the improvement effect of adding separate powders on the grain boundary is far less than that of adding the Al-Ti-B alloy powder.

[0108] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as within the scope described in this specification.

[0109] The above-described embodiments only represent several implementation manners of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent should be subject to the appended claims.

Claims

1. A preparation method of a sintered neodymium iron boron magnet, characterized in that, In terms of mass fraction, the preparation raw materials include: aluminum-titanium-boron alloy powder below 1%, lubricant below 0.3%, and neodymium-iron-boron alloy powder above 98.7%. Among them, the composition of the aluminum-titanium-boron alloy powder is Al a Ti b B c M d , M is selected from at least one of Co, Cu, Fe, V, Nb, Ta, Zr or Mg, a, b, c, d are all mass fractions, and 92.3% ≤ a ≤ 94.7%, 4.5% ≤ b ≤ 5.5%, 0.8% ≤ c ≤ 1.2%, 0% ≤ d ≤ 1%.

2. The preparation method of the sintered neodymium iron boron magnet according to claim 1, characterized in that, The mass fraction of the aluminum-titanium-boron alloy powder is below 0.7%.

3. The preparation method of the sintered neodymium iron boron magnet according to claim 2, characterized in that, By mass fraction, the preparation raw materials include: 0.2%-0.5% of aluminum-titanium-boron alloy powder, 0.05%-0.15% of lubricant, and 99.35%-99.75% of neodymium-iron-boron alloy powder.

4. The preparation method of the sintered neodymium iron boron magnet according to any one of claims 1-3, characterized in that, The particle size of the aluminum-titanium-boron alloy powder is 2μm-20μm.

5. The preparation method of the sintered neodymium iron boron magnet according to any one of claims 1-3, characterized in that, The composition of the Nd-Fe-B alloy powder is Nd x Re y Fe 100-x-y-m-n M m B n , where Re is selected from at least one of La, Ce, Y, Pr, Sm, Eu, Gd, Ho, Dy or Tb, M is selected from at least one of V, Ti, Cr, Ni, Mn, Zr, Cu, Ga, Co, Al, In, Nb, Ta, Ag, Sn, Pb, W, Mo, Bi, Mg or Pd, x, y, m, n are all mass fractions, and 14 ≤ x ≤ 32, 0 ≤ y ≤ 15, 0 ≤ m ≤ 5, 0.8 ≤ n ≤ 1.

2.

6. The preparation method of the sintered neodymium iron boron magnet according to claim 5, characterized in that, The Re is selected from at least one of Pr, La, Ce, Y or Gd; and / or, 21≤x≤26, 6≤y≤8, 0.6≤m≤3.2, 0.9≤n≤0.

98.

7. The preparation method of the sintered neodymium iron boron magnet according to claim 1, characterized in that, The particle size of the neodymium-iron-boron alloy powder is 2.6μm-3.4μm.

8. The preparation method of the sintered neodymium iron boron magnet according to any one of claims 1-3, characterized in that, In the sintering process, the sintering temperature is 1050°C - 1120°C, the sintering time is 2h - 8h, and the vacuum degree is lower than 5×10 -2 Pa.

9. The preparation method of the sintered neodymium iron boron magnet according to claim 8, wherein, After the sintering treatment step, a first tempering treatment and a second tempering treatment are carried out. The first tempering temperature is 850°C-950°C, the time is 1h-3h, the second tempering temperature is 430°C-550°C, and the time is 3h-6h.

10. A sintered neodymium-iron-boron magnet prepared by the method for preparing a sintered neodymium-iron-boron magnet according to any one of claims 1-9.

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