An R-T-B type neodymium iron boron magnet, its preparation method and application

Abstract

The present invention discloses an R-T-B type neodymium iron boron magnet and a preparation method thereof. By mass ratio of 100%, the magnet comprises the following components: 27.0 - 35.0 wt% of R, where R is at least one rare earth element including Nd; 0.80 - 0.93 wt% of B; 0.1 - 0.50 wt% of Cu; 0.2 - 0.5 wt% of Ga; 0 - 0.5 wt% of M, where M is at least one of Zr and Ti, and the sum of the contents of Cu, Ga and M is greater than 0.9 times the content of B; 0.1 - 1.5 wt% of Al; the balance is Fe, Co and inevitable impurities, and Fe accounts for more than 95 wt% of the total content of Fe, Co and impurities. In this application, by adjusting the proportions of the elements of R, Cu, Ga and M, and the sum of the contents of Cu, Ga and M is greater than 0.9 times the content of B, before the alloy cast sheet is made into powder, the alloy cast sheet is subjected to heat preservation treatment at 750 ± 50 °C, which can, on the premise of ensuring 90 vol% of the main phase, form an R-Ga-Cu-M phase with a volume fraction of more than 40 vol% at the grain boundaries of the magnet, and at the same time, to a certain extent, reduce the existence of the R-T-Ga phase, avoiding the reduction of Hcj of the magnet due to the excessive R-T-Ga phase.

Description

Technical Field

[0001] The present invention belongs to the field of rare earth permanent magnet materials, and particularly relates to an R-T-B type neodymium iron boron magnet, a preparation method thereof, and an application thereof. Background Art

[0002] The R-T-B series sintered magnet (R is at least one of rare earth elements and must contain Nd, T is a transition metal element and must contain Fe) uses the Nd 2 Fe 14 B type compound as the main phase, which is currently the magnet with the highest performance among permanent magnets. Due to its excellent magnetic properties, it is widely used in air-conditioning compressors, wind power generation, and the automotive field.

[0003] In order to obtain a higher Hcj, a large amount of heavy rare earth elements, such as Dy and Tb, are often added to the magnet. However, with the increase of heavy rare earth elements, the residual magnetic flux density Br of the magnet decreases significantly. Therefore, in recent years, the method of grain boundary diffusion is usually adopted to coat a layer of heavy rare earth element compound on the surface of the magnet, so that the surface heavy rare earth diffuses into the magnet interior, and the outer shell part of the main phase grains is magnetized by the heavy rare earth elements, while suppressing the decrease of Br and improving the Hcj of the magnet.

[0004] Heavy rare earth elements such as Dy and Tb have the disadvantages of limited production, unstable supply, and high price, which increase the comprehensive cost. Therefore, high-performance R-T-B series sintered magnets prepared without using or using extremely small amounts of heavy rare earth elements have attracted attention.

[0005] WO2013 / 008756A limits the B content to a relatively small range (4.5 - 6.2 atomic% of B), and selects one or more metal elements M among Al, Ga, and Cu, which can generate R 2 T 17 phase, ensuring R 2 T 17 phase as the raw material to generate a transition metal-rich phase R 6 T 13 M, thereby reducing the usage content of heavy rare earth and improving the Hcj of the R-T-B series sintered magnet.

[0006] It is described in the JP1996264363A bulletin that heat treatment of the Nd-Fe-B alloy cast sheet prepared by the strip casting method at 800 - 1100 °C can improve the particle size distribution after crushing the alloy cast sheet, thereby improving the Hcj of the magnet. However, after treatment in this temperature range, the advantage of grain refinement of the internal structure of the alloy cast sheet will also disappear, resulting in a decrease in the Hcj of the magnet.

[0007] CN110619984A discloses an R-Fe-B series sintered magnet with low B content. By reducing the B content, an R-T-Ga phase is formed in the crystal grains. However, the R-T-Ga phase also has certain magnetism. When there is a large amount of R-T-Ga in the crystal grains of the sintered neodymium iron boron magnet, it will prevent the increase of Hcj. In order to suppress the generation amount of the R-T-Ga phase in the R-T-B series magnet to the lowest level, by adjusting the amounts of R and B and reducing R 2 T 17 phase formation, set the amounts of R and Ga within the range corresponding to the most appropriate R 2 T 17 phase generation amount, so as to form more R-Ga phases and R-Ga-Cu phases in the grain boundaries and obtain a magnet with high Br and high Hcj.

[0008] CN106716571B discloses a method for manufacturing an R-T-B series sintered magnet. After heating the magnet to a temperature above 730 °C and below 1020 °C, it is cooled by rapid cooling. After heating to a temperature of 440 °C - 550 °C, the generation of the R-T-Ga phase can be suppressed and the R-Ga-Cu phase can be generated. However, rapid cooling will cause the fracture of the sintered magnet and affect the performance of the magnet. But when preparing the alloy cast sheet, especially when using the thin strip continuous casting method with a rapid cooling roll to spin and cast, the distribution of elements such as Ga and M in the alloy cast sheet is uneven, resulting in a lower Hcj. Summary of the Invention

[0009] In order to improve the above technical problems, the present invention provides an R-T-B type neodymium iron boron magnet. Calculated by 100% by mass ratio, the magnet contains the following components: 27.0 - 35.0 wt% of R, where R is at least one rare earth element including Nd;

[0010] 0.80 - 0.93 wt% of B;

[0011] 0.10 - 0.50 wt% of Cu;

[0012] 0.20 - 0.50 wt% of Ga;

[0013] 0 - 0.50 wt% of M, where M is at least one of Zr and Ti, and the sum of the contents of Cu, Ga, and M is greater than 0.9 times the content of B;

[0014] 0.10 - 1.50 wt% of Al;

[0015] The balance is Fe, Co, and inevitable impurities, and Fe accounts for more than 95 wt% of the total content of Fe, Co, and impurities.

[0016] According to an embodiment of the present invention, the R-T-B type neodymium iron boron magnet comprises 28.0 to 33.0 wt% of R, where R is at least one rare earth element including Nd;

[0017] 0.80 to 0.90 wt% of B;

[0018] 0.22 to 0.38 wt% of Cu;

[0019] 0.25 to 0.40 wt% of Ga;

[0020] 0.10 to 0.30 wt% of M, where M is at least one of Zr and Ti, and the sum of the contents of Cu, Ga and M is greater than 0.9 times the content of B;

[0021] 0.10 to 1.00 wt% of Al;

[0022] The balance is Fe, Co and inevitable impurities; and Fe accounts for more than 95 wt% of the total content of Fe, Co and impurities.

[0023] According to an embodiment of the present invention, R includes Nd and further includes at least one of La, Ce, Pr, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y and Sc; preferably, R is Nd and Dy.

[0024] According to an embodiment of the present invention, the R-T-B type neodymium iron boron magnet contains an R 2 Fe 14 B-type main phase, and the proportion of the main phase is 90 vol% or more, preferably 92 vol% or more.

[0025] According to an embodiment of the present invention, at least 40 vol% of the R-Ga-Cu-M phase is contained at the grain boundary of the R-T-B type neodymium iron boron magnet, preferably 45 vol% or more, more preferably 50 vol% or more; among them, the R-Ga-Cu-M phase includes 40.0 wt% - 85.0 wt% of R; 2.0 wt% - 10.0 wt% of Ga; 1.0 wt% - 6.0 wt% of Cu and 0.4 wt% - 4.0 wt% of M, where R and M have the above meanings.

[0026] The present invention also provides a preparation method of the above-mentioned R-T-B type neodymium iron boron magnet, and the method comprises the following steps:

[0027] (1) Prepare an R-T-B type neodymium iron boron magnet alloy;

[0028] (2) Under an inert atmosphere, reheat the R-T-B type neodymium iron boron magnet alloy in step (1), cool it, and prepare an R-T-B type neodymium iron boron magnet alloy ingot;

[0029] (3) Hydrogenate and crush the R-T-B type neodymium iron boron magnet alloy ingot in step (2), press it into shape, sinter it, and then perform heat treatment to obtain the R-T-B type neodymium iron boron magnet.

[0030] According to an embodiment of the present invention, in step (1), the method for preparing the R-T-B type neodymium iron boron magnet alloy includes: dissolving the raw materials for preparing the R-T-B type neodymium iron boron magnet to prepare an alloy solution, and then rapidly cooling the alloy solution to prepare the R-T-B type neodymium iron boron magnet alloy.

[0031] According to an embodiment of the present invention, in step (1), the temperature for dissolving the raw materials is 1000 - 1500 °C, preferably 1400 - 1500 °C; the holding time during dissolution is 5 - 15 min, exemplarily 10 min.

[0032] According to an embodiment of the present invention, in step (1), the raw materials for preparing the R-T-B type neodymium iron boron magnet alloy are 27.0 - 35.0 wt% of the above-mentioned R, where R is at least one rare earth element including Nd;

[0033] 0.80 - 0.93 wt% of B;

[0034] 0.1 - 0.50 wt% of Cu;

[0035] 0.2 - 0.50 wt% of Ga;

[0036] 0 - 0.50 wt% of M, where M is at least one of Zr and Ti, and the sum of the contents of Cu, Ga, and M is greater than 0.9 times the content of B;

[0037] 0.10 - 1.50 wt% of Al;

[0038] The balance is Fe, Co, and inevitable impurities, and Fe accounts for more than 95 wt% of the total content of Fe, Co, and impurities.

[0039] According to an embodiment of the present invention, in step (1), the cooling process can adopt the strip continuous casting method.

[0040] According to an embodiment of the present invention, in step (1), the alloy solution is rapidly cooled on a rotating rapid cooling roll to prepare the crystallized R-T-B type neodymium iron boron magnet alloy.

[0041] According to a preferred embodiment of the present invention, in step (1), the method for preparing the R-T-B type neodymium iron boron magnet alloy includes:

[0042] R with a content of 27.0 to 35.0 wt%, where R is selected from at least one rare earth element including Nd; 0.80 to 0.93 wt% of B; 0.10 to 0.50 wt% of Cu; 0 to 0.50 wt% of M, where M is at least one of Zr and Ti; 0.10 to 1.50 wt% of Al; 0.20 to 0.50 wt% of Ga, and the sum of the contents of Cu, Ga, and M is greater than 0.9 times the content of B; the balance is Fe, Co, and inevitable impurities. Heat at 1000 to 1500 °C to completely dissolve each component to prepare an alloy solution; rapidly cool the alloy solution on a rotating rod to prepare an R-T-B type neodymium-iron-boron magnet alloy.

[0043] According to an embodiment of the present invention, in step (2), the temperature of the secondary heating is 700 to 800 °C, preferably 750 °C; the heating rate during the secondary heating is 5 - 10 °C / min, preferably 7 °C / min.

[0044] According to an embodiment of the present invention, in step (2), the heat preservation treatment device needs to be rotated during heat preservation.

[0045] According to an embodiment of the present invention, in step (2), the pressure is 10 - 15 KPa, preferably 13 KPa.

[0046] According to an embodiment of the present invention, in step (2), after the secondary heating, a heat preservation treatment is carried out, and the heat preservation time is 240 - 360 min, preferably 300 min.

[0047] According to an embodiment of the present invention, in step (2), the inert atmosphere is argon or nitrogen.

[0048] According to an embodiment of the present invention, in step (2), the cooling is first slow cooling and then rapid cooling;

[0049] Among them, slow cooling means that in an inert atmosphere of 80 - 100 kPa, the temperature of the alloy is lowered to 500 - 550 °C, and the cooling rate is 4 - 8 °C / min;

[0050] Rapid cooling means that the alloy at a temperature of 500 - 550 °C is cooled to below 80 °C, and the cooling rate is 15 - 20 °C / min.

[0051] According to an embodiment of the present invention, the slow cooling time is 25 - 40 min, preferably 30 min.

[0052] According to a preferred embodiment of the present invention, the cooling is first slow cooling and then rapid cooling; slow cooling means cooling by introducing argon gas at 80 - 100 kPa into a vacuum heat treatment furnace for 30 minutes, which reduces the temperature of the alloy cast sheet to 500 - 550 °C, and the cooling rate is about 5 °C / min; rapid cooling means accelerating the cooling of the alloy cast sheet by turning on the blower, with a cooling rate of 15 - 20 °C / min, reducing the temperature of the alloy cast sheet to below 80 °C, and then taking it out of the furnace for recycling to prepare an R-T-B type neodymium iron boron magnet alloy cast sheet.

[0053] According to a preferred embodiment of the present invention, step (2) is specifically as follows: putting the prepared R-T-B type neodymium iron boron magnet alloy into a rotary vacuum heat treatment furnace, heating it to the target temperature of 750 ± 50 °C at a heating rate of 5 - 10 °C / min. After reaching the target temperature, keep it warm for 240 - 360 minutes while rotating, and introduce 10 - 15 KPa of argon gas for protection during the heat preservation. After the heat preservation is completed, stop rotating, and use the cooling methods of slow cooling and rapid cooling to cool it to room temperature and then take it out of the furnace to prepare an R-T-B type neodymium iron boron magnet alloy cast sheet. Through this treatment method, the alloy cast sheet is heated evenly during the heat preservation process, which is beneficial to the uniform and stable precipitation of the R-Ga-Cu-M phase.

[0054] According to the embodiment of the present invention, in step (3), the processes of using the hydrogen embrittlement method to crush the R-T-B type neodymium iron boron magnet alloy cast sheet and re-crushing the hydrogen embrittled fine powder to obtain jet mill powder are carried out.

[0055] Exemplarily, put the obtained alloy cast sheet into a hydrogen embrittlement furnace, introduce hydrogen with a purity of 99.5%, carry out hydrogen absorption reaction for crushing, and after the processes of hydrogen absorption, replacement, dehydrogenation, and cooling, crush the alloy into fine powder.

[0056] According to the embodiment of the present invention, a jet mill equipment is selected to crush the fine powder, and the crushing power is impact crushing by inert gas, preferably nitrogen.

[0057] According to the embodiment of the present invention, a lubricant can also be added to the jet mill equipment; the lubricant is selected from organic solvents such as volatile esters or alcohols, for example, zinc stearate.

[0058] According to the embodiment of the present invention, the content of the lubricant is 0.1 wt% - 1.0 wt% of the jet mill powder content; exemplarily, it is 0.1 wt%, 0.2 wt%, 0.5 wt%, 0.8 wt%, 1.0 wt%.

[0059] According to the embodiment of the present invention, in step (3), the pressing and forming includes: after pressing and forming the above jet mill powder in a magnetic field, secondary pressing and forming is carried out by an isostatic press.

[0060] According to an embodiment of the present invention, the magnetic induction intensity in the magnetic field is 1.5 to 1.8 T.

[0061] According to an embodiment of the present invention, the primary forming density after hot pressing in the magnetic field is 3 to 5 g / cm 3 .

[0062] According to an embodiment of the present invention, in step (3), the compacted green compact is sintered using a vacuum heat treatment furnace.

[0063] According to an embodiment of the present invention, in step (3), the sintering temperature is 900 - 1200 °C; the sintering time is 100 to 450 min, preferably 300 min.

[0064] According to an embodiment of the present invention, in step (3), the heat treatment temperature is 550 - 700 °C, preferably 600 - 640 °C, and the time is 180 to 300 min, preferably 240 min.

[0065] It should be noted that the heat treatment temperature range of the present invention is a conventional selection in this industry, so no special tests and verifications are carried out in the implementation cases.

[0066] The present invention also provides the application of the above R-T-B type neodymium iron boron magnet in the field of motors.

[0067] The beneficial effects of the present invention:

[0068] In the prior art, in magnets with low B content, the reduction of the secondary phase increases the volume fraction of the main phase, and the Br of the magnet increases. By adding a certain content of Al, Cu, Ga, etc., an RT phase is formed in the magnet. To increase the coercivity Hcj of the magnet, we need to remove the RT phase and form an R-T-Ga phase and an R-Ga-Cu phase. However, the R-T-Ga phase also has certain magnetism. While making full use of the RT phase in the magnet, the formation of the R-T-Ga phase needs to be suppressed. 2 T 17 phase, in order to increase the coercivity Hcj of the magnet, we need to remove the RT 2 T 17 phase and form an R-T-Ga phase and an R-Ga-Cu phase. However, the R-T-Ga phase also has certain magnetism. While making full use of the RT 2 T 17 phase in the magnet, the formation of the R-T-Ga phase needs to be suppressed.

[0069] In this application, by adjusting the ratios of the R, Cu, Ga, and M elements, and the sum of the contents of Cu, Ga, and M is greater than 0.9 times the content of B. Before the alloy cast sheet is made into powder, the alloy cast sheet is subjected to an isothermal treatment at 750 ± 5 °C. It is possible to form an R-Ga-Cu-M phase with a volume fraction of more than 40 vol% at the grain boundaries of the magnet on the premise of ensuring 90 vol% of the main phase, and at the same time, to reduce the existence of the R-T-Ga phase to a certain extent, avoiding the reduction of the Hcj of the magnet due to the excessive R-T-Ga phase. Description of the Drawings

[0070] Figure 1 It is the morphology diagram of the grain boundary phase in Example 1; where △ represents the test area of grain boundary phase point 1, ○ represents the test area of grain boundary phase point 2, and □ represents the test area of grain boundary phase point 3. Specific implementation manners

[0071] The technical solutions of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only used to illustrate and explain the present invention exemplarily, and should not be construed as limiting the protection scope of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0072] Unless otherwise specified, the raw materials and reagents used in the following embodiments are all commercially available products, or can be prepared by known methods.

[0073] Examples 1-3 and Comparative Examples 1-3

[0074] The raw materials selected in Examples 1-3 and Comparative Examples 1-3 are: 99.5% pure Nd, Dy, industrial ferroboron (B-Fe), industrial Fe, Co, Cu, Ti, Zr, Ga, Al with a purity of 99.9%.

[0075] The preparation methods of the magnets in Examples 1-3 and Comparative Examples 1-3 are as follows:

[0076] (1a) Melting process: Weigh the raw materials according to the respective ratios in Table 1 (the units are all wt%), put the prepared raw materials into a new aluminum-silicon-zirconium crucible, and carry out melting in a high-frequency induction vacuum melting furnace. The melting temperature is 1400 - 1500 °C. After the temperature rises, keep it warm for 10 min.

[0077] (1b) Casting process: Charge argon into the high-frequency induction vacuum melting furnace to 80 kPa, and use the thin strip continuous casting method with a rapid cooling roll to carry out casting to obtain the required alloy, and stir and cool it to room temperature on a rapid cooling disk.

[0078] Table 1

[0079] Serial number Nd Dy B Cu Ga Ti Zr Al Fe Co Example 1 29.5 0.1 0.88 0.35 0.3 0.1 0.1 0.15 66.52 2.0 Example 2 29.5 0.1 0.88 0.35 0.3 0.2 0 0.15 66.52 2.0 Example 3 29.5 0.1 0.88 0.35 0.3 0 0.2 0.15 66.52 2.0 Comparative Example 1 29.5 0.1 0.95 0.4 0.3 0.1 0.1 0.15 66.40 2.0 Comparative Example 2 29.5 0.1 0.88 0.2 0.2 0.1 0.1 0.15 66.77 2.0 Comparative Example 3 29.5 0.1 0.95 0.2 0.2 0.1 0.1 0.15 66.70 2.0

[0080] (2) Put the obtained alloy cast sheet into a rotatable vacuum heat treatment furnace for secondary heat treatment. The heating rate is 7 °C / min, the holding temperature is 750 °C, and argon gas with a pressure of 13 kPa is filled for protection during holding. It is held while rotating, and the holding time is 300 min. After the holding is completed, slow cooling is first carried out, and then rapid cooling. Slow cooling means filling 90 kPa of argon gas in the vacuum heat treatment furnace for cooling, and the time is 30 min. Slow cooling reduces the temperature of the alloy cast sheet to 530 °C, and the cooling rate is 5 °C / min. Rapid cooling means turning on the fan to accelerate the cooling of the alloy cast sheet, and the cooling rate is 20 °C / min. The temperature of the alloy cast sheet is reduced to below 80 °C, and it is taken out of the furnace for recycling to prepare the R-T-B type neodymium iron boron magnet alloy cast sheet.

[0081] (3a) Hydrogen embrittlement process: Put the obtained alloy cast sheet into a hydrogen embrittlement furnace, fill hydrogen with a purity of 99.5%, and carry out hydrogen absorption reaction and crushing. After the processes of hydrogen absorption, replacement, dehydrogenation, and cooling, the alloy is crushed into fine powder.

[0082] (3b) Jet mill process: Add the hydrogen embrittled fine powder into a jet mill device based on the fluidized bed principle, and use an inert gas impact, generally nitrogen, with a pressure of 0.6 MPa to obtain jet mill powder with appropriate particle size.

[0083] (3c) Add zinc stearate as a lubricant to the jet mill powder, and the addition amount is 0.2 wt% of the mixed jet mill powder. Use a mixer to mix well for 3 hours and send it to the next process.

[0084] (3d) Compression molding process: Use a molding press to compress the mixed jet mill powder in an orientation magnetic field of 1.8 T, and the primary molding density is 4.1 g / cm 3 . After the pressing is completed, it is first packaged with a plastic bag, and then vacuum sealed. Use a cold isostatic press for secondary molding to increase the green density.

[0085] (3e) Sintering aging process: Put the billet after two pressings into a vacuum heat treatment furnace, sinter at a sintering temperature of 1060 °C in vacuum for 300 min, then cool to room temperature, and carry out secondary aging heat treatment. The temperature of the secondary aging heat treatment is 620 °C, and the time is 240 min to obtain the final product.

[0086] Monitor the magnetic properties and conduct salt spray tests on the finished product.

[0087] Example 1 and Comparative Examples 4-8

[0088] The differences between Comparative Examples 4-8 and Example 1 lie in that the holding temperature, cooling rate, or whether to rotate during holding in step (2) are different. The treatment methods in Example 1 and Comparative Examples 4-8 are shown in Table 2 below:

[0089] Table 2

[0090]

[0091] Test Example

[0092] Magnetic property testing and composition testing and magnetic property evaluation process for the magnets prepared in Examples 1-3 and Comparative Examples 1-8: For the sintered magnets, a NIM-62000 type large-block rare earth permanent magnet non-destructive measurement system from the National Institute of Metrology, China was used for magnetic property monitoring.

[0093] Corrosion resistance testing: At a temperature of 120 °C, a 96-hour salt spray test was carried out, and the appearance of the surface protective functional layer of the Nd-Fe-B magnet was observed to judge its corrosion resistance in turn.

[0094] Composition determination: Each component was determined using a high-frequency inductively coupled plasma emission spectrometer; the O content was determined using a gas analysis device based on the gas dissolution-infrared absorption method, the N content was determined using a gas analysis device based on the gas dissolution-thermal conductivity method, and the C content was determined using a gas analysis device based on the combustion-infrared absorption method.

[0095] FE-EPMA detection: The vertical orientation surface of the sintered magnet was polished and detected using a field emission electron probe microanalyzer. First, the R-Ga-Cu-M content in the magnet was determined by quantitative analysis Quantative and surface scanning Mapping. The test conditions were an acceleration voltage of 15 KV and a probe beam current of 50 nA. Then, the volume fraction of the R-Ga-Cu-M phase was statistically analyzed through backscattered electron images BSE. The specific method was to randomly take 20 BSE images with a magnification of 2000 times and use image analysis software for proportion statistics.

[0096] The proportions of the constituent phases, the main phase and the R-Ga-Cu-M phase, of the sintered raw magnets in Examples 1-4 and Comparative Examples 1-8 were detected by FE-EPMA to confirm the proportion of the R-Ga-Cu-M phase in the grain boundary phase. The R-Ga-Cu-M phase includes R: 40.0 wt%-85.0 wt%; Ga: 2.0 wt%-10.0 wt%; Cu: 1.0 wt%-6.0 wt%; M: 0.4 wt%-4.0 wt%. Then, through image analysis, the constituent proportions of the main phase and the R-Ga-Cu-M phase in the field of view of the microstructure observation (observation range 50 μm * 50 μm) were obtained. The test results are shown in Tables 3 and 4 below. Table 5 and Figure 1 FE-EPMA detection results for three points of the grain boundary phase in Example 1, where point 1 and point 2 are the R-Ga-Cu-M phase, and point 3 does not belong to the R-Ga-Cu-M phase.

[0097] Figure 1 Morphology map of the grain boundary phase in Example 1; Figure 1Among them, △ represents the test area of grain boundary phase point 1, ○ represents the test area of grain boundary phase point 2, and □ represents the test area of grain boundary phase point 3.

[0098] Table 3

[0099]

[0100] Table 4

[0101]

[0102] Table 5

[0103]

[0104] As shown in Table 3, Example 1 is the optimal formula. Compared with Example 1, Examples 2 and 3 only contain Zr and Ti, which have little effect on the performance, and both can obtain higher Hcj and corrosion resistance.

[0105] Compared with Example 1, in Comparative Example 1, the content of element B exceeds the range. Although the R-Ga-Cu-M phase is formed, the proportion content is very low, and the Hcj and corrosion resistance of the magnet are reduced.

[0106] Compared with Example 1, in Comparative Example 2, each element is within the range required by the present invention. However, since [Cu]+[Ga]+[M]>0.9[B] is not satisfied, although the R-Ga-Cu-M phase is formed at the grain boundary, the proportion content is relatively low, and the Hcj and corrosion resistance of the magnet are significantly reduced.

[0107] Compared with Example 1, in Comparative Example 3, each element is not within the protection range and [Cu]+[Ga]+[M]>0.9[B] is not satisfied, and no R-Ga-Cu-M phase is formed in the grain boundary, and both the Hcj and corrosion resistance of the magnet are relatively low.

[0108] As shown in Table 4, compared with Example 1, in Comparative Example 4, the holding temperature is 500 °C, which is lower than the normal temperature control range. Although the R-Ga-Cu-M phase is formed at the grain boundary, the proportion content is relatively low and cannot meet the requirements. Similarly, compared with Example 1, in Comparative Example 5, the holding temperature is 900 °C, and although the R-Ga-Cu-M phase is formed at the grain boundary, the proportion content is relatively low and cannot meet the requirements.

[0109] Compared with Example 1, in Comparative Example 6, the material is not rotated during the holding process, and the material is not heated evenly enough. The proportion of the R-Ga-Cu-M phase in the grain boundary cannot meet the requirements, indicating that the uniformity of heating needs to be ensured during the process.

[0110] In Comparative Example 7 and Comparative Example 8, by changing the cooling method, slow cooling and rapid cooling were respectively used for cooling. R-Ga-Cu-M phase was generated in the grain boundary phase, but the proportion was lower than that in the present invention, and the corresponding Hcj and corrosion resistance were also lower than those of the present invention.

[0111] In summary, the magnets prepared by the formula and method in the present invention have excellent Hcj and corrosion resistance.

[0112] The above has given an exemplary description of the embodiments of the present invention. However, the protection scope of the present invention is not limited to the above embodiments. Any modifications, equivalent replacements, improvements, etc. made by those skilled in the art within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An R-T-B type neodymium iron boron magnet, characterized in that, by mass ratio of 100%, the magnet comprises the following components: 27.0 - 35.0 wt% of R, where R is at least one rare earth element including Nd; 0.80 - 0.93 wt% of B; 0.10 - 0.50 wt% of Cu; 0.20 - 0.50 wt% of Ga; 0.20 - 0.30 wt% of M, where M is at least one of Zr and Ti, and the sum of the contents of Cu, Ga and M is greater than 0.9 times the content of B; 0.10 - 1.50 wt% of Al; the balance is Fe, Co and inevitable impurities, and Fe accounts for more than 95 wt% of the total content of Fe, Co and impurities; the R-T-B type neodymium iron boron magnet contains at least 40 vol% of R-Ga-Cu-M phase at the grain boundary; wherein, the R-Ga-Cu-M phase includes 40.0 wt% - 85.0 wt% of R; 2.0 wt% - 10.0 wt% of Ga; 1.0 wt% - 6.0 wt% of Cu and 0.4 wt% - 4.0 wt% of M.

2. The magnet according to claim 1, characterized in that, the R-T-B type neodymium iron boron magnet comprises 28.0 - 33.0 wt% of R, where R is at least one rare earth element including Nd; 0.80 - 0.90 wt% of B; 0.22 - 0.38 wt% of Cu; 0.25 - 0.40 wt% of Ga; 0.20 - 0.30 wt% of M, where M is at least one of Zr and Ti, and the sum of the contents of Cu, Ga and M is greater than 0.9 times the content of B; 0.10 - 1.00 wt% of Al; the balance is Fe and Co and inevitable impurities; and Fe accounts for more than 95 wt% of the total content of Fe, Co and impurities.

3. The magnet according to claim 1, characterized in that, the R includes Nd, and also includes at least one of La, Ce, Pr, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y and Sc.

4. The magnet according to claim 1, characterized in that, The R-T-B type neodymium iron boron magnet contains R 2 Fe 14 type main phase, and the proportion of the main phase is more than 90 vol%.

5. A method for preparing the magnet according to any one of claims 1 - 4, characterized in that, the method comprises the following steps: (1) Prepare an R-T-B type neodymium iron boron magnet alloy; (2) Under an inert atmosphere, reheat the R-T-B type neodymium iron boron magnet alloy in step (1), cool it, and prepare an R-T-B type neodymium iron boron magnet alloy ingot; (3) Hydrogenate and crush the R-T-B type neodymium iron boron magnet alloy ingot in step (2), press it into shape, sinter it, and then perform heat treatment to prepare an R-T-B type neodymium iron boron magnet.

6. The method according to claim 5, characterized in that, in step (1), the method for preparing the R-T-B type neodymium iron boron magnet alloy includes: dissolving the raw materials for preparing the R-T-B type neodymium iron boron magnet to prepare an alloy solution, and then rapidly cooling the alloy solution to prepare an R-T-B type neodymium iron boron magnet alloy.

7. The method according to claim 5, characterized in that, In step (2), the temperature of the secondary heating is 700 - 800 °C; the heating rate during the secondary heating is 5 - 10 °C / min.

8. The method according to claim 5, wherein, in step (2), the heat preservation treatment device needs to be rotated during heat preservation.

9. The method according to claim 5, wherein, in step (2), the pressure is 10 - 15 KPa.

10. The method according to claim 7, wherein, in step (2), after the secondary heating, heat preservation treatment is carried out, and the heat preservation time is 240 - 360 min.

11. The method according to claim 5, wherein, in step (2), the cooling is first slow cooling and then rapid cooling; wherein, slow cooling means that in an inert atmosphere of 80 - 100 kPa, the temperature of the alloy is reduced to 500 - 550 °C, and the cooling rate is 4 - 8 °C / min; rapid cooling means that the alloy with a temperature of 500 - 550 °C is cooled to below 80 °C, and the cooling rate is 15 - 20 °C / min.

12. The method according to claim 11, wherein, the time of slow cooling is 25 - 40 min.

13. The method according to claim 5, wherein, in step (3), the processes of crushing the R-T-B type neodymium iron boron magnet alloy cast sheet by the hydrogen embrittlement method and re-crushing the fine powder after hydrogen embrittlement to obtain fluidized bed mill powder.

14. The method according to claim 13, wherein, in step (3), the pressing and forming includes: after pressing and forming the above-mentioned fluidized bed mill powder in a magnetic field, secondary pressing and forming is carried out by an isostatic press.

15. The method according to claim 14, wherein, the magnetic induction intensity in the magnetic field is 1.5 - 1.8 T.

16. The method according to claim 5, wherein, The primary forming density after being pressed and formed in a magnetic field is 3 to 5 g / cm 3 .

17. The method according to claim 5, wherein, in step (3), the pressed blank after pressing and forming is sintered using a vacuum heat treatment furnace.

18. The method according to claim 5, wherein, in step (3), the sintering temperature is 900 - 1200 °C; the sintering time is 100 - 450 min.

19. The method according to claim 5, wherein, in step (3), the heat treatment temperature is 550 - 700 °C, and the time is 180 - 300 min.

20. The application of the R-T-B type neodymium iron boron magnet according to any one of claims 1 - 4 in the field of motors.

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