Neodymium-iron-boron rare earth permanent magnet, preparation method and application thereof

Abstract

This invention discloses a neodymium iron boron rare earth permanent magnet, its preparation method, and its applications. The neodymium iron boron rare earth permanent magnet comprises: R: 28.5–33 wt%, RL including Pr, Pr ≥ 14 wt%, RH including one or more of Dy, Tb, Gd, and Ho; Co: 12–20 wt%; Al: 0.5–1.5 wt%; X: 0.3–1.5 wt%; B: 0.88–1.05 wt%; the balance being Fe; its microstructure includes a main phase M, a grain boundary phase A, and a grain boundary phase B; the main phase M is R2(Fe, Co). 14 B is the main phase, comprising 90-94%; grain boundary phase A is R(Fe,Co)2, comprising 5-8%; and grain boundary phase B is R4(Fe,Co)3, comprising 1-2%. This NdFeB rare earth permanent magnet has a high Co content, a high Curie temperature, a low temperature coefficient, good mechanical properties, a high magnetic energy product, and high coercivity.

Description

TECHNICAL FIELD

[0001] The present application relates to a neodymium-iron-boron rare earth permanent magnet and a preparation method and application thereof. BACKGROUND

[0002] The residual magnetism temperature coefficient (a) of the conventional neodymium-iron-boron rare earth permanent magnet is about -0.1% / ℃ to -0.12% / ℃, and the coercive force temperature coefficient (β) is about -0.6% / ℃ to -0.8% / ℃, so the magnetic performance thereof decays quickly with the increase of temperature, and the general working temperature is not more than 200℃, which limits the application of the neodymium-iron-boron rare earth permanent magnet in the high temperature field. Although the temperature coefficient of the samarium-cobalt permanent magnet is low, the residual magnetism temperature coefficient (a) is about -0.035% / ℃, and the coercive force temperature coefficient (β) is about -0.25% / ℃, but the samarium-cobalt permanent magnet has the disadvantages of high brittleness, poor bending strength, and low magnetic energy product, and is difficult to meet the increasing mechanical reliability and energy efficiency requirements in the field of permanent magnet motor.

[0003] Chinese patent application CN1067134A discloses a preparation method of a low temperature coefficient neodymium-iron-boron, and a rare earth permanent magnet with low temperature coefficient is prepared by adding Co, Mo, Al and Dy2O3 elements, but the residual magnetism and the magnetic energy product of the magnet prepared by the method are low, the coercive force is poor, the Co addition amount is low, and the improvement range of the temperature coefficient is limited.

[0004] Chinese patent application CN1308344A discloses a heat-resistant low temperature coefficient magnet containing Co, Ga and other elements, and the use temperature can reach 150℃, but the Co addition amount is low, the Curie temperature is low, the improvement range of the residual magnetism temperature coefficient is limited, and the residual magnetism is low and the coercive force is poor due to the existence of the Co soft magnetic phase after adding Co, and even if a large amount of high coercive force elements such as Dy and Tb are added, the coercive force is still less than 2000kA / m.

[0005] Chinese patent application CN1696324A discloses a high coercive force magnet with high temperature resistance by adding Co, Cu, Al and Nb, but the magnetic energy product is low, the temperature coefficient is limited, and the sintered magnet needs to be rapidly cooled in the preparation process to avoid the precipitation of the soft magnetic phase, so the preparation process is complex and is not suitable for large-scale production.

[0006] Chinese patent CN101364465B discloses a Co-containing rare earth permanent magnet with nano TiO2, ZrO2, MgO and ZnO nanocrystals, and the coercive force of the magnet is improved by adding a large amount of Dy, Tb and Pr, so as to improve the irreversible loss of magnetic flux, but the Co addition amount is low, and the temperature coefficient is not obviously improved.

[0007] In summary, the prior art mainly exists Co addition amount is low, Curie temperature is low, residual magnetism temperature coefficient is not obvious, and the low coercive force and other product defects, at the same time, in order to avoid adding Co after the manufacturing process of soft magnetic phase precipitation, ensure the coercive force of the magnet, need to add a large number of heavy rare earth, using rapid cooling and other special process, manufacturing difficulty is high, the manufacturing cost is high. SUMMARY

[0008] The present application provides a kind of neodymium iron boron rare earth permanent magnet and its preparation method and application to solve the defects of low Co addition amount, low Curie temperature, low residual magnetism temperature coefficient and low coercive force in prior art neodymium iron boron rare earth permanent magnet.The Co content of the neodymium iron boron rare earth permanent magnet described in the application is high, the Curie temperature is high, the temperature coefficient is low, and the mechanical properties are good, the magnetic energy product is high, and the coercive force is high.

[0009] To achieve the above object, the technical scheme adopted by the present application is as follows.

[0010] The present application provides a kind of neodymium iron boron rare earth permanent magnet, which comprises the following components in the following amounts:

[0011] R: 28.5-33wt%, R is a rare earth element, R includes light rare earth element RL and heavy rare earth element RH, RL includes Pr, Pr≥14wt%, RH includes one or more of Dy, Tb, Gd and Ho;

[0012] Co: 12-20wt%;

[0013] Al: 0.5-1.5wt%;

[0014] X: 0.3-1.5wt%, X is one or more of Cu, Ga, Bi, Sn, Nb, Zr and Ti;

[0015] B: 0.88-1.05wt%;

[0016] The balance is Fe;

[0017] Wherein wt% represents the mass percentage of the neodymium iron boron rare earth permanent magnet, and the total of each component is 100wt%;

[0018] The microstructure of the neodymium iron boron rare earth permanent magnet includes main phase M, grain boundary phase A and grain boundary phase B; the main phase M is R2(Fe, Co) 14 B, the volume percentage of the main phase is 90-94%; the grain boundary phase A is R(Fe, Co)2, the volume percentage of the grain boundary phase A is 5-8%; the grain boundary phase B is R4(Fe, Co)3, and the volume percentage of the grain boundary phase B is 1-2%.

[0019] The present application selects Pr≥14wt% and Al (0.5-1.5wt%) while Co (12-20wt%) is high, R2Co 17 The generation of the phase, so that the temperature coefficient can be reduced, while improving the remanence, coercivity, magnetic energy product and mechanical properties. Because the main phase M is R2(Fe, Co) 14 B, which is the main source of magnetism of the magnet, where Co replaces part of the traditional R2Fe 14 B main phase, the Curie temperature of the main phase is increased, so the volume percentage of the main phase M is high, the total volume percentage of the grain boundary phase A and the grain boundary phase B is low, the remanence of the magnet is high, and the temperature coefficient is relatively better (absolute value is small), but the coercivity is relatively low; and because the neodymium iron boron is typically intergranular fracture, the grain boundary phase plays a role in connecting the main phase grains and preventing crack propagation, and the reduction of the total volume percentage of the grain boundary phase will reduce the mechanical properties, but compared with the general neodymium iron boron, due to the presence of the Co-rich grain boundary phase A, which has a MgCu2 type cubic crystal structure, the slip system is more than the traditional hexagonal structure of the neodymium-rich phase, so the strength itself is better than the general neodymium-rich grain boundary phase during deformation, and the mechanical properties are still better than the traditional low-Co and no-Co magnets.

[0020] In the present application, the content of Pr is preferably 14wt%-24wt%, for example 14wt%, 15wt%, 16wt%, 18wt%, 20wt%, 23wt% or 24wt%.

[0021] In the present application, the content of Nd is preferably 1wt%-14wt%, for example 14wt%, 10wt%, 12wt%, 7.5wt%, 9wt%, 10wt%, 6wt%, 2wt% or 1wt%.

[0022] In the present application, the content of RH is preferably 2wt%-9wt%, for example 4.5wt%, 7wt%, 9wt%, 7.5wt%, 8wt%, 6wt%, 2wt% or 5wt%.

[0023] Preferably, RH includes Dy, and the content of Dy is 0.2wt%-5wt%, for example 3wt%, 1.5wt%, 5wt%, 4wt%, 0.2wt%, 2wt% or 1wt%.

[0024] Preferably, RH includes Tb, and the content of Tb is 1wt%-5wt%, for example 2.5wt%, 3wt%, 4wt%, 2wt%, 1wt%, 1.8wt%, 1.5wt% or 5wt%.

[0025] Preferably, RH includes Gd, and the content of Gd is 0.5wt%-1wt%.

[0026] Preferably, the RH comprises Ho, and the content of Ho is 0.5wt% to 2wt%, for example 1wt%, 0.5wt%, 2wt% or 1.5wt%.

[0027] In the present application, the content of Co is for example 13wt%, 19wt%, 12wt%, 15wt%, 17wt%, 20wt%, 16wt% or 18wt%.

[0028] In the present application, the content of Al is for example 0.8wt%, 0.7wt%, 0.6wt%, 0.5wt%, 1.5wt%, 0.55wt%, 1.1wt% or 1.3wt%.

[0029] Preferably, the X comprises Cu, and the content of Cu is 0.15wt% to 0.3wt%, for example 0.2wt%, 0.15wt% or 0.3wt%.

[0030] Preferably, the X comprises Ga, and the content of Ga is 0.3wt% to 0.6wt%, for example 0.5wt%, 0.3wt% or 0.6wt%.

[0031] Preferably, the X comprises Bi, and the content of Bi is 0.1wt% to 0.2wt%.

[0032] Preferably, the X comprises Sn, and the content of Sn is 0.1wt% to 0.3wt%.

[0033] Preferably, the X comprises Nb, and the content of Nb is 0.1wt% to 0.3wt%, for example 0.2wt%.

[0034] Preferably, the X comprises Zr, and the content of Zr is 0.1wt% to 0.2wt%.

[0035] Preferably, the X comprises Ti, and the content of Ti is 0.1wt% to 0.3wt%, for example 0.15wt% or 0.2wt%.

[0036] In the present application, preferably, the main phase M comprises the following contents of each component:

[0037] R: 26.6wt% to 30.55wt%; wherein, Pr: >12.5wt%, Nd: 0 to 12.5wt%, RH: 1.85wt% to 9.0wt%;

[0038] Co: 11.8wt% to 20wt%;

[0039] B: 0.88wt% to 1.01wt%;

[0040] Fe: 48.5-58.5 wt.%;

[0041] wherein wt.% means the percentage of the mass of the main phase M, and the sum of the components is 100 wt.%.

[0042] Preferably, the main phase M further comprises one or more of Al, Cu, Zr, Ga and O.

[0043] In the present application, the grain boundary phase A is an RT2 type phase, having a MgCu2 type structure, and is paramagnetic at room temperature. The grain boundary phase A is a "Nd and Co-rich and Fe-poor" grain boundary phase.

[0044] Preferably, the grain boundary phase A comprises the following contents of the components:

[0045] R: 52.8-62 wt.%; wherein Pr: 24-50 wt.%, Nd: 0-26.5 wt.%, RH: 2.0-10 wt.%;

[0046] Co: 15-25 wt.%;

[0047] Fe: 12-25 wt.%;

[0048] Al: 0.19-0.55 wt.%

[0049] X: 0.1-0.6 wt.%;

[0050] O: 0-0.5 wt.%;

[0051] wherein wt.% means the percentage of the mass of the grain boundary phase A, and the sum of the components is 100 wt.%.

[0052] In the present application, the grain boundary phase B is an R4T3 type phase, having a Nd4Co3 type structure. The grain boundary phase B is a "Nd-rich and Co and Fe-poor" grain boundary phase. The grain boundary phase B is close to the Nd-rich phase in the traditional low Co formula system, and its composition is mainly rare earth metal and its oxide or R-(T, X) alloy phase, wherein T is Fe or Co, and X is one or more of Cu, Ga, Bi, Sn, Nb, Zr and Ti as described above, mainly playing a demagnetization coupling role between the grains, and improving the coercivity.

[0053] Preferably, the grain boundary phase B comprises the following contents of the components:

[0054] R: 75-90.3 wt.%; wherein Pr: 42.5-90 wt.%, Nd: 0-42.5 wt.%, RH: 0.3-1.5 wt.%;

[0055] Co: 6-10 wt.%;

[0056] Fe: 2-10 wt.%;

[0057] Al: 0-0.2 wt.%

[0058] X: 1.0-10 wt.%;

[0059] O: 0.5-1.5 wt.%;

[0060] wherein wt.% means mass percentage of the grain boundary phase B.

[0061] Preferably, the content of Co in the grain boundary phase A, c(A), is greater than the content of Co in the main phase M, c(M), and c(A)-c(M)>3 wt.%. Ensuring that the grain boundary phase A has sufficient Co element to form the RT2 system paramagnetic phase, which is conducive to improving the coercivity of the magnet.

[0062] Preferably, the content of RH in the grain boundary phase A is higher than the main phase M and higher than the grain boundary phase B. RH is concentrated in the grain boundary phase A, which improves the magnetic properties of the Co-rich grain boundary and avoids the degradation of the coercivity of the magnet.

[0063] Preferably, the content of RH in the grain boundary phase B is lower than the main phase M and lower than the grain boundary phase A. The low content of RH in the grain boundary phase B means that more RH can be obtained in the grain boundary phase A or the main phase M, which is conducive to improving the coercivity of the magnet.

[0064] Preferably, the content of X (especially Cu and Ga) in the grain boundary phase B is higher than the main phase M and higher than the grain boundary phase A. When X elements are distributed in the main phase, the remanence of the main phase is reduced, while the distribution in the grain phase B has no effect on the remanence, and can form R-X grain boundary alloy phase, increase the demagnetization coupling between the grains, and improve the coercivity of the magnet.

[0065] In the present application, the Nd-Fe-B rare earth permanent magnet can further comprise a heterogeneous phase, such as a rare earth oxide phase RO or a ZrB2 / TiB2 phase.

[0066] wherein the content of the heterogeneous phase can be 0.05%-0.55%, such as 0.22%, 0.25%, 0.19%, 0.20%, 0.29%, 0.19%, 0.55%, 0.23%, 0.09%, 0.21%, 0.18%, 0.37% or 0.41%.

[0067] In the present application, the volume percentage of the main phase is, for example, 90.45%, 90.00%, 91.81%, 92.73%, 92.11%, 93.66%, 93.23%, 92.81%, 93.45%, 93.22%, 91.53% or 92.33%.

[0068] In the present invention, the volume percentage of the grain boundary phase A is, for example, 5.00%, 8.00%, 7.81%, 6.45%, 6.23%, 6.80%, 5.12%, 5.89%, 6.32%, 5.84%, 5.79%, 7.05%, or 6.43%.

[0069] In the present invention, the volume percentage of the grain boundary phase B is, for example, 0.78%, 1.30%, 2.00%, 1.54%, 0.75%, 0.90%, 0.67%, 0.65%, 0.78%, 0.50%, 0.81%, 1.05%, or 0.83%.

[0070] In a specific embodiment, the microstructure of the Nd-Fe-B rare earth permanent magnet comprises 94.00% of the main phase M, 5.00% of the grain boundary phase A, 0.78% of the grain boundary phase B, and 0.22% of the impurity phase.

[0071] In a specific embodiment, the microstructure of the Nd-Fe-B rare earth permanent magnet comprises 90.45% of the main phase M, 8.00% of the grain boundary phase A, 1.30% of the grain boundary phase B, and 0.25% of the impurity phase.

[0072] In a specific embodiment, the microstructure of the Nd-Fe-B rare earth permanent magnet comprises 90.00% of the main phase M, 7.81% of the grain boundary phase A, 2.00% of the grain boundary phase B, and 0.19% of the impurity phase.

[0073] In a specific embodiment, the microstructure of the Nd-Fe-B rare earth permanent magnet comprises 91.81% of the main phase M, 6.45% of the grain boundary phase A, 1.54% of the grain boundary phase B, and 0.2% of the impurity phase.

[0074] In a specific embodiment, the microstructure of the Nd-Fe-B rare earth permanent magnet comprises 92.73% of the main phase M, 6.23% of the grain boundary phase A, 0.75% of the grain boundary phase B, and 0.29% of the impurity phase.

[0075] In a specific embodiment, the microstructure of the Nd-Fe-B rare earth permanent magnet comprises 92.11% of the main phase M, 6.80% of the grain boundary phase A, 0.90% of the grain boundary phase B, and 0.19% of the impurity phase.

[0076] In a specific embodiment, the microstructure of the Nd-Fe-B rare earth permanent magnet comprises 93.66% of the main phase M, 5.12% of the grain boundary phase A, 0.67% of the grain boundary phase B, and 0.55% of the impurity phase.

[0077] In a specific embodiment, the microstructure of the Nd-Fe-B rare earth permanent magnet comprises 93.23% of the main phase M, 5.89% of the grain boundary phase A, 0.65% of the grain boundary phase B, and 0.23% of the impurity phase.

[0078] In a specific embodiment, the microstructure of the Nd-Fe-B rare earth permanent magnet comprises 92.81% main phase M, 6.32% grain boundary phase A, 0.78% grain boundary phase B and 0.09% impurity phase.

[0079] In a specific embodiment, the microstructure of the Nd-Fe-B rare earth permanent magnet comprises 93.45% main phase M, 5.84% grain boundary phase A, 0.50% grain boundary phase B and 0.21% impurity phase.

[0080] In a specific embodiment, the microstructure of the Nd-Fe-B rare earth permanent magnet comprises 93.22% main phase M, 5.79% grain boundary phase A, 0.81% grain boundary phase B and 0.18% impurity phase.

[0081] In a specific embodiment, the microstructure of the Nd-Fe-B rare earth permanent magnet comprises 91.53% main phase M, 7.05% grain boundary phase A, 1.05% grain boundary phase B and 0.37% impurity phase.

[0082] In a specific embodiment, the microstructure of the Nd-Fe-B rare earth permanent magnet comprises 92.33% main phase M, 6.43% grain boundary phase A, 0.83% grain boundary phase B and 0.41% impurity phase.

[0083] In the present application, preferably, the temperature coefficient of remanence of the Nd-Fe-B rare earth permanent magnet at 20-100℃ is |α|<0.056% / ℃, and the temperature coefficient of coercivity of the Nd-Fe-B rare earth permanent magnet at 20-100℃ is |β|<0.55% / ℃.

[0084] In the present application, preferably, the Curie temperature Tc of the Nd-Fe-B rare earth permanent magnet is >450℃.

[0085] In the present application, preferably, the coercivity Hcj of the Nd-Fe-B rare earth permanent magnet is ≥25kOe.

[0086] The present application also provides a preparation method of the Nd-Fe-B rare earth permanent magnet, which comprises sequentially subjecting a raw material composition of the Nd-Fe-B rare earth permanent magnet to the following steps: smelting, casting, hydrogen decrepitation, forming, sintering and aging treatment.

[0087] In the present application, the smelting can be prepared according to the conventional method in the art, for example, smelting in a high-frequency vacuum induction smelting furnace.

[0088] In the present application, the vacuum degree of the high-frequency vacuum induction smelting furnace can be 5×10 -2 Pa.

[0089] The temperature of the smelting can be below 1600℃.

[0090] The smelting is generally carried out in an alumina crucible. The alumina crucible introduces a part of Al into the Nd-Fe-B rare earth permanent magnet.

[0091] In the present application, the casting process can be a conventional casting process in the art, for example, the molten liquid obtained by smelting is cooled by rotating roller in Ar atmosphere.

[0092] Preferably, the pressure of the Ar atmosphere is 5.5 x 10 4 Pa.

[0093] Preferably, the cooling rate is 10 2 ℃ / s to 10 4 ℃ / s. The cooling can be achieved by passing cooling water in the roller. Preferably, the inlet temperature of the cooling water is ≤ 25℃.

[0094] In the present application, the hydrogen breaking process can be a conventional hydrogen breaking process in the art, for example, hydrogen absorption, hydrogen desorption, and cooling treatment.

[0095] Preferably, the hydrogen absorption is carried out under a hydrogen pressure of 0.05 to 0.25 MPa. The hydrogen desorption is carried out under the condition of vacuumizing and heating.

[0096] In the present application, the hydrogen breaking process can be a conventional hydrogen breaking process in the art, for example, hydrogen absorption, hydrogen desorption, and cooling treatment.

[0097] The jet mill pulverization can be carried out under a nitrogen atmosphere with an oxidizing gas content of 100 ppm or less. The oxidizing gas refers to oxygen and / or moisture.

[0098] The pressure in the pulverization chamber of the jet mill pulverization can be 0.58 MPa.

[0099] The time of the jet mill pulverization can be 3 hours.

[0100] Preferably, the particle size of the powder after pulverization is 3.5-4.5 μm.

[0101] After pulverization, a lubricant such as zinc stearate can be added to the powder by conventional means in the art. The amount of the lubricant added can be 0.10-0.15% of the weight of the mixed powder, for example, 0.12%.

[0102] In the present application, the molding process can be a conventional molding process in the art, for example, magnetic field orientation molding method. When the magnetic field orientation molding method is used, the pressure of the orientation press molding is greater than 80 MPa, the orientation magnetic field is greater than 1.2 T, and the pressure holding time is 4-6 s.

[0103] After the magnetic field orientation molding, the magnet can be further densified by cold isostatic pressing. The pressure of the cold isostatic pressing is 150-160 MPa.

[0104] In the present application, the sintering process can be a conventional sintering process in the art, for example, preheating, sintering, and cooling under vacuum conditions.

[0105] The vacuum condition is for example 5x10 -3 Pa.

[0106] The preheating temperature can be 300-600℃. The preheating time can be 1-2h. Preferably, the preheating is at 300℃ and 600℃ for 1h each.

[0107] The sintering temperature can be a conventional sintering temperature in the art, for example, 1040-1090℃.

[0108] The sintering time can be a conventional sintering time in the art, for example, 4h.

[0109] Before cooling, Ar gas can be introduced to reach a pressure of 0.05-0.1MPa.

[0110] Preferably, no rapid cooling process is used in the sintering. The rapid cooling process refers to a cooling process with a cooling speed of 80℃ / min or higher.

[0111] In the present application, the aging treatment includes primary aging treatment and secondary aging treatment.

[0112] The temperature of the primary aging treatment is preferably 860-960℃, for example, 900℃. In the primary aging treatment, the temperature rising rate to 860-960℃ is preferably 3-5℃ / min. The starting temperature of the temperature rising can be room temperature. The time of the primary aging treatment can be 3h.

[0113] The temperature of the secondary aging treatment is preferably 430-600℃. In the secondary aging treatment, the temperature rising rate to 430-600℃ is preferably 3-5℃ / min. The starting temperature of the temperature rising can be room temperature. The time of the secondary aging treatment can be 3h.

[0114] In the present application, the room temperature refers to 25℃±5℃.

[0115] The present application also provides a use of the Nd-Fe-B rare earth permanent magnet in electronic components.

[0116] The electronic components can be conventional in the art, for example, in a motor.

[0117] On the basis of common knowledge in the art, the above preferred conditions can be combined arbitrarily, i.e., to obtain each preferred example of the present application.

[0118] The reagents and raw materials used in the present application are commercially available.

[0119] The positive progress effect of the present application is that:

[0120] The Nd-Fe-B rare earth permanent magnet of the present application, with high content of Co added, forms low-melting-point grain boundary phase of RT2 type and R4T3 type structure by mutual cooperation of Pr and Al elements, thus avoiding the defects of R2Co 17 soft magnetic phase in traditional high-Co magnets, which greatly reduces the coercive force. The magnet of the present application has high remanence (11.5-13.5 kGs), coercive force (up to 28 kOe or more) and squareness (>95%), low remanence temperature coefficient (|a|<0.056% / °C, 20-100°C) and coercive force temperature coefficient (|b|<0.55% / °C, 20-100°C), high Curie temperature (Tc>450°C) and excellent heat resistance. BRIEF DESCRIPTION OF DRAWINGS

[0121] Figure 1 SEM-BSE of different phases of the Nd-Fe-B rare earth permanent magnet in Example 1. DETAILED DESCRIPTION

[0122] The present application will be further described by way of examples, but the present application is not limited to the examples. The experimental methods in the following examples, for which no specific conditions are indicated, are selected according to conventional methods and conditions, or according to the instructions of the commercial products.

[0123] Examples 1-13 and Comparative Examples 1-7

[0124] The raw material composition formula of the Nd-Fe-B rare earth permanent magnet in Examples 1-13 and Comparative Examples 1-7 is shown in Table 1. The raw materials were proportioned according to the raw material composition formula of the Nd-Fe-B rare earth permanent magnet in Table 1, and the following steps were performed in sequence.

[0125] (1) Melting process: the prepared raw materials were placed in an alumina crucible according to the formula shown in Table 1, and vacuum melting was performed at a temperature of 1600°C or lower in a high-frequency vacuum induction melting furnace under a vacuum of 5x10 -2 Pa.

[0126] (2) Casting process: the molten liquid after vacuum melting was cast by rotating rollers under an Ar atmosphere at a pressure of 5.5x10 4 Pa, and then cooling water (inlet temperature ≤25°C) was introduced into the rollers to cool at a cooling rate of 10 2 °C / s-10 4 °C / s.

[0127] (3) Hydrogen decrepitation process: at room temperature, pure hydrogen gas with a purity of 99.9% is introduced into a hydrogen decrepitation furnace, and the hydrogen pressure is maintained at 0.15 MPa. After sufficient hydrogen absorption, the vacuum is pumped and the temperature is raised, and the hydrogen is fully removed. Then, the hydrogen decrepitation powder is obtained after cooling and crushing.

[0128] (4) Jet mill crushing: the hydrogen decrepitation powder is jet milled for 3 hours under a nitrogen atmosphere with an oxygen content of 100 ppm or less, and the pressure in the crushing chamber is 0.58 MPa. Fine powder is obtained. The oxidizing gas refers to oxygen and / or moisture.

[0129] (5) Zinc stearate is added to the jet milled powder, and the amount of zinc stearate added is 0.12% of the weight of the mixed powder. Then, the V-type mixer is used for sufficient mixing.

[0130] (6) Magnetic field forming process: a right-angle orientation type magnetic field forming machine is used to press the zinc stearate added powder in an orientation magnetic field of 1.6 T at a forming pressure of more than 80 MPa for 4-6 s. Then, an isostatic pressing machine is used to cold isostatic press the magnet at a pressure of 150-160 MPa to further densify the magnet.

[0131] (7) Sintering process: each formed body is moved to a sintering furnace for sintering. The sintering is carried out under a vacuum of 5x10 -3 Pa, preheated at 300°C and 600°C for 1 hour respectively, sintered at a temperature of 1040°C for 4 hours, then Ar gas is introduced to reach a pressure of 0.1 MPa, and then cooled to room temperature at a cooling rate of less than 80°C / min.

[0132] (9) Aging process: the sintered body is heated in high-purity Ar gas at a heating rate of 5°C / min from room temperature to 900°C, and heat treated for 3 hours (primary aging), and then cooled to room temperature. Then, it is heated at a heating rate of 5°C / min from room temperature to 600°C, and heat treated for 3 hours (secondary aging), to obtain a neodymium-iron-boron rare earth permanent magnet.

[0133] Table 1 Raw material composition formula of neodymium-iron-boron rare earth permanent magnet (wt%)

[0134]

[0135]

[0136] Effect Example 1: Phase composition and composition detection of neodymium-iron-boron rare earth permanent magnet

[0137] The electron backscatter images (SEM-BSE) of different phases of the neodymium-iron-boron rare earth permanent magnet in Example 1 are shown in FIG. 1, Figure 1 Figure 1 where the main phase M, the crystal phase A and the crystal phase B are shown.​

[0138] The volume percentage of each phase in the neodymium-iron-boron rare earth permanent magnet in examples 1-13 and comparative examples 1-7 is shown in Table 2, and the component composition of each phase is shown in Table 3.

[0139] Table 2 Phase composition of neodymium-iron-boron rare earth permanent magnet

[0140]

[0141]

[0142] The percentages in Table 2 are volume percentages, which are estimated according to the Delesse Law of stereology, i.e. V V (Component volume ratio) = A A (area ratio of component on random section) is equal to the volume ratio of the component.

[0143] Table 3 Component composition of each phase of neodymium-iron-boron rare earth permanent magnet

[0144]

[0145]

[0146]

[0147] Effect example 2: performance test of magnet

[0148] The neodymium-iron-boron rare earth permanent magnet is subjected to magnetic performance detection using the PFM-14 pulse magnetic performance measuring instrument of China Institute of Metrology. Table 4 is the magnetic performance detection result.

[0149] Table 4 Magnetic performance of neodymium-iron-boron rare earth permanent magnet

[0150]

[0151] As shown in Table 4, the permanent magnet of the embodiment has high remanence, coercivity and squareness, and has low remanence temperature coefficient and coercivity temperature coefficient, and high magnet Curie temperature, and excellent heat resistance.

Claims

1. A neodymium iron boron rare earth permanent magnet, characterized in that, It includes the following components in the following amounts: R: 28.5~33wt%, R is a rare earth element, including light rare earth element RL and heavy rare earth element RH; RL includes Pr, with a content of 14wt%~16wt%; RH includes one or more of Dy, Tb, Gd and Ho, with a content of 5wt%~9wt%; Co: 12~20wt%; Al: 0.5~1.5wt% X: 0.3~1.5wt%, where X is one or more of Cu, Ga, Bi, Sn, Nb, Zr and Ti; B: 0.88~1.05wt% The balance is Fe; Wherein wt% represents the mass percentage of the neodymium iron boron rare earth permanent magnet, and the total of all components is 100wt%; The microstructure of the neodymium iron boron rare earth permanent magnet includes a main phase M, a grain boundary phase A, and a grain boundary phase B; the main phase M is R2(Fe, Co). 14 B, wherein the main phase has a volume percentage of 90-94%; the grain boundary phase A is R(Fe,Co)2, and the volume percentage of grain boundary phase A is 5-8%; the grain boundary phase B is R4(Fe,Co)3, and the volume percentage of grain boundary phase B is 1-2%. The Co content c(A) in the grain boundary phase A is greater than the Co content c(M) in the main phase M, and c(A) - c(M) > 3wt%; The RH content in the grain boundary phase A is higher than that in the main phase M and also higher than that in the grain boundary phase B.

2. The neodymium iron boron rare earth permanent magnet according to claim 1, characterized in that, The content of Pr is 14wt%, 15wt%, or 16wt%; And / or, the RL further includes Nd; And / or, the RH content is 7wt%, 9wt%, 7.5wt%, 8wt%, 6wt%, or 5wt%; And / or, the RH includes Dy, the content of which is 0.2wt%~5wt%; And / or, the RH includes Tb, and the content of Tb is 1wt%~5wt%; And / or, the RH includes Gd, with a Gd content of 0.5wt% to 1wt%; And / or, the RH includes Ho, with a Ho content of 0.5wt%~2wt%; And / or, the content of Co is 13wt%, 19wt%, 12wt%, 15wt%, 17wt%, 20wt%, 16wt%, or 18wt%; And / or, the Al content is 0.8wt%, 0.7wt%, 0.6wt%, 0.5wt%, 1.5wt%, 0.55wt%, 1.1wt%, or 1.3wt%; And / or, X comprises Cu, wherein the Cu content is 0.15wt%~0.3wt%; And / or, the X comprises Ga, wherein the Ga content is 0.3wt%~0.6wt%; And / or, the X comprises Bi, wherein the content of Bi is 0.1wt%~0.2wt%; And / or, the X includes Sn, with a Sn content of 0.1wt% to 0.3wt%; And / or, the X includes Nb, the content of which is 0.1wt%~0.3wt%; And / or, the X includes Zr, with a Zr content of 0.1wt%~0.2wt%; And / or, the X includes Ti, with a Ti content of 0.1wt% to 0.3wt%.

3. The neodymium iron boron rare earth permanent magnet according to claim 2, characterized in that, The Nd content is 1wt%~14wt%; And / or, the content of Dy is 3wt%, 1.5wt%, 5wt%, 4wt%, 0.2wt%, 2wt%, or 1wt%; And / or, the Tb content is 2.5wt%, 3wt%, 4wt%, 2wt%, 1wt%, 1.8wt%, 1.5wt%, or 5wt%; And / or, the content of Ho is 1 wt%, 0.5 wt%, 2 wt%, or 1.5 wt%; And / or, the Cu content is 0.2 wt%, 0.15 wt%, or 0.3 wt%; And / or, the Ga content is 0.5wt%, 0.3wt%, or 0.6wt%; And / or, the Nb content is 0.2 wt%; And / or, the content of Ti is 0.15wt% or 0.2wt%.

4. The neodymium iron boron rare earth permanent magnet according to claim 3, characterized in that, The Nd content is 14wt%, 10wt%, 12wt%, 7.5wt%, 9wt%, 10wt%, 6wt%, 2wt%, or 1wt%.

5. The neodymium iron boron rare earth permanent magnet according to claim 1, characterized in that, The main phase M comprises the following components in the following amounts: R: 26.6~30.55wt%; of which, Pr: >12.5wt%, Nd: 0~12.5wt%, RH: 1.85~9.0wt%; Co: 11.8~20wt% B: 0.88~1.01wt% Fe: 48.5~58.5 wt% Wherein, wt% represents the mass percentage of the main phase M, and the total of all components is 100 wt%; And / or, the grain boundary phase A comprises the following components in varying amounts: R: 52.8~62wt%; of which, Pr: 24~50wt%, Nd: 0~26.5wt%, RH: 2.0~10wt%; Co: 15~25wt%; Fe: 12~25wt%; Al: 0.19~0.55wt% X: 0.1~0.6wt%; O: 0~0.5wt% Where wt% represents the mass percentage of the grain boundary phase A, and the total of all components is 100 wt%; And / or, the grain boundary phase B comprises the following components in varying amounts: R: 75~90.3wt%; of which, Pr: 42.5~90wt%, Nd: 0~42.5wt%, RH: 0.3~1.5wt%; Co: 6~10wt%; Fe: 2~10wt% Al: 0~0.2wt% X: 1.0~10wt% O: 0.5~1.5wt% Where wt% represents the mass percentage of the grain boundary phase B.

6. The neodymium iron boron rare earth permanent magnet according to claim 5, characterized in that, The main phase M also includes one or more of Al, Cu, Zr, Ga, and O.

7. The neodymium iron boron rare earth permanent magnet according to claim 1, characterized in that, The content of X in the grain boundary phase B is higher than that in the main phase M and also higher than that in the grain boundary phase A.

8. The neodymium iron boron rare earth permanent magnet according to claim 1, characterized in that, The neodymium iron boron rare earth permanent magnet also includes impurity phases; And / or, the volume percentage of the main phase is 90.45%, 90.00%, 91.81%, 92.73%, 92.11%, 93.66%, 93.23%, 92.81%, 93.45%, 93.22%, 91.53%, or 92.33%; And / or, the volume percentage of the grain boundary phase A is 5.00%, 8.00%, 7.81%, 6.45%, 6.23%, 6.80%, 5.12%, 5.89%, 6.32%, 5.84%, 5.79%, 7.05%, or 6.43%; And / or, the volume percentage of the grain boundary phase B is 0.78%, 1.30%, 2.00%, 1.54%, 0.75%, 0.90%, 0.67%, 0.65%, 0.78%, 0.50%, 0.81%, 1.05%, or 0.83%.

9. The neodymium iron boron rare earth permanent magnet according to claim 8, characterized in that, The content of the impurity phase is 0.05%~0.55%.

10. The neodymium iron boron rare earth permanent magnet according to claim 9, characterized in that, The content of the impurity phase is 0.22%, 0.25%, 0.19%, 0.20%, 0.29%, 0.19%, 0.55%, 0.23%, 0.09%, 0.21%, 0.18%, 0.37%, or 0.41%.

11. The neodymium iron boron rare earth permanent magnet according to claim 1, characterized in that, The microstructure of the neodymium iron boron rare earth permanent magnet comprises 94.00% main phase M, 5.00% grain boundary phase A, 0.78% grain boundary phase B, and 0.22% impurity phase; Alternatively, the microstructure of the neodymium iron boron rare earth permanent magnet comprises 90.45% main phase M, 8.00% grain boundary phase A, 1.30% grain boundary phase B, and 0.25% impurity phase; Alternatively, the microstructure of the neodymium iron boron rare earth permanent magnet comprises 90.00% main phase M, 7.81% grain boundary phase A, 2.00% grain boundary phase B, and 0.19% impurity phase; Alternatively, the microstructure of the neodymium iron boron rare earth permanent magnet comprises 91.81% main phase M, 6.45% grain boundary phase A, 1.54% grain boundary phase B, and 0.2% impurity phase; Alternatively, the microstructure of the neodymium iron boron rare earth permanent magnet comprises 92.73% main phase M, 6.23% grain boundary phase A, 0.75% grain boundary phase B, and 0.29% impurity phase; Alternatively, the microstructure of the neodymium iron boron rare earth permanent magnet comprises 92.11% main phase M, 6.80% grain boundary phase A, 0.90% grain boundary phase B, and 0.19% impurity phase; Alternatively, the microstructure of the neodymium iron boron rare earth permanent magnet comprises 93.66% main phase M, 5.12% grain boundary phase A, 0.67% grain boundary phase B, and 0.55% impurity phase; Alternatively, the microstructure of the neodymium iron boron rare earth permanent magnet comprises 93.23% main phase M, 5.89% grain boundary phase A, 0.65% grain boundary phase B, and 0.23% impurity phase; Alternatively, the microstructure of the neodymium iron boron rare earth permanent magnet comprises 92.81% main phase M, 6.32% grain boundary phase A, 0.78% grain boundary phase B, and 0.09% impurity phase; Alternatively, the microstructure of the neodymium iron boron rare earth permanent magnet comprises 93.45% main phase M, 5.84% grain boundary phase A, 0.50% grain boundary phase B, and 0.21% impurity phase; Alternatively, the microstructure of the neodymium iron boron rare earth permanent magnet comprises 93.22% main phase M, 5.79% grain boundary phase A, 0.81% grain boundary phase B, and 0.18% impurity phase; Alternatively, the microstructure of the neodymium iron boron rare earth permanent magnet comprises 91.53% main phase M, 7.05% grain boundary phase A, 1.05% grain boundary phase B, and 0.37% impurity phase; Alternatively, the microstructure of the neodymium iron boron rare earth permanent magnet comprises 92.33% main phase M, 6.43% grain boundary phase A, 0.83% grain boundary phase B, and 0.41% impurity phase.

12. The neodymium iron boron rare earth permanent magnet according to claim 1, characterized in that, The remanence temperature coefficient of the neodymium iron boron rare earth permanent magnet at 20~100℃ is |α|<0.056% / ℃, and the coercivity temperature coefficient at 20~100℃ is |β|<0.55% / ℃; And / or, the Curie temperature Tc of the neodymium iron boron rare earth permanent magnet is greater than 450°C; And / or, the coercivity Hcj of the neodymium iron boron rare earth permanent magnet is ≥25kOe.

13. A method for preparing a neodymium iron boron rare earth permanent magnet as described in any one of claims 1 to 12, characterized in that, It includes sequentially subjecting the raw material composition of the NdFeB rare earth permanent magnet to the following steps: smelting, casting, hydrogen calcination, forming, sintering and aging treatment.

14. The method for preparing a neodymium iron boron rare earth permanent magnet according to claim 13, characterized in that, The melting is carried out in a high-frequency vacuum induction melting furnace. And / or, the casting is carried out in an Ar atmosphere by passing the molten liquid obtained from melting through rotating rollers for cooling; And / or, the hydrogen breakdown can be achieved by hydrogen absorption, dehydrogenation, and cooling treatment; And / or, the hydrogen is further pulverized after being broken down; And / or, the forming process is a magnetic field orientation forming method; And / or, the sintering includes preheating, sintering, and cooling under vacuum conditions; And / or, the timeliness processing includes primary timeliness processing and secondary timeliness processing.

15. The method for preparing a neodymium iron boron rare earth permanent magnet according to claim 14, characterized in that, The vacuum degree of the high-frequency vacuum induction melting furnace is 5×10⁻⁶. -2 Pa; And / or, the melting temperature is below 1600°C; And / or, the melting is carried out in an alumina crucible; And / or, the pressure of the Ar atmosphere is 5.5 × 10⁻⁶. 4 Pa; And / or, in the casting, the cooling rate is 10. 2 ℃ / sec ~10 4 ℃ / second; And / or, in the casting process, the cooling is achieved by introducing cooling water through the rollers, and the inlet temperature of the cooling water is ≤25°C; And / or, the hydrogen absorption is carried out under a hydrogen pressure of 0.05~0.25MPa; And / or, the dehydrogenation is carried out under conditions of simultaneous vacuuming and heating; And / or, the pulverization is an air jet mill pulverization; And / or, the particle size of the pulverized powder is 3.5-4.5 μm; And / or, after the pulverization, a lubricant is added to the powder; And / or, when using the magnetic field orientation molding method, the orientation pressing pressure is greater than 80MPa, the orientation magnetic field is greater than 1.2T, and the holding time is 4-6s; And / or, after the magnetic field orientation is formed, cold isostatic pressing can be used for further pressing; And / or, the vacuum condition is 5 × 10⁻⁶. -3 Pa; And / or, the preheating temperature is 300~600℃; And / or, the preheating time is 1~2 hours; And / or, the sintering temperature is 1040~1090℃; And / or, the sintering time is 4 hours; And / or, during the sintering process, Ar gas is introduced before cooling to achieve a pressure of 0.05-0.1 MPa; And / or, a rapid cooling process is not used in the sintering process; And / or, the temperature of the first-stage aging treatment is 860~960℃; And / or, in the first-stage aging treatment, the heating rate to 860~960℃ is 3~5℃ / min; And / or, the time for the first-level time-sensitive processing is 3 hours; And / or, the temperature of the secondary aging treatment is 430~600℃; And / or, in the secondary aging treatment, the heating rate to 430~600℃ is 3~5℃ / min; And / or, the duration of the secondary aging process is 3 hours.

16. The method for preparing a neodymium iron boron rare earth permanent magnet according to claim 15, characterized in that, The air jet milling is carried out in a nitrogen atmosphere with an oxidizing gas content of less than 100 ppm; And / or, the grinding chamber pressure of the air jet mill is 0.58 MPa; And / or, the air jet milling time is 3 hours; And / or, the lubricant is zinc stearate; And / or, the amount of lubricant added is 0.10~0.15% of the weight of the mixed powder; And / or, the pressure of the cold isostatic pressing is 150-160 MPa; And / or, the preheating is performed at 300°C and 600°C for 1 hour each; And / or, the temperature of the first-stage aging treatment is 900°C.

17. The method for preparing a neodymium iron boron rare earth permanent magnet according to claim 16, characterized in that, The amount of lubricant added is 0.12% of the weight of the mixed powder.

18. An application of a neodymium iron boron rare earth permanent magnet as described in any one of claims 1 to 12 in electronic components.

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