Neodymium-iron-boron magnet and method for producing same

Abstract

The present application discloses a kind of neodymium-iron-boron magnet and its preparation method.The neodymium-iron-boron magnet includes main phase crystal grain and its shell and the Nd-rich phase adjoining the main phase crystal grain;The main phase crystal grain includes Nd2Fe 14 B;Or, the main phase crystal grain includes Nd2Fe 14 B and Pr2Fe 14 B;The shell includes (Nd / Dy)2Fe 14 B and / or (Nd / Tb)2Fe 14 B;The thickness of the shell is 0.1-6 μm;The Nd-rich phase includes R6Fe 13 B phase, and the R is one or more of Nd, Pr, Dy and Tb.The method of the present application effectively reduces the diffusion amount of heavy rare earth elements into the main phase, forms a thinner heavy rare earth shell, and can further optimize and improve the high-temperature performance of the magnet.

Description

TECHNICAL FIELD

[0001] The present application relates to a neodymium-iron-boron magnet and a method for manufacturing the same. BACKGROUND

[0002] There are many methods for optimizing the grain boundary in the neodymium-iron-boron industry at present, for example, adding a single low-melting-point element to increase fluidity or adding heavy rare earth elements to increase the magnetic crystal anisotropy field in the formula design, such as the double-alloy method. This method prepares an auxiliary alloy by adding a high proportion of Dy or Tb, separately melts the auxiliary alloy and the main alloy, and then according to the product performance, the two are proportioned again during the hydrogen breaking stage or the airflow grinding stage. Although the neodymium-iron-boron magnet prepared in this way has improved magnetic properties compared with the single-alloy process, most of the Dy and Tb will enter the main phase through the sintering and aging process, greatly reducing the utilization rate of heavy rare earth, and causing a certain cost and resource waste.

[0003] Patent document CN111636035A discloses a heavy rare earth alloy, a neodymium-iron-boron permanent magnet material, raw materials and a preparation method. By controlling the content of Ti and / or Zr and the total amount of heavy rare earth elements, Ti and / or Zr are combined with B, thereby avoiding excessive heavy rare earth metals from being combined with B. At the same time, the high-melting-point compound is a non-ferromagnetic phase, which can pin and increase the magnetic coupling effect at the grain boundary, hinder the formation of the anti-magnetization domain, reduce the amount of heavy rare earth metals diffusing into the main phase, and improve the performance of the magnet. However, this solution still has room for further optimization. The amount of Dy, Tb and other heavy rare earth elements diffusing into the main phase is still quite large, and the thickness of the shell formed by these heavy rare earth elements outside the main phase is relatively deep.

[0004] Therefore, the double-alloy method still needs further improvement to effectively form a relatively thin shell of expensive heavy rare earth elements such as Dy and Tb around the main phase to reduce the degree of diffusion of heavy rare earth elements into the main phase. SUMMARY

[0005] The present application provides a neodymium-iron-boron magnet and a method for manufacturing the same to solve the problem of heavy rare earth elements diffusing into the main phase in the prior art. The method effectively reduces the amount of heavy rare earth elements diffusing into the main phase, forms a thinner heavy rare earth shell, and further optimizes and improves the high-temperature performance of the magnet.

[0006] The present application solves the above technical problems through the following technical solutions.

[0007] The present application provides a neodymium-iron-boron magnet, which comprises main phase grains and a shell thereof, and a Nd-rich phase adjacent to the main phase grains.

[0008] The main phase grains comprise Nd2Fe 14 B; or the main phase grains comprise Nd2Fe14 B and Pr2Fe 14 B;

[0009] The shell layer comprises (Nd / Dy)2Fe 14 B and / or (Nd / Tb)2Fe 14 B;

[0010] The thickness of the shell layer is 0.1-6 μm.

[0011] The Nd-rich phase comprises R6Fe 13 B phase, wherein R is one or more of Nd, Pr, Dy and Tb.

[0012] In the present application, preferably, the thickness of the shell layer is 0.1-5 μm, more preferably 0.1-5 μm, and further more preferably 0.1-4 μm.

[0013] In the present application, preferably, the shell layer accounts for 30%-60% of the volume percentage of the Nd-Fe-B magnet, more preferably 45-56%, for example 45.7%, 50.3%, 50.78% or 52.7%.

[0014] In the present application, preferably, the Nd-rich phase further comprises ZrB2 and / or TiB2.

[0015] In the present application, preferably, the Nd-rich phase further comprises a first grain boundary phase comprising Fe, T and B, wherein T is Zr and / or Ti.

[0016] In the present application, preferably, the Nd-rich phase further comprises a second grain boundary phase comprising Nd, Ga, Al, Fe and Dy.

[0017] The present application further provides a preparation method of the Nd-Fe-B magnet as described above, comprising the following steps:

[0018] S1. Preparing a main alloy sheet and an auxiliary alloy sheet respectively;

[0019] The raw material of the main alloy sheet comprises LH1, RH1, X1, Y1, Fe and B; the LH1 is Nd or PrNd alloy; the RH1 is one or more of Tb, Dy, Ho and Gd; the X1 is one or more of Ti, Zr and Nb; and the Y1 is one or more of Al, Cu, Ga and Co.

[0020] The raw material of the main alloy sheet contains the LH1, the RH1, the X1 and the Y1, wherein the mass percentage of the LH1 in the main alloy sheet is 25-27.5%, the mass percentage of the RH1 in the main alloy sheet is 0-10%, the mass percentage of the X1 in the main alloy sheet is 0.05-0.6%, and the mass percentage of the Y1 in the main alloy sheet is 0.05-3.5%; and the sum of the mass percentages of the elements in the main alloy sheet is 100%.

[0021] The raw material of the auxiliary alloy sheet contains the RH2, the X2 and Fe, wherein the RH2 is Tb and / or Dy, and the X2 is one or more of Ti, Zr and Nb.

[0022] The raw material of the auxiliary alloy sheet contains the RH2 and the X2, wherein the mass percentage of the RH2 in the auxiliary alloy sheet is 10-85%, and the mass percentage of the X2 in the auxiliary alloy sheet is 0-8%; and the sum of the mass percentages of the elements in the auxiliary alloy sheet is 100%.

[0023] S2. The mixture of the hydrogen-crushed or micro-pulverized main alloy sheet and auxiliary alloy sheet is subjected to orientation pressing, isostatic pressing and sintering, thereby obtaining the Nd-Fe-B material.

[0024] The mass percentage of the main alloy sheet in the total mass of the main alloy sheet and the auxiliary alloy sheet is more than 82% but less than 100%.

[0025] In S1, the raw material of the main alloy sheet contains the PrNd alloy, which refers to an alloy of Pr and Nd. Preferably, the mass percentage of Pr in the PrNd alloy is 0-34% and is not 0. More preferably, the mass percentage of Pr in the PrNd alloy is 0-7% and is not 0.

[0026] In S1, preferably, the mass percentage of the LH1 in the raw material of the main alloy sheet is 25-27%, for example, 25.2% or 26.58%.

[0027] In S1, preferably, the mass percentage of the RH1 in the raw material of the main alloy sheet is 0-5% and is not 0. More preferably, the mass percentage of the RH1 in the raw material of the main alloy sheet is 3-5%, for example, 4%, 4.2% or 4.4%.

[0028] In S1, preferably, the RH1 in the raw material of the main alloy sheet is Dy and / or Gd.

[0029] Preferably, when the raw material of the main alloy sheet contains Dy, the mass percentage of Dy in the main alloy sheet is 4-5%, for example, 4% or 4.2%.

[0030] Preferably, when the raw material of the main alloy piece contains Gd, the mass percentage of Gd in the main alloy piece is 0-1%, for example, 0.4%.

[0031] In S1, preferably, in the raw material of the main alloy piece, the mass percentage of X1 in the main alloy piece is 0.1-0.3%, for example, 0.2%.

[0032] In S1, preferably, when the raw material of the main alloy piece contains Zr, the mass percentage of Zr in the main alloy piece is 0-0.5% and is not 0, for example, 0.1%.

[0033] In S1, preferably, when the raw material of the main alloy piece contains Ti, the mass percentage of Ti in the main alloy piece is 0.05-0.3%, for example, 0.2%.

[0034] In S1, preferably, in the raw material of the main alloy piece, the mass percentage of Y1 in the main alloy piece is 1.5-3.5%, for example, 1.96%, 2.09% or 3.1%.

[0035] In S1, preferably, when the raw material of the main alloy piece contains Co, the mass percentage of Co in the main alloy piece is 1-3%, more preferably 1-2.5%, for example, 1.19% or 2.2%.

[0036] In S1, preferably, when the raw material of the main alloy piece contains Cu, the mass percentage of Cu in the main alloy piece is 0.1-0.5%, more preferably 0.2-0.3%, for example, 0.21% or 0.3%.

[0037] In S1, preferably, when the raw material of the main alloy piece contains Al, the mass percentage of Al in the main alloy piece is 0.05-0.7%, more preferably 0.2-0.45%, for example, 0.2%, 0.3% or 0.43%.

[0038] In S1, preferably, when the raw material of the main alloy piece contains Ga, the mass percentage of Ga in the main alloy piece is 0.1-0.4%, more preferably 0.25-0.4%, for example, 0.26%.

[0039] In S1, preferably, when the raw material of the main alloy piece contains Cu and Ti, the mass ratio of Cu to Ti is (1-1.5):1.

[0040] In S1, preferably, when the raw material of the main alloy piece contains Ti, Cu and Al, the total amount of Ti, Cu and Al accounts for 0.05-2% of the mass percentage of the main alloy piece, more preferably 0.3-1.25%, further more preferably 0.7-0.9%, for example 0.71% or 0.84%.

[0041] In S1, preferably, in the raw material of the main alloy piece, B accounts for 0.88-1.05% of the mass percentage of the main alloy piece, more preferably 0.95-1%, for example 0.98%.

[0042] In a preferred embodiment of S1, the content of Nd is 26.58%; the content of Dy is 4%; the content of Co is 1.19%; the content of Cu is 0.21%; the content of Al is 0.3%; the content of Ga is 0.26%; the content of Ti is 0.2%; the content of B is 1%; the content of Fe is 66.26%; the percentage refers to the mass percentage of the components in the raw material of the main alloy piece.

[0043] In a preferred embodiment of S1, the content of Nd is 26.58%; the content of Dy is 4%; the content of Gd is 0.4%; the content of Co is 2.2%; the content of Cu is 0.21%; the content of Al is 0.43%; the content of Ga is 0.26%; the content of Ti is 0.2%; the content of B is 1%; the content of Fe is 64.72%; the percentage refers to the mass percentage of the components in the raw material of the main alloy piece.

[0044] In a preferred embodiment of S1, the content of Nd is 25.2%; the content of Dy is 4.2%; the content of Co is 1.19%; the content of Cu is 0.3%; the content of Al is 0.2%; the content of Ga is 0.4%; the content of Zr is 0.1%; the content of Ti is 0.2%; the content of B is 0.98%; the content of Fe is 67.23%; the percentage refers to the mass percentage of the components in the raw material of the main alloy piece.

[0045] In a preferred embodiment of S1, the content of PrNd alloy is 26.58%; the content of Dy is 4%; the content of Co is 1.19%; the content of Cu is 0.21%; the content of Al is 0.3%; the content of Ga is 0.26%; the content of Ti is 0.2%; the content of B is 1%; the content of Fe is 66.26%; the percentage refers to the mass percentage of the components in the raw material of the main alloy piece; the mass ratio of Pr to Nd in the PrNd alloy is 25:75.

[0046] In S1, preferably, the main alloy piece is prepared by smelting and casting the raw material of the main alloy piece, and the operation and conditions of smelting and casting can be conventional in the art.

[0047] Preferably, the melting temperature of the raw material of the main alloy piece is 1500-1550°C in the preparation method of the main alloy piece.

[0048] Preferably, the pouring temperature of the casting is 1400-1450°C in the preparation method of the main alloy piece.

[0049] Preferably, the rotating speed of the copper roller of the casting is 35-55 rmp / min in the preparation method of the main alloy piece.

[0050] Preferably, the water inlet temperature of the copper roller of the casting is below 30°C in the preparation method of the main alloy piece.

[0051] Preferably, the water outlet temperature of the copper roller of the casting is below 55°C in the preparation method of the main alloy piece.

[0052] In S1, preferably, the mass percentage of RH2 in the raw material of the auxiliary alloy piece is 35-85%, more preferably 40-60%, for example, 55%.

[0053] In S1, preferably, when the raw material of the auxiliary alloy piece contains Dy, the mass percentage of Dy in the auxiliary alloy piece is 40-75%, for example, 55%.

[0054] In S1, preferably, when the raw material of the auxiliary alloy piece contains Zr, the mass percentage of Zr in the auxiliary alloy piece is 0-8%, for example, 7.3%.

[0055] In S1, preferably, the raw material of the auxiliary alloy piece further contains Nd, and the mass percentage of Nd in the auxiliary alloy piece is 0-15%.

[0056] In S1, preferably, the raw material of the auxiliary alloy piece further contains B, and the mass percentage of B in the auxiliary alloy piece is 0-1.5%, preferably 0-0.9%, for example, 0.4%.

[0057] In a preferred embodiment of S1, the content of Dy in the auxiliary alloy piece is 55%; the content of Zr is 7.3%; the content of Fe is 37.7%; the percentages refer to the mass percentages of the components in the raw material of the auxiliary alloy.

[0058] In a preferred embodiment of S1, the content of Nd in the auxiliary alloy piece is 15%; the content of Dy is 40%; the content of B is 0.4%; the content of Fe is 44.6%; the percentages refer to the mass percentages of the components in the raw material of the auxiliary alloy.

[0059] In S1, preferably, the auxiliary alloy sheet is prepared from raw materials of the auxiliary alloy sheet by smelting and casting, and the operation and conditions of smelting and casting can be conventional in the art.

[0060] In the preparation method of the auxiliary alloy sheet, preferably, the smelting temperature of the raw materials of the auxiliary alloy sheet is 1500-1550°C.

[0061] In the preparation method of the auxiliary alloy sheet, preferably, the pouring temperature of the casting is 1500-1550°C.

[0062] In the preparation method of the auxiliary alloy sheet, preferably, the rotating speed of the copper roller of the casting is 35-55 rmp / min.

[0063] In the preparation method of the auxiliary alloy sheet, preferably, the water inlet temperature of the copper roller of the casting is below 30°C.

[0064] In the preparation method of the auxiliary alloy sheet, preferably, the water outlet temperature of the copper roller of the casting is below 55°C.

[0065] In S2, preferably, the mass percentage of the main alloy sheet in the total mass of the main alloy sheet and the auxiliary alloy sheet is above 90% and not 100%, more preferably 94-95%.

[0066] In S2, preferably, the mixture of the main alloy sheet and the auxiliary alloy sheet is subjected to hydrogen crushing, micro-pulverization, orientation pressing, isostatic pressing and sintering to obtain the Nd-Fe-B material.

[0067] Alternatively, the main alloy sheet and the auxiliary alloy sheet are subjected to hydrogen crushing and micro-pulverization respectively, the fine powder after micro-pulverization of the main alloy sheet and the auxiliary alloy sheet is mixed, and the mixed fine powder is subjected to orientation pressing, isostatic pressing and sintering to obtain the Nd-Fe-B material.

[0068] In S2, the operation and conditions of hydrogen crushing, micro-pulverization, orientation pressing, isostatic pressing and sintering can be conventional in the art.

[0069] In the hydrogen crushing, preferably, the dehydrogenation temperature is 540-560°C.

[0070] In the hydrogen crushing, preferably, the process ends when the pressure drop is less than 0.04 MPa for no less than 10 min.

[0071] In the micro-pulverization, preferably, the micro-pulverization is air jet milling.

[0072] In the air jet milling, preferably, the oxygen supplement is 0-70 ppm.

[0073] Preferably, the fine powder obtained by the micro-pulverization has a particle size distribution of 3.5-4.5 μm.

[0074] Preferably, the magnetizing current of the oriented pressing is controlled at 950-970 A, for example, 960 A.

[0075] Preferably, the green compact obtained by the oriented pressing has a green compact density of 3.7-4.3 g / cm 3 , for example, 4.1 g / cm 3 .

[0076] Preferably, the sintering treatment is performed at a temperature of 1025-1150 °C, for example, 1070-1080 °C.

[0077] Preferably, the sintering treatment is performed for a time of 4-10 hours, for example, 8 hours.

[0078] Preferably, the sintering treatment is followed by an aging treatment.

[0079] Preferably, the aging treatment is a primary aging and / or a secondary aging. The primary aging is preferably performed at a temperature of 850-940 °C for a time of 2-5 hours. The secondary aging is preferably performed at a temperature of 420-640 °C for a time of 2-5 hours.

[0080] On the basis of common knowledge in the art, the above-mentioned preferred conditions can be combined arbitrarily, thereby obtaining preferred examples of the present application.

[0081] The reagents and raw materials used in the present application are commercially available.

[0082] The positive progress effect of the present application is that:

[0083] In the present application, by improving the raw materials of the main alloy sheet and the auxiliary alloy sheet and by matching the process conditions, the diffusion amount of heavy rare earth elements into the main phase is effectively reduced, a thinner heavy rare earth shell layer is formed, and the high-temperature performance of the magnet is further optimized and improved. The heavy rare earth elements are dispersedly distributed in the main phase and the grain boundary in the traditional double-alloy method, which results in excessive waste of heavy rare earth elements.

[0084] In a preferred mode of the present application, the sintered sample can be directly subjected to a secondary aging treatment. The high-temperature performance of the sintered sample is not only superior to that of the sample subjected to a primary aging treatment after sintering, but also superior to that of the sample subjected to a primary aging and a secondary aging after sintering. The highlight of the process is that the subsequent primary aging or secondary aging process can be directly cancelled, thereby saving the process and greatly reducing the process cost. BRIEF DESCRIPTION OF DRAWINGS

[0085] Figure 1H cj Performance changes.

[0086] Figure 2 EPMA images of Example 3. DETAILED DESCRIPTION

[0087] The present application is further illustrated by the following examples without thereby limiting the present application to the examples described. The experimental methods in the following examples, for which no specific conditions are mentioned, are selected according to the conventional methods and conditions, or according to the instructions of the commercial products.

[0088] Example 1

[0089] (1) According to the formulation as shown in Table 1, the raw materials of the main alloy sheet and the auxiliary alloy sheet are melted and cast to prepare the main alloy sheet and the auxiliary alloy sheet, respectively.

[0090] The melting temperature of the main alloy sheet is 1500-1550℃, the casting temperature is 1400-1450℃, the rotating speed of the copper roller for casting is 35-55 rmp / min, the water inlet temperature of the copper roller for casting is ≤30℃, the water outlet temperature of the copper roller for casting is ≤55℃, and the main alloy sheet is obtained.

[0091] The melting temperature of the auxiliary alloy sheet is 1500-1550℃, the casting temperature is 1500-1550℃, the rotating speed of the copper roller for casting is 35-55 rmp / min, the water inlet temperature of the copper roller for casting is ≤30℃, the water outlet temperature of the copper roller for casting is ≤55℃, and the auxiliary alloy sheet is obtained.

[0092] (2) Hydrogen breaking process: the mixture of the main alloy sheet and the auxiliary alloy sheet in step (1) is subjected to hydrogen breaking treatment at 550℃ for 3 hours to obtain the coarsely crushed powder.

[0093] (3) Micro-crushing process: the coarsely crushed powder in step (2) is subjected to micro-crushing in the air flow mill in an atmosphere with oxygen supplement of 0-70 ppm to obtain the micro-crushed powder with an average particle size of D50=3.5-4.5 μm.

[0094] (4) Oriented pressing process: the magnetizing current is controlled at 960 A, and the pressing density is 4.1 g / cm 3 .

[0095] (5) Isostatic pressing process.

[0096] (6) Sintering process: the sample obtained in step (5) is sintered at a sintering temperature of 1070-1080℃ for 8 hours.

[0097] Table 1 Formulation of raw materials of Examples 1-7

[0098]

[0099]

[0100] Wherein, " / " indicates that the component is not present; PrNd is a PrNd alloy with a mass ratio of 25:75.

[0101] Example 2

[0102] According to the formula shown in Table 1, steps (1) to (6) are the same as in Example 1. The sample obtained in step (6) is subjected to first-stage aging, and the first-stage aging condition is heat treatment at 900°C for 3 hours.

[0103] Example 3

[0104] According to the formula shown in Table 1, steps (1) to (6) are the same as in Example 1. The sample obtained in step (6) is subjected to secondary aging, and the conditions for secondary aging are heat treatment at 600°C for 3 hours.

[0105] And, as Figure 1 As shown, verification experiments were conducted at different secondary aging temperatures. It was found that during the change of the secondary temperature from 540℃ to 640℃, the H2 of the sample at 180℃... cj The sample remains in a relatively stable performance state, indicating that it has low sensitivity to the secondary aging temperature, which is beneficial for stable mass production and can avoid temperature interference with its performance.

[0106] Example 4

[0107] According to the formula shown in Table 1, steps (1) to (6) are the same as in Example 1. The sample obtained in step (6) is subjected to first-stage aging and second-stage aging. The first-stage aging condition is heat treatment at 900°C for 3 hours; the second-stage aging condition is heat treatment at 600°C for 3 hours.

[0108] Example 5

[0109] According to the formula shown in Table 1, steps (1) to (6) are the same as in Example 1.

[0110] Example 6

[0111] According to the formula shown in Table 1, steps (1) to (6) are the same as in Example 1.

[0112] Example 7

[0113] According to the formula shown in Table 1, steps (1) to (6) are the same as in Example 1.

[0114] Comparative Example 1

[0115] (1) According to the formula as shown in Table 2, the raw materials of the main alloy sheet are prepared into the main alloy sheet after smelting and casting.

[0116] The smelting temperature of the main alloy sheet is 1500-1550℃, the casting temperature of the casting is 1400-1450℃, the rotating speed of the copper roller of the casting is 50rmp / min, the water inlet temperature of the copper roller of the casting is ≤30℃, and the water outlet temperature of the copper roller of the casting is ≤55℃, so that the main alloy sheet is obtained.

[0117] (2) Hydrogen crushing process: the main alloy sheet in step (1) is subjected to hydrogen crushing treatment at 550℃ for 3 hours at room temperature, so that the coarse crushing powder is obtained.

[0118] (3) Micro-crushing treatment: the coarse crushing powder in step (2) is subjected to micro-crushing in the airflow mill in the atmosphere with oxygen supplement of 0-70ppm, so that the micro-crushing powder with average particle size of D50=3.5-4.5μm is obtained.

[0119] (4) Orientation pressing process: the magnetizing current is controlled at 960A, and the pressing density is 4.1g / cm 3 .

[0120] (5) Isostatic pressing process.

[0121] (6) Sintering process: the sample obtained in step (5) is sintered in inert gas atmosphere, and the sintering temperature is 1025-1150℃ for 8 hours.

[0122] (7) The sample obtained in step (6) is subjected to primary aging and secondary aging. The primary aging condition is heat treatment at 900℃ for 3 hours, and the secondary aging condition is heat treatment at 600℃ for 3 hours.

[0123] Comparative Example 2

[0124] According to the formula as shown in Table 2, the smelting temperature of the auxiliary alloy sheet is 1380-1420℃, the casting temperature of the casting is 1340-1360℃, the rotating speed of the copper roller of the casting is 26.8-27.2rmp / min, the water inlet temperature of the copper roller of the casting is ≤30℃, and the water outlet temperature of the copper roller of the casting is ≤55℃.

[0125] The sintering temperature of the sintering process is 1060-1070℃. The primary aging condition is heat treatment at 895-905℃ for 3 hours, and the secondary aging condition is heat treatment at 485-495℃ for 3 hours.

[0126] The rest of the process parameters are the same as those in Comparative Example 1.

[0127] Comparative Example 3

[0128] According to the formula as shown in Table 2, steps (1)-(7) are the same as those in Comparative Example 2.

[0129] Table 2 raw material formulation of comparative examples 1-3

[0130]

[0131]

[0132] wherein " / " means no component; PrNd is a PrNd alloy with a mass ratio of 25:75.

[0133] Effect examples

[0134] Magnetic performance test: the magnetic performance of the neodymium-iron-boron magnet was detected using a PFM14.CN forming type super high coercivity permanent magnet measuring instrument of China Institute of Metrology. The results measured for each example and comparative example are shown in Tables 3-5.

[0135] Table 3 comparison of microstructure parameters and magnetic properties of examples 3, 5-7 and comparative examples 1-3

[0136]

[0137]

[0138] As can be seen from Table 3, the present application can effectively reduce the diffusion amount of heavy rare earth elements into the main phase, so that a thin shell layer of heavy rare earth elements is formed around the main phase, and the obtained neodymium-iron-boron magnet has excellent high temperature performance.

[0139] In example 7, due to the addition of Pr element, the coercivity can be improved at room temperature, but in a high temperature environment, the thermal stability is not as good as the sample in which only Nd element is added in the light rare earth element.

[0140] Table 4 comparison of magnetic properties of comparative examples 1-3 and examples 1-4 at 20℃

[0141]

[0142] Table 5 comparison of magnetic properties of comparative examples 1-3 and examples 1-4 at 180℃

[0143]

[0144] By comparing the data in Tables 4-5, it is found that compared with the traditional process (for example, comparative examples 3-5), the present application can directly perform secondary aging process under the condition of saving 0.9-1.5% of heavy rare earth elements by mass percentage, the room temperature performance is similar, and the H cj and β(H cj ) at 180℃ are significantly better than the traditional process, and have excellent high temperature characteristics.

[0145] AsFigure 2 and Table 6, EPMA maps and heavy rare earth shell layer thickness results for Example 3.

[0146] Table 6 Heavy rare earth shell layer thickness for Example 3

[0147] Sample Thickness (pm) D1 1.266 D2 0.636 D3 1.204 D4 0.636 D5 2.341

[0148] Although the above describes specific embodiments of the present application, those skilled in the art will understand that these are merely examples, and the scope of protection of the present application is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present application, and such changes and modifications fall within the scope of protection of the present application.

Claims

1. A neodymium iron boron magnet, characterized in that, It comprises a main phase grain and its shell, and an Nd-rich phase adjacent to the main phase grain; The main phase grains contain Nd2Fe 14 B; or, the main phase grains contain Nd2Fe 14 B and Pr2Fe 14 B; The shell contains (Nd / Dy)2Fe 14 B and / or (Nd / Tb)2Fe 14 B; The thickness of the shell is 0.1~6μm; The Nd-rich phase contains R6Fe. 13 Phase B, wherein R is one or more of Nd, Pr, Dy, and Tb; The method for preparing the neodymium iron boron magnet includes the following steps: S1. A main alloy sheet and an auxiliary alloy sheet are prepared separately; the main alloy sheet is made from the raw material of the main alloy sheet by melting and casting; the auxiliary alloy sheet is made from the raw material of the auxiliary alloy sheet by melting and casting. In the preparation method of the auxiliary alloy sheet, the melting temperature of the raw material of the auxiliary alloy sheet is 1500~1550℃, the casting temperature is 1500~1550℃, and the rotation speed of the casting copper roller is 35~55 rpm / min. The mass percentage of the main alloy sheet to the total mass of the main alloy sheet and the auxiliary alloy sheet is 82%-95%; The raw materials of the main alloy sheet include: LH1, RH1, X1, Y1, Fe and B; LH1 is an Nd or PrNd alloy; RH1 is one or more of Tb, Dy, Ho and Gd; X1 is one or more of Ti, Zr and Nb; and Y1 is one or more of Al, Cu, Ga and Co. In the raw materials of the main alloy sheet, LH1 accounts for 25-27.5% of the mass percentage of the main alloy sheet, RH1 accounts for 0-10% of the mass percentage of the main alloy sheet, X1 accounts for 0.05-0.6% of the mass percentage of the main alloy sheet, and Y1 accounts for 0.05-3.5% of the mass percentage of the main alloy sheet; the sum of the mass percentages of all elements in the main alloy sheet is 100%. The auxiliary alloy sheet is made of the following raw materials: RH2, X2 and Fe; RH2 is Tb and / or Dy, and X2 is one or more of Ti, Zr and Nb. In the raw materials of the auxiliary alloy sheet, RH2 accounts for 10-85% of the mass percentage of the auxiliary alloy sheet, and X2 accounts for 0-8% of the mass percentage of the auxiliary alloy sheet; the sum of the mass percentages of all elements in the auxiliary alloy sheet is 100%. S2. The mixture of the main alloy sheet and the auxiliary alloy sheet, which has been hydrogen-crushed or micronized, is subjected to orientation pressing, isostatic pressing and sintering to obtain the neodymium iron boron magnet.

2. The neodymium iron boron magnet as described in claim 1, characterized in that, The thickness of the shell layer is 0.1~5μm; And / or, the shell layer accounts for 30% to 60% of the volume of the neodymium iron boron magnet; And / or, the Nd-rich phase also contains ZrB2 and / or TiB2; And / or, the Nd-rich phase further comprises: a first grain boundary phase containing Fe, T and B, wherein T is Zr and / or Ti; And / or, the Nd-rich phase further comprises: a second grain boundary phase containing Nd, Ga, Al, Fe and Dy.

3. The neodymium iron boron magnet as described in claim 1, characterized in that, The thickness of the shell layer is 0.1~5μm; And / or, the shell layer accounts for 45-56% of the volume of the neodymium iron boron magnet.

4. The neodymium iron boron magnet as described in claim 1, characterized in that, The thickness of the shell is 0.1~4μm; And / or, the shell layer accounts for 45.7%, 50.3%, 50.78%, or 52.7% of the volume of the neodymium iron boron magnet.

5. A method for preparing a neodymium iron boron magnet as described in any one of claims 1-4, characterized in that, The steps include: S1. A main alloy sheet and an auxiliary alloy sheet are prepared separately; the main alloy sheet is obtained by melting and casting the raw material of the main alloy sheet; the auxiliary alloy sheet is obtained by melting and casting the raw material of the auxiliary alloy sheet; in the preparation method of the auxiliary alloy sheet, the melting temperature of the raw material of the auxiliary alloy sheet is 1500~1550℃, the casting temperature is 1500~1550℃, and the rotation speed of the copper roller in the casting is 35~55 rpm / min; S2. The mixture of the main alloy sheet and the auxiliary alloy sheet, which has been hydrogen-crushed or micronized, is subjected to orientation pressing, isostatic pressing and sintering to obtain the neodymium iron boron magnet.

6. The method for preparing a neodymium iron boron magnet as described in claim 5, characterized in that, In S1, the raw material of the main alloy sheet contains Pr, which accounts for 0 to 34% of the mass percentage of the PrNd alloy, and is not 0. And / or, in S1, the LH1 accounts for 25-27% of the mass percentage of the main alloy sheet in the raw materials of the main alloy sheet; And / or, in S1, the RH1 in the raw materials of the main alloy sheet accounts for 0~5% of the mass percentage of the main alloy sheet, and is not 0; And / or, in S1, the raw material of the main alloy sheet, RH1 is Dy and / or Gd; And / or, in S1, when the raw material of the main alloy sheet contains Dy, the mass percentage of Dy in the main alloy sheet is 4-5%; And / or, in S1, when the raw material of the main alloy sheet contains Gd, the mass percentage of Gd in the main alloy sheet is 0-1%; And / or, in S1, X1 accounts for 0.1~0.3% of the mass percentage of the main alloy sheet in the raw materials of the main alloy sheet; And / or, in S1, when the raw material of the main alloy sheet contains Zr, the mass percentage of Zr in the main alloy sheet is 0~0.5%, and not 0; And / or, in S1, when the raw material of the main alloy sheet contains Ti, the mass percentage of Ti in the main alloy sheet is 0.05~0.3%; And / or, in S1, the Y1 accounts for 1.5~3.5% of the mass percentage of the main alloy sheet in the raw materials of the main alloy sheet; And / or, in S1, when the raw material of the main alloy sheet contains Co, the mass percentage of Co in the main alloy sheet is 1-3%; And / or, in S1, when the raw material of the main alloy sheet contains Cu, the mass percentage of Cu in the main alloy sheet is 0.1~0.5%; And / or, in S1, when the raw material of the main alloy sheet contains Al, the mass percentage of Al in the main alloy sheet is 0.05~0.7%; And / or, in S1, when the raw material of the main alloy sheet contains Ga, the mass percentage of Ga in the main alloy sheet is 0.1~0.4%; And / or, in S1, when the raw material of the main alloy sheet contains Cu and Ti, the mass ratio of Cu to Ti is (1~1.5):1; And / or, in S1, when the raw material of the main alloy sheet contains Ti, Cu and Al, the total amount of Ti, Cu and Al accounts for 0.05~2% of the mass percentage of the main alloy sheet; And / or, in S1, B accounts for 0.88~1.05% of the mass percentage of the main alloy sheet in the raw materials of the main alloy sheet.

7. The method for preparing a neodymium iron boron magnet as described in claim 5, characterized in that, In S1, the raw material of the main alloy sheet contains Pr, which accounts for 0 to 7% of the mass of the PrNd alloy, and is not 0. And / or, in S1, the LH1 accounts for 25.2% or 26.58% of the mass percentage of the main alloy sheet in the raw materials of the main alloy sheet; And / or, in S1, the RH1 accounts for 3-5% of the mass percentage of the main alloy sheet in the raw materials of the main alloy sheet; And / or, in S1, when the raw material of the main alloy sheet contains Dy, the mass percentage of Dy in the main alloy sheet is 4% or 4.2%; And / or, in S1, when the raw material of the main alloy sheet contains Gd, the mass percentage of Gd in the main alloy sheet is 0.4%; And / or, in S1, X1 accounts for 0.2% of the mass percentage of the main alloy sheet in the raw materials of the main alloy sheet; And / or, in S1, when the raw material of the main alloy sheet contains Zr, the mass percentage of Zr in the main alloy sheet is 0.1%; And / or, in S1, when the raw material of the main alloy sheet contains Ti, the mass percentage of Ti in the main alloy sheet is 0.2%; And / or, in S1, the Y1 in the raw materials of the main alloy sheet accounts for 1.96%, 2.09%, or 3.1% of the mass of the main alloy sheet; And / or, in S1, when the raw material of the main alloy sheet contains Co, the mass percentage of Co in the main alloy sheet is 1~2.5%; And / or, in S1, when the raw material of the main alloy sheet contains Cu, the mass percentage of Cu in the main alloy sheet is 0.2~0.3%; And / or, in S1, when the raw material of the main alloy sheet contains Al, the mass percentage of Al in the main alloy sheet is 0.2~0.45%; And / or, in S1, when the raw material of the main alloy sheet contains Ga, the mass percentage of Ga in the main alloy sheet is 0.25~0.4%; And / or, in S1, when the raw material of the main alloy sheet contains Ti, Cu and Al, the total amount of Ti, Cu and Al accounts for 0.3~1.25% of the mass percentage of the main alloy sheet; And / or, in S1, B accounts for 0.95~1% of the mass percentage of the main alloy sheet in the raw materials of the main alloy sheet.

8. The method for preparing a neodymium iron boron magnet as described in claim 5, characterized in that, In S1, the RH1 in the raw materials of the main alloy sheet accounts for 4%, 4.2%, or 4.4% of the mass of the main alloy sheet; And / or, in S1, when the raw material of the main alloy sheet contains Co, the mass percentage of Co in the main alloy sheet is 1.19% or 2.2%; And / or, in S1, when the raw material of the main alloy sheet contains Cu, the mass percentage of Cu in the main alloy sheet is 0.21% or 0.3%; And / or, in S1, when the raw material of the main alloy sheet contains Al, the mass percentage of Al in the main alloy sheet is 0.2%, 0.3%, or 0.43%; And / or, in S1, when the raw material of the main alloy sheet contains Ga, the mass percentage of Ga in the main alloy sheet is 0.26%; And / or, in S1, when the raw material of the main alloy sheet contains Ti, Cu and Al, the total amount of Ti, Cu and Al accounts for 0.7~0.9% of the mass percentage of the main alloy sheet; And / or, in S1, B accounts for 0.98% of the mass percentage of the main alloy sheet in the raw materials of the main alloy sheet.

9. The method for preparing a neodymium iron boron magnet as described in claim 5, characterized in that, In S1, when the raw material of the main alloy sheet contains Ti, Cu and Al, the total amount of Ti, Cu and Al accounts for 0.71% or 0.84% ​​of the mass percentage of the main alloy sheet.

10. The method for preparing a neodymium iron boron magnet as described in claim 6, characterized in that, In the main alloy sheet, the content of Nd is 26.58%; the content of Dy is 4%; the content of Co is 1.19%; the content of Cu is 0.21%; the content of Al is 0.3%; the content of Ga is 0.26%; the content of Ti is 0.2%; the content of B is 1%; and the content of Fe is 66.26%. The percentage refers to the mass percentage of the component in the raw material of the main alloy sheet. Alternatively, in the main alloy sheet, the content of Nd is 26.58%; the content of Dy is 4%; the content of Gd is 0.4%; the content of Co is 2.2%; the content of Cu is 0.21%; the content of Al is 0.43%; the content of Ga is 0.26%; the content of Ti is 0.2%; the content of B is 1%; and the content of Fe is 64.72%. The percentages refer to the mass percentage of the components in the raw materials of the main alloy sheet. Alternatively, in the main alloy sheet, the content of Nd is 25.2%; the content of Dy is 4.2%; the content of Co is 1.19%; the content of Cu is 0.3%; the content of Al is 0.2%; the content of Ga is 0.4%; the content of Zr is 0.1%; the content of Ti is 0.2%; the content of B is 0.98%; and the content of Fe is 67.23%. The percentages refer to the mass percentage of the components in the raw materials of the main alloy sheet. Alternatively, in the main alloy sheet, the content of PrNd alloy is 26.58%; the content of Dy is 4%; the content of Co is 1.19%; the content of Cu is 0.21%; the content of Al is 0.3%; the content of Ga is 0.26%; the content of Ti is 0.2%; the content of B is 1%; and the content of Fe is 66.26%. The percentage refers to the mass percentage of the component in the raw material of the main alloy sheet; the mass ratio of Pr to Nd in the PrNd alloy is 25:

75.

11. The method for preparing a neodymium iron boron magnet as described in claim 5, characterized in that, In S1, RH2 accounts for 35-85% of the mass percentage of the auxiliary alloy sheet in the raw materials of the auxiliary alloy sheet; And / or, in S1, when the raw material of the auxiliary alloy sheet contains Dy, the mass percentage of Dy in the auxiliary alloy sheet is 40-75%; And / or, in S1, when the raw material of the auxiliary alloy sheet contains Zr, the mass percentage of Zr in the auxiliary alloy sheet is 0-8%; And / or, in S1, the raw material of the auxiliary alloy sheet further includes Nd, and the mass percentage of Nd in the auxiliary alloy sheet is 0~15%; And / or, in S1, the raw material of the auxiliary alloy sheet further includes B, and B accounts for 0~1.5% of the mass percentage of the auxiliary alloy sheet.

12. The method for preparing a neodymium iron boron magnet as described in claim 5, characterized in that, In S1, RH2 accounts for 40-60% of the mass percentage of the auxiliary alloy sheet in the raw materials of the auxiliary alloy sheet; And / or, in S1, when the raw material of the auxiliary alloy sheet contains Dy, the mass percentage of Dy in the auxiliary alloy sheet is 55%; And / or, in S1, when the raw material of the auxiliary alloy sheet contains Zr, the mass percentage of Zr in the auxiliary alloy sheet is 7.3%; And / or, in S1, the raw material of the auxiliary alloy sheet further includes B, and the mass percentage of B in the auxiliary alloy sheet is 0~0.9%.

13. The method for preparing a neodymium iron boron magnet as described in claim 5, characterized in that, In S1, RH2 accounts for 55% of the mass percentage of the auxiliary alloy sheet in the raw materials of the auxiliary alloy sheet; And / or, in S1, the raw material of the auxiliary alloy sheet further includes B, and B accounts for 0.4% of the mass percentage of the auxiliary alloy sheet.

14. The method for preparing a neodymium iron boron magnet as described in claim 11, characterized in that, In the auxiliary alloy sheet, the content of Dy is 55%; the content of Zr is 7.3%; and the content of Fe is 37.7%. The percentage refers to the mass percentage of the component in the raw material of the auxiliary alloy. Alternatively, in the auxiliary alloy sheet, the Nd content is 15%; the Dy content is 40%; the B content is 0.4%; and the Fe content is 44.6%. The percentages refer to the mass percentage of the components in the raw materials of the auxiliary alloy.

15. The method for preparing a neodymium iron boron magnet as described in claim 5, characterized in that, In the preparation method of the main alloy sheet, the melting temperature of the raw material of the main alloy sheet is 1500~1550℃. And / or, in the method for preparing the main alloy sheet, the casting temperature is 1400~1450℃; And / or, in the method for preparing the main alloy sheet, the rotational speed of the casting copper roller is 35~55 rpm / min; And / or, in the method for preparing the main alloy sheet, the water inlet temperature of the cast copper roller is below 30°C; And / or, in the method for preparing the main alloy sheet, the water outlet temperature of the cast copper roller is below 55°C; And / or, in the method for preparing the auxiliary alloy sheet, the water inlet temperature of the cast copper roller is below 30°C; And / or, in the method for preparing the auxiliary alloy sheet, the outlet water temperature of the cast copper roller is below 55°C.

16. The method for preparing a neodymium iron boron magnet as described in claim 5, characterized in that, The mass percentage of the main alloy sheet to the total mass of the main alloy sheet and the auxiliary alloy sheet is more than 90% and not more than 100%. And / or, in S2, the mixture of the main alloy sheet and the auxiliary alloy sheet is subjected to hydrogen crushing, micro-pulverization, orientation pressing, isostatic pressing and sintering to obtain the NdFeB magnet; or, the main alloy sheet and the auxiliary alloy sheet are subjected to hydrogen crushing and micro-pulverization respectively, the fine powders of the main alloy sheet and the auxiliary alloy sheet after micro-pulverization are mixed, and the mixed fine powders are subjected to orientation pressing, isostatic pressing and sintering to obtain the NdFeB magnet.

17. The method for preparing a neodymium iron boron magnet as described in claim 5, characterized in that, The mass percentage of the main alloy sheet to the total mass of the main alloy sheet and the auxiliary alloy sheet is 94-95%.

18. The method for preparing a neodymium iron boron magnet as described in claim 16 or 17, characterized in that, The dehydrogenation temperature of the hydrogen crushing is 540~560℃; And / or, the hydrogen decomposition process ends when the pressure drop is <0.04 MPa and not less than 10 min; And / or, the micro-pulverization is performed by an air jet mill; And / or, the particle size distribution of the fine powder obtained by the micro-pulverization is between 3.5 and 4.5 μm; And / or, the magnetizing current of the orientation pressing is controlled at 950A~970A; And / or, the compact density of the compact obtained by the orientation pressing is 3.7~4.3 g / cm³. 3 ; And / or, the sintering temperature is 1025~1150℃; And / or, the sintering treatment time is 4 to 10 hours; And / or, the sintering process is followed by an aging process.

19. The method for preparing a neodymium iron boron magnet as described in claim 18, characterized in that, The oxygen supply for the air jet mill is 0~70ppm; And / or, the magnetizing current for the orientation pressing is controlled at 960A; And / or, the compact density of the compact obtained by the orientation pressing is 4.1 g / cm³. 3 ; And / or, the sintering temperature is 1070~1080℃; And / or, the sintering process takes 8 hours.

20. The method for preparing a neodymium iron boron magnet as described in claim 18, characterized in that, The aging process is a first-level aging process and / or a second-level aging process; the temperature for the first-level aging process is 850~940℃, and the time for the first-level aging process is 2~5 hours; the temperature for the second-level aging process is 420~640℃, and the time for the second-level aging process is 2~5 hours.

Images