Patent Application
20250069785
The invention relates to a neodymium-iron-boron magnet material, a preparation method, and use thereof.
Permanent magnetic materials were developed as key materials to support electronic devices. R-T-B series permanent magnet materials are known to have the highest performance among permanent magnets and are used in voice coil motors for hard disk drives, motors for electric vehicles, motors for industrial equipment, etc.
At present, the intrinsic coercivity of neodymium-iron-boron magnets without heavy rare earth additions when Br is 14.0 kGs is only about 18.3 kOe, which is less than ⅓ of the theoretical intrinsic coercivity of NdFeB. Therefore, how to further improve the intrinsic coercivity of R-T-B series permanent magnet materials without using heavy rare earths or using less heavy rare earths is currently a research direction in this field.
The prior art discloses methods of increasing coercivity by reducing the particle size of magnetic powder. For example, CN 111968813 A discloses that no dehydrogenation treatment is performed after the hydrogen decrepitation process, and the grain boundary phase of the obtained NdFeB-based magnetic powder is a rare earth-rich phase with a low oxygen content, which is beneficial to reducing the loss of rare earth elements in the sintered magnet and inhibiting the grain growing during the sintering process, thereby improving the organizational structure of the sintered magnet and improving the magnetic and mechanical properties of the sintered magnet. However, the extent to which this method can improve the intrinsic coercivity is limited, wherein when Br is 14.6 kGs, the intrinsic coercivity is only about 14.42 kOe. In addition, there is a defect that microcracks are easily formed inside the magnet during the sintering dehydrogenation process, resulting in a decrease in the bending strength of the magnet.
Therefore, how to further optimize the formula of magnet materials to obtain neodymium-iron-boron magnet materials with better magnetic properties is an urgent technical problem that needs to be solved.
The technical problem to be solved by the present invention is to overcome the defects in the existing technology that rely on heavy rare earths to improve the intrinsic coercivity of neodymium-iron-boron magnets, and provide a neodymium-iron-boron magnet material and its preparation method and use. According to the present invention, by controlling the compositions and manufacturing process, the formation of the Nd—O phase having an FCC type crystal structure is suppressed, and its volume percentage in the grain boundary phase is controlled within 20%. Thus, the obstruction of the Nd—O phase having the FCC type crystal structure with a higher melting point to the fluidity of the Nd-rich phase during the aging process is reduced, which is conducive to the formation of a continuous and uniform intergranular Nd-rich phase, thereby enhancing the demagnetizing coupling ability of the grain boundary phase and improving the consistency of the intrinsic coercivity of the magnet.
During the research and development process, the inventor creatively discovered that the Nd—O phase having a FCC type crystal structure in the neodymium-iron-boron magnet material is not conducive to the formation of a continuous and uniform intergranular Nd-rich phase, and additionally, it further consumes Nd in the magnet and forms agglomerates in the intergranular triangular zone, resulting in an increase in the Fe content in the intergranular phase, and further causing the alloying between Fe and the main phase to intensify, resulting in a decrease in the proportion of the main phase and a decrease in magnet performance.
The present invention mainly solves the above technical problems through the following technical solutions.
The invention provides a neodymium-iron-boron magnet material, comprising following components of:
In the invention, the R can have a content of 28.50-32.00 wt %, such as 28.65 wt %, 29.20 wt %, 29.50 wt %, 29.51 wt %, 30.15 wt %, 30.20 wt %, 30.30 wt %, 31.31 wt % or 32.00 wt %, wherein wt % refers to a weight percentage of R in the neodymium-iron-boron magnet material.
In the present invention, the R may be a conventional rare earth element in the art, and may generally include a light rare earth element and/or a heavy rare earth element.
Wherein, the light rare earth element can be Pr and/or Nd.
Wherein, the light rare earth element can have a content of 28.50-32.00 wt %, such as 28.50 wt %, 29.00 wt %, 29.50 wt %, 29.51 wt %, 30.00 wt %, 30.20 wt %, 30.51 wt % or 32.00 wt %, wherein wt % refers to a weight percentage of the light rare earth element in the neodymium-iron-boron magnet material.
When the R comprises Pr, the Pr can have a content of 5.00-10.00 wt %, such as 5.40 wt %, 6.50 wt %, 7.38 wt %, 7.50 wt %, 7.63 wt % or 8.00 wt %, wherein wt % refers to a weight percentage of Pr in the neodymium-iron-boron magnet material.
When the R comprises Nd, the Nd can have a content of 20.00-32.00 wt %, such as 22.00 wt %, 22.13 wt %, 22.50 wt %, 22.88 wt %, 23.50 wt %, 24.60 wt %, 28.50 wt %, 29.00 wt %, 29.50 wt %, 30.20 wt % or 32.00 wt %, wherein wt % refers to a weight percentage of Nd in the neodymium-iron-boron magnet material.
Wherein, the heavy rare earth element can be Dy and/or Tb.
The heavy rare earth element can have a content of 0.10-3.00 wt %, such as 0.15 wt %, 0.20 wt %, 0.30 wt % or 0.80 wt %, wherein wt % refers to a weight percentage of the heavy rare earth element in the neodymium-iron-boron magnet material.
When the R comprises Dy, the Dy can have a content of 0.10-3.00 wt %, such as 0.15-1.00 wt %, also such as 0.15 wt %, 0.20 wt %, 0.30 wt % or 0.80 wt %, wherein wt % refers to a weight percentage of Dy in the neodymium-iron-boron magnet material.
In the invention, the Al can have a content of 0.00-0.80 wt %, such as 0.05-0.80 wt %, also such as 0.05 wt %, 0.10 wt %, 0.30 wt %, 0.45 wt %, 0.50 wt % or 0.80 wt %, wherein wt % refers to a weight percentage of the Al in the neodymium-iron-boron magnet material.
In the invention, the Cu preferably have a content of 0.13-0.50 wt %, such as 0.15 wt %, 0.20 wt %, 0.30 wt %, 0.35 wt % or 0.40 wt %, wherein wt % refers to a weight percentage of the Cu in the neodymium-iron-boron magnet material.
In the invention, the B can have a content of 0.86-1.00 wt %, such as 0.86 wt %, 0.92 wt %, 0.94 wt %, 0.96 wt %, 0.98 wt % or 1.00 wt %, wherein wt % refers to a weight percentage of the B in the neodymium-iron-boron magnet material.
In the invention, the Fe can have a content of 64.50-69.00 wt %, such as 64.72 wt %, 66.24 wt %, 66.33 wt %, 67.06 wt %, 67.14 wt %, 67.18 wt %, 67.52 wt %, 67.98 wt %, 68.13 wt %, 68.23 wt % or 68.27 wt %, wherein wt % refers to a weight percentage of the Fe in the neodymium-iron-boron magnet material.
In the invention, the neodymium-iron-boron magnet material further comprises one or more of Ga, Co, Zr and Ti.
When the neodymium-iron-boron magnet material further comprises Ga, the Ga can have a content of 0.00-1.00 wt %, excluding 0, such as 0.05-0.80 wt %, also such as 0.15 wt %, 0.20 wt %, 0.40 wt %, 0.50 wt % or 0.60 wt %, wherein wt % refers to a weight percentage of Ga in the neodymium-iron-boron magnet material.
When the neodymium-iron-boron magnet material further comprises Co, the Co can have a content of 0.20-2.00 wt %, such as 0.30 wt %, 0.40 wt %, 0.50 wt %, 0.80 wt %, 1.00 wt % or 1.50 wt %, wherein wt % refers to a weight percentage of Co in the neodymium-iron-boron magnet material.
When the neodymium-iron-boron magnet material further comprises Zr, the Zr can have a content of 0.05-0.60 wt %, such as 0.08 wt %, 0.10 wt %, 0.15 wt %, 0.30 wt %, 0.40 wt % or 0.50 wt %, wherein wt % refers to a weight percentage of Zr in the neodymium-iron-boron magnet material.
When the neodymium-iron-boron magnet material further comprises Ti, the Ti can have a content of 0.05-0.40 wt %, such as 0.05 wt % or 0.08 wt %, wherein wt % refers to a weight percentage of Ti in the neodymium-iron-boron magnet material.
In a preferable embodiment of the invention, the neodymium-iron-boron magnet material comprises following components of:
In a preferable embodiment of the invention, the neodymium-iron-boron magnet material comprises following components of:
In a preferable embodiment of the invention, the neodymium-iron-boron magnet material comprises following components of:
In a preferable embodiment of the invention, the neodymium-iron-boron magnet material comprises following components of:
In a preferable embodiment of the invention, the neodymium-iron-boron magnet material consists of any of the following formulas:
In the invention, the volume percentage of a Nd—O phase having a FCC type crystal structure in a grain boundary phase of the neodymium-iron-boron magnet material is preferably ≤15.0%, such as 1.5%, 1.6%, 1.7%, 2.3%, 2.3%, 3.4%, 8.9%, 9.5%, 10.0%, 12.0% or 15.0%.
In the present invention, the grain boundary phase of the neodymium-iron-boron magnet material generally further contains an Nd-rich phase.
Wherein, the volume percentage of the Nd-rich phase to the grain boundary phase of the neodymium-iron-boron magnet material is preferably 9.0-15.0%, such as 9.2%, 9.4%, 9.5%, 9.6%, 10.2%, 10.5%, 10.8% or 14.2%.
In the invention, the neodymium-iron-boron magnet material can have an oxygen content≤600 ppm, such as 408 ppm, 415 ppm, 448 ppm, 453 ppm, 455 ppm, 456 ppm, 463 ppm, 468 ppm, 476 ppm or 487 ppm.
In the present invention, the neodymium-iron-boron magnet material can have a main phase average grain size of 7.0-8.0 μm, such as 7.0 μm, 7.1 μm, 7.2 μm, 7.3 μm, 7.5 μm or 7.6 μm.
The invention further provides a preparation method for a neodymium-iron-boron magnet material, comprising following steps of subjecting a raw material composition for the neodymium-iron-boron magnet material to smelting, casting, pulverization, shaping, sintering and aging treatments in turn, wherein:
In the present invention, the composition formula of the raw material composition of the neodymium-iron-boron magnet material may be the same as the composition formula of the neodymium-iron-boron magnet material.
In the invention, the magnetic powder obtained after the pulverization preferably has a particle size D50 of 4.0-4.2 μm, such as 4.0 μm or 4.1 μm.
In the invention, the magnetic powder obtained after the pulverization has a particle size D90/D10 ratio which is preferably ≤3.7, such as 3.4, 3.5, 3.6 or 3.7.
In the present invention, the particle size of the magnetic powder obtained after the pulverization generally refers to the particle size of the magnetic powder after the pulverization and before the shaping.
In the present invention, if the particle size of the magnetic powder obtained after the pulverization is too small, local oxidation will easily occur during the subsequent pressing and sintering process, causing the proportion of Nd—O compounds to increase to 20% or more; if the particle size of the magnetic powder obtained after the pulverization is too large, although the proportion of the Nd—O phase having a FCC type crystal structure can be controlled within 20%, defects within the main phase particles will increase, resulting in a decrease in coercivity.
In the invention, the magnetic powder obtained after the pulverization has an oxygen content≤300 ppm, such as 150 ppm, 160 ppm, 170 ppm, 180 ppm, 190 ppm, 200 ppm, 220 ppm, 250 ppm, 280 ppm or 290 ppm.
In the present invention, the smelting process may be a conventional smelting process in this field.
Wherein, the vacuum degree for the smelting can be 5×10−2 Pa (absolute pressure).
Wherein, the melting temperature can be 1550° C. or less, such as 1510° C.
In the present invention, the casting process may be a conventional casting process in this field.
Wherein, the casting process may adopt a rapid solidification casting method.
Wherein, the casting temperature can be 1390-1460° C., such as 1400° C.
Wherein, the thickness of the alloy casting sheet obtained after the casting can be 0.25-0.40 mm.
In the invention, the pulverization can be performed in a gas atmosphere with an oxidizing gas content of 100 ppm or less, for example, a gas atmosphere with an oxidizing gas content of 10 ppm, 20 ppm, 30 ppm, 50 ppm, 60 ppm or 70 ppm, wherein the oxidizing gas content refers to a mass percentage of oxygen or moisture in a gas of the gas atmosphere.
In the invention, the pulverization can comprise hydrogen decrepitation pulverization and jet mill pulverization.
Wherein, the hydrogen decrepitation pulverization generally comprises hydrogen absorption, dehydrogenation and cooling treatments in turn.
The hydrogen absorption can be carried out under the condition of hydrogen pressure of 0.085 MPa (absolute pressure).
The dehydrogenation can be carried out under a condition of evacuation and heating.
The dehydrogenation can be carried out at a temperature of 300-600° C., such as 500° C.
Wherein, the jet mill pulverization can be performed in a gas atmosphere with an oxidizing gas content of 100 ppm or less, for example, a gas atmosphere with an oxidizing gas content of 10 ppm, 20 ppm, 30 ppm, 50 ppm, 60 ppm or 70 ppm, wherein the oxidizing gas content refers to a mass percentage of oxygen or moisture in a gas of the gas atmosphere.
In the present invention, a lubricant, such as zinc stearate, can be added to the pulverized magnetic powder before shaping. The added amount of the lubricant can be 0.05-0.15%, such as 0.10%, of the mass of the pulverized magnet.
In the present invention, the molding may adopt a magnetic field shaping method.
Wherein, the magnetic field shaping can be performed under a magnetic field intensity of 1.8-2.5 T.
In the present invention, the sintering process may be a conventional sintering process in this field.
Wherein, the sintering temperature may be 1020-1100° C., such as 1085° C.
Wherein, the sintering time may be 4-8 h, such as 6 hours.
Wherein, the cooling after sintering can be performed in a protective atmosphere, for example, in an Ar gas atmosphere of 0.05 MPa (absolute pressure).
In the present invention, the aging treatment can be a conventional aging treatment in this field, which generally includes a primary aging treatment and a secondary aging treatment.
Wherein, the temperature of the primary aging treatment may be 800-1000° C., such as 900° C.
Wherein, the time of the primary aging treatment may be 2-6 hours, for example, 3 hours.
Wherein, the temperature of the secondary aging treatment may be 400-600° C., such as 480° C.
Wherein, the time of the secondary aging treatment may be 2-6 hours, such as 3.5 hours.
The invention further provides a neodymium-iron-boron magnet material prepared by the preparation method for a neodymium-iron-boron magnet material.
The invention further provides a neodymium-iron-boron magnet material, wherein a volume percentage of a Nd—O phase having a FCC type crystal structure in an intergranular triangular zone of the neodymium-iron-boron magnet material in a grain boundary phase of the neodymium-iron-boron magnet material is equal to or less than 20%; and
During the research and development process, the inventor creatively discovered that by controlling the proportion of the Nd—O phase having a FCC type crystal structure in the grain boundary phase within 20%, the obstruction of the Nd—O phase having the FCC type crystal structure with a higher melting point to the fluidity of the Nd-rich phase during the aging process is reduced, which is conducive to the formation of a continuous and uniform intergranular Nd-rich phase, thereby enhancing the demagnetizing coupling ability of the grain boundary phase and improving the consistency of the intrinsic coercivity of the magnet.
In the present invention, the oxygen content in the neodymium-iron-boron magnet material may be less than 600 ppm, such as 448 ppm, 455 ppm or 456 ppm.
In the present invention, the average grain size of the neodymium-iron-boron magnet material may be less than or equal to 7 μm, or may be 7.0-8.0 μm, such as 7.0 μm, 7.2 μm or 7.6 μm.
In the present invention, by controlling the proportion of the Nd—O phase having a FCC type Nd—O crystal structure within 20%, the average size of the crystal grains is effectively controlled, the volume ratio of the main phase in the magnet is increased, and the fluidity of the grain boundary phase during heat treatment is increased, thereby improving the remanence and coercivity of the magnet.
In the present invention, the volume proportion of the Nd—O phase having a FCC type crystal structure in the grain boundary phase is preferably ≤15.0%, such as 1.5%, 1.6%, 1.7%, 2.3%, 2.3%, 3.4%, 8.9%, 9.5%, 10.0%, 12.0% or 15.0%.
The invention further provides use of the neodymium-iron-boron magnet material as a raw material for preparing an electronic component.
In the present invention, the grain boundary phase may have the meaning conventionally understood in the art, and generally refers to the collective name for the area formed by the two-granule grain boundary phase and the intergranular triangular zone. The two-granule grain boundary phase is generally the grain boundary phase between two main phase particles. The intergranular triangular zone generally refers to an intergranular phase that is in direct contact with three or more main phase grains at the same time.
“D90/D10” mentioned in the present invention represents the concentration degree of particle distribution. In the industry relating to magnetic materials, the smaller the value of D90/D10, the better the concentration degree of the particle size distribution.
On the basis of common sense in the field, the above preferred conditions can be combined arbitrarily to obtain preferred examples of the present invention.
The reagents and raw materials used in the present invention are all commercially available.
The positive progressive effects of the present invention are as follows:
The present invention is further described below by means of examples, but the present invention is not limited to the scope of the described examples. Experimental methods that do not indicate specific conditions in the following examples should be selected according to conventional methods and conditions, or according to product specifications.
The raw materials were prepared according to the ingredients for a neodymium-iron-boron magnet material shown in Table 1 and the neodymium-iron-boron magnet material was prepared according to the following steps:
The hydrogen decrepitation pulverization comprised hydrogen absorption, dehydrogenation and cooling treatment. Wherein, the hydrogen absorption was carried out under a hydrogen pressure of 0.085 MPa (absolute pressure); the dehydrogenation was carried out under the condition of evacuation while raising temperature; and the dehydrogenation temperature was 500° C.
The jet mill pulverization was performed with an oxidizing gas content of 100 ppm or less. The powder obtained by jet mill pulverization had a particle size D50 of 4.1 μm and D90/D10=0.37. The oxidizing gas content refers to the mass percentage of oxygen and/or moisture content in the gas for “jet mill pulverization”. The pressure in the grinding chamber of the jet mill pulverization was 0.70 MPa (absolute pressure). After the pulverization, a lubricant zinc stearate was added to the powder in an amount of 0.10% of the weight of the mixed powder.
Raw materials were prepared according to the formulas shown in Table 1 below, wherein: the oxidizing gas content, the particle size D50, D90/D10, and oxygen content of the powder after jet mill pulverization in step (3) are shown in Table 2 below; the temperatures for the secondary aging in step (6) are shown in Table 2 below. Other preparation processes are the same as in Example 1.
Notes: In Table 3, the testing equipment used for powder particle size is the MS3000 Malvern laser particle size analyzer; the tester for powder oxygen content is HORIBA EMGA-830 oxygen, carbon and hydrogen combined analyzer; and the testing instrument used for oxidation gas content is the DH-2100 electrochemical trace oxygen analyzer.
1. Determination of ingredients: The R-T-B magnets prepared in Examples 1-11 and Comparative Examples 1-7 were measured using a high-frequency inductively coupled plasma optical emission spectrometer (ICP-OES). The test results are shown in Table 3 below.
The values of the Fe contents in the neodymium-iron-boron magnet materials in the above Examples and Comparative Examples are obtained by subtracting the contents of respective elements from 100% a. Those skilled in the art know that the Fe content contains some inevitable impurities introduced during the preparation process.
By using the closed loop demagnetization curve testing equipment NIM-62000 manufactured by the China Institute of Metrology, the neodymium-iron-boron magnet materials obtained in Examples 1-11 and Comparative Examples 1-7 were tested for magnetic properties at a testing temperature of 20° C. to obtain the data on remanence (Br), intrinsic coercivity (Hcj), maximum magnetic energy product (BHmax) and squareness (Hk/Hcj). The testing results are shown in Table 4.
The neodymium-iron-boron magnet material prepared in Example 1 was subjected to TEM examination, and its microstructure is shown in
Notes: In Table 5, Volume Percentage of Nd—O Phase having FCC Type Crystal Structure refers to: the volume of the Nd—O phase having FCC type crystal structure/the volume of the grain boundary phase of the magnet*1000%; Volume Percentage of Nd-rich Phase refers to: the volume of the Nd-rich phase/the volume of the grain boundary phase of the magnet*100%; Average Grain Size of Magnet refers to the average grain size of the main phase grains; and the instrument used to measure the oxygen content of the magnet is the HORIBA EMGA-830 oxygen, carbon and hydrogen combined analyzer.
According to Table 4 and Table 5, the following conclusions can be drawn:
| Number | Date | Country | Kind |
|---|---|---|---|
| 202210475096.1 | Apr 2022 | CN | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CN2022/129741 | 11/4/2022 | WO |
