High-abundance rare earth permanent magnet material and preparation method thereof

Abstract

The application belongs to the field of rare earth permanent magnet materials, and particularly relates to a high-abundance rare earth permanent magnet material and a preparation method thereof. x Fe 100‑x‑y‑z M y B z The raw materials are weighed according to the mass ratio, the mass ratio of Re:(Fe, M):B is 29:70:1, and the content of the rare earth element Ce accounts for 25-30% of the total rare earth content; (2) the raw materials are sequentially subjected to induction melting, rapid quenching, mechanical crushing and screening of particle size, so that the magnetic powder with a grain size of 20-100 nm is obtained; (3) hot-press forming: the magnetic powder is placed in a mold, a temperature is kept at 600-700 DEG C in a vacuum environment, a pressure of 150-250 MPa is applied, and the pressure is kept for 1-3 minutes, so that a dense hot-pressing blank is obtained; (4) hot deformation forming: the dense hot-pressing blank is deformed at 800-900 DEG C and 50-150 MPa, the deformation amount is not less than 70%, and after being kept for 30-60 seconds, a hot-deformed magnet is obtained. The preparation method has high Ce content, low cost and excellent magnetic properties of the obtained permanent magnet.

Description

Technical Field

[0001] This invention belongs to the field of rare earth permanent magnet materials, specifically relating to a high-abundance rare earth permanent magnet material and its preparation method. Background Technology

[0002] Due to their excellent magnetic properties, Nd-Fe-B permanent magnet materials have been widely used in many fields such as home appliances, hybrid vehicles, wind power generation, and aerospace. However, the large-scale consumption of commonly used rare earth elements Nd, Pr, Dy, and Tb in Nd-Fe-B permanent magnet materials has led to increasingly expensive raw material costs, especially Nd and Pr, which account for over 80 wt.%. Simultaneously, high-abundance rare earth elements such as La and Ce, which are often mined as byproducts, are being stockpiled, exacerbating the uneven utilization of rare earth resources. Currently, considering the abundant reserves and low cost of the high-abundance rare earth element Ce, the introduction of Ce into Nd-Fe-B magnets to prepare novel Ce-containing magnets has attracted widespread attention.

[0003] In sintered magnets, high-abundance rare-earth permanent magnets have been prepared by partially substituting Ce for Nd / Pr. However, the magnetic properties decrease with increasing Ce content. The Ce substitution amount in sintered magnets is typically 20–30 wt.%, resulting in a coercivity below 12 kOe, which does not meet market application requirements. The main reasons are: First, Ce₂Fe 14 The low intrinsic magnetic properties of the B phase directly affect the magnetic properties. Second, excessive Ce content easily forms a CeFe2 impurity phase with Fe, which disrupts the stability of the main phase and dilutes the magnetism. Third, the micron-sized crystalline structure of sintered magnets also limits the improvement of coercivity. These factors restrict the application of sintered Ce-containing rare-earth permanent magnets. Summary of the Invention

[0004] The purpose of this invention is to provide a high-abundance rare-earth permanent magnet material and its preparation method. By selecting the component ratio and coordinating the corresponding processes, the permanent magnet material with high Ce content exhibits excellent magnetic properties.

[0005] The technical solution to achieve the objective of this invention is: a method for preparing high-abundance rare-earth permanent magnet materials, comprising the following steps:

[0006] Step (1): Weigh the raw materials: For the chemical formula Re x Fe 100-x-y-z M y B z The ingredients are formulated according to the following mass ratio, wherein Re is one or more rare earth elements such as Ce, Nd, and Pr, and M is one or more rare earth elements such as Co, Al, and Ga, with 25≤x≤32, 3≤y≤8, and 0.8≤z≤1.4. The mass ratio of Re:(Fe,M):B is 29:70:1, and the content of rare earth element Ce accounts for 25-30% of the total rare earth content.

[0007] Step (2): Preparation of magnetic powder: The raw materials weighed in step (1) are subjected to induction melting, rapid quenching and spinning, mechanical crushing and particle size screening in sequence to obtain magnetic powder with a grain size of 20-100nm.

[0008] Step (3): Hot pressing: Place the magnetic powder prepared in step (2) into a mold, maintain the temperature at 600-700℃ in a vacuum environment, apply a pressure of 150-250MPa, and hold for 1-3 minutes to obtain a dense hot pressing blank;

[0009] Step (4): Hot deformation forming: The dense hot-pressed blank obtained in step (3) is deformed at 800-900℃ and 50-150MPa with a deformation of not less than 70%, and held for 30-60 seconds to obtain a hot-deformed magnet.

[0010] Furthermore, in step (2), the speed of the rapid quenching strip is 5-30 m / s.

[0011] Furthermore, the diameter of the dense hot-pressed blank prepared in step (3) is 16±2mm and the height is 10±1mm.

[0012] Furthermore, the diameter of the thermally deformable magnet prepared in step (4) is 30±3mm and the height is 3±0.3mm.

[0013] A high-abundance rare-earth permanent magnet material is prepared using the method described above.

[0014] Furthermore, the permanent magnet material is composed of Re2Fe 14 The Re2Fe phase consists of a main phase and a grain boundary phase. 14 The B main phase consists of sheet-like nanocrystals.

[0015] Compared with the prior art, the significant advantages of this invention are:

[0016] This invention uses cheaper Ce to replace 25-30 wt.% of Nd / Pr, reducing material costs. By rationally setting the raw material composition and subsequent hot pressing / hot deformation forming, the short, low-temperature process of hot pressing / hot deformation suppresses the formation of CeFe2 impurity phases, resulting in a final material composed of a stable main phase and grain boundaries, thus improving the performance of high-Ce-content permanent magnets. Furthermore, the hot pressing / hot deformation technique produces permanent magnets with a sheet-like nanocrystalline structure, achieving higher coercivity than sintered magnets with micron-sized crystals. Attached Figure Description

[0017] Figure 1 This is a demagnetization curve of a high-abundance rare-earth permanent magnet at room temperature.

[0018] Figure 2This is a room temperature XRD pattern of a cross-section of a high-abundance permanent magnet.

[0019] Figure 3 This is a scanning electron microscope image of a high-abundance permanent magnet. Detailed Implementation

[0020] Example

[0021] (1) The chemical formula is based on the mass ratio Re x Fe 100-x-y-z M y B z The ingredients are batched and induction smelted, wherein Re is Ce, Nd, Pr rare earth elements, M is one or more of Co, Al, Ga elements, 25≤x≤32, 3≤y≤8, 0.8≤z≤1.4, Re:(Fe,M):B is in a mass ratio of 29:70:1, and the content of high-abundance rare earth element Ce accounts for 30% of the total rare earth content by mass.

[0022] (2) The Re that has been induction melted x Fe 100-x-y-z M y B z The master alloy is placed in a single-roller spinning furnace for rapid quenching and spinning at a speed of 10 m / s to obtain rapidly quenched strips with a grain size of 20-100 nm.

[0023] (3) Re x Fe 100-x-y-z M y B z The rapid quenching strips are mechanically crushed and then screened into rapid quenching magnetic powder with uniform particle size.

[0024] (4) Re x Fe 100-x-y-z M y B z The rapidly quenched magnetic powder is placed in a hot press mold with a diameter of 16.3 mm. The magnetic powder is heated to 650°C in a vacuum environment and a pressure of 200 MPa is applied. The temperature and pressure are maintained for 2 minutes to obtain a dense hot press blank with a height of 10 mm.

[0025] (5) The hot-pressed blank is placed in a hot deformation mold with a diameter of 30 mm. The hot-pressed blank is heated to 850°C in a vacuum environment and a pressure of 60 MPa is applied. After the deformation of the sample in the direction of applied pressure is 70%, the temperature and pressure are maintained for 30 seconds. Finally, a hot-deformed magnet with a height of 3 mm is obtained.

[0026] (6) The demagnetization curve of the magnet prepared in step (5) is measured using a pulse magnetic field meter (PFM). Figure 1This is a demagnetization curve at room temperature for a high-abundance rare-earth permanent magnet. It can be seen that the coercivity is 14.4 kOe, the remanence is 12.5 kGs, and the maximum energy product is 37.3 MGOe.

[0027] (7) The phase structure of the cross section of the high-abundance permanent magnet prepared in step (5) was measured by X-ray diffraction (XRD). Figure 2 This is the room temperature XRD pattern of the cross-section of a high-abundance permanent magnet. It can be seen that the main characteristic peaks of this high-abundance permanent magnet all belong to the characteristic peaks of Nd-Fe-B, with a 2:14:1 main phase structure and no obvious impurity peaks.

[0028] (8) The microstructure of the high-abundance permanent magnet was measured by scanning electron microscopy (SEM) on the magnet prepared in step (5). Figure 3 This is a scanning electron microscope image of a high-abundance permanent magnet. It can be seen that the main phase of the high-abundance rare-earth permanent magnet prepared by hot pressing / hot deformation technology is a plate-like nanocrystalline structure.

Claims

1. A method for preparing a high-abundance rare-earth permanent magnet material, characterized in that, Includes the following steps: Step (1): Weigh the raw materials: For the chemical formula Re x Fe 100-x-y-z M y B z The ingredients are formulated according to the following mass ratio, wherein Re is one or more rare earth elements such as Ce, Nd, and Pr, and M is one or more rare earth elements such as Co, Al, and Ga, with 25≤x≤32, 3≤y≤8, and 0.8≤z≤1.

4. The mass ratio of Re:(Fe,M):B is 29:70:1, and the content of rare earth element Ce accounts for 25-30% of the total rare earth content. Step (2): Preparation of magnetic powder: The raw materials weighed in step (1) are subjected to induction melting, rapid quenching and spinning, mechanical crushing and particle size screening in sequence to obtain magnetic powder with a grain size of 20-100nm. Step (3): Hot pressing: Place the magnetic powder prepared in step (2) into a mold, maintain the temperature at 600-700℃ in a vacuum environment, apply a pressure of 150-250MPa, and hold for 1-3 minutes to obtain a dense hot pressing blank; Step (4): Hot deformation forming: The dense hot-pressed blank obtained in step (3) is deformed at 800-900℃ and 50-150MPa with a deformation of not less than 70%, and held for 30-60 seconds to obtain a hot-deformed magnet.

2. The method according to claim 1, characterized in that, In step (2), the speed of the rapid quenching strip is 5-30 m / s.

3. The method according to claim 2, characterized in that, The diameter of the dense hot-pressed blank prepared in step (3) is 16±2mm and the height is 10±1mm.

4. The method according to claim 3, characterized in that, The diameter of the thermally deformable magnet prepared in step (4) is 30±3mm and the height is 3±0.3mm.

5. A high-abundance rare-earth permanent magnet material, characterized in that, Prepared using the method described in any one of claims 1-4.

6. The permanent magnet material according to claim 5, characterized in that, Permanent magnet material is made of Re2Fe 14 The Re2Fe phase consists of a main phase and a grain boundary phase. 14 The B main phase consists of sheet-like nanocrystals.

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