A magnetic diffusion alloy powder for diffusion of NdFeB magnets and its application

Abstract

The invention discloses a magnetic diffusion alloy powder of a diffused NdFeB magnet and a preparation method and application thereof. The magnetic diffusion alloy powder of the diffused NdFeB magnet has the following components expressed in atomic percentage: R x T y M 100‑x‑y , wherein R is selected from at least one of the rare earth elements Nd, Pr, Dy, Tb, and Ho, 13

Description

Technical field:

[0001] The invention relates to a magnetic diffusion alloy powder used for diffusion of NdFeB magnets and application thereof. Background technology:

[0002] In the 1980s, the Japanese discovered the 2:14:1 type Nd-Fe-B permanent magnet. This type of magnet is widely used due to its high magnetic energy product, high coercivity and simple preparation method. It is currently the most produced and widely used rare earth permanent magnet material. At present, rare earth permanent magnets are an important cornerstone of the operation of modern society and are widely used in almost every field and industry involving electromagnetism.

[0003] At present, the coercivity of 2:14:1 Nd-Fe-B permanent magnets is the most important factor that restricts their application in high-temperature working environments. Among them, the main method to improve the coercivity of Nd-Fe-B permanent magnets is to form a shell with a high anisotropy field on the surface of the magnet through a diffusion process. In the current diffusion process, the combination of diffusion alloy powder and magnet is mainly to coat the diffusion powder on the surface of the magnet using glue coating. The glue coating process is prone to leaving carbon residue during the diffusion heat treatment process, and the presence of the carbon residue directly hinders and affects the diffusion effect.

[0004] The improvement of the grain boundary diffusion process of Nd-Fe-B permanent magnets mainly involves the following aspects: 1. Improvement of the composition in the diffusion process, such as the use of mixed metal powders, mixed heavy rare earth ion compounds, multi-phase structural alloys, etc.; 2. Improvement of the bonding method between the diffusion powder and the magnet, such as physical vapor deposition (PVD), chemical vapor deposition (CVD), and glue coating; 3. Improvement of the atmosphere and working temperature before and after the heat treatment in the process; 4. Improvement of the equipment involved in the process; In these diffusion processes, there are many restrictions on the bonding method between the diffusion metal powder and the NdFeB magnet. Physical vapor deposition (PVD) and chemical vapor deposition (CVD) require the use of specific equipment, such as vacuum evaporation coating machines, vacuum sputtering coating machines, and vacuum ion coating machines. At the same time, the space is small and cannot load a large number of magnets. At the same time, a large amount of electricity is consumed for production testing, which is costly. Summary of the invention:

[0005] The purpose of the present invention is to provide a magnetic diffusion alloy powder of a diffused NdFeB magnet and its application, which solves the problems of high cost of physical vapor deposition (PVD) and chemical vapor deposition (CVD) in the prior art and the carbon residue remaining in the glue coating process that easily affects the diffusion effect.

[0006] The present invention is achieved through the following technical solutions:

[0007] A magnetic diffusion alloy powder of a diffused NdFeB magnet, the composition expressed in atomic percentage is:

[0008] R x T y M 100-x-y

[0009] Among them, R is selected from at least one of rare earth elements Nd, Pr, Dy, Tb, and Ho, and its function is to endow the diffusion alloy powder with magnetism and improve the magnetic properties of commercially available N-series NdFeB magnets, where 13 < x < 75; T is selected from at least one of ferromagnetic elements Fe, Co, and Ni in the magnetic iron group, which endows the diffusion alloy powder with magnetism, where 25 < y < 87; M is selected from any one of low-melting-point metal elements such as Ga, Al, Zn, Cu, Mg, Ca, Sn, and Bi, which plays the role of reducing the diffusion temperature and increasing the depth of diffusion of the diffusion alloy powder into commercially available N-series NdFeB magnets, and 0 ≤ 100 - x - y < 16.

[0010] The alloy phase structure characteristics of the magnetic diffusion alloy powder are as follows: The rare earth element R with a low melting point and the low-melting-point metal M will preferentially combine to form low-melting-point and rare earth-rich phases with atomic ratios of R2M, R3M, RM, and RM. The rare earth element R with a low melting point and the ferromagnetic element T in the magnetic iron group will form atomic ratios of R3T, R7T3, RT, RT2, RT3, R2T7, RT5, and R2T 17 and at least one of the ferromagnetic phase or paramagnetic phase of T.

[0011] The preparation method of the magnetic diffusion alloy powder is as follows: The magnetic diffusion alloy powder is obtained through melting + ball milling and other chemical combination + crushing methods. The purpose of melting and chemical combination is to melt metal blocks into magnetic alloys, and the purpose of crushing is to crush the alloys into alloy powders of a certain size. Other chemical combination + crushing methods also include: induction melting, arc melting, rapid solidification casting, reduction diffusion and other chemical combination processes and high-energy ball milling, air flow milling, machine automatic grinding and other crushing processes.

[0012] The NdFeB magnet to be diffused can be magnetized to a specific magnetization intensity (for example, a 20 g NdFeB magnet can attract and lift at least 1 kg of Fe with a magnetization intensity of 1.4 T), so the magnetized magnet can fully utilize magnetic force to adsorb a specified mass of magnetic diffusion alloy powder.

[0013] The present invention also protects the application of the magnetic diffusion alloy powder for preparing diffusion NdFeB magnets, including the following steps: The commercially available N-series NdFeB magnets magnetized to a specific magnetization intensity use magnetism to adsorb the above-mentioned magnetic diffusion alloy powder of the present invention, and then undergo a diffusion heat treatment at 700 - 1000 °C for 2 - 6 hours, and after cooling to room temperature, a tempering process is carried out to obtain a diffusion NdFeB magnet. The precise parameters of tempering are determined by DSC thermogravimetry for its specific range. The tempering temperature is 450 - 550 °C, preferably 500 °C for 2 hours.

[0014] The beneficial effects of the present invention are as follows:

[0015] (1) The present invention does not rely on other relatively expensive equipment. It mainly uses the magnetic force of the diffused NdFeB magnet itself to attract the magnetic diffusion alloy powder containing paramagnetic phase or ferromagnetic phase. In addition, the quality of the adsorbed diffusion alloy powder can be determined by the magnetic force of the NdFeB magnet (controlling the upper limit of the adsorbed diffusion powder quality) and the quality of the directly added diffusion powder (actually controlling the adsorbed diffusion powder quality). The requirements for equipment in production are reduced;

[0016] (2) It avoids the influence of residual carbon residue on the diffusion effect caused by the common use of glue to bond the diffusion powder in the prior art. Specific implementation method:

[0017] The following is a further description of the present invention, rather than a limitation of the present invention.

[0018] Embodiment 1:

[0019] A pure metal block of Pr, Nd, Dy, Fe, and Al with an atomic ratio of 6.5:26:32.5:25:10 was placed in a crucible and the alloy was melted by vacuum induction melting at 5 kW for 5 min. The alloy was then poured onto a copper roller with a rotation speed of 10 m / s to form a quick-setting alloy sheet. The sheet was then ground with an automatic grinder to a suitable size that could pass through a 10-mesh standard sieve to obtain 100 g of magnetic diffusion alloy powder (Pr 0.1 Nd 0.4 Dy 0.5 ) 65 Fe 25 Al 10 Take a square N50 series magnet and magnetize it to 0.2-1.2 T. Weigh the ground diffusion alloy powder (Pr 0.1 Nd 0.4 Dy 0.5 ) 65 Fe 25 Al 10 The mass of the diffusion alloy powder is 0.5-5.0wt% of the magnet, and the diffusion alloy powder is evenly scraped on the surface of the magnet with a thin plastic sheet. The magnets that are mutually attracted by magnetic force are placed in a sintering furnace and kept at 900℃ for 4 hours, cooled to room temperature, then heated to 500℃ and kept for 2 hours, and finally cooled to room temperature to obtain the diffused magnet. Its performance parameters are shown in Table 1.

[0020] Table 1 shows the magnetic properties data before and after magnet treatment

[0021]

Claims

1. An application of a magnetic diffusion alloy powder of a diffused NdFeB magnet, characterized in that: The method for preparing a diffused NdFeB magnet comprises the following steps: taking a NdFeB magnet, magnetizing it to 0.2-1.2 T, magnetically adsorbing a magnetic diffusion alloy powder by the NdFeB magnet magnetized to a specific magnetization strength, and then subjecting the NdFeB magnet to a diffusion heat treatment at 700-1000°C for 2-6 hours, cooling it to room temperature, and then subjecting it to a tempering process at 450-550°C to obtain a diffused NdFeB magnet; the composition of the magnetic diffusion alloy powder expressed in atomic percentage is: Among them, R is selected from at least one of rare earth elements Nd, Pr, Dy, Tb, Ho, and 13 < x < 75; T is selected from at least one of ferromagnetic iron group elements Fe, Co, and 25 < y < 87; M is selected from any one of low melting point metal elements Ga, Al, Zn, Cu, Mg, Ca, Sn, Bi, and 0 ≤ 100 - x - y < 16; the preparation method of the magnetic diffusion alloy powder is as follows: melting into a magnetic alloy by means of vacuum induction melting, and then crushing it into alloy powder of a certain size; the alloy phase structure characteristics of the magnetic diffusion alloy powder are as follows: the rare earth element R with a low melting point forms a low melting point and rare earth-rich phase with an atomic ratio of R2M, R3M, RM, RM with the low melting point metal M, and the rare earth element R with a low melting point will form an atomic ratio of R3T, R7T3, RT, RT2, RT3, R2T7, RT5, R2T 17 with at least one of ferromagnetic phases or paramagnetic phases.

2. The use according to claim 1, characterized in that: The tempering process is 500℃ for 2 hours.

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