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CN-115691997-B - Terbium-free sintered NdFeB permanent magnet and preparation method thereof

CN115691997BCN 115691997 BCN115691997 BCN 115691997BCN-115691997-B

Abstract

The invention provides a terbium-free sintered neodymium-iron-boron permanent magnet and a preparation method thereof, and belongs to the technical field of permanent magnets. According to the invention, a base alloy cast sheet with a specific composition, a dysprosium alloy cast sheet with a specific composition and dysprosium oxide are mixed, and hydrogen crushing, air flow grinding powder preparation, orientation molding, sintering and tempering treatment are sequentially carried out, so that the terbium-free sintered neodymium-iron-boron permanent magnet is obtained. According to the invention, dysprosium alloy cast sheets and dysprosium oxide are used as auxiliary alloys, the microstructure of the base alloy cast sheets can be regulated and controlled through a hydrogen crushing process, an air flow grinding process, a sintering process and a tempering process, and finally the terbium-free neodymium-iron-boron permanent magnet with extremely high performance is prepared, so that rare earth resources terbium is saved to a certain extent, the production cost is reduced, and the balance utilization of rare earth resources is promoted.

Inventors

  • XIA FENG
  • CHEN CHEN
  • FU YULONG
  • WANG ZICHAO
  • ZHENG HAILONG
  • LIU YONGHONG
  • SUN CAINA
  • WANG YU

Assignees

  • 包头金山磁材有限公司

Dates

Publication Date
20260512
Application Date
20221013

Claims (9)

  1. 1. The preparation method of the terbium-free sintered NdFeB permanent magnet comprises the following steps: Providing a base alloy casting sheet, wherein the base alloy casting sheet comprises, by mass, 1.2-2% of M 1 24.5~25%,M 2 , 5-6% of Dy, 0.88-0.92% of B and the balance of Fe, wherein M 1 is Pr and Nd, M 2 is Ti and Co or Ti, co and M 3 , M 3 is one or more of Cu, ga, zr and V, and the thickness of the base alloy casting sheet is 2-3 mm; the dysprosium alloy casting sheet comprises, by mass, M 4 -42%, co 2-4%, B0.6-0.8%, ti 0.1-0.2%, and the balance Fe, wherein M 4 is Nd and Dy, the mass ratio of Nd to Dy in M 4 is (1-X) X, the X is 0.6-0.9, and the thickness of the dysprosium alloy casting sheet is 2-3 mm; mixing the base alloy cast sheet, the dysprosium alloy cast sheet and the dysprosium oxide, and sequentially carrying out hydrogen crushing, air flow grinding, powder preparation, orientation molding, sintering and tempering treatment to obtain the terbium-free sintered neodymium-iron-boron permanent magnet, wherein the mass ratio of the dysprosium alloy cast sheet to the dysprosium oxide is (27-30): 1, and the total mass of the dysprosium alloy cast sheet and the dysprosium oxide is 6-10% of the mass of the base alloy cast sheet.
  2. 2. The preparation method of claim 1, wherein the mass ratio of Pr to Nd in M 1 is (65-70): 30-35.
  3. 3. The preparation method according to claim 1, wherein the mass ratio of Ti to Co in the M 2 is (0.1-0.3): 1.0-1.8.
  4. 4. The preparation method of the hydrogen crushing device according to claim 1, wherein the hydrogen crushing device comprises a hydrogen absorption treatment and a dehydrogenation treatment which are sequentially carried out, wherein the temperature of the hydrogen absorption treatment is 315-325 ℃, the heat preservation time is 40-50 min, the temperature of the dehydrogenation treatment is 615-625 ℃, and the heat preservation time is 4-6 h.
  5. 5. The preparation method according to claim 1 or 4, wherein the air-flow milling is performed in the presence of a lubricant, the mass of the lubricant is 1.5-2.5 per mill of the mass of coarse powder obtained after the hydrogen is crushed, the milling pressure of the air-flow milling is 5.9-6.1 MPa, the powder outlet speed is 145-155 kg/h, and the particle size d50 of fine powder obtained after the air-flow milling is 2.5-3 μm.
  6. 6. The method according to claim 1, wherein the orientation molding is performed under conditions of a magnetic induction of 1.3 to 1.5T and a molding pressure of 3 to 6MPa, and the density of the green body obtained after the orientation molding is 3.85 to 3.95g/cm 3 .
  7. 7. The method according to claim 1, wherein the sintering conditions include a vacuum degree of < 5.5X10 -3 Pa, a temperature of 1077 to 1080 ℃ and a holding time of 4 to 6 hours.
  8. 8. The production method according to claim 1 or 7, wherein the tempering treatment includes a first tempering treatment, a second tempering treatment, and a third tempering treatment which are sequentially performed; the first tempering treatment conditions comprise that the vacuum degree is less than 8 multiplied by 10 -3 Pa, the temperature is 800-850 ℃, and the heat preservation time is 2-3 hours; The second tempering treatment conditions comprise vacuum degree <5×10 -3 Pa, temperature 890-920 ℃ and heat preservation time 4-5 h; The third tempering treatment condition comprises that the vacuum degree is less than 5.5X10 -3 Pa, the temperature is 490-520 ℃, and the heat preservation time is 5-7 h.
  9. 9. The terbium-free sintered neodymium-iron-boron permanent magnet prepared by the preparation method of any one of claims 1-8.

Description

Terbium-free sintered NdFeB permanent magnet and preparation method thereof Technical Field The invention relates to the technical field of extremely high permanent magnets, in particular to a terbium-free sintered NdFeB permanent magnet and a preparation method thereof. Background The existing sintered NdFeB permanent magnet meeting the requirement of extremely high performance (Hcj > 30) in GB/T13560-2017 generally needs to be added with a large amount of heavy rare earth terbium to improve coercive force, and the price of terbium is higher and is about 6 times of that of dysprosium, so that the production cost of the extremely high-performance sintered NdFeB permanent magnet is higher. Although the use of terbium can be reduced to a certain extent by utilizing the existing grain boundary diffusion technology to prepare the sintered NdFeB permanent magnet, the use of terbium cannot be avoided, and the protection of terbium heavy rare earth is not facilitated. Under the age background of sustainable development of resources, the development of terbium-free sintered NdFeB permanent magnets with extremely high performance has important significance. Disclosure of Invention The invention aims to provide a terbium-free sintered neodymium-iron-boron permanent magnet and a preparation method thereof, and the terbium-free sintered neodymium-iron-boron permanent magnet prepared by the method avoids using expensive heavy rare earth terbium resources and can meet the extremely high performance requirements in GB/T13560-2017. In order to achieve the above object, the present invention provides the following technical solutions: The invention provides a preparation method of a terbium-free sintered NdFeB permanent magnet, which comprises the following steps: Providing a base alloy casting sheet, wherein the base alloy casting sheet comprises, by mass, 1.2-2% of M 1 24.5～25％,M2, 5-6% of Dy, 0.88-0.92% of B and the balance of Fe, wherein M 1 is Pr and Nd, M 2 is Ti and Co or Ti, co and M 3, and M 3 is one or more of Cu, ga, zr and V; The manufacturing method comprises the steps of providing a dysprosium alloy casting sheet, wherein the dysprosium alloy casting sheet comprises, by mass, M 4 -42%, co 2-4%, B0.6-0.8%, ti 0.1-0.2%, and the balance of Fe, M 4 is Nd and Dy, the mass ratio of Nd to Dy in M 4 is (1-X) X, and the X is 0.6-0.9; And mixing the base alloy cast sheet, the dysprosium alloy cast sheet and dysprosium oxide, and sequentially carrying out hydrogen crushing, air flow grinding to obtain powder, orientation forming, sintering and tempering to obtain the terbium-free sintered neodymium-iron-boron permanent magnet. Preferably, the mass ratio of Pr to Nd in the M 1 is (65-70): 30-35. Preferably, the mass ratio of Ti to Co in the M 2 is (0.1-0.3): 1.0-1.8. Preferably, the mass ratio of the dysprosium alloy casting sheet to the dysprosium oxide is (27-30) 1, and the total mass of the dysprosium alloy casting sheet and the dysprosium oxide is 6-10% of the mass of the base alloy casting sheet. Preferably, the hydrogen crushing comprises hydrogen absorption treatment and dehydrogenation treatment which are sequentially carried out, wherein the temperature of the hydrogen absorption treatment is 315-325 ℃, the heat preservation time is 40-50 min, the temperature of the dehydrogenation treatment is 615-625 ℃, and the heat preservation time is 4-6 h. Preferably, the air flow grinding powder is carried out in the presence of a lubricant, the mass of the lubricant is 1.5-2.5 per mill of the mass of coarse powder obtained after hydrogen crushing, the grinding pressure of the air flow grinding powder is 5.9-6.1 MPa, the powder outlet speed is 145-155 kg/h, and the granularity d50 of fine powder obtained after the air flow grinding powder is 2.5-3 mu m. Preferably, the orientation molding is performed under the conditions that the magnetic induction intensity is 1.3-1.5T and the molding pressure is 3-6 MPa, and the density of the green body obtained after the orientation molding is 3.85-3.95 g/cm 3. Preferably, the sintering operation conditions comprise a vacuum degree of < 5.5X10 -3 Pa, a temperature of 1077-1080 ℃ and a heat preservation time of 4-6 h. Preferably, the tempering treatment includes a first tempering treatment, a second tempering treatment, and a third tempering treatment which are sequentially performed; the first tempering treatment conditions comprise that the vacuum degree is less than 8 multiplied by 10 -3 Pa, the temperature is 800-850 ℃, and the heat preservation time is 2-3 hours; The second tempering treatment conditions comprise vacuum degree <5×10 -3 Pa, temperature 890-920 ℃ and heat preservation time 4-5 h; The third tempering treatment condition comprises that the vacuum degree is less than 5.5X10 -3 Pa, the temperature is 490-520 ℃, and the heat preservation time is 5-7 h. The invention provides the terbium-free sintered NdFeB permanent magnet prepared by the preparation method. The inventio