A method for preparing high-performance crystal-textured anisotropic R2Fe 14 B magnetic powder method

Abstract

The application discloses a method for preparing high-performance crystal texture anisotropic R2Fe 14 B magnetic powder, which comprises the following steps: preparing rare earth iron boron single crystal particles with R2Fe 14 B complete positive division, then transforming the particles into R2Fe 14 B polycrystal aggregate by grain boundary diffusion of Mn-based alloy with anti-ferromagnetic property, and obtaining crystal texture anisotropic R2Fe 14 B magnetic powder. The application uses the rare earth iron boron single crystal particles with R2Fe 14 B complete positive division as starting materials of the HDDR reaction, and avoids disordered rare earth-rich phase; the grain boundary diffusion of the crystal texture R2Fe 14 B aggregate by the Mn-based alloy with anti-ferromagnetic property, not only achieves effective control of the content of non-magnetic grain boundary phase, and is beneficial to maintaining high remanence, but also is beneficial to eliminating the anti-magnetization nucleation point at the grain boundary, and forming strong pinning of magnetic domain wall movement, and finally realizes the common improvement of remanence and coercivity.

Description

Technical Field

[0001] This invention relates to the field of rare earth magnetic materials preparation, specifically to a method for preparing high-performance crystal-textured anisotropic R2Fe. 14 B. Magnetic powder method. Background Technology

[0002] Rare earth iron boron magnets exist in two forms: sintered magnets and bonded magnets. Among them, the sintered rare earth iron boron magnet has a laboratory-scale magnetic energy product of approximately 460 kJ / m. 3 The magnetic energy product is between 360 and 400 kJ / m 3 Sintered magnets can be mass-produced; while bonded magnets, due to their ease of manufacturing thin-walled and complex-shaped magnets with precise dimensions, have also found wide application. Currently, information products such as computers are developing towards miniaturization and high performance, placing higher demands on the magnetic properties of bonded rare-earth permanent magnets. Specifically, since bonded rare-earth permanent magnets are mainly used as stator or rotor magnets for various micromotors in these information products, the miniaturization and high performance requirements of these products demand that these micromotors output higher power while reducing size. Therefore, magnets with higher magnetic properties and smaller, more precise dimensions are required. For this reason, it is necessary to develop bonded magnets with higher magnetic properties.

[0003] Anisotropic bonded magnets have received widespread attention due to their significantly superior performance compared to the currently mainstream isotropic rare-earth iron-boron bonded magnets. However, to prepare high-performance anisotropic bonded magnets, it is essential to first produce high-performance anisotropic rare-earth iron-boron magnetic powder. Currently, there are two main technologies for producing high-performance anisotropic rare-earth iron-boron magnetic powder: one is the Hydrogenation-Disproportionation-Desorption-Recombination (HDDR) process; the other is through hot pressing and hot deformation technology. Because the HDDR process has lower costs and produces anisotropic rare-earth iron-boron magnetic powder with superior performance compared to the hot pressing and hot deformation process, current research focuses primarily on how to utilize the HDDR process to produce high-performance anisotropic rare-earth iron-boron magnetic powder.

[0004] The hydrogen absorption-disproportionation-dehydrogenation-recombination process (HDDR) has attracted much attention as the most effective method for producing magnetic powder for anisotropic magnets. This process was discovered in 1989 by Takeshita and Nakayama et al. of Mitsubishi Corporation in Japan while studying the effect of hydrogen atmosphere on the sintering process of NdFeB. Upon its initial report, this process immediately sparked a global research boom in the preparation of anisotropic NdFeB magnetic powder using the HDDR process. Over the past 30 years, through the joint efforts of domestic and international researchers, key technologies for the preparation of HDDR anisotropic rare-earth iron-boron magnetic powder have been mastered, and significant progress has been made in the study of the anisotropy formation mechanism of HDDR. These important advances provide crucial technical support and theoretical guidance for the mass production of HDDR anisotropic rare-earth iron-boron magnetic powder.

[0005] However, our years of research have shown that it is difficult to obtain anisotropic NdFeB magnetic powder with both high remanence and high coercivity using only the HDDR process. This is because to obtain high remanence, a microstructure with high crystal texture is required; and to obtain high coercivity, a suitable amount of NdFeB-rich grain boundary phase must be present in the parent alloy, thereby ensuring a certain amount of NdFeB-rich grain boundary phase between the grains after HDDR processing. Unfortunately, the NdFeB-rich phase in the initial NdFeB alloy and the NdFeB-rich phase present at the grain boundaries in the HDDR magnetic powder are disordered. This interferes with the hydrogen disproportionation process of the NdFeB alloy and the dehydrogenation and recombination process of the disproportionation decomposition products during the HDDR process. Specifically, the disordered NdFeB-rich grain boundary phase reduces the highly ordered columnar disproportionation structure formed after the hydrogen disproportionation decomposition of the NdFeB alloy, and this highly ordered disproportionation structure is a necessary condition for the formation of anisotropy. In addition, during the recombination process, the disordered NdFeB-rich grain boundary phase also interferes with Nd2Fe 14 The preferred formation of B crystal nuclei leads to ordered Nd2Fe 14 The amount of B crystal nuclei formed is reduced, so the crystal texture of the current HDDR magnetic powder is not very high, and the magnetic energy product of the magnetic powder (~40 MGOe) is still some distance from its theoretical value (64 MGOe). Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing high-performance crystal-textured anisotropic R2Fe. 14 The method for B-type rare-earth iron-boron magnetic powder, where R represents neodymium and / or praseodymium. This invention is based on the idea that ordered construction of functional units helps in the research and development of high-performance materials that surpass traditional properties. This invention proposes a method for achieving both high remanence and high coercivity in permanent magnet materials through the ordered construction of functional units in a step-by-step manner. Based on this, a method is proposed that mainly involves three key steps to construct corresponding functional units, ultimately achieving crystal-textured rare-earth iron-boron magnetic powder with high remanence and high coercivity. The three key steps include:

[0007] (1) Preparation of R2Fe 14 B-type rare earth iron boron single crystal particles with complete positive fractionation;

[0008] (2) Use a suitable HDDR process (i.e., R2Fe) to process rare earth iron boron single crystal particles. 14 B single crystal particles undergo appropriate hydrogen absorption, disproportionation, dehydrogenation, and recombination reactions with hydrogen gas, transforming into R2Fe with a grain size of approximately 200-400 nanometers and a consistent c-axis orientation. 14 B polycrystalline aggregates, i.e., anisotropic R2Fe with perfect crystal texture. 14 B magnetic powder, in preparation for achieving high remanence;

[0009] (3) Using Mn, which has antiferromagnetic properties a X 100-a (X = Sb or Sn or Sm, 15 ≤ a ≤ 75) alloys for R2Fe 14 By employing grain boundary diffusion in polycrystalline aggregates, the coercivity of these aggregates is enhanced, ultimately achieving a combined increase in remanence and coercivity. This results in an anisotropic R2Fe crystal texture exhibiting high coercivity and high remanence, characteristic of a core-shell structure. 14 B magnetic powder.

[0010] Specifically, the steps of the above method are as follows:

[0011] 1) Prepare a alloy of rare earth elements neodymium (and / or praseodymium), iron, and iron-boron by smelting technology to obtain an alloy with a nominal chemical composition of R2Fe. 14 B is a rare earth iron boron alloy ingot with positive fraction, where R represents Nd and / or Pr;

[0012] 2) The R2Fe 14 Rare earth iron-boron alloy ingots with positive boron content are annealed at 1000-1200℃ for 50-200 hours to obtain single-phase R2Fe with a grain size of 100-200 micrometers. 14 B alloy ingots;

[0013] 3) Single-phase R2Fe 14 B alloy ingots were subjected to hydrogen crushing to obtain single-crystal R2Fe with a particle size of 100-200 micrometers. 14 B particles;

[0014] 4) The above single crystal R2Fe 14 Particle B was heated to between 780 and 840°C under vacuum conditions, and then 0.2 × 10⁻⁶ ppm was introduced. 5 ~1.0×10 5Hydrogen gas from Pa undergoes hydrogen absorption and disproportionation decomposition reactions for 0.5–4 hours to obtain a highly ordered disproportionation decomposition structure with self-assembly characteristics, featuring α-Fe as the matrix, RH2 as rod-shaped atoms, and B atoms uniformly distributed in the iron matrix. Subsequently, hydrogen atoms are slowly extracted from RH2 over 10–40 minutes via a dehydrogenation reaction, allowing them to undergo a dehydrogenation recombination reaction with α-Fe and B atoms characterized by preferred nucleation, ultimately forming R2Fe. 14 B is a type of magnetic powder with a grain size of about 200~400 nanometers and a crystal texture with the same orientation along the c-axis.

[0015] 5) Pass the magnetic powder prepared in step 4) through a Mn group that has antiferromagnetic properties. a X 100-a Grain boundary diffusion of alloy powder yields anisotropic R2Fe with a crystal texture characterized by high coercivity and high remanence, exhibiting core-shell structure features. 14 B magnetic powder.

[0016] Furthermore, step 2) above is performed in a high vacuum (≤5×10⁻⁶). -3 Annealing is performed under the condition of (Pa).

[0017] Preferably, step 3) above is at 1.0 × 10 5 ~2.0×10 5 Hydrogen crushing is performed using hydrogen gas at 200~350℃.

[0018] Preferably, the pumping rate for the dehydrogenation reaction in step 4) above is 1×10⁻⁶. -6 ~5×10 -6 m 3 / s.

[0019] The antiferromagnetic Mn mentioned in step 5) above a X 100-a Alloy powder can be prepared by the following method: high-purity Mn and high-purity Sb, Sn, or Sm are smelted together to prepare antiferromagnetic Mn. a X 100-a The alloy ingot is then processed into thin strips using rapid quenching technology, followed by mechanical crushing to obtain Mn with a particle size of approximately 2-6 micrometers. a X 100-a alloy powder.

[0020] Step 5) above can specifically involve using 97-99 wt% of the R2Fe obtained in step 4). 14 B-crystal textured magnetic powder and 1-3 wt% antiferromagnetic Mn a X 100-aAlloy powders are mixed and then subjected to diffusion heat treatment at 600~800℃ for 1~3 hours to obtain anisotropic rare earth iron boron magnetic powder with crystal texture, high coercivity and high remanence, featuring a core-shell structure.

[0021] This invention utilizes R2Fe 14 Using fully positively fractionated rare-earth iron-boron single crystal particles as the starting material for the HDDR reaction avoids the disordered rare-earth-rich phase, thus improving the performance of R2Fe in the HDDR reaction process. 14 The influence of the hydrogen absorption disproportionation decomposition process of raw material B and the dehydrogenation and recombination process of the corresponding intermediate disproportionation products (α-Fe as the matrix and RH2 as columnar particles) ultimately yielded a crystal textured aggregate composed of fine grains of approximately 200-400 nanometers, with the c-axis orientation consistent with the initial rare earth iron boron single crystal particles. Based on this, a method for improving the crystal texture of R2Fe was proposed. 14 Grain boundary diffusion of B aggregates exhibits antiferromagnetic Mn. a X 100-a The alloy not only achieves effective control over the content of non-magnetic grain boundary phases, which is beneficial for maintaining high remanence; but also utilizes antiferromagnetic Mn a X 100-a Alloys also help to eliminate demagnetization nucleation points at grain boundaries and form strong pinning of magnetic domain wall motion, ultimately achieving a combined improvement in remanence and coercivity. Attached Figure Description

[0022] Figure 1 Nd2Fe was shown 14 After being processed by a suitable HDDR process, the B single crystal particles are then subjected to antiferromagnetic Mn... 17 Sn 83 Alloy diffusion treatment yields the final crystal texture Nd2Fe 14 Hysteresis loop of B magnetic powder. Detailed Implementation

[0023] The present invention is further described below through embodiments, but these embodiments are not intended to limit the scope of the invention in any way.

[0024] Example 1

[0025] 1) High-purity rare earth element neodymium, high-purity iron, and high-purity iron-boron alloy are used to prepare Nd2Fe alloy with a nominal chemical composition through induction melting technology. 14 B-positive NdFeB alloy ingots;

[0026] 2) Nd2Fe 14 B-positive alloy ingots are cast at 1050℃ and under high vacuum (≤5×10⁻⁶). -3 Annealing at 0.5 Pa for 72 hours yielded pure single-phase Nd2Fe with a grain size of approximately 150 micrometers.14 B alloy ingots;

[0027] 3) Single-phase Nd2Fe 14 B alloy ingots at 1.0×10 5 Hydrogen gas at 250°C was used for hydrogen crushing at 250°C for 1 hour to obtain single-crystal Nd₂Fe with a particle size of approximately 150 micrometers. 14 B particles;

[0028] 4) The above single-crystal Nd2Fe 14 Particle B was heated to 820°C under vacuum conditions, and then 0.3 × 10⁻⁶ ppm was introduced. 5 Pa was subjected to hydrogen absorption and disproportionation decomposition reaction for 2 hours to obtain a highly ordered disproportionation decomposition product with self-assembly structure characteristics, featuring α-Fe as the matrix, NdH2 rods, and B atoms uniformly distributed in the iron matrix; subsequently, 2×10 -6 m 3 A dehydrogenation rate of / s slowly removes hydrogen atoms from NdH2 over 40 minutes, causing them to undergo a dehydrogenation-recombination reaction with α-Fe and B atoms characterized by preferred nucleation, followed by a reaction under high vacuum (≤5×10⁻⁶). -3 Further heating under (Pa) conditions for 15 minutes eventually forms Nd2Fe. 14 B is a type of magnetic powder with a grain size of about 300 nanometers and a crystal texture with the same orientation along the c-axis.

[0029] 5) High-purity Mn and high-purity Sn are smelted to prepare a product with a nominal chemical composition of Mn. 17 Sn 83 The alloy ingot was cast, and then the alloy was rapidly quenched into thin strips at a roll speed of 50 m / s using rapid quenching technology. Subsequently, Mn particles with a particle size of about 3 micrometers were obtained by mechanical crushing. 17 Sn 83 powder;

[0030] 6) Take 98.5 wt% of the Nd2Fe after HDDR treatment in step 4). 14 B magnetic powder and 1.5 wt% Mn 17 Sn 83 The powders were mixed and then subjected to diffusion heat treatment at 680℃ for 1 hour to obtain anisotropic Nd₂Fe₃ with a crystal texture characterized by high coercivity and high remanence, exhibiting core-shell structure features. 14 B magnetic powder.

[0031] Step 6) Obtaining anisotropic crystal texture Nd2Fe 14 The hysteresis loop of B magnetic powder is as follows Figure 1 As shown, it can be seen that after following the technical route of the present invention, the remanence and coercivity of neodymium iron boron magnetic powder have been greatly improved.

[0032] The saturation magnetization, remanence, coercivity, and energy product of the material were measured using VSM, and the results are as follows:

[0033] Ms=165 emu / g, Mr=154 emu / g, iHc=14000 Oe, (BH)max=48.5 MGOe.

[0034] Example 2

[0035] 1) Using induction melting technology, high-purity rare earth elements neodymium and praseodymium, high-purity iron, and high-purity iron-boron alloys are combined to prepare Nd alloys with a nominal chemical composition of Nd. 1.2 Pr 0.8 Fe 14 B-positive NdFeB alloy ingots;

[0036] 2) Nd 1.2 Pr 0.8 Fe 14 The alloy ingot with positive B content was annealed at 1050℃ for 60 hours to obtain pure single-phase Nd with a grain size of approximately 150 micrometers. 1.2 Pr 0.8 Fe 14 B alloy ingots;

[0037] 3) Single-phase Nd 1.2 Pr 0.8 Fe 14 B alloy ingots at 1.0×10 5 Hydrogen gas at 250°C was used to break down Nd2 crystals at 250°C for 1 hour to obtain single-crystal Nd2 with a particle size of approximately 150 micrometers. 1.2 Pr 0.8 Fe 14 B particles;

[0038] 4) The above single-crystal Nd 1.2 Pr 0.8 Fe 14 Particle B was heated to 820°C under vacuum conditions, and then 0.28 × 10⁻⁶ ppm was introduced. 5 The hydrogen absorption and disproportionation decomposition reaction of Pa was carried out for 2 hours to obtain a highly ordered disproportionation product with self-assembly structure characteristics, featuring α-Fe as the matrix, NdH2 and PrH2 as rods, and B atoms uniformly distributed in the iron matrix; subsequently, 5×10 -6 m 3 A dehydrogenation rate of / s slowly removes hydrogen atoms from NdH2 and PrH2 within 30 minutes, causing them to undergo a dehydrogenation-recombination reaction with α-Fe and B atoms characterized by preferred nucleation, and then in a high vacuum (≤5×10⁻⁶). -3 Further heating for 15 minutes under (Pa) conditions eventually forms Nd1.2 Pr 0.8 Fe 14 B is a type of magnetic powder with a grain size of about 300 nanometers and a crystal texture with the same orientation along the c-axis.

[0039] 5) High-purity Mn and high-purity Sb are smelted to prepare a product with a nominal chemical composition of Mn. 19 Sb 81 The alloy ingots were cast, and then the alloy was rapidly quenched into thin strips at a roll speed of 50 m / s. Subsequently, mechanical crushing was used to obtain Mn particles with a particle size of about 3 micrometers. 19 Sb 81 powder;

[0040] 6) Take 98.5 wt% of the Nd2 after HDDR treatment in step 4) 1.2 Pr 0.8 Fe 14 B magnetic powder and 1.5 wt% Mn 19 Sb 81 The powders were mixed and then subjected to diffusion heat treatment at 720°C for 1 hour to obtain anisotropic Nd2 crystal textures with high coercivity and high remanence, exhibiting core-shell structure characteristics. 1.2 Pr 0.8 Fe 14 B magnetic powder.

[0041] The saturation magnetization, remanence, coercivity, and energy product of the material were measured using VSM, and the results are as follows:

[0042] Ms=165 emu / g, Mr=155 emu / g, iHc=14300 Oe, (BH)max=49 MGOe.

[0043] Example 3

[0044] 1) High-purity rare earth element neodymium, high-purity iron, and high-purity iron-boron alloy are used to prepare Nd2Fe alloy with a nominal chemical composition through induction melting technology. 14 B-positive NdFeB alloy ingots;

[0045] 2) Nd2Fe 14 The alloy ingot with positive B content was annealed at 1050℃ for 72 hours to obtain pure single-phase Nd2Fe with a grain size of approximately 150 micrometers. 14 B alloy ingots;

[0046] 3) Single-phase Nd2Fe 14 B alloy ingots at 1.0×10 5 Hydrogen gas at 250°C was used for hydrogen crushing at 250°C for 1 hour to obtain single-crystal Nd₂Fe with a particle size of approximately 150 micrometers.14 B particles;

[0047] 4) The above single-crystal Nd2Fe 14 Particle B was heated to 820°C under vacuum conditions, and then 0.4 × 10⁻⁶ ppm was introduced. 5 The hydrogen absorption and disproportionation decomposition reaction of Pa was carried out for 2 hours to obtain a highly ordered disproportionation product with self-assembled structural characteristics, featuring α-Fe as the matrix, NdH2 as rods, and B atoms uniformly distributed in the iron matrix; subsequently, 4×10 -6 m 3 A dehydrogenation rate of / s slowly removes hydrogen atoms from NdH2 over 30 minutes, causing them to undergo a dehydrogenation-recombination reaction with α-Fe and B atoms characterized by preferred nucleation, followed by a reaction under high vacuum (≤5×10⁻⁶). -3 Further heating under (Pa) conditions for 15 minutes eventually forms Nd2Fe. 14 B is a type of magnetic powder with a grain size of about 300 nanometers and a crystal texture with the same orientation along the c-axis.

[0048] 5) High-purity Mn and high-purity Sm are smelted to prepare a product with a nominal chemical composition of Mn. 29 Sm 71 The alloy ingots were cast, and then the alloy was rapidly quenched into thin strips at a roll speed of 50 m / s. Subsequently, mechanical crushing was used to obtain Mn particles with a particle size of about 3 micrometers. 29 Sm 71 powder.

[0049] 6) Take 98 wt% of the Nd2Fe after HDDR treatment in step 4) 14 B magnetic powder and 2 wt% Mn 29 Sm 71 The powders were mixed and then subjected to diffusion heat treatment at 700℃ for 1 hour to obtain anisotropic Nd₂Fe₃ with a crystal texture characterized by high coercivity and high remanence, exhibiting core-shell structure features. 14 B magnetic powder.

[0050] The saturation magnetization, remanence, coercivity, and energy product of the material were measured using VSM, and the results are as follows:

[0051] Ms=165 emu / g, Mr=152 emu / g, iHc=14000 Oe, (BH)max=48 MGOe.

Claims

1. A method of making high performance, crystallographically textured, anisotropic R2Fe 14 B magnetic powders comprising the steps of: 1) Prepare alloys of rare earth elements neodymium and / or praseodymium, iron, and iron-boron by smelting technology to obtain alloys with a nominal chemical composition of R2Fe. 14 B is a rare earth iron boron alloy ingot with positive fraction, where R represents Nd and / or Pr; 2) The R2Fe 14 Rare earth iron-boron alloy ingots with positive boron content are annealed at 1000-1200℃ for 50-200 hours to obtain single-phase R2Fe with a grain size of 100-200 micrometers. 14 B alloy ingots; 3) Single-phase R2Fe 14 B alloy ingots were subjected to hydrogen crushing to obtain single-crystal R2Fe with a particle size of 100-200 micrometers. 14 B particles; 4) Single crystal R2Fe 14 Particle B was heated to between 780 and 840°C under vacuum conditions, and then 0.2 × 10⁻⁶ ppm was introduced. 5 ~1.0×10 5 Hydrogen gas from Pa undergoes hydrogen absorption and disproportionation decomposition reactions for 0.5–4 hours to obtain a highly ordered disproportionation decomposition structure with self-assembly characteristics, featuring α-Fe as the matrix, RH2 as rod-shaped atoms, and B atoms uniformly distributed in the iron matrix. Subsequently, hydrogen atoms are slowly extracted from RH2 over 10–40 minutes via a dehydrogenation reaction, allowing them to undergo a dehydrogenation recombination reaction with α-Fe and B atoms characterized by preferred nucleation, ultimately forming R2Fe. 14 B is a type of magnetic powder with a grain size of 200~400 nanometers and a crystal texture with the same orientation along the c-axis; 5) Take 97-99 wt% of the R2Fe obtained in step 4). 14 B-crystal textured magnetic powder and 1-3 wt% antiferromagnetic Mn a X 100-a Alloy powders are mixed and then subjected to diffusion heat treatment at 600-800℃ for 1-3 hours to obtain anisotropic rare-earth iron-boron magnetic powder with a core-shell structure, exhibiting high coercivity and high remanence. X represents Sb, Sn, or Sm, and Mn... a X 100-a The alloy powder is Mn 17 Sn 83 powder, Mn 19 Sb 81 powder or Mn 29 Sm 71 powder.

2. The method as described in claim 1, characterized in that, Step 2) In ≤5×10 -3 Annealing was performed under a high vacuum of Pa.

3. The method as described in claim 1, characterized in that, Step 3) at 1.0×10 5 ~2.0×10 5 Hydrogen crushing is performed using hydrogen gas at 200~350℃.

4. The method as described in claim 1, characterized in that, The pumping rate for the dehydrogenation reaction in step 4) is 1×10⁻⁶. -6 ~5×10 -6 m 3 / s.

5. The method as described in claim 1, characterized in that, The antiferromagnetic Mn described in step 5) a X 100-a The alloy powder was prepared by the following method: Mn and X were smelted to produce Mn with antiferromagnetic properties. a X 100-a The alloy ingot is then processed into thin strips using rapid quenching technology, followed by mechanical crushing to obtain Mn particles with a particle size of 2-6 micrometers. a X 100-a alloy powder.

Images