阅读说明：本技术 提高烧结钕铁硼磁体性能的方法 (Method for improving performance of sintered neodymium-iron-boron magnet ) 是由 陈秀雷 彭众杰 朱晓男 相春杰 丁开鸿 于 2019-11-06 设计创作，主要内容包括：本发明涉及一种提高烧结钕铁硼磁体性能的方法,其属于钕铁硼磁体制作方法技术领域。包括如下工艺步骤：先将钕铁硼合金片进行粗破碎处理；将粗破碎后的合金片进行吸氢处理,然后再进行脱氢处理,向脱氢处理的钕铁硼合金片中加入润滑剂,使用气流磨以氮气介质进行磨粉,得到磁粉；向磁粉中混入润滑剂,经过磁场取向、成型、等静压、烧结、时效等过程,得到钕铁硼烧结磁体。本发明的有益效果是：改进的脱氢处理工艺能有效降低磁粉的氮化率,降低磁体中氮元素的含量,并且磁体中碳元素的含量也得到降低,从而在不降低剩磁的前提下,提高了矫顽力；改进的烧结工艺有效抑制了烧结过程中磁体微裂纹的产生,使磁体的力学性能得到改善。(The invention relates to a method for improving the performance of a sintered neodymium-iron-boron magnet, and belongs to the technical field of manufacturing methods of neodymium-iron-boron magnets. The method comprises the following process steps: firstly, coarsely crushing the neodymium iron boron alloy sheet; carrying out hydrogen absorption treatment on the alloy sheet after coarse crushing, then carrying out dehydrogenation treatment, adding a lubricant into the neodymium iron boron alloy sheet after dehydrogenation treatment, and grinding the neodymium iron boron alloy sheet into powder by using a nitrogen medium through an air flow mill to obtain magnetic powder; and mixing a lubricant into the magnetic powder, and performing the processes of magnetic field orientation, molding, isostatic pressing, sintering, aging and the like to obtain the neodymium iron boron sintered magnet. The invention has the beneficial effects that: the improved dehydrogenation treatment process can effectively reduce the nitridation rate of the magnetic powder, reduce the content of nitrogen element in the magnet and reduce the content of carbon element in the magnet, thereby improving the coercive force on the premise of not reducing residual magnetism; the improved sintering process effectively inhibits the generation of micro-cracks of the magnet in the sintering process, and improves the mechanical property of the magnet.)

1. A method for improving the performance of a sintered NdFeB magnet is characterized by comprising the following process steps:

the method comprises the following steps: firstly, coarsely crushing the neodymium iron boron alloy sheet prepared by the rapid hardening thin strip method;

step two: carrying out hydrogen absorption treatment on the neodymium iron boron alloy sheet after the coarse crushing treatment under the hydrogen absorption pressure of 0.10-0.25 Mpa for 1-3.5 h, and then carrying out dehydrogenation treatment to obtain the neodymium iron boron alloy sheet after the dehydrogenation treatment, wherein the temperature of the dehydrogenation treatment is 300-400 ℃, and the time of the dehydrogenation treatment is 0.5-5 h;

step three: adding a lubricant into the neodymium iron boron alloy sheet subjected to dehydrogenation treatment, and grinding the neodymium iron boron alloy sheet into powder by using a nitrogen medium through an air flow mill to obtain magnetic powder;

step four: and mixing a lubricant into the magnetic powder, performing magnetic field orientation, molding, isostatic pressing, sintering and aging processes to obtain the neodymium iron boron sintered magnet, wherein during sintering, the temperature is firstly increased from the normal temperature to 250 ℃ and is kept for 2 hours, then the temperature is increased to 550 ℃ and is kept for 2 hours, then the temperature is increased to 750 ℃ and is kept for 2 hours, and finally the temperature is increased to 1010-1040 ℃ and is kept for 2 hours-5 hours.

2. The method for improving the performance of the sintered neodymium-iron-boron magnet according to claim 1, wherein the method comprises the following steps: and the temperature of the dehydrogenation treatment in the second step is 340-380 ℃, and the dehydrogenation treatment time is 1-3 h.

3. The method for improving the performance of the sintered neodymium-iron-boron magnet according to claim 1, wherein the method comprises the following steps: the hydrogen element content range of the magnetic powder after dehydrogenation treatment in the second step is 300 ppm-850 ppm.

4. The method for improving the performance of the sintered neodymium-iron-boron magnet according to claim 1, wherein the method comprises the following steps: and step four, during sintering, when the temperature is increased from 550 ℃ to 750 ℃, the temperature increase rate is controlled to be between 1 ℃/min and 4 ℃/min.

5. The method for improving the performance of the sintered neodymium-iron-boron magnet according to claim 4, wherein the method comprises the following steps: and step four, during sintering, when the temperature is increased from 550 ℃ to 750 ℃, the temperature increase rate is controlled to be 2 ℃/min to 3 ℃/min.

6. The method for improving the performance of the sintered neodymium-iron-boron magnet according to claim 1, wherein the method comprises the following steps: the green body formed in step four has a single weight of up to 600 g.

Technical Field

The invention relates to a method for improving the performance of a sintered neodymium-iron-boron magnet, and belongs to the technical field of manufacturing methods of neodymium-iron-boron magnets.

Background

The ndfeb magnet is widely applied to the fields of storage equipment, electronic components, wind power generation, motors and the like due to excellent magnetic properties, and along with the expansion of the application fields, the magnetic properties of the ndfeb magnet need to be further improved in order to be used under severe conditions and meet the requirements on the magnetic properties. At present, the remanence of the batch neodymium iron boron product can reach about ninety percent of the theoretical saturation magnetization of the neodymium iron boron, and the coercive force is difficult to reach one third of the theoretical value under the condition of not weighting rare earth, so that the method has a larger promotion space.

The most effective method for high coercivity of Nd-Fe-B magnet on the premise is to add heavy rare earth elements Dy and Tb to replace the main phase Nd₂Fe₁₄Nd element in B. Nd (neodymium)₂Fe₁₄The magnetocrystalline anisotropy field constant HA of B is 5600KA/m, Dy₂Fe₁₄The magnetic crystal anisotropy field constant HA of B is 12000KA/m, Tb₂Fe₁₄The magnetocrystalline anisotropy field constant of B is HA 17600KA/m, from which it can be seen that the coercivity of the neodymium iron boron magnet can be significantly improved by substitution with heavy rare earth elements. However, the price of heavy rare earth is high, and in order to reduce the use amount of heavy metal elements, the grain boundary diffusion method is often adopted to carry out heavy rare earth element permeation on the magnet, but the diffusion depth is limited, so that the method is only suitable for a sheet magnet.

In order to reduce the cost of raw materials and the use amount of heavy rare earth, the technological process is improved, and the optimization of the technological method of each procedure in the production process becomes an important means. In order to obtain finer magnetic powder, the process commonly used in the industry is to perform hydrogen crushing treatment on neodymium iron boron alloy, then use a jet mill to prepare powder, and finally perform the working procedures of molding, sintering, aging and the like to obtain the neodymium iron boron magnet. The neodymium iron boron magnetic powder crushed by hydrogen is easy to oxidize and nitride due to the increase of the surface area in the process of milling by an air flow mill, and although the magnetic performance can be improved by thinning the particle size of the magnetic powder, part of the magnetic performance can be sacrificed by the increase of the oxygen content and the nitrogen content.

Chinese patent CN106504838A provides a process for dehydrogenation at 550-600 deg.C and controlling dehydrogenation time below 8h, and aims to make hydrogen-treated powder have higher hydrogen content and increase hydrogen-treated powderBrittleness, and high grinding efficiency. The chinese patent CN106683814B adjusts the process of hydrogen absorption, dehydrogenation and powder milling by jet mill for neodymium iron boron alloy to be that after hydrogen absorption, powder milling by jet mill and dehydrogenation. The method improves the milling efficiency of the jet mill, simultaneously the hydride plays a role in protecting during milling, the oxidation and nitridation of the powder are reduced, and the orientation degree of the magnetic powder during molding orientation can also be improved by dehydrogenation after milling. However, if the dehydrogenation is carried out at 500-600 ℃ by using the conventional dehydrogenation process, the purpose of partial dehydrogenation is achieved only by reducing the dehydrogenation time, and the residual hydrogen element is Nd₂Fe₁₄BH_XAnd Re-H_yIn the form of (1), wherein Nd₂Fe₁₄BH_XThe orientation degree in the molding process is affected, and the improvement of the remanence is not facilitated. If more hydrogen remains, the subsequent sintering process is not specially treated, so that the dehydrogenation is too fast, and magnet cracks are easily generated, and if the powder is completely dehydrogenated after being milled, the magnetic powder is easily oxidized and nitrided due to lack of hydrogen element protection in the subsequent process, and the lubricant added into the magnetic powder generates more carbon element residues in the subsequent sintering degassing process, so that the performance is not favorably improved.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides a method for improving the performance of a sintered neodymium-iron-boron magnet.

The technical scheme for solving the technical problems is as follows:

a method for improving the performance of a sintered neodymium-iron-boron magnet comprises the following process steps:

the method comprises the following steps: firstly, coarsely crushing the neodymium iron boron alloy sheet prepared by the rapid hardening thin strip method;

step two: carrying out hydrogen absorption treatment on the neodymium iron boron alloy sheet after the coarse crushing treatment under the hydrogen absorption pressure of 0.10-0.25 Mpa for 1-3.5 h, and then carrying out dehydrogenation treatment to obtain the neodymium iron boron alloy sheet after the dehydrogenation treatment, wherein the temperature of the dehydrogenation treatment is 300-400 ℃, and the time of the dehydrogenation treatment is 0.5-5 h;

step three: adding a lubricant into the neodymium iron boron alloy sheet subjected to dehydrogenation treatment, and grinding the neodymium iron boron alloy sheet into powder by using a nitrogen medium through an air flow mill to obtain magnetic powder;

step four: and mixing a lubricant into the magnetic powder, performing the processes of magnetic field orientation, molding, isostatic pressing, sintering, aging and the like to obtain the neodymium iron boron sintered magnet, wherein during sintering, the temperature is firstly increased from the normal temperature to 250 ℃ and is kept for 2 hours, then the temperature is increased to 550 ℃ and is kept for 2 hours, then the temperature is increased to 750 ℃ and is kept for 2 hours, and finally the temperature is increased to 1010-1040 ℃ and is kept for 2 hours-5 hours.

Preferably, the temperature of the dehydrogenation treatment in the second step is 340-380 ℃, and the dehydrogenation treatment time is 1-3 h.

Preferably, the hydrogen element content in the magnetic powder after dehydrogenation treatment in the second step is 300ppm to 850 ppm.

Preferably, when the temperature is increased from 550 ℃ to 750 ℃ in the sintering in the fourth step, the temperature increase rate is controlled to be between 1 ℃/min and 4 ℃/min.

Preferably, when the temperature is increased from 550 ℃ to 750 ℃ in the sintering in the fourth step, the temperature increase rate is controlled to be 2 ℃/min to 3 ℃/min.

Preferably, the green body formed in step four has a basis weight of up to 600 g.

The invention has the beneficial effects that: forming Re after hydrogen absorption of the Nd-Fe-B alloy sheet₂Fe₁₄BHx and Re-Hy, wherein Re is rare earth element, because the dehydrogenation temperature is 300-400 deg.C and the dehydrogenation time is 0.5-5 h, the reaction mainly generated in the temperature range is Re₂Fe₁₄BHx+Re-Hy—Re₂Fe₁₄B+x/2H₂+ Re-Hy, i.e. Re occurs mainly₂Fe₁₄BHx phase, while the Re-Hy phase undergoes little dehydrogenation. In the process of milling powder by the jet mill, the rare earth-rich phase which is easy to oxidize and nitride exists in the form of Re-Hy, so that the oxidation and nitridation rates of the magnetic powder can be effectively reduced. At the same time, the presence of the rare earth-rich phase in the form of a hydride increases the milling efficiency. In the subsequent magnetic field orientation forming process, the main phase basically contains no hydrogen, which is also beneficial to improving the orientation degree of magnetic powder and increasing the remanence of the magnet. The reaction Re-Hy-Re + y/2H occurs at the temperature of 750 ℃ in the sintering process₂Hydrogen evolution and magnetismThe residual carbon element in the powder is combined to generate hydrocarbon, and the hydrocarbon is discharged out of the blank, so that the content of the carbon element in the blank is reduced, and the coercive force of the magnet is favorably improved. When the temperature is raised to 750 ℃ at 550 ℃, the temperature raising rate is controlled to be between 1 ℃/min and 4 ℃/min, and microcracks generated in the magnet due to too fast dehydrogenation can be effectively prevented, so that the mechanical property of the magnet is guaranteed.

Detailed Description

The principles and features of this invention are described below in conjunction with examples which are set forth to illustrate, but are not to be construed to limit the scope of the invention.

The components PrNd content is 31.0 wt.%, Dy content is 1.50 wt.%, B content is 0.96 wt.%, Co content is 1.0 wt.%, Al content is 0.45 wt.%, Cu content is 0.15 wt.%, Ga content is 0.10 wt.%, Ti content is 0.08 wt.%, and the balance is Fe and inevitable impurities, a thin strip alloy sheet is prepared by a rapid solidification thin strip method, hydrogen absorption treatment is carried out after coarse crushing, the hydrogen absorption pressure is 0.10 MPa-0.25 MPa, the hydrogen absorption time is 1 h-3.5 h, and then dehydrogenation is carried out at 300 ℃ -400 ℃, and the dehydrogenation time is 0.5h-5 h. And testing the hydrogen content in the neodymium iron boron alloy sheet after dehydrogenation. Adding a conventional ester lubricant into the magnetic powder subjected to dehydrogenation treatment, wherein the adding amount is 0.05 wt.%, and uniformly mixing. Milling with a jet mill, wherein milling gas is nitrogen, the milling particle size is 3.8 mu m, and 0.10 wt.% of ester lubricant is added into the jet mill. Obtaining a neodymium iron boron sintered magnet through the processes of magnetic field orientation, molding, isostatic pressing, sintering and aging; the magnetic field orientation and shaping are carried out under a protective atmosphere (argon or nitrogen atmosphere), the oriented magnetic field strength is 1.8T, and the unit weight of the pressed green compact is 600g or less. Sintering and aging are carried out in a vacuum furnace with the vacuum degree of 5 multiplied by 10^-1Pa below; the sintering process comprises the steps of firstly heating from normal temperature to 250 ℃ and preserving heat for 2h, then heating to 550 ℃ and preserving heat for 2h, then heating to 750 ℃ and preserving heat for 2h, and controlling the heating rate to be between 1 ℃/min and 4 ℃/min when the temperature is raised to 750 ℃ at 550 ℃. Finally, the temperature is raised to 1010 to 1040 ℃, the temperature is kept for 2 to 5 hours, and then the conventional aging treatment is carried out. Testing the content of carbon, nitrogen and hydrogen elements and magnetic property of the finally obtained magnet, and processing the magnet into a standard part of 5mm by 35mmAnd testing the bending strength, and testing five groups.