WO2015103905A1 - Method for improving magnetic performance of sintered neodymium-iron-boron permanent magnet - Google Patents

Method for improving magnetic performance of sintered neodymium-iron-boron permanent magnet Download PDF

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WO2015103905A1
WO2015103905A1 PCT/CN2014/091623 CN2014091623W WO2015103905A1 WO 2015103905 A1 WO2015103905 A1 WO 2015103905A1 CN 2014091623 W CN2014091623 W CN 2014091623W WO 2015103905 A1 WO2015103905 A1 WO 2015103905A1
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magnet
permanent magnet
temperature
sintered
neodymium
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French (fr)
Chinese (zh)
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陈岭
郭帅
闫阿儒
邸敬慧
陈仁杰
丁广飞
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中国科学院宁波材料技术与工程研究所
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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/34—Methods of heating
    • C21D1/42—Induction heating
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
    • H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
    • H01F1/047—Alloys characterised by their composition
    • H01F1/053—Alloys characterised by their composition containing rare earth metals
    • H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
    • H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
    • H01F1/0571—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes
    • H01F1/0575—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together
    • H01F1/0577—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together sintered
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
    • B22F2998/10—Processes characterised by the sequence of their steps
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2999/00—Aspects linked to processes or compositions used in powder metallurgy
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C2202/00—Physical properties
    • C22C2202/02—Magnetic
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/25—Process efficiency

Definitions

  • the invention relates to the technical field of NdFeB permanent magnets, and relates to a method for improving the magnetic properties of sintered NdFeB permanent magnets.
  • rare earth permanent magnet materials As a kind of functional material with important influence, rare earth permanent magnet materials have been widely used in energy, transportation, communication, machinery, medical, computer, home appliances, and national defense technology, and have penetrated into all aspects of national economy and people's death, and their output and The use has become one of the important indicators to measure the country's comprehensive national strength and the level of national economic development. At present, China has become the world's largest production base of rare earth permanent magnets, and is also an important application market.
  • sintered NdFeB magnets are mainly prepared by powder metallurgy method, including the following technologies: (1) Near-rapid solidification scale ingot casting technology: the raw materials are placed in a vacuum quick-setting furnace in proportion, and then poured into a fast-rotating copper after melting. On the roll, a strip having a plate-like crystal structure is formed; (2) a hydrogen breaking and a gas flow milling technology: the hydrogen breaking is to place the quick-condensing strip in a hydrogen environment, and after the hydrogen absorption and dehydrogenation processes, the quick-condensing strip is made.
  • the belt is cracked along the Nd-rich phase; the airflow milling process uses high-pressure gas to accelerate the particles above the speed of sound, causing them to collide with each other and pulverize to obtain magnetic powder with appropriate particle size and concentration; (3) Powder magnetic field orientation and forming technology: The magnetic powder is loaded into the mold for magnetic field orientation and pressure molding. The strong pulse magnetic field can improve the orientation of the green body, and the cold isostatic pressure can increase the density of the green body. (4) Sintering technology: in vacuum or protective atmosphere The green body is sintered densely and rapidly cooled at a temperature slightly lower than the melting point of the main phase; (5) Heat treatment technique: the sintered magnet is tempered according to different magnet compositions.
  • the sintered NdFeB magnet prepared by the powder metallurgy method has a magnetic energy product of up to 59.6 MGOe [Yutaka Matsuura, J. Magn. Magn. Mater, 2006, 303: 344-347.], which has reached 93% of the magnetic energy product limit of 64 MGOe. .
  • the sintered NdFeB magnet prepared by the powder metallurgy method has a low coercive force.
  • the coercive force of the sintered NdFeB magnet without heavy rare earth addition is only about 20kOe, and the coercive force after adding heavy rare earth is only about 30kOe, which is much lower than the theoretical value of 70kOe of the sintered NdFeB magnet.
  • the method for optimizing the microstructure of the magnet is mainly to use the heat treatment technique described in the above (5) to temper the vicinity of the melting point of the Nd-rich phase to improve the microstructure of the Nd-rich phase wrapped around the main phase grains.
  • the heat treatment technique described in the above (5) to temper the vicinity of the melting point of the Nd-rich phase to improve the microstructure of the Nd-rich phase wrapped around the main phase grains.
  • there are still problems in the magnet such as sharp corners and defects of the main phase grains, and the thin Nd-rich phase layer wrapped outside the main phase grains is not uniform and continuous, and the Nd-rich phase cannot be formed. Very good magnetic isolation, hence the magnet The coercivity is low.
  • the technical object of the present invention is to provide a method for improving the magnetic properties of sintered NdFeB permanent magnets in view of the current state of the sintered NdFeB magnets.
  • the technical solution adopted by the present invention to achieve the above technical object is: a method for improving the magnetic properties of a sintered NdFeB permanent magnet, the NdFeB permanent magnet processed by the sintering technique, or after being processed by a sintering technique and a heat treatment technique
  • the NdFeB permanent magnet is placed in an induction furnace for induction heating to adjust the output power of the induction furnace, so that the temperature of the sintered NdFeB permanent magnet is raised to the heating temperature, then the temperature is maintained, and then cooled; the heating temperature is higher than the rich The melting point temperature of the phase.
  • the induction heating principle of the induction furnace is that the induction furnace comprises an induction coil, and when an alternating current is applied to the induction coil, an alternating magnetic field is generated, and an induced current is generated in the workpiece located therein to heat the workpiece.
  • the sintered NdFeB permanent magnet when the sintered NdFeB permanent magnet is placed in an induction furnace for induction heating, an alternating current passes through the induction coil, and an alternating magnetic field is generated around the induction coil, and the Nd-Fe-B permanent magnet is under the action of an alternating magnetic field. An induced potential is generated to form a current (eddy current) at a certain depth on the surface of the magnet, thereby heating the magnet to raise the temperature.
  • the magnet temperature is greater than the melting temperature of the enthalpy-rich phase (about 500 ° C)
  • the Nd-rich phase in the magnet forms a liquid phase, producing the following effects:
  • the eddy current effect generated by the induction coil has a strong electromagnetic stirring effect on the enthalpy-rich liquid phase, and the flowing liquid phase causes the defects in the magnet and the sharp angle of the main phase crystal grains to be eliminated, and the liquid phase distribution is more uniform and continuous, forming a very high
  • a good magnetic isolation layer, the microstructure of the magnet is optimized, and the purpose of improving the coercive force of the magnet and the squareness of the demagnetization curve is achieved;
  • the induction heating has a high heating rate and high energy utilization rate, which can effectively shorten the reaction time and achieve the purpose of high efficiency and energy saving.
  • the induction heating is carried out in a vacuum or inert gas atmosphere.
  • the heating temperature is greater than the melting temperature of the yttrium-rich phase and less than or equal to 880 °C.
  • the temperature is maintained after the temperature of the sintered NdFeB permanent magnet reaches the heating temperature; further preferably, the holding time is 15 minutes to 24 hours; most preferably, the holding time is 20 minutes to 12 hours.
  • the NdFeB permanent magnet after the above induction heating can be tempered by the existing heat treatment technique to further optimize the microstructure of the magnet.
  • the sintered magnet is subjected to induction eddy current heating to make the yttrium-rich phase into a liquid phase, and inductive electromagnetic field acts on the one hand.
  • the eddy current effect generated by the coil has a strong electromagnetic stirring effect on the enthalpy-rich liquid phase, which optimizes the microstructure of the magnet.
  • the magnetic field generated by the induction coil can make the main phase crystal grains in the liquid phase easily rotate in the direction of the coil. , thereby increasing the degree of orientation of the magnet.
  • Embodiment 1 is a demagnetization of a magnet before and after induction heat treatment measured in steps 2) and 7) of Embodiment 1 of the present invention. curve;
  • Embodiment 2 is a demagnetization curve of a magnet before and after induction heat treatment measured in steps 2) and 7) of Embodiment 2 of the present invention
  • Embodiment 3 is a demagnetization curve of a magnet before and after induction heat treatment measured in steps 2) and 7) of Embodiment 3 of the present invention
  • Figure 4 is a demagnetization curve of the magnet before and after the induction heat treatment measured in steps 2) and 7) of Example 4 of the present invention.
  • the magnetic properties of the sintered NdFeB magnet are improved by induction heating, and the specific process steps are as follows:
  • the Nd-Fe-B magnet subjected to high-temperature sintering and tempering at 500 ° C for 2 hours was processed into a cylindrical shape.
  • the cylinder has a diameter of about 10 mm and a height of about 10 mm.
  • the surface is polished with sandpaper and cleaned.
  • the magnet treated by the step 1) is subjected to a normal temperature magnetic property test using a NIM-500C permanent magnet material high temperature measuring system to obtain a demagnetization curve of the magnet before the induction heating treatment, see FIG.
  • the magnetic performance parameters are shown in Table 1.
  • step 3 The magnet after the test in step 2) is placed in the quartz crucible of the vacuum induction furnace, the furnace chamber is evacuated, the air pressure is as low as 1.4 ⁇ 10 -2 Pa, and then the chamber is cleaned twice by Ar gas, and then refilled. Argon gas makes the furnace gas pressure reach 0.04 MPa.
  • the induction coil of the vacuum induction furnace is connected with alternating current, and the magnet is inductively heated.
  • the temperature of the magnet is raised to about 600 ° C, and then the temperature is kept for 20 minutes, and then the magnet is poured into a copper cooling mold. After completely cooling, remove the magnet.
  • the magnet treated in the step 4) is placed in an electric resistance furnace, and subjected to vacuum heat treatment at a temperature of 500 ° C for 2 hours, and after the end of the heat preservation, it is rapidly cooled to room temperature.
  • the magnetic properties of the sintered NdFeB magnet are improved by induction heating, and the specific process steps are basically the same as those in Embodiment 1, except that the temperature in the step 4) is heated to 780 ° C after induction heating. The temperature is kept warm and the holding time is 30 minutes.
  • the magnetic properties of the sintered NdFeB magnet are improved by induction heating, and the specific process steps are basically the same as those in Embodiment 1, except that in step 3), the inside of the furnace chamber of the vacuum induction furnace is vacuum, and the air pressure is lower than 7.8 ⁇ 10 -3 Pa; in step 4), after the magnet is heated by induction heating, the temperature is raised to 700 ° C and then kept at this temperature for 30 minutes.
  • the magnetic properties of the sintered NdFeB magnet are improved by induction heating, and the specific process steps are basically the same as those in Embodiment 1, except that in step 3), the inside of the furnace chamber of the vacuum induction furnace is vacuum, and the air pressure is lower than 8.0. ⁇ 10 -3 Pa; In step 4), after the magnet is heated by induction heating, the temperature is raised to 700 ° C and then kept at this temperature for 2 hours.
  • Table 1 Comparison of magnetic properties of the magnets in Examples 1-4 before and after induction heating treatment.
  • the magnetic properties of the sintered NdFeB magnet are improved by induction heating, and the specific process steps are basically the same as those in Embodiment 1, except that in the step 1), the Nd-Fe-B magnet is directly sintered at a high temperature. Processed into a cylindrical shape without tempering heat treatment. The specific process steps are:
  • the Nd-Fe-B magnet subjected to high-temperature sintering treatment is processed into a cylindrical shape.
  • the cylinder has a diameter of about 10 mm and a height of about 10 mm.
  • the surface is polished with sandpaper and cleaned.
  • step 2) The magnet obtained in step 1) is placed in a quartz crucible of a vacuum induction furnace, and the furnace chamber is evacuated to a pressure of 1.4 ⁇ 10 -2 Pa, and then the chamber is cleaned twice by Ar gas, and then filled with argon.
  • the gas is such that the gas pressure of the furnace reaches 0.05 MPa.
  • the induction coil of the vacuum induction furnace is supplied with alternating current, and the magnet is inductively heated.
  • the temperature of the magnet is raised to about 880 ° C, and then the temperature is kept for 20 minutes, and then the magnet is poured into a copper cooling mold. After completely cooling, remove the magnet.
  • step 4) Put the magnet treated in step 3) into an electric resistance furnace, heat-treat it at a temperature of 500 ° C, and keep warm. After 2 hours, the temperature was quickly cooled to room temperature after the end of the incubation.
  • Example 2 Comparison of magnetic properties of the magnets measured in step 5) of Example 5 and step 2) in Example 1.

Abstract

Provided is a method for improving the magnetic performance of a sintered neodymium-iron-boron permanent magnet. According to the method, a sintered magnet undergoes inductive eddy current heating to turn a neodymium-rich phase thereof into a liquid phase, thus on the one hand, under the effect of an induced electromagnetic field, the flow of the neodymium-rich liquid phase can be intensified through electromagnetic stirring of induced eddy currents, so as to optimize the microstructure of the magnet; and on the other hand, main phase grains are more prone to rotate along the magnetic field direction of an induction coil, further increasing the degree of orientation of the magnet. Experiments prove that the coercive force of the sintered neodymium-iron-boron permanent magnet is somewhat improved, so does the squareness thereof. And meanwhile, both the remanence and the maximum magnetic energy product of the permanent magnet are also boosted. In addition, the method has the advantages of cleanliness without any pollution, high energy efficiency, great simplicity and practicability and so forth, and accordingly is highly promising in application.

Description

一种提高烧结钕铁硼永磁体磁性能的方法Method for improving magnetic properties of sintered NdFeB permanent magnets 技术领域Technical field
本发明涉及钕铁硼永磁体技术领域，具有涉及一种提高烧结钕铁硼永磁体磁性能的方法。The invention relates to the technical field of NdFeB permanent magnets, and relates to a method for improving the magnetic properties of sintered NdFeB permanent magnets.
背景技术Background technique
稀土永磁材料作为一种具有重要影响力的功能材料，已被广泛应用于能源、交通、通讯、机械、医疗、计算机、家电、以及国防科技等领域，深入到国计民生的各个方面，其产量和用量已成为衡量国家综合国力和国民经济发展水平的重要标志之一。目前，我国已成为全球最大的稀土永磁生产基地，同时也是重要的应用市场。As a kind of functional material with important influence, rare earth permanent magnet materials have been widely used in energy, transportation, communication, machinery, medical, computer, home appliances, and national defense technology, and have penetrated into all aspects of national economy and people's livelihood, and their output and The use has become one of the important indicators to measure the country's comprehensive national strength and the level of national economic development. At present, China has become the world's largest production base of rare earth permanent magnets, and is also an important application market.
二十世纪八十年代，以金属间化合物Nd2Fe14B为基础的第三代永磁材料问世，凭借优异的永磁特性成为名符其实的“磁王”。烧结钕铁硼(Nd-Fe-B)磁体是目前性能最优异，应用范围最广的永磁材料。In the 1980s, the third generation of permanent magnet materials based on the intermetallic compound Nd 2 Fe 14 B was introduced, and it became a real "magnetic king" with its excellent permanent magnet characteristics. Sintered neodymium iron boron (Nd-Fe-B) magnets are currently the most excellent and widely used permanent magnet materials.
为了进一步满足在电动汽车、风力发电等领域的实际需求，永磁体必须具有高的矫顽力。目前，工业生产中提高永磁体矫顽力的主要方法是添加重稀土Dy、Tb等元素。但是，该方法存在两方面的问题：(1)重稀土添加会降低永磁体剩磁；(2)重稀土资源稀缺，生产成本高昂。因此，探寻提高永磁体矫顽力的新方法对拓展其应用范围具有重要意义。In order to further meet the actual needs in the fields of electric vehicles, wind power generation, etc., permanent magnets must have high coercive force. At present, the main method for increasing the coercive force of permanent magnets in industrial production is to add elements such as heavy rare earths Dy and Tb. However, this method has two problems: (1) heavy rare earth addition will reduce permanent magnet remanence; (2) heavy rare earth resources are scarce and production cost is high. Therefore, exploring new methods to improve the coercive force of permanent magnets is of great significance to expand its application range.
目前，烧结钕铁硼磁体主要采用粉末冶金方法制备，具体包括如下技术：(1)近快速凝固鳞片铸锭技术：将原材料按比例放入真空速凝炉中，熔融后浇注到快速旋转的铜辊上，形成具有片状晶结构的条带；(2)氢破和气流磨制粉技术：氢破是将速凝条带置于氢气环境，经过吸氢和脱氢过程，使速凝条带沿富Nd相开裂；气流磨制粉工艺是利用高压气体将颗粒加速到音速以上，使之相互撞击而粉碎，获得粒度适宜、分布集中的磁粉；(3)粉末磁场取向与成型技术：将磁粉装入模具，进行磁场取向、加压成型，采用强脉冲磁场能够提高生坯取向度、采用冷等静压等方发能够提高生坯致密度；(4)烧结技术：在真空或保护气氛下以稍低于主相熔点的温度将生坯烧结致密、并快速冷却；(5)热处理技术：根据不同磁体成分对烧结后的磁体进行回火处理。At present, sintered NdFeB magnets are mainly prepared by powder metallurgy method, including the following technologies: (1) Near-rapid solidification scale ingot casting technology: the raw materials are placed in a vacuum quick-setting furnace in proportion, and then poured into a fast-rotating copper after melting. On the roll, a strip having a plate-like crystal structure is formed; (2) a hydrogen breaking and a gas flow milling technology: the hydrogen breaking is to place the quick-condensing strip in a hydrogen environment, and after the hydrogen absorption and dehydrogenation processes, the quick-condensing strip is made. The belt is cracked along the Nd-rich phase; the airflow milling process uses high-pressure gas to accelerate the particles above the speed of sound, causing them to collide with each other and pulverize to obtain magnetic powder with appropriate particle size and concentration; (3) Powder magnetic field orientation and forming technology: The magnetic powder is loaded into the mold for magnetic field orientation and pressure molding. The strong pulse magnetic field can improve the orientation of the green body, and the cold isostatic pressure can increase the density of the green body. (4) Sintering technology: in vacuum or protective atmosphere The green body is sintered densely and rapidly cooled at a temperature slightly lower than the melting point of the main phase; (5) Heat treatment technique: the sintered magnet is tempered according to different magnet compositions.
按照粉末冶金方法制备的烧结钕铁硼磁体的磁能积可达59.6MGOe[Yutaka Matsuura,J.Magn.Magn.Mater,2006,303:344-347.]，已经达到磁能积理论极限64MGOe的93％。但是，另一方面，按照粉末冶金方法制备的烧结钕铁硼磁体的矫顽力却较低。目前，无重稀土添加的烧结钕铁硼磁体的矫顽力仅约为20kOe，添加重稀土后的矫顽力也仅约为30kOe，远低于烧结钕铁硼磁体的矫顽力理论值70kOe。The sintered NdFeB magnet prepared by the powder metallurgy method has a magnetic energy product of up to 59.6 MGOe [Yutaka Matsuura, J. Magn. Magn. Mater, 2006, 303: 344-347.], which has reached 93% of the magnetic energy product limit of 64 MGOe. . However, on the other hand, the sintered NdFeB magnet prepared by the powder metallurgy method has a low coercive force. At present, the coercive force of the sintered NdFeB magnet without heavy rare earth addition is only about 20kOe, and the coercive force after adding heavy rare earth is only about 30kOe, which is much lower than the theoretical value of 70kOe of the sintered NdFeB magnet.
究其原因，主要是目前制备的磁体实际微观结构与理论模型有较大差距。目前，优化磁体微观结构的方法主要是采用上述(5)中所述的热处理技术，在富Nd相熔点附近进行回火处理，以改善富Nd相包裹在主相晶粒***的微观结构。但是，经现有的热处理技术处理后，磁体中仍存在主相晶粒有尖角、缺陷，包裹在主相晶粒外的富Nd相薄层不够均匀连续等问题，导致富Nd相无法形成很好的磁隔离作用，因而磁体 矫顽力较低。The reason is mainly because the actual microstructure of the currently prepared magnets has a large gap with the theoretical model. At present, the method for optimizing the microstructure of the magnet is mainly to use the heat treatment technique described in the above (5) to temper the vicinity of the melting point of the Nd-rich phase to improve the microstructure of the Nd-rich phase wrapped around the main phase grains. However, after the treatment by the existing heat treatment technology, there are still problems in the magnet, such as sharp corners and defects of the main phase grains, and the thin Nd-rich phase layer wrapped outside the main phase grains is not uniform and continuous, and the Nd-rich phase cannot be formed. Very good magnetic isolation, hence the magnet The coercivity is low.
发明内容Summary of the invention
本发明的技术目的是针对上述烧结钕铁硼磁体的现状，提供一种提高烧结钕铁硼永磁体磁性能的方法。The technical object of the present invention is to provide a method for improving the magnetic properties of sintered NdFeB permanent magnets in view of the current state of the sintered NdFeB magnets.
本发明实现上述技术目的所采用的技术方案为：一种提高烧结钕铁硼永磁体磁性能的方法，将经过烧结技术处理后的钕铁硼永磁体，或者经过烧结技术与热处理技术处理后的钕铁硼永磁体放入感应炉中进行感应加热，调节感应炉的输出功率，使烧结钕铁硼永磁体的温度升高至加热温度后保温，然后冷却；所述的加热温度高于富钕相的熔点温度。The technical solution adopted by the present invention to achieve the above technical object is: a method for improving the magnetic properties of a sintered NdFeB permanent magnet, the NdFeB permanent magnet processed by the sintering technique, or after being processed by a sintering technique and a heat treatment technique The NdFeB permanent magnet is placed in an induction furnace for induction heating to adjust the output power of the induction furnace, so that the temperature of the sintered NdFeB permanent magnet is raised to the heating temperature, then the temperature is maintained, and then cooled; the heating temperature is higher than the rich The melting point temperature of the phase.
所述的感应炉的感应加热原理为：该感应炉包括感应线圈，当对该感应线圈通入交流电时，产生交变磁场，使位于其中的工件中产生感应电流加热该工件。The induction heating principle of the induction furnace is that the induction furnace comprises an induction coil, and when an alternating current is applied to the induction coil, an alternating magnetic field is generated, and an induced current is generated in the workpiece located therein to heat the workpiece.
在本发明中，将烧结钕铁硼永磁体放入感应炉中进行感应加热时，交变电流通过感应线圈，感应线圈周围产生交变磁场，Nd-Fe-B永磁体在交变磁场作用下产生感应电势，在磁体表面一定深度形成电流(涡流)，从而加热该磁体使其升温。当磁体温度大于富钕相的熔点温度(约500℃)时，磁体中的富Nd相形成液相，产生以下效应：In the present invention, when the sintered NdFeB permanent magnet is placed in an induction furnace for induction heating, an alternating current passes through the induction coil, and an alternating magnetic field is generated around the induction coil, and the Nd-Fe-B permanent magnet is under the action of an alternating magnetic field. An induced potential is generated to form a current (eddy current) at a certain depth on the surface of the magnet, thereby heating the magnet to raise the temperature. When the magnet temperature is greater than the melting temperature of the enthalpy-rich phase (about 500 ° C), the Nd-rich phase in the magnet forms a liquid phase, producing the following effects:
(1)感应线圈产生的涡流效应对富钕液相具有强烈的电磁搅拌作用，流动的液相使磁体中的缺陷和主相晶粒尖角得以消除，液相分布更加均匀、连续，形成很好的磁隔离层，磁体微观结构得到优化，实现了提高磁体矫顽力和退磁曲线方形度的目的；(1) The eddy current effect generated by the induction coil has a strong electromagnetic stirring effect on the enthalpy-rich liquid phase, and the flowing liquid phase causes the defects in the magnet and the sharp angle of the main phase crystal grains to be eliminated, and the liquid phase distribution is more uniform and continuous, forming a very high A good magnetic isolation layer, the microstructure of the magnet is optimized, and the purpose of improving the coercive force of the magnet and the squareness of the demagnetization curve is achieved;
(2)感应线圈通入交变电流后能够产生沿线圈轴向的磁场，使得处于液相中的主相晶粒容易发生沿磁场方向的转动，进而提高磁体的取向度，剩磁和磁能积增加；(2) After the induction coil is connected to the alternating current, a magnetic field along the axial direction of the coil can be generated, so that the main phase crystal grains in the liquid phase are likely to rotate in the direction of the magnetic field, thereby improving the orientation degree of the magnet, the remanence and the magnetic energy product. increase;
另外，相比于电阻丝加热或石墨加热炉加热等常规的加热方法，感应加热升温速度快，能量利用率高，能够有效缩短反应时间，达到高效节能的目的。In addition, compared with the conventional heating method such as resistance wire heating or graphite heating furnace heating, the induction heating has a high heating rate and high energy utilization rate, which can effectively shorten the reaction time and achieve the purpose of high efficiency and energy saving.
作为优选，所述的感应加热在真空或惰性气体保护环境中进行。Preferably, the induction heating is carried out in a vacuum or inert gas atmosphere.
作为优选，所述的加热温度大于富钕相的熔点温度，并且小于或等于880℃。Preferably, the heating temperature is greater than the melting temperature of the yttrium-rich phase and less than or equal to 880 °C.
作为优选，当烧结钕铁硼永磁体的温度达到加热温度后进行保温；进一步优选，所述的保温时间为15分钟～24小时；最优选，所述的保温时间为20分钟～12小时。Preferably, the temperature is maintained after the temperature of the sintered NdFeB permanent magnet reaches the heating temperature; further preferably, the holding time is 15 minutes to 24 hours; most preferably, the holding time is 20 minutes to 12 hours.
经过上述感应加热后的钕铁硼永磁体，可以采用现有的热处理技术进行回火处理，以进一步优化磁体微观结构。The NdFeB permanent magnet after the above induction heating can be tempered by the existing heat treatment technique to further optimize the microstructure of the magnet.
综上所述，本发明在制备烧结钕铁硼永磁体的工艺中，将经烧结处理后的磁体进行感应涡流加热，使其富钕相成为液相，在感应电磁场的作用下，一方面感应线圈产生的涡流效应对富钕液相具有强烈的电磁搅拌作用，使磁体微观结构得到优化；另一方面感应线圈产生的磁场能够使处于液相中的主相晶粒容易发生沿线圈方向的转动，进而提高磁体的取向度。实验证实，经过本发明处理的烧结钕铁硼永磁体的矫顽力与方形度均有所提高，同时，永磁体的剩磁与最大磁能积也得到提高。另外，该方法具有清洁无污染、能量利用率高、简单易行等优点，具有良好的应用前景。In summary, in the process for preparing a sintered NdFeB permanent magnet, the sintered magnet is subjected to induction eddy current heating to make the yttrium-rich phase into a liquid phase, and inductive electromagnetic field acts on the one hand. The eddy current effect generated by the coil has a strong electromagnetic stirring effect on the enthalpy-rich liquid phase, which optimizes the microstructure of the magnet. On the other hand, the magnetic field generated by the induction coil can make the main phase crystal grains in the liquid phase easily rotate in the direction of the coil. , thereby increasing the degree of orientation of the magnet. Experiments have confirmed that the coercive force and squareness of the sintered NdFeB permanent magnet treated by the present invention are improved, and the remanence and maximum magnetic energy product of the permanent magnet are also improved. In addition, the method has the advantages of clean and pollution-free, high energy utilization, simple and easy to operate, and has a good application prospect.
附图说明DRAWINGS
图1是本发明实施例1中步骤2)和步骤7)测得的感应热处理前后磁体的退磁 曲线；1 is a demagnetization of a magnet before and after induction heat treatment measured in steps 2) and 7) of Embodiment 1 of the present invention. curve;
图2是本发明实施例2中步骤2)和步骤7)测得的感应热处理前后磁体的退磁曲线；2 is a demagnetization curve of a magnet before and after induction heat treatment measured in steps 2) and 7) of Embodiment 2 of the present invention;
图3是本发明实施例3中步骤2)和步骤7)测得的感应热处理前后磁体的退磁曲线；3 is a demagnetization curve of a magnet before and after induction heat treatment measured in steps 2) and 7) of Embodiment 3 of the present invention;
图4是本发明实施例4中步骤2)和步骤7)测得的感应热处理前后磁体的退磁曲线。Figure 4 is a demagnetization curve of the magnet before and after the induction heat treatment measured in steps 2) and 7) of Example 4 of the present invention.
具体实施方式detailed description
下面结合附图与实施例对本发明作进一步详细描述，需要指出的是，以下所述实施例旨在便于对本发明的理解，而对其不起任何限定作用。The present invention is further described in detail below with reference to the accompanying drawings and embodiments, which are to be understood that the embodiments described below are intended to facilitate the understanding of the invention.
实施例1：Example 1:
本实施例中，利用感应加热提高烧结钕铁硼磁体的磁性能，具体工艺步骤为：In this embodiment, the magnetic properties of the sintered NdFeB magnet are improved by induction heating, and the specific process steps are as follows:
1)将经过高温烧结和500℃回火2小时处理后的Nd-Fe-B磁体加工成圆柱型。圆柱直径约10mm，高度约10mm，表面用砂纸打磨光亮并清洗干净。1) The Nd-Fe-B magnet subjected to high-temperature sintering and tempering at 500 ° C for 2 hours was processed into a cylindrical shape. The cylinder has a diameter of about 10 mm and a height of about 10 mm. The surface is polished with sandpaper and cleaned.
2)将经过步骤1)处理后的磁体利用NIM-500C永磁材料高温测量***进行常温磁性能测试，得到感应加热处理前磁体的退磁曲线，参见图1。磁性能参数见表1。2) The magnet treated by the step 1) is subjected to a normal temperature magnetic property test using a NIM-500C permanent magnet material high temperature measuring system to obtain a demagnetization curve of the magnet before the induction heating treatment, see FIG. The magnetic performance parameters are shown in Table 1.
3)将步骤2)测试后的磁体装入真空感应炉的石英坩埚内，对炉腔抽真空，使气压低至1.4×10-2Pa，然后通Ar气体清洗炉腔2次，再充入氩气，使炉体气压达到0.04MPa。3) The magnet after the test in step 2) is placed in the quartz crucible of the vacuum induction furnace, the furnace chamber is evacuated, the air pressure is as low as 1.4×10 -2 Pa, and then the chamber is cleaned twice by Ar gas, and then refilled. Argon gas makes the furnace gas pressure reach 0.04 MPa.
4)真空感应炉的感应线圈内通入交流电，对磁体进行感应加热，通过控制加热功率，使磁体温度升高至约600℃后在该温度保温20分钟，然后将磁体倒入铜制冷却模具，完全冷却后取出磁体。4) The induction coil of the vacuum induction furnace is connected with alternating current, and the magnet is inductively heated. By controlling the heating power, the temperature of the magnet is raised to about 600 ° C, and then the temperature is kept for 20 minutes, and then the magnet is poured into a copper cooling mold. After completely cooling, remove the magnet.
5)将步骤4)处理后的磁体放入电阻炉中，进行真空热处理，温度500℃，保温时间2小时，保温结束后快速冷却到室温。5) The magnet treated in the step 4) is placed in an electric resistance furnace, and subjected to vacuum heat treatment at a temperature of 500 ° C for 2 hours, and after the end of the heat preservation, it is rapidly cooled to room temperature.
6)用上述步骤2)中的NIM-500C永磁材料高温测量***测试步骤5)处理后的磁体的室温退磁曲线，参见图1。磁性能参数见表1。得到利用本发明方法处理后磁体的磁性能。6) Test the room temperature demagnetization curve of the treated magnet with the NIM-500C permanent magnet material high temperature measuring system in step 2) above, see Fig. 1. The magnetic performance parameters are shown in Table 1. The magnetic properties of the magnets treated by the method of the invention are obtained.
实施例2：Example 2:
本实施例中，利用感应加热提高烧结钕铁硼磁体的磁性能，具体工艺步骤与实施例1基本相同，所不同的是步骤4)中磁体经感应加热后温度升高至780℃后在该温度保温，保温时间为30分钟。In this embodiment, the magnetic properties of the sintered NdFeB magnet are improved by induction heating, and the specific process steps are basically the same as those in Embodiment 1, except that the temperature in the step 4) is heated to 780 ° C after induction heating. The temperature is kept warm and the holding time is 30 minutes.
实施例3：Example 3:
本实施例中，利用感应加热提高烧结钕铁硼磁体的磁性能，具体工艺步骤与实施例1基本相同，所不同的是：步骤3)中真空感应炉的炉腔内部为真空，气压低于7.8×10-3Pa；步骤4)中，磁体经感应加热后温度升高至700℃后在该温度保温，保温时间为30分钟。In this embodiment, the magnetic properties of the sintered NdFeB magnet are improved by induction heating, and the specific process steps are basically the same as those in Embodiment 1, except that in step 3), the inside of the furnace chamber of the vacuum induction furnace is vacuum, and the air pressure is lower than 7.8×10 -3 Pa; in step 4), after the magnet is heated by induction heating, the temperature is raised to 700 ° C and then kept at this temperature for 30 minutes.
实施例4： Example 4:
实施例中，利用感应加热提高烧结钕铁硼磁体的磁性能，具体工艺步骤与实施例1基本相同，所不同的是：步骤3)中真空感应炉的炉腔内部为真空，气压低于8.0×10-3Pa；步骤4)中，磁体经感应加热后温度升高至700℃后在该温度保温，保温时间为2小时。In the embodiment, the magnetic properties of the sintered NdFeB magnet are improved by induction heating, and the specific process steps are basically the same as those in Embodiment 1, except that in step 3), the inside of the furnace chamber of the vacuum induction furnace is vacuum, and the air pressure is lower than 8.0. ×10 -3 Pa; In step 4), after the magnet is heated by induction heating, the temperature is raised to 700 ° C and then kept at this temperature for 2 hours.
图1至图4所示为实施例1至实施例4中经感应加热处理前后的Nd-Fe-B磁体的退磁曲线。表1归纳了实施例1至实施例4中经感应加热处理前后的Nd-Fe-B磁体的磁性能结果。1 to 4 show the demagnetization curves of the Nd-Fe-B magnets before and after the induction heat treatment in Examples 1 to 4. Table 1 summarizes the magnetic property results of the Nd-Fe-B magnets before and after the induction heat treatment in Examples 1 to 4.
以上磁性测量结果表明，实施例1-4，即利用感应涡流热处理时间20分钟或以上后，磁体的矫顽力(Hcj)与方形度(Hk/Hcj)均有所提高，具体为：矫顽力增加0.85～1.85kOe，方形度增加0.01～0.02；同时，磁体的剩磁(Br)与最大磁能积((BH)max均得到提高，具体为：剩磁增加0.07～0.16kOe，最大磁能积((BH)max)增加0.36～1.63MGOe。The above magnetic measurement results show that in Examples 1-4, after the induction eddy current heat treatment time of 20 minutes or more, the coercive force (Hcj) and squareness (Hk/Hcj) of the magnet are improved, specifically: coercivity The force is increased by 0.85 to 1.85 kOe, and the squareness is increased by 0.01 to 0.02. At the same time, the remanence (Br) and the maximum magnetic energy product ((BH) max of the magnet are improved, specifically: the residual magnetism is increased by 0.07 to 0.16 kOe, and the maximum magnetic energy product is increased. ((BH) max ) increased by 0.36 to 1.63 MGOe.
表1：实施例1-4中磁体进行感应加热处理前后的磁性能对比。Table 1: Comparison of magnetic properties of the magnets in Examples 1-4 before and after induction heating treatment.
Figure PCTCN2014091623-appb-000001
Figure PCTCN2014091623-appb-000001
实施例5：Example 5:
本实施例中，利用感应加热提高烧结钕铁硼磁体的磁性能，具体工艺步骤与实施例1基本相同，所不同的是在步骤1)中，将Nd-Fe-B磁体经过高温烧结后直接加工成圆柱型，而不经过回火热处理。具体工艺步骤为：In this embodiment, the magnetic properties of the sintered NdFeB magnet are improved by induction heating, and the specific process steps are basically the same as those in Embodiment 1, except that in the step 1), the Nd-Fe-B magnet is directly sintered at a high temperature. Processed into a cylindrical shape without tempering heat treatment. The specific process steps are:
1)将经过高温烧结处理后的Nd-Fe-B磁体加工成圆柱型。圆柱直径约10mm，高度约10mm，表面用砂纸打磨光亮并清洗干净。1) The Nd-Fe-B magnet subjected to high-temperature sintering treatment is processed into a cylindrical shape. The cylinder has a diameter of about 10 mm and a height of about 10 mm. The surface is polished with sandpaper and cleaned.
2)将步骤1)得到的磁体装入真空感应炉的石英坩埚内，对炉腔抽真空，使气压低至1.4×10-2Pa，然后通Ar气体清洗炉腔2次，再充入氩气，使炉体气压达到0.05MPa。2) The magnet obtained in step 1) is placed in a quartz crucible of a vacuum induction furnace, and the furnace chamber is evacuated to a pressure of 1.4×10 -2 Pa, and then the chamber is cleaned twice by Ar gas, and then filled with argon. The gas is such that the gas pressure of the furnace reaches 0.05 MPa.
3)真空感应炉的感应线圈内通入交流电，对磁体进行感应加热，通过控制加热功率，使磁体温度升高至约880℃后在该温度保温20分钟，然后将磁体倒入铜制冷却模具，完全冷却后取出磁体。3) The induction coil of the vacuum induction furnace is supplied with alternating current, and the magnet is inductively heated. By controlling the heating power, the temperature of the magnet is raised to about 880 ° C, and then the temperature is kept for 20 minutes, and then the magnet is poured into a copper cooling mold. After completely cooling, remove the magnet.
4)将步骤3)处理后的磁体放入电阻炉中，进行真空热处理，温度500℃，保温 时间2小时，保温结束后快速冷却到室温。4) Put the magnet treated in step 3) into an electric resistance furnace, heat-treat it at a temperature of 500 ° C, and keep warm. After 2 hours, the temperature was quickly cooled to room temperature after the end of the incubation.
5)用实施例1中所采用的NIM-500C永磁材料高温测量***测试步骤4)处理后的磁体的磁性能，结果与实施例1的步骤2)中测量得到的磁性能进行比较，参见表2中所示。5) The magnetic properties of the treated magnets in the step 4) were tested using the NIM-500C permanent magnet material high temperature measuring system used in Example 1, and the results were compared with the magnetic properties measured in the step 2) of Example 1, see Table 2 is shown.
表2：实施例5中步骤5)与实施例1中步骤2)测得的磁体磁性能对比Table 2: Comparison of magnetic properties of the magnets measured in step 5) of Example 5 and step 2) in Example 1.
Figure PCTCN2014091623-appb-000002
Figure PCTCN2014091623-appb-000002
上述磁性能对比表明，经过感应加热处理后，磁体的矫顽力与方形度均有所提高，同时，磁体的磁体的剩磁与最大磁能积也得到提高。The comparison of the above magnetic properties shows that after the induction heating treatment, the coercive force and squareness of the magnet are improved, and the remanence and maximum magnetic energy product of the magnet of the magnet are also improved.
以上所述的实施例对本发明的技术方案和有益效果进行了详细说明，应理解的是以上所述仅为本发明的具体实施例，并不用于限制本发明，凡在本发明的原则范围内所做的任何修改和改进等，均应包含在本发明的保护范围之内。 The embodiments described above are illustrative of the technical solutions and the beneficial effects of the present invention. It is to be understood that the foregoing description is only exemplary embodiments of the present invention and is not intended to limit the scope of the present invention. Any modifications, improvements, etc., which are made, are intended to be included within the scope of the present invention.

Claims (6)

  1. 一种提高烧结钕铁硼永磁体磁性能的方法，其特征是：将经过烧结技术处理后的钕铁硼永磁体，或者经过烧结技术与热处理技术处理后的钕铁硼永磁体放入感应炉中进行感应加热，调节感应炉的输出功率，使烧结钕铁硼永磁体的温度升高至加热温度后保温，然后冷却；A method for improving the magnetic properties of sintered NdFeB permanent magnets, characterized in that the NdFeB permanent magnet processed by the sintering technology or the NdFeB permanent magnet processed by the sintering technology and the heat treatment technology is placed in an induction furnace Inductive heating is performed to adjust the output power of the induction furnace, so that the temperature of the sintered NdFeB permanent magnet is raised to a heating temperature, then kept warm, and then cooled;
    所述的加热温度高于富钕相的熔点温度。The heating temperature is higher than the melting temperature of the enthalpy-rich phase.
  2. 如权利要求1所述的提高烧结钕铁硼永磁体磁性能的方法，其特征是：所述的感应加热在真空或惰性气体保护环境中进行。The method of claim 1, wherein the induction heating is performed in a vacuum or inert gas atmosphere.
  3. 如权利要求1所述的提高烧结钕铁硼永磁体磁性能的方法，其特征是：所述的加热温度小于或等于880℃。A method of improving the magnetic properties of a sintered NdFeB permanent magnet according to claim 1, wherein said heating temperature is less than or equal to 880 °C.
  4. 如权利要求1所述的提高烧结钕铁硼永磁体磁性能的方法，其特征是：所述的保温时间为15分钟～24小时。The method of claim 1 , wherein the holding time is from 15 minutes to 24 hours.
  5. 如权利要求4所述的提高烧结钕铁硼永磁体磁性能的方法，其特征是：所述的保温时间为20分钟～12小时。The method of claim 4, wherein the holding time is from 20 minutes to 12 hours.
  6. 如权利要求1至5中任一权利要求所述的提高烧结钕铁硼永磁体磁性能的方法，其特征是：冷却后采用热处理技术进行回火处理。 The method for improving the magnetic properties of a sintered NdFeB permanent magnet according to any one of claims 1 to 5, characterized in that the tempering treatment is performed by a heat treatment technique after cooling.
PCT/CN2014/091623 2014-01-07 2014-11-19 Method for improving magnetic performance of sintered neodymium-iron-boron permanent magnet WO2015103905A1 (en)

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