WO2024148692A1 - 一种热变形磁体及其制备方法 - Google Patents

一种热变形磁体及其制备方法 Download PDF

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WO2024148692A1
WO2024148692A1 PCT/CN2023/086848 CN2023086848W WO2024148692A1 WO 2024148692 A1 WO2024148692 A1 WO 2024148692A1 CN 2023086848 W CN2023086848 W CN 2023086848W WO 2024148692 A1 WO2024148692 A1 WO 2024148692A1
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hot
preparation
precursor
magnet
steel sleeve
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French (fr)
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岳明
李迁
李玉卿
刘卫强
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Beijing University of Technology
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Beijing University of Technology
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    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
    • H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets

Definitions

  • the present application relates to the technical field of magnetic materials, and in particular to a thermally deformed magnet and a preparation method thereof.
  • magnetic materials have become one of the important materials required for the development of high-tech society.
  • the application of magnetic materials has involved all aspects of the development of modern society, such as new energy technology, medical equipment, aviation and other industries.
  • high-end permanent magnetic materials have become the core component of high-performance motors. Therefore, with the improvement of scientific and technological levels, the demand for magnetic materials in social development and industrial innovation will become more and more vigorous, and the application prospects of magnetic materials will be broader. Therefore, the in-depth research and development of magnetic materials directly promotes the development of society, industrial innovation and human progress.
  • Hot deformation processing methods are mainly based on upsetting and back extrusion.
  • the upsetting method has uneven deformation, and the magnetic properties of the hot deformed magnets prepared are also uneven. It is necessary to cut off the areas with small deformation on the upper and lower surfaces in the later processing, resulting in a lot of waste; moreover, the conventional upsetting deformation method also requires a two-step heating process, especially the second step of the hot deformation process, which takes a long time and high temperature, so the energy consumption is large and the process is complicated.
  • the back extrusion deformation method can also be used to prepare hot deformed magnets, magnetic rings or magnetic tiles, but this method also needs to go through two high-temperature processes, and the three steps of heating, cooling and demolding are required in the hot pressing and hot deformation processes.
  • the process is complicated and time-consuming. Therefore, it is difficult to produce continuously, the production efficiency is low, a lot of energy is consumed, and the preparation cost is high. Among them, low production efficiency is the bottleneck that restricts the large-scale production of this technology and hot deformed magnetic rings.
  • Japanese patent JPH023905A which uses ingot rolling to produce NdFeB materials. With the same rare earth-rich phase element content, the rolled NdFeB magnet is finally obtained, and the magnetic properties are tested at different positions on the cross section. The maximum magnetic energy product increases from 10MGOe to 23MGOe, and then decreases to 10MGOe.
  • Japanese patent JPH2794755B2 by rolling the ingot NdFeB material at 750-1150°C, the deformation amount each time is more than 30%, and the sample after rolling is heat treated at 400-700°C. The final (BH)max ⁇ 30MGOe, Hcj range is 5-12kOe.
  • the NdFeB materials involved in the above patents are all ingots. After single or multiple rolling, the magnetic properties of the magnets are too low and the uniformity is poor, and the coercive force is also low, which has no practical application value.
  • the present application provides a method for preparing a thermally deformed magnet, comprising:
  • the precursor After hot pressing amorphous or nanocrystalline magnetic powder into a precursor, the precursor is packaged in a steel sleeve and vacuumized, and then hot-rolled after heat preservation at 600-1000°C;
  • the size of the grains inside the precursor is less than 100 nanometers.
  • the present application provides a new technology for preparing hot deformed magnets by a two-step method of hot pressing and hot deformation.
  • the precursor is prepared by hot pressing, and the size of the internal grains of the precursor is controlled to be less than 100 nanometers, which is conducive to the magnet having higher magnetic properties after the subsequent heat preservation and hot rolling process.
  • the size of the steel sleeve can be flexibly adjusted, so that the size of the thermal deformation magnet can be flexibly adjusted, thereby realizing the production of thermal deformation magnets with different performance and size requirements.
  • heat preservation treatment at 600-1000°C before hot rolling can be beneficial to controlling the growth process of the grains inside the magnet during the hot rolling process, so that the hot-rolled magnet has higher magnetic properties.
  • the size of the crystal grains inside the precursor is controlled to be less than 50 nanometers, more preferably less than 30 nanometers.
  • the temperature of hot rolling is the same as the temperature of the insulation treatment.
  • the precursor is a block precursor.
  • the heat preservation treatment time is 10 to 30 minutes.
  • Carrying out heat preservation treatment under the above conditions can effectively control the growth process of the grains inside the magnet during the hot rolling process, and further improve the magnetic properties of the hot-rolled magnet.
  • the reduction ratio in the hot rolling process is above 60%.
  • the reduction ratio is the ratio of the reduction in thickness of the steel sleeve to its original thickness.
  • a hot-deformed magnet with excellent magnetic properties can be obtained by controlling the reduction ratio to 60%.
  • single-pass rolling or multi-pass rolling can be adopted, and the deformation amount between different passes can be flexibly adjusted.
  • the temperature of the hot pressing is 300-500°C.
  • the hot pressing pressure is 500-1000 MPa.
  • the heat pressing time is 1 to 5 minutes.
  • the size of the grains inside the precursor can be effectively controlled, so that the magnetic properties of the magnet after hot rolling treatment are further improved.
  • the density of the precursor is more than 95% of the theoretical density of the magnetic powder material.
  • the vacuum degree of the vacuum treatment is below 0.06 Pa.
  • the preparation method further comprises: cutting the steel sleeve after hot rolling to obtain the hot deformed magnet.
  • the specific implementation process includes but is not limited to using wire cutting, slicer or laser cutting machine to cut and separate the steel sleeve and the thermally deformed magnet.
  • molybdenum disulfide and/or boron nitride is coated on the inner wall of the steel sleeve as a release agent.
  • the present application also provides a thermally deformed magnet prepared by any of the above embodiments.
  • the preparation method of the present application has the dual advantages of being conducive to large-scale efficient production and easy to control the external dimensions of the magnet.
  • the manufacturing process is no longer limited by the vacuum degree and multi-step heating, the process is simple, and energy consumption and cost can be reduced.
  • the energy consumption and cost are lower than the hot pressing-hot deformation method, and the production efficiency is improved.
  • the prepared magnet has the characteristics of high magnetic energy product and high coercive force, and has a wide range of applications and high application value.
  • FIG. 1 is a process flow chart of an embodiment of the present application.
  • FIG. 2 is a physical photograph of the NdFeB thermally deformed magnet of Example 1 of the present application.
  • FIG. 3 is an X-ray diffraction diagram of the NdFeB thermal deformation magnet of Example 1 of the present application.
  • FIG. 4 is a fracture morphology diagram of the NdFeB thermally deformed magnet of Example 1 of the present application.
  • a quenching strip can be obtained by a melt quenching method, and then the quenching strip can be crushed to obtain quenching powder.
  • ultrafine powder can be obtained by a high-energy ball milling method.
  • Commercially available quenching powders can also be used, such as MQU series magnetic powders purchased from Magnequench (Tianjin) Co., Ltd.
  • the amorphous or nanocrystalline magnetic powder used can have a nanometer-scale grain size, or it can be amorphous and crystallized during hot pressing and hot deformation.
  • the alloy composition of the amorphous or nanocrystalline magnetic powder For example, RE 2 Fe 14 B or RECo 5 single-phase alloys can be used, where RE represents Nd, Sm or other rare earth elements or a combination thereof.
  • a mold with the same size as the steel sleeve is used for hot pressing.
  • a corresponding hot-pressed block precursor can be prepared, which can be a cube, a cuboid, a cylinder or a cylinder with other cross-sections.
  • the vacuuming process generally uses a vacuum device such as a mechanical pump, a diffusion pump or a molecular pump, a vacuum steel pipe is welded at one end of the steel sleeve, and then the vacuum steel pipe is sealed to meet the vacuum requirement.
  • a vacuum device such as a mechanical pump, a diffusion pump or a molecular pump
  • a vacuum steel pipe is welded at one end of the steel sleeve, and then the vacuum steel pipe is sealed to meet the vacuum requirement.
  • the steel sleeve is rolled at a temperature of 600-1000°C.
  • the hot rolling process can be carried out in air. There is no specific requirement for the heating rate, such as 20-200°C/minute; after heat preservation, the steel sleeve is rolled and deformed, and the steel sleeve is pushed from one end of the roller to the other end of the roller to be formed.
  • This process can be single-pass or multi-pass rolling.
  • molybdenum disulfide or boron nitride can be uniformly applied to the inner wall of the steel sleeve in advance as a demoulding agent. After rolling, the steel sleeve and the thermally deformed magnet can be cut and separated by wire cutting, slicer and laser cutting machine.
  • This embodiment provides a thermal deformation magnet, and the preparation method thereof is as follows:
  • the commercially available NdFeB quick-quenching magnetic powder was used as the raw material, and the precursor was prepared by hot pressing process.
  • the hot pressing temperature was 500°C
  • the pressing pressure was 500MPa
  • the heat preservation was 1 minute.
  • the heat-deformed precursor material was obtained, and its density was 7.52g/cm3 (98.9% of the theoretical density of the magnetic powder material) and the average grain size was 50 nanometers.
  • the precursor was loaded into a steel sleeve of matching size and vacuum was drawn to make the vacuum degree inside the steel sleeve reach 5 ⁇ 10-2Pa.
  • the packaged steel sleeve was heat-insulated at a temperature of 600°C for 10 minutes, and then hot-rolled.
  • the hot rolling adopted a single-pass rolling process with a reduction rate of 60%.
  • Molybdenum disulfide release agent was evenly applied to the inner wall of the steel sleeve in advance, and then mechanical cutting was used to obtain the NdFeB heat-deformed magnet (as shown in Figure 2).
  • the X-ray diffraction pattern of the NdFeB heat-deformed magnet is shown in Figure 3.
  • the fracture morphology of the NdFeB heat-deformed magnet is shown in Figure 4.
  • This embodiment provides a thermal deformation magnet, and the preparation method thereof is as follows:
  • the precursor is prepared by hot pressing process with high-energy ball-milled samarium cobalt amorphous magnetic powder as raw material.
  • the hot pressing temperature is 300°C
  • the pressing pressure is 1000MPa
  • the heat preservation is 5 minutes.
  • the heat-deformed precursor material is obtained, and its density is 8.46g/cm3 (99.5% of the theoretical density of magnetic powder material) and the average grain size is 30 nanometers.
  • the precursor is loaded into a steel sleeve of matching size and evacuated to make the vacuum degree inside the steel sleeve reach 1 ⁇ 10-2 Pa.
  • the packaged steel sleeve is heat-insulated at a temperature of 1000°C for 30 minutes, and then hot-rolled.
  • the hot rolling adopts a three-pass rolling process with a reduction rate of 90%.
  • the boron nitride release agent is evenly applied to the inner wall of the steel sleeve in advance, and the samarium cobalt heat-deformed magnet is obtained by mechanical cutting.
  • This comparative example provides a thermal deformation magnet, and the preparation method thereof is as follows:
  • the ball-milled NdFeB ingot alloy powder is used as the raw material, and the precursor is prepared by hot pressing process.
  • the hot pressing temperature is 500°C
  • the pressing pressure is 500MPa
  • the heat preservation is 1 minute.
  • the thermal deformation precursor material is obtained, and its density is 7.53g/cm3 (99.1% of the theoretical density of magnetic powder material) and the average grain size is 5.5 microns (5500 nanometers).
  • the precursor is loaded into a steel sleeve of matching size and evacuated to make the vacuum degree inside the steel sleeve reach 5 ⁇ 10-2 Pa.
  • the packaged steel sleeve is heat-insulated at a temperature of 600°C for 10 minutes, and then hot rolled.
  • the hot rolling adopts a single-pass rolling process with a reduction rate of 60%.
  • Molybdenum disulfide release agent is evenly applied to the inner wall of the steel sleeve in advance, and then mechanical cutting is used to obtain the NdFeB hot Deformed magnet.
  • This comparative example provides a heat-deformed magnet, and the preparation method is different from that of Example 2 in that after the precursor is packaged, it is directly hot-rolled without heat preservation, as follows:
  • the precursor is prepared by hot pressing process using high-energy ball-milled samarium cobalt amorphous magnetic powder as raw material.
  • the hot pressing temperature is 300°C
  • the pressing pressure is 1000MPa
  • the heat preservation is 5 minutes to obtain the hot deformation precursor material with a density of 8.46g/cm3 (99.5% of the theoretical density of magnetic powder material) and an average grain size of 30 nanometers.
  • the precursor is loaded into a steel sleeve of matching size and evacuated to make the vacuum inside the steel sleeve reach 1 ⁇ 10-2 Pa.
  • the packaged steel sleeve is directly hot rolled, and the hot rolling adopts a three-pass rolling process with a reduction rate of 90%.
  • the boron nitride release agent is evenly applied to the inner wall of the steel sleeve in advance, and the samarium cobalt hot deformation magnet is obtained by mechanical cutting.
  • the magnetic properties of the heat-deformed magnets prepared in the above embodiments and comparative examples were tested. Specifically, a 1.5 ⁇ 1.5 ⁇ 1.5 mm sample was cut from the front end, middle part and rear end of the bar magnet removed after hot rolling, and after the sample was magnetized, its hysteresis loop was tested using a vibrating sample magnetometer to obtain the coercive force of the magnet.
  • the magnet prepared by the preparation method of the present application has a higher magnet coercive force.
  • the magnet prepared by the present application has very good uniformity, is easy to industrialize and mass produce without causing a large amount of material waste.

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  • Power Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Inorganic Chemistry (AREA)
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Abstract

本申请涉及磁性材料技术领域，尤其涉及一种热变形磁体及其制备方法。制备方法包括：将非晶或纳米晶磁粉经过热压制成前驱体后，对前驱体进行钢套封装和抽真空处理，然后在600～1000℃下保温处理后进行热轧；其中，所述前驱体内部晶粒的尺寸小于100纳米。本申请的制备方法具有利于大规模高效生产和易于控制磁体外形尺寸的双重优势。制造过程不再受限于真空度和多步加热的限制，工艺简单，可减低能源消耗，降低成本，能耗与成本均低于热压-热变形法，提高生产效率。所制备的磁体具有高磁能积和高矫顽力的特点，应用范围广泛且应用价值高。

Description

一种热变形磁体及其制备方法
相关申请的交叉引用
本申请要求于2023年01月09日提交的申请号为202310029328.5，名称为“一种热变形磁体及其制备方法”的中国专利申请的优先权，其通过引用方式全部并入本文。
技术领域
本申请涉及磁性材料技术领域，尤其涉及一种热变形磁体及其制备方法。
背景技术
随着信息技术和新能源技术的发展，磁性材料成为高科技社会发展所需的重要材料之一。磁性材料的应用己经涉及到现代社会发展的方方面面，比如在新能源技术、医疗设备、航空等行业有着广泛而深入的应用。尤其是在近年来迅速发展的新能源汽车行业，高端永磁材料己经成为高性能电动机的核心组成部分。因此随着科学技术水平的提高，社会发展和工业创新对磁性材料的需求将越来越旺盛，磁性材料的应用前景会更加广阔，因此对磁性材料的深入研究和发展直接地推动着社会的发展、工业的创新和人类的进步。
近些年，采样热变形技术制备高性能稀土永磁体的研究取得了较好进展。热变形加工方法中主要以镦粗和背向挤压为主。其中镦粗法由于变形不均匀，所制备的热变形磁体磁性能也不均匀，需要后期加工中切除上下面形变量小的区域，造成大量的浪费；而且，常规镦粗变形方法也需要两步加热过程，特别是第二步的热变形过程，时间长，温度高，因此能耗大，工艺复杂。另外，背向挤压变形方式也可以用来制备热变形磁体、磁环或磁瓦，但是该方法同样需要经历两个高温过程，且在热压和热变形过程中都需要加热、冷却和脱模三个环节，工序繁杂且耗时很长，因此，难以连续生产，生产效率低，消耗大量能源，制备成本高。其中生产效率低是制约该技术及热变形磁环实现规模化生产的瓶颈。
已有日本专利JPH023905A，通过铸锭轧制钕铁硼材料，通过调控不 同富稀土相的元素含量，最终得到轧制钕铁硼磁体，并且在横截面上对其进行不同位置处的磁性能测试，其最大磁能积由10MGOe增加到23MGOe，再减小到10MGOe。日本专利JPH2794755B2，通过对铸锭钕铁硼材料在750-1150℃进行轧制，使每次的变形量在30％以上，轧制以后的样品进行400-700℃的热处理。最终的(BH)max<30MGOe，Hcj范围为5-12kOe。上述专利所涉及的钕铁硼材料均为铸锭，通过单道次或者多道次轧制后磁体磁性能过低且均匀性差，而且矫顽力也较低，不具有实际应用价值。
发明内容
为了解决上述现有技术的缺陷，本申请提供了一种热变形磁体的制备方法，包括：
将非晶或纳米晶磁粉经过热压制成前驱体后，对前驱体进行钢套封装和抽真空处理，然后在600～1000℃下保温处理后进行热轧；
其中，所述前驱体内部晶粒的尺寸小于100纳米。
本申请提供了通过热压和热变形两步法制备热变形磁体的新技术。通过热压的方式制备前驱体，同时控制前驱体内部晶粒的尺寸小于100纳米，有利于经过后续保温和热轧过程后，磁体具有较高的磁性能。
通过对前驱体进行钢套封装，能够灵活调整钢套尺寸，使得热变形磁体的尺寸灵活调整，实现不同性能及尺寸要求的热变形磁体生产。
而且，本申请还发现在热轧之前在600～1000℃下保温处理能够有利于控制热轧过程中磁体内部晶粒的长大过程，使得经过热轧的磁体具有更高的磁性能。
优选地，控制前驱体内部晶粒的尺寸为50纳米以下，更优选为30纳米以下。
在具体实施过程中，热轧的温度与保温处理的温度相同。
在具体实施过程中，所述前驱体为块状前驱体。
作为本申请的一种优选的实施方案，保温处理的时间为10～30min。
在上述条件下进行保温处理，能够有效地控制热轧过程中磁体内部晶粒的长大过程，进一步提高经过热轧的磁体的磁性能。
作为本申请的一种优选的实施方案，热轧过程的压下率为60％以上。
在本申请中，压下率为钢套厚度减少量与其原始厚度的比值。
在本申请中，控制压下率为60％即可获得磁性能优异的热变形磁体。
在具体实施过程中，在热轧过程中，可采用单道次轧制或者多道次轧制，可灵活调整不同道次之间的变形量。
作为本申请的一种优选的实施方案，所述热压的温度为300～500℃。
作为本申请的一种优选的实施方案，所述热压的压力为500～1000MPa。
作为本申请的一种优选的实施方案，所述热压的时间为1～5min。
控制热压的时间在上述范围内时，能够有效地控制前驱体内部晶粒的大小，使得经过热轧处理之后的磁体磁性能进一步提升。
作为本申请的一种优选的实施方案，所述前驱体的密度为磁粉材料理论密度的95％以上。
作为本申请的一种优选的实施方案，抽真空处理的真空度为0.06Pa以下。
作为本申请的一种优选的实施方案，制备方法还包括：在热轧之后对钢套切割获得热变形磁体。
在具体实施过程中，包括但不限于采用线切割、切片机或激光切割机切割分离钢套和热变形磁体。
作为本申请的一种优选的实施方案，在抽真空处理之前，在钢套内壁涂覆二硫化钼和/或氮化硼作脱模剂。
进一步，本申请还提供了上述任一实施方案所制备的热变形磁体。
与现有技术相比，本申请的有益效果在于：
本申请的制备方法具有利于大规模高效生产和易于控制磁体外形尺寸的双重优势。制造过程不再受限于真空度和多步加热的限制，工艺简单，可减低能源消耗，降低成本，能耗与成本均低于热压-热变形法，提高生产效率。所制备的磁体具有高磁能积和高矫顽力的特点，应用范围广泛且应用价值高。
附图说明
图1是本申请实施例的工艺流程图。
图2是本申请实施例1的钕铁硼热变形磁体的实物照片。
图3是本申请实施例1的钕铁硼热变形磁体的X射线衍射图。
图4是本申请实施例1的钕铁硼热变形磁体的断口形貌图。
具体实施方式
在本申请中，对非晶或纳米晶磁粉没有特别的限制，例如可以通过熔体快淬法获得快淬带，然后将快淬带碾碎获得快淬粉。又例如可以通过高能球磨法获得超细粉体。也可以使用商购获得的快淬粉，例如购自麦格昆磁(天津)有限公司的MQU等系列的磁粉。使用的非晶或纳米晶磁粉可以具有纳米级的晶粒尺寸，也可以是非晶态，并在热压和热变形过程中晶化。对于非晶或纳米晶磁粉的合金组成没有特别的限制，例如可以使用RE2Fe14B或RECo5单相合金，其中RE代表Nd、Sm或其他稀土元素或它们的组合。
在本申请中，热压过程没有特殊的限制，一般使用与钢套配套尺寸的磨具进行热压。根据热轧钢套的尺寸制备相应的热压块状前驱体即可，可以是正方体、长方体、圆柱体或者其他截面的柱体。
在本申请中，抽真空过程一般采用机械泵、扩散泵或分子泵等真空装置，在钢套一端进行焊接真空钢管，随后将真空钢管进行密封以达到真空要求。
在本申请中，在600-1000℃的温度下对钢套进行轧制。热轧过程在空气中进行即可。升温速率没有特定要求，如20-200℃/分钟；保温后进行轧制变形，将钢套由轧辊一端推送至轧辊另一端成型。此过程可以采用单道次或者多道次轧制。
在本申请中，可以提前在钢套内壁均匀涂抹二硫化钼或者氮化硼作为脱模剂。轧制以后可以利用线切割、切片机和激光切割机等进行切割分离钢套和热变形磁体。
为使本申请的目的、技术方案和优点更加清楚，下面将对本申请中的技术方案进行清楚、完整地描述，显然，所描述的实施例是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本申请保护的范围。
实施例中未注明具体技术或条件者，均为常规方法或者按照本领域的文献所描述的技术或条件进行，或者按照产品说明书进行。所用试剂和仪器等未注明生产厂商者，均为可通过正规渠道商购买得到的常规产品。
下述实施例的工艺流程图如图1所示。
实施例1
本实施例提供了一种热变形磁体，其制备方法如下：
以市售钕铁硼快淬磁粉为原料，采用热压工艺制备前驱体，热压温度500℃，压制压力500MPa，保温1分钟，制得热变形前驱体材料，其密度为7.52g/cm3(磁粉材料理论密度的98.9％)，平均晶粒尺寸50纳米。将前驱体装入尺寸匹配的钢套并抽中真空，使钢套内部的真空度达到5×10-2Pa。将封装好的钢套进行保温处理，温度600℃，保温10分钟，然后进行热轧，热轧采用单道次轧制工艺，压下率60％。提前在钢套内壁均匀涂抹二硫化钼脱模剂，然后采用机械切割获得钕铁硼热变形磁体(如图2所示)。钕铁硼热变形磁体的X射线衍射图如图3所示。钕铁硼热变形磁体的断口形貌图如图4所示。
实施例2
本实施例提供了一种热变形磁体，其制备方法如下：
以高能球磨钐钴非晶磁粉为原料，采用热压工艺制备前驱体，热压温度300℃，压制压力1000MPa，保温5分钟，制得热变形前驱体材料，其密度为8.46g/cm3(磁粉材料理论密度的99.5％)，平均晶粒尺寸30纳米。将前驱体装入尺寸匹配的钢套并抽中真空，使钢套内部的真空度达到1×10-2Pa。将封装好的钢套进行保温处理，温度1000℃，保温30分钟，然后进行热轧，热轧采用三道次轧制工艺，压下率90％。提前在钢套内壁均匀涂抹氮化硼脱模剂，采用机械切割获得钐钴热变形磁体。
对比例1
本对比例提供了一种热变形磁体，其制备方法如下：
以球磨钕铁硼铸锭合金粉末为原料，采用热压工艺制备前驱体，热压温度500℃，压制压力500MPa，保温1分钟，制得热变形前驱体材料，其密度为7.53g/cm3(磁粉材料理论密度的99.1％)，平均晶粒尺寸5.5微米(5500纳米)。将前驱体装入尺寸匹配的钢套并抽中真空，使钢套内部的真空度达到5×10-2Pa。将封装好的钢套进行保温处理，温度600℃，保温10分钟，然后进行热轧，热轧采用单道次轧制工艺，压下率60％。提前在钢套内壁均匀涂抹二硫化钼脱模剂，然后采用机械切割获得钕铁硼热 变形磁体。
对比例2
本对比例提供了一种热变形磁体，制备方法仅与实施例2不同的是前驱体封装后，不保温直接进行热轧处理，具体如下：
以高能球磨钐钴非晶磁粉为原料，采用热压工艺制备前驱体，热压温度300℃，压制压力1000MPa，保温5分钟，制得热变形前驱体材料，其密度为8.46g/cm3(磁粉材料理论密度的99.5％)，平均晶粒尺寸30纳米。将前驱体装入尺寸匹配的钢套并抽中真空，使钢套内部的真空度达到1×10-2Pa。将封装好的钢套直接进行热轧，热轧采用三道次轧制工艺，压下率90％。提前在钢套内壁均匀涂抹氮化硼脱模剂，采用机械切割获得钐钴热变形磁体。
试验例
对上述实施例和对比例制备的热变形磁体的磁性能进行测试。具体的方法是，在热轧后去除的条形磁体的前端、中部和后端分别切取一个1.5×1.5×1.5mm的样品，样品充磁后，采用振动样品磁强计测试其磁滞回线以获得磁体矫顽力。
结果如表1所示。
表1磁体的矫顽力(单位：kOe)
由表1可见，本申请的制备方法所制备的磁体具有较高的磁体矫顽力，同时根据不同位置处磁体的测试结果看，本申请所制备的磁体具有非常好的均匀性，易于工业化批量生产且不会造成大量的材料浪费。
最后应说明的是：以上实施例仅用以说明本申请的技术方案，而非对其限制；尽管参照前述实施例对本申请进行了详细的说明，本领域的普通技术人员应当理解：其依然可以对前述各实施例所记载的技术方案进行修改，或者对其中部分技术特征进行等同替换；而这些修改或者替换，并不使相应技术方案的本质脱离本申请各实施例技术方案的精神和范围。

Claims (10)

  1. 一种热变形磁体的制备方法，其特征在于，包括：
    将非晶或纳米晶磁粉经过热压制成前驱体后，对前驱体进行钢套封装和抽真空处理，然后在600～1000℃下保温处理后进行热轧；
    其中，所述前驱体内部晶粒的尺寸小于100纳米。
  2. 根据权利要求1所述的制备方法，其特征在于，保温处理的时间为10～30min。
  3. 根据权利要求1或2所述的制备方法，其特征在于，热轧过程的压下率为60％以上。
  4. 根据权利要求1～3中任一项所述的制备方法，其特征在于，所述热压的温度为300～500℃，所述热压的压力为500～1000MPa。
  5. 根据权利要求4所述的制备方法，其特征在于，所述热压的时间为1～5min。
  6. 根据权利要求1～5中任一项所述的制备方法，其特征在于，所述前驱体的密度为磁粉材料理论密度的95％以上。
  7. 根据权利要求1～6中任一项所述的制备方法，其特征在于，抽真空处理的真空度为0.06Pa以下。
  8. 根据权利要求1～7中任一项所述的制备方法，其特征在于，还包括：在热轧之后对钢套切割获得热变形磁体。
  9. 根据权利要求8所述的制备方法，其特征在于，在抽真空处理之前，在钢套内壁涂覆二硫化钼和/或氮化硼作脱模剂。
  10. 一种热变形磁体，其特征在于，其由权利要求1～9中任一项所述的制备方法制得。
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