WO2022134662A1 - 烧结钕铁硼磁体及其防腐蚀处理方法 - Google Patents

烧结钕铁硼磁体及其防腐蚀处理方法 Download PDF

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WO2022134662A1
WO2022134662A1 PCT/CN2021/117726 CN2021117726W WO2022134662A1 WO 2022134662 A1 WO2022134662 A1 WO 2022134662A1 CN 2021117726 W CN2021117726 W CN 2021117726W WO 2022134662 A1 WO2022134662 A1 WO 2022134662A1
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organic acid
alcohol
magnet
heat treatment
corrosion
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PCT/CN2021/117726
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English (en)
French (fr)
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白晓刚
于海华
潘广麾
韩雪
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天津三环乐喜新材料有限公司
北京中科三环高技术股份有限公司
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Priority to JP2023504003A priority Critical patent/JP7497514B2/ja
Priority to DE112021002982.7T priority patent/DE112021002982T5/de
Publication of WO2022134662A1 publication Critical patent/WO2022134662A1/zh
Priority to US18/162,934 priority patent/US20230178274A1/en

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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
    • 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
    • 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
    • H01F41/0253—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 for manufacturing permanent magnets
    • H01F41/026—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 for manufacturing permanent magnets protecting methods against environmental influences, e.g. oxygen, by surface treatment

Definitions

  • the invention relates to the technical field of sintered neodymium iron boron magnets, in particular, to a sintered neodymium iron boron magnet with corrosion resistance and a method for anti-corrosion treatment.
  • NdFeB sintered neodymium iron boron
  • NdFeB magnets used in drive motors of hybrid vehicles or electric vehicles, or installed in IPM (internal permanent magnet) motors such as inverter air conditioner compressors since the magnets are sealed in the motor by organic binders such as resin after installation, it is not easy to Corrosion, only need to consider the anti-corrosion performance of magnets exposed to air conditions during storage, transportation, etc. Therefore, it is only necessary to form a simple corrosion-resistant layer on the surface of the magnet.
  • Chinese patent application CN101809690A discloses that in an atmosphere with an oxygen partial pressure of 1 ⁇ 10 2 Pa to 1 ⁇ 10 5 Pa and a water vapor partial pressure of less than 1000 Pa, by controlling the heating rate to be 100°C/hour to 1800°C/hour, at 350°C
  • the magnet with a thickness of 6 mm is heat-treated at °C ⁇ 450°C.
  • the surface modification of the NdFeB magnet is achieved by oxidative heat treatment, so as to obtain a good surface anti-oxidation modified film to achieve the purpose of corrosion resistance on the surface of the magnet.
  • the present invention provides an anti-corrosion treatment method for sintered NdFeB magnets, which includes:
  • the ratio of oxygen partial pressure to water vapor partial pressure in the oxidizing atmosphere containing alcohol and/or organic acid is 1-300:1; the temperature of the heat treatment is ⁇ 300°C, and the time is 10-200min.
  • the heat treatment of the sintered NdFeB magnet in an oxidizing atmosphere containing alcohol and/or organic acid includes:
  • the sintered NdFeB magnet whose surface is coated with an aqueous solution containing alcohol and/or organic acid is placed in an atmosphere with an oxygen partial pressure of 5 ⁇ 10 2 to 1 ⁇ 10 4 Pa and a water vapor partial pressure of 50 to 150 Pa for heat treatment.
  • the heat treatment of the sintered NdFeB magnet in an oxidizing atmosphere containing alcohol and/or organic acid includes:
  • the sintered NdFeB magnet is heat-treated in an atmosphere with an oxygen partial pressure of 5 ⁇ 10 2 to 1 ⁇ 10 4 Pa and an alcohol and/or organic acid-containing water vapor partial pressure of 50 to 150 Pa.
  • the alcohol and/or organic acid-containing aqueous solution contains 0.1-10 wt % of alcohol and/or organic acid.
  • the alcohol and/or organic acid-containing water vapor contains 0.1-10 wt % of alcohol and/or organic acid.
  • the sintered NdFeB magnet is immersed in the aqueous solution containing alcohol and/or organic acid for 30s-10min, so that the surface of the sintered NdFeB magnet is coated with the sintered NdFeB magnet.
  • the alcohol is methanol, ethanol, 1-propanol, 2-methyl-1-propanol, 2-methyl-2-propanol, 1-butanol, 2-butanol
  • the organic acid is one or more selected from formic acid, acetic acid, propionic acid, oxalic acid, malonic acid, butyric acid and maleic acid.
  • the amount ratio of the alcohol to the organic acid is 1:2-5.
  • the heat treatment temperature is 200 ⁇ 300° C.
  • the time is 15 ⁇ 200 min.
  • the present invention also provides a sintered NdFeB magnet, which includes a corrosion-resistant film layer with a thickness of 0.2-3 ⁇ m, and the corrosion-resistant film layer is obtained by the above-mentioned anti-corrosion treatment method.
  • heat treatment is performed in a specific temperature range lower than 300° C. without controlling the heating rate of the heat treatment, which can not only ensure that the magnetic properties of the NdFeB magnets do not decrease, but also Improve the corrosion resistance of the NdFeB magnet surface and reduce the generation of surface cracks on the NdFeB magnet.
  • the method of the present invention is applicable to NdFeB magnets with any oxygen content and specifications, and can perform oxidative heat treatment on NdFeB magnets in a specific temperature range below 300°C (heat treatment of sintered NdFeB magnets in an oxidative environment). ) to form a corrosion-resistant film.
  • FIG. 1 is a schematic diagram showing the relationship between the magnetic property loss rate and temperature in an embodiment of the present invention.
  • sintered neodymium iron boron magnet is sometimes simply referred to as “magnet” for brevity.
  • the anti-corrosion treatment method for sintered NdFeB magnets provided by the present invention includes:
  • the sintered NdFeB magnets are heat treated in an oxidizing atmosphere containing alcohol and/or organic acid.
  • the ratio of oxygen partial pressure to water vapor partial pressure in the oxidizing atmosphere containing alcohol and/or organic acid is 1-300:1.
  • the temperature of heat treatment is ⁇ 300°C, and the time is 10 ⁇ 200min.
  • heat treatment is performed in a specific temperature range lower than 300° C. without controlling the heating rate of the heat treatment, which can not only ensure that the magnetic properties of the NdFeB magnets do not decrease, but also Improve the corrosion resistance of the NdFeB magnet surface and reduce the generation of surface cracks on the NdFeB magnet.
  • the method of the present invention is applicable to NdFeB magnets with any oxygen content and specifications, and can perform oxidative heat treatment on NdFeB magnets in a specific temperature range below 300° C. to form a corrosion-resistant film.
  • the heat treatment described in the present invention includes a heating process before the heat treatment, a heat treatment process and a cooling process after the heat treatment.
  • the present invention whether it is the heating process, the heat treatment process, or the cooling process, it is all carried out in an oxidizing atmosphere. It can not only suppress the stability of the corrosion-resistant film formed on the surface of the magnet due to changes in the moisture content in the atmosphere, but also prevent the reduction of the magnetic properties of the magnet caused by condensation on the surface of the magnet during the cooling process.
  • the heat treatment of the sintered NdFeB magnet in an oxidizing atmosphere containing alcohol and/or organic acid may include:
  • the sintered NdFeB magnet whose surface is coated with an aqueous solution containing alcohol and/or organic acid is placed in an atmosphere with an oxygen partial pressure of 5 ⁇ 10 2 to 1 ⁇ 10 4 Pa and a water vapor partial pressure of 50 to 150 Pa for heat treatment.
  • the magnet By applying an aqueous solution containing alcohol and/or organic acid on the surface of the magnet or placing the magnet in an environment containing water vapor containing alcohol and/or organic acid, the magnet is finally placed in an oxidizing atmosphere containing alcohol and/or organic acid.
  • the above-mentioned oxidizing atmosphere is favorable for forming a desired anti-corrosion film on the surface of the magnet at a relatively low heat treatment temperature.
  • the principle is speculated as follows: a dense iron oxide layer is formed on the surface of the magnet, and its main component is expected to be Fe 2 O 3 (hematite).
  • the outside of the magnet is placed in an oxidizing atmosphere containing an organic acid, and the organic acid will initially oxidize the iron in the magnet at a lower temperature, and then the oxygen and/or water vapor in the oxidizing atmosphere will promote its further oxidation reaction and increase the Fe 2 O3 generation efficiency, accelerates the surface oxidation process of the magnet.
  • alcohol if alcohol is contained in the oxidizing atmosphere, hydrogen may be generated during the oxidative heat treatment of iron in the magnet.
  • the addition of alcohol can improve the solubility of hydrogen, which is beneficial to accelerate the oxidation reaction of iron in the magnet. Therefore, the oxidizing atmosphere containing alcohol and/or organic acid can accelerate the further oxidation of the surface of the magnet by oxygen and water vapor, thereby reducing the heat treatment temperature to provide the energy required for magnet oxidation.
  • the oxygen partial pressure is lower than 5 ⁇ 10 2 Pa, the oxygen content in the oxidizing atmosphere will be too low, which will lead to the formation of the corrosion-resistant film on the surface of the magnet for too long, or the formed corrosion-resistant film cannot reach enough. Corrosion resistance and stability. If it is higher than 1 ⁇ 10 4 Pa, the corrosion resistance of the magnet surface may not be greatly improved, and the production cost may also be increased.
  • the partial pressure of water vapor When the partial pressure of water vapor is lower than 150Pa, on the one hand, it can restrain the magnet from reacting in an oxidizing atmosphere with high water vapor pressure to generate a large amount of hydrogen by-products, thereby restraining the magnet from embrittlement due to the hydrogen generated by adsorption and reducing the magnetic properties.
  • the amount of magnetite (Fe 3 O 4 ) in the produced iron oxide can be reduced, thereby increasing the ratio of hematite (Fe 2 O 3 ).
  • the aqueous solution containing alcohol and/or organic acid can be applied to the surface of the sintered NdFeB magnet by means of soaking, spraying or brushing.
  • the aqueous solution containing alcohol and/or organic acid is preferably applied to the surface of the sintered NdFeB magnet by soaking.
  • the sintered NdFeB magnet can be soaked in an aqueous solution containing alcohol and/or organic acid, so that the surface of the sintered NdFeB magnet can be coated with the aqueous solution containing alcohol and/or organic acid.
  • the above-mentioned alcohol and/or organic acid-containing aqueous solution preferably contains 0.1 to 10 wt % of alcohol and/or organic acid.
  • the above-mentioned aqueous solution containing alcohol and/or organic acid more preferably contains 0.1-5wt% alcohol and/or organic acid, and the soaking time may be 30s-10min.
  • the alcohol and/or organic acid-containing water vapor preferably contains 0.1 to 10% by weight of alcohol and/or organic acid.
  • the alcohol used in the present invention can be methanol, ethanol, 1-propanol, 2-methyl-1-propanol, 2-methyl-2-propanol, 1-butanol, 2-butanol, n-pentanol , one or more of 2-ethoxyethanol and 2-(2-butoxyethoxy)ethanol.
  • other alcohols with similar properties can be used.
  • the organic acid used in the present invention is a fatty acid, which can be compatible or miscible with water (the solubility is greater than 60g/100g water), and the acidity coefficient PKa is less than 5 (the smaller the PKa value, the stronger the dissociation ability and the stronger the acidity at the same concentration. ), preferably one or more of formic acid, acetic acid, propionic acid, oxalic acid, malonic acid, butyric acid and maleic acid. Other acids with similar properties can also be used.
  • the dosage ratio of alcohol and organic acid is preferably 1:2-5. The combined action of alcohol and organic acid is conducive to the full reaction of the oxidation reaction at lower temperature.
  • the temperature of the heat treatment is preferably 200 to 300°C.
  • the temperature is lower than 200°C, it is difficult to form a corrosion-resistant film on the surface of the magnet, or the formed film may be too thin to achieve the purpose of anti-corrosion.
  • the temperature is higher than 300°C, excessive oxidation of the surface of the magnet may be caused, and a large amount of hydrogen will be generated, which will adversely affect the magnetic properties of the magnet.
  • the time for the heat treatment is 10 to 200 min, more preferably 15 to 200 min. If the time is too short, it may be difficult to form the desired corrosion-resistant film on the surface of the magnet. If the time is too long, it will only consume energy and increase production costs.
  • the present invention also provides a sintered NdFeB magnet with good corrosion resistance. It includes a corrosion-resistant film layer with a thickness of 0.2-3 ⁇ m.
  • the corrosion-resistant film layer is obtained by the above-mentioned anti-corrosion treatment method. If the thickness of the corrosion-resistant film is too thin, it may not be able to exert sufficient corrosion resistance. If it is too thick, it will be difficult to obtain, and the production cost will also be increased.
  • a nitrogen-oxygen analyzer was used to test the oxygen content of the magnet, and the equipment used was the ON-330 type, Chongqing Yanrui Instrument Co., Ltd.
  • the method for evaluating the magnetic characteristics of the magnet is: first, the magnet is saturated and magnetized by a magnetizer, and then placed in a Helmholtz coil to measure its magnetic flux value in turn:
  • Magnetic property loss rate (%) (A-B)/A ⁇ 100, where A is the magnetic flux value of the magnet without oxidative heat treatment, and B is the magnetic flux value of the oxidative heat treatment.
  • Magnet corrosion resistance evaluation method under the conditions of temperature 120 °C, relative humidity 100%, pressure 2atm high temperature and high humidity, test time 96h, after removing the magnetic powder from the surface of the magnet after the test, test the weight of the magnet before and after the test.
  • Nd 31 Dy 0.5 Co 1.0 Cu 0.25 Al 0.5 B 0.98 Fe bal (weight percent) alloy ingot is produced by smelting process, and the ingot alloy is coarsely pulverized, hydrogen-crushed, and air-milled into fine powder according to conventional methods, powder D50 is 4.5 ⁇ m.
  • the fine powder into the magnetic field orientation device for compression, and the orientation magnetic field strength is 1.5T, and then press molding. Then, the molded body was taken out from the pressing device, put into a vacuum sintering furnace, sintered at 1070°C for 3 hours, and tempered at 600°C for 4 hours to obtain a blank magnet.
  • a 5 mm sintered magnet (hereinafter referred to as "sintered sample base 1").
  • the oxygen content of the sintered sample base 1 was measured by a nitrogen-oxygen analyzer to be 0.08 wt %.
  • the sintered sample substrate 1 was soaked in an aqueous solution containing ethanol and acetic acid, wherein the mass ratio of ethanol and acetic acid was 1:1, the total content of ethanol and acetic acid in the aqueous solution was 0.1 wt%, and the ratio of ethanol and acetic acid was 1:3 . After soaking for 5 minutes, take it out and place it in an atmosphere with an oxygen partial pressure of 5 ⁇ 10 2 Pa and a water vapor partial pressure of 25 Pa, heated to 200° C., and heat treated for 60 minutes. Then, the temperature is lowered in the same atmosphere.
  • the thickness of the surface corrosion-resistant film, the corrosion resistance of the magnet, and the number of surface cracks were measured, as shown in Table 1, Table 2, and Table 3 for details.
  • the sintered sample base 1 was subjected to oxidative heat treatment in the same manner as in Example 1.
  • the aqueous solution is an aqueous solution containing ethanol and propionic acid, wherein the mass ratio of ethanol and propionic acid is 1:2, and the total content of ethanol and acetic acid in the aqueous solution is 1.0 wt %.
  • the thickness of the surface corrosion-resistant film layer and the corrosion resistance of the magnet are measured, as shown in Table 1 and Table 2 for details.
  • the sintered sample base 1 was subjected to oxidative heat treatment in the same manner as in Example 1. Unlike Example 1, the total content of ethanol and acetic acid in the aqueous solution was 3.0 wt%.
  • the sintered sample substrate 1 was directly placed in an atmosphere with an oxygen partial pressure of 5 ⁇ 10 2 Pa and a water vapor partial pressure of 25Pa, wherein the water vapor contained 3.0wt% ethanol and acetic acid, and the mass ratio of ethanol and acetic acid was 1:3.
  • the temperature was raised to 250°C, and heat treatment was performed for 60min. Then, the temperature is lowered in the same atmosphere.
  • the sintered sample base 1 was subjected to oxidative heat treatment in the same manner as in Example 4. Unlike Example 4, the heat treatment temperature was 300°C.
  • the sintered sample base 1 was subjected to oxidative heat treatment in the same manner as in Example 5.
  • the difference from Example 5 is that the water vapor contains 5.0 wt % ethanol and acetic acid, wherein the mass ratio of ethanol and acetic acid is 1:4.
  • the thickness of the surface corrosion-resistant film, the corrosion resistance of the magnet, and the number of surface cracks are measured, as shown in Table 1, Table 2, and Table 3 for details.
  • An aqueous solution containing 2-methyl-1-propanol was brushed on the surface of the sintered sample substrate 2, wherein the content of 2-methyl-1-propanol was 2.0 wt %.
  • the magnet was placed in an atmosphere with an oxygen partial pressure of 5 ⁇ 10 3 Pa and a water vapor partial pressure of 100Pa (oxygen partial pressure/water vapor partial pressure of 50), heated to 300°C, and heat-treated for 15 minutes. Then, the temperature is lowered in the same atmosphere.
  • the thickness of the surface corrosion-resistant film layer and the corrosion resistance of the magnet are measured, as shown in Table 1 and Table 2 for details.
  • the sintered sample substrate 2 was soaked in an aqueous solution containing 2-ethoxyethanol, wherein the content of 2-ethoxyethanol was 2.5 wt %. After soaking for 30s, the magnet was placed in an atmosphere with an oxygen partial pressure of 1 ⁇ 10 4 Pa and a water vapor partial pressure of 100Pa (oxygen partial pressure/water vapor partial pressure of 100), heated to 250°C, and heat-treated for 100min. Then, the temperature is lowered in the same atmosphere.
  • the thickness of the surface corrosion-resistant film layer and the corrosion resistance of the magnet are measured, as shown in Table 1 and Table 2 for details.
  • the sintered sample base 3 was soaked in an aqueous solution containing malonic acid, wherein the content of malonic acid was 2.5 wt %. After 50 minutes, the magnet was placed in an atmosphere with an oxygen partial pressure of 1 ⁇ 10 4 Pa and a water vapor partial pressure of 50 Pa (oxygen partial pressure/water vapor partial pressure of 200), heated to 250° C., and heat-treated for 100 minutes. Next, the temperature reduction step is performed in the same atmosphere.
  • the thickness of the surface corrosion-resistant film layer and the corrosion resistance of the magnet are measured, as shown in Table 1 and Table 2 for details.
  • the sintered sample substrate 3 was soaked in an aqueous solution containing 2-(2-butoxyethoxy)ethanol and maleic acid, wherein 2-(2-butoxyethoxy)ethanol and isovaleric acid
  • the total content of the magnet is 5.0wt%, and the mass ratio of 2-(2-butoxyethoxy)ethanol and maleic acid is 1:5.
  • the magnet is placed in an oxygen partial pressure of 9 ⁇ 10 3 Pa, In an atmosphere with a water vapor partial pressure of 150 Pa (oxygen partial pressure/water vapor partial pressure of 60), the temperature was raised to 200° C., and the heat treatment was performed for 200 min. Then, the temperature is lowered in the same atmosphere.
  • the thickness of the surface corrosion-resistant film layer and the corrosion resistance of the magnet are measured, as shown in Table 1 and Table 2 for details.
  • the sintered sample base 3 was subjected to oxidative heat treatment in the same manner as in Example 10. Different from Example 10, the mass ratio of 2-(2-butoxyethoxy)ethanol and maleic acid was 2:1.
  • the thickness of the surface corrosion-resistant film layer and the corrosion resistance of the magnet are measured, as shown in Table 1 and Table 2 for details.
  • the sintered sample substrate 1 was placed in an atmosphere with an oxygen partial pressure of 1 ⁇ 10 4 Pa and a water vapor partial pressure of 100 Pa (oxygen partial pressure/water vapor partial pressure of 100), heated to 300° C., and heat-treated for 200 min. Then, the temperature is lowered in the same oxidizing atmosphere.
  • the sintered sample substrate 1 was immersed in an aqueous solution containing ethanol and acetic acid, wherein the mass ratio of ethanol and acetic acid was 1:1, and the total content of ethanol and acetic acid was 5.0 wt %. After soaking for 60min, take out without oxidation heat treatment.
  • the sintered sample substrate 1 was immersed in an aqueous solution containing ethanol and acetic acid, wherein the mass ratio of ethanol and acetic acid was 1:1, and the total content of ethanol and acetic acid was 5.0 wt %. After soaking for 5 minutes, take it out and place it in an atmosphere with an oxygen partial pressure of 1 ⁇ 10 4 Pa and a water vapor partial pressure of 50 Pa (oxygen partial pressure/water vapor partial pressure of 200), heated to 150° C., and heat treated for 200 minutes. Then, the temperature is lowered in the same atmosphere.
  • the sintered sample base 1 was subjected to oxidative heat treatment in the same manner as in Example 3. Different from Example 1, the heat treatment temperature was 330°C.
  • the thickness of the corrosion-resistant film on the surface of the magnet and the loss rate of the magnetic properties are measured, as shown in Table 1 and Figure 1 for details.
  • the sintered sample base 1 was subjected to oxidative heat treatment in the same manner as in Example 3. Different from Example 1, the heat treatment temperature was 380°C.
  • the thickness of the corrosion-resistant film on the surface of the magnet and the loss rate of the magnetic properties are measured, as shown in Table 1 and Figure 1 for details.
  • the sintered sample base 1 was subjected to oxidative heat treatment in the same manner as in Example 3. Different from Example 1, the heat treatment temperature was 420°C.
  • the thickness of the corrosion-resistant film on the surface of the magnet and the loss rate of the magnetic properties are measured, as shown in Table 1 and Figure 1 for details.
  • the sintered sample substrate 1 was placed in an atmosphere with an oxygen partial pressure of 1 ⁇ 10 4 Pa and a water vapor partial pressure of 100 Pa (oxygen partial pressure/water vapor partial pressure of 100), heated to 400° C., and heat-treated for 200 min. Then, the temperature is lowered in the same atmosphere.
  • Example 1 Corrosion-resistant film thickness/ ⁇ m Example 1 1.0 Example 2 1.2 Example 3 1.8 Example 4 2.3 Example 5 2.8
  • Example 6 4
  • Example 7 0.5
  • Example 8 0.8
  • Example 9 1.0
  • Example 10 3 Example 11 1.5 Comparative Example 4 3.2 Comparative Example 5 3.8 Comparative Example 6 4.3
  • the method of the present invention can obtain a corrosion-resistant film layer.
  • the thickness of the film layer is larger.
  • the thickness of the corrosion-resistant film obtained by adding alcohol and acid treatment in an oxidative atmosphere was larger than that obtained by adding alcohol or acid treatment alone, and adding more organic compounds in an oxidizing atmosphere than alcohol The acid formed a thicker film under the same conditions.
  • FIG. 1 shows the magnetic property loss rates of the magnets of Examples 3 to 5 and Comparative Examples 4 to 6.
  • the temperature of the oxidation heat treatment is between 200 and 300 °C, and the loss rate of the magnetic properties of the magnet obtained after heat treatment is very low. It can be considered that the oxidation heat treatment in this temperature range will not affect the magnetic properties of the magnet. After °C, with the increase of the heat treatment temperature, the magnetic properties of the magnet decrease significantly.

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Abstract

本发明公开了一种烧结钕铁硼磁体及其防腐蚀处理方法。该方法包括：在含醇和/或有机酸的氧化性气氛中对所述烧结钕铁硼磁体进行热处理；其中，该含醇和/或有机酸的氧化性气氛中氧分压和水蒸气分压的比为1～300:1；该热处理的温度≤300℃，时间为10～200min。本发明通过在氧化性气氛中加入醇和/或有机酸，在低于300℃的特定温度范围内进行热处理，无需控制热处理的升温速率，既能保证钕铁硼磁体的磁特性不下降，又能提高钕铁硼磁体表面的耐腐蚀性能，同时减少钕铁硼磁体表面裂纹的产生。而且本发明方法对任何氧含量及规格的钕铁硼磁体均适用，均可以在低于300℃的特定温度范围内对钕铁硼磁体进行氧化热处理形成耐腐蚀性膜层。

Description

烧结钕铁硼磁体及其防腐蚀处理方法 技术领域
本发明涉及烧结钕铁硼磁体技术领域，具体地，涉及一种具有耐腐蚀性的烧结钕铁硼磁体及其防腐蚀处理方法。
背景技术
近年来烧结钕铁硼(NdFeB)磁体的发展十分迅速，该材料主要是由稀土金属钕Nd、铁Fe和硼B等元素通过粉末冶金工艺制备而成。由于可以使用资源丰富且廉价的原材料，且具有高的磁特性，该材料已经广泛应用于机械、医疗、汽车等诸多领域。但由于该磁体含有性质活泼的稀土元素Nd，因而耐腐蚀性很差，在湿热的环境中极易生锈腐蚀，进而造成磁性能下降或损坏。磁体的防腐蚀问题制约了NdFeB磁体的应用。
对于NdFeB磁体应用在混合动力汽车或电动汽车的驱动电机、或装入变频空调压缩机等IPM(内部永久磁铁)电机中，由于磁体安装后被树脂等有机粘结剂密封在电机中，不容易腐蚀，只需要考虑磁体在储存、运输等暴露在空气条件下造成的防腐蚀性能。因此仅需要在磁体表面形成简单耐腐蚀层即可。
中国专利申请CN101809690A公开了在氧分压为1×10 2Pa～1×10 5Pa、水蒸气分压低于1000Pa的气氛下，通过控制升温速率为100℃/小时～1800℃/小时，于350℃～450℃对厚6mm的磁体进行热处理。通过氧化热处理实现NdFeB磁体表面改性，从而获得良好的表面防氧化的改性膜层以达到磁体表面耐腐蚀的目的。但对于批量处理厚度低于2mm的较薄磁体，由于热处理温度较高，降温速率较快时，易导致磁体表面出现裂纹，影响合格率，降温速率较慢，则需要较长时间降至室温，影响生产效率。
发明内容
为了解决上述问题之一，本发明提供了一种烧结钕铁硼磁体的防腐蚀处理方法，其包括：
在含醇和/或有机酸的氧化性气氛中对所述烧结钕铁硼磁体进行热处理；
其中，所述含醇和/或有机酸的氧化性气氛中氧分压和水蒸气分压的比为1～300:1；所述热处理的温度≤300℃，时间为10～200min。
在本发明的一些实施例中，在含醇和/或有机酸的氧化性气氛中对所述烧结钕铁硼磁体进行热处理包括：
将表面涂覆有含醇和/或有机酸的水溶液的烧结钕铁硼磁体置于氧分压为5×10 2～1×10 4Pa、水蒸气分压为50～150Pa的气氛下进行热处理。
在本发明的一些实施例中，在含醇和/或有机酸的氧化性气氛中对所述烧结钕铁硼磁体进行热处理包括：
将所述烧结钕铁硼磁体置于氧分压为5×10 2～1×10 4Pa、含醇和/或有机酸的水蒸气的分压为50～150Pa的气氛下进行热处理。
在本发明的一些实施例中，所述含醇和/或有机酸的水溶液中含有0.1～10wt％的醇和/或有机酸。
在本发明的一些实施例中，所述含醇和/或有机酸的水蒸气中含有0.1～10wt％的醇和/或有机酸。
在本发明的一些实施例中，将所述烧结钕铁硼磁体浸泡在所述含醇和/或有机酸的水溶液中30s～10min，以使所述烧结钕铁硼磁体表面涂覆上所述含醇和/或有机酸的水溶液，其中所述含醇和/或有机酸的水溶液中含有0.1～5wt％的醇和/或有机酸。
在本发明的一些实施例中，所述醇为甲醇、乙醇、1-丙醇、2-甲基-1-丙醇、2-甲基-2-丙醇、1-丁醇、2-丁醇、正戊醇、2-乙氧基乙醇、2-(2-丁氧基乙氧基)乙醇中的一种或几种；
所述有机酸为甲酸、乙酸、丙酸、乙二酸、丙二酸、丁酸、顺丁烯二酸中的一种或几种。
在本发明的一些实施例中，所述醇与所述有机酸的用量比为1:2-5。
在本发明的一些实施例中，所述热处理温度为200～300℃，时间为15～200min。
进一步地，本发明还提供了一种烧结钕铁硼磁体，其包括0.2～3μm厚的耐腐蚀性膜层，所述耐腐蚀性膜层通过上述防腐蚀处理方法制得。
本发明通过在氧化性气氛中加入醇和/或有机酸，在低于300℃的特定温度范围内进行热处理，无需控制热处理的升温速率，既能保证钕铁硼磁体的磁特性不下降，又能提高钕铁硼磁体表面的耐腐蚀性能，同时减少钕铁硼磁体表面裂纹的产生。
此外，因处理温度较低，避免了降温过程中钕铁硼磁体表面裂纹的产生，提高了钕铁硼磁体的成品率。
而且本发明方法对任何氧含量及规格的钕铁硼磁体均适用，均可以在低于300℃的特定温度范围内对钕铁硼磁体进行氧化热处理(在氧化性环境下烧结钕铁硼磁体热处理)形成耐腐蚀性膜层。
本发明的附加方面和优点将在下面的描述中部分给出，部分将从下面的描述中变得明显，或通过本发明的实践了解到。
附图说明
图1为本发明实施例中磁特性损失率与温度的关系示意图。
具体实施方式
以下结合附图和实施例，对本发明的具体实施方式进行更加详细的说明，以便能够更好地理解本发明的方案以及其各个方面的优点。然而，以下描述的具体实施方式和实施例仅是说明的目的，而不是对本发明的限制。
特别需要指出的是，所有类似的替换和改动对本领域技术人员来说是显而易见的，它们都被视为包括在本发明。本发明的方法及应用已经通过较佳实施例进行了描述，相关人员明显能在不脱离本发明内容、精神和范围内对本文所述的方法和应用进行改动或适当变更与组合，来实现和应用本发明技术。
下文中，为了简洁，“烧结钕铁硼磁体”有时简称为“磁体”。
本发明提供的烧结钕铁硼磁体的防腐蚀处理方法，包括：
在含醇和/或有机酸的氧化性气氛中对烧结钕铁硼磁体进行热处理。
其中，含醇和/或有机酸的氧化性气氛中氧分压和水蒸气分压的比为1～300:1。热处理的温度≤300℃，时间为10～200min。
本发明通过在氧化性气氛中加入醇和/或有机酸，在低于300℃的特定温度范围内进行热处理，无需控制热处理的升温速率，既能保证钕铁硼磁体的磁特性不下降，又能提高钕铁硼磁体表面的耐腐蚀性能，同时减少钕铁硼磁体表面裂纹的产生。
而且本发明方法对任何氧含量及规格的钕铁硼磁体均适用，均可以在低于300℃的特定温度范围内对钕铁硼磁体进行氧化热处理形成耐腐蚀性膜层。
需要特别说明的是，本发明所述的热处理包括了热处理之前的升温过程、热处理过程和热处理之后的降温过程。
本发明中，无论是升温过程、热处理过程，还是降温过程，都是在氧化性气氛中进行的。既可抑制因大气中水分含量变动影响磁体表面形成的耐腐蚀性膜层的稳定性，又可防止降温过程中磁体表面结露导致磁体磁特性的降低。
本发明中，在含醇和/或有机酸的氧化性气氛中对烧结钕铁硼磁体进行热处理可包括：
将表面涂覆有含醇和/或有机酸的水溶液的烧结钕铁硼磁体置于氧分压为5×10 2～1×10 4Pa、水蒸气分压为50～150Pa的气氛下进行热处理。
或将烧结钕铁硼磁体置于氧分压为5×10 2～1×10 4Pa、含醇和/或有机酸的水蒸气的分压为50～150Pa的气氛下进行热处理。
通过在磁体表面施加包含醇和/或有机酸水溶液或者将磁体放入包含醇和/或有机酸的水蒸气的环境中，最终使磁体置于形成包含醇和/或有机酸的氧化性气氛中。上述氧化性气氛有利于在较低的热处理温度即可在磁体表面形成预期的防腐蚀膜层。其原理推测如下：磁体表面形成致密铁氧化层，其期望主要成分为Fe 2O 3(赤铁矿)，常规工艺中需要在一定高温下才能形成上述氧化物。将磁体外部置于含有机酸的氧化性气氛中，在较低温度下有机酸对磁体中铁进行初氧化，之后在氧化性气氛中的氧气和/或水蒸气促使其进一步氧化反应，提高Fe 2O 3生成效率，加速磁体的表面氧化过程。此外，在氧化性气氛中包含醇，磁体中铁的氧化热处理过程中可能产生氢，添加醇能提高氢的溶解度，进而利于加速磁体中的铁发生氧化反应。因此，包含醇和/或有机酸的氧化性气氛能够加速氧及水蒸气对磁体的表面进一步氧化，进而可降低热处理温度提供磁体氧化所需能量的需求。
氧分压如果低于5×10 2Pa，会使得氧化性气氛中氧含量过少，从而导致磁体表面生成耐腐蚀性膜层的时间过长，或者形成的耐腐蚀性膜层不能达到足够的耐腐蚀性和稳定性。如果高于1×10 4Pa，磁体表面的耐腐蚀性能可能无法得到很大的提高，还可能会增加生产成本。
水蒸气分压低于150Pa，一方面可以抑制磁体在高水蒸气压的氧化性气氛中反应生成大量的氢副产物，进而抑制磁体因吸附生成的氢而脆化，降低磁特性。另一方面，可以降低生成的氧化铁中磁铁矿(Fe 3O 4)的量，从而提高赤铁矿(Fe 2O 3)的比例。
其中，可以采用浸泡、喷涂或刷涂的方式将含醇和/或有机酸的水溶液涂覆至烧结钕铁硼磁体表面。
本发明优选采用浸泡的方式将含醇和/或有机酸的水溶液涂覆至烧结钕铁硼磁体表面。具体地，可将烧结钕铁硼磁体浸泡在含醇和/或有机酸的水溶液中，以使烧结钕铁硼磁体表面涂覆上含醇和/或有机酸的水溶液。
本发明中，上述含醇和/或有机酸的水溶液优选含有0.1～10wt％的醇和/ 或有机酸。上述含醇和/或有机酸的水溶液更优选含有0.1～5wt％的醇和/或有机酸，此时浸泡的时间可为30s～10min。
上述含醇和/或有机酸的水蒸气中优选含有0.1～10wt％的醇和/或有机酸。
本发明所用的醇，可为甲醇、乙醇、1-丙醇、2-甲基-1-丙醇、2-甲基-2-丙醇、1-丁醇、2-丁醇、正戊醇、2-乙氧基乙醇、2-(2-丁氧基乙氧基)乙醇中的一种或几种。当然，可以为其他有类似性质的醇。
本发明所用的有机酸为脂肪酸，可以与水相容或者混溶(溶解度大于60g/100g水)，且酸度系数PKa小于5(PKa值越小表示相同浓度下解离能力越强，酸性越强)，优选甲酸、乙酸、丙酸、乙二酸、丙二酸、丁酸、顺丁烯二酸中的一种或几种。也可为其他有类似性质的酸。在使用时，醇和有机酸的用量比优选为1:2-5。醇和有机酸的共同作用，有利于氧化反应在较低温度下反应充分。
本发明中，热处理的温度优选为200～300℃。当温度低于200℃时，在磁体表面形成耐腐蚀性膜层比较难，或者形成的膜层有可能太薄，不能达到防腐蚀目的。当温度高于300℃时，有可能造成磁铁表面的过度氧化，并伴随生成大量的氢，对磁体的磁特性带来不良影响。
本发明中热处理的时间为10～200min，更优选为15～200min。时间过短，有可能难以在磁体表面形成希望的耐腐蚀性膜层，时间过长，只会消耗能量，增加生产成本。
进一步地，本发明还提供一种具有良好防腐蚀性能的烧结钕铁硼磁体。其包括0.2～3μm厚的耐腐蚀性膜层。该耐腐蚀性膜层通过上述防腐蚀处理方法制得。耐腐蚀性膜层的厚度太薄有可能不能发挥充分的耐腐蚀性，若太厚，又比较难制得，而且也会增加生产成本。
下面参考具体实施例，对本发明进行说明。下述实施例中所取工艺条件数值均为示例性的，其可取数值范围如前述发明内容中所示，对于未特别注明的工艺参数，可参照常规技术进行。除特别指出，本发明提供的技术方案中所用试剂、仪器均可由常规渠道或市场购得。
下面实施例中采用氮氧分析仪测试磁体氧含量，所用设备为ON-330型，重庆研瑞仪器有限公司。
磁体磁特性评估方法为：将磁体先通过充磁机饱和充磁，然后放入赫姆霍兹线圈中依次测量其磁通值：
磁特性损失率(％)＝(A-B)/A×100，其中A为未进行氧化热处理的磁体的磁通值，B为进行氧化热处理的磁通值。
磁体耐腐蚀性评估方法：在温度120℃，相对湿度100％，压力2atm高温高湿条件下，试验时间96h，清除试验后磁体表面的脱离的磁粉后，测试磁体的试验前后的重量。
磁体表面的裂纹统计：将50块磁体放入氧化性气氛中进行热处理后，统计表面出现裂纹的磁体数目。
制备烧结试样基体
制备例1
采用熔炼工艺制造Nd 31Dy 0.5Co 1.0Cu 0.25Al 0.5B 0.98Fe bal(重量百分比)合金铸锭，将铸锭合金按常规方法进行粗粉碎、氢破碎、经气流磨制成细粉末，粉末D50为4.5μm。将细粉末放入磁场定向装置中进行压缩，取向磁场强度1.5T，压制成型。然后，把成型体从压制装置中取出来，放入真空烧结炉中于1070℃烧结3h，600℃回火4h得到毛坯磁体，把毛坯磁体通过机械加工，制得厚0.5mm×纵向5mm×横向5mm的烧结磁体(下面称作“烧结试样基体1”)。采用氮氧分析仪测试烧结试样基体1的氧含量为0.08wt％。
测量磁体耐腐蚀性，具体请见表2。
制备例2
采用同烧结试样基体1的相同制备方法得到毛坯磁体：Nd 18.5Dy 11.7Co 0.9Cu 0.32Al 0.9B 0.95Fe bal(重量百分比)，经过机械加工后得到厚5mm×纵向7mm×横向7mm的烧结试样基体2，采用氮氧分析仪测量其 氧含量为0.1wt％。
制备例3
采用同烧结试样基体1的相同制备方法得到毛坯磁体：Nd 18.5Dy 11.7Co 0.9Cu 0.32Al 0.9B 0.95Fe bal(重量百分比)，经过机械加工后得到厚8mm×纵向7mm×横向7mm的烧结试样基体3，采用氮氧分析仪测量其氧含量为0.2wt％。
防腐蚀处理
实施例1
将烧结试样基体1浸泡在含乙醇和乙酸的水溶液中，其中乙醇和乙酸的质量比为1：1，水溶液中乙醇和乙酸的含量总共为0.1wt％，乙醇和乙酸的比为1:3。浸泡5min后拿出置于氧分压为5×10 2Pa、水蒸气分压为25Pa的气氛中，加热升温到200℃，热处理60min。接着在相同气氛中进行降温。
处理完成后，测量表面耐腐蚀性膜层厚度、磁体耐腐蚀性、及表面裂纹数目，具体见表1、表2和表3。
实施例2
采用实施例1相同的方法对烧结试样基体1进行氧化热处理。与实施例1不同的是，水溶液为含乙醇和丙酸的水溶液，其中乙醇和丙酸的质量比为1:2，水溶液中乙醇和乙酸的含量总共为1.0wt％。
处理完成后，测量表面耐腐蚀性膜层厚度、磁体耐腐蚀性，具体见表1、表2。
实施例3
采用实施例1相同的方法对烧结试样基体1进行氧化热处理。与实施 例1不同的是，水溶液中乙醇和乙酸的含量总共为3.0wt％。
处理完成后，测量磁体磁特性损失率、表面耐腐蚀性膜层厚度、磁体耐腐蚀性，具体见图1、表1、表2。
实施例4
将烧结试样基体1直接置于氧分压为5×10 2Pa、水蒸气分压为25Pa的气氛下，其中水蒸气中包含有3.0wt％乙醇和乙酸，其中，乙醇和乙酸质量比为1：3。升温到250℃，热处理60min。接着在相同气氛中进行降温。
处理完成后，测量磁体磁特性损失率、表面耐腐蚀性膜层厚度、磁体耐腐蚀性，具体见图1、表1、表2。
实施例5
采用实施例4相同的方法对烧结试样基体1进行氧化热处理。与实施例4不同的是，热处理温度为300℃。
处理完成后，测量磁体磁特性损失率、表面耐腐蚀性膜层厚度、磁体耐腐蚀性，具体见图1、表1、表2。
实施例6
采用实施例5相同的方法对烧结试样基体1进行氧化热处理。与实施例5不同的是，水蒸气中含有5.0wt％乙醇和乙酸，其中，乙醇和乙酸质量比为1：4。
处理完成后，测量表面耐腐蚀性膜层厚度、磁体耐腐蚀性、表面裂纹数目，具体见表1、表2和表3。
实施例7
在烧结试样基体2表面刷涂含2-甲基-1-丙醇的水溶液，其中，2-甲基-1-丙醇的含量为2.0wt％。涂完15min后将磁体置于氧分压为5×10 3Pa、水 蒸气分压为100Pa(氧分压/水蒸气分压为50)的气氛中，加热升温到300℃，热处理15min。接着在相同气氛中进行降温。
处理完成后，测量表面耐腐蚀性膜层厚度、磁体耐腐蚀性，具体见表1和表2。
实施例8
将烧结试样基体2浸泡在含2-乙氧基乙醇的水溶液中，其中，2-乙氧基乙醇的含量为2.5wt％。浸泡30s后将磁体置于氧分压为1×10 4Pa、水蒸气分压为100Pa(氧分压/水蒸气分压为100)的气氛中，加热升温到250℃，热处理100min。接着在相同气氛中进行降温。
处理完成后，测量表面耐腐蚀性膜层厚度、磁体耐腐蚀性，具体见表1和表2。
实施例9
将烧结试样基体3浸泡在含丙二酸的水溶液中，其中，丙二酸的含量为2.5wt％。50min后将磁体置于氧分压为1×10 4Pa、水蒸气分压为50Pa(氧分压/水蒸气分压为200)的气氛中，加热升温到250℃，热处理100min。接着在相同气氛中进行降温工序。
处理完成后，测量表面耐腐蚀性膜层厚度、磁体耐腐蚀性，具体见表1和表2。
实施例10
将烧结试样基体3浸泡在含2-(2-丁氧基乙氧基)乙醇和顺丁烯二酸的水溶液中，其中，2-(2-丁氧基乙氧基)乙醇和异戊酸的含量共为5.0wt％，2-(2-丁氧基乙氧基)乙醇和顺丁烯二酸的质量比为1:5。80min后将磁体置于氧分压为9×10 3Pa、水蒸气分压为150Pa(氧分压/水蒸气分压为60)的气氛中，加热升温到200℃，热处理200min。接着在相同气氛中进行降温。
处理完成后，测量表面耐腐蚀性膜层厚度、磁体耐腐蚀性，具体见表1和表2。
实施例11
采用实施例10相同的方法对烧结试样基体3进行氧化热处理。与实施例10不同的是，2-(2-丁氧基乙氧基)乙醇和顺丁烯二酸的质量比为2：1。
处理完成后，测量表面耐腐蚀性膜层厚度、磁体耐腐蚀性，具体见表1和表2。
对比例1
将烧结试样基体1置于氧分压为1×10 4Pa、水蒸气分压为100Pa(氧分压/水蒸气分压为100)的气氛中，加热升温到300℃，热处理200min。接着在相同氧化性气氛中进行降温。
处理完成后，测量磁体耐腐蚀性，具体见表2。
对比例2
将烧结试样基体1浸泡在含乙醇和乙酸的水溶液中，其中乙醇和乙酸的质量比为1：1，乙醇和乙酸共含5.0wt％。浸泡60min后拿出不进行氧化热处理。
处理完成后，测量磁体耐腐蚀性，具体见表2。
对比例3
将烧结试样基体1浸泡在含乙醇和乙酸水溶液中，其中乙醇和乙酸的质量比为1：1，乙醇和乙酸共含5.0wt％。浸泡5min后拿出置于氧分压为1×10 4Pa、水蒸气分压为50Pa的气氛中(氧分压/水蒸气分压为200)，加热升温到150℃，热处理200min。接着在相同气氛中进行降温。
处理完成后，测量磁体耐腐蚀性，具体见表2。
对比例4
采用实施例3相同的方法对烧结试样基体1进行氧化热处理。与实施例1不同的是，热处理温度为330℃。
处理完成后，测量磁体表面耐腐蚀性膜层厚度、磁特性损失率，具体见表1和图1。
对比例5
采用实施例3相同的方法对烧结试样基体1进行氧化热处理。与实施例1不同的是，热处理温度为380℃。
处理完成后，测量磁体表面耐腐蚀性膜层厚度、磁特性损失率，具体见表1和图1。
对比例6
采用实施例3相同的方法对烧结试样基体1进行氧化热处理。与实施例1不同的是，热处理温度为420℃。
处理完成后，测量磁体表面耐腐蚀性膜层厚度、磁特性损失率，具体见表1和图1。
对比例7
将烧结试样基体1置于氧分压为1×10 4Pa、水蒸气分压为100Pa(氧分压/水蒸气分压为100)的气氛中，加热升温到400℃，热处理200min。接着在相同气氛中进行降温。
处理完成后，测量磁体表面裂纹数目，具体见表3。
表1
  耐腐蚀性膜层厚度/μm
实施例1 1.0
实施例2 1.2
实施例3 1.8
实施例4 2.3
实施例5 2.8
实施例6 4
实施例7 0.5
实施例8 0.8
实施例9 1.0
实施例10 3
实施例11 1.5
对比例4 3.2
对比例5 3.8
对比例6 4.3
从表1可知，本发明的方法可以得到耐腐蚀性膜层。而且，对比实施例3～5和对比例4～6可知，随着温度的增加，该膜层的厚度越大。此外，发现氧化性气氛中添加醇和酸处理得到的耐腐蚀性膜层厚度大于单独添加醇或酸处理得到的耐腐蚀性膜层厚度，并且在氧化性气氛中相比于醇添加更多的有机酸在相同条件下形成的膜层更厚一些。
表2
Figure PCTCN2021117726-appb-000001
Figure PCTCN2021117726-appb-000002
从表2中可知，采用实施例1～11的本发明方法得到的表面的耐腐蚀性膜层的磁体的失重远低于对比例1～3及磁体试样基体1的失重，具有非常好的耐腐蚀性。
表3
Figure PCTCN2021117726-appb-000003
从表3可知，本发明方法可以明显降低磁体表面裂纹的数量。
图1示出了实施例3～5、对比例4～6的磁体的磁特性损失率。
从图1可知，氧化热处理温度在200～300℃之间，经热处理后得到的磁体磁特性损失率很低，可以认为在此温度范围内进行氧化热处理不会影响磁体的磁性能，而超过300℃之后，随着热处理温度的升高，磁体的磁特性降低比较明显。
显然，上述实施例仅仅是为清楚地说明本发明所作的举例，而并非对实施方式的限定。对于所属领域的普通技术人员来说，在上述说明的 基础上还可以做出其它不同形式的变化或变动。这里无需也无法对所有的实施方式予以穷举。而由此所引申出的显而易见的变化或变动仍处于本发明的保护范围之中。

Claims (10)

  1. 一种烧结钕铁硼磁体的防腐蚀处理方法，其特征在于，包括：
    在含醇和/或有机酸的氧化性气氛中对所述烧结钕铁硼磁体进行热处理；
    其中，所述含醇和/或有机酸的氧化性气氛中氧分压和水蒸气分压的比为1～300:1；所述热处理的温度≤300℃，时间为10～200min。
  2. 根据权利要求1所述的防腐蚀处理方法，其特征在于，在含醇和/或有机酸的氧化性气氛中对所述烧结钕铁硼磁体进行热处理包括：
    将表面涂覆有含醇和/或有机酸的水溶液的烧结钕铁硼磁体置于氧分压为5×10 2～1×10 4Pa、水蒸气分压为50～150Pa的气氛下进行热处理。
  3. 根据权利要求1所述的防腐蚀处理方法，其特征在于，在含醇和/或有机酸的氧化性气氛中对所述烧结钕铁硼磁体进行热处理包括：
    将所述烧结钕铁硼磁体置于氧分压为5×10 2～1×10 4Pa、含醇和/或有机酸的水蒸气的分压为50～150Pa的气氛下进行热处理。
  4. 根据权利要求2所述的防腐蚀处理方法，其特征在于，所述含醇和/或有机酸的水溶液中含有0.1～10wt％的醇和/或有机酸。
  5. 根据权利要求3所述的防腐蚀处理方法，其特征在于，所述含醇和/或有机酸的水蒸气中含有0.1～10wt％的醇和/或有机酸。
  6. 根据权利要求4所述的防腐蚀处理方法，其特征在于，将所述烧结钕铁硼磁体浸泡在所述含醇和/或有机酸的水溶液中30s～10min，以使所述烧结钕铁硼磁体表面涂覆上所述含醇和/或有机酸的水溶液，其中所述含醇和/或有机酸的水溶液中含有0.1～5wt％的醇和/或有机酸。
  7. 根据权利要求1所述的防腐蚀处理方法，其特征在于，所述醇为甲 醇、乙醇、1-丙醇、2-甲基-1-丙醇、2-甲基-2-丙醇、1-丁醇、2-丁醇、正戊醇、2-乙氧基乙醇、2-(2-丁氧基乙氧基)乙醇中的一种或几种；
    所述有机酸为甲酸、乙酸、丙酸、乙二酸、丙二酸、丁酸、顺丁烯二酸中的一种或几种。
  8. 根据权利要求1所述的防腐蚀处理方法，其特征在于，所述醇与所述有机酸的用量比为1：2-5。
  9. 根据权利要求1所述的防腐蚀处理方法，其特征在于，所述热处理温度为200～300℃，时间为15～200min。
  10. 一种烧结钕铁硼磁体，其特征在于，包括0.2～3μm厚的耐腐蚀性膜层，所述耐腐蚀性膜层通过权利要求1～9中任一所述防腐蚀处理方法制得。
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