A method for surface treatment of corrosion-resistant sintered NdFeB magnets

Abstract

The invention relates to a method for treating the surface of a corrosion-resistant sintered NdFeB magnet. The method is applicable to sintered NdFeB magnets of various compositions, and the method includes pre-surface pretreatment of NdFeB magnets, grain refinement process on the surface of magnets, atmosphere protection measures during the refinement process and subsequent ultra-low temperature stress relief process. The invention realizes the effective control of the crystal grains on the surface layer of the magnet through the high- and low-frequency composite impact of the cemented carbide sphere on the magnet, and realizes the improvement of the corrosion resistance of the magnet on the basis of ensuring the original magnetic performance, and the method improves the corrosion resistance of the magnet compared with other methods. Corrosive measures avoid the influence of other elements added on the magnetic properties of the magnet and reduce costs. The process is simple, the requirements for equipment are relatively low, and it is beneficial to realize the batch processing of the magnet surface, and has a very wide application value.

Description

technical field

[0001] The invention belongs to the technical field of rare earth permanent magnet materials, and in particular relates to a batch magnet surface treatment method for improving the corrosion resistance of the magnet surface which is simple and feasible. Background technique

[0002] Due to its excellent magnetic properties, NdFeB permanent magnets are called "Magnetic King" and are widely used in aerospace, wind power generation, energy-saving home appliances, electronic appliances and new energy vehicles. And with the continuous progress of manufacturing technology and the improvement of people's awareness of environmental protection, it has attracted market attention in the three major fields of energy saving and environmental protection, new energy and new energy vehicles, and has become an indispensable material in daily work and life. The rapid growth rate of ~20% shows good development prospects.

[0003] In addition to the magnetic properties of the m...

Examples

Embodiment 1

[0026] (1) Cut the sintered NdFeB magnets into cylinders of φ20*15mm as required.

[0027] (2) Prepare degreasing liquid in the ultrasonic degreasing tank at the ratio of 50 g degreasing spirit per liter of water, and heat it up to 50 g. o C heat preservation treatment, then put the cut magnetic blocks into the ultrasonic degreasing tank, turn on the ultrasonic device for degreasing for 3 min, and then carry out secondary water washing, each washing time is 5-15 s.

[0028] (3) Put the prepared 3% nitric acid solution into the pickling tank, then put the magnet into the pickling tank, and shake it for cleaning. The pickling time is 10-20 s. The pickled magnet needs to be quickly taken out for secondary washing. , each washing time is 5-15 s, followed by ultrasonic vibration treatment, after it is observed that the oxide scale on the surface of the magnet is completely peeled off, take it out, and carry out drying treatment, and the drying temperature is 40 o C, the drying tim...

Embodiment 2

[0040]The surface grains of NdFeB magnets are refined by using the ultrasonic impact effect of the sphere on the magnet. As shown in Example 1, a magnet sample with refined surface grains was prepared by high-frequency impact of a sphere. The difference is that the sphere material and sphere diameter used in step (4) have changed. The magnetic properties of magnets made by ultrasonic impact of spheres with different diameters and types are shown in Table 3. An electrochemical workstation was used to measure the electrochemical corrosion potential and current density of the magnets under ultrasonic impact of cemented carbide balls with different diameters, as shown in Table 4.

[0041] Table 3 Magnetic properties of magnets made by ultrasonic impact of spheres with different diameters and types

[0042] sample Br / kGs Hcj / kOe (BH)max / MGOe 1mm carbide ball (10min) 14 16.8 47.59 3mm carbide ball (10min) 13.72 15.95 46.33 1mm stainless steel ...

Embodiment 3

[0047] The surface grains of NdFeB magnets are refined by using the ultrasonic impact effect of the sphere on the magnet. As shown in Example 1, a magnet sample with refined surface grains was prepared by high-frequency impact of a sphere. The difference is: step (5) is not ventilated or different types of inert gases, such as nitrogen and argon, are introduced. The magnetic properties of the prepared samples under different atmospheres are shown in Table 5. An electrochemical workstation was used to measure the electrochemical corrosion potential and current density changes of the magnet surface under ultrasonic impact in different atmospheres, as shown in Table 6.

[0048] Table 5 Magnetic properties of magnets prepared by ultrasonic shock in different atmospheres

[0049] sample Br / kGs Hcj / kOe (BH)max / MGOe Ar protection (10min) 14 16.8 47.59 CO2 protection (10min) 13.98 16.54 47.27 N2 protection (10min) 13.96 16.84 47.27 Air (...

technical field

[0001] The invention belongs to the technical field of rare earth permanent magnet materials, and in particular relates to a batch magnet surface treatment method for improving the corrosion resistance of the magnet surface which is simple and feasible. Background technique

[0002] Due to its excellent magnetic properties, NdFeB permanent magnets are called "Magnetic King" and are widely used in aerospace, wind power generation, energy-saving home appliances, electronic appliances and new energy vehicles. And with the continuous progress of manufacturing technology and the improvement of people's awareness of environmental protection, it has attracted market attention in the three major fields of energy saving and environmental protection, new energy and new energy vehicles, and has become an indispensable material in daily work and life. The rapid growth rate of ~20% shows good development prospects.

[0003] In addition to the magnetic properties of the m...

Examples

Embodiment 1

[0026] (1) Cut the sintered NdFeB magnets into cylinders of φ20*15mm as required.

[0027] (2) Prepare degreasing liquid in the ultrasonic degreasing tank at the ratio of 50 g degreasing spirit per liter of water, and heat it up to 50 g. o C heat preservation treatment, then put the cut magnetic blocks into the ultrasonic degreasing tank, turn on the ultrasonic device for degreasing for 3 min, and then carry out secondary water washing, each washing time is 5-15 s.

[0028] (3) Put the prepared 3% nitric acid solution into the pickling tank, then put the magnet into the pickling tank, and shake it for cleaning. The pickling time is 10-20 s. The pickled magnet needs to be quickly taken out for secondary washing. , each washing time is 5-15 s, followed by ultrasonic vibration treatment, after it is observed that the oxide scale on the surface of the magnet is completely peeled off, take it out, and carry out drying treatment, and the drying temperature is 40 o C, the drying tim...

Embodiment 2

[0040]The surface grains of NdFeB magnets are refined by using the ultrasonic impact effect of the sphere on the magnet. As shown in Example 1, a magnet sample with refined surface grains was prepared by high-frequency impact of a sphere. The difference is that the sphere material and sphere diameter used in step (4) have changed. The magnetic properties of magnets made by ultrasonic impact of spheres with different diameters and types are shown in Table 3. An electrochemical workstation was used to measure the electrochemical corrosion potential and current density of the magnets under ultrasonic impact of cemented carbide balls with different diameters, as shown in Table 4.

[0041] Table 3 Magnetic properties of magnets made by ultrasonic impact of spheres with different diameters and types

[0042] sample Br / kGs Hcj / kOe (BH)max / MGOe 1mm carbide ball (10min) 14 16.8 47.59 3mm carbide ball (10min) 13.72 15.95 46.33 1mm stainless steel ...

Embodiment 3

[0047] The surface grains of NdFeB magnets are refined by using the ultrasonic impact effect of the sphere on the magnet. As shown in Example 1, a magnet sample with refined surface grains was prepared by high-frequency impact of a sphere. The difference is: step (5) is not ventilated or different types of inert gases, such as nitrogen and argon, are introduced. The magnetic properties of the prepared samples under different atmospheres are shown in Table 5. An electrochemical workstation was used to measure the electrochemical corrosion potential and current density changes of the magnet surface under ultrasonic impact in different atmospheres, as shown in Table 6.

[0048] Table 5 Magnetic properties of magnets prepared by ultrasonic shock in different atmospheres

[0049] sample Br / kGs Hcj / kOe (BH)max / MGOe Ar protection (10min) 14 16.8 47.59 CO2 protection (10min) 13.98 16.54 47.27 N2 protection (10min) 13.96 16.84 47.27 Air (...