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NdFeB sintered magnet with coating and preparation method thereof

A technology of sintered magnets and NdFeB, applied in coatings, magnetic objects, inductors/transformers/magnets, etc., can solve problems such as excessive use of heavy rare earth Dy and Tb, rapid degradation of NdFeB structure, and degradation of magnet performance. The effect of stable product quality, promotion of balanced utilization of rare earth resources, and reduction of consumption

Active Publication Date: 2018-09-21
严高林
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, this method will cause excessive use of heavy rare earths Dy and Tb, resulting in unnecessary waste; more importantly, in the pickling process, nitric acid will quickly react with part of the Nd-rich phase and Nd-rich phase in NdFeB. 2 Fe 14 Phase B reacts to form non-magnetic substances; and in the subsequent electroplating process, NdFeB and the hydrogen generated by electroplating undergo "hydrogen explosion", that is, Hydrogen Decrepitation reaction, part of the NdFeB structure degrades rapidly, and the magnet performance decreases

Method used

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  • NdFeB sintered magnet with coating and preparation method thereof
  • NdFeB sintered magnet with coating and preparation method thereof

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Effect test

Embodiment 1

[0031] Take NdFeB sintered magnets as the anode, and perform electrophoresis pretreatment on the anode, and use the steel plate as the cathode, and make the particle size 0.7 micron DyF 3 The powder is mixed into an organic solvent to make an electrophoretic solution. The organic solvent is composed of industrial ethanol, ethyl acetate, and industrial methanol, and its volume ratio is 9:0.5:0.5. DyF in the electrophoretic solution 3The concentration of the powder is 5g / L, and the DC power supply is turned on at a DC voltage of 30V for electrophoretic deposition, and then the sintered NdFeB magnet is removed from the electrophoretic solution and dried; the obtained coating sample is diffused at 700°C , lasted 7h, followed by annealing at 400°C for 1h under vacuum conditions, and finally a magnet was obtained.

Embodiment 2

[0033] Take NdFeB sintered magnets as the anode, and carry out electrophoresis pretreatment on the anode, and the steel plate as the cathode, and the particle size is 0.6 micron TbF 3 The powder is mixed into an organic solvent to make an electrophoretic solution. The organic solvent is composed of industrial ethanol and ethyl acetate, and its volume ratio is 9:1. TbF in the electrophoretic solution 3 The concentration of the powder is 5.5g / L, and the DC power is turned on at a DC voltage of 30V for electrophoretic deposition, and then the NdFeB sintered magnet is removed from the electrophoretic solution and dried; the obtained coating sample is processed at 710 ° C Diffusion lasted for 8h, followed by annealing at 420°C for 2h under vacuum, and finally a magnet was obtained.

Embodiment 3

[0035] Sintered NdFeB magnets are used as anodes, and the anodes are subjected to electrophoresis pretreatment, steel plates are used as cathodes, and the particle size is 0.67 microns DyF 3 The powder is mixed into an organic solvent to make an electrophoretic solution. The organic solvent is composed of industrial ethanol and industrial methanol, and its volume ratio is 9:1. DyF in the electrophoretic solution 3 The concentration of the powder is 5g / L, and the DC power supply is switched on at a DC voltage of 30V for electrophoretic deposition, and then the sintered NdFeB magnet is removed from the electrophoretic solution and dried; the obtained coating sample is diffused at 720°C , lasted 7h, followed by annealing at 430°C under vacuum for 1h, and finally a magnet was obtained.

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Abstract

Disclosed is a NdFeB sintered magnet with coating. A dysprosium (Dy) or terbium(Tb)-containing transition layer is formed inside a magnet body ,which is in contact with a dysprosium fluoride or Terbium fluoride coating, of the NdFeB sintered magnet. A preparation method of the NdFeB sintered magnet with coating includes (1), taking NdFeB sintered magnet as a positive electrode, taking a steel plate as a negative electrode, preparing electrophoresis buffer by mixing DyF3 or TbF3 powder into an organic solvent, performing electrophoretic deposition, removing the magnet from the electrophoresis buffer until mass of the DyF3 or TbF3 coating is 1-2.5wt% of that the magnet, and then drying; (2), dispersing the dried magnet at the temperature of 700-950 DEG C, performing vacuum annealing, coolingto obtain the NdFeB sintered magnet with coating; the concentration of DyF3 or TbF3 powder of the electrophoresis buffer is 5-7g / L. According to the preparation method, operation is facilitated, requirements on processing conditions are low, quality of products is stable, and production cost is saved as usage of heavy rare earth DyF3 or TbF3 is saved.

Description

technical field [0001] The invention relates to a neodymium-iron-boron sintered magnet and a preparation method thereof, in particular to a coated neodymium-iron-boron sintered magnet and a preparation method thereof. Background technique [0002] The sintered Nd-Fe-B magnet known as the "magnet king" has been widely used in various fields due to its excellent magnetic properties since its invention in 1983, but its low temperature stability limits its application in high temperature fields. In recent years, with the rise of electric vehicles and wind power generation, there is an urgent need for a large number of high-coercivity bulk sintered Nd-Fe-B magnets. At the same time, a large number of mobile smart phones and small or micro precision motors also require a large number of high-coercivity Force rare earth permanent magnet. The main ways to improve the coercive force of sintered magnets are the control and distribution of grain microstructure, and the addition of hea...

Claims

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Application Information

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IPC IPC(8): H01F7/02H01F1/057H01F41/02C25D13/02C25D13/22
Inventor 严高林
Owner 严高林
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