Preparation method of NdFeB magnet with high coercivity

Abstract

The invention relates to a preparation method of an NdFeB magnet with high coercivity. The method includes the following steps that heavy rare earth powder is mixed with an anti-oxidizing agent, a binder and an organic solvent to prepare uniform slurry, wherein the heavy rare earth powder refers to one or a mixture of Dy, hydrogenated dysprosium, Tb and terbium hydride, the mass ratio of the heavyrare earth powder in the slurry is 40-80%, the mass ratio of the anti-oxidizing agent is 5-20%, the mass ratio of the binder is 2-10% and the balance organic solvent, and the anti-oxidizing agent refers to the anti-oxidizing agent containing fluorine; after the slurry covers the surface of a sintered magnet, the thickness of the slurry is controlled to 20-100 micrometers, and drying is then conducted; the dried magnet is then sintered, and aging treatment is conducted. The method can reduce the use amount of heavy rare earth powder such as Dy and Tb, meanwhile, the requirement of the grain boundary diffusion technology for the size of a product is met, the problem that fluoride and oxide coating powder is easy to fall off is solved, and the manufacturing process is simple.

Description

technical field [0001] The invention relates to a method for preparing an NdFeB magnet, in particular to a method for preparing an NdFeB magnet with high coercive force, and belongs to the technical field of magnet preparation technology. Background technique [0002] Nd-Fe-B magnets are widely used due to their superior performance, especially due to the demand for energy-saving motors in automotive and electronic applications, the market application of sintered NdFeB will be further expanded. The improvement of remanence and coercive force of NdFeB material is conducive to its rapid growth in the motor market, but the improvement of coercive force in the traditional process is always at the expense of remanence, and in order to improve the coercivity must use a larger The specific gravity of the heavy rare earth element Dy / Tb causes a sharp increase in the cost of the magnet. [0003] The method (K.Machida, H.Kawasaki, T.Suzuki, M.Ito and T.Horikawa, "GrainBoundary Tailor...

AI Technical Summary

Problems solved by technology

In order to achieve a high coercive force improvement effect, it is necessary to repeatedly coat the slurry, which is complicated to operate, and a large amount of Tb or Dy powder adheres to the surface of the magnetic sheet after treatment, which needs to be machined or cleaned to remove it. The process is complicated and causes waste; coating The slurry covering the surface of the magnet is still powdery after drying and is easy to fall off, and the coercive force of the magnet cannot be greatly improved after treatment

The disadvantage of the metal alloy-only method is that it is difficult to coat the surface of the magnet with a large and uniform coat weight of the metal alloy

[0005] In addition, the neodymium in the magnet has high chemical activity, is easily oxidized, and has poor corrosion resistance. In a humid environment, a corrosive micro-battery is formed on the surface of the magnet, which increases the corrosion rate. The existing anti-corrosion ability of the NdFeB surface increases Technologies include electroplating, organic coatings and composite coatings, etc., all working to improve the electrochemical characteristics of magnets

However, the above-mentioned method of improving the coercive force and remanence of NdFeB magnets by using the grain boundary diffusion process of heavy rare earth oxides and fluorides does not play a favorable role in the surface treatment of magnets.