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Method for preparing highly corrosion-resistant sintered NdFeB magnet

A NdFeB, high corrosion-resistant technology, applied in the direction of magnetic objects, inductance/transformer/magnet manufacturing, magnetic materials, etc., can solve problems such as insufficient diffusion at low temperature, uneven distribution of diffusion elements, and insufficient depth of diffusion layer, etc. , to achieve the effect of eliminating the heat treatment diffusion process, increasing the diffusion temperature, and improving the microstructure

Inactive Publication Date: 2017-05-31
EARTH PANDA ADVANCE MAGNETIC MATERIAL
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, the melting point of the used diffusion source metal oxide (magnesium oxide, zinc oxide) in this invention is too high, and what is added is the traditional process of grain boundary diffusion+heat treatment, and the temperature during heat treatment is too low to meet the requirements of sufficient diffusion. need
And this method uses the sintered magnet as the substrate, the substrate has high density, and the grain boundary phase is evenly distributed. During heat treatment, the diffusion channel of magnesium oxide or zinc oxide with high melting point is narrowed or even blocked, so the depth of the diffusion layer is not enough. The problem of uneven distribution of elements still cannot be solved

Method used

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  • Method for preparing highly corrosion-resistant sintered NdFeB magnet
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  • Method for preparing highly corrosion-resistant sintered NdFeB magnet

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0032] Example 1: 6mm thick sintered magnet surface covered with Al 2 o 3 grain boundary diffusion heat treatment

[0033] Step 1. Fe and Pr with a purity of 99.9% 22.5 Nd 77.5 、Dy 80 Fe 20 , Fe 81.4 B 18.6 Other raw materials according to (Pr, Nd) 12.5 Dy 1.0 Fe bal Nb 0.1 B 6.0 (bal: refers to the proportion of the above ingredients removed, and the remaining proportion) for proportioning. Use a vacuum induction furnace to smelt and throw the strips to make alloy thin strips, which are crushed by hydrogen to make coarse powder, and then jet milled to make fine magnetic powder with an average particle size of 5um;

[0034] Step 2. The prepared NdFeB magnetic powder is oriented and pressed under 1.8T magnetic field and 16MPa; then oil-cooled and isostatic pressed under 225MPa to make a green body, and the holding time is 30S.

[0035] Step 3. Put the green body into the RVS-10G vacuum sintering furnace for vacuum low-temperature pre-sintering. The sintering temperat...

Embodiment 2

[0044] Example 2: 5mm thick sintered magnet surface covered with TiO 2 grain boundary diffusion heat treatment

[0045] Step 1. Fe and Pr with a purity of 99.9% 22.5 Nd 77.5 、Dy 80 Fe 20 , Fe 81.4 B 18.6 Other raw materials according to (Pr, Nd) 12.8 Dy 1.0 Fe bal co 0.3 Nb 0.2 B 6.0 Make a ratio. Melt in a vacuum induction furnace and throw the strips to make thin alloy strips, crush them with hydrogen to make coarse powders, and then go through jet mills to make fine magnetic powders with an average particle size of about 4um.

[0046] Step 2. The prepared magnetic powder is oriented and pressed under 2.0T magnetic field and 16MPa; then it is oil-cooled and isostatically pressed under 250MPa to form a green body, and the holding time is 25S.

[0047] Step 3. Put the green body into the RVS-10G vacuum sintering furnace for vacuum low-temperature pre-sintering. The sintering temperature is 870°C, the holding time is 3.5h, and the vacuum degree is 1.0×10 -2 Pa, ai...

Embodiment 2 and comparative example 2

[0053] Table 2 Example 2 and Comparative Example 2 magnet corrosion resistance and magnet magnetic performance comparison

[0054]

[0055] The above results show that for the sintered NdFeB magnets of the same composition, the grain boundary diffusion metal oxide (TiO 2 ) can significantly improve its corrosion resistance, and at the same time ensure the magnetic properties of the magnet, and have a small increase.

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Abstract

The invention provides a method for preparing a highly corrosion-resistant sintered NdFeB magnet. The method comprises the following steps: performing orientation pressing on sintered NdFeB magnetic powder in a 1.5-2.0T oriented magnetic field under the pressure of 16MPa, performing cold press molding on a pressed shape in an oil-cooled isostatic pressing machine so as to obtain a green body; performing low-temperature vacuum pre-sintering on the green body in a vacuum sintering furnace at the temperature of 850-890 DEG C for 3-3.5 hours so as to obtain a magnet; taking the magnet as a substrate, and covering a non-rare-earth compound layer on the surface of the substrate by adopting a magnetron sputtering method; performing high-temperature sintering in the vacuum sintering furnace for 2-3 hours, performing secondary tempering treatment, filling inert gases of 20-22MPa for applying pressure in the temperature treatment process, thereby obtaining the highly corrosion-resistant sintered NdFeB magnet. According to the magnetron sputtering manner, a diffusion source is attached to the surface of the magnet, grain boundary diffusion is completed in the sintering process, the base bonding force is improved, and the diffusion depth and corrosion resistance are improved.

Description

technical field [0001] The invention belongs to the field of rare earth permanent magnet materials, in particular to a preparation method of a highly corrosion-resistant sintered NdFeB magnet. [0002] technical background [0003] Since its birth in 1983, sintered NdFeB material has been deeply researched and developed due to its excellent magnetic properties, and has become the pillar of the permanent magnet industry. But its poor corrosion resistance severely limits its application range. Therefore, how to improve its corrosion resistance has become an important research topic in the production and use of sintered NdFeB materials in recent decades. The main reasons for the poor corrosion resistance of NdFeB materials are as follows: Since the sintered magnet has a multi-phase structure, the active chemical properties of the Nd-rich phase at the grain boundary determine that it is prone to chemical corrosion (oxidative corrosion); and the huge gap between the grain boundar...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H01F1/057H01F1/08H01F41/02
CPCH01F1/0576B22F2998/10H01F1/0577H01F41/0266B22F3/02B22F3/04B22F3/1007B22F2003/242B22F2003/248
Inventor 张鹏杰张浩吴玉程陈静武庞亚俊衣晓飞黄秀莲
Owner EARTH PANDA ADVANCE MAGNETIC MATERIAL
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