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Process for production of surface-modified rare earth sintered magnets and surface-modified rare earth sintered magnets

A technology for surface modification and sintering of magnets, which is used in the manufacture of inductors/transformers/magnets, permanent magnets, magnetic materials, etc. It can solve the problems of being easily oxidized and corroded, and achieve the effect of reducing and suppressing the magnetic properties.

Active Publication Date: 2012-07-25
HITACHI METALS LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0002] Rare earth sintered magnets such as R-Fe-B sintered magnets represented by Nd-Fe-B sintered magnets are currently used in various fields because they can use abundant and inexpensive materials and have high magnetic properties. Use, but because it contains highly reactive rare earth metals: R, it has the characteristics of being easily oxidized and corroded in the atmosphere

Method used

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  • Process for production of surface-modified rare earth sintered magnets and surface-modified rare earth sintered magnets
  • Process for production of surface-modified rare earth sintered magnets and surface-modified rare earth sintered magnets
  • Process for production of surface-modified rare earth sintered magnets and surface-modified rare earth sintered magnets

Examples

Experimental program
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Effect test

Embodiment 1

[0067] After washing with alcohol, the magnet test pieces were subjected to aging treatment at 490°C for 2.5 hours in vacuum. Under the atmosphere of 33.3), heat treatment was carried out at 400° C. for 15 minutes to obtain a surface-modified magnet test piece. In addition, the temperature rise of the magnet test piece from room temperature to the heat treatment temperature is carried out at a rate of about 900°C / hour in an atmosphere (oxygen partial pressure 20000Pa, water vapor partial pressure 12.9Pa) at a dew point of -40°C. (heating time 25 minutes). In addition, the temperature drop after the heat treatment was also performed in the same atmosphere. After the magnet test piece was embedded in resin and ground, a sample was prepared using an ion beam cross-section processing device (SM 09010: manufactured by JEOL Ltd.), and the cross-sectional observation was performed with a digital microscope (VHX-200: manufactured by Keyence Corporation). , the thickness of the modif...

Embodiment 2

[0069] With the magnet body test piece after alcohol washing, after adopting the same condition as embodiment 1 to carry out heat treatment, be 5Pa at oxygen partial pressure, water vapor partial pressure is 2.5 * 10 -3 Heat treatment was performed at 500° C. for 5 minutes in an atmosphere of Pa, whereby a surface-modified magnet test piece was obtained. The magnet test piece was evaluated in the same manner as in Example 1. As a result, the thickness of the modified layer formed on the surface of the magnet test piece was about 5.5 μm, and its composition was the same as that of the surface-modified magnet obtained in Example 1. The modified layer in the bulk test piece was the same (Table 1).

Embodiment 3

[0071] For the magnet test piece washed with alcohol, when the oxygen partial pressure is 5Pa, the water vapor partial pressure is 2.5×10 -3 Under Pa atmosphere, heat treatment was carried out at 500°C for 5 minutes, and then heat treatment was carried out under the same conditions as in Example 1, thereby obtaining a surface-modified magnet test piece. The magnet test piece was evaluated in the same manner as in Example 1. As a result, the thickness of the modified layer formed on the surface of the magnet test piece was about 4.1 μm, and its composition was the same as that of the surface-modified magnet obtained in Example 1. The modified layer in the bulk test piece was the same (Table 1).

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Abstract

The invention provides a rare earth sintered magnet which is improved in corrosion resistance by oxidizing heat treatment to such a level as to exhibit satisfactory corrosion resistance even in an atmosphere of varying humidity and which is reduced in the deterioration of magnetic characteristics due to oxidizing heat treatment and a process for the production of the magnet. A surface-modified rare earth sintered magnet characterized in that the surface modified part is an at least three-layered surface modification layer which comprises a main layer containing R, Fe, B and oxygen, an amorphous layer containing at least R, Fe and oxygen, and an outermost layer containing hematite-base iron oxide as the main constituent in this order from the inside of the magnet; and a process for the production of the magnet, characterized by comprising the step of subjecting a magnet body to heat treatment in an atmosphere of oxygen partial pressure of 1 OE102 to 1 OE105Pa and water vapor partial pressure of 0.1 to 1000Pa (exclusive of 1000Pa) at 200 to 600 DEG C.

Description

technical field [0001] The present invention relates to a rare earth sintered magnet having excellent magnetic properties and a method for producing the same, having sufficient corrosion resistance even in an environment where humidity fluctuates, such as a transportation environment without humidity control or a storage environment. Background technique [0002] Rare earth sintered magnets such as R-Fe-B sintered magnets represented by Nd-Fe-B sintered magnets are currently used in various fields because they can use abundant and inexpensive materials and have high magnetic properties. Use, but because it contains highly reactive rare earth metals: R, it has the characteristics of being easily oxidized and corroded in the atmosphere. Therefore, in general, rare earth sintered magnets are used after forming a corrosion-resistant film such as a metal film or a resin film on the surface. This corrosion-resistant film is formed on the surface of the magnet. However, it is of ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H01F41/02C23C8/12C23C8/16H01F1/053H01F1/08
CPCC23C8/16H01F1/0577C23C8/12H01F41/026
Inventor 藤原真秀吉村公志菊川笃
Owner HITACHI METALS LTD
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