R-Fe-B rare earth sintered magnet and method for producing same

Abstract

In a method for producing an R-Fe-B rare earth sintered magnet, there is firstly prepared an R-Fe-B rare earth sintered magnet body which contains, as the main phase, R2Fe14B compound crystal grains containing a light rare earth element RL (at least one of Nd and Pr) as a main rare earth element R, and then a heavy rare earth element RH is diffused into the rare earth sintered magnet body from the surface thereof by heating the sintered magnet body while supplying the heavy rare earth element RH (at least one substance selected from the group consisting of Dy, Ho and Tb) to the surface of the sintered magnet body.

Description

technical field [0001] The present invention relates to having R 2 Fe 14 R-Fe-B series rare earth sintered magnet with B-type compound grains (R is a rare earth element) as the main phase and its manufacturing method, particularly involving light rare earth element RL (at least one of Nd and Pr) as the main phase. R-Fe-B series rare earth sintered magnet in which main rare earth element R and part of light rare earth element RL are replaced by heavy rare earth element RH (at least one selected from Dy, Ho, and Tb) and its manufacturing method . Background technique [0002] Take Nd 2 Fe 14 R-Fe-B rare earth sintered magnets with B-type compounds as the main phase are known to have the highest performance among permanent magnets, and are used in voice coil motors (VCM) for hard disk drives and electric motors for hybrid vehicles, etc. All kinds of motors and home appliances, etc. When R-Fe-B based rare earth sintered magnets are used in various devices such as motors, e...

AI Technical Summary

Problems solved by technology

[0018] In addition, in the method of Patent Document 4, a large amount of rare earth metals is also deposited on parts other than the magnets inside the device (for example, the inner wall of the vacuum chamber) during the film formation process, so it is not compatible with the resource saving of heavy rare earth elements, which are precious resources. Contradict

[0019] In addition, in the embodiment targeting low-boiling rare earth metals such as Yb, the coercive force of each R-Fe-B system micro-magnet is surely restored, but during the diffusion heat treatment, the R-Fe-B system magnet and the adsorbed metal Fusion, or difficult to separate from each other after treatment, in fact it is difficult to avoid unreacted adsorbed metal (RH) remaining on the surface of the sintered magnet

This not only reduces the ratio of magnetic components in the formed magnet, resulting in weakened magnetic properties, but also tends to oxidize due to the very strong activity of the rare earth metal itself. preferred

In addition, since rotation and vacuum heat treatment for mixing and stirring are required to be performed at the same time, it is necessary to maintain heat resistance, pressure (air density), and a special device equipped with a rotation mechanism at the same time. In mass production, equipment investment and quality are stable. manufacturing problems

In addition, when powder is used as the raw material for adsorption, it becomes an important cause of safety problems (fire and harm to the human body) and the time-consuming and labor-intensive manufacturing process, which increases the cost.

[0020] In addition, in the embodiment targeting the high-boiling rare earth metal containing Dy, since both the adsorption material and the magnet are heated by high frequency, it is not easy to heat only the rare earth metal to a sufficient temperature to hold the magnet at the opposite magnetic field. Low temperature to the extent that the properties are not affected, the magnet is limited to the powder state or extremely small form that is difficult to guide heating

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