Tdk Corporation

Hironari Okada

Kazuya Sakamoto

Tetsuya Hidaka

Kazuo Sato

Takeshi Sakamoto

Tomomi Yamamoto

Yasuyuki Nakayama

An R-T-B system permanent magnetcomprises a magnet bodycomprising a sintered body comprising at least a main phase comprising RTB grains (wherein R represents one or more rare earth elements, and T represents one or more transition metal elements including Fe or Fe and Co essentially) and a grain boundary phase containing R in a larger amount than the main phase, the magnet bodyhaving a 300 &#x3bc;m or less thick (not inclusive of zero thick) hydrogen-rich layerhaving a hydrogen concentration of 300 ppm or more formed in the surface layer portion, and an overcoatcovering the surface of the magnet bodycan improve the corrosion resistance of the R-T-B system permanent magnetwith an overcoatformed thereon without degrading the magnetic properties thereof. The present invention can be applied to formation of the overcoatby electrolytic plating, can fully ensure the corrosion resistance as a primary target of the overcoatformation without substantially degrading the production efficiency, and can provide the R-T-B system permanent magnetwith a high dimensional precision by suppressing the partial collapse (detachment of grains) of the surface thereof.

R-T-B system permanent magnet

An R-T-B system rare earth permanent is provided, which comprises a sintered body comprising: an RTB phase (wherein R represents one or more rare earth elements (providing that the rare earth elements include Y) and T represents one or more transition metal elements essentially containing Fe, or Fe and Co) as a main phase; and a grain boundary phase containing a higher amount of R than the above main phase, wherein, when Pc (permeance coefficient) is 2, if a total flux is defined as funder the application of an effective magnetic field of 240 kA/m (providing that an effective magnetic field=an applied magnetic field&#x2212;a demagnetizing field, and each value of them is absolute value), if a total flux is defined as funder the application of an effective magnetic field of 800 kA/m, and if a total flux is defined as funder the application of an effective magnetic field of 2,000 kA/m, a magnetization rate a (=f/f&#xd7;100) is 40% or more, and a magnetization rate b (=f/f&#xd7;100) is 90% or more.

R-T-B system rare earth permanent magnet

Growing community of inventors

Tokyo, Japan

Hironari Okada