Shin-etsu Chemical Co., Ltd.

Hiroaki Nagata

Tadao Nomura

Takehisa Minowa

Hajime Nakamura

Koichi Hirota

Tetsuya Kume

Ken Ohashi

Yoshio Tawara

Kazuaki Sakaki

Masayuki Kamata

Yuuji Gouki

Kenichi Uesaka

A sintered magnet body (RTMB) coated with a powder mixture of an intermetallic compound (RM, RTM, RMH), alloy (MM) or metal (M) powder and a rare earth (R) oxide is diffusion treated. The Roxide is partially reduced during the diffusion treatment, so a significant amount of Rcan be introduced near interfaces of primary phase grains within the magnet through the passages in the form of grain boundaries. The coercive force is increased while minimizing a decline of remanence.

Rare earth permanent magnets and their preparation

The invention provides an R&#x2014;Fe&#x2014;B sintered magnet consisting essentially of 12-17 at % of Nd, Pr and R, 0.1-3 at % of M, 0.05-0.5 at % of M, 4.8+2*m to 5.9+2*m at % of B, and the balance of Fe, containing R(Fe,(Co))B intermetallic compound as a main phase, and having a core/shell structure that the main phase is covered with a grain boundary phases. The sintered magnet has an average grain size of less than 6 &#x3bc;m, a crystal orientation of more than 98%, and a degree of magnetization of more than 96%, and exhibits a coercivity of at least 10 kOe despite a low or nil content of Dy, Tb, and Ho.

R-Fe-B sintered magnet and making method

The invention provides an R&#x2014;Fe&#x2014;B sintered magnet consisting essentially of 12-17 at % of Nd, Pr and R, 0.1-3 at % of M, 0.05-0.5 at % of M, 4.8+2*m to 5.9+2*m at % of B, and the balance of Fe, containing R(Fe,(Co))B intermetallic compound as a main phase, and having a core/shell structure that the main phase is covered with grain boundary phases. The sintered magnet exhibits a coercivity of at least 10 kOe despite a low or nil content of Dy, Tb and Ho.

R&#x2014;Fe&#x2014;B sintered magnet and making method

A rare earth magnet is prepared by disposing a R-T-B sintered body comprising a RTB compound as a major phase in contact with an R-M alloy powder and effecting heat treatment for causing Relement to diffuse into the sintered body. The alloy powder is obtained by quenching a melt containing Rand M. Rand Rare rare earth elements, T is Fe and/or Co, M is selected from B, C, P, Al, Si, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Zr, Nb, Mo, Ag, In, Sn, Sb, Hf, Ta, W, Pt, Au, Pb, and Bi.

Rare earth magnet and its preparation

A rare earth sintered magnet is an anisotropic sintered body comprising NdFeB crystal phase as primary phase and having the composition RTMSiBwherein Ris a rare earth element inclusive of Sc and Y, T is Fe and/or Co, M is Al, Cu, Zn, In, P, S, Ti, V, Cr, Mn, Ni, Ga, Ge, Zr, Nb, Mo, Pd, Ag, Cd, Sn, Sb, Hf, Ta, or W, 'a' to 'e' are 12&#x2264;a&#x2264;17, 0&#x2264;c&#x2264;10, 0.3&#x2264;d&#x2264;7, 5&#x2264;e&#x2264;10, and the balance of b, wherein Dy and/or Tb is diffused into the sintered body from its surface.

Rare earth sintered magnet and making method

The invention provides an R&#x2014;Fe&#x2014;B sintered magnet consisting essentially of 12-17 at % of R, 0.1-3 at % of M, 0.05-0.5 at % of M, 4.8+2*m to 5.9+2*m at % of B, and the balance of Fe, containing R(Fe,(Co))B intermetallic compound as a main phase, and having a core/shell structure that the main phase is covered with a HR-rich layer and a (R,HR)&#x2014;Fe(Co)-Mphase wherein HR is Tb, Dy or Ho. The sintered magnet exhibits a coercivity &#x2267;10 kOe despite a low content of Dy, Tb, and Ho.

R-Fe&#x2014;B sintered magnet and making method

A rare earth permanent magnet is prepared by disposing a powdered metal alloy containing at least 70 vol % of an intermetallic compound phase on a sintered body of R&#x2014;Fe&#x2014;B system, and heating the sintered body having the powder disposed on its surface below the sintering temperature of the sintered body in vacuum or in an inert gas for diffusion treatment. The advantages include efficient productivity, excellent magnetic performance, a minimal or zero amount of Tb or Dy used, an increased coercive force, and a minimized decline of remanence.

Rare earth permanent magnet and its preparation

A rare earth permanent magnet of a composition, Ce(CO.sub.1-x-y-a Fe.sub.x Cu.sub.y M.sub.a).sub.z, where a, x, y, and z are: 0.005&lt;1&lt;0.10; 0.20&lt;x&lt;0.40; 0.10&lt;y&lt;0.30; 4.8&lt;z&lt;6.0; and M is zirconium, titanium, nickel, and/or manganese. A method for manufacturing the magnet is disclosed comprising the steps of: applying a first solid solution heat treatment to an alloy ingot having the above composition at temperatures from 900.degree. to 1100.degree. C. for 10 minutes to 100 hours; pulverizing the alloy ingot; obtaining a magnet body from this pulverized alloy by the powder metallurgy method; sintering the magnet body; applying a second solid solution heat treatment to the sintered magnet body at 900.degree.-100.degree. C. for 10 minutes to 100 hours; and applying aging heat treatment to the sintered magnet.

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Echizen, Japan

Hiroaki Nagata