Shin-etsu Chemical Co., Ltd.

Ryuji Hamada

Takehisa Minowa

Masaki Kasashima

Kazuaki Sakaki

Masanobu Shimao

Masao Yoshikawa

Kazuo Tamura

Hydrogen embrittlement is prevented in SmCo-based magnets and RFeB-based magnets by metal plating the magnet, then carrying out heat treatment, or by forming a metal oxide or metal nitride layer on the metal plating layer or directly on the magnet itself.

Rare earth element sintered magnet and method for producing rare earth element sintered magnet

A corrosion resistant rare earth magnet is characterized by comprising a rare earth permanent magnet represented by R-T-M-B wherein R is at least one rare earth element inclusive of Y, T is Fe or Fe and Co, M is at least one element selected from among Ti, Nb, Al, V, Mn, Sn, Ca, Mg, Pb, Sb, Zn, Si, Zr, Cr, Ni, Cu, Ga, Mo, W, and Ta, the contents of the respective elements are 5 wt %&#x2266;R&#x2266;40 wt %, 50 wt %&#x2266;T&#x2266;90 wt %, 0 wt %&#x2266;M&#x2266;8 wt %, and 0.2 wt %&#x2266;B&#x2266;8 wt %, and a coating on a surface of the permanent magnet comprising a silicone resin, a flake metal fine powder, and a complexing agent.

Corrosion-resistant rare earth element magnet

On a surface of a rare earth permanent magnet R&mdash;T&mdash;M&mdash;B wherein R is a rare earth element, T is Fe or Fe and Co, M is Ti, Nb, Al, V, Mn, Sn, Ca, Mg, Pb, Sb, Zn, Si, Zr, Cr, Ni, Cu, Ga, Mo, W or Ta, 5 wt %&lE;R&lE;40 wt %, 50 wt %&lE;90 wt %, 0 wt %&lE;M&lE;8 wt %, and 0.2 wt %&lE;B&lE;8 wt %, a solution comprising a flake fine powder of Al, Mg, Ca, Zn, Si, Mn or an alloy thereof and a silicone resin is applied and baked to form an adherent composite coating, thereby providing a corrosion resistant rare earth permanent magnet.

Corrosion resistant rare earth magnet and its preparation

An R&mdash;Fe&mdash;B permanent magnet wherein R is Nd or a combination of Nd with a rare earth element is prepared by casting an R&mdash;Fe&mdash;B alloy, crushing the alloy in an oxygen-free atmosphere of argon, nitrogen or vacuum, effecting comminution, compaction, sintering, aging, and cutting and/or polishing the magnet to give a finished surface. The magnet is then heat treated in an argon, nitrogen or low-pressure vacuum atmosphere having a limited oxygen partial pressure, obtaining a highly oil resistant sintered permanent magnet having corrosion resistance and hydrogen barrier property even in a high pressure hot environment of refrigerant and/or lubricant as encountered in compressors.

Preparation of rare earth permanent magnets

A neodymium/iron/boron permanent magnet is provided with high corrosion resistance by forming a coating layer of a vitrified sodium silicate on the surface. The vitreous coating layer of sodium silicate is formed by coating the surface of the permanent magnet with an aqueous coating solution of water glass followed by drying of the coating layer and vitrification of the dried coating layer by a heat treatment under specified conditions. Characteristically, the thus formed vitreous coating layer of sodium silicate is subjected to a leaching treatment with water at a specified temperature for a specified length of time in order to remove away residual sodium content leachable in water so that the troubles due to absorption of moisture by the alkali constituent in the sodium silicate coating layer can be largely dissolved.

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Takefu, Japan

Ryuji Hamada