Abstract: A method of producing a magnet roll in which a magnetic property comparable to that obtained by an injection molding can be obtained in spite of an extrusion molding. According to a first embodiment, the yoke width of the magnetic-field extrusion die is varied along an extrusion direction. According to a second embodiment, a pipe filled with resin bonded magnet material is used as a shaft. According to a third embodiment, a shaft having a groove which is filled with magnet is used. According to a fourth embodiment, a shaft provided with surface magnetic charge is used. According to a fifth embodiment, a magnetized region of a shaft is set to be shorter than the length of a main magnet. According to a sixth embodiment, an extruded matter is moved while stored in a sizing metal mold having a magnetic circuit structure.

Abstract: A highly rustproof resin-bonded magnet made by using a specific rustproofing resin for coating the particles of a magnetic powder, bonding them to form a molded body, or coating its surface, or for two or all of those purposes. The specific resin is selected from ones containing groups of atoms having a power of forming a coordinate bond and a reducing action. More specifically, it is (a) a high molecular compound produced by reacting with an epoxy resin one or more of a polyhydric phenol having adjacent hydroxyls, a polyhydric phenolic carboxylic acid having adjacent hydroxyls, an ester of a polyhydric phenol and a polyhydric alcohol having adjacent hydroxyls, and a polycyclic and polyhydric phenol having adjacent hydroxyls, (b) a redox resin as a reduction agent, or (c) a high molecular compound produced by curing a mixture of ascorbic acid, or a derivative thereof, and an epoxy resin.

Abstract: A sintered or bonded permanent magnet formed from a material consisting mainly of iron, particularly a Nd-Fe-B alloy, and having a high corrosion resistance has a surface coated with a resin obtained by the polycondensation of tannic acid, phenols and aldehydes. A bonded magnet is also made from a powder of any such material composed of particles coated with any such resin.

Abstract: A highly rustproof resin-bonded magnet made by using a specific rustproofing resin for coating the particles of a magnetic powder, bonding them to form a molded body, or coating its surface, or for two or all of those purposes. The specific resin is selected from ones containing groups of atoms having a power of forming a coordinate bond and a reducing action. More specifically, it is (a) a high molecular compound produced by reacting with an epoxy resin one or more of a polyhydric phenol having adjacent hydroxyls, a polyhydric phenolic carboxylic acid having adjacent hydroxyls, an ester of a polyhydric phenol and a polyhydric alcohol having adjacent hydroxyls, and a polycyclic and polyhydric phenol having adjacent hydroxyls, (b) a redox resin as a reduction agent or (c) a high molecular compound produced by curing a mixture of ascorbic acid, or a derivative thereof, and an epoxy resin.

Abstract: A sintered or bonded permanent magnet formed from a material consisting mainly of iron, particularly a Nd-Fe-B alloy, and having a high corrosion resistance has a surface coated with a resin obtained by the polycondensation of tannic acid, phenols and aldehydes; a bonded magnet is also made from a powder of any such material composed of particles coated with any such resin.