R-FE-B PERMANENT MAGNET BEING EXCELLENT IN ELECTRICAL INSULATING PROPERTIES, HEAT RESISTANCE AND CORROSION RESISTANCE AND MANUFACTURE THEREOF

摘要

PURPOSE: To obtain a permanent magnet for an automobile being excellent in electrical insulating properties, heat resistance and corrosion resistance by providing a polyimide film of a specified film thickness on the surface of an R-Fe-B permanent magnet body of which the main phase is constituted of tetragonal crystals, with a ground metal film of a specified film thickness interlaid. CONSTITUTION: A polyimide film of a film thickness 2.0-10μm is provided on the surface of an R-Fe-B permanent magnet body of which the main phase is constituted of tetragonal crystals, with a ground metal film of a film thickness 1.0-3.0μm interlaid. The reason why the thickness of a ground metal provided on the cleaned surface of a magnet is limited to 1.0-3.0μm is that the thickness less than 1.0μm and that exceeding 3.0μm are both undesirable since the former is insufficient for the adhesion to the surface of the magnet and the latter causes a rise in the cost as the ground film. The reason why the thickness of polyimide resin is limited to 2.0-10μm is that the thickness less than 2.0μm and that exceeding 10μm are both undesirable since the former makes it impossible to obtain a film being excellent in electrical insulating properties, heat resistance and corrosion resistance and the latters causes a rise in the cost of manufacture.