MANUFACTURING METHOD OF RARE EARTH PERMANENT MAGNET

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PROBLEM TO BE SOLVED : To provide a high oilproof sintered permanent magnet, with ease at a low cost, which has corrosive resistance and hydrogen barrier property even in the atmosphere of high temperature and high pressure of coolant and lubricating oil, by forming a protective film in a thermal process after treating the surface of a processed R-T-B permanent magnet in an alkali solution containing alkanolamine. SOLUTION : In the manufacturing method of the R-T-B rare earth permanent magnet, it is submerged in a coolant and/or lubricating oil for long hours. The R-T-B sintered magnet is cut and/or polished to finish the surface, and then it is submerged in the alkali solution containing alkanolamine for 1-100 hours. Then, it is thermally treated at 200-350°C for 0.5-24 hours in the atmosphere in which the oxygen partial pressure is 1.3×103 Pa (10 Torr) or higher. Since the surface of the R-T-B permanent magnet processed is treated in the alkali solution containing alkanolamine and then subjected to a thermal process to form a protective film, the high oilproof sintered permanent magnet having corrosive resistance and hydrogen barrier property even in such atmosphere of high temperature and high pressure of coolant and lubricated oil can be constituted simply at a low cost. COPYRIGHT : (C)2009, JPO&INPIT