| 摘要 |
PURPOSE:To contrive substantial improvement in magnetic characteristics by a method wherein liquid nitrogen is used as a cooling medium, and the generation of cracks, breaking and the like are suppressed. CONSTITUTION:34wt% each of Neodymium (purity 100%), boron (99.5%) and electrolytic iron (99.9%) and 1.3wt% of iron as the remainder are weighed, an alloy is formed using an arc melting furnace, and a starting raw alloy is obtained. Then, the pulverizing device such as a jaw crusher, a stamping mill, a Braun mill and the like is used according to the particle size, and the final average grain size of 3.5mum (FSSS) is obtained. A cold molding is performed on the obtained hard magnetic powder in order to give an orientational property and the shape of magnet. (The pressure is 2ton/cm<2>, impressing magnetic field is 70,000e, and magnetic field direction is the press direction.) Then, a sintering treatment is performed in Ar gas atmosphere at 1,050-1,150 deg.C for an hour for the purpose of improving density, and a quick cooling is performed in liquid nitrogen. Subsequently, an aging treatment is performed at 600 deg.C for an hour for the purpose of improving coercive force, and then an ordinary oil quenching process is performed. |
