| 摘要 |
PURPOSE:To obtain a permanent magnet which has a higher anisotropy and the higher density of the sinter by a method wherein a molding of magnetic powder whose thermal expansion coefficient is anisotropic prepared in a magnetic field is subjected to an anisotropic pressurized heat treatment during or before a sintering process. CONSTITUTION:Nd-Fe-B alloy powder obtained by a powder metallurgy method is molded by compression in a magnetic field. A stainless steel container 2 in which the magnetic powder is molded is placed in a high temperature static hydraulic pressure applicator 1 and a pressure is applied to the stainless steel container 2 for an anisotropic pressurized heat treatment and then sintering/annealing is performed by a temperature control. The thermal expansion coefficient of Nd2Fe14B1, the main phase of this magnet, is a positive value about 4.8X10<-6>/ deg.C along the direction of an easy-to-magnetize axis, while it is a negative value about -3.3X10<-6>/ deg.C along the direction of an axis perpendicular to the easy-to-magnetize axis. From this point of view, in accordance with the temperature rise under the high pressure applied to the side surface through the cylindrical container, a moment along the longitudinal direction of the container is created in the C-axis and the rotation of the powder is controlled along the longitudinal direction of the container so that the orientation can be improved, whereby a permanent magnet with excellent magnetic characteristics can be obtained. |
