| 摘要 |
PURPOSE:To manufacture a high performance permanent magnet at a low cost by a method wherein an ingot having a specific average grain diameter and having rare-earth elements, iron and boron as basic components is subjected to a hot rolling with a specific strain speed. CONSTITUTION:When a permanent magnet whose main components are rare- earth elements (including Y), iron and boron, the casting is carried out so as to make its average grain diameter not larger than 20mum. With this process, the permanent magnet can be rolled in a wide range of a strain speed. Then the permanent magnet is subjected to a hot rolling with the strain speed in a range of 10<-4>-10<2>/sec to make it anisotropic. If the strain speed exceeds the above range, crackings are developed in the ingot and the sufficient rolling can not be performed. On the other hand, the lower limit of the strain speed is the minimum strain speed allowable from a viewpoint of productivity. If the strain speed is lower than the above range, not only the productivity is degraded but also, as the magnet is held under a high temperature for a long time, crystal grain growth is induced and the coercive force is degraded. |
