PURPOSE: To provide a circular magnet which has a high radial magnetic characteristic that has a magnetic anisotropy gradually increasing from the center towards an edge by making the most use of a warm-worked magnet and by improving the processing method.
CONSTITUTION: An Nd13.8FebalCo7.5B6Ga1.25 alloy is manufactured by arc melting. This alloy is injected onto a single roll which rotates at the speed of 20m/sec. in an Ar atmosphere to make an unfixed form flake. Then, the obtained flake is roughly smashed into a green compact of 500μm or smaller and the green compact is compressed by hot pressing. After that, the green compact is subjected to warm plastic forming at 750°C between an upper and a lower punch having a certain curvature to form a circular magnet. The radius of curvature of the lower punch is fixed, 65mm, while that of the upper punch is variable, 69, 65, or 61. The shape of the compact is so adjusted that the final expansion angle of the circular magnet may be fixed, 55°C, and the maximum height of the center of the magnet may be uniform, 10mm. By this method, a circular magnet having an improved magnetic characteristic can be manufactured stably.
SHINODA MAKOTO
TOKUNAGA MASAAKI
