| 摘要 |
PURPOSE:To improve the distribution of magnetic characteristics by a method wherein a compression processing is performed on the inner circumferential part only of a billet at the prescribed temperature in order to give the compressive distortion of 0.05 or more in absolute value of logarithmic distortion in axial direction of the billet. CONSTITUTION:Cutting and machining operations are performed on the rod formed by performing an extrusion-processing on an Mn-Al-C alloy, and a cylindrical billet 1 is obtained. This billet 1 is inserted between a bottom force 4 and a constraint metal mold 2, maintained at the temperature of 530-830 deg.C, and a compression-processing is performed on the inner circumferential part of the billet 1 using a movable punch 3. At that time, the compressive distortion of 0.05 or more in absolute value of logarithmic distortion is imparted. Then, after machining processing has been performed on the inner surface of the billet 1, the inner circumference of the billet is magnetized. As a result, the distribution of the magnetic characteristics in radial direction can be improved.
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