| 摘要 |
PURPOSE:To obtain an Mn-Al-C alloy magnet showing high magnetic properties when subjected to inside peripheral magnetization, by subjecting a billet of the titled polycrystalline alloy magnet which is previously made anisotropic to compression working so that compressive strain is lower in the outside peripheral part than in the inside peripherals part and by subjecting the inside peripheral part of the billet to further compression forming into recessed and projecting shape. CONSTITUTION:The cylindrical billet 1 composed of polycrystalline Mn-Al-C alloy magnet which is previously made anisotropic is subjected to compression working at 530-830 deg.C by the use of a punch 2 of recessed and projecting shape for forming the inside peripheral surface of the billet 1. Then, as the compression working proceeds, the inside diameter of the billet 1 is reduced and a part of the inside peripheral surface is brought into contact with the surface of the punch 2. Moreover, the compression working is allowed to proceed, so that inside peripheral surface of the billet 1 is practically brought into contact with the surface of the punch 2 while the outside peripheral surface is kept in contact with the surface of an outer die 4. In this way, a recessed and projecting part is formed at the inside peripheral surface of the billet 1, so that Mn-Al-C alloy magnet showing high magnetic properties when subjected to inside peripheral magnetization can be obtained.
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