| 摘要 |
PURPOSE:To prevent remaining of inner strain and to obtain a sintered body, which can be readily assembled, by providing projections on a rod part or mandrel part for forming the inner diameter part of a cylindrical molded body. CONSTITUTION:Projections 22 are provided on one end part of a mandrel 20. When a cylindrical molded body 24 is released, grooves 26 are formed in the axial direction on the inner surface of the body 24. The molded body 24 having such grooves is burned. Then large inner acting stress due to difference between the contracting ratio in the direction of the diameter and the contacting ratio in the circumferential direction is concentrated at the parts of the grooves 26 during the burning step, especially during the cooling step from the high temperature state to room temperature. Microcracks and the like are not yielded at parts other than the grooves 26. The microcracks and the like are divided at the parts of the grooves 26 without fail. Therefore, complicated breakdown is not yielded. The cylindrical state is readily recovered. The inner strain does not remain. Microcracks are not yielded at the other places. Thus a magnet characterized by high mechanical strength and excellent magnetic characteristics is obtained.
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