アトマイズ法および単ロール法により作製したSm-Fe系粉末窒化物の磁気特性

概要

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Sm-Fe-N hard magnetic materials are good candidates for high performance bonded magnets. Rapid-quenching method should be highly favorable for the fabrication of isotropic magnet powder with high coercivity. We report here the magnetic properties of Sm-Fe-N powders produced by three kinds of rapid-quenching processes. Sm2Fe17 powders were prepared by gas-atomization (GA), rotating-disk atomization (RDA), and melt-spinning (MS) methods. The Sm2Fe17 GA powder had dendritic solidification structure, while the RDA powder had microcrystalline structure with size of 3-5μm. Coercivities (HcJ ) of their nitrides were 56 (for GA) and 217 kA/m (for RDA). The HcJ of nitrided Sm2Fe17 MS powder with wheel velocity (Vs) of 5-20 m/s, which had also microcrystalline structure, was 53 to 509 kA/m. These coercivity values are not sufficient for practical value (600 kA/m) for bonded magnet applications. From the study of additive effects, it was found that C, C-Si, C-Ga, or C-Al addition decreased the grain size of quenched Sm2Fe17 powder. Consequently, high coercivity was obtained; the HcJ of nitrided Sm2Fe15C1Si1 MS powder with Vs of 10 m/s was 898 kA/m, and 708 kA/m for the nitrided Sm2Fe15C1Si1 RDA powder. The compression-molded bonded magnet made from Sm2Fe18Si0.1Nx MS powder showed a high (BH)max of 82.7 kJ/m3.
電気製鋼研究会の論文