Magnetic Properties of Nitrided Sm-Fe Powders Prepared by Gas-Atomization, Rotating-Disk Atomization and Melt-Spinning Processes

摘要

Magnetic properties of nitrided Sm-Fe powder produced through relatively low cooling-rate rapid-quenching process such as gas-atomization (GA), rotating-disk atomization (RDA), or melt-spinning (MS) with wheel velocity (V_s)N30 m/s have been investigated. The Sm_2Fe_17 GA powder had dendritic solidification structure, while the RDA powder had microcrystalline structure with size of 3-5 mum. Coercivities (H_cJ) of their nitrides were 56 (for GA) and 217 kA/m (for RDA). The H_cJ of nitrided Sm_2Fe_17 MS powders with V_s of 5-20 m/s, which had also microcrystalline structures, were 53 to 509 kA/m. These coercivity values are not sufficient 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 crystal size of quenched Sm_2Fe_17 powder. Consequently, high coercivities were obtained in nitrided powders produced by the low cooling-rate processes; the H_cJ of nitrided Sm_2Fe_15C_1Si_1MS powder with V_s of 10 m/s was 898 kA/m, and 708 kA/m for the nitrided Sm_2Fe_15C_1Si_1RDA powder. Thus, it is expected that hard magnetic Sm-Fe-N powders will be produced inexpensively by using these processes.