粉体および粉末冶金
Online ISSN : 1880-9014
Print ISSN : 0532-8799
ISSN-L : 0532-8799
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71 巻, 2 号
February
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研究論文
研究論文
  • 圧粉磁心の絶縁皮膜に用いられるファヤライトの形成
    黄 晸煥, 宇都野 正史, 松原 賢, 三富 将敬
    2024 年 71 巻 2 号 p. 47-50
    発行日: 2024/02/15
    公開日: 2024/02/15
    [早期公開] 公開日: 2023/12/09
    DOIhttps://doi.org/10.2497/jjspm.23-00057
    ジャーナル オープンアクセス
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    For powder magnetic cores, a spinel ferrite insulating layer offers the advantages of high magnetic flux density and low iron loss. However, FeO is generated in the insulting layer after annealing at 873 K, which causes a decrease in electrical resistivity. To overcome this problem, we focused on fayalite (Fe2SiO4), which exhibits a high electrical resistivity and is stable even at temperatures above 1273 K. Fe2SiO4 can be formed by a reaction between FeO and SiO2. Therefore, if Fe powder particles mixed with both spinel ferrite and SiO2 are heated at a temperature that is sufficiently high to form FeO, Fe2SiO4 is expected to be produced, and the resulting particles are likely to exhibit high electrical and thermal resistance. To examine this possibility, a mixture of Fe3O4 of spinel-type ferrite, SiO2, and Fe powder was heated at 1023 K, and the structure and composition of the resulting material were investigated. Analyses using X-ray diffraction and Fourier-transform infrared spectroscopy confirmed the formation of Fe2SiO4, which showed a high electrical resistivity. These results indicate that Fe2SiO4 can be used as an insulating layer for powder magnetic cores.

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  • 液相カーボンコーティングによるステンレス鋼粒子の流動性向上
    郷田 隼
    2024 年 71 巻 2 号 p. 51-55
    発行日: 2024/02/15
    公開日: 2024/02/15
    [早期公開] 公開日: 2023/12/20
    DOIhttps://doi.org/10.2497/jjspm.23-00049
    ジャーナル オープンアクセス
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    A uniform carbon coating was applied to stainless steel (SUS316L) particles by liquid-phase carbon coating using soluble carbon material. The resulting carbon-coated stainless steel particles have improved powder flowability, especially angle of repose and spatula angle, comparing with uncoated stainless steel particles, because of the lubricating properties of the carbon layer. Carr’s flowability index was improved from 80.5 to 91. Furthermore, when sintered or melted objects were prepared from carbon-coated stainless steel particles with heating over 1250 K, the carbon coat layer reduced the oxide layer (especially chromium oxide) of the stainless steel. By heating over 1250 K, carbon coat layer removed oxygen from surface of stainless steel and also itself disappeared, therefore carbon coat layer improved purity of melted objects without changes of components and structures. The liquid-phase carbon coating improved the flowability of the stainless steel particles while not adversely affecting their sintering and melting properties.

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