• Title/Summary/Keyword: 소결자석

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Effect of Strip-cast Conditions on the Formation of Microstructures in Nd-Fe-B alloys (Strip-cast 조건이 Nd-Fe-B 합금의 미세조직 형성에 미치는 영향)

  • Lee, D.H.;Jang, T.S.;Kim, D.H.;Kim, Andrew S.
    • Journal of the Korean Magnetics Society
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    • v.12 no.1
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    • pp.34-40
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    • 2002

  • In order to improve the microstructure of the strip cast Nd-Fe-B alloys that are frequently used for production of high energy sintered magnets, influence of various strip casting conditions on the microstructure and phase formation and distribution were investigated. Nd-Fe-B strips consisting of microstructures suitable for preparation of high energy sintered magnets could be obtained when the wheel speed was below 5 m/s. The compositional limit that can avoid the crystallization of free iron in the as-cast state was estimated to be Nd$\_$14/Fe$\_$79/B$\_$7/. Regardless of the compositional variation, <001> preferred orientation of Nd$_2$Fe$\_$14/B normal to the strip surface was always occurred below 5 m/s, which would eventually enhance the grain alignment during pressing the powder under a magnetic field. While the coercivity of the strip cast alloys increased with the increase of the wheel speed, mainly due to the refinement of Nd$_2$Fe$\_$14/B grains, it decreased with the reduction of Nd content in the alloy composition as the formation of free iron increased.

  • https://doi.org/10.4283/JKMS.2002.12.1.034 인용 PDF KSCI

The Effect of Additional Elements and Grain Size Distribution on the Magnetic Properties of the Nd-Fe-B Sintered Magnets (Nd-Fe-B계 소결자석의 자기적 특성에 미치는 첨가원소와 결정립 분포의 영향)

  • Hong, Yeon-Gi;Kim, Jong-O
    • Korean Journal of Materials Research
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    • v.8 no.9
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    • pp.819-824
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    • 1998

  • The influence of casting cooling rate during the preparation of ingots on the grain size distribution and the magnetizing ability of $\textrm{Nd}_{16}\textrm{Fe}_{72}\textrm{V}_{4}\textrm{B}_{8}$ sintered magnets were investigated. Sintered magnets prepared from copper mold which allow a higher cooling rate, show a smaller grain size distribution and god magnetizing ability. The effects of adding bride forming elements, such as Cr, Mn, Nb, and W on the magnetic properties of Nd-Fe-B sintered magnets were also investigated. Both Cr and W addition increase coercivity and the resultant $\textrm{Nd}_{16}\textrm{Fe}_{72}\textrm{Cr}_{4}\textrm{B}_{9}$ alloy exhibits a similar magnetizing ability in comparison with $\textrm{Nd}_{16}\textrm{Fe}_{72}\textrm{V}_{4}\textrm{B}_{8}$ alloy.

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Characteristic of Iron Oxide and the Magnetic Properties of Sr-ferrite by Roasting Temperature of Iron Oxide (산화철 배소에 따른 분체 특성 및 Sr-ferrite 자석의 소결 특성)

  • Jang Se-Dong
    • Resources Recycling
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    • v.12 no.6
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    • pp.19-25
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    • 2003

  • This experiment was carried out to examine the effect of iron oxide roasting for Sr-ferrite magnet. Chloride content was decreased with raising the 2 nd roasting temperature of iron oxide for ruthner process iron oxide. The optimization temperature for roasting of ruthner process iron oxide was around $800^{\circ}C$ as average particle size 1.5∼1.9 $\mu\textrm{m}$, apparent bulk density 1.4 g/$m\ell$ and chloride content 0.05%. The relation between Br and HcJ by sintering temperature for Sr-ferrite magnet was found to be Br≒-0.258HcJ＋494. In case of having a vibrating disk mill for the ruthner process iron oxide, the magnetic properties were Br 421 mT and HcJ 251 kA/m.

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