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수소반응속도 제어에 의한 Nd-Fe-B-Ga-Nb 합금의 미세조직 이방화율 향상에 관한 연구
이상협,김동환,유지훈,이동원,김병기,Lee, S.H.,Kim, D.H.,Yu, J.H.,Lee, D.W.,Kim, B.K. 한국분말야금학회 2010 한국분말재료학회지 (KPMI) Vol.17 No.1
HDDR treated anisotropic Nd-Fe-B powders have been widely used for the sheet motors and the sunroof motors of hybrid or electric vehicles, due to their excellent magnetic properties. Microstructural alignment of HDDR treated powders are mostly depending on the hydrogen reaction in disproportionation step, so the specific method to control hydrogenation reaction is required for improving magnetic properties. In disproportionation step, hydrogenation pressure and reaction time were controlled in the range of 0.15~1.0 atm for 15~180 min in order to control the micorstructural alignment of $Nd_2Fe_{14}B$ phase and, at the same time, to improve remanence of HDDR treated magnet powders. In this study, we could obtain a well aligned anisotropic Nd-Fe-B-Ga-Nb alloy powder having high remanence of 12 kG by reducing hydrogen pressure down to 0.3 atm in disproportionation step.
HDDR 반응시 수소화 반응이 Nd-Fe-B계 분말의 미세조직과 자기적 특성에 미치는 영향
이상협,유지훈,김양도,Lee, S.H.,Yu, J.H.,Kim, Y.D. 한국분말야금학회 2011 한국분말재료학회지 (KPMI) Vol.18 No.5
The HDDR(hydrogenation-disproportionation-desorption-recombination) process can be used as an effective way of converting no coercivity Nd-Fe-B material, with a coarse $Nd_2Fe_{14}B$ grain structure to a highly coercive one with a fine grain. Careful control of the HDDR process can lead to an anisotropic $Nd_2Fe_{14}B$ without any post aligning process. In this study, the effect of hydrogen gas input at various temperature in range of $200{\sim}500^{\circ}C$ of hydrogenation stage (named Modified-solid HDDR, MS-HDDR) on the magnetic properties has been investigated. The powder from the modified-solid HDDR process exhibits Br of 11.7 kG and iHc of 10.7 kOe, which are superior to those of the powder prepared using the normal HDDR process.