• Title/Summary/Keyword: 펄스자장

Search Result 4, Processing Time 0.085 seconds

펄스자장을 이용한 고이방화 Nd-Fe-B자석의 종축자장성형방법

  • 김동환;장동열;김승호;김상면;장태석
    • Proceedings of the Korean Magnestics Society Conference
    • /
    • /
    • pp.34-35
    • /
    • 2003
  • 고에너지적 Nd-Fe-B계 소결자석 제조를 위한 펄스자장 성형시, 금형 및 다양한 성형조건이 자석의 이방화율 향상에 미치는 영향에 대하여 조사하였다. 일반적으로 butterfly, disk or coin 형태의 자석을 제조하는 방법으로는, 종축자장성형법(Axial Die Press, ADP)을 이용하여 최종제품의 near-net shape으로 성형 및 소결하는 방법과, 횡축자장성형법(Transverse Die Press, TDP)을 이용하여 blick or cylinder 형태로 제조한 후 여러 단계의 가공공정을 거쳐 최종제품으로 제조하는 방법이 적용되고 있다. 그러나, ADP의 경우 분말의 자장정렬 후 성형단계에서 성형밀도가 증가함에 따라 배향의 틀어짐 현상이 증가하므로 이방화율 향상의 한계가 있어 (BH)$_{MAX}$+iHc=54 이상의 자석은 제조되기 어렵고, TDP의 경우 고이방화 자석의 제조가 가능하나 복잡한 형상의 제품을 직접 성형할 수 없어 성형/소결 후 복잡한 가공공정을 거쳐야 하므로 재료의 손실뿐만 아니라 고가의 가공비용이 소요되므로 경제적인 문제점을 갖게 된다. 반면에, 펄스자장 종축성형방법(PDP)은 3T~5T의 펄스자장을 이용하여 분말의 정렬 및 성형을 동시에 수행함으로써 TDP보다 향상된 배향율이 얻어질 수 있으며, ADP으로만 실현 가능한 복잡한 형성의 자석을 near-net shape으로 제조가 가능한 잇점이 있다.다.

  • PDF

Construction of a Pulsed Field Magnetometer and Magnetic Properties Measurement of Rare Earth Permanent Magnets (고자장 펄스마그네토미터 구성 및 희토류 영구자석의 자성측정)

  • 김윤배;우병칠;박포규;김만중;김택기
    • Journal of the Korean Magnetics Society
    • /
    • v.7 no.4
    • /
    • pp.212-216
    • /
    • 1997
  • A pulsed field magnetometer with maximum applied field of 130 kOe has been constructed. The pulsed field generated by a 18 kJ capacitor bank system combined with a pulse coil was damped oscillation with the period of 10.12 ms. Magnetic hysteresis loop was measured by induction method during 10.12 ms of a pulse duration from the first positive to the second positive peak. The difference from DC magnetic properties due to the eddy current effect was inferred below 3% for the NdFeB magnet with the diameter below 5 mm.

  • PDF

Axial Pressing Method Using Pulse Magnetizing Field for the Preparation of Nd-Ee-B Sintered Magnets (펄스자장을 이용한 고이방화 Nd-Fe-B자석의 종축자장성형방법)

  • Kim, Dong-Hwan;Kang, Byung-Kil;Jang, Dong-Youl;Kim, Andrew S.;Kim, Sang-Myun;Jang, T.S.
    • Journal of the Korean Magnetics Society
    • /
    • v.13 no.4
    • /
    • pp.182-186
    • /
    • 2003
  • A new axial pressing method using pulse magnetizing field was studied to improve the remanence of Nd-Fe-B sintered magnets. In order to make near-net shape green compacts of butterfly, disk, or coin magnets, conventional axial-type pressing has been normally used. However, compared to the transverse-type pressing, it is not possible to obtain higher remanence by this method because the magnetic alignment of powder begins to deteriorate when the density of green compacts increases over a critical value. On the other hand, we found that an axial pressing under pulse magnetizing field was very effective to increase the degree of magnetic alignment of powder, yielding remanences even higher than those obtained by the transverse pressing. In this study, it was revealed that appropriate tapping density and how to apply pulse magnetic held were important to improve the grain alignment and thus remanence of Nd-Fe-B sintered magnet.

A High Precision Pulsed Field Magnetometer for Magnetic Properties Measurements of Rare Earth Magnets (희토류 영구자석의 자성측정을 위한 고감도 펄스마그네토미터)

  • Kim, Y.B.;Kapustin, G.A.
    • Journal of the Korean Magnetics Society
    • /
    • v.15 no.4
    • /
    • pp.250-255
    • /
    • 2005
  • A 8 MA/m-class pulsed field magnetometer has been constructed by composing a pulsed field magnet, a pickup coil, analog integrators, a digital storage oscilloscope and a personal computer. For precision measurements, a 3-axis compensation principle has been applied for the fabrication of pickup coil, and the compensation level of the order of $10^{-6}$ and the sensitivity of $5{\cdot}10^{-7}\;Am^2$ for magnetic moment have been obtained. The high sensitivity of the magnetometer is good enough for measurements of magnetic properties of rare earth magnets in small size or thin films shorter than $3\;mm{\phi}$ in diameter.