| 摘要 |
PURPOSE:To obtain a ferrite magnetic core which has high surface resistance to the extent that the direct wiring on the surface is possible and excellent magnetic characteristics by oxidizing the surface of Mn-Zn system ferrite formed to a shape appropriate for an inductance element. CONSTITUTION:After Mn-Zn system ferrite which has low resistance but high permeability is formed to a shape appropriate for an inductance element, e.g., shape of drum, heated to approx. 1,300-1,350 deg.C and is held for approx. 3hr in N2 which contains O2 of partial pressure ratio of 1%-10%. Then, the atmosphere is turned into O2 of partial pressure ratio of 0.1-1.0%, cooled at the cooling speed of -200--300 deg.C/h and normal Mn-Zn ferrite is made. After a surface oxide layer is formed by raising the temperature to approx. 800-1,100 deg.C again in the air, the ferrite is cooled.
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