Abstract: In order to meet the requirement of low loss of iron core for high-frequency transformer, the heat treatment process of Fe_72.7Si₁₇B_6.8Nb_2.6Cu_0.9 nanocrystalline iron core was studied, and the variation of dynamic and static soft magnetic properties of the iron core annealed without magnetic field for different time and with different magnetic field intensity was discussed. The results show that when no magnetic field is applied, the core loss is the lowest when the holding time is 60 min, which is P_{20 kHz/0.5 T}=11.82 W/kg, and its static soft magnetic properties is in the optimal state when the holding time is 30 min, which is H_{c30 min}=1.86 A/m. After the transverse magnetic field is applied, the remanence and coercivity of the DC magnetic properties are significantly reduced, H_{c40 mT}=0.64 A/m, and the loss reaches the lowest when the applied magnetic field intensity is 50 mT, which is P_{20 kHz/0.5 T}=10.53 W/kg. Eddy current loss plays a leading role in the core loss in the high frequency range. The high frequency loss of the new nanocrystalline iron core is greatly reduced after transverse magnetic field heat treatment, and its permeability is excellent.

Key words: nanocrystalline iron core, heat treatment, iron loss, soft magnetic properties