Effects of rolling conditions on microstructure and magnetic properties of thin gauged 3% Si–Fe sheets (abstract)

Abstract

To match the requirements for development of transformer cores with lower iron losses, many new materials are under development including amorphous materials, 6.5% Si–Fe sheets and thin gauged 3% Si–Fe sheets. Among these materials, the thin gauged 3% Si–Fe sheets are attracting attention due to their good magnetic properties and scientific interest. Arai et al. reported that the magnetic properties of the sheets were comparable to those of the amorphous materials and (110)[001] preferred orientation of the sheets are developed by tertiary recrystallization.1 The 100 μm thick 3% Si–Fe sheets were prepared via conventional metallurgical processes including melting and casting, hot rolling to 25 mmT at 1200 °C, first cold rolling to 0.5 mmT, intermediate annealing at 800 °C for 30 min, second cold rolling to 0.25 mmT, intermediate annealing at 800 °C for 30 min, final cold rolling to 100 μm and final annealing at 1200 °C for 1 h in a vacuum of 5×10−6 Torr. Among these processes, the cold rolling process is an important one because preferred orientation of the sheets was developed in the process. Nakano et al. reported that there was an optimum cold rolling ratio to get required magnetic properties of the sheets.2 Recently, we found that the reduction rate, i.e., number of passes, as well as reduction ratio affected the preferred orientation and magnetic properties of the sheets. The number of passes in the first cold rolling process was changed from 7 to 60 and B10 values of the final sheets were changed from 1.30 to 1.84 T according to the number of passes. From x-ray experiments, it was found that intensity of (110) peak in the cold rolled and annealed sheets strongly affected the magnetic properties of the final sheets. We will discuss the relationship between the reduction rate and preferred orientation, and magnetic properties of the thin gauged 3% Si–Fe sheets.