Magnetic performance and microstructure characterisation of powder metallurgy Fe–6.5 wt-% Si high-silicon steel

Abstract

Powder metallurgy high-silicon steel strip (Fe–6.5 wt-% Si) was prepared by directly sintering followed by rolling using gas atomised powder with low oxygen content. Due to its poor formability, the gas atomised powder was directly sintered with something heavy of 1 kg overlaid on powder top. The relative density of sintered samples was about 94.1% and the porosity was 5.9%. The pore pinning effect prevented the formation of extremely large grains during sintering, which was beneficial for subsequent rolling. The grain size was controlled in the range of 100–300 μm. After cold rolling, a large number of sub-grain boundaries and deformation bands were generated, which increased the strength to 1190 MPa. It was worth noting that these two would disappear after annealing. Instead, ordered B2 and D0₃ phases were formed, and the texture of high-silicon steel was mainly {100}<110>. A low iron loss W10/50 value of 0.55 W kg⁻¹ was achieved.