Study on microstructure and texture of a new-type low Si high Mn non-oriented silicon steel 50W250

Abstract

A new method to fabricate a high grade non-oriented silicon steel was provided, in which the significant feature is low Si high Mn. Metallographic microscopy, X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to investigate the microstructure, texture evolution and precipitates characteristics, respectively. It is found that hot rolled sheet had a distinct stratification appearance. Fine equiaxed grains occupy the surface while subsurface and center regions were dominated by deformed microstructure and equiaxed grains. After normalizing, the microstructure of hot rolled sheet completely recrystallized. A number of shear bands were observed attributed to cold rolling. With the increase of annealing temperature or time, the average grain size of final annealed sheet increases. Annealed at 1000 °C for 7 min, annealed sheet exhibits highest and lowest fraction of {001}<100> cube texture and {112}<11-1> copper texture, respectively. The average grain size of final sheet also reaches peak, and it is 117.65 µm. In addition, the fine precipitates mainly include spherical MnS, CuS, regular hexahedral AlN, TiN and partly approximate spherical composite precipitates. The average size and distribution density are 132.10 nm and 1.62 × 1012 cm−3, respectively. Under the condition annealed at 1000 °C for 7 min, the core loss P1.5/50 is 2.461 W · Kg−1 and the magnetic induction B50 is 1.699 T.