Effect of rolling temperature on the microstructure, texture, and magnetic properties of strip-cast grain-oriented 3% Si steel

The effect of rolling temperature on the evolution of microstructure, texture, and magnetic properties of ultra-low-carbon grain-oriented silicon steel was studied in strip-casting process. Dynamic strain-aging (DSA) behavior was observed during warm rolling in the temperature range of ~ 200 to 400 °C based on the fact that majority of the inhibitor elements remained in solution during the strip-casting process. Considering the initial coarse grains with strong {100} fiber prior to rolling, the cold-rolled specimen exhibited pronounced α-fiber and weak γ-fiber texture. However, intense shear bands and high stored energy regardless of the orientation were obtained in the warm-rolled specimens at the DSA temperature, accompanied by weak α-fiber and strong γ-fiber texture. While homogenous microstructure with lower stored energy was observed in the case of high temperature, the differences in shear bands and stored energy governed by the rolling temperature were strongly related to the extent of DSA effect, which is attributed to distinct characteristic of rolling and recrystallization texture. After recrystallization annealing, fine-grained homogeneous microstructure with strong Goss and γ-fiber texture was obtained at the DSA temperature, while relatively random texture with much more α-fiber and θ-fiber components was observed in the case of high temperature. The microstructure and texture of primary annealed sheets exhibited sufficient Goss grains and favorable surrounding matrix with pronounced γ-fiber texture, which was responsible for the perfect secondary recrystallization annealing in the warm-rolled specimens at the DSA temperature. The present study suggests that texture optimization of strip-cast grain-oriented silicon steel can be achieved by warm rolling in the appropriate temperature range, with improved magnetic properties.