Effect of two-stage cold-rolling on microstructure， texture，mechanical and magnetic properties of ultrathin-gauge non-oriented silicon steel

Ultrathin-gauge non-oriented silicon steel sheets are produced by both one-stage and two-stage cold-rolling processes.The effects of rolling and annealing on the evolution of microstructure， texture， mechanical， and magnetic properties are investigated. It is found that the microstructure resulting from one-stage cold-rolling primarily comprised fibrous deformation structures， resulting in refined grain size after final recrystallization. Notably， the ｛001｝〈110〉 and ｛223｝〈110〉 textures persisted in the low-temperature recrystallized state，which is inherited from cold-rolled sheets. Conversely， during high-temperature annealing， a notable texture transformation occurs， with the α* and γ textures emerging as the dominant features. The two-stage cold-rolling method promotes the formation of shear bands， leading to a larger grain size in the final annealed structure. These shear bands served as crucial nucleation sites for Goss grains， thereby facilitating the development of Goss texture during the annealing process. Furthermore， the ｛001｝〈110〉 texture aligned along the λ orientation line towards the ｛001｝〈010〉 texture， accompanied by a gradual decrease in the intensity of the γ texture. As the annealing temperature increases， the iron loss initially decreases rapidly and slowly， whereas the magnetic induction intensity initially rises before stabilizing. Compared with the one-stage cold-rolling method， the ultrathin-gauge non-oriented silicon steel prepared by the two-stage cold-rolling method has lower iron loss and higher magnetic induction intensity. This superior performance can be attributed to the formation of shear bands， which enhance the formation of favorable Goss and Cube textures， the suppression of detrimental γ texture， and the attainment of a larger recrystallized grain size.With increasing the annealing temperature， the yield strength of both the one-stage and two-stage cold-rolling annealed sheets initially decreases dramatically before trending to be stabilized. The yield strength of ultra-thin non-oriented silicon steel produced by the one-stage cold-rolling method is higher than that produced by two-stage cold-rolling. The optimal comprehensive properties （both mechanical and magnetic properties） are achieved through a two-stage cold-rolling process followed by annealing at 800 ℃， which yields a mid/high frequency-iron loss P10/400 of 12.34 W/kg， P of 36.12 W/kg， a magnetic induction intensity B50 of 1.71 T and a yield strength of 389 MPa.