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The improvement of recrystallization texture and magnetic properties in grain-oriented electrical steel with trace Bi addition processed by strip casting process was studied in this study. Low casting temperature and sufficient liquid steel flow during strip casting process enabled relatively homogeneous distribution of Bi in the as-cast strip, which accelerated the precipitation during solidification and cooling process. As a result, relatively high density of duplex MnS + AlN, MnS and AlN was formed at grain boundaries and inside grain. Due to the synergistic effect of continuous precipitation and fragmentation of coarse precipitates during cold rolling, the number density of precipitates was increased and mean size was decreased along the processing route. High density of precipitates is attributed to severe inhomogeneous plastic deformation, which promoted the formation of high density in-grain shear bands during cold rolling and recrystallization Goss texture during annealing. Homogeneous microstructure with average grain size of ~ 11.6 μm, strong Goss texture with intensity of 2.5 multiples of random distribution, fine precipitates with number density of ~ 1.9 × 109 /cm2 and mean size of ~ 49 nm were formed after primary recrystallization annealing. Furthermore, grain-oriented electrical steel with Bi addition experienced complete secondary recrystallization of exact Goss grains during high-temperature annealing, which is attributed to beneficial optimization of Goss texture and strong inhibition effect, and superior magnetic induction B8 of 1.91 T was obtained. It is expected that this study paves a new way for fabrication of high-performance grain-oriented electrical steel.

The study described here focuses on the microstructure and mechanical properties of a novel hot-rolled medium-Mn steel (Fe–0.25C–4Mn–1.88Al–0.6Si–0.04Nb–0.08V, wt%) that contained only 4 wt% Mn and modest Al content of 1.88 wt%. It was found that a relatively high content (25–53 vol%) of retained austenite was obtained by intercritical annealing process. With increase in intercritical annealing temperature from 700 to 740 and to 760 °C, retained austenite fraction increased from 25.1 to 53.2% and then decreased to 46.1%. Besides, mechanical stability of retained austenite in 700–760 °C intercritically annealed steels decreased with increase in intercritical annealing temperature. The 720 °C intercritically annealed steel yielded excellent mechanical properties with yield strength of 766 MPa, tensile strength of 951 MPa, total elongation of 48.6% and PSE of 46.22 GPa·%, achieved by a high volume fraction of retained austenite (46%) with relatively high mechanical stability. Thus, the 4% Mn steel present in this study indicated excellent mechanical properties of medium-Mn steels can be achieved using low alloy content.

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.

Strip-cast grain-oriented 4.5% Si steel was produced by short-term isochronal secondary annealing (15 min) and isothermal annealing (1000 °C) under hydrogen atmosphere. The relationship between the evolution of grain structure and magnetic properties was elucidated. It was observed that during isochronal annealing, abnormal grain growth occurred followed by normal grain growth with the increase of annealing temperature. Additionally, decreasing the primary annealing temperature accelerated the isochronal annealing kinetics, and near complete abnormal grain growth with optimal magnetic properties was obtained at lower temperature. Furthermore, during isothermal annealing, abnormal grain growth successfully occurred and magnetic properties were continuously improved with the increase of annealing time. The optimal magnetic properties were superior to those of isochronal annealing because of sharper secondary Goss texture and reduced retention of second-phase particles. The grain-oriented 4.5%Si steel in the present study indicated superior properties and better workability than the previously reported non-oriented 6.5%Si steel. Thus, grain-oriented 4.5%Si steel produced by short-term secondary annealing can potentially replace non-oriented 6.5%Si steel.